We present HST spectroscopy for 45 cataclysmic variables (CVs), observed with HST/COS and HST/STIS. For 36 CVs, the white dwarf is recognisable through its broad Ly a absorption profile and we measure the white dwarf effective temperatures (T-eff) by fitting the HST data assuming log g = 8.35, which corresponds to the average mass for CV white dwarfs (similar or equal to 0.8M(circle dot)). Our results nearly double the number of CV white dwarfs with an accurate temperature measurement. We find that CVs above the period gap have, on average, higher temperatures (< T-eff > similar or equal to 23 000 K) and exhibit much more scatter compared to those below the gap (< T-eff >similar or equal to 15 000 K). While this behaviour broadly agrees with theoretical predictions, some discrepancies are present: ( i) all our new measurements above the gap are characterized by lower temperatures (T-eff similar or equal to 16 000-26 000 K) than predicted by the present-day CV population models (T-eff similar or equal to 38 000-43 000 K); (ii) our results below the gap are not clustered in the predicted narrow track and exhibit in particular a relatively large spread near the period minimum, which may point to some shortcomings in the CV evolutionary models. Finally, in the standard model of CV evolution, reaching the minimum period, CVs are expected to evolve back towards longer periods with mean accretion rates. M less than or similar to 2 x 10(-11)M(circle dot)yr(-1), corresponding to T-eff less than or similar to 11 500 K. We do not unambiguously identify any such system in our survey, suggesting that this major component of the predicted CV population still remains elusive to observations.

The ionization and thermal balances are considered for a gas that is ionized by a dilute radiation field, taking into account the diffuse ionizing radiation produced by the gas. A number of models are constructed in which the electron temperature and the ionization of the elements H, He, C, N, 0, Ne, and Mg are determined for optically thin and optically thick gases ionized by ultraviolet synchrotron radiation under different conditions. Conclusions are then drawn about the general characteristics of ionization by synchrotron radiation. It is shown that, in an optically thin gas, because of the insensitive frequency- dependence of synchrotron radiation each element occupies a number of different stages of ionization at any one point in the gas. It is also shown that in an optically thick gas the heavy elements remain ionized to much greater distances from the source than hydrogen and helium, and that the gas becomes thermally unstable when H and He have become almost completely neutral. In addition, observations of the emission -line intensities of the Crab Nebula are compared with a model of this object. Considerable disagreement exists between the observed and predicted intensities, and possible reasons for the discrepancy are discussed.

Intermittent sun exposure and sun sensitivity factors are the most well described risk factors for the development of cutaneous melanoma (CM). Other potential environmental risks for CM, such as arsenic, are rarely examined. Total sun exposure has not been a consistent risk factor for CM, but recall bias in self-reporting sun exposure throughout life may limit the ability to detect a true association. Objective measures of sun exposure including remotely sensed ambient ultra-violet radiation (UVR) may allow for better capture of total sun exposure. In three chapters, spatially derived factors (ambient UVR, environmental soil arsenic, drinking water arsenic) were observed to determine their relevance in exposure assessment and subsequent risk for CM.UVR trends were investigated using available satellite data (1978-2014) to generate inferences for UVB changes over time in the United States. We found that UVB changed across the study area, but these changes lack biological relevance based on the magnitude of changes observed. Thus, a more objective measure of lifetime ambient sun exposure may be estimated using 30-year average UVR by month in future studies. The spatial correlation between environmental soil arsenic and drinking water across the state of Iowa was investigated. Arsenic concentrations in soil were not significantly spatially correlated with either municipal public water source or non-municipal water source arsenic concentrations. Based on these findings, soil arsenic may not serve as a valid surrogate marker for arsenic in drinking water.In Chapter 5, we assessed the relationship of spatially derived estimates of lifetime ambient UVR, environmental arsenic exposure from soil and drinking water, and CM in a population-based case-control study. Our findings suggest that total sun exposure is positively associated with CM, while arsenic concentration in environmental soil and drinking water were not associated. Sun exposure measured through ambient UVR exposure may allow for better understanding of the association between cumulative or total sun exposure and CM. Additionally, more studies need to be completed to estimate the potential risks for CM in regions where high arsenic concentrations may not be endemic.

