Gause's exclusion principle revisited: artificial modified species and competition

Gause's principle of competition between two species is studied when one of them is sterile. We study the condition for total extinction in the niche, namely, when the sterile population exterminates the native one by an optimal use of resources. A mathematical Lotka-Volterra non linear model of interaction between a native and sterile species is proposed. The condition for total extinction is related to the initial number $M_{o}$ of sterile individuals released in the niche. In fact, the existence of a critical sterile-population value $M_{c}$ is conjectured from numerical analysis and an analytical estimation is found. When spatial diffusion (migration) is considered a critical size territory is found and, for small territory, total extinction exist in any case. This work is motived by the extermination agriculture problem of fruit flies in our region.Comment: 11 pages. Published in Jour.Phys.A Math.Gen. 33, 4877 (2000

Co-Inoculation of Plant-Growth-Promoting Bacteria Modulates Physiological and Biochemical Responses of Perennial Ryegrass to Water Deficit

Perennial ryegrass is a forage commonly used in temperate regions for livestock feeding; however, its yield is affected by reduced biomass production under water deficit. In a previous study, three co-inoculations of beneficial bacteria were selected based on their ability to promote plant growth under reduced water availability. The aim of this work was to elucidate some mechanisms by which the selected bacteria can help improve the response of perennial ryegrass to water deficit. Ryegrass plants were inoculated with each of the co-inoculations (Herbaspirillum sp. AP02 Herbaspirillum sp. AP21; Herbaspirillum sp. AP02–Pseudomonas sp. N7; Herbaspirillum sp. AP21–Azospirillum brasilense D7) and subjected to water deficit for 10 days. Physiological and biochemical measurements were taken 10 days after stress and shortly after rehydration. The results showed that bacteria had a positive effect on shoot biomass production, dissipation of excess energy, and proline and chlorophyll pigments during the days of water deficit (p < 0.05). The leaf water status of the inoculated plants was 12% higher than that of the uninoculated control after rehydration. Two Herbaspirillum strains showed greater potential for use as biofertilizers that help ameliorate the effects of water deficit

Efecto del tiempo y temperatura en el color generado por el proceso de tostado del café evaluado con la metodología de superficie de respuesta

En promedio el 95% de la producción nacional cafetalera es destinada a la exportación y el resto al consumo interno, el café es una importante fuente generadora de empleo y demandante de insumos, bienes y servicios, a lo largo de toda la cadena de valor (productores, comerciantes, acopiadores, transportistas, distribuidores, tostadores, comerciantes grandes y pequeños, administradores, entidades financieras, exportadores, técnicos y profe- sionales en todos los sectores mencionados, tostadurias, cafeterías, así como la agroindustria, entre otros). Siendo fuente de empleo para 123 mil familias que equivalen a 1 millón peruanos. Desde el año 1992 hasta el año 2001 se apreció un mayor incremento de las áreas y de los volúmenes de producción nacional (Abad, 2003). Con respecto al café tostado se pretende conocer los factores que determinan su procesamiento como el tiempo y temperatura que dependen del café a tostar por lo cual se intenta estudiar la temperatura y el tiempo apropiados para este fin evaluando el cambio de coloración de los granos tostados mediante el análisis de las imágenes por computadora. A este análisis de imágenes se le denomina visión artificial que es una herramienta eficaz en el desarrollo de diferentes tareas, ya que la imágenes digitales permiten la extracción de características cuantitativas y cualitativas de los objetos tales como la forma, tamaño y color (Sandoval, 2003).Este trabajo pretende servir de referencia a todo aquel que desee investigar acerca de la aplicación de los sistemas de visión por computadora en el control mediante color de alimentos y en especial de café tostado

Parallel Evolution of Quasi-separatrix Layers and Active Region Upflows

Persistent plasma upflows were observed with Hinode's EUV Imaging Spectrometer (EIS) at the edges of active region (AR) 10978 as it crossed the solar disk. We analyze the evolution of the photospheric magnetic and velocity fields of the AR, model its coronal magnetic field, and compute the location of magnetic null-points and quasi-sepratrix layers (QSLs) searching for the origin of EIS upflows. Magnetic reconnection at the computed null points cannot explain all of the observed EIS upflow regions. However, EIS upflows and QSLs are found to evolve in parallel, both temporarily and spatially. Sections of two sets of QSLs, called outer and inner, are found associated to EIS upflow streams having different characteristics. The reconnection process in the outer QSLs is forced by a large-scale photospheric flow pattern which is present in the AR for several days. We propose a scenario in which upflows are observed provided a large enough asymmetry in plasma pressure exists between the pre-reconnection loops and for as long as a photospheric forcing is at work. A similar mechanism operates in the inner QSLs, in this case, it is forced by the emergence and evolution of the bipoles between the two main AR polarities. Our findings provide strong support to the results from previous individual case studies investigating the role of magnetic reconnection at QSLs as the origin of the upflowing plasma. Furthermore, we propose that persistent reconnection along QSLs does not only drive the EIS upflows, but it is also responsible for a continuous metric radio noise-storm observed in AR 10978 along its disk transit by the Nan\c{c}ay Radio Heliograph.Comment: 29 pages, 10 figure

Geological map of Bolivia

There are no author-identified significant results in this report

Factorizing the time evolution operator

There is a widespread belief in the quantum physical community, and in textbooks used to teach Quantum Mechanics, that it is a difficult task to apply the time evolution operator Exp{-itH/h} on an initial wave function. That is to say, because the hamiltonian operator generally is the sum of two operators, then it is a difficult task to apply the time evolution operator on an initial wave function f(x,0), for it implies to apply terms operators like (a+b)^n. A possible solution of this problem is to factorize the time evolution operator and then apply successively the individual exponential operator on the initial wave function. However, the exponential operator does not directly factorize, i. e. Exp{a+b} is not equal to Exp{a}Exp{b}. In this work we present a useful procedure for factorizing the time evolution operator when the argument of the exponential is a sum of two operators, which obey specific commutation relations. Then, we apply the exponential operator as an evolution operator for the case of elementary unidimensional potentials, like the particle subject to a constant force and the harmonic oscillator. Also, we argue about an apparent paradox concerning the time evolution operator and non-spreading wave packets addressed previously in the literature.Comment: 24 pages; added references; one figure change

Knowledge, perceived effectiveness and qualification of traffic rules, police supervision, sanctions and justice

Road safety is a complex process that not only depends on technical and environmental improvements, but in a major part from human factors. In this sense, recent empirical studies have remarked the need to study the interaction between subject and laws, at the glance of several elements preceding road behavior. This is the case of attitudes, opinions and perceptions in the field of road safety, factors that influence the interaction with issues such as traffic rules, police supervision, penalties and justice in traffic. The objective of this study was to describe the self-rated knowledge and perceptions regarding traffic norms and its interaction with road safety among drivers. For this study, a sample of 1100 Spanish drivers was obtained from a national sampling process. The results showed that the clear majority of drivers consider they know in a sufficient manner the traffic norms, and consider them as effective. Concerning police supervision, almost 70% of them consider that it is effective, but generally assumes that traffic agents prefer to be located in strategical places to catch offenders, rather than in really dangerous places. Regarding sanctions, drivers conceived the punishment to road offenders principally as educational and tax-collection measures. Finally, the general assessment of justice in traffic provided by Spanish drivers has shown a regular-low valuation degree. The obtained results invite to discuss about the interaction between traffic norms and road user, with the aim of promoting a positive law enforcement as a manner to build road safety culture

Pecuária de precisão: pesquisas em saúde e comportamento alimentar.

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