Le systeme bidimensionnel etudié dans cette thèse est un film de Langmuir, film constitué d'une unique couche de molécules amphiphiles à l'interface eau-air. Une transition du premier ordre, observée dans une monocouche d'acide NBD-stéarique révèle la coexistence entre une phase cristalline et une phase liquide. Les domaines monocristallins se présentent sous la forme de longs bâtonnets, parfaitement adaptés aux études mécaniques. Nous étudions certaines propriétés de ce cristal bidimensionnel. La première étude concerne la rupture de ce solide bidimensionnel. Un cristal maintenu fléchi dans le plan de l'eau se rompt après une durée bien déterminée. Cette durée s'est avérée être fonction de la déformation appliquée au cristal. A fortescontraintes, on second mode de rupture coexiste : un certains nombre de cristaux cassent intantanément tandis que d'autres présentent une rupture différée. La seconde étude s'intéresse à la fusion des cristaux en équilibre avec leur phase liquide. La fusion peut être provoquée par trois processus distincts : deux processus thermodynamiques (réchauffement et décompression) et un processus photochimique. Ce dernier s'est avéré dû à une réaction photochimique réversible avec l'oxygène de l'air, conduisant a l'abaissement du point de fusion du cristal. Les trois processus de fusion conduisent à des observations similaires, indiquant ainsi l'existence d'un mécanisme commun dans l'initiation de la fusion. Les observation montrent que l'intérieur du crystal fond bien avant ses bords. De plus, la fusion d'un cristal maintenu déformé a lieu le long d'une ligne ou la contrainte s'annule. Nous suggérons que le mécanisme responsable de ce phénomène est la migration de défauts, probablement des dislocations, à l'endoit du cristal non déformé.; Ces défauts jouant le rôle de centres de nucléation de la fusion. Ces résultats montrent le rôle primordial des défauts dans la fusion à deux dimension.

The paper describes how a two-dimensional absolute measuring system can explicitly be realized. The theoretical background, the experimental setup, the evaluation algorithm, and the results of measurement are discussed in detail.

Orientador: Marinônio Lopes Cornélio / Banca: Antônio José da Costa Filho / Banca: André Luiz Galo / Resumo: Esse trabalho tem por objetivo estudar as transições conformacionais, induzidas termicamente, na Ribonuclease A. Esta abordagem foi realizada aplicando!se a técnica de calorimetria diferencial de varredura (DSC) e infravermelho médio com transformada de Fourier (FTIR), associando a técnica de análise de correlação bidimensional (2D! COS), variável!variável (VV) e sample sample (SS). A partir dos dados de DSC determinamos a variação de entalpia do sistema (∆Hcal) que foi de 587 kJ/mol. Também identificamos as temperaturas de pré (36, 39, 43, 49 e 59°C), pós transição (71°C) e temperatura de melting (65°C), além da determinação do ∆Hcal para cada uma das transições. A análise de correlação bidimensional sample!sample (SS) também foi capaz de identificar as mesmas temperaturas encontradas por DSC. Por sua vez, a análise de correlação bidimensional variável!variável (VV) descreveu a evolução conformacional das estruturas secundárias da proteína durante o desenovelamento térmico / Abstract: This work aims to study the thermally!induced conformational transitions in Ribonuclease A. This approach was performed by applying the technique of differential scanning calorimetry (DSC) and medium infrared Fourier transform spectroscopy (FTIR), linking the technique of correlation analysis (2D!COS), variable!variable (VV) and sample !sample (SS). From DSC data determine the enthalpy change of the system (SHcal) which was 587 kJ / mol. We identified the pre temperatures (36, 39, 43, 49 and 59 ° C), post transition (71 ° C) and melting temperature (65 ° C), besides determination of SHcal for each transition. The two!dimensional correlation analysis sample! sample (SS) was also able to identify the same temperatures found by DSC. In turn, the two!dimensional correlation analysis of variable!variable (VV) described the conformation evolution of the protein secondary structures during thermal unfolding / Mestre

