Spatial variability of soil properties and soil erodibility in the Alqueva reservoir watershed

The aim of this work is to investigate how the spatial variability of soil properties and soil erodibility (K factor) were affected by the changes in land use allowed by irrigation with water from a reservoir in a semiarid area. To this end, three areas representative of different land uses (agroforestry grassland, lucerne crop and olive orchard) were studied within a 900 ha farm. The interrelationships between variables were analyzed by multivariate techniques and extrapolated using geostatistics. The results confirmed differences between land uses for all properties analyzed, which was explained mainly by the existence of diverse management practices (tillage, fertilization and irrigation), vegetation cover and local soil characteristics. Soil organic matter, clay and nitrogen content decreased significantly, while the K factor increased with intensive cultivation. The HJ-Biplot methodology was used to represent the variation of soil erodibility properties grouped in land uses. Native grassland was the least correlated with the other land uses. The K factor demonstrated high correlation mainly with very fine sand and silt. The maps produced with geostatistics were crucial to understand the current spatial variability in the Alqueva region. Facing the intensification of land-use conversion, a sustainable management is needed to introduce protective measures to control soil erosion

Primordial magnetic fields constrained by CMB anisotropies and dynamo cosmology

Magneto-curvature stresses could deform magnetic field lines and this would give rise to back reaction and restoring magnetic stresses [Tsagas, PRL (2001)]. Barrow et al [PRD (2008)] have shown in Friedman universe the expansion to be slow down in spatial section of negative Riemann curvatures. From Chicone et al [CMP (1997)] paper, proved that fast dynamos in compact 2D manifold implies negatively constant Riemannian curvature, here one applies the Barrow-Tsagas ideas to cosmic dynamos. Fast dynamo covariant stretching of Riemann slices of cosmic Lobachevsky plane is given. Inclusion of advection term on dynamo equations [Clarkson et al, MNRAS (2005)] is considered. In absence of advection a fast dynamo is also obtained. Viscous and restoring forces on stretching particles decrease, as magnetic rates increase. From COBE data ($\frac{{\delta}B}{B}\approx{10^{-5}}$), one computes stretching $\frac{{\delta}V^{y}}{V^{y}}=1.5\frac{{\delta}B}{B}\approx{1.5{\times}10^{-5}}$. Zeldovich et al has computed the maximum magnetic growth rate as ${\gamma}_{max}\approx{8.0{\times}10^{-1}t^{-1}}$. From COBE data one computes a lower growth rate for the magnetic field as ${\gamma}_{COBE}\approx{6.0{\times}10^{-6}t^{-1}}$, well-within Zeldovich et al estimate. Instead of the Harrison value $B\approx{t^{{4/3}}}$ one obtains the lower primordial field $B\approx{10^{-6}t}$ which yields the $B\approx{10^{-6}G}$ at the $1s$ Big Bang time.Comment: Dept of theoretical physics-UERJ-Brasi

Épocas de colheita, produção e qualidade de sementes de capim gordura.

Durante tres anos (1978 a 1980) foram realizados experimentos de producao de sementes de capim-gordura (Melinis minutiflora, Beauv), utilizando-se uma pastagem natural, estabelecida em solo de topografia inclinada representativo da Zona da Mata do Estado de Minas Gerais. O objetivo dos experimentos foi avaliar o potencial de producao, a melhor epoca de colheita de sementes desta especie e a sua viabilidade apos o armazenamento por um ano em condicoes ambientais. As melhores producoes foram obtidas quando as sementes colhidas apresentavam de 36 a 43% de umidade. O periodo mais favoravel para a realizacao da colheita, variou consideravelmente nos tres anos, numa amplitude de 20 a 35 dias apos a antese. Em cada ano, o período otimo de colheita foi de aproximadamente sete dias. Colheitas efetuadas quatro dias apos esse periodo ocasionaram uma perda media de 54% na producao de sementes puras viaveis. Sementes desta graminea apresentaram-se ligeiramente dormentes durante os primeiros meses de armazenamento. Nos tres anos, os maiores indices de germinacao foram 40, 79 e 45% e, valor cultural de 19, 43 e 37%, respectivamente, obtidos no sexto mes de armazenamento, declinando apos o nono mes

