© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

Glossary (see also Volume IIA Glossary)

This glossary includes words useful in the study of nanomedicine, mostly from the fields of physics, engineering, chemistry, biochemistry, biology, anatomy and medicine. Specialists are cautioned that terms may be described, but not rigorously defined, in order to encourage the quickest possible cross-disciplinary understanding by the nonspecialist reader. A very small number of the entries identify new terms introduced for the first time in this text. Much of the material was compiled or modified from pre-existing sources including the following References: 9, 10, 750, 763, 869, 996, 997, 1095, 1259, 1736, 2219-2221, 2223, 2224.

Ab initio -- from the beginning; from first principles.

Abscess -- a circumscribed collection of pus appearing in acute or chronic localized infection, and associated with tissue destruction and frequently with swelling; a cavity formed by liquefaction necrosis within solid tissue.

Abstraction -- specific removal of bonded atom from a structure. A reaction that removes an atom from a structure.

AC -- alternating current.

Accommodation -- voluntarily thickening the lens of the eye to focus diverging rays of light from nearby objects on the fovea of the retina; visual focusing on nearby objects.

Acellular -- cell-free.

Acetylcholine -- a chemical neurotransmitter.

Acetylcholinesterase -- enzyme that rapidly degrades acetylcholine.

Acidophilic -- acid-loving.

Acoustomechanical conversion -- conversion of acoustic energy into mechanical energy.

Action potential -- complete sequence of electrical events accompanying and following the nerve impulse.

Active site -- the restricted part of a protein to which a substrate binds.

Adduct -- in chemistry, an addition product or complex; in biomechanics, to draw together physically separated components.

Adiabatic -- change in pressure or volume without loss or gain of heat.

Adipocyte -- fat cell.

Adipose -- fatty; pertaining to fat.

ADP -- adenosine diphosphate; has one energy-rich phosphate bond.

Adrenergic -- activated or energized by adrenalin (epinephrine).

Adsorption -- attachment of a substance to the surface of another material.

Aerobic -- needing oxygen to live or function.

Aerobots (aerobotics) -- aerial (flying) robots.

Afferent -- in relation to nerves or blood vessels, conducting toward structure or organ; carrying impulses toward a center, as when sensory nerves carry sensory information toward the brain or spinal cord.

Affinity (constant) -- the strength of the binding of a ligand to a receptor, or the reciprocal of the dissociation rate constant; a measure of the binding energy of a ligand in a receptor; the greater the affinity, the more securely the receptor binds the ligand.

AFM -- see Atomic Force Microscope.

Aft -- toward the rear.

Agglutinin -- an antibody present in the blood that attaches to antigens, such as those found on the surfaces of red blood cells, causing them to clump together; agglutinins cause transfusion reactions when blood from a different group is given.

Agonist -- in pharmacology, a drug which binds to a receptor and thus stimulates the receptor's function, possibly mimicking the body's own regulatory function. Compare antagonist.

Albumin -- one of a group of simple proteins widely distributed in plant and animal tissues.

ALC -- airborne lethal concentration.

Algorithm -- in general, a formula or set of rules for solving a particular problem; in medicine, a set of steps used in diagnosing and treating a disease.

Alimentary -- pertaining to the digestive tract.

Alimentography -- a physical description (and mapping) of the human alimentary canal.

Aliquot -- a portion obtained by dividing the whole into equal parts without a remainder; loosely, any one of two or more samples of something, of the same volume or weight.

Alkali -- strongly basic substance, especially the metal hydroxides, usually associated with the alkali metals (e.g. sodium and potassium).

Allele -- one of several alternative forms of a gene occupying a given locus on paired chromosomes.

Alloantigen -- a substance present in certain individuals that stimulates antibody production in other members of the same species, but not in the original donor. See also antiserum.

Allometric scaling laws -- in biology, scaling laws that involve a biological variable that is an exponential function of the mass of the organism.

Allosteric control -- the ability of an interaction at one site of a protein to influence the activity of another site.

Allotropic -- pertains to the existence of a chemical element or compound in two or more distinct forms with different physical and chemical properties (e.g. diamond and graphite are allotropes of C).

Alphanumeric -- able to contain both alphabetic and numeric characters.

Alveolus (alveolar) -- in anatomy, a small cell or cavity; a saclike dilation. Most commonly, a small air sac found at the lowest levels of the branching tube system comprising the lungs.

AM -- amplitude modulation.

Amide -- a molecule containing an amine bonded to a carboxyl group (e.g. CONH₂). Amide bonds link amino acids in peptides and proteins.

Amine -- a molecule containing N with a single bond to C and two other single bonds to H or C (but not an amide); the amine group or moiety (e.g. -NH₂).

Amino acid -- a molecule containing both an amine and a carboxylic acid group; there are 20 genetically encoded amino acids in biology.

Amniotic -- pertaining to the amnion (the innermost of the fetal membranes).

Amphipathic -- molecular structures which have two surfaces or ends, one of which is hydrophilic and the other of which is hydrophobic. Lipids are amphipathic, and some protein regions may form amphipathic helices with one charged face and one neutral face.

Anabolism -- the constructive phase of metabolism and the opposite of catabolism; in anabolism, a cell takes from the blood the substances required for repair and growth, building them into a cytoplasm, thus converting nonliving material into the living cytoplasm of the cell.

Anaerobic -- able to live or function without oxygen.

Analgesia -- absence of normal sense of pain.

Analog -- pertaining to data measurable and representable through continuously variable physical quantities. Compare digital.

Anaphase -- the phase of mitosis (cell division) beginning with centromere division and the movement of chromosomes away from the metaphase plate toward opposite spindle poles.

Anaphylactoid-type reaction -- a physiological response similar to anaphylaxis.

Anaphylaxis -- the immediate transient kind of immunologic (allergic) reaction characterized by contraction of smooth muscle and dilation of capillaries due to release of pharmacologically active substances (e.g. histamine, bradykinin, serotonin, etc.); a powerful allergic response. Anaphylaxis is classically initiated by the combination of antigen (allergen) with mast cell-fixed, cytophilic antibody (chiefly IgE immunoglobulin), but can also be initiated by relatively large quantities of serum aggregates (antibody-antigen complexes, and other) that seemingly activate complement leading to production of anaphylatoxin.

Anastomose -- to open one structure into another directly or by connecting channels, usually said of blood vessels, lymphatics, and hollow viscera; to unite by means of an anastomosis, or a connection between formerly separate structures.

AND gate -- a logical gate that returns a high (1) output if and only if both input signals are high (1). See bit.

Anergic -- unresponsive.

Aneutronic -- without neutrons.

Angioedema -- a condition characterized by development of urticaria (hives) and edematous (swollen with excessive fluid) areas of skin, mucous membranes, or viscera.

Angiogenesis -- growth of new blood vessels, especially capillaries.

Anion -- a negatively charged ion.

Anisotropic -- not isotropic.

Anode -- the positive pole of an electrical source.

ANS -- see autonomic nervous system.

Antagonist -- in pharmacology, a drug that prevents receptor function. Compare agonist.

Anterior -- the front of the human body, on or nearest the abdominal surface; the front of something.

Anteroinferior -- in front and below.

Anteroposterior -- passing from front to rear.

Anthropogenic -- caused by human activity.

Antibody -- a protein (immunoglobulin) produced by B-lymphocyte cells that recognizes a particular foreign antigen, thus triggering the immune response.

Antigen -- any molecule or foreign substance that, when introduced into the body, provokes synthesis of an antibody, thus stimulating an immune response.

Antiserum -- serum that contains demonstrable antibody or antibodies specific for one (monovalent) or more (polyvalent) antigens.

Aorta -- the largest artery in the human body, leading away from the heart.

Apheresis -- removal of blood from an individual patient, separating certain elements (e.g. red cells, platelets, white cells) for use elsewhere, and reintroducing the remaining components into the patients; also known as cytapheresis, hemapheresis, leukapheresis, pheresis, and plasmapheresis, depending on the type of cells being harvested.

Apical -- pertaining to the apex (e.g. the point of a cone) of a structure.

Apoptosis -- an orderly disintegration of eukaryotic cells into membrane-bound particles that may then be phagocytosed by other cells.

Aqueous humor -- transparent liquid contained in the anterior chamber of the eyeball in front of the lens.

Aromatic compounds -- in chemistry, ring or cyclic compounds related to benzene, many having a fragrant odor.

Arrhythmia -- irregularity or loss of rhythm, especially of the heartbeat.

Arteriovenous -- relating to both arteries and veins.

Artery -- in anatomy, a blood vessel that sends blood to the tissues from the heart.

Aseptic -- characterized by the absence of living pathogenic organisms; a state of sterility.

Asperities -- protruding elements of roughness on a surface, e.g., burrs or spurs.

Asphyxia -- condition of hypoxia caused by insufficient oxygen intake.

Assembler -- see molecular assembler.

Asymptotic -- in geometry and mathematics, a curve that approaches closer and closer, but never quite reaches, another curve or line.

Asynchronous --not synchronized in time.

atm -- atmosphere, a unit of pressure; mean air pressure at Earth's surface is 1 atmosphere (~1.01 x 10⁵ N/m²).

Atomic Force Microscope (AFM) -- an instrument that uses atomic forces between a sample and a sharp scanning needle tip to image surfaces to molecular accuracy by mechanically probing their surface contours; the AFM measures the tiny upward and downward motions of the tip as the tip is dragged over the surface, producing an atomic-resolution topographic map of the surface. The AFM has also been used to physically manipulate individual molecules.

Atom laser -- a laserlike device that uses beams of coherent atoms rather than photons.

ATP -- adenosine triphosphate; has two energy-rich phosphate bonds.

Auscultation -- the process of listening for sounds within the body, usually to the sounds of thoracic or abdominal viscera, in order to detect some abnormal condition, or to detect fetal heart sounds, or to diagnose vascular abnormalities such as arteriovenous fistulas.

Autogenous control -- in medical nanorobotics, the conscious control of in vivo nanorobotic systems by the human user or patient; in biochemistry, the action of a gene product that either inhibits (negative autogenous control) or activates (positive autogenous control) expression of the gene coding for it.

Autonomic (nervous system) -- the part of the nervous system that is concerned with the control of involuntary bodily functions.

Automated engineering -- Engineering design done by a computer system, with detailed designs generated from broad specifications with little or no human help, a specialized form of artificial intelligence.

Automated manufacturing -- molecular manufacturing that requires little human labor.

Autosomes -- all the chromosomes except the sex chromosomes; a diploid cell has two copies of each autosome.

Avascular -- having no blood vessels.

Avulsion -- a tearing away forcibly of a part or structure.

Axisymmetric -- symmetric relative to a geometric axis.

Axon -- the (usually long and straight) protoplasmic process of a neuron that conducts impulses away from the cell body. There is usually one to a neuron cell.

Axoplasm -- the cytoplasm (neuroplasm) of an axon that encloses the neurofibrils.

Bacterium -- a single-celled prokaryotic microorganism, typically ~1-10 micron (~1000 nm) in diameter or length.

Bacteriophages -- viruses that infect selected bacteria; often abbreviated as phages.

Barographics -- pressure mapping of the human body.

Baronatation -- in medical nanorobotics, locomotion through a frozen fluid by applying mechanical pressure along the path travelled to induce melting ahead, followed by regelation (refreezing) behind.

Basal lamina -- basement lamina, e.g. basement membrane.

Basal Metabolic Rate (BMR) -- a measure of the metabolic rate taken with the patient fasting and at rest. The oxygen consumed in breathing under these conditions indicates the minimum rate of chemical reactions in the body.

Basement membrane (basement lamina) -- a thin layer of delicate noncellular material of a fine filamentous texture underlying the epithelium; its principal component is collagen.

Base pair (bp) -- a complementary purine-pyrimidine hydrogen-bonded residue pair, one from each strand of DNA double helix, designating one unit (bp) of sequence. A partnership of adenine (A) with thymine (T) or of cytosine (C) with guanine (G) in a DNA double helix; other pairs can be formed in RNA under certain circumstances.

Basophil -- a type of granulocytic white blood cell comprising less than 1% of all leukocytes, that is essential to the nonspecific immune response to inflammation because of its important role in releasing histamine and other chemicals that act on blood vessels.

Bearing -- A mechanical device that permits the motion of a component (ideally, with minimal resistance) in one or more degrees of freedom while resisting motion (ideally, with a stiff restoring force) in all other degrees of freedom.

Beriberi -- a thiamine deficiency disease, characterized by peripheral neurologic, cerebral, and cardiovascular abnormalities; early deficiency produces fatigue, irritation, poor memory, sleep disturbances, precordial pain, anorexia, abdominal discomfort, and constipation.

Biaxial -- pertaining to two distinct geometric or spatial axes.

Bicuspid -- having two cusps.

Bifurcate -- to separate into two separate branches.

Billion -- this book follows the American convention in which a billion is 10⁹.

Bilobate -- having two lobes.

Bimorph -- a simple mechanical actuator capable of flexing in a single plane.

Binding -- the process by which a molecule (or ligand) becomes bound, that is, confined in position (and often orientation) with respect to a receptor. Confinement occurs because structural features of the receptor create a potential well for the ligand; van der Waals and electrostatic interactions commonly contribute.

Binding energy -- in chemistry, the reduction in the free energy of a system that occurs when a ligand binds to a receptor. In nuclear physics, the energy which binds neutrons and protons together in an atomic nucleus, which may be calculated from the decrease in mass that would occur if the appropriate numbers of neutrons and protons were brought together to form the nucleus in question; Fe⁵⁶ has the maximum binding energy of any nucleus. Generally used to describe the total energy required to remove something, or to take a system apart into its constituent particles.

Binding site -- the active region of a receptor; any site at which a chemical species of interest tends to bind.

Biocompatibility -- the ability of the body to tolerate the presence or implantation of foreign objects.

Bioinformatics -- most generally, the study and compilation of the information content of biological materials, especially genetic materials.

Biomimetic -- mimicking biology.

Biosensor -- A device that senses and analyzes biological information (e.g. temperature, pressure, chemical content, etc.), commonly using a biological recognition mechanism combined with a physical transduction technique.

Biotechnology -- The application of biological systems and organisms to technical and industrial processes, with production carried out using intact organisms (e.g. yeasts and bacteria) or natural substances from organisms (e.g. enzymes), or by modifying the genetic structure of organisms (genetic engineering); most generally, the engineering of all biological systems, even completely artificial organic living systems, using biological instrumentalities.

Birefringence -- in optics, a crystal having a different index of refraction for different polarizations of incident light (e.g. calcite).

Bit -- a binary digit. In a binary code, one of the two possible characters, usually 0 (e.g. low voltage) and 1 (e.g. high voltage); in information theory, the fundamental unit of information.

Blackbody radiator -- an absorber which ideally absorbs all electromagnetic energy incident upon it; such an ideal absorber is also an ideal emitter of such radiant energy.

Blepharitis -- inflammation of the edges of the eyelids involving hair follicles and glands that open onto the surface.

Blockade -- prevention of the action of something, such as the effect of a drug or of a body function (e.g. halting immune system blood cleansing, by overloading the RES).

B-lymphocytes (B-cells) -- thymus-independent white blood cells responsible for synthesizing antibodies.

Boolean functions -- see logic gate.

Bose-Einstein condensate -- low-temperature collection of bosons (particles with integral spin, e.g. deuterium nuclei and alpha particles) in their ground state.

Bottom-up -- an approach to nanotechnology that aims to construct nanodevices molecule by molecule, making larger and larger objects with atomic precision.

Boutons terminaux -- bulblike expansions at the tips of axons that come into synaptic contact with the cell bodies of other neurons.

bp -- see base pair.

Brachiation -- locomotion by alternately swinging the arms (e.g. swinging hand-over-hand).

Bradycardia -- slowness of heartbeat or heart action.

Bronchial -- pertaining to the lungs.

Bronchiography -- a physical description (and mapping) of the human bronchial system.

Brownian assembly -- Brownian motion in a fluid brings molecules together in various positions and orientations; if molecules have suitable complementary surfaces, they can bind, assembling to form a specific structure. The term also may apply to the self-assembly of nanoscale parts having complementary surfaces.

Brownian motion -- random motion of small particles in a fluid owing to thermal agitation, first observed in 1827 by Robert Brown; originally attributed to a vital force, Brownian motion plays a vital role in the assembly and activity of the molecular structures of life.

Bruit -- an adventitious (arising sporadically) sound of venous or arterial origin, heard upon auscultation, such as murmurs at the carotid (a major artery) bifurcation.

Bubonic plague -- the usual form of plague; primarily a disease of rodents that is transmitted to humans by fleas that have bitten infected animals.

Buccal -- pertaining to the cheeks (mouth).

Buckyballs -- ball-like molecules of fullerene carbon, C₆₀.

Bulimia -- excessive and insatiable appetite for food.

Bulk technology -- technology in which atoms and molecules are manipulated in bulk, rather than individually.

Bumpers -- in medical nanorobotics, expansible surfaces placed at interfaces between adjacent nanorobots to achieve a tight seal between nanodevices.

Byte -- a sequence of N adjacent bits operated on as a unit for the sake of convenience and frequently used as a measure of memory or information, with one byte corresponding to a single alphabetic character or some other symbol; N may equal 8, 16, 32, 64, or 128, in different 20th century computers.

c (velocity) -- the speed of light, in vacuo.

CAD -- Computer-Aided Design.

Caliber -- inside diameter of a tube or cylinder.

Calmodulin -- a 17,000-dalton protein that binds calcium ions in eukaryotic cells, thereby becoming the agent for many or most of the cellular effects ascribed to calcium ions.

CAM -- Computer-Aided Manufacturing.

Cam -- in mechanical engineering, a mechanical component that translates or rotates to move a contoured surface past a follower; the contours impose a sequence of motions (potentially complex) on the follower. See follower.

cAMP -- cyclic AMP (adenosine monophosphate), an intracellular messenger molecule.

Capillary -- in anatomy, a thin-walled tiny blood vessel, averaging 8 microns in diameter.

Capsid -- the external protein coat of a virus particle.

