Science Glossary (T-Z)

T-cells, or T-lymphocytes, play an important role in human immunity. They are formed in the thymus gland and react highly specifically against the particular type of antigen that initiated their development.
Telemetrically pertains to telemetry, the science of sensing and measuring information at some remote location (spacecraft) and transmitting the data to a convenient location for reading or recording (ground station).
The telencephalon is the part of the embryonic brain that develops into the forebrain, which contains the cerebral hemispheres, olfactory lobes, pineal gland, pituitary gland and optic chiasma.
Terrestrial means originating from the Earth.
A thermocouple is a thermoelectric couple used to measure temperature differences.
Throughput is the output or production of a computer program over a period of time.
Time cue
Time cues, which are present in everyday life, make it possible for plants and animals to recognize and respond to their environment. Examples of time cues include time of day, season of year, phase of the moon, etc.
Total Body Water (TBW)
Total body water (TBW) is all the water in the body, including water inside and outside the cells, including water in the GI and urinary tracts.
Torque is the turning effect produced when force is applied to a rotational axis.
Total hardness
A tracer is a substance that can be readily identified, such as an isotope, used to trace the course of a chemical or biological process or determine the size of a space that cannot be directly measured.
Transcranial doppler
A transcranial doppler is a scan performed to provide information about the presence, quality, and changing nature of blood circulation to the brain. It measures the rate of blood flow through cerebral arteries. Narrowed blood vessels produce high flow rates, indicating possible narrowing or a spasm of a blood vessel; high rates may also indicate and arteriovenous malformation.
Transpiration is the act or process of giving off vapor containing waste product through the stomata of plant tissue or pores of the skin.
Transport ATPase
A treadmill is a device operated by walking on the moving steps of a wheel or treading an endless sloping belt.
Trypanothione reductase
Trypanothione reductase is the key enzyme in the transmission of Chagas disease, a blood disease caused by the protozoan genus Trypanosoma.
Trypsin inhibitor
Trypsin inhibitor is a protease inhibitor, stopping the protein breakdown that trypsin produces.
Turbidity means having sediment or foreign particles stirred up or suspended, usually within a liquid.

Ultraviolet radiation
Ultraviolet (UV) radiation results from wavelengths of energy from just beyond the violet in the visible spectrum to the border of the x-ray region. Exposure to types of UV radiation can cause damage to the body, namely the skin. The layer of ozone in the earth's stratosphere normally forms a protective shield, blocking the majority of the sun's harmful UV rays from reaching the ground.
An umbilical is any of various external electrical lines or fluid tubes which connects one portion of a system to another.
Uric acid
Uric acid is the end product of urine breakdown; it is the major form in which metabolic nitrogen is excreted from the body.

Vagal pertains to the vagus nerve, the cranial nerves essential for speech, swallowing, and the sensibilities and functions of many parts of the body. The vagus nerve communicates through 13 main branches, connecting to four areas in the brain.
Valsalva maneuver
The valsalva maneuver is an attempt to forcibly exhale with the nose and mouth closed.
Van refers to the enzymes found in bacteria that is resistant to the antibiotic Vancomycin.
Vapor diffusion crystallization
Vapor diffusion crystallization is a technique used for protein crystal growth by mixing a protein solution and precipitating solution into a single liquid drop. As water leaves the liquid drop through vaporization, the protein solution becomes more concentrated causing the protein to crystallize.
Vasomotor pertains to the nerves and muscles that control the constriction or dilation of blood vessels.
VEE capsid
VEE capsid protein is the one domain of a proteinase required for the replication of Venezuelan Equine Encephalitis Virus. It is a target for antiviral drugs.
Vegetative means non-reproductive or relating to the nonsexual organs of a plant, such as root, stem and leaves.
Vitamin D
Vitamin D is a fat-soluble vitamin that enhances the absorption of calcium and phosphorus from the intestine and promotes their deposition onto the bone.
Volatile means evaporating readily at normal temperatures and pressures, i.e., capable of being readily vaporized.
Volitional means voluntary, or done by an act of will.

A wavelength is the distance between two successive points at which the wave has the same phase. For example, visible light has a wavelength of between 400 nm (violet) to 750 nm (red).

X-ray computed tomography
X-ray computed tomography is a technique that utilizes x-ray light to generate a image, via a computer, of the surface structure of a geological sample.
X-ray diffraction
X-ray diffraction is a method for studying microscopic crystal form and structure.
Xylem is a woody plant tissue that is vascular in function, enabling transport of water with dissolved minerals within the plant, usually upward.

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Page last updated: 07/16/1999