Effect of Equal Channel Angular Pressing (ECAP) on Wear Behavior of Al-7075 Alloy

AbstractEqual-channel angular pressing (ECAP) is an effective fabrication process for obtaining ultrafine grained materials. In order to investigate the effect of grain refinement during ECAP on wear properties of Al 7075 alloy, the specimens were pressed up to four passes by route BC at room temperature. Followed by ECAP, dry sliding wear tests have been conducted using a pin-on-disk machine under different loads of 10, 20 and 30N at a constant sliding speed of 0.23 ms-1. Microstructural observations were undertaken using transmission electron microscopy (TEM) and the surface of worn specimens was investigated by scanning electron microscopy (SEM). The effect of load and ECAP process on the mass loss, have been explained with respect to microstructure and wear mechanism. Comparison of wear resistance of specimens shows that by using ECAP process, wear resistance of the specimens increases considerably due to the formation of very fine grains during ECAP

The ecotoxicology of carbon nanotubes in the marine environment

With their high aspect ratio, strength, light weight and electrical conductivity single-walled carbon nanotubes (SWCNTs) provide properties of great interest to industry, and, consequently, are finding use in an ever increasing number of products and applications, which will eventually lead to their appearance in the environment. The toxicity of SWCNT, however, is controversial, mainly because of the inconsistency of results, owing to a lack of understanding of the behaviour of SWCNTs in environmental media. The present study explored the ecotoxicology of engineered SWCNTs and their interacton with other contaminants as well as their potential for trophic transfer. A series of co-contaminant experiments was performed to understand the interaction of SWCNTs with dissolved metals at low-level and non-toxic concentrations of both. The results showed that any nano-scale effects were negated by the tendency of uncoated SWCNTs to agglomerate in seawater. However, SWCNTs, in combination with natural organic matter (NOM), remained suspended for long enough to become available to filter-feeding mussels. A potentiating toxicological effect was observed, expressed as DNA strand breaks obtained using the comet assay and oxidative stress, on divalent metals afforded by negatively charged SWCNT agglomerates in seawater at concentrations as low as 5μg L-1. This is supported by the observation that SWCNTs alone were only toxic at concentrations ≥100μg L-1 and that the SWCNT-induced DNA damage was correlated with oxidative stress only in the absence of metals The potential for trophic transfer was assessd using the green algae (Tetraselmis suecica). Light microscopical observations, confirmed by SEM and Raman spectroscopy, showed that SWCNTs adhered to the external algal cell walls and TEM results suggested internaization. A direct effect of SWCNT exposure on the algae was a significant decrease in chlorophyll a concentrations and cell viability. Algea fed to mussels in the presence of SWCNTs led to a signifiacntly increased pseudofaeces production, suggesting selective feeding. However, histological sections of the mussel digestive gland following exposure showed evidence of SWCNTs containing algal and toxicological tests signs of DNA dmage and oxidative stress. In conclusion, the observed SWCNT-algal interaction may facilitate trophic transfer of SWCNTs up the food chain with potential consequences for human health. If these laboratory experiments are confirmed in the natural environment, the present results will have implications for the understanding of the role of carbon nanotubes in environmental metal dynamics, toxicology, and consequently, regulatory requirements

The correlation of microstructure and mechanical properties of in-situ Al-Mg2Si cast composite processed by equal channel angular pressing

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (α) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 μm after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity

Behavioral feasibility of the clinical nursing information system

Background: Analysis of humanitarian issues affecting the implementation time of information systems to increase the acceptance of these systems is essential. Objective: The aim of this study was to assess the behavioral feasibility of the clinical nursing information system. Methods: An applied cross-sectional study was conducted with 348 nurses in 2015. Data were collected by face to face interviews and a questionnaire containing 33 questions, which were rated on a 5-point Likert scale. Face and content validity of the questionnaire was confirmed, and its reliability was estimated 0.90 through Cronbach's alpha coefficient. Data were analyzed using chi-square tests and t-test. Results: An average score of behavioral feasibility was 67.44. The rate of supply provided for implementing the clinical nursing information system was 55.2, which was in a semi-favorable level. The necessity of system deployment in the clinical nursing sector had the highest frequency (88.2) and interference of redesigning structures with the current work had the lowest frequency (43.6). Conclusion: The possibility of implementation of the clinical nursing information system in a behavioral dimension is at a semi-favorable level. To increase the acceptance of the system, presenting a new system as a positive change and further training of the nurses is recommended. © 2019 Jeddi et al

Echocardiographic findings and joint hypermobility: Patients with mitral valve prolapse vs. healthy controls

Background: Mitral valve prolapse is a relatively common valvular abnormality in most communities and joint hypermobility (JHM) is also seen in many healthy people as well as in certain clinical disorders, such as Marfan syndrome. The present study was designed to investigate the association between joint hypermobility and mitral valve prolapse (MVP) in an Iranian population sample. Methods: Fifty-seven patients with nonrheumatic and isolated mitral anterior leaflet prolapse (24 men and 33 women, mean age 23.5 +/-2.3) and 51 healthy subjects (20 men and 31 women, mean age 22.9+/-2.3) were studied. The presence of JHM was evaluated according to the Carter-Wilkinson & Beighton criteria. Echocardiographic examination was performed in all subjects and the correlation between the echocardiographic features of the mitral valve and the hypermobility score were investigated. Results: The frequency of JHM in patients with MVP was found to be significantly higher than that of controls (26.3 vs. 7.8), with mean JHM scores of 3.1+/-2.2 and 1.9+/-1.7, respectively. The patients in the MVP group had significantly increased the anterior mitral leaflet thickness (AMLT, 3.4+/-0.4 mm vs. 3.0+/-0.3 mm; p<0.0005) and maximal leaflet displacement (MLD, 2.4+/-0.3 mm vs. 1.5+/-0.2 mm; p<0.0005) compared to the controls. Conclusions: We detect a statistically significant relationship between isolated MVP and joint hypermobility as well as between the severity of JHM and echocardiographic features of the mitral leaflets. These results suggest a common etiology for MVP and JHM, which should be investigated in future well-conducted studies. © 2008, Tehran University of Medical Sciences. All rights reserved