Carbohydrates -- a group of chemical substances, including sugars, glycogen, starches, dextrins, and celluloses, that contain only C, H, and O; usually the ratio of H:O is 2:1. Glucose and its polymers (including starch and cellulose) represent the most abundant organic chemical compounds on Earth.

Carbonyl -- a chemical moiety consisting of O with a double bond to C (e.g. -CO-). If the C is bonded to N, the resulting structure is termed an "amide"; if it is bonded to O, it is termed a carboxylic acid or an ester linkage.

Carboxylic acid -- a molecule that includes a C having a double bond to O and a single bond to OH (e.g. -COOH).

Carbyne -- a chain of carbon atoms with alternating single and triple bonds.

Cardiac -- pertaining to the heart.

Cardiostasis -- pertaining to a heart that has stopped beating.

Carnot efficiency -- in thermodynamics, the energy efficiency of a heat engine (a device that converts thermal energy into mechanical energy).

Cartilage -- specialized type of dense connective tissue consisting of cells embedded in a firm, compact fibrous collagenous matrix.

Cartotaxis -- in medical nanorobotics, in vivo nanorobotic navigation by following a series of landmarks recorded on a previously drawn map.

Catabolism -- the destructive phase of metabolism, the opposite of anabolism. Catabolism includes all processes in which complex substances are converted into simpler substances (the end products commonly being excreted), usually with the release of energy.

Catalysis -- increase in the speed of a chemical reaction or process produced by the presence of a catalyst (a substance that is not consumed in the net chemical reaction or process).

Catalyst -- a chemical species or other structure that facilitates a chemical reaction without itself undergoing a permanent change.

Catacholamines -- biologically active amines (e.g. epinephrine, norepinephrine) derived from the amino acid tyrosine, that have marked effects on the nervous and cardiovascular systems, on metabolic rate and temperature, and on smooth muscle.

Cathode -- the negative pole of an electrical source.

Cation -- a positively charged ion.

Caudal (caudad, inferior) -- away from the head or the lower part of a structure (literally means "toward the tail").

Cauterize -- to apply a cautery (an agent or device used for scarring, burring, or cutting the skin or tissues by means of heat, electric current, or caustic chemicals).

Cavitation -- in physics, the formation of bubbles in a fluid during high-power sonication of that fluid; in medicine, formation of a cavity by either normal or pathological biological processes.

Cell -- a small biological structural unit, surrounded by a plasma membrane, making up living things.

Cell engineering -- deliberate artificial modifications to biological cellular systems on a cell-by-cell basis.

Cell surgery -- in medical nanorobotics, modifying cellular structures using medical nanomachines.

Cell typing -- a method of identifying a cell's type by comparing it to a typology of cell characteristics.

Cellular immunity -- immunity resulting from activation of sensitized T-lymphocytes.

Cellular topographics -- description of the cell and its parts.

Central Processing Unit (CPU) -- the main computational engine of a computer, responsible for interpreting and executing instructions to process information.

Centrioles -- small hollow cylinders consisting of microtubules, residing within the centrosomes, that become located near the poles during mitosis (cell division).

Centromere -- a constricted region of a chromosome that divides the chromosome into two arms; the attachment point for the spindle fiber concerned with chromosome movement during mitosis (cell division).

Centrosomes -- the regions from which microtubules are organized at the poles of a mitotic (dividing) cell; see also MTOC.

Centrum -- middle part.

Cephalic (cephalad, superior) -- nearest or toward the head or the upper part of a structure; also, pertaining to the head or top.

Cervical -- usually pertaining to, or in the region of, the neck (i.e. below the skull); more generally, pertaining to the neck of an organ, such as the uterine cervix.

C fiber -- an unmyelinated nerve fiber, 0.4-1.2 microns in diameter, conducting nerve impulses at 0.7-2.3 m/sec.

Chalcogenide -- a glassy material containing arsenic and selenium.

Chaperone -- a molecular chaperone is a protein needed for the assembly or proper folding of some other target protein, but which is not itself a component of the target protein complex.

Chemical force microscopy -- an AFM with a functionalized tip, used to probe the chemical characteristics (especially adhesiveness) of surface-bound molecules.

Chemoelectric conversion -- conversion of chemical energy into electrical energy.

Chemoergic -- pertaining to the conversion of chemical energy into forms of energy of various other kinds.

Chemographics -- chemical mapping of the human body.

Chemomechanical conversion -- conversion of chemical energy into mechanical energy.

Chemotactic -- pertaining to chemotaxis.

Chemotactic nanosensor -- in medical nanorobotics, a nanosensor used to determine the chemical characteristics of surfaces, possibly configured as a pad coated with an array of reversible, perhaps reconfigurable, artificial molecular receptors.

Chemotaxis -- the movement of additional white blood cells to an area of inflammation in response to the release of chemical mediators by neutrophils, monocytes, or injured tissue.

Chiral -- a chiral molecule is an asymmetric molecule that cannot be superimposed on its mirror image. The molecule has two forms, or isomers, called enantiomorphs, that are mirror images of each other, the solutions of which rotate the plane of polarized light in different directions, left (levo) or right (dextro), making the enantiomers levorotatory or dextrorotatory. Only levorotatory amino acids are present in biological systems.

Chirurgeon -- surgeon (obsolete).

Cholinergic -- activated or energized by acetylcholine.

CHON -- Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

Choroideremia -- congenital absence of the choroid of the eye; progressive degeneration of the choroid, leading to complete blindness, due to X-linked chromosome inheritance.

Chromatin -- the complex of DNA and protein in the nucleus of the interphase eukaryotic cell; individual chromosomes cannot be distinguished in it.

Chromomorphic -- in medical nanorobotics, a nanorobot capable of altering its external surface color or other external surface optical characteristics.

Chromophore -- a color-producing chemical substance.

Chromosome -- a discrete unit of the genome carrying many genes; a structure in the nucleus of a eukaryotic cell containing a long linear molecule of duplex DNA (and an approximately equal mass of proteins) which conveys genetic information.

Chronobiology -- that aspect of biology concerned with the timing of biological events, especially repetitive or cyclic phenomena in individual organisms; the study of biological clocks.

Chronocyte -- in medical nanorobotics, a theorized mobile, mass-storage (nanorobotic) device, similar to a communicyte, that may be used as a mobile source of precisely synchronized universal time inside the human body.

Chronometer -- a clock or other timekeeping device.

Cilium -- in anatomy, hairlike processes projecting from epithelial cells, as in the bronchi, for propelling mucus, pus, and dust particles, or in the inner ear, for sensing fluid motion to allow hearing; in microbiology, a means of manipulation and propulsion for motile microorganisms.

Circadian -- pertaining to physiological events that occur at approximately 24-hour intervals.

Circumcorporeal -- around or surrounding the human body.

Circumvascular -- around or surrounding a blood vessel.

Cisterna -- a reservoir or cavity.

Clinical -- founded on actual observation and treatment of patients, as distinguished from data or facts obtained by experimentation or pathology; pertaining to a clinic.

Clinicopathological correlation -- correlating (1) the signs and symptoms manifested by a patient, plus the results of any laboratory studies, with (2) the findings of the gross and histological examination of the patient's tissue, to arrive at a correct diagnosis.

Clyster -- an enema (obsolete).

Cochlea -- the coiled, fluid-filled structure of the inner ear that transduces sound, allowing hearing.

Codon -- in DNA and RNA, a sequence of three nucleotidyl residues designating an amino acid to be placed in polypeptide sequence during translation.

Coenzyme -- a substance that enhances or is necessary for the action of enzymes; coenzymes are of smaller molecular size than the enzymes themselves, are dialyzable and relatively heat-stable, and are usually easily dissociable from the protein portion of the enzyme. See also vitamins.

Collagen -- the major protein of the white fibers of connective tissue, cartilage, and bone, rich in glycine, alanine, proline, and hydroxyproline (amino acids), low in sulfur, and completely lacking in tryptophan (another amino acid); the collagen family comprises ~25% of all mammalian protein.

Colloid -- see macromolecule.

Comminution -- breaking into fragments.

Communicyte -- in medical nanorobotics, a theorized mobile, mass-storage (nanorobotic) device that can be used for information transport throughout the human body.

Complement -- a group of proteins in the blood that influences the inflammatory process and serves as the primary mediator in the antigen-antibody reactions of the B-cell mediated immune response. Components of complement are labeled C1-C9; C3 and C5 are most commonly involved in promoting vasodilation, chemotaxis, opsonization of antigens, lysis of cells, and blood clotting.

Complementary -- supplying something that is lacking in another object, system, or entity; (shapes) fitting together tightly without any gaps.

Compliance -- the reciprocal of stiffness; in a linear elastic system, displacement equals force times compliance.

Computerized Axial Tomography (CAT) -- see Computerized Tomography.

Computerized Tomography (CT) -- tomography in which transverse planes of tissue are swept by a pinpoint radiographic beam (e.g. X-rays) and a computerized analysis of the variance in absorption produces a precise reconstructed image of that area.

Conformation -- molecular folding; a molecular geometry that differs from other geometries chiefly by rotation about single or triple bonds; distinct conformations (termed conformers) are associated with distinct potential wells. Typical biomolecules and products of organic synthesis can interconvert among many conformations. Typical diamondoid structures are locked into a single potential well, and thus lack conformational flexibility.

Congeries -- a collection of things or parts in a single mass or aggregate.

Conjugated -- in chemistry, a conjugated pi system is one in which pi bonds alternate with single bonds; the resulting electron distribution gives the intervening single bonds partial double-bond character, the pi electrons become delocalized (useful in molecular wires), and the energy of the system is reduced. More generally, joined or paired.

Conjugation -- in medical nanorobotics, the docking of two or more nanorobots for the purpose of exchanging information, energy or materials, or to establish a larger multirobotic structure; in biology, the union of two unicellular organisms accompanied by an interchange of nuclear material, as in Paramecium.

Conjunctiva -- a mucous membrane that lines the eyelid and is reflected onto the eyeball.

Conserved -- in genomics, a portion of genetic code that remains almost unchanged among many different species.

Convection -- conveyance of heat in liquids or gases by movement or currents of the heated fluids.

Coordinated Universal Time (UTC) -- in observational astronomy and chronometry, the local time at the meridian of Greenwich near London, England; a precision time stamp that is broadcast continuously by radio (e.g. NIST's station WWV).³³⁰²

Corium -- the layer of the skin lying immediately under the epidermis.

Corneal -- pertaining to the cornea (the clear, transparent anterior portion of the fibrous coat of the eye comprising about one-sixth of its surface).

Coronal -- vertical, but at right angles to sagittal sections, dividing the body into anterior (front) and posterior (back) portions.

Cortex (cortical) -- the outer layer of an organ or of the body. Compare medulla.

Covalent bond -- in chemistry, a bond formed by sharing a pair of electrons between two atoms.

CPU -- see Central Processing Unit.

Cranial -- nearest or toward the head.

Crepitation -- a crackling sound heard in certain diseases, such as the rale heard in pneumonia; a grating sound heard on movement of ends of a broken bone; a clicking or crackling sound often heard in movements of joints, such as the temporomandibular (jaw), elbow, or patellofemoral (knee) joints, due to roughness and irregularities in the articulating surfaces.

Crinal -- pertaining to hair.

Crista -- in cell biology, a projection, sometimes branched, of the inner wall of a mitochondrion into its fluid-filled cavity; in anatomy, a ridge of sensory cells inside the ampulla, thrusting hair endings into the cupula (the cells respond to rotary acceleration and deceleration of the head).

Critical pressure -- the highest pressure at which gas and liquid may exist as separate phases at any temperature.

Critical temperature -- the highest temperature at which gas and liquid may exist as separate phases at any pressure.

Cross-links -- in biochemistry, additional bonds formed between normally separate parts of a polymer, typically increasing the tensile strength and stiffness of the chain.

Cryobiology -- the study of the effects of cold on biological systems.

Cryogenic -- producing, of pertaining to, low temperatures, typically the temperature of liquid nitrogen (77 K) or below.

Cryonic suspension -- a currently non-standard medical technique that attempts to prevent the permanent cessation of life, usually by promptly immersing the body of a post-pronouncement patient in a storage fluid maintained at cryogenic temperatures. A person who is cryonically suspended cannot be revived by 20th century medical technology because the freezing process does too much damage, but once frozen the patient's biological condition does not further deteriorate. The procedure is attempted in the belief that future medical technology may allow reversal of tissue damage and the successful revival of the patient.

Crystallescence -- in medical nanorobotics, the crystallization of solid solute that is offloaded by nanorobot sorting rotors at a concentration that exceeds the solvation capacity of the surrounding solvent.

Cutaneous -- pertaining to the skin.

Cyclic -- a structure is termed cyclic if its covalent bonds form one or more rings.

Cycloaddition -- a chemical synthesis reaction in which two unsaturated molecules (or moieties within a molecule) bond to form a ring.

Cystic -- (usually) pertaining to the gallbladder or urinary bladder.

Cytapheresis -- see apheresis.

Cytoambulation -- in medical nanorobotics, cell surface walking.

Cytocarriage -- in medical nanorobotics, the commandeering of a natural motile cell, by a medical nanorobot, for the purposes of in vivo transport (of the nanorobot), or to perform a herding function (of the affected cell), or for other purposes.

Cytocide -- the killing of living cells.

Cytography -- a physical description (and mapping) of the living cell.

Cytoidentification -- identification of cell type.

Cytokine -- a group of extracellular biochemical substances that may be produced by a variety of cells, for the purposes of chemical messaging, regulation, and control; proteins that exert changes in the function or activity of a cell, such as differentiation, proliferation, secretion, or motility.

Cytology (cytological) -- the study of biological cells.

Cytometrics -- the quantitative measurement of cell sizes, shapes, structures, and numbers.

Cytonatation -- in medical nanorobotics, swimming around inside a living cell.

Cytonavigation -- in medical nanorobotics, navigation inside the cell; cellular navigation.

Cytopenetration -- in medical nanorobotics, entry into cells by penetrating the plasma membrane.

Cytoplasm -- the filling substance between the plasma membrane and the nucleus of a cell.

Cytoskeletolysis -- in medical nanorobotics, purposeful destruction of the cellular cytoskeleton by a nanorobot, for cytocidal purposes.

Cytoskeleton -- the internal structural framework of a cell consisting of at least three types of filaments (microfilaments, microtubules, and intermediate filaments), forming a dynamic framework for maintaining cell shape and motion and allowing rapid changes in the three-dimensional structure of the cell.

Cytosol -- the liquid that fills all of the cytoplasmic region, except for fluids filling the interior of the cell organelles.

Cytotomography -- tomographic imaging of an individual cell.

Cytotoxic -- tending to kill cells.

Cytovehicle -- in medical nanorobotics, a living cell that has been commandeered by a medical nanorobot for use during cytocarriage.

Dalton -- unit of molecular weight (1 dalton ~ 1 proton).

DC -- direct current.

Decoction -- liquor extract, from vegetable matter boiled in water.

Deglutition -- swallowing.

Degrees of Freedom (DOF) -- distinct axes of allowed mechanical motion; the number of directions that a mechanism is free to translate or rotate.

Demarcation -- in medical nanorobotics, a crude form of functional navigation in which artificial conditions detectable by in vivo medical nanorobots are created at or near the target treatment site, such as warm or cold spots, pressure spots, or injected chemical plumes.

Denaturation -- conversion of a protein from the physiological conformation to some other (possibly inactive) conformation.

Dendrimers -- large, regularly-branching molecules.

Dendrite -- a branched protoplasmic process of a neuron that conducts impulses toward the cell body. There are usually many to a cell, forming synaptic connections with other neurons.

De novo -- created anew.

Deoxyribonucleic acid (DNA) -- a complex molecule of very high molecular weight encoding genetic information. DNA consists of deoxyribose (a sugar), phosphoric acid, and four bases (purines or pyrimidines), arranged as two long chains that twist around each other to form a double helix joined by bonds between the complementary purine and pyrimidine components (analogous to rungs on a twisted ladder). DNA is present in the chromosomes of all cells and is the chemical basis of heredity and the carrier of genetic information for almost all organisms (e.g. except the RNA virus, etc.).

Dermatoglyphics -- the study of dermal ridge patterns of fingers, toes, palms and soles.

Dermis -- inner layer of the skin that lies below the epidermis.

Desiccate -- removal of water; dehydration.

Desquamation -- shedding epidermis in scales or shreds.

Diagnosis -- the determination of the cause and nature of a disease, in order to provide a logical basis for treatment and prognosis.

Dialysis -- the passage of a solute through a membrane; process of diffusing blood across a semipermeable membrane to remove toxic materials and to maintain fluid, electrolyte, and acid-base balance in cases of impaired kidney function.

Diametral -- pertaining to a diameter.

Diamondoid -- structures that resemble diamond in a broad sense; strong, stiff structures containing dense, three-dimensional networks of covalent bonds, formed chiefly from first and second row atoms with a valence of three or more. Many of the most useful diamondoid structures will be rich in tetrahedrally coordinated carbon.

Diamondophagy -- eating diamond.

Diapedesis -- transendothelial migration (passing through blood vessel endothelial coated walls) to exit the bloodstream and enter the surrounding tissues.

Diaphragm -- in human anatomy, the musculomembranous partition between the abdominal and thoracic cavities, whose motions induce lung movements, enabling respiration.

Diaphysis -- the shaft or middle part of a long cylindrical bone.

Diastereomeric -- having two stereoisomers.

Diastole -- the normal period in the heart cycle during which the muscle fibers loosen and lengthen, the heart dilates, and the cavities fill with blood; roughly, the period of relaxation alternating with systole or contraction.

Diathermy -- local elevation of temperature within the tissues, produced by high-frequency (~MHz) current, ultrasonic waves, or microwave radiation.

Dielectric -- a material capable of storing electrical energy; the interior of a capacitor.

Diels-Alder cycloaddition -- in chemical synthesis, the cycloaddition of a conjugated diolefin (an olefin or alkene is a hydrocarbon possessing one or more double bonds in the carbon chain). Diels-Alder reactions are highly stereospecific.

