On the classical-quantum correspondence for the scattering dwell time

Using results from the theory of dynamical systems, we derive a general expression for the classical average scattering dwell time, tau_av. Remarkably, tau_av depends only on a ratio of phase space volumes. We further show that, for a wide class of systems, the average classical dwell time is not in correspondence with the energy average of the quantum Wigner time delay.Comment: 5 pages, 1 figur

Biocontrole da mela do feijoeiro comum (Rhizoctonia solani) por rizobactérias em condições de campo.

Neste trabalho, buscou-se testar oito rizobactérias obtidas de plantios de feijoeiro nos campos experimentais da Embrapa Rondônia e previamente selecionadas em casa-de-vegetação

Beef cattle stocking rate, a key to the conservation of the pastoral system in Brazilian biomes.

Abstract: In Brazil, beef cattle are raised in predominantly extensive systems. The feeding base is represented by native and/or cultivated pastures. The latter may be in a well conserved state or may present some degree of degradation. The amount of animals per hectare, supported by the pasture by each time unit, is basically related to the pasture production. There is interaction between quality and production, and changes in these parameters are strongly affected by the stocking rate. Therefore, the adjustment in the stocking rate is the most important management factor and the main determinant of animal production and pasture composition. Municipal data from the 2006 agriculture and cattle raising business census were considered with the objective to analyze, by means of typologies, the use of pastoral areas in Brazil. In the census, the producers declared their pastoral areas according to the following classification: native pasture areas (PN), cultivated pasture areas in good conservation status (PC) and cultivated pasture areas with some degree of degradation (PCD). They also indicated the number of bovine in each type of pasture. The data were submitted to exploratory factorial analysis, with varimax rotation. The first two factors (extracted by main components) explained 0.83 of the (co)variance, and the estimate of the Kaiser-Mayer-Olkin (KMO) adequacy test was 0.76, which meant good adjustment of the variables selected. The commonalities of the variables selected, PN area; total pasture area (TP), bovines in PN (Bov_PN); bovines in PCD area (Bov_PCD); bovines in PC area (Bov_PC); bovines in total pasture area (Bov_APT); and the stocking rate (TxLota) were 0.65; 0.97; 0.77; 0.74; 0.79; 0.87; and 0.99, respectively. The first factor was associated with the variables PN, TP, Bov_PN, Bov_PCD, Bov_PC, and Bov_APT, which directs to the latent variable correlated to those municipalities with large pasture areas, in general, and also with the largest cattle population. The variable TxLota presented the most significant factorial load in the second factor, that is, all those municipalities with the greatest concentration of cattle per unit area are represented in the second factor. The municipalities that were best represented in factor_1 are different from the ones represented in factor_2. The non-parametric correlation between the classifications of the two groups of municipalities formed by the factorial scores in the first and the second factors is small (0,24). This indicates that the context of those municipalities with the highest stocking rate is a lot different from the ones with the largest areas and cattle herds. The application of livestock development policies in the different Brazilian biomes should take into account all the distinguishing features of the municipalities, regarding their context, especially the pasture areas and their vocation for primary livestock production.ICAS VI

Polarization of photospheric lines from turbulent dynamo simulations

We employ the magnetic and velocity fields from turbulent dynamo simulations to synthesize the polarization of a typical photospheric line. The synthetic Stokes profiles have properties in common with those observed in the quiet Sun. The simulated magnetograms present a level of signal similar to that of the Inter-Network regions. Asymmetric Stokes V profiles with two, three and more lobes appear in a natural way. The intensity profiles are broadened by the magnetic fields in fair agreement with observational limits. Furthermore, the Hanle depolarization signals of the Sr I 4607 A line turn out to be within the solar values. Differences between synthetic and observed polarized spectra can also be found. There is a shortage of Stokes V asymmetries, that we attribute to a deficit of structuring in the magnetic and velocity fields from the simulations as compared to the Sun This deficit may reflect the fact that the Reynolds numbers of the numerical data are still far from solar values. We consider the possibility that intense and tangled magnetic fields, like those in the simulations, exist in the Sun. This scenario has several important consequences. For example, less than 10% of the existing unsigned magnetic flux would be detected in present magnetograms. The existing flux would exceed by far that carried by active regions during the maximum of the solar cycle. Detecting these magnetic fields would involve improving the angular resolution, the techniques to interpret the polarization signals, and to a less extent, the polarimetric sensitivity.Comment: Accepted for publication in ApJ. 20 pag. 11 fig

Symplectic evolution of Wigner functions in markovian open systems

The Wigner function is known to evolve classically under the exclusive action of a quadratic hamiltonian. If the system does interact with the environment through Lindblad operators that are linear functions of position and momentum, we show that the general evolution is the convolution of the classically evolving Wigner function with a phase space gaussian that broadens in time. We analyze the three generic cases of elliptic, hyperbolic and parabolic Hamiltonians. The Wigner function always becomes positive in a definite time, which is shortest in the hyperbolic case. We also derive an exact formula for the evolving linear entropy as the average of a narrowing gaussian taken over a probability distribution that depends only on the initial state. This leads to a long time asymptotic formula for the growth of linear entropy.Comment: this new version treats the dissipative cas

Selecção de áreas de prospecção com recurso aos SIG na região de Mogovolas-Iuluti-Chalaua-norte de Moçambique

As mineralizações em pegmatitos são abundantes no Norte de Moçambique e a sua prospeção e exploração remonta, pelo menos desde o tempo de ocupação colonial o que explica o interesse das empresas mineiras na aquisição de áreas para pesquisa e exploração. O objectivo deste artigo é fazer uma análise preliminar básica, através de um Sistema de Informação Geográfica (SIG) visando a produção de mapas de favorabilidade ou previsionais. O estudo centrou-se no posto administrativo de Iuluti e Chalaua, onde são exploradas gemas (turmalinas e granadas) associadas a pegmatitos. Toda a informação sobre a cartografia geológica existente foi introduzida num SIG, e processada com uma abordagem “Data Driven” e “Knowledge Driven”, criando um mapa preditivo que identifica a favorabilidade de algumas zonas dentro da regiãoThe mineralization in pegmatites are abundant in northern Mozambique and its exploration and exploitation dates back at least from the time of colonial occupation that explains the interest of mining companies in the acquisition of areas for concession. The purpose of this article is to make a basic preliminary analysis through Geographic Information System (GIS), in order to produce maps of favorability or potential maps for many mineral commodities. The study focused on the administrative post of Iuluti and Chalaua, which is explored for gems (garnets, tourmalines). All the information about the existing geological mapping were introduced into a GIS and processed on "Data Driven” and “Knowledge Driven" approach, creating a predictive map that identifies the favorability of the region