7,003 research outputs found

    Predictive current control with instantaneous reactive power minimization for a four-leg indirect matrix converter

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    This paper presents the experimental valida¬tion of a predictive current control strategy with minimiza¬tion of the instantaneous reactive input power for a Four-Leg Indirect Matrix Converter (4Leg-IMC). The topology includes an input matrix converter stage, which provides the dc voltage for a four-leg voltage source converter (VSC) output stage. The VSC’s fourth leg provides a path for the zero sequence load current. The control technique is based on a finite control set model predictive control (FCS-MPC) strategy, whereby the switching states for the input and out¬put converters are selected by evaluating a predictive cost function. This results in a simpler approach than that seen in other well-known modulation methods, such as three-dimensional space vector modulation (3D-SVM). Positive dc voltage, (a requirement for the safe operation of the IMC) and minimization of the instantaneous input reactive power are obtained, while maintaining good tracking of the load reference currents. Furthermore, soft switching is achieved by synchronizing the state changes in the input stage with the application of zero voltage space vectors in the inverter stage. The control strategy is experimentally verified using a laboratory prototype

    What are the effects of maternal and pre-adult environments on ageing in humans, and are there lessons from animal models?

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    An open issue in research on ageing is the extent to which responses to the environment during development can influence variability in life span in animals, and the health profile of the elderly in human populations. Both affluence and adversity in human societies have profound impacts on survivorship curves, and some of this effect may be traceable to effects in utero or in infancy. The Barker Hypothesis that links caloric restriction in very early life to disruptions of glucose-insulin metabolism in later life has attracted much attention, as well as some controversy, in medical circles. It is only rarely considered by evolutionary biologists working on phenotypic plasticity, or by biogerontologists studying model organisms such as C. elegans or Drosophila. One crucial mechanism by which animals can respond in an adaptive manner to adverse conditions, for example in nutrition or infection, during development is phenotypic plasticity. Here we begin with a discussion of adaptive plasticity in animals before asking what such phenomena may reveal of relevance to rates of ageing in animals, and in humans. We survey the evidence for effects on adult ageing of environmental conditions during development across mammalian and invertebrate model organisms, and ask whether evolutionary conserved mechanisms might be involved. We conclude that the Barker Hypothesis is poorly supported and argue that more work in human populations should be integrated with multi-disciplinary studies of ageing-related phenomena in experimental populations of different model species that are subjected to nutritional challenges or infections during pre-adult development

    Endothelial Progenitor Cells as a Potential Biomarker in Interstitial Lung Disease Associated with Rheumatoid Arthritis

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    Interstitial lung disease (ILD) increases morbidity and mortality in patients with rheumatoid arthritis (RA). Although the pathogenesis of ILD associated with RA (RA-ILD(+)) remains poorly defined, vascular tissue is crucial in lung physiology. In this context, endothelial progenitor cells (EPC) are involved in endothelial tissue repair. However, little is known about their implication in RA-ILD(+). Accordingly, we aimed to investigate the potential role of EPC related to endothelial damage in RA-ILD(+). EPC quantification in peripheral blood from 80 individuals (20 RA-ILD(+) patients, 25 RA-ILD(-) patients, 21 idiopathic pulmonary fibrosis (IPF) patients, and 14 healthy controls) was performed by flow cytometry. EPC were considered as CD34(+), CD45(low), CD309(+) and CD133(+). A significant increase in EPC frequency in RA-ILD(+) patients, as well as in RA-ILD(-) and IPF patients, was found when compared with controls (p < 0.001, p = 0.02 and p < 0.001, respectively). RA-ILD(+) patients exhibited a higher EPC frequency than the RA-ILD(-) ones (p = 0.003), but lower than IPF patients (p < 0.001). Our results suggest that EPC increase may represent a reparative compensatory mechanism in patients with RA-ILD(+). The degree of EPC frequency may help to identify the presence of ILD in RA patients and to discriminate RA-ILD(+) from IPF

    Massive star formation and tidal structures in HCG 31

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    We present new broad-band optical and near-infrared CCD imaging together with deep optical intermediate-resolution spectroscopy of the Hickson Compact Group 31. We analyze the morphology and colors of the stellar populations of the galaxies, as well as the kinematics, physical conditions and chemical composition of the ionized gas in order to get a more complete view on the origin and evolution of the system. We estimate the ages of the most recent star formation bursts of the system, finding an excellent consistency among the values obtained with different indicators and starburst models. We find that member F hosts the youngest starburst of the group, showing a substantial population of Wolf-Rayet stars. The chemical abundances are fairly similar in all the members of the group despite their very different absolute magnitudes. We argue that the use of traditional metallicity-luminosity relations based on the absolute BB-magnitude is not appropriate for dwarf starburst galaxies, because their luminosity is dominated by the transient contribution of the starburst to the blue luminosity. We think that members E and F of the group are candidate tidal dwarf galaxies because of their high metallicity, their kinematics, and the absence of underlying old stellar populations. Finally, we propose that HCG~31 is suffering several almost simultaneous interaction processes. The most relevant of these processes are: (a) the merging of members A and C, that would have produced two optical tidal tails; and (b) a fly-by encounter between G and the A+C complex, that would have produced an \ion{H}{1} tidal tail from the stripping of the external gas of A+C, from which members F and E have originated.Comment: Accepted for publication in ApJS, 41 pages, 15 figures, 9 table

