Nitrogen-fixation is an essential biochemical reaction involving the reduction of inert, atmospheric dinitrogen (N2) into biochemically accessible ammonia (NH3). Organisms that are capable of this process are collectively called “diazotrophs” and are ubiquitous in marine and terrestrial environments. Despite the wide distribution, little is known about the biological nature of the diverse groups of diazotrophs. This study was designed to address the influence of light and nutrients on nitrogen fixation and growth in several marine diazotrophic symbioses collectively termed “Diatom-Diazotroph Associations (DDAs).” The organisms of interest included the diatoms Hemiaulus haukii Grunow and Hemiaulus membranaceus Cleve, and their diazotrophic endosymbiont Richelia intracellularis Schmidt. The study included acetylene reduction assays, growth rate, and nutrient analysis experiments on both associations in order to better understand the similarities and differences within and between the two DDAs. The results indicate distinct differences in nitrogen fixation rates within and between the species. In the nitrogen addition experiment, the “no added nitrogen” treatment had the highest N2-fixation rate (N2-fixmax = 7.43 x 10-5 nmols N2 heterocyst-1min-1), followed by the added nitrate treatment (N2-fixmax = 6.49 x 10-5 nmols N2 heterocyst-1min-1) and the added ammonium treatment (N2-fixmax = 3.79 x 10-5 nmols N2 heterocyst-1min-1). The maximum growth rate occurred in the “added ammonium” treatment (0.42 divisions day-1), which had a higher percentage of asymbiotic cells than the two other treatments. The maximum recorded rate of N2-fixation for H. haukii was 7.43 x 10-5 nmol N2 heterocyst-1min-1 and the maximum value of N2-fixation for H. membranaceus was 1.88 x 10-4 nmol N2 heterocyst-1min-1. The maximum growth rate for H. haukii was 0.99 divisions day-1, and 1.06 divisions day-1 for H. membranaceus. Growth followed light saturation kinetics in H. haukii with a compensation light intensity (IC) of 10 µmol quanta m-2sec-1 and saturation light intensity (IK) of 100 µmol quanta m-2sec-1. H. haukii and H.membranaceus expressed light saturation kinetics in N2-fixation. N2-fixation was generally limited to the light period, with no evidence of a morning or evening enhancement. The DDAs grew solely on N2-fixation and did not use nitrate. This study contributes to current knowledge of DDAs and their role in global marine nitrogen fixation. / text

Azijos žemyne formuojasi pasaulio geopolitinis-ekonominis centras. Vienos svarbiausių valstybių šiame procese yra Kinijos Liaudies Respublika (toliau Kinija), Indija ir Pietų Korėja. Geopolitinio-ekonominio centro formavimosi laikotarpiu komplikuotas ir probleminis tampa valstybių ekonominio saugumo užtikrinimas. Iškyla klausimas kokias priemones ir kuo remiantis pasitelkia šios valstybės savo ekonominio saugumo stiprinimui. Šio tyrimo objektas yra Kinijos, Indijos ir Pietų Korėjos ekonominė diplomatija. Darbo tikslas: pritaikyti ir kritiškai įvertinti Herscher-Ohlin-Vanek (HOV) modelį įvykdant Kinijos, Indijos ir Pietų Korėjos ekonominės diplomatijos lyginamąją analizę po įstojimo į Pasaulio Prekybos Organizaciją. Tikslui pasiekti iškeliami šie uždaviniai: 1) ištirti saugumo kaitą ir ekonominės diplomatijos sampratą; 2) įvertinti HOV modelį bei jo metodologinį pritaikymą Kinijos, Indijos ir Pietų Korėjos ekonominės diplomatijos analizei; 3) išanalizuoti esminius Kinijos, Indijos ir Pietų Korėjos ekonominės diplomatijos bruožus; 4) ištirti Kinijos, Indijos ir Pietų Korėjos ekonominės diplomatijos įrankių panaudojimą ekonominiam saugumui užtikrinti; 5) empiriškai palyginus Kinijos, Indijos ir Pietų Korėjos ekonominės diplomatijos įrankius kritiškai įvertinti HOV modelį. Tyrimui naudojami metodai: aprašomasis metodas, kokybinių ir kiekybinių metodų sintezė, ekonominės diplomatijos HOV modelis bei lyginamasis metodas. Atlikus tyrimą gauti rezultatai, jog HOV modelis daugeliu... [toliau žr. visą tekstą] / In Asia develops new world geopolitical-ecanomic centre. Of most important countries in this process are China, India and South Korea. Complicated period of geopolitical-economic centre formation rises vulnerabilies and challenges for the assurance of these countries economic security. Rises questions that means and why use these countries for their economic security strengthening. The object of this research is the economic diplomacy of China, India and South Korea. The goal is: to use and critically evaluate Herscher-Ohlin-Vanek model after accomplished comparative analysis of China, India and South Korea economic diplomacy after their join to the World Trade Organization. The tasks are: 1) to survey the fluctuation of security and conception of economic diplomacy; 2) to evaluate HOV model and its methodological application to the analysis of China, India and South Korea economic diplomacy; 3) to analyse essential features of China, India and South Korea economic diplomacy; 4) to examine China, India and South Korea economic diplomacy tools appliance for the assurance of economic security; 5) after empirical comparision of China, India and South Korea economic diplomacy tools to critically evaluate HOV model. For the research are used: descriptive method, the synthesis of qualitive and quantitive methods, economic diplomacy HOV model and comparative analysis. After research obtained results show that HOV model in most of cases can be used to explain countries‘ economic... [to full text]

Nesta tese foi estudado o espalhamento Raman intensificado pela superfície (SERS) em regime de detecção de uma molécula em eletrodo de prata ativado por ciclos de oxidação e redução. Neste regime, de baixas concentrações, são observadas intensas flutuações de intensidade SERS as quais foram controladas neste substrato pela aplicação de potencial ao eletrodo, o que foi associado a alterações na concentração de moléculas adsorvidas na superfície do eletrodo. Além da dependência com o potencial aplicado, foram estudadas através de simulações Monte Carlo, a contribuição nestas flutuações da constante de adsorção das moléculas, do número de \"hot spots\" (regiões de altas intensificações SERS) e do tipo de \"hot spot\" (em termos de eficiência para detecção de espectros de uma molécula). Através destas simulações foram verificadas flutuações de intensidade muito semelhantes às observadas experimentalmente. Além das flutuações de intensidade foram também observadas flutuações de intensidades relativas, como por exemplo, das relações de intensidades anti-Stokes/Stokes, as quais foram interpretadas segundo um modelo de ressonância, através do qual foi possível estimar as energias de ressonância nos \"hot spots\". Alguns dos resultados indicaram a contribuição de ressonâncias finas, as quais foram interpretadas como resultado de interferências entre ressonâncias de plasmon de superfície. Interferências como estas foram demonstradas através de simulações pelo método DDA (\"Discrete Dipole appoximation\") em modelos simples de \"hot spots\" formados por nanobastões de Au. / In this thesis it was studied surface-enhanced Raman scattering (SERS) at single-molecule detection on Ag electrode activated by oxidation and reduction cycles. At this low concentration limit it was observed strong SERS intensity fluctuations that were controlled by the applied potential to the electrode and this control was associated to changes in surface concentration of adsorbed molecules. Furthermore, it was studied through Monte Carlo simulations the influence of adsorption constant, number of \"hot spots\" (regions of high SERS enhancements) and type of \"hot pot\" (in terms of efficiency for single-molecule detection). With such simulations, it was verified fluctuations of SERS intensities very similar to experimental observations. Besides absolute intensity fluctuations, we also observed fluctuations of relative intensities as, for instance, the. anti-Stokes to Stokes intensity ratios. These fluctuations were interpreted according to a resonance model, which made possible the estimative of resonance energies at the SERS \"hot spots\". Some of these results indicated the existence of sharp resonances that were interpreted as a result of interferences among surface plasmon resonances, which were demonstrated through DDA (Discrete Dipole Approximation) simulations in simple models of \"hot spots\" formed by Au nanorods

