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Search Results: 1 - 10 of 2144 matches for " Germà "
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Analysis of Pseudoreplicants to Evaluate Natural Regeneration after Applying Prescribed Burns in a Temperate Forest of Mexico  [PDF]
José Germán Flore Garnica
Open Journal of Forestry (OJF) , 2012, DOI: 10.4236/ojf.2012.21002
Abstract: Although fire is one of the most important disturbing factors of forest in Mexico, little it is known on the effects of fire on the particular Mexican forest ecosystems. This is remarked for the fact that the effects of fires on vegetation vary among different types of forests. This lack of knowledge has constrained the use of fire, as a silvicultural tool. Therefore, the purpose of this project was to evaluate the effects of fire on regeneration, under burns. This work was carried out in a pine forest stand at Tapalpa Saw in Jalisco State, Mexico, dominated by Pinus michoacana and Pinus oocarpa. The study evaluated the effects of two techniques of prescribed burning: 1) backing, and 2) head fire. The sample plots were burned on 25 and 26 March 1991, before the rain season. One month before and 2 years after burning several measurements were made in order to evaluate the effect of fire on regeneration. Due to the limitations to work with “real” replicates (for treatments an control), original sample units (20 × 30 m) were divided into 5 × 5 m smaller sample units, which were considered as pseudoreplicants. Therefore, such analysis did not avoid introducing systematic error (bias) and minimize random error. Nevertheless, the variability within the pseudoreplicants was considerable in order to assume certain significance of the resulting estimations. Therefore, despite that this was a nonreplicated study; the results suggest strong ecological evidence that prescribed fire enhance natural regeneration of Pinus michoacana and Pinus oocarpa. In general, it is concluded that prescribed burning could be a valuable forest management tool in regions with similar conditions to the study area, in order to improve regeneration. However, further research is needed before prescribed fires can be applied with confidence in many Mexican forest conditions.
Is the Space-Time a Superconductor?  [PDF]
Wenceslao Santiago-Germán
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.410174
Abstract:

At the fundamental level, the 4-dimensional space-time of our direct experience might not be a continuum and discrete quantum entities might “collectively” rule its dynamics. Henceforth, it seems natural to think that in the “low-energy” regime some of its distinctive quantum attributes could, in principle, manifest themselves even at macroscopically large scales. Indeed, when confronted with Nature, classical gravitational dynamics of spinning astrophysical bodies is known to lead to paradoxes: to untangle them, dark matter or modifications to the classical law of gravity are openly considered. In this article, the hypothesis of a fluctuating space-time acquiring “at large distances” the properties of a Bose-Einstein condensate is pushed forward: firstly, it is shown that a natural outcome of this picture is the production of monopoles, dyons, and vortex lines of “quantized” gravitomagnetic—or gyrogravitational—flux along the transition phase; the minimal supported “charge” (and multiples of it) being directly linked with a nonzero (minimal) vacuum energy. Thus, a world of vibrating, spinning, interacting strings whose only elements in their construction are our topological concepts of space and time is envisioned, and they are proposed as tracers of the superfluid features of the space-time: the archetypal embodiment of these physical processes being set by the “gravitational roton”, an analogue of Landau’s classic higher-energy excitation used to explain the superfluid properties of helium II. The far and the near field asymptotics of string line solutions are presented and used to deduce their pair-interaction energy. Remarkably, it is found that two stationary, axis-aligned, quantum space-time vortices with the same sense of spin not only exhibit zones of repulsion but also of attraction, depending on their relative geodetic distance.

