Search results for "sigma"
showing 10 items of 346 documents
Elastic properties of the sigma W-Re phase: A first principles investigation
2017
Abstract We perform density functional theory (DFT) calculations to obtain the formation enthalpy and six independent elastic constants for the 32 possible occupations of the five non-equivalent sites of the σ -phase. The obtained results suggest linear correlation between bulk modulus and Re concentration and between shear modulus and formation enthalpy. The results are used to parameterize a sublattice model with ideal mixing on each sublattice for the free energy and elastic constants. The model allows one to predict the equilibrium composition on each sublattice and hence elastic constants as a function of global Re concentration and temperature of the W-Re alloy.
Experimental and numerical investigation on a new FSW based metal to composite joining technique
2018
Abstract In the last decades, different techniques were proposed to join aluminum sheets with composites materials. Each of them has advantages and weak points over the others and new techniques and patents are continuously developed to overcome these difficulties. In this paper an experimental and numerical investigation on a new Friction Stir Welding based approach to mechanically join AA6082-T6 to self-reinforced polypropylene is presented. The aluminum sheet is pre-holed along both the sides of the weld line and a pinless tool generates the heat and pressure needed to prompt back-extrusion of the composite. New experimental fixtures and hole designs were investigated in order to enhance…
Roles for RpoS in survival of Escherichia coli during protozoan predation and in reduced moisture conditions highlight its importance in soil environ…
2017
The soil is a complex ecosystem where interactions between biotic and abiotic factors determine the survival and fate of microbial inhabitants of the system. Having previously shown that Escherichia coli requires the general stress response regulator, RpoS, to survive long term in soil, it was important to determine what specific conditions in this environment necessitate a functional RpoS. This study investigated the susceptibility of soil-persistent E. coli to predation by the single-celled eukaryotes Acanthamoeba polyphaga and Tetrahymena pyriformis, and the role RpoS plays in resisting this predation. Strain-specific differences were observed in the predation of E. coli strains, with so…
(+)-Pentazocine reduces oxidative stress and apoptosis in microglia following hypoxia/reoxygenation injury
2016
Abstract Background Sigma-1 receptors (σ 1 R) are highly expressed in neurons as well as microglia and have been shown to modulate the inflammatory response in the central nervous system and thus may serve as possible target for neuroprotective strategies. The aim of the present study was to test the effect of (+)-pentazocine, a putative σ 1 R agonist, in an in vitro model of microglia activation. Methods Microglia (BV2 cells) was exposed (3 h) to 1% oxygen and reoxygenation was allowed for 24 h. Cells were treated with different concentrations (1, 10, 25 and 50 μM) of (+)-pentazocine in the presence or absence of NE-100 (1 μM), a well established σ 1 R antagonist. Cell viability and apopto…
The Sigma-1 Receptor at the Crossroad of Proteostasis, Neurodegeneration, and Autophagy.
2020
Neurodegenerative diseases are linked to dysfunctional proteostasis and disturbed autophagy. Here, we discuss how the sigma-1 receptor (Sig-1R) may act at the intersection of this interaction, as loss-of-function mutations of this unique chaperone are associated with defective autophagy and its pharmacological activation induces autophagic activity.
Genetic inactivation of the sigma-1 chaperone protein results in decreased expression of the R2 subunit of the GABA-B receptor and increased suscepti…
2021
There is a growing body of evidence demonstrating the significant involvement of the sigma-1 chaperone protein in the modulation of seizures. Several sigma-1 receptor (Sig1R) ligands have been demonstrated to regulate the seizure threshold in acute and chronic seizure models. However, the mechanism by which Sig1R modulates the excitatory and inhibitory pathways in the brain has not been elucidated. The aim of this study was to compare the susceptibility to seizures of wild type (WT) and Sig1R knockout (Sig1R−/−) mice in intravenous pentylenetetrazol (PTZ) and (+)-bicuculline (BIC) infusion-induced acute seizure and Sig1R antagonist NE-100-induced seizure models. To determine pos…
Transcriptional regulation of theNε‐fructoselysine metabolism inEscherichia coliby global and substrate‐specific cues
2020
Thermally processed food is an important part of the human diet. Heat-treatment, however, promotes the formation of so-called Amadori rearrangement products, such as fructoselysine. The gut microbiota including Escherichia coli can utilize these compounds as a nutrient source. While the degradation route for fructoselysine is well described, regulation of the corresponding pathway genes frlABCD remained poorly understood. Here, we used bioinformatics combined with molecular and biochemical analyses and show that fructoselysine metabolism in E. coli is tightly controlled at the transcriptional level. The global regulator CRP (CAP) as well as the alternative sigma factor σ32 (RpoH) contribute…
The proof of Birman’s conjecture on singular braid monoids
2003
Let B_n be the Artin braid group on n strings with standard generators sigma_1, ..., sigma_{n-1}, and let SB_n be the singular braid monoid with generators sigma_1^{+-1}, ..., sigma_{n-1}^{+-1}, tau_1, ..., tau_{n-1}. The desingularization map is the multiplicative homomorphism eta: SB_n --> Z[B_n] defined by eta(sigma_i^{+-1}) =_i^{+-1} and eta(tau_i) = sigma_i - sigma_i^{-1}, for 1 <= i <= n-1. The purpose of the present paper is to prove Birman's conjecture, namely, that the desingularization map eta is injective.
"Table 3" of "Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC"
2022
Production cross section of charm-anticharm quark pairs per unity of rapidity at midrapidity $\mathrm{d}\sigma^{\mathrm{c\overline{c}}}/\mathrm{d}y|_{|y| < 0.5}$ in pp collisions at $\sqrt{s} = 2.76$, $5.02$, and $7$ TeV.
"Table 1" of "J/$\psi$ suppression at forward rapidity in Pb-Pb collisions at $\mathbf{\sqrt{s_{{\rm NN}}} = 5.02}$ TeV"
2017
Differential cross section ${\rm d}^2\sigma^{\rm pp}_{{\rm J}/\psi}/{\rm d}y{\rm d}p_{\rm T}$ for inclusive J/$\psi$ cross section in pp collisions at $\sqrt{s}=5.02$ TeV. The first uncertainty is statistical, the second is the uncorrelated systematic, while the third one is a $p_{\rm T}$-correlated systematic uncertainty.