Made available in DSpace on 2015-03-26T13:35:17Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1691868 bytes, checksum: 62324ed588f110298d6a2dc7a9e33ca9 (MD5) Previous issue date: 2011-07-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Phase transitions into absorbing states, configurations from which the system can not escape, are currently a topic in the frontier of nonequilibrium Statistical Physics. Along with a growing interest in phase transitions on complex topologies, there are still many problems being investigated in regular networks, such as the effects of quenched disorder, diffusion, etc. In recent decades, complex networks have been a subject of increasing interest in the scientific community due to the fact that they describe a wide diversity of systems of both technological and intellectual relevance. Gathering the huge size and dynamic nature of real complex networks, the Statistical Physics approach has proven to be very convenient because of its connection with graph theory and the possibility of characterizing the macroscopic phenomena emerging in terms of the dynamics of the basic elements composing the system. In the first part of this dissertation, we have performed simulations using the quasi-stationary (QS) method proposed by Oliveira and Dickman for the contact process (CP), the susceptible-infected-susceptible (SIS) and the contact replication process (PRC) models in three dimensions, besides reproducing some results already known in the literature with the QE method. Using this method, we determined, for the first time, the moment ratios of the order parameter for the directed percolation (DP) class in three dimensions. We have also shown that the mean-field exponents for the three-dimensional PRC reported in the literature, are transients observed in the spreading analysis. In the second part, we have investigated the phase transition in a new model, proposed in this dissertation: the threshold contact process (TCP). Analyses were performed on regular and scale-free networks. We show that the TCP belongs to the DP universality class in regular networks. In scale-free networks, we show that the critical exponents for the finite-size scaling analysis of the quasi-stationary density of active sites and for the lifetime are the same obtained for the CP on scale-free networks, both in the heterogeneous mean-field theory, and in the QS simulations. / Transições de fase para estados absorventes, configurações das quais o sistema não pode escapar, são atualmente um tópico na fronteira da física estatística fora do equilíbrio. Concomitantemente com um crescente interesse em tais transições de fase em topologias complexas, ainda há muitos problemas em aberto sendo investigados em redes regulares, tais como os efeitos de desordem congelada, difusão, etc. Nas últimas décadas, redes complexas tem sido alvo de crescente interesse da comunidade científica devido ao fato de estas descreverem uma grande variedade de sistemas que possuem relevância tanto tecnológica quanto intelectual. Levando em conta a natureza dinâmica e o enorme tamanho das redes complexas reais, a abordagem da Física Estatística mostra-se muito conveniente devido a sua ligação com a teoria de grafos e a possibilidade de caracterizar fenômenos macroscópicos emergentes em termos da evolução dinâmica de elementos básicos que compoem o sistema. Na primeira parte desta dissertação, realizamos simulações pelo método quase-estacionário (QE) proposto por Oliveira e Dickman para o processo de contato (PC), para o modelo suscetível-infectado-suscetível (SIS) e para o processo de replicação por contato (PRC), em três dimensões, além de reproduzir alguns resultados já conhecidos pelo método QE. Utilizando este método, foi possível determinar as razões entre momentos dos parâmetros de ordem para a classe da percolação direcionada em três dimensões. Também mostramos que os expoentes de campo médio para o PRC tridimensional relatados na literatura são um transiente observado na análise de espalhamento. Na segunda parte, investigamos a transição de fase em um novo modelo, proposto nesta dissertação: o processo de contato por limiar (PCL). Análises foram realizadas em redes regulares e sem escala. Mostramos que o PCL pertence à classe da percolação direcionada em redes regulares. Em redes sem escala, mostramos que os expoentes críticos da análise de escalonamento de tamanho finito da densidade quase-estacionária de sítios ativos e do tempo de vida são os mesmos que foram obtidos para o PC em redes sem escala, tanto na teoria de campo médio heterogênea, quanto nas simulações QE.