Spatial Distribution of Fuel Models Based on the Conditional-Fuel-Loading Concept  [PDF]
José Germán Flores Garnica
Journal of Environmental Protection (JEP) , 2018, DOI: 10.4236/jep.2018.92009
Abstract: Fuel model mapping has followed in general two trends: 1) indirect inferences, where some factors, presumably associated with fuel production, are related to a given fuel model; and 2) experts consulting, which has been used to classify and to validate other people classifications. However, reliance on expert judgment implies a subjective approach. Thus, I propone the integration of geostatistic techniques and the Conditional-Fuels-Loading concept (CFL) to define a more objective perspective in the fuel-model mapping. The information used in this study was collected in a forest of Chihuahua, Mexico, where fuels were inventoried in 554 (1000 m2) sample plots. These sample plots were classified using the CFL; and ordinary kriging (Gaussian, spherical and exponential) was used to interpolate the fuel-model values. Using the Akaike’s Information Criterion the spherical model performed best. The methodology allowed a finer definition of spatial distribution of fuel models. Some advantages of the CFL are: 1) it is based on actual fuel loads, and not only on vegetation structure and composition; 2) it is objective and avoids the bias of different classifiers (experts); and 3) it avoids the need of the advice of experts.
Structure and Density Analysis of a Semi Desert Ecosystem Disturbed by Fire  [PDF]
José Germán Flores Garnica
Open Journal of Forestry (OJF) , 2018, DOI: 10.4236/ojf.2018.82011
Abstract: In Mexico, forest ecosystems are disturbed by fires and generally these are considered to have negative impacts. However, it is important to consider that fire is an element of these ecosystems, and is important for its functionality. So it should be understood that in many cases the effects of a forest fire are beneficial, which can be determined through studies of population dynamics of these ecosystems. However, most of these studies currently focused only on aspects of species composition, with few cases concerning the analysis of the structure and density. In this study, a comparative analysis of the vegetation showed that conditions prevailing between burned and unburned areas of a site covered by microphyll desert species (shrubs and mesquite). The results suggest that the structure and density conditions of vegetation between burned and unburned areas are not statistically different. This is highlighted because one year after the fire occurred there is no evidence that fire had altered the structure and density of vegetation. Moreover, both in burned and unburned areas, vegetation had a healthy condition. Finally, although this may suggests that the fire was of low intensity, which resulted in a low impact on vegetation, in future studies it is recommended to determine if the same results are observed under different possible fire behavior and intensity.
An Inexact Restoration Package for Bilevel Programming Problems  [PDF]
Elvio A. Pilotta, Germán A. Torres
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.330181
Abstract: Bilevel programming problems are a class of optimization problems with hierarchical structure where one of the con-straints is also an optimization problem. Inexact restoration methods were introduced for solving nonlinear programming problems a few years ago. They generate a sequence of, generally, infeasible iterates with intermediate iterations that consist of inexactly restored points. In this paper we present a software environment for solving bilevel program-ming problems using an inexact restoration technique without replacing the lower level problem by its KKT optimality conditions. With this strategy we maintain the minimization structure of the lower level problem and avoid spurious solutions. The environment is a user-friendly set of Fortran 90 modules which is easily and highly configurable. It is prepared to use two well-tested minimization solvers and different formulations in one of the minimization subproblems. We validate our implementation using a set of test problems from the literature, comparing different formulations and the use of the minimization solvers.
Patogenecidad de agrobacterium tumefaciens en algunas especies de plantas de flóres de exportación
Ovalle Germán,Benincore Germán,Arbeláez Germán
Agronomía Colombiana , 1984,
Abstract: Tres aislamientos de tumefaelens Agrobaeterlum de rosa de las plantas afectadas con agalla de la corona en la Sabana de Bogotá se han caracterizado e identificado por pruebas de laboratorio y mediante la inoculación en plantas de tomate, zanahoria y remolacha. Patogenicidad fue probado en el campo de rosas, claveles, limonium, chrysanthermum y plantas gipsophila que son especies importantes en el país para la producción de flores de exportación. Su patogenia se ha probado también en las plantas de eucaliptus, remolacha, tomate y geranio, anfitriones común de las bacterias, estas pruebas se llevaron a cabo en 45 plantas de día y el material de propagación. Los aislamientos fueron altamente patógena de plantas de rosa y eucallptus, moderadamente patógenas de clavel y de hielo y estadísticas presentados pathogeneclty muy bajo en chrysanthemun. No hubo infección en gypsophila. Las plantas de tomate, la remolacha y el geranio presente una alta susceptibilidad a la bacteria y pueden ser de gran utilidad para el diagnóstico. Three isolates of Agrobaeterlum tumefaelens from rose plants affected with crown gall in the Savanna of Bogota have been characterized and identified by laboratory test and by inoculation in tomato plants, carrot and beet root disks. Pathogenecity was tested in the field on rose, carnation, statice, chrysanthermum and gipsophila plants which are important species in the country for the production of export flowers. Their pathogenecity was also tested on eucaliptus, beet, tomato and geranium plants, common hosts of the bacteria; these tests were carried out on 45 days old plants and propagation material. The isolates were highly pathogenic on rose and eucallptus plants, moderately pathogenic on carnation and stat ice and presented very low pathogeneclty on chrysanthemun. There was no Infection on gypsophila. Tomato, beet and geranIum plants present high susceptibility to the bacteria and can be of great usefuiness for the diagnosis of the disease.
