Influence of the crack propagation rate in the obtaining opening and closing stress intensity factor by finite element method

Crack propagation simulation began with the development of the finite element method; the analyses were conducted to obtain a basic understanding of the crack growth. Today structural and materials engineers develop structures and materials properties using this technique as criterion design. The aim of this paper is to verify the effect of different crack propagation rates in determination of crack opening and closing stress of an ASTM specimen under a standard suspension spectrum loading from FD&E SAE Keyhole Specimen Test Load Histories by finite element analysis. The crack propagation simulation was based on release nodes at the minimum loads to minimize convergence problems. To understand the crack propagation processes under variable amplitude loading, retardation effects are discussed

Crack simulation models in variable amplitude loading - a review

This work presents a review of crack propagation simulation models considering plane stress and plane strain conditions. It is presented also a chronological different methodologies used to perform the crack advance by finite element method. Some procedures used to edit variable spectrum loading and the effects during crack propagation processes, like retardation, in the fatigue life of the structures are discussed. Based on this work there is no consensus in the scientific community to determine the best way to simulate crack propagation under variable spectrum loading due the combination of metallurgic and mechanical factors regarding, for example, how to select and edit the representative spectrum loading to be used in the crack propagation simulation

description of the methodological approach

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Saphenofemoral arteriovenous fistula as hemodialysis access

<p>Abstract</p> <p>Background</p> <p>An upper limb arteriovenous (AV) fistula is the access of choice for haemodialysis (HD). There have been few reports of saphenofemoral AV fistulas (SFAVF) over the last 10-20 years because of previous suggestions of poor patencies and needling difficulties. Here, we describe our clinical experience with SFAVF.</p> <p>Methods</p> <p>SFAVFs were evaluated using the following variables: immediate results, early and late complications, intraoperative and postoperative complications (up to day 30), efficiency of the fistula after the onset of needling and complications associated to its use.</p> <p>Results</p> <p>Fifty-six SFAVF fistulas were created in 48 patients. Eight patients had two fistulas: 8 patent (16%), 10 transplanted (20%), 12 deaths (24%), 1 low flow (2%) and 20 thrombosis (39%) (first two months of preparation). One patient had severe hypotension during surgery, which caused thrombosis of the fistula, which was successfully thrombectomised, four thrombosed fistulae were successfully thrombectomised and revised on the first postoperative day. After 59 months of follow-up, primary patency was 44%.</p> <p>Conclusion</p> <p>SFAVF is an adequate alternative for patients without the possibility for other access in the upper limbs, allowing efficient dialysis with good long-term patency with a low complication rate.</p

Glycation potentiates α-synuclein-associated neurodegeneration in synucleinopathies

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Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Características morfológicas e estudo da vascularização do corpo lúteo cíclico de cabras ao longo do ciclo estral

Corpus luteum is a temporary endocrine gland that regulates either the estrous cycle and pregnancy. It presents extreme dependency on the adequate blood supply. This work aims to evaluate goat corpus luteum (CL) vascular density (VD) over the estrous cycle. For that purpose, 20 females were submitted to estrus synchronization/ovulation treatment using a medroxyprogesterone intra-vaginal sponge as well as intramuscular (IM) application of cloprostenol and equine chorionic gonadotrophine (eCG). After sponge removal, estrus was identified at about 72hs. Once treatment was over, female goats were then subdivided into 4 groups (n=5 each) and slaughtered on days 2, 12, 16 and 22 after ovulation (p.o). Ovaries were collected, withdrawn and weighted. CL and ovaries had size and area recorded. Blood samples were collected and the plasma progesterone (P4) was measured through RIA commercial kits. The VD was 24.42±6.66, 36.26±5.61, 8.59±2.2 and 3.97±1.12 vessels/mm² for days 2, 12, 16 and 22 p.o, respectively. Progesterone plasma concentrations were 0.49±0.08, 2.63±0.66, 0.61±0.14 and 0.22±0.04ng/ml for days 2, 12, 16 e 22 p.o, respectively. Studied parameters were affected by the estrous cycle phase. Values greater than 12 p.o were observed. In the present work we observed that ovulation occurred predominantly in the right ovary (70% of the animals), which in turn presented bigger measures than the contra lateral one. There is a meaningful relationship between the weight and size of the ovary and these of CL (r=0.87, r=0.70, respectively, p<0.05). It is possible to conclude that morphology of goat's ovaries and plasma progesterone concentration changed according to estrous cycle stages. We propose these parameters can be used as indicators of CL functional activity.O corpo lúteo é uma glândula endócrina temporária que regula tanto o ciclo estral quanto a prenhez, apresentando extrema dependência de aporte sanguíneo adequado. Objetivaram-se avaliar mudanças morfométricas dos ovários e densidade vascular (DV) dos corpos lúteos (CL) de cabras ao longo do ciclo estral (AOLC). Vinte animais foram submetidos ao tratamento para indução/sincronização do estro, usando esponjas intravaginais commedroxiprogesterona, associadas a aplicações intramusculares de cloprostenol e gonadotrofina coriônica eqüina. Após remoção das esponjas, o estro foi identificado em aproximadamente de 72h. Concluído o tratamento, as cabras foram subdivididas em 4 grupos (n=5 cada) para abate nos dias 2, 12, 16 e 22 após ovulação (p.o.). Posteriormente, foram retirados os ovários e realizadas as mensurações de peso, tamanho e área do órgão e dos CL. Amostras de sangue foram coletadas e a progesterona sérica (P4) mensurada utilizando-se RIA convencional. A DV média dos CL AOLC foi 24,42±6,66; 36,26±5,61; 8,59±2,2 e 3,97±1,12 vasos/mm2 para os dias 2, 12, 16 e 22 p.o., respectivamente. A concentração média de P4 foi de 0,49±0,08; 2,63±0,66; 0,61±0,14 e 0,22±0,04ng/ml para os dias 2, 12, 16 e 22 p.o., respectivamente. Os parâmetros em estudo também se mostraram afetados pela fase do ciclo estral, sendo observados os maiores (p < 0,05) valores no dia 12 p.o. Neste experimento, a ovulação ocorreu predominantemente no ovário direito (70% dos animais), o qual apresentou medidas maiores que o contralateral. Observou-se ainda alta correlação significativa entre o peso do ovário e o do CL (r=0,87; p<0,05) e entre o tamanho destes órgãos (r=0,70; p<0,05). Conclui-se que, a morfologia dos ovários de cabras e a concentração sérica de progesterona variam em função da fase do ciclo estral e podem ser utilizadas como parâmetro na avaliação funcional do órgão

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Local hydrological conditions influence tree diversity and composition across the Amazon basin

Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures