La turbulence plasma engendre un transport anormal de la chaleur et des particules qui dégrade l’efficacité d’un réacteur de fusion. La mesure de la turbulence plasma dans un tokamak est donc essentielle à la compréhension et au contrôle de ce phénomène. Parmi les instruments de mesure à disposition, le réflectomètre à balayage installé sur le tokamak Tore Supra a accès à la densité du plasma et ses fluctuations depuis le bord jusqu’au centre des décharges, avec une excellente résolution spatiale (mm) et temporelle (µs), de l’ordre des échelles de la turbulence. Cette thèse est dédiée à la caractérisation de la turbulence plasma dans Tore Supra à partir de mesures de réflectométrie à balayage ultrarapide. Des analyses de corrélations ont permis d’évaluer les échelles spatiales et temporelles de la turbulence ainsi que sa vitesse radiale. Dans la première partie, la caractérisation des propriétés de la turbulence à partir des profils de densité reconstruits est discutée, notamment au travers d’une comparaison avec les données des sondes de Langmuir. Ensuite une étude paramétrique est présentée mettant en relief l’effet de la collisionalité sur la turbulence, dont une interprétation est proposée en termes de stabilisation d’une turbulence électronique due aux électrons piégés. Finalement, on illustre comment le chauffage additionnel produit une modification locale de la turbulence dans le plasma proche des parois, se traduisant par une augmentation de la vitesse des structures et une diminution de leur temps de corrélation. L’effet supposé des potentiels rectifiés générés par l’antenne est étudié à l’aide de simulations. / The performance of a fusion reactor is closely related to the turbulence present in the plasma. The latter is responsible for anomalous transport of heat and particles that degrades the confinement. The measure and characterization of turbulence in tokamak plasma is therefore essential to the understanding and control of this phenomenon. Among the available diagnostics, the sweeping reflectometer installed on Tore Supra allows to access the plasma density fluctuations from the edge to the centre of the plasma discharge with a fine spatial (mm) and temporal resolution (µs ) , that is of the order of the characteristic turbulence scales.This thesis consisted in the characterization of plasma turbulence in Tore Supra by ultrafast sweeping reflectometry measurements. Correlation analyses are used to quantify the spatial and temporal scales of turbulence as well as their radial velocity. In the first part, the characterization of turbulence properties from the reconstructed plasma density profiles is discussed, in particular through a comparative study with Langmuir probe data. Then, a parametric study is presented, highlighting the effect of collisionality on turbulence, an interpretation of which is proposed in terms of the stabilization of trapped electron turbulence in the confined plasma. Finally, it is shown how additional heating at ion cyclotron frequency produces a significant though local modification of the turbulence in the plasma near the walls, resulting in a strong increase of the structure velocity and a decrease of the correlation time. The supposed effect of rectified potentials generated by the antenna is investigated via numerical simulations.

Thawing of fresh frozen plasma (FFP) in South Africa is not standardized and thawing at high temperatures may cause clotting factor activation and disseminated intravascular coagulation (DIC). This research project studies the in-vitro effects of thawing FFP at various temperatures on coagulation. Twenty units of FFP were each divided into 4 satellite bags which were respectively thawed at 22ºC, 37ºC, 45ºC and 60ºC and tested for Fibrinogen, DDimers, PT, PTT, r value, Alpha Angle and Maximum Amplitude (MA). FFP thawed at 60ºC showed significant differences suggesting clotting factor inactivation. FFP thawed at 45ºC showed significantly elevated D-Dimers. Clotting factors thawed at 22ºC may be partially inactivated. High thawing temperatures may activate and then denature the factors therein. Twenty two degrees may partially inactivate FFP until it is warmed to body temperature. The clinical implications and recommendations of this study are to thaw FFP at 37ºC.

