5,761 research outputs found

    Modeling heat transfer from quench protection heaters to superconducting cables in Nb3Sn magnets

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    We use a recently developed quench protection heater modeling tool for an analysis of heater delays in superconducting high-field Nb3Sn accelerator magnets. The results suggest that the calculated delays are consistent with experimental data, and show how the heater delay depends on the main heater design parameters.Comment: 8 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

    Optimizing Photonic Nanostructures via Multi-fidelity Gaussian Processes

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    We apply numerical methods in combination with finite-difference-time-domain (FDTD) simulations to optimize transmission properties of plasmonic mirror color filters using a multi-objective figure of merit over a five-dimensional parameter space by utilizing novel multi-fidelity Gaussian processes approach. We compare these results with conventional derivative-free global search algorithms, such as (single-fidelity) Gaussian Processes optimization scheme, and Particle Swarm Optimization---a commonly used method in nanophotonics community, which is implemented in Lumerical commercial photonics software. We demonstrate the performance of various numerical optimization approaches on several pre-collected real-world datasets and show that by properly trading off expensive information sources with cheap simulations, one can more effectively optimize the transmission properties with a fixed budget.Comment: NIPS 2018 Workshop on Machine Learning for Molecules and Materials. arXiv admin note: substantial text overlap with arXiv:1811.0075

    Comparison of dimethyl sulfoxide treated highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) electrodes for use in indium tin oxide-free organic electronic photovoltaic devices

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    Indium tin oxide (ITO)-free organic photovoltaic (OPV) devices were fabricated using highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the transparent conductive electrode (TCE). The intrinsic conductivity of the PEDOT:PSS films was improved by two different dimethyl sulfoxide (DMSO) treatments – (i) DMSO was added directly to the PEDOT:PSS solution (PEDOT:PSSADD) and (ii) a pre-formed PEDOT:PSS film was immersed in DMSO (PEDOT:PSSIMM). X-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (CAFM) studies showed a large amount of PSS was removed from the PEDOT:PSSIMM electrode surface. OPV devices based on a poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk hetrojunction showed that the PEDOT:PSSIMM electrode out-performed the PEDOT:PSSADD electrode, primarily due to an increase in short circuit current density from 6.62 mA cm−2 to 7.15 mA cm−2. The results highlight the importance of optimising the treatment of PEDOT:PSS electrodes and demonstrate their potential as an alternative TCE for rapid processing and low-cost OPV and other organic electronic devices

    A multiwavelength study of young massive star forming regions: II. The dust environment

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    We present observations of 1.2-mm dust continuum emission, made with the Swedish ESO Submillimeter Telescope, towards eighteen luminous IRAS point sources, all with colors typical of compact HII regions and associated with CS(2-1) emission, thought to be representative of young massive star forming regions. Emission was detected toward all the IRAS objects. We find that the 1.2-mm sources associated with them have distinct physical parameters, namely sizes of 0.4 pc, dust temperatures of 30 K, masses of 2x10^3 Msun, column densities of 3x10^23 cm^-2, and densities of 4x10^5 cm^-3. We refer to these dust structures as massive and dense cores. Most of the 1.2-mm sources show single-peaked structures, several of which exhibit a bright compact peak surrounded by a weaker extended envelope. The observed radial intensity profiles of sources with this type of morphology are well fitted with power-law intensity profiles with power-law indices in the range 1.0-1.7. This result indicates that massive and dense cores are centrally condensed, having radial density profiles with power-law indices in the range 1.5-2.2. We also find that the UC HII regions detected with ATCA towards the IRAS sources investigated here (Paper I) are usually projected at the peak position of the 1.2-mm dust continuum emission, suggesting that massive stars are formed at the center of the centrally condensed massive and dense cores.Comment: 6 figures, accepted by Ap

    Splenic Artery Aneurysm Presenting as Extrahepatic Portal Vein Obstruction: A Case Report

