PREDICTION OF PATH-DEPENDENT FAILURE IN ALUMINUM SHEET METALS UNDER FORMING OPERATIONS

1.IntroductionGurson[1]developedayieldcriterionforvoidedmaterialsofwhichthematricesaremodeledbythevonMisesyieldcriterion.Liaoetal.[2]developedamacroscopicyieldcriterionthatcanaccountforthematrixplasticanisotropycharacterizedbyHill'squadraticanisotropicyieldcriterion.Theaimofthisworkistodevelopafailurepredictionmethodologythatcanbeusedtopredictfailureinanisotropic,rate--sensitivesheetmetalsunderformingprocesses.TheMarciniak--Kuczynskiapproach[3]isadoptedherebyassumingaslightlyhighervoidvolume…     

Identification of Lysophosphatidylcholine–Chlorohydrin in Human Atherosclerotic Lesions

Lysophosphatidylcholine (LysoPtdCho) levels are elevated in sera in patients with atherosclerosis and in atherosclerotic tissue. Previous studies have shown that reactive chlorinating species attack plasmalogens in human coronary artery endothelial cells (HCAEC), forming lysoPtdCho and lysoPtdCho–chlorohydrin (lysoPtdCho–ClOH). The results herein demonstrate for the first time that lysoPtdCho–ClOH is elevated over 60-fold in human atherosclerotic lesions. In cultured HCAEC, 18:0 lysoPtdCho–ClOH led to a statistically significant increase in P-selectin cell-surface expression, but unlike 18:1 lysoPtdCho did not lead to cyclooxygenase-2 protein expression. These data show that 18:0 lysoPtdCho–ClOH is elevated in atherosclerotic tissue and may have unique pro-atherogenic properties compared to lysoPtdCho.     

Quantification of Pentafluorobenzyl Oxime Derivatives of Long Chain Aldehydes by GC–MS Analysis

Negative ion mass spectrometric techniques, for compounds having good ionization properties, such as pentafluorobenzyl derivatives, are believed to be more sensitive than positive ion methods. Preparation of PFB oximes of fatty aldehydes from crude lipid extracts is problematic due to the release of free aldehydes from plasmalogens during derivatization. Accordingly, in these studies plasmalogens were removed by silicic acid column chromatography prior to pentafluorobenzyl derivatization. This simple purification step to remove plasmalogens is shown to facilitate the quantification of long-chain aldehydes by analysis of their pentafluorobenzyl oxime derivatives utilizing gas chromatography–mass spectrometry in the negative ion chemical ionization mode. The limit of detection for long chain fatty aldehydes using this method is 0.5 pmol and it is linear over two orders of magnitude. Silicic acid column chromatography followed by electrospray ionization mass spectrometry demonstrated that plasmalogens were removed (the detection limit for this analyses was ≤0.3 pmol). Furthermore, we have exploited the utility and sensitivity of this method to identify increases in hexadecanal and octadecanal in 3-amino-1,2,4-triazole treated human neutrophils. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Validation of scales measuring attitudes, self-efficacy, and intention related to smoking among middle school students.

Attitudes toward smoking, self-efficacy to avoid smoking, and smoking intention, widely cited correlates of youth smoking prevention, are often measured in large-scale youth tobacco surveys. The psychometric properties of these scales have not been well studied among middle school youth. We examined the factorial, discriminate, and convergent validity of these scales among sixth to eighth graders from a convenience sample of 22 Texas middle schools (51.2% female; 51.21% White, 32.1% Hispanic, 16.9% African American, and 8.8% Other; 67.8% nonsmokers, 21.9% experimental smokers; 3.3% former smokers; and 7.6% current smokers). Confirmatory factor analysis and invariance testing suggest that smoking attitudes, self-efficacy, and intention have evidence of construct validity in this multiethnic sample, and the scales are appropriate to assess these constructs among middle school adolescents. Additional studies are needed to establish additional evidence of validity of these constructs in other middle school samples and other subgroups (e.g. current, experimental, and former smokers). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The fluid-filling system for the Borexino solar neutrino detector

The system for controlled filling of the nested flexible scintillator containment vessels in the Borexino solar neutrino detector is described. The design and operation principles of pressure and shape monitoring systems are presented for gas filling, gas displacement by water, and water displacement by scintillator. System specifications for safety against overstressing the flexible nylon vessels are defined as well as leak-tightness and cleanliness requirements. The fluid-filling system was a major engineering challenge for the Borexino detector.     

