Дисертації з теми "Strange stars"

Classical Cepheids are key probes of both stellar astrophysics and cosmology as standard candles and pulsating variable stars. It is important to understand Cepheids in unprecedented detail in preparation for upcoming Gaia, James Webb Space Telescope (JWST) and extremely-large telescope observations. Cepheid eclipsing binary stars are ideal tools for achieving this goal, however there are currently only three known systems. One of those systems, OGLE-LMC-CEP1812, raises new questions about the evolution of classical Cepheids because of an apparent age discrepancy between the Cepheid and its red giant companion. We show that the Cepheid component is actually the product of a stellar merger of two main sequence stars that has since evolved across the Hertzsprung gap of the HR diagram. This post-merger product appears younger than the companion, hence the apparent age discrepancy is resolved. We discuss this idea and consequences for understanding Cepheid evolution.

Nesta dissertação, estuda-se estrelas compactas constituídas por uma forma estável do plasma ultra-relativístico de {\\it quarks} e glúons, a {\\it strange quark matter} ou matéria estranha, com pequena fração de elétrons para manter a neutralidade de carga. São abordadas, aqui, soluções matemáticas razoáveis que descrevem com simplicidade e agilidade certas propriedade dessas estrelas, a começar pela importantíssima relação massa-raio. Um perfil gaussiano para a densidade de energia foi escolhido como ponto de partida para contruir uma solução matemática para o problema e são apresentadas as motivações para tal escolha. Prova-se que o perfil escolhido não soluciona as Equações de Einstein exatamente e uma solução aproximada é fornecida. A seguir, as conhecidas soluções Tolman IV e Buchdahl I foram utilizadas para modelar uma estrela estranha com base no estudo de Alcock, Farhi e Olinto. Discute-se, ainda, como foi redescoberta a solução exata de Finch e Skea e discute-se, também, a solução exata para uma estrela de {\\it quarks} de Komathiraj e Maharaj, construída para um problema ligeiramente diferente, que incluía a existência de um campo elétrico. Conclui-se o trabalho comparando os resultados numéricos de Alcock, Farhi e Olinto com a solução aproximada aqui desenvolvida, apresentando o intervalo de validade desta solução. Além disso, são feitas comparações entre as diferentes soluções exatas e as características que cada uma delas exibe, e discute-se qual delas deve-se utilizar, tendo em mente que característica da estrela estranha se quer estudar. Os caminhos existentes para solucionar as Equações de Einstein, quando se quer modelar um objeto compacto, são discutidos e apontam-se quais os problemas que alguém encontrará ao seguir cada caminho. Por fim, relaciona-se a construção da relação massa-raio com a diferenciação dos tipos de objetos compactos que podem, em princípio, existir.
In this dissertation we study compact stars constituted by a stable form of ultra-relativistic quark-gluon plasma, the strange matter, with a small fraction of electrons to keep the neutrality of charge. We address here reasonable mathematical solutions that describe with simplicity and agility some properties of these stars, beginning by the important mass-radius relationship. A gaussian energy density profile was chosen as the starting point for the construction of a mathematical solution for this problem and the motivations for this choice was presented. We prove that this profile is not an exact solution for the Einstein Field Equations and an approximated solution is presented. Following, the previous known solutions of Tolman IV and Buchdahl I were used to model a strange star, based on the work of Alcock, Farhi and Olinto. We discuss the rediscovery of the exact solution of Finch and Skea and also the exact solution for a quark star by Komathiraj and Maharaj, constructed to a problem slightly different, that includes the existence of an electric field. We conclude this work comparing the numerical results of Alcock, Farhi and Olinto with the approximated solution here developed, presenting the range of validity of this solution. Furthermore, comparisons were made between the different exact solutions and the features displayed by each one and we discuss which solution must be used when one have in mind which features of the strange star one wants to study. The existent ways for solving the Einstein Equations when we want to model a compact star are discussed and we point out the problems that one will find in following each way. At last, we make a relation between the mass-radius relationship and the differentiation of the many types of compact objects that could, in principle, exist.