Made available in DSpace on 2014-06-11T19:22:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-05-27Bitstream added on 2014-06-13T20:29:19Z : No. of bitstreams: 1 martins_db_me_sjrp.pdf: 1774906 bytes, checksum: cae913e873e102a5cfd5c4dddccc9e4d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esse trabalho tem por objetivo estudar as transições conformacionais, induzidas termicamente, na Ribonuclease A. Esta abordagem foi realizada aplicando!se a técnica de calorimetria diferencial de varredura (DSC) e infravermelho médio com transformada de Fourier (FTIR), associando a técnica de análise de correlação bidimensional (2D! COS), variável!variável (VV) e sample sample (SS). A partir dos dados de DSC determinamos a variação de entalpia do sistema (∆Hcal) que foi de 587 kJ/mol. Também identificamos as temperaturas de pré (36, 39, 43, 49 e 59°C), pós transição (71°C) e temperatura de melting (65°C), além da determinação do ∆Hcal para cada uma das transições. A análise de correlação bidimensional sample!sample (SS) também foi capaz de identificar as mesmas temperaturas encontradas por DSC. Por sua vez, a análise de correlação bidimensional variável!variável (VV) descreveu a evolução conformacional das estruturas secundárias da proteína durante o desenovelamento térmico / This work aims to study the thermally!induced conformational transitions in Ribonuclease A. This approach was performed by applying the technique of differential scanning calorimetry (DSC) and medium infrared Fourier transform spectroscopy (FTIR), linking the technique of correlation analysis (2D!COS), variable!variable (VV) and sample !sample (SS). From DSC data determine the enthalpy change of the system (SHcal) which was 587 kJ / mol. We identified the pre temperatures (36, 39, 43, 49 and 59 ° C), post transition (71 ° C) and melting temperature (65 ° C), besides determination of SHcal for each transition. The two!dimensional correlation analysis sample! sample (SS) was also able to identify the same temperatures found by DSC. In turn, the two!dimensional correlation analysis of variable!variable (VV) described the conformation evolution of the protein secondary structures during thermal unfolding

