| light reactions | In photosynthesis, aseries of reactions in which light energy isconverted to chemical energy with the help of chlorophyll. ATP iscreated along with hydrogen ions and electrons as water molecules aresplit apart. (09 Oct 1997) |
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| light reflex | A red glow reflected from the fundus of the eye when a light is cast upon the retina, as in retinoscopy. Synonym: eye reflex, fundus reflex, pupillary reflex. Synonym: pyramid of light. (05 Mar 2000) |
| light scattering | Particles suspended in a solution will cause scattering of light and the extent of the scattering is related to the size and shape of the particles (in a somewhat complex relationship). (18 Nov 1997) |
| light sense | The ability to perceive variations in the degree of light or brightness. (05 Mar 2000) |
| light sleep | A condition of half sleep. Synonym: light sleep. Origin: dys-+ G. Nystaxis, drowsiness (05 Mar 2000) |
| light treatment | Treatment with light. For example, a newborn with jaundice may be put under the lights. (12 Dec 1998) |
| light water | <radiobiology> Ordinary H2O, as opposed to heavy water, which contains atoms of the heavier isotopes of hydrogen, deuterium and/or tritium. See: hydrogen, isotope, deuterium, tritium, heavy water. (09 Oct 1997) |
| light wire appliance | An orthodontic appliance utilizing small gauge labial wires with expansion and contraction loops formed into it and attached to bands fitted to individual teeth; sometimes called Begg light wire differential force technique. (05 Mar 2000) |
| light-activated resin | A resin which uses visible or ultraviolet light to excite a photoinitiator which interacts with an amine to form free radicals and initiate polymerization. Used mainly in restorative dentistry. Synonym: light-activated resin. (05 Mar 2000) |
| light-adapted eye | An eye that has been exposed to light, with bleaching of rhodopsin (visual purple) and insensitivity to low illumination. Synonym: photopic eye. (05 Mar 2000) |
| light-cured resin | A resin which uses visible or ultraviolet light to excite a photoinitiator which interacts with an amine to form free radicals and initiate polymerization. Used mainly in restorative dentistry. Synonym: light-activated resin. (05 Mar 2000) |
| light-hearted | Free from grief or anxiety; gay; cheerful; merry. Light-heartedly, Light-heartedness. Source: Websters Dictionary (01 Mar 1998) |
| light-horseman | 1. A soldier who serves in the light horse. 2. <zoology> A West Indian fish of the genus Ephippus, remarkable for its high dorsal fin and brilliant colours. Source: Websters Dictionary (01 Mar 1998) |
| light-ion fusion | <radiobiology> Light-Ion-Beam-Driven Inertial Confinement fusion, using beams of light ions driven at implosion targets. Pulsed-power driven accelerators are relatively efficient and cost-effective, but beam-focusing is a technical hurdle for this approach. (09 Oct 1997) |
| light-near dissociation | A stronger near pupil response than light response; due to weak pupillomotor input, Argyll Robertson pupil, dorsal midbrain syndrome, or to misdirection of ciliary muscle fibres into the iris sphincter. Synonym: light-near dissociation. (05 Mar 2000) |
| consensual light reflex | Contraction of the pupil of the fellow eye in consensus with the pupil of the illuminated eye. Synonym: consensual light reflex, indirect pupillary reaction. (05 Mar 2000) |
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| P light chain | <protein> Myosin light chain that can be phosphorylated by myosin light chain kinase, as a result of phosphorylation, the myosin is activated. (18 Nov 1997) |
| polarised light | Light in which, as a result of reflection or transmission through certain media, the vibrations are all in one plane, transverse to the ray, instead of in all planes. (05 Mar 2000) |
| polarized light | <microscopy> Light that is vibrating in one plane (plane-polarized light), light with a rotary vibration (circular polarized light), or light that is vibrating elliptically (elliptically polarized light). Moonlight and skylight are polarized, as is much reflected light, cloud light is polarized under certain conditions. However, naturally polarized light is, on the whole, rather imperfectly polarized. (05 Aug 1998) |
| polarized light microscope | <instrument, microscopy> A microscopical polarizcope, i.e., a compound microscope which is equipped with two polars and a Bertrand lens, chemists and mineralogists are the principal users. (05 Aug 1998) |
