Simulations of extensional flow in microrheometric devices

We present a detailed numerical study of the flow of a Newtonian fluid through microrheometric devices featuring a sudden contraction–expansion. This flow configuration is typically used to generate extensional deformations and high strain rates. The excess pressure drop resulting from the converging and diverging flow is an important dynamic measure to quantify if the device is intended to be used as a microfluidic extensional rheometer. To explore this idea, we examine the effect of the contraction length, aspect ratio and Reynolds number on the flow kinematics and resulting pressure field. Analysis of the computed velocity and pressure fields show that, for typical experimental conditions used in microfluidic devices, the steady flow is highly three-dimensional with open spiraling vortical structures in the stagnant corner regions. The numerical simulations of the local kinematics and global pressure drop are in good agreement with experimental results. The device aspect ratio is shown to have a strong impact on the flow and consequently on the excess pressure drop, which is quantified in terms of the dimensionless Couette and Bagley correction factors. We suggest an approach for calculating the Bagley correction which may be especially appropriate for planar microchannels

Oxidative stress in the brain and arterial hypertension

Universidade Federal de São Paulo, Dept Physiol, BR-04023060 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Physiol, BR-04023060 São Paulo, BrazilWeb of Scienc

Higher number of Helicobacter pylori CagA EPIYA C phosphorylation sites increases the risk of gastric cancer, but not duodenal ulcer

<p>Abstract</p> <p>Background</p> <p><it>Helicobacter pylori </it>infection is one of the most common infections worldwide and is associated with gastric cancer and peptic ulcer. Bacterial virulence factors such as CagA have been shown to increase the risk of both diseases. Studies have suggested a causal role for CagA EPIYA polymorphisms in gastric carcinogenesis, and it has been shown to be geographically diverse. We studied associations between <it>H. pylori </it>CagA EPIYA patterns and gastric cancer and duodenal ulcer, in an ethnically admixed Western population from Brazil. CagA EPIYA was determined by PCR and confirmed by sequencing. A total of 436 patients were included, being 188 with gastric cancer, 112 with duodenal ulcer and 136 with gastritis.</p> <p>Results</p> <p>The number of EPIYA C segments was significantly associated with the increased risk of gastric carcinoma (OR = 3.08, 95% CI = 1.74 to 5.45, p < 10^-3) even after adjustment for age and gender. Higher number of EPIYA C segments was also associated with gastric atrophy (p = 0.04) and intestinal metaplasia (p = 0.007). Furthermore, patients infected by <it>cag</it>A strains possessing more than one EPIYA C segment showed decreased serum levels of pepsinogen I in comparison with those infected by strains containing one or less EPIYA C repeat. Otherwise, the number of EPIYA C segments did not associate with duodenal ulcer.</p> <p>Conclusions</p> <p>Our results demonstrate that infection with <it>H. pylori </it>strains harbouring more than one CagA EPIYA C motif was clearly associated with gastric cancer, but not with duodenal ulcer.</p> <p>Higher number of EPIYA C segments was also associated with gastric precancerous lesions as demonstrated by histological gastric atrophic and metaplastic changes and decreased serum levels of pepsinogen I.</p

Genotyping of Brazilian Giardia duodenalis human axenic isolates

Giardia duodenalis is a complex species that comprises at least seven distinct genetic groups (A to G), but only genotypes A and B are known to infect humans and a wide variety of other mammals. Regardless of biological, biochemical and antigenic analysis, several isolates maintained in vitro were not genetically typed yet. So, in the present study, five Brazilian axenic isolates obtained from asymptomatic and symptomatic patients were typed in order to determine the major genetic groups to which the isolates belonged. DNA was extracted from axenic trophozoites, fragments of glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi) genes were amplified by PCR and the isolate genotyping was carried out using restriction fragment length polymorphism (RFLP) and DNA sequencing for both genes. The results revealed that all isolates were assigned to genotype A at both analyzed loci. Indeed, DNA sequence analysis classified the four isolates obtained from asymptomatic individuals into subtype AII, while the isolate obtained from the symptomatic patient was typed as subtype AI. Despite of the limited number of isolates assessed, the findings presented herein provide interesting insights on the occurrence of Giardia genotypes in Brazil and hold the perspective for future molecular and epidemiological investigations

Structure of the TPR Domain of AIP: Lack of Client Protein Interaction with the C-Terminal alpha-7 Helix of the TPR Domain of AIP Is Sufficient for Pituitary Adenoma Predisposition

PMCID: PMC3534021This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

On domain walls in a Ginzburg-Landau non-linear S^2-sigma model

The domain wall solutions of a Ginzburg-Landau non-linear $S^2$-sigma hybrid model are unveiled. There are three types of basic topological walls and two types of degenerate families of composite - one topological, the other non-topological- walls. The domain wall solutions are identified as the finite action trajectories (in infinite time) of a related mechanical system that is Hamilton-Jacobi separable in sphero-conical coordinates. The physical and mathematical features of these domain walls are thoroughly discussed.Comment: 26 pages, 18 figure