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Microgravity Research Opportunities for the 1990s: Appendix A Microgravity Research Opportunities for the 1990s A Glossary Advective: A mode of heat and species transport associated with the directed motion of a fluid as often induced by volume changes accompanying phase transformations. Anisotropic: The variation of some material property with respect to direction or spatial orientation. REPORT MENU NOTICE MEMBERSHIP Austenite: The high-temperature phase in steel consisting of carbon dissolved in PREFACE face-centered cubic iron. EXECUTIVE SUMMARY PART I Batch technique: One of several strategies for crystallization in which a CHAPTER 1 supersaturated condition for one dissolved component is established by mixing CHAPTER 2 solutions and other additives into a single batch solution. In the typical application, PART II this solution is then left undisturbed during precipitation of the supersaturated CHAPTER 3 component in the form of crystals. CHAPTER 4 CHAPTER 5 CHAPTER 6 Biochemical assays: Methods of detecting and monitoring protein or other CHAPTER 7 biological activities. The activity of an enzyme, for example, may be monitored by PART III the disappearance of reactants or the appearance of products from the reaction it CHAPTER 8 catalyzes. APPENDIX A APPENDIX B Biological macromolecule: One of a diversity of large molecules (relative molecular weights typically 5000 or more) characteristic of biological systems, such as proteins, nucleic acids (e.g., DNA), and polysaccharides. file:///C|/SSB_old_web/mgoppappenda.htm (1 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Biomimetic synthesis: Synthesis by processes that mimic those found in biological systems. An example is the composite organic mineral structure of abalone shell. Bridgman: A technique for effecting bulk crystal growth by application of a temperature gradient to a solution of the components. Calorimetry: A classical measurement technique based on the temperature change observed in a material arising from the admission or release of a known quantity of heat energy. Cell fusion: The merging of more than one cell into a single entity surrounded by a composite membrane, with concomitant mixing of cell contents. Cell matrix: A structural component organizing and shaping cells in organs and tissue. A common molecular component of mammalian matrix is collagen. Chemotaxis: A behavioral response of certain living organisms mediated by interactions of a receptor with a specific chemical that causes movement of the organism in response to a gradient in concentration of the chemical. An example is the movement of certain bacteria toward the source of a soluble nutrient. Chromatography: A collection of methods for separating solution components by differential flow rates through a porous medium due to differences in size, charge, or binding affinity for the medium. Coercivity: The magnitude of the magnetic field intensity required to reverse the magnetic induction from one state of magnetization to its opposing orientation. Commercial enzymes: Although biological materials have been used in generating products of commercial value for centuries, in recent times the sources of the utility of some of these materials have been identified as enzymes, an example of which is rennin, an enzyme used in commercial cheese production. More recently, interest has grown in the design and manufacture of enzyme products with commercial value. An example is the engineering of thermostable protein-degrading enzymes such as subtilisin as additives conferring improved stain-removing properties on laundry products. Constitutive equations: Equations that relate electric displacement with electric field intensity and magnetic induction with magnetic field intensity. Containerless: The description of materials processes carried out in microgravity that precludes the need for a supporting vessel or crucible and thereby eliminates sources of contamination at high temperatures. Convective: A mode of heat and species transport in fluid systems caused by bulk (macroscopic) motion of the fluid. file:///C|/SSB_old_web/mgoppappenda.htm (2 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Cuprate superconductors: A class of high-temperature superconductors based on layered intermetallic compounds containing copper oxide and metals such as yttrium, barium, and bismuth. CVD: Chemical vapor deposition. Czochralski method: A technique for effecting bulk crystal growth in which a "seed" crystal grows by its gradual withdrawal from a stationary melt phase. Dendritic: A branched, tree-like, form of crystal growth, commonly occurring in the solidification of metals and alloys during casting and welding. Diffusivity: The transport coefficient that relates the net flux of species or heat flowing in response to a gradient of the concentration or temperature, respectively, established in the material. Electrofusion: Cell fusion facilitated by application of electric fields. Electromagnetic