This diploma thesis deals with the development of local government in the Municipality of Starý Plzenec, which is located in the Pilsen Region. The main task of the first part (Theoretical background) is a public administration with a focus on the basic territorial administrative unit. Furthermore, it discusses the municipal election system, pays attention to the communal party spectrum and the phenomenon of independence. It also describes the communal political coalition and the typology of local models of democracy. The second part (Practical part) represents the Municipality of Starý Plzenec, its development and basic demographic data. It analyses the economic activity in the Municipality, the character of the building and its budget. Besides that, it compares the results of local elections since 1994 and deals with the current local politicians, the style of local policy and assigns the Municipality to a model democracy.

In recent years, new technologies have led to disruption and change within most industries, resulting in the emergence of digitally-born start-ups. The purpose of this thesis is to complement the scarce theory about what the drivers of business model adaptation in start-ups consist of and how the adaptation process is managed to stay competitive. The findings not only provide theoretical contributions, but can also help managers to steer their start-upsthrough the growth phase.The research is set within the realms of business model theory in the strategic management field. An exploratory study with a qualitative, inductive approach was chosen to gain insights into the business model dynamics of nine firms from the fintech and healthtech industries.The results showed that foreign market adaptation, industry dynamics, funding, and legislation are perceived challenges, whereas legislation and exogenous shocks are opportunities that drive business model adaptation in start-ups. The business model elements of strategic decision-making, resources and capabilities, and network and partners were found to be integral to the adaptation process, as their core components not only need to be adapted to the environment but also aligned with each other. Those components should be revised in an iterative trial-and-error process driven by feedback.

Denna autoetnografiska studie handlar om genuskonstruktion i PC-spel. Studien bedrivs med feministisk ansats och syftet var att undersöka handlingsutrymmet gällande performativa och subversiva genushandlingar i fyra olika spel. Frågeställningen för denna studie är: Hur uttrycker spelare och spelkaraktärer traditionella och subversiva genushandlingar i relation till den förprogrammerade koden i spel? Fyra spel från olika genrer med enbart kvinnliga protagonister valdes ut; Tomb Raider, Child of Light, Life is Strange och Gone Home. Dessa spel analyserades med hjälp av Butlers teorier gällande genuskonstruktion, och Malabys teorier om spel som en performativ process. Tidigare forskning tar upp kvinnors underrepresentation i spel, spelsexismens utveckling, kvinnliga karaktärers utveckling och transgressive play i online-världen. Under analysen återberättades spelen och forskarens subjektiva upplevelse av dem för att sedan kunna analyseras. De faktorer som togs under beaktning vid analysen var; genusperformativa, subversiva genushandlingar och den heterosexuella matrisen. Resultatet visade att det fanns möjlighet till både genusperformativa och subversiva genushandlingar, samt att man antingen kunde understryka eller ifrågasätta den heterosexuella matrisen, vilket vi visar med hjälp av utvalda delar från spelen. Slutsatsen vi ankommer till är att trots att vi som spelare tillåts att utföra både performativa och subversiva genushandlingar begränsas vi av spelets kodning, och vissa genusuttryck är ofrånkomliga och utförs oberoende av spelaren. I diskussionen talar vi om sexism i spel på en mer allmän nivå, att homosexualitet i någon form förekommer i ¾ av vårt urval vilken kan vara ett bevis på mångfald eller en slump. Vi bemöter också våra egna fördomar gällande urvalet. Som vidare forskning föreslår vi liknande studier men med andra metoder än den autoetnografiska. Vi anser att denna studies samhällsrelevans ligger i hur vi belyser hur spel, som en växande medieform, både begränsar och möjliggör alternativa förståelser för genus. PC-spel är, liksom övrig media, inte immuna mot att reflektera skadliga normer som sexism och behöver därför ges tillbörlig akademisk tyngd.

