985 resultados para 1. Plasma Physics


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The present study investigates the concentrations and patterns of organochlorine pesticides (OCPs) and their metabolites in liver and plasma of two ringed seal populations (Phoca hispida): lower contaminated Svalbard population and more contaminated Baltic Sea population. Among OCPs, p,p'-DDE and sum-chlordanes were the highest in concentration. With increasing hepatic contaminant concentrations and activities of xenobiotic-metabolizing enzymes, the concentrations of 3-methylsulfonyl-p,p'-DDE and the concentration ratios of pentachlorophenol/hexachlorobenzene increased, and the toxaphene pattern shifted more towards persistent Parlar-26 and -50 and less towards more biodegradable Parlar-44. Relative concentrations of the chlordane metabolites, oxychlordane and -heptachlorepoxide, to sum-chlordanes were higher in the seals from Svalbard compared to the seals from the Baltic, while the trend was opposite for cis- and trans-nonachlor. The observed differences in the OCP patterns in the seals from the two populations are probably related to the catalytic activity of xenobiotic-metabolizing enzymes, and also to differences in dietary exposure.

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Not complete until the 6th ed., London, 1864-65.

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Vascular monocyte retention in the subintima is pivotal to the development of cardiovascular disease and is facilitated by up-regulation of adhesion molecules on monocytes/endothelial cells during oxidative stress. Epidemiological studies have shown that cardiovascular disease risk is inversely proportional to plasma levels of the dietary micronutrients, vitamin C and vitamin E (α-tocopherol). We have tested the hypothesis that α-tocopherol supplementation may alter endothelial/monocyte function and interaction in subjects with normal ascorbate levels (> 50 μM), as ascorbate has been shown to regenerate tocopherol from its oxidised tocopheroxyl radical form in vitro. Healthy male subjects received α-tocopherol supplements (400 IU RRR-α-tocopherol /day for 6 weeks) in a placebo-controlled, double-blind intervention study. There were no significant differences in monocyte CD11b expression, monocyte adhesion to endothelial cells, plasma C-reactive protein or sICAM- 1 concentrations post-supplementation. There was no evidence for nuclear translocation of NF-κB in isolated resting monocytes, nor any effect of α-tocopherol supplementation. However, post-supplementation, sVCAM-1 levels were decreased in all subjects and sE-selectin levels were increased in the vitamin C-replete group only; a weak positive correlation was observed between sE-selectin and α-tocopherol concentration. In conclusion, α-tocopherol supplementation had little effect on cardiovascular disease risk factors in healthy subjects and the effects of tocopherol were not consistently affected by plasma vitamin C concentration. © W. S. Maney & Son Ltd.

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Monocytes play a central role in inflammatory responses through systemic antigen presentation and cytokine secretion. Regulation of monocyte adhesion molecule and inflammatory gene expression is via redox sensitive transcription factors. Therefore we have investigated the hypothesis that dietary antioxidant supplementation with vitamins C (250mg/d) or E (400iU/d) for six weeks can modulate monocyte ICAM-1 expression in healthy male subjects with low plasma vitamin C at baseline. In a randomised, double-blind, crossover study, ICAM-1 mRNA and protein was analysed using quantitative RTPCR with ELISA measurement of PCR products and by flow cytometry and ELISA respectively. Monocyte numbers were unaltered by supplementation. Subjects with low plasma vitamin C (<50uM) prior to supplementation expressed higher levels of monocyte ICAM-1 mRNA, and showed a significant (50%) reduction in ICAM-1 mRNA expression after 6 weeks of 250mg/d vitamin C supplementation compared to subjects with normal plasma vitamin C. This was paralleled by a reduction in plasma sICAM-1. Vitamin E supplementation had no effect on ICAM-1 expression. For the first time, these results show that dietary vitamin C can modulate monocyte ICAM-1 gene expression in vivo, where regulation of gene expression represents a novel mechanism for benefit from dietary antioxidants.

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This paper describes physics of nonlinear ultra-short laser pulse propagation affected by plasma created by the pulse itself. Major applications are also discussed. Nonlinear propagation of the femtosecond laser pulses in gaseous and solid transparent dielectric media is a fundamental physical phenomenon in a wide range of important applications such as laser lidars, laser micro-machining (ablation) and microfabrication etc. These applications require very high intensity of the laser field, typically 1013â1015 TW/cm2. Such high intensity leads to significant ionisation and creation of electron-ion or electron-hole plasma. The presence of plasma results into significant multiphoton and plasma absorption and plasma defocusing. Consequently, the propagation effects appear extremely complex and result from competitive counteraction of the above listed effects and Kerr effect, diffraction and dispersion. The theoretical models used for consistent description of laser-plasma interaction during femtosecond laser pulse propagation are derived and discussed. It turns out that the strongly nonlinear effects such self-focusing followed by the pulse splitting are essential. These phenomena feature extremely complex dynamics of both the electromagnetic field and plasma density with different spatio-temporal structures evolving at the same time. Some numerical approaches capable to handle all these complications are also discussed. ©2006 American Institute of Physics

