Radiolysis of ammonia-containing ices by energetic, heavy and highly charged ions inside dense astrophysical environments

Deeply inside dense molecular clouds and protostellar disks, the interstellar ices are protected from stellar energetic UV photons. However, X-rays and energetic cosmic rays can penetrate inside these regions triggering chemical reactions, molecular dissociation and evaporation processes. We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV Ni^13+) with ammonia-containing ices in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed inside a high vacuum chamber coupled to the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France.\textit{In-situ} analysis is performed by a Fourier transform infrared spectrometer (FTIR) at different fluences. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide due to heavy cosmic ray ion analogs are ~2x10^{-13}, 1.4x10^{-13} and 1.9x10^{-13} cm$^2$, respectively. In the presence of a typical heavy cosmic ray field, the estimated half life for the studied species is 2-3x10^6 years. The ice compaction (micropore collapse) due to heavy cosmic rays seems to be at least 3 orders of magnitude higher than the one promoted by (0.8 MeV) protons . In the case of the irradiated H2O:NH3:CO ice, the infrared spectrum at room temperature reveals five bands that were tentatively assigned to vibration modes of the zwitterionic glycine (+NH3CH2COO-).Comment: Accepted to be published in Astronomy and Astrophysics; Number of pages: 12; Number of Figures: 7; Number of Tables:

A calcareous nannofossil and organic geochemical study of marine palaeoenvironmental changes across the Sinemurian/Pliensbachian (early Jurassic, ~191Ma) in Portugal

The Sinemurian/Pliensbachian boundary (~ 191 Ma) is acknowledged as one of the most important steps in the radiation of planktonic organisms, especially primary producers such as dinoflagellates and coccolithophores. To date, there is no detailed study documenting changes in planktonic assemblages related to palaeoceanographic changes across this boundary. The aim of this study is to characterize the palaeoenvironmental changes occurring across the Sinemurian/Pliensbachian boundary at the São Pedro de Moel section (Lusitanian Basin, Portugal) using micropalaeontology and organic geochemistry approaches. Combined calcareous nannofossil assemblage and lipid biomarker data document for a decrease in primary productivity in relation to a major sea-level rise occurring above the boundary. The Lusitanian Basin was particularly restricted during the late Sinemurian with a relatively low sea level, a configuration that led to the recurrent development of black shales. After a sharp sea-level fall, the basin became progressively deeper and more open during the earliest Pliensbachian, subsequently to a major transgression. This sea-level increase seems to have been a global feature and could have been related to the opening of the Hispanic Corridor that connected the Tethys and palaeo-Pacific oceans. The palaeoceanographic and palaeoclimatic changes induced by this opening may have played a role in the diversification of coccolithophores with the first occurrence or colonization of Tethyan waters by placolith-type coccoliths

Aperture-free star formation rate of SDSS star-forming galaxies

Large area surveys with a high number of galaxies observed have undoubtedly marked a milestone in the understanding of several properties of galaxies, such as star-formation history, morphology, and metallicity. However, in many cases, these surveys provide fluxes from fixed small apertures (e.g. fibre), which cover a scant fraction of the galaxy, compelling us to use aperture corrections to study the global properties of galaxies. In this work, we derive the current total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming galaxies, using an empirically based aperture correction of the measured $\rm H\alpha$ flux for the first time, thus minimising the uncertainties associated with reduced apertures. All the $\rm H\alpha$ fluxes have been extinction-corrected using the $\rm H\alpha/H\beta$ ratio free from aperture effects. The total SFR for $\sim$210,000 SDSS star-forming galaxies has been derived applying pure empirical $\rm H\alpha$ and $\rm H\alpha/H\beta$ aperture corrections based on the Calar Alto Legacy Integral Field Area (CALIFA) survey. We find that, on average, the aperture-corrected SFR is $\sim$0.65dex higher than the SDSS fibre-based SFR. The relation between the SFR and stellar mass for SDSS star-forming galaxies (SFR--$\rm M_\star$) has been obtained, together with its dependence on extinction and $\rm H\alpha$ equivalent width. We compare our results with those obtained in previous works and examine the behaviour of the derived SFR in six redshift bins, over the redshift range $\rm 0.005 \leq z\leq 0.22$. The SFR--$\rm M_\star$ sequence derived here is in agreement with selected observational studies based on integral field spectroscopy of individual galaxies as well as with the predictions of recent theoretical models of disc galaxies

Aplicação da sequência ultra/nanofiltração para valorização e redução do impacto ambiental de lactossoro de quijo de ovelha

