Yield conditions for deformation of amorphous polymer glasses

Shear yielding of glassy polymers is usually described in terms of the pressure-dependent Tresca or von Mises yield criteria. We test these criteria against molecular dynamics simulations of deformation in amorphous polymer glasses under triaxial loading conditions that are difficult to realize in experiments. Difficulties and ambiguities in extending several standard definitions of the yield point to triaxial loads are described. Two definitions, the maximum and offset octahedral stresses, are then used to evaluate the yield stress for a wide range of model parameters. In all cases, the onset of shear is consistent with the pressure-modified von Mises criterion, and the pressure coefficient is nearly independent of many parameters. Under triaxial tensile loading, the mode of failure changes to cavitation.Comment: 9 pages, 8 figures, revte

Gene-educational attainment interactions in a multi-population genome-wide meta-analysis identify novel lipid loci

Introduction: Educational attainment, widely used in epidemiologic studies as a surrogate for socioeconomic status, is a predictor of cardiovascular health outcomes.Methods: A two-stage genome-wide meta-analysis of low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglyceride (TG) levels was performed while accounting for gene-educational attainment interactions in up to 226,315 individuals from five population groups. We considered two educational attainment variables: "Some College" (yes/no, for any education beyond high school) and "Graduated College" (yes/no, for completing a 4-year college degree). Genome-wide significant (p < 5 x 10(-8)) and suggestive (p < 1 x 10(-6)) variants were identified in Stage 1 (in up to 108,784 individuals) through genome-wide analysis, and those variants were followed up in Stage 2 studies (in up to 117,531 individuals).Results: In combined analysis of Stages 1 and 2, we identified 18 novel lipid loci (nine for LDL, seven for HDL, and two for TG) by two degree-of-freedom (2 DF) joint tests of main and interaction effects. Four loci showed significant interaction with educational attainment. Two loci were significant only in cross-population analyses. Several loci include genes with known or suggested roles in adipose (FOXP1, MBOAT4, SKP2, STIM1, STX4), brain (BRI3, FILIP1, FOXP1, LINC00290, LMTK2, MBOAT4, MYO6, SENP6, SRGAP3, STIM1, TMEM167A, TMEM30A), and liver (BRI3, FOXP1) biology, highlighting the potential importance of brain-adipose-liver communication in the regulation of lipid metabolism. An investigation of the potential druggability of genes in identified loci resulted in five gene targets shown to interact with drugs approved by the Food and Drug Administration, including genes with roles in adipose and brain tissue.Discussion: Genome-wide interaction analysis of educational attainment identified novel lipid loci not previously detected by analyses limited to main genetic effects.Pathophysiology, epidemiology and therapy of agein

Multi-ancestry study of blood lipid levels identifies four loci interacting with physical activity

Many genetic loci affect circulating lipid levels, but it remains unknown whether lifestyle factors, such as physical activity, modify these genetic effects. To identify lipid loci interacting with physical activity, we performed genome-wide analyses of circulating HDL cholesterol, LDL cholesterol, and triglyceride levels in up to 120,979 individuals of European, African, Asian, Hispanic, and Brazilian ancestry, with follow-up of suggestive associations in an additional 131,012 individuals. We find four loci, in/near CLASP1, LHX1, SNTA1, and CNTNAP2, that are associated with circulating lipid levels through interaction with physical activity; higher levels of physical activity enhance the HDL cholesterol-increasing effects of the CLASP1, LHX1, and SNTA1 loci and attenuate the LDL cholesterol- increasing effect of the CNTNAP2 locus. The CLASP1, LHX1, and SNTA1 regions harbor genes linked to muscle function and lipid metabolism. Our results elucidate the role of physical activity interactions in the genetic contribution to blood lipid levels

Preliminary X-ray crystallographic analysis of ornithine acetyltransferase (Rv1653) from Mycobacterium tuberculosis

Rv1653, an ornithine acetyltransferase from M. tuberculosis, has been crystallized and diffraction data have been collected to 1.7 Å resolution

Viscoelastic Effects on Intralaminar Fracture Toughness of Epoxy/Carbon-fibre Laminates

The Double Torsion technique has been applied to characterize the fracture resistance of a unidirectional an a woven epoxy/ carbon-fire composite material. The crack speed has been varied by about four orders of magnitude for testing temperatures ranging form below the glass transition of the rubber modifier of the epoxy matrix to the glass transition of the matrix itself. A noteworthy variation was found in the fracture toughness and surface morphology of the unidirectional composite. Decreasing fracture toughness values were observed by increasing crack speed at 23 °C, which is somewhat unusual for viscoelastic materials. Results have been discussed in the framework of viscoelastic fracture mechanics, and the fracture behavior at different rates and temperatures has been shown to be related to different viscoelastic mechanisms

Synthetic cannabinoid receptor agonists: analytical profiles and development of QMPSB, QMMSB, QMPCB, 2F-QMPSB, QMiPSB, and SGT-233

A diverse assortment of molecules designed to explore the cannabinoid receptor system and considered new psychoactive substances (NPS) have become known as synthetic cannabinoid receptor agonists (SCRAs). One group of SCRAs that has received little attention involves those exhibiting sulfamoyl benzoate, sulfamoyl benzamide, and N-benzoylpiperidine based structures. In this study, quinolin-8-yl 4-methyl-3-(piperidine-1-sulfonyl)benzoate (QMPSB), quinolin-8-yl 4-methyl-3-(morpholine-4-sulfonyl)benzoate (QMMSB), quinolin-8-yl 4-methyl-3-(piperidine-1-carbonyl)benzoate (QMPCB, SGT-11), quinolin-8-yl 3-(4,4-difluoropiperidine-1-sulfonyl)-4-methylbenzoate (2F-QMPSB, QMDFPSB, SGT-13), quinolin-8-yl 4-methyl-3-[(propan-2-yl)sulfamoyl]benzoate (QMiPSB, SGT-46), and 3-(4,4-difluoropiperidine-1-sulfonyl)-4-methyl-N-(2-phenylpropan-2-yl)benzamide (SGT-233) were extensively characterized (including data on impurities). The analytical profiles may be useful to researchers and scientists who deal with the emergence of NPS during forensic and clinical investigations. The detection of QMPSB was first published in 2016 but it is worth noting that Stargate International, a company originally formed to develop harm reduction solutions, were involved in the investigation and development of these six compounds for potential release between 2011 and early 2014. Whilst information on the prevalence of use of these particular compounds at the present time is limited, one of the key outcomes of the research performed by Stargate International reviewed here was to set the stage for the quinolin-8-yl ester head group that ultimately led to hybridization with an N-alkyl-1H-indole core to give SGT-21 and SGT-32, which became later known as PB-22 (QMPSB/JWH-018 hybrid) and BB-22, respectively, thus, opening the door to a range of SCRAs carrying the quinolin-8-yl head group from about 2012 onwards