Publications by authors named "A Bretana"

In actinide systems, the 5electrons experience a uniquely delicate balance of effects and interactions having similar energy scales, which are often difficult to properly disentangle. This interplay of factors such as the dual nature of 5-states, strong electronic correlations, and strong spin-orbit coupling results in electronically unusual and intriguing behavior such as multi-k antiferromagnetic ordering, multipolar ordering, Mott-physics, mixed valence configurations, and more. Despite the inherent allure of their exotic properties, the exploratory science of even the more basic, binary systems like the actinide oxides has been limited due to their toxicity, radioactivity, and reactivity.

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We present the results of computer simulations on a class of percolative systems, called protected percolation, that violates the Harris criterion. The Harris criterion states whether the critical behavior at a phase transition from a disordered state to an ordered state will be altered by impurities. We incorporate impurities into our simulations to test whether the critical exponents for protected percolation are altered by impurities.

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Emodin is an anthraquinone obtained from Rheum palmatum rootstocks. Here we tested the cytotoxic effects of emodin on Trypanosoma cruzi epimastigotes, as well as the morphological changes that were induced by this compound in the parasite. Emodin was permeable and blocked in vitro cell division of T.

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Blood samples from a splenectomized bovine, experimentally inoculated with blood from a field cow living in southwestern Venezuela, were processed for transmission and scanning electron microscopy. The blood sample showed multiple infection with hemoparasites of the genera Anaplasma marginale, Eperythrozoon wenyonii and Trypanosoma vivax. Scanning electron microscope showed that the blood from bovines with multiple infection had profound deformation in knob-like protruding structures with reduced cellular volume similar to echinocyte red blood cells.

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Clinical evidence and the use of experimental models in laboratory animals indicate that the intestine is a reservoir of microorganisms that can cause systemic infection in the human. The purpose of this work was to study the possible effect of intestinal obstruction (IO) on the mechanical and chemical barriers that bring protection against microorganisms crossing from the intestinal lumen towards the systemic tissues. We demonstrated that 24 hours after IO, histological and ultrastructural alterations do occur, seriously compromising the structure of the intestinal barrier in 100% of the studied animals.

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