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1-10 A B C D E F G H I J K L M N O P Q R S T U V W XYZR+
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"R+" is an acronym used by NASA to identify time by relating to the landing of the Space Shuttle or any spacecraft. R stands for Return, so that R+2 means two days after the space craft returned to Earth.
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The R-R interval (normally about 0.8 seconds) is a measure of time lapsed between the R waves, electrical signals given off by the beating of the heart, and measured and recorded on an electrocardiogram (EKG). The R waves occur during the contraction (also called depolarization or systole) of the heart and are part of the QRS complex. An R wave is noticeable as the largest upward spike on the EKG recording of a normal heartbeat, usually measuring slightly less than one millivolt.
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R2A media is a non-selective media that supplies nutrients and support growth for a variety of heterotrophic bacteria. It is used in the isolation and total count of bacteria found in water.
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Radar is a method of detecting distant objects and determining their position, velocity, or other characteristics by analysis of very high frequency radio waves reflected from their surfaces. Radar also refers to the equipment used in such detecting.
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The radial immunodiffusion test is an agarose gel based test in which the antigen diffuses outward into an antibody-containing gel. A ring of precipitate is formed which provides visual evidence of equivalence and concentration is evaluated by measuring the diameter of the arc.
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Radiation is energy in the form of particles or waves emitted in straight lines from a source such as a star or the nucleus of unstable radioactive atoms.
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Radiation biology is the study of the ways in which radiation affects biological tissue and organisms.
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A radiation dose is the quantity of radiation received.
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Radioactive describes the spontaneous disintegration of atomic nuclei accompanied by the emission of small particles. Depending on the type of emission, scientists define alpha (helium nuclei), beta (electrons or positrons), and gamma radiation (short-wavelength electromagnetic waves).
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Radioactive carbon is an isotope of carbon with two extra electrons, also known as carbon-14. Carbon-14 is used in life sciences research to mark metabolic compounds. In carbon dating it is used to determine, for example, the age of dinosaur bones.
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Radioimmunoassay refers to a method of measuring hormones in the blood. Most hormones are present in extremely minute quantities, and require a highly sensitive technique such as this. In radioimmunoassay, an antibody is developed that is highly specific for the hormone being measured. A small quantity of the antibody is mixed with a quantity of fluid (usually plasma) containing the hormone to be measured. Standard hormones, tagged with a radioactive isotope, are also added to the mixture. There is not enough antibody to bind with both the tagged hormone and with the hormone to be measured. The natural hormone and the tagged hormone compete for binding sites. The quantity of each of the hormones that binds is proportional to the concentration of each. After binding has reached equilibrium, the quantity of radioactive hormone bound with antibody is measured. If a large amount of radioactive hormone has bound with antibody, then only a small amount of natural hormone was available to compete with the radioactive hormone.
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Radioenzymatic assay is an enzyme used as the indicator system; when the enzyme and the antigen-antibody complex bind, a color indicator or other easily recognizable sign occurs.
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Radiograph is a medical term for an X-ray. It is a film produced by X-ray.
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Radiography is a method of examining the body by directing X-rays through it to produce images called radiographs on photographic plates or fluorescent screens. Radiography is used to diagnosis such disorders as broken bones, gastric ulcers, and stones in the kidney or gallbladder, when inspection from outside the body is insufficient for diagnosis. Radiography is also used in dentistry for detecting dental cavities and other such diagnoses.
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Radioimmunoassay refers to a method of measuring hormones in the blood. Most hormones are present in extremely minute quantities, and require a highly sensitive technique such as this. In radioimmunoassay, an antibody is developed that is highly specific for the hormone being measured. A small quantity of the antibody is mixed with a quantity of fluid (usually plasma) containing the hormone to be measured. Standard hormones, tagged with a radioactive isotope, are also added to the mixture. There is not enough antibody to bind with both the tagged hormone and with the hormone to be measured. The natural hormone and the tagged hormone compete for binding sites. The quantity of each of the hormones that binds is proportional to the concentration of each. After binding has reached equilibrium, the quantity of radioactive hormone bound with antibody is measured. If a large amount of radioactive hormone has bound with antibody, then only a small amount of natural hormone was available to compete with the radioactive hormone.
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A radioisotope is an unstable radioactive isotope that decays to a stable state by emitting radiation.