Differentiation -- acquisition of character or functions that are different from those of the original type; specialization of cell type within a cell line of increasingly specialized types, by a change in physical form of a cell.

Diffusion -- a process by which populations of molecules intermingle and become mixed as a result of their incessant thermal motions.

Digital -- pertaining to the use of combinations of bits to represent all quantities that arise during a problem or computation. Compare analog.

Dimer -- in chemistry, a combination of two similar or identical molecules, usually by elimination of H₂O or a similar small molecule between the two, or by simple noncovalent association.

Diode -- an electronic device that allows current to flow in only one direction.

Diploe -- in anatomy, spongy tissue that lies between two layers of the compact bone of the skull.

Diploid -- a set of chromosomes that contains two copies of each autosome plus two sex chromosomes; generally found in the somatic body cells.

Dipole -- two equal and opposite charges separated by a distance. See also electric dipole moment.

Disassembler -- in molecular nanotechnology, a nanomachine or system of nanomachines able to take an object apart while at each step recording the structure and composition of that object at the molecular level.

Disassimilation -- in biology, changing assimilated material into less complex compounds for the production of energy.

Disease -- see volitional normative model of disease.

Disequilibration -- in medical nanorobotics, maintenance or inducement of a state of perpetual ionic, chemical, or energetic disequilibrium in a living cell by a medical nanorobot, usually for the purpose of inducing cytocide.

Dispersion force (London dispersion force) -- see van der Waals forces.

Dissociation -- in chemistry, the separation of a molecular complex into simpler molecules due to lytic reaction, heat, or ionization.

Dissociation constant -- For systems in which ligands of a particular kind bind to a receptor in a solvent, there will be a characteristic frequency with which existing ligand-receptor complexes dissociate as a result of thermal excitation, and a characteristic frequency with which empty receptors bind ligands as a result of Brownian encounters, forming new complexes. The frequency of binding is proportional to the concentration of the ligand in solution. The dissociation constant is the magnitude of the ligand concentration at which the probability that the receptor will be found occupied is 0.5.

Distal -- away from a source or a point of attachment or origin; in the extremities, farthest from the trunk.

Diurnal -- daily.

DNA -- see deoxyribonucleic acid.

DNAase -- an enzyme that attacks bonds in DNA.

DNA polymerase -- an enzyme that synthesizes a daughter strand of DNA under direction from a DNA template; may be involved in repair or replication.

DOF -- see Degrees of Freedom.

Domain -- in protein chemistry, a discrete continuous part of the amino acid sequence that can be equated with a particular function; proteins such as immunoglobulins may possess several active domains.

Dorsal -- the backside of the human body, nearest the spine; the backside of something.

Ductility -- see plasticity.

Duodenum -- the first ~12 inches of the small intestine.

Dysopsonic -- tending to remove opsonization molecules that have become adhered to an exposed in vivo surface.

ECG (EKG) -- electrocardiogram.

ECM -- see extracellular matrix.

Edema -- swollen with excessive fluid.

EEG -- electroencephalogram.

Efferent -- in relation to nerves or blood vessels, conducting away from a structure or organ; carrying impulses away from a center, as when motor nerves carry impulses from the brain and spinal cord to an effector (e.g. a muscle).

Effervescence -- in medical nanorobotics, bubble formation by a gaseous solute that is offloaded by nanorobot sorting rotors at a concentration that exceeds the solvation capacity of the surrounding solvent.

Eigenmode -- in linear matrix algebra, a nonzero solution of the characteristic equation of a vector or tensor system.

Elasticity -- a property of an object or material, wherein the object or material returns to its original shape after a force is applied and then removed.

Electret -- a material that retains a permanent charge.

Electric dipole moment -- a measure of the strength of an electric dipole (in units of coulomb-meters). See also dipole.

Electrodynamics -- in physics, the study of the motions of charged particles.

Electrolyte -- a substance that, in solution, conducts an electric current and is decomposed by the passage of an electric current; a solution that is a conductor of electricity.

Electrometer -- an instrument for detecting or measuring differences of electrical potential (e.g. volts) by the effects of electrostatic forces.

Electron Beam Lithography (EBL) -- lithography using electron beams rather than light beams.

Electronegativity -- a measure of the tendency of an atom (or moiety) to withdraw electrons from structures to which it is bonded. In most circumstances, sodium (Na) tends to donate electron density (low electronegativity) whereas fluorine (F) tends to withdraw electron density (high electronegativity); nitrogen (N) and oxygen (O) are also electronegative atoms.

Electrophoresis -- the movement of charged colloidal particles through the medium in which they are dispersed as a result of changes in electrical potential; used in the analysis of protein mixtures because protein particles move with different characteristic velocities dependent principally on the number of charges carried by each particle.

Electroporation -- insertion of macromolecules (e.g. DNA) into cells by employing a brief intense pulse of electricity to open cellular pores.

Electrostatic Force Microscope (EFM) -- a kind of SPM that images electrostatic forces.

Electrostatic force -- a force arising between charged bodies produced by electrostatic fields.

Embolus -- a mass of undissolved matter (solid, liquid, or gaseous) present in a blood or lymphatic vessel, brought there by the blood or lymph current.

Emesis -- vomiting; may be chemically induced using an emetic.

emf -- in physics, "electromotive force" (typically, the electrical potential established across the terminals of a battery), measured in volts.

Emissivity -- relative intensity of emission of electromagnetic radiation by a heated body, as compared to a blackbody radiator whose emissivity is defined as 1.

EMP -- electromagnetic pulse (e.g. as typically generated during a nuclear explosion).

Enantiomer -- in chemistry, a special class of stereoisomers whose structure is not superimposable on its mirror image; a chiral molecule. Two enantiomers of a compound have identical chemical properties, but differ in a characteristic physical property, the ability to rotate the plane of plane-polarized light.

Endocrine gland -- a gland that secretes biochemical substances (especially hormones) directly into the bloodstream.

Endocytosis -- a process by which proteins arriving at the surface of a cell are internalized, being transported inside the cell within membranous vesicles.

Endoergic -- a transformation that absorbs energy; such a reaction increases molecular potential energy. Opposite of exoergic.

Endogenous -- originating inside an organ, part, or system.

Endohedral -- lying entirely within a (fullerene) cage molecule.

Endometrial -- pertaining to the lining of the uterus.

Endoplasmic reticulum -- in cell biology, a highly convoluted sheet of membranes, extending from the outer layer of the nuclear envelope into the cytoplasm.

Endosome -- the vacuole formed when material is absorbed into a cell by the process of endocytosis; the vacuole fuses with lysosomes.

Endothelium -- a form of squamous epithelium consisting of flat cells that line the blood and lymphatic vessels, the heart, and various other body cavities.

Endothermic -- a transformation that absorbs energy in the form of heat. A typical endothermic reaction increases both entropy and molecular potential energy, and thus is analogous to a gas expanding while absorbing heat and compressing a spring. Opposite of exothermic.

Energy -- in physics, a conserved quantity that can be interconverted among many forms, including kinetic energy, potential energy, and electromagnetic energy.

Engulf formation -- in medical nanorobotics, a configuration that may be adopted by a metamorphic nanorobot, in which the nanorobot reshapes itself to create an interior cavity capable of trapping a living cell, virion, or other biological particle.

Enthalpy -- in thermodynamics, the internal energy of a system plus the product of its volume and the external pressure.

Entropy -- in the physical sciences, a measure of uncertainty regarding the state of a system; free energy can be extracted by converting a low-entropy state to a high-entropy state. In other contexts, the term is often used by analogy to describe the extent of randomness and disorder in a system and the consequent lack of knowledge or information about it.

Enucleated cell -- a cell from which the nucleus has been removed.

Enzyme - a protein molecule that often acts as a specific catalyst, facilitating specific chemical or metabolic reactions necessary for cell growth and reproduction; a biological chemosynthetic molecular machine.

Eosinophil -- a type of granulocytic white blood cell comprising 1%-4% of all leukocytes, that is known to destroy parasitic organisms and to play a major role in allergic reactions (some of the major chemical mediators that cause bronchoconstriction in asthma are released by eosinophils).

Epidermis -- the outer epithelial portion of the skin.

Epitaxial methods -- a class of methods for inducing crystal growth.

Epithelium -- the avascular layer of cells forming the epidermis of the skin and the surface layer of mucous (secreting mucus) and serous (secreting serum or serumlike fluid) membranes, including the glands. The cells rest on a basement membrane and lie closely approximated to each other with little intercellular material between them.

Epitope -- any component of an antigen molecule that functions as an antigenic determinant by permitting the attachment of certain antibodies.

Equilibrium -- a system is said to be at equilibrium (with respect to some set of feasible transformations) if that system has minimal free energy. A system containing objects at different temperatures is in disequilibrium, because heat flow can reduce the free energy (causing the different temperatures to converge). Springs have equilibrium lengths, reactants and products in solution have equilibrium concentrations, thermally excited systems have equilibrium probabilities of occupying various states, and so forth.

Ergoacoustic -- pertaining to the conversion of energy of various kinds into acoustic energy.

Ergooptical (ergophotonic) -- pertaining to the conversion of energy of various kinds into optical (photonic) energy.

Eructations -- producing gas from the stomach, usually with a characteristic sound; belching.

Erysipelas -- acute febrile disease with localized inflammation, eruption and redness of skin and subcutaneous tissue, accompanied by systemic signs and symptoms, caused by a hemolytic streptococcus.

Erythrocyte -- red blood cell.

Erythropoietin -- a hormone that controls the production rate of red blood cells in the human body.

Euchromatin -- all of the genome in the interphase nucleus, except for the heterochromatin.

Eukaryote -- an organism or cell that contains its genome within a nucleus.

Eutactic -- characterized by precise molecular order.

Excimer laser -- a kind of high-energy ultraviolet (UV) laser based on excited state transitions.

Excision -- an act of cutting away or taking out.

Excluded volume -- the presence of one molecule or moiety reduces the physical volume available for other molecules or moieties to occupy, thus partially crowding them out.

Excoriation -- abrasion of the epidermis or of the coating of any organ of the body by trauma, chemicals, burns, or other causes.

Exfusion -- generally, to remove from the body; distinguished from infusion.

Exocrine -- external secretion of a gland.

Exocytosis -- the process of secreting proteins from a cell into the surrounding medium, by transport in membranous vesicles from the endoplasmic reticulum, through the Golgi, to storage vesicles, and finally (upon a regulatory signal) through the plasma membrane.

Exodermal -- lying outside of the skin surface.

Exoergic -- a transformation that releases energy; such a reaction decreases molecular potential energy. Opposite of endoergic.

Exogenous -- originating outside an organ, part, or system.

Exohedral -- lying entirely outside a (fullerene) cage molecule.

Exons -- portions of genes represented in mRNA.

Exothermic -- a transformation that releases energy in the form of heat. Exoergic reactions in solution are commonly exothermic. Opposite of endothermic.

Exploratory engineering -- design and analysis of systems that are theoretically possible but cannot be built yet, owing to the limitations of currently available tools.

Exponential -- refers to a mathematical function (e.g. y = 10^x) which has an exponented quantity as its independent variable (e.g. x); more informally, may denote a very steeply rising (or falling) quantity, function or variable.

Extracellular -- outside of the cell.

Extracellular matrix (ECM) -- an extracellular fibrous scaffolding that helps organize cells into tissues.

Extrasomatic -- originating or existing outside of the human body.

Extravasation -- exiting the bloodstream.

Exudate -- accumulation of a fluid in a cavity; matter that penetrates through vessel walls into adjoining tissue; the production of pus or serum.

Ex vivo -- outside of the living human body.

Facultative -- having the ability to do something which is not mandatory.

Fascia -- a fibrous membrane covering, supporting, and separating muscles; also, unites the skin with underlying (e.g. muscular) tissue.

Fatty acid -- a hydrocarbon in which one of the H atoms has been replaced by a carboxyl group.

Febrile -- pertaining to fever.

Fenestrated -- having openings.

Fibroblast -- a stellate or spindle-shaped motile cell with cytoplasmic processes present in connective tissue, capable of forming collagen fibers.

Fission (fissile) -- in physics, the release of energy when an atomic nucleus more massive than Fe⁵⁶ (see binding energy) is split into two or more less massive fragments; the fission of nuclei lighter than Fe⁵⁶ is typically endoergic. In microbiology, a method of asexual reproduction in bacteria, protozoa, and other lower forms of life; in cell biology, the partition of one organelle into two, as for example the fissioning mitochondrion.

Fistula -- in anatomy, an abnormal tubelike passage from a normal cavity or tube to a free surface or to another cavity; may be due to congenital incomplete closure of parts, or may result from abscesses, injuries, or inflammatory processes.

Flagellum -- in cell biology, a whiplike locomotory organelle consisting of nine double peripheral microtubules and two single central microtubules.

Flatus -- gas in the digestive tract; expelling of gas from a body orifice, especially the anus (e.g. to fart).

FLOP -- in computer science, a floating point operation, an individual computational step as software executes in a computer. A floating point number is a number expressed as a product of a bounded number and an exponential scale factor, as in scientific notation.

Fluidity -- in cellular biomechanics, a property of cell membranes, indicating the ability of lipids to move laterally within their particular monolayer.

Flux (fluence) -- generally, a rate of flow.

FM -- frequency modulation.

Follower -- in mechanical engineering, a mechanical component in a cam system that is driven through a pattern of displacements as it rests against a moving contoured surface. See cam.

Foramen magnum -- in anatomy, an opening in the occipital bone through which passes the spinal cord from the brain.

Formed elements -- the cellular components of the blood, usually including red cells, white cells, and platelets.

Fourier transform -- in mathematical physics, the expression of a complex waveform as a weighted sum of an infinite series of monofrequency waves.

Fovea -- the clearest point of vision in the retina of the eye.

Fractionation -- to separate components of a mixture into distinct molecular submixtures or pure components.

Free energy -- a measure of the ability of a system to do work, such that a reduction in free energy could in principle yield an equivalent quantity of work. The Helmholtz free energy describes the free energy within a system; the Gibbs free energy does not.

Fresnel lens -- a glass lens cast in a series of adjacent annular rings of various heights and shapes, commonly employed in lighthouses to produce powerful directed beams of light.

Friction Force Microscopy (FFM) -- a kind of SPM that measures the frictional force between a sample and a sharp tip.

FTP -- file transfer protocol (used for large-block data transfers on the Internet).

Fullerene -- a closed-cage molecule consisting of linked pentagons, hexagons, heptagons, or other polygonal elements; originally referred to carbon-only structures but has since been broadened to represent the entire class of molecules having this geometry, regardless of atomic constituency.

Functionalized -- in chemistry, an otherwise chemically inert structure is functionalized when a chemically active ligand or moiety is covalently bonded to it.

Functional navigation -- in medical nanorobotics, a form of nanorobotic navigation in which nanodevices seek to detect subtle variations in their environment, comparing sensor readings with target tissue/cell profiles and then congregating wherever a precisely defined set of preconditions exists.

Fundamental mode -- the lowest natural frequency of vibration of an object or system.

Fusion -- in physics, the release of energy when atomic particles of total atomic mass less than the atomic mass of Fe⁵⁶ (see binding energy) join together to form a more massive single particle; the fusion of nuclei heavier than Fe⁵⁶ is typically endoergic. In cell biology, fusion is the merging of vesicles budded from the ER into the Golgi complex, or of endosomes with lysosomes, or of the contents of two cells by artificial means without the destruction of either, resulting in a heterokaryon that, for at least a few generations, will reproduce its kind (this was once an important method in assigning loci to chromosomes). In sensory physiology, the sensation that results when two different sensory qualities merge to give a third quality, such as the fusion of red and yellow into orange. Most generally, to combine together.

g -- unit of gravitational acceleration (9.81 m/sec²); describes the mean gravitation force experienced by a mass at rest on Earth's surface.

Galvanic -- pertaining to electrical direct current, usually chemically generated.

Gamete -- either type of reproductive or germ cell (e.g. sperm or egg) with haploid chromosome content. Compare somatic cell.

Ganglion -- a mass of nervous tissue composed principally of nerve-cell bodies and lying outside the brain or spinal cord (e.g. the chains of ganglia that form the main sympathetic trunks, or the dorsal root ganglion of a spinal nerve).

Gangrene -- a necrosis (death) of tissue, usually due to deficient, obstructed, or lost blood supply; it may be localized to a small area or it may involve an entire organ or extremity.

Gastro -- pertaining to the stomach.

Gate -- see logic gate.

GDP -- guanosine diphosphate.

Gene -- a segment of a chromosome; an hereditary unit comprised of DNA occupying a locus in the genome which bears base sequential information for regulation, for transcription into RNA, or for transcription into mRNA destined for translation into protein.

Genome -- the total hereditary material of a cell, containing the entire chromosomal set found in each nucleus of a given species.

Genomics -- concerning the genome, the study of genes and how they affect the human body.

Genotype -- the basic combination of genes of an organism. The genetic constitution of an organism.

Geodesic -- pertaining to the mapping of the surface of the Earth.

Germ line -- the cell line from which gametes derive.

GHz -- gigahertz; billions of cycles per second.

Gibbs free energy -- equals the Helmholtz free energy plus the product of the system volume and the external pressure. Changes in the Gibbs free energy at a constant pressure thus include work done against external pressure as a system undergoes volumetric changes.

Gimbal -- in mechanical engineering, a device consisting of a pair of rings pivoted on axes at right angles to each other so that one is free to swing within the other.

Glioblastoma -- a neuroglial (brain) cell tumor.

Global Positioning System (GPS) -- a system of Earth-orbiting satellites that broadcasts navigational radio signals, allowing a ground receiver to precisely fix its position on the Earth's surface.

Glottis -- the sound-producing apparatus of the larynx, consisting of two vocal cords and the intervening space.

Glucose -- simple blood sugar (C₆H₁₂O₆).

Glycocalyx -- a thin layer of glycoprotein and polysaccharide that covers the surface of some cells, such as muscle cells, fibroblasts, pericytes, and epithelial cells, and contributes to the basal lamina.

