“The influence of physical aging on the beta relaxation in La60Ni15Al25 bulk metallic glass has been investigated by mechanical spectroscopy. The amplitude of the beta relaxation (Delta G”) decreases while its relaxation selleck kinase inhibitor time (tau(beta)) increases during aging. We find that, as in organic glasses, the changes of ln (tau(beta)) and ln (Delta G(max)) are linearly correlated with ln (tau(beta)) = b -a ln (G”(max)).
This behavior is discussed in term of the asymmetric double-well potential (ADWP) model, with U and Delta the energies characterizing the ADWP. It is suggested that during aging the ratio U/Delta remains approximately constant, with a value close to the coefficient describing the linear correlation between ln (tau(beta)) and ln (G”(max))(U/Delta similar to a). Moreover, the NCT-501 cost evolution versus aging time of Delta G(max) can be described by a simple stretched exponential equation giving values of tau(aging)
consistent with tan(delta) measurements during aging. The very similar behavior of the beta relaxation during aging in metallic glasses and organic material strongly suggests a common nature for this relaxation. (c) 2014 AIP Publishing LLC.”
“PII proteins are signal transduction that sense cellular nitrogen status and relay this signals to other targets. Azospirillum brasilense is a nitrogen fixing bacterium, which associates with grasses and cereals promoting beneficial effects on plant growth and crop yields. A. brasilense contains two PII encoding genes, named glnB and glnZ. In this paper, glnB was mutagenised in order to identify amino acid residues involved in GlnB signaling. Two variants were obtained by random mutagenesis, GlnBL13P and GlnBV100A and a site directed mutant, GlnBY51F, was obtained. Their ability to complement nitrogenase activity of glnB mutant strains of A. brasilense were determined. The variant
proteins were also overexpressed in Escherichia call, Selleck Barasertib purified and characterized biochemically. None of the GlnB variant forms was able to restore nitrogenase activity in glnB mutant strains of A. brasilense LFH3 and 7628. The purified GlnBY51F and GlnBL13P proteins could not be uridylylated by GlnD, whereas GlnBV100A was uridylylated but at only 20% of the rate for wild type GlnB. Biochemical and computational analyses suggest that residue Leu13, located in the alpha helix 1 of GlnB, is important to maintain GlnB trimeric structure and function. The substitution V100A led to a lower affinity for ATP binding. Together the results suggest that NifA activation requires uridylylated GlnB bound to ATP. (C) 2014 Elsevier GmbH. All rights reserved.”
“Objective: To investigate the spontaneous pregnancy reduction (SPR) rate, SPR-related factors and the effects of SPR on pregnancy outcomes in the patients with multiple pregnancies undergoing in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET).