PubMed Health⌕ Search

Biomedical subjects

N Peek

Publications and source records attributed to N Peek.

4 recordsLinked to original sources
PubMed2003

[A case of diphtheria in the Netherlands due to an infection with Corynebacterium ulcerans].

A 58-year-old woman was admitted due to a pseudomembranous pharyngitis. The patient had not been vaccinated against diphtheria. Corynebacterium ulcerans was cultured from a throat swab. The production of diphtheria toxin by these bacteria was demonstrated with PCR and an immunoprecipitation test. The patient was cared for in respiratory isolation and was treated with benzylpenicillin. She quickly recovered and was discharged four days after admission. A contact investigation did not reveal any dissemination of the toxin-producing C. ulcerans and a source was not found. In spite of the large-scale vaccination against diphtheria which has taken place in the Netherlands since 1953, a physician has to consider diphtheria in the differential diagnosis of patients who present with a clinical syndrome compatible with this disease. Either Corynebacterium diphtheriae or C. ulcerans could be the pathogen responsible.

Corynebacterium↗
PubMed1999

Using sensitivity analysis for efficient quantification of a belief network.

Sensitivity analysis is a method to investigate the effects of varying a model's parameters on its predictions. It was recently suggested as a suitable means to facilitate quantifying the joint probability distribution of a Bayesian belief network. This article presents practical experience with performing sensitivity analyses on a belief network in the field of medical prognosis and treatment planning. Three network quantifications with different levels of informedness were constructed. Two poorly-informed quantifications were improved by replacing the most influential parameters with the corresponding parameter estimates from the well-informed network quantification; these influential parameters were found by performing one-way sensitivity analyses. Subsequently, the results of the replacements were investigated by comparing network predictions. It was found that it may be sufficient to gather a limited number of highly-informed network parameters to obtain a satisfying network quantification. It is therefore concluded that sensitivity analysis can be used to improve the efficiency of quantifying a belief network.

Algorithms↗
PubMed1996

Radionuclides in fishes and mussels from the Farallon Islands Nuclear Waste Dump Site, California.

The Farallon Islands Nuclear Waste Dump Site (FINWDS), approximately 30 miles west of San Francisco, California, received at least 500 TBq encapsulated in more than 47,500 containers from approximately 1945 to 1970. During several seasons in 1986/87 deep-sea bottom feeding fishes (Dover sole = Microstomus pacificus; sablefish = Anoplopoma fimbria; thornyheads = Sebastolobus spp.) and intertidal mussels (Mytilus californianus) were collected from the vicinity of the FINWDS and from comparable depths at a reference site near Point Arena, CA. Tissues were analyzed for several radionuclides (137Cs, 238Pu, 239+240Pu, and 241Am). Radionuclide concentrations for fish mussel tissue ranged from non-detectable to 4,340 mBq kg(-1) wet weight, with the following means for Farallon fishes: 137Cs = 1,110 mBq kg(-1); 238Pu = 390 mBq kg(-1); 239+240Pu = 130 mBq kg(-1); and 241Am = 1,350 mBq kg(-1). There were no statistically significant differences in the radionuclide concentrations observed in samples from the Farallon Islands compared to reference samples from Point Arena, CA. Concentrations of both 238Pu and 241Am in fish tissues (from both sites) were notably higher than those reported in literature from any other sites world-wide, including potentially contaminated sites. Concentrations of 239+24OPu from both sites were typical of low values found at some contaminated sites worldwide. These results show approximately 10 times higher concentrations of 239+240Pu and approximately 40-50 times higher concentrations of 238Pu than those values reported for identical fish species from 1977 collections at the FINWDS. Radionuclide concentrations were converted to a hypothetical per capita annual radionuclide intake for adults, yielding the following values of annual Committed Effective Dose Equivalent (CEDE) from ionizing radiation emitted from these radionuclides: 0.000 mSv y(-1) for 137Cs, 0.009 mSv Y(-1) for 228Pu, and 0.003 mSv y(-1) for 239+240Pu. For 241Am, projected CEDE for Dover sole, sablefish, and thornyheads were higher, averaging 0.03 mSv y(-1). The observed isotopic ratio of 238Pu/239+240Pu was about 4 (which is two orders of magnitude higher than the ratio of 0.03 associated with fallout from weapons tests and accidental releases in the north temperate zone of the earth), indicating a considerably higher environmental mobilization for 238Pu compared to 239+240Pu. Likewise, the observed ratio of 241Am/239+240Pu of about 30 was nearly two orders of magnitude higher than the fallout ratio of 0.43 in the north temperate zone of the earth. The projected ionizing radiation CEDE to people from the ingestion of fish with fallout radionuclides was three times higher for 241Am than from the plutonium isotopes.

Alpha Particles↗