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Radiology is the science of high-energy radiation and of the sources and the chemical, physical, and biologic effects of such radiation. It is also the branch of medicine concerned with the use of radiation for the diagnosis and treatment of disease.
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A radiometer is a device for determining the penetrative power of X-rays; also called a roentgenometer.
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The radius is the outer and shorter bone of the forearm.
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A raster is the pattern formed by a scanning beam (such as an electron beam) when it moves from side to side and top to bottom so that the beam scans the entire object. It is also a pattern of dots that form an image, such as that on a television or computer screen.
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Readaptation is the adjustment of the organism and its physiological processes to its previous state. For example, after being in microgravity or weightlessness, astronauts must readapt to earth gravity by strengthening their muscles.
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Real-time is a term used to describe an activity as it is occurring. For example, if a researcher on Earth is engaged in a conversation with an astronaut in space, the event is said to occur in real-time. Listening to a recording of this conversation at a later date would not be considered real-time.
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Recovery refers to the day and time when the spacecraft lands and human, animal and plant organisms are re-introduced to earth gravity; sometimes abbreviated R+0, to indicate zero days after recovery, i.e., day of landing.
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Recumbency is the state of lying back or reclining.
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Recumbent means lying down or leaning backwards.
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A red blood cell contains the pigment hemoglobin, which has the principle role of the transport of oxygen.
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Red blood cell mass is the amount of red blood cells in the body.
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Reflectance is the ratio of the total radiant flux, as of light, reflected by a surface to the total striking the surface.
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The Regulatory Physiology discipline is composed of seven subdisciplines: 1) Circadian Rhythms (biological rhythms like the sleep/wake cycle), 2) Endocrinology (study of the regulation of body processes by hormones), 3) Fluid and Electrolyte Regulation (regulation of body fluid and electrolytes by the kidneys and by specialized mechanisms), 4) Hematology (study of red blood cells and their production), 5) Immunology (study of the immune system which protects the body from infection), 6) Metabolism and Nutrition, and 7) Temperature Regulation.
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Relativistic particles are particles that move at such high speeds (close to the speed of light) that their properties (such as mass) change significantly in accordance with the theory of relativity. An example is a relativistic electron.
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REM, or Rapid Eye Movement, refers to a certain phase of sleep during which the muscles of the eyeballs are in constant motion behind the eyeballs. This is the phase in which dreaming is thought to occur.
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REM latency is defined as the elapsed time from sleep onset, i.e., the first appearance of Stage 2 sleep until the onset of the first REM period of the night.
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Remote sensing is the ability to measure, observe or study something distant through the use of special instruments, devices or electronics, such as the use of satellites to study crop growth.
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"Renal" refers to relating to the kidney.
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Renal clearance is used to express the ability of the kidneys to clean or clear the plasma of various substances.
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Renal physiology is the study of the processes, metabolism and function of the renal system, which is composed of the kidneys as its main component.
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A renal stone, or kidney stone, is a hard pebble-like mass commonly composed of calcium oxalate that forms within the kidney. Some kidney stones cause pain and must be removed from the body using surgery or ultrasound techniques.
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Renal stones are formed from the renal stone-forming salts calcium oxalate, calcium phosphate, uric acid, struvite and cystine. The most common substance making up renal stones is calcium oxalate, which makes up about 70% of all formed stones.
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The renal system contains the kidneys as its primary component. The system functions primarily to regulate the fluid and electrolyte balance throughout the body by controlling the thirst sensation and the urinary excretion process.
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Renal, fluid and electrolyte physiology is the study of fluid and electrolyte regulation within the body. The kidneys regulate the body's fluid and electrolyte balance. If kidney (renal) function is impaired, dehydration, loss of electrolytes and dysfunction of the circulatory system result.
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Renin converts angiotensinogen to angiotensin, a substance which constricts blood vessels.
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A gene whose phenotype can be assayed in a transformed organism, and which is used in, for example, promoter bashing to show when and where a gene is functioning in a plant or cell.
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A Reserve Science Activity is a science activity that is not scheduled in the crew timeline. These activities are performed when additional crew time becomes available.
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Residual volume (RV) is the volume of air still remaining in the lungs after the most forceful expiration; this volume averages about 1200 ml.
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Resolidification is the term used to describe the solidification of a material, such as a alloy, metal or salt, after it is treated and has become more fluid. The term resolidification indicates that the material was solid before the treatment began. Examples for such treatments are heating up or applying pressure or combinations of both.
