| first-order reaction | A reaction the rate of which is proportional to the concentration of the single substance undergoing change; radioactive decay is a first-order process, defined by the equation -(dN/dt)=kN, where N is the number of atoms subject to decay (reaction), t is time, and k is the first-order decay (reaction) constant, i.e., the fraction of all atoms decaying per unit of time. See: decay constant, order. (05 Mar 2000) |
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| first parallel pelvic plane | The upper opening of the true pelvis, bounded anteriorly by the pubic symphysis and the pubic crest on either side, laterally by the iliopectineal lines, and posteriorly by the promontory of the sacrum. Synonym: apertura pelvis superior, aditus pelvis, first parallel pelvic plane, pelvic brim, pelvic inlet, pelvic plane of inlet, plane of inlet. (05 Mar 2000) |
| first rank symptoms | Those symptom's that, when present, indicate that the diagnosis of schizophrenia is likely, provided that organic or toxic aetiology is ruled out: delusion of control, thought broadcasting, thought withdrawal, thought insertion, hearing one's thoughts spoken aloud, auditory hallucinations that comment on one's behaviour, and auditory hallucinations in which two voices carry on a conversation. Synonym: first rank symptoms, schneiderian first rank symptoms. (05 Mar 2000) |
| first-set rejection | Allograft transplantation between two organisms not previously sensitised to the graft tissue. Necrosis of the graft usually occurs within 10 days of transplantation. (05 Mar 2000) |
| first stage of labour | The part of labour when the cervix dilates fully (to 10 centimeters). The first stage of labour is also called the stage of dilatation. (12 Dec 1998) |
| first temporal convolution | A longitudinal gyrus on the lateral surface of the temporal lobe between the lateral (sylvian) fissure and the superior temporal sulcus. Synonym: gyrus temporalis superior, first temporal convolution, superior temporal convolution. (05 Mar 2000) |
| first visceral cleft | <anatomy> The cleft between the hyoid and mandibular arches of the embryo; the external auditory meatus is developed from its dorsal portion. Synonym: first visceral cleft. (05 Mar 2000) |
| lateral femoral tuberosity | The epicondylus located proximal to the lateral condyle. Synonym: epicondylus lateralis ossis femoris, lateral femoral tuberosity. (05 Mar 2000) |
| lateral process of calcaneal tuberosity | The lateral projection from the posterior part of the calcaneus. Synonym: processus lateralis tuberis calcanei. (05 Mar 2000) |
| lesser tuberosity of humerus | The anterior of the two tubercles of the neck of the humerus on which the subscapularis is inserted. Synonym: tuberculum minus humeri, lesser tuberosity of humerus. (05 Mar 2000) |