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C Ross

Publications and source records attributed to C Ross.

171 records · Page 10Linked to original sources
PubMedDate not supplied

Jaws 2: a description of in-air beam profiles for half blocked and dynamically wedged radiation fields.

In a recent paper [Med. Phys. 19, 1441 (1992)] it was shown that the field size dependence of on-axis relative output from a linear accelerator can be well described by a model comprising two components. One component represents radiation emanating from a point source and the other represents radiation from a field size dependent distributed source. In this communication the application of the model is extended to off-axis situations and demonstrates that a good description of the dependence of off-axis output on collimator configuration can be obtained. Of particular clinical relevance in this regard is the beam profile of half blocked fields which are adequately reproduced. The model has also been applied to the study of profiles generated by simulated dynamic wedging.

Humans↗
PubMedDate not supplied

Allocare, predation risk, social structure and natal coat colour in anthropoid primates.

Many primate species have a natal coat coloured differently from the coat colour of adults and, in some cases, the natal coat is very different from that of older animals with the infant being conspicuous and/or brightly coloured. This study uses data from 82 anthropoid species to investigate possible correlates of conspicuous natal coat colour (CNC), using comparative, phylogenetically controlled analyses. Five hypotheses were tested using statistical tests on both species data and phylogenetically controlled data. The analyses show some support for the hypothesis that CNCs have evolved to promote allocare but the degree of CNC does not correlate with predation rates, arboreality, or relative testes size.

Adaptation, Physiological↗
PubMedDate not supplied

The evolution of non-maternal care in anthropoid primates: a test of the hypotheses.

The amount of non-maternal care (allocare) found in primates varies greatly from species to species. Our paper examines this variation and focuses on possible reasons why mothers in some anthropoid primate species are prepared to relinquish their infants to other carers whereas others are not. We use data collected from the literature to test a number of hypotheses that attempt to explain the observed variation in non-maternal care. Analyses were carried out using comparative methods that control for the influence of both body size and phylogeny on life-history and ecological variation. The results support previous studies of both primates and other mammals in finding a clear link between the amount of allocare provided and female reproductive rates. Species with high allocare levels grow rapidly post-natally and wean their infants at a younger age (but at the same relative size) than species of the same body size with lower allocare levels. This early weaning allows high allocare species to support higher birth rates than low allocare species but does not result in earlier maturation. Our results, therefore, suggest that mothers allow non-maternal care of their infants in order to increase their own reproductive output. It is not clear whether such a strategy also benefits the infant, as we could find no link between the presence of allocare and early maturation (which would increase the infant's reproductive output) or between allocare levels and infant survival (as measured by vulnerability to infanticide). This suggests that mothers and infants might come into conflict over transfer to other carers, as the benefits to the mother may not be accompanied by benefits to the infant. However, although mothers may benefit from allocare in some circumstances, they will not be expected to allow allocare if the costs are high (e.g. if there is a high risk to the infant).

Altruism↗
PubMedDate not supplied

Lead and zinc removal by laboratory-scale constructed wetlands.

Constructed wetlands have the potential to trap and remove metals in mine wastewater. To determine the effectiveness of constructed wetlands for treating selected heavy metals in neutral mine effluent typical of lead mines, eight laboratory-scale constructed wetlands were set up to treat a synthetic, slightly alkaline, mine water containing 34.2 mg/L sulfate (SO4(2-)), 50 micrograms/L lead (Pb), and 300 micrograms/L zinc (Zn). After 45 days, one of the wetlands was switched to treat a synthetic smelter effluent with a much greater load of SO4(2-), sodium (Na+), and Pb. Temperature, hydraulic loading, and substrate composition typically did not affect treatment efficiency. The pH of the effluent was reduced from 8.0 to 8.5 to near neutral. The average removal in the eight wetlands was 90% for Pb and 72% for Zn. In wetlands operating on synthetic mine water, SO4(2-) was completely removed, likely by conversion to sulfide by sulfate-reducing bacteria. In the wetland operating on synthetic smelter effluent, only approximately 25% of 6 g/L influent sulfate was removed, and a breakthrough period of 4 days for Na+ was observed. Whole effluent toxicity assays on undiluted wetland effluent from wetlands treating mine and smelter water had 100% survival of fathead minnows and Daphnia magnia. Survival of Ceriodaphnia dubia was zero in undiluted effluent, but 75 to 100% survival was observed when the effluent was diluted to one-half strength.

Animals↗
PubMedDate not supplied

A comparison of modified methenamine silver and toluidine blue stains for the detection of Pneumocystis carinii in bronchoalveolar lavage specimens from immunosuppressed patients.

Pneumonia due to Pneumocystis carinii is an increasingly frequent occurrence; a prompt, accurate diagnosis is important to successfully manage this infection. Methenamine silver and toluidine blue stainings of material recovered by bronchoalveolar lavage (BAL) have been the most widely employed techniques for detecting Pneumocystis organisms. The value of these two staining techniques for the detection of Pneumocystis organisms was prospectively compared in 220 BAL specimens obtained from 186 immunosuppressed individuals. The patients included those with disease-related and therapy-related immunosuppression; half of the BAL specimens came from organ transplant recipients. The results indicate that neither method is superior to the other and that both will correctly identify almost all Pneumocystis infections if a sufficient aliquot of BAL material is examined systematically by trained individuals. The toluidine blue method is somewhat simpler to perform, however. The reasons for discrepant results between the two staining methods were analyzed.

False Negative Reactions↗
PubMedDate not supplied

Time of the month.

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Adult↗
PubMedDate not supplied

Partial exchange transfusion in the treatment of severe falciparum malaria.

BACKGROUND: Exchange transfusion as an adjunct to the treatment of severe falciparum malaria has been widely recommended, although there is no well-designed clinical trial to prove its efficacy. The amount of compatible blood required for total exchange is rarely available in areas endemic for malaria and the risks of the procedure including transfusion-related infections are high. METHODS: Partial transfusion with four units of blood was given to a patient with severe falciparum malaria (80% parasitaemia) whose condition deteriorated on conventional treatment with intravenous quinine. RESULTS: This brought about prompt clinical improvement and reduction in parasitaemia. CONCLUSION: Partial transfusion with one or two litres of blood is a promising and viable alternative to total exchange transfusion.

Adult↗
PubMedDate not supplied

One year outcome evaluation of an alcohol and drug abuse prevention program in a Québec high school.

This article presents the results of a one-year outcome evaluation of a school-based alcohol- and drug-abuse prevention program targeting adolescents in Quebec. This evaluation concerns the school component of the program and includes the first seven classroom interventions. The design is a pre- and post-intervention assessment of both the experimental (n = 145 students) and the control school (n = 179 students). Results obtained do not reveal any significant effect of the program on knowledge and beliefs regarding the use of alcohol and drugs, or any modification in self-efficacy with respect to decision making and ability to resist external pressure concerning the decision to use marijuana/hashish. The results do show, however, a decrease among the exposed students in self-efficacy within the context of alcohol use. Such a result may be a consequence of the program's capacity to raise the students' level of awareness of their susceptibility to social influences. It is plausible that in order to have positive effects, classroom interventions such as the present one need to be supplemented by additional activities targeting youths' environment.

Adolescent↗