975 resultados para Quark stars
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Aquest projecte final explica algunes tècniques de producció relacionades amb la música electrònica, que també són aplicables a la música pop en general. Es descriuen els processos realitzats en dues parts, que parteixen de la producció de dos singles, Stars i Never mind. En la descripció del primer single s'hi expliquen tots els processos relacionats amb la coproducció i mescla d'una cançó de música electrònica, explorant-ne les possibilitats tant a nivell tècnic com artístic. El segon single, de composició pròpia i dut a terme majoritàriament a l'estudi de gravació, comprèn processos compositius a partir d'instruments virtuals i la seva posterior re-interpretació amb instruments acústics en diferents sessions de gravació, així com les tècniques utilitzades per la seva postproducció. L'objectiu principal ha estat aprendre a definir un so propi com a productor a partir de la combinació d'elements acústics i electrònics, i també repassar algunes tècniques de producció apreses durant la meva estada a l'ESMUC. La feina com a sonòleg i compositor queda documentada amb la descripció de tots aquests processos, deixant-ne constància per a futurs treballs.
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We have around ninety chemical elements available in nature, which were produced mainly by nuclear reactions inside stars. The fusion reactions are the main synthesis process which generates the light and intermediate masses elements. The synthesis begins with the hydrogen burning reaching the region of iron mass nuclei. Heavier elements are synthesized by neutron capture processes, forming exotic nuclei with large neutron excess. These systems present characteristics very different from nuclei inside of stable atoms; they only occur in particular astrophysical environments or are produced artificially in special laboratory conditions. This work discusses some properties of the exotic nuclei and how they participate in the synthesis of elements.
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This thesis contains dynamical analysis on four different scales: the Solar system, the Sun itself, the Solar neighbourhood, and the central region of the Milky Way galaxy. All of these topics have been handled through methods of potential theory and statistics. The central topic of the thesis is the orbits of stars in the Milky Way. An introduction into the general structure of the Milky Way is presented, with an emphasis on the evolution of the observed value for the scale-length of the Milky Way disc and the observations of two separate bars in the Milky Way. The basics of potential theory are also presented, as well as a developed potential model for the Milky Way. An implementation of the backwards restricted integration method is shown, rounding off the basic principles used in the dynamical studies of this thesis. The thesis looks at the orbit of the Sun, and its impact on the Oort cloud comets (Paper IV), showing that there is a clear link between these two dynamical systems. The statistical atypicalness of the orbit of the Sun is questioned (Paper I), concluding that there is some statistical typicalness to the orbit of the Sun, although it is not very significant. This does depend slightly on whether one includes a bar, or not, as a bar has a clear effect on the dynamical features seen in the Solar neighbourhood (Paper III). This method can be used to find the possible properties of a bar. Finally, we look at the effect of a bar on a statistical system in the Milky Way, seeing that there are not only interesting effects depending on the mass and size of the bar, but also how bars can capture disc stars (Paper II).
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This thesis summarizes studies of a class of white dwarfs (WDs) called DQ WDs. White dwarfs are the remnants of ordinary stars like our Sun that have run out of nuclear fuel. WDs are classified according to the composition of their atmosphere and DQ WDs have an atmosphere made of helium and carbon. The carbon comes in either atomic or molecular form and in some cases the strong spectral absorption features cover the entire optical wavelength region. The research presented here utilizes spectropolarimetry, which is an observational technique that combines spectroscopy and polarization. Separately these allow to study the composition of a target and the inhomogeneous distribution of matter in the target. Put together they form a powerful tool to probe the physical properties in the atmosphere of a star. It is espacially good for detecting magnetic fields. The papers in this thesis describe efforts to do a survey of DQ white dwarfs with spectropolarimetry in order to search for magnetic fields in them. Paper I describes the discovery of a new magnetic cool DQ white dwarf, GJ841B. Initial modeling of molecular features on DQ WDs showed inconsistencies with observations. The first possible solution to this problem was stellar spots on these WDs. To investigate the matter, two DQ WDs were monitored for photometric variability that could arise from the presence of such spots. Paper II summarizes this short campaign and reports the negative results. Paper III reports observations of the rest of the objects in our survey. The paper includes the discovery of polarization from another cool DQ white dwarf, bringing the total of known magnetic cool DQs to three. Unfortunately the model used in this thesis cannot, in its present state, be used to model these objects nor are the observations of high enough spectroscopic resolution to do so.
