Дисертації з теми "CTAT"

This thesis studies the properties and behaviour of phase-separated hydrogels prepared by interaction of hyaluronan with oppositely charged surfactants. Three representatives of surfactants, namely cetyltrimethylammonium bromide, chloride and p-toluensulfonate (CTAB, CTAC, CTAT), were selected for comparison. Using the method of rheology, the fact that the system of Hya-CTAT forms the most rigid hydrogels has been proved. Higher molecular weight of hyaluronan has also direct influence on the volume and stiffness of the newly formed hydrogels. Preparation methods were compared as well. Mixing the stock solutions of entry components appeard to be the most suitable. Small-angle X-ray scattering was used for determination of shape and size of surfactant's micelles, concluding that it has no effect on the volume of formed gels. The results of this study indicate that given gels are to a certain extent competitive and incorporation of hyaluronan into their structure is desirable with respect to its biological activity. This offers a potential usage of these substances in the field of medical applications.

Les solutions de surfactants s'agrégent pour former des microstructures qui dépendent de la concentration et de la température. On étudie un surfactant cationique, le Tosyl-Céthyltrimethylammonium (CTAT) en solution dans l'eau pour des concentrations inférieures à 11%. Dans une première partie, on étudie des concentrations faibles (0
Surfactant solutions are known to aggregate and to form microstructures depending upon concentration and temperature. Herein we study water/Cethyltrimethylammonium- Tosilate (CTAT) systems for concentrations under 11%w. CT AT is a cationic surfactant. In a first part we study low concentration systems (O

NMR methods have been designed and employed in studying ofcomplex liquids and solids formed by surfactants. PGSE NMRexperiments are easily biased by convection; this artifact canbe avoided by changing the sample holder and by usingconvection-compensated pulse sequences. The temperaturedistribution within samples was controlled using thetemperature dependent order parameter for CBr₂H₂dissolved in a thermotropic nematic solvent.Electronic ringing that often spoils accurate NMR experimentsfor broad lines was removed by the using composite pulses andquadrupole echo sequences with appropriate phase cycles.

Field-dependent⁸¹Br and³⁵Cl NMR relaxation studies in micellar solutions ofC₁₆TAX surfactants showed that the structure ordynamics of the hydration shell is more influenced by thesurfactant cation for bromide than for chloride, in agreementwith their position in the Hoffmeister series. The presence ofa small but significant frequency-dependent relaxation showedthat the lateral self diffusion of the anions may be reduced ascompared to its bulk value in diluted solutions but only with afactor of 1.0 - 2.5. The ions are clearly not "bound" to thesurface. A field-dependent²H NMR relaxation study on the CTABr-α-d2and benzene-d6showed an initial one-dimensional micellargrowth followed by the appearance of microemulsion droplets onaddition of benzene. The local mobility of the benzene wasreduced when solubilized in small amounts, consistent with aninitial average location of benzene at the micellar interface.The surfactant diffusion coefficients fromconvection-compensated PGSE NMR experiments in the C₁₂E₈-D₂O system showed monotonous growth of the micellesupon increasing temperature. Emulsion droplets in the C₁₂E₅-decane-D₂O system where shown to coarsen according to theOstwald ripening theory after being brought out of equilibriumby a temperature drop. X-ray scattering and²H NMR line-shape and relaxation experimentssuggested that complex solids formed by a partly-sulfatedpolysaccharide and C_nTAB exhibit regular ordering at both microscopicand mesoscopic length scales.

Keywords: CTAB, CTAC, C₁₂E₈, C₁₂E₅, decane, benzene, CBr₂H₂, polysaccharide, micelle, microemulsion, emulsion,Ostwald ripening, NMR,⁸¹Br,³⁵Cl,²H, field- dependent spin relaxation, PGSE, selfdiffusion, convection, ringing, thermometer, generalized Blochequations, EXORCYCLE, quadrupole echo, SAXS, WAXS, cryo-TEM.

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.
Includes bibliographical references (leaf 49).
by Seung Yong Albert Lee.
S.B.and M.Eng.

Mestrado em Finanças
CTT - Correios de Portugal é a empresa líder de mercado em Portugal na área de correio e encomendas. Sendo que a empresa também já conta com alguma experiência no mercado de serviços financeiros, sendo esta uma área com notável crescimento de vendas. Atualmente, a empresa prepara o lançamento do Banco Postal de modo a maximizar a extensa rede de lojas. Com o lançamento deste banco, a empresa pretende expandir a oferta de produtos e encorajar o cross-selling. Os CTT pretendem também usar a imagem que os consumidores têm da marca para lançar o banco, tendo como público-alvo a classe média e os consumidores mais conservadores. O objetivo deste projeto é analisar e avaliar a empresa de modo a compreender se as ações estão sub ou sobrevalorizada e, assim, poder dar uma recomendação de compra/venda ao investidor. Esta avaliação foi não só focada na empresa, mas também no seu ambiente envolvente (enquadramento macroeconómico e concorrentes). Além disso, foi realizada uma análise de sensibilidade de modo a ser possível observar como o preço da ação iria reagir a uma variação quer na taxa de crescimento perpétuo, quer no custo de capitais próprios. Com esta avaliação e tendo em consideração alguns pressupostos, foi possível chegar a um preço de €12,04 a 31/12/2014. Nesta mesma data, o preço de mercado era de €8,02, sendo assim possível concluir que as ações estavam desvalorizadas, dado que o investidor conseguiria ter ganhos. Deste modo, a recomendação final seria de comprar a ação.
CTT - Correios de Portugal is the leading company in Portugal for the mail and express business units. Having also already experience with financial services, being a growing division for the company. Currently, the company is trying to leverage the wide retail network with the launching of a Postal Bank aiming at expand the product offer and encourage the cross-selling. CTT also want to take advantage of the brand perception consumers have, targeting average-income and more conservative consumers. The goal of this project is to understand if the stocks are under or overvalued and according to this, give a final recommendation to the investor. This valuation was focused not only on the company but also on its environment (macroeconomic framework and peers). Moreover, it was performed a sensitivity analysis, in order to observe how would the stock's price respond with a variation on the perpetual growth rate and cost of equity. With this assessment and having in consideration the assumptions taken, it was possible to reach to a target price on 31/12/2014 of €12.14. Being the market value on this date of €8.02, it is possible to conclude that the stocks were undervalued, given that the investor was able to have a potential gain. Hence, the recommendation given to investors was to buy CTT's shares.

Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Includes bibliographical references (p. 73).
Reliable, error-free software is hard to come by, and this is especially true for newer, larger, or more complex programs. CTAS, an air traffic control tool, falls into this category, making it a good candidate for research on error compensation. Specifically, this thesis addresses the issue of thread crashes in one portion of CTAS. We reimplement the thread structure in question around a simpler problem, and develop a failure detector and an accompanying repair mechanism to monitor it. These add-on components provide the application with thread consistency by swiftly and transparently recovering from crashes, thereby yielding a more stable, self-sufficient, and generally more reliable operating environment.
by Farid Jahanmir.
M.Eng.and S.B.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Surfactant-polymer interactions are widely used when required rheological properties for specific applications, such as the production of fluids for oil exploration. Studies of the interactions of chitosan with cationic surfactants has attracted attention by being able to cause changes in rheological parameters of the systems making room for new applications. The commercial chitosan represents an interesting alternative to these systems, since it is obtained from partial deacetylation of chitin: the residues sites acetylated can then be used for the polymer-surfactant interactions. Alkyl ethoxylated surfactants can be used in this system, since these non-ionic surfactants can interact with hydrophobic sites of chitosan, modifying the rheology of solutions or emulsions resultants, which depends on the relaxation phenomenon occurring in these systems. In this work, first, inverse emulsions were prepared from chitosan solution as the dispersed phase and cyclohexane as the continuous phase were, using CTAB as a surfactant. The rheological analysis of these emulsions showed pronounced pseudoplastic behavior. This behavior was attributed to interaction of "loops" of chitosan chains. Creep tests were also performed and gave further support to these discussions. Subsequently, in order to obtain more information about the interaction of chitosan with non-ionic surfactants, solutions of chitosan were mixed with C12E8 and and carried out rheological analysis and dynamic light scattering. The systems showed marked pseudoplastic behavior, which became less evident when the concentration of surfactant was increased. Arrhenius and KWW equations were used to obtain parameters of the apparent activation energy and relaxation rate distribution, respectively, to which were connected to the content of surfactant and temperature used in this work
As intera??es tensoativo-pol?mero s?o amplamente usadas quando s?o necess?rias propriedades reol?gicas para aplica??es espec?ficas, como a produ??o de fluidos para explora??o do petr?leo. Estudos das intera??es de quitosana com tensoativos cati?nicos tem chamado aten??o por serem capazes de causar mudan?as nos par?metros reol?gicos dos sistemas abrindo espa?o para novas aplica??es. A quitosana comercial representa uma alternativa interessante para estes sistemas, uma vez que ela ? obtida a partir da desacetila??o parcial da quitina: os s?tos acetilados residuais podem, ent?o, ser usados para as intera??es pol?mero-tensoativo. Tensoativos alquil etoxilados podem ser utilizados neste sistema, pois estes tensoativos n?o i?nicos podem interagir com s?tios hidrof?bicos da quitosana, modificando a reologia de solu??es ou emuls?es resultantes, os quais dependem do fen?meno de relaxa??o ocorrendo nestes sistemas. Neste trabalho, primeiramente, foram preparadas emuls?es inversas de solu??o de quitosana como fase dispersa e cicloexano como fase cont?nua usando CTAB como tensoativo. A an?lise reol?gica destas emuls?es mostrou pronunciado comportamento pseudopl?stico. Esta pseudoplasticidade foi atribu?da ? intera??o por la?os loops de cadeias de quitosana. Ensaios de flu?ncia tamb?m foram executados e deram maior suporte a estas discuss?es. Em seguida, a fim de se obter maiores informa??es sobre as intera??es da quitosana com tensoativos n?o i?nicos, solu??es de quitosana foram misturadas com C12E8 e levadas ?s an?lises reol?gica e de espalhamento din?mico de luz. Os sistemas tiveram elevado comportamento pseudopl?stico, o qual se tornava menos evidente, quando o teor de tensoativo foi aumentado. Equa??es de Arrhenius e de KWW foram usadas para obter par?metros de energia de ativa??o aparente e de distribui??o da taxa de relaxa??o, respectivamente, aos quais foram relacionados em fun??o do teor de tensoativo e da temperatura, usados neste trabalho

Mestrado em Decisão Económica e Empresarial
No problema de transportes de serviço postal dos CTT (PTC), os veículos, que distribuem e recolhem o correio, podem imobilizar num ponto, depois de efectuarem um certo trajecto, podendo, mais tarde, realizar um novo trajecto a partir do ponto de imobilização. Este problema pode caracterizar-se como uma generalização do Vehicle Routing Problem (VRP), em que os veículos imobilizados, não tendo a necessidade de voltar ao depósito no trajecto inicialmente efectuado, terão de regressar num novo trajecto a realizar num período do dia diferente. Para além desta questão muito particular, outras especificidades do PTC fazem-no diferir do VRP, surgindo algumas em variantes do VRP como se descreverá. Neste trabalho apresenta-se uma heurística melhorativa de pesquisa local para a resolução do PTC, que apresenta resultados positivos, mas que pode ser melhorada, nomeadamente na possibilidade de reduzir o número de viagens imobilizadas.
In the problem of transportation of CTT (PTC), the vehicles can immobilize at the end of its journey, and afterwards resume a new route from the point of immobilization to the depot. This problem can be characterized as a Vehicle Routing Problem (VRP), in which vehicles routes are divided in two separate sets: delivery routes and pick up routes to be performed in a different period of time. At the end of delivery routes, the vehicle does not need to return to the depot. Therefore, pick up routes may begin either on an immobilization point or at the depot, but both must end at the base depot of the vehicle. In addition to this very particular point, other aspects of the PTC, make it differ from the VRP, as it will be described. In this work, an improvement local search heuristic to solve the PTC, will be present. Computational experiment shows good performance of the proposed heuristic, but it can be improved, including the possibility of reducing the number of immobilized trips.

Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Tannenbaum, Allen; Committee Member: Skrinjar, Oskar; Committee Member: Yezzi, Anthony. Part of the SMARTech Electronic Thesis and Dissertation Collection.