Em procariotos, RNAs antisense (asRNAs) constituem a classe de RNAs não codificantes (ncRNAs) mais numerosa detectada por métodos de avaliação de transcritoma em larga escala. Apesar da grande abundância, pouco se sabe sobre mecanismos regulatórios e aspectos da conservação evolutiva dessas moléculas, principalmente em arquéias, onde o mecanismo de degradação de RNAs dupla fita (dsRNAs) é um fenômeno pouco conhecido. No presente estudo, utilizando dados de dRNA-seq, identificamos 1626 inícios de transcrição primários antisense (aTSSs) no genoma de Halobacterium salinarum NRC-1, importante organismo modelo para estudos de regulação gênica no domínio Archaea. Integrando dados de expressão gênica obtidos a partir de 18 bibliotecas de RNA-seq paired-end, anotamos 846 asRNAs a partir dos aTSSs mapeados. Encontramos asRNAs em ~21% dos genes anotados, alguns desses relacionados a importantes características desse organismo como: codificadores de proteínas que constituem vesículas de gás e da proteína bacteriorodopsina, além de vários genes relacionados a maquinaria de tradução e transposases. Além desses, encontramos asRNAs em genes pertencentes a sistemas de toxinas-antitoxinas do tipo II e utilizando dados públicos de dRNA-seq, evidenciamos que esse é um fenômeno que ocorre em bactérias e arquéias. A interação de um ncRNA com seu RNA alvo pode ser dependente de proteínas, em arquéias, a proteína LSm é uma chaperona de RNA homóloga a Hfq de bactérias, implicada no controle pós-transcricional. Utilizamos dados de RIP-seq de RNAs imunoprecipitados com LSm e identificamos 91 asRNAs interagindo com essa proteína, para 81 desses, o mRNA do gene sense também foi encontrado interagindo. Buscando por aTSSs presentes nas mesmas regiões de genes ortólogos, identificamos 160 aTSSs que dão origem a asRNAs em H. salinarum possivelmente conservados em Haloferax volcanii. A expressão dos asRNAs anotados foi avaliada ao longo de uma curva de crescimento e em uma linhagem knockout de um gene que codifica uma RNase R, possível degradadora de dsRNAs em arquéias. Encontramos um total de 144 asRNAs diferencialmente expressos ao longo da curva de crescimento, para 56 desses o gene sense também está diferencialmente expresso, caracterizando possíveis mecanismos de regulação em cis por esses RNAs. Na linhagem knockout, encontramos cinco asRNAs diferencialmente expressos e apenas para um desses o gene sense também está diferencialmente expresso, resultado que não nos permitiu inferir um possível papel de degradação de dsRNAs da RNAse R em H. salinarum NRC-1. Nesse trabalho apresentamos um mapeamento completo do transcritoma antisense primário de H. salinarum NRC-1 com resultados que consistem em um importante passo na direção da compreensão do envolvimento da transcrição antisense na regulação gênica pós-transcricional desse organismo modelo do terceiro domínio da vida.
Antisense RNAs (asRNAs) constitute the most numerous class of non-coding RNAs (ncRNAs) detected by transcriptome highthroughput methods in prokaryotes. Despite this abundance, little is known about regulatory mechanisms and evolutionary aspects of these molecules, mainly in archaea, where the mechanism of double-strand RNA (dsRNA) degradation remains poorly understood. In this study, using dRNA-seq data, we identified 1626 antisense transcription start sites (aTSSs) in the genome of Halobacterium salinarum NRC-1, an important model organism for gene expression regulation studies in Archaea. By integrating gene expression data from 18 RNA-seq paired-end libraries, we were able to annotate 846 asRNAs from mapped aTSSs. We found asRNAs in ~21% of annotated genes including genes related to important characteristics of this organism, such as: gas vesicle proteins, bacteriorhodopsin, translation machinery and transposases. We also found asRNAs in type II toxin-antitoxin systems and using public dRNA-seq data, we show evidences that this phenomenon might be conserved in archaea and bacteria. The interaction of a ncRNA with its target may depend on intermediary proteins action. In archaea, the LSm protein is a RNA chaperone homologous to bacterial Hfq, involved in post-transcriptional regulation. We used RIP-seq data from RNAs immunoprecipitated with LSm and identified 91 asRNAs interacting with this protein, for 81 of these the mRNA of the sense gene is also interacting. We searched for aTSSs present in the same region of orthologous genes in the Haloferax volcanii. We found 160 aTSSs that originated asRNAs in H. salinarum NRC-1 that might be conserved in this two archaea. The expression of annotated asRNAs was analyzed over a growth curve and in a knockout strain for RNase R gene. We found 144 asRNA differentially expressed over the growth curve, for 56 of these the sense gene was also differentially expressed, characterizing possible cis regulators asRNAs. In the knockout strain we found five differentially expressed asRNAs and only one asRNA/gene pair, this result does not allow us to infer a dsRNA degradation in vivo activity for this RNase in H. salinarum NRC- 1. This work contributes to the discovery of the antisense transcriptome in H. salinarum NRC- 1 a relevant step to uncover the post-transcriptional gene regulatory network in this archaeon.

