| acceleration | The act of accelerating, or the state of being accelerated; increase of motion or action; as, a falling body moves toward the earth with an acceleration of velocity; opposed to retardation. "A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration." (I. <astronomy> Taylor) Acceleration of the moon, the increase of the moon's mean motion in its orbit, in consequence of which its period of revolution is now shorter than in ancient times. Acceleration and retardation of the tides. See Priming of the tides, under Priming. Diurnal acceleration of the fixed stars, the amount by which their apparent diurnal motion exceeds that of the sun, in consequence of which they daily come to the meridian of any place about three minutes fifty-six seconds of solar time earlier than on the day preceding. Acceleration of the planets, the increasing velocity of their motion, in proceeding from the apogee to the perigee of their orbits. Origin: L. Acceleratio: cf. F. Acceleration. Source: Websters Dictionary (01 Mar 1998) |
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| acceleration phase | <cell biology, cell culture> A period of increasing growth before the log phase in a culture of microbes. After the culture is started on a medium, at first there is no growth (the lag phase) and then the microbes start to gradually grow (acceleration phase) until they reach a constant maximum rate of growth (log phase). (15 Jan 1998) |
| angular acceleration | The rate of change of angular velocity; e.g., when a centrifuge rotor is speeding up, or when there is a simultaneous change in velocity and direction, as in an aircraft in a tight spin. (05 Mar 2000) |
| radial acceleration | The centripetal acceleration of a particle or vehicle moving along a curved path at a constant velocity; e.g., turning a curve in an automobile, pulling out of a dive, or performing a loop manoeuvre in an aircraft. In aviation, acceleration varies directly with the square of the air speed and inversely with the radius of the turn (a = V2/r, where V is air speed and r is radius of turn). (05 Mar 2000) |
| linear acceleration | The rate of change of velocity without a change in direction; e.g., when the speed of an aircraft increases while flying a straight pathway. (05 Mar 2000) |
| accretionary growth | Growth by an increase of intercellular material. (05 Mar 2000) |
| appositional growth | Growth accomplished by the addition of new layers on those previously formed; e.g., the addition of lamellae in the formation of bone; it is the characteristic method of growth when rigid materials are involved. (05 Mar 2000) |
| auxetic growth | Growth by increase in the size of component cells. Synonym: intussusceptive growth. (05 Mar 2000) |
| bacterial growth | Growth of a bacterial culture either by increase in cell material or cell number. (05 Mar 2000) |
| B-cell differentiation/growth factors | Various substances, usually obtained from the supernatant of T-cell cultures, such as interleukin 4, 5, and 6. These substances are necessary for B-cell growth, maturation, and differentiation into plasma cells or B memory cells. (05 Mar 2000) |
| biphasic growth curve | <cell culture, microbiology> A particular type of growth curve seen in cultured microorganisms in which they have two exponential growth stages separated by a plateau phase. This double-hump curve is produced when the microbes are cultured using two carbon sources, one of which must be used up before the second can be used. (19 Jan 1998) |
| bovine growth hormone | <endocrinology> A hormone secreted by the bovine pituitary gland. It is used to increase milk production by improving the feed efficiency in dairy cattle. (14 Nov 1997) |
| brain-derived growth factor | <growth factor> Small basic protein purified from pig brain, a member of the family of neurotrophic factors that also includes Nerve Growth Factor and neurotrophin 3. In contrast to nerve growth factor, brain-derived neurotrophic factor is predominanantly (though not exclusively) localised in the CNS. It supports the survival of primary sensory neurons originating from the neural crest and ectodermal placodes that are not responsive to NGF. In the brain brain-derived neurotrophic factor has a trophic action on retinal, cholinergic, and dopaminergic neurons, and in the peripheral nervous system it acts on both motor and sensory neurons. Acronym: BDGF (12 Dec 1998) |
| capon-comb-growth test | A test for androgenic activity, based upon the stimulation of comb growth in capons (castrated cockerels) or immature roosters. Synonym: capon-comb-growth test, cock's comb test. (05 Mar 2000) |
| radial growth phase | The early pattern of growth of cutaneous malignant melanoma, in which tumour cells spread laterally in the epidermis. (05 Mar 2000) |