O objetivo deste trabalho é estudar o nível de organização dos cristalitos de surfactantes aniônico, catiônico e zwiteriônico com o aumento na densidade destas moléculas sobre um cristal de germânio. As análises foram realizadas por espectroscopia de infravermelho com transformada de Fourier acoplada à técnica de reflexão total atenuada (FTIR-ATR). Este estudo apresenta importantes aspectos na organização do dodecilsulfato de sódio (SDS), do N-hexadecil-N,N-dimetil-3-amônio-1-propanosulfato (HPS), do brometo de hexadeciltrimetilamônio (CTAB) e do brometo de dodeciltrimetilamônio (DTAB). No SDS é observado um deslocamento de 1.7 cm-1 para valores de maior frequência na banda de estiramento assimétrico do CH2, vass (CH2), enquanto que é observado um deslocamento de 0.9 cm-1 na banda de estiramento simétrico, vsim (CH2). Este deslocamento para valores de maior frequência nas bandas de estiramento está associado com um aumento na desorganização da cadeia alifática com o aumento na densidade de moléculas sobre o elemento de ATR. A banda de deformação angular do CH2, δ(CH2), apresenta um valor em 1468 cm-1 que é também um indicativo de desorganização. No CTAB não é observado variações acentuadas nos valores das frequências vibracionais. Na banda vass (CH2) do DTAB é observado um deslocamento de 4.5 cm-1 para valores de menor frequência. Embora seja observado valores próximos de 2920 cm-1 para a banda vass (CH2), que é um indicativo do estado líquido de surfactantes, o que é observado nesse estudo são cristalitos de DTAB. O deslocamento da banda vsim (CH2) do DTAB é da ordem de 2 cm-1. Estas mudanças nas bandas vass (CH2) e vsim (CH2) são um indicativo da diminuição nas conformações gauche e um aumento nas conformações trans ao longo da cadeia alifática. O valor da freqüência em torno de 1472 cm-1 para a banda δ(CH2) é também um indicativo de uma maior organização na cadeia de CH2 do DTAB. Para o HPS é observado um deslocamento de 2.6 e 2.7 cm-1 para valores de maior frequência nas bandas vass (CH2) e vsim (CH2), respectivamente. A banda δ(CH2) do HPS apresenta um deslocamento de 4 cm-1 para valores de maior frequência. A variação nas bandas vass (CH2), vsim (CH2), e δ(CH2) ressalta o aumento na desorganização da cadeia alifática com o aumento na densidade de moléculas de HPS sobre o germânio.
The objective of this work is study the order level of anionic, cationic and zwitterionic surfactants with the increase of their density packing on the surface of a germanium element. The analyses were performed by a Fourier transform infrared-attenuated total reflection spectroscopy. This study shows important insights on the conformational order of sodium dodecyl sulfate (SDS), N-hexadecyl-N-N -dimethyl-3-ammonio-1-propane-sulfonate (HPS), hexadecyl-trimethylammonium bromide (CTAB) and dodecyl trimethylammonium bromide (DTAB). It is observed a shift of 1.7 and 0.9 cm-1 to higher frequency values of the CH2 asymmetric (vass (CH2)) and symmetric (vsim(CH2)) stretching bands for the SDS molecules, respectively. The latter shift to higher frequency values is associated with the disorder of the aliphatic chain due to the increase of density packing of SDS molecules on the germanium element. The CH2 scissoring band [δ (CH2)] shows a value in 1468 cm-1, which is also an indicative of conformational disorder. It is not observed any accentuated change on the vibrational frequency values of the CTAB molecules. The vass (CH2) band of the DTAB molecules is shifted 4.5 cm-1 to lower frequency values. Although it is observed values near 2920 cm-1 for the vass(CH2) band, indicating a surfactant liquid phase, it is shown in this study that there are indeed DTAB crystallites. The shift of DTAB vsim(CH2) band is around 2 cm-1. These changes in vass(CH2) and vsim(CH2) band are an indicative of a decrease in gauche conformations and an increase in all-trans conformations over the aliphatic chain. The frequency value around 1472 cm-1 for the δ(CH2) band is also an indicative of the order in CH2 chain of DTAB. It is observed a shift of 2.6 and 2.7 cm-1 to higher frequency values of vass (CH2) and vsim(CH2) bands of the HPS molecule, respectively. The δ(CH2) band of the HPS molecule presents a shift of 4 cm-1 to higher frequency values. These variations in vass (CH2), vsim(CH2), and δ(CH2) bands stand out the disorder of the aliphatic chain due to the increase of the density packing for the HPS molecules on the germanium surface.

Ultimamente têm-se buscado tratamentos menos invasivos para o câncer, como os que utilizam campos magnéticos ou luz, e dentre esses últimos, aqueles que fazem uso de materiais, geralmente metálicos, com propriedade de ressonância plasmônica de superfície. O tratamento hipertérmico encaixa-se neste perfil e já apresenta resultados promissores com nanoshells de sílica recoberta por ouro e com nanobarras de ouro maciço, apesar de pouco se saber sobre o mecanismo de ação e sobre como as vias de morte celular são ativadas em tal tratamento. A síntese das nanobarras envolve o uso do composto brometo de cetiltrimetilamônio (CTAB), o qual permanece aderido à superfície das mesmas, porém é caracterizado por apresentar extrema citotoxicidade, fato que incita a modificação do recobrimento das nanopartículas por um biopolímero mais compatível. Estudos recentes indicam que o CTAB aderido à membrana não apresenta citotoxicidade considerável, porém há poucos dados que confirmem tal hipótese na literatura. Este trabalho se propôs a investigar a via de ativação da morte celular, bem como confirmar a hipótese de que as partículas recobertas por CTAB podem ser utilizadas para tratamento antitumoral fototérmico in vivo de forma segura. Para isso, nanobarras de ouro foram sintetizadas pelo método de seeding, sendo parte delas centrifugadas e lavadas com água deionizada por três vezes para retirar o CTAB e a outra parte deixada com CTAB no meio. As partículas foram testadas in vitro pelo teste de citotoxicidade pelo [brometo de 3-(4, 5-dimetiltiazol-2-yl)-2,5-difeniltetrazólio] (MTT) nas linhagens celulares HTC, HepG2, HT-29 e 786-O, e também foram testadas quanto à sua viabilidade com o tempo decorrido desde sua síntese. Após confirmar que as nanobarras centrifugadas e lavadas podem ser utilizadas no tratamento hipertérmico sem riscos à saúde e após verificar que as seeds e as nanobarras devem ser utilizadas até 48 horas depois de sua síntese, as nanopartículas foram utilizadas para tratamento de tumor de Ehrlich (induzido no dorso de camundongos). Para isso, foram organizados quatro grupos experimentais: L (camundongos não receberam nanopartículas, irradiados com laser em 808 nm), N (camundongos receberam nanopartículas, não irradiados com laser), H (camundongos receberam nanopartículas e irradiados com laser em 808 nm) e Controles (camundongos não receberam nanopartículas nem irradiação por laser). O material tumoral foi coletado após a irradiação e submetido à análise histológica, ao teste de quimiluminescência para avaliar a lipoperoxidação de membrana e ao teste de TRAP (do inglês, Total Radical-Trapping Antioxidant Parameter) para avaliar a capacidade antioxidante total. Após a irradiação com 2 W/\'CM POT.2\' ou 720 mW/\'CM POT.2\' de intensidade, houve evidente redução do volume tumoral nos animais do grupo H tratados com laser na maior potência utilizada, com um aumento de 47ºC (temperatura final de 79ºC) observado localmente. Nos animais do grupo H tratados com laser na menor potência utilizada, os danos foram menores. Os animais dos grupos L e H apresentaram semelhante lipoperoxidação, maior que no grupo N (estatisticamente significante somente nos animais tratados com laser em intensidade de 2 W/\'CM POT.2\'), e a capacidade antioxidante dos tumores dos animais do grupo H foi elevada no protocolo com laser em 2 W/\'CM POT.2\'. Os resultados indicam que a necrose é a via de morte ativada prioritariamente neste caso e que o tratamento com as nanobarras se mostrou eficaz.
Less invasive cancer treatments, likewise those based on magnetic fields or light, are in the most common aims of researchers nowadays. Regarding light based treatments, those in which metallic, plasmonic materials are highlighted in research field. Hiperthermic treatment fits this profile, once it already presents promising results with gold-coated silica nanoshells and with gold nanorods, although little is known about its action mechanism or about how cell death pathways are activated. The compound cetyltrimethylammonium bromide (CTAB) is necessary for the nanorods synthesis, but is known to be extremely cytotoxic, fact that instigates the modification of nanorods surface coating by a compatible biopolymer. Recent studies indicate that surface-adhered CTAB does not present significant cytotoxicity, but there are few evidences to confirm this hypothesis in the literature. This study aims to investigate the cell death pathway that can be activated, as well as to confirm the possibility of safe CTAB-coated nanoparticles use in antitumor in vivo treatments. For that, gold nanorods were synthesized by the seeding method and part of them were centrifuged and washed with deionized water to eliminate CTAB of the solution and the rest remained with CTAB. The particles were tested in vitro by [3-(4, 5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) cytotoxicity test, in HTC, HepG2, HT-29 and 786-O cancer cell lines, and investigated regarding their viability through time after their synthesis. After confirming that centrifuged and washed nanorods can be used in hiperthermic therapy without health risks, and after find out that seeds and nanorods must be used within 48 hours after their synthesis, those nanoparticles were used for in vivo hyperthermic Ehrlich tumor (induced on the back of mices) treatment. Four experimental groups were organized: L (mice did not receive nanoparticles, treated with laser at 808 nm), N (mice received nanoparticles, not treated with laser), and H (mice received nanoparticles and treated with laser at 808 nm) and Controls (mice did not receive nanoparticles and were not treated with laser). A tumor biopsy was taken after laser irradiation and was subjected to histological analysis, by a chemiluminescence assay to evaluate membrane lipoperoxidation, and by Total Radical-Trapping Antioxidant Parameter (TRAP) assay as well, to evaluate total antioxidant capacity. After irradiation with laser (intensities of 2 W/\'CM POT.2\' or 720 mW/\'CM POT.2\'), there was an evident tumor volume reduction in animals of H group treated with higher power laser, with a 47ºC rise in temperature (final temperature was 79ºC) observed locally. The damages in the tumors irradiated with lower power laser were less intense. The animals of L and H groups showed similar membrane lipoperoxidation, which was more intense than in N animals (statistically significant just in the animals treated with higher intensity of radiation). The antioxidant capacity of H animals tumor was elevated also in the animals treated with higher energy. Our results indicate that necrosis is the main activated cell death pathway in this case, and that nanorods treatment is worth it.

Abstract This essay discusses the negotiation of the Comprehensive Test Ban Treaty (CTBT) and the process that led up to a signed agreement. The CTBT forbids all nuclear weapon test explosions and all other types of nuclear explosions. The purpose of the study was to distinguish the critical steps of the negotiations that resulted in the success of the CTBT. Based on these insights, my intention was to identify relevant events and actors in the process around the Fissile Material Cut-off Treaty (FMCT), which has been on the nuclear disarmament agenda for over a decade. Furthermore, my ambition was that the examination of the CTBT negotiation would give me some clarity in what the next step would be to get the FMCT back on track. By using the method of process tracing I intended to achieve the purpose of the essay. I found that the examination of the CTBT process was very helpful in understanding the complexity of multilateral negotiations and that it is not always possible to reach an agreement through completely fair deals. I think that the negotiation of an FMCT will be equally difficult provided the Conference on Disarmament does not decide to transform its structure and procedures.

This thesis investigates CTAB/alcohol/hexane/water reverse micelles, where the alcohol is butanol, pentanol, hexanol and heptanol, through the use of nuclear magnetic resonance (NMR). Diffusion and relaxation measurements showed the alcohol is distributed between the reverse micelle (RM) interface and the continuous phase, and exchanges between these two environments. The exchange of pentanol in the CTAB/pentanol/hexane/water RM was investigated using 20 relaxation exchange spectroscopy (REXSY), and was determined to be on the order of milliseconds. The proportion of alcohol in the interface was determined for all microemulsions which decreases as a function of increasing alcohol size. Each microemulsion was investigated by molecular simulations which produced oblate shaped droplets, which was associated with a non-homogeneous distribution of alcohol in the interface. CTAB was determined to be present in solely the interface of the microemulsions with the exception of the CTAB/pentanol/hexane/water RM. The CTAB/pentanol/hexane/water RM behaves differently as initially the CTAB was distributed between the RM and the continuous phase however, after time, the surfactant is re-distributed so that CTAB is present in only the interface. The RM sizes were determined using the CTAB diffusion coefficients. The droplet sizes decreased as a function of alcohol chain length, with the exception of the CTAB/pentanol/hexane/water RM which, after time, gave the largest droplet of all the microemulsions.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.
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Este trabalho tem como objetivo apresentar e descrever o processo de construção de um Núcleo de Educação a Distância, dentro do SENAI de Santa Catarina, no Centro de Tecnologia em Automação e Informática - CTAI, apresentando um relato das experiências e trabalhos desenvolvidos desde as primeiras iniciativas em educação a distância, até a estrutura atual, bem como as competências adquiridas pelo núcleo no desenvolvimento e aplicação de projetos e programas realizados a distância, enfatizando a criação de um ambiente virtual próprio, denominado DIDATIX e que posteriormente deu origem ao Portal do Conhecimento em EAD, que é o local que agrega todos os cursos e atividades a distância desenvolvidas, bem como as intenções de continuidade.

