Friction anisotropy at Ni(100)/(100) interfaces: Molecular dynamics studies

The friction of surfaces moving relative to each other must derive from the atomic interaction at interfaces. However, recent experiments bring into question the fundamental understanding of this phenomenon. The analytic theories predict that most perfect clean incommensurate interfaces would produce no static friction, whereas commensurate aligned surfaces would have very high friction. In contrast recent experiments show that the static friction coefficient between clean but 45° misoriented Ni(001) surfaces is only a factor of 4 smaller than for the aligned surfaces (θ∼0°) and clearly does not vanish (θ is defined as the rotation angle between the relative crystallographic orientations of two parallel surfaces). To understand this friction anisotropy and the difference between analytic theory and experiment, we carried out a series of nonequilibrium molecular dynamics simulations at 300 K for sliding of Ni(001)/Ni(001) interfaces under a constant shear force. Our molecular dynamics calculations on interfaces with the top layer roughed (and rms roughness of 0.8 Å) lead to the static frictional coefficients in good agreement with the corresponding experimental data. On the other hand, perfect smooth surfaces (rms roughness of 0 Å) lead to a factor of 34–330 decreasing of static friction coefficients for misaligned surfaces, a result more consistent with the analytic theories. This shows that the major source of the discrepancy is that small amounts of roughness dramatically increase the friction on incommensurate surfaces, so that misaligned directions are comparable to aligned directions

Comments on the 'China model'

This paper reviews the articles by Pan and by Zhu on the China Model. The review of Pan is critical, that of Zhu sympathetic. Pan is criticised for taking an unquestioning attitude towards state supporting ideologies and failing to adequately account for the effects of changes in family structure and class structure in China over the past 50 years. The reviewer broadly agrees with Zhu's comments about a future steady state economy. The article provides statistical data from the recent economic and demographic histories of China and Japan to back up the general conclusions drawn by Zhu

Caractérisation électrique de matériaux en composite pour fuselages d'avions

RÉSUMÉ Depuis plusieurs années, l’augmentation du coût du pétrole se fait sentir sur le plan international. Le pétrole étant une source primaire d’énergie largement exploité, il joue un rôle très important dans l’économie mondiale, surtout dans le domaine du transport. Ainsi afin de rester compétitif, les entreprises œuvrant en transport se doivent de modifier leur approche lors des phases de conception de nouveaux produits ou d’amélioration de produit existants. Dans le domaine de l’aéronautique par exemple, la réduction de poids dans la structure des avions demeure un aspect important, même primaire, lors de la conception de nouveaux modèles afin de les rendre plus légers et plus efficaces. Dans le cadre de ce projet, la recherche est en relation avec de nouveaux matériaux structuraux plus légers pour de nouveaux avions. À ce jour, plusieurs recherches ont été entamées afin de trouver un substitut adéquat aux matériaux présents (aluminium) dans la structure des avions. Plusieurs matériaux innovants tel que l’aluminium-lithium et le composite à base de fibre de carbone attirent beaucoup d’attention en tant que candidat de remplacement. Ce dernier présente des propriétés mécaniques (légèreté et rigidité) supérieures à l’aluminium. Ses propriétés électriques par contre demeurent peu connues. L’objectif de ce projet, proposé par Bombardier, est de trouver une technique convenable qui permettrait de caractériser le composite afin d’en ressortir ces propriétés électriques (permittivité (εr), conductivité(σ), etc.). Dans ce mémoire, les études préexistantes et plusieurs approches pour la caractérisation du composite sont présentées et discutées. Ces approches ont pour but de mieux anticiper le comportement électrique du composite sous test. Une comparaison entre éléments connus (ex. aluminium) et le composite est aussi entreprise afin de bien le situer au niveau électrique, plus particulièrement au niveau de la conductivité pour de basses fréquences (≈1 MHz) jusqu’à de hautes fréquences (≈12 GHz). Finalement, plusieurs tests de simulations sont réalisés afin de reproduire les résultats obtenus et approximer la valeur de la permittivité/ conductivité du composite.----------ABSTRACT In the last decade or so, the rise of oil price is being felt all over the world. Oil being one of the primary sources of energy highly exploited, it plays a great role in the today’s world economy, especially in the transport domain. To remain competitive, companies striving in this domain need therefore to modify their approach in the design phase of new or improved products. In the aerospace industry for example, weight reduction in aircraft structures have become a primordial aspect in the design phase of new models making them lighter and more efficient.In the framework of this project, the research is related to new weight-reduction of structural materials used in aircrafts. As of today, much research effort has been undertaken to find good substitutes to replace the materials presently used (aluminum). Several materials such as aluminum-lithium and carbon fibre composite bring great interest as substitutes. This last one presents superior mechanical properties over aluminum such as lightweight and rigidity; its electrical properties though remain still ambiguous. The objective of this project, proposed by Bombardier Core EMC, is to find a way to characterize the composite in a conventional way that would allow an extraction of its electrical properties (permittivity (εr), conductivity (σ), etc). In this Master thesis, the existing studies and characterization approaches for the composite material are presented and discussed. These approaches will help anticipate the electrical behaviour of the composite material under test. A comparison between known elements (ex: aluminum) and the composite material will also be tackled in order to gauge its conductivity level, particularly for low frequencies (≈1 MHz), and up to high frequencies (≈ 12 GHz). Finally, some tests have been simulated with electromagnetic modelling software in order to reproduce and validate the experimental results. At the end of the thesis, a discussion/conclusion presenting the results and validating their integrity is given. The results enable us to do an estimation of the composite’s conductivity and to observe its attenuation properties in function of the frequency. The tests were made with composite laminated panels without wire mesh. The wire mesh here is a copper matrix integrated at the exterior surface of the composite for added electromagnetic protection

