Lipídios em solução aquosa formam uma variedade de estruturas diferentes que incluem monocamadas de surfactantes na interface água-ar, conhecidas como monocamadas de Langmuir, como também vesículas unilamelares ou plurilamelares no interior da solução. Sob variação de temperatura, estas estruturas apresentam diferentes fases, observadas através de calorimetria ou variação isotérmica de pressão lateral. Entre as fases apresentadas por estas estruturas, as duas mais importantes se diferenciam pela ordem das cadeias lipídicas. Entendemos que do ponto de vista das fases termodinâmicas, simplificado e qualitativo, monocamadas de Langmuir e bicamadas lipídicas constituem o mesmo sistema físico sob vínculos diferentes. Neste trabalho, desenvolvemos um modelo estatístico para o estudo da transição ordem-desordem destes sistemas, que inclui flutuações de densidade, estas ausentes no modelo de Doniach, de 1980, a base para muitos estudos teóricos para transições de fase de sistemas lipídicos. Flutuações de densidade são fundamentais na descrição de vesículas lipídicas carregadas, compostas de surfactante cuja cabeça polar se dissocia em água. O estudo em laboratório das propriedades térmicas e estruturais de membranas artificiais de lipídios carregados _e relativamente recente, e foi desenvolvido em grande parte no Laboratório de Biofísica do IFUSP. Tais membranas apresentam comportamento distinto das membranas neutras, notoriamente influenciado pela concentração de sal na solução. Isto motivou o desenvolvimento de uma segunda versão do modelo, na qual passamos a descrever a cabeça polar do lipídio em termos de um par de cargas opostas, sendo que a camada lipídica foi acoplada ao modelo primitivo restrito na rede, que desempenha o papel da solução salina. O primeiro modelo foi estudado por aproximação de campo médio e por simulações de Monte Carlo, e o segundo modelo foi investigado apenas através de simulações numéricas. O estudo do modelo carregado foi precedido por uma investigação criteriosa das técnicas de simulação de sistemas com interação Coulombiana, resultando no desenvolvimento de uma metodologia adequada a condições de contorno não isotrópicas e com custo computacional reduzido. Os modelos estatísticos propostos por nós levaram a dois resultados importantes. O modelo para camadas lipídicas neutras é, até hoje, o único modelo estatístico que descreve tanto a transição gel-fluido de bicamadas lipídicas, como a transição líquido condensado - líquido expandido\" de monocamadas de Langmuir, além de descrever também a transição líquido expandido gás na interface água-ar. O modelo para camadas lipídicas que se dissociam em água reproduz a variação abrupta na dissociação, concomitante com a transição ordem-desordem, propriedade que permite interpretar estudos experimentais relativos à condutividade das soluções lipídicas correspondentes. / Lipids in aqueous solution form a variety of different structures which include monolayers of surfactants at the water-air interface, known as Langmuir monolayers, as well as unilamellar or plurilamellar vesicles within the solution. Under temperature variation, these structures display different phases, observed through calorimetry or isothermal variation of lateral pressure. Among the phases presented by these structures, the two most important differ in the order of the lipid chains. From the point of view of the thermodynamic phases, our understanding is that Langmuir monolayers and lipid bilayers constitute the same physical system under different constraints. In this work, we develop a statistical model for the order - disorder transition of lipid bilayers which adds density fluctuations to Doniach\'s 1980 model, which has been considered the basis for many theoretical studies for lipid systems phase transitions. Density fluctuations are essential in the description of the properties of charged vesicles in solution, which consist of surfactants whose polar head dissociates in water. The study in the laboratory of thermal and structural properties of artificial charged lipid membranes is relatively new, and was developed largely in the IFUSP Laboratory of Biophysics. Such membranes exhibit distinct behavior if compared to neutral membranes, notoriously influenced by the solution salt concentration. The experimental investigations motivated us to develop a second model, in which we describe the polar headgroups through a pair of opposite charges. The lipid layer is attached to the lattice restricted primitive model, which plays the role of the saline solution. The first model was studied both through a mean-field approximation as well as through Monte Carlo simulations, whereas the second model was investigated only through numerical simulations. The study of the charged model was preceded by a thorough investigation of the simulation techniques for Coulomb interaction systems, leading to the development of a methodology suitable for non isotropic boundary conditions and with reduced computational cost. The statistical models proposed by us led to two important results. To our knowledge, our model for neutral lipid layers is the only statistical model which, aside from describing simultaneously both the gel-fluid transition of lipid bilayers and the condensed liquid - expanded liquid transition of Langmuir monolayers, also describes the gas- expanded liquid transition at the air-water interface. The model for lipid layers that dissociate in water reproduces the abrupt change in dissociation, concomitant with the order-disorder transition, a property that allows us to interpret experimental studies related to conductivity of the corresponding lipid solutions.

