Selection of a Realistic Viscous Vortex Tangential Velocity Profile for Computer Simulation of Vortex-Structure Interaction

Structure loading by vortices is a relevant phenomenon in numerous fields of engineering significance. Computer modelling is a powerful tool that can be used to study the loading produced on structures by impacting vortices. Realistic simulation of vortex-loading of structures necessitates the use of a realistic vortex tangential velocity profile (TVP). The present study compiles measured TVPs from various types of experimentally-produced vortices as well as real-world tornado and hurricane vortices. The measured TVPs are compared with commonly-used, analytical TVPs. Analytical TVPs that realistically represent the range of measured TVPs are identified and selected for use in future computer simulation studies

Oscillatory instabilities during formic acid oxidation on Pt(100), Pt(110) and Pt(111) under potentiostatic control. II. Model calculations

A kinetic model is developed for the electrocatalytic oxidation of formic acid on Pt under potentiostatic control. The model development proceeds stepwise via a simple model of the electrocatalytic CO oxidation. The full model consists of four coupled, nonlinear ordinary differential equations. The scanned and stationary current/outer potential (I/U) behavior, stationary current oscillations, two-parameter bifurcation diagrams and stirring effects are simulated using realistic model parameters. The numerical findings are found to be consistent with the experimental results given by Strasser et al. The model reproduces period-1 as well as mixed-mode oscillations. Furthermore, a mechanistic analysis of the model was performed: two suboscillators are identified whose characteristics allow a plausible interpretation of the observed dynamics. After a classification of the suboscillators into previously described categories, an attempt is made to identify the minimal mechanistic requirements for electrochemical current oscillations

Hydrogen Flare Stack Diffusion Flames - Low and High Flow Instabilities, Burning Rates, Dilution Limits, Temperatures, and Wind Effects

Combustion characteristics and safety factors for hydrogen diffusion flames in flare stack operation

Rfx6 Maintains the Functional Identity of Adult Pancreatic β Cells.

SummaryIncreasing evidence suggests that loss of β cell characteristics may cause insulin secretory deficiency in diabetes, but the underlying mechanisms remain unclear. Here, we show that Rfx6, whose mutation leads to neonatal diabetes in humans, is essential to maintain key features of functionally mature β cells in mice. Rfx6 loss in adult β cells leads to glucose intolerance, impaired β cell glucose sensing, and defective insulin secretion. This is associated with reduced expression of core components of the insulin secretion pathway, including glucokinase, the Abcc8/SUR1 subunit of KATP channels and voltage-gated Ca2+ channels, which are direct targets of Rfx6. Moreover, Rfx6 contributes to the silencing of the vast majority of “disallowed” genes, a group usually specifically repressed in adult β cells, and thus to the maintenance of β cell maturity. These findings raise the possibility that changes in Rfx6 expression or activity may contribute to β cell failure in humans

Inflammatory bowel disease-specific autoantibodies in HLA-B27-associated spondyloarthropathies: Increased prevalence of ASCA and pANCA

Aims: An association between inflammatory bowel disease (IBD) and spondyloarthropathies (SpA) has repeatedly been reported. The aim of the present study was to investigate whether serologic markers of IBD, e. g. antibodies against Saccharomyces cerevisiae (ASCA), antibodies against exocrine pancreas (PAB) and perinuclear antineutrophil cytoplasmic antibodies (pANCA) are present in HLA-B27-associated SpA. Methods: 87 patients with HLA-B27-positive SpA and 145 controls were tested for ASCA, PAB and pANCA employing ELISA or indirect immunofluorescence, respectively. Antibody-positive patients were interviewed regarding IBD-related symptoms using a standardized questionnaire. Results/Conclusion: When compared to the controls, ASCA IgA but not ASCA IgG levels were significantly increased in patients with SpA, in particular in ankylosing spondylitis (AS) and undifferentiated SpA (uSpA). pANCA were found in increased frequency in patients with SpA whereas PAB were not detected. The existence of autoantibodies was not associated with gastrointestinal symptoms but sustains the presence of a pathophysiological link between bowel inflammation and SpA. Copyright (C) 2004 S. Karger AG, Basel