Effect of different contact formulations used in commercial FEM software packages on the results of hot forging simulations

Commercial FEM-software packages are widely used in the industry to predict material flow, temperaturedistribution and die load during the forging process. Contact in conjunction with plastic material behaviour,which is typical for forging simulations, leads to highly nonlinear equations in the FEM algorithms, whichmay cause problems in numerical convergence. Some FEM software providers handle this problem byautomatic contact damping or similar algorithms. However, the user has mostly no detailed information aboutadjustments and prediction accuracy. The only possibility for the user to have an impact on the contactbehaviour is to set a friction factor and to choose a friction model (e.g. Coloumb or Shear) appropriate to theinvestigated process. Friction factors are often measured by standard tests like the ring compression test whichshould be valid for all used software packages. In this paper a benchmark between three software programs isperformed based on a model for ring compression tests under typical hot forging conditions. The commercialFEM-software programs Deform2D, Forge2007 and Abaqus are compared by generating a nomogram for eachsoftware package. For all simulations identical physical (temperature, flow curves etc.) as well as numericalinfluence parameters are used. The simulations show a significant divergence in the results depending on theused FEM-software. This leads to the conclusion that a friction coefficient which is true for one softwarepackage can not be transferred directly into another one

Differential endothelial cell gene expression by African Americans versus Caucasian Americans: a possible contribution to health disparity in vascular disease and cancer

<p>Abstract</p> <p>Background</p> <p>Health disparities and the high prevalence of cardiovascular disease continue to be perplexing worldwide health challenges. This study addresses the possibility that genetic differences affecting the biology of the vascular endothelium could be a factor contributing to the increased burden of cardiovascular disease and cancer among African Americans (AA) compared to Caucasian Americans (CA).</p> <p>Methods</p> <p>From self-identified, healthy, 20 to 29-year-old AA (n = 21) and CA (n = 17), we established cultures of blood outgrowth endothelial cells (BOEC) and applied microarray profiling. BOEC have never been exposed to <it>in vivo </it>influences, and their gene expression reflects culture conditions (meticulously controlled) and donor genetics. Significance Analysis of Microarray identified differential expression of single genes. Gene Set Enrichment Analysis examined expression of pre-determined gene sets that survey nine biological systems relevant to endothelial biology.</p> <p>Results</p> <p>At the highly stringent threshold of False Discovery Rate (FDR) = 0, 31 single genes were differentially expressed in AA. <it>PSPH </it>exhibited the greatest fold-change (AA > CA), but this was entirely accounted for by a homolog (<it>PSPHL</it>) hidden within the <it>PSPH </it>probe set. Among other significantly different genes were: for AA > CA, <it>SOS1, AMFR, FGFR3; and for AA < CA, ARVCF, BIN3, EIF4B. </it>Many more (221 transcripts for 204 genes) were differentially expressed at the less stringent threshold of FDR <.05. Using the biological systems approach, we identified shear response biology as being significantly different for AA versus CA, showing an apparent tonic increase of expression (AA > CA) for 46/157 genes within that system.</p> <p>Conclusions</p> <p>Many of the genes implicated here have substantial roles in endothelial biology. Shear stress response, a critical regulator of endothelial function and vascular homeostasis, may be different between AA and CA. These results potentially have direct implications for the role of endothelial cells in vascular disease (hypertension, stroke) and cancer (via angiogenesis). Also, they are consistent with our over-arching hypothesis that genetic influences stemming from ancestral continent-of-origin could impact upon endothelial cell biology and thereby contribute to disparity of vascular-related disease burden among AA. The method used here could be productively employed to bridge the gap between information from structural genomics (for example, disease association) and cell function and pathophysiology.</p

A Dynamic Landscape for Antibody Binding Modulates Antibody-Mediated Neutralization of West Nile Virus

Neutralizing antibodies are a significant component of the host's protective response against flavivirus infection. Neutralization of flaviviruses occurs when individual virions are engaged by antibodies with a stoichiometry that exceeds a required threshold. From this “multiple-hit” perspective, the neutralizing activity of antibodies is governed by the affinity with which it binds its epitope and the number of times this determinant is displayed on the surface of the virion. In this study, we investigated time-dependent changes in the fate of West Nile virus (WNV) decorated with antibody in solution. Experiments with the well-characterized neutralizing monoclonal antibody (MAb) E16 revealed a significant increase in neutralization activity over time that could not be explained by the kinetics of antibody binding, virion aggregation, or the action of complement. Additional kinetic experiments using the fusion-loop specific MAb E53, which has limited neutralizing activity because it recognizes a relatively inaccessible epitope on mature virions, identified a role of virus “breathing” in regulating neutralization activity. Remarkably, MAb E53 neutralized mature WNV in a time- and temperature-dependent manner. This phenomenon was confirmed in studies with a large panel of MAbs specific for epitopes in each domain of the WNV envelope protein, with sera from recipients of a live attenuated WNV vaccine, and in experiments with dengue virus. Given enough time, significant inhibition of infection was observed even for antibodies with very limited, or no neutralizing activity in standard neutralization assays. Together, our data suggests that the structural dynamics of flaviviruses impacts antibody-mediated neutralization via exposure of otherwise inaccessible epitopes, allowing for antibodies to dock on the virion with a stoichiometry sufficient for neutralization

Forgiatura La Metallurgia Italiana -n

INTRODUCTION Friction is a major factor in determining the characteristics of metals as they are formed. In forging, friction is a key factor in the pattern of metal flow and die wear. In general, excessive friction has a negative influence on die wear, product quality, product cost, and productivity. It is therefore common to use various lubricants to reduce friction during metal forming operations. Major factors affecting friction include the normal stress along the die-material interface, the lubrication condition, the relative velocity, the temperature, the roughness and the mechanical properties of the material and/or the die. A detailed investigation of these factors is not easy because the die-material interface in metal forming is under high pressure and temperature. Thus, friction in this area is still somewhat of a mystery even though many researchers have performed detailed studies in various ways for a long tim