Nesta tese foi estudado o espalhamento Raman intensificado pela superfície (SERS) em regime de detecção de uma molécula em eletrodo de prata ativado por ciclos de oxidação e redução. Neste regime, de baixas concentrações, são observadas intensas flutuações de intensidade SERS as quais foram controladas neste substrato pela aplicação de potencial ao eletrodo, o que foi associado a alterações na concentração de moléculas adsorvidas na superfície do eletrodo. Além da dependência com o potencial aplicado, foram estudadas através de simulações Monte Carlo, a contribuição nestas flutuações da constante de adsorção das moléculas, do número de \"hot spots\" (regiões de altas intensificações SERS) e do tipo de \"hot spot\" (em termos de eficiência para detecção de espectros de uma molécula). Através destas simulações foram verificadas flutuações de intensidade muito semelhantes às observadas experimentalmente. Além das flutuações de intensidade foram também observadas flutuações de intensidades relativas, como por exemplo, das relações de intensidades anti-Stokes/Stokes, as quais foram interpretadas segundo um modelo de ressonância, através do qual foi possível estimar as energias de ressonância nos \"hot spots\". Alguns dos resultados indicaram a contribuição de ressonâncias finas, as quais foram interpretadas como resultado de interferências entre ressonâncias de plasmon de superfície. Interferências como estas foram demonstradas através de simulações pelo método DDA (\"Discrete Dipole appoximation\") em modelos simples de \"hot spots\" formados por nanobastões de Au. / In this thesis it was studied surface-enhanced Raman scattering (SERS) at single-molecule detection on Ag electrode activated by oxidation and reduction cycles. At this low concentration limit it was observed strong SERS intensity fluctuations that were controlled by the applied potential to the electrode and this control was associated to changes in surface concentration of adsorbed molecules. Furthermore, it was studied through Monte Carlo simulations the influence of adsorption constant, number of \"hot spots\" (regions of high SERS enhancements) and type of \"hot pot\" (in terms of efficiency for single-molecule detection). With such simulations, it was verified fluctuations of SERS intensities very similar to experimental observations. Besides absolute intensity fluctuations, we also observed fluctuations of relative intensities as, for instance, the. anti-Stokes to Stokes intensity ratios. These fluctuations were interpreted according to a resonance model, which made possible the estimative of resonance energies at the SERS \"hot spots\". Some of these results indicated the existence of sharp resonances that were interpreted as a result of interferences among surface plasmon resonances, which were demonstrated through DDA (Discrete Dipole Approximation) simulations in simple models of \"hot spots\" formed by Au nanorods

Procedural Content Generation (PCG) and Dynamic Difficulty Adjustment (DDA) have been used separately in games to improve player experience. We explore using PCG and DDA together in a feedback loop to keep a player in the "flow zone." The central tenet of this work is a conjecture about how the shape of the performance versus difficulty curve changes at the boundaries of the flow zone. Based on this conjecture, we have developed an algorithm that detects when the player has left the flow zone and appropriately adjusts the difficulty to bring the gameplay back into flow, even as the skill of the player is changing. We developed a game-independent algorithm, implemented our algorithm for the open-source Infinite Mario Bros (IMB) game and conducted a user study that supports the hypothesis that players will enjoy the game more with DDA - PCG algorithm.