Després de dècades d'observacions, és evident que les partíicules del model estàndard són insuficients per explicar el fort desequilibri gravitacional observat a diverses regions astronòmiques, de diferents escales cosmològiques, des de satèl·lits de la Via Làctia fins a cúmuls de galàxies. Si bé és veritat que algunes teories suggereixen a una modificació de les lleis gravitacionals actuals, l'existència d'una partícula (o un grup de partícules) nova, interaccionant de forma feble amb les partícules del model estàndard està considerada com l'opció més viable. Estimacions recents prediuen que aquest tipus de matèria fosca és 4 vegades més present que la matèria del model estàndard, modelant així la formació de les grans estructures de l'univers al llarg de la vida d'aquest. Un escenari general de la matèria fosca és el dels WIMPs, partícules genèriques massives, amb masses entre pocs GeVs i alguns TeV, interaccions de l'ordre de les interaccions dèbils del model estàndard, i o bé estables o amb temps de vida mitjana prou llargs. L'escenari WIMP ha estat llargament debatut, i té l'avantatja d'estar a l'abast dels instruments més potents construïts a la terra, proporcionant així possibles deteccions independents que podria validar el descobriment. En particular em centro en cerques indirectes de matèria fosca, on s'espera que WIMPs anihilats o decaient emetin rajos gamma amb energies detectables per telescopis IACT, com per exemple els telescopis MAGIC, actualment operant des de La Palma o la futura xarxa de telescopis CTA. El senyal esperat de rajos gamma d'aquesta matèria fosca pot ser moderadament extensa, comparada amb el camp de visió dels IACTs, cosa que afegeix certa complexitat a les cerques de matèria fosca realitzades per a aquests telescopis. En aquesta tesi, he contribuït a l'esforç realitzat per MAGIC en cerques indirectes de matèria fosca a diferents nivells d'analisis. He desenvolupat una eina per gestionar volums massius de dades que són típicament generats per MAGIC, però també per tota la comunitat experimental de física d'altes energies. També he desenvolupat un MonteCarlo per a fonts extenses que s'ajusta a l'emissió esperada de la font, obtenint així les funcions correctes de resposta de l'instrument. Finalment, un mètode per a optimitzar la configuració d'apuntat durant les observacions de fonts moderadament extenses amb IACTs ha estat proposat. El mètode té en compte la resposta finita dels IACTs al llarg de tot el camp de visió per a proporcionar la distància òptima a la qual el telescopi ha d'apuntar a la font, així com, quina seria la regió d'integració més adient. Apliquem aquest mètode per primera vegada a cerques de matèria fosca en galàxies satèl·lits de la Via Làctia. També exposo la meva contribució al telescopi més gran que operarà a CTA, el LST, que dominarà la sensibilitat de cerques de WIMPs estàndard. Límits a la secció eficaç i/o temps de vida mitjana són imposats mitjançant 60 hores d'observació de la galàxia Triangulum-II i 202 hores del cúmul de galàxies de Perseus. En ambdues cerques, fem ús del mètode de màxima versemblança, optimitzat per a la morfologia espacial i energètica del senyal esperat de rajos gamma. Obtenim sensibilitats a la secció eficaç de 3·10^{-26}~\cm^{3}\s^{-1} i temps de vida mitjana de 0.3·10^{25}~\s, essent aquests els resultats més restrictius obtinguts amb MAGIC en cerques de WIMPs.
Decades of observational evidences have been accumulated to show that Standard Model (SM) particles cannot totally explain the strong gravitational unbalance observed in several astronomical regions, at all cosmological scales, from that of Milky Way (MW) satellite galaxies, to that of Cluster of Galaxies (CGs). Although some theories argue for the modification of the gravitational laws, the existence of a new massive particle (or a set of them), interacting only weakly with SM particles, provides a preferred explanation. It is estimated that this form of Dark Matter (DM) roughly accounts for 4 times the amount of SM matter, therefore shaping the evolution of cosmic structures along the history of the Universe. A well-motivated general framework for DM is that of a Weakly Interacting Massive Particle (WIMP), generic massive particles with a mass range expected between few GeVs and few hundreds TeV, interaction strengths at the weak scale, and either stable or very long lived. The WIMP paradigm has been long debated, and has the advantage of being at reach by different of the top-class instruments of the current times, so that a putative discovery could be validated independently. We focus on the indirect search of DM, where annihilating or decaying WIMPs are expected to emit gamma rays at energies detectable by Imaginc Atmospheric Cherenkov Telescopes (IACTs), as the currently operating MAGIC telescopes or the future Cherenkov Telescope Array (CTA). The expected DM signal can be moderate extended when compared to IACTs Field of View (FoV), what challenges the performance of the \acrshort{dm} search of these instruments. In this thesis, I contribute to the MAGIC ongoing efforts on indirect DM searches at different analysis levels. A tool for handling the massive data products generated by current high energy experiments is developed. More over, a tailored Monte Carlo (MC) for moderate extended sources is proposed as an upgrade of the current general MC for extended sources. Finally, a method to optimize the pointing strategy of IACTs while observing moderate extended sources taking into account the off-axis performance of the instrument has also been developed and, implemented for the first time to indirect DM searches on highly DM dominated nearby dwarf Sphereoidal galaxies (dSphs). I also show my contribution to the largest telescope to be part of CTA, the Large Size Telescopes, that will dominate the CTA sensitivity for standard WIMP searches. Constraints on the WIMP thermally averaged cross-section and/or decay life-time are put with 60~hours of data in the recently discovered dSph Triangulum-II and 202~hours on the Perseus CG. On both searches, we apply a binned likelihood analysis optimized for the spectral and morphological features of gamma-ray signals of DM from annihilating or decaying WIMPs. We reach sensitivities to the thermally averaged cross-section of 3·10^{-26}~\cm^{3}\s^{-1} and decay life-times of 0.3·\times10^{25}~\s, being this the most constraining MAGIC results on WIMP searches.

Mestrado em Contabilidade, Fiscalidade e Finanças Empresariais
Os CTT - Correios de Portugal, S.A, (CTT) são um grupo empresarial português, fundado em 1520, líder no negócio dos correios. A empresa foi alvo de privatização com início em 2013 e fim em 2014, tornando-se atualmente a única empresa Portuguesa com 100% do seu capital em "free float" no PSI20. Os desafios para o futuro dos CTT passam por contrariar o efeito negativo das novas tecnologias no negócio dos correios, tirar partido da tendência de crescimento das encomendas de forma a ganhar participação no mercado e desenvolver o negócio do banco postal que integra o negócio dos serviços financeiros. Este trabalho tem por o objetivo estimar o valor da ação e da empresa dos CTT à data de 31 de Dezembro de 2015. A avaliação foi realizada utilizando o Método dos Fluxos de Caixa Atualizados, especificamente o método do WACC e o Método dos Múltiplos. Estes métodos adequam-se a empresas com uma estrutura financeira constante, como é o caso dos CTT. Para analisar a robustez da avaliação, procedeu-se a uma análise de sensibilidade e de cenários. De acordo com os pressupostos assentes, o valor da empresa é de 1.646.832 Euros, correspondendo a uma valor por ação de 10,40 Euros. Com esta avaliação concluímos que a 31 de Dezembro de 2015 a empresa estava subavaliada uma vez que a cotação de mercado era 8,85 Euros por ação. De acordo com a análise de sensibilidade, o valor da ação varia entre 9 e 11.
The CTT - Correios de Portugal, S.A, (CTT) is a Portuguese business group, founded in 1520, leader in the postal business. The company was privatized starting in 2013 and ending in 2014, becoming the only Portuguese company with 100% of its capital in "free float" in the PSI20. The challenges for CTT's future are to counteract the negative effect of new technologies on the postal business, take advantage of the trend of package growth in order to gain market share and develop the business of the CTT bank that integrates the financial services business. The purpose of this paper is to estimate the value of the CTT company's share as of December 31, 2015. The valuation was performed using the updated Cash Flow Method, specifically the WACC method and the Multiplex Method. These methods are suitable for companies with a constant financial structure, as is the case of CTT. In order to analyze the robustness of the evaluation, a sensitivity and scenario analysis evaluation was performed. According to the established assumptions, the value of the company is 1,646,832 Euros, corresponding to a value per share of 10,40 Euros. With this evaluation we conclude that at 31 December 2015 the company was undervalued, since the market quotation was 8.85 Euros per share. According to the sensitivity analysis, the share value varies between 9 and 11.
N/A

This study examines whether a trend following managed futures fund can improve its performance by changing its position sizing method. Trades for a simple trend following strategy was simulated on 47 futures contracts over the period 1990-2012, using varying methods for determining position size. Eleven different position sizing methods where investigated, among them Target Volatility, Omega Optimization and correlation ranking methods. Both methods previously detailed in academic papers as well as novel approaches was implemented, and compared to the baseline performance of the strategy. The results from this study show that the Target Volatility method, and to some degree Max Drawdown Minimize and Dynamic Stop Lock-In, improved the performance of strategy. The final recommendation for a trend following managed futures fund is to use Target Volatility as position sizing method, possibly in conjunction with Max Drawdown Minimize.
Denna studie undersöker huruvida en trendföljande managed futures-fond kan förbättra sina resultat genom att ändra positionsskalningsmetod. Handel med en enkel trendföljande strategi simulerades på 47 futureskontrakt åren 1990-2012, för olika metoder att för bestämma positionsstorlek. Elva positionsskalningmetoder undersöktes, exemplevis Target Volatility, Omega Optimization och metoder baserade i korrelationsrankning. Både tidigare beskrivna metoder och nya tillvägagångssätt testades, och jämfördes med den grundläggande strategin med avseende på risk och avkastning. Denna studies resultat visar att framförallt Target Volatility, och i viss uträckning Max Drawdown Minimize och Dynamic Stop Lock-In förbättrade nyckeltalen för den handlade strategin. Den slutgiltiga rekommendationen för en trendföljande managed futures-fond är att använda Target Volatility som positionsskalningsmetod, möjligtvis tillsammans med Max Drawdown Minimize.

Dans ce travail, nous avons élaboré, par voie sol-gel, un nouveau verre bioactif mésoporeux : 92S6 (92% SiO2, 6% CaO, et 2% P2O5). Cette synthèse a été développée en variant les paramètres telles que la température, la nature du tensioactif (ionique (le CTAB) ou non ionique (le P123)) et la longueur de la chaîne carbonée pour chaque type de tensioactif et en étudiant leurs effets sur les propriétés texturales du verre. Des études physico-chimiques et biologiques in vitro ont été menées sur ces biomatériaux. Par la suite, nous avons réalisé une étude structurale de l'eau confinée dans les pores du verre synthétisé qui a révélé une modification de l'ordre locale en comparaison avec l'état massique (bulk). Ceci permet un contrôle de la quantité de principe actif à incorporer dans les pores, du taux d'adsorption et de la cinétique de libération. La diffraction des Rayons X aux petits angles, l'analyse texturale par BET et les images de la microscopie électronique en transmission ont mis en évidence l'influence des paramètres de synthèse sur les propriétés texturales des verres synthétisés. En effet, l'échantillon synthétisé avec le tensioactif ionique (CTAB) présente une structure mésoporeuse non ordonné, alors que l'utilisation du tensioactif non-ionique (P123) favorise l'obtention d'un verre mésoporeux ayant une structure poreuse ordonnée. Dans le cas des verres synthétisés avec les différentes longueurs de la chaîne carbonée des tensioactifs, nous avons démontré que la longueur de la chaîne alkyle du tensioactif ionique détermine la morphologie des particules et les caractéristiques texturales des 3 verres, alors que nous avons noté une absence de différences significatives dans la texture des matériaux dans le cas des 3 verres synthétisés avec les tensioactifs non ioniques. Nous avons aussi mis en évidence l'influence de la température de synthèse sur les propriétés texturales des verres synthétisés. Nous avons démontré que la température de synthèse agit sur le diamètre des pores de manière différente selon la nature du tensioactif. L'augmentation de la température de synthèse conduit à une augmentation de la dimension des cavités dans le cas des verres synthétisés avec le P123, alors que dans le cas des verres synthétisés avec le tensioactif ionique CTAB, l'augmentation de la température de synthèse conduit à une diminution des diamètres des pores. Nous avons démontré que la morphologie des particules et les caractéristiques texturales des verres influent sur la bioactivité de ces derniers. Nous avons obtenu des verres bioactifs comme en témoigne la formation de la couche d'hydroxyapatite à leurs surfaces une fois immergés dans le SBF, ce qui explique l'intérêt des ces verres dans le domaine de la chirurgie orthopédique
In this study, a new mesoporous bioactive glass 92S6 (92% SiO2, 6% CaO, and 2% P2O5), was prepared by sol-gel method. The purpose of this study was first to investigate the effect of synthesis parameters such as aging temperature, surfactant type and surfactant carbon chain length on the glass textural properties and then to investigate these effect on the glass bioactivity. Then, we conducted a structural study of water confined in the pores of the synthesized glass. This study revealed a change of the local order of confined water in comparison with the bulk. This allows control of drugs to be incorporated into the pores, the adsorption rate and the release kinetics. The small-angle XRD patterns (SAXRD), the Brunauer–Emmett–Teller (BET) method and the Transmission Electron Microscopy (TEM) studies evidence the influence of the structure-directing agent (ionic surfactant CTAB or non-ionic P123) in the generation of unorganized or well ordered pores in the 92S6 glass. We also demonstrated that when we synthesized glasses with a same composition using the same technique (sol-gel), in presence of surfactants with different carbon chain length, there is a direct correlation between the surfactant and textural properties and structural characteristics. As observed from small-angle XRD patterns and TEM images, synthesis at different temperatures lead to the formation of mesoporous glasses. The properties of these glasses are extremely dependent on the synthesis temperature. We demonstrated also that the bioactivity may be significantly modified by a change on glass textural properties. Finally, the samples were analyzed to quantify the apatite formation ability when soaked in SBF solution. The physico-chemical studies showed apatite-like phases formed at the glasses surface when soaked in SBF. So, our mesoporous glasses are bioactive. These characteristic mesoporous glasses will display good future applications in bone tissue repairing and engineering