Glycogen -- a polysaccharide commonly called animal starch, with chemical formula (C₆H₁₀O₅)_n; glycogen is the form in which carbohydrate is stored in the animal body (mostly in the liver and muscles) for future conversion into sugar. The formation of glycogen from carbohydrate sources is called glycogenesis, while the reverse process is called glycogenolysis.

Glycolysis -- enzyme-mediated energy-yielding anaerobic hydrolysis of glucose to lactic acid in various cells and tissues, notably muscle.

Glycoprotein -- a protein molecule with carbohydrate moieties attached.

Glycosylation -- the covalent bonding of carbohydrate moieties to another molecule.

Golgi complex/apparatus -- in cell biology, individual stacks of membranes near the endoplasmic reticulum involved in glycosylating proteins and sorting them for transport to different intracellular locations.

Gorget -- in surgery, an instrument grooved to protect soft tissues from injury as a pointed instrument is inserted into a body cavity.

G-proteins -- guanine nucleotide-binding trimeric proteins that reside in the plasma membrane. When bound by GDP, the trimer remains intact and is inert; when GDP is replaced by GTP, the trimer separates into a monomer and a dimer, one of which may then activate or repress a target protein.

GPS -- see Global Positioning System.

Gradient -- a slope or grade; an increase or decrease of varying degrees or the curve that represents such; rate of change of temperature, pressure, chemical concentration, or other physical variable, as a function of time, distance, frequency, etc.

Granules -- a small, grainlike body. Small granules may be found in cells, containing stores of nutrients; large granules may be formed in tissues following a granulomatous reaction.

Granulocyte -- a granular leukocyte; a polymorphonuclear (nucleus composed of two or more lobes or parts) leukocyte, including basophils, eosinophils, and neutrophils.

Granuloma -- a nodular inflammatory lesion, usually small or granular, that is firm, persistent, and contains compactly grouped mononuclear phagocytes.

Granulomatous reaction -- producing a granuloma, a granular tumor or growth, usually of lymphoid and epithelioid cells; an encapsulation reaction to the presence of a foreign object in the body that cannot be readily phagocytosed.

Gravimeter -- a device for measuring gravitational acceleration.

Ground state -- the lowest-energy state of a system. A system in its electronic ground state cannot further reduce its energy by an electronic transition, but may still contain vibrational energy.

GTP -- guanosine triphosphate.

Gustatory -- pertaining to the sense of taste.

Halogen -- pertaining to fluorine, chlorine, bromine, iodine, or astatine.

Haploid -- a set of chromosomes that contains one copy of each autosome and one sex chromosome.

Haploid number -- the number of chromosomes in sperm or ova (23 in humans), half the number found in somatic (e.g. diploid) cells; characteristic of the gametes of diploid organisms.

Haptic -- operated by, or pertaining to, the sense of touch.

Harmonic oscillator -- in physics, any system of particles that displays harmonic (periodic oscillating) motion, such as a pendulum or spring with an attached mass; a system in which a mass is subject to a linear restoring force. A harmonic oscillator vibrates at a fixed frequency, independent of amplitude.

Haustra -- in anatomy, the sacculated pouches of the colon.

Hawk -- to make an audible effort to force up phlegm from the throat.

Hct -- see hematocrit.

Heat -- as defined in thermodynamics, heat is the energy that flows between two systems as a result of temperature differences, as distinguished from thermal energy. (A system contains neither heat nor work, but can produce heat or do work.)

Heat capacity -- the ratio of the heat input to the temperature increase in a system.

Hectomicron -- 100 microns.

Helmholtz free energy -- the internal energy of a system minus the product of its entropy and temperature.

Hemapheresis -- see apheresis.

Hemato -- pertaining to blood.

Hematocrit (Hct) -- volume-fraction or bloodstream concentration of erythrocytes (red blood cells), expressed as a percentage.

Hematoma -- a swelling or mass of blood (usually clotted), confined to an organ, tissue, or other space, caused by a break in a blood vessel.

Hemobaric -- pertaining to blood pressure.

Hemolytic -- tending to destroy red blood cells, liberating hemoglobin.

Hemorrhagic -- pertaining to bleeding.

Hemostasis -- arrest of bleeding.

Hepatic -- pertaining to the liver.

Hepatocyte -- the most common tissue cell found in the liver.

Heterochromatin -- regions of the genome that remain permanently in a highly condensed state and are not genetically expressed.

Histamine -- a chemical substance, produced from the amino acid histidine, normally present in the body; exerts a pharmacological action when released from injured cells.

Histaminergic -- activated or energized by histamine.

Histology -- the study of tissues.

Histonatation -- in medical nanorobotics, locomotion (swimming) through tissues by a nanorobot.

Histonavigation -- in medical nanorobotics, navigation through tissues by a nanorobot.

Histones -- conserved DNA-binding proteins of eukaryotes that form the nucleosome, the basic subunit of chromatin; histones are rich in arginine and lysine residues.

HLA complex -- Histocompatibility Locus Antigens, formerly known as Human Leukocyte Antigen (or Associated) complex.

Holliday junction -- a connection between two DNA duplex molecules (as during recombination), wherein one duplex rotates relative to the other, creating a junction with 3-D topology.³¹⁵⁴

Homeodomain -- a DNA-binding motif in a transcriptional regulator that identifies, or at least is common in, the genes concerned with early embryonic developmental regulation.

Homeostasis -- in physiology, a state of equilibrium of the internal environment of the body that is maintained by dynamic processes of feedback and regulation; homeostasis is a dynamic equilibrium (changing balance), keeping cells within the physical and chemical limits that can support life.

Homeothermic -- tending to maintain a constant temperature, despite temperature variations in the surrounding environment.

Homochirality -- chirality is a property of certain asymmetric molecules, the property being that the mirror images of the molecules cannot be superimposed one on the other while facing in the same direction. Homochirality is the preference of a process or system for a single optical isomer in a pair of isomers.

Homologous -- similar in form (e.g. fundamental structure and origin), but not necessarily in function.

Hormone -- a chemical substance that originates in an organ, gland, or part and is conveyed through the blood to another part of the body, stimulating that other part by chemical action to increase functional activity or to increase secretion of another hormone.

Hyaline cartilage -- true cartilage; a smooth and pearly layer that covers the articular (place of union between two or more bones) surfaces of bones.

Hydrocarbon -- a molecule consisting only of H and C.

Hydrodynamics -- in physics, the study of the action of and motion of (and in) water and other liquids.

Hydrogen bond -- the weak bond between a positively charged hydrogen atom that is covalently bound to one electronegative atom, and another electronegative atom.

Hydrolysis -- a (hydrolytic) reaction in which a covalent bond is broken with the incorporation of a water molecule.

Hydrophilicity -- tending to mix with water; wettable. Hydrophilic groups interact with water, so that hydrophilic regions of protein or the faces of a lipid bilayer reside in an aqueous environment.

Hydrophobic force -- water molecules are linked by a network of hydrogen bonds; a nonpolar nonwetting surface such as wax cannot form hydrogen bonds, hence repels water.

Hydrophobicity -- tending not to mix with water; nonwetting. Hydrophobic groups repel water, so that they interact with one another to generate a nonaqueous environment.

Hydrostatic -- pertaining to the pressure of fluids or to fluid properties when in equilibrium.

Hygroscopic -- readily absorbing and retaining moisture.

Hypercholesterolemia -- presence of an abnormal amount of cholesterol in the cells and plasma of the circulating blood.

Hypergolic -- refers to two substances which, although stable when stored separately, spontaneously combust or react when mixed.

Hypogravity -- conditions of below-normal gravity (e.g. microgravity in Earth orbit).

Hypotension -- low blood pressure.

Hypoxia -- a condition in which the tissues are not receiving enough oxygen to sustain their metabolic activity.

Hypsithermal limit -- the maximum amount of energy that may be released at Earth's surface, as a result of human technological activities, without significantly altering the natural global energy balance; estimated as 10¹³-10¹⁵ watts.

Hz -- hertz (MKS unit of frequency); cycles per second of an oscillation.

Iatrogenic disorder -- an adverse condition induced in a patient by the actions of a physician.

Icosahedral -- a solid figure with 20 planar faces.

Iliac crest -- in anatomy, pertaining to the top of the ilium (the uppermost of the three sections of the hipbone).

Immunoglobulin -- see antibody.

Impedance -- opposition to flow (e.g. fluid, electrical, etc.) when flow is steady, or the driving pressure per unit flow when flow is changing; the resistance of an acoustic system to being set in motion.

Incision -- a cut made with a knife.

In cyto -- within a biological cell.

Inertia -- in physics, the tendency of a body to remain in its kinematic state (e.g. at rest or in motion) until acted upon by an outside force; in biology, sluggishness or lack of activity.

Infarct -- an area of tissue in an organ or part that undergoes necrosis following cessation of blood supply.

Inferior -- beneath or lower; often refers to the undersurface of an organ or indicates a structure below another structure. See also caudal.

Infrasonic -- inaudible (to human ears); sounds with acoustic frequencies less than ~16 Hz.

Infusion -- the introduction of a fluid, other than blood, into a vein.

Inmessaging -- in medical nanorobotics, conveyance of information from a source external to the human body, or external to working nanodevices, to a receiver located inside the human body.

Inner ear -- the portion of the ear consisting of the cochlea, containing the sensory receptors for hearing, and the vestibule and semicircular canals, which include the receptors for balance and the sense of position.

Innervated -- having nerves.

In nucleo -- within the nucleus of a cell.

In sanguo -- within the bloodstream.

Integral membrane protein -- in cell biology, an amphipathic protein embedded in the lipid bilayer of the cell which cannot be extracted from the membrane without disrupting the lipid bilayer; most integral proteins are transmembrane proteins.

Intercalated -- inserted between two others, as something interposed.

Intercostal -- between the ribs.

Interferometry -- measurement of very small spatial or frequency displacements using wave interference patterns.

Intermolecular -- an interaction (e.g. a chemical reaction) between different molecules.

Internal energy -- the sum of the kinetic and potential energies (including electromagnetic field energies) of the particles that make up a system.

Interphase -- in cell biology, the quiescent period of time between mitotic cell divisions.

Interstitial -- pertaining to extracellular interstices or spaces within an organ or tissue.

Intracellular fluid -- all of the fluid inside a cell; the cytosol plus the fluid inside each organelle, including the nucleus.

Intracorporeal -- inside the human body.

Intramolecular -- an interaction (e.g. chemical reaction) within a single molecule. Intramolecular interactions between widely separated parts of a molecule resemble intermolecular interactions in most respects.

Intraperitoneal -- within the peritoneal (abdominal) cavity.

Intravascular -- inside a blood vessel.

In vacuo -- in a vacuum (viz. the ablative case of the 2nd-declension Latin adjective "vacuus").

Invaginate -- to place or receive into a sheath; to receive within itself or into another part.

In vivo -- inside the living human body.

Ion -- an atom or molecule with a net charge.

Ion Beam Lithography (IBL) -- lithography using ions rather than light beams.

Ion channels -- a large heterogeneous family of voltage-activated proteins that control the permeability of cells to specific ions by opening or closing in response to differences in potentials across the plasma membrane. Ion channels participate in the generation and transmission of electrical activity in the nervous system and in the hormonal regulation of cellular physiology.

Ionic bond -- a chemical bond resulting chiefly from the electrostatic attraction between positive and negative ions.

Ionosphere -- an upper region of Earth's atmosphere.

IR -- infrared.

Ischemia -- local and temporary deficiency of blood supply due to obstruction of the circulation into a body part.

Isoareal -- occurring without any change in surface area.

Isobaric -- held, or existing, at a constant pressure.

Isomer -- one of two more chemical substances that have the same molecular formula but different chemical and physical properties due to a different arrangement of the atoms in the molecule; for example, dextrose is an isomer of levulose. Isomers may be geometric, optical, or structural. See also chiral, enantiomer, stereochemistry, and stereoisomer.

Isomagnetic -- having the same magnetic field strength.

Isometric -- in general, having equal dimensions; in physiology (or biomechanics), denoting a condition wherein the ends of a contracting muscle (or motor protein) are held fixed so that contraction produces increased tension at constant overall length.

Isoporous -- having pores of the same size.

Isostatic -- denoting a condition in which there is equal pressure on every side; in hydrostatic equilibrium.

Isotherm -- region, section, or surface of constant temperature.

Isothermal -- held, or existing, at a constant temperature.

Isotonic -- animal cells containing a solution which exerts an osmotic pressure approximately equal to that of the surrounding fluid are isotonic or isoosmotic to that fluid. Stronger solutions that cause cells to shrink are hypertonic; weaker solutions that cause cells to swell are hypotonic.

Isotope -- any of two or more forms of the same chemical element that have nearly identical chemical properties but which differ in the number of neutrons contained in each atomic nucleus; many isotopes are radioactive.

Isotropic -- the same in all directions.

Isovolemic -- occurring without any change in volume.

IV -- intravenous (inserted into a vein).

J -- joule (MKS unit of energy).

Kelvins (K) -- kelvin degrees (MKS unit of temperature).

Keratin -- a sulfur-rich scleroprotein or albuminoid present largely in cuticular (pertaining to cuticles) structures.

Keratinocyte -- a cell of the epidermis, and parts of the mouth, that produces keratin.

kg -- kilogram (MKS unit of mass).

KHz -- kilohertz; thousands of cycles per second.

Kinematic -- pertaining to motion.

Kinesthesis -- sensations of position, movement, direction and extent from the limbs, neck and body trunk.

Kinetic energy -- energy resulting from the motion of masses.

Kupffer cells -- macrophages lining the sinusoids of the liver.

Labial -- pertaining to the lips.

Lacrimal -- pertaining to the tears (eye fluid).

Lamellipodium -- a cytoplasmic veil produced on all sides of a migrating polymorphonuclear leukocyte (granulocyte).

Laminar (Poiseuille) flow -- fluid flow that moves exclusively along separate and independent parallel flow planes (i.e. streamlines), generally with an axisymmetric parabolic profile if in a tube. Laminar flow minimizes the impedance (resistance) and energy dissipation of fluid flow.

Langmuir-Blodgett (LB) film -- a technique for producing highly regular stacks of monomolecular films.

Lateral -- on the side, or farthest from, the midsagittal plane; away from the midline of the body (to the side).

Lathe -- in mechanical engineering, a machine for shaping an object, by holding and turning the object rapidly against the edge of a cutting tool.

LD50 -- a dose of or exposure to a toxic influence that produces death in 50% of organisms exposed to it.

LED -- light emitting diode.

Leukapheresis -- see apheresis.

Leukocytes (white blood cells) -- the primary effector cells that respond to infection and tissue damage in the human body. There are two types: granulocytes (including basophils, eosinophils, and neutrophils) and agranulocytes (including monocytes and lymphocytes). Leukocytes are formed from two stem cell populations in the bone marrow. The myeloid stem cell line produces granulocytes and monocytes, while the lymphoid stem cell line produces lymphocytes. Lymphoid cells travel to the thymus, spleen and lymph nodes, where they mature and differentiate into active, antigen-specific lymphocytes.

Leukokine -- a cytokine secreted by a leukocyte.

Leukotaxis -- active amoeboid movement of leukocytes, especially neutrophils, either toward (positive leukotaxis) or away from (negative leukotaxis) certain microorganisms or substances that frequently are formed in inflamed tissue; the property of attracting or repelling leukocytes.

Ligand -- in protein chemistry, a small molecule that is (or can be) bound by a larger molecule; in organometallic chemistry, a moiety bonded to a central metal atom (this latter definition is more common in general chemistry).

Ligation -- the formation of a phosphodiester bond to link two adjacent bases separated by a nick in one strand of a double helix of DNA; the term can also be applied to blunt-end ligation and to the joining of RNA.

Linear -- in control theory, describes systems in which an output is directly proportional to an input.

Lingual -- pertaining to the tongue.

Lipid bilayer -- in cell biology, the form taken by a concentration of lipids in which the hydrophobic fatty acids occupy the interior and the hydrophilic polar heads face the exterior; primary constituent of the plasma membranes of cells.

Lipids -- molecules having hydrophilic polar heads, containing phosphate (phospholipid), sterol (such as cholesterol), or saccharide (glycolipid) connected to a hydrophobic tail consisting of fatty acid.

Lipofuscin -- brown pigment granules representing lipid-containing nondegradable residues of lysosomal digestion.

Lipophilic -- having an affinity for lipids (fats).

Lipophobic -- repulsed by lipids (fats).

Liposomes -- the sealed concentric microscopic shells formed when certain lipid substances are in an aqueous solution. See also micelles.

Lithography -- a technique for surface patterning commonly used to make semiconductor devices.

Lithotomy -- in surgery, incision of a duct or organ, especially of the bladder, to remove a calculus (any abnormal concretion within the animal body, usually composed of mineral salts, commonly called stone).

Lithotripsy -- crushing of a stone in the bladder or urethra.

Load error -- in control theory, minimum range of variation in a control variable that is necessary to provoke a response from a control system.

Logic gate -- in digital logic, a component that can switch the state of an output depending on the states of one or more inputs; a device implementing any of the elementary logic (or Boolean) functions (e.g. AND, NAND, NOR, NOT, OR, XOR). A logic gate is characterized by the relationship between its inputs and outputs, and not by its internal mechanisms.

Loin (lumbar) -- lower part of the back and sides, between the thorax (ribs) and the pelvis (hips).

LPS -- lipopolysaccharide, the lipid used to construct the outer leaflet of the outer bilayer membrane of Gram-negative bacteria.

LR oscillator -- an electrical oscillator circuit comprised of resistors and inductors (solenoids).

Lumbar -- see loin.

Lumen -- the interior, especially of a compartment bounded by membranes, as for instance the endoplasmic reticulum or the mitochondrion.

Luminal -- pertaining to the interior of a cavity, tube, or vessel.

Lymph -- an alkaline fluid found in the lymphatic system.

Lymphatic system -- includes all structures involved in the conveyance of lymph from the tissues to the bloodstream, including lymph capillaries, lacteals, lymph nodes, lymph vessels, main lymph ducts, and cisterna chyli.