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Statistical analyses of measurements that can be described by statistical models are of essence in astronomy and in scientific inquiry in general. The sensitivity of such analyses, modelling approaches, and the consequent predictions, is sometimes highly dependent on the exact techniques applied, and improvements therein can result in significantly better understanding of the observed system of interest. Particularly, optimising the sensitivity of statistical techniques in detecting the faint signatures of low-mass planets orbiting the nearby stars is, together with improvements in instrumentation, essential in estimating the properties of the population of such planets, and in the race to detect Earth-analogs, i.e. planets that could support liquid water and, perhaps, life on their surfaces. We review the developments in Bayesian statistical techniques applicable to detections planets orbiting nearby stars and astronomical data analysis problems in general. We also discuss these techniques and demonstrate their usefulness by using various examples and detailed descriptions of the respective mathematics involved. We demonstrate the practical aspects of Bayesian statistical techniques by describing several algorithms and numerical techniques, as well as theoretical constructions, in the estimation of model parameters and in hypothesis testing. We also apply these algorithms to Doppler measurements of nearby stars to show how they can be used in practice to obtain as much information from the noisy data as possible. Bayesian statistical techniques are powerful tools in analysing and interpreting noisy data and should be preferred in practice whenever computational limitations are not too restrictive.
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State-of-the-art predictions of atmospheric states rely on large-scale numerical models of chaotic systems. This dissertation studies numerical methods for state and parameter estimation in such systems. The motivation comes from weather and climate models and a methodological perspective is adopted. The dissertation comprises three sections: state estimation, parameter estimation and chemical data assimilation with real atmospheric satellite data. In the state estimation part of this dissertation, a new filtering technique based on a combination of ensemble and variational Kalman filtering approaches, is presented, experimented and discussed. This new filter is developed for large-scale Kalman filtering applications. In the parameter estimation part, three different techniques for parameter estimation in chaotic systems are considered. The methods are studied using the parameterized Lorenz 95 system, which is a benchmark model for data assimilation. In addition, a dilemma related to the uniqueness of weather and climate model closure parameters is discussed. In the data-oriented part of this dissertation, data from the Global Ozone Monitoring by Occultation of Stars (GOMOS) satellite instrument are considered and an alternative algorithm to retrieve atmospheric parameters from the measurements is presented. The validation study presents first global comparisons between two unique satellite-borne datasets of vertical profiles of nitrogen trioxide (NO3), retrieved using GOMOS and Stratospheric Aerosol and Gas Experiment III (SAGE III) satellite instruments. The GOMOS NO3 observations are also considered in a chemical state estimation study in order to retrieve stratospheric temperature profiles. The main result of this dissertation is the consideration of likelihood calculations via Kalman filtering outputs. The concept has previously been used together with stochastic differential equations and in time series analysis. In this work, the concept is applied to chaotic dynamical systems and used together with Markov chain Monte Carlo (MCMC) methods for statistical analysis. In particular, this methodology is advocated for use in numerical weather prediction (NWP) and climate model applications. In addition, the concept is shown to be useful in estimating the filter-specific parameters related, e.g., to model error covariance matrix parameters.
