Les nombreuses pressions naturelles et anthropiques qui pèsent sur les écosystèmes coralliens font craindre leur disparition pour les années futures. Parmi les mesures de conservation, la cryoconservation permet de maintenir en sécurité les échantillons sur le long terme et à coût réduit. Les premiers travaux sur la cryoconservation des Anthozoaires incitent à développer davantage la méthode de vitrification plutôt que la congélation lente. Dans ce contexte, cette thèse propose d'expérimenter la technique de vitrification sur plusieurs formes pluricellulaires dont les apex, les planulae, les polypes primaires, les polypes isolés et les balles tissulaires (TB), toutes issues du Scléractiniaire Pocillopora damicornis. Les meilleurs résultats ont été produits avec les TB obtenues après exposition à une solution de KSW puis traitées selon la méthode V Cryo-plate. L'éthylène glycol (EG) s'est avéré le cryoprotecteur (CPA) le mieux toléré jusqu'à 4.0 M pendant 20 min à température ambiante (RT). Les mélanges binaires et ternaires de CPA ont cependant permis d'obtenir de meilleures tolérances des TB qu'avec les solutions individuelles. L'utilisation de solutions successives a permis d'obtenir des survies jusqu'à 4.5 M selon le protocole : 1.5 M EG + 0.5 M Glycérol (Gly) (5 min, RT) puis 1.5 M DMSO + 1.5 M EG + 1.5 M Gly (10 min, 0°C) et enfin 1.5 M EG + 0.5 M Gly (5 min, RT). L'intégrité des cellules épithéliales de l'ectoderme apparaît essentielle au maintien des TB durant et après les traitements. Si le protocole de vitrification n'a pu être mis au point, en revanche, l'utilisation des TB à des fins de cryoconservation apparaît très intéressante pour de futures investigations. / Numerous environmental and anthropic pressures threaten reef ecosystems, rising concerns on species loss in coming years. Among conservation measures, cryopreservation ensures the safe and cost-effective long-term conservation of biological material. The first publications focusing on Anthozoa cryopreservation reported that the vitrification approach was preferable to the slow-cooling approach. In this context, this thesis aimed at investigating a vitrification technique with several pluricellular forms of the Scleractinian Pocillopora damicornis including apexes, planulae, primary polyps, isolated polyps and tissue balls (TB). The best results were obtained using TBs produced by exposing coral branches to a KSW solution. TBs were cryopreserved using the V Cryo-plate method. The highest TB tolerance was obtained after exposure to solution containing ethylene glycol (EG) concentrated to 4.0 M for 20 min at room temperature (RT). Binary and ternary cryoprotectant (CPA) solutions were better tolerated by TBs compared with individual cryoprotectant solutions. Exposure of TBs to a series of cryoprotectant solutions with progressively increased concentration allowed obtaining TB tolerance to cryoprotectant with a concentration of 4.5 M with: 1.5 M EG + 0.5 M Glycerol (Gly) (5 min, RT), 1.5 M DMSO + 1.5 M EG + 1.5 M Gly (10 min, 0°C) and then 1.5 M EG + 0.5 M Gly (5 min, RT). Epithelial cells from the ectoderm were essential to maintain TB integrity during and following CPA treatments. Successful cryopreservation was not achieved in this work; however, it demonstrated that the use of TBs constitutes a promising way for further cryopreservation research.