It is plausible that the hydromagnetic flow in the Earth's core which sustains the geomagnetic field is driven by small-scale buoyant blobs, with the buoyancy being of either compositional or thermal origin. The possibility and importance of the $\alpha$-effect, a mean-field induction effect by small-scale flow and field, by blob convection in the Earth's core are studied assuming that the flows driven by blobs do not interact with each other. / In a rotating hydromagnetic system such as the Earth's core, various types of flows are possible due to the effects of Coriolis, Lorentz and viscous forces. With a balance between Coriolis and Lorentz forces and with Coriolis dominant, the wake is a foreshortened Taylor column. With same force balance but with Lorentz dominant, the wake is elongated in the direction of the ambient magnetic field. It is believed that one or both of the wakes having a Lorentz-Coriolis force balance are relevant for the Earth's core. / To dominant order in the magnetic Reynolds number (assumed small), the integral of helicity and electromotive force over all space, produced by any buoyancy field which decays to zero at infinity, is zero. Analyses of distribution of leading order helicity and electromotive force are carried out in detail for a spherically symmetric blob. The electromotive force integrated over the plane perpendicular to the rotation direction is found to be parallel to the ambient magnetic field, as modeled by the $\alpha$-effect. If there are enough blobs (of order $10\sp7$), this electromotive force contributes significantly to the geodynamo. / The constraint of symmetry must be broken to have non-zero net helicity. Four symmetry breakers are considered: non-linear effect, the effect of rigid non-conducting boundary, the effect of large-scale geostrophic flow, and the effect of non-uniform ambient magnetic field. Order of magnitude of helicities are estimated and found to be either zero or very small. Some other effect is necessary to get significant non-zero helicity. / Source: Dissertation Abstracts International, Volume: 57-06, Section: B, page: 3621. / Major Professor: David E. Loper. / Thesis (Ph.D.)--The Florida State University, 1996.

Flow was created in freely suspended liquid crystal films in the smectic C phase using gradients in the surface tension to drive the motion. The director field was distorted into a pattern of vortices which wind upon themselves while the gradient was being applied. The dependence of the pattern in the director field for topological defects of index S = +1,0, or $-$1 are reported. The flow pattern for the S = $-$1 defect has not been observed in other flow fields. The diffusion constant for the c-director orientation is extracted from the orientation field patterns under flow and are compared to other independent measurements. / Source: Dissertation Abstracts International, Volume: 57-02, Section: B, page: 1172. / Major Professor: David van Winkle. / Thesis (Ph.D.)--The Florida State University, 1995.

