Clues to the nature of damped Lyman alpha systems from chemical evolution models

The evolution of the metallicity of damped Lyman alpha systems (DLAs) is investigated in order to understand the nature of these systems. The observational data on chemical abundances of DLAs are analysed with robust statistical methods, and the abundances are corrected for dust depletion. The results of this analysis are compared to predictions of several classes of chemical evolution models: one-zone dwarf galaxy models, multizone disk models, and chemodynamical models representing dwarf galaxies. We compare the observational data on the [alpha/Fe] and [N/alpha] ratios to the predictions from the models. In DLAs, these ratios are only partially reproduced by the dwarf galaxy one-zone model and by the disk model. On the other hand, the chemodynamical model for dwarf galaxies reproduces the properties of nearly all DLAs. We derive the formation epoch of dwarf galaxies, and we find that dwarf galaxies make a significant contribution to the total neutral gas density in DLAs, and that this contribution is more important at high redshifts (z > 2-3). We propose a scenario in which the DLA population is dominated by dwarf galaxies at high redshifts and by disks at lower redshifts. We also find that Lyman Break Galaxies (LBGs) may constitute a sequence rather than present a sharp dichotomy between the two populations. We also arise the possibility that we could be missing a whole population of high HI density column objects, with metallicities intermediate between those of DLAs and LBGs. Finally, we discuss the possibility that relying only on the observations of DLAs could lead to an underestimate of the metal content of the high redshift Universe.Comment: 23 pages, 19 figures. Accepted for publication in MNRA

Efeito da curcumina no tratamento de micróglias infectadas pelo vírus Zika

Dissertação (mestrado) — Universidade de Brasília, Faculdade de Medicina, Pós-graduação em Medicina Tropical, 2021.O relato de numerosos casos de microcefalia no Brasil entre 2015 e 2016 alertou a comunidade científica mundial. O principal motivo foi a sua relação com os casos de infecção pelo vírus Zika. A organização mundial da saúde alertou para a necessidade do desenvolvimento de tratamentos para a infecção e prevenções ao desenvolvimento da microcefalia. Neste contexto, a curcumina tem se mostrado uma molécula de interesse para estudos com o vírus Zika, pois há na literatura evidências da sua ação sobre os flavivírus e já está demonstrada sua capacidade anti-inflamatória. Portanto, o objetivo deste trabalho foi avaliar se a curcumina tem a capacidade de interferir nos mecanismos de morte celular e de autofagia induzidos pelo vírus e se esta molécula possui ação imunomoduladora, importante na prevenção da neuroinflamação que ocorre durante a infecção. A melhor compreensão destes mecanismos poderá contribuir para o desenvolvimento de novas medidas terapêuticas e diminuir a morbidade da infecção pelo vírus Zika. As micróglias murinas de linhagem BV2 foram infectadas com MOI 0,1 e MOI 1 do vírus Zika (cepa PE/243) e tratadas com 0,31 μM, 0,62 μM, 1,25 μM, 2,5 μM e 5 μM de curcumina. A viabilidade celular foi avaliada pelo teste de redução do MTT e lida em espectrofotômetro. A expressão da caspase-3, da mTOR e da LC3 foram avaliadas por teste antígeno- anticorpo por citometria de fluxo. A morte celular foi avaliada pela marcação por anexina/iodeto de propídio, lido em citometria de fluxo. A produção de espécies reativas de oxigênio e de nitrogênio foram avaliadas pelas sondas DCF-DA e DAF-FM, respectivamente, em citometria de fluxo. A dosagem das citocinas foi realizada por kit CBA (BD), em citometria de fluxo. Os dados mostraram que o vírus Zika apresentou um efeito citopático sobre as células BV2 e a curcumina reverteu parcialmente esta citotoxicidade. Este efeito citopático do vírus foi resultado principalmente da indução da apoptose sem aumentar a produção de caspase-3 pelas micróglias. Já a curcumina, mesmo sem alterar o número de células apoptóticas, reduziu a sinalização pela caspase-3. Observamos também que o vírus Zika induz a autofagia nas micróglias sem alterar a expressão de mTOR, enquanto o tratamento com a curcumina induziu ainda mais a autofagia através da redução da expressão de mTOR. O vírus Zika induziu uma resposta inflamatória pelas células BV2 com aumento da produção de IFN-γ, TNF-α, IL-6, IL-10, IL-17, MCP-1. Esta resposta inflamatória foi controlada pela curcumina, reduzindo a produção de IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ e TNF-α nos grupos de células infectadas com MOI 0,1 do vírus e que receberam o tratamento de 2,5 μM e 5 μM. Por fim, observamos que a infecção aumentou a produção de EROs pelas células BV2. Apenas as células estimuladas com MOI 0,1 apresentaram a produção aumentada de ERNS. Em contrapartida, células na presença de MOI 1 produziram menos ERNs. Em conclusão, observou-se que o tratamento com a curcumina apresentou um efeito pró-oxidante durante a infecção pelo vírus Zika.The report of numerous cases of microcephaly in Brazil between 2015 and 2016 have alerted the world scientific community. The main reason for it was the relation between cases of infection by zika virus. The World Health Organization alerted the need of development of treatments for the microcephaly infection and prevention. On this context, curcumin has shown itself as an interesting molecule for studies with zika virus because it has evidences of its action above flavivirus and anti-inflammatory capacity all over the literature. Therefore, the aim of the present work has been to analyze if curcumin interfered on cell death and autophagy pathways induced by the virus and if this molecule has immunomodulator action, which is important for the prevention of the neuroinflammation that happens during the infection. The best understanding of these pathways can contribute for the development of new therapeutic measures and decrease the morbidity of zika virus infection. The BV2 cell line of murine microglia were infected by MOI 0,1 e MOI 1 of zika virus (strain PE/243) and treated with 0.31 μM, 0.62 μM, 1.25 μM, 2.5 μM and 5 μM of curcumin. The cellular viability was evaluated by the test of MTT reduction and read in spectrophotometer. The expression of caspase-3, mTOR and LC3 has been evaluated by antigen-antibody test and read in flow cytometry. The cell death was evaluated by annexin/propidium iodide target and also read in flow cytometry. The production of reactive oxygen species and nitrogen was evaluated by DCF- DA and DAF-FM probes, respectively, in flow cytometry. The cytokine dosage has been done by CBA kit (BD) in flow cytometry. Our data has shown that zika virus presented a cytopathic effect in BV2 cells and curcumin has partly reversed this cytotoxicity. This cytopathic effect of the virus has happed mainly because of the induction of cell apoptosis, without increasing the production of caspase-3 by microglia. Curcumin, on the other hand, even without changing the number of apoptotic cells, has reduced the signaling by caspase-3. We also have observed that zika virus induced autophagy on microglia without changing mTOR expression, while the treatment with curcumin induced even more autophagy by the reduction of mTOR expression. Zika virus induced an inflammatory response by BV2 cells with an increase on IFN- γ, TNF-α, IL-6, IL-10, IL1-17, MCP-1 production. This inflammatory response has been controlled by curcumin, decreasing IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ and TNF- α production on groups of cells infected by virus MOI 0,1 which received the treatment of 2,5 μM and 5 μM. In the end. We have observed that the infection increased EROs production by the BV2 cells. In addiction, only cells stimulated by small amount of virus has shown increasing of ERNs production. On the other hand, cells infected by large amount of virus produced less ERNs. We have seen that the treatment with curcumin presented a pro-oxidant effect during zika virus infection