Proceedings of Renaissance of the regions of Southern Europe, University of Évora: july 10-11, 2014.The by‐products of agro‐industries, due to its high content of nutritive substances, in particular proteins and carbohydrates, have been the subject of intense investigation with a view to their recovery/reuse, towards sustainability. One of these by‐products is ovine cheese whey, that is mainly produced in Southern European countries, as a result of the production of ovine cheeses of Protected Designation of Origin. In most cases, that whey is disposed off into public sewage, causing problems in conventional treatment plants, due to its high organic load. In some countries, e.g. Portugal, Spain and Italy, part of the ovine cheese whey is further processed to obtain whey cheeses, designated by different names, such as requeijão, requesón and ricotta. However, not all of these cheese whey can be transformed due to the high volumes generated. Membrane technology has emerged as a significant innovation for recovery and treatment, because it is more economical than other alternatives, require much less land area than competing technologies and may produce water suitable for multiple proposes. In this work, an example of using membrane processes in the recovery of ovine cheese whey is presented. The operations of ultrafiltration (UF) and nanofiltration (NF) of ovine cheese whey were investigated with the objective of producing added‐value products, such as protein concentrates by UF, lactose concentrates by NF and final permeates with a very low organic load. UF experiments were performed with skimmed cheese whey, both in total recirculation and concentration modes. The equipment used was a plate‐and‐frame unit (Lab Unit M20). Ultrafiltration was performed with organic membranes ETNA 10PP with a surface area of 0,072 m2 and a cut‐off of 10 kDa. Ultrafiltration allowed a clear separation between the protein fraction and a fraction rich in lactose and minerals. About 40% of organic matter, expressed as COD was retained. Nanofiltration of UF permeates was done with membranes NFT50 with a membrane surface area of 0,072 m2..This operation allowed a high retention of lactose (98.8%) and the production of a permeate with a very low organic load. The retention of organic matter, in terms of COD was about 93%. The sequence of operations UF/NF allowed to produce two added‐value products, reducing at the same time the organic pollution of the final stream. Nevertheless, the quality of the final water should be assessed, according with the intended use.RESUMO. Os subprodutos das agro‐indústrias, devido ao seu elevado teor em substâncias nutritivas, em particular proteínas e hidratos de carbono, têm sido objecto de uma intensa investigação com objectivos de recuperação/reutilização, tendo em vista um desenvolvimento sustentável. Um destes subprodutos é o soro de queijo de ovelha, produzido principalmente nos países do sul da Europa, como resultado da produção de queijos de ovelha de Denominação de Origem Protegida. Na maioria dos casos, o soro produzido é lançado nos esgotos municipais, causando problemas em estações de tratamento convencionais, devido à sua elevada carga orgânica. Em alguns países, como Portugal, Espanha e Itália, parte do soro é processado para obtenção de queijos de soro, designados por nomes diferentes, como requeijão, requesón e ricota. No entanto, nem todo o soro produzido pode ser transformado, devido aos elevados volumes gerados. As tecnologias de membranas surgiram como uma inovação significativa para a recuperação/tratamento de vários produtos, dado que relativamente a outros processos alternativos, são mais económicas, podendo produzir água de qualidade adequada para diversos fins. Neste trabalho, é apresentado um exemplo de utilização de processos de membrana na recuperação de soro de queijo de ovelha. As operações de ultrafiltração (UF) e nanofiltração (NF) foram investigadas com o objetivo de produzir produtos de valor acrescentado, como concentrados proteicos por UF, concentrados de lactose por NF e permeados finais, com cargas orgânicas baixas. Os ensaios de UF foram realizados com soro desnatado, em recirculação total e em concentração. O equipamento utilizado foi um módulo de pratos planos (Lab Unidade M20). Na ultrafiltração, foram usadas membranas orgânicas ETNA 10PP, de área superficial 0.072 m2 e com um peso molecular de corte de 10 kDa. A ultrafiltração permitiu uma nítida separação entre a fração proteica e uma fração rica em lactose e sais minerais. Cerca de 40% da matéria orgânica, expressa como CQO, foi retida. Na nanofiltração dos permeados da UF utilizaram‐se membranas NFT50, com uma área de superfície de 0.072 m2. Esta operação permitiu uma elevada retenção de lactose (98.8%) e a obtenção de um permeado com uma carga orgânica bastante reduzida. O factor de retenção da matéria orgânica, em termos de CQO, foi cerca de 93%. A sequência de separações UF / NF permitiu produzir dois produtos de valor acrescentado, reduzindo ao mesmo tempo a poluição orgânica da corrente final. No entanto, a qualidade da água final deve ser avaliada, de acordo com o uso pretendido

Clone size distributions in networks of genetic similarity

We build networks of genetic similarity in which the nodes are organisms sampled from biological populations. The procedure is illustrated by constructing networks from genetic data of a marine clonal plant. An important feature in the networks is the presence of clone subgraphs, i.e. sets of organisms with identical genotype forming clones. As a first step to understand the dynamics that has shaped these networks, we point up a relationship between a particular degree distribution and the clone size distribution in the populations. We construct a dynamical model for the population dynamics, focussing on the dynamics of the clones, and solve it for the required distributions. Scale free and exponentially decaying forms are obtained depending on parameter values, the first type being obtained when clonal growth is the dominant process. Average distributions are dominated by the power law behavior presented by the fastest replicating populations.Comment: 17 pages, 4 figures. One figure improved and other minor changes. To appear in Physica

On a generalised model for time-dependent variance with long-term memory

The ARCH process (R. F. Engle, 1982) constitutes a paradigmatic generator of stochastic time series with time-dependent variance like it appears on a wide broad of systems besides economics in which ARCH was born. Although the ARCH process captures the so-called "volatility clustering" and the asymptotic power-law probability density distribution of the random variable, it is not capable to reproduce further statistical properties of many of these time series such as: the strong persistence of the instantaneous variance characterised by large values of the Hurst exponent (H > 0.8), and asymptotic power-law decay of the absolute values self-correlation function. By means of considering an effective return obtained from a correlation of past returns that has a q-exponential form we are able to fix the limitations of the original model. Moreover, this improvement can be obtained through the correct choice of a sole additional parameter, $q_{m}$. The assessment of its validity and usefulness is made by mimicking daily fluctuations of SP500 financial index.Comment: 6 pages, 4 figure