O modelo estocástico Raise and Peel é estudado nesta tese. Para isto é utilizado o método de simulação por Monte Carlo junto com os métodos de diagonalização exata e numérica do operador de Liouville. Este modelo estocástico é um modelo de crescimento unidimensional com dois parâmetros livres. Um parâmetro de absorção local e um parâmetro de dessorção não local. Em função destes dois parâmetros se observa um rico diagrama de fase, apresentando regiões massivas, regiões criticamente auto-organizadas, estados quase-estacionários e transições a múltiplos estados absorventes. O principal resultado deste trabalho é ressaltar a existência de células de Jordan no operador de Liouville. Células de Jordan que crescem com o tamanho do sistema e portanto no limite termodinâmico a dinâmica assintótica pode ser mascarada. A nível numérico estas células de Jordan podem levar a errôneas interpretações de fases criticas quando são na realidade fases massivas ou vice-versa. Portanto dependendo da condição inicial observa-se que a presença de células de Jordan pode levar à determinação errônea de expoentes críticos e a observações de tempos de decaimentos excessivamente grandes. Tudo isto ressalta a necessidade de se determinar os expoentes críticos e os tempos de decaimento por diversos métodos, sempre que for possível, além de se controlar o comportamento destas quantidades considerando a evolução do modelo com diferentes condições inicias. Entre outros resultados que obtivemos observamos a existência de estados quase-estacionários com tempos de vida que crescem muito mais rápido que uma lei de potencia do tamanho do sistema. Encontramos o expoente critico dinâmico z=1, no caso da transição a estados multi-absorventes. Este resultado ocorreu tanto nos casos sem absorção como nos casos sem dessorção. O modelo exibe também uma fase rugosa com um expoente de rugosidade próximo de zero quando a taxa de absorção é maior que a taxa dessorção. E finalmente observamos que o modelo estudado em condições periódicas de contorno pode ser enxergado como um modelo KPZ em 1+1 dimensões, sujeito a dois tipos de perturbações. Uma das pertubações sendo relevante e a outra irrelevante. / The stochastic model Raise and Peel is studied in this thesis. we use the Monte Carlo simulation method together with the exact and numerical diagonalization methods of the Liouville operator. This stochastic model is a one-dimensional growth model with two free parameters. A local absorption parameter and a non-local desorption one. As a function of these two parameters, a rich phase diagram is observed, presenting massive regions, critically self-organized regions, quasi-stationary states and transitions to multiple absorbing states. The main result of this work is to emphasize the existence of Jordan cells in the Liouville operator. Jordan cells that grow with the size of the system and therefore in the thermodynamic limit the asymptotic dynamics can be masked. At the numerical level, these Jordan cells can lead to erroneous interpretations of massive phases as being massless critical ones or vice versa. Therefore depending on the initial condition, it is observed that the presence of Jordan cells can lead to the erroneous determination of critical exponents and produce excessively large lifetimes. Due to these effects, it is necessary to determine the critical exponents and the lifetimes by several distinct methods whenever possible, besides controlling the behavior of these quantities, by considering the evolution with different initial conditions. Among other results, we found the existence of quasi-stationary states with lifetimes that grow much faster than a power law of the systems size. We obtained a dynamic critical exponent z = 1 in the transition to multi-absorbent states in both cases without absorption or desorption. The model also shows a rough phase with a roughness exponent close to zero when the absorption rate is higher than the desorption rate. Finally, we observed that the model studied under periodic boundary conditions, can be seen as a KPZ model in 1 + 1 dimensions, under the effect of two perturbations. One of them being relevant and the other one irrelevant.