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Resolution is the ability optically to distinguish details such as the separation of closely approximated objects.
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Resorption is the act of removal by physiological absorption.
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Respiration is the act of breathing air into and out of the lung so that vital gases can be absorbed into the body.
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Respiratory means relating to breathing, i.e., inhaling and exhaling (respiration).
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The respiratory exchange ratio is the ratio of carbon dioxide output to oxygen intake. The value changes under different metabolic conditions, but the average value is considered to be 0.825.
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The respiratory quotient is the ratio of carbon dioxide output to oxygen usage.
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Respiratory rate is the rate of breathing (respiration) expressed as breaths per minute.
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Respiratory syncytial virus is an RNA-containing virus of the genus Pneumovirus that causes minor respiratory infection with rhinitis and cough in adults, but is capable of causing bronchitis and bronchopneumonia in young children; named for its tendency to form syncytia in tissue culture.
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The respiratory system is the combination of organs and tissues associated with breathing. It includes the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and lungs (and also the diaphragm and other muscles associated with breathing movements).
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Retention is the process of holding back, or retaining. During the excretion of fluids from the body by the kidneys, electrolytes and other substances dissolved in urine are excreted, while retention of water occurs, producing a more concentrated urine.
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A reticulocyte is an immature red blood cell or erythrocyte.
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Reticuloendothelial refers to a tissue that consists of phagocytic cells lining the vascular and lymph channels. Phagocytic cells that are located in the liver, bone marrow and spleen. The phagocytic cells like the macrophages chemically digest the red blood cells and set free hemoglobin.
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The retina is a sensory membrane that lines the eye and is composed of several layers, including one that contains the light sensitive cells (rods and cones). The retina receives the image formed by the lens and converts it into chemical and nervous signals, which reach the brain by way of the optic nerve.
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Retinal means pertaining to the retina.
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A retrorocket is a rocket engine whose exhaust is directed to hinder, stop or reverse motion.
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Retrosternal pertains to the area behind the sternum.
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Revitalization refers to the process of imparting new life or vigor to (as in cleansing the air of impurities).
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Rhodotorula rubra: A common species of yeast, easy to identify by its orange color. It is commonly found in air and water contaminants.
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Rhopalia are structures of the jellyfish which contain specialized sensory structures. Each rhopalium typically contains organs that detect chemicals, light, touch and equilibrium (orientation).
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RNA-ribonucleic acid is a biomolecule composed of three main forms which are transfer, ribosome, and messenger RNA. Each of these join together to form a complex that synthesizes proteins in the cell cytosol.
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Rod denotes a morphologic type of bacteria.
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A roentgen is an international unit of exposure dose of gamma (or x-) radiation. In field dosimetry, one roentgen is essentially equal to one rad. It is named for the German scientist and discoverer of x-rays, Wilheim Conrad Roentgen.
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Roentgenography is photography with the use of X-rays.
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A roentgeonogram is a shadow picture made on a sensitized film or plate by means of X-rays or roentgen rays; it is better known as an X-ray.
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Roll is the up or down angle of the aircraft or shuttle wing off of the horizontal plane.
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The root module of the Svet greenhouse is also called the vegetation module. It is inserted into the bottom of the plant growth chamber and has two sections, or cuvettes, called K1 and K2. Each cuvette has two rows for seed planting. It is filled with a granular substance called Balkanine, which is similar in appearance to kitty litter, and has water and air supplied by a compressor and pump.
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Rose bengal agar (RB) is a sodium salt agar base that is used in the isolation and maintenance of fungi.
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Rose bengal medium is a selective medium used for the isolation of yeasts and molds.
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The Rosette stage is an early stage of plant growth. Many plants, when developing, develop leaves first to support photosynthesis, and then develop a stem. During this stage, the plants look like rosettes.
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Rotatores are rotator muscles; a number of short transversospinal muscles chiefly developed in the thoracic region.
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Rubella is the name given to German or three-day measles. It is caused by the rubella virus and is characterized by enlargement of lymph nodes, usually with little fever. High incidence of abnormalities are found in children that are infected during the first several months of fetal life.
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Rubeola is a term that has been used as a synonym for two different viral diseases of man, namely measles (morbilli) and rubella. Presently, rubeola is often used as a synonym for measles.
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The Russian Space Agency is the Russian government agency responsible for all Russian space activities, such as launching and maintaining the Mir Space Station.