    High prevalence of fecal carriage of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a pediatric unit in Madagascar

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    <p>Abstract</p> <p>Background</p> <p>Extended-spectrum β-lactamase (ESBL)-producing <it>Enterobacteriaceae </it>have spread worldwide but there are few reports on carriage in hospitals in low-income countries. ESBL-producing <it>Enterobacteriaceae </it>(ESBL-PE) have been increasingly isolated from nosocomial infections in Antananarivo, Madagascar.</p> <p>Methods</p> <p>we conducted a prevalence survey in a pediatric unit from March to April 2008 Patient rectal swabs were sampled on the first and the last day of hospitalization. Medical staff and environment were also sampled. Rectal and environmental swabs were immediately plated onto Drigalski agar supplemented with 3 mg/liter of ceftriaxon.</p> <p>Results</p> <p>Fecal carriage was detected in 21.2% of 244 infants on admission and 57.1% of 154 on discharge, after more than 48 hours of hospitalization (p < 0.001). The species most frequently detected on admission were <it>Escherichia coli and Klebsiella pneumoniae </it>(36.9%), whereas, on discharge, <it>K. pneumoniae </it>was the species most frequently detected (52.7%). ESBL-associated resistances were related to trimethoprim-sulfamethoxazole (91.3%), gentamicin (76.1%), ciprofloxacin (50.0%), but not to amikacin and imipenem. The increased prevalence of carriage during hospitalization was related to standard antimicrobial therapy.</p> <p>Conclusion</p> <p>The significant emergence of multidrug-resistant enteric pathogens in Malagasy hospitals poses a serious health threat requiring the implementation of surveillance and control measures for nosocomial infections.</p

    Long-term follow-up of certolizumab pegol in uveitis due to immune-mediated inflammatory diseases: multicentre study of 80 patients

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    ObjectivesTo evaluate effectiveness and safety of certolizumab pegol (CZP) in uveitis due to immune-mediated inflammatory diseases (IMID).MethodsMulticentre study of CZP-treated patients with IMID uveitis refractory to conventional immunosuppressant. Effectiveness was assessed through the following ocular parameters: best-corrected visual acuity, anterior chamber cells, vitritis, macular thickness and retinal vasculitis. These variables were compared between the baseline, and first week, first, third, sixth months, first and second year.ResultsWe studied 80 (33 men/47 women) patients (111 affected eyes) with a mean age of 41.6 +/- 11.7 years. The IMID included were: spondyloarthritis (n=43), Behcet's disease (n=10), psoriatic arthritis (n=8), Crohn's disease (n=4), sarcoidosis (n=2), juvenile idiopathic arthritis (n=1), reactive arthritis (n=1), rheumatoid arthritis (n=1), relapsing polychondritis (n=1),ConclusionsCZP seems to be effective and safe in uveitis related to different IMID, even in patients refractory to previous biological drugs

    Clinical Risk Score to Predict Pathogenic Genotypes in Patients With Dilated Cardiomyopathy

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    Background: Although genotyping allows family screening and influences risk-stratification in patients with nonischemic dilated cardiomyopathy (DCM) or isolated left ventricular systolic dysfunction (LVSD), its result is negative in a significant number of patients, limiting its widespread adoption. Objectives: This study sought to develop and externally validate a score that predicts the probability for a positive genetic test result (G+) in DCM/LVSD. Methods: Clinical, electrocardiogram, and echocardiographic variables were collected in 1,015 genotyped patients from Spain with DCM/LVSD. Multivariable logistic regression analysis was used to identify variables independently predicting G+, which were summed to create the Madrid Genotype Score. The external validation sample comprised 1,097 genotyped patients from the Maastricht and Trieste registries. Results: A G+ result was found in 377 (37%) and 289 (26%) patients from the derivation and validation cohorts, respectively. Independent predictors of a G+ result in the derivation cohort were: family history of DCM (OR: 2.29; 95% CI: 1.73-3.04; P &lt; 0.001), low electrocardiogram voltage in peripheral leads (OR: 3.61; 95% CI: 2.38-5.49; P &lt; 0.001), skeletal myopathy (OR: 3.42; 95% CI: 1.60-7.31; P = 0.001), absence of hypertension (OR: 2.28; 95% CI: 1.67-3.13; P &lt; 0.001), and absence of left bundle branch block (OR: 3.58; 95% CI: 2.57-5.01; P &lt; 0.001). A score containing these factors predicted a G+ result, ranging from 3% when all predictors were absent to 79% when ≥4 predictors were present. Internal validation provided a C-statistic of 0.74 (95% CI: 0.71-0.77) and a calibration slope of 0.94 (95% CI: 0.80-1.10). The C-statistic in the external validation cohort was 0.74 (95% CI: 0.71-0.78). Conclusions: The Madrid Genotype Score is an accurate tool to predict a G+ result in DCM/LVSD

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+μ+νW^+ \rightarrow \mu^+\nu and WμνW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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