Detta examensarbete analyserar effekterna av volatilitet och korrelation på trading strategier brukade av Commodity Trading Advisors (CTA´s). Denna studie bygger på en kvantitativ analys av data som insamlats från Barclay Hedge database. Studien har genomförts i samarbete med RPM Risk & Portfoliomanagement i Stockholm, Sverige. Traditionellt sett, när globala marknader visar på högre volatilitet än genomsnittet, har detta identifierats som ett tecken på en björnmarknad med negativ avkastning på aktier. Förhållandet mellan volatilitet och negativ avkastning på aktier var initialt uppmärksammat av Black år 1976. Förhållandet mellan volatilitet och korrelation mellan marknaderna har analyserats i denna uppsats och resultaten tyder på att högre nivåer av volatilitet för även med sig högre nivåer av korrelation. Den uppmäta korrelationen mellan volatilitet och korrelation var så hög som 0,7. CTA´s handlar så kallade Managed Futures, framtida kontrakt på råvaror, där varje kontrakt har en lång och kort position vilket gör det möjligt att nå en positiv avkastning även under hög volatilitet. De tre mest använda strategierna för CTA´s, short term trading (kortsiktig handel), fundamental handel och Trendföljande handel, presenteras i denna studie och deras möjlighet att bära positiv avkastning i en mycket volatil marknad härleds. Resultaten tyder på att en hög volatilitetsregim med hög korrelation gynnar den kortsiktiga handelsstrategin mer än fundamental och trendföljande handel.
This master thesis analyses the impacts of volatility and correlation on common strategies for Commodity Trading Advisors (CTAs). It is based on a quantitative analysis of data gathered from the Barclay Hedge database. The study was done in cooperation with RPM Risk and Portfolio Management based in Stockholm, Sweden. Traditionally, when global markets see higher levels of volatility this has been identified as a sign of a bear market with negative returns on equities. The relationship between volatility and negative returns on equities was first acknowledged by Black in 1976. The relationship between volatility and correlation between markets has been analyzed in this thesis and the findings suggest that higher levels of volatility brings with it higher levels of correlation. The correlation between volatility and correlation is as high as 0.7. CTAs trade future contracts where every contract has a long and short position which is making it possible to reach positive returns even under extreme volatility. The three most popular strategies for CTAs, Short Term trading, Fundamental trading and Trend Following, are presented in this study and their possibility to have positive returns in highly volatile environments is derived from the analysis. The findings suggest that in a high volatility regime with high correlation Short Term trading strategy has been the most profitable.

There is a growing common effort in the very high energy community towards the development of new research infrastructures to answer the fundamental questions of modern high-energy astrophysics and astroparticle physics. The Cherenkov Telescope Array Observatory (CTAO) is an international project aiming to deploy two separate arrays to observe the whole VHE sky between E = 20 GeV up to E = 300 TeV in a long term plan of about 30 years of operations. CTA is designed to increase the sensitivity by a factor 10 at 1 TeV, to enlarge the detection area, the angular resolution and the field of view over the facilities operating today. The observatory will be characterized by high flexibility, enhanced monitoring and deep survey capabilities, short time scale and simultaneous observations in multiple fields. This PhD thesis addresses the optical design study and testing of dual mirror Imaging Atmospheric Cherenkov Telescopes (IACTs) for the incoming CTAO. All of the IACTs facilities currently operating rely on single mirror solutions, which are mostly parabolic or Davies-Cotton optical designs, however there is a novel interest in the development of dual mirror configurations following the Schwarzschild-Couder optical design. This peculiar design, based on two highly aspherical mirrors promises wide-field, aplanatic telescopes characterized by small f-numbers and more compact structures. Dual mirror solutions allow use smaller camera pixels (3-6 mm) based on Silicon Photo Multiplier technology in substitution of the larger Photo Multiplier Tubes (1 inch) currently in use. The increased complexity in terms of optics manufacturing, replication and alignment is motivated from the attractive new capabilities of such configuration. In this context the Italian National Institute for Astrophysics (INAF) supported by the Italian Ministry of Education, University and Research (MIUR), is developing a small sized telescope prototype for CTA, named ASTRI, which is based upon the Schwarzschild-Couder optical design. The present work deals with the challenging realization of this optical configuration that has never been applied to IACTs. After two introductory chapters on the gamma-ray astronomy and the ASTRI optical design and its main subsystems (chapters 1 and 2), the performances of this system are compared with those of the other common wide-field telescopes in use for Cherenkov observations and for other applications in astrophysics (chapter 3). This comparative study is based on a commercial ray tracing software into which the optical designs of the envisaged telescopes are reproduced. Subsequently in chapter 4, an extended study of the ASTRI capabilities in relation to the performance and environmental requirements issued by CTA is presented in a detailed analysis of compliance supported by ray tracing simulations, finite element analysis and tolerance studies. In chapter 5 the work on the qualification tests of the secondary mirror gives an insight into the complexity of the Schwarzschild-Couder optics. The realization of this optical element is challenging in relation to currently available technologies, in particular concerning the cost requirements imposed by the CTA project. These constraints and the large sagitta of the mirror (190 mm) requires the use of the hot slumping technique in substitution of the cold slumping and diamond milling approaches usually used in the manufacturing of mirrors for Cherenkov applications. The results of a careful and extended test campaign on a mirror prototype have indicated that this manufacturing technique can provide a reliable engineering process of production for such large, highly aspherical optics. With a perspective on the science with future large telescopes as those provided by CTA, an assessment study upon the potentialities of the Intensity Interferometry (II) technique is carried out in chapter 6. In particular, a new kind of observation based on II is explored; the method aims to estimate the direct distance of the celestial objects. The order of magnitudes of the problem parameters space and the sensitivity that CTA and other future large observatories should achieve is estimated by means of numerical simulations. A short-term concept of experiment to assess the reliability of this new method is also discussed in relation to a pilot measurement that could be pursued with the state of the art technology.
Vi é un crescente interesse nella comunita’ dell'astrofisica delle alte energie verso lo sviluppo di nuove infrastrutture di ricerca per rispondere alle questioni fondamentali della moderna astrofisica delle alte energie e della fisica delle astroparticelle. Il Cherenkov Telescope Array é un progetto internazionale che ha lo scopo di costruire due array separati per osservare l'intero cielo alle altissime energie tra 20 GeV e 300 TeV lungo un periodo di attivita’ di almeno 30 anni. CTA é pensato per aumentare la sensibilita’ di un fattore 10 ad 1 TeV, per allargare l'area di detection, la risoluzione angolare e il campo di vista rispetto ai telescopi attualmente operanti. L'osservatorio sara’ caratterizzato da un'elevata flessibilita’, potenziate capacita’ di monitoraggio e survey profonde, osservazioni a piccole scale temporali e osservazioni simultanee in campi multipli. Questa tesi dottorato si concentra sullo studio del disegno ottico e dei test di un telescopio Cherenkov a due specchi per l'osservatorio CTA. Sebbene tutti i telescopi Cherenkov operanti oggigiorno, si basino su uno specchio singolo, perlopiu’ secondo disegni parabolici o Davies-Cotton, c’é un nuovo interesse nello sviluppo di configurazioni a due specchi secondo la configurazione Schwarzschild-Couder. Questo disegno peculiare, basato su due specchi altamente asferici definisce dei telescopi aplanatici con ampi campi di vista caratterizzati da f/# molto piccoli (sistemi molto veloci) e strutture piu’ compatte. Soluzioni a due specchi consentono l'uso di pixels piu’ piccoli (3-6 mm) basati sulla tecnologia dei foto-moltiplicatori al silicio in sostituzione ai piu’ grandi tubi foto-moltiplicatori (1 pollice) attualmente in uso. L'aumento di complessita’ in termini di lavorazione delle ottiche, replica ed allineamento é motivato dalle promettenti, nuove, performance di questa configurazione. In questo contesto l'Istituto Nazionale per l'Astrofisica (INAF) supportato dal Ministero Italiano per l'Educazione, l'Universita’ e la Ricerca (MIUR), sta sviluppando un telescopio di piccola taglia per CTA, chiamato ASTRI, e basato su un disegno ottico Schwarzschild-Couder. Il presente lavoro si confronta con la difficile realizzazione di questa configurazione ottica che non é mai stata applicata ai telescopi Cherenkov. Dopo un capitolo introduttivo sull'astronomia gamma e sul disegno ottico di ASTRI (capitoli 1 e 2), le performance di questo sistema ottico sono comparate con quelle dei comuni telescopi a grande campo in uso per osservazioni Cherenkov e per altre applicazioni in astrofisica (capitolo 3). Successivamente nel capitolo 4, un esteso studio delle caratteristiche e delle performance di ASTRI in relazione ai requisiti di performance e ambientali richiesti da CTA é presentato in una dettagliata analisi di compatibilita’ supportata da simulazioni di ray tracing, analisi agli elementi finiti e studi di tolleranza. Nel capitolo 5 i test di qualifica dello specchio secondario danno una visione della complessita’ delle ottiche Schwarzschild-Couder. La realizzazione di questo elemento ottico é difficile in relazione alle tecnologie esistenti e in particolare agli stretti vincoli di costo imposti dal progetto CTA. Questi vincoli e la grande sagitta dello specchio (190 mm) richiedono l'uso della tecnica dello slumping a caldo in sostituzione dello slumping a freddo o della fresatura a diamante generalmente usati per la produzione di ottiche Cherenkov. I risultati di un'estesa campagna di test su alcuni prototipi di specchio ha accertato che questa tecnica di produzione puo’ supportare un affidabile processo di ingegnerizzazione per grandi specchi altamente asferici. Con uno sguardo alla scienza con i futuri grandi telescopi come CTA, é stato effettuato anche uno studio di valutazione sulle potenzialita’ della tecnica dell'interferometria di intensita’ (riportato nel capitolo 6). In particolare, é stato investigato un nuovo tipo di osservazione basato sull'interferometria di intensita’; questo metodo si propone di stimare la distanza geometrica degli oggetti celesti. Gli ordini di grandezza dello spazio dei parametri del problema e la sensibilita’ che CTA e altre grandi osservatori del futuro dovrebbero raggiungere sono stimati a mezzo di simulazioni numeriche. In questa cornice é anche discusso un possibile esperimento per testare la precisione del metodo con le attuali tecnologie a disposizione.