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Tässä tutkimuksessa tarkastellaan television vaaliohjelmia ja niihin liittynyttä sanomalehtijulkisuutta 1960-luvun alusta 1980-luvun lopulle. Tarkastelun kohteena ovat sekä eduskunta- että presidentinvaalien vaaliohjelmat. Tutkimusaineisto koostuu Yleisradion hallinto- ja ohjelmaneuvostojen pöytäkirjoista, vaaliohjelmien televisiotallenteista sekä vaaliohjelmia käsittelevistä sanomalehtikirjoituksista. Lehtiaineisto on kerätty Helsingin Sanomista, Ilta-Sanomista, Iltalehdestä, Aamulehdestä, Kansan Uutisista, Suomenmaasta sekä Suomen Sosialidemokraatista. Sanomalehtiaineistoa on täydennetty Yleisradion leikearkistoon kerätyillä lehtileikkeillä. Tutkimuksessa on analysoitu toisaalta television vaaliohjelmien kehitystä ja toisaalta vaaliohjelmiin liittynyttä sanomalehtikirjoittelua. Television vaaliohjelmien kehityksen osalta tutkimuksessa on kuvattu, millä tavoin vaaliohjelmia on eri aikoina tehty ja millaisia poliittisia kiistoja niiden tekemiseen on liittynyt. Sanomalehtiaineiston analyysissa on tarkasteltu sitä, mihin seikkoihin vaaliohjelmia käsittelevissä kirjoituksissa on kiinnitetty huomiota, millä tavoin lehdet ovat suhtautuneet ohjelmien toteutukseen ja millainen rooli ohjelmilla on nähty olleen vaalikampanjoinnissa. Väitöskirjan näkökulma on historiallinen, mikä merkitsee ajallisten kontekstien keskeisyyttä analyysissa. Tutkimuksessa on kiinnitetty huomiota sekä poliittisessa kulttuurissa että mediamaisemassa tapahtuneisiin muutoksiin. Vaaliohjelmat olivat 1960-luvulla tarkkaan säänneltyjä puolueiden välisiä keskustelutilaisuuksia, joissa toimittajilla ei ollut näkyvää roolia. Ohjelmien toteutuksesta vastasivat puoluemandaateilla toimineet Yleisradion ohjelma- ja hallintoneuvoston jäsenet, joten ohjelmien toteutuksen yksityiskohdista vastasivat puolueet. Puolueet riitelivät usein vaaliohjelmien toteutuksesta, mikä osoittaa, että puolueille television vaaliohjelmat olivat tärkeitä poliittisia foorumeita jo 1960-luvulta lähtien. Vaaliohjelmat jakautuivat kahteen erilaiseen ohjelmaformaattiin; vaalitentteihin ja suureen vaalikeskusteluun. Vaalitenteissä kunkin puolueen edustajat olivat vuorollaan ”altavastaajina”, joille muiden puolueiden edustajat esittivät kysymyksiä. Suuri vaalikeskustelu oli perinteisempi paneelikeskustelu, jossa poliitikot selvittivät vuorotellen kantojaan ajankohtaisiin poliittisin kysymyksiin. 1970-luvun puolivälissä vaalitenttien toteutuksessa tapahtui suuria muutoksia, kun toimittajat syrjäyttivät poliitikot vaalitenttien kyselijöinä. Suuri vaalikeskustelu säilyi ennallaan. Sanomalehtien suhtautuminen vaaliohjelmiin oli 1960- ja 1970-luvuilla huomattavasti pidättyvämpää kuin poliitikkojen. Sanomalehdistön näkökulmasta television vaaliohjelmien tärkeimpänä tehtävänä oli puolueiden poliittisten linjausten esittely. Vaaliohjelmia käsittelevissä teksteissä esiteltiin pääasiassa poliitikkojen ohjelmissa pitämiä puheenvuoroja. Puoluelehdissä puheenvuorojen sisältöä arvioitiin aatteellisista lähtökohdista, sitoutumattomissa sanomalehdissä neutraalimmin. Vaaliohjelmien toteutukseen liittynyt kritiikki kohdistui toisaalta poliitikkojen puoluepropagandaan, toisaalta poliitikkojen liialliseen varovaisuuteen. Sanomalehtien suhtautuminen vaaliohjelmiin säilyi ennallaan myös 1970-luvulla, jolloin vaaliohjelmia alettiin tehdä toimittajavetoisesti. Ainoa muutos liittyi vaaliohjelmakritiikkiin, joka kohdistui nyt poliitikkojen ohella myös toimittajiin, joiden katsottiin olleen ohjelmissa liian hyökkääviä. Suurin muutos vaaliohjelmiin liittyneessä kirjoittelussa tapahtui 1980-luvulla. Vaaliohjelmia käsitteleviä kirjoituksia julkaistiin sanomalehdistössä monikertainen määrä 1970-lukuun verrattuna. Samalla myös vaaliohjelmia käsittelevien kirjoitusten näkökulmat alkoivat muuttua, kun ohjelmin visuaalinen ulottuvuus alkoi olla yhä näkyvämmin esillä sanomalehtiin laadituissa analyyseissa. Lehdet alkoivat teettää säännöllisesti erilaisia tutkimuksia poliitikkojen pärjäämisestä ohjelmissa ja kirjoittaa vaalikeskusteluiden voittajista ja häviäjistä. Lisäksi lehtijutuissa arvioitiin poliitikkojen esiintymistä ja vaaliohjelmista välittyviä vaikutelmia. Vuoden 1982 presidentinvaaleissa uusista näkökulmista kirjoittivat erityisesti iltapäivälehdet, mutta vuosikymmenen jälkipuoliskolla samankaltaisia lähestymistapoja omaksuivat myös Helsingin Sanomat ja Aamulehti. Niiden vaaliohjelmia käsittelevissä uutisissa kiinnitettiin yhä useammin huomiota poliitikkojen esiintymiseen, pukeutumiseen ja tunnetiloihin. Puoluelehtien suhtautuminen vaaliohjelmiin säilyi kuitenkin ennallaan, ja myös vaaliohjelmakritiikki säilyi suurelta osin muuttumattomana. 1980-luvun aikana television vaaliohjelmat muuttuivat lehdistön käsittelyssä puolueiden tavoitteita esittelevistä keskustelutilaisuuksista poliitikkojen ja puolue johtajien henkilökohtaisia ominaisuuksia mittaaviksi esiintymiskokeiksi ja suuriksi mediatapahtumiksi, joiden katsottiin toisinaan jopa ratkaisseen vaalin tuloksen. Nostaessaan television vaaliohjelmat kampanjajournalisminsa ytimeen, sanomalehdet vahvistivat television poliittista roolia.
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The Sun is a crucial benchmark for how we see the universe. Especially when it comes to the visible range of the spectrum, stars are commonly compared to the Sun, as it is the most thoroughly studied star. In this work I have focussed on two aspects of the Sun and how it is used in modern astronomy. Firstly, I try to answer the question on how similar to the Sun another star can be. Given the limits of observations, we call a solar twin a star that has the same observed parameters as the Sun within its errors. These stars can be used as stand-in suns when doing observations, as normal night-time telescopes are not built to be pointed at the Sun. There have been many searches for these twins and every one of them provided not only information on how close to the Sun another star can be, but also helped us to understand the Sun itself. In my work I have selected _ 300 stars that are both photometrically and spectroscopically close to the Sun and found 22 solar twins, of which 17 were previously unknown and can therefore help the emerging picture on solar twins. In my second research project I have used my full sample of 300 solar analogue stars to check the temperature and metallicity scale of stellar catalogue calibrations. My photometric sample was originally drawn from the Geneva-Copenhagen-Survey (Nordström et al. 2004; Holmberg et al. 2007, 2009) for which two alternative calibrations exist, i.e. GCS-III (Holmberg et al. 2009) and C11 (Casagrande et al. 2011). I used very high resolution spectra of solar analogues, and a new approach to test the two calibrations. I found a zero–point shift of order of +75 K and +0.10 dex in effective temperature and metallicity, respectively, in the GCS-III and therefore favour the C11 calibration, which found similar offsets. I then performed a spectroscopic analysis of the stars to derive effective temperatures and metallicities, and tested that they are well centred around the solar values.
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This doctoral dissertation presents studies of the formation and evolution of galaxies, through observations and simulations of galactic halos. The halo is the component of galaxies which hosts some of the oldest objects we know of in the cosmos; it is where clues to the history of galaxies are found, for example, by how the chemical structure is related to the dynamics of objects in the halo. The dynamical and chemical structure of halos, both in the Milky Way’s own halo, and in two elliptical galaxies, is the underlying theme in the research. I focus on the density falloff and chemistry of the two external halos, and on the dynamics, density falloff, and chemistry of the Milky Way halo. I first study galactic halos via computer simulations, to test the long- term stability of an anomalous feature recently found in kinematics of the Milky Way’s metal-poor stellar halo. I find that the feature is transient, making its origin unclear. I use a second set of simulations to test if an initially strong relation between the dynamics and chemistry of halo glob-ular clusters in a Milky Way-type galaxy is affected by a merging satellite galaxy, and find that the relation remains strong despite a merger in which the satellite is a third of the mass of the host galaxy. From simulations, I move to observing halos in nearby galaxies, a challenging procedure as most of the light from galaxies comes from the disk and bulge components as opposed to the halo. I use Hubble Space Tele scope observations of the halo of the galaxy M87 and, comparing to similar observations of NGC 5128, find that the chemical structure of the inner halo is similar for both of these giant elliptical galaxies. I use Very Large Telescope observations of the outer halo of NGC 5128 (Centaurus A) and, because of the difficultly in resolving dim extragalac- tic stellar halo populations, I introduce a new technique to subtract the contaminating background galaxies. A transition from a metal-rich stellar halo to a metal-poor has previously been discovered in two different types of galaxies, the disk galaxy M31 and the classic elliptical NGC 3379. Unexpectedly, I discover in this third type of galaxy, the merger remnant NGC 5128, that the density of metal-rich and metal-poor halo stars falls at the same rate within the galactocentric radii of 8 − 65 kpc, the limit of our observations. This thesis presents new results which open opportunities for future investigations.
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The cosmological standard view is based on the assumptions of homogeneity, isotropy and general relativistic gravitational interaction. These alone are not sufficient for describing the current cosmological observations of accelerated expansion of space. Although general relativity is extremely accurately tested to describe the local gravitational phenomena, there is a strong demand for modifying either the energy content of the universe or the gravitational interaction itself to account for the accelerated expansion. By adding a non-luminous matter component and a constant energy component with negative pressure, the observations can be explained with general relativity. Gravitation, cosmological models and their observational phenomenology are discussed in this thesis. Several classes of dark energy models that are motivated by theories outside the standard formulation of physics were studied with emphasis on the observational interpretation. All the cosmological models that seek to explain the cosmological observations, must also conform to the local phenomena. This poses stringent conditions for the physically viable cosmological models. Predictions from a supergravity quintessence model was compared to Supernova 1a data and several metric gravity models were studied with local experimental results. Polytropic stellar configurations of solar, white dwarf and neutron stars were numerically studied with modified gravity models. The main interest was to study the spacetime around the stars. The results shed light on the viability of the studied cosmological models.
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O efeito de diferentes combinações de gomas sobre os parâmetros de textura instrumental de queijo tipo petit-suisse probiótico foi avaliado. Queijos petit-suisse foram produzidos utilizando-se massa-base de queijo quark preparada com o starter Streptococcus thermophilus e os probióticos Lactobacillus acidophilus e Bifidobacterium longum. Três formulações de queijo petit-suisse foram preparadas, a partir de massa-base de queijo quark adicionada de 0,75% do produto final da mistura de gomas - xantana (X), carragena (C), guar (G), pectina (P): F1 = 2,5X:2,5C:5G; F2 = 2X:3C:5P; F3 = 5C:5G. Os parâmetros avaliados após 1, 7, 14 e 21 dias de armazenamento do produto a 4±1ºC incluíram a contagem de probióticos, a textura instrumental, o pH e a umidade. As populações de probióticos mantiveram-se acima de 6,40 log UFC/g para L. acidophilus e de 7,30 log UFC/g para B. longum. Houve diferença significativa entre as formulações (p<0,05) para todos os parâmetros de textura, exceto a firmeza de F1. O pH e a umidade apresentaram comportamento semelhante para as três formulações. Dentre as formulações estudadas, F1 foi considerada a melhor, por sua firmeza mais estável durante o período de armazenamento.
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ResumoObjetivo:Determinar a efetividade de 20 sessões de estimulação elétrica nervosa transcutânea (TENS) parassacral com periodicidade de duas vezes semanais no tratamento da urgência ou urge-incontinência urinária em crianças e adolescentes.Métodos:Ensaio clínico fase II, envolvendo pacientes com idade entre 5 e 14 anos com urgência ou urge-incontinência urinária. Realizadas 20 sessões de TENS, duas vezes por semana (aparelho Dualpex 961 Quark®). Os resultados foram avaliados pelo diário miccional, ultrassonografia dinâmica do trato urinário inferior (USGD-TUI) pré e pós-tratamento e questionário sobre perdas urinárias em cada sessão.Resultados:A idade média das 25 crianças envolvidas no estudo foi 7,80 ± 2,22 anos, sendo a maioria do sexo feminino (92%) e com urge-incontinência (92%). A comparação dos eventos de perda urinária pré e pós-tratamento foi estatisticamente significativa (p = 0,04); houve regressão do sintoma de perda urinária referida pelos acompanhantes em todas as crianças que completaram a 20ª sessão; os parâmetros da USGD-TUI, embora não estatisticamente significativos, demonstraram redução do percentual de crianças com contrações detrusoras (62,5% para 43,5%); maior adequação do volume vesical pré-miccional (4,2% versus 19,0%), respectivamente pré e pós-tratamento.Conclusões:A eletroestimulação realizada em duas sessões semanais demonstrou efetividade e metade dos pacientes apresentou regressão da incontinência urinária a partir da 12ª sessão, porém, é necessário maior número de pacientes para confirmação dos resultados obtidos.
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Martin Heidegger's interpretation of the ancients was born out of something like a crisis in the interpretation of the Greeks, which can be characterized as nothing other than the realization of the idea that the Greek philosophers put a serious question mark over existence. This idea, which had its germination in Prussia with Jakob Burckhart and his teacher, but first came to be seriously cultivated in the Philosophy of Friedrich Nietzsche, was the first in depth investigation into whether the Greeks, on the one hand, questioned existence or, on the other hand, put a question mark over existence. To question existence is rather innocuous, since it amounts to little more, in the end, than a child looking up at the stars and asking what it all means. To put a question mark over existence, however, is another business entirely. For the Greeks, as the life work of Martin Heidegger amply demonstrates, the nature of Greek thinking and the objects towards which it is directed follows so absolutely from the tragic view of the human person that, in a certain sense, philosophy is Greek and could only have developed in Greece. Perhaps stating it a little less categorically, philosophy could have developed elsewhere at least to the extent that something like they way the Greeks understood life was at the forefront: presence, in other words. This thesis deals with the problem ofHeidegger's relation to the Greeks, specifically in terms of his understanding of the Greeks and presence. It is the position of this dissertation that the Greek notion of presence is, as Heidegger understands it, the homeliness of the hearth that radiates through all the things that humans concern themselves with. This is thought by Heidegger, as the Greeks did, specifically in contrast with the uncanninesslunhomeliness of the hqrnan apart from his or her concern with things. Therefore, the thesis is an attempt at exposing the relation between presence and the unhomely by situating it withing Greek existence and the meaning of the Greek Philosopher. In order to support this position, the thesis has been divided into five parts. The first two chapters deal with Heidegger's explanation of the relation between Greek notion of physics (Phusis), metaphysics (specifically in relation to an analysis of time and motion in Greek thought), and what Heidegger calls the fundamental attunement of Dasein (boredom). More exactly, it deals with these issues only so far as they allow us to bring out something like the notion of 'presence' in relation to things and homelessness or restlessness in relation to the human being. The rationale for these two chapters in relation to the central problem of the paper