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    Splenic artery aneurysms are the most common visceral aneurysm occuring predominantly in females. They are usually asymptomatic, and the symptomatic presentation includes chronic abdominal pain of varied severity or an acute rupture with hypotension. Splenic artery aneurysm causing extrahepatic portal hypertension is very rare and is due to splenic vein thrombosis that develops secondary to compression by the aneurysm. We report one such rare presentation of splenic artery aneurysms in a pregnant female with the features of EHPVO (variceal bleed, hypersplenism) treated by splenectomy along with excision of the aneurysm

    A Study of CO Emission in High Redshift QSOs Using the Owens Valley Millimeter Array

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    Searches for CO emission in high-redshift objects have traditionally suffered from the accuracy of optically-derived redshifts due to lack of bandwidth in correlators at radio observatories. This problem has motivated the creation of the new COBRA continuum correlator, with 4 GHz available bandwidth, at the Owens Valley Radio Observatory Millimeter Array. Presented here are the first scientific results from COBRA. We report detections of redshifted CO(J=3-2) emission in the QSOs SMM J04135+10277 and VCV J140955.5+562827, as well as a probable detection in RX J0911.4+0551. At redshifts of z=2.846, z=2.585, and z=2.796, we find integrated CO flux densities of 5.4 Jy km/s, 2.4 Jy km/s, and 2.9 Jy km/s for SMM J04135+10277, VCV J140955.5+562827, and RX J0911.4+0551, respectively, over linewidths of Delta(V_{FWHM}) ~ 350 km/s. These measurements, when corrected for gravitational lensing, correspond to molecular gas masses of order M(H_2) ~ 10^{9.6-11.1} solar masses, and are consistent with previous CO observations of high-redshift QSOs. We also report 3-sigma upper limits on CO(3-2) emission in the QSO LBQS 0018-0220 of 1.3 Jy km/s. We do not detect significant 3mm continuum emission from any of the QSOs, with the exception of a tentative (3-sigma) detection in RX J0911.4+0551 of S_{3mm}=0.92 mJy/beam.Comment: 18 pages, 5 figures, 2 tables, accepted to ApJ. Changes made for version 2: citations added, 2 objects added to Table 2 and Figure

    Neuromuscular Electrical Stimulation for Infants with Neonatal Brachial Plexus Palsy: A Pilot Study

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    Background: Biceps recovery is a critical determinant for treatment decision-making in patients with neonatal brachial plexus palsy (NBPP). One treatment intervention used by therapists is neuromuscular electrical stimulation (NMES), but its use remains controversial. This study’s aim was to determine the effect and safety of NMES on biceps function in infants with NBPP compared to standard therapy. Methods: In this pilot, randomized controlled study, patients were randomized to the NMES treatment or control/sham group. Inclusion criteria were infants 3 to 9 months of age with a confirmed diagnosis of NBPP and biceps weakness, without other comorbidities. The parents administered the NMES (treatment or control) 30 min daily. Outcomes of active range of motion (AROM), muscle strength, and morphometric measurements were assessed by one of two blinded therapists at enrollment and 1-, 2-, and 3-month follow-up intervals. Results: Seventeen patients (10 NMES, seven control) participated in the study. Despite equal group demographics, the treatment group demonstrated significant improvement in elbow flexion AROM after the first month of NMES compared to the control group (improvement 31° vs. -3°, P = .047). No adverse effects were reported. Conclusion: Use of NMES can be beneficial and should be considered in the early rehabilitation protocol for infants with NBPP

    Factors influencing the implementation of fall-prevention programmes: a systematic review and synthesis of qualitative studies

