10,833 research outputs found

    Evaporative Deposition Patterns Revisited: Spatial Dimensions of the Deposit

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    A model accounting for finite spatial dimensions of the deposit patterns in the evaporating sessile drops of colloidal solution on a plane substrate is proposed. The model is based on the assumption that the solute particles occupy finite volume and hence these dimensions are of the steric origin. Within this model, the geometrical characteristics of the deposition patterns are found as functions of the initial concentration of the solute, the initial geometry of the drop, and the time elapsed from the beginning of the drying process. The model is solved analytically for small initial concentrations of the solute and numerically for arbitrary initial concentrations of the solute. The agreement between our theoretical results and the experimental data is demonstrated, and it is shown that the observed dependence of the deposit dimensions on the experimental parameters can indeed be attributed to the finite dimensions of the solute particles. These results are universal and do not depend on any free or fitting parameters; they are important for understanding the evaporative deposition and may be useful for creating controlled deposition patterns.Comment: 34 pages, 14 figures, LaTeX; submitted to Physical Review

    Careers Service Work with Adults: A Survey

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    This report summarises the findings from a postal survey of all Careers Service Companies in England about their adult guidance services and services to employers. The survey was conducted by the Centre for Guidance Studies (University of Derby) and the National Institute for Careers Education and Counselling (NICEC) for the Department for Education and Employment (DfEE)

    The prevalence of metabolic syndrome and its related factors among adults in Palestine: a meta-analysis

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    Background: Metabolic syndrome (MetS)is increasingly becoming a challenging public health issue in Palestine. The current burden of MetS in the country is unknown. There has been limited research on the prevalence of MetS. This meta-analysis is the first to estimate the population prevalence of MetS and its related factors among adults in Palestine.Methods: A PRISMA systematic search appraisal and meta-analysis were conducted. A systematic literature search of PubMed, Scopus and Google Scholar was conducted in December 2014 up to February 2015. Generic, methodological and statistical data was extracted from the eligible studies which reported MetS prevalence. A random effect meta-analysis was conducted on crude MetS prevalence rates. Heterogeneity was assessed by Cochran’s Q and I2 tests. Subgroup analyses were also performed according to the predefined criteria.Results: The literature search yielded a total of 49 studies. Eight papers were included in the final analysis with sample size ranging 163 to 992. In addition, 2937 cases with MetS among people aged 15 years or more were estimated in Palestine between 2001 and 2014. There was high heterogeneity among studies (I2 = 95.8% p<0.001). The prevalence of MetS was 37.0% among adult Palestinians population ranging from 17 to 59.5%. Subgroup analysis did not show source of heterogeneity based on subject's health status and MetS criteria.Conclusion: Our meta-analysis clearly demonstrates that MetS is highly prevalent (37.0%) among Palestinian adults. The high prevalence of MetS in Palestine should be seriously considered and planners should take steps to reduce it.Keywords: Prevalence, Metabolic syndrome, Meta-analysis, Palestin

    The Development of Novel Nanodiamond Based MALDI Matrices for the Analysis of Small Organic Pharmaceuticals

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    The utility of novel functionalized nanodiamonds (NDs) as matrices for matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) is described herein. MALDI-MS analysis of small organic compounds (<1000 Da) is typically complex due to interferences from numerous cluster ions formed when using conventional matrices. To expand the use of MALDI for the analysis of small molecules, , novel matrices were designed by covalently linking conventional matrices (or a lysine moiety) to detonated NDs. Four new functionalized NDs were evaluated for their ionization capabilities using five pharmaceuticals with varying molecular structures. Two ND matrices were able to ionize all tested pharmaceuticals in the negative ion mode, producing the deprotonated ions [M-H]-. Ion intensity for target analytes was generally strong with enhanced signal-to-noise ratios compared with conventional matrices. The negative ion mode is of great importance for biological samples as interference from endogenous compounds is inherently minimized in the negative ion mode. Since the molecular structures of the tested pharmaceuticals did not suggest that negative ion mode would be preferable, this result magnifies the importance of these findings. On the other hand, conventional matrices primarily facilitated the ionization as expected in the positive ion mode, producing either the protonated molecules [M+H]+ or cationic adducts (typically producing complex spectra with numerous adduct peaks). The data presented in this study suggests that these matrices may offer advantages for the analysis of low molecular weight pharmaceuticals/metabolites

