Parabolic dunes in north-eastern Brazil

In this work we present measurements of vegetation cover over parabolic dunes with different degree of activation along the north-eastern Brazilian coast. We are able to extend the local values of the vegetation cover density to the whole dune by correlating measurements with the gray-scale levels of a high resolution satellite image of the dune field. The empirical vegetation distribution is finally used to validate the results of a recent continuous model of dune motion coupling sand erosion and vegetation growth.Comment: 18 pages, 14 figures, aubmitted to Geomorpholog

Implication of Urban Occupation Patterns in the Natural Infiltration

The article aims to contribute to the study of urban form and hydrological impacts relations, especially with regard to a recharge of the aquifers. The focus on the natural water infiltration and recharge of aquifers is due to the similarities between the characteristics of the physical environment conducive to aquifer recharge and urbanization, which lead to urban occupation of recharge areas. To address the proposed objective, the study developed a methodological framework that relates elements of the urban form, intervening factors of urban infiltration and water sensitive urban design guidelines. To accomplish this, recent literature were reviewed in urban drainage, water-sensitive urbanism and urban morphology, seeking to organize and identify the links between them. The intervening factors of natural infiltration found in the literature were: (i) Sealing of the soil; (ii) soil compaction; and (iii) reduction of tree cover. The urban morphological elements related to these factors were: (i) streets; (ii) public spaces; and (iii) lots. The analysis characteristics of each of these morphological elements were identified from the revised intervening factors and urban design guidelines. The use of the framework for the analysis of the Lago Paranoá Basin in the DF – Distrito Federal, Brazil, demonstrated the validity of the identified analysis criteria for the study of the urban form hydrological impact. In addition, it confirmed the premise of the study that more details about the urban occupation form are needed, besides the percentage of impervious surfaces, for the evaluation and planning of water sensitive cities

Self-similar magnetoresistance of Fibonacci ultrathin magnetic films

We study numerically the magnetic properties (magnetization and magnetoresistance) of ultra-thin magnetic films (Fe/Cr) grown following the Fibonacci sequence. We use a phenomenological model which includes Zeeman, cubic anisotropy, bilinear and biquadratic exchange energies. Our physical parameters are based on experimental data recently reported, which contain biquadratic exchange coupling with magnitude comparable to the bilinear exchange coupling. When biquadratic exchange coupling is sufficiently large a striking self-similar pattern emerges.Comment: 5 pages, 5 EPS figures, REVTeX, accepted for publication in Phys. Rev.

Comparação entre protocolos de extração de DNA para Ramularia areola.

bitstream/CNPA/19684/1/COMTEC240.pd

A DIESEL ENGINE CONVERTED INTO OTTO CYCLE ENGINE: THE INFLUENCE OF THE SPARK ADVANCE ON ITS PERFORMANCE AND ON NOx EMISSIONS

This paper analyzes the performance of a diesel engine converted into an Otto cycle engine and its Nitrogen dioxide emissions in terms of the spark advance variation. The tests were conducted on a Perkins diesel engine 1104C - 44TAG turbocharged, whose compression ratio was reduced to 9.33:1. After conversion the engine started operating with liquefied petroleum gas (LPG) and running just with stoichiometric mixtures. The tests have been limited to 10 to 40 kW, always at 1800 rpm. During the experiments the ignition advance angle ranged from 5º up to 27º (BTDC), using the increment of 5°, whenever possible. Particularly at 40 kW, the range of the ignition advance was 15º to 20º. The results showed a significant influence of the spark advance angle on the fuel consumption, on the temperature and on the NOx emissions, as well as on the magnitude of the generated power

Non-inertial effects on a non-relativistic quantum harmonic oscillator in the presence of a screw dislocation

We investigate non-inertial effects induced by a rotating frame on a non-relativistic quantum harmonic oscillator as well as of the topology associated to a screw dislocation, which corresponds to a distortion of a vertical line into a vertical spiral. To do this, we obtain the analytical solutions of the time-independent Schr\"odinger equation for this harmonic oscillator potential in this background. The expressions for the energy spectrum are obtained and the solutions for four quantum states, namely $n=0,1,2$ and $3$, are analysed. Our results show that the presence of the topological defect (screw dislocation) as well the fact that we are analysing the system from the point of view of a rotating frame, changes the solutions of Schr\"odinger equation and the corresponding spectrum. Now these quantities depend on the angular velocity of the rotating frame, $\Omega$, and also on the parameter $\beta$, which codifies the presence of the screw dislocation. Particularly, with respect to the energy spectrum of the system the changing is such that when $\Omega$ increases, the energy can increase or decrease depending on the values we assign to the eigenvalues of the angular and linear momenta. Additionally, we observe that the values of the parameter $\beta$ that characterizes the screw dislocation causes a shift in the energy spectrum