Eel osmotic stress transcriptional factor 1 (Ostf1) is highly expressed in gill mitochondria-rich cells, where ERK phosphorylated

<p>Abstract</p> <p>Background</p> <p>Osmotic stress transcriptional factor 1 (Ostf1) was firstly identified in tilapia in 2005. Then numerous studies have investigated its regulation and expression profile in fish gill tissues in related to osmoregulation. Generally, hyperosmotic stress induced <it>ostf1 </it>mRNA expression level, however there is no report studying the cellular localization of Ostf1 expression in any osmoregulatory tissue. In this study immunohistochemical (IHC) approach was used to study the cellular localization of Ostf1 in gill cells of Japanese eels.</p> <p>Findings</p> <p>Ostf1 protein was found to be localized in branchial mitochondria-rich/chloride cell (MRC/CC) as revealed by Naα5 and CFTR co-localization. The protein was detectable at day 3 after fresh water to seawater transfer and was mainly localized in MRCs. Moreover, elevated levels of extracellular signal regulated kinase (ERK) phosphorylation was observed at day 3 of the transfer and was co-localized with MRCs.</p> <p>Conclusions</p> <p>Our data identified Ostf1 expression in gill MRCs. The observation supports the role of Ostf1 in osmosensing and/or osmoregulation in fish gills, particularly its functional relationship with MRCs. The observation of the co-expression of pERK and Ostf1 in MRCs suggests a cross-talk mechanism between the mitogen-activated protein kinases (MAPKs) and Ostf1 in response to hyperosmotic challenge. To summarize, this report has addressed the cellular localization of Ostf1 and provides evidence to illustrate the involvement of Ostf1 and ERK on osmosensing and osmoregulatory function of gill MRCs.</p

Determination of 6-benzylthioinosine in Mouse and Human Plasma by Liquid Chromatography–Tandem Mass Spectrometry