    The diastereoselective Meth-Cohn epoxidation of camphor-derived vinyl sulfones

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    Some camphor-derived vinyl sulfones bearing oxygen functionality at the allylic position have been synthesized and their nucleophilic epoxidation reactions under Meth-Cohn conditions have been explored. The γ-oxygenated camphor-derived vinyl sulfones underwent mildly diastereoselective nucleophilic epoxidation reactions, affording the derived sulfonyloxiranes in up to 5.8:1 dr. The observed diastereoselectivities were sensitive to the reaction conditions employed. In contrast, no stereoselectivity was observed in the nucleophilic epoxidation of the corresponding γ-oxygenated isobornyl vinyl sulfone. A tentative mechanism has been proposed to explain the origins of the diastereoselectivit

    Dynamical friction for accelerated motion in a gaseous medium

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    Dynamical friction arises from the interaction of a perturber and the gravitational wake it excites in the ambient medium. This interaction is usually derived assuming that the perturber has a constant velocity. In realistic situations, motion is accelerated as for instance by dynamical friction itself. Here, we study the effect of acceleration on the dynamical friction force. We characterize the density enhancement associated with a constantly accelerating perturber with rectilinear motion in an infinite homogeneous gaseous medium and show that dynamical friction is not a local force and that its amplitude may depend on the perturber's initial velocity. The force on an accelerating perturber is maximal between Mach 1 and Mach 2, where it is smaller than the corresponding uniform motion friction. In the limit where the perturber's size is much smaller than the distance needed to change the Mach number by unity through acceleration, a subsonic perturber feels a force similar to uniform motion friction only if its past history does not include supersonic episodes. Once an accelerating perturber reaches large supersonic speeds, accelerated motion friction is marginally stronger than uniform motion friction. The force on a decelerating supersonic perturber is weaker than uniform motion friction as the velocity decreases to a few times the sound speed. Dynamical friction on a decelerating subsonic perturber with an initial Mach number larger than 2 is much larger than uniform motion friction and tends to a finite value as the velocity vanishes in contrast to uniform motion friction.Comment: Published in MNRAS. Revised version (minor typos corrected

    Preoperative clinical predictors of difficult laryngeal exposure for microlaryngoscopy: The laryngoscore.

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    To identify a clinical predictor score for difficult laryngeal exposure (DLE) during operative microlaryngoscopy.Prospective cohort study in two academic institutions.We evaluated 319 patients before microlaryngoscopy for benign and malignant glottic diseases by a standardized preoperative assessment protocol (Laryngoscore) that included 11 parameters: interincisors gap (IIG), thyro-mental distance, upper jaw dental status, trismus, mandibular prognathism, macroglossia, micrognathia, degree of neck flexion-extension, history of previous open-neck and/or radiotherapy, Mallampati's modified score, and body mass index (BMI). Each parameter was assessed to obtain a total score. Patients were divided into five classes according to the anterior commissure (AC) visualization: class 0, complete AC visualization with large-bore laryngoscopes in the Boyce-Jackson position; class I, as class 0 with external laryngeal counterpressure; class II, as class I in the flexion-flexion position; class III, as class II using small-bore laryngoscopes; and class IV, impossible AC visualization.Class 0-I-II (good/acceptable laryngeal exposure) presented a median score < 6. This value was chosen as cutoff for distinguishing favorable versus difficult/impossible laryngeal exposures. When the Laryngoscore was < 6, good laryngeal exposure was observed in 94\% of patients, whereas when ≥ 6, DLE was encountered in 40\%. When considering a Laryngoscore of ≥ 9, 67\% of patients had a DLE. At univariate analysis, IIG, upper jaw dental status, macroglossia, micrognathia, degree of neck flexion-extension, and BMI statistically impacted on DLE (P < 0.05).The Laryngoscore is a good predictor of DLE and assists in selecting the ideal candidates for operative microlaryngoscopy.2b. Laryngoscope, 124:2561-2567, 2014
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