958 resultados para Kohan, Martín


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Aims. We aim to investigate the chemistry and gas phase abundance of HNCO and the variation of the HNCO/CS abundance ratio as a diagnostic of the physics and chemistry in regions of massive star formation. Methods. A numerical-chemical model has been developed which self-consistently follows the chemical evolution of a hot core. The model comprises of two distinct stages. The first stage follows the isothermal, modified free-fall collapse of a molecular dark cloud. This is immediately followed by an increase in temperature which represents the switch on of a central massive star and the subsequent evolution of the chemistry in a hot, dense gas cloud (the hot core). During the collapse phase, gas species are allowed to accrete on to grain surfaces where they can participate in further reactions. During the hot core phase surface species thermally desorb back in to the ambient gas and further chemical evolution takes place. For comparison, the chemical network was also used to model a simple dark cloud and photodissociation regions. Results. Our investigation reveals that HNCO is inefficiently formed when only gas-phase formation pathways are considered in the chemical network with reaction rates consistent with existing laboratory data. This is particularly true at low temperatures but also in regions with temperatures up to ~200 K. Using currently measured gas phase reaction rates, obtaining the observed HNCO abundances requires its formation on grain surfaces – similar to other “hot core” species such as CH3OH. However our model shows that the gas phase HNCO in hot cores is not a simple direct product of the evaporation of grain mantles. We also show that the HNCO/CS abundance ratio varies as a function of time in hot cores and can match the range of values observed. This ratio is not unambiguously related to the ambient UV field as been suggested – our results are inconsistent with the hypothesis of Martín et al. (2008, ApJ, 678, 245). In addition, our results show that this ratio is extremely sensitive to the initial sulphur abundance. We find that the ratio grows monotonically with time with an absolute value which scales approximately linearly with the S abundance at early times.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In the past few years, attosecond techniques have been implemented for the investigation of ultrafast dynamics in molecules. The generation of isolated attosecond pulses characterized by a relatively high photon flux has opened up new possibilities in the study of molecular dynamics. In this paper, we report on experimental and theoretical results of ultrafast charge dynamics in a biochemically relevant molecule, namely, the amino acid phenylalanine. The data represent the first experimental demonstration of the generation and observation of a charge migration process in a complexmolecule, where electron dynamics precede nuclear motion. The application of attosecond technology to the investigation of electron dynamics in biologically relevant molecules represents a multidisciplinary work, which can open new research frontiers: those in which few-femtosecond and even subfemtosecond electron processes determine the fate of biomolecules. It can also open new perspectives for the development of new technologies, for example, in molecular electronics, where electron processes on an ultrafast temporal scale are essential to trigger and control the electron current on the scale of the molecule.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The presence of SF3B1 gene mutations is a hallmark of refractory anemia with ring sideroblasts (RARS). However, the mechanisms responsible for iron accumulation that characterize the Myelodysplastic Syndrome with ring sideroblasts (MDS-RS) are not completely understood. In order to gain insight in the molecular basis of MDS-RS, an integrative study of the expression and mutational status of genes related to iron and mitochondrial metabolism was carried out. A total of 231 low-risk MDS patients and 81 controls were studied. Gene expression analysis revealed that iron metabolism and mitochondrial function had the highest number of genes deregulated in RARS patients compared to controls and the refractory cytopenias with unilineage dysplasia (RCUD). Thus mitochondrial transporters SLC25 (SLC25A37 and SLC25A38) and ALAD genes were over-expressed in RARS. Moreover, significant differences were observed between patients with SF3B1 mutations and patients without the mutations. The deregulation of genes involved in iron and mitochondrial metabolism provides new insights in our knowledge of MDS-RS. New variants that could be involved in the pathogenesis of these diseases have been identified.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this work, olive stone (OS) was utilized to investigate its capacity as biosorbent for methylene blue (MB) and Cr(III), which are usually present in textile industry effluents. Equilibrium and kinetic experiments were performed in batch experiments. The biosorption process followed pseudo-second-order kinetics. The equilibrium data were fitted with several models, but Langmuir and Sips models best reproduced the experimental results. Maximum biosorption capacities were 3.296 mg/g (0.0116 mmol/g) and 4.990 mg/g (0.0960 mmol/g) for MB and Cr(III), respectively. Several operation variables, such as
biosorbent mass, flow rate, and initial concentration on the removal of dye and metal, were evaluated in column system. The removal efficiency improved as OS mass increased and decreased when flow rate and initial concentration increased. Also, MB uptake was substantially decreased by increasing the initial concentration of Cr(III), ranging from 6.09 to 2.75 mg/g. These results show that the presence of Cr(III) significantly modifies the biosorption capacity of MB by the OS. These results suggest that OS is a potential low-cost food industry waste for textile industry wastewater treatment.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Resonance-enhanced multiphoton ionization of H2 + exposed to elliptically polarized VUV laser pulses is investigated. Differential cross sections for nuclei and electron are obtained using numerical solutions of the time-dependent Schrödinger equation. In this work in progress, we explore the dependence of the dissociative ionization observables with the polarization of the light.