Dental caries is a multifactorial, bacterial, chronic infection that affects millions of people in the world and has become a public health problem. Also referred to as tooth decay, this disease is one of the most common disorders throughout the world, second only to the common cold. Dental caries is the most common chronic childhood disease in the United States and is 5 to 7 times more common than asthma. According to the World Oral Health Report in 2003, dental caries affect 60-80% of school children and a vast majority of adults. Dental caries is a chronic bacterial infection of the hard tissue of the tooth that is characterized by alternating phases of demineralization and remineralization. Dental decay can lead to significant pain and dysfunction that can interfere with basic functions such as eating, sleeping, and speaking. If left untreated, dental caries can result in cavities forming and eventually tooth loss. Although the prevalence and severity of dental caries has decreased over the years, this disease can be better controlled with proper fluoride exposure. Fluoride therapy has become the cornerstone strategy in the prevention of dental caries development and progression. With fluoride being available in various forms, fluoride exposure and/or treatment has greatly increased and has led to decreased incidences of dental caries. Fluoride has the ability to control the initiation and progression of carious lesions, mainly through the promotion of remineralization and the reduction in tooth enamel demineralization. Whether administered systemically or topically, the use of fluoride has proven to be effective in reducing the prevalence of dental caries. The aim of this review is to compare the topical methods of fluoride therapy with systemic applications. The goal is to evaluate the various forms of fluoride treatments based on cost effectiveness, safety, concentration and dosage of fluoride, ease of application, and accessibility to the community. This review will also identify the populations that are most susceptible to dental caries. The purpose of this review is to examine the benefits and risks of the various options of fluoride treatments in order to determine which would be the most the effective, safe, and efficient means of preventing dental caries in high risk populations. Based on the literature review, it was determined that the populations with the greatest risk for dental caries comprised of young children who were from lower socioeconomic backgrounds and elderly adults over the age of 65. After comparing the various forms of fluoride therapies, it was found that systemic fluoride treatments, mainly water fluoridation, would be the most effective in preventing dental caries in high caries risk populations.

Progress in the description of stellar evolution is driven by the collaborative effort of nuclear physics, astrophysics and astronomy. Using those developments, the theory of the origin of elements in the Universe is challenged. This thesis addresses the problem behind the abundance of 44Ti and the origin of 26Al. The mismatch between the predicted abundance of 44Ti as produced by the only sites known to be able to create 44Ti, core collapse supernovae (CCSNe), and the observations, highlight the current uncertainty that exists in the physics of these stars. Several satellite based γ-ray observations of the isotope 44Ti have been reported in recent times and confirm the disagreement. As the amount of this isotope in stellar ejecta is thought to critically depend on the explosion mechanism, the ability to accurately model the observed abundance would be a pivotal step towards validating that theory. The most influential reaction to the amount of 44Ti in supernovae is 44Ti(α, p)47V. Here we report on a direct study of this reaction conducted at the REX-ISOLDE facility, CERN. The experiment was performed at a centre of mass energy 4.15±0.23 MeV, which is, for the first time, well within the Gamow window for core collapse supernovae. The experiment employed a beam of 44Ti extracted from highly irradiated components of the SINQ spallation neutron source of the Paul Scherrer Institute. No yield above background was observed, enabling an upper limit for the rate of this reaction to be determined. This result is below expectation, suggesting that the 44Ti(α, p)47V reaction proceeds more slowly than previously thought. Implications for astrophysical events, and remnant age, are discussed. In Wolf-Rayet and asymptotic giant branch (AGB) stars, the 26gAl(p,γ)27Si reaction is expected to govern the destruction of the cosmic γ-ray emitting nucleus 26Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of several resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the 26gAl(d, p)27Al reaction as a method for constraining the strengths of key astrophysical resonances in the 26gAl(p,γ)27Si reaction. In particular, the results indicate that the resonance at Er = 127 keV in 27Si determines the entire 26gAl(p, γ)27Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars. The measurements of spectroscopic factors for many states in 27Al and a shell model calculation of nuclear properties of rp-resonant states in 27Si also allow for testing the structure model.