Os processos envolvidos em condução eletrônica de polímeros condutores são muito complicados devido à intricada morfologia estrutural de tais materiais. Realizamos medidas de condutividade alternada em filmes de polianilina em uma grande faixa de freqüência, variando o grau de dopagem dos filmes e temperatura. Ao mesmo tempo, desenvolvemos um modelo estatístico de rede de resistores para descrever a estrutura polimérica e para simular as componentes real e imaginária de sua resistividade alternada. Leva-se em conta a polidispersividade do material, assim como os mecanismos de transportes de carga intracadeia e intercadeia. Pela aplicação de uma técnica de matriz de transferência, o modelo reproduz medidas de resistividade alternada realizadas em filmes de polianilina em diferentes graus de dopagem e em diferentes temperaturas. Nossos resultados indicam que os mecanismos intercadeias governam o comportamento da resistividade em regiões de baixa freqüência enquanto que, para altas freqüências, mecanismos intracadeia são dominantes. Essa simulação foi desenvolvida para redes bi e tridimensional. Aplicamos, também, esse método para estudar sistemas isoenergéticos de estrutura desordenada (poliacetileno estirado), sistemas isoenergéticos de estrutura desordenada (poliacetileno não-estirado) e sistemas não-isoenergéticos de estrutura desordenada (polianilina). Finalmente, uma comparação entre esses três materiais, permitiu-se discutir, em detalhes, a distribuição de barreiras de energia potencial e a diferença dos níveis de energia que controlam o mecanismo de salto dos portadores eletrônicos. / The processes involved in electronic conduction of conducting polymers are very complicated due to the intricate morphological structure of such materials. We carried out alternating conductivity measurements in polyaniline films in a large frequency range, varying the doping degree of the films and temperature. At the same time, we developed a statistical model of resistor networks to describe a polymer structure and to simulate the real and imaginary components of their ac resistivities. This model takes into account the polydispersiveness of the material as well as intrachain and interchain charge transport mechanisms. By the application of a transfer-matrix technique, it reproduces ac resistivity measurements carried out with polyaniline films in different doping degrees and temperatures. Our results indicate the interchain mechanisms govern the resistivity behavior in the low frequency region while, for higher frequencies, intrachain mechanisms are dominated. These simulations were developed in bi and tridimensional lattice. We also applied this method to study ordered structure in isoenergetic systems (stretched polyacetylene), disordered structure in isoenergetic systems (normal polyacetylene), and disordered structure in non-isoenergetic systems (polyaniline). Finally, a comparison between these three materials, allowed us to discuss in detail the energy barriers distribution and the difference in energy levels, which control the hopping mechanisms of the electronic carriers.

Nuclear magnetic resonance (NMR) is a highly versatile analytical technique for studying molecular configuration, conformation, and dynamics, especially of biomacromolecules such as proteins. However, due to the intrinsic properties of NMR experiments, results from the NMR instruments require a refencing step before the down-the-line analysis. Poor chemical shift referencing, especially for 13C in protein Nuclear Magnetic Resonance (NMR) experiments, fundamentally limits and even prevents effective study of biomacromolecules via NMR. There is no available method that can rereference carbon chemical shifts from protein NMR without secondary experimental information such as structure or resonance assignment. To solve this problem, we constructed a Bayesian probabilistic framework that circumvents the limitations of previous reference correction methods that required protein resonance assignment and/or three-dimensional protein structure. Our algorithm named Bayesian Model Optimized Reference Correction (BaMORC) can detect and correct 13C chemical shift referencing errors before the protein resonance assignment step of analysis and without a three-dimensional structure. By combining the BaMORC methodology with a new intra-peaklist grouping algorithm, we created a combined method called Unassigned BaMORC that utilizes only unassigned experimental peak lists and the amino acid sequence. Unassigned BaMORC kept all experimental three-dimensional HN(CO)CACB-type peak lists tested within ± 0.4 ppm of the correct 13C reference value. On a much larger unassigned chemical shift test set, the base method kept 13C chemical shift referencing errors to within ± 0.45 ppm at a 90% confidence interval. With chemical shift assignments, Assigned BaMORC can detect and correct 13C chemical shift referencing errors to within ± 0.22 at a 90% confidence interval. Therefore, Unassigned BaMORC can correct 13C chemical shift referencing errors when it will have the most impact, right before protein resonance assignment and other downstream analyses are started. After assignment, chemical shift reference correction can be further refined with Assigned BaMORC. To further support a broader usage of these new methods, we also created a software package with web-based interface for the NMR community. This software will allow non-NMR experts to detect and correct 13C referencing errors at critical early data analysis steps, lowering the bar of NMR expertise required for effective protein NMR analysis.

