Noisy inflows cause a shedding-mode switching in flow past an oscillating cylinder

Vortex streets formed behind oscillating bluff bodies consist of arrays of groups of two, three, or four vortices classified as 2S, P+S, and 2P shedding modes, respectively. The prevailing dominant mode depends primarily on the amplitude and the frequency of the oscillation and on the Reynolds number. We investigate the effect of noise at the inflow on the stability of these vortex modes in laminar flow past a circular cylinder. We employ stochastic simulations based on a new polynomial chaos method to study the shedding-mode switching from a P+S pattern to a 2S mode in the presence of noise.     

BLOCH modes dressed by evanescent waves and the generalized Goos-Hänchen effect in photonic crystals

It is common knowledge that in an infinite periodic medium, for instance, an infinite photonic crystal, the direction of propagation of a monochromatic wave packet is given by the normal to the isofrequency diagram. We show that this is no longer true in a finite size medium, due to the existence of evanescent waves near the interfaces of the photonic crystal. We derive a renormalized isofrequency diagram giving the correct direction. We give a physical interpretation, showing that this phenomenon can be considered as a generalized Goos-H?nchen effect.     

Supported choline hydroxide (ionic liquid) as heterogeneous catalyst for aldol condensation reactions

Choline hydroxide was used as a basic catalyst for aldol condensation reactions to produce new C-C bonds between several ketones and aldehydes. Choline supported on MgO exhibits higher TOF values than other well known basic catalysts in these reactions.     

广义基的多重散射理论

提出了任意函数基表象中的多重散射理论. 基于这个框架, 一组新基的多重散射计算表明其收敛性比传统的球谐函数基的要好, 从而可以实现更快和更节省物理内存的计算. 另外, 将多重散射矩阵分为传播矩阵和散射矩阵, 很好地描述了散射性质和减小了多重散射计算中块矩阵的尺寸.     

Modeling the interactions of a peptide-major histocompatibility class I ligand with its receptors. I. Recognition by two αβ T cell receptors

A three-dimensional model of the complex between an Influenza Hemagglutinin peptide, Ha_255–262, and its restricting element, the mouse major histocompatibility complex (MHC) class I molecule, K^k, was built by homology modeling and subsequently refined by simulated annealing and restrained molecular dynamics. Next, three-dimensional models of two different T cell receptors (TCRs) both specific for the Ha_255–262/K^k complex were generated based on previously published TCR X-ray structures. Finally, guided by the recently published X-ray structures of ternary TCR/peptide/MHC-I complexes, the TCR models were successfully docked into the Ha_255–262/K^k model. We have previously used a systematic and exhaustive panel of 144 single amino acid substituted analogs to analyze both MHC binding and T cell recognition of the parental viral peptide. This large body of experimental data was used to evaluate the models. They were found to account well for the experimentally obtained data, lending considerable support to the proposed models and suggesting a universal docking mode for TCRs to MHC-peptide complexes. Such models may also be useful in guiding future rational experimentation.     

Optical management in high‐efficiency thin‐film silicon micromorph solar cells with a silicon oxide based intermediate reflector

In the effort to increase the stable efficiency of thin film silicon micromorph solar cells, a silicon oxide based intermediate reflector (SOIR) layer is deposited in situ between the component cells of the tandem device. The effectiveness of the SOIR layer in increasing the photo‐carrier generation in the a‐Si:H top absorber is compared for p–i–n devices deposited on different rough, highly transparent, front ZnO layers. High haze and low doping level for the front ZnO strongly enhance the current density (J_sc) in the μc‐Si:H bottom cell whereas J_sc in the top cell is influenced by the angular distribution of the transmitted light and by the reflectivity of the SOIR related to different surface roughness. A total J_sc of 26.8 mA/cm² and an initial conversion efficiency of 12.6% are achieved for 1.2 cm² cells with top and bottom cell thicknesses of 300 nm and 3 μm, and without any anti‐reflective coating on the glass. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Applications of 13C Nmr spectroscopy to structural assignment of derivatives of 2,3,4,5,6,7-hexahydro-1H-2-benzazonine

Treatment of 1,1-dimethyl-2-tolylpiperidinium halides with sodium amide in liquid ammonia affords derivatives of 2,3,4,5,6,7-hexahydro-1H-2-benzazonine via the Sommelet-Hauser rearrangement. Structures of the reaction products have been established by ¹³C nmr. In the case of 1,1-dimethyl-2-benzylpiperidinium halide, only an elimination reaction takes place.