Using 3 fb-1 of pp collision data collected at √s = 7 and 8 TeV by the LHCb experiment in the 2011 and 2012 data taking periods, the decays B⁰s → ϕπ+π- and B⁰d → ϕπ+π- have been studied in the π+π- invariant mass range below 1600 MeV/c². The B⁰s,d → ϕπ+π- branching fractions are determined to be: B(B⁰s → ϕπ+π-;mππ < 1600) = [3:72 ± 0:18 ± 0:38 ± 0:38] x 10-6 B(B⁰d → ϕπ+π-,mππ < 1600) = [1:75 ± 0:25 ± 0:42 ± 0:14] x 10-7 where the first uncertainty is statistical, the second is systematic, and the third comes from the normalisation mode B⁰s → ϕϕ. From the π+π- mass distribution and fits to angular distributions, the resonant decay mode B⁰s → ϕf₀(980) is observed and the branching fraction is measured to be: B(B⁰s → ϕf₀(980); f₀(980) → π+π-) = [1:23 ± 0:15 ± 0:12 ± 0:12] x 10-6 The fit also requires contributions from B⁰s → ϕf2(1270). A search for a P-wave contribution from B⁰s → ϕρ⁰(770) finds evidence at ~ 4σ but confirmation will require more data. An upper limit of the B⁰s → ϕρ⁰(770) decay branching fraction at 90% C.L. is measured to be: B(B⁰s → ϕρ⁰(770)) < 4 x 10-7.

Durante décadas, a visão prevalente em ecologia de microrganismos era de que os fatores ambientais locais seriam os únicos agentes estruturantes das comunidades e dos padrões de coexistência das espécies. Entretando, estudos recentes têm fornecido evidência de que processos ligados a dispersão possam ser tão importantes quanto o ambiente local na estruturação das comunidades, reacendendo o debate em torno da hipótese clássica sobre a ubiquidade dos microrganismos. Neste estudo, nós examinamos os padrões de coexistência do fitoplâncton e os possíveis determinantes da variação espacial na composição das comunidades em 9 lagoas do sul do Brasil. Nós testamos se as espécies fitoplanctônicas apresentam um padrão não aleatório de coexistência através de um modelo nulo e se distância espacial ou a distância ambiental possuem relação com a similaridade na composição das comunidades. Nós também investigamos se as variáveis ambientais locais são bons preditores da abundância das espécies. Na análise de coexistência, nós não observamos um padrão significativo de estruturação dentro das lagoas, mas encontramos um padrão não-aleatório e segregado das espécies ao longo das lagoas, indicando que as espécies coexistem menos do que o esperado ao acaso nesta escala. A similaridade na composição das comunidades mostrou correlação significativa com a distância ambiental, mas não foi correlacionada com a distância geográfica entre os sítios. Além disso, a variação na abundância das espécies apresentou correlação significativa com as variáveis ambientais locais (transparência da água, condutividade, nitrato e ortofosfato). Em conclusão, nossos resultados apoiam a visão de que a variação espacial do fitoplâncton é melhor explicada pelo ambiente local. Nós não testamos a influência de variáveis históricas e filogenéticas sobre esses padrões, que podem ser temas de estudos futuros, a fim de elucidar ainda mais essas questões. / For decades, the main hypothesis in microbial ecology was that local environment would be the only mechanism structuring communities and patterns of species coexistence. However, recent studies have provided evidence that processes related to dispersion can be as important as the local environment for shaping biological communities, stimulating new debates on the classical hypothesis about the ubiquity of microorganisms. In this study, we examined the phytoplankton coexistence patterns and possible determinants of spatial variation in community composition in 9 lakes of southern Brazil. First, we use a null model analysis for tested whether the phytoplankton species show a nonrandom pattern of coexistence. We also tested whether spatial distance or environmental distance act as potential factors controlling community composition. Finally, we investigated whether local environmental variables are good predictors of species abundance. We did not observe a significant pattern of coexistence species in the within-lakes analysis, but we found a nonrandom pattern of coexistence and segregation of species across-lakes analysis, indicating that the species coexist less than expected by chance on this scale. Phytoplankton community composition showed a strong positive correlation with the environmental distance but was not correlated with the geographical distance between sites. Moreover, the variation in the abundance of species showed significant correlation with local environmental variables (water transparency, conductivity, nitrate and orthophosphate). In conclusion, our results support the view that the spatial variation of phytoplankton is best explained by the local environmental conditions. We suggest that the influences of historical and phylogenetic variables on these patterns, here not measured, be analyzed in future studies, to further elucidate these questions.