Brain Sciences – An Open Access Journal
Germán Barrionuevo
Brain Sciences , 2011, DOI: 10.3390/brainsci1010001
Abstract: During the first ten years that followed “The Decade of the Brain”, the quest of neuroscience for understanding brain function in health and disease has greatly expanded to include molecular, developmental, cognitive and evolutionary aspects of the nervous system. This increased multidisciplinary effort has been complemented by the spectacular development of highly sophisticated experimental methods. Neuroscientists can now perform studies ranging from molecular and imaging analysis of single pre- and postsynaptic neuronal processes to imaging of neural activity in the whole brain during perceptual and motor behavioral tasks. At the same time, theoretical advances in neuroscience have been aided by the rapid development of mathematical and computational simulations of biologically and functionally realistic single cells and complex neural networks across multiple spatiotemporal scales. Therefore, neuroscientists are more than ever in a position to deliver answers to basic, medical and biotechnological questions related to brain function and dysfunction. [...]
Un esbozo del sistema epistemológico de Quine
Guerrero Pino,Germán;
Discusiones Filosóficas , 2011,
Abstract: this article has as its main purpose to offer a reconstruction of quine's epistemological system. i will undertake this task in general terms, emphasizing its main elements, its central thesis, the relationships that hold among these elements and their coherence.
La captación estadística de los asalariados agropecuarios: Reflexiones en torno a sus problemas mediante un ejercicio de comparación entre censos de población y agropecuarios (Argentina, 2001/2002)
Rosati,Germán;
Mundo agrario , 2011,
Abstract: the count of the agricultural employment (particularly of the waged employment) using official statistical sources has presented several problems and limitations. the high levels of work instability, seasonality and informality have produced numerous difficulties in the quantification of rural employment. the recent processes which affect the agricultural work force (such as its residence urbanization, the reduction of productive and occupational cycles and the decline of labor requirements because of the mechanization of certain crops) seem to have increased those difficulties. former approximations to theses problems showed that populations census and agricultural census throws divergent results in the quantification of the employees in agriculture. a comparative analysis of the results obtained in argentina by the national population and households census of 2001 and the national agricultural census of 2002 is presented in this paper. its objective is to perform an approximation to the different numbers of agricultural wage earners which both sources provide. besides, it will be attempted a link with the different agrarian and social structures and territories, trying to find out if they explain part of those divergent results. in order to accomplish those objectives, it was created a county-level database with the total number of agricultural wage earner. it also contained a set of indicators of the social and agrarian structure (quantity of pauper farmers, levels of urbanization, land distribution, etc.)
EL PROBLEMA DE LA EVALUACIóN DE LAS TEORíAS CIENTíFICAS
Guerrero Pino,Germán;
Discusiones Filosóficas , 2008,
Abstract: in this paper, i intend to defend the thesis that, in the process of evaluating scientific theories, there are logical and observational elements, but these are not unique: there are pragmatic elements too. the individual judgment of the scientists of a particular community and the state of development of a theory are pragmatic elements in the evaluation process. so, we can say that in this process a logical and a pragmatic rationality are involved.
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