75 research outputs found

    Carotid intima media thickness and blood biomarkers of atherosclerosis in patients after stroke or myocardial infarction

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    Aim To test if circulating levels of markers of inflammation, endothelial function, and chronic infections, as well as association between these markers and carotid intima media thickness (CIMT), depend on the stage of atherosclerosis expressed as a history of a major vascular event. Methods The associations were analyzed separately in 75 healthy controls, 79 patients 3-6 months after the first-ever non-cardioembolic ischemic stroke (IS), and 37 patients 3-6 months after the first-ever myocardial infarction (MI). Data were collected prospectively in 2005. We measured high sensitivity C-reactive protein (hs-CRP), procalcitonin, E-selectin, intercellular adhesion molecule-1 (ICAM-1), serum level of immune complexes (IC), and identified antibodies against Herpes simplex virus type 1 (HSV), Cytomegalovirus, Chlamydia pneumonia, and Helicobacter pylori. Correlations with CIMT were determined using Pearson R and verified after adjustment for age, sex, hypertension, diabetes, and statin therapy. Results Median ICAM-1 concentration was significantly lower in controls than in post-IS patients (188 μg/L vs 215 μg/L), and significantly lower in post-IS patients than in post-MI patients (215 μg/L vs 260 μg/L). Control patients also had significantly lower IC level (0.03 U/L) and HSV antibody index (6.0) compared to both post-IS (0.6 U/L, 9.6) and post-MI (0.4 U/L, 9.2) patients. CIMT was correlated with age (Pearson R = 0.38, P = 0.001) in the control group, immune complexes (R = 0.26, P = 0.023) in the post-IS group, and with hs-CRP (R = 0.40, P = 0.017) in the post-MI group. These correlations were confirmed using multiple regression analysis. Conclusions Our study supports linear correlations between CIMT and IC and hs-CRP levels. However, these associations seem to depend on the type of vascular burden

    Understanding the Origins of Bacterial Resistance to Aminoglycosides through Molecular Dynamics Mutational Study of the Ribosomal A-Site

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    Paromomycin is an aminoglycosidic antibiotic that targets the RNA of the bacterial small ribosomal subunit. It binds in the A-site, which is one of the three tRNA binding sites, and affects translational fidelity by stabilizing two adenines (A1492 and A1493) in the flipped-out state. Experiments have shown that various mutations in the A-site result in bacterial resistance to aminoglycosides. In this study, we performed multiple molecular dynamics simulations of the mutated A-site RNA fragment in explicit solvent to analyze changes in the physicochemical features of the A-site that were introduced by substitutions of specific bases. The simulations were conducted for free RNA and in complex with paromomycin. We found that the specific mutations affect the shape and dynamics of the binding cleft as well as significantly alter its electrostatic properties. The most pronounced changes were observed in the U1406C∶U1495A mutant, where important hydrogen bonds between the RNA and paromomycin were disrupted. The present study aims to clarify the underlying physicochemical mechanisms of bacterial resistance to aminoglycosides due to target mutations

    Research of pushing force of bullets made of W-Cu-BNα sinters with different content of dispersed W-BNα phase

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    W pracy przedstawiono wyniki badań modelowych pocisków do nabojów 9 × 19 mm Parabellum wykonanych ze spiekanych kompozytów Cu-W-BNα. Badania polegały na przepychaniu pocisków przez stożek przejściowy oraz cylindryczny odcinek przewodu lufy pomiarowej kalibru 9 mm. Celem tych badań było określenie wpływu zawartości fazy rozproszonej w kompozytach Cu-W-BNα na wartość siły przepychania.Results of examination of the model bullets of 9 × 19 mm Parabellum made of copper composites with dispersed phase of tungsten and boron nitride particles are presented in this paper (W-BNα). The study consisted in pushing the bullets through forcing cone and cylindrical section of the barell of 9-mm caliber. The aim of this study was to determine the effect of W-BNα content on the force pushing value