Este estudo é dedicado ao entendimento do decaimento D+ K++. Desenvolvemos dois modelos que abordam aspectos complementares dos principais processos dinâmicos que atuam em tal decaimento: o v´ertice fraco, onde ocorre a transição c Ws, e as interações entre os três mesons no estado final. Este trabalho foi motivado por um resultado experimental importante sobre o decaimento D+ K++, no qual a fase em onda S de um par K do estado final não coincide com a fase do espalhamento K livre, chamado puzzle das fases. No primeiro modelo, as interações de estado final foram descritas por sucessivos reespalhamentos dos pares K, enquanto o vértice fraco foi aproximado por uma função sem estrutura. O espalhamento K é um ingrediente fundamental e é calculado usando uma lagrangiana efetiva quiral com ressonâncias. As amplitudes do decaimento são calculadas perturbativamente, ate a segunda ordem do reespalhamento K, para as três topologias acessíveis ao sistema. Os resultados do primeiro modelo mostram a importância das interações de estado finais, sendo o efeito da interação própria de três corpos essencial para a boa descrição dos dados experimentais obtida a partir de uma das topologias. No segundo modelo, o vértice fraco do decaimento é calculado a partir de uma teoria efetiva que acopla o setor leve de SU(3) ao setor do charme e descreve todas as interações, fortes e fracas, entre os dois setores. Esse modelo inclui a dependência correta de momento nos vértices e contém essencialmente três melhorias: (i) incorpora corretamente a estrutura de onda P no vértice fraco ao usar correntes do tipo V A; (ii) inclue o vértice V DK parametrizado em termos de fatores de forma monopolares; e (iii) inclue no vértice V a transição W intermediada pela ressonância , o que d´a origem a um fator de forma forte. Os resultados do segundo modelo mostram que o efeito dos fatores de forma no vértice D K são pequenos e mais importantes em altas energias. A inclusão do meson como uma ressonância é muito significativa e desloca a fase para 90o no limiar, o que explica o comportamento qualitativo dos dados experimentais na mesma região. / This study describer the D+ K++ decay. We developed two models for complementary issues of the main dynamic process in this system: the weak vertex, where the transition c Ws takes place, and the interactions between the three mesons in the final state. This work was motivated by important experimental results for D+ K++ decay in which the S wave phase for a K pair in the final state does not agree with the phase from K free scattering amplitude, which is here named phase puzzle. In the first model, the interaction in the final states are treated as successive rescattering between K pairs, and the weak vertex is approximated as structureless functions. The K amplitude is a fundamental ingredient and is calculated using an effective quiral lagrangian with resonances. The decay amplitudes were solved perturbatively up to second order in K rescattering for all the three topologies that can contribute. The results for the first model show the importance of final state interactions where the proper three body effect are essential for the good description of experimental data, obtained from one of the topologies. In the second model, the weak vertex is calculated using an effective theory that couples the light SU(3) sector to the charm sector and describes all interactions, strong and weak, between the two sectors. This model includes the correct momentum dependences at verticies and contain mainly three improvements: (i) correctly incorporates the P- wave momentum structure in the vertex through the use of V A currents; (ii) includes V DK vertex parametrized by monopoles form factors; and (iii) includes in the V vertex the W transition intermediated by a r resonance, which gives rise to a strong form factor. The results for the second model show that the form factors effects on D K vertex are small and more important at higher energy. The inclusion of the meson as a resonance is very significant and dislocates the phase shift from zero to 90o at threshold, which explains the qualitative experimental data behaviour in the same region.

<div>In this work new methodologies for measuring and monitoring nuclear decay parameters is explored. A determination of the tritium half-life by measuring the current of a betavoltaic device is presented. The benefits of this approach in exploring the possibility of time dependence of nuclear decay parameters is discussed.</div>