Wong Ka Wah = 奇異星的特性 / 黃嘉華.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.
Includes bibliographical references (leaves 98-101).
Text in English; abstracts in English and Chinese.
Wong Ka Wah = Qi yi xing de te xing / Huang Jiahua.
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- History of Compact Stars --- p.1
Chapter 1.2 --- The Proposal of Strange Quark Stars --- p.2
Chapter 1.3 --- Outline of the Thesis --- p.3
Chapter 2 --- Cold Equation of State from Perturbative QCD --- p.6
Chapter 2.1 --- Description of Strange Quark Matter --- p.7
Chapter 2.2 --- MIT Bag Model --- p.8
Chapter 2.3 --- Perturbative QCD --- p.10
Chapter 2.4 --- Comparison with MIT Bag Model --- p.11
Chapter 3 --- Static Structure of Strange Stars --- p.16
Chapter 3.1 --- Static Equilibrium --- p.16
Chapter 3.2 --- Models --- p.18
Chapter 3.3 --- Results of Global Properties and Discussions --- p.18
Chapter 4 --- Stability of Strange Quark Matter --- p.25
Chapter 4.1 --- Absolute Stable Condition --- p.25
Chapter 4.2 --- Weak Stable Condition --- p.26
Chapter 4.3 --- Stability Condition Compared to Neutron Stars --- p.27
Chapter 4.4 --- Conclusion --- p.28
Chapter 5 --- Effect of Massive Strange Quarks --- p.31
Chapter 5.1 --- Numerical Analysis of the Effect of Strange Quark Mass on the EOS --- p.33
Chapter 5.2 --- Structure of Strange Stars with Strange Quark Mass --- p.37
Chapter 5.3 --- Conclusion --- p.38
Chapter 6 --- QCD Phase Transition in a Compact Star --- p.46
Chapter 6.1 --- Cooling Properties --- p.47
Chapter 6.1.1 --- Heat capacity of quark stars --- p.49
Chapter 6.1.2 --- Luminosity of quark stars --- p.50
Chapter 6.1.3 --- Microphysics of the neutron star cooling --- p.54
Chapter 6.2 --- Handling of the Phase Transition --- p.56
Chapter 6.3 --- The Models --- p.59
Chapter 6.4 --- Results --- p.60
Chapter 6.4.1 --- Method 1 --- p.61
Chapter 6.4.2 --- Method 2 --- p.66
Chapter 6.5 --- Discussion and Conclusion --- p.66
Chapter 7 --- Formation of a Strange Star --- p.73
Chapter 7.1 --- Formalism of the Problem --- p.73
Chapter 7.2 --- Lagrangian Hydrodynamics --- p.74
Chapter 7.3 --- Hot Equation of State --- p.75
Chapter 7.3.1 --- Nuclear Matter EOS --- p.75
Chapter 7.3.2 --- Quark Matter EOS --- p.77
Chapter 7.3.3 --- Mixed Phase --- p.78
Chapter 7.4 --- Initial Models --- p.78
Chapter 7.5 --- Results --- p.80
Chapter 7.6 --- Discussion and Conclusion --- p.81
Chapter 8 --- Conclusion --- p.95
Bibliography --- p.98
Chapter A --- Solving the EOS --- p.102
Chapter B --- Solving C from Eq. (7.10) --- p.105

碩士
國立臺灣大學
物理學研究所
89
【Abstract】 The neutron star or strange quark star can be described by the differential equations including the mass equation, the hydrostatic equilibrium equation (TOV), and the equation of state (EOS). In this thesis, we try to describe the rotation of stars and to obtain the structure of a neutron star or strange quark star with the modified differential equations. Through the numerical analysis we compare the different Chandrasekhar limits between dense stars with rotations and without. Our major findings include： (1)The maximum stellar mass (Chandrasekhar limit) for rotating strange stars with angular velocity W0＝5×103 sec－1 is larger than the one without rotation by about 4.63﹪while, for neutron stars, the rate of increase is 4.55﹪. (2)The role played by the differential rotation W1 could in principle be as important as the average rotation W0 if W1~W0.

In this thesis a very comprehensive model of rotating neutron stars has been constructed, which is based on the Quark-Meson Coupling model (QMC model), using the method developed by Hartle for slowly rotating compact stars. To determine tidal Love number method suggested by ’Hinderer’ is adopted. In this thesis, neutron star properties are calculated at the rotation frequency of 500 Hz and compared for three EoSs which are based on pure nuclear matter, full baryon octet (both are constructed by taking nuclear structure into consideration) and finally strange quark matter (which is based on the MIT bag model) at the core in β equilibrium. Various universalities have been predicted among the neutron star properties such as dimensionless quadrupole moment vs compactness, dimensionless moment of inertia vs M/R, dimensionless moment of inertia vs dimensionless quadrupole moment and dimensionless moment of inertia vs dimensionless tidal deformability. The significance of the low energy density region and crust is also shown.
Thesis (MPhil) -- University of Adelaide, School of Physical Sciences, 2019

Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeiros
In this thesis, we investigated the strange quark matter (SQM) composed of the spin-up and spin-down; up, down and strange quarks at finite temperature in the presence of the strong magnetic field using the MIT bag model. We computed the total free energy of the spin polarized SQM at finite temperature in the presence of the strong magnetic field. We found that the free energy gets a minimum at a particular value of the spin polarization parameter showing a meta-stable state. The calculation shown that by increasing temperature, the equation of state of spin polarized SQM becomes stiffer. Also, using the general relativistic TOV equation, we studied the structure of the spin polarized strange quark star (SQS). We calculated the maximum mass and corresponding radius of spin polarized SQS at different temperatures and magnetic fields. We shown that the gravitational mass of spin polarized SQS rapidly increases by increasing the central energy density. We also indicated that the mass and the radius of the spin polarized SQS decreases by increasing both temperature and magnetic field.

The topic of the diploma thesis is a comparison of the old and new left in the Czech Republic. The diploma thesis focuses on a comparison of the selected relevant left-wing political groups operating in the Czech Republic. The thesis examines differences and similarities between the KSČM, the socialist wing of ČSSD on one side and the Green Party and the left-liberal tendencies and offshoots of the ČSSD (such Idealists) on the other hand. The work is divided into three main parts. The first part of the thesis is theoretical. The theoretical part defines main terms such as a political party, political movement, left-right axis of the political spectrum, the old left, the new left etc. The explanation of the terms is very important for understanding the thesis. In the second part of this thesis, I analyze single significant and relevant political parties. I focus on the origin and development of political parties and their electoral program, their attitude to selected issues, electorate, potential cooperation between themselves and so on. The third part is comparative. The goal of this thesis is to find out whether the analyzed political parties fulfill leftist characteristic. Next goal of this thesis is to find out whether the classification on left-right axis of the political spectrum is still...

This thesis analyzes the rise of populist parties in southern Europe - italian Five Star Movement, greek SYRIZA and spanish Podemos. The aim is to define the key factors, that contributed to the perception of these protest political formations as political alternatives. The thesis chronologically follows development of examined political parties. Further it defines their strategy in terms of levels of protests and programme. Finally it outlines probable transformations of party systems, which is caused by the rise of protest parties.

This work considers finds of medieval glass in the historic centre of Prague on the basis of archaeological material from the National Herritage Institute excavations. Besides the typology of glass vessels, special attention is paid to the concerning the social level of the society of that time, resp. the study of glass imports that can inform us of the commercial or cultural contacts of the given locality. Especially the enameled glass play an important role in studies of the extraordinary social and economic status. The archaeological evidences of medieval glass has been found in Prague since the end of the 19 th century. The end of the sixtieths brought large finds of medieval glass fragments which most has not been studied as yet. Some of them are included into this work, which is aimed at the region of Old and New Town, whereas the finds of Prague Castle has been left aside. In the study of the popularity of glass tableware, it is possible to observe the process well documented in the majority of Czech towns. In Prague glass ware fragments appeared quite early, already in the 12th century and also in the following century glass presented luxury ware intended for the highest social level. Towards the end of the 13th century the situation began to change. During the first half of the 14th century we...