Corrections to the Boltzmann mean free path in disordered systems with finite size scatterers

The mean free path is an essential characteristic length in disordered systems. In microscopic calculations, it is usually approximated by the classical value of the elastic mean free path. It corresponds to the Boltzmann mean free path when only isotropic scattering is considered, but it is different for anisotropic scattering. In this paper, we work out the corrections to the so called Boltzmann mean free path due to multiple scattering effects on finite size scatterers, in the s-wave approximation, ie. when the elastic mean free path is equivalent to the Boltzmann mean free path. The main result is the expression for the mean free path expanded in powers of the perturbative parameter given by the scatterer density.Comment: 12 page

Benzo[a]pyrene and beta-naphthoflavone mutagenic activation by European eel (Anguilla anguilla L.) S9 liver fraction

Is Anguilla anguilla L. (eel) liver ethoxyresorufin O-deethylase (EROD) induction absolutely necessary in order to convert promutagens as benzo[a]pyrene (BaP) into a mutagenic compound? Eels were exposed for 8 h to clean (control) and 0.3 microM beta-naphthoflavone (BNF)-contaminated water. The 8-h exposure to 0.3 microM BNF brought about a very high EROD induction (10 pmol/min/mg protein) compared to control animals (1 pmol/min/mg protein). The Ames test (Maron and Ames, 1983) was carried out with Salmonella typhimurium TA 98 strain (TA98 His-) and eel isolated S9 liver fraction was used as a metabolic BaP activator. The BaP and BNF dose range concentrations tested were 0 (blank), 0.015, 0.08, 0.15, 0.38, 0.75, 1.5, 3.8, and 7.5 microM/plate and 0 (blank), 0.412, 1.235, 3.704, 11.1, 33.0, and 100 nM BNF, respectively. A dose-response relationship between BaP concentration and mutagenic activity was observed in the presence of S9 fractions in control and 0.3 microM BNF-exposed eels. Significant positive results, as TA98 His+ revertants, were observed at 0.38, 0.75, 1.5, 3.8, and 7.5 microM BaP/plate induced by BNF S9 fractions. Significant BaP mutagenic activation by liver control S9 was detected only at 1.5, 3.8, and 7.5 microM/plate. The BaP 1.5, 3.8, and 7.5 microM/plate mutagenic activation by BNF S9 and control S9 were not significantly different. Relative to BNF activation, it was only possible to detect His+ reversion at 11.1 nM BNF concentration with 0.3 microM BNF-induced S9. The above results demonstrate that the eel S9 liver fraction has the capacity to biotransform high BaP concentrations and convert it into a mutagenic compound with or without previous liver BNF biotransformation induction. The same does not apply to low BaP concentrations, where liver S9 induction by BNF is necessary to promote mutagenesis.publishe

Genotoxic and biochemical responses in caged eel (Anguilla anguilla L.) after short-term exposure to harbour waters

European eel (Anguilla anguilla L.) were caged and exposed in situ for 8 and 48 h to the Aveiro offward fishing harbour water (HW) and to clean seawater under laboratory conditions (Control). Eel liver biotransformation (Phase I) was measured as ethoxyresorufin-O-deethylase (EROD) activity, cytochrome P450 (P450) and glutathione S-transferase (GST) activity (Phase II). Genotoxic responses were determined as blood, liver and kidney DNA strand breaks as well as erythrocytic nuclear abnormalities (ENAs). HW failed to significant increase liver EROD, GST activities and ENA frequency. Nevertheless, P450 content was significantly increased after 8 and 48 h exposure. Genotoxicity measured as DNA integrity decrease was found in blood after 8 and 48 h exposure to HW, whereas in liver and kidney, it was observed after 48 h exposure to HW. Blood, kidney and liver genotoxicity may be due to the presence of polycyclic aromatic hydrocarbons (PAHs) which are genotoxic compounds and the main HW organic contaminants.publishe

A dynamic method for charging-up calculations: the case of GEM

The simulation of Micro Pattern Gaseous Detectors (MPGDs) signal response is an important and powerful tool for the design and optimization of such detectors. However, several attempts to simulate exactly the effective charge gain have not been completely successful. Namely, the gain stability over time has not been fully understood. Charging-up of the insulator surfaces have been pointed as one of the responsible for the difference between experimental and Monte Carlo results. This work describes two iterative methods to simulate the charging-up in one MPGD device, the Gas Electron Multiplier (GEM). The first method uses a constant step for avalanches time evolution, very detailed, but slower to compute. The second method uses a dynamic step that improves the computing time. Good agreement between both methods was reached. Despite of comparison with experimental results shows that charging-up plays an important role in detectors operation, should not be the only responsible for the difference between simulated and measured effective gain, but explains the time evolution in the effective gain.Comment: Minor changes in grammatical statements and inclusion of some important information about experimental setup at section "Comparison with experimental results