levitator: A device consisting of a high-frequency coil that provides a magnetic lifting force and heating for a conducting material placed within the coil. Electroosmosis: Transport across a semipermeable membrane driven by electrical potential difference. Electrophoresis: Separation of charged molecules based on differential mobilities in an imposed electrostatic field. Electrowinning: The process of recovery of metallics from low-grade ores by leaching the mineral with an acidic solution followed by electrolytic precipitation. Ellipsometry: An optical technique used for determining the index of refraction and other optical properties of the surface of a material by analyzing the elliptically polarized light reflected from the surface. Embryogenesis: The collection of complex developmental processes involved in going from ovum to embryo. Emissivity: The optical property of a material body that relates the absorbed energy flux for a given wavelength to that of a perfectly absorbing substance. Endocrine cell: A cell from one of a number of different glands that secrete molecules, known as hormones, that influence the behavior of other cells. Epitaxy: The growth on a crystalline substrate of a crystalline layer with an ordered file:///C|/SSB_old_web/mgoppappenda.htm (3 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A structure that is determined by the crystal structure of the substrate. As used in this report, the epitaxial layer has the same structure as the substrate. Eutectic: A thermodynamic reaction in which a liquid transforms into two solid phases upon cooling. Fermentation: A process involving enzymatically controlled breakdown of nutrients in the absence of air by living organisms such as yeast. Flammability limit: Mixture ratio limits of fuel to oxidizer above and below which a propagating flame will not sustain itself. g-jitter (gravity-jitter): The spectral range of oscillatory accelerations arising from crew motions, machinery, rocket firings, and so on, occurring in orbiting spacecraft. GBP: Gravity Probe-B—an experimental test of magnetogravitational effects predicted by Einstein's general theory of relativity. Genome: The collection of genetic material that encodes all of the components, the assembly, and the development of an organism. Glovebox: A hermetically sealed environment accessible to hand manipulation by gloves that are an integral part of the environmental enclosure. Glycoprotein: A protein that is modified after synthesis by the attachment of oligomeric assemblages of carbohydrate. The attachment sites and the nature of the attached carbohydrate are determined by the action of enzymes. Heterostructure: Term usually applied to semiconductors. A multilayered, single- crystal structure with the layers having different compositions, but with nearly defect- free interfaces as the result of being either lattice matched or thin enough that stress has not been relieved by the formation of defects. Hybridoma: A fused cell combining a cell with desired properties with a cancer cell that confers reproductive immortality on the fusion product. Hydrothermal growth: Synthesis in high-pressure aqueous systems at temperatures above 100°C. Hypereutectic: Describing compositions of an alloy that are above the eutectic point. Hysteresis: The memory effect exhibited in some property by systems changing from one state to another, such as from the magnetized to the unmagnetized condition. file:///C|/SSB_old_web/mgoppappenda.htm (4 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Immiscibility: The property of liquid alloys over certain temperatures, pressures, and compositions by which they separate into distinct phases, such as oil and water at room temperature and atmospheric pressure. Immunoglobulins: Proteins whose function it is to recognize and bind to dangerous or foreign molecules, matter, or cells, and to flag them for destruction or elimination. Incongruent melting: Melting with decomposition. Intercellular communication: The process by which cells influence the behavior of other cells in a multicellular organism. Communication occurs most commonly by chemical means and involves the interactions of a bewildering variety of secreted chemicals with specific cellular receptors. Intermetallic: Referring to phases of nearly fixed atomic proportions, usually exhibiting limited mutual solubility, and occurring away from the ends of the phase diagram. Isoelectronic: Having the same electronic structure. Isostatic pressing: A process for consolidating powders by application of pressure equally from all sides. Lambda point: For 4He, the temperature (2.1780 K), at atmospheric pressure, at which the transformation between the fluids helium I and helium II takes place. At this point the heat capacity of the system increases without limit as the transition temperature is approached from above or below. Landau-Darrieus instability: A fluid interface instability occurring when there is a density difference across the interface and