Transformações induzidas na estrutura produtiva de pequenos produtores pelas medidas de política econômica, Cruzeiro do sul - RS, período 1971/72 a 1975/76.

Ao longo da primeira metade da presente década houve importantes mudanças na estrutura produtiva do setor agropecuário, estimuladas por políticas que pretendam fazer com que a agricultura se desenvolvesse ao ritmo da economia nacional em seu conjunto. Este artigo apresenta um estudo preliminar das mudanças ocorridas, a nível de exploração, em um município ocupado por pequenos produtores com produção diversificada. Os dados de campo foram obtidos em dois levantamentos, o primeiro deles em setembro de 1972 e o segundo em janeiro de 1977, sendo que os produtores entrevistados foram os mesmos nas duas oportunidades. Entre os resultados alcançados, destaca-se um forte incremento das culturas consorciadas que perderam muita importância. Com referência à pecuária, destacam-se incrementos na suinocultura e na produção de leite. Em relação à utilização de recursos observa-se um incremento na utilização de maquinaria e uma redução na utilização de mãode-obra contratada, especialmente nos estabelecimentos de maior área (entre 25 e 100 hectares). A renda da operação agrícola apresenta uma evolução favorável somente no caso desses estabelecimentos maiores

Multi-wavelength observations of afterglow of GRB 080319B and the modeling constraints

We present observations of the afterglow of GRB 080319B at optical, mm and radio frequencies from a few hours to 67 days after the burst. Present observations along with other published multi-wavelength data have been used to study the light-curves and spectral energy distributions of the burst afterglow. The nature of this brightest cosmic explosion has been explored based on the observed properties and it's comparison with the afterglow models. Our results show that the observed features of the afterglow fits equally good with the Inter Stellar Matter and the Stellar Wind density profiles of the circum-burst medium. In case of both density profiles, location of the maximum synchrotron frequency $\nu_m$ is below optical and the value of cooling break frequency $\nu_c$ is below $X-$rays, $\sim 10^{4}$s after the burst. Also, the derived value of the Lorentz factor at the time of naked eye brightness is $\sim 300$ with the corresponding blast wave size of $\sim 10^{18}$ cm. The numerical fit to the multi-wavelength afterglow data constraints the values of physical parameters and the emission mechanism of the burst.Comment: 8 Pages, 3 Figures, Accepted for publication to Astronomy and Astrophysics on 02/04/200

La reconstrucción de un palimpsesto románico mediante técnicas no destructivas

The Gothic Cathedral of Tortosa (1346), is superposed over a Romanesque building (1178) as a palimpsest, which there is no physical evidence. The geophysical survey (2102-13), has provided some relevant data from the previous seo, which have enabled the location of some of its main features: apse, pillars of the nave and façade. With these data it is possible to understand the fitting of the process, constructive/ deconstructive of both buildings. The study concludes that the main structural elements of both buildings fit as a gear, and the possible dimensions of the Romanesque Seo are deducted through the evidences found in the subsoil.La catedral gótica de Tortosa (1346), se superpone sobre una construcción románica (1178) a modo de alimpsesto, de la cual no existe ninguna evidencia física. La prospección geofísica (2102-13), ha aportado algunos datos relevantes de la anterior seo, que han precisado la ubicación de alguna de sus partes principales: ábside, pilares de la nave y fachada. Con estos datos se puede entender el encaje del proceso, constructivo/deconstructivo de ambos edificios. El estudio concluye que los elementos estructurales más importantes de ambas edificaciones encajan a manera de engranaje, y se deducen las posibles dimensiones de la Seo románica en base a las evidencias encontradas en el subsuelo

Experiments in vortex avalanches

Avalanche dynamics is found in many phenomena spanning from earthquakes to the evolution of species. It can be also found in vortex matter when a type II superconductor is externally driven, for example, by increasing the magnetic field. Vortex avalanches associated with thermal instabilities can be an undesirable effect for applications, but "dynamically driven" avalanches emerging from the competition between intervortex interactions and quenched disorder constitute an interesting scenario to test theoretical ideas related with non-equilibrium dynamics. However, differently from the equilibrium phases of vortex matter in type II superconductors, the study of the corresponding dynamical phases - in which avalanches can play a role - is still in its infancy. In this paper we critically review relevant experiments performed in the last decade or so, emphasizing the ability of different experimental techniques to establish the nature and statistical properties of the observed avalanche behavior.Comment: To be published in Reviews of Modern Physics April 2004. 17 page