O fibrinogênio é uma glicoproteína presente no plasma composta por duas subunidades idênticas formadas por três pares de cadeias polipeptídicas (Aα Bβ e ϒ), interligadas por pontes dissulfeto. A trombina cliva o fibrinogênio, liberando os fibrinopeptídeos A e B, formando fibrina e, conseqüentemente, o coágulo. Esse trabalho descreve a purificação e caracterização do fibrinogênio a partir do plasma da serpente Bothrops jararaca (B. jararaca). O fibrinogênio purificado foi obtido através de adsorção com cloreto de bário, precipitações com sulfato de amônio e cromatografia de gel filtração. O fibrinogênio de B. jararaca apresentou massa molecular de 370 kDa em condições não reduzidas e, em condições reduzidas, apresentou massas moleculares de 71, 60 e 55 kDa, similares às cadeias Aα Bβ e ϒ dos fibrinogênio humano e bovino (64, 56 e 47 kDa, respectivamente). Através do seqüenciamento da região amino-terminal das cadeias polipeptídicas por degradação de Edman, foram obtidos os oito primeiros aminoácidos de cada cadeia do fibrinogênio de B. jararaca. As seqüências foram: Gly-Asp-Pro-Glu-Asp-Tyr-Leu-Gly para a cadeia Aα, Gly-Ser-Asp-His-Asp-Asp-Glu para a cadeia Bβ e Glu-Ser-X-Leu-Asp-Glu-Glu-Gly para a cadeia ϒ . As seqüências foram então comparadas com a de outros animais já descritos (NCBI-National Center for Biotechnology Information, www.ncbi.nih.gov), mas devido ao pequeno número de aminoácidos obtidos não foi possível observar similaridades. Através de espectrometria de massa (MALDI-TOF) foram observadas algumas seqüências peptídicas, mas não foi possível obter a seqüência completa do fibrinogênio de B. jararaca. Essas seqüências não apresentaram homologia significante com outras seqüências já descritas. O fibrinogênio de B. jararaca foi coagulado pela trombina bovina enquanto que os venenos das serpentes B. jararaca, Crotalus durissus terrificus e Lachesis muta rhombeata não foram capazes de induzir a formação de coágulo. Além disso, os anticorpos anti-fibrinogênio de B. jararaca produzidos em coelho não reconheceram o fibrinogênio humano. Contudo, os anticorpos anti-fibrinogênio humano reconheceram o fibrinogênio de B. jararaca. Assim, mesmo apresentando similaridades entre os fibrinogênios de B. jararaca e de mamíferos, eles possuem comportamentos distintos, podendo sugerir que a B. jararaca apresenta uma molécula de fibrinogênio diferente do humano para evitar um possível auto-envenenamento. / Fibrinogen is a plasma glycoprotein that is composed of two sets of three nonidentical polypeptide chains (Aα Bβ and ϒ ) which are covalently linked by disulfide bonds. Thrombin cleaves fibrinogen to form fibrin and, consequently, the fibrin clot. This work describes the purification and characterization of fibrinogen from Bothrops jararaca (B. jararaca) snake plasma. Purified fibrinogen was obtained by barium chloride adsorption, ammonium sulfate precipitation and gel filtration chromatography. B. jararaca fibrinogen showed a molecular mass of 370 kDa in non-reducing conditions, similar to human and bovine fibrinogen with 340 kDa. Reduced fibrinogen showed three chains of 71, 60 and 55 kDa, which are similar to the molecular masses of human and bovine Aα Bβ and ϒ fibrinogen chains (64, 56 and 47 kDa, respectively). B. jararaca fibrinogen was clotted by bovine thrombin, however, B. jararaca, Crotalus durissus terrificus and Lachesis muta rhombeata venoms were not able to induce fibrin formation. The N-terminal sequence of B. jararaca fibrinogen chains from PVDF membranes showed only the first eight amino acids residues from each chain. The Nterminal sequence was Gly-Asp-Pro-Glu-Asp-Tyr-Leu-Gly for Aα chain, Gly-Ser-Asp- His-Asp-Asp-Glu for Bβ chain, and Glu-Ser-X-Leu-Asp-Glu-Glu-Gly for ϒ chain. The B. jararaca fibrinogen chains N-terminal sequences were compared to other animal Nterminal sequences previously described. However, due to low signal detection during Edman degradation, the sequence results were not sufficient to provide an accurate Blast search identity (NCBI-National Center for Biotechnology Information, www.ncbi.nih.gov). Mass spectrometry (MALDI-TOF) analysis provides some peptide sequences that did not present the complete sequences. Besides, anti-B. jararaca fibrinogen produced in rabbit did not recognize human fibrinogen while anti-human fibrinogen recognized B. jararaca fibrinogen. Thus, despite B. jararaca fibrinogen presents a molecular mass similar to human fibrinogen, the former shows distinctive features, which protect B. jararaca snakes from a fortuitous ingress of snake venom proteins into snake circulation, which could cause a self-envenomation

by Kwok Kar Yee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1981. / Bibliography: leaves 140-154.

<p> The self-regulation of cosmic ray (CR) transport in the interstellar and intracluster media has long been viewed through the lenses of linear and quasilinear kinetic plasma physics. Such theories are believed to capture the essence of CR behavior in the pres- ence of self-generated turbulence, forming the basis for the so-called &ldquo;self-confinement paradigm,&rdquo; which has been proposed to explain the isotropic propagation of CRs in the interstellar medium. However, the coupled nonlinear equations that describe the time-dependent system of CRs and electromagnetic fields are analytically intractable in the general case. Thus, obtaining analytical solutions has always relied on simplify- ing assumptions that remove potentially critical details arising from the nonlinearities of the problem. </p><p> We utilize the Particle-in-Cell (PIC) numerical method to study the time- dependent nonlinear behavior of the gyroresonant streaming instabilities, self- consistently following the combined evolution of particle distributions and self- generated wave spectra in one-dimensional periodic and aperiodic simulations. In the periodic case, we demonstrate that the early growth of instability conforms to the predictions from linear physics, but that the behavior can vary depending on the properties of the initial CR distribution. We emphasize that the nonlinear stages of instability depend strongly on the initial anisotropy of CRs. We derive estimates for the wave amplitudes at saturation and the time scales for relaxation of the CR distribution. In the aperiodic case, we show that the expansion of CRs from small injection regions naturally induces highly anisotropic CR distributions. Pitch-angle diffusion of CRs is then limited by the predominantly right-handed circularly polarized self-generated turbulence, allowing bulk CR drift velocities of ?0.5c. We compare against a set of analytical solutions to the CR expansion problem and find that they do not accurately predict the time-dependent properties of the CR population. We briefly study the wave damping processes of nonlinear Landau iii damping and ion-neutral friction in order to assess the viability of performing damped CR streaming simulations in the future with the PIC method. </p><p>