Loop Quantum Cosmology: A Status Report

The goal of this article is to provide an overview of the current state of the art in loop quantum cosmology for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general; and, cosmologists who wish to apply loop quantum cosmology to probe modifications in the standard paradigm of the early universe. An effort has been made to streamline the material so that, as described at the end of section I, each of these communities can read only the sections they are most interested in, without a loss of continuity.Comment: 138 pages, 15 figures. Invited Topical Review, To appear in Classical and Quantum Gravity. Typos corrected, clarifications and references adde

CHC22 clathrin mediates traffic from early secretory compartments for human GLUT4 pathway biogenesis

Post-prandial blood glucose is cleared by Glucose Transporter 4 (GLUT4) released from an intracellular GLUT4 storage compartment (GSC) to the surface of muscle and adipose tissue in response to insulin. Here we map the biosynthetic pathway for human GSC formation, which involves the clathrin isoform CHC22. We observe that GLUT4 transits more slowly through the early secretory pathway than the constitutively-secreted GLUT1 transporter, and show CHC22 colocalizes with p115 in the endoplasmic-reticulum-to-Golgi-intermediate compartment (ERGIC). We find CHC22 functions in membrane traffic from the early secretory pathway during formation of the replication vacuole of Legionella pneumophila, which also acquires components of the GLUT4 pathway. We show that p115 but not GM130 is required for GSC formation, indicating GSC biogenesis from the ERGIC bypasses the Golgi. This GSC biogenesis pathway is attenuated in mice, which lack CHC22, and rely mainly on recapture of surface GLUT4 to populate their GSC. GLUT4 traffic to the GSC is enhanced by CHC22 function at the human ERGIC, which has implications for pathways to insulin resistance

Transketolase catalysed upgrading of l-arabinose: the one-step stereoselective synthesis of l-gluco-heptulose

Conversion of biomass using biocatalysis is likely to become a technology that contributes significantly to the future production of chemical building blocks, materials and transport fuels. Here the synthesis of a value-added chemical from L-arabinose, a major component of the carbohydrates in sugar beet pulp (SBP), in a concise and sustainable manner has been investigated. Biocatalytic conversions using transketolase variants have been developed for the efficient, scalable synthesis of a rare naturally occurring ketoheptose, L-gluco-heptulose, from L-arabinose. New active E. coli TK mutants that readily accept L-arabinose were identified using a versatile colorimetric screening assay and the reaction was performed on a preparative scale

An Integrated Biorefinery Concept for Conversion of Sugar Beet Pulp into Value-added Chemicals and Pharmaceutical Intermediates

Over 8 million tonnes of sugar beet are grown annually in the UK. Sugar beet pulp (SBP) is the main by-product of sugar beet processing which is currently dried and sold as a low value animal feed. SBP is a rich source of carbohydrates, mainly in the form of cellulose and pectin, including D-glucose (Glu), L-arabinose (Ara) and D-galacturonic acid (GalAc). This work describes the technical feasibility of an integrated biorefinery concept for fractionation of SBP and conversion of these monosaccharides into value-added products. SBP fractionation is initially carried out by steam explosion under mild conditions to yield soluble pectin and insoluble cellulose fractions. The cellulose is readily hydrolysed by cellulases to release Glu that can then be fermented by a commercial Yeast strain to produce bioethanol with a high yield. The pectin fraction can be either fully hydrolysed, using physico-chemical methods, or selectively hydrolysed, using cloned arabinases and galacturonases, to yield Ara-rich and GalAc-rich streams. These monomers can be separated using either Centrifugal Partition Chromatography (CPC) or ultrafiltration into streams suitable for subsequent enzymatic upgrading. Building on our previous experience with transketolase (TK) and transaminase (TAm) enzymes, the conversion of Ara and GalAc into higher value products was explored. In particular the conversion of Ara into L-gluco-heptulose (GluHep), that has potential therapeutic applications in hypoglycaemia and cancer, using a mutant TK is described. Preliminary studies with TAm also suggest GluHep can be selectively aminated to the corresponding chiral aminopolyol. Current work is addressing upgrading of the remaining SBP monomer, GalAc, and modelling of the biorefinery concept to enable economic and Life Cycle Analysis (LCA)

A SARS-CoV-2 protein interaction map reveals targets for drug repurposing

The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 respiratory disease, has infected over 2.3 million people, killed over 160,000, and caused worldwide social and economic disruption1,2. There are currently no antiviral drugs with proven clinical efficacy, nor are there vaccines for its prevention, and these efforts are hampered by limited knowledge of the molecular details of SARS-CoV-2 infection. To address this, we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins physically associated with each using affinity-purification mass spectrometry (AP-MS), identifying 332 high-confidence SARS-CoV-2-human protein-protein interactions (PPIs). Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (29 FDA-approved drugs, 12 drugs in clinical trials, and 28 preclinical compounds). Screening a subset of these in multiple viral assays identified two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the Sigma1 and Sigma2 receptors. Further studies of these host factor targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19