Gravitation and Duality Symmetry

By generalizing the Hodge dual operator to the case of soldered bundles, and working in the context of the teleparallel equivalent of general relativity, an analysis of the duality symmetry in gravitation is performed. Although the basic conclusion is that, at least in the general case, gravitation is not dual symmetric, there is a particular theory in which this symmetry shows up. It is a self dual (or anti-self dual) teleparallel gravity in which, due to the fact that it does not contribute to the interaction of fermions with gravitation, the purely tensor part of torsion is assumed to vanish. The ensuing fermionic gravitational interaction is found to be chiral. Since duality is intimately related to renormalizability, this theory may eventually be more amenable to renormalization than teleparallel gravity or general relativity.Comment: 7 pages, no figures. Version 2: minor presentation changes, references added. Accepted for publication in Int. J. Mod. Phys.

Gravitomagnetic Moments of the Fundamental Fields

The quadratic form of the Dirac equation in a Riemann spacetime yields a gravitational gyromagnetic ratio \kappa_S = 2 for the interaction of a Dirac spinor with curvature. A gravitational gyromagnetic ratio \kappa_S = 1 is also found for the interaction of a vector field with curvature. It is shown that the Dirac equation in a curved background can be obtained as the square--root of the corresponding vector field equation only if the gravitational gyromagnetic ratios are properly taken into account.Comment: 8 pages, RevTeX Style, no figures, changed presentation -- now restricted to fields of spin 0, 1/2 and 1 -- some references adde

Mass Generation from Lie Algebra Extensions

Applied to the electroweak interactions, the theory of Lie algebra extensions suggests a mechanism by which the boson masses are generated without resource to spontaneous symmetry breaking. It starts from a gauge theory without any additional scalar field. All the couplings predicted by the Weinberg-Salam theory are present, and a few others which are nevertheless consistent within the model.Comment: 11 pages; revtex; title and PACS have been changed; comments included in the manuscrip

Seed longevity chart to predict viability of corn seed during open storage.

The simplified equation Vt = Vi – tg E.p is to predict the percentage of viability of any corn (Zea mays L.) seed lot after any period of time under open storage conditions. Based upon that equation, the objective of this work was to set a practical seed longevity chart to predict viability of corn seed lot during storage. From data of five corn seed lots stored at Sete Lagoas, MG, the value of the storage index (V) was calculated. This value (V = 120 days) corresponded exactly to the time taken in days for the initial germination of corn seeds stored to fall to a certain germination value observed in the accelerated aging test. Once the storage index (V) is estimated, the viability chart which illustrates the relationship between initial germination, seed deterioration rate and storagecondition over time can be constructed. The chart can be used by any seed producer once the value of storage index (V) in situ is determined. The application of the seed viability chart to short-term seed storage seems to be promising for seed growers. This predictive model is the first attempt of incorporating the effect of seed quality, the deterioration rate and the storage environmental conditions (temperature and relative humidity) into a seed longevity chart of an open storage. A equação simplificada Vt = Vi - tgb. p foi desenvolvida para predizer a perda da viabilidade de semente de milho (Zea mays L.) em armazém convencional. Com base nessa equação, o objetivo deste trabalho foi desenhar um gráfico prático de longevidade da semente, para predizer a viabilidade dos lotes de semente de milho durante o armazenamento. Cinco lotes de milho híbrido BRS 201 foram armazenados nas condições ambientais de Sete Lagoas, MG, e o valor do índice de armazenamento (s) foi calculado. Esse valor (s) de 120 dias corresponde ao tempo que a semente levou para sua viabilidade inicial cair a uma certa porcentagem de germinação, no teste de envelhecimento acelerado, para os lotes de milho. Uma vez que o índice (s) é determinado, o gráfico de longevidade pode ser construído, o qual ilustra a relação entre a germinação inicial, a taxa de deterioração e as condições do armazenamento. Aplica-se o gráfico com informações úteis, desde que o valor do índice de armazenamento seja calculado para as condições in situ do seu armazém. A aplicação do gráfico de longevidade para médio prazo de armazenamento é promissora para os produtores de sementes. Esse modelo predicante é a primeira tentativa de incorporar o efeito da qualidade da semente, a taxa de deterioração e as condições de armazenamento convencional num gráfico, para predizer a longevidade da semente