The slope of the ultraviolet continuum emissions from a galaxy between 1250 and 2600 Å provides insights about several facets of the galaxy. Mainly, it is well-correlated with the amount of dust. This work presents a search for objects whose UV-continuum slopes are excessively steep, as well as suggestions for follow-up. The method used is looking through existing data sets, and proposing follow-up of the outliers in the distribution of slopes. Close to fifteen objects with slopes beyond what is easily explained by theory are presented. Since these lie beyond the realm of current theories, confirmations of these may hint at more extreme stellar populations than those currently known. This may include excessively metal-poor stars such as population III stars, or stellar populations where the initial mass function (IMF) for some reason may be biased towards massive stars. Steeper slopes are in general indicative of a lack of dust and an abundance of hot, blue stars; this is due to the reddening caused by dust, and emissions from cooler stars being peaked at longer wavelengths.

This thesis describes an experimental study of high intensity, pulsed, optically pumped, far-infrared (FIR) lasers. The work was motivated by the need for a radiation source for the measurement of the ion temperature in magnetically confined, high temperature plasmas (e.g. tokamak plasmas), using Thomson scattering. Constraints imposed by the plasma parameters, the scattering geometry and available detector sensitivities lead to the requirement of a radiation source wavelength between 30μm and 1mm and a source power . 1 MW in a bandwidth 60 MHz. Results are presented for a 496μm, 500 watt, methyl fluoride (CH₃F) cavity laser, with a bandwidth of and < 30MHz, which was optically pumped by a 9.55μm CO₂ laser. Results are also presented for an optically excited mirrorless, super-radiant, CH₃F laser, which generated over 0.6MW of FIR radiation within a bandwidth of about 300MHz. The performance of this laser has also been simulated by a computer model, which allows the optimum operating parameters to be predicted. An assembly constructed on the principle of the injection laser, in which low power narrow-band oscillator radiation is used to control the output of a super-radiant system, has been used to generate 250 kW of 496 andmu;m radiation, with a bandwidth of < 60 MHz. Investigations of the FIR output from heavy water vapour (D₂O) in a super-radiant laser assembly, optically excited by several different CO₂ laser wavelengths, have resulted in the generation of 60 ns (FWHM) pulses of FIR radiation with average powers of 1.3, 9.2 and 15.8MW, at wavelengths of 385, 119 and 66μm, respectively. All these lasers were found to have a higher CO₂ to FIR photon conversion efficiency than the 496μm CH₃F laser. In addition, the energy level spacing in D₂O is such that the molecule can generate narrow bandwidth radiation more readily than the CH₃F molecule. From this work it is concluded that an injection laser assembly, similar to that used with CH₃F, but containing D₂O vapour, optically pumped by a 9.26μm CO₂ laser and generating several megawatts of 385μm radiation, would satisfy the source requirements mentioned above.

Quantum mechanical motion of electrons in atoms and molecules is at the heart of many photophysical and photochemical processes. As the natural timescale of electron dynamics is in the range of femtoseconds or shorter, ultrashort pulses are required to study such phenomena. The ultrashort pulse light-matter interaction at high intensity regime can however dramatically alter the atomic and molecular structures. Our current understanding of such transient electronic modification is far from complete, especially when complicated light-induced couplings are involved. In this dissertation, we investigated how a femtosecond strong-field pulse can control or modify the evolution of atomic or molecular polarization, representing electric dipole excitation in various systems. Extreme ultraviolet (XUV) attosecond pulse trains are used to coherently prepare superposition of excited states in various atomic and molecular systems. A subsequent phase-locked infrared (IR) femtosecond pulse is applied to perturb the dipoles, and transient changes in the transmitted XUV spectra are measured. This scheme is termed as XUV attosecond transient absorption spectroscopy. In the first study, we applied this technique to study the modification of Rydberg states in dilute helium gas. We observed several transient changes to the atomic structure, including the ac Stark shift, laser-induced quantum phase, laser-induced continuum structure, and quantum path interference. When the experiments were extended to the study of a dense helium gas sample, new spectral features in the absorption spectra emerged which cannot be explained by linear optical response models. We found that these absorption features arise from the interplay between the XUV resonant pulse propagation and the IR-imposed phase shift. A unified physical model was also developed to account for various scenarios. Extending our work to argon atoms, we studied how an external infrared field can be used to impulsively control different photo-excitation pathways and the transient absorption lineshape of an otherwise isolated autoionizing state. It is found that by controlling the field polarization of the IR pulse, we can modify the transient absorption line shape from Fano-like to Lorentzian-like profiles. Unlike atoms, in our study of autoionizing states of the oxygen molecule, we observed both positive and negative optical density changes for states with different electronic symmetries. The predictions of two distinct and simplified dipole perturbation models were compared against both the experimental results and a full theoretical calculation in order to understand the origin of the sign of absorption change. We relate this symmetry-dependent sign change to the Fano parameters of static photoabsorption. The same approach was applied to study molecular nitrogen, in which we observed the decay dynamics of IR perturbed doubly-excited Rydberg states with many vibrational progressions. In addition, we also conducted experiments to investigate Rydberg state dynamics of other molecular systems such as carbon dioxide. In summary, we experimentally explored the ephemeral light-induced phenomena associated with excited states of atoms and molecules. These studies provide real-time information on ultrafast electronic processes and provide strategies for direct time-domain control of the light-matter interaction.

