Uso de un sistema para la gestión del aprendizaje (LMS) de código libre en la Universidad Tecnológica del Suroeste de Guanajuato (UTSOE)

The use of the Information and Communication Technologies (ICT) in Learning Environment allows achieving the maximum interaction between Teachers and Students.The Virtual Learning Environments are computer programs that benefit the learning facilitating the communication between users. Open Source software allow to create the own online modular learning environment with a fast placed in service. In the present paper the use of a Learning Management Systems (LMS) as continuous education tool is proposed

Generalist Pollen-Feeding Beetles during the Mid-Cretaceous.

The Cretaceous fossil record of amber provides a variety of evidence that is essential for greater understanding of early pollination strategies