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This work has analyzed the contribution of the development of activities of a research project applied in the teaching-learning process, hoping that the students of the Technical Course in Agroindustry of the Federal Institute of Education, Science and Technology ? Campus Iguatu, in the class of fruits and vegetables processing as active agents, comprehend and solidify their knowledge. In that sense, students of the Technical Course in Agroindustry produced teaching materials that could be used for the capacity of the producers of Vila Cajazeiras, with formulation techniques that could assemble value to the fruit of umbucaj? (Spondias sp). To evaluate the pedagogical process, two groups of 16 students have been created. The first group consisted of students from the Technical Course in Agroindustry with the curriculum in the integrated course (test group) and the second, students from the Technical Course in Agroindustry with the curriculum in the modulated course (control group). These students had already taken the class of fruits and vegetables processing the semester before. The evaluation method used was to evaluate the attitude of the individual, building a questionnaire about the umbu-caj? fruit with affirmatives referent to the necessary concepts and knowledge to comprehend these steps. This instrument has been applied in three different steps. For the control group, the instrument has been applied only once. In the extension activity, 16 people from the community have participated. The students were evaluated by the producers that participated in the extension activity. The processed product, nectar of umbu-caj?, has been evaluated referencing the physical-chemical, sensorial and microbiological parameters. In the physical-chemical determinations, the current legislation has been used to compare the results. In the sensorial evaluations, accepting tests have been used. As for the teaching-learning process, it has been observed that the test scores for each subject have been gradually rising as the learning would materialize, reaching the final test with more homogeneous answers. The medium scores were 4,8; 5,2 and 6,9 for T1, T2 and T3, respectively. As the students were being inserted in the context of the contemplated units of the class, it has been noted that the developed activities contributed to elevate their knowledge. In the control group the learning level was lower than in the test group. The results of the second group (control group) indicate that the students of the first group (test group) obtained higher comprehension of the proposed activities in this project, making this student search for interdisciplinary, produce his own learning, establish non-traditional pedagogical relations and learn new methods to assimilate new information and processing technologies of the umbu-caj? fruit, to better support its proposed work. Therefore, this work was important to link the student to the researching world, making him an active agent of all the process, assigning him with responsibility and making it possible for him to create different ways of constructing his own knowledge.
O presente trabalho analisou a contribui??o do desenvolvimento de atividades de um projeto de pesquisa aplicado no processo de ensino-aprendizagem, esperando-se que os estudantes do Curso T?cnico em Agroind?stria do Instituto Federal de Educa??o, Ci?ncia e Tecnologia - Campus Iguatu, da disciplina de processamento de frutos e hortali?as, como agentes ativos, compreendessem e solidificassem o conhecimento. Nesse sentido, estudantes do Curso T?cnico em agroind?stria produziram o material did?tico que pudesse ser utilizado para a capacita??o dos produtores da Vila Cajazeiras, com t?cnicas de formula??es para que eles pudessem agregar valor ao fruto do umbu-caj? (Spondias sp). Para avaliar o processo pedag?gico, foram constitu?dos dois grupos de 16 estudantes, sendo o primeiro do Curso T?cnico em Agroind?stria da matriz curricular do Curso integrado (Grupo Teste) e o segundo, por alunos do Curso T?cnico em Agroind?stria da matriz curricular do curso modulado (Grupo Controle). Esses alunos j? haviam cursado a disciplina de processamento de frutos e hortali?as no semestre anterior. Utilizou-se o m?todo de avalia??o de atitude do indiv?duo construindo-se question?rio relativo ao fruto do umbu-caj? com afirmativas referentes aos conceitos e conhecimentos necess?rios para compreender estas etapas. Esse instrumento foi aplicado em tr?s etapas diferentes. Para o Grupo controle, o instrumento foi aplicado apenas uma vez. Na atividade de extens?o participaram 16 pessoas da comunidade. Os alunos foram avaliados pelos produtores que participaram da atividade de extens?o. O produto processado, n?ctar de umbu-caj?, foi avaliado em rela??o aos par?metros f?sico-qu?micos, sensoriais e microbiol?gicos. Nas determina??es f?sico-qu?micas, para comparar os resultados, utilizou-se a legisla??o vigente. Nas avalia??es sensoriais, utilizaram-se testes de aceita??o. Quanto ao processo de ensino-aprendizagem, verificou-se que a m?dia para cada sujeito foi aumentando gradativamente nos testes, ? medida que a aprendizagem se concretizava, chegando ao ?ltimo teste com uma maior homogeneidade nas respostas, cujas m?dias foram 4,8; 5,2 e 6,9 para T1, T2 e T3, respectivamente. Na medida em que os alunos foram sendo inseridos no contexto das unidades contempladas na disciplina, verificou-se que as atividades desenvolvidas contribu?ram para elevar seu n?vel de conhecimento. O Grupo Controle o n?vel de aprendizagem foi menor do que no grupo teste. Os resultados obtidos no segundo grupo (grupo controle) indicaram que os estudantes do primeiro grupo (grupo teste) obtiveram melhor compreens?o das atividades propostas neste projeto, proporcionando a esse aluno buscar a interdisciplinaridade, produzir seus pr?prios conhecimentos, estabelecer rela??es pedag?gicas n?o-tradicionais e aprender outro m?todo para assimilar novos conhecimentos e tecnologias de processamento do fruto de umbu-caj?, para melhor fundamentar a sua proposta de trabalho. Portanto, o trabalho foi importante para vincular o estudante ao mundo da pesquisa, fazendo-o um agente ativo de todo o processo, atribuindo-lhe responsabilidade e possibilitando-lhe um modo diferente de construir seu pr?prio conhecimento.

CTA har vært utsatt for sterkt kritikk av eksperter. Dette er kritikk som spesielt fokuserer på metodens validitet og gjennomførelse. Denne masteroppgaven fokuserer på brukbarhetstester med et annet perspektiv; brukernes opplevelse av metoden. Oppgaven prøver finne ut om, og eventuelt i hvor stor grad, testsituasjonen påvirker testresultatene. I dette studiet gjennomføres til sammen 20 brukbarhetstester. Testene ble gjennomført i to runder på et nettsted for ”Studentsamskipnaden i Trondheim". Studiet viser at RTA og CTA oppleves forskjellig av testbrukerne, og at opplevelsen av CTA har innvirkning på resultatene. CTA- testdeltagerne brukte lengre tid på å gjennomføre oppgavene og metoden avdekket i tillegg falske brukskvalitetsproblem. Alle testdeltagerne kom med flere negative tilbakemeldinger på CTA, mens det stort sett var positive tilbakemeldinger på RTA metoden. Den negative kritikken av CTA var gjennomgående temaer som; mislikte å bli filmet, dobbel kognitiv belasting, vanskelig å sette ord på tanker, prestasjonsangst, press til å snakke, dårlig tid til oppgaveløsning, vanskelig å holde verbaliseringen gående og tenker annerledes enn de snakker.

Pulmonary embolism (PE) is an obstruction within the pulmonary arterial tree and in the majority of cases arises from a thrombosis that has travelled to the lungs via the venous system. Pulmonary embolism (PE) is a fatal condition which affects all age groups and is the third most common cause of death in the US. Computed tomographic angiography (CTA) imaging has recently emerged as an accurate method in the diagnosis of pulmonary embolism. Each CTA scan contains hundreds of CT images, so the accuracy and efficiency of interpreting such a large image data set is complicated due to various PE look-alikes and human factors such as attention span and eye fatigue. Moreover, manual reading and interpreting a large number of slices is time consuming and it is difficult to find all the pulmonary embolisms (PE) in a data set. Consequently, it is highly desirable to have a computer aided detection (CAD) system to assist radiologists in detecting and characterizing emboli in an accurate, efficient and reproducible manner. A computer aided detection (CAD) system for detection of pulmonary embolism is proposed in CTA images. Our approach is performed in three stages: firstly the pulmonary artery tree is extracted in the region of the lung and heart in order to reduce the search area (PE occurs inside the pulmonary artery) and aims to reduce the false detection rate. The pulmonary artery is separated from the surrounding organs by analyzing the second derivative of the Hessian matrix and then a hybrid method based on region growing and a new customized level set is used to extract the pulmonary artery (PA). In the level set implementation algorithm, a new stopping criterion is applied, a consideration often neglected in many level set implementations. In the second stage, pulmonary embolism candidates are detected inside the segmented pulmonary artery, by an analysis of three dimensional features inside the segmented artery. PE detection in the pulmonary artery is implemented using five detectors. Each detector responds to different properties of PE. In the third stage, filtering is used to exclude false positive detections associated with the partial volume effect on the artery boundary, flow void, lymphoid tissue, noise and motion artifacts. Soft tissue between the bronchial wall and the pulmonary artery is a common cause of false positive detection in CAD systems. A new feature, based on location is used to reduce false positives caused by soft tissue. The method was tested on 55 data scans (20 training data scans and 35 additional data scans for evaluation containing a total of 195 emboli). The system provided a segmentation of the PA up to the 6th division, which includes the sub-segmental level. Resulting performance gave 94% detection sensitivity with an average 4.1 false positive detections per scan. We demonstrated that the proposed CAD system can improve the performance of a radiologist, detecting 19 (11 %) extra PE which were not annotated by the radiologist.

Mestrado em Marketing
A forma como uma organização cuida dos seus colaboradores reflete-se na forma de como os colaboradores vão cuidar dos clientes. A construção e a valorização de uma marca, são fatores chave na criação de vantagem competitiva. A literatura apresenta diferentes abordagens ao Brand Equity, sendo que este conceito merece grande interesse do ponto de vista académico, debruçando-se sobre a perspetiva do consumidor e a perspetiva financeira. O Employee Brand Equity (EBE), a terceira dimensão, ocorre quando um colaborador tem um conhecimento efetivo acerca da marca para a qual trabalha, refletindo-se em comportamentos e atitudes relacionadas com os objetivos que a marca pretende transmitir para o exterior. O EBE permite fornecer insights de como a organização pode gerir internamente a sua marca bem como permite avaliar os benefícios subsequentes do modelo para a marca uma vez que é extremamente relevante para o setor dos serviços. O presente trabalho centra-se no papel do colaborador na construção e entrega da promessa da marca CTT - Correios de Portugal S.A. Foi avaliada a relação entre as diferentes variáveis que constituem o modelo EBE sendo que a metodologia adotada passou pela realização de um estudo quantitativo com aplicação de questionários online aos colaboradores da marca, obtido-se 619 respostas. Foram realizadas análises para aferir o impacto das variáveis nas dimensões, sendo que os resultados demonstram que a escala aplicada por King et al., (2012) se adequa. Os resultados confirmam a importância do colaborador na construção do valor da marca, como principal fonte para o público externo.
The development of a brand, is considered critical factor of success, which creates competitive advantage in the market. This work focus on Brand Equity by Employee perspective, also called "third perspective of Brand Equity". There are two perspectives which deserve interest in marketing literature and in management environment: consumer based brand equity and financial based brand equity. Employee Brand Equity (EBE), occurs when an Employee have knowledge about the brand, which is reflected on behaviors and attitudes related with the brand goals to external public. EBE gives the insights about how the company can manage internally the brand, consenting evaluate the benefits through brand and holding strong relevance for service organizations. The present study has the focal point the role of employee in brand promise delivery in CTT - Correios de Portugal S.A. Data was collected through a quantitative online survey resulting in a sample of 619 employees. We analyze the relationship between the variables using a multiple regression analyses to evaluate the impact of the variables in the constructs. Our results demonstrating that the scale developed previously by King et al., (2012) fit in the context of this study. The results confirm the Brand Endorsement and Brand Loyalty as consequent variables of EBE, considering that the Brand Endorsement have and stronger impact than Brand Loyalty. Moreover, the Brand Commitment is influenced positively by the Role Clarity. The results confirm that the brand commitment of employees are important when we're talking about Brand Equity. Employees are channel for external consumer.
info:eu-repo/semantics/publishedVersion

Computed tomography angiography (CTA) of the brain poses challenges on the imaging system; the contrast between blood vessels and surrounding soft tissue is very low, and to render small intricate vessel structures high spatial resolution is needed. Higher precision angiography would facilitate more accurate diagnosis of pathological conditions. The aim of this work was to analyze the factors which contribute to the image quality in cerebrovascular imaging contexts and make a comparison between state-of-the-art energy-integrating and photon counting CT systems. A geometrical model was devised to mimic the conditions of cerebral angiography. Different parameters and detectors were used to reconstruct images of a spherical head phantom. Compton noise was added to several image acquisitions after a Monte Carlo study was used to estimate the scatter to primary ratio (SPR) with a spherical phantom. The images were evaluated qualitatively and quantitatively. A real phantom was scanned with an experimental photon counting detector and compared with the simulated approach. The work resulted in qualitative reconstructed images, a decrease in SPR when introducing air gaps and improved resolution but worsened contrast as a result of smaller detector sizes. The SPR was shown to be higher in cone-beam geometry than fan-beam geometry. Electronic noise present with energy integrating detectors was shown to degrade image quality significantly in low dose imaging, reducing contrast when imaging vascular-like structures. Photon counting detectors without electronic noise could provide greater image quality and better diagnostic information.

This thesis studies the performance, performance persistence, survival and flow of Commodity Trading Advisors, also known as CTAs or Managed Futures Funds. One of the main contributions of this thesis is the novel classification of CTA strategies. This is obtained by hand-collecting information frequently by directly contacting the funds in the database. I thus identify two main trading styles: Systematic and Discretionary CTAs which are the main focus of this thesis. I further separate Systematic CTAs into trend-followers with differing trading horizon. This novel dataset allows me to reconsider many hitherto studied issues in the CTA space with an application to these sub-strategies. The first section investigates the differences in mortality between Systematic and Discretionary CTAs, over the longest horizon than of any in the literature. A detailed survival analysis over the full range of CTA strategies is provided. Systematic CTAs have a higher median survival than Discretionary CTAs, 12 vs. 8 years. I hand collect information on reasons for exit from the database. I propose new filters that will better identify real failures among funds in the graveyard database. Separating graveyard funds into real failure I re-examine the attrition rate of CTAs. The real failure rate is 11.1%, lower than the average yearly attrition rate of 17.3% of CTAs. The effect of various covariates including several downside risk measures is investigated in predicting CTA failure. Controlling for performance, HWM, minimum investment, fund age and lockup, funds with higher downside risk measures have a higher hazard rate. Compared to other downside risk measures, the volatility of returns is less able to predict failure. Funds that receive larger inflows are able to survive longer than funds that do not. Large Systematic CTAs have the highest probability of survival. The second part studies the performance and performance persistence of Systematic and Discretionary CTAs. Controlling for biases, after fees the average CTA is able to add value. These results are strongest for large Systematic CTAs. I extend the sevenfactor model of Fung-Hsieh (2004a) and find that this model is better able to explain the returns of Systematic rather than Discretionary CTAs. I find three structural breaks in the risk loadings of CTAs different to hedge fund breaks: September 1998, March 2003 and July 2007. Using these breaks I show that systematic CTAs were able to deliver significant alpha in every sub-period. I also find evidence of significant performance persistence. However, these findings are heavily contingent on the strategy followed: the persistence of Discretionary CTAs is driven by small funds whereas large funds drive the performance persistence of Systematic funds. These results have important implications for institutional investors who face capital allocation constraints. They also suggest that contrary to the previous findings, the CTA industry does not appear to be heading towards zero alpha. The final section looks at the relationship between fund-flows and performance. Investors chase past performance, the fund- flow -performance is significant and concave for some strategies. Although there is some long-term performance persistence of Systematic funds with the highest inflows, there is no smart money effect in the CTA literature. I find no evidence of capacity constraints among Systematic CTAs. Investors are thus not able to smartly allocate funds to future best performers and take full advantage of the liquidity that CTAs offer.