Durante o período de operação de um empreendimento mineiro, oportunidades de aumento de capacidade produtiva podem gerar ganhos significativos para uma empresa. Para os casos em que se viabiliza maior capacidade de produção da mina deve-se avaliar a capacidade de processamento da usina de beneficiamento, que assim inclui melhorias de desempenho ou expansão mediante adição de equipamentos. Este trabalho contempla a descrição das etapas de amostragem, caracterização do minério, a modelagem do circuito existente e a simulação para aumento da capacidade do circuito de moagem da usina da Mineração Serra Grande da AngloGold Ashanti, situada no município de Crixás no interior de Goiás. Os cenários simulados foram (1) adição de um terceiro moinho de bolas em série aos moinhos existentes, (2) adição de um terceiro moinho de bolas em paralelo ao circuito existente, (3) adição de um moinho vertical para processamento do produto dos dois moinhos de bolas existentes e (4) adição de uma prensa de rolos após o circuito de britagem. O propósito das quatro simulações foi avaliar a viabilidade técnica dos circuitos selecionados mediante modelagem matemática e simulação de processos, assim como dimensionar os novos equipamentos para tal fim. / During operation of the mining cycle, increases the throughput would generate significant capital savings for a company. For cases that enables higher mine production capacity, it must be evaluated plant capacity and also performance improvements or expansion by adding new equipment. This study includes the description of the sampling methodology, the minerals analysis, modeling of the existing circuit and simulation for a possible expansion, specifically for the grinding circuit at Mineração Serra Grande plant of AngloGold Ashanti group, located in Crixás, Goiás. the studied scenarios were: (1) adding a third ball mill in series with existing two ball mills, (2) adding a third ball mill in parallel with existing mills, (3) adding a vertical mill in series with existing mills and (4) adding high pressure grinding rolls to existing mills. The four simulations intend assess the technical feasibility of the circuits selected by mathematical modeling and simulation of processes and design new equipment for this purpose.

O tênis de mesa é um dos esportes de raquete mais rápidos do mundo, exigindo muito pouco tempo para planejar e executar seus movimentos. Neste sentido, detectar a quantidade de rotação da bola, velocidade e direção torna-se fundamental para produzir respostas motoras eficientes. Entretanto, existem algumas questões que ainda não foram exploradas como o quanto a disponibilidade das informações auditiva e visual interfere na acurácia da percepção da rotação da bola e no tempo necessário para perceber estas rotações. O propósito do presente estudo foi analisar a influência da informação auditiva e visual na percepção da rotação da bola e no desempenho no tênis de mesa. Os atletas profissionais foram submetidos a dois estudos: o primeiro destinado a verificar a contribuição da informação auditiva e visual na percepção da rotação da bola e no tempo necessário para essa percepção. O segundo, proposto para avaliar a influência da informação auditiva no desempenho da tarefa de contra-ataque no tênis de mesa. Participaram do estudo 22 mesatenistas de alto rendimento de ambos os sexos (21 homens e 1 mulher) com média de idade de 22,55 ± 6,15. O teste de percepção de rotação (estudo 1) analisou o número de acertos e o tempo de reação por meio de uma rotina desenvolvida no software Matlab (Apêndice D). Os atletas visualizavam a tela de um computador e respondiam em um teclado o mais rápido possível. Os atletas analisaram um movimento de forehand nas intensidades de rotação: muita rotação (bola girando a aproximadamente 140 r/s); média (bola girando a aproximadamente 105 r/s); pouca rotação (bola girando a aproximadamente 84 r/s); batida chapada (bola girando a aproximadamente 70 r/s), nas seguintes condições: a) informação auditiva; b) informação visual; c) informação auditiva e visual. Os atletas analisaram 20 bolas para cada condição sendo cinco de cada tipo de efeito. Para o teste de desempenho (estudo 2) o atleta teve que responder adequadamente com o movimento de contra-ataque de forehand em um alvo previamente marcado na mesa. Foram golpeadas 80 bolas nas mesmas intensidades de rotação mencionadas acima. Os atletas foram avaliados em duas condições: com informação auditiva e sem informação auditiva. Os resultados do estudo 1 revelaram que mesatenistas foram capazes de perceber a magnitude de rotação da bola nas três condições. O percentual de