Effects of Tree and Tillage Systems on the Productivity of the Herbaceous Stratum in Silvopastoral Systems in the Southwest of Córdoba, Argentina

In the southwest of Córdoba, Argentina, there are lands with severe water erosion, due to the interaction of rolling pampas, high intensity precipitation, loam soil, and farming systems based on annual crops (Cantero et al., 1998). In an attempt to mitigate the erosive processes, a silvopastoral system was established in which winter forage was combined with trees. To improve the physical condition of the soil, two tillage systems were implemented. The objective of this paper was to determine the effect of trees and tillage systems on the production of forage

Mycobiota and mycotoxins present in finished fish feeds from farms in the Rio de Janeiro State, Brazil

The aim of the present study was to determine species of the fungal genera Aspergillus, Fusarium, and Penicillium and fumonisin B1 (FB1), aflatoxin B1 (AFB1), and ochratoxin A (OTA) contamination from feed intended for fish farms. A total of 60 samples were sampled from tilapia farms in the Rio de Janeiro State, Brazil. The quantitative enumeration of fungi as colony-forming units per gram of feed (CFU/g) was performed using the surface spread method in different culture media. The results were expressed as fungal isolation frequency and relative density. Fungal total counts ranged from <1 × 102 to 4.7 × 104 CFU/g. Fusarium counts were not observed. Among toxigenic genera, Aspergillus (68%) was the most prevalent, followed by Penicillium species (60%). Aspergillus niger aggregate (36%), Aspergillus flavus (35%), and Penicillium citrinum (71%) were the most prevalent species. A high percentage of samples (98%) were contaminated with FB1 levels, while 55% and 3.3% were contaminated with AFB1 and OTA, respectively. The simultaneous occurrence of these mycotoxins emphasizes the need for further research in the area to better assess the risk to the health of fish farms and their implications for the health of consumers of this meat.Fil: Barbosa, Tatiana S.. Universidade Federal Rural do Rio de Janeiro ; BrasilFil: Pereyra, Carina Maricel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Microbiología e Inmunología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Soleiro, Carla A.. Universidade Federal Rural do Rio de Janeiro ; Brasil. Conselho Nacional de Desenvolvimiento Científico y Tecnológico; BrasilFil: Dias, Erica O.. Universidade Federal Rural do Rio de Janeiro ; BrasilFil: Oliveira, Aguida A.. Universidade Federal Rural do Rio de Janeiro ; Brasil. Conselho Nacional de Desenvolvimiento Científico y Tecnológico; BrasilFil: Keller, Kelly M.. Universidade Federal Rural do Rio de Janeiro ; Brasil. Conselho Nacional de Desenvolvimiento Científico y Tecnológico; BrasilFil: Silva, Pedro P. O.. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Cavaglieri, Lilia Reneé. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Microbiología e Inmunología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rosa, Carlos Alberto da Rocha. Universidade Federal Rural do Rio de Janeiro ; Brasil. Conselho Nacional de Desenvolvimiento Científico y Tecnológico; Brasi

Detailed Interstellar Polarimetric Properties of the Pipe Nebula at Core Scales

We use R-band CCD linear polarimetry collected for about 12000 background field stars in 46 fields of view toward the Pipe nebula to investigate the properties of the polarization across this dark cloud. Based on archival 2MASS data we estimate that the surveyed areas present total visual extinctions in the range 0.6 < Av < 4.6. While the observed polarizations show a well ordered large scale pattern, with polarization vectors almost perpendicularly aligned to the cloud's long axis, at core scales one see details that are characteristics of each core. Although many observed stars present degree of polarization which are unusual for the common interstellar medium, our analysis suggests that the dust grains constituting the diffuse parts of the Pipe nebula seem to have the same properties as the normal Galactic interstellar medium. Estimates of the second-order structure function of the polarization angles suggest that most of the Pipe nebula is magnetically dominated and that turbulence is sub-Alvenic. The Pipe nebula is certainly an interesting region where to investigate the processes prevailing during the initial phases of low mass stellar formation.Comment: 20 pages, 23 figures, Accepted for The Astrophysical Journa

High order fast Laplace solvers for the Dirichlet problem on general regions

Highly accurate finite difference schemes are developed for Laplace&#x27;s equation with the Dirichlet boundary condition on general bounded regions in R/sup n/. A second order accurate scheme is combined with a deferred correction or Richardson extrapolation method to increase the accuracy. The Dirichlet condition is approximated by a method suggested by Heinz-Otto Kreiss. A convergence proof of his, previously not published, is given which shows that, for the interval size h, one of the methods has an accuracy of at least O(h/sup 5/./sup 5/) in L/sub 2/. The linear systems of algebraic equations are solved by a capacitance matrix method. The results of our numerical experiments show that highly accurate solutions are obtained with only a slight additional use of computer time when compared to the results obtained by second order accurate methods