The progression of genetically inherited cardiomyopathies from an altered protein structure to the clinical presentation of the disease is not well understood. One of the main roadblocks to mechanistic insight remains a lack of high-resolution structural information of multiprotein complexes within the cardiac sarcomere. One example is the tropomyosin (Tm) overlap region of the thin filament that is crucial for the function of the cardiac sarcomere. To address this central question, we devised coupled experimental and computational methods to characterize the baseline function and structure of the Tm overlap, as well as the effects that mutations causing divergent patterns of ventricular remodeling have on both structure and function.

Il cadmio (Cd) è un metallo pesante che si può trovare sulla crosta terrestre associato con altri elementi più comuni, come l’ossigeno, il cloro e il zolfo. Tuttavia, essendo stato massicciamente rilasciato nell’ambiente dall’uomo, il Cd è attualmente considerato uno dei più comuni inquinanti ambientali. Infatti, è presente in tutti i comparti (aria, acque, suolo e sottosuolo). I lavoratori sono maggiormente esposti all’inalazione di particelle contenenti cadmio, mentre la popolazione non occupazionalmente esposta è esposta al Cd attraverso il fumo di sigaretta e l’ingestione di acque e cibi contaminati. Nel 1993, il Cd è stato classificato come cancerogeno (gruppo 1) per l’uomo dall’Agenzia Internazionale per la Ricerca sul Cancro (IARC), ma i meccanismi molecolari alla base della sua cancerogenesi sono ancora poco noti. Sappiamo però che il Cd è un agente non genotossico. Questo metallo non provoca direttamente mutazioni del DNA, ma può agire mediante l’alterazione dei meccanismi epigenetici e dell’espressione genica, l’induzione di stress ossidativo, l’inibizione dei meccanismi di riparo del DNA e l’interazione con proteine coinvolte nel controllo del ciclo cellulare, nell’apoptosi e nelle difese cellulari. Il cadmio può inoltre interferire con l’omeostasi di molti metalli essenziali, tra cui lo zinco, il calcio e il ferro. In particolare, il Cd sembra essere in grado di sostituire lo zinco nelle proteine che possiedono motivi zinc-finger, compromettendone la funzionalità. Per studiare più approfonditamente la carcinogenesi indotta da Cd, abbiamo deciso di utilizzare il Cell Transformation Assay (CTA), uno dei test in vitro più avanzati per lo screening del potenziale di cancerogenesi e per comprendere il meccanismo d'azione delle sostanze chimiche. In effetti, questi saggi sono in grado di riprodurre le fasi chiave delle trasformazioni neoplastiche in vivo. In questo contesto, gli scopi di questo lavoro di tesi sono stati: i) studiare i meccanismi attraverso cui il Cd induce la trasformazione cellulare; ii) implementare uno dei test in vitro più avanzati per valutare il potenziale della carcinogenesi chimica. Abbiamo prima analizzato il transcrittoma delle C3H10T1 / 2Cl8 dopo 24 ore di trattamento con Cd e di cellule completamente trasformate (foci). Poi ci siamo concentrati sulle modifiche metaboliche e/o nella morfologia e nella funzione dei mitocondri causate dal Cd. Abbiamo applicato la tecnica del Seahorse, saggi enzimatici e dei metaboliti per verificare la prima ipotesi; la microscopia confocale a fluorescenza a scansione laser, l'analisi dell'immagine e la tecnica della citometria a flusso per la seconda. Alla fine, abbiamo confrontato il transcrittoma di due diverse linee cellulari umane: le HepG2 e SHSY5Y. La prima è una linea cellulare di carcinoma epatico, la seconda è una linea cellulare di neuroblastoma. L'OECD ha stabilito che il CTA rappresenta il saggio centrale per la valutazione della cancerogenesi nell’ambito di un approccio integrato. In particolare, a causa dei limiti delle attuali metodologie nell’affrontare adeguatamente l'identificazione di sostanze chimiche non genotossiche, la comunità scientifica e normativa ha riconosciuto la necessità di sviluppare il cosiddetto Integrated Approach to Testing and Assessment (IATA). Tale approccio considera tutte le informazioni disponibili, incluse quelle derivanti da dati ambientali ed epidemiologici per analizzare più endpoint cellulari e molecolari correlati agli hallmark del cancro e migliorare la valutazione del potenziale di cancerogenicità di una sostanza. In quest’ottica, si è inserito il presente progetto di tesi, in cui studi di tipo meccanicistico, tra cui quelli in silico, sono stati affiancati da saggi in vitro sulla base di un approccio integrato che è in grado di fornire numerose informazioni utili alla comprensione del processo di cancerogenesi e dei meccanismi sottostanti.
Cadmium (Cd) is a heavy metal that is commonly found in the earth’s crust combined with other elements such as oxygen, chlorine, or sulfur. However, having been released into the environment for decades by anthropogenic activities (Thevenod, 2009), Cd is now considered one of the most common environmental contaminants. In particular, Cd can occur in air, water, soil and subsoil. Workers are mainly exposed to the inhalation of Cd-containing particles. The non-occupational population absorbs low concentration of Cd through cigarette smoking, ingestion of contaminated water and food. Cd was classified by the World Health Organization’s International Agency for Research on Cancer (IARC) as a human carcinogen (Group 1) in 1993. However, the molecular mechanisms underpinning the process of Cd carcinogenicity are still not fully understood. Cd, as a non-genotoxic agent, cannot directly cause DNA mutations. Cd can instead act through the alteration of epigenetic mechanisms and gene expression, the induction of oxidative stress, the inhibition of DNA repair mechanisms and the interaction with proteins involved in cell cycle control, apoptosis and cellular defence system. Otherwise, Cd can interfere with the homeostasis of many essential metals, such as zinc, calcium and iron. Cd is able to displace zinc in the proteins with zinc-finger motifs, impairing their functionality. To better investigate the Cd-induced carcinogenesis, we decided to use the Cell Transformation Assay (CTA), one of the most advanced in vitro tests to screen the carcinogenic potential and to understand the mechanism of action of chemical substances. Indeed, these assays offer several advantages in comparison to the in vivo bioassays in rodents, especially their characteristic to reproduce key stages of in vivo transformation. In this context, the purposes of this thesis work were: i) to investigate the mechanisms by which cadmium induces cellular transformation; ii) to implement one of the most promising in vitro assays to assess the potential of chemical carcinogenesis. We exploited the use of CTA by jointly applying different techniques. We first carried out a transcriptomic analyses to evidence deregulated pathways in C3H10T1/2Cl8 after 24h of Cd treatment or in foci-derived transformed cells. These two conditions have allowed to analyse the early events inducing the malignant phenotype and the features of transformed cells. Consequently, we focused on metabolic rewiring and modifications of mitochondrial structure and function caused by Cd. We applied seahorse methods, spectrophotometric enzymatic and metabolite assays to verify the first hypothesis; to investigate the second theory, we applied the laser scanning confocal fluorescence microscopy, image analysis and flow cytometry technique. In the end, we have compared the transcriptome of two different human cell lines: HepG2 and SHSY5Y. HepG2 is a hepatocellular carcinoma cell line, and SYSH5Y is a neuroblastoma cell line. We studied this comparison to look for genes with common deregulation in both the cell lines. Due to the limits of the current methods in adequately addressing the identification of non-genotoxic chemicals, the scientific and regulatory community has recognised the need to develop the so-called Integrated Approach to Testing and Assessment (IATA) (Corvi et al., 2017). This approach considers all the existing information, including environmental and epidemiological data, traditional and alternative toxicity tests, to analyse multiple endpoints related to cancer hallmarks and to improve the assessment of the carcinogenic potential of a substance. In this perspective, the present thesis project included mechanistic studies and in vitro assays on the basis of an integrated approach which, using multiple sources, is able to provide many useful information for understanding the carcinogenesis process and the underlying mechanisms.

Translation quality assessment remains pertinent in both translation theory and in the industry. Specifically, the process of assessing a target document's quality or a person's translation competence involves a lot of time and money on the part of various governments, organizations and individuals. In response to this issue, this project builds on the ongoing research of Hague et al. (2012), who seek to determine the capabilities of a computerized translation test for the French-to-English and Spanish-to-English language pairs. Specifically, Hague et al. (2012) question whether a good score on a detect-and-correct style computerized translation test that is calculated by a computer also indicates a good score on a traditional full translation test that is calculated by hand. This project seeks to further this research by seeking to answer the same question using an Arabic-to-English language pair. The methods used in this research involve testing individuals using two different style translation tests and then comparing the results. The first style translation test involves a detect-and-correct format where a subject is given a list of project specifications in the form of a translation brief, a source text passage and a corresponding target text passage that has errors introduced throughout. The subject is expected to detect and fix the errors while leaving the rest of the text alone. A score is given for this test using an automated algorithm. The second style test is a traditional translation test where a subject is given the same translation brief and a source text. The subject is expected to produce an acceptable target text, which is subsequently scored by hand. Thereafter, various forms of analysis are used to determine the relationship between the scores of the two types of tests. The results of this research do not strongly suggest that a high score on the detect-and-correct portion of the test indicates a high score on a hand-graded full translation test for the subject population used. However, this research still provides insight, especially concerning whether the detect-and-correct portion of the test actually measures translation competence and concerning second language acquisition (SLA) programs and their intentions. In addition, this research provides insight into logistical issues in testing such as the impact text difficulty and length may have on a detect-and-correct style test as well as the negative impact the American Translators Association (ATA) grading practices of weighting errors and capping errors can have on an experiment such as the one described in this research.

This thesis work is about the Cherenkov Telescope Array (CTA). The Cherenkov Telescope Array is the next generation ground-based observatory for gamma-ray astronomy. It will consist of more than 100 Imaging Air Cherenkov Telescopes. deployed in the northern and southern hemispheres. It will enable to gain a factor of ten in sensitivity compared to current experiments. The content of this thesis consists in an introductory part, in which basic concepts about high energy astrophysics are summarized. Then the principle of operation of ground-based Cherenkov telescopes is then described, along with some details about the hardware and software subsystems. The last part deals with the study of the extragalactic population of blazar type gamma-ray sources that could be detected by an array of four Large-sized Telescopes (LST) deployed in the northern site of CTA.

Orientador : Pedro L.O. Volpe
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Mestrado

Silver nanoparticles (NPs) were synthesized and stabilized by a simple method in aqueous solution, by the reduction of silver nitrate with stannous chloride (SnCl2.2H2O) and cetyl trimethyl ammonium bromide (CTAB)through day light irradiation. Thereby, the silver nanoparticles were colloidally stabilized by CTAB as a surfactant. The synthesis of silver NPs with different size were possible by changing the reaction conditions such as reagent ratio. The silver NPs were characterized by Dynamic Light Scattering (DLS) and UV-visible spectroscopy. A very strong plasmon resonance peak at 400-500 nm in the UV-visible spectra is a clear consequence of the silver NPs production. The synthesized silver NPs showed good stability by using CTAB. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20633

Band Gap Reference circuits are integral part of Analog Integrated Circuits. Their function is to provide a constant reference voltage independent of temperature and supply variations. Two major building blocks of band gap reference circuits are CTAT (Complementary to absolute temperature) and PTAT (Proportional to absolute temperature). The important characteristics of CTAT circuits is the inverse relationship of their output voltage with temperature while the PTAT circuits have proportional dependence. By combining the circuits exhibiting the CTAT and PTAT nature, a constant dependence of voltage on temperature can be achieved which can be used as reference voltage for other analog circuits. Design of CTAT and PTAT circuits and their simulation using the Cadence Design Systems Software have been presented in this dissertation.

