8,885 research outputs found
Stellar equilibrium configurations of white dwarfs in the gravity
In this work we investigate the equilibrium configurations of white dwarfs in
a modified gravity theory, na\-mely, gravity, for which and
stand for the Ricci scalar and trace of the energy-momentum tensor,
respectively. Considering the functional form , with
being a constant, we obtain the hydrostatic equilibrium equation for
the theory. Some physical properties of white dwarfs, such as: mass, radius,
pressure and energy density, as well as their dependence on the parameter
are derived. More massive and larger white dwarfs are found for
negative values of when it decreases. The equilibrium configurations
predict a maximum mass limit for white dwarfs slightly above the Chandrasekhar
limit, with larger radii and lower central densities when compared to standard
gravity outcomes. The most important effect of theory for massive
white dwarfs is the increase of the radius in comparison with GR and also
results. By comparing our results with some observational data of
massive white dwarfs we also find a lower limit for , namely, .Comment: To be published in EPJ
Different serological cross-reactivity of Trypanosoma rangeli forms in Trypanosoma cruzi-infected patients sera
<p>Abstract</p> <p>Background</p> <p>American Trypanosomiasis or Chagas disease is caused by <it>Trypanosoma cruzi </it>which currently infects approximately 16 million people in the Americas causing high morbidity and mortality. Diagnosis of American trypanosomiasis relies on serology, primarily using indirect immunofluorescence assay (IFA) with <it>T. cruzi </it>epimastigote forms. The closely related but nonpathogenic <it>Trypanosoma rangeli </it>has a sympatric distribution with <it>T. cruzi </it>and is carried by the same vectors. As a result false positives are frequently generated. This confounding factor leads to increased diagnostic test costs and where false positives are not caught, endangers human health due to the toxicity of the drugs used to treat Chagas disease.</p> <p>Results</p> <p>In the present study, serologic cross-reactivity between the two species was compared for the currently used epimastigote form and the more pathologically relevant trypomastigote form, using IFA and immunoblotting (IB) assays. Our results reveal an important decrease in cross reactivity when <it>T. rangeli </it>culture-derived trypomastigotes are used in IFA based diagnosis of Chagas disease. Western blot results using sera from both acute and chronic chagasic patients presenting with cardiac, indeterminate or digestive disease revealed similar, but not identical, antigenic profiles.</p> <p>Conclusion</p> <p>This is the first study addressing the serological cross-reactivity between distinct forms and strains of <it>T. rangeli </it>and <it>T. cruzi </it>using sera from distinct phases of the Chagasic infection. Several <it>T. rangeli</it>-specific proteins were detected, which may have potential as diagnostic tools.</p
Progression of myopathology in Kearns-Sayre syndrome
We report on the progression of myopathology by comparing two biopsies from a patient with a Kearns-Sayre-Syndrome. The first biopsy was taken in 1979 and showed 10% ragged-red fibers. Myopathic changes were slight including internal nuclei and fiber splitting in 10% of the fibers. Electron microscopy revealed typical mitochondrial abnormalities with regard to number and shape. In 1989 a second biopsy was performed for an extended analysis of mitochondrial DNA. This time less than 5% of all fibers were ragged-red. Severe myopathic changes could be detected which so far has rarely been reported in mitochondrial cytopathy
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