O presente trabalho apresenta um estudo do processo de nitretação iônica de aços rápidos, como método de tratamento superficial para o aumento da resistência ao desgaste de ferramentas de corte. Utilizando-se os equipamentos de nitretação iônica em desenvolvimento no laboratório de Metalurgia Física da UFRGS foram nitretados corpos de prova do aço rápido AlSI M2 variando-se diversos parâmetros do processo. As amostras foram caracterizadas quanto a morfologia das camadas formadas, profundidade, perfil de microdureza e microdureza superficial. Foram avaliadas condições de tratamento quanto ao aumento da resistência à erosão e testadas ferramentas de corte de aço rápido em serviço. As técnicas de análise empregadas incluíram ensaio de microdureza, ensaio de erosão, metalografia (utilizando-se de microscopia ótica e eletrônica de varredura) e acompanhamento da produtividade de ferramentas na indústria. Discutiu-se neste trabalho o crescimento da camada nitretada em aços rápidos com a variação da composição da mistura de gases e temperatura da peça, as características das camadas formadas e a aplicabilidade do processo a ferramentas de corte. Além disso, os experimentos serviram para auxiliar no desenvolvimento dos equipamentos de nitretação iônica, de técnicas de controle do processo e de procedimentos de análise. / In this work the possibility of applying plasma nitriding to high-speed tool steels was investigated as a technique for improving wear resistance of cutting tools. Using the facilities developed at the Laboratório de Metalúrgia Física - UFRGS, samples of AISI M2 high-speed steel were nitrided under several different conditions. The sarnples produced were characterized with respect to the morphology of the nitrided layers, hardness and wear resistance. The analysis techniques used were: metallography (optical and scanrung electron microscopy-SEM), microhardness (determination of superficial hardness and microhardness pro file of the cross section o f the layers), erosion tests, and, as some tools were nitrided, their performance was evaluated under working conditions in the industry. The effect of variantion of the process parameters on composition and depth of the nitrided layers and the applicability of the plasma nitriding process to cutting tools were discussed. Additionally, the experiments done were very important on the development of the plasma nitriding equipment at UFRGS.