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    BACKGROUND: More than a third of people over the age of 65 years fall each year. Falling can lead to a reduction in quality of life, mortality, and a risk of prolonged hospitalisation. Reducing and preventing falls has become an international health priority. To help understand why research evidence has often not been translated into changes in clinical practice, we undertook a systematic review and synthesis of qualitative research in order to identify what factors serve as barriers and facilitators to the successful implementation of fall-prevention programmes. METHODS: We conducted a review of literature published between 1980 and January 2012 for qualitative research studies that examined barriers and facilitators to the effective implementation of fall-prevention interventions among community-dwelling older people and healthcare professionals. Two reviewers independently screened studies for inclusion, extracted data, and assessed methodological quality according to predefined criteria. Findings were synthesised using meta-ethnography. RESULTS: Of the 5010 articles identified through database searching, 19 were included in the review. Analysis of the 19 studies revealed limited information about the mechanisms by which barriers to implementation of fall-prevention interventions had been overcome. Data synthesis produced three overarching concepts: (1) practical considerations, (2) adapting for community, and (3) psychosocial. A line of argument synthesis describes the barriers and facilitators to the successful implementation of fall-prevention programmes. These concepts show that the implementation of fall-prevention programmes is complex and multifactorial. This is the first systematic review and synthesis of qualitative studies to examine factors influencing the implementation of fall-prevention programmes from the perspectives of both the healthcare professional and the community-dwelling older person. CONCLUSIONS: The current literature on barriers and facilitators to the implementation of fall-prevention programmes examines a variety of interventions. However, the ways in which the interventions are reported suggests there are substantial methodological challenges that often inhibit implementation into practice. We recommend that successful implementation requires individuals, professionals, and organisations to modify established behaviours, thoughts, and practice. The issues identified through this synthesis need to be fully considered and addressed if fall-prevention programmes are to be successfully implemented into clinical practice.National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care (CLAHRC) for the South West of EnglandEuropean Regional Development FundEuropean Social Fund Convergence Programme for Cornwall and the Isles of Scill

    A Foundational Population Genetics Investigation of the Sexual Systems of Solanum (Solanaceae) in the Australian Monsoon Tropics Suggests Dioecious Taxa May Benefit from Increased Genetic Admixture via Obligate Outcrossing

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    Solanum section Leptostemonum is an ideal lineage to test the theoretical framework regarding proposed evolutionary benefits of outcrossing sexual systems in comparison to cosexuality. Theoretically, non-cosexual taxa should support more genetic diversity within populations, experience less inbreeding, and have less genetic structure due to a restricted ability to self-fertilize. However, many confounding factors present challenges for a confident inference that inherent differences in sexual systems influence observed genetic patterns among populations. This study provides a foundational baseline of the population genetics of several species of different sexual systems with the aim of generating hypotheses of any factor—including sexual system—that influences genetic patterns. Importantly, results indicate that dioecious S. asymmetriphyllum maintains less genetic structure and greater admixture among populations than cosexual S. raphiotes at the same three locations where they co-occur. This suggests that when certain conditions are met, the evolution of dioecy may have proceeded as a means to avoid genetic consequences of self-compatibility and may support hypotheses of benefits gained through differential resource allocation partitioned across sexes. Arguably, the most significant finding of this study is that all taxa are strongly inbred, possibly reflective of a shared response to recent climate shifts, such as the increased frequency and intensity of the region’s fire regime

    Red Galaxy Growth and the Halo Occupation Distribution

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    We have traced the past 7 Gyr of red galaxy stellar mass growth within dark matter halos. We have determined the halo occupation distribution, which describes how galaxies reside within dark matter halos, using the observed luminosity function and clustering of 40,696 0.2<z<1.0 red galaxies in Bootes. Half of 10^{11.9} Msun/h halos host a red central galaxy, and this fraction increases with increasing halo mass. We do not observe any evolution of the relationship between red galaxy stellar mass and host halo mass, although we expect both galaxy stellar masses and halo masses to evolve over cosmic time. We find that the stellar mass contained within the red population has doubled since z=1, with the stellar mass within red satellite galaxies tripling over this redshift range. In cluster mass halos most of the stellar mass resides within satellite galaxies and the intra-cluster light, with a minority of the stellar mass residing within central galaxies. The stellar masses of the most luminous red central galaxies are proportional to halo mass to the power of a third. We thus conclude that halo mergers do not always lead to rapid growth of central galaxies. While very massive halos often double in mass over the past 7 Gyr, the stellar masses of their central galaxies typically grow by only 30%.Comment: Accepted for publication in the ApJ. 34 pages, 22 Figures, 5 Table
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