Is Λ\LambdaCDM an effective CCDM cosmology?

We show that a cosmology driven by gravitationally induced particle production of all non-relativistic species existing in the present Universe mimics exactly the observed flat accelerating $\Lambda$CDM cosmology with just one dynamical free parameter. This kind of scenario includes the creation cold dark matter (CCDM) model [Lima, Jesus & Oliveira, JCAP 011(2010)027] as a particular case and also provides a natural reduction of the dark sector since the vacuum component is not needed to accelerate the Universe. The new cosmic scenario is equivalent to $\Lambda$CDM both at the background and perturbative levels and the associated creation process is also in agreement with the universality of the gravitational interaction and equivalence principle. Implicitly, it also suggests that the present day astronomical observations cannot be considered the ultimate proof of cosmic vacuum effects in the evolved Universe because $\Lambda$CDM may be only an effective cosmology.Comment: 6 pages, 2 figures, changes in the abstract, introduction, new references and typo correction

Asteroseismology and Magnetic Cycles

Small cyclic variations in the frequencies of acoustic modes are expected to be a common phenomenon in solar-like pulsators, as a result of stellar magnetic activity cycles. The frequency variations observed throughout the solar and stellar cycles contain information about structural changes that take place inside the stars as well as about variations in magnetic field structure and intensity. The task of inferring and disentangling that information is, however, not a trivial one. In the sun and solar-like pulsators, the direct effect of the magnetic field on the oscillations might be significantly important in regions of strong magnetic field (such as solar- / stellar-spots), where the Lorentz force can be comparable to the gas-pressure gradient. Our aim is to determine the sun- / stellar-spots effect on the oscillation frequencies and attempt to understand if this effect contributes strongly to the frequency changes observed along the magnetic cycle. The total contribution of the spots to the frequency shifts results from a combination of direct and indirect effects of the magnetic field on the oscillations. In this first work we considered only the indirect effect associated with changes in the stratification within the starspot. Based on the solution of the wave equation and the variational principle we estimated the impact of these stratification changes on the oscillation frequencies of global modes in the sun and found that the induced frequency shifts are about two orders of magnitude smaller than the frequency shifts observed over the solar cycle.Comment: 4 pages, 6 figures, ESF Conference: The Modern Era of Helio- and Asteroseismology, to be published on 3 December 2012 at Astronomische Nachrichten 333, No. 10, 1032-103

Impact of micro-telluric lines on precise radial velocities and its correction

Context: In the near future, new instruments such as ESPRESSO will arrive, allowing us to reach a precision in radial-velocity measurements on the order of 10 cm/s. At this level of precision, several noise sources that until now have been outweighed by photon noise will start to contribute significantly to the error budget. The telluric lines that are not neglected by the masks for the radial velocity computation, here called micro-telluric lines, are one such noise source. Aims: In this work we investigate the impact of micro-telluric lines in the radial velocities calculations. We also investigate how to correct the effect of these atmospheric lines on radial velocities. Methods: The work presented here follows two parallel lines. First, we calculated the impact of the micro-telluric lines by multiplying a synthetic solar-like stellar spectrum by synthetic atmospheric spectra and evaluated the effect created by the presence of the telluric lines. Then, we divided HARPS spectra by synthetic atmospheric spectra to correct for its presence on real data and calculated the radial velocity on the corrected spectra. When doing so, one considers two atmospheric models for the synthetic atmospheric spectra: the LBLRTM and TAPAS. Results: We find that the micro-telluric lines can induce an impact on the radial velocities calculation that can already be close to the current precision achieved with HARPS, and so its effect should not be neglected, especially for future instruments such as ESPRESSO. Moreover, we find that the micro-telluric lines' impact depends on factors, such as the radial velocity of the star, airmass, relative humidity, and the barycentric Earth radial velocity projected along the line of sight at the time of the observation.Comment: Accepted in A&

New Constraints on the Variable Equation of State Parameter from X-Ray Gas Mass Fractions and SNe Ia

Recent measurements are suggesting that we live in a flat Universe and that its present accelerating stage is driven by a dark energy component whose equation of state may evolve in time. Assuming two different parameterizations for the function $\omega(z)$, we constrain their free parameters from a joint analysis involving measurements from X-Ray luminosity of galaxy clusters and SNe type Ia data.Comment: paper, 6 pages, 1 figure Accepted by Int. Journal of Modern Physics D (IJPMD

Macular and Optic Disc Edema and Retinal Vascular Leakage in Familial Amyloid Polyneuropathy with a Transthyretin Val30Met Mutation: a Case Report