acertos foi de 77,5%, 91,14% e 96,36% para as condições de informação auditiva, visual e combinadas, respectivamente. Quanto ao tempo de reação, os resultados revelaram que na condição somente informação auditiva (2,32 ± 0,41 s) os atletas demoraram mais tempo para responder do que em relação a condição somente informação visual (2,07 ± 0,36 s), já na condição informação auditiva e visual (1,85 ± 0,35 s) os atletas se mostraram mais rápidos ainda concordando com as informações número de acertos obtidas neste estudo. Para o estudo 2 os resultados revelaram que quando os atletas contra-atacaram na condição informação auditiva, o número de acertos foi de 37,69 ± 5,43 enquanto, quando a audição dos atletas foi privada a média de acertos foi 33,15 ± 6,84. Os resultados apontaram que mesatenistas foram capazes de utilizar as informações auditiva e visual para perceber a magnitude da rotação da bola no golpe forehand, porém, no estudo 1 quando as informações foram combinadas o número de acertos aumentou 5,22% e o tempo de reação diminuiu 0,22 s. No estudo 2 Quando a informação auditiva foi privada houve uma diminuição na média do número de acertos de 4,54. / Table tennis is one of the fastest racket sports in the world, requiring very little time to plan and execute your moves. In this sense, detecting a quantity of ball spin, velocity and direction becomes fundamental to produce efficient motor responses. However, there are some questions that have not yet been explored for example how much the availability of auditory and visual information interferes with the accuracy of the perception of the rotation of the ball and the time needed to perceive these rotations. The purpose of the present study is to analyze the influence of auditory and visual information on the perception of ball rotation and performance in table tennis. The volunteers were submitted to two studies: the first one to verify the contribution of the auditory and visual information in the perception of the rotation of the ball and in the time necessary for this perception. The second, proposed to evaluate the influence of auditory information on the performance of the counter-attack task in table tennis. Twenty-two high-level table tennis players men and women (21 men and 1 woman) with a mean age of 22.55 ± 6.15 participated in the study. The rotation perception test (study 1) analyzed the number of hits and the reaction time through a routine developed in Matlab software. The athletes visualized the screen of a computer and answered in a keyboard as soon as possible. The athletes analyzed a forehand movement in the rotation intensities: fast spin (spinning ball foward at 140 r/s); medium spin (105 r/s); slow spin (84 r/s); flat hit (70 r/s), under the following conditions: a) auditory information; b) visual information; c) auditory and visual information. The athletes analyzed 20 balls for each condition, five of each type of rotation. For the performance test (study 2) the athlete had to respond adequately with the forehand counterattack movement on a previously marked target at the table. 80 balls were struck at the same intensities of rotation mentioned above. The athletes were evaluated in two conditions: with auditory information and without auditory information. The results of the study 1 revealed that table tennis players were able to perceive the magnitude of rotation of the ball in the three conditions. The percentage of correct answers was 77.5%, 91.14% and 96.36% for auditory, visual and combined information conditions, respectively. Regarding the reaction time, the results revealed that in the condition only auditory information (2.32 ± 0.41 s) the athletes took more time to respond, since in the condition only visual information (2.07 ± 0.36 s) delayed a little less and in the condition auditory and visual information (1.85 ± 0.35 s) the athletes showed themselves to be faster still agreeing with the information number of hits obtained in this study. For the study 2 the results revealed that when the athletes counterattacked in the auditory information condition, the number of hits was 37.69 ± 5.43, whereas when the hearing of the athletes was private the average hit was 33.15 ± 6.84. The results indicated that table tennis players were able to use auditory and visual information to realize the magnitude of the ball rotation in the forehand blow, however, in study 1 when the informations were combined the number of right answered increased 5.22% and the reaction time decreased by 0.22 s. In study 2 When the auditory information was depriving, there was a decrease in the average number of hits 4.54.