Neste trabalho analisamos algumas consequências físicas de uma cosmologia acelerada com interação no chamado setor cósmico escuro (energia escura + matéria escura fria). A componente de energia escura é representada por uma densidade de energia do vácuo que varia com o tempo e cuja lei de decaimento tem a seguinte forma: $\\Lambda = \\Lambda_0 + {3\\alpha}/{a^{2}}$, onde $\\Lambda_0$ é o termo de vácuo usual, $\\alpha$ é um parâmetro livre e $a(t)$ o fator de escala. Nesse contexto discutimos a tensão existente entre os dados de Supernovas (que preferem um Universo fechado, $\\Omega_{\\kappa} > 0$) e os dados da radiação cósmica de fundo que favorecem um Universo espacialmente plano ($\\Omega_{\\kappa} = 0$). Considerando que o termo variável simula uma curvatura (pois ambos possuem a mesma dependência no fator de escala), mostramos que sua contribuição atua no sentido de aliviar a tensão SNe Ia-CMB existente no modelo de concordância cósmica padrão ($\\Lambda CDM$, $\\alpha=0$). O modelo resolve o problema da idade do Universo e para $a>>1$, tal como ocorre com $\\Lambda CDM$, também evolui para um estágio de Sitter. O parâmetro $\\alpha$ é limitado através de uma análise estatística conjunta envolvendo dados de Supernovas, CMB ({\\it shift parameter}) e oscilações acústicas dos bárions (BAO). Separando o termo de vácuo em duas componentes ($\\Omega_{\\Lambda 0}$ e $\\Omega_{\\alpha 0}$) um teste $\\chi^{2}$ fornece os seguintes valores para o modelo plano: $\\Omega_{m0} = 0,27 \\pm 0,02$, $\\Omega_{\\Lambda 0} = 0,74 \\pm 0,02$ e $\\Omega_{\\alpha 0} = -0,01 \\pm 0,03$. / In this work we analyze some physical consequences of an accelerating cosmology endowed with interaction in the cosmic dark sector (dark energy + cold dark matter). The dark energy component is represented by a time-dependent vacuum energy whose decay law has the following form: $\\Lambda = \\Lambda_0 + {3\\alpha}/{a^{2}}$, where $\\Lambda_0$ is the standard vacuum term, $\\alpha$ is a free parameter and $a(t)$ is the scale factor. In this context we discuss the existing tension between Supernovas (SNe Ia, which prefer a closed Universe, $\\Omega_{\\kappa} > 0$) and the cosmic background radiation (CMB) data (which are favoring a spatially flat Universe, $\\Omega_{\\kappa} = 0$). By considering that the variable $\\Lambda$-term mimics a curvature (since both terms have the same dependence on the scale factor), we show that its contribution helps to alleviate the tension SNe Ia-CMB existing in the standard cosmic concordance model. The present model solves the age of the Universe problem and for $a>>1$, it also evolves to a de Sitter model as occur with the $\\Lambda CDM$ scenario. The contribution of the $\\alpha$ parameter is limited through a joint statistical analysis involving Supernovas, CMB ({\\it shift parameter}) and baryon acoustic oscillations (BAO). By separating the variable vacuum term in two components ($\\Omega_{\\Lambda 0}$ e $\\Omega_{\\alpha 0}$), a $\\chi^{2}$ test furnishes the following values for the free parameters of the flat model: $\\Omega_{m0} = 0,27 \\pm 0,02$, $\\Omega_{\\Lambda 0} = 0,74 \\pm 0,02$ and $\\Omega_{\\alpha 0} = -0,01 \\pm 0,03$.

Neste trabalho são apresentados resultados experimentais referentes ao decaimento beta do Nb POT.92, obtidos a partir de medidas da atividade gama residual que segue a reação Nb POT.93 (gamma, n). A alimentação do nível a 2067 keV do Zr POT.92 foi determinada com boa precisão. A não observação de transições gama que envolvem os níveis 0 POT.+ e 4 POT.+ do Zr POT.92 permitiram, a partir de uma analise estatística rigorosa determinar-se limites superiores para a alimentação desses níveis. Os resultados experimentais obtidos, bem como diversos outros disponíveis na bibliografia especializada, foram analisados a luz do modelo de camadas, explorando-se especialmente a contribuição do orbital de nêutrons g IND.7/2 nos primeiros níveis excitados do Zr POT.92. Os cálculos foram feitos usando-se valores publicados para os elementos de matriz da interação residual próton-próton e supondo-se uma interação delta superficial para a interação nêutron-nêutron. / We have investigated the beta decay of Nb POT.92 measuring the residual gamma activities associated with the Nb POT.93 (gamma, n) reaction. The beta branch to the 2067 keV Zr POT.92 level has been determined. Unobserved gamma-rays, with a rigorous statistical analysis, allow the determination of upper limits to beta transitions to the 0 POT.+ and 4 POT.+ levels of Zr POT.92. We have compared ours and other published results with the predictions of shells model, exploring the g IND.7/2 neutron orbit contribution to the levels of Zr POT.92 The shell model calculations have been made using published values for the proton-proton matrix elements. The neutron-neutron matrix elements have been determined assuming a surface delta interaction.