In this thesis, we have tried to explain the regular and irregular(chaotic) dynamics of worm like micellar solutions on applying shear, through a detailed study of the equation of motion of a nematic order parameter tensor coupled to a hydrodynamic velocity field. We have assumed spatial variations only along one direction i.e. the gradient direction(1D model). The resulting phase diagram shows various interesting steady states or phases such as spatiotemporal chaos, temporal and spatiotemporal periodicities, and alignment of the director axis along the imposed flow field. The coupling of the orientational degrees of freedom of the order parameter with the hydrodynamic flow field holds the key to the appearance of dynamic shear bands in the system. We have solved numerically a set of coupled nonlinear equations to obtain the order parameter stress developed in the system; the magnitude of the order parameter tensor, the biaxiality parameter and the orientation of the director axis of the nemato gens under shear have also been studied in detail. To study the phase diagram obtained by time integration of the equation of motion mathematically, a stability analysis of the fixed point of motion for various parameter values has been performed so that the location of the chaotic-to-aligned phase boundary is verified. Also in the periodic region of the phase diagram, the stability of limit cycles is tested by analysing the fixed point of the corresponding Poincare map. Stability analysis of the periodic orbits leads to the observation that in the parameter space, there are regions of phase coexistence where chaotic or spatiotemporally intermittent behaviour coexists with periodic behaviour. When corrections in the imposed velocity field due to the order parameter stress were taken into account and the order parameter response was looked into at several points in the parameter space, the modified equations of motion were found to reproduce the earlier behaviour in all the different regimes if the value of a dimensionless viscosity parameter is taken to be such that the bare viscous stress overrides the order parameter stress. The phase boundaries are however different from the ones seen in the earlier model. However, for a choice of the viscosity parameter such that the order parameter stress and the bare viscous stress are comparable, we see two distinctly different attractors: a banded, periodic one that is common to both α1equalto 0, and not equal to 0 and a banded chaotic one for α1not equal to 0. Here, α1is a parameter that governs the nonlinearity in the stretching of the order parameter tensor along the direction of the applied shear. Quantitative analysis of the various chaotic attractors throws up not only positive Lyapunov exponents but also that the banded chaos is a “flip-flop” kind of chaos where the switching between two long-lived states of high and lows hear stress is chaotic, where as the behaviour in either of the two states is periodic, with either a single, isolated frequency or a bunch of harmonics. Also, the spatial correlation of the shear stress in the chaotic attractors is of much larger range than the temporal correlation, the latter being almost delta-function-like. On increasing the temperature of the system till it is above the isotropic–nematic transition temperature in the absence of shear, we find that under shear, similar attractors as those in the nematic case are observed, both for passive advection and for the full 1D hydrodynamics. This is an encouraging result since actual experiments are performed at a temperature for which the system is in the isotropic phase in the absence of shear. Thus for the 1D system, the parameter space has been explored quite extensively. Considering spatial variations only along the gradient axis of the system under shear is not enough since experiments have observed interesting behaviour in the vorticity plane in which Taylor velocity rolls were noted. Hence taking the system to 2D was necessary. Our numerical study of the 2D system under shear is incomplete because we came across computational difficulties. However, on shorter time scales we have seen a two-banded state with an oscillating interface and Taylor velocity rolls as well. The methodology used for the 2D study can also be used to reproduce the 1D results by the simple step of taking initial condition with no variation in the vorticity direction. This automatically ensures that no variation in the vorticity direction ever builds up because the equations of motion ensure that these variations in the system do not grow by themselves unless fed in at the start. Using this method, we were able to reproduce all the attractors found in the 1D calculation. Thus the 1D attractors have been observed using two different methods of calculation. Further work on the full 2D numerics needs to be done because we believe that spatiotemporally complex steady-state attractor s exist in the 2D system also for appropriate values of the parameters.

In this thesis, we have tried to explain the regular and irregular(chaotic) dynamics of worm like micellar solutions on applying shear, through a detailed study of the equation of motion of a nematic order parameter tensor coupled to a hydrodynamic velocity field. We have assumed spatial variations only along one direction i.e. the gradient direction(1D model). The resulting phase diagram shows various interesting steady states or phases such as spatiotemporal chaos, temporal and spatiotemporal periodicities, and alignment of the director axis along the imposed flow field. The coupling of the orientational degrees of freedom of the order parameter with the hydrodynamic flow field holds the key to the appearance of dynamic shear bands in the system. We have solved numerically a set of coupled nonlinear equations to obtain the order parameter stress developed in the system; the magnitude of the order parameter tensor, the biaxiality parameter and the orientation of the director axis of the nemato gens under shear have also been studied in detail. To study the phase diagram obtained by time integration of the equation of motion mathematically, a stability analysis of the fixed point of motion for various parameter values has been performed so that the location of the chaotic-to-aligned phase boundary is verified. Also in the periodic region of the phase diagram, the stability of limit cycles is tested by analysing the fixed point of the corresponding Poincare map. Stability analysis of the periodic orbits leads to the observation that in the parameter space, there are regions of phase coexistence where chaotic or spatiotemporally intermittent behaviour coexists with periodic behaviour. When corrections in the imposed velocity field due to the order parameter stress were taken into account and the order parameter response was looked into at several points in the parameter space, the modified equations of motion were found to reproduce the earlier behaviour in all the different regimes if the value of a dimensionless viscosity parameter is taken to be such that the bare viscous stress overrides the order parameter stress. The phase boundaries are however different from the ones seen in the earlier model. However, for a choice of the viscosity parameter such that the order parameter stress and the bare viscous stress are comparable, we see two distinctly different attractors: a banded, periodic one that is common to both α1equalto 0, and not equal to 0 and a banded chaotic one for α1not equal to 0. Here, α1is a parameter that governs the nonlinearity in the stretching of the order parameter tensor along the direction of the applied shear. Quantitative analysis of the various chaotic attractors throws up not only positive Lyapunov exponents but also that the banded chaos is a “flip-flop” kind of chaos where the switching between two long-lived states of high and lows hear stress is chaotic, where as the behaviour in either of the two states is periodic, with either a single, isolated frequency or a bunch of harmonics. Also, the spatial correlation of the shear stress in the chaotic attractors is of much larger range than the temporal correlation, the latter being almost delta-function-like. On increasing the temperature of the system till it is above the isotropic–nematic transition temperature in the absence of shear, we find that under shear, similar attractors as those in the nematic case are observed, both for passive advection and for the full 1D hydrodynamics. This is an encouraging result since actual experiments are performed at a temperature for which the system is in the isotropic phase in the absence of shear. Thus for the 1D system, the parameter space has been explored quite extensively. Considering spatial variations only along the gradient axis of the system under shear is not enough since experiments have observed interesting behaviour in the vorticity plane in which Taylor velocity rolls were noted. Hence taking the system to 2D was necessary. Our numerical study of the 2D system under shear is incomplete because we came across computational difficulties. However, on shorter time scales we have seen a two-banded state with an oscillating interface and Taylor velocity rolls as well. The methodology used for the 2D study can also be used to reproduce the 1D results by the simple step of taking initial condition with no variation in the vorticity direction. This automatically ensures that no variation in the vorticity direction ever builds up because the equations of motion ensure that these variations in the system do not grow by themselves unless fed in at the start. Using this method, we were able to reproduce all the attractors found in the 1D calculation. Thus the 1D attractors have been observed using two different methods of calculation. Further work on the full 2D numerics needs to be done because we believe that spatiotemporally complex steady-state attractor s exist in the 2D system also for appropriate values of the parameters.

Soft condensed matter (SCM) systems are ubiquitous in nature. SCM systems contain mesoscopic structures in the size range 10 nm to 1 am that are held together by weak entropic forces. These materials are therefore easily perturbed by external fields such as shear, gravity and electric and magnetic fields and are novel systems for studying non-equilibrium phenomena. The elastic constants of these materials are ≈ 109 times smaller than conventional atomic fluids and hence it is possible to measure the viscoelastic response of these materials using commercial instruments such as rheometers. The relaxation time in SCM systems are of the order of milliseconds as compared to atomic systems where relaxation times are of the order of picoseconds. It is easy to study the effect of shear on SCM, as the shear rates attainable by commercial rheometers are of the order of the inverse of their relaxation times. The dynamics of SCM systems and their local rheological properties obtained using the method of probe diffusion can be quantified through dynamic light scattering experiments. The structure of SCM systems can be quantified using diffraction techniques such as small angle x-ray scattering. In this thesis we report experimental studies on the linear and nonlinear rheology and the dynamics of surfactant cetyltrimethylammonium tosylate (CTAT), which forms cylindrical wormlike micelles, studied using bulk rheology and dynamic light scattering (DLS) technique, respectively. We have also studied the phase behaviour of the ternary system formed by cetyltrimethylammonium 3-hydroxy-napthalene 2-carboxylate (CTAHN), sodium bromide (NaBr) and water using small angle x-ray scattering (SAXS). In Chapter 1, we discuss why SCM systems are suitable for studying non-equilibrium phenomena such as the effect of shear on the structure and dynamics of condensed matter. This is followed by a discussion on the chemical structure, phase behaviour and self assembling properties of the amphiphilic molecules in water. We then discuss the intermacromolecular forces such as van der Waals interaction, the screened Coulomb repulsion and hydrophobic and hydration forces. The systems that have been the subject of our experimental studies, viz. CTAT and CTAHN/NaBr/water have also been discussed in detail. This is followed by a theoretical background of linear and nonlinear rheology, dynamic light scattering and small angle x-ray scattering techniques. Next we describe the stress relaxation mechanisms in wormlike micelles. This is followed by a discussion on some standard techniques of nonlinear time series analysis, in particular the evaluation of the delay time L, the embedding dimension m, the correlation dimension ν and the Lyapunov exponent λ. We have also mentioned a few examples of experimental systems where chaos has been observed. We have also discussed in detail the various routes to chaos namely, the period-doubling route, the quasiperiodic route and the intermittency route. The concluding part of this chapter summarises the main results of the thesis. Chapter 2 discusses the experimental apparatus used in our studies. We have discussed the different components of the MCR-300 stress-controlled rheometer (Paar Physica, Germany). The rheo-small angle light scattering experiments and the direct visualisation experiments done using a home-made shear cell are also discussed. Next we describe the various experiments that can be done using a commercial rheometer. The frequency response and flow experiments have been discussed with some examples from our own work on entangled, cylindrical micelles. This is followed by a discussion on the various components of our dynamic light scattering (DLS) setup (Brookhaven Instruments, USA). Particle sizing of submicrometer colloidal spheres using our DLS setup has been discussed with an example of an angle-resolved DLS study of 0.05µm polystyrene colloids. Next we describe the various components of the SAXS setup (Hecus M. Braun, Austria). As an example application of SAXS we have quantified the structure of the lamellar phase formed by the surfactant CTAHN/water. We finally describe the sample preparation methods employed by us for the different experiments. Our nonlinear rheology experiments on viscoelastic gels of surfactant CTAT (cCT AT= 2wt%) in the presence of salt sodium chloride (NaCl) at various concentrations has been discussed in Chapter 3. We observe a plateau in the measured flow curve and this is attributed to a mechanical instability of the shear banding type. The slope of this plateau can be tuned by the addition of salt NaCl. This slope is due to a concentration difference between the shear bands arising from a Helfand-Fredrickson mechanism. This is confirmed by the presence of a “Butterfly” light scattering pattern in SALS experiments performed simultaneously with rheological measurements. We have carried out experiments at six different salt concentrations 10mM < cN aCl<1M, which yield plateau slopes (α) ranging from 0.07 < α < 0.4. We find that a minimum slope of 0.12, corresponding to a salt concentration of 25mM NaCl, is essential to see a “Butterfly” pattern indicating the onset of flow-concentration coupling at this α value. After this we turn our attention to stress/shear rate relaxation experiments. The remainder of this chapter is split in four parts. We show in Part-I that the routes to rheochaos in stress relaxation experiments is via Type-II intermittency. Interestingly in shear rate relaxation, the route is via Type-III intermittency. We also show that flow-concentration coupling is essential to see the route to rheochaos. This section also brings out the crucial role played by orientational ordering of the nematics during rheochaos using SALS measurements performed simultaneously with rheological measurements. In part-II, we study the spatio-temporal dynamics of the shear induced band en route to rheochaos. Our direct visualisation experiments show that the complex dynamics observed in stress/shear rate relaxation measurements during the route to rheochaos is a manifestation of the spatio-temporal dynamics of the high shear band. In part-III, we describe the results of our stress/shear rate relaxation measurements at a fixed shear rate/stress with temperature as the control parameter and thereby control the micellar length. We see the Type-II intermittency route to rheochaos in stress relaxation measurements and the Type-III intermittency route to rheochaos in shear rate relaxation measurements. We conclude this section by showing the results of linear rheology measurements carried out at different temperatures. We estimate the mean micellar length ¯L, reptation time τrepand the breaking time τbreak. We show that L¯ increases by ≈ 58%, as the sample goes through the route to rheochaos. In Part-I of this chapter we had only qualitatively discussed the correlations between the measured time series of stress and the VH scattered intensity during the Type-II intermittency route to rheochaos. In part-IV we have attempted to quantify the correlations between the two time series using the technique of linear and nonlinear Granger causality. We have also studied the phase space dynamics of the two time series using the technique of Cross Recurrence Plots. We show that there exists a causal feedback mechanism between the stress and the VH intensity with the latter having a stronger causal effect. We have also shown that the bivariate time series share similar phase space dynamics using the method of Cross Recurrence Plots. In chapter 4, we have studied the dynamics of wormlike micellar gels of surfactant CTAT using the DLS technique. We report an interesting result in the dynamics of these systems: concentration fluctuations in semidilute wormlike-micelle solutions of the cationic surfactant Cetyltrimethylammonium Tosylate (CTAT) at wavenumber q have a mean decay rate α qz, with z -̃1.8, for a wide range of surfactant concentrations just above the overlap value c∗. The process we are seeing is thus superdiffusive, like a L´evy flight, relaxing on a length scale L in a time of order less than L2 . The rheological behaviour of this system is highly non-Maxwellian and indicates that the micelle-recombination kinetics is diffusion-controlled (DC) (micelles recombine with their original partners). With added salt (100mM NaCl) the rheometric behaviour turns Maxwellian, indicating a crossover to a mean-field (MF) regime (micelles can recombine with any other micellar end). The concentration fluctuations, correspondingly, show normal diffusive behaviour. The stress relaxation time, moreover is about twenty times slower without salt than with 100mM NaCl. Towards the end of this chapter, we propose an explanation of these observations based on the idea that stress due to long-lived orientational order enhances concentration fluctuations in DC regime. In the previous chapter we had studied the dynamics of wormlike micellar gels of pure CTAT 2wt% and found superdiffusive relaxation of concentration fluctuations due to a nonlinear coupling of long-lived stress and orientational fluctuations to the con- centration. In chapter 5 we present results from dynamic light scattering experiments to quantify the diffusive motion of polystyrene (PS) colloids in the same system. This chapter is split in two parts. In Part-I, we discuss dynamics of PS particles of radius 115 nm and 60 nm in CTAT 2wt%. The radius of the colloidal spheres is comparable to the mesh size ξ = 80 nm of the wormlike micellar network and hence we are probing the network dynamics. We find that ∆r2(t) is wavevector independent at small and large lag times. However at intermediate times, we find an anomalous wavevector dependence which we believe arises from the rapid restructuring of the gel network. This anomalous wavevector dependence of ∆r2(t) disappears as the temperature is increased. In Part-II we discuss the dynamics of PS particles of radius 25 nm and 10 nm, smaller than ξ, in CTAT 1wt% & 2wt%. We once again find an anomalous wavevector dependence of ∆r2(t) at intermediate times for the 2wt% sample. Surprisingly, at large times the particle motion is not diffusive, rather ∆r2(t) saturates. We do not have a clear understanding of this as yet. Also for the 10 nm particle, the motion at small lag times is superdiffusive. The motion of these particles is probably influenced by the superdiffusion of concentration fluctuations observed in pure CTAT 2wt% system (chapter 4). In chapter 6, we report the observation of an intermediate mesh phase with rhom- bohedral symmetry, corresponding to the space group R¯3m, in the ternary system consisting of CTAHN/NaBr/water. It occurs at lower temperatures between a random mesh phase (LDα ) and a lamellar phase (Lα) on increasing the surfactant concentration φs. The micellar aggregates, both in the intermediate and random mesh phases, are found to be made up of a two-dimensional network of rod-like segments, with three rods meeting at each node. SAXS studies also show the presence of small angle peaks corresponding to ad−spacing of 25 nm. Freeze fracture electron microscopy results shows that this peak may correspond to the presence of nodule like structures with no long-range correlations. The thesis concludes with a summary of main results and a brief discussion of the scope for future work in Chapter 7.

