Black hole shadow of a rotating polytropic black hole by the Newman--Janis algorithm without complexification

In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman--Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed.Comment: 9 pages, 2 figures, some references adde

Radiative non-isothermal Bondi accretion onto a massive black hole

In this paper, we present the classical Bondi accretion theory for the case of non-isothermal accretion processes onto a supermassive black hole (SMBH), including the effects of X-ray heating and the radiation force due to electron scattering and spectral lines. The radiation field is calculated by considering an optically thick, geometrically thin, standard accretion disk as the emitter of UV photons and a spherical central object as a source of X-ray emission. In the present analysis, the UV emission from the accretion disk is assumed to have an angular dependence, while the X-ray/central object radiation is assumed to be isotropic. This allows us to build streamlines in any angular direction we need to. The influence of both types of radiation is evaluated for different flux fractions of the X-ray and UV emissions with and without the effects of spectral line driving. We find that the radiation emitted near the SMBH interacts with the infalling matter and modifies the accretion dynamics. In the presence of line driving, a transition resembles from pure type 1 & 2 to type 5 solutions (see Fig2.1 of Frank etal. 2002), which takes place regardless of whether or not the UV emission dominates over the X-ray emission. We compute the radiative factors at which this transition occurs, and discard type 5 solution from all our models. Estimated values of the accretion radius and accretion rate in terms of the classical Bondi values are also given. The results are useful for the construction of proper initial conditions for time-dependent hydrodynamical simulations of accretion flows onto SMBH at the centre of galaxies.Comment: 10 pages, 10 figures, Accepted to be published in A&

Occupational Health and Safety Prevention Plan in Water Treatment Plant

The research was carried out at the "El Guarumo" drinking water plant located in Santa Ana, province of Manabí, Ecuador. The objective of the investigation was the proposal of a plan of prevention of occupational risks that allows the management of the labor risks in said plant. The main tools used were: survey, interview, checklist, LEST questionnaire for the diagnosis of the current situation in terms of working conditions, the risk identification matrix and the binary method of risk assessment. The main results obtained were the identification of the risks in their different categories, observing that the critical risk factors are related to the physical overexertion, the uncomfortable postures and the manual lifting of the load. Among the important risks are falling objects, skin contact with toxic substances and mental overwork, closely related to work pressures and job security? It was possible to carry out the proposal of preventive and corrective measures in order to properly manage the risks and contribute to the safety and health of the workers

Evaluation of soil quality in different land-use systems of South Brazil.

Resumo. 5° ELAETAO

Isotopic δ\u3csup\u3e15\u3c/sup\u3eN Signature of Grass-Alone and Grass-Legume Tropical Pastures to Estimate Sources of Nitrogen to Grasses in Farmer Managed Pastures

Vast areas of tropical forest have been converted into pastures sown with introduced grasses (Urochloa spp.). The majority of pastures exist in some stage of degradation, which has dramatic ecological and economic consequences. Our objective was to determine isotopic 15N signature of grass alone and grass-legume pastures to estimate sources of nitrogen (N) to grasses in farmer managed pastures. This work contributes to enhancing the sustainability of tropical pastures in forest margins through the integration of legumes. The overarching hypothesis tested was that legumes associated with grasses will improve nutrient supply via symbiotic fixation and mobilization of soil phosphorus (P) reserves increasing belowground inputs and recycling of carbon (C), N and P. We have done preliminary research in ten paired plots of productive grass-alone vs. grass-legume pastures on farms located in the Caquetá region of Colombia. Pasture productivity and sources of plant N uptake using 15N isotope natural abundance methods have been analysed. The integration of legumes increased biomass production by about 74%, and N and P uptake by two-fold. The legumes derived about 80% of their N via symbiotic fixation, showing the significance of this process to N nutrition despite the acidic soil conditions. The isotopic 15N signature of grasses in grass-alone vs. grass-legume pastures suggested that sources of grass N are affected by pasture composition. Furthermore, low δ15N found in some grass-alone pastures, indicate that other N sources apart from soil mineral N are being exploited. The role of different processes like symbiosis with arbuscular mycorrhiza fungi, biological nitrification inhibition or associative N fixation need to be further studied to provide a more comprehensive interpretation of N exploitation in grass-alone pastures

Association between parental perceptions of residential neighbourhood environments and childhood obesity in Porto, Portugal

Portugal has one of the highest rates of childhood obesity in Europe. Few studies have explored the relationship between parents’ perceptions of their residential neighbourhood (safety concerns and amenities of the built environment) and their children’s weight status. This study aims to examine the associations between parents’ perceptions of their residential neighbourhood and overweight/obesity among their children. Methods: Anthropometric measures of height and weight were taken for 2690 children in preschools and elementary schools in Porto. Body mass index (kg/m2 ) was calculated, and the International Obesity Taskforce (IOTF) cut-offs were used. Parents completed the ‘Environmental Module’ standard questionnaire of the International Physical Activity Prevalence Study. Chi-square tests and the logistic regression model adjusted for age, gender, maternal education and school cluster were used to examine the associations between parents’ perceptions of their residential neighbourhood and overweight/obesity among their children. Results: In this sample, 31.8% of the children were overweight (including obese). Significant associations were found between child obesity and the following residential environmental characteristics: the odds of children being obese were lower if their parents believed that it was safe (low/no crime rate) to walk/cycle at night (OR = 0.65, 95% CI = 0.54–0.79) and during the day (OR = 0.70, 95% CI = 0.55–0.86) and that it was easy and pleasant (pedestrian safety) to walk in their neighbourhoods (OR = 0.73, 95% CI = 0.58–0.90) and when local sidewalks were well maintained and unobstructed (OR = 1.18, 95% CI = 1.01–1.40). Conclusion: Parental perceptions of neighbourhood safety and the quality of local sidewalks are significantly associated with obesity values