Cotransfer of the Eαd and Aβd genes into L cells results in the surface expression of a functional mixed-isotype Ia molecule

Ia molecules play a key role in antigen recognition by T lymphocytes. To analyze the structural features of the individual α and β chains relevant to the assembly of intact Ia molecules, mouse fibroblasts were contransfected with various combinations of haplotype- and isotype-mismatched Ia α/β gene pairs. Two important points emerged. First, the level of surface expression of a given haplotype-mismatched AαAβ pair appears to depend upon the α and β chain alleles involved. Second, transfection with some isotype-mismatched combinations such as EαdAβd results in a significant level of surface expression of a stable mixed-isotype dimer, which also appears to be normally expressed at a low level by an Iad-positive B lymphoma. Moreover, a T-cell hybridoma specific for human gamma globulin and restricted by the Ed molecule was found to be efficiently stimulated by the EαdAβd-positive transfectant in the presence of antigen. The stimulation was specifically inhibited by monoclonal antibodies directed to either the Ia or the L3T4 molecule. These findings suggest that the estimates of the potential number of Ia molecules available in an animal for restricting T-lymphocyte recognition of antigens must be revised

El amor mas verdadero, Durandarte y Belerma : Comedia famosa, y burlesca por el Doctor Mosen Guillen Pierres

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When to Strike: Exploring the Variables That Lead To Successful Decapitation Strikes

The purpose of this thesis is to determine how different variables can affect a terrorist group\u27s reaction to a targeted leadership strike, known as a decapitation strike. Decapitation strikes often produce unwanted results, such as a splintering of the terrorist group, or a failure to destroy the group. It is important that we understand which variables can lead to a group\u27s destruction after a decapitation strike, to maximize the decapitation\u27s effectiveness. In my research I have determined that group size, group ideological extremism, and the role of the leader targeted all have a substantial impact on the success of the decapitation strike. Using these three variables, I will examine three groups which have varying size, extremism, and leadership, and determine whether the decapitation strikes were successful and how these variables affected the results

Development of the automation and control of a microgravity experiment by means of LabVIEW

This master thesis is part of an experimental project carried out at the Space Exploration Laboratory of the Universitat Politècnica de Catalunya, by a five master¿s students team, under the guidance of Ricard Gonzalez Cinca, to study the use of acoustic waves, for heat transfer enhancement, in a gas medium and with the innovation of been done under microgravity conditions, which have never been done before. The objective of the experiment is to obtain new knowledge in this field, which might help Scientifics develop a new version of a thermal control system. The students had the opportunity to experiment under microgravity conditions, by being selected for the Drop Your Thesis Programme, provided by ESA academy, allowing the students to develop the experiment at the Space Exploration Laboratory and test it in the ZARM drop tower. The experiment was divided into different subsystems: mechanical, software, electronics, mathematical simulations and testing. Each subsystem was developed by one of the masters students. This master thesis is focused on the software part of the experiment, designed using LabVIEW from National Instruments. This document is divided into three main parts, starting with the introduction to the experiment, which explains the experiment background information, as well as the Your Thesis Programme, then it continues with the introduction of the experiment software platform, LabVIEW. The thesis finalises with an explanation of the experiment control software developed

Efficiency of initiating cell adhesion in hydrodynamic flow

We theoretically investigate the efficiency of initial binding between a receptor-coated sphere and a ligand-coated wall in linear shear flow. The mean first passage time for binding decreases monotonically with increasing shear rate. Above a saturation threshold of the order of a few 100 receptor patches, the binding efficiency is enhanced only weakly by increasing their number and size, but strongly by increasing their height. This explains why white blood cells in the blood flow adhere through receptor patches localized to the tips of microvilli, and why malaria-infected red blood cells form elevated receptor patches (knobs).Comment: 4 pages, Revtex, 4 Postscript figures included, to appear in PR

A multi-model X-FEM strategy dedicated to frictional crack growth under cyclic fretting fatigue loadings.

International audienceA 2D X-FEM/LATIN numerical model (eXtended Finite Element Method/Large Time Increment method) is proposed in this paper for the analysis of fretting fatigue problems and the simulation of the crack propagation under such loadings. The half-analytical two-body contact analysis allows to capture accurately the pressure and the cyclic tractions exerted at the interface that induce non-proportional multi-axial loading. These distributions are then used as input data for determining critical location for crack initiation and crack inclination based on Dang Van's criterion. The frictional contact conditions of the fretting fatigue cracks have an important impact on the crack behaviour. In this respect, contact with friction between the crack faces is finely modeled within the X-FEM frame. The obtained results are compared and validated with a half-analytical reference model. The numerical simulations reveal the robustness and the efficiency of the proposed approach for a wide range of fretting loadings and friction coefficients values along crack faces. The crack growth directions are then predicted accurately based on the use of criteria adapted to multi-axial non-proportional fatigue. Four cases dealing with crack propagation are then presented. It is shown how the crack length, the tangential loading modify the crack path during the propagation process

Biomolecule association rates do not provide a complete description of bond formation.: Biomolecule association rates

International audienceThe efficiency of many cell-surface receptors is dependent on the rate of binding soluble or surface-attached ligands. Much effort was exerted to measure association rates between soluble molecules (three-dimensional k(on)) and, more recently, between surface-attached molecules (two-dimensional [2D] k(on)). According to a generally accepted assumption, the probability of bond formation between receptors and ligands is proportional to the first power of encounter duration. Here we provide new experimental evidence and review published data demonstrating that this simple assumption is not always warranted. Using as a model system the (2D) interaction between ICAM-1-coated surfaces and flowing microspheres coated with specific anti-ICAM-1 antibodies, we show that the probability of bond formation may scale as a power of encounter duration that is significantly higher than 1. Further, we show that experimental data may be accounted for by modeling ligand-receptor interaction as a displacement along a single path of a rough energy landscape. Under a wide range of conditions, the probability that an encounter of duration t resulted in bond formation varied as erfc[(t(0)/t)(1/2)], where t(0) was on the order of 10 ms. We conclude that the minimum contact time for bond formation may be a useful parameter to describe a ligand-receptor interaction, in addition to conventional association rates

Comedia famosa, y burlesca. El amor más verdadero, Durandarte, y Belerma / por el Doctor Monsieur Guillen Pierres

Precede al tít.: "Num. 254."Datos de imp. obtenidos del colofónSign.: A-B4.Texto a 2 col