Contact conductivity detection in poly(methyl methacrylate)-based microfluidic devices for analysis of mono- and polyanionic molecules

An on-column contact conductivity detector was developed for the analysis of various mono- and polyanionic compounds separated by electrophoresis chips fabricated in poly(methyl methacrylate) (PMMA) using hot embossing techniques from Ni electroforms. The detector consisted of a pair of Pt wires (127 microm diameter) with an end-to-end spacing of approximately 20 microm and situated within the fluidic channel. The waveform applied to the electrode pair was a bipolar pulse with a frequency of 5.0 kHz and was used to reduce the charging current from measurement so that the current recorded at the end of one pulse is more representative of the solution conductivity. Using the detector, separations of amino acids, peptides, proteins, and oligonucleotides were demonstrated. For the amino acids and peptides, free-solution zone electrophoresis was performed. A calibration plot for the amino acid alanine was found to be linear from approximately 10 to 100 nM in a carrier electrolyte consisting of 10 mM triethylamonium acetate. The concentration detection limit was found to be 8.0 nM, with the corresponding mass detection limit equal to 3.4 amol (injection volume = 425 pL). The protein separations with conductivity detection were performed using MEKC, in which the carrier electrolyte contained the anionic surfactant sodium dodecyl sulfate (SDS) above its cmc. Near baseline resolution was achieved in the PMMA microchip for a solution containing 8 different proteins. In the case of the DNA fragments, capillary electrochromatography was used with a C18-modified PMMA chip and a carrier electrolyte containing an ion-pairing agent.     

QSAR studies of the pyrethroid insecticides. Part 3. A putative pharmacophore derived using methodology based on molecular dynamics and hierarchical cluster analysis

Previous studies of the conformational behaviour of a group of synthetic pyrethroid insecticides have been extended to a more structurally diverse set. This includes compounds with different backbones and differing stereochemistry, with both Types I and II biological activity. These compounds also encompass a large range of biological activities. A parameterisation of the CHARMM force field for these compounds has been performed and the extra parameters are reported. Conformational sampling, using molecular dynamics (MD), has been performed for each of the 41 active structures. The accessible conformations of each have been characterised by the values of the common torsion angles using hierarchichal cluster analysis (HCA). A further CA, based on the centroids derived from the conformational sampling, identified a conformation common to at least 39 of the 41 structures. The critical torsion angles of this conformation lie at the centre of the molecule about the ester linkage and are defining an extended conformation, which differs from the minimum energy conformation of deltamethrin used previously. This may represent a putative pharmacophore for kill. The methods used here improve significantly on those used previously. The CHARMM force field was parameterised for the compounds and an improved method of conformational sampling, based on centroid clustering, has also been used.     

Proteolytic cleavage and activation of PAK2 during UV irradiation-induced apoptosis in A431 cells

Exposure of mammalian cells to ultraviolet (UV) light elicits a cellular response and can also lead to apoptotic cell death. In this report, we show that a 36-kDa myelin basic protein (MBP) kinase detected by an in-gel kinase assay can be dramatically activated during the early stages of UV irradiation-triggered apoptosis of A431 cells. Immunoblot analysis revealed that this 36-kDa MBP kinase could be recognized by an antibody against the C-terminal regions of a family of p21Cdc42/Rac-activated kinases (PAKs). By using this antibody and a PAK2-specific antibody against the N-terminal region of PAK2 as studying tools, we further demonstrated that UV irradiation caused cleavage of PAK2 to generate a 36-kDa C-terminal catalytic fragment and a 30-kDa N-terminal fragment in A431 cells. The appearance of the 36-kDa C-terminal catalytic fragment of PAK2 matched exactly with the activation of the 36-kDa MBP kinase in A431 cells upon UV irradiation. In addition, UV irradiation also led to activation of CPP32/caspase-3, but not ICH-1L/caspase-2 and ICE/caspase-1, in A431 cells and the kinetics of activation of CPP32/caspase-3 appeared to correlate well with that of DNA fragmentation and of cleavage/activation of PAK2, respectively. Moreover, blockage of activation of CPP32/caspase-3 by pretreating the cells with two specific tetrapeptidic inhibitors for caspases (Ac-DEVD-cho and Ac-YVAD-cmk) could significantly attenuate the extent of cleavage/activation of PAK2 induced by UV irradiation. Collectively, the results demonstrate that cleavage and activation of PAK2 can be induced during the early stages of UV irradiation-triggered apoptosis and indicate the involvement of CPP32/caspase-3 in this process.