Neste trabalho analisamos algumas consequências físicas de uma cosmologia acelerada com interação no chamado setor cósmico escuro (energia escura + matéria escura fria). A componente de energia escura é representada por uma densidade de energia do vácuo que varia com o tempo e cuja lei de decaimento tem a seguinte forma: $\\Lambda = \\Lambda_0 + {3\\alpha}/{a^{2}}$, onde $\\Lambda_0$ é o termo de vácuo usual, $\\alpha$ é um parâmetro livre e $a(t)$ o fator de escala. Nesse contexto discutimos a tensão existente entre os dados de Supernovas (que preferem um Universo fechado, $\\Omega_{\\kappa} > 0$) e os dados da radiação cósmica de fundo que favorecem um Universo espacialmente plano ($\\Omega_{\\kappa} = 0$). Considerando que o termo variável simula uma curvatura (pois ambos possuem a mesma dependência no fator de escala), mostramos que sua contribuição atua no sentido de aliviar a tensão SNe Ia-CMB existente no modelo de concordância cósmica padrão ($\\Lambda CDM$, $\\alpha=0$). O modelo resolve o problema da idade do Universo e para $a>>1$, tal como ocorre com $\\Lambda CDM$, também evolui para um estágio de Sitter. O parâmetro $\\alpha$ é limitado através de uma análise estatística conjunta envolvendo dados de Supernovas, CMB ({\\it shift parameter}) e oscilações acústicas dos bárions (BAO). Separando o termo de vácuo em duas componentes ($\\Omega_{\\Lambda 0}$ e $\\Omega_{\\alpha 0}$) um teste $\\chi^{2}$ fornece os seguintes valores para o modelo plano: $\\Omega_{m0} = 0,27 \\pm 0,02$, $\\Omega_{\\Lambda 0} = 0,74 \\pm 0,02$ e $\\Omega_{\\alpha 0} = -0,01 \\pm 0,03$. / In this work we analyze some physical consequences of an accelerating cosmology endowed with interaction in the cosmic dark sector (dark energy + cold dark matter). The dark energy component is represented by a time-dependent vacuum energy whose decay law has the following form: $\\Lambda = \\Lambda_0 + {3\\alpha}/{a^{2}}$, where $\\Lambda_0$ is the standard vacuum term, $\\alpha$ is a free parameter and $a(t)$ is the scale factor. In this context we discuss the existing tension between Supernovas (SNe Ia, which prefer a closed Universe, $\\Omega_{\\kappa} > 0$) and the cosmic background radiation (CMB) data (which are favoring a spatially flat Universe, $\\Omega_{\\kappa} = 0$). By considering that the variable $\\Lambda$-term mimics a curvature (since both terms have the same dependence on the scale factor), we show that its contribution helps to alleviate the tension SNe Ia-CMB existing in the standard cosmic concordance model. The present model solves the age of the Universe problem and for $a>>1$, it also evolves to a de Sitter model as occur with the $\\Lambda CDM$ scenario. The contribution of the $\\alpha$ parameter is limited through a joint statistical analysis involving Supernovas, CMB ({\\it shift parameter}) and baryon acoustic oscillations (BAO). By separating the variable vacuum term in two components ($\\Omega_{\\Lambda 0}$ e $\\Omega_{\\alpha 0}$), a $\\chi^{2}$ test furnishes the following values for the free parameters of the flat model: $\\Omega_{m0} = 0,27 \\pm 0,02$, $\\Omega_{\\Lambda 0} = 0,74 \\pm 0,02$ and $\\Omega_{\\alpha 0} = -0,01 \\pm 0,03$.

The main purpose of this study was to determine if validity coefficients for ACT scores, both composite scores and subject area test scores, and high school grade point average (HSGPA) decayed or held stable over eight semesters of undergraduate study in science, technology, engineering, and mathematics (STEM) fields at civilian four-year institutions, and whether the decay patterns differed from those found in non-STEM fields at the same institutions. Data from 62,212 students at 26 four-year institutions were analyzed in a hierarchical meta-analysis in which student major category (SMC), gender, and admission selectivity levels were considered potential moderators. Four sets of analyses were run. The first was by the three SMCs: STEM-Quantitative majors, STEM-Biological majors, and non-STEM majors. The second was SMC by gender. The third was SMC by admission selectivity level. The fourth was SMC by gender by admission selectivity level. The results across all four analyses indicated that ACT score validity coefficients for STEM-Quantitative and STEM-Biological majors decayed less over eight semesters than the validity coefficients for non-STEM majors did. This was true for the uncorrected and corrected validity coefficients. For the HSGPA validity coefficients, this was true for the corrected validity coefficients. Non-STEM majors had very similar validity decay patterns regardless of the level of analysis. However, four of the eight STEM subgroups in the final set of analyses had minimal amounts of decay, and in some instances small amounts of validity growth.