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Biomedical subjects

A Wren

Publications and source records attributed to A Wren.

10 recordsLinked to original sources
PubMed2001

Evolutionary driver scheduling with relief chains.

Public transport driver scheduling problems are well known to be NP-hard. Although some mathematically based methods are being used in the transport industry, there is room for improvement. A hybrid approach incorporating a genetic algorithm (GA) is presented. The role of the GA is to derive a small selection of good shifts to seed a greedy schedule construction heuristic. A group of shifts called a relief chain is identified and recorded. The relief chain is then inherited by the offspring and used by the GA for schedule construction. The new approach has been tested using real-life data sets, some of which represent very large problem instances. The results are generally better than those compiled by experienced schedulers and are comparable to solutions found by integer linear programming (ILP). In some cases, solutions were obtained when the ILP failed within practical computational limits.

Algorithms↗
PubMed1996

The effect of manual removal of the placenta on post-cesarean endometritis.

OBJECTIVE: To determine if intraoperative glove change and placental delivery method affect the post-cesarean endometritis rate. METHODS: After informed consent, women who required cesarean were randomly assigned to one of four study groups: 1) no glove change plus manual placental extraction, 2) no glove change plus spontaneous placental delivery, 3) glove change plus manual extraction, and 4) glove change plus spontaneous delivery. Bilateral glove change by both primary and assistant surgeons occurred immediately after delivery of the newborn and before delivery of the placenta. External uterine massage and traction on the umbilical cord were performed to assist spontaneous delivery of the placenta. A first-generation cephalosporin was routinely administered after umbilical cord clamping for prophylaxis of post-cesarean endometritis. RESULTS: Of 760 women entered into the study, we included 643 who did not have intrapartum chorioamnionitis or cesarean hysterectomy. The four groups were comparable with respect to selected maternal and intrapartum characteristics, including maternal and gestational age, parity, presence of labor, and the presence and duration of membrane rupture. The postoperative endometritis rate was significantly higher in women whose placentas were extracted manually (31 versus 22%, P = .01). Operator glove change did not alter the incidence of endometritis (relative risk 1.0, 95% confidence interval 0.79-1.3). CONCLUSION: Manual extraction of the placenta is associated with a significantly greater risk of post-cesarean endometritis than that observed with assisted spontaneous placental delivery. Intraoperative glove change does not decrease post-cesarean endometritis.

Adult↗
PubMed1977

A new animal model for the prediction of antidepressant activity.

Animal models presently in use for the screening of potential antidepressant drugs yield numerous false positives and false negatives. In search of a more specific model, we have studied the effects of psychotropic compounds on the behavioural changes induced in rats by the removal of the olfactory bulbs. We have observed that subchronic treatment with antidepressants in general reverses the behavioural alterations displayed by bulbectomized rats in tests of conditioned behaviour. The present paper describes a brief test, the so-called anxiosoif test, which may be used to assess the effects of drugs on the behaviour of bulbectomized rats. Removal of the olfactory bulbs leads to increased water intake in the anxiosoif test and to an attenuation of avoidance when the drinking spout is electrified. This latter effect can be reversed by subchronic treatment with the antidepressant drugs amitriptyline and mianserine (Org GB 94). It is suggested that the behavior of bulbectomized rats may be used as a specific tool in the prediction of antidepressant activity of novel compounds.

Animals↗