The role of differential rotation in the evolution of the r-mode instability

We discuss the role of differential rotation in the evolution of the l=2 r-mode instability of a newly born, hot, rapidly-rotating neutron star. It is shown that the amplitude of the r-mode saturates in a natural way at a value that depends on the amount of differential rotation at the time the instability becomes active. It is also shown that, independently of the saturation amplitude of the mode, the star spins down to a rotation rate that is comparable to the inferred initial rotation rates of the fastest pulsars associated with supernova remnants.Comment: 4 pages, 2 figures, in Proceedings of the 5th International Workshop "New Worlds in Astroparticle Physics", Faro, Portugal, 8-10 January 200

Nonlinear evolution of r-modes: the role of differential rotation

Recent work has shown that differential rotation, producing large scale drifts of fluid elements along stellar latitudes, is an unavoidable feature of r-modes in the nonlinear theory. We investigate the role of this differential rotation in the evolution of the l=2 r-mode instability of a newly born, hot, rapidly rotating neutron star. It is shown that the amplitude of the r-mode saturates a few hundred seconds after the mode instability sets in. The saturation amplitude depends on the amount of differential rotation at the time the instability becomes active and can take values much smaller than unity. It is also shown that, independently of the saturation amplitude of the mode, the star spins down to rotation rates that are comparable to the inferred initial rotation rates of the fastest pulsars associated with supernova remnants. Finally, it is shown that, when the drift of fluid elements at the time the instability sets in is significant, most of the initial angular momentum of the star is transferred to the r-mode and, consequently, almost none is carried away by gravitational radiation.Comment: 10 pages, 5 figure

The influence of differential rotation on the detectability of gravitational waves from the r-mode instability

Recently, it was shown that differential rotation is an unavoidable feature of nonlinear r-modes. We investigate the influence of this differential rotation on the detectability of gravitational waves emitted by a newly born, hot, rapidly-rotating neutron star, as it spins down due to the r-mode instability. We conclude that gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation at the time the r-mode instability becomes active is not very high.Comment: 8 pages, 6 figures, revtex

Modos r de oscilação em estrelas de neutrões

Tese dout., Física - Astrofísica, Universidade do Algarve, 2007This thesis is devoted to the study of r-modes in neutron stars. Its aim is to determine the in°uence of di®erential rotation on the evolution of the r-mode insta- bility and on the detectability of gravitational waves from the r-mode. Di®erential rotation, as shown recently, is an unavoidable feature of nonlinear r-modes. We analyse the role played by this di®erential rotation on the evolution of the r-mode instability in newly-born neutron stars. We show that, due to the presence of dif- ferential rotation, the amplitude of the r-mode saturates in a natural way, whereas the angular velocity of the star decreases to values compatible with observational data. We also study the detectability of gravitational waves emitted by newly-born neutron stars, due to the r-mode instability, taking into account di®erential rotation. We show that the detectability of these waves depends crucially on the di®erential rotation associated to the r-mode instability. For small initial di®erential rotation, gravitational waves could be detected by the advanced laser interferometer detectors LIGO and Virgo, if the neutron star is located less than 20 Mpc away from Earth.Faculdade de Ciências e Tecnologia ( FCT

Comparison of levels of anxiety and depression among active and sedentary elderly

BACKGROUND: The anxiety and depression are a public health problem in the elderly. Currently some studies have been shown a positive association between physical activity and good mental health. OBJECTIVE: To compare the possible relationship between levels of anxiety and depression among active and sedentary elderly. METHODS: The sample comprised a total of 72 patients divided into one group of 38 elderly subjects (GS) and another group of 34 physically assets (GA). These answered a questionnaire with socio-demographic characteristics and the Hospital Anxiety and Depression Scale. RESULTS: The variables that influenced the presence of anxiety and depression were the level of physical activity (p < 0,001) and the level of instruction (p < 0,01). The GS showed 38 more probability to develop symptoms of anxiety and depression and subjects without qualifications had 11 more probability to develop these symptoms. For the GS 35 (92,1%) patients had levels of anxiety or depression and 3 (7,9%) did not. In GA, the presence of anxiety or depression were observed only in 8 (23,5%) and the remaining 26 (76,5%) revalidates not any kind of these symptoms (p < 0,05). DISCUSSION: Practicing physical activity may represent a very important factor to reduce levels of anxiety and depression in elderly.CONTEXTO: A ansiedade e a depressão constituem um problema de saúde pública nos idosos. Atualmente, tem-se demonstrado uma associação positiva entre a prática de atividade física e a boa saúde mental. OBJETIVO: Comparar a relação entre os níveis de ansiedade e depressão entre idosos ativos e sedentários. MÉTODOS: A amostra foi constituída por 72 idosos, divididos num grupo de 38 idosos sedentários (GS) e outro grupo (GA) de 34 fisicamente ativos. Estes responderam a um questionário com características sociodemográficas e a Escala de Ansiedade e Depressão para Hospital Geral. RESULTADOS: As variáveis que influenciaram a presença de ansiedade ou depressão foram o nível de atividade física (p < 0,001) e de escolaridade (p < 0,01). O GS apresentou 38 vezes mais de probabilidade de vir a desenvolver sintomas de ansiedade e depressão e os indivíduos sem habilitações apresentam 11 vezes mais de probabilidade de vir a desenvolver esses sintomas. No GS, 35 (92,1%) idosos apresentaram níveis de ansiedade ou depressão e 3 (7,9%) não apresentaram. No GA apenas 8 (23,5%) apresentaram níveis de ansiedade ou depressão e 26 (76,5%) não revelaram esses sintomas (p < 0,05). CONCLUSÃO: A prática da atividade física pode representar um fator importante para reduzir os níveis de ansiedade e depressão em idosos

Measurements of the leptonic branching fractions of the τ\tau

Data collected with the DELPHI detector from 1993 to 1995 combined with previous DELPHI results for data from 1991 and 1992 yield the branching fractions B({\tau \rightarrow \mbox{\rm e} \nu \bar{\nu}}) = (17.877 \pm 0.109_{stat} \pm 0.110_{sys} )\% and $B({\tau \rightarrow \mu \nu \bar{\nu}}) = (17.325 \pm 0.095_{stat} \pm 0.077_{sys} )\%$

Time to Switch to Second-line Antiretroviral Therapy in Children With Human Immunodeficiency Virus in Europe and Thailand.

Background: Data on durability of first-line antiretroviral therapy (ART) in children with human immunodeficiency virus (HIV) are limited. We assessed time to switch to second-line therapy in 16 European countries and Thailand. Methods: Children aged <18 years initiating combination ART (≥2 nucleoside reverse transcriptase inhibitors [NRTIs] plus nonnucleoside reverse transcriptase inhibitor [NNRTI] or boosted protease inhibitor [PI]) were included. Switch to second-line was defined as (i) change across drug class (PI to NNRTI or vice versa) or within PI class plus change of ≥1 NRTI; (ii) change from single to dual PI; or (iii) addition of a new drug class. Cumulative incidence of switch was calculated with death and loss to follow-up as competing risks. Results: Of 3668 children included, median age at ART initiation was 6.1 (interquartile range (IQR), 1.7-10.5) years. Initial regimens were 32% PI based, 34% nevirapine (NVP) based, and 33% efavirenz based. Median duration of follow-up was 5.4 (IQR, 2.9-8.3) years. Cumulative incidence of switch at 5 years was 21% (95% confidence interval, 20%-23%), with significant regional variations. Median time to switch was 30 (IQR, 16-58) months; two-thirds of switches were related to treatment failure. In multivariable analysis, older age, severe immunosuppression and higher viral load (VL) at ART start, and NVP-based initial regimens were associated with increased risk of switch. Conclusions: One in 5 children switched to a second-line regimen by 5 years of ART, with two-thirds failure related. Advanced HIV, older age, and NVP-based regimens were associated with increased risk of switch

Estudo de subestruturas em aglomerados de Galáxias

Esta dissertação apresenta dois métodos de detecção de subestruturas em aglomerados de Galáxias e os resultados da sua aplicação a um conjunto de 4 destes sistemas. Nos capítulos 2 e 3, relembramos as principais propriedades dos aglomerados de Galáxias e qual o interesse em estudá-los. Também damos a definição de subestruturas e ressaltamos a sua importância do ponto de vista da Cosmologia. Os capítulos 4 e 5 são consagrados à descrição detalhada destes métodos, sendo o primeiro, o Kernel adaptativo aplicado à distribuição espacial e cinemática das Galáxias e o segundo, o Modelo de Visão Multi-escalas, aplicado à análise da emissão em raios-X difusa dos aglomerados e, por consequência, à distribuição do gás intraglomerado. No final destes dois capítulos, também são apresentados os resultados da aplicação destes métodos a nossa amostra de aglomerados. No capítulo 6, é feita uma análise comparativa dos resultados obtidos com cada método. No último capítulo, apresentamos as conclusões mais importantes deste trabalho, apontando, tentativamente, alguns desenvolvimentos possíveis. Dois apêndices finalizam o nosso trabalho, os quais detalham questões levantadas na nossa análise que não estão diretamente ligadas ao problema da detecção de subestruturas. ABSTRACT: This dissertation presents two methods for the detection of substructures in clusters of galaxies and the results of their application to a group of 4 clusters. In chapters 2 and 3, we remember the main properties of clusters of galaxies and give the definition of substructures. We also try to show why the study of substructures in clusters of galaxies is so important for Cosmology. Chapters 4 and 5 describe these two methods, the first one, the adaptative Kernel, is applied to the study of the spatial and kinematical distribution of the cluster galaxies. The second one, the MVM (Multiscale Vision Model), is applied to analyse the cluster diffuse X-ray emission, that is to say, the intracluster gas distribution. At the end of these two chapters, we also present the results of the application of these methods to our sample of clusters. In chapter 6, we draw the conclusions from the comparison of the results we obtain with each method. In the last chapter, we present the main conclusions of this work trying to point out possible developments. We close with two appendices in which we detail some questions raised in this work not directly linked to the problem of substructures detection.Number of Pages: 14