A tensorial framework for strain induced damage of plastically deformed metals

A tensorial framework for strain induced ductile damage of plastically deformed metals is developed in terms of both plastic flow theory and continuum damage mechanics. A symmetric second order damage rate tensor is used in order to study various processes with large finite deformations in combination with damage analysis. The definition of this tensor is physically meaningful since its volumetric and deviatoric parts describe the damage increments caused by an increase in the void volume and by a change in the shape of the void, respectively. Such a view on damage kinetics leads to the introduction of two measures for damage assessment which allow predicting not only a risk of macroscopic failure but also the onset of void coalescence. Material functions appearing in the constitutive equations for damage are determined both by own experiments and by known results from literature. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

4-Aminobenzimidazole-1-methylthymine: a model for investigating Hoogsteen base-pairing between adenine and thymine

We report the infrared spectrum of the 4-aminobenzimidazole-1-methylthymine (4ABI:1MT) heterodimer, detected by femtosecond multiphoton ionization. Based on calculations of both the harmonic and the anharmonic frequencies, the observed vibrational spectrum is assigned to a structure that mimics the Hoogsteen base pairing of adenine and thymine. A notable observation made in the course of this study is that there is a significant imbalance in the observed strengths of the H-bonds. While the N···H-N bond reveals a large red shift of >700 cm(-1) for the NH stretch frequency, the N-H···O bond is characterized by only a 50 cm(-1) shift. The importance of this observation in the formation of Hoogsteen duplexes by thymine-based oligonucleotides is discussed.     

Effect of amyloid beta peptides Aβ<Subscript>1–28</Subscript> and Aβ<Subscript>25–40</Subscript> on model lipid membranes

To investigate the molecular interaction of amyloid beta peptides Aβ_1–28 or Aβ_25–40 with model lipid membranes differential scanning calorimetry (DSC) and DPH and TMA DPH fluorescence anisotropy approaches were used. The main transition temperature (T _m) and enthalpy change (ΔH) of model lipid membranes composed of DMPC/DPPG on addition of Aβ_25–40 or Aβ_25–40 at 10:1 (w/w) phospholipid/peptide ratio either non-aggregated or previously aggregated were examined. The effect of Aβ_1–28 and Aβ_25–40 on the membrane fluidity of liposomes made of DMPC/DPPG (98:2 w/w) was determined by fluorescence anisotropy of incorporated DPH and TMA DPH. The results of this study provide information that Aβ_1–28 preferentially interacts with the hydrophilic part of the model membranes, while Aβ_25–40 rather locates itself in the hydrophobic core of the bilayer where it reduces the order of the phospholipids packing.     

GaAs(1-x)Bix: A Promising Material for Optoelectronics Applications

Bismuth alloying with GaAs has promised greater advantages in the realization of more convenient mid and near IR photonic devices owing to its novel and unique properties. The coexistence of faster band gap reduction and a strong increase in spin-orbit splitting energy with an increase in Bi concentration is one of those. However, the realization of practical devices is hindered due to several critical issues associated with the electronic properties of this material. Many of these limitations primarily arise due the difficulty obtaining high-quality structures. In this article, we review the growth and properties of GaAs_(1?x)Bi_x. We have provided a comprehensive study of the properties by considering both from a fundamental perspective and also on their potential device applications.