3,068 research outputs found

    The Gibbs-Thomson formula at small island sizes - corrections for high vapour densities

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    In this paper we report simulation studies of equilibrium features, namely circular islands on model surfaces, using Monte-Carlo methods. In particular, we are interested in studying the relationship between the density of vapour around a curved island and its curvature-the Gibbs-Thomson formula. Numerical simulations of a lattice gas model, performed for various sizes of islands, don't fit very well to the Gibbs-Thomson formula. We show how corrections to this form arise at high vapour densities, wherein a knowledge of the exact equation of state (as opposed to the ideal gas approximation) is necessary to predict this relationship. Exploiting a mapping of the lattice gas to the Ising model one can compute the corrections to the Gibbs-Thomson formula using high field series expansions. We also investigate finite size effects on the stability of the islands both theoretically and through simulations. Finally the simulations are used to study the microscopic origins of the Gibbs-Thomson formula. A heuristic argument is suggested in which it is partially attributed to geometric constraints on the island edge.Comment: 27 pages including 7 figures, tarred, gzipped and uuencoded. Prepared using revtex and espf.sty. To appear in Phys. Rev.

    Leptin Regulates CD16 Expression on Human Monocytes in a Sex-Specific Manner

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    Fat mass is linked mechanistically to the cardiovascular system through leptin, a 16 kDa protein produced primarily by adipocytes. In addition to increasing blood pressure via hypothalamic-sympathetic pathways, leptin stimulates monocyte migration, cytokine secretion, and other functions that contribute to atherosclerotic plaque development. These functions are also characteristics of CD16-positive monocytes that have been implicated in the clinical progression of atherosclerosis. This investigation sought to determine if leptin promoted the development of such CD16-positive monocytes. Cells from 45 healthy men and women with age ranging from 20 to 59 years were analyzed. Circulating numbers of CD14++16++ monocytes, which are primary producers of TNFα, were positively related to plasma leptin concentrations (P \u3c 0.0001), with a stronger correlation in men (P \u3c 0.05 for leptin × sex interaction). In vitro, recombinant human leptin induced CD16 expression in a dose-related manner (P = 0.02), with a stronger influence on monocytes from men (P = 0.03 for leptin × sex interaction). There were no sex-related differences in total leptin receptor expression on any monocyte subtypes, relative expression of long versus short isoforms of the receptor, or soluble leptin receptor concentrations in the plasma. The number of circulating CD14+16++ monocytes, which preferentially migrate into nascent plaques, was positively related to systolic blood pressure (R = 0.56, P = 0.0008) and intima-media thickness (R = 0.37, P = 0.03), and negatively related to carotid compliance (R = -0.39, P = 0.02). These observations indicate that leptin promotes the development of CD16-positive monocyte populations in a sex-specific manner and that these subpopulations are associated with diminished vascular function

    Is the apparently protective effect of maternal nicotine replacement therapy (NRT) used in pregnancy on infant development explained by smoking cessation?: secondary analyses of a randomised controlled trial.

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    Objective: To investigate relationships between maternal smoking status in pregnancy and infant development. The largest RCT of nicotine replacement therapy (NRT) for smoking cessation in pregnancy, the Smoking and Nicotine in Pregnancy (SNAP) trial, found that at one month after randomisation, smoking cessation rates were doubled in the NRT group compared to the placebo group. At delivery, there was no significant difference in cessation rates between groups. Surprisingly, infants born to women randomised to NRT were more likely to have unimpaired development at 2 years. We hypothesized that this apparently protective effect was due to smoking cessation caused by NRT and so, investigate this relationship using the same cohort.Design: Secondary analysis of a randomised controlled trial.Setting: Seven antenatal hospitals in the Midlands and North-West England.Participants: Eight hundred and eighty-four (884) pregnant smokers randomised to receive either NRT patches or visually-identical placebo in the SNAP trial. Participants’ smoking behaviour were recorded at randomisation, one month after their target quit date and at delivery.Methods: Using logistic regression models, we investigated associations between participants’ smoking measures and infant development (assessed using the Ages and Stages questionnaire) at 2 years.Main outcome measures: 2-year infant development. Results: Developmental impairment was reported for 12.7% of study 2 year olds. Maternal heaviness of smoking at randomisation (odds ratio [OR]: 1.26, 95% confidence interval [95% CI]: 0.82-1.96, p = 0.091), validated smoking abstinence recorded at one month after a quit date (OR: 1.02, 95% CI: 0.60-1.74, p = 0.914) and validated smoking abstinence recorded at one month after a quit date and at the end of pregnancy (OR: 1.52, 95% CI: 0.81-2.85, p = 0.795) were not independently associated with infant developmental impairment at 2 years.Conclusion: We found no evidence that NRT treatment improved infants' developmental outcomes through smoking cessation

    Metropolitan Social Environments and Pre-HAART/HAART Era Changes in Mortality Rates (per 10,000 Adult Residents) among Injection Drug Users Living with AIDS

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    Background Among the largest US metropolitan areas, trends in mortality rates for injection drug users (IDUs) with AIDS vary substantially. Ecosocial, risk environment and dialectical theories suggest many metropolitan areas characteristics that might drive this variation. We assess metropolitan area characteristics associated with decline in mortality rates among IDUs living with AIDS (per 10,000 adult MSA residents) after highly active antiretroviral therapy (HAART) was developed. Methods This is an ecological cohort study of 86 large US metropolitan areas from 1993–2006. The proportional rate of decline in mortality among IDUs diagnosed with AIDS (as a proportion of adult residents) from 1993–1995 to 2004–2006 was the outcome of interest. This rate of decline was modeled as a function of MSA-level variables suggested by ecosocial, risk environment and dialectical theories. In multiple regression analyses, we used 1993–1995 mortality rates to (partially) control for pre-HAART epidemic history and study how other independent variables affected the outcomes. Results In multivariable models, pre-HAART to HAART era increases in ‘hard drug’ arrest rates and higher pre-HAART income inequality were associated with lower relative declines in mortality rates. Pre-HAART per capita health expenditure and drug abuse treatment rates, and pre- to HAART-era increases in HIV counseling and testing rates, were weakly associated with greater decline in AIDS mortality. Conclusions Mortality among IDUs living with AIDS might be decreased by reducing metropolitan income inequality, increasing public health expenditures, and perhaps increasing drug abuse treatment and HIV testing services. Given prior evidence that drug-related arrest rates are associated with higher HIV prevalence rates among IDUs and do not seem to decrease IDU population prevalence, changes in laws and policing practices to reduce such arrests while still protecting public order should be considered

    The Freshman, vol. 6, no. 1

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    The Freshman was a weekly, student newsletter issued on Mondays throughout the academic year. The newsletter included calendar notices, coverage of campus social events, lectures, and athletic teams. The intent of the publication was to create unity, a sense of community, and class spirit among first year students

    Structure-from-motion with varying principal point

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    We consider the problem of structure-from-motion (SfM) for images with fixed calibration but varying principal point. This scenario occurs for archival imagery taken using historic glass plate and film cameras without fiducial markers, when images have been inconsistently cropped or when image plates are broken into multiple fragments.We derive initialisation and pose estimation methods and regularisation penalties tuned specifically for this scenario leading to a complete archival imagery SfM pipeline. This problem is of special importance if imiage data set is limited. We illustrate the performance of our methods on challenging real world examples from image archives. Specifically, we use archival images of the East coast of Greenland from the British Arctic Air Route Expedition (BAARE). This is of particular glaciological interest for measuring historic ice loss. We use a modern digital elevation model (ArcticDEM), masked to stable regions, as ground truth to evaluate our method
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