Estimativas nacionais e internacionais indicam que a síndrome coronariana aguda é uma das principais causas de internação hospitalar e óbito. A maioria desses pacientes tem diagnóstico de síndrome coronariana aguda sem supradesnivelamento do segmento ST (SCASSSST) e possui amplo espectro de gravidade, que varia de acordo com características clínicas e laboratoriais. A estratificação de risco é essencial para auxiliar na decisão clínica, discriminando quais pacientes se beneficiam de estratégias mais agressivas. Os escores TIMI e GRACE são os mais utilizados e com valor prognóstico estabelecido por estudos de coorte prospectiva. O strain longitudinal bidimensional (S2DL) permite a quantificação da deformidade miocárdica por meio do rastreamento de \"marcas acústicas\" naturais do músculo cardíaco pelo ultrassom, apresentando valores reduzidos na presença de isquemia miocárdica. O objetivo principal desse trabalho foi identificar, por meio do S2DL do ventrículo esquerdo, quais pacientes com SCASSSST apresentam estenose coronariana maior ou igual a 70%. Os objetivos secundários foram: 1) Identificar a porcentagem de pacientes categorizados como de baixo risco e moderado risco, segundo os escores TIMI e GRACE, que apresentaram estenose coronária maior ou igual a 70%; 2) Determinar um valor de corte do S2DL e número mínimo de segmentos adjacentes acometidos que se correlacionem com o território irrigado pela coronária comprometida (com estenose maior ou igual a 70%) nos pacientes portadores de SCASSSST. Total de 100 pacientes com Idade de 60±11,4, 62% do sexo masculino e predomínio de pacientes (p) de baixo e moderado risco cardiovascular (80% pelo escore TIMI e 99% pelo escore GRACE). Divididos em grupo A (34p) com estenose coronária < 70% e grupo B (66p) com estenose coronária >=70%. Os escores clínicos foram maiores no grupo B (TIMI 3,59±1,4; p=0,008 e GRACE 88,7±24,18; p=0,040). O strain longitudinal global (SLG) permitiu identificar os pacientes com estenose coronária >=70% (AUC=0,72, sensibilidade=50%, especificidade=90%, valor preditivo positivo= 75,1% e valor preditivo negativo=74,9%). No grupo B, 72,8% e 98,5% foram categorizados como de baixo e moderado risco pelos escores TIMI e GRACE, respectivamente. O strain longitudinal segmentar (SLS) permitiu identificar a coronária culpada pelo evento isquêmico, com valor de cut-off e número mínimo de segmentos estimados em: -14 e 4 segmentos para coronária descendente anterior, -16 e 3 segmentos para a coronária circunflexa e coronária direita. Concluímos que o SLG mostrou ser acurado em discriminar pacientes com estenose coronária grave, mesmo naqueles com escore de risco baixo e moderado pelos escores TIMI e GRACE. O SLS permite estimar a área de miocárdio isquêmico por meio do número de segmentos com deformidade alterada, e conhecer a coronária culpada mais provável. / National and international estimates indicate that acute coronary syndrome is one of the major causes of hospitalization and death. Most of these patients have a diagnosis of non-ST-elevation acute coronary syndrome (NSTE-ACS) and have wide spectrum of severity. Risk stratification is essential to assist in clinical decision. The TIMI and GRACE risk scores are the most used and the prognostic values were established by prospective cohort study. Myocardial strain by speckle tracking is a technique based on widely available two-dimensional grayscale echocardiography, enabling the accurate evaluation of global and regional myocardial function, and it is has been shown to be sensitive to abnormalities caused by ischemia. The main objective of this study was to identify, through global longitudinal strain, whose patients (p) with NSTE-ACS had >= 70 % coronary stenosis. The secondary objectives were: 1) Identify the percentage of p categorized as low or moderate risk according to the TIMI and GRACE risk scores , who showed coronary stenosis >= 70 % ; 2) Determine a cutoff value of regional strain and the minimum number of segments allowing the identification of the culprit coronary artery in p with NSTE-ACS. Hundred (p) with diagnosis NSTE-ACS were stratified according to TIMI and GRACE risk scores, and all p underwent coronary angiography. Global longitudinal strain (GLS) and territorial strain (TS) were calculated. Age 60 ± 11.4, 62% male. Majority were low and moderate cardiovascular risk (TIMI score by 80 % and 99 % by the GRACE score). They were divided into group A (34p) with coronary stenosis < 70 % and group B (66p) with coronary stenosis >= 70 %. Clinical scores were higher in group B (TIMI 3.59 ± 1.4, p = 0.008 and 88.7 ± GRACE 24.18, p = 0.040). SLG was accurate identifying p with coronary stenosis >= 70 % (AUC = 0.72, p=0.001, sensitivity = 50 %, specificity = 90 %, positive predictive value = 75.1 % and negative predictive value = 74.9 %). Group B were low and moderate cardiovascular risk 72.8 % by TIMI risk score and 98.5 % by GRACE risk scores. TS was able to identify the culprit coronary in an ischemic event with cutoff values and minimum number of damaged segments as follow: -14 and 4 segments for anterior descending coronary, -16 and 3 segments to the circumflex coronary and right coronary. SLG has proved accurate in discriminating patients with severe coronary stenosis, even in those with low and moderate risk by TIMI and GRACE risk scores. TS estimates the area of ischemic myocardium by the number of segments with abnormal deformity, and suggests the most likely culprit coronary.

Magneto-transport study on high mobility electron systems in both 2D- and 3D- case has attracted intense attention in past decades. This thesis focuses on the magnetoresistance behavior in 3D topological insulator Bi2Te3 and GaAs/AlGaAs 2D electron system at low magnetic field range 0.4T the first drop at T~3.4K to tndium superconductor and considered the second drop at lower temperature as the proximity effect that occurred near the interface between these two materials. On the other hand, GaAs/AlGaAs heterostructure, as a III-V semiconductor family, has been extensively studied for exploring many interesting phenomena due to the extremely high electron mobility up to 10^7 cm^2/Vs. In this thesis, two interesting phenomena are present and discussed in a GaAs/AlGaAs system, which are the electron heating induced tunable giant magnetoresistance study and phase inversion in Shubnikov-de Haas oscillation study, respectively. By applying elevated supplementary dc current bias, we found a tunable giant magnetoresistance phenomenon which is progressively changed from positive to giant negative magnetoresistance. The observed giant magnetoresistance is successfully simulated with a two-term Drude model at all different dc biases, I_{dc}, and temperature, T. In addition, as increasing the dc current bias, a phase inversion behavior was observed in Shubnikov-de Haas oscillation, which was further demonstrated by the simulation with an exponential damped cosine function. This thesis also presents an ongoing project, which is the observation and fabrication of 2D layered materials. The studied 2D layered materials includes graphene, biron nitride, Molybdenum disulfide, etc. At the end, a future work about fabrication of the 2D layered materials devices as well as the suggestion about the measurement are discussed.