<p>Statistical distributions are used to model behaviour of real VoIP traffic. We investigate call holding and inter-arrival times as well as speech patterns. The consequences of using an inappropriate model for network dimensioning are briefly discussed. Visual examination is used to compare well known distributions with empirical data. Our results support the general opinion that the Exponential distribution is not appropriate for modelling call holding time. We find that the distribution of talkspurt periods is well modelled by the Lognormal distribution and the silence periods by the generalized Pareto distribution. It is also observed that the call inter-arrival times tend to follow a heavy tailed distribution.</p>

Sunken oil is difficult to locate because remote sensing techniques cannot as yet provide views of sunken oil over large areas. Moreover, the oil may re-suspend and sink with changes in salinity, sediment load, and temperature, making deterministic fate models difficult to deploy and calibrate when even the presence of sunken oil is difficult to assess. For these reasons, together with the expense of field data collection, there is a need for a statistical technique integrating limited data collection with stochastic transport modeling. Predictive Bayesian modeling techniques have been developed and demonstrated for exploiting limited information for decision support in many other applications. These techniques brought to a multi-modal Lagrangian modeling framework, representing a near-real time approach to locating and tracking sunken oil driven by intrinsic physical properties of field data collected following a spill after oil has begun collecting on a relatively flat bay bottom. Methods include (1) development of the conceptual predictive Bayesian model and multi-modal Gaussian computational approach based on theory and literature review; (2) development of an object-oriented programming and combinatorial structure capable of managing data, integration and computation over an uncertain and highly dimensional parameter space; (3) creating a new bi-dimensional approach of the method of images to account for curved shoreline boundaries; (4) confirmation of model capability for locating sunken oil patches using available (partial) real field data and capability for temporal projections near curved boundaries using simulated field data; and (5) development of a stand-alone open-source computer application with graphical user interface capable of calibrating instantaneous oil spill scenarios, obtaining sets maps of relative probability profiles at different prediction times and user-selected geographic areas and resolution, and capable of performing post-processing tasks proper of a basic GIS-like software. The result is a predictive Bayesian multi-modal Gaussian model, SOSim (Sunken Oil Simulator) Version 1.0rc1, operational for use with limited, randomly-sampled, available subjective and numeric data on sunken oil concentrations and locations in relatively flat-bottomed bays. The SOSim model represents a new approach, coupling a Lagrangian modeling technique with predictive Bayesian capability for computing unconditional probabilities of mass as a function of space and time. The approach addresses the current need to rapidly deploy modeling capability without readily accessible information on ocean bottom currents. Contributions include (1) the development of the apparently first pollutant transport model for computing unconditional relative probabilities of pollutant location as a function of time based on limited available field data alone; (2) development of a numerical method of computing concentration profiles subject to curved, continuous or discontinuous boundary conditions; (3) development combinatorial algorithms to compute unconditional multimodal Gaussian probabilities not amenable to analytical or Markov-Chain Monte Carlo integration due to high dimensionality; and (4) the development of software modules, including a core module containing the developed Bayesian functions, a wrapping graphical user interface, a processing and operating interface, and the necessary programming components that lead to an open-source, stand-alone, executable computer application (SOSim - Sunken Oil Simulator). Extensions and refinements are recommended, including the addition of capability for accepting available information on bathymetry and maybe bottom currents as Bayesian prior information, the creation of capability of modeling continuous oil releases, and the extension to tracking of suspended oil (3-D).