Lymphocyte -- a morphologically distinct variety of leukocytes, comprising 20%-44% of all white blood cells. But only ~2% of all lymphocytes present in the human body are in the bloodstream; most reside elsewhere, particularly in the lymph and the lymph nodes. B-lymphocytes differentiate into antibody-secreting plasma cells, whereas T-lymphocytes play diverse regulatory roles in the immune response.

Lysis (lytic) -- in microbiology, the death of a bacterium at the end of a bacteriophage infective cycle when the bacterium bursts open to release the progeny of an infecting phage; also applies to eukaryotic cells, as for example infected cells that are attacked by the immune system. More generally, dissolution or decomposition.

Lysosomes -- small bodies inside cells, enclosed by membranes, that contain hydrolytic enzymes that are part of the cell's digestive apparatus.

Lysozyme (muramidase) -- an enzyme that is destructive to cell walls of certain bacteria, found in white blood cells of the granulocytic and monocytic series.

m -- meter (MKS unit of length).

M -- see molarity.

Macromolecule -- a molecule of colloidal size, typically 1-100 nm in diameter or length, consisting most notably of proteins, nucleic acids, and polysaccharides.

Macrophage -- a monocyte that has left the circulation and settled and matured in a tissue; found in large numbers in the spleen, lymph nodes, alveoli, and tonsils, with ~50% found in the liver as Kupffer cells. Along with neutrophils, macrophages are the major phagocytic cells of the immune system, able to recognize (and then ingest) foreign antigens via chemical receptors on the surface of their cell membranes. Macrophages also serve a vital role by processing antigens and presenting them to T-cells, activating the specific immune response.

Macroscopic -- easily visible to the human naked eye; typically ~1 mm³ or larger.

Macrosensing -- in medical nanorobotics, the detection of global somatic states (inside the human body) and extrasomatic states (sensory data originating outside of the human body) by in vivo nanorobots.

Magnetic Force Microscope (MFM) -- a kind of SPM that images surfaces using magnetic forces.

Maillard reaction -- in food science, the "browning" reaction that occurs between proteins and reducing sugars as they are heated.

Major histocompatibility complex (MHC) -- the complex of HLA genes on the short arm of human chromosome 6.

Manometer (manometry) -- a device for measuring liquid or gaseous pressure such as blood, spinal fluid, or atmosphere (air).

Manustupration -- masturbation.

Margination -- adhesion of leukocytes to endothelial cells lining the walls of a blood vessel, during the relatively early stages of inflammation; more generally, the process of differential radial migration among suspended particles of different sizes during fluid flow through a tube.

Massometer -- in medical nanorobotics, a nanosensor device for measuring the mass of individual molecules or small physical objects to single-proton resolution.

Mast cells -- cells resident in connective tissue just below epithelial surfaces, serous cavities, and around blood vessels, that synthesize, store, and release (upon stimulation) histamine and other local chemical mediators of inflammation (e.g. leukotrienes).

Mastication -- chewing.

Mechanical nanocomputers -- nano-sized computers that use mechanical rather than chemical or electronic logic switches.

Mechanomechanical conversion -- conversion of one form of mechanical energy into another form of mechanical energy.

Mechanochemistry -- the chemistry of processes in which mechanical systems operating with atomic-scale precision guide, drive, or are driven by chemical transformations; in more general usage, the chemistry of processes in which energy is converted from mechanical to chemical form, or vice versa (aka. piezochemistry).

Mechanosynthesis -- chemical synthesis controlled by mechanical systems operating with atomic-scale precision, enabling direct positional selection of reaction sites; synthetic applications of mechanochemistry.

Medial -- middle or nearest to the midsagittal plane; toward the midline of a body or vessel.

Medulla (medullary) -- the inner or central portion of an organ. Compare cortex.

Medulla oblongata -- enlarged portion of the spinal cord in the cranium, after the cord enters the foramen magnum of the occipital bone; the lower portion of the brain stem.

Melanoma -- a malignant, darkly pigmented mole or tumor of the skin.

Membrane -- in cell biology, an asymmetrical lipid bilayer that has lateral fluidity and contains proteins; in anatomy, a thin, soft, pliable layer of tissue that lines a tube or cavity, covers an organ or structure, or separates one part from another.

Membrane proteins -- in cell biology, plasma membrane proteins that have hydrophobic regions that allow part or all of the protein structure to reside within the membrane; the bonds involved in this association are usually noncovalent.

Membranolytic -- causing the physical failure of a membrane.

MEMS -- see microelectromechanical systems.

Meniscus -- the curved upper surface of a liquid in contact with a container.

-mer -- see oligomer.

Mesenchyme -- a diffuse network of cells forming the embryonic mesoderm and giving rise to connective tissues, blood, and blood vessels, the lymphatic system, and cells of the RES.

Mesentery -- a peritoneal fold encircling the greater part of the small intestines and connecting the intestine to the posterior abdominal wall.

Mesoderm -- a tissue layer in the embryo from which arises all connective tissues, including the muscular, skeletal, circulatory, lymphatic, and urogenital systems, and the linings of the body cavities.

Mesoscopic -- lying midway in size between the nanoscale (~nanometers) and the microscale (~microns).

Mesothelium -- the layer of cells derived from the mesoderm that lines the primitive body cavity; in the adult, it becomes the epithelium covering the serous membranes.

Messenger molecule -- a chemically recognizable molecule which can convey information after it is received and decoded by an appropriate chemical sensor.

Messenger RNA (mRNA) -- the RNA whose sequence corresponds to that of exons in the transcribed gene, which embodies the codons and is translated into the protein gene product.

Metabolism -- the sum of all physical and chemical changes that take place within an organism; all energy and material transformations that occur within living cells, including anabolism and catabolism.

Metamorphic -- in medical nanorobotics, capable of adopting multiple physical configurations via smooth changes from one configuration to another.

Metaphase -- stage of mitosis (cell division) in which all chromosomes are aligned equidistant between the spindle poles.

Metastable state -- a high energy state that requires an input of energy to relax to the ground state.

Metastasize -- usually refers to the manifestation of a malignancy (e.g. of cancerous body cells) as a secondary growth arising from the primary growth, but in a new location.

Metazoa -- all multicellular life.

Metrology -- the science of weights and measures.

MeV -- million electron volts (unit of energy).

MHC -- see major histocompatibility complex.

MHz -- megahertz; millions of cycles per second.

Micelle -- a self-assembling hollow spheroidal aggregate of amphipathic lipids in a polar liquid (e.g. aqueous) medium.

Michaelis-Menten enzyme -- an enzyme whose saturation kinetics obey the Michaelis-Menten equation, which describes the half-maximal reaction velocity as a function of substrate concentration; certain enzymes and other ligand-binding proteins such as hemoglobin may obey sigmoid (e.g., Hill equation) substrate saturation kinetics instead.

Microbarom -- a low-amplitude, slowly-varying atmospheric pressure wave.

Microbiotagraphics -- mapping the microbiotic populations present in the human body.

Microelectromechanical systems (MEMS) -- micron-scale devices combining electronic and mechanical elements.

Micron -- one-millionth of a meter; a micrometer.

Micro-opto-mechanical systems (MOMS) -- micron-scale devices combining electronic, optical and mechanical elements.

Microsensors -- micron-scale chemical and physical sensors.

Microtubules -- filaments consisting of dimers of tubulin; interphase microtubules are reorganized into spindle fibers during mitosis (cell division), when they are responsible for chromosome movement.

Microvasculature -- pertaining to the very fine blood vessels of the body.

Midsagittal -- vertical at midline, dividing the body into right and left halves.

Mince -- progressive reduction in size of biological tissue samples by mechanical means; more generally, to cut or chop into very small pieces, or to subdivide minutely.

MIPS -- a conventional measure of computing speed, defined as millions of instructions per second.

Mitochondrion -- a self-reproducing organelle that provides energy for eukaryotic cells via oxidative phosphorylation.

Mitosis -- in cell biology, the division of a eukaryotic somatic cell. The four (or five) sequential stages are prophase, (prometaphase), metaphase, anaphase, and telophase; the absence of mitosis is the interphase.

MKS -- meter-kilogram-second; standard system of units adopted by the international physics community.

Moiety -- a portion of a molecular structure having some property of interest.

Molality -- in chemistry, moles of solute per kilogram of solvent.

Molar -- in anatomy, pertaining to a grinding (back) tooth.

Molarity (M) -- in chemistry, moles of solute per liter of solvent.

Mole -- a number of instances of something (e.g. molecular objects) equal to ~6.023 x 10²³ objects.

Molecular assembler -- a general-purpose device for molecular manufacturing, able to guide chemical reactions by positioning individual molecules to atomic accuracy (e.g. mechanosynthesis) and to construct a wide range of useful and stable molecular structures according to precise specifications.

Molecular Beam Epitaxy (MBE) -- a technique for producing single-layer crystals.

Molecular electronics -- any system of atomically precise electronic devices of nanometer dimensions, especially if made of discrete molecular parts rather than the continuous bulk materials found in 20th century semiconductor devices.

Molecular machine -- a mechanical device that performs a useful function using components of nanometer scale and a well-defined molecular structure; may include both artificial nanomachines and naturally occurring devices found in biological systems.

Molecular machine system -- a system of molecular machines.

Molecular manipulator -- a manipulator device able to position molecular tools with high precision, for example to direct varying sequences of mechanosynthetic steps; a major component of a molecular assembler.

Molecular manufacturing -- manufacturing using molecular machinery, giving molecule-by-molecule control of products via positional chemical synthesis, to produce complex molecular structures manufactured to precise specifications.

Molecular medicine -- a variety of pharmaceutical techniques and gene therapies that address specific molecular diseases or molecular defects in biological systems.

Molecular mill -- a mechanochemical molecular transport and processing system characterized by limited motions and repetitive operations without programmable flexibility.

Molecular nanotechnology -- thorough, inexpensive control of the structure of matter based on molecule-by-molecule control of products and byproducts; the products and processes of molecular manufacturing, including molecular machinery; a technology based on the ability to build structures to complex, atomic specifications by mechanosynthesis or other means; most broadly, the engineering of all complex mechanical systems constructed from the molecular level.

Molecular recognition -- a chemical term referring to processes in which molecules adhere in a highly specific way, forming a larger structure; a possible enabling technology for nanotechnology.

Molecular sorting rotor -- a class of nanomechanical device capable of selectively binding (or releasing) molecules from (or to) solution, and of transporting these bound molecules against significant concentration gradients.

Molecular surgery (molecular repair) -- in medical nanorobotics, the analysis and physical correction of molecular structures in the body using medical nanomachines.

Molecular systems engineering -- design, analysis, and construction of systems of molecular parts working together to carry out a useful purpose.

Molecule -- group of atoms held together by chemical bonds; the typical unit manipulated by molecular nanotechnology.

Monkeywrenching -- in medical nanorobotics, the mechanical or chemical jamming of cellular equilibrium processes, with a cytocidal objective. See also disequilibration.

Monocyte -- a mononuclear phagocytic white blood cell derived from the myeloid stem cells, that is short-lived (~1 day half-life) and circulates in the bloodstream from which it moves into tissues, at which point it matures into a macrophage (which is long-lived). Monocytes represent 3%-8% of all white blood cells.

Monomer -- any molecule that can be bound to similar molecules to form a polymer.

Morcellation -- fragmentation of biological materials as they are excised from the body.

Morphogen -- a (biochemical) factor that induces development of particular cell types in a manner that depends on its concentration.

Morphology -- the science of structure and form, without regard to function.

Motif -- main element, theme, or design feature that may occur in slightly different forms.

Motile -- capable of voluntary movement. Opposite of sessile.

MRFM -- magnetic resonance force microscope.

MRI -- magnetic resonance imaging.

mRNA -- see messenger RNA.

MTOC -- microtubule organizing center; a cellular structure from which microtubules may be extended. The major MTOCs in a mitotic (dividing) cell are the centrosomes.

Mucosa -- a mucous membrane; the moist tissue layer that lines a hollow organ or body cavity.

Muller cells -- neuroglial cells with fine fibers that form supporting elements of the retina.

Multivalent -- in chemistry, able to form more than one covalent or ionic bond; in biomedicine, efficacious in more than one direction, or active against several strains of an organism.

Mutagenesis, site-directed -- a biotechnological technique whereby a gene encoding an enzyme is mutated, then overexpressed in a unicellular host, then characterized. By altering the base sequence of a single codon, site-directed mutagenesis can replace a given amino acid with any other protein amino acid, and can also generate multiple point mutants.

Mycelium -- the mass of hyphae (branching tubular cells characteristic of the growth of filamentous fungi) making up a colony of fungi.

Myelin -- a fatlike substance forming a sheath around the axons of certain nerves; composed of lipids and protein.

Myocardium -- heart muscle.

Myoepithelium -- tissue containing contractile epithelial cells (e.g. contractile spindle-shaped cells arranged longitudinally or obliquely around sweat glands and around the secretory alveoli of the mammary and salivary glands).

Myopotential -- pertaining to an action potential in an axon innervating a muscle cell.

N -- in physics, newton (MKS unit of force); in solution chemistry, see normal.

Naked DNA -- DNA that is not surrounded by an outer protein envelope.

Nanapheresis -- in medical nanorobotics, the removal of bloodborne medical nanorobots from the body using apheresis-like processes.

NAND gate -- a logical gate equivalent to a negated (NOT-) AND gate.

nano -- a prefix meaning one billionth (1/1,000,000,000); more specifically, may refer to sizes of ~10^-9 meters or to physical objects constructed or processes performed at the atomic or molecular scale.

Nanocentrifuge -- in medical nanorobotics, a proposed nanodevice that can spin materials at very high speed, imparting rotational accelerations of up to one trillion gravities (g's), thus permitting rapid sortation.

Nanochronometer -- in medical nanorobotics, a proposed clock or timing mechanism constructed of nanoscale components.

Nanoclusters -- nanoscale aggregates of atoms or molecules.

Nanocomputer -- a proposed computer with parts built on a molecular scale, possibly employing molecular electronics, mechanical rod logic, or biological molecules.

Nanocrit (Nct) -- in medical nanorobotics, volume-fraction or bloodstream concentration of medical nanorobots, expressed as a percentage.

Nanolithography -- the process of transferring nanometer-sized surface patterns.

Nanomachine -- functional machine systems on the scale of nanometers; an artificial mechanical device constructed with precise molecular order using nanometer-scale components; any molecular structure large and complex enough to function as a machine.

Nanomanipulator -- a nanorobotic manipulator device.

Nanomanufacturing -- see molecular manufacturing.

Nanomechanical -- pertaining to nanomachines.

Nanomedicine -- (1) the comprehensive monitoring, control, construction, repair, defense, and improvement of all human biological systems, working from the molecular level, using engineered nanodevices and nanostructures; (2) the science and technology of diagnosing, treating, and preventing disease and traumatic injury, of relieving pain, and of preserving and improving human health, using molecular tools and molecular knowledge of the human body; (3) the employment of molecular machine systems to address medical problems, using molecular knowledge to maintain and improve human health at the molecular scale.

Nanometer -- a billionth of a meter, roughly the diameter of 3-7 atoms.

Nanorobot -- a computer-controlled robotic device constructed of nanometer-scale components to molecular precision, usually microscopic in size (often abbreviated as "nanobot").

Nanosensor -- a chemical or physical sensor constructed using nanoscale components, usually microscopic or submicroscopic in size.

Nanosieving -- in medical nanorobotics, a nanodevice that can sort molecules or other nanoscale objects by physical sieving.

Nanosystem -- a set of nanoscale components, characterized by precise molecular order, working together to serve a set of purposes; complex nanosystems can be of macroscopic size.

Nanotechnology -- engineering and manufacturing at nanometer scales; any technology related to features of nanometer scale, including thin films, fine particles, chemical synthesis, advanced microlithography, and so forth, as well as complex mechanical systems constructed from the molecular level.

Nanotubes -- hollow fullerene tubes, including but not limited to single- and multi-walled carbon nanotubes, with submicroscopic, often nanoscale, diameters and a wide range of continuous lengths.

NASA -- National Aeronautics and Space Administration.

Nasal septum -- in anatomy, the cartilage, covered with mucous membrane, that divides the two nostrils and nasal passages.

Nasopharynx -- in anatomy, the nasal passages, mouth, and upper throat.

Natation -- swimming.

Naturophilia -- an exclusive love of Nature, disdaining everything that is artificial or technological.

Nauseogenic -- tending to produce nausea.

Navicyte -- in medical nanorobotics, a mobile, mass-storage (nanorobotic) device, similar to a communicyte, that may be used to establish a navigational network inside the human body.

N/C -- numeric control machining (e.g. computer-aided manufacturing).

Nct -- see nanocrit.

Necrosis (necrotic) -- the death of areas of tissue or bone, surrounded by healthy parts.

Neoplastic -- pertaining to, or of the nature of, new and abnormal tissue (i.e. neoplasm) formation and growth.

Neurofibrils -- a filamentous aggregation of microfilaments and microtubules found in the main cell body, dendrites, and axon of the nerve cell, and sometimes in its synaptic endings.

Neuron -- a nerve cell, the principal structural and functional unit of the nervous system.

Neuropeptide -- any of a variety of neurotransmitter peptides found in neural tissue (e.g. endorphins, enkephalins).

Neurotransmitter -- a biochemical substance released when the axon terminal of a presynaptic neuron is excited. The substance travels across the synapse to act on the target cell to either inhibit or excite it.

Neutrophil -- the most common type of granulocytic white blood cell. Neutrophils are responsible for much of the body's protection against infection. Comprising ~60% of all white blood cells, neutrophils play the primary role in inflammation, easily recognizing foreign antigens and destroying them through phagocytosis. Neutrophils also may overreact to stimuli and become involved in tissue destruction, as in rheumatoid arthritis, myocardial reperfusion injury, respiratory distress syndrome, and ulcerative colitis.

NIST -- National Institute of Standards and Technology.

NMR -- see Nuclear Magnetic Resonance.