La réponse optique de nano-objets métalliques et semi-conducteurs a été étudiée par spectroscopie par modulation spatiale (SMS), une technique permettant de détecter des nano-objets individuels et d'en mesurer quantitativement la section efficace d'extinction. Dans le cadre de ce travail, nous avons systématiquement corrélé ces mesures optiques à une caractérisation bi- voire tridimensionnelle de leur morphologie, permettant une comparaison précise des mesures avec des simulations numériques. Le premier volet de cette thèse décrit une étude détaillée de l'effet de la déposition de nano-objets métalliques de forme allongée (nanobâtonnets et nanobipyramides) sur un substrat absorbant. Nos expériences montrent qu'elle conduit à un élargissement de la résonance plasmon de surface, dont l'ampleur dépend fortement de la forme et de l'encapsulation des nano objets. En combinant la SMS avec une approche pompe-sonde, nous avons pu mesurer la réponse ultrarapide de nano-bipyramides d'or individuelles, qui contient une contribution de plusieurs de leurs modes de vibration, permettant d'accéder à leur fréquence et taux d'amortissement, en s’attachant en particulier à l'effet d'une encapsulation diélectrique des bipyramides. Au cours de cette thèse, nous avons étendu l'application de la SMS à des nano-objets très allongés avec une dimension micrométrique (nanofils et nanopointes), dans le but notamment d'étudier leur réponse optique, leur interaction avec une nanoparticule d’or et d’obtenir des informations sur leur profil d'absorption, une information essentielle pour l'interprétation d'expériences d'émission électronique (effet de champ) ou ionique (tomographie de sonde atomique) / The optical response of metallic and semi-conductor nano-objects has been studied by spatial modulation spectroscopy (SMS), a technique allowing to detect single nano-objects and to quantitatively measure their extinction cross-sections. During my thesis, we have systematically correlated these optical measurements with the 2D or 3D characterization of their morphology, allowing a precise comparison of the measurements with numerical simulations. The first part of my PhD thesis describes a detailed study of the effect of the deposition of elongated nano-objects on an absorbing substrate. Our experiments show a spectral broadening of the surface plasmon resonance, whose extent highly depends on the shape and the encapsulation of the nano-objects. By combining SMS with a pump-probe approach, we were able to measure the ultrafast response of single gold nano-bipyramids. This response contains a contribution from several vibration modes, allowing extraction of their frequencies and damping times. In particular, we have addressed the effect of a dielectric encapsulation of bipyramids on their vibrational quality factors. During this thesis, we extended the use of SMS to very elongated nano-objects with a micrometric dimension (nanowires and nanotips), with the goal of studying their optical response, their interaction with a gold nanosphere and obtaining information on their absorption profile, as required to interpret electronic (field effect) or ionic (atom-probe tomography) emission experiments

Abstract Previous reports on the effects of enhanced UV-B radiation on bryophytes have been equivocal. This study shows that mosses not only respond to enhanced UV-B, but they are affected by changes in ambient radiation. The studies were conducted with two model species common in northern environments; red-stemmed feather moss (Pleurozium schreberi) and juniper haircap moss (Polytrichum juniperinum). Both species showed high concentrations of methanol-extractable UV-absorbing compounds (UACs) with high spring-time and early-summer UV, whereas in P. juniperinum, the concentration was affected by early-summer drought. The UACs of P. juniperinum increased again towards autumn suggesting a role in winter hardening. The (spring-time) cell wall-bound UV screen was important to both species. The fundamental adaptation of P. juniperinum to open and exposed environments was reflected in relatively higher concentrations of total UACs compared to P. schreberi. The enhanced UV-B experiments in situ were conducted over two years in Oulu and six years at the FUVIRC site in Sodankylä. Some of the effects of UV-B were seen within the first years of the experiments, or even within hours, while others were observed after several years. Five or six years of enhanced UV-B treatment increased the methanol-extractable UACs of P. schreberi and decreased the green shoot growth of P. juniperinum. The immediate light environment was proposed to have an impact on the varying UAC concentrations. Some mitigating effects of UV-A were observed as well. Off-site measured, reconstructed and modelled UV radiation data was used for comparisons of light environment in situ, or when performing a reconstructive research with historical samples. The environmental sample banks can provide a useful tool to study past environmental conditions, and even reconstruct past radiation levels. It was shown in this study that UACs in P. schreberi and P. juniperinum have fundamental roles as UV-B screens in the cell walls, but there is also a variable response with the soluble fraction that reacts and adapts to the changes in UV radiation. The responses to increasing UV-B radiation vary in magnitude and in time. As P. schreberi and P. juniperinum possess circumboreal and cosmopolitan distributions, the effects of UV-B on these species and consequently on ecosystems has a broad application.