Time dependent deformations in concrete, both creep and shrinkage, play a critical role in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. These strains result in lossess, through release of prestress, and thereby influence the safety of these structures. The present study comprises of an experimental and analytical program to assess the levels of creep and shrinkage in normal and heavy density concrete. The experimental program includes tests on creep using standard cylinder specimen, while shrinkage studies have been conducted using prism specimen, both under controlled environmental conditions. The experimental results suggest that creep and shrinkage strains are higher in heavy density concrete than in normal concrete. This may be attributed to the relatively smaller pore structure of heavy density concrete, that results in larger availability of free water and a relatively slower hydration process in comparison to normal concrete. While there is some scatter in the results, creep strains decrease with age of loading and both creep and shrinkage strains are smaller when the relative humidity is higher. Statistical model reported in the literature for normal concrete is able to predict the test results for both normal and heavy density concrete quite well. Long term predictions of creep and shrinkage using this model, accounting for uncertainties, is also projected and shown to predict some long term measured results not used in the model calibration. The long term predictions are sensitive to the initial data used in model calibration.

Demand for energy is constantly growing both in the world and in Turkey. Sustainable development being an important concept, development of small hydro power projects has been popular in recent years. Eastern Black Sea Basin in Turkey has a lot of small hydro power potential because of high amount of precipitation and existence of steep slopes. Since the amount of river runoff is the only parameter that is variable in order to determine the power potential, it is vital to estimate the project discharge in ungauged basins accurately that have hydro power potential. Projects discharges of hydro-power plants in ungauged basins have been calculated using conventional methods up to now. This study aims to introduce a statistical model in linear and multi-variate form using the topographical and morphological parameters derived from GIS and hydro-meteorological variables to estimate the specific flow duration curves of potential small hydro-power locations for the selected study areas in Eastern Black Sea Region namely Solakli and Karadere basins. As well as developing an annual regression model using the annual values of hydro-meteorological parameters / seasonal regression model (spring season) has also been developed by including the mean seasonal (spring) air temperature variable instead of snow covered area (SCA) in addition to basin parameters. By studying the spring model, effect of different variables from the annual model were tested and discussed with some recommendations for the future studies.

New and renewable energy resources are important in view of reduction of greenhouse gasses causing climate change and in eliminating of dependence on foreign sources in energy respects. Within this context, hydraulic energy is evaluated as one of the prior energy resources that should be utilized. Turkey has 26 basins and Eastern Black Sea Basin is one of the most feasible basins with a lot of small hydroelectric power plants. In the other hand, there is not enough number of discharge gauging stations in the basin. For that reason, up to now generally area ratio method has been used to estimate the project discharges of small hydroelectric power plants. Objective of this study is to estimate &ldquo / the project discharge&rdquo / which is corresponding to 5 flow percentiles (5%, 10%, 15%, 20%, 25%) depending on topographical, meteorological, hydrologic and soil-land cover parameters through developing a multilinear statistical model for Iyidere Basin as a part of Eastern Black Sea Basin. Perimeter of the basin, the ratio of the basin perimeter to the main stream length of the same basin, the drainage frequency, the mean slope of basin, v the mean annual precipitation and the curve number are the parameters that have been analysed for the multilinear statistical model. Principal Component Analysis, Multiple Regression Analysis and Stepwise Regression Analysis have been run for the data sets. For the computed discharges validation has been done. As a result of validation, it has been seen that the stepwise regression gives much closer discharge values to the observed values than the multiple regression results.