Solder joints serve as both mechanical and electrical connections between elements in a package. They are subjected to shear strains generated as a result of the different behaviors of the elements in the package (tension and compression) due to the differences in coefficients of thermal expansion during service conditions. Some of the causes of solder joint failures are due to the following: Vibration: small rapid displacements of parts of the assembly. This is not necessarily an issue with electronic components but larger parts like automobiles. Humidity: the package being exposed to water or ionic species can undergo corrosion if an electrical bias exists resulting in electrical opens or electrical shorts if the corrosion products are electrically conductive. Thermal Aging: this occurs during the lifetime of the solder interconnects, the package can be exposed to high ambient temperature or high dissipated heat during use. The micro-structure of the solder joint becomes more coarse and brittle. Mechanical Shock: the package undergoes shock during a short term exposure to high loads. Thermo-mechanical fatigue: this type of failure arises as a result of the solder joints going through cyclic strains, due to different coefficients of thermal expansion of individual components in the package during service. The most prevalent long-term reliability issues that can cause interconnect failure are thermal aging and thermo-mechanical fatigue. This study aims to evaluate the reliability of solder joints using finite element method, considering solder joint failure due to thermo-mechanical fatigue. Three variations of the BGA (Ball Grid Array) package are evaluated using the finite element analysis. The SAC305 series lead (pb) free alloy of 96.5% tin, 3% silver, and 0.5% copper is employed for this study.

Thesis (Ph. D. (Physics)) -- University of Limpopo, 2013 / A combination of ball milling experiments and ab initio calculations in this study successfully yielded results that shed light into understanding the fundamental basis for immiscibility and the concept of mechanical alloying in Ti-Mg system. In addition, the conditions for achieving extended solid solubility in elements that usually do not dissolve in each other under thermodynamic equilibrium conditions have been predicted using ultrasoft (US) and norm-conserving (NC) pseudopotentials. Hydostatic pressures required to stabilize ordered phases were determined. Our new systematic representation of martensitic transformation (MT) paths as a result of dislocation necessary to induce α→FCC, α→BCC and α→ω phase transitions led to, for the first time, a direct determination of CRSS and tensile strength for Ti and Mg HCP metals. Furthermore, a new ω phase which is less stable than α phase at 0 GPa is proposed. Based on this phase, α→ω deformation path which yielded the onset of uniaxial transition pressure of 4.167 GPa is reported. Attempts of synthesizing Ti-Mg solid solutions by means of Simoloyer high energy ball mill were not successful; however, nanocrystalline Mg-TiH2-x composites were instead formed. These results were attributed to quick formation of metastable Ti hydrides or cold welding at early stages of BM prior to alloying, thus serving as possible obstacles to forming such solid solutions. The deformed Ti crystals adsorbed H+ from the stearic acid leading to formation of metastable orthorhombic TiH2-x phase which later transformed to a tetragonal TiH2-x or even cubic TiH2 when stoichiometric amount of H2 had been adsorbed. Although the yield was significantly lower, the product of milling a mixture of coarse Mg and fine Ti particles was comprised of Ti particles adhering around ductile Mg particles in a core shell manner. The adhesion of the fine hard titanium particles on the surface of the large ductile magnesium particles impeded the further plastic deformation of the titanium particles, thus suppressing the formation of the faults necessary for mechanical alloying. Nanocrystalline Ti powder of about 40 nm was produced by 30h ball milling. During BM of Ti powder, solid-state transformation from HCP to FCC occurred in the presence of PCA with lattice parameters of 4.242 and 4.240 Å after 24 and 30 h, respectively, v due to protonation. When Ti powder was milled in the absence of PCA, no phase transformation was observed for both uninterrupted and interrupted milling cycles. In addition, nanocrystalline Mg powder with crystallite size varying between 60 and below 40 nm was produced by ball milling. However, no solid-state transformation took place even if the powder was milled for 90 h. Therefore, we evidently report for the first time that the interstitial H+ is the driving force for α → FCC phase transformation in ball milled Ti powder. Our theoretical results predicted the ω phase to be the ground-state structure of Ti at 0K and P=0 GPa, in support of other previously reported calculations. We noticed that the stability of the α phase was surpassed by that of the FCC lattice at ~ 100 GPa, corresponding with sudden