An old quasar in a young dark energy-dominated universe?

Dark energy is the invisible fuel that seems to drive the current acceleration of the Universe. Its presence, which is inferred from an impressive convergence of high-quality observational results along with some apparently sucessful theoretical predictions, is also supported by the current estimates of the age of the Universe from dating of local and high-$z$ objects. In this paper we test the viability of several dark energy scenarios in the light of the age estimates of the high redshift ($z=3.91$) quasar APM 08279+5255. Using a chemodinamical model for the evolution of spheroids, we first reevaluate its current estimated age, as given by Hasinger et al. (2002). An age of 2.1 Gyr is set by the condition that Fe/O abundance ratio (normalized to solar values) of the model reaches 3.3, which is the best fit value obtained in the above reference. It is shown that for the currently accepted value of the matter density parameter, most of the existing dark energy scenarios cannot accomodate this old high redshift object unless the Hubble parameter is as low as $H_o = 58$ $\rm{km.s^{-1}.Mpc^{-1}}$, as recently advocated by Sandage and collaborators. Even considering less stringent age limits, only cosmological models that predicts a considerably old Universe at high-$z$ can be compatible with the existence of this object. This is the case of the conventional $\Lambda$CDM scenario and some specific classes of brane world cosmologies.Comment: 7 pages, 3 figures, uses mn.cl

Profile comparison of the 6–9 μm polycyclic aromatic hydrocarbon bands in starburst-dominated galaxies