Resumo: Neste trabalho foram estudadas as propriedades elétricas e dielétricas de um compósito à base de poliuretano derivado de óleo de mamona (PU) e negro de fumo (NF). As amostras de PU/NF foram preparadas com quantidades fixas de prépolímero e poliol (seguindo uma fração 10/7 em massa) e com diferentes quantidades de NF. Medidas de espectroscopia de impedância permitiram analisar as propriedades elétricas do compósito em campo elétrico alternado em diferentes temperaturas, enquanto que, o método de quatro pontas foi utilizado para calcular a condutividade dc das diferentes amostras. Neste trabalho, também, foi desenvolvido um modelo estatístico bidimensional de redes de resistores e capacitores que gera a estrutura morfológica e calcula a condutividade alternada do compósito PU/NF a partir de uma técnica de matriz de transferência proposto por Derrida . As curvas da permissividade real e imaginária em função da frequência para amostras de PU/NF com diferentes proporções de NF demonstraram o mesmo comportamento qualitativo, ou seja, possuindo maiores valores para baixas frequências e altas temperaturas e decrescendo com aumento da frequência. As medidas de permissividade dielétrica imaginária apresentaram picos de relaxação devido ao processo de polarização interfacial entre o negro de fumo e a matriz polimérica. No entanto, esses picos são mais pronunciados quando se utiliza o módulo elétrico, que minimiza os efeitos de condução dc. O modelo estatístico reproduziu bem os dados experimentais obtidos das medidas de espectroscopia de impedância. A partir dos ajustes teórico-experimentais pode-se observar que a condutividade elétrica para a amostra 99/01 ocorre predominantemente por condução eletrônica nas regiões isolantes, obedecendo ao modelo modificado de Abrahams e Miller. Entretanto, para as amostras 95/05 e 90/10 o modelo de Abrahams e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work we investigated the electrical properties of the polyurethane derived from castor oil (PUR) and carbon black (CB) composite. Samples of PUR/CB were prepared by fixed quantities of the pre-polymer and polyol (following a ratio of 10/7 by weight) and mixing different amount of the CB. Measurement of impedance spectroscopy was used to analyze the transport properties of the composite as function of applied electric field at different temperatures. The method of four probes was used to measurement the dc conductivity of the PUR/CB composites. A statistical model two-dimensional was developed based on networks of resistors and capacitors that generates the morphological structure and calculates the alternating conductivity of the PUR/CB composite using a transfer matrix technique proposed by Derrida et al. The plots of real and imaginary permittivity as a function of frequency for the samples of PUR/CB with different amount CB showed the same qualitative behavior with higher values for low frequencies and high temperatures. Measurement of imaginary dielectric permittivity showed peaks due to the process of interfacial polarization relaxation between the carbon black and polymeric matrix. However, these peaks are more pronounced when using the electrical modulus, which minimizes the effects of dc conduction. The statistical model reproduced well the experimental data obtained from the measurement of impedance spectroscopy. From theoretical and experimental settings it can be observed that the electrical conductivity for the 99/01 sample is predominantly by electron conduction in the insulating regions, in according at modified model of Miller and Abrahams. However, for samples 95/05 and 90/10 model of Abrahams and Miller dominates at low frequencies (below 103 Hz) and the Drude model is predominant in the higher frequency (above 104 Hz). / Orientador: Darcy Hiroe Fujii Kanda / Coorientador: Haroldo Naoyuki Nagashima / Banca: José Antônio Malmonge / Banca: Rodrigo Fernando Bianchi

Made available in DSpace on 2014-12-17T14:53:18Z (GMT). No. of bitstreams: 1 PauloRCB.pdf: 649782 bytes, checksum: 7b869bb155abf3578ea09e633db4f807 (MD5) Previous issue date: 2006-05-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work presents a study in quality of health care, with focus on consulting appointment. The main purpose is to define a statistical model and propose a quality grade of the consulting appointment time. The time considered is that from the day the patient get the appointment done to the day the consulting is realized. It is used reliability techniques and functions that has as main characteristic the analysis of data regarding the time of occurrence certain event. It is gathered a random sample of 1743 patients in the appointment system of a University Hospital - the Hospital Universit?rio Onofre Lopes - of the Federal University of Rio Grande do Norte, Brazil. The sample is randomly stratified in terms on clinical specialty. The data were analyzed against the parametric methods of the reliability statistics and the adjustment of the regression model resulted in the Weibull distribution being best fit to data. The quality grade proposed is based in the PAHO criteria for a consulting appointment and result that no clinic got the PAHO quality grade. The quality grade proposed could be used to define priority for improvement and as criteria to quality control / Este trabalho apresenta um estudo sobre qualidade em servi?os de sa?de, com enfoque para o atendimento ambulatorial. Determinar o melhor modelo estat?stico e a proposi??o de um padr?o de qualidade para o tempo agendado para consulta ambulatorial, ? o objetivo do presente estudo. Para isso, foram utilizadas as t?cnicas de confiabilidade que tem como principal caracter?stica a an?lise de dados referente ao tempo de ocorr?ncia de determinado evento. Observou-se dados de 1.743 pacientes que agendaram consulta no Hospital Universit?rio Onofre Lopes - Natal/RN, onde coletou-se informa??es referentes ao tipo de tratamento, especialidade, tipo de marca??o e o tempo at? o atendimento ambulatoria1. Os dados foram analisados segundo os m?todos n?o param?tricos da estat?stica de confiabilidade e atrav?s do ajuste do modelo de regress?o. Concluiu-se que as covari?veis que influenciam o tempo at? o atendimento ambulatorial ? o tipo de marca??o e a especialidade, o modelo que melhor se adequa aos dados ? o Weibull e 20,83% das especialidades enquadram-se no padr?o B de qualidade, sendo este o melhor padr?o obtido