sharp rise in c/a ratio, hence attributed to α → FCC phase transition. Similar results were obtained for Mg at 50 GPa, although in this case the crossing of lattice energies coincided with minimum c/a. However, using our proposed HCP→BCC MT path mechanism for Mg, it is evident that the minimum c/a at 50 GPa corresponds to a change in the preferred deformation slip from basal (below 10 GPa) to prismatic rather than phase transition. Nonetheless, the proposed MT model predicts that both elemental Ti and Mg prefer to deform via prismatic slip as indicated by lower shear stress as well as CRSS values compared to those calculated for basal slip. Theoretical findings from ab initio calculations on hypothetical ordered Ti-Mg phases indicated absence of intermetallic phases at equilibrium conditions, in agreement with experimental data. However, the formation becomes possible at 80 GPa and above with respect to c/a ratio but requires at least 200 GPa with respect to stable lattices. Using calculated heats of formation, elasticity and DOS, it has been possible to show that L12 TiMg3 could not form even at high pressure as 250 GPa. Nonetheless, both approaches indicate that forming an intermetallic compound between Ti and Mg requires a crystal structure change, α→FCC for Ti and HCP→BCC for Mg. Proposed DFT-based solid solution model for predicting phase stability and elastic properties of binary random alloys, with Mg-Li system serving as a test case, successfully yielded reliable results comparable to experimental data. This method was successfully applied to study an immiscible Ti-Mg system and the solubility limit vi was for the first time theoretically established. Based on formation energy of Ti-Mg solid solutions, our calculations predicted for the first time that the solubility of up to 60 and 100 at.% Mg into Ti with the use of USP and NCP, respectively, to be thermodynamically favourable with necessary lattice kinetics being the main challenge. Nonetheless, NCP proved to be reliable in predicting structural and elastic properties of disordered alloys.

Silicon nanoparticles (SiNPs) are regarded as a promising alternative of traditional II-VI quantum dots in the field of bio-applications due to their photoluminescence and bio-compatibility. <br>Chapter 1 reviews various synthetic routes and applications of SiNPs. <br>Chapter 2 describes the mechanochemical synthesis of photoluminescent SiNPs with an organic ligand shell through reactive high energy ball milling (RHEBM). The morphology and size distribution of as-prepared SiNPs were determined by TEM. The bonding modes of the ligand shell including their mole fractions were investigated based on NMR and FTIR spectra of the as-prepared SiNPs.<br>Chapter 3 introduces the removal of the iron impurities, which were introduced into the SiNPs product from the milling media, stainless steel, by a physical method (GPC) and a chemical method (washing by HCl aqueous solution). The effect of the iron impurities to the optical properties of SiNPs is discussed.<br>Chapter 4 exhibits the surface functionalization of SiNPs with various functional groups through thiol-ene click reactions of vinyl-terminated SiNPs with various thiols. In addition, SiNP nanoclusters and DNA-conjugated SiNPs were prepared through thiol-ene click reactions of vinyl-terminated SiNPs with a tetrathiol-terminated crosslinker and a thiol-functionalized DNA, respectively<br>Chapter 5 is a miscellaneous chapter which includes the preparation of SiNPs through RHEBM of silicon wafers with 2,3-dimethyl-1,3-butadiene, and the effect of UV irradiation at 254 nm to the chemical structures and optical properties of SiNPs. / acase@tulane.edu

Previous work has shown that when inorganic compounds are milled with quartz in a high energy ball mill the elements are sequestered into the quartz matrix and cannot be easily recovered by simple extraction methods. In this study lead (II) oxide, copper (II) oxide, magnesium oxide, zinc oxide and sodium hydroxide were milled with quartz sand and the recoveries of the metals investigated in detail. The standard EPA3050B method (acid digestion of sediments, sludge and soils) for extractable metals was compared to exhaustive HF digestion method based on ASTM C146-94a (test methods for chemical analysis of glass sand) and UDC 666.123:543.06 (chemical analysis of soda-lime and borosilicate glass). From these two analyses the total recovery of metals was determined. It was found that the elements extracted by the EPA3050B method decreased in an approximately logarithmic way with milling time. The metals are apparently strongly sequestered into the fractured quartz. Total HF digestion of the insoluble matrix gave good recovery of the “lost” elements. A reliable analytical procedure has been developed and the mechanisms leading to this sequestering are discussed. Particle size analysis and electron microscopy of milled samples support a process of brittle alloy formation as the proposed mechanism whereby the elements are sequestered into the milled quartz.