Polycyclic aromatic hydrocarbons (PAHs) are of great astrochemical and astrobiological interest due to their potential to form prebiotic molecules. We analyse the 7.7 and 8.6 μm PAH bands in 126 pre-dominantly starburst-dominated galaxies extracted from the Spitzer/IRS ATLAS project. Based on the peak positions of these bands, we classify them into the different A, B, and C Peeters’ classes, which allows us to address the potential characteristics of the PAH-emitting population. We compare this analysis with previous work focused on the 6.2 μm PAH band for the same sample. For the first time in the literature, this statistical analysis is performed on a sample of galaxies. In our sample, the 7.7 μm complex is equally distributed in A and B object’s class while the 8.6 μm band presents more class B sources. Moreover, 39 per cent of the galaxies were distributed into A class objects for both 6.2 and 7.7 μm bands and only 18 per cent received the same A classification for the three bands. The ‘A A A’ galaxies presented higher temperatures and less dust in their interstellar medium. Considering the redshift range covered by our sample, the distribution of the three bands into the different Peeters’ classes reveals a potential cosmological evolution in the molecular nature of the PAHs that dominate the interstellar medium in these galaxies, where B class objects seem to be more frequent at higher redshifts and, therefore, further studies have to be addressed

O desenho e o design de moda: da ideia ao produto / Fashion design: from the idea to the product

Este artigo fundamenta-se em uma pesquisa em andamento no Programa de Pós?Graduação em Design da PUC-Rio, sob a orientação do Prof. Dr. Carlos Eduardo Félix da Costa.  Tem como objeto analisar a dificuldade dos alunos de Faculdades de Design de Moda na transposição de uma representação mental para uma representação real (desenho de moda/ilustração de moda, desenho técnico). Tal dificuldade redunda em um produto final - a roupa -, na maioria das vezes, desvinculado da representação mental geradora da ideia. Objetiva-se propor subsídios facilitadores para o trânsito livre na tríade proposta: ideia–desenho–produto. O ponto de partida deste estudo é a observação desta dificuldade em sala de aula, a investigação e a identificação dos fatores que dificultam esta transposição, tendo como suporte a aplicação de algumas técnicas artísticas tradicionais, a partir de experimentação, com o intuito de promover a liberação de fatores que bloqueiam a criatividade do aluno e que desenvolvem a visão espacial. Um estudo de caso corrobora os aspectos apresentados neste artigo

Constraining scalar-tensor quintessence by cosmic clocks

Scalar-tensor quintessence models can be constrained by identifying suitable cosmic clocks which allow to select confidence regions for cosmological parameters. In particular, we constrain the characterizing parameters of non-minimally coupled scalar-tensor cosmological models which admit exact solutions of the Einstein field equations. Lookback time to galaxy clusters at low intermediate, and high redshifts is considered. The high redshift time-scale problem is also discussed in order to select other cosmic clocks such as quasars.Comment: 13 pages, 8 figures. to be published in Astron & Astrop

The SCUBA Bright Quasar Survey (SBQS): 850micron observations of the z>4 sample

We present initial results of a new, systematic search for massive star-formation in the host galaxies of the most luminous and probably most massive z>=4 radio-quiet quasars (M(B) 10^13Lsun). A total of 38 z>=4 radio-quiet quasars have been observed at the JCMT using SCUBA at 850microns: 8 were detected (>3sigma) with S(850microns)>~ 10mJy (submillimetre-loud). The new detections almost triple the number of optically selected, submillimetre-loud z>~4 radio-quiet quasars known to date. We include a detailed description of how our quasar sample is defined in terms of radio and optical properties. There is no strong evidence for trends in either detectability or 850microns flux with absolute magnitude, M(B). We find that the weighted mean flux of the undetected sources is 2.0 +/- 0.6mJy, consistent with an earlier estimate of \~3mJy based on more sensitive observations of a sample z>~4 radio-quiet quasars (McMahon et al., 1999). This corresponds to an inferred starformation rate of \~1000Msun/yr, similar to Arp220. The typical starformation timescale for the submillimetre-bright sources is ~1Gyr, 10 times longer than the typical accretion-driven e-folding timescale of ~5x10^7 years. Our 850micron detection of the z=4.4 quasar PSS J1048+4407 when analysed in conjunction with 1.2mm single-dish and interferometric observations suggests that this source is resolved on angular scales of 1-2" (6-12 kpc). In addition, we present a new optical spectrum of this source, identifying it as a broad absorption line (BAL) quasar. The new redshift is outside that covered in a recent CO line search by Guilloteau et al., (1999), highlighting the need for accurate redshifts for the obervation and interpretation of high-redshift line studies.Comment: 16 pages, 11 figures. Accepted by Monthly Notices of the Royal Astronomical Societ