Spin relaxation in a complex environment

We report the study of a model of a two-level system interacting in a non-diagonal way with a complex environment described by Gaussian orthogonal random matrices (GORM). The effect of the interaction on the total spectrum and its consequences on the dynamics of the two-level system are analyzed. We show the existence of a critical value of the interaction, depending on the mean level spacing of the environment, above which the dynamics is self-averaging and closely obey a master equation for the time evolution of the observables of the two-level system. Analytic results are also obtained in the strong coupling regimes. We finally study the equilibrium values of the two-level system population and show under which condition it thermalizes to the environment temperature.Comment: 45 pages, 49 figure

Rendimiento de grano de cultivares de trigo en una serie histórica en la Región Semiárida Pampeana. Efecto de la fertilización nitrogenada bajo riego con agua de alto contenido de sales

In the Semiarid Central Pampa Region, with ow nitrogen content of the soils, about 26 % of the area cultivated with wheat is fertilized with nitrogen. However, water availability limits wheat production due to tow rainfall and a very marked water deficit during winter and summer. Therefore, complementary irrigation might contribute to increase the production or this crop, but the implementation of this technology has important restrictions, due to the abundance of highly saline ground water. In order to explain the yield increases due to a higher utilization or nitrogen in wheat, in modem cultivars respect to old cultivars we studied: a) a historical sequence of wheat cultivars in the Semiarid Pampa Region with respect to vegetative growth parameters and yield and b) the yield, with response of the genotypes to nitrogen fertilization with high - salt water irrigation. The experiment was carried out in, five genotypes released between 1954 and 1989. two levels of nitrogen fertilization and two levels of water availability. Our results showed that modem cultivars had a better yield index than the old ones. The yield response to nitrogen fertilization was different and the cultivars also differed in growth and yield in response to the irrigation with saline water. The grain yield response to nitrogen fertilization, in some genotypes, may not occur when irrigation with high salt content water is applied.La región semiárida central pampeana, dado las características de su suelo, de bajo contenido de nitrógeno, se fertiliza el 26% de la superficie cultivada con trigo. Sin embargo, la disponibilidad hídrica es el factor ambiental más Importante que podría limitar la producción de trigo en esta región, debido a las escasas precipitaciones y a un marcado déficit hídrico en invierno y verano por lo que, la aplicación de riego complementario podría contribuir a la mejora de la producción de este cultivo; sin embargo, la utilización de este, tiene importantes restricciones debido a la abundancia de acuíferos con alto contenido de sales En funci6n de una explicación del aumento del rendimiento en base a una mejor utilizaci6n del nitrógeno en trigo, en los cultivares modernos respecto de los cultivares antiguos, se estudió: a) en una serie histórica de cultivares de trigo, en la Región Semiárida Pampeana el comportamiento de parámetros de crecimiento vegetativo y rendimiento en grano y b) la respuesta de los genotipos a la fertilización nitrogenada bajo riego con agua de alto contenido de sales. El experimento se realizó a campo, y se trabajó con 5 genotipos liberados entre 1954 y 1989, dos niveles de nitrógeno y dos niveles de disponibilidad hídrica. Nuestros resultados mostraron una mejora en el índice de cosecha de los cultivares modernos respecto de los antiguos. La respuesta de los cultivares a la fertilización nitrogenada fue diferente en los parámetros de crecimiento y rendimiento en función del riego con agua salina. La respuesta del rendimiento en grano a la fertilización nitrogenada, en algunos genotipos, puede no manifestarse en condiciones de riego con agua de alto contenido de sales

A Survey of Stochastic Simulation and Optimization Methods in Signal Processing

International audienceModern signal processing (SP) methods rely very heavily on probability and statistics to solve challenging SP problems. SP methods are now expected to deal with ever more complex models, requiring ever more sophisticated computational inference techniques. This has driven the development of statistical SP methods based on stochastic simulation and optimization. Stochastic simulation and optimization algorithms are computationally intensive tools for performing statistical inference in models that are anal ytically intractable and beyond the scope of deterministic inference methods. They have been recently successfully applied to many difficult problems involving complex statistical models and sophisticated (often Bayesian) statistical inference techniques. This survey paper offers an introduction to stochastic simulation and optimization methods in signal and image processing. The paper addresses a variety of high-dimensional Markov chain Monte Carlo (MCMC) methods as well as deterministic surrogate methods, such as variational Bayes, the Bethe approach, belief and expectation propagation and approximate message passing algorithms. It also discusses a range of optimization methods that have been adopted to solve stochastic problems, as well as stochastic methods for deterministic optimization. Subsequently, area as of overlap between simulation and optimization, in particular optimization-within-MCMC and MCMC-driven optimization are discussed

Quantum master equation for a system influencing its environment

A perturbative quantum master equation is derived for a system interacting with its environment, which is more general than the ones derived before. Our master equation takes into account the effect of the energy exchanges between the system and the environment and the conservation of energy in a finite total system. This master quantum describes relaxation mechanisms in isolated nanoscopic quantum systems. In its most general form, this equation is non-Markovian and a Markovian version of it rules the long-time relaxation. We show that our equation reduces to the Redfield equation in the limit where the energy of the system does not affect the density of state of its environment. This master equation and the Redfield one are applied to a spin-environment model defined in terms of random matrices and compared with the solutions of the exact von Neumann equation. The comparison proves the necessity to allow energy exchange between the subsystem and the environment in order to correctly describe the relaxation in isolated nanoscopic total system.Comment: 39 pages, 10 figure

Determinación experimental de la transmisión total de energía solar de fachadas vidriadas constituidas por doble vidriado hermético

Para el análisis de la eficiencia energética de un edificio se requiere del conocimiento de entre otros, la componente solar incidente que ingresa al mismo a través de los elementos vidriados. Existen métodos de cálculo, pero para determinarlo experimentalmente se utilizó una cámara de ensayos de 10 por 10 metros sobre la que se instaló una fachada vidriada. Se efectuaron mediciones de irradiación solar total incidente tanto sobre plano horizontal como vertical, también la irradiación solar reflejada y la transmitida durante el mes de agosto de 2009. Se debió realizar una selección de los datos a utilizar para obtener relaciones constantes representativas de la transmitancia y reflectancia solar del elemento vidriado, en un intervalo de tiempo definido. Se establece un método de medición que permite determinar las componentes solares bajo ciertas condiciones del día de medición que debe ser diáfano, orientación establecida e intervalo de máximos valores coincidentes.Knowledge of the incident solar component transmitted into the building through glazing is necessary for thermal energy analysis. There are calculation methods but we used a glazed facade installed in a 10 m x 10 m test chamber to make the experimental determination. Total incident solar irradiation measurements over horizontal and vertical planes were realized; also reflected and transmitted solar irradiations were measured during August 2009. Data selection had to be done for obtaining representative constant ratios for solar transmittance and reflectance during a defined time interval. A measurement method for determination of solar components under certain conditions for clear-sky day of measurement, orientation and interval of coincident maximum values, was established.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Caracterización química del aceite y harina residual de Solanum sisymbriifolium lam

Seeds from Solanum sisymbriifolium Lam harvested at Olavarría (Buenos Aires, Argentine) were defatted with hexane and the raw oil obtained with a yield of 20,6 % dry basis. The physicochemical characteristics of crude oil were: refractive index: 1,4610 (at 25ºC), iodine value: 112,8; saponification index: 170,0; unsaponifiable matter: 14,0 % and free fatty acid content: 2,4 (mg KOH/g). The fatty acid composition of seed oil was studied by gas-liquid chromatography. Major fatty acids of seed oil were: linoleic (52,3%), oleic (23,4 %) and palmitic acid (16,4 %). The residual seed meal contained moderate level of crude protein (14,75%, dry basis), low level of available lysine (2,25 g/16gN) and high content of crude fiber (51,5%, dry basis). Total and phytic acid phosphorous, calcium, ash, sugar and polysaccharides contents are reported.Semillas de Solanum sisymbriifolium Lam cosechadas en Olavarría (prov. de Buenos Aires, Argentina) se trataron con hexano (soxhlet) obteniéndose el aceite crudo (rendimiento:20,6%) y la harina residual de extracción. Las características fisicoquímicas del aceite crudo fueron: Índice de refracción: 1.4610 (a 25ºC); Índice de iodo: 112,8; Índice de saponificación: 170,0; Insaponificable: 14,0%, Índice de acidez: 2,4 (mgKOH/g). Se determinó la composición acídica del aceite por cromatografía gas-líquido. Los ácidos grasos mayoritarios fueron: ácido linoleico (52,3%), ácido oleico (23,4%) y ácido palmítico (16,4%). La harina residual de extracción contenía una moderada proporción de proteína cruda (14,75% b.s), baja proporción de lisina disponible (2,25 g/16gN) y un alto contenido de fibra cruda (51,5 %b.s). Se informan valores de fósforo total y de ácido fítico, cenizas, calcio e hidratos de carbono