137 research outputs found

    Surgical treatment of necrotizing infections of soft tissue

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    В работе представлены результаты лечения 114-ти больных с некротическими инфекциями мягких тканей, находившихся на лечении в ВМКЦ ЮР с 2008 по 2012 г. Из них некротический целлюлит наблюдался у 16 больных (14,1 %), фасциит – у 10 (8,8 %), мионекроз – у 10 (8,8 %), целлюлофасциит – у 48 (42,1 %), целлюлофасциомиозит – у 30 (26,3 %). Оперативные вмешательства носили многоэтапный характер и заключались в радикальной хирургической обработке с иссечением всех нежизнеспособных тканей. Большинству больных (89 %) выполнялись повторные некрэктомии (от 2-х до 10-ти). При тяжелых послеоперационных нарушениях у 12-ти больных (10,5 %) выполнены ампутации конечностей. Умерло 3-е больных (2,6 %) от нарастающей полиорганной недостаточности.There are presented the results of treatment of 114 patients with a necrotizing soft tissue infections who were treated at the Military-Medical Clinical Centre of the Southern Region from 2008 to 2012. Necrotizing cellulitis among them was observed in 16 patients (14,1 %), fasciitis – in 10 (8,8 %), myonecrosis – in 10 (8,8 %), tsellyulofastsiit had in 48 (42,1 %), tsellyulofastsiomiositis – in 30 (26,3 %). Surgical interventions had multi– stage character and consisted in a radical surgical treatment with excision of all devitalized tissue. Most patients (89 %) required repeated necrosectomy (from 2 to 10). In severe postoperative disorders in 12 patients (10,5 %), was performed the following limb amputation. Three patients died (2.6 %) from the rise of multiple organ failure

    Optoelectronic Properties of Carbon Nanorings: Excitonic Effects from Time-Dependent Density Functional Theory

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    The electronic structure and size-scaling of optoelectronic properties in cycloparaphenylene carbon nanorings are investigated using time-dependent density functional theory (TDDFT). The TDDFT calculations on these molecular nanostructures indicate that the lowest excitation energy surprisingly becomes larger as the carbon nanoring size is increased, in contradiction with typical quantum confinement effects. In order to understand their unusual electronic properties, I performed an extensive investigation of excitonic effects by analyzing electron-hole transition density matrices and exciton binding energies as a function of size in these nanoring systems. The transition density matrices allow a global view of electronic coherence during an electronic excitation, and the exciton binding energies give a quantitative measure of electron-hole interaction energies in the nanorings. Based on overall trends in exciton binding energies and their spatial delocalization, I find that excitonic effects play a vital role in understanding the unique photoinduced dynamics in these carbon nanoring systems.Comment: Accepted by the Journal of Physical Chemistry

    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

    Water Deficient Environment Accelerates Proton Exchange: Acetone-Water Reaction Catalyzed by Calix[4]hydroquinone Nanotubes

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    Calix[4]hydroquinone nanotubes possess the unique property to catalyze proton exchange between water and acetone. Since concerted proton transfer mechanisms could be excluded previously, stepwise proton transfer via ionic intermediates created by predissociation of CHQ OH groups is studied using state-of-the-art quantum chemical methodology. In fact, the presence of charged species, protonated acetone or deprotonated hydroquinone, leads to a substantial decrease of the proton transfer energy barrier and to calculated reaction rates that provide an explanation for the experimentally observed proton exchange. Furthermore, our quantum chemical investigation demonstrates that the catalytic activity of CHQ aggregates is not based on a reduction of the energy barrier connected with proton transfer but on the desolvation of acetone and prevention of solvent water cluster formation. © 2009 American Chemical Society

    Catalytic Role Of Calix[4]Hydroquinone In Acetone-Water Proton Exchange: A Quantum Chemical Study Of Proton Transfer Via Keto-Enol Tautomerism

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    Calix[4]hydroquinone has recently attracted considerable interest since it forms stable tubular aggregates mediated solely by hydrogen bonding and π-π-stacking interactions. These aggregates trap specifically various small organic molecules and, in particular, catalyze the proton exchange of water with acetone. Using correlated quantum chemical methods, the mechanism of the observed proton exchange mediated by keto-enol tautomerism of acetone is investigated in detail. Starting with an investigation of keto-enol tautomerism of acetone-water clusters, it appears that four catalytic water molecules are optimal for the catalysis and that additional solvent water molecules lead to a decrease in efficiency. Analyses of the partial charges revealed a decrease of the polarization of the reactive hydrogen bonds due to the additional water molecules. As a next step, hydroquinone-acetone-water complexes were studied as models for the situation in the CHQ moieties. However, the computations revealed that the proton transfer reaction becomes less efficient when one catalytic water molecule is replaced by hydroquinone. Although concerted proton transfer via keto-enol tautomerism of acetone seems to be the predominant mechanism in supercritical water, it is no longer the rate-determining reaction mechanism for the catalyzed acetone-water proton exchange observed in tubular CHQ. Nevertheless, a key feature of the catalytic function of tubular CHQ has been identified to be the stiff hydrogen bonding network and the exclusion of additional solvent water molecules. © 2008 American Chemical Society

    Chemical Reaction CO+OH •

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    The supercritical carbon dioxide medium, used to increase efficiency in oxy combustion fossil energy technology, may drastically alter both rates and mechanisms of chemical reactions. Here we investigate potential energy surface of the second most important combustion reaction with quantum chemistry methods. Two types of effects are reported: formation of the covalent intermediates and formation of van der Waals complexes by spectator CO2 molecule. While spectator molecule alter the activation barrier only slightly, the covalent bonding opens a new reaction pathway. The mechanism includes sequential covalent binding of CO2 to OH radical and CO molecule, hydrogen transfer from oxygen to carbon atoms, and CH bond dissociation. This reduces the activation barrier by 11 kcal/mol at the rate-determining step and is expected to accelerate the reaction rate. The finding of predicted catalytic effect is expected to play an important role not only in combustion but also in a broad array of chemical processes taking place in supercritical CO2 medium. It may open a new venue for controlling reaction rates for chemical manufacturing
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