A cloração é largamente utilizada para a desinfecção de águas de abastecimento e residuárias, porém o potencial de toxicidade da cloração por seus subprodutos torna o processo menos atrativo. O dióxido de cloro surge como alternativa de desinfecção, porém a sua geração envolve reações bastante dependentes das concentrações de reagentes, das condições físico-químicas, podendo gerar também subprodutos prejudiciais à saúde humana. Outras tecnologias alternativas, como o ozônio e a radiação ultravioleta apareceram como processos tecnicamente viáveis. Neste trabalho buscou-se realizar revisão crítica da literatura existente sobre a desinfecção realizada com radiação ultravioleta e ozônio, bem como investigar e interpretar os aspectos relevantes do desempenho da desinfecção de efluentes de esgoto sanitário com ozônio e com radiação ultravioleta na inativação de coliformes totais e coliformes fecais. Na parte experimental avaliou-se as doses de 80, 95 e 120 mg/L e tempos de contato de 20, 30 e 35 minutos para a desinfecção com ozônio. Na desinfecção com radiação ultravioleta, utilizou-se de tempos de exposição de 10, 30, e 60 segundos, mantendo-se a mesma intensidade média de radiação e variando-se a espessura de lâmina líquida. Nos aspectos observados no decorrer desta pesquisa, verificou-se que para as condições analisadas, a desinfecção com radiação ultravioleta mostrou-se como técnica mais simples e eficaz para a inativação de coliformes fecais e coliformes totais quando comparada à ozonização, apresentando assim vários aspectos favoráveis no que concerne ao modo de operação, a influência da qualidade do efluente bruto, ao controle do processo, entre outros. / The Chlorinate is widely used for the disinfection of waste and drinking water, however the toxicity potential by the by-products of chlorinate renders the process less attractive. The chlorine dioxide comes up as a disinfection alternative, but its production involves highly reagent concentration and physical-chemical condition dependant reactions, also being able to create human health hazardous by-products. Other alternative technologies, like ozone and ultraviolet radiation have risen as technically viable processes. It this work, is has been attempted to review critically the existing literature about the effluent disinfection of sanitary waste, using a comparative approach between the disinfection in which ozone and ultraviolet radiation were used, as well as to investigate and interpret the relevant aspects of sanitary waste effluents disinfection with ozone and ultraviolet radiation on the inactivation of otal and fecal coliforms. In the experimental part doses of 80, 95 and 120 mg/L and contact times of 20, 30 and 35 minutes have been evaluated for the ozone disinfection process. For the ultraviolet method, exposure times of 10, 30 and 60 seconds have been used, keeping the same mean intensity of radiation and varying water layer thickness. With regard to the observed of thios research, is has been verified that, for the analyzed conditions, the ultraviolet disinfection has showed the simplest and most effective method of the inactiviation of fecal andtotal coliforms when compared the ozone method, thus showing several favorable aspects concerning the operation mode, the wal effuent quality influence, the process control, among others.

