131 research outputs found

    Kinetics of Graphene Growth on Liquid Copper by Chemical Vapor Deposition

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    We report a combined experimental and computational study of the kinetics of graphene growth during chemical vapor deposition on a liquid copper catalyst. The use of liquid metal catalysts offers bright perspectives for controllable large-scale, high-quality synthesis technologies of two-dimensional materials. We carried out a series of growth experiments varying CH4-to-H2 pressure ratios and deposition temperature. By monitoring the graphene flake morphology in real time during growth using in situ optical microscopy in radiation mode, we explored the morphology and kinetics of the growth within a wide range of experimental conditions. Following an analysis of the flakes' growth rates, we conclude that the growth mode was attachment-limited. The attachment and detachment activation energies of carbon species are derived as 1.9 +- 0.3 eV and 2.0 +- 0.1 eV, respectively. We also conducted free-energy calculations by a moment tensor potential trained to density functional theory data. Our simulations propose that carbon dimers are most likely the active carbon species during growth, with attachment and detachment barriers of 1.71 +- 0.15 eV and 2.09 +- 0.02 eV, respectively, being in good agreement with the experimental results

    Distribution of Psychological Instability Among Surgeons.

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    peer reviewed[en] BACKGROUND: High emotional instability (i.e., neuroticism) is associated with poor mental health. Conversely, traumatic experiences may increase neuroticism. Stressful experiences such as complications are common in the surgical profession, with neurosurgeons being particularly affected. We compared the personality trait neuroticism between physicians in a prospective cross-sectional study. METHODS: We used an online survey using the Ten-Item Personality Inventory, an internationally validated measure of the 5-factor model of personality dimensions. It was distributed to board-certified physicians, residents, and medical students in several European countries and Canada (n = 5148). Multivariate linear regression was used to model differences between surgeons, nonsurgeons, and specialties with occasional surgical interventions with respect to neuroticism, adjusting for sex, age, age squared, and their interactions, then testing equality of parameters of adjusted predictions separately and jointly using Wald tests. RESULTS: With an expected variability within disciplines, average levels of neuroticism are lower in surgeons than nonsurgeons, especially in the first part of their career. However, the course of neuroticism across age follows a quadratic pattern, that is, an increase after the initial decrease. The acceleration of neuroticism with age is specifically significant in surgeons. Levels of neuroticism are lowest towards mid-career, but exhibit a strong secondary increase towards the end of the surgeon's career. This pattern seems driven by neurosurgeons. CONCLUSIONS: Despite initially lower levels of neuroticism, surgeons suffer a stronger increase of neuroticism together with age. Because, beyond well-being, neuroticism influences professional performance and health care systems costs, explanatory studies are mandatory to enlighten causes of this burden

    Distribution of psychological instability among surgeons

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    Background High emotional instability, i.e. neuroticism, is associated with poor mental health. Conversely, traumatic experiences may increase neuroticism. Stressful experiences such as complications are common in the surgical profession, with neurosurgeons being particularly affected. We compared the personality trait neuroticism between physicians in a prospective cross-sectional study. Methods 5,148). Multivariate linear regression was used to model differences between surgeons, non-surgeons and specialties with occasional surgical interventions with respect to neuroticism, adjusting for gender, age, age squared and their interactions, then testing equality of parameters of adjusted predictions separately and jointly using Wald tests. Results With an expected variability within disciplines, average levels of neuroticism are lower in surgeons than non-surgeons, especially in the first part of their career. However, the course of neuroticism across age follows a quadratic pattern, i.e., an increase after the initial decrease. The acceleration of neuroticism with age is specifically significant in surgeons. Levels of neuroticism are lowest towards mid-career, but exhibit a strong secondary increase towards the end of the surgeons’ career. This pattern seems driven by neurosurgeons. Conclusion Despite initially lower levels of neuroticism, surgeons suffer a stronger increase of neuroticism together with age. Since, beyond well-being, neuroticism influences professional performance and healthcare systems costs, explanatory studies are mandatory to enlighten causes of this burden

    Copy number and gene expression differences between African American and Caucasian American prostate cancer