Introduction: Familial amyloid polyneuropathy is a group of autosomal dominant disorders characterized by extracellular amyloid deposition in several target organs. This paper aims to report an unusual manifestation of retinal vascular leakage including optic disc and macular edema in a patient with familial amyloid polyneuropathy. Case presentation: A 37-year-old Portuguese Caucasian man with Val30Met transthyretin-related familial amyloid polyneuropathy presented with rapidly progressing visual loss in his left eye. He had undergone liver transplantation at the age of 30 with neurologic stabilization. Fundoscopy and fluorescein angiogram revealed optic disc and macular edema as well as vessel wall staining with leakage in the posterior pole and mid-periphery, without vitreous opacities. A diagnostic work-up for infectious, autoimmune and neoplasic conditions was negative. Systemic immunosuppression was increased but without improvement. Sustained resolution of macular edema was observed after intravitreal injection of dexamethasone implant and laser panretinal photocoagulation. Conclusions: To the best of our knowledge, this is the first report of a rare ocular manifestation of familial amyloid polyneuropathy which represents a new therapeutic challenge. Intravitreal injection of sustained release dexamethasone implant and panretinal photocoagulation may be an effective eye-saving therapeutic approach.info:eu-repo/semantics/publishedVersio

Efeito de cobertura verde com leguminosa perene na supressão da infestação de plantas daninhas do café em produção.

O objetivo deste trabalho foi avaliar o potencial de controle de espécies leguminosas perenes sobre as plantas daninhas do café (Coffea arabica) em produção. O experimento foi instalado em Patrocínio-MG, utilizando-se uma lavoura de café com idade de 8 anos, variedade catuaí, linhagem IAC-99, tendo espaçamento de 3,80 x 0,70m. Foram aplicados 10 tratamentos em esquema fatorial 4x2+2: 4 espécies de leguminosas perenes: (Arachis pintoi, Macrotyloma axillare, Neonotonia wightii e Calopogonium mucunoides); 2 espaçamentos de plantio das leguminosas (2 linhas de 0,50 m e 3 linhas entre 0,25 m) e 2 tratamentos adicionais de controle das plantas daninhas (capina manual e controle químico). O delineamento foi de blocos casualizados com 4 repetições. Não houve efeito do espaçamento de plantio das leguminosas na cobertura do solo, na infestação de plantas daninhas e no índice produtivo do café. No geral as leguminosas proporcionaram menor infestação das plantas daninhas, comparadas à capina manual e controle químico, sendo que no primeiro ano as espécies Macrotyloma axillare, Calopogonium mucunoides e Arachis pintoi obtiveram menores infestações, porém no segundo ano de condução do experimento, as espécies Macrotyloma axillare e Neonotonia wightii seguida pelo Arachis pintoi foram as que apresentaram menores infestações de plantas daninhas. Na cobertura do solo pelas leguminosas, inicialmente no primeiro ano, a espécie Arachis pintoi apresentou uma taxa de cobertura inferior às demais, porém no segundo ano essa espécie foi superior. Dentre as espécies de plantas daninhas identificadas, independente do tratamento utilizado, o picão-preto (Bidens pilosa) foi o mais freqüente, tanto no primeiro como no segundo ano. Não houve interferência das espécies leguminosas no índice produtivo do café

A thorough analysis of the short- and mid-term activity-related variations in the solar acoustic frequencies

The frequencies of the solar acoustic oscillations vary over the activity cycle. The variations in other activity proxies are found to be well correlated with the variations in the acoustic frequencies. However, each proxy has a slightly different time behaviour. Our goal is to characterize the differences between the time behaviour of the frequency shifts and of two other activity proxies, namely, the area covered by sunspots and the 10.7cm flux. We define a new observable that is particularly sensitive to the short-term frequency variations. We then compare the observable when computed from model frequency shifts and from observed frequency shifts obtained with the Global Oscillation Network Group (GONG) for cycle 23. Our analysis shows that on the shortest time-scales the variations in the frequency shifts seen in the GONG observations are strongly correlated with the variations in the area covered by sunspots. However, a significant loss of correlation is still found. We verify that the times when the frequency shifts and the sunspot area do not vary in a similar way tend to coincide with the times of the maxima of the quasi-biennial variations seen in the solar seismic data. A similar analysis of the relation between the 10.7cm flux and the frequency shifts reveals that the short-time variations in the frequency shifts follow even more closely those of the 10.7cm flux than those of the sunspot area. However, a loss of correlation between frequency shifts and 10.7cm flux variations is still found around the same times.Comment: 7 pages, 6 figures, accepted for publication in MNRA