Age constraints and fine tuning in variable-mass particle models

VAMP (variable-mass particle) scenarios, in which the mass of the cold dark matter particles is a function of the scalar field responsible for the present acceleration of the Universe, have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. We find that only a narrow region in parameter space leads to models with viable values for the Hubble constant and dark energy density today. In the allowed region, the dark energy density starts to dominate around the present epoch and consequently such models cannot solve the coincidence problem. We show that the age of the Universe in this scenario is considerably higher than the age for noncoupled dark energy models, and conclude that more precise independent measurements of the age of the Universe would be useful in distinguishing between coupled and noncoupled dark energy models.

Connection between UHECR's and supermassive relic particles

One of the models proposed for the origin of ultra high energy cosmic rays (UHECR's) suggests that these events are the decay products of relic superheavy metastable particles, which we call S particles. These particles can be produced in the reheating period following the inflationary epoch of the early Universe. We study this possibility and obtain constraints on some parameters such as the lifetime and direct couplings of the X-particle to the inflaton field from the requirement that they are responsible for the observed UHECR flux.

Particle creation due to tachyonic instability in relativistic stars

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Refiguração do tempo histórico pela ficção

M. Bakhtin afirma que a representação de acontecimentos, relações e processos no romance deve abranger a totalidade de uma época nela deve haver uma peculiar concatenação, literariamente expressa, espácio-temporal. Essa formulação contém elementos basilares para o entendimento e análise do romance, objeto deste estudo, Leite derramado de 2009 de Chico Buarque. A narrativa figura, pelo menos, duas grandes épocas históricas do Brasil: uma que vai do início do século XIX até 1930 e outra que vai desse momento ao início do XXI. É a representação da saga histórica da decadência de uma categoria social (fração da classe dominante), personificada na família Assumpção, com seus valores éticos e culturais, suas concepções de mundo e seu comportamento, estilizando sua dissolução social e moral. Ao fazer isso o romance coloca inúmeros problemas desde humano-existenciais até histórico-políticos para a reflexão do leitor.

As Independências do Brasil: ponderações teóricas em perspectiva historiográfica

O tema da Independência do Brasil produziu verdadeiras linhagens historiográficas ao longo de quase dois séculos. Este ensaio visa a sublinhar a característica fundamental da historiografia que é sua própria historicidade, por meio de um exercício comparativo entre os quadros teóricos de interpretação histórica vigentes há três décadas e os que vigoram hoje em dia.

High precision GPS network with precise ephemerides and earth body tide model

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Vidas presas: uma tentativa de compreensão da tragédia da criminalidade junto às suas personagens prisioneiras

Cet article présente une recherche sur les facteurs producteurs de la criminalité réalisée au début de la décennie 80 qui, en s'appuyant sur longs entretiens réalisées avec des prisonnières, a élaboré un ensemble d'hypothèses afin de comprendre les relations constitutives que ce phénomène maintient avec la pauvreté, avec la violence policière/pénitentiaire et avec les propres savoirs par lesquels ses actes et ses auteurs deviennent objet de connaissance. Sa présentation, aujourd'hui, vise deux objectifs: le premier, en hommage et reconnaissance à Sylvia Leser de Mello, est celui d'offrir un simple exemple, parmi tant d'autres, d'une des nombreuses aventures de recherche rendue possible par son orientation. Le second est celui de partager avec des chercheurs qui s'intéressent au même thème une étude qui, polémique et innovatrice à l'époque de sa réalisation, conserve sa pertinence face, actuellement, aux caractéristiques particulièrement graves présentées par les questions abordées.

The strands of the F ring disturbed by its closest satellites

Some Voyager images showed that the F ring of Saturn is composed of at least four separate, non-intersecting, strands covering about 45 degrees in longitude. According to Murray et al. [Murray, C.D., Gordon, M., Giuliatti Winter, S.M. Unraveling the strands of Saturn's F ring. Icarus 129, 304, 1997.] this structure may be caused by undetected satellites embedded in the gaps.Due to precession, the satellites Prometheus and Pandora and the ring particles can experience periodic close encounters. Giuliatti Winter et al. [Giuliatti Winter, S.M, Murray, C.D., Gordon, M. Perturbations to Saturn's F-ring strands at their closest approach to Prometheus. Plan. Space Sciences, 48, 817, 2000.] analysed the behaviour of these four strands at closest approach with the satellite Prometheus. Their work suggests that Prometheus can induce the ring particles to scatter in the direction of the planet, thus increasing the population of small bodies in this region.In this work we analysed the effects of Prometheus on the radial structure of Saturn's F ring during the Voyager and early Cassini epochs. Our results show that at Voyager epoch Prometheus, and also Pandora, had a negligible influence in the strands. However, during the Cassini encounter Prometheus could affect the strands significantly, scattering particles of the inner strand in the direction of the planet. This process can contribute to the replenishment of material in the region between the F ring and the A ring, where two rings have recently been discovered [Porco, C. et al. Cassini imaging science. Initial results on Saturn's rings and small Satellites. Science, 307, 1226, 2005].We also analyse the behaviour of undetected satellites under the effects of these two satellites by computing the Lyapunov Characteristic Exponent. Our results show that these satellites have a chaotic behaviour which leads to a much more complex scenario. The new satellite S/2004 S6 also presents a chaotic behaviour with can alter the dynamic of the system, since this satellite crosses the orbit of the strands. (C) 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.