Nociceptors -- pain receptors.

Nodes of Ranvier -- constrictions of the myelin sheath of a myelinated nerve fiber.

Nonpolar liquid -- a liquid consisting of molecules that have zero electric dipole moment (e.g. ethane, benzene, liquefied carbon dioxide). Compare polar liquid.

NOR gate -- a logical gate equivalent to a negated (NOT-) OR gate.

Normal (N) -- in solution chemistry, 1 liter of solution which contains 1 gram-equivalent of solute.

Nosogenic -- tending to cause disease.

NOT gate -- a logical gate that inverts or negates the input signal, as its output.

NSOM -- Near-field Scanning Optical Microscope.

Nuclear cortex -- a proteinaceous layer on the inside of the cellular nuclear envelope, consisting of up to three kinds of laminin proteins.

Nuclear envelope -- a layer consisting of two membranes surrounding the cellular nucleus, penetrated by nuclear pores and bounded on the interior by the nuclear cortex.

Nuclear lamina -- see nuclear cortex.

Nuclear Magnetic Resonance (NMR) -- in physics and radiology, an analytical technique that relies on the absorption of certain electromagnetic frequencies by atomic nuclei.

Nuclear matrix -- a network of fibers surrounding and penetrating the cell nucleus.

Nuclear pores -- holes in the cellular nuclear envelope used for transport of macromolecules.

Nucleic acids -- polymers of nucleotidyl residues.

Nucleoelectric conversion -- conversion of nuclear energy into electrical energy.

Nucleography -- a physical description (and mapping) of the nucleus of a human cell.

Nucleolus -- an RNA-rich spherical body made up of dense fibers and granules within the cell nucleus, associated with chromosomal loci for rRNA genes, created by the transcription of rRNA genes.

Nucleoplasm -- the protoplasm of a cell nucleus.

Nucleosides -- compounds consisting of a purine or pyrimidine attached to ribose or deoxyribose at the 1' carbon.

Nucleosome -- the basic structural subunit of chromatin, consisting of 146 base pairs of DNA wrapped around a core of eight histone protein molecules.

Nucleotide (nucleotidyl) -- phosphorylated nucleosides; nucleotidyl residues are the monomeric units of RNA and DNA. The building blocks of nucleic acids. Each nucleotide is composed of sugar (ribose or deoxyribose), phosphate, and one of four nitrogen bases (purine or pyrimidine). The sequence of the bases within the nucleic acid determines what proteins will be made.

Nucleus -- in physics, the positively-charged core of an atom, an object of ~0.00001 atomic diameters containing >99.9% of the atomic mass; in cell biology, a cellular organelle containing the genome, separated from the cytoplasm by a membrane.

Nyctalopia -- a vitamin A deficiency disease, characterized by decreased ability to see in reduced illumination or at night.

Obligate -- to make necessary or require, without alternative.

Occipital -- pertaining to the back part of the head.

Occlusal surface -- in dental medicine, the masticating surface of the premolar and molar teeth.

Olfaction (olfactory) -- pertaining to the sense of smell.

Oligomer -- any short polymeric molecular chain consisting of well-defined subunits; N-mer refers to an oligomer that has exactly N subunits.

Oligonucleotide -- a polymeric chain that consists of a small number of (possibly different) nucleotides.

Opsonin -- a biochemical substance that coats foreign antigens, making them more susceptible to macrophages and other leukocytes, thus increasing phagocytosis of the organism. Complement and antibodies are the two main opsonins in human blood.

Opsonization -- the coating action of opsonins, thus facilitating phagocytosis.

Organelle -- most commonly described subcellular compartment, located in the cytoplasm, that is surrounded by a membrane (e.g. lysosome, mitochondrion).

Organography -- a physical description (and mapping) of the body organs.

OR gate -- a logical gate that returns a high (1) output if either input signal is high (1). See bit.

Orthogonal -- at right angles; mutually perpendicular.

Orthotropic -- capable of alternating between bent and straight configurations.

Osmosis -- the passage of solvent through a semipermeable membrane that separates solutions of different concentrations.

Osmotic pressure -- the pressure that would develop if a solution is enclosed in a solvent-permeable membrane that is impermeable to all solutes present, and is then surrounded by pure solvent.

Osseous -- pertaining to bone.

Ossicle -- any small bone, especially one of the three bones of the ear.

Osteoblast -- a bone-forming cell derived from mesenchyme to form the osseous matrix in which it becomes enclosed as an osteocyte.

Osteoclast -- a giant multinuclear cell with abundant acidophilic cytoplasm, formed in the bone marrow of growing bones, which functions to absorb and remove unwanted osseous tissue.

Osteocyte -- a mesodermal bone-forming cell that has become entrapped within the bone matrix, helping to maintain bone as living tissue.

Osteography -- a physical description (and mapping) of the human skeletal system.

Osteomalacia -- a vitamin D deficiency disease, characterized by a gradual and painful softening and bending of the bones.

Ostium -- small opening, especially one into a tubular organ.

Otolith -- a crystalline particle of calcium carbonate and protein, adhering to the gelatinous membrane of the maculae (thickened areas in the utricle and saccule) of the inner ear.

Ouabain -- a glycoside (C₂₉H₄₄O₁₂^.H₂O) obtained from the wood of Acocanthera ouabaio or from the seeds of Strophanthus gratus; its action is qualitatively identical to that of the digitalis glycosides (e.g. increasing the contractility of cardiac muscle).

Outmessaging -- in medical nanorobotics, conveyance of information from a transmitter located inside the human body, especially from working nanodevices, to the patient or to a recipient external to the human body.

Ovariotomy -- incision into an ovary.

Oxidation -- in chemistry, a combination with oxygen, or an increase in positive valence of an ion, atom, or molecule, either by the loss from it of hydrogen or by the loss of one or more electrons. In bacteriology, the aerobic disassimilation of substrates with the production of energy and water; in contrast to fermentation, the transfer of electrons is accomplished via the respiratory chain, which utilizes oxygen as the final electron acceptor.

Oxidation-reduction reaction (redox) -- chemical interaction in which one substance is oxidized and loses electrons, thus is increased in positive valence, while another substance gains an equal number of electrons by being reduced, thus is decreased in positive valence.

Oxyglucose -- pertaining to a chemoergic energy conversion system involving the glucose/oxygen reaction; a glucose (fuel) and oxygen (oxidant) supply or mixture.

Palatine -- pertaining to the palate (roof of the mouth).

Papilla -- in anatomy, a small nipple-like protuberance or elevation.

Paracrine control -- a general form of bioregulation in which one cell type in a tissue selectively influences the activity of an adjacent cell type by secreting chemicals that diffuse into the tissue and act specifically on cells in that area.

Paradigm -- a conceptual model, pattern, or system.

Parenchyma -- the essential parts of an organ that are concerned with its function as opposed to its framework; opposite of stroma. The distinguishing or specific cells of a gland or organ, contained within and supported by the connective tissue framework.

Parenteral -- denoting any medication route other than the alimentary canal, such as intravenous, subcutaneous, intramuscular, or mucosal.

Parietal -- pertaining to, or forming, the walls of a cavity; often specifically refers to the parietal bone, one of two bones that together form the roof and sides of the skull.

Partition -- in medical nanorobotics, a cessation of the process of conjugation.

Parturition -- act of giving birth to young; childbirth.

Passivation -- the covalent bonding of a layer of atoms to a surface, in order to neutralize (occupy) any dangling surface bonds, thus chemically stabilizing the surface.

Patency -- the state of being freely open.

Pathogen -- a microorganism or agent capable of producing disease.

Pathognomonic -- characteristic or indicative of a disease; relating to one or more of the typical symptoms of a disease.

Pathological -- diseased or due to a disease; more informally, pertaining to an adverse condition.

PEG -- polyethylene glycol.

Pellagra -- a niacin deficiency disease, characterized by gastrointestinal disturbances, erythema (inflammatory skin redness) followed by desquamation (shedding epidermis in scales or shreds), and nervous and mental disorders.

Peptide -- a short chain of amino acids joined by amide bonds, up to 100 residues in length.

Peptidergic -- activated or energized by neuropeptides.

Peptidoglycan layer -- the dense material consisting of cross-linked polysaccharide chains present in the cell wall of most bacteria.

Periaxonal -- near or around the neural axon.

Perineum -- in anatomy, the area between the thighs extending from the coccyx to the pubis and lying below the pelvic diaphragm; the structures forming the pelvic floor.

Perinuclear space -- in cell biology, the space that lies between the inner and outer membranes of the nuclear envelope.

Periportal -- near the portal end.

Periosteum -- in anatomy, the fibrous membrane forming the investing covering of bones except at their articular (joint) surfaces.

Peripheral -- pertaining to a part of a body or object that is away from the center.

Peripheral protein -- a non-amphipathic protein bound to the hydrophilic region of an integral membrane protein, or bound to the hydrophilic heads of plasma membrane lipids, of a cell; most peripheral proteins are located near the cytoplasmic side of the plasma membrane.

Peristalsis -- a progressive wavelike movement that occurs involuntarily in hollow tubes of the body, especially the alimentary canal; it is characteristic of tubes possessing longitudinal and circular layers of smooth muscle fibers.

Peritoneum -- in anatomy, the serous membrane reflected over the viscera and lining the abdominal cavity.

Periurethral -- in anatomy, located near or around the urethra (which discharges urine).

Permittivity (relative) -- in physics, the dielectric constant, a measure of the ability of a material to store electrical energy.

Peroxisome -- in cell biology, an organelle found in vertebrate animal cells that contains a great number and variety of enzymes important in cell metabolism.

PET -- Positron Emission Tomography; see Computerized Tomography.

Phage -- see bacteriophage.

Phagocyte -- a cell with the ability to ingest and destroy particulate substances such as bacteria, protozoa, cells and cell debris, dust particles, and colloids.

Phagocytosis -- ingestion and digestion of bacteria and particles by phagocytes.

Pharmacodynamics -- the study of the action of drugs on living organisms, and the physiological and clinical changes produced in organisms by those drugs.

Pharmacogenetics -- the study of the influence of hereditary factors on the response of individual organisms to drugs; a branch of genetics dealing with hereditary aspects of drug metabolism.

Pharmacokinetics -- study of the metabolism of drugs with particular emphasis on the time required for absorption, duration of action, distribution in the body, and method of excretion.

Pharmacyte -- in medical nanorobotics, a theorized (nanorobotic) device capable of delivering precise doses of biologically active chemicals to individually-addressed human body tissue cells (e.g. cell-by-cell drug delivery).

Pharynx -- the passageway for air from the nasal cavity to the larynx (also acting as a resonating cavity), and for food from the mouth to the esophagus; more specifically, a musculomembranous tube extending from the base of the skull to the level of the 6th cervical vertebra, where the tube becomes continuous with the esophagus.

Phase -- fraction of a periodic cycle, often expressed as an angle.

Phasic (muscular) -- refers to muscles with origins and insertions on skeleton or skin, that have rapid, brief contraction cycles. Compare tonic.

Phenotype -- the appearance or other characteristics of an organism, resulting from the interaction of its genetic constitution with the environment; any observable characteristic that expresses the genotype of an individual.

Pheresis -- see apheresis.

Pheromone -- a substance permitting chemical communication between animals, and between certain insects, of the same species; may affect development, reproduction, or behavior of like individuals.

Phonons -- in physics, a quantum of acoustic energy, analogous to the quantum of electromagnetic energy, the photon. Thermal excitations in a crystal (lattice vibrations) or in an elastic continuum can be described as a population of phonons (analogous to blackbody electromagnetic radiation).

Photolithography -- a surface patterning technique that employs light, used to make semiconductor devices.

Physiognomy -- the countenance (physical features) of the face.

Phytotoxic -- pertaining to a poisonous plant.

Piezoelectric -- the property of some materials to generate a voltage when mechanical stress is applied, and vice versa.

Pinocytosis -- the process by which cells absorb or ingest nutrients and fluid, in which minute incuppings or invaginations are first formed in the surface of the plasma membrane and then close to form fluid-filled vesicles; resembles phagocytosis.

Pixel -- abbreviation for picture element; a single square cell within a two-dimensional geometric grid or array.

Plague -- see bubonic plague, pneumonic plague.

Planetary gear -- in machinery, an epicyclic train of gears as found in an automobile transmission, for the purpose of transforming the rotational speeds of rotating shafts.

Plasma -- in anatomy, the fluid (noncellular) part of the lymph and of the blood, usually distinguished from the serum obtained after coagulation; in cell biology, the part of the protoplasm (cell substance) outside of the nucleus.

Plasma membrane -- the outermost membrane of a cell, with cell contents on one side and the extracellular environment on the other side; the continuous membrane defining the boundary of every cell.

Plasmapheresis -- see apheresis.

Plasmid -- an autonomous self-replicating extrachromosomal circular DNA molecule present intracellularly and symbiotically in most bacteria, encoding a protein product that confers drug resistance or some other advantageous phenotype. Plasmids reproduce inside the bacterial cell but are not essential to its viability, and can influence a great number of bacterial functions.

Plasticity -- a property of an object or material, wherein the object or material suffers a permanent deformation in its original shape after a force is applied and then removed.

Platelet -- a round or ovoid 2-4 micron disk found in the blood of vertebrates; platelets play an important role in blood coagulation and hemostasis.

Plateletocrit -- volume-fraction or bloodstream concentration of platelets, expressed as a percentage.

Pleura -- serous membranes that enfold both lungs and are reflected on the walls of the thorax and diaphragm, and are moistened with a serous secretion that reduces friction during the respiratory movements of the lungs.

Pluripotent -- concerning an embryonic stem cell that can differentiate into many different kinds of cells.

Plexus -- an extensive two-dimensional meshwork.

Pneumatic -- driven to motion or extension by pressurized gas or fluid.

Pneumonic plague -- highly virulent and frequently fatal form of plague, having an extensive involvement of the lungs.

Poiseuille flow -- laminar (nonturbulent) fluid flow.

Polarization -- in optical physics, a change effected in a ray of light passing through certain media, whereby the transverse vibrations of the emerging ray occur in one plane only, instead of in all planes as in the ordinary incident light; in biology and electrical physics, the development of differences in electrical potential between two points on an object, such as between the inside and outside of a cell wall or along the length of a piezoelectric bone subjected to shear stress.

Polar liquid -- a liquid consisting of molecules that have an electric dipole moment (e.g. water, ethanol, liquefied ammonia). Compare nonpolar liquid.

Polymer -- a long molecular chain of well-defined linked subunits.

Polymorphonuclear leukocyte -- see granulocyte.

Polynucleotides -- polymers of nucleotidyl residues, as in RNA and DNA.

Polysaccharide -- complex carbohydrates of high molecular weight; one of a group of carbohydrates that upon hydrolysis yields more than two molecules of simple sugars.

Polysome (polyribosome) -- an mRNA associated with a series of ribosomes engaged in translation.

Polyyne -- see carbyne.

Portal -- in anatomy, pertaining to any porta or entrance to an organ, but especially to the portal vein through which nutrient-laden blood is carried from the gastrointestinal tract to the liver for filtration.

Positional navigation -- in medical nanorobotics, a form of nanorobotic navigation in which nanodevices know their exact location inside the human body to ~micron accuracy continuously at all times.

Positional synthesis -- in molecular nanotechnology, control of chemical reactions by precisely positioning specific moieties; possibly a basic component of molecular assemblers.

Positron Emission Tomography (PET) -- see Computerized Tomography.

Posterior -- the backside of the human body; the backside of something.

Postpartum -- after childbirth.

Potential energy -- the energy associated with a configuration of particles, as distinct from their motions.

Power -- the rate at which energy is produced or consumed.

Precession -- movement of the axis of rotation of a fixed-pivot gyroscope under the influence of gravity, describing a conical surface.

(to) Present -- used as verb in medicine, meaning "to exhibit" a symptom or a condition (a medical idiom).

Presentation semaphore -- in medical nanorobotics, a mechanical device used to display specific antigens, chemical ligands, or other molecular objects to the external environment, with the purpose of selectively modifying the chemical or other surface characteristics of a nanorobot exterior.

Process -- used as a noun in cell biology and medicine; a projection or outgrowth of bone or tissue.

Prognosis -- a judgement or forecast, based upon a correct diagnosis, of the future course of a disease or injury, and the patient's prospects for partial or full recovery.

Prokaryote -- in microbiology, an organism or cell that lacks a nucleus.

Prometaphase -- stage of mitosis (cell division) beginning with a fragmentation of the nuclear membrane and marked by kinetochore formation on the centromeres of the condensed chromosomes.

Promoter -- a region of DNA involved in the binding of RNA polymerase to initiate transcription.

Pronouncement -- a legally sufficient assertion of the biological death of a patient, usually attested by a physician.

Prophase -- stage of mitosis (cell division) during which the chromosomes begin to condense within the still-intact nucleus, the nucleolus disperses, and the mitotic spindle begins to develop.

Prophylaxis -- that which helps to prevent disease.

Proprioception -- sensations of position and movement, including kinesthesis and the vestibular senses.

Protease -- a class of enzymes that break down, or hydrolyze, the peptide bonds that join the amino acids in a protein.

Proteasomes -- an extra-lysosomal ATP-driven system for selectively degrading endogenous ubiquinated proteins in virtually all human cells.

Protein -- a long chain of amino acids joined by amide bonds, exceeding 100 residues in length; shorter chains are peptides. More generally, living cells contain many molecules that consist of amino acid polymers folded to form more-or-less definite three-dimensional structures, termed proteins. Short polymers lacking definite three-dimensional structures are termed peptides. Many proteins incorporate structures other than amino acids, either as covalently attached side chains or as bound ligands. Molecular objects made of protein form much of the molecular machinery of living cells.

Protein engineering (protein design) -- design and construction of new artificial proteins with desired functions; a possible enabling technology for molecular manufacturing.

Proteolytic -- hastening the hydrolysis (breakdown) of proteins, usually by enzyme action, into simpler substances.

Proteomics -- the study of proteins and how they affect the human body.