The diploma thesis is focused on the dependence of heat storage on thermal conductivity, which is characterized by the thermal conductivity coefficient. Two basic materials were chosen for the measurements – universal plaster mixture and gypsum plaster. The thermal conductivity of the materials was increased by adding milled graphite powder, which conducts the heat very well. The taken samples were then examined for differences in the behaviour in the non-stationary thermal field and thermal-technical parameters – the specific heat capacity and the thermal conductivity coefficient – were determined.

This thesis outlines an iterative approach for determining the scattered wave for two dimensional multiple acoustic scattering problems using high order local absorbing boundary conditions and second order finite difference. We seek to approximate the total wave as it is scattered off of multiple arbitrarily shaped obstacles. This is done by decomposing the scattered wave into the superposition of single scattered waves. We then repeatedly solve the single scattering system for each obstacle, while updating the boundary conditions based off the incident wave and the scattered wave off the other obstacles. We solve each single scattering by enclosing the obstacle in a circular artificial boundary and generating a curvilinear coordinate system for the computational region between the obstacle and the artificial boundary. We impose an absorbing boundary condition, specifically Karp's Farfield Expansion ABC, on the artificial boundary. We use a finite difference method to discretize the governing equations and to discretize the absorbing boundary conditions. This will create a linear system whose solution will approximate the single scattered wave. The forcing vector of the linear system is determined from the total influence on the obstacle boundary from the incident wave and the scattered waves from the other obstacles. In each iteration, we solve the singular acoustic scattering problem for each obstacle by using the scattered wave approximations from the other obstacles obtained from the previous iteration. The iterations continue until the solutions converge. This iterative method scales well to multiple scattering configurations with many obstacles, and achieves errors on the order of 1E-5 in less than five minutes. This is due to using LU factorization to solve the linear systems, paired with parallelization. I will include numerical results which demonstrate the accuracy and advantages of this iterative technique.

A Markov chain is introduced to the major steps of the process of learning a subject matter by a group of students in the classroom, in order to obtain a mathematical representation of the above process. A classroom experiment for learning mathematics is also presented illustrating the applicability of our results in practice.

In this work, hydrophilic fluorene-based derivatives that contain ethylene oxide substituents, have been synthesized and characterized for potential use as new fluorophores for bioimaging applications and for fluorescence sensing of heavy metals. Symmetrical and unsymmetrical fluorene derivatives based on structural types of acceptor-pi-acceptor, acceptor-pi-donor, and donor-pi-donor were characterized by TGA, UV-vis absorption, fluorescence emission, lifetime, anisotropy, and two-photon absorption (2PA) cross section. They were found to possess high thermal stability, high photostability, high fluorescence quantum yields, and generally large two-photon absorption cross sections, making them quite suitable for new probes in single-photon absorption and two-photon absorption fluorescence microscopy imaging. Novel hydrophilic fluorene derivatives were synthesized from fluorene in multiple steps employing the metal-catalyzed Heck coupling reaction, the Stille reaction, the Sonogashira reaction, the Ullmann condensation reaction, and "click" chemistry. To increase the hydrophilicity of the new compounds, ethylene oxide substituents were utilized for to impart water solubility. An alternative alkylation methodology using ethyleneoxy tosylates was introduced for the synthesis of ethylene oxide-containing fluorene derivatives. Several of these hydrophilic derivatives were incubated into various cell lines as new probes for both conventional and two-photon absorption fluorescence bioimaging. These compounds were biocompatible, exhibiting low cytotoxicity as determined by cell viability studies, and displayed colocalization for selected cellular organelles. In addition, hydrophilic bis(1,2,3-triazolyl)fluorene derivatives were found to exhibit sensitive fluorescence responses in the presence of certain heavy metal, and were selective for sensing zinc and mercury over other a number of other metal ions relevant to living cells or other biological environments. The UV-vis absorption and fluorescence emission spectra of the complexes exhibited a blue-shifted absorption and emission for selective metal chelation upon binding to zinc and mercury(II) ions, resulting in an approximately two-fold enhanced fluorescence response. Fluorescence titration studies revealed that the complexes of 1:2 and 1:3 ligand to metal formed with binding constant values of 108 and 1014 for zinc and mercury ions, respectively. Finally, preliminary experiments were performed to explore the possibility of employing select hydrophilic fluorene-based derivatives in the synthesis of hydrophilic fluorescent gold nanoparticles. Although results are very preliminary, the aim is to use such materials for other biomedical applications, such as surface enhanced scattering resonance and noninvasive photothermal therapy to diagnose and to treat cancers. Thus, this research had led to the discovery of alternative methodologies for synthesis of hydrophilic fluorene derivatives by alkylation with alkyl tosylates and synthesis of hydrophilic fluorescent molecule capped gold nanoparticles. Furthermore, several novel hydrophilic fluorene-based derivatives were synthesized and characterized for their linear and nonlinear photophysical properties, and are now available for further examination of their bioimaging and sensing applications.