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    <p>Abstract</p> <p>Background</p> <p>The goal of our study was to investigate the molecular underpinnings associated with the relatively aggressive clinical behavior of prostate cancer (PCa) in African American (AA) compared to Caucasian American (CA) patients using a genome-wide approach.</p> <p>Methods</p> <p>AA and CA patients treated with radical prostatectomy (RP) were frequency matched for age at RP, Gleason grade, and tumor stage. Array-CGH (BAC SpectralChip2600) was used to identify genomic regions with significantly different DNA copy number between the groups. Gene expression profiling of the same set of tumors was also evaluated using Affymetrix HG-U133 Plus 2.0 arrays. Concordance between copy number alteration and gene expression was examined. A second aCGH analysis was performed in a larger validation cohort using an oligo-based platform (Agilent 244K).</p> <p>Results</p> <p>BAC-based array identified 27 chromosomal regions with significantly different copy number changes between the AA and CA tumors in the first cohort (Fisher's exact test, P < 0.05). Copy number alterations in these 27 regions were also significantly associated with gene expression changes. aCGH performed in a larger, independent cohort of AA and CA tumors validated 4 of the 27 (15%) most significantly altered regions from the initial analysis (3q26, 5p15-p14, 14q32, and 16p11). Functional annotation of overlapping genes within the 4 validated regions of AA/CA DNA copy number changes revealed significant enrichment of genes related to immune response.</p> <p>Conclusions</p> <p>Our data reveal molecular alterations at the level of gene expression and DNA copy number that are specific to African American and Caucasian prostate cancer and may be related to underlying differences in immune response.</p

    LSST: from Science Drivers to Reference Design and Anticipated Data Products

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    (Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2^2 field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5σ\sigma point-source depth in a single visit in rr will be ∌24.5\sim 24.5 (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg2^2 with ÎŽ<+34.5∘\delta<+34.5^\circ, and will be imaged multiple times in six bands, ugrizyugrizy, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg2^2 region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to r∌27.5r\sim27.5. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

    Report on the sixth blind test of organic crystal-structure prediction methods

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    The sixth blind test of organic crystal-structure prediction (CSP) methods has been held, with five target systems: a small nearly rigid molecule, a polymorphic former drug candidate, a chloride salt hydrate, a co-crystal, and a bulky flexible molecule. This blind test has seen substantial growth in the number of submissions, with the broad range of prediction methods giving a unique insight into the state of the art in the field. Significant progress has been seen in treating flexible molecules, usage of hierarchical approaches to ranking structures, the application of density-functional approximations, and the establishment of new workflows and "best practices" for performing CSP calculations. All of the targets, apart from a single potentially disordered Z` = 2 polymorph of the drug candidate, were predicted by at least one submission. Despite many remaining challenges, it is clear that CSP methods are becoming more applicable to a wider range of real systems, including salts, hydrates and larger flexible molecules. The results also highlight the potential for CSP calculations to complement and augment experimental studies of organic solid forms

    Interventions aimed at preventing and reducing overweight/obesity among children and adolescents:a meta-synthesis

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    The prevalence of child and adolescent obesity has been a major worldwide problem for decades. To stop the number of youth with overweight/obesity from increasing, numerous interventions focusing on improving children's weight status have been implemented. The growing body of research on weight-related interventions for youth has been summarized by several meta-analyses aiming to provide an overview of the effectiveness of interventions. Yet, the number of meta-analyses is expanding so quickly and overall results differ, making a comprehensive synopsis of the literature difficult. To tackle this problem, a meta-synthesis was conducted to draw informed conclusions about the state of the effectiveness of interventions targeting child and adolescent overweight. The results of the quantitative synthesis of 26 meta-analyses resulted in a standardized mean difference (SMD) of -0.12 (95%CI: -0.16, -0.08). Several moderator analyses showed that participant and intervention characteristics had little impact on the overall effect size. However, a moderator analysis distinguishing between obesity treatment and obesity prevention studies showed that obesity treatment interventions (SMD: -0.048, 95%CI: -0.60, -0.36) were significantly more effective in reducing body mass index than obesity prevention interventions (SMD: -0.08, 95%CI: -0.11, -0.06). Overall, the results of this meta-synthesis suggest that interventions result in statistically significant effects albeit of relatively little clinical relevance
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