The potential for significant performance increases, using ceramic materials in un-lubricated rolling element bearing applications, has been the subject of research over the past two decades. Practical advantages over steel include increased ability to withstand high loads, severe environments and high speeds. However, widespread acceptance has been limited by the inability to predict wear life for ceramic bearing applications. In this thesis, the rolling contact wear of 52100 bearing steel and Over-aged Magnesia-Partially-Stabilised Zirconia (OA-Mg-PSZ) ceramic are examined using a newly developed rolling contact wear test rig. The new wear test rig simulates the system geometry of an un-lubricated hybrid (ceramic and steel) ball bearing. The new wear test rig is versatile in that it allows low cost samples to be utilised resulting in a larger number of samples that can be tested. Wear samples of 52100 bearing steel and OA-Mg-PSZ produced by the new wear test rig were examined for mass loss and wear depth. The wear behavior of both the steel and ceramic material showed a dependence on operating variables time and load. Load was varied between 300N to 790N. Typical mass loss after 1 hour of testing 52100 bearing steel at 790N was 0.03 grams as compared to OA-Mg-PSZ which was 0.001 grams. The rolling contact wear of the OA-Mg-PSZ was an order of magnitude lower than that of the 52100 bearing steel. The wear mechanism for 52100 bearing steel was typical of plastic deformation and shearing near and below the surface of rolling contact. Once cracks extend to reach the surface, thin flat like sheets are produced. In OA-Mg-PSZ the wear mechanism initially is that of plastic deformation on the scale of the surface asperities with asperity polishing occurring followed by lateral cracks and fatigue spallation. Results obtained using the new rolling contact wear test rig led to the establishment of a new equation for wear modeling of 52100 bearing steel and OA-Mg-PSZ ceramic materials.

Thesis (Ph. D.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 7, 2007). Includes bibliographical references.

En accord avec Eloi (2009), tous les spécialistes s'accordent à reconnaître le rôle prépondérant du passeur dans la performance d'une équipe de volley-ball. Il n'existe paradoxalement, que peu de travaux disponibles sur ce thème. Cette thèse a pour objet l'élaboration d'une modélisation de son activité décisionnelle au haut niveau, en situation de match. L'enjeu est de caractériser la complexité des décisions tactiques, en soulignant les relations dynamiques entre les aspects circonstanciés et les sources d'influence plus générales. En adaptant la modélisation de Mouchet (2003), nous opérons une friction de plusieurs paradigmes scientifiques qui proposent différents modèles explicatifs de la cognition, apportant un éclairage particulier sur les conduites décisionnelles. Notre posture épistémologique consiste à appréhender la complexité (Morin, Le Moigne, 1999 ; Le Moigne, 1999) par une approche systémique, en investiguant les conduites décisionnelles en situation écologique et en prenant en compte le point de vue du sujet. Nous faisons l'hypothèse que le système d'influence, constitué de la culture, de l'environnement momentané et de l'expérience de la personne, imprègne l'activité décisionnelle, en étant compacté dans l'action en cours. Chaque joueur construit son propre monde en intégrant les différents niveaux selon une logique singulière. Notre étude porte sur quatre études de cas de passeurs français internationaux. Pour recueillir des données de la " partie cachée " (Gouju, 2001), nous avons mis en place une méthodologie constituée d'une observation armée, d'un entretien semi directif, d'une simulation, et de rétroactions vidéo (principe de triangulation).