A grande maioria das infecções causadas em ambientes médicos-odontológicas é proveniente de contaminações cruzadas, quando se tem contato entre diferentes instrumentos e /ou aparelhos contaminados após procedimentos médicos. Atualmente o padrão aceito e amplamente utilizado para esterilização de instrumental são os equipamentos chamados de autoclaves, em que é reconhecido e aceito pelos órgãos legisladores. Porém alguns tipos de instrumental e material não podem ser esterilizados utilizando este método tendo uma outra vertente que é aplicação de agentes químicos. Esses criam problemas socioambientais relacionados a sua utilização e descarte. Dessa forma, o objetivo deste trabalho foi desenvolver uma autoclave multifuncional com a utilização de gás ozônio, ultravioleta e calor úmido, em que se testou e analisou microbiológica os protocolos de esterilização, obtendo entendimento e otimização do mesmo. Os resultados mostraram-nos que a configuração desenvolvida atingiu aspectos de esterilidade nos protocolos de esterilização avaliados. Entretanto tem a necessidade de aprofundar estudos aplicando o baixo vácuo para o entendimento quanto a utilização quanto os protocolos do funcionamento e uma futura otimização para produção em larga escala. / Most of infection in the medical-dental office is prevenient of cross-contamination, when have the contact with different instrumental and materials without basic control after the process and contact on patient. This point have the standard protocol was accept and described in literature, its utilizing for instrumental sterilizing is the autoclave, it is recognized by organs legislators. However, some instrumental and materials not be accept in this method, on this is necessary one method second in this case is chemical on the instrumentation, but created environmental problem in relation its application. Therefore, this research made the proof of conception in the multifunctional autoclave with the option ozone, ultraviolet and moist heat, what it is analyzing the microbiological protocols of the sterilizing, understanding and optimization the sterilizing process. This results show us which this constructive configuration in this work reached aspects of the sterilizing in the protocols, describe in this text. In the future research in this subject could be study the strongly aspects about the vacuum process before the sterilizing process with ozone gas and development and optimization the prototype for make the scaling up.