Protoplasm -- a thick, viscous colloidal substance that constitutes the physical basis of all living activities; the entire contents of a living cell.

Protozoa -- the simplest animals, mostly unicellular although some are colonial.

Proximal -- near the source or point of attachment or origin; in the extremities, closer to the trunk.

Proximal probes -- a generic name for devices that exploit interactions between a sample and a sharp probe tip; a family of devices capable of fine positional control and sensing, including scanning tunneling microscopes and atomic force microscopes; a possible enabling technology for molecular manufacturing.

Pseudopod -- in microbiology, a temporary protruding protoplasmic process in protozoa for the purpose of taking up food and aiding in locomotion.

Pseudostratified -- apparently composed of layers.

Psychosomatic -- pertaining to the influence of the mind or of higher functions of the brain upon the functions of the body, especially in relation to bodily disorders or disease.

Puerperal -- relating to the period after childbirth.

Pulmonary -- pertaining to the lungs.

Purgative -- an agent used for purging the bowels.

Purine -- parent molecule of a group of heterocyclic compounds (e.g. adenine, caffeine, guanine, uric acid, xanthine), which have fused five- and six-member carbon-nitrogen rings. Purines are the end products of nucleoprotein digestion; they may be synthesized in the body, and break down to form uric acid.

Pyemia -- septicemia due to pyogenic (pus-forming) organisms causing multiple abscesses.

Pylorus -- the lower orifice of the stomach, opening into the duodenum.

Pyrimidine -- parent molecule of a group of heterocyclic compounds (e.g. cytosine, thymine, uracil), which have a six-member carbon-nitrogen ring.

Pyroelectric -- producing electrical energy directly from heat.

Q (resonator or circuit) -- in engineering, a measure of the sharpness of a resonance peak.

Quantum computer -- a computer that relies upon quantum effects such as superposition and interference.

Quantum confinement -- restriction of particle to small physical regions so that quantum effects are exhibited. See also tunneling.

Quantum dot -- a zero-dimensional quantum system.

Quantum dot lasers -- lasers that exploit the energy levels of quantum dots.

Quantum Hall effect -- phenomenon in which certain semiconductors at low temperatures display quantized resistance.

Quantum mechanics -- theory of matter and radiation in which certain physical properties are quantized.

Quantum uncertainty -- a measurement indeterminacy associated with the dual wave/particle nature of matter; e.g. the Heisenberg uncertainty principle.

Qubits -- quantum bits; the equivalent of bits, for quantum computers.

Racemic (mixture) -- a mixture of two optical isomers in equal amounts; a racemic mixture does not show optical activity.

Radiolarian -- an order of single-celled sea animals with long slender pseudopodia and a perforated outer skeleton of silica.

Radionuclide -- a radioactive isotope.

Rale -- an abnormal sound heard upon auscultation of the chest. Rales are produced by the passage of air through bronchi that contain secretion or exudate, or that are constricted by spasm or a thickening of bronchial walls.

RAM -- random access memory (a data storage device for computers).

Raoult's law -- in an ideal solution, molar weights of non-volatile non-electrolytes, when dissolved in a definite weight of a given solvent under the same conditions, lower the solvent's freezing point, elevate its boiling point, and reduce its vapor pressure equally for all such solutes.

Ratchet -- a hinged catch (pawl) arranged so as to engage with a toothed wheel or bar whose teeth slope in one direction, thus imparting forward movement and preventing backward movement.

RBC -- red blood cell (erythrocyte).

RC time -- the characteristic exponential decay time of an RC (resistor-capacitor) circuit; the capacitive time constant of a circuit.

Reaction -- in chemistry, a process that transforms one or more chemical species into others; typical reactions make or break bonds, while others change the state of ionization or other properties taken to distinguish chemical species. In medicine, a response of a living organism to a chemical, mechanical, or other stimulus.

Reagent -- a chemical species that undergoes change as a result of a chemical reaction.

Receptor -- most generally, a structure that can capture a molecule (often of a specific type in a specific orientation) owing to complementary surface shapes, charge distributions, and so forth, without forming a covalent bond. In biology, a receptor is a transmembrane protein, located in the plasma membrane, that binds a ligand in a domain on the extracellular side, and as a result has a change in activity of the cytoplasmic domain of the protein.

Recombination -- in genetics, the inclusion of a chromosomal part or extrachromosomal element of one microbial strain in the chromosome of another; the interchange of chromosomal parts between different microbial strains. Most generally, the joining together of gene combinations in the offspring that were not present in the parents.

Red blood cell (RBC) -- see erythrocyte.

Redox -- see oxidation-reduction reaction.

Reduced mass -- many dynamical properties of a system consisting of two interacting masses m₁ and m₂ are equivalent to those of a system in which one mass is fixed in space and the other has a mass (the reduced mass) with the value m₁m₂ / (m₁ + m₂). The reduced mass description has fewer dynamical variables.

Reference man -- a man 22 years of age, weight 70 kg, engaged in light physical activity in a 20 ^oC environment, consuming ~2800 Kcal/day.

Reference woman -- a woman 22 years of age, weight 58 kg, engaged in light physical activity in a 20 ^oC environment, consuming ~2000 Kcal/day.

Refractive index -- in optics, the ratio of the sine of the angle of incidence to the sine of the angle of refraction when light is transmitted through a refracting substance (that bends the light beam).

Regioselectivity -- selection of the precise position of a ligand group addition to a molecule, e.g. ortho-, meta-, and para- positions in substituted benzenes.

Register -- a temporary storage location for an array of bits of data within a digital logic system.

Relaxation time -- the measure of the rate at which a disequilibrium distribution decays toward an equilibrium distribution.

Renal -- pertaining to the kidney.

Replicator -- any system that can build copies of itself when provided with the appropriate raw materials and energy.

Repression -- the ability of bacteria to prevent synthesis of certain enzymes when the products of those enzymes are present; more generally, the inhibition of transcription (or translation) by the binding of repressor protein to a specific site on DNA or mRNA.

Repressor protein -- a protein molecule that binds to an operator on DNA or RNA to prevent transcription or translation, respectively.

RES -- see reticuloendothelial system.

Resection -- the partial excision of a bone or other structure.

Residue -- in biochemistry, a portion of a single amino acid or nucleotide, linked as part of a peptide/protein or polynucleotide polymer chain, respectively.

Resistor -- in electrical engineering, an electronic device that resists the flow of current.

Resonance -- in engineering and in control theory, the tendency of an object or system to vibrate or oscillate at a characteristic frequency.

Resonant tunneling -- increased probability of quantum tunneling under favorable resonance conditions.

Respirocrit -- in medical nanorobotics, the volume-fraction or bloodstream concentration of respirocyte¹⁴⁰⁰ nanorobots, expressed as a percentage.

Respirocyte -- in medical nanorobotics, a theorized bloodborne spherical 1-micron (nanorobotic) device having a 1000-atm pressure vessel with active pumping powered by endogenous serum glucose, that serves as a mechanical artificial red blood cell.¹⁴⁰⁰

Reticular -- relating to a reticulum.

Reticulum -- a fine network formed by cells, or formed of certain structures within cells, or formed of connective tissue between cells.

Reticuloendothelial system (RES) -- in anatomy, the network of fixed and mobile phagocytes that engulf (and dispose of) foreign antigens and cell debris found inside the human body.

Reticuloendothelium -- tissue of the reticuloendothelial system (RES); the system of mononuclear phagocytes located in the reticular connective tissue of the body that is responsible for the phagocytosis of damaged or old cells, cellular debris, foreign substances, and pathogens, removing them from the circulation.

Reticuloplasm -- the fluid that fills the lumen of the endoplasmic reticulum.

Retinitis -- inflammation of the retina of the eye.

Reversible computer -- a computer capable of reversing its computational steps (after storing the final answer), thus recovering most of the energy that was employed during the computation.

Reynolds number -- the ratio of inertial to viscous forces in fluid flow. Macroscopic objects and flows typically experience Reynolds numbers >> 1, where mass and inertia dominate object motions; microscopic and especially nanoscale objects and flows typically experience Reynolds numbers << 1, where the viscosity of the environment dominates object motions.

rf -- radio frequency.

Rheology -- study of the deformation and flow properties of materials, especially fluids, such as blood.

Ribonucleic acid (RNA) -- the ribonucleotide polymer into which DNA is transcribed.

Ribosomal RNA (rRNA) -- the RNA components of ribosomes.

Ribosome -- a naturally occurring molecular machine that manufactures proteins according to instructions derived from the cell's genes; a cytoplasmic ribonucleoprotein complex that serves as the site of translation in the cell. Each ribosome has a large and a small subunit, 60S and 40S in eukaryotes. These subunits dissociate and reassociate in a cycle related to their functions, during translation.

Rickets -- a vitamin D deficiency disease characterized by overproduction and deficient calcification of osteoid (bony) tissue, with associated skeletal deformities, enlargement of the liver and spleen, profuse sweating, and general tenderness of the body when touched.

Rigidity -- see stiffness.

RMS -- root mean square. Refers to a kind of average molecular speed; the speeds of individual molecules vary over a wide range of magnitude, with a characteristic temperature-dependent distribution of molecular speeds.

RNA -- see ribonucleic acid.

RNAase -- an enzyme that attacks bonds in RNA.

RNA polymerase -- an enzyme that synthesizes RNA under direction from a DNA template (formally described as DNA-dependent RNA polymerase).

Robot -- a programmable device usually consisting of mechanisms for sensing and mechanical manipulation, often connected to (or including) a computer that provides control.

Rough ER -- regions of endoplasmic reticulum that are associated with ribosomes.

Rouleaux -- stack-of-coins configuration of a cluster of red blood cells.

rRNA -- see ribosomal RNA.

Rugosity -- condition of being folded or wrinkled; surface roughness.

Sacculation -- formation into a sac or sacs; group of sacs, collectively.

Saccule -- the smaller of the two membranous sacs in the vestibule (central cavity) of the osseous labyrinth (the inner ear).

Sagittal -- in anatomy, a vertical plane or section that divides the body into right and left portions.

Salt bridge -- in biochemistry, an ionic bond between charged groups that are part of larger covalent structures; salt bridges occur in many proteins.

SAM -- in microscopy, a Scanning Acoustic Microscope; in polymer chemistry, a self-assembled monolayer or a spontaneously assembled monolayer.

Sanguinatation -- in medical nanorobotics, locomotion (especially swimming by a nanorobot) through the bloodstream.

Sapphirophagy -- eating sapphire (corundum).

Sarcoplasmic reticulum -- specialized, elaborate smooth ER, found in muscle cells.

Saturated -- a molecule which is a closed-shell species lacking double or triple bonds; forming a new bond to a saturated molecule requires the cleavage of an existing bond.

Scanning Electron Microscope (SEM) -- a kind of microscope that uses electrons rather than light.

Scanning Force Microscope -- see Atomic Force Microscope.

Scanning Probe Microscope (SPM) -- a class of microscope (including AFMs and STMs) that exploits physical interactions that are sensitive to the separation of a sample and a sharp tip.

Scanning Tunneling Microscope (STM) -- an instrument able to image conducting surfaces to atomic accuracy. A sharp conductive tip is moved across a conductive surface close enough (typically a nanometer or less) to permit a substantial tunneling current. In a common mode of operation, a constant voltage is established and the current is monitored and kept constant by controlling the height of the tip above the surface using a feedback circuit, ultimately producing an atomic-resolution map of the surface reflecting a combination of topography and electronic properties. Increasing the voltage enables a researcher to move atoms around, pile them up, or trigger chemical reactions.

Schistosomiasis -- a parasitic disease due to infestation with blood flukes; endemic throughout Asia, Africa, and tropical America.

Sclerosis (sclerotic) -- hardening of a tissue or organ, especially due to excessive growth of fibrous tissue; also, thickening and hardening of the tissue layers comprising the walls of an artery.

Scurvy -- a vitamin C deficiency disease characterized by hemorrhagic manifestations and abnormal formation of bones and teeth, including spongy condition of the gums, sometimes with ulceration.

Self-assembly -- see Brownian assembly.

Semaphores -- see presentation semaphores.

Semicircular canals -- superior, posterior, and inferior passages forming part of the inner ear.

Semilunar -- shaped like a crescent.

Sepsis -- the presence of various pus-forming and other pathogenic organisms, or their toxins, in the blood or tissues.

Septic -- pertaining to or caused by sepsis.

Septicemia -- septic fever; systemic disease caused by the multiplication of microorganisms in the circulating blood.

Septum -- a wall dividing two cavities (e.g. the interalveolar septa between the alveoli).

Serotonin -- a biochemical substance, 5-hydroxytryptamine (5-HT), that is present in platelets, gastrointestinal mucosa, mast cells, and in carcinoid tumors. Serotonin is a potent vasoconstrictor involved in neural mechanisms important in sleep and sensory perception.

Serous membrane -- a membrane lining a serous cavity, specifically the pleural (lung), peritoneal (abdominal), and pericardial (heart) cavities.

Serum -- the watery portion of the blood after coagulation; a fluid found when clotted blood is left standing long enough for the clot to shrink. More generally, any serous fluid, especially the fluid that moistens the surfaces of serous membranes.

Sessile -- incapable of voluntary movement. Opposite of motile.

Shear -- a shear deformation is one that displaces successive layers of a material transversely with respect to one another, like a crooked stack of cards. Shear is a dimensionless quantity measured by the ratio of the transverse displacement to the thickness over which it occurs.

Shear modulus -- shear stress divided by shear strain (units of force per unit area).

Shirr -- a series of parallel rows of short, running stitches with gatherings between rows.

Sinoatrial node -- a node at the junction of the superior vena cava with the right cardiac atrium (one of the upper chambers of the heart), regarded as the starting point of the heartbeat.

Sinusoid -- resembling a sinus (a cavity having a relatively narrow opening); a minute blood vessel found in such organs as the liver, spleen, adrenal glands, and bone marrow, that is slightly larger than a capillary and has a lining of reticuloendothelium.

Site-directed mutagenesis -- see mutagenesis.

Smooth ER -- in cell biology, regions of endoplasmic reticulum that are devoid of ribosomes.

SNR -- signal-to-noise (power) ratio.

Solenoid -- in physics and electrical engineering, a coil of wire carrying an electric current; an electromagnet.

Solute -- the dissolved substance in a solution.

Solvation -- the process of dissolving a solute in a solvent, making a solution.

Solvent -- a substance, usually a liquid, that can hold another substance in solution.

Somatic -- in general, relating to the body, as opposed to the mind or soul; corporeal.

Somatic cell -- in cell biology, all the cells of an organism except those of the germ line (gametes).

Somatography -- a physical description (and mapping) of the human body.

Somesthesis -- sensations from the skin and viscera, including pressure, warmth, cold, and pain.

Sonication -- to bombard with high-energy acoustic waves, often for the purpose of fragmenting or destroying the sonicated object.

Sonolucent -- in ultrasonography, the condition of not reflecting the ultrasound waves back to their source.

Sonoluminescence -- generation of visible light during high-powered sonication of a fluid, usually water.

Sortation -- the act of separating or sorting, especially of molecular species.

Sorting rotor -- see molecular sorting rotor.

Species -- in chemistry, a distinct kind of molecule, ion, or other structure.

Specific gravity -- relative density, as a ratio to the density of pure water.

Specificity -- in biochemistry, defines the degree to which a receptor can distinguish between similar ligands.

Specular reflection -- in physics, reflection as from a mirror, requiring that the wavelength of the reflected wave is smaller than the characteristic dimension of the reflector.

Sphincter -- in anatomy, circular muscle constricting an orifice. In normal tonic (i.e. under tension or in contraction) condition, it closes the orifice; the muscle must relax in order to allow the orifice to open.

Spindle -- in cell biology, the reorganized structure of a eukaryotic cell that is passing through mitosis (cell division); the nucleus has been dissolved and chromosomes are attached to the spindle by microtubules.

Splenic -- pertaining to the spleen.

SPM -- see Scanning Probe Microscope.

Sputum -- substance expelled by coughing or clearing the throat.

Squamous cell -- a flat, scaly epithelial cell.

SQUID -- superconducting quantum interference device.

Stable -- in the physical sciences, a system is termed stable if no rearrangement of its parts can produce a system having lower free energy; in biology, a living system is stable so long as homeostasis can be maintained.

Stationkeeping -- active maintenance of location in a specific physical place, area, or volume.

Stellate -- star-shaped.

Steric -- pertaining to the spatial relationships among atoms in a molecular structure; in particular, pertaining to the space-filling properties of a molecule.

Steric hindrance -- in chemistry, slowing of the rate of a chemical reaction owing to the presence of molecular structures possessed by the reagents that mechanically interfere with the motions associated with the reaction, typically by obstructing the reaction site; in hematodynamics, the reduction in hematocrit near small blood vessel bifurcations due to the elongation and orientation of red cells along the direction of shear flow.

Stereochemistry -- the branch of chemistry concerned with the three-dimensional spatial relationships among atoms in molecules and the effects of such relationships on the properties (especially optical rotation) of molecules.

Stereoisomers -- isomeric forms that have different configurations in space; may be geometric (non-enantiomeric, achiral) or enantiomeric (chiral).

Steroids -- a large family of chemical substances, comprising many hormones, vitamins, body constituents, and drugs, each containing the tetracyclic cyclopentophenanthrene skeleton.

Stewart platform -- in engineering, a manipulator employing a 6-DOF mobile platform.

Sticky ends -- in biochemistry, complementary single strands of DNA that protrude from opposite ends of a duplex or from ends of different duplex (two-stranded) molecules; can be generated by staggered cuts in duplex DNA.

Stiffness -- in mechanical engineering, the stiffness of a system with respect to a deformation (e.g. the stiffness of a spring with respect to stretching) is the second derivative of the energy with respect to the corresponding displacement. Positive stiffness is associated with stability, and a large stiffness can result in a small positional uncertainty in the presence of thermal excitation. Negative stiffnesses correspond to unstable locations on the potential energy surface.

Stirling engine -- invented by Robert Stirling in 1816; generates power not by burning fuels explosively in an otherwise empty cylinder, but by heating and cooling working gas from the outside of a cylinder which always contains a pressurized working gas.