No presente trabalho foram geradas diferentes condições superficiais em amostras e brocas do aço rápido AISI M2 através de polimento, lixamento e jateamento das superfícies. As amostras e brocas foram nitretadas a plasma variando-se a temperatura, para duas diferentes composições da mistura gasosa: 5%vol. N2 e 76% vol. N2 em hidrogênio. As superfícies (não nitretadas e nitretadas) foram caracterizadas quanto a microestrutura, rugosidade, microdureza, composição química, composição ele fases e o estado ele tensões residuais. Embora algumas análises tenham sido realizadas nas brocas, a maior parte delas foi feita nas amostras cilíndricas tendo-se em vista a geometria complexa das ferramentas que dificulta a caracterização direta. Algumas ferramentas nitretadas a plasma foram testadas em ambiente de produção e as brocas foram submetidas a ensaios de usinagem. Durante os ensaios de usinagem com brocas os esforços de corte e o desgaste de flanco foram avaliados. A mistura gasosa pobre em nitrogênio evitou a formação da zona de compostos e, com o emprego da mistura gasosa rica em nitrogênio foi formada uma zona de compostos de (carbo)nitretos e-Fe2.3(C)N na superfície das amostras. Foram medidas altas tensões residuais compressivas na zona de difusão de amostras nitretadas, mostrando um aumento com o aumento da temperatura de nitretação a plasma para o caso de amostras polidas. Uma significativa influência do estado superficial antes da nitretação nas propriedades finais obtidas foi encontrada e seus principais aspectos discutidos: menores profundidades de camada em amostras lixadas e jateadas quando comparadas a amostras polidas foram atribuídas as altas tensões residuais compressivas presentes na superfície e logo abaixo da superfície antes da nitretação, especialmente para o caso de amostras jateadas. Testes com ferramentas em ambiente industrial de produção demostraram possibilidades de ganho de vida significativos com a nitretação a plasma. Em ensaios de laboratório as brocas submetidas ao jateamento apresentaram o melhor comportamento, o que foi explicado principalmente pela remoção de material recalcado sobre os gumes e a introdução de tensões residuais compressivas. Juntamente com o jateamento prévio a utilização da mistura gasosa pobre em nitrogênio na nitretação a plasma levou aos menores valores ele desgaste de flanco, enquanto a mistura rica em nitrogênio reduziu os esforços de furação. / In the present work different surface conditions were generated on samples and drills of AISI M2 high speed steel by polishing and sand blasting processes. Samples and drills were plasma nitrided at different temperatures with two different compositions of the gas mixture: 5vol.% N2 and 76vol.% N2 in hydrogen. Surfaces of non-nitrided and nitrided samples were characterized concerning the microstructure, roughness, microhardness, chemical composition, phase composition and the state of residual stresses. Even though some of the analyses were carried on drills, most part of them were carried on samples since tools possess a complex shape which difficults the direct characterization. Some plasma nitrided tools were tested in industrial production and the drills submitted to machining tests. During machining tests the drilling forces and flank wear were evaluated. The gas mixture of 5vol% N2 avoided the compound layer formation during plasma nitriding. It was found a E-(carbo)nitride layer on top of samples plasma nitrided with the use of 76vol.% N2 gas mixture. High compressive residual stresses were measured on samples surface in diffusion zone, which increased with nitriding temperature for polished samples. A significant influence of the surface state prior nitriding on final properties was found and their main aspects discussed: thioner nitrided layers on ground and sand blasted samples were attributed to high compressive residual stresses on surface and near surface areas before nitriding, specially for the case of sand blasted samples. The industrial production tests demonstrated good possibilities of tool-life improvement by the application of plasma nitriding. In the machining tests with drills, the plasma nitrided drills which were sand blasted before showed the best behavior, which was explained by the removal of overlapped material from cutting edges and introduction of compressive residual stresses. Associated to prior sand blasting the lower nitrogen concentration in the gas atmosphere gave the smallest drill flank wear while the higher nitrogen concentration gave a reduction of drilling forces.

The physics of partially neutralized plasmas is largely unexplored, partly because of the difficulty of confining such plasmas. Plasmas are confined in a stellarator without the need for a plasma current, and regardless of the degree of neutralization. The Columbia Non-neutral Torus (CNT) is a stellarator dedicated to the study of non-neutral, and partially neutralized plasmas. This thesis describes the first systematic studies of plasmas of arbitrary neutrality. The degree of neutralization of the plasma can be parameterized through the quantity η ≡ |n_e - Z n_i|/|n_e + Z n_i|. In CNT, η can be varied continuously from pure electron (η = 1) to quasi-neutral (η ≈ 0) by adjusting the neutral pressure in the chamber, which controls the volumetric ionization rate. Pure electron plasmas are in macroscopically stable equilibria, and have strong self electric potentials dictated by the emitter filament bias voltage on the magnetic axis. As η decreases, the plasma potential decouples from the emitter, and spontaneous fluctuations begin to appear. Partially neutralized plasmas (10^-3 < η < 10^-1) generally exhibit multi-mode oscillations in CNT. However, when magnetized ions are present, the electron-rich plasma oscillates at a single dominant mode (20 - 100 kHz). As the plasma approaches quasi-neutrality (η < 10^-5), it also reverts to single mode behavior (1 - 20 kHz). A parametric characterization of the single mode fluctuations detected in plasmas of arbitrary neutrality is presented in this thesis along with measurements of the spatial structure of the oscillations. The single mode fluctuations observed for η ≈ 0.01 to 0.8 are identified as an ion resonant instability propagating close to the E × B velocity of the plasma. The experiments also show that these oscillations present a poloidal mode number m = 1, and a toroidal number n = 0, which is identical to the spatial structure of the diocotron instability in pure-toroidal traps, and implies that the ion-driven instability breaks parallel force balance and the conservation of poloidal flux in CNT. The low frequency oscillations detected in the quasi-neutral regime are a global instability convected by the E × B flow of the plasma. In this case, the mode aligns almost perfectly with the field lines, and presents a resonant m = 3 poloidal structure.