mass transport across the interface. Lewis number: Nondimensional number consisting of the ratio of the thermal and mass diffusivities. Liposomes: Aqueous compartments enclosed by lipid bilayer membranes. Artificial liposomes are constructed to encapsulate substances for controlled delivery in biological systems. Liquid-liquid diffusion: A method of crystallization in which two different solutions, miscible or immiscible, are brought in contact to form an interface, with or without the benefit of a semipermeable membrane. Subsequent diffusion across the interface establishes a supersaturated condition for one of the dissolved components, typically a protein, resulting in precipitation of that component in the form of crystals. file:///C|/SSB_old_web/mgoppappenda.htm (5 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Liquidus: The curve giving the compositions and temperatures at which a liquid and a crystalline phase may coexist in thermodynamic equilibrium. LPE: Lambda-point experiment-a high-resolution determination of the heat capacity of liquid 4He at superfluid transition ( -point). Macromolecular: Referring to large molecules such as those found in biological systems, where a relative molecular weight of 2000 to 5000 daltons or greater is implied, or those studied by polymer sciences. Macrosegregation: The redistribution of solute atoms between the solid and liquid phases during solidification, with redistribution occurring over distances that are large compared to the size scale of the solid-liquid microstructure. Martensite: A hard, metastable phase occurring spontaneously in certain rapidly cooled (quenched) steels, consisting of iron and carbon with a tetragonal crystal structure. Membrane: A semipermeable molecular barrier. The most well known example, the cell membrane, surrounds the cell and separates the interior from external surroundings. The typical biological membrane is a bilayer of lipid molecules exposing polar head groups to both exterior and interior. Mesoscopic: Referring to a scale of size characterizing the microstructure of materials that typically fall in the range 10-5 to 10-2 cm (i.e., intermediate between microscopic and macroscopic). Metastable: The thermodynamic condition of a phase or assembly of matter in which the minimum energy state is not accessible without first passing through a state of higher energy. Such states can persist for long periods of time. Monoclonal antibody: A single specific immunoglobulin antibody reproduced in an immortalized cell line by artificial methods. Monodispersions: Polymer systems that are homogeneous in molecular weight. Monomer: A molecule consisting of a group of atoms that constitute the chain repeat of a polymer. Monotectic: A thermodynamic reaction in which a liquid alloy, upon cooling, separates into a new liquid phase and a crystalline phase. Nanomaterials: Generic designation of bulk solid and thin film materials prepared by special processing methods to consist of ultrafine crystallites with diameters of less than 10-8 m. Such materials have a preponderant number of their atoms in interfacial locations and as a consequence display unusual properties. file:///C|/SSB_old_web/mgoppappenda.htm (6 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Nanostructures: An arrangement of almost atomically thin, contiguous layers of semiconducting materials, usually operating as an optoelectronic device. Such devices often exhibit unusual behavior based on quantum effects that depend on the reduced dimensions of the crystalline layers. Nucleic acid (sequence): A linear polymer of a mixture of four purine- or pyrimidine-ribose-phosphate monomers. Depending on the type of ribose, the nucleic acid is either DNA or RNA. In genetically active DNA or RNA, the sequence of purines and pyrimidines, taken in triplets, encodes the sequence of amino acids in a protein. Oligomers: Polymers made up of two, three, or four monomer units. Organelle: One of several kinds of distinct particulate bodies, either entirely membranous or an organized unit surrounded by a membrane, found within cells. Most organelles-the cell nucleus is an example-are associated with important cell functions, and the cells that contain them (eukaryotic cells) are reckoned to be more advanced than those without (prokaryotic cells). Ostwald ripening: The general thermodynamic and kinetic tendency of dispersed collections of fine particles to interact and lower their energy by exhibiting shrinkage and eventual disappearance of smaller particles and simultaneous growth and dominance of larger particles. Peptide: Part or all of a protein. Any chemical entity including a peptide bond (i.e., a bond joining amino and carboxylate groups by elimination of a water molecule). Peritectic: A thermodynamic reaction in which a solid, upon heating, decomposes to a liquid phase and a new crystalline phase. pH: The negative logarithm (base 10) of the hydrogen ion concentration. In an aqueous solution, the accessible range of pH is from 1 