Nowadays vehicle design paradigm influences not only the effectiveness of the different means of transport, but also the environment and economy in a critical way. The assessment of the consequences that design choices have on society at large are necessary to understand the limits of the methods and techniques currently employed. One of the mechanisms set in motion is the planned obsolescence of products and services. This has affected vehicle design paradigm in such a way that the variety in the market has shadowed the primary function of vehicle systems: the transport of persons and goods. Amongst the consequences of the expansion of such market is the exponential rise on combustion emissions to the atmosphere, which has become a great hindrance for humans health and survival of ecosystems. The development of evaluation tools for such consequences and their piloting mechanisms is needed so as to implement an ECO2  (Ecological and Economical) vehicle design paradigm. Moreover, the multifunctional design paradigm that drives aeronautical and vehicle engineering is an ever-growing demand of smart materials and structures, able to fulfil multiple requirements in an effective way. The understanding of certain phenomena intrinsic to the introduction of novel materials has found certain limits due to the complexity of the models needed. This work presents as a first step an assessment of the causes and consequences of the vehicle exponential market growth based on the analysis of the planned obsolescence within. Furthermore, a method for the acoustic response analysis of multilayered structures including anisotropic poroelastic materials is introduced. The methodology consists in a plane wave approach as a base for introducing the complex mechanic and acoustic equations governing anisotropic homogeneous media, e.g. open-celled foams, into an alternative mathematical tool manipulating physical wave amplitudes propagation within the studied media. In addition, this method is coupled to a power partitioning and energetic assessment tool so as to understand the phenomena present in complex multilayered designs. / <p>QC 20150323</p>

Магистерская диссертация на тему «СТРОЕНИЕ КОРНЕЙ ОСОК ИЗ МЕСТООБИТАНИЙ С РАЗНОЙ СТЕПЕНЬЮ УВЛАЖНЕНИЯ» состоит из 52 страниц машинописного текста, включая 19 рисунков, 2 таблицы и 113 литературных источников. Работа посвящена изучению морфологического и анатомического строения корней осок из местообитаний с разной степенью увлажнения и разных экоморф, или экологических групп по отношению к увлажнению. В исследованный материал входят собственные сборы и зафиксированные растительные образцы научных руководителей. Цель – изучение строения корней осок из местообитаний с разной степенью увлажнения и разных экоморф по отношению к увлажнению. Задачи: Изучить внешние признаки корневых систем и строение поглощаю-щих корней у осок разных экоморф и местообитаний; Установить, какие признаки и в какой степени связаны с экоморфой видов, а какие изменяются под действием режима увлажнения местообитаний независимо от принадлежности к экоморфе. Растения собраны в начале июня в период цветения большинства исследован-ных видов 2019-2021 гг. в местообитаниях, образующих градиент по увлажнению: водоем-луг-лес-сухой склон. Экологические группы по степени увлажнения среды (гигрофиты, мезофиты, ксеромезофиты) выделены по литературному источнику [Овеснов и др., 2007]. С помощью стандартных методик структурной ботаники изучены внешние признаки корневых систем и строение поглощающих корней 23 вида осок. Регистрировали параметры: число порядков ветвления корней, тип волосков, длина типичных волосков, диаметр корня; диаметр стелы; толщину паренхимы; число слоев клеток в паренхиме; число слоев клеток в экзодерме, толщину коры. Расчетные показатели – парциальный объем коры и стелы, %. В работе представлены 2 способа формирования учетных единиц. При анализе экологических групп, учетной единицей считается вид. Исследуя группы осок из местообитаний с разной степенью увлажнения, учетной единицей считается особь. Статистический анализ проводился с помощью программы STATISTICA 10. Использовали однофакторный