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R J Barker

Publications and source records attributed to R J Barker.

11 recordsLinked to original sources
PubMed2001

Efficiency gain from auxiliary data requiring additional nuisance parameters.

In a mark-recapture study of an animal population, live-recapture information may be supplemented by resightings from marked animals obtained throughout the period of the study and the two types of data analyzed simultaneously. The resighting data can only contribute to estimates of survival probability if they are jointly modeled with the live-recapture data and require the inclusion of additional nuisance parameters. We show that, under quite general conditions, estimates of the original parameters are estimated with the same, or improved, precision despite the inclusion of the nuisance parameters. Banding data from female goldeneye ducks (Bucephala clangula) are used as an illustration.

Animals↗
PubMed1989

Comparison of thick films, in vitro culture and DNA hybridization probes for detecting Plasmodium falciparum malaria.

Using blood from volunteers with sporozoite induced malaria, a comparison was made of the sensitivity and specificity of Giemsa stained thick film examination, in vitro culture, and 4 different DNA probes for detecting parasitemia. Between 9 and 13 days after sporozoite inoculation, patent parasitemia (4-550 parasites/microliters) was detected by thick film examination of 0.5 microliters blood in 7 volunteers. Cultures of 1 ml blood obtained 7 days after sporozoite inoculation were positive in all volunteers who eventually developed patent parasitemia. The DNA hybridization probes detected parasites in only 5-28% of smear- or culture-positive samples.

Animals↗
PubMed1980

Pesticides and honey bees: nectar and pollen contamination in alfalfa treated with dimethoate.

Medicago sativa L. (Leguminosae) sprayed with O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate (dimethoate) had only 0.5 ppm of dimethoate in pollen one day later, but 3 ppm in nectar one week later, and 1 ppm in nectar two weeks later. As little as 1 ppm added to syrup fed to caged workers of Apis mellifera L. (Apidae) inhibited cholinesterase and reduced survival. Bees given a choice between treated and untreated syrups showed no preference; this suggests that the levels of dimethoate found in nectar are toxic and not repellent.

Animals↗
PubMed1977

Some carbohydrates found in pollen and pollen substitutes are toxic to honey bees.

Carbohydrates in some pollen substitutes (galactose, lactose, raffinose, stachyose, glucuronic acid, galacturonic acid, polygalacturonic acid, and pectin) were toxic to caged adult Apis mellifera L. These toxins can be diluted to safe levels by sucrose. Collected nectar apparently dilutes the toxic sugars in pollen thus permitting assimilation of essential nutrients from pollen.

Animals↗