RSM and v2 -f predictions of an impinging jet in a cross flow on a heated surface and on a pedestal

The objective of this study is to compare the performance of the v 2 -f and the Reynolds Stress Model (RSM) turbulence model with a two-layer wall treatment for the prediction of the mean velocity field, the turbulence characteristics and the heat transfer rate of the normal impinging jet and also impinging jet in a cross-flow configuration. The numerical predictions are validated against detailed experimental measurements, using PIV and a low-wavelength infrared imaging system, for the measurement of turbulent flow features and surface temperatures. A linear pressure-strain model is used in the RSM. The turbulent heat fluxes are modeled by the eddy-diffusivity hypothesis with a constant value of the turbulent Prandtl number. The mesh is refined enough near the solid walls (y+≈1) to adequately resolve the boundary layers. The results show several complex flow-related phenomena that affect the cooling performance, such as stagnation point, separation region, curvature effects and re-circulating wake flows. These phenomena have to be accurately captured before a good prediction of the heat transfer rate can be attained. A comparison between the v 2 -f and RSM results in the stagnation region, in the other near-wall regions and in the free shear region will be presented in order to evaluate the performance of the two models

Decreased agonist affinity and chloride conductance of mutant glycine receptors associated with human hereditary hyperekplexia.

Hereditary hyperekplexia is a dominant neurological disorder associated with point mutations at the channel-forming segment M2 of the glycine receptor alpha 1 subunit. Voltage-clamp recordings from the heterologously expressed mutants (alpha 1R271L or alpha 1R271Q) revealed 146- to 183-fold decreased potencies of glycine to activate the chloride channel, and significantly reduced maximal whole-cell currents as compared with wild-type receptors. In contrast, the ability of the competitive antagonist strychnine to block glycine-induced currents was similar in all cases. Radioligand binding assays showed a 90- to 1365-fold reduction in the ability of glycine to displace [3H]strychnine from its binding site on the mutant receptors. Paralleling the reductions in whole-cell current, the elementary main-state conductances of the mutants (alpha 1R271L, 64 pS; alpha 1R271Q, 14 pS) were lower than that of the wild-type receptor (86 pS). The decreased agonist affinities and chloride conductances of the mutants are likely to cause neural hyperexcitability of affected patients by impairing glycinergic inhibition. In addition, our data reveal that structural modifications of the ion-channel region can affect agonist binding to the glycine receptor

Structure, diversity and synaptic localization of inhibitory glycine receptors.

The inhibitory glycine receptor (GlyR) mediates postsynaptic inhibition in spinal cord, brain stem and other regions of the vertebrate central nervous system. Biochemical and molecular approaches have identified different developmentally and regionally regulated GlyR isoforms that result from the differential expression of at least four genes coding for different variants of the ligand-binding alpha subunit. Molecular studies have allowed identification of GlyR subunit domains implicated in ligand binding, channel formation and receptor assembly. At the postsynaptic membrane, the GlyR colocalizes with a 93-kDa tubulin-binding peripheral membrane protein, gephyrin. Antisense inhibition of gephyrin expression prevents GlyR accumulation at postsynaptic membrane specialization. Thus, gephyrin is essential for postsynaptic receptor topology