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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The present study investigated the concentrations and patterns of PBDEs and hydroxylated (OH) PBDE analogues in two ringed seal populations: less contaminated Svalbard and more contaminated Baltic Sea. Mean concentration of hepatic sum-PBDE, which was dominated by BDE47, was six times higher in the ringed seals from the Baltic Sea compared to the seals from Svalbard. BDE47/sum-PBDE was higher in the seals from Svalbard compared to that for Baltic seals, while the trend was opposite for BDE153 and 154. The geographical difference in contaminant pattern of PBDEs in ringed seals could be explained by biotransformation via oxidative metabolism and/or by dietary differences. OH-PBDEs were detectable in the majority of plasma samples from both locations, and dominated by bioaccumulation of naturally occurring congeners. Low levels of 3-OH-BDE47 and 4'-OH-BDE49 in the Baltic ringed seals suggested minor oxidative biotransformation of BDE47. In the Baltic seals, BDE153/sum-PBDEs and BDE154/sum-PBDEs increased and BDE28/sum-PBDE decreased with increasing sum-POP concentration, which suggests BDE153 and 154 are more persistent than BDE28. Contrasting diets of the ringed seals in these two locations may influence the PBDE congener pattern due to selective long-range transport and direct effluent emissions to Svalbard and the Baltic, respectively.

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<p>To characterize non-thermal atmospheric pressure plasmas experimentally, a large variety of methods and techniques is available, each having its own specific possibilities and limitations. A rewarding method to investigate these plasma sources is laser Thomson scattering. However, that is challenging. Non-thermal atmospheric pressure plasmas (gas temperatures close to room temperature and electron temperatures of a few eV) have usually small dimensions (below 1 mm) and a low degree of ionization (below 10<sup>-4</sup>). Here an overview is presented of how Thomson scattering can be applied to such plasmas and used to measure directly spatially and temporally resolved the electron density and energy distribution. A general description of the scattering of photons and the guidelines for an experimental setup of this active diagnostic are provided. Special attention is given to the design concepts required to achieve the maximum signal photon flux with a minimum of unwanted signals. Recent results from the literature are also presented and discussed.</p>

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Poster presented at the 2015 Keystone Symposia Conference X5: HIV Vaccines. Banff, Alberta, Canada, 22-27 March 2015

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This short review article explores the practical use of diamond-like carbon (DLC) produced by plasma enhanced chemical vapour deposition (PECVD). Using as an example issues relating to the DLC coating of a hand-held surgical device, we draw on previous works using atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, tensiometry and electron paramagnetic resonance. Utilising data from these techniques, we examine the surface structure, substrate-film interface and thin film microstructure, such as sp2/sp3 ratio (graphitic/diamond-like bonding ratio) and sp2 clustering. We explore the variations in parameters describing these characteristics, and relate these to the final device properties such as friction, wear resistance, and diffusion barrier integrity. The material and device characteristics are linked to the initial plasma and substrate conditions.

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Ethanol consumption damages the prostate, and testosterone is known by anti-inflammatory role. The cytokines were investigated in the plasma and ventral prostate of UChB rats submitted or not to testosterone therapy by ELISA and Western blot, respectively. Additionally, inflammatory foci and mast cells were identified in the ventral prostate slides stained by hematoxylin and eosin and toluidine blue, respectively. Inflammatory foci were found in the ethanol-treated animals and absent after testosterone therapy. Plasma levels of IL-6 and IL-10 were not changed while TNFα and TFG-β1 were increased in the animals submitted testosterone therapy. Regarding to ventral prostate, IL-6 did not alter, while IL-10, TNFα, and TFG-β1 were increased after testosterone therapy. Ethanol increases NFR2 in addition to high number of intact and degranulated mast cell which were reduced after testosterone therapy. So, ethanol and testosterone differentially modulates the cytokines in the plasma and prostate.

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We report on the shape resonance spectra of phenol-water clusters, as obtained from elastic electron scattering calculations. Our results, along with virtual orbital analysis, indicate that the well-known indirect mechanism for hydrogen elimination in the gas phase is significantly impacted on by microsolvation, due to the competition between vibronic couplings on the solute and solvent molecules. This fact suggests how relevant the solvation effects could be for the electron-driven damage of biomolecules and the biomass delignification [E. M. de Oliveira et al., Phys. Rev. A 86, 020701(R) (2012)]. We also discuss microsolvation signatures in the differential cross sections that could help to identify the solvated complexes and access the composition of gaseous admixtures of these species.