Pressure effect in the X-ray intrinsic position resolution in noble gases and mixtures

A study of the gas pressure effect in the position resolution of an interacting X- or gamma-ray photon in a gas medium is performed. The intrinsic position resolution for pure noble gases (Argon and Xenon) and their mixtures with CO2 and CH4 were calculated for several gas pressures (1-10bar) and for photon energies between 5.4 and 60.0 keV, being possible to establish a linear match between the intrinsic position resolution and the inverse of the gas pressure in that energy range. In order to evaluate the quality of the method here described, a comparison between the available experimental data and the calculated one in this work, is done and discussed. In the majority of the cases, a strong agreement is observed

Simulation of gain stability of THGEM gas-avalanche particle detectors

Charging-up processes affecting gain stability in Thick Gas Electron Multipliers (THGEM) were studied with a dedicated simulation toolkit. Integrated with Garfield++, it provides an effective platform for systematic phenomenological studies of charging-up processes in MPGD detectors. We describe the simulation tool and the fine-tuning of the step-size required for the algorithm convergence, in relation to physical parameters. Simulation results of gain stability over time in THGEM detectors are presented, exploring the role of electrode-thickness and applied voltage on its evolution. The results show that the total amount of irradiated charge through electrode's hole needed for reaching gain stabilization is in the range of tens to hundreds of pC, depending on the detector geometry and operational voltage. These results are in agreement with experimental observations presented previously

Análise evolutiva da produção de coco no estado de sergipe frente ao crescimento da cultura no Nordeste e no Brasil.

O cultivo do coqueiro é realizado em vários países, sendo que no Brasil é considerada uma frutífera de grande importância econômica e social em virtude da ampla variabilidade de produtos que podem ser obtidos com a sua exploração, além de desempenhar papel ecológico em ambientes fragilizados. Nos últimos anos no Brasil o cultivo de coco vem desencadeando transformações em termos econômicos e produtivos promovendo um novo arranjo geo-produtivo. O objetivo deste trabalho é contextualizar a evolução da cultura do coco no estado de Sergipe frente aos cenários produtivos da região Nordestina e Brasileira. A metodologia utilizada foi embasada na estatística descritiva como método de sintetizar uma série de valores, de 1990 a 2009, obtido através de órgão oficial brasileiro. No Brasil as maiores plantações e produções de coco se concentram na região do Nordeste. A cocoicultura no estado de Sergipe representa importante fonte de renda para muitos produtores, ocupando aproximadamente 42.000 mil ha, dos quais 80% estão localizados em área de baixada litorânea e tabuleiros costeiros. Atualmente é o estado com a segunda maior produção de coco no país e o terceiro em área plantada, destinado principalmente a produção de coco seco. Embora nos últimos anos haja uma redução de participação do estado de Sergipe em termos de área plantada com a fruta, observa-se que a contribuição do estado para a produção nordestina e brasileira aumentou substancialmente, graças ao incremento em produtividade. Fato este que demonstra a evolução tecnológica nos últimos 20 anos com a cultura do coqueiro. Mesmo assim o cenário geoeconômico e político do estado de Sergipe demonstram caráter de preocupação frente as transformações que se evidenciam, como expansão do cultivo de coco à outras regiões e, possivelmente na maior importação de coco beneficiado de outros países, que culminam no aumento de competitividade do setor

5G mobile challenges: A feasibility study on achieving carbon neutrality

Increasingly mobile data traffic and high quality service demand has driven fast standards development and new mobile technologies deployment. Traffic demand in 5G networks is expected to rise unprecedentedly, bringing mobile network operators (MNOs) additional challenges, and added pressure regarding carbon footprint reduction. This work aims to study the environmental and financial feasibility of MNOs becoming carbon neutral, by developing biotic carbon dioxide sequestration programs. If feasibility exists, it would be extended and applied to future networks and other environmental scenarios. It is shown that achieving carbon neutrality is possible for heterogeneous deployments, especially when low energy powered base stations like femtocells exist and that the financial costs of such aim might represent little or negligible additional cost expenditure, with the added value of greener and environmental friendly network operation.info:eu-repo/semantics/acceptedVersio