is that in Heidegger's elucidation of physics and metaphysics, he conducts his analysis in such a way that he explicitly uncovers that dimension of human existence that he calls the fundamental attunement of Dasein. This fundamental attunement is, in tum, similar to what the Greeks understood as the deinon, the uncanninesslunhomeliness of the human. The third and fourth chapters take as their explicit themes the problem of the Greek understanding of the assertion and the ways in which the person can comport himlherself toward things, two issues which are not separable. The rationale for these two chapters in relation to the central theme of the paper is that Heidegger's analysis of these two areas in Greek thought brings out precisely why the philosopher and the philosophical way of life is the highest mode of existence for the Greeks and how this is thought specifically in tenns of the uncanniness of humans. The final cijapter gives a complete elucidation of presence as the homeliness of the hearth and shows specifically how this is thought of in contradistinction to the uncanny/unhomely for the Greeks. 1I1 This last chapter also explains Martin Heidegger's reaction to the Greek's interpretation of the highest mode of existence, and what he posited as a counter-thought. The essay as a whole is an attempt to fully concertize an important dimension of Heidegger' s understanding of the Greeks, that is, the relation between presence and the deinon or Greek notion ofunhomely, which, to my la)owledge, has not been offered anywhere in commentaries on Heidegger.
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This thesis demonstrates that mUSIC stars who attain cultural icon status heavily contribute to the fashion styles of the time. Where as style and music have always had a connection, icons such as Britney Spears are now dictating popular style so much so that music artists are becoming full-fledged fashion designers. While much analysis is devoted to Britney Spears, her largest contributions do not lie in the rise of teenage sexuality, but in establishing music artists as vehicles of consumption. The artists' signature has now become a brand and ~ term "signabrand" has been created to define such a trend. To understand such a shift, a review of past literature devoted to fashion and music, largely consisting of subculture theory is examined, followed by a combination of content analysis, political economy, fashion and postmodem theory to address how music stars attain icon status and guide style.
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L’étoile Wolf-Rayet WR 46 est connue pour sa variabilité complexe sur des échelles de temps relativement courtes de quelques heures et sur des échelles de temps plus longues de plusieurs mois. Des décalages périodiques mais intermittents en vitesse radiale ont déjà été observés dans ses raies d’émission optiques. Plusieurs périodes photométriques ont aussi été mesurées dans le passé. Des pulsations non-radiales, une modulation liée à la rotation rapide, ou encore la présence d’un compagnon de faible masse dont la présence reste à confirmer ont été proposées pour expliquer le comportement de l’étoile sur des échelles de temps de quelques heures. Dans un effort pour dévoiler sa vraie nature, nous avons observé WR 46 avec le satellite FUSE sur plusieurs cycles de variabilité à court terme. Nous avons trouvé des variations sur une échelle de temps d’environ 7,5 heures dans le continu ultraviolet lointain, dans l’aile bleue de la composante d’absorption du profil P Cygni du doublet de O vi 1032, 1038, ainsi que dans la composante d’absorption du profil P Cygni de S vi 933, 944. Nous avons également récupéré des données archivées de cette étoile obtenues avec le satellite XMM-Newton. La courbe de lumière en rayons X montre des variations sur une échelle de temps similaire aux courbes de lumière du continu ultraviolet et ultraviolet lointain, et le spectre rayons X de WR 46 est très mou avec un pic d’émission à des énergies plus faibles que 1 keV. Nous discutons des différentes contraintes sur la nature de la variabilité de cette étoile que ces nouvelles observations aident à poser. Parmi les scénarios suggérés, nous concluons que celui des pulsations non-radiales est le plus probable, bien que nous soyons encore loin d’une compréhension détaillée de WR 46.