The paper describes how a two-dimensional absolute measuring system can explicitly be realized. The theoretical background, the experimental setup, the evaluation algorithm, and the results of measurement are discussed in detail.

In this report, we present some of the results achieved by investigating two-dimensional monomial cellular automata modulo m, where m is a non-zero positive integer. Throughout the experiments, we work with the von Neumann neighbourhood and apply the same local rule based on modular multiplication. The purpose of the study is to examine the behaviour of these cellular automata in three different environments, (i.e. the infinite plane, the finite plane and the torus), by means of elementary number theory. We notice how the distance between each pair of cells with state 0 influences the evolution of the automaton and the convergence of its configurations. Similar impact is perceived when the cells attain the values of Euler's-<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cphi" />function or of integers with common divisors with m, when m &gt; 2. Alongside with the states of the cells, the evolution of the automaton, as well as the convergence of its configurations, are also decided by the values attributed to m, whether it is a prime, a prime power or a multiple of primes and/or prime powers.

van der Waals heterostructures meet other low-dimensional materials. Stacking of about 1 nm thick nanosheets with out-of-plane anchor groups functionalized with fullerenes integrates this zero-dimensional material into layered heterostructures with a well-defined chemical composition and without degrading the mechanical properties. The developed modular and highly applicable approach enables the incorporation of other low-dimensional materials, e.g. nanoparticles or nanotubes, into heterostructures significantly extending the possible building blocks.

Polychlorinated Biphenyls (PCBs) are a group of 209 ‘man-made’ chlorinated organic compounds that were widely used in the 20th century for a variety of industrial uses. PCBs were first commercially produced in the 1929 and were manufactured until the 1980s when their use was phased out due to environmental and human health risks. However, due to their widespread use and persistence they are ubiquitous in the environment and remain a contaminant of concern. The structural properties that determine the persistence of PCBs in humans were therefore elucidated by statistical analysis of data from the National Health and Nutrition Examination Survey (NHANES). PCBs with chlorine bonding in the 2,5-and 2,3,6- positions (and 2- in di- and tri-chlorinated congeners) were rapidly biotransformed and so can be classed as episodic congeners whereas PCBs with chlorine bonding in the 2,3,4-, 2,4,5-, 3,4,5-, and 2,3,4,5- positions were more resistant to biotransformation and can therefore be classed as steady state congeners. A fundamental requirement of using PCB signatures for environmental fingerprinting is an effective analytical method capable of producing high resolution signatures from biological samples. An extraction and clean-up method was developed that was successfully applied to different biological matrices (blood and tissues). A two dimensional gas chromatography with time of flight mass spectrometry (GCxGC-ToFMS) method was designed and optimised to provide a congener specific method capable of identifying 200 out of the 209 PCBs, with detection limits in human serum in the range of 1 to 10 ng g-1 lipid. The extraction and detection methods were used to determine the source of PCB contamination and age date exposure in workers at a transformer dismantling plant. A total of 84 different PCB congeners were identified in the sera of 30 workers with concentrations of the 7 indicator PCBs ranging from 1.2 - 39 μg g-1 lipid. Analysis of PCB signatures was able to distinguish recent from prolonged exposure and also identified an additional source of inhalation exposure in a subgroup of workers. Analysis of 12 different tissue types obtained from the common guillemot (Uria aalge) suggested a high degree of perpetuation between the PCB signature in different tissue types. This shows that comparative assessments can be undertaken between animals using different tissue types and that small (1 g) samples of blood can be used as a non-lethal sampling technique. The regional provenance of 25 wrecked Leach’s storm petrels (Oceanodroma leucorhoa) was also determined using PCB signatures. Results from GCxGC-ToFMS analysis revealed distinctively different PCB signatures in birds from Canada and Europe. The findings reported in this thesis enhance our understanding of PCB signatures in the environment and show how they can be used effectively to age date and identify the source of exposure in humans and animals.