A síntese de imagens é uma ferramenta valiosa na compreensão de diversos fenômenos da natureza. Nos últimos anos várias abordagens têm sido propostas para sintetizar tais fenômenos. A grande maioria de tais abordagens têm se centralizado no desenvolvimento de modelos procedurais. Porém, cada uma destas técnicas simula exclusivamente um fenômeno natural. Um dos métodos de síntese de imagens fotorealísticas mais proeminente é denominado de Traçado de Raios (Ray Tracing). Contudo, apesar de produzir imagens de excelente qualidade, este método é computacionalmente muito oneroso. A síntese de fenômenos naturais utilizando-se o traçado de raios é um desafio. É importante que este problema seja abordado, apesar da sua complexidade, pois a simulaçao fotorealista da natureza é muito importante para os cientistas e pesquisadores desde o surgimento dos computadores. Um algoritmo versátil e rápido para a síntese de fenômenos da natureza através do traçado de raios utilizando campos de altitude é proposto. O algoritmo utiliza uma modificação do algoritmo do Analisador Diferencial Digital de Bresenham para atravesar uma matriz bidimensional de valores de altitude. A determinação das primitivas geométricas a serem interseccionadas por um raio é obtida num tempo ( N ) , sendo N o número de altitudes no campo de altitude. Este trabalho faz uma comparação em termos de velocidade e realismo deste método com outras abordagens convencionais; e discute as implicações que a implementação deste método traz. Finalmente, destaca-se a simplicidade e versatilidade que este método proporciona devido à pequena quantidade de parâmetros necessária para a síntese de fenômenos naturais utilizando o traçado de raios. Para a criação de animações basta a especificação de novos parâmetros num intervalo de tempo diferente. / Visualization is a powerful tool for better undestanding of several natural phenomena. In recent years, several techniques have been proposed. Considerable interest in natural scene synthesis has focused on procedural models. However, these techniques produce synthetic scenes of only one natural phenomenon. Ray tracing is one of the most photorealistic methods of image syntesis. While providing images of excellent quality, ray tracing is a computationally intensive task. Natural scene synthesis is a challenging problem within the realm of ray tracing. It is important to tackle this problem, despite of its complexity, because photorealistic simulation have been important to scientific community since the appearance of computers. A fast and versatile algorithm for ray tracing natural scenes through height fields is presented. The algorithm employs a modified Bresenham DDA to traverse a two dimensional array of values. The objects tested for intersection are located in ( N ) time where N is the number of values in the field. This work compares the speed-up and photorealism achieved in natural scene synthesis using this method with other algorithms and discusses the implications of implementing this approach. As a final point, the simplicity and versatility of synthesizing complex natural scenes from a few parameters and data is especially attractive. Animated sequences require only the additional specifications of time modified parameters or data.

Light scattering and surface Plasmon calculations were done on a variety of novel geometries using the DDSCAT software package, which simulates the scattering of objects using the discrete dipole approximation method. Calculations were done on core shell nanoparticles consisting of a silver shell and a TiO2 core in order to determine changes in the extinction spectrum and the near field patterns. Several geometries were tested, including spheres, cylinders, and hexagons, each of varying size and number. It was determined that when geometries were coupled together, there was significant near field enhancement where the geometries were in contact. This enhancement along with the increase in extinction in the visible region of the light spectrum makes these nanoparticles idea for solar cell technology, where they would increase efficiency.

To interpret the data from spaceborn lidar measurements, one must have a basic understanding of the backscattering of oriented ice particles. The conventional raytracing method is not applicable to the scattering of light by oriented particles. In this study, the dipole approximation (DDA) method is employed to the scattering of light on oriented hexagonal ice columns and plates with various tilting angles. It is found that the oriented hexagonal ice particles tend to have strong backscattering intensity with low depolarization ratios which are strongly dependant on the tilting angle of oriented particles. The present results show that the e ffect of particle orientation plays an important role in determining the optical properties of ice clouds consisting of horizontally oriented ice crystals.