O presente trabalho desenvolveu um estudo sobre a blenda polimérica Polipropileno/Poli(3-hidroxibutirato) (PP/PHB). Os principais objetivos desta pesquisa foram estudar a compatibilização da blenda PP/PHB, a influência da prévia fotodegradação sobre a biodegradação da blenda e o comportamento individual do PHB frente a fotodegradação. As blendas PP/PHB foram obtidas nas composições 90/10, 80/20, 70/30 e 60/40 (em peso) numa extrusora dupla-rosca. O estudo da compatibilização foi feito para a blenda PP/PHB 80/20 contendo ou não 10% dos seguintes compatibilizantes: polipropileno grafitizado com anidrido maleico (PP-g-MAn), poli(etileno-co-acrilato de metila) (P(E-co-MA)), poli(etileno-co-metacrilato de glicidila) (P(E-co-GMA)) e poli(etileno-co-acrilato de metila-co-metacrilato de glicidila) (P(E-co-MA-co-GMA)). A caracterização dos materiais foi realizada através de análises morfológicas, químicas e ensaios mecânicos (tração e impacto). Os resultados obtidos permitiram classificar a eficácia dos compatibilizantes na seguinte ordem: P(E-co-MA-co-GMA) >> P(E-co-MA) > P(E-co-GMA) PP-g-MAn. A fotodegradação do PHB foi investigada expondo-se este material numa câmara de envelhecimento artificial por 3, 6, 9 e 12 semanas. O efeito da radiação UV no PHB foi monitorado através de mudanças na sua massa molar, estruturas química e cristalina, bem como nas suas propriedades térmicas, morfológicas, óticas, mecânicas e de biodegradação. A radiação UV causou uma série de mudanças em todas as propriedades analisadas. Estes efeitos, entretanto, não se mostraram muito severos e um dos motivos apontados para isso foi a baixa transmitância da radiação UV apresentada pela amostra de PHB estudada, o que gerou um perfil de degradação muito pronunciado neste material. As blendas PP/PHB em todas as suas composições foram submetidas à radiação UV por 2 e 4 semanas e tiveram a sua biodegradabilidade avaliada por ensaios de perda de massa e de respirometria de Bartha (medida da produção de CO2). Os materiais antes e após as diferentes degradações foram caracterizados através de análises químicas, térmicas, morfológicas e de massa molar. Primeiramente, observou-se que, antes de qualquer degradação, a biodegradação da fase PHB foi suprimida dentro das blendas, o que foi atribuído ao PHB constituir a fase dispersa das misturas. A prévia fotodegradação retardou a biodegradação do PHB e acelerou a biodegradação do PP e de todas as blendas PP/PHB. A maior capacidade biodegradativa do PP e das blendas foi relacionada à cisão de cadeia e formação de grupos funcionais oxidados durante a exposição à radiação ultravioleta. / In this work Polypropylene/Poly(3-hydroxybutyrate) (PP/PHB) blend was studied. In particular the compatibilization and the influence of a previous photodegradation on the biodegradation of the blend were investigated. In order to understand the photodegradation of the blends it was also necessary to study the photodegradation of PHB. The compositions of the PP/PHB blends studied ranged from 90/10 to 60/40 (by weight). These blends were obtained using a twin screw extruder. The compatibilization was evaluated using a PP/PHB blend 80/20 containing or not 10% of the following compatibilizers: maleic anhydride grafted polypropylene (PP-g-MAH), poly(ethylene-co-methyl acrylate) (P(E-co-MA)), poly(ethylene-co-glycidyl methacrylate) (P(E-co-GMA)) and poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (P(E-co-MA-co-GMA)). The blends obtained were characterized through their morphological, chemical and mechanical properties (tensile and impact tests). The results obtained enabled the classification of the compatibilizers efficiency in the following order: P(E-co-MA-co-GMA) >> P(E-co-MA) > P(E-co-GMA) PP-g-MAH. PHB photodegradability was investigated through its exposure to artificial UV radiation in a weathering chamber for 3, 6, 9 and 12 weeks. The photodegradation effect was followed by changes of molecular weight, of chemical and crystalline structures, of thermal, morphological, optical and mechanical properties, as well as of biodegradability. UV radiation caused several changes in all the properties evaluated, however, these effects were not very severe. These results could be explained in light of the low UV radiation transmittance of the PHB sample studied, which caused a strong degradation profile for this material. PP/PHB blends in all compositions were exposed to UV radiation for 2 and 4 weeks and had their biodegradability evaluated using the weight loss and the Bartha respirometer tests (CO2 production measurement). The materials before and after the different degradations were characterized by chemical, thermal, morphological and molar mass analysis. First, it was observed that, before any degradation, the biodegradation of the PHB phase was suppressed in the blends, most likely due to the fact that PHB was the dispersed phase within the mixtures studied. Previous photodegradation delayed PHB biodegradation and sped up the biodegradation of PP and all PP/PHB blends. The greater biodegradability of PP and blends was attributed to the chain scission and formation of oxidized functional groups taking place during ultraviolet radiation exposure.

Irradiamos amostras de DNA com luz UVA em diferentes condições para estudar os possíveis mecanismos envolvidos na indução de lesões de DNA por essa radiação. As lesões de DNA formadas após as irradiações foram quantificadas com enzimas de reparo de DNA que reconhecem e clivam os sítios contendo bases oxidadas e dímeros de pirimidina (CPDs). Complementando essas análises, foram realizados ensaios com anticorpos e HPLC-ED. NaCl e uma maior concentração de DNA são capazes de diminuir a indução de CPDs. Danos gerados por estresse oxidativo são inibidos na presença de azida de sódio e quelantes de metais, indicando o envolvimento de oxigênio singlete e reações de Fenton, na geração dessas lesões. Água deuterada e DNA mais concentrado aumentaram a indução de bases oxidadas. Quanto maior a quantidade de DNA irradiado, mais oxigênio singlete é formado, o que indica um possível mecanismo de fotossensibilização endógeno. / DNA samples were irradiated with UVA light in different conditions for studying the possible mechanisms involved in the induction of DNA lesions by this radiation. DNA lesions formed after irradiation were quantified with DNA repair enzymes, which recognize and cleave the sites containing oxidized bases and pyrimidine dimers (CPDs). Complementing these analyses, tests were performed with antibodies and HPLC-ED. NaCl and more concentrated DNA are capable of reducing the induction of CPDs. Damage caused by oxidative stress is inhibited in the presence of sodium azide and metal chelators, indicating the involvement of singlet oxygen and Fenton reactions, in the generation of these lesions. Deuterated water and more concentrated DNA increased the induction of oxidized bases. The bigger the amount of irradiated DNA, the more singlet oxygen is formed, which indicates a possible endogenous photosensitization mechanism.