374 research outputs found

    Molecular dynamics simulation study of elastic properties of HMX

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    Journal ArticleAtomistic simulations were used to calculate the isothermal elastic properties for b-, a-, and d-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The room-temperature isotherm for each polymorph was computed in the pressure interval 0≤p≤10.6 GPa and was used to extract the initial isothermal bulk modulus Ko and its pressure derivative using equations of state employed previously in experimental studies of the b-HMX isotherm

    Temperature dependent shear viscosity coefficient of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX ): a molecular dynamics simulation study

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    Journal ArticleEquilibrium molecular dynamics methods were used in conjunction with linear response theory and a recently published potential-energy surface [J. Phys. Chem. B 103, 3570 (1999)] to compute the liquid shear viscosity and self-diffusion coefficient of the high explosive HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) over the temperature domain 550-800 K. Predicted values of the shear viscosity range from 0.0055 Pa *s at the highest temperature studied up to 0.45 Pa *s for temperatures near the melting point

    Molecular dynamics simulations of HMX crystal polymorphs using a flexible molecule force field

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    Journal ArticleMolecular dynamics simulations using a recently developed quantum chemistry-based atomistic force field [J. Phys. Chem. B 103 (1999) 3570] were performed in order to obtain unit cell parameters, coefficients of thermal expansion, and heats of sublimation for the three pure crystal polymorphs of octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX). The predictions for β-, α-, and δ-HMX showed good agreement with the available experimental data

    Bidirectional mapping between self-consistent field theory and molecular dynamics

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    Copyright (2007) AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Journal of Chemical Physics 127 and may be found at http://dx.doi.org.proxy.lib.uwaterloo.ca/10.1063/1.2776261A bidirectional mapping scheme that bridges particle-based and field-based descriptions for polymers is presented. Initial application is made to immiscible homopolymer blends. The forward mapping (upscaling) approach is based on the use of molecular dynamics simulations to calculate interfacial density profiles for polymer molecular weights that can be readily relaxed using standard simulation methods. These profiles are used to determine the optimal, effective interaction parameter that appears in the one-parameter self-consistent field theory treatment employed in the present work. Reverse mapping from a field representation to a particle-based description is accomplished by the application of a density-biased Monte Carlo method that generates representative chain configurations in the blend using statistical weights derived from fields obtained from self-consistent field theory.This work was supported by the Los Alamos National Laboratory Exploratory Research component of the Laboratory Directed Research and Development program. This work was carried out under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52–06NA25396

    Risperidone Provides Better Improvement of Sleep Disturbances Than Haloperidol Therapy in Schizophrenia Patients With Cannabis-Positive Urinalysis

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    A high percentage of persons with Schizophrenia also uses Cannabis and this may potentially alter the therapeutic benefits of the antipsychotic medications prescribed. The aim of this study was to assess the impact of Cannabis usage on antipsychotic therapy of sleep disturbances in schizophrenia subjects. Male subjects, ≥18 years, admitted to the University Hospital of the West Indies psychiatric ward between October 2015 and October 2016, and diagnosed with schizophrenia were recruited for the study. Following written informed consent to the study, subjects were prescribed either risperidone monotherapy or haloperidol monotherapy orally for 14 days and classified as Cannabis users (CU) or non-users (non-CU), with presence/absence of Cannabis metabolite in urine samples. After 1 week of admission, subjects wore the Actiwatch-2 device, to record sleep data for 7 consecutive nights. Inferential statistical analysis involved non-parametric tests, expressed as median and inter-quartile ranges (IQR), with p<0.05 considered statistically significant. Fifty subjects were assessed, with a median (IQR) age of 28 (14) years. Majority (30; 60%) were CU, displaying longer sleep latency (SL) than non-CU when receiving haloperidol; but equivalent SL when receiving risperidone. In comparison to non-CU, the CU also displayed longer time in bed, but shorter durations asleep, awoke more frequently during the nights and for longer durations, whether receiving haloperidol or risperidone. This resulted in lower sleep efficiency for the CU (<85%) compared to the non-CU (≥85%). Over the study period, sleep efficiency was significantly improved for non-CU receiving either risperidone (p = 0.032) or haloperidol (p = 0.010); but was only significantly improved with risperidone for the CU (p = 0.045). It is apparent that the presence of Cannabis may be impacting the therapeutic benefits of antipsychotic drugs on sleep. In schizophrenia subjects with concomitant Cannabis use, risperidone is more beneficial than haloperidol in improving sleep efficiency

    Book reviews

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44490/1/10745_2005_Article_BF01531428.pd

    Effects of a penthiopyrad and picoxystrobin fungicide mixtureon phoma stem canker (Leptosphaeria spp.) on UK winteroilseed rape

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    © Koninklijke Nederlandse Planteziektenkundige Vereniging 2016. This is a pre-copyedited, author-produced PDF of an article accepted for publication in European Journal of Plant Pathology following peer review. The final publication [Sewell, T.R., Moloney, S., Ashworth, M. et al., European Journal of Plant Pathology (2016) 145: 675-685, first published online April 5, 2016] is available at Springer via doi: http://dx.doi.org/10.1007/s10658-016-0916-8In the UK, fungicides are often used to controlphoma stem canker on winter oilseed rape. Field trialswere established near Boxworth, Cambridgeshire for fourcropping seasons (2011/2012, 2012/2013, 2013/2014 and2014/15) to test the efficacy of a new fungicide mixtureRefinzar® (penthiopyrad + picoxystrobin) by comparisonto an existing fungicide Proline 275® (prothioconazole)against phoma stem canker (Leptosphaeria spp.) andthe effect on winter oilseed rape (cv. Catana) yield. Ineach season, weather data were collected from a weatherstation at Boxworth and the release of ascospores wasmonitored using a nearby Burkard spore sampler. Thepatterns of ascospore release differed between seasonsand related to weather conditions. Fungicidespenthiopyrad + picoxystrobin and prothioconazole wereapplied in October/November when 10 % of plants hadphoma leaf spotting (T1, early), 4/8 weeks after T1 (T2,late) or at both T1 and T2 (combined). When phoma leafspot symptoms were assessed in autumn/winter,penthiopyrad + picoxystrobin and prothioconazole bothdecreased numbers of phoma leaf spots caused byL. maculans; there were few leaf spots caused byL. biglobosa. Penthiopyrad + picoxystrobin andprothioconazole both reduced phoma stem canker severitybefore harvest compared to the untreated control butdid not increase yield in these seasons when epidemicswere not severe. In 2013/2014, the presence ofL. maculans and L. biglobosa in upper stem lesions orstem base cankers was determined by species-specificPCR. The proportions of stems with L. maculans DNAwere much greater than those with L. biglobosa DNA forboth upper stem lesions and basal stem cankers. Theseresults suggest that both penthiopyrad + picoxystrobinand prothioconazole can decrease phoma stem cankerseverity on winter oilseed rape in severe disease seasons.Peer reviewe
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