oalib

OALib Journal期刊

ISSN: 2333-9721

费用：99美元

投稿

时间不限

( 2673 )

( 2672 )

( 2208 )

( 2024 )

自定义范围…

匹配条件： “Mansonia A; Rey B” ，找到相关结果约665202条。
列表显示的所有文章，均可免费获取
第1页/共665202条
每页显示 条
Efecto del pisoteo en sistemas de producción de cerdos a campo sobre propiedades del suelo
Rodríguez M,Adriana; Pulido M,Mansonia A; Rey B,Juan C; Lobo L,Deyanira; Araque,Humberto; Rivero,Carmen;
Agronomía Tropical , 2010,
Abstract: the objective of this study was to evaluate the tendency of changes produced by the trampling in production systems from pigs to fi eld (pf) on the properties of a mollisol ground of venezuela. the sampling was based with pigson a factorial design 2x3, a factor of two levels: pastures (pwp) and pig paddocks without (ppw) and soil depth atf three levels (0-5, 5-10 y 10-20 cm). in each plot four points were selected at random according to previous variability analysis. at each point was determined ph, electrical conductivity (ec) and organic carbon (oc) content of the soil, and assessing structural condition, structural stability to wet sieving, drop impact, and water movement. the results showed significant differences between treatment for the variables bulk density (bd), pores with radio <15 μm, mechanical resistance to the penetration (mrp) and oc, while for ph and ec only significant differencesby effect of the presence or absence of pigs. this suggest that pigs trampling have an modifier effect on soil properties evaluated, in this case further evidence of negative changes such as, increase of bd and pores with radio <15 μm and the diminution of the total porosity and infiltration rate
Catálogo de las muestras de fauna de la Comunidad de Madrid conservadas en la colección de Tejidos y ADN del Museo Nacional de Ciencias Naturales
Rey, I.,Dorda, B. A.
Graellsia , 2006,
Abstract: This work presents the catalogue of preserved samples of animal species (vertebrate and invertebrate) from Comunidad de Madrid kept in the Tissues and DNA Collection of the Museo Nacional de Ciencias Naturales. Percentages are shown, calculated against the total number of samples and animal class kept in the collection. This information shows the effort developed by the Museo Nacional de Ciencias Naturales to preserve at the genomic level the greatest possible level of genomic biodiversity in Comunidad de Madrid. Este trabajo presenta el catálogo de muestras conservadas en la colección de Tejidos y ADN de las especies animales (vertebrados e invertebrados) de la Comunidad de Madrid. Se proporcionan los porcentajes frente al total de las muestras conservadas en la colección y las clases animales representadas. Esta información pone de manifiesto el esfuerzo que el Museo Nacional de Ciencias Naturales realiza para conservar a nivel genómico el mayor porcentaje posible de la diversidad actual de la Comunidad de Madrid.
Identifying cryptic speciation across groundwater populations: first COI sequences of Bathynellidae (Crustacea, Syncarida)
Camacho, A. I.,Dorda, B. A.,Rey, I.
Graellsia , 2011,
Abstract: The biodiversity of groundwater fauna remains poorly known and understood. Groundwater biodiversity studies are strongly affected by habitat inaccessibility and taxonomic crisis. The objective of this work was to investigate levels of genetic divergence across populations of Bathynellacea, a small crustacean group that lives exclusively in groundwater, in order to evaluate the extent of cryptic speciation in morphologically constrained clades. Partial sequences of cytochrome oxidase I (COI) have been obtained, for the first time in Bathynellidae. Specimens analyzed of the genus Vejdovskybathynella were obtained from six populations morphologically assignable to a single species; all of them are located in different areas of one of the largest karst systems (110 km of galleries topographied) known in Spain. The analyses of molecular data demonstrate the presence of three highly divergent genetic units, possibly corresponding to undescribed new species. The results of this study provide the first molecular data that complement morphological knowledge in order to address phylogenetic studies to try to resolve the relations between genera and species of the Bathynellidae family. We conclude that the evolutionary scenario of this special group of subterranean crustaceans cannot be revealed only by using morphological information due to the presence of very old lineages of cryptic species, as has been brought to light with the molecular data obtained here. La biodiversidad de la fauna de las aguas subterráneas