3,373 research outputs found

    Unusual microwave response and bulk conductivity of very thin fese0.3te0.7 films as a function of temperature

    Full text link
    Results of X-band microwave surface impedance measurements of FeSe1-xTex very thin film are reported. The effective surface resistance shows appearance of peak at T less and near Tc when plotted as function of temperature. The authors suggests that the most well-reasoned explanation can be based on the idea of the changing orientation of the microwave magnetic field at a SN phase transition near the surface of a very thin film. The magnetic penetration depth exhibits a power-law behavior of delta lambda proportional to T with an exponent n = 2.4 at low temperatures, which is noticeably higher than in the published results on FeSe1-xTexsingle crystal. However the temperature dependence of the superfluid conductivity remains very different from the behavior described by the BCS theory. Experimental results are fitted very well by a two-gap model with delta1/kTc=0.43 and delta2/kTc=1.22,thus supporting s(+-)- wave symmetry. The rapid increase of the quasiparticle scattering time is obtained from the microwave impedance measurements.Comment: 13 pages, 13 figure

    Effect of the size of GdBCO-Ag secondary magnet on the static forces performance of linear synchronous motors

    Get PDF
    Bulk high temperature superconductor magnets (HTSM) have a higher flux-generating capability compared to conventional permanent magnets (PMs). These materials potentially can be used in high temperature superconducting (HTS) linear synchronous motors (LSMs) as superconducting secondary magnets, what will result in a reduced volume and weight as well as in higher force density and efficiency of these devices when compared to conventional PMs. The focus of this paper is on the effect of size of the secondary HTSM on the static performance (thrust force and normal force) of a LSM. In order to obtain high-field HTSM as the secondary, single grain bulk GdBCO-Ag superconductors of diameter 20 mm, 30 mm and 40 mm, which have higher Jc and trapped fields than YBCO superconductors, were used in this device for the first time following application by the same optimized magnetization condition. It was found that both thrust and normal forces increase and saturate with the increasing size of the HTSM secondary at the small size range, and then potentially distort when the physical size of the HTSM secondary approaches the pole pitch of the linear three-phase primary windings of the LSM. Furthermore, more experiments of a larger-sized multi-seeded HTSM secondary, confirmed that the relationship between the HTSM secondary size and the pole pitch of the primary is an important factor for achieving higher thrust and normal forces. It is suggested that the multi-pole HTSM secondary will be more beneficial to future HTS LSM designs since the single-pole HTSM secondary size should be equal to or smaller than the stator pole pitch in the paper.This is the final version. It was first published by IOP at http://iopscience.iop.org/0953-2048/27/11/115016/article?fromSearchPage=tru

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

    Get PDF
    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum

    A Concise and Versatile Double-Cyclization Strategy for the Highly Stereoselective Synthesis and Arylative Dimerization of Aspidosperma Alkaloids

    Get PDF
    Building cycles: A strategy for the concise, stereoselective synthesis of aspidosperma alkaloids and related structures via a common putative diiminium ion intermediate is reported. The approach enables the dimerization of aspidosperma-type structures at the sterically hindered C2 position. The intermediate is prepared in one step from the shown lactam through an electrophilic double-cyclization cascade (see scheme; Tf=trifluoromethanesulfonyl).National Institute of General Medical Sciences (U.S.) (GM074825

    Systematic review of methods used in meta-analyses where a primary outcome is an adverse or unintended event

    Get PDF
    addresses: Peninsula College of Medicine and Dentistry, St Luke's Campus, University of Exeter, Exeter, UK. [email protected]: PMCID: PMC3528446types: Journal Article; Research Support, Non-U.S. Gov't© 2012 Warren et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Adverse consequences of medical interventions are a source of concern, but clinical trials may lack power to detect elevated rates of such events, while observational studies have inherent limitations. Meta-analysis allows the combination of individual studies, which can increase power and provide stronger evidence relating to adverse events. However, meta-analysis of adverse events has associated methodological challenges. The aim of this study was to systematically identify and review the methodology used in meta-analyses where a primary outcome is an adverse or unintended event, following a therapeutic intervention

    Country-specific birth weight and length in type 1 diabetes high-risk HLA genotypes in combination with prenatal characteristics

    Get PDF
    Objective:To examine the relationship between high-risk human leukocyte antigen (HLA) genotypes for type 1 diabetes and birth size in combination with prenatal characteristics in different countries.Study Design:Four high-risk HLA genotypes were enrolled in the Environmental determinants of Diabetes in the Young study newborn babies from the general population in Finland, Germany, Sweden and the United States. Stepwise regression analyses were used to adjust for country, parental physical characteristics and environmental factors during pregnancy.Result:Regression analyses did not reveal differences in birth size between the four type 1 diabetes high-risk HLA genotypes. Compared with DQ 4/8 in each country, (1) DQ 2/2 children were heavier in the United States (P=0.028) mostly explained however, by parental weight; (2) DQ 2/8 (P=0.023) and DQ 8/8 (P=0.046) children were longer in Sweden independent of parents height and as well as (3) in the United States for DQ 2/8 (P=0.023), but again dependent on parental height.Conclusion:Children born with type 1 diabetes high-risk HLA genotypes have comparable birth size. Longitudinal follow-up of these children should reveal whether birth size differences between countries contribute to the risk for islet autoimmunity and type 1 diabetes.Journal of Perinatology advance online publication, 28 April 2011; doi:10.1038/jp.2011.26

    Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

    Get PDF
    Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

    Fish sperm motility assessment as a tool for aquaculture research, a historical approach

    Full text link
    [EN] Fish sperm motility is nowadays considered the best biomarker for the quality of fish spermatozoa, and sperm motion parameters from more than 300 fish species have been reported in more than 1500 scientific articles covering a wide range of topics, from molecular biology to ecology. The most studied topics have been (i) the sperm storage (involving both the use of chilled¿storage protocols for short¿term periods and sperm cryopreservation techniques for long¿term storage), (ii) the sperm physiology (fathom in the spermatozoa activation process and the whole propulsion machinery of the sperm cells) and (iii) the broodstock management (covering aspects such as rearing conditions, dietary requirements or hormonal induction treatments). In addition, other aquaculture and ecological topics, such as (iv) the knowledge of the breeding cycle of the species, (v) the phenomenon of the sperm competition and (vi) ecotoxicological studies for the evaluation of aquatic environments, have also been approached from the evaluation of sperm motion performance. Therefore, fish sperm motility assessment can serve as a potential tool for aquaculture and ecological purposes, covering key topics of fundamental and applied research. This review gives an overview of the major research areas in which fish sperm motility has been applied successfully.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 642893 (IMPRESS). VG has a postdoc grant from the UPV (PAID-10-16).Gallego Albiach, V.; Asturiano Nemesio, JF. (2018). Fish sperm motility assessment as a tool for aquaculture research, a historical approach. Reviews in Aquaculture (Online). 1-28. https://doi.org/10.1111/raq.12253S12

    Planned repeat cesarean section at term and adverse childhood health outcomes: a record-linkage study

    Get PDF
    Global cesarean section (CS) rates range from 1% to 52%, with a previous CS being the commonest indication. Labour following a previous CS carries risk of scar rupture, with potential for offspring hypoxic brain injury, leading to high rates of repeat elective CS. However, the effect of delivery by CS on long-term outcomes in children is unclear. Increasing evidence suggests that in avoiding exposure to maternal bowel flora during labour or vaginal birth, offspring delivered by CS may be adversely affected in terms of energy uptake from the gut and immune development, increasing obesity and asthma risks, respectively. This study aimed to address the evidence gap on long-term childhood outcomes following repeat CS by comparing adverse childhood health outcomes after (1) planned repeat CS and (2) unscheduled repeat CS with those that follow vaginal birth after CS (VBAC).A data-linkage cohort study was performed. All second-born, term, singleton offspring delivered between 1 January 1993 and 31 December 2007 in Scotland, UK, to women with a history of CS (n = 40,145) were followed up until 31 January 2015. Outcomes assessed included obesity at age 5 y, hospitalisation with asthma, learning disability, cerebral palsy, and death. Cox regression and binary logistic regression were used as appropriate to compare outcomes following planned repeat CS (n = 17,919) and unscheduled repeat CS (n = 8,847) with those following VBAC (n = 13,379). Risk of hospitalisation with asthma was greater following both unscheduled repeat CS (3.7% versus 3.3%, adjusted hazard ratio [HR] 1.18, 95% CI 1.05-1.33) and planned repeat CS (3.6% versus 3.3%, adjusted HR 1.24, 95% CI 1.09-1.42) compared with VBAC. Learning disability and death were more common following unscheduled repeat CS compared with VBAC (3.7% versus 2.3%, adjusted odds ratio 1.64, 95% CI 1.17-2.29, and 0.5% versus 0.4%, adjusted HR 1.50, 95% CI 1.00-2.25, respectively). Risk of obesity at age 5 y and risk of cerebral palsy were similar between planned repeat CS or unscheduled repeat CS and VBAC. Study limitations include the risk that women undergoing an unscheduled CS had intended to have a planned CS, and lack of data on indication for CS, which may confound the findings.Birth by repeat CS, whether planned or unscheduled, was associated with an increased risk of hospitalisation with asthma but no difference in risk of obesity at age 5 y. Greater risk of death and learning disability following unscheduled repeat CS compared to VBAC may reflect complications during labour. Further research, including meta-analyses of studies of rarer outcomes (e.g., cerebral palsy), are needed to confirm whether such risks are similar between delivery groups
    corecore