| myosin light chain | <protein> The light chains of the muscle protein myosin. Each molecule of myosin is composed of two heavy chains and two pairs of light chains. The light chains have a molecular weight of about 20 kD and there is one dissimilar pair of light chains associated with each heavy chain. The proteins all have sequence homology to calmodulin, but not all with calcium binding activity. Several types are known: regulatory light chains (LC 2, DNTB light chains) probably regulate the ATPase activity of the heavy chain directly (through the binding of calcium) or indirectly (activating when they themselves are phosphorylated by myosin light chain kinase) and essential light chains (LC 1, LC 3, alkali light chains), which have a more subtle and apparently nonessential role. In molluscan muscle the EDTA light chains (similar to LC 2 from vertebrate muscle) confer calcium sensitivity on the myosin itself. The light chains are "calmodulin-like" proteins that bind calcium. Two of them can be removed easily, and two with difficulty. The light chains bind the heavy chains in the vicinity of the head groups of the myosin. (12 Dec 1998) |
| myosin light chain kinase | <enzyme> An enzyme that phosphorylates myosin light chains in the presence of ATP to yield myosin-light chain phosphate and ADP, and requires calcium and calmodulin. The 20-kD light chain is phosphorylated more rapidly than any other acceptor, but light chains from other myosins and myosin itself can act as acceptors. The enzyme plays a central role in the regulation of smooth muscle contraction. Chemical name: ATP:myosin-light-chain O-phosphotransferase Registry number: EC 2.7.1.117 (12 Dec 1998) |
| curing light | <dentistry> A special UV light used to help attach brackets to your teeth (08 Jan 1998) |
| pupillary light-near dissociation | A stronger near pupil response than light response; due to weak pupillomotor input, Argyll Robertson pupil, dorsal midbrain syndrome, or to misdirection of ciliary muscle fibres into the iris sphincter. Synonym: light-near dissociation. (05 Mar 2000) |
| pyramid of light | A triangular area at the anterior inferior part of the tympanic membrane, running from the umbo to the periphery, where there is seen a bright reflection of light. Synonym: cone of light, light reflex, Politzer's luminous cone, red reflex, Wilde's triangle. Malacarne's pyramid, a lobule on the undersurface of the cerebellum, the posterior portion of the vermis. (05 Mar 2000) |
| swinging light test | Test to detect a relative afferent defect in one eye by watching pupillary movements. With the patient fixing in the distance, the light is held on each eye for about a second, and quickly moved to the other eye. Assuming no defect of the innervation to the iris sphincter in one eye (which would produce an anisocoria in light), the eye with the weaker light response has a relative afferent pupillary defect. This asymmetry of pupillomotor input can be estimated by holding neutral density filters in front of the better eye until the pupillary responses of the two eyes are balanced. Synonym: swinging light test. (05 Mar 2000) |
| drummond light | A very intense light, produced by turning two streams of gas, one oxygen and the other hydrogen, or coal gas, in a state of ignition, upon a ball of lime; or a stream of oxygen gas through a flame of alcohol upon a ball or disk of lime; called also oxycalcium light, or lime light. The name is also applied sometimes to a heliostat, invented by Drummond, for rendering visible a distant point, as in geodetic surveying, by reflecting upon it a beam of light from the sun. Origin: From Thomas Drummond, a British naval officer. Source: Websters Dictionary (01 Mar 1998) |
| immunoglobulins, light-chain | Polypeptide chains, consisting of 211 to 217 amino acid residues, isolated from immunoglobulins and having a molecular weight of approximately 22 kD. There are two major types of light chains, kappa and lambda. In man they are found in a ratio of 60% to 40%, respectively. Both chains consist of linear repeating, similar, but not identical, segments of about 110 amino acid residues. In each segment a disulfide bond establishes a tightly folded approximately 60-membered loop or domain. Adjacent domains are linked by less tightly folded regions. Both light chains contain two such domains. Two light and two heavy chains make one immunoglobulin molecule, but both light chains in one ig are of the same type. (12 Dec 1998) |
| incident light | <microscopy> Sometimes denotes any over-stage lighting not included by methods of vertical illumination. (05 Aug 1998) |
| infrared light | See: infrared. Invisible light, historic term for X-rays. (05 Mar 2000) |