Soft condensed matter (SCM) systems are ubiquitous in nature. SCM systems contain mesoscopic structures in the size range 10 nm to 1 am that are held together by weak entropic forces. These materials are therefore easily perturbed by external fields such as shear, gravity and electric and magnetic fields and are novel systems for studying non-equilibrium phenomena. The elastic constants of these materials are ≈ 109 times smaller than conventional atomic fluids and hence it is possible to measure the viscoelastic response of these materials using commercial instruments such as rheometers. The relaxation time in SCM systems are of the order of milliseconds as compared to atomic systems where relaxation times are of the order of picoseconds. It is easy to study the effect of shear on SCM, as the shear rates attainable by commercial rheometers are of the order of the inverse of their relaxation times. The dynamics of SCM systems and their local rheological properties obtained using the method of probe diffusion can be quantified through dynamic light scattering experiments. The structure of SCM systems can be quantified using diffraction techniques such as small angle x-ray scattering. In this thesis we report experimental studies on the linear and nonlinear rheology and the dynamics of surfactant cetyltrimethylammonium tosylate (CTAT), which forms cylindrical wormlike micelles, studied using bulk rheology and dynamic light scattering (DLS) technique, respectively. We have also studied the phase behaviour of the ternary system formed by cetyltrimethylammonium 3-hydroxy-napthalene 2-carboxylate (CTAHN), sodium bromide (NaBr) and water using small angle x-ray scattering (SAXS). In Chapter 1, we discuss why SCM systems are suitable for studying non-equilibrium phenomena such as the effect of shear on the structure and dynamics of condensed matter. This is followed by a discussion on the chemical structure, phase behaviour and self assembling properties of the amphiphilic molecules in water. We then discuss the intermacromolecular forces such as van der Waals interaction, the screened Coulomb repulsion and hydrophobic and hydration forces. The systems that have been the subject of our experimental studies, viz. CTAT and CTAHN/NaBr/water have also been discussed in detail. This is followed by a theoretical background of linear and nonlinear rheology, dynamic light scattering and small angle x-ray scattering techniques. Next we describe the stress relaxation mechanisms in wormlike micelles. This is followed by a discussion on some standard techniques of nonlinear time series analysis, in particular the evaluation of the delay time L, the embedding dimension m, the correlation dimension ν and the Lyapunov exponent λ. We have also mentioned a few examples of experimental systems where chaos has been observed. We have also discussed in detail the various routes to chaos namely, the period-doubling route, the quasiperiodic route and the intermittency route. The concluding part of this chapter summarises the main results of the thesis. Chapter 2 discusses the experimental apparatus used in our studies. We have discussed the different components of the MCR-300 stress-controlled rheometer (Paar Physica, Germany). The rheo-small angle light scattering experiments and the direct visualisation experiments done using a home-made shear cell are also discussed. Next we describe the various experiments that can be done using a commercial rheometer. The frequency response and flow experiments have been discussed with some examples from our own work on entangled, cylindrical micelles. This is followed by a discussion on the various components of our dynamic light scattering (DLS) setup (Brookhaven Instruments, USA). Particle sizing of submicrometer colloidal spheres using our DLS setup has been discussed with an example of an angle-resolved DLS study of 0.05µm polystyrene colloids. Next we describe the various components of the SAXS setup (Hecus M. Braun, Austria). As an example application of SAXS we have quantified the structure of the lamellar phase formed by the surfactant CTAHN/water. We finally describe the sample preparation methods employed by us for the different experiments. Our nonlinear rheology experiments on viscoelastic gels of surfactant CTAT (cCT AT= 2wt%) in the presence of salt sodium chloride (NaCl) at various concentrations has been discussed in Chapter 3. We observe a plateau in the measured flow curve and this is attributed to a mechanical instability of the shear banding type. The slope of this plateau can be tuned by the addition of salt NaCl. This slope is due to a concentration difference between the shear bands arising from a Helfand-Fredrickson mechanism. This is confirmed by the presence of a “Butterfly” light scattering pattern in SALS experiments performed simultaneously with rheological measurements. We have carried out experiments at six different salt concentrations 10mM < cN aCl<1M, which yield plateau slopes (α) ranging from 0.07 < α < 0.4. We find that a minimum slope of 0.12, corresponding to a salt concentration of 25mM NaCl, is essential to see a “Butterfly” pattern indicating the onset of flow-concentration coupling at this α value. After this we turn our attention to stress/shear rate relaxation experiments. The remainder of this chapter is split in four parts. We show in Part-I that the routes to rheochaos in stress relaxation experiments is via Type-II intermittency. Interestingly in shear rate relaxation, the route is via Type-III intermittency. We also show that flow-concentration coupling is essential to see the route to rheochaos. This section also brings out the crucial role played by orientational ordering of the nematics during rheochaos using SALS measurements performed simultaneously with rheological measurements. In part-II, we study the spatio-temporal dynamics of the shear induced band en route to rheochaos. Our direct visualisation experiments show that the complex dynamics observed in stress/shear rate relaxation measurements during the route to rheochaos is a manifestation of the spatio-temporal dynamics of the high shear band. In part-III, we describe the results of our stress/shear rate relaxation measurements at a fixed shear rate/stress with temperature as the control parameter and thereby control the micellar length. We see the Type-II intermittency route to rheochaos in stress relaxation measurements and the Type-III intermittency route to rheochaos in shear rate relaxation measurements. We conclude this section by showing the results of linear rheology measurements carried out at different temperatures. We estimate the mean micellar length ¯L, reptation time τrepand the breaking time τbreak. We show that L¯ increases by ≈ 58%, as the sample goes through the route to rheochaos. In Part-I of this chapter we had only qualitatively discussed the correlations between the measured time series of stress and the VH scattered intensity during the Type-II intermittency route to rheochaos. In part-IV we have attempted to quantify the correlations between the two time series using the technique of linear and nonlinear Granger causality. We have also studied the phase space dynamics of the two time series using the technique of Cross Recurrence Plots. We show that there exists a causal feedback mechanism between the stress and the VH intensity with the latter having a stronger causal effect. We have also shown that the bivariate time series share similar phase space dynamics using the method of Cross Recurrence Plots. In chapter 4, we have studied the dynamics of wormlike micellar gels of surfactant CTAT using the DLS technique. We report an interesting result in the dynamics of these systems: concentration fluctuations in semidilute wormlike-micelle solutions of the cationic surfactant Cetyltrimethylammonium Tosylate (CTAT) at wavenumber q have a mean decay rate α qz, with z -̃1.8, for a wide range of surfactant concentrations just above the overlap value c∗. The process we are seeing is thus superdiffusive, like a L´evy flight, relaxing on a length scale L in a time of order less than L2 . The rheological behaviour of this system is highly non-Maxwellian and indicates that the micelle-recombination kinetics is diffusion-controlled (DC) (micelles recombine with their original partners). With added salt (100mM NaCl) the rheometric behaviour turns Maxwellian, indicating a crossover to a mean-field (MF) regime (micelles can recombine with any other micellar end). The concentration fluctuations, correspondingly, show normal diffusive behaviour. The stress relaxation time, moreover is about twenty times slower without salt than with 100mM NaCl. Towards the end of this chapter, we propose an explanation of these observations based on the idea that stress due to long-lived orientational order enhances concentration fluctuations in DC regime. In the previous chapter we had studied the dynamics of wormlike micellar gels of pure CTAT 2wt% and found superdiffusive relaxation of concentration fluctuations due to a nonlinear coupling of long-lived stress and orientational fluctuations to the con- centration. In chapter 5 we present results from dynamic light scattering experiments to quantify the diffusive motion of polystyrene (PS) colloids in the same system. This chapter is split in two parts. In Part-I, we discuss dynamics of PS particles of radius 115 nm and 60 nm in CTAT 2wt%. The radius of the colloidal spheres is comparable to the mesh size ξ = 80 nm of the wormlike micellar network and hence we are probing the network dynamics. We find that ∆r2(t) is wavevector independent at small and large lag times. However at intermediate times, we find an anomalous wavevector dependence which we believe arises from the rapid restructuring of the gel network. This anomalous wavevector dependence of ∆r2(t) disappears as the temperature is increased. In Part-II we discuss the dynamics of PS particles of radius 25 nm and 10 nm, smaller than ξ, in CTAT 1wt% & 2wt%. We once again find an anomalous wavevector dependence of ∆r2(t) at intermediate times for the 2wt% sample. Surprisingly, at large times the particle motion is not diffusive, rather ∆r2(t) saturates. We do not have a clear understanding of this as yet. Also for the 10 nm particle, the motion at small lag times is superdiffusive. The motion of these particles is probably influenced by the superdiffusion of concentration fluctuations observed in pure CTAT 2wt% system (chapter 4). In chapter 6, we report the observation of an intermediate mesh phase with rhom- bohedral symmetry, corresponding to the space group R¯3m, in the ternary system consisting of CTAHN/NaBr/water. It occurs at lower temperatures between a random mesh phase (LDα ) and a lamellar phase (Lα) on increasing the surfactant concentration φs. The micellar aggregates, both in the intermediate and random mesh phases, are found to be made up of a two-dimensional network of rod-like segments, with three rods meeting at each node. SAXS studies also show the presence of small angle peaks corresponding to ad−spacing of 25 nm. Freeze fracture electron microscopy results shows that this peak may correspond to the presence of nodule like structures with no long-range correlations. The thesis concludes with a summary of main results and a brief discussion of the scope for future work in Chapter 7.

Nano-sized gold particles are generated by exploiting the laser ablation synthesis in solution technique (LASiS) from gold metal disc. We report on the kinetics of gold nanoparticle (AuNP) production during LASiS and the resulting size distributions. Studies were conducted as a function of laser irradiation in pure water samples, with anionic surfactants, sodium dodecylsulphate (SDS), and cationic surfactants, cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC), in water. Our investigations provide a mechanistic insight into the laser-induced formation kinetics involved in AuNP production via 1064 nm laser irradiation in aqueous solution. This has been achieved by developing a kinetic model involving three different AuNP size regimes. Specifically, we have found that there is no apparent influence of the SDS concentration around the surfactant critical micelle concentration (CMC) on particle size during AuNP production. This is in contrast to results observed for size reduction via 532-nm irradiation where a clear CMC effect has previously been observed. [Yamada et al, J. Phys. Chem. B, 2006, 110, 11751-11756] In addition, we also explore the surface oxidation states of produced AuNPs in various surfactants using X-ray photoelectron spectroscopy (XPS). Our investigations shows the Au¹¹¹ chemical oxidation state was present in produced AuNPs in high concentrations of CTAB and CTAC, but absent in those produced in pure water and SDS solution. Prior to XPS investigations on the LASiS prepared AuNPs, a study to observe the behavior of gold during irradiation of X-rays was performed. We report on the time evolution of the Au oxidation state in sodium tetrachloroaurate NaAuCl₄ as a function of soft X-ray exposure time. Our investigations provide mechanistic insight into the photoreduction kinetics from Au¹¹¹ to Au¹ and then subsequently Au¹ to Au⁰.We unambiguously show that XPS photoreduction occurs in stepwise fashion via the Au¹ state.
Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2012