| second incisor | Second maxillary or mandibular permanent or deciduous tooth on either side of the midsagittal plane of the head. Synonym: lateral incisor. (05 Mar 2000) |
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| second law of thermodynamics | <physics> All of the chemical and physical processes in a closed system tend to drive that system toward maximum entropy. Clausius statement: No device can operate in a cycle and allow heat to transfer from a colder body to a hotter body unless other compensating activities are taking place. Kelvin-Planck statement: no device can operate in a constant-temperature cycle and convert the heat it receives into work, unless other other compensating activities are taking place. (09 Oct 1997) |
| second line chemotherapy | <oncology> Chemotherapy given for a tumour which has already failed to respond to a first chemotherapy regimen (called first line). (16 Dec 1997) |
| second-look operation | Exploratory celiotomy within a year after apparently curative resection of intra-abdominal cancer, in patients with no sign or symptom of recurrence, to resect an occult tumour if present. (05 Mar 2000) |
| second meiotic division | The second of two consecutive divisions of the nucleus of an eukaryotic cell during the process of meiosis. It includes the following stages of meiosis: prophase II, metaphase II, anaphase II, and telophase II. (09 Oct 1997) |
| second molar | Seventh permanent or fifth deciduous tooth in the maxilla and mandible on either side of the midsagittal plane of the head following the arch form. (05 Mar 2000) |
| second-order conditioning | The use of a previously successfully conditioned stimulus as the unconditioned stimulus for further conditioning. (05 Mar 2000) |
| second-order kinetics | A term describing the reaction rate of a chemical reaction in which the rate is proportional to the product of the concentrations (in moles) of two of the reactants (also called bimolecular kinetics), or to the square of the molar concentration of the reactant if there is only one. Such a reaction might have an equation like rate = k[A][B] or rate = k[A]2, where k is the reaction rate constant, [A] is the concentration of reactant A, and [B] is the concentration of reactant B. (09 Oct 1997) |
| second parallel pelvic plane | The plane extending from the middle of the posterior surface of the pubic symphysis to the junction of the second and third sacral vertebrae, and laterally passing through the ischial bones over the middle of the acetabulum. Synonym: second parallel pelvic plane, wide plane. (05 Mar 2000) |
| second set rejection | An accelerated rejection of a transplant that occurs when an individual has been previously sensitised to the graft. (05 Mar 2000) |
| second sight | 1. <ophthalmology> Improved near vision in the aged as a result of increased refractivity of the nucleus of the lens causing myopia. Synonym: senile lenticular myopia. 2. The power of discerning what is not visible to the physical eye, or of foreseeing future events. Such as are of a disastrous kind, the capacity of a seer or prophetic vision. Source: Websters Dictionary (01 Mar 1998) |
| second signaling system | <psychology> Pavlovian term for speech in which words are considered to be the second signals capable of producing conditioned responses. (05 Mar 2000) |
| second sound | The second sound heard on auscultation of the heart; signifies the beginning of diastole and is due to closure of the semilunar valves. Synonym: second sound. (05 Mar 2000) |
| second-stability region | <radiobiology> A high pressure region where the plasma becomes stable to the pressure-gradient-driven ballooning instability. The plasma is stable in the limit of small pressure gradients, becomes unstable at some intermediate pressure, and then becomes stable again at still higher pressures. Tokamaks operating in the second-stability region would be more attractive because the higher pressures (beta) would provide more fusion reactivity per unit volume of plasma, allowing smaller reactors to be built. (09 Oct 1997) |
| second stage of labour | <obstetrics> The part of labour from the full dilatation of the cervix until the baby is completely out of the birth canal. The second stage of labour is also called the stage of expulsion. (12 Dec 1998) |