Diatom-diazotroph associations contribute extensively to vertical flux in the modern ocean, and are linked to extensive sedimentary layers in the paleo-record formed either by rapidly sinking aggregates or more slowly sinking cells and chains. Although diatom sinking rates have been extensively studied, the sinking rates of these diatom symbioses are poorly documented. The effect of silicate and phosphate limitation on the sinking rate of Hemiaulus hauckii and its symbiont Richelia intracellularis were determined in semi-continuous cultures using a SETCOL. TEP (transparent exopolymer particle) was measured concurrently for linkages to aggregate formation. Although cells occurred in chains of 1-20 cells long, aggregate formation did not occur in semi-continuous cultures. There was no significant effect of P or Si limitation on sinking rates compared to controls. Although H. hauckii possess a symbiont that lacks gas vesicles, sinking rates (0.04-0.72 m/day) were within the range predicted by size-rate relationships. A portion of each H. hauckii experimental measurement ascended as well with significant differences found between the lowered P 80% exchange and the lowered Si with 80% exchange (p=0.05) and between the lowered Si with 80% exchange and the Si control batch culture (p=0.039). TEP production did not change significantly between treatments. However, a fraction of TEP in each population was positively buoyant as well, with ascent rates between 0.32-0.49 m/day. This study confirms an earlier report of positive buoyancy in TEP as well as noting that a significant fraction of the Hemiaulus symbiosis can be ascending within the population. / text

A síntese de imagens é uma ferramenta valiosa na compreensão de diversos fenômenos da natureza. Nos últimos anos várias abordagens têm sido propostas para sintetizar tais fenômenos. A grande maioria de tais abordagens têm se centralizado no desenvolvimento de modelos procedurais. Porém, cada uma destas técnicas simula exclusivamente um fenômeno natural. Um dos métodos de síntese de imagens fotorealísticas mais proeminente é denominado de Traçado de Raios (Ray Tracing). Contudo, apesar de produzir imagens de excelente qualidade, este método é computacionalmente muito oneroso. A síntese de fenômenos naturais utilizando-se o traçado de raios é um desafio. É importante que este problema seja abordado, apesar da sua complexidade, pois a simulaçao fotorealista da natureza é muito importante para os cientistas e pesquisadores desde o surgimento dos computadores. Um algoritmo versátil e rápido para a síntese de fenômenos da natureza através do traçado de raios utilizando campos de altitude é proposto. O algoritmo utiliza uma modificação do algoritmo do Analisador Diferencial Digital de Bresenham para atravesar uma matriz bidimensional de valores de altitude. A determinação das primitivas geométricas a serem interseccionadas por um raio é obtida num tempo ( N ) , sendo N o número de altitudes no campo de altitude. Este trabalho faz uma comparação em termos de velocidade e realismo deste método com outras abordagens convencionais; e discute as implicações que a implementação deste método traz. Finalmente, destaca-se a simplicidade e versatilidade que este método proporciona devido à pequena quantidade de parâmetros necessária para a síntese de fenômenos naturais utilizando o traçado de raios. Para a criação de animações basta a especificação de novos parâmetros num intervalo de tempo diferente. / Visualization is a powerful tool for better undestanding of several natural phenomena. In recent years, several techniques have been proposed. Considerable interest in natural scene synthesis has focused on procedural models. However, these techniques produce synthetic scenes of only one natural phenomenon. Ray tracing is one of the most photorealistic methods of image syntesis. While providing images of excellent quality, ray tracing is a computationally intensive task. Natural scene synthesis is a challenging problem within the realm of ray tracing. It is important to tackle this problem, despite of its complexity, because photorealistic simulation have been important to scientific community since the appearance of computers. A fast and versatile algorithm for ray tracing natural scenes through height fields is presented. The algorithm employs a modified Bresenham DDA to traverse a two dimensional array of values. The objects tested for intersection are located in ( N ) time where N is the number of values in the field. This work compares the speed-up and photorealism achieved in natural scene synthesis using this method with other algorithms and discusses the implications of implementing this approach. As a final point, the simplicity and versatility of synthesizing complex natural scenes from a few parameters and data is especially attractive. Animated sequences require only the additional specifications of time modified parameters or data.