to 14 by virtue of the dissociation of water. Acidic conditions have pH values lower than 7; basic, higher. Phase partitioning: Fractionation of mixtures based on differential solubilities of components in two or more immiscible phases. Polymerization: Chemical process in which individual monomers are converted into polymers. Polymers: Substances made up of large molecules formed by the union of simple molecules. Polymorphic: One of many possible crystallographic forms for a solid material of given chemical composition. file:///C|/SSB_old_web/mgoppappenda.htm (7 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Polyphase: A mixture or microstructure containing two or more coexisting phases. Precipitant: A compound or solution that, when added to the solution of a component that is to be precipitated, establishes a supersaturated condition for that component and causes the desired precipitation. Protein activity: The ability of a protein to perform its function. This function may require one or more of several different kinds of activities. If the protein is an enzyme, its activity is measured by its ability to catalyze a specific biochemical reaction. If the protein is a receptor on a cell surface, its activity is measured as its ability to recognize and bind a specific ligand and to transduce that ligand-binding event as a chemical signal within the cell. Proteins: Heterogeneous linear polymers of amino acids connected by peptide bonds in sequences specified by the genetic messages encoded in DNA. In aqueous environments, these molecules typically adopt characteristic three- dimensional folded structures that endow them with the properties required for the functions they perform. Pyrolysis: Gasification of a condensed-phase substance with, perhaps, chemical change by the application of heat. Rayleigh-Taylor instability: The instability of the interface separating two fluids having different densities when the lighter fluid is accelerated toward the heavier fluid. Receptor-ligand interactions: The collection of phenomena comprising and attending the recognition and binding of a receptor to a specific ligand molecule and the transduction of that event through the cell membrane. Recombinant DNA techniques: The collection of techniques that are the basis for genetic engineering capabilities. Included are isolation of a specific RNA message, cloning of DNA complementary to the message, insertion of this DNA into transferable genetic elements, and infection of a foreign host cell with these genetic elements for expression of the selected gene. Reynolds number: A dimensionless number indicating the ratio of inertial to viscous forces in a fluid flow. Ribosome: The assembly of proteins that translates a genetic instruction in the form of an RNA message and synthesizes the encoded protein. Shadowgraph, schlieren: Methods of making visible the disturbances in fluid flows by refracting light through density gradients in the fluids. Sintering: The process of powder particle bonding and coalescence by diffusion. file:///C|/SSB_old_web/mgoppappenda.htm (8 of 10) [6/18/2004 11:18:55 AM]
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Microgravity Research Opportunities for the 1990s: Appendix A Solutal: Referring to alloy additions and/or chemical impurities, such as solutal convection. SQUID: Superconducting Quantum Interference Device that provides state-of-the- art magnetic field measurements. Stoichiometry: The whole-number relationship between the number of moles of each element constituting a chemical compound. Stokes regime: Flows with a Reynolds number of less than 1. Superalloys: Any of the complex nickel-based alloys used for high-temperature service in gas turbines and jet engines. Supercool: Referring to the persistence of a (metastable) liquid phase at temperatures below the normal melting point, where, strictly speaking, only the crystalline form is thermodynamically stable. Thermocapillary: Referring to changes in surface tension due to temperature variations that can generate fluid motions. Thermodiffusion: The transport of matter induced by application of a temperature gradient. Thermophoresis: The kinetic phenomenon in which a small particle or molecule moves spontaneously and collinearly to the applied thermal gradient. Thermosolutal: Referring to combined convection effects arising from density gradients associated with alloy additions and temperature. Virus: One of a complex variety of parasitic particles capable of replicating itself by infection of a host cell and consisting in its simplest form of an RNA or DNA genome surrounded by a coat of viral protein. Viscoelastic: Referring to mechanical behavior in which both fluid-like (viscous) and solid-like (elastic) characteristics are exhibited. Weldments: A generic term referring to joints and connections between like and unlike materials made without mechanical fasteners, usually by fusing the materials together. file:///C|/SSB_old_web/mgoppappenda.htm (9 of 10) [6/18/2004 11:18:55 AM]