This paper described the development and validation of a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the quantitative determination of 6-benzylthioinosine (6BT), a novel myeloid leukemia differentiation-inducing agent, in mouse and human plasma. In this method, 2-amino-6-benzylthioinosine (2A6BT) was used as internal standard and ethyl acetate was used as organic solvent for the extraction of 6BT and internal standard from plasma samples. The extracted samples were separated on YMC ODS-AQ® column (2.0 mm × 50 mm), and the eluates from the column were monitored by the positive-electrospray-ionization tandem mass spectrometer (ESI+-MS/MS). Quantification of 6BT by internal calibration with 2A6BT was carried out using multiple-reaction-monitoring (MRM) mode. This method had a linear calibration range of 3.00–1.00 × 103 ng/mL with correlation coefficients of 1.00 and 0.999 in mouse and human plasma. The lower limit of quantification (LLOQ) was 3.00 ng/mL in either mouse or human plasma. The method had recovery of 6BT of 82–87% from mouse plasma and 90–98% from human plasma. Both accuracy (as percent error) and precision (as coefficient of variation) of the method were ≤±15% within the calibration range. This method had been successfully applied to the pharmacokinetic study of 6BT in male C57 mice with intraperitoneal (i.p.) injection at the dose of 1 mg 6BT per kilogram mouse

A smoothed particle hydrodynamics algorithm for haptic rendering of dental filling materials

Using haptic interfaces to assist the training of skills within the curriculum of undergraduate dentists provides a unique opportunity to advance rendering algorithms and engineering of haptic devices. In this paper we use the dental context to explore a rendering technique called smoothed particle hydrodynamics (SPH) as a potential method to train students on appropriate techniques for insertion of filling material into a previously prepared (virtual) dental cavity. The paper also considers how problems of haptic rendering might be implemented on a Graphical Processing Unit (GPU) that operates in the haptics control loop. The filling simulation used 3000 particles to represent the cavity boundary (approx. 1400 particles), tool (approx. 42 particles) and filling material (approx. 1600 particles), running at an average of 447Hz. Novel smoothing function in SPH was developed and its flexibility is presented

Polarization of macrophages toward M2 phenotype is favored by reduction in iPLA2β (group VIA phospholipase A2)*

Macrophages are important in innate and adaptive immunity. Macrophage participation in inflammation or tissue repair is directed by various extracellular signals and mediated by multiple intracellular pathways. Activation of group VIA phospholipase A2 (iPLA2β) causes accumulation of arachidonic acid, lysophospholipids, and eicosanoids that can promote inflammation and pathologic states. We examined the role of iPLA2β in peritoneal macrophage immune function by comparing wild type (WT) and iPLA2β−/− mouse macrophages. Compared with WT, iPLA2β−/− macrophages exhibited reduced proinflammatory M1 markers when classically activated. In contrast, anti-inflammatory M2 markers were elevated under naïve conditions and induced to higher levels by alternative activation in iPLA2β−/− macrophages compared with WT. Induction of eicosanoid (12-lipoxygenase (12-LO) and cyclooxygenase 2 (COX2))- and reactive oxygen species (NADPH oxidase 4 (NOX4))-generating enzymes by classical activation pathways was also blunted in iPLA2β−/− macrophages compared with WT. The effects of inhibitors of iPLA2β, COX2, or 12-LO to reduce M1 polarization were greater than those to enhance M2 polarization. Certain lipids (lysophosphatidylcholine, lysophosphatidic acid, and prostaglandin E2) recapitulated M1 phenotype in iPLA2β−/− macrophages, but none tested promoted M2 phenotype. These findings suggest that (a) lipids generated by iPLA2β and subsequently oxidized by cyclooxygenase and 12-LO favor macrophage inflammatory M1 polarization, and (b) the absence of iPLA2β promotes macrophage M2 polarization. Reducing macrophage iPLA2β activity and thereby attenuating macrophage M1 polarization might cause a shift from an inflammatory to a recovery/repair milieu

tele-substitution reactions in the synthesis of a promising class of 1,2,4-Triazolo[4,3- a]pyrazine-based antimalarials

We have discovered and studied a tele-substitution reaction in a biologically important heterocyclic ring system. Conditions that favor the tele-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base or the use of softer nucleophiles, less polar solvents, and larger halogens on the electrophile. Using results from X-ray crystallographic and isotope labeling experiments, a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the in vivo active antiplasmodium compounds of Series 4 of the Open Source Malaria consortium. © 2020 American Chemical Society. All rights reserved