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Thermal degradation and gaseous products evolving from the pyrolysis of sewage sludge, aimed at agricultural soil amendment, were investigated using Thermogravimetric Analysis in conjunction with Fourier Transform Infrared Analysis (TG-FTIR). The materials were studied in temperatures ranging from 30 to 800 ºC. Furthermore infrared spectra of sewage sludge samples were performed as a complementary technique. In parallel the sewage sludge was spiked with ibuprofen in order to test whether the mentioned techniques are able to detect the drug. Thermal analysis showed the range of 200-400ºC as the most characteristic for weight loss, corresponding with the organic matter volatilization, while the range of 500-800ºC was also characteristic and due to the volatilization of carbonates. On the other hand, ibuprofen-spiking tests identified at temperature range (150-250ºC) where the compound totally volatilizes, therefore, in this work, the detection of ibuprofen by TGA was established for concentrations higher than 0.5 g/kg sludge, concentration 102 times higher than the concentrations measured by other authors in regular sewage sludge (Martín, et al., 2010). A correlation has been found between the ibuprofen concentrations in the sludge and the intensity of the absorption bands, both for FT-IR spectra at the maximum emission temperature for ibuprofen (232ºC) as for the FT-IR spectra of the non-pyrolyzed samples.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Within the pedagogical community, Serious Games have arisen as a viable alternative to traditional course-based learning materials. Until now, they have been based strictly on software solutions. Meanwhile, research into Remote Laboratories has shown that they are a viable, low-cost solution for experimentation in an engineering context, providing uninterrupted access, low-maintenance requirements, and a heightened sense of reality when compared to simulations. This paper will propose a solution where both approaches are combined to deliver a Remote Laboratory-based Serious Game for use in engineering and school education. The platform for this system is the WebLab-Deusto Framework, already well-tested within the remote laboratory context, and based on open standards. The laboratory allows users to control a mobile robot in a labyrinth environment and take part in an interactive game where they must locate and correctly answer several questions, the subject of which can be adapted to educators' needs. It also integrates the Google Blockly graphical programming language, allowing students to learn basic programming and logic principles without needing to understand complex syntax.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Practical sessions are the backbone of qualification in engineering education. It leads to a better understanding and allows mastering scientific concepts and theories. The lack of the availability of practical sessions at many universities and institutions owing to the cost and the unavailability of instructors the most of the time caused a significant decline in experimentation in engineering education over the last decades. Recently, with the progress of computer-based learning, remote laboratories have been proven to be the best alternative to the traditional ones, regarding to its low cost and ubiquity. Some universities have already started to deploy remote labs in their practical sessions. This contribution compiles diverse experiences based on the deployment of the remote laboratory, Virtual Instrument Systems in Reality (VISIR), on the practices of undergraduate engineering grades at various universities within the VISIR community. It aims to show the impact of its usage on engineering education concerning the assessments of students and teachers as well.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Vias de Comunicação e Transportes

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Trabalho de Projeto submetido à Escola Superior de Teatro e Cinema para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Teatro - especialização em Teatro e Comunidade.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The aim of this study was to undertake a comparative analysis of the practices and information behaviour of European information users who visit information units specialising in European information in Portugal and Spain. The study used a quantitative methodology based on a questionnaire containing closed questions and one open question. The questions covered the general sociological profile of the respondents and their use of European Document Centres, in addition to analysing aspects associated with information behaviour relating to European themes. The study therefore examined data on the preferred means and sources for accessing European information, types of documents and the subjects investigated most. The use of European databases and the Internet to access material on Europe was also studied, together with the reasons which users considered made it easy or difficult to access European information, and the aspects they valued most in accessing this information. The questionnaire was administered in European Document Centres in 2008 and 2010.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The existing parking simulations, as most simulations, are intended to gain insights of a system or to make predictions. The knowledge they have provided has built up over the years, and several research works have devised detailed parking system models. This thesis work describes the use of an agent-based parking simulation in the context of a bigger parking system development. It focuses more on flexibility than on fidelity, showing the case where it is relevant for a parking simulation to consume dynamically changing GIS data from external, online sources and how to address this case. The simulation generates the parking occupancy information that sensing technologies should eventually produce and supplies it to the bigger parking system. It is built as a Java application based on the MASON toolkit and consumes GIS data from an ArcGis Server. The application context of the implemented parking simulation is a university campus with free, on-street parking places.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Presenta los resultados obtenidos durante la prospección efectuada a bordo del buque japonés "Shinko Maru 2" entre el 04 de noviembre y el 17 de diciembre de 1989, cuyo objetivo principal fue evaluar la factibilidad de explotar comercialmente el Dosidicus gigas (ORBIGNY) "calamar gigante" o "pota" en el mar peruano. El área de estudio comprendió desde los 03°30 ' S hasta el Callao (12°00 'S). Se emplearon dos sistemas de captura: con calamareras automáticas y luces de atracción (JIGGING) y otra con redes de deriva (DRIFT NET), llevándose a cabo 32 y 24 operaciones de pesca respectivamente.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Presenta los estimados de biomasa, distribución delos principales recursos pelágicos: anchoveta, sardina, jurel y caballa existentes en el Perú y se determina así mismo el grado de mezcla de estos recursos a partir de los lances de comprobación y la interrelación recurso/ambiente.