STM -- see Scanning Tunneling Microscope.

Stoichiometric -- in chemistry, pertaining to the precise quantities of reagents required to complete a chemical reaction; in particular, to the exact amounts needed to balance the chemical reaction equation.

Strain -- in mechanical engineering, strain (a dimensionless quantity) is a measure of the deformation resulting from stress (an applied force per unit area); the displacement of one point with respect to another, divided by their equilibrium separation in the absence of stress. In chemistry, a molecular fragment generally has some equilibrium geometry (e.g. bond lengths, interbond angles) when the rest of the molecular structure does not impose special constraints (e.g. bending bonds to form a small ring); deviations from this molecular equilibrium geometry are described as strain, and increase the energy of the molecule. Strain in the mechanical engineering sense also causes strain in the chemical sense.

Stratum corneum -- in anatomy, the outermost (horny) layer of the epidermis, consisting of many layers of flat, keratinized, enucleated cells.

Streamline -- the movement or flow of a small portion of fluid, especially in relation to a solid body which lies in the path of this flow. Compare turbulence.

Stress -- in mechanical engineering, the force per unit area applied by one part of an object to another. Pressure is an isotropic compressive stress. Suspending a mass from a fiber places the fiber in tensile stress. Gluing a layer of rubber between two plates and then sliding one plate over the other (while holding their separation constant) places the rubber in shear stress. Twisting one end of a rod while holding fixed the other end places the rod in torsional stress.

Striated -- striped; marked by streaks or striae (lines or bands elevated above or depressed below surrounding tissue, or differing in color or texture).

Stroma -- foundation-supporting tissues of an organ, defining the framework of an organ; opposite of parenchyma.

Sublimation -- in chemistry, passing directly from solid to vapor state.

Submaxillary -- below the maxilla (upper jaw).

Substrate -- in biology, the substance acted upon and changed by an enzyme; in replicator theory, the set of all material inputs to the replication process.

Superconductivity -- in physics, a physical phenomenon in which the electrical resistance of certain materials drops to zero at moderate or low temperatures.

Superficial -- near the surface of the skin, as opposed to keep inside the body.

Superior -- upper or higher than; situated above something else. See also cephalic.

Supine -- lying on the back, with the face up.

Suppuration -- producing or associated with the generation of pus, often involving an infection with pyogenic (pus-forming) bacteria.

Supraglottal -- located above the glottis.

Supramolecular chemistry -- the study of interactions between molecules; chemistry beyond the molecule; the chemistry of the noncovalent bond.

Surfactant -- in physical chemistry, a chemical agent that lowers surface tension.

Sympathetic (nervous system) -- a major component of the autonomic nervous system, consisting of ganglia, nerves (mostly motor, some sensory), and plexuses that supply the involuntary muscles.

Synapse -- the point of junction between two neurons in a neural pathway, where the termination of the axon of one neuron comes into close proximity with the cell body or dendrites of another neuron.

Synovial membrane -- a membrane lining the capsule of a joint.

Synthesis -- in chemistry, the production of a specific molecular structure by a series of chemical reactions.

System -- in engineering usage, a set of components working together to serve a common set of purposes.

Systems theory -- in clinical medicine, an approach that considers the human being as a whole as opposed to his parts; human beings are considered as open systems constantly exchanging information, matter, and energy with the environment.

Systole -- the normal period in the heart cycle during which the muscle fibers tighten and shorten, the heart constricts, and the cavities empty of blood; roughly, the period of contraction alternating with diastole or relaxation. Occurs in the interval between the first and second heart sounds during which blood is surged through the aorta and pulmonary artery.

Tachometer -- a device for measuring the speed of rotation.

Tachyiatria -- the art of curing quickly.

Teleoperation -- remote control.

Telepresence -- in control engineering, teleoperation with full sensor feedback (see virtual reality system).

Telomerase -- in biochemistry, the ribonucleoprotein enzyme that creates repeating units of one strand at the telomere, by adding individual bases.

Telomere -- the natural end of a chromosome; the telomeric DNA sequence consists of a simple repeating unit (in humans, TTAGGG) with a protruding single-stranded end that may fold into a hairpin.

Telophase -- the final stage of mitosis (cell division), in which chromosomes at opposite spindle poles begin to decondense as spindle fibers disappear and the nuclear membrane reforms.

Temperature -- a system in which internal vibrational modes have equilibrated with one another can be said to have a particular temperature; two systems are at different temperatures if heat flows between them when they are brought into physical contact. The most common measurement units of temperature are Centigrade or Celsius (^oC), Fahrenheit (^oF), and Kelvin (K).

Temporal -- pertaining to time.

Tensile -- pertaining to extension or stretching.

Teragravity -- one trillion times normal terrestrial gravity.

Tessellation -- in physical geometry, laid out or paved in a mosaic pattern of small squares or blocks, usually with the objective of completely covering a surface or completely filling a volume.

Tetanic -- in medicine, tending to produce spasms characteristic of tetanus.

Tether -- a cable, tube, or other physical linkage that allows information, matter, or energy to flow between two or more objects.

Thermal conductivity -- transport of thermal energy due to a temperature gradient; the energy flux (W/m²) per unit of spatial temperature gradient (K/m) equals the coefficient of thermal conductivity (W/m-K).

Thermal energy -- the internal energy present in a system as a result of the energy of thermally equilibrated vibrational modes and other motions (including both kinetic energy and molecular potential energy); the mean thermal energy of a classical harmonic oscillator is kT.

Thermal expansion coefficient -- the rate of change of length with respect to temperature for a particular material.

Thermogenesis -- the production of heat, especially in the body (e.g. by shivering).

Thermogenic limit -- in medical nanorobotics, the maximum amount of waste heat that may safely be released by a population of in vivo medical nanorobots that are operating within a given tissue volume.

Thermography -- temperature mapping of the human body.

Thiol -- in chemistry, an -SH group, or a molecule containing such a group; also known as a sulfhydryl or mercapto group.

Thoracic -- in anatomy, pertaining to the chest or thorax.

Thorax -- that part of the body between the base of the neck superiorly and the diaphragm inferiorly.

Thrombus -- blood clot.

THz -- terahertz; trillions of cycles per second.

Tight-receptor structure -- in molecular nanotechnology, a molecular receptor structure in which a bound ligand of a particular kind is confined on all sides by repulsive interactions. A tight-receptor structure discriminates strongly against all molecules larger than the target.

Tinnitis -- a subjective ringing or tinkling sound in the ear.

Titer -- in analytical chemistry, the standard of strength of a volumetric test solution; assay value of an unknown measure by volumetric means.

T-lymphocytes (T-cells) -- White blood cells that are produced in the bone marrow but later mature in the thymus. T-cells are important in the body's defense against certain bacteria and fungi, help B-cells make antibodies, and assist in the recognition and rejection of foreign tissues.

Tomography -- a noninvasive imaging technique designed to show detailed images of structures in a selected plane of tissue by blurring images of structures in all other planes.

Tonic (muscular) -- refers to muscles arranged around hollow structures that contract slowly and can hold for a long period of time. Compare phasic.

Tonic (osmotic) -- see isotonic.

Tonic (physiological) -- pertaining to or characterized by tension or contraction; in a state of continuous action, denoting especially a muscular contraction.

Top-down -- an approach to nanotechnology that aims to construct nanodevices by progressive miniaturization of existing bulk components.

Torque -- in physics, a force that produces torsion.

Torsional -- relating to, producing, or resulting from twisting.

Toxic shock -- a disease caused by the release of toxins produced by certain strains of various bacteria.

Trabecular -- inner part of organ or body.

Transcription -- synthesis of RNA on a DNA template.

Transcutaneous (percutaneous) -- effected through the skin.

Transdermal -- through the skin.

Transducer -- any mechanism or device that can convert energy or signals from one physical form to another.

Transduction -- in physics and engineering, the conversion of energy or signals from one form to another; in biology and biotechnology, a phenomenon causing genetic recombination in bacteria in which DNA is carried from one bacterium to another, usually by a bacteriophage.

Transendothelial migration -- see diapedesis.

Transfer RNA (tRNA) -- the adaptor RNA that carries amino acid residues into polypeptide linkage during translation, as the codon sequence in mRNA is read.

Transgenic organism -- in biotechnology, an organism modified by the insertion of foreign genetic material into its germ line cells. Recombinant DNA techniques are commonly used to produce transgenic organisms.

Translation -- in biochemistry, the synthesis of protein on the mRNA template; the process of reading the codon sequence in mRNA to synthesize the corresponding polypeptide with the involvement of ribosomes, tRNA, and many enzymes.

Transmembrane -- crossing the plasma membrane of a living cell.

Transmembrane protein -- in cell biology, a membrane component, wherein a hydrophobic region or regions of the protein resides within the membrane, and hydrophilic regions are exposed on one or both sides of the membrane. See integral membrane protein.

Transtegumental -- crossing or passing through the skin or covering of a body.

Transvenue outmessaging -- in medical nanorobotics, outmessaging from the nanorobots present within the body of one patient to the nanorobots present in another (physically separated) human body.

Transverse -- horizontal, hence at right angles to both sagittal and coronal sections, dividing the body into upper and lower portions; more generally, extending crossways or from side to side.

Triage -- in emergency medicine, the screening of sick and wounded patients during war, disasters, or other emergencies. During triage, patients are classified into one of three groups: (1) those who will not survive even if given treatment, (2) those who will recover without treatment, and (3) those who need treatment in order to survive (the priority treatment group).

Tribology -- the study of friction.

Trichinosis -- a pathogenic disease caused by ingestion of Trichinella spiralis in raw or insufficiently cooked infected pork.

Trillion -- this book follows the American convention in which a trillion is 10¹².

Trimer -- in chemistry, a compound of three similar or identical molecules.

Triple point -- a single condition of temperature and pressure in which three distinct phases of a substance (e.g. solid, liquid, and gas) can exist simultaneously and in equilibrium.

tRNA -- see transfer RNA.

Trypanosomiasis -- any disease caused by trypanosomes (asexual protozoan flagellates parasitic in the blood plasma of many vertebrates).

Tubulin -- a protein present in the microtubules of cells, which are polymers of alpha tubulin (~53,000 dalton) and beta tubulin (~55,000 dalton) dimers.

Tunneling -- in quantum physics, a probabilistic effect in classically-forbidden transitions that is a consequence of the wave nature of matter. In classical physics, a particle or system cannot penetrate regions of negative energy (e.g. barrier regions in which the potential energy is greater than the system energy). In quantum physics, a wave function of significant amplitude may extend into and beyond such regions; if the wave function extends into another region of positive energy, the barrier is crossed with some nonzero probability, a process called tunneling (since the barrier is penetrated rather than climbed).

Turbulence -- in hydrodynamics, fluid flow which does not follow parallel streamlines, which has a blunt (nonparabolic) profile in tube flow, and often involves eddies, vortices, and significant variations in fluid velocities, accelerations and shear stress between adjacent fluid elements. Turbulence dissipates more energy, and presents more resistance to flow, than laminar flow.

Turgid -- swollen.

Turing machine -- a programmable computing device.

Tympanic -- pertaining to the tympanum (the middle ear or tympanic cavity; eardrum).

Ubiquitin -- a small protein present in eukaryotic cells that combines with other proteins and makes those other proteins susceptible to destruction; this protein is also important in promoting the functions of proteins that make up the ribosomes.

Ullage -- the amount by which a fluid container falls short of being full.

Ultrasonic -- inaudible (to human ears) sounds with frequencies greater than ~20,000 Hz.

Unsaturated -- possessing double or triple bonds; capable of making additional covalent bonds.

Urethra -- a canal for the discharge of urine extending from the bladder to the outside of the body.

Urticaria -- vascular reaction of the skin characterized by the eruption of pale evanescent wheals (round elevations of the skin, white in the center with a pale red periphery), which are associated with severe itching; hives.

UTC -- see coordinated universal time.

Utricle -- the larger of the two membranous sacs in the vestibule (central cavity) of the osseous labyrinth (the inner ear).

UV -- ultraviolet.

Uveitis -- a nonspecific term for any intraocular inflammatory disorder, usually of the uveal tract structures (iris, ciliary body, and choroid, forming the pigmented layer) although nonuveal parts such as the retina and cornea may also be involved.

Valence -- in chemistry, regarding covalent compounds, the valence of an atom is the number of bonds that the atom forms to other atoms. In immunology, antiserum contains antibodies that may have specificity for one (monovalent) or more (polyvalent) antigens.

Vallate papilla -- one of a group of papillae (small nipple-like protuberances or elevations) forming a V-shaped row on the posterior dorsal surface of the tongue.

Van der Waals forces -- weak electrostatic forces between atoms and molecules; any of several intermolecular attractive forces not resulting from ionic charges; also known as the London dispersion force.

Vascular -- containing, or pertaining to, blood or lymph vessels.

Vasculocyte -- in medical nanorobotics, a theorized (nanorobotic) device capable of performing repairs of an injured vascular luminal surface.

Vasculography -- a physical description (and mapping) of the human vascular system.

Vasoconstriction -- in physiology, a decrease in the diameter of blood vessels.

Vasodilation -- in physiology, an increase in the diameter of blood vessels.

Vaults -- in cell biology, barrel-shaped protein particles found in the cytoplasm, that are of the right size size and shape to be able to dock at the nuclear pore complex.

Vein -- in anatomy, generally, a blood vessel that returns blood from the tissues to the heart.

Velum palatinum -- the soft palate.

Vena cava -- the largest vein in the human body, leading toward the heart.

Venesection -- blood-letting (phlebotomy, venotomy).

Ventral -- the front of the human body, hence on or nearest the abdominal surface; pertaining to the belly.

Ventricle -- either of two lower chambers of the heart.

Ventricular fibrillation -- the primary mechanism and arrhythmia seen in sudden cardiac arrest (cessation of blood circulation).

Vernier -- a short, graduated scale, permitting accurate measurement of the relative movement of mechanical parts.

Vertigo -- the sensation of moving around in space; sometimes used as a synonym for dizziness, lightheadedness, or giddiness.

Vesicles -- small bodies bounded by membrane, derived by budding from one membrane and often able to fuse with another membrane.

Vesicles (endocytotic) -- membranous particles that transport proteins through endocytosis; also known as clathrin-coated vesicles, having on their surfaces a layer of the protein clathrin.

Vesicles (exocytic) -- membranous particles that transport and store proteins during exocytosis.

Vestibular senses -- sensory receptors in the labyrinth of the human inner ear that respond to human head position and movement, imparting a sense of balance.

Virion -- a physical virus particle.

Virtual reality system -- a combination of computer and interface devices (goggles, gloves, etc.) that presents a user with the illusion of being in a three dimensional world of computer-generated objects. These three dimensional environments and force-feedback systems can aid in the visualization of complex molecules, and in telepresence systems.

Virucide -- the destruction of active or dormant virus particles.

Virus -- A parasite (consisting primarily of genetic material enclosed in a protein capsid shell) that invades cells and takes over their molecular machinery in order to copy itself.

Viscera -- internal organs enclosed within a cavity, especially the abdominal organs.

Viscosity -- resistance of a fluid to shearing, when the fluid is in motion.

Vitamins (biology) -- a group of organic substances, present in minute amounts in natural foodstuffs, that are essential to normal metabolism, growth, and development of the body. Vitamins serve principally to regulate metabolic processes and to play a role in energy transformations, usually acting as coenzymes in enzymatic systems. See also coenzyme.

Vitamins (engineering) -- in machine replication theory, vitamin parts are components of a self-replicating machine which the machine is incapable of producing itself, therefore these vital parts must be supplied from an external source.

Vitreous humor -- in anatomy, a delicate network enclosing in its meshes a clear watery fluid filling the interior of the eyeball behind the lens.

Volitional normative model of disease -- in medical nanorobotics, disease is said to be present in a human being upon either: (1) the failure of optimal physical (e.g. biological) functioning, or (2) the failure of desired (by the patient) functioning.

Vomeronasal organ -- in anatomy, a small tubular epithelial sac lying on the anteroinferior surface of the nasal septum.

Voxel (volume pixel) -- abbreviation for volume element; a single cubic cell within a three-dimensional geometric solid grid or array.

W -- watt (MKS unit of power).

Watt governor -- in control engineering, a governor is a mechanism by which the speed of an engine, turbine, wheel, or motor may be regulated. The Watt governor employs rotating weights attached to a pivoted lever arm; the weights extend as the pair rotates faster, depressing the attached lever arm and throttling the motor down, thus slowing the rotation, and vice versa.

Wave function -- in quantum mechanics, a complex mathematical function extending over the configuration space of a material system.

WBC -- white blood cell (see leukocyte).

White blood cell (WBC) -- see leukocyte.

Whitlow -- in medicine, a suppurative inflammation at the end of a finger or toe.

Work -- in physics, the energy transferred by applying a force across a distance; for example, lifting a mass does work against gravity and stores gravitational potential energy.

WWV -- a radio station that continuously broadcasts the exact Coordinated Universal Time.

Xenotransplantation -- transplantation of cells or organs from an organism of a different species.

Xerophthalmia -- a vitamin A deficiency disease, characterized by extreme dryness of the conjunctiva with keratinization of epithelium.

Young's modulus -- in mechanical engineering, a modulus relating tensile (or compressive) stress to strain in a rod that is free to contract or expand transversely. The relevant measure of strain is the elongation divided by the initial length (see also strain and stress).

Zippocytes -- in medical nanorobotics, a theorized medical nanorobot that can rapidly perform incision-wound repairs to the dermis and epidermis; dermal zippers.

Zwitterions -- dipolar ions that contain positive and negative charges of equal strength, and are therefore not attracted to either anode or cathode; in a neutral solution, some amino acids function as zwitterions.

Zymogenic -- pertaining to a substance (a zymogen or proenzyme) that develops into an enzyme capable of producing or causing fermentation or digestion (e.g. pepsinogen, trypsinogen); a cell that produces zymogens (proenzymes).

Last updated on 28 February 2003