дисперсионный анализ (F) (ANOVA) Непараметриче-ские критерии Краскела –Уоллиса (H) и Критерий (χ2) Пирсона. Результаты магистерской диссертации показали, что признаками тонких корней изученных осок, наиболее чувствительными к режиму увлажнения, являются: число порядков ветвления корней; встречаемость выпуклых корневых волосков; длина типичных корневых волосков; диаметр среза, толщина коры; выраженность экзодермы; У изученных осок от переувлажненных местообитаний к засушливым: а) увеличивается число порядков ветвления корней; б) уменьшаются: встречаемость выпуклых корневых волосков, длина корневых волосков, диаметр среза, толщина первичной коры за счет уменьшения слоев экзодермы. Несмотря на таксоноспецифичное строения корней осок, существует явно выраженная экологическая пластичность ряда признаков внутри обширного рода Carex. Полученные результаты согласуются с опубликованными данными. Результаты были представлены в устном докладе на Всероссийской конференции молодых ученых «Экология: факты, гипотезы, модели», проходившей в апреле 2021 года. Планируется публикация данных в сборнике конференции в виде тезисов. / The master's thesis on the topic "STRUCTURE OF SEDGE ROOTS FROM HAB-ITS WITH DIFFERENT DEGREES OF HUMIDIFICATION" consists of 52 pages of typewritten text, including 19 figures, 2 tables and 113 literature sources. The work is devoted to the study of the morphological and anatomical structure of sedge roots from habitats with varying degrees of moisture and different ecological groups. The analysis of the work consists of materials from our collection and recorded plant material [Konoplenko et al., 2017]. The goal is to study the structure of sedge roots from habitats with varying degrees of moisture and different ecomorphs in relation to moisture. Tasks: 1) To study the external signs of root systems and the structure of absorbing roots in sedges of different ecomorphs and habitats; 2) Establish which features and to what extent are associated with the ecomorph of the species, and which ones change under the influence of the habitat moistening regime, regardless of belonging to the ecomorph. To tackle these problems, the plants were collected in habitats forming a moisture gradient: reservoir-meadow-forest-dry slope. The ecological groups of sedge species were identified according to the literature [Ovesnov et al., 2007] according to the degree of en-vironmental moisture: hygrophytes, mesophytes, Xeromesophytes. Using the methods of structural botany, the external signs of root systems and the structure of absorbing roots of 23 species of sedges were studied. The following parameters were recorded: the number of orders of root branching, hair type, length of typical hairs, root diameter; stele diameter; parenchyma thickness; the number of cell layers in the parenchyma; the number of cell layers in the exoderm, the thickness of the cortex. Integral indicators - the partial volume of the cortex and ste-le,%. Statistical analysis was carried out using the STATISTICA 10 program. One-way analysis of variance (F) (ANOVA) was used. Nonparametric Kruskal-Wallis tests (H) and Pearson's test (χ2). The results of the master's thesis showed that the features of the thin roots of the studied sedges, the most sensitive to the moisture regime, are:the number of orders of root branching; the occurrence of convex root hairs; length of typical root hairs; cut diameter, bark thickness; the severity of exoderm; In the studied sedges, from waterlogged to arid habitats: a) the number of orders of branching of roots increases; b) decrease: the occurrence of convex root hairs, length of root hairs, cut diameter, thickness of the primary cortex due to a decrease in exoderm layers. Despite the taxon-specific structure of sedge roots, there is a pronounced ecological plasticity of a number of characters within the vast genus Carex. The results obtained are consistent with published data. These results were presented in an oral report at the All-Russian Conference of Young Scientists "Ecology: Facts, Hypotheses, Models", held in April 2021. It is planned to publish data in the conference collection in the form of abstracts.