ELECTRICITY GENERATION FROM BIOMASS GASIFICATION

Brazil is among the ten largest consumers of electricity in the world, and in the last decades its demand for electricity has been continuously increasing. As a consequence it has not been capable to ensure enough expansion of its electric power network, mostly affecting isolated communities. The present study discusses the use of a system formed by an Indian residue biomass gasifier and a 36 kVA engine-generator, which should generate 20 kWe, using gas-alone mode engine. The engine was, originally, a MWM D229-4 diesel engine, which was converted into an Otto cycle to run only with producer gas. The system performance was evaluated for different engine’s advance ignition angles, and two types of biomass. As the Indian gasifier was designed to operate just with dual-fuel mode to feed a gas-alone engine, some changes in the gasifier's water cleaning system were required. The modifications enabled the system to improve the power generation which overcame the 20 kWe reaching 26 kWe. Technical and economic considerations showed that the bioelectricity based on bio-residual gasifier may be a viable and ecological option for regions having enough biomass residue and not served by the system network

Wakes in Dilatonic Current-Carrying Cosmic Strings

In this work, we present the gravitational field generated by a cosmic string carrying a timelike current in the scalar-tensor gravities. The mechanism of formation and evolution of wakes is fully investigated in this framework. We show explicitly that the inclusion of electromagnetic properties for the string induces logarithmic divergences in the accretion problem.Comment: Revised version to be published in the Phys. Rev.

Avaliação de leguminosas arbóreas para recuperação de solos e repovoamento em áreas degradadas, Irauçuba-CE.

Resumo: O modelo atual de exploração agropecuária na caatinga vem causando conseqüências desastrosas sobre os recursos naturais, com perdas consideráveis da biodiversidade de sua cobertura arbórea. Faz-se necessário o desenvolvimento de alternativas para recuperação florestal de imensas áreas degradadas nos sertões nordestinos. Assim, foi conduzido, no período de 2003 a 2005, em Irauçuba, CE, um experimento visando selecionar espécies leguminosas arbóreas simbiontes para a recuperação de áreas degradadas. Foram estabelecidas, por meio de mudas: Albizia lebeck, Prosopis juliflora, Piptadenia macrocarpa, Caesalpinia bracteosa, Gliricidia sepium, Caesalpinia ferrea, Mimosa hostilis, Leucaena leucocephala, Bauhinia cheilantha, Erythrina velutina, Mimosa caesalpinifolia e Parkinsonia aculeata. Os resultados sugerem que para Irauçuba e outras regiões semelhantes no Nordeste Brasileiro, a P. juliflora, a M. hostilis, a C. ferrea e a G. sepium são recomendadas para programas de recomposição florestal. [Leguminous trees evaluation for recuperation of soils and forestry recomposition of degraded areas, Irauçuba-CE]. Abstract: The present model of agriculture and livestock exploration in the caatinga region is resulting in érrea1dia consequences on the natural resources, with high losses of the biodiversity of its tree cover. The development of alternatives for the forestry recuperation of immense 1érre in the Northeastern hinterland is strongly needed. Thus, na experiment was carried out in Irauçuba, Ceará in order to select symbiont leguminous trees for reclamation of degraded 1érre. Albizia lebeck, Prosopis juliflora, Piptadenia macrocarpa, Caesalpinia bracteosa, érrea1dia sepium, Caesalpinia 1érrea, Mimosa hostilis, Leucaena leucocephala, Bauhinia cheilantha, Erythrina velutina, Mimosa caesalpinifolia e Parkinsonia aculeata were established by seedlings. The results indicated that P. juliflora, M. hostilis, C. ferrea and G. sepium may be recommended for forestry recuperation for Irauçuba and other similar regions in Northeastern Brazil.Edição dos Resumos do Congresso Brasileiro de Agroecologia, 5., Guarapari, ES de 01 a 04 de outubro de 2007