    Study of Cu–W–BNa composites fragmentation during the compression impact test

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    W pracy przedstawiono wyniki badań udarowego ściskania próbek wykonanych ze spiekanego kompozytu cermetalowego Cu-W-BNα o różnej zawartości fazy ceramicznej, a mianowicie: 0,5; 1, 1,5 i 3 procent (mas.). Badania ściskania wykonano na zmodernizowanym młocie Charpy'ego. Prędkość uderzenia młota wynosiła ok. 5,5 m/s, a wartość energii kinetycznej bijaka była równa 281,86 J. Odzyskane po próbach ściskania fragmenty zniszczonych próbek poddano analizie sitowej. Określono udziały masowe i ilościowe poszczególnych frakcji wymiarowych fragmentów. Na podstawie uzyskanych wyników stwierdzono, że istnieje powiązanie między zawartością azotku boru w kompozycie a rozkładem frakcji wymiarowych odzyskanych odłamków. Wzrost zawartości BN w kompozycie powoduje zwiększanie się liczby najmniejszych fragmentów w uzyskanym w eksperymencie materiale.Research of the compression impact test of samples made of sintered cermetals Cu-W-BNα with different contents of ceramics phase namely 0.5; 1, 1.5 and 3% (wt.) have been presented in this paper. The compression tests were carried out using modified Charpy machine. The velocity of impact was 5.5 m/s and a value of the kinetic energy of ram was 281.82 J. Fragments of the tests damaged samples recovered after compression were subjected to a sieve analysis. The mass of particles distribution and number of particles distribution for size particle fraction were determined. On the basis of the obtained results, it was found that there is dependence between contents of boron nitride and particles size distribution. Increase in BN contents causes increase in the smallest particle number of the investigated materials

    Analysis of a side surface radial velocity of a plastic-rigid cylindrical rod during perpendicular striking a rigid plate

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    Wyprowadzono zamknięte wzory w postaci elementarnych analitycznych funkcji, które jednoznacznie określają dynamikę sztywno-plastycznego pręta uderzającego w nieodkształcalną płytę. Materiał pręta modelowano w strefie odkształceń plastycznych liniowym wzmocnieniem. Rozwiązanie obejmuje duże odkształcenia pręta. Uzyskane w pracy wyniki teoretyczne dobrze aproksymują dane eksperymentalne.The closed formulae in the form of elementary analytic functions, which uniquely determined the dynamics of the plastic-rigid rod striking a rigid plate, have been derived. The material of the rod has been modelled to linear strain hardening. The formulae are rightful for large strains of the rod. The theoretical results of the paper are conformable to experimental data

    Thin Film ZnO as Sublayer for Electric Contact for Bulk GaN with Low Electron Concentration

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    Fabrication of low resistivity ohmic contacts to N polarity gallium nitride crystal is an important issue for the construction of the vertical current flow devices like laser diodes and high brightness light emitting diodes. Gallium nitride is a challenging material because of the high metal work function required to form a barrier-free metal-semiconductor interface. In practice, all useful ohmic contacts to GaN are based on the tunneling effect. Efficient tunneling requires high doping of the material. The most challenging task is to fabricate high quality metal ohmic contacts on the substrate because the doping control is here much more difficult that in the case of epitaxial layers. In the present work we propose a method for fabricating low resistivity ohmic contacts on N-side of GaN wafers grown by hydride vapor phase epitaxy. These crystals were characterized by a n-type conductivity and the electron concentration of the order of 1017\text{}^{17} cm3\text{}^{-3}. The standard Ti/Au contact turned out to be unsatisfactory with respect to its linearity and resistance. Instead we decided to deposit high-n type ZnO layers (thickness 50 nm and 100 nm) prepared by atomic layer deposition at temperature of 200°C. The layers were highly n-type conductive with the electron concentration in the order of 1020\text{}^{20} cm3\text{}^{-3}. Afterwards, the metal contact to ZnO was formed by depositing Ti and Au. The electrical characterization of such a contact showed very good linearity and as low resistance as 1.6 × 103\text{}^{-3} Ω cm2\text{}^{2}. The results indicate advantageous properties of contacts formed by the combination of the atomic layer deposition and hydride vapor phase epitaxy technology

    Soil microbial activity as influenced by compaction and straw mulching

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    Field study was performed on Haplic Luvisol soil to determine the effects of soil compaction and straw mulching on microbial parameters of soil under soybean. Treatments with different compaction were established on unmulched and mulched with straw soil. The effect of soil compaction and straw mulching on the total bacteria number and activities of dehydrogenases, protease, alkaline and acid phosphatases was studied. The results of study indicated the decrease of enzymes activities in strongly compacted soil and their increase in medium compacted soil as compared to no-compacted treatment. Mulch application caused stimulation of the bacteria total number and enzymatic activity in the soil under all compaction levels. Compaction and mulch effects were significant for all analyzed microbial parameters (P<0.001)
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