Zeolites functionalised with essential oils as new fungicidal materials for citrus fruits

Postharvest diseases produced by fungi are one of the main problems affecting the quality of agricultural products during storage. In citrus fruits, the largest economic losses are caused by wound pathogens, in particular, by Penicillium digitatum (PD), Penicillium italicum (PI) and Geotrichum citri-aurantii (GC), causing citrus green mould, blue mould and sour rot, respectively

Magnetic Nanoparticles Hyperthermia in A Non-Adiabatic and Radiating Process

We investigate the magnetic nanoparticles hyperthermia in a non-adiabatic and radiating process through the calorimetric method. Specifically, we propose a theoretical approach to magnetic hyperthermia from a thermodynamic point of view. To test the robustness of the approach, we perform hyperthermia experiments and analyse the thermal behavior of magnetite and magnesium ferrite magnetic nanoparticles dispersed in water submitted to an alternating magnetic field. From our findings, besides estimating the specific loss power value from a non-adiabatic and radiating process, thus enhancing the accuracy in the determination of this quantity, we provide physical meaning to a parameter found in literature that still remained not fully understood, the effective thermal conductance, and bring to light how it can be obtained from experiment. In addition, we show our approach brings a correction to the estimated experimental results for specific loss power and effective thermal conductance, thus demonstrating the importance of the heat loss rate due to the thermal radiation in magnetic hyperthermia

Micro and mesoporous materials with essential oils as sustainable biocide materials

Over the last few years policy is shifting towards more sustainable models, and agriculture is changing together. Legislative changes in the use of pesticides lead to the search for new materials that guarantee the needs of the present without compromising future generations. Consequently, there is an increasing necessity to develop new sustainable materials with fungicidal properties to preserve the quality of fresh horticultural produce during storage. Postharvest diseases of citrus fruits, mainly caused by wound pathogens such as Penicillium digitatum (PD), Penicillium italicum (PI) and Geotrichum citri-aurantii (GC), can produce large economic losses [1]. Many studies have been conducted to find biocide materials that may control the development of these fungi. It has been reported that silver-functionalised zeolitic materials are effective to reduce decay on oranges infected by these fungi [2], but the release of silver may be a problem due to strict regulations associated with food products. An alternative can be the use natural substances as thyme and cinnamon essential oils supported on zeolites as biocidal agents against PD, PI and GC. In vitro studies using Faujasite zeolites impregnated with essential oils at different concentrations showed a significant fungal growth inhibition, obtaining the best results with thyme essential oil. In subsequent in vivo studies, LTA and MCM-22 zeolites synthesized from silica extracted from rice husks, SiO2 and a pillared clay with 20% by weight of thyme essential oil were applied to oranges artificially inoculated with each fungus. Results showed that the antifungal activity highly depended on the fungus and the material used. LTA zeolite with 20% thyme essential oil was the most active antifungal material. As another alternative, silica mesoporous materials were synthetised and impregnated with pomegranate peel extract (PPE) in aqueous or methanolic medium. In in vitro studies, these materials inhibited the growth of PD by 80% compared to the control without functionalised silica. Furthermore, in vivo studies with oranges artificially inoculated with each fungus showed the biocidal activity of the PPE-functionalised materials, especially against PD and PI. Nevertheless, optimization of these materials is still necessary to improve their disease control and general performance

Elaboración y caracterización de celdas y paneles solares de silicio cristalino para su ensayo en el satélite SAC-A

Se describen los procesos utilizados para la elaboración de un conjunto de celdas y paneles fotovoltaicos que serán incluidos en el satélite argentino SAC-A, para su ensayo en ambiente espacial. Seis de las celdas serán utilizadas como sensores para la determinación de la posición angular del satélite. Los procesos mencionados incluyen la elaboración de celdas, su interconexión y el armado de los paneles. Las celdas solares fueron caracterizadas eléctricamente antes y después de su integración en los paneles. Se presentan las primeras experiencias de daño producido por bombardeo con protones y neutrones en laboratorio.Tema: Conversión Fotovoltaica.Asociación Argentina de Energía Sola