Middle Proterozoic vein-hosted gold deposits in the Pontes e Lacerda region, southwestern Amazonian craton, Brazil

Structural, geochemical, and isotope studies were carried out on the gold deposits of the Pontes e Lacerda region (Mato Grosso state, Brazil), where rocks of the Aguapei and Rondoniano mobile belts (southwestern Amazonian craton) occur. The orebodies are hosted in metavolcanic, gneiss-granite, quartzite, tonalite, and granite units. Tectonics involve oblique overthrusting (from northeast to southwest), which led to the formation of recumbent folds and thrusts (pathways for the mineralizing fluids), upright folds, and faults with dominant strike-slip component. These unconformities represent potential sites for mineralization. During geological mapping, it was observed that the orebodies consist of quartz, pyrite, and gold, and that the hydrothermal alteration zone contains quartz, sericite, pyrite (altered to limonite), and magnetite (altered to hematite). Chalcopyrite, galena, and sphalerite occur only in the Onça deposit. Chemical analysis of sulfides indicates high contents of Bi, Se, and Te in sulfides and gold, suggesting plutonic involvement in the origin of hydrothermal solutions. K-Ar dating of hydrothermal sericites from gold veins yielded ages in the range from 960 to 840 Ma, which may indicate the age of original crystallization of sericite. Pb-Pb dating in galenas yielded model ages in the range from 1000 to 800 Ma for the Onça deposit, which is in agreement with K-Ar ages. Pb-isotopic ratios indicate high U/Pb and low Th/Pb for the upper-crustal Pb source before incorporation in galena crystals. The Pontes e Lacerda gold deposits yielded ages correlated to the Aguapei event and probably were formed during a Proterozoic contractional tectonic period in the southwestern part of the Amazon craton, which may characterize an important metallogenic epoch in the Pontes e Lacerda region.

Parcelamento da adubação nitrogenada na cultura do milho irrigado em sistema plantio direto

The purpose of this study was to evaluate the best time for application of N for an irrigated corn crop in a no-tillage system in the State of Alagoas. Three corn hybrids were used (TORK, FORT and BRS-3003) with four application times (days after sowing - DAS) for fertilizing with nitrogen as top dressing, consisting of the following treatments: 1) 120 kg ha-1 at 15 DAS, 2) 60 kg ha-1 at 15 DAS and 60 kg ha-1 at 30 DAS, 3) 120 kg ha-1 at 30 DAS, 4) 60 kg ha-1 at 30 DAS and 60 kg ha -1 at 45 DAS and 5) control treatment without N fertilization. The experimental design was in randomized blocks with four replications in a subdivided plot scheme. The components of the production studied were: final population of plants ha-1, numbers of corn ears ha-1 length of corn ears and number of rows of grains of corn and mass of 1000 grains. The productivities of grains obtained did not present significant differences among the treatments that received fertilization with nitrogen, independent of the time of application and number of split applications. It is concluded that in the notillage system in Alagoas spliting the manuring with nitrogen (top dressing) is not necessary.

Evaluación genética de búfalos de la raza Murrah para la producción de leche en el día de control y a los 305 días de lactancia

There were analyzed 4757 complete lactations of the Murrah breed, daughters of 187 bulls, with the goal of verifying the viability upon employing the test-day (PDLC), on substitution of the milk yield at 305th day of lactation (PL305), in the genetic evaluations. The components of variance for the PDLC1 to PDLC9 and for the PL305 were estimated in uni-traits analysis according to maximum restricted likelihood method. The used model included the genetic direct additive random effects, of residual and permanent environment. There were considered as fixed effects, the contemporary group and the number of milkings and the age of the cow at the moment of parity co-variable (quadratic and linear effect). The contemporary groups were constituted by the herd-year-month of control for the PDLC and by herd-year-epoch of parity for PL305. The estimates of heritability for the PDLC and PL305 were 0.12 to 0.23 and 0.22, respectively. The correlations of order of the predicted genetic values for the 187 bulls, obtained between the PDLC and the PL305, were from moderate to high, varying from 67.74 to 83.12. From the minimum selection of the 10% of the best bulls relating to the predicted genetic value for the PL305, the coincidence among the classification of these animals was over 68%, when evaluated by the PDLC3,PDLC4,PDLC5 and PDLC6. Upon selecting the 5% of the best animals that coincidence presented a lower value.

Influência da combinação e modernização dos sistemas que integram o GNSS no georreferenciamento de imóveis rurais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Solução rápida das ambigüidades GPS para aplicações no posicionamento relativo de linhas de base curtas

Pós-graduação em Ciências Cartográficas - FCT

Heleny Guariba: luta e paixão no teatro brasileiro

Pós-graduação em Artes - IA

Sobre as causas evolutivas da cognição humana

Pós-graduação em Filosofia - FFC