sigue siendo poco conocida. Los estudios de diversidad biológica de las aguas subterráneas se ven negativamente afectados por la inaccesibilidad del hábitat y la crisis taxonómica. El objetivo de este trabajo es estudiar los niveles de divergencia genética de poblaciones de Bathynellacea, un peque o grupo de crustáceos que viven exclusivamente en las aguas subterráneas, para evaluar la extensión de la especiación críptica en clados morfológicamente constre idos. Las secuencias parciales de citocromo oxidasa I (COI) se han obtenido, por primera vez, de varios ejemplares de la familia Bathynellidae. Los ejemplares analizados del género Vejdovskybathynella proceden de seis poblaciones, morfológicamente asignables a una única especie, de uno de los sistemas kársticos más grandes de Espa a (110 km de galerías topografiadas). El análisis de datos moleculares demuestra la presencia de tres unidades con elevada divergencia genética, dos de ellas posiblemente correspondientes a nuevas especies sin describir. Los resultados de este estudio proporcionan los primer
Thermodynamics of quantum degenerate gases in optical lattices
P. B. Blakie,A. -M. Rey,A. Bezett
Physics , 2006, DOI: 10.1134/S1054660X07020259
Abstract: The entropy-temperature curves are calculated for non-interacting Bose and Fermi gases in a 3D optical lattice. These curves facilitate understanding of how adiabatic changes in the lattice depth affect the temperature, and we demonstrate regimes where the atomic sample can be significantly heated or cooled by the loading process. We assess the effects of interactions on a Bose gas in a deep optical lattice, and show that interactions ultimately limit the extent of cooling that can occur during lattice loading.
Determination of α-tocopherol in pork with high intramuscular fat content
Rey, A.,López, C.,Scares, M.,Isabel, B.
Grasas y Aceites , 1996,
Abstract: Extraction of α-tocopherol from pork samples with low (3%) (LF) or high (9%) (HF) amount of intramuscular fat have been carried out by three different methods, two of them based in saponification plus extraction of α-tocopherol and the other one without saponification. All samples were spiked with five different amount of α-tocopherol prior to analysis. In LF samples, recovery was in the range 85-95% in all cases, with not significant differences between methods. Recovery was much lower in HF samples when using methods which involve prior saponification of muscle samples (50-60%). Changes in KOH concentration did not improve markedly the recovery. The method based on direct extraction provided much better recovery in HF samples (85- 92%) and consequently is recommended for samples high in fat. Se han utilizado tres métodos de cuantificación de α-tocoferol en muestras de tejido muscular de cerdos con un contenido en grasa intramuscular del 3% (LF) y del 9% (HF). Dos de los métodos saponifican la muestra antes de extraer el α-tocoferol, y el tercero utiliza una extracción directa con solventes. Antes del análisis se a adieron cinco cantidades de α-tocoferol en cada caso. La recuperación del α-tocoferol en las muestras de bajo contenido en grasa intramuscular fue en todos los casos alrededor del 85-95%, sin encontrarse diferencias según el método utilizado. En las muestras con alto contenido en grasa intramuscular la recuperación fue mucho menor cuando se utilizaron los métodos que saponifican la muestra (50-60%). Al a adir mayor concentración de KOH no se mejoró sustancialmente la recuperación. El método basado en extracción directa con solventes proporcionó una recuperación superior (85-92%) y es por tanto el que se recomienda para muestras con alto contenido en grasa intramuscular.
The sensitivity of stand-scale photosynthesis and transpiration to changes in atmospheric CO2 concentration and climate
B. Kruijt,C. Barton,A. Rey,P. G. Jarvis
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 1999,
Abstract: The 3-dimensional forest model MAESTRO was used to simulate daily and annual photosynthesis and transpiration fluxes of forest stands and the sensitivity of these fluxes to potential changes in atmospheric CO2 concentration ([CO2]), temperature, water stress and phenology. The effects of possible feed-backs from increased leaf area and limitations to leaf nutrition were simulated by imposing changes in leaf area and nitrogen content. Two different tree species were considered: Picea sitchensis (Bong.) Carr., a conifer with long needle longevity and large leaf area, and Betula pendula Roth., a broad-leaved deciduous species with an open canopy and small leaf area. Canopy photosynthetic production in trees was predicted to increase with atmospheric [CO2] and length of the growing season and to decrease with increased water stress. Associated increases in leaf area increased production further only in the B. pendula canopy, where the original leaf area was relatively small. Assumed limitations in N uptake affected B. pendula more than P. sitchensis. The effect of increased temperature was shown to depend on leaf area and nitrogen content. The different sensitivities of the two species were related to their very different canopy structure. Increased [CO2] reduced transpiration, but larger leaf area, early leaf growth, and higher temperature all led to increased water use. These effects were limited by feedbacks from soil water stress. The simulations suggest that, with the projected climate change, there is some increase in stand annual `water use efficiency', but the actual water losses to the atmosphere may not always decrease.
Theory of correlations between ultra-cold bosons released from an optical lattice
E. Toth,A. M. Rey,P. B. Blakie
Physics , 2008, DOI: 10.1103/PhysRevA.78.013627
Abstract: In this paper we develop a theoretical description of the correlations between ultra-cold bosons after free expansion from confinement in an optical lattice. We consider the system evolution during expansion and give criteria for a far field regime. We develop expressions for first and second order two-point correlations based on a variety of commonly used approximations to the many-body state of the system including Bogoliubov, meanfield decoupling, and particle-hole perturbative solution about the perfect Mott-insulator state. Using these approaches we examine the effects of quantum depletion and pairing on the system correlations. Comparison with the directly calculated correlation functions is used to justify a Gaussian form of our theory from which we develop a general three-dimensional formalism for inhomogeneous lattice systems suitable for numerical calculations of realistic experimental regimes.
Hysteresis in vibrated granular media
A. Prados,J. Javier Brey,B. Sanchez-Rey
Physics , 1999, DOI: 10.1016/S0378-4371(00)00115-1
Abstract: Some general dynamical properties of models for compaction of granular media based on master equations are analyzed. In particular, a one-dimensional lattice model with short-ranged dynamical constraints is considered. The stationary state is consistent with Edward's theory of powders. The system is submitted to processes in which the tapping strength is monotonically increased and decreased. In such processes the behavior of the model resembles the reversible-irreversible branches which have been recently obaserved in experiments. This behavior is understood in terms of the general dynamical properties of the model, and related to the hysteresis cycles exhibited by structural glasses in thermal cycles. The existence of a "normal" solution, i.e., a solution of the master equation which is monotonically approached by all the other solutions, plays a fundamental role in the understanding of the hysteresis effects.
Simple model with facilitated dynamics for granular compaction
J. Javier Brey,A. Prados,B. Sanchez-Rey
Physics , 1999, DOI: 10.1103/PhysRevE.60.5685
Abstract: A simple lattice model is used to study compaction in granular media. As in real experiments, we consider a series of taps separated by large enough waiting times. The relaxation of the density exhibits the characteristic inverse logarithmic law. Moreover, we have been able to identify analytically the relevant time scale, leading to a relaxation law independent of the specific values of the parameters. Also, an expression for the asymptotic density reached in the compaction process has been derived. The theoretical predictions agree fairly well with the results from the Monte Carlo simulation.
Approximated profiles for discrete solitons in DNLS lattices
J Cuevas,G James,P G Kevrekidis,B A Malomed,B Sanchez-Rey
Physics , 2007,
Abstract: We study four different approximations for finding the profile of discrete solitons in the one-dimensional Discrete Nonlinear Schr\"odinger (DNLS) Equation. Three of them are discrete approximations (namely, a variational approach, an approximation to homoclinic orbits and a Green-function approach), and the other one is a quasi-continuum approximation. All the results are compared with numerical computations.
第1页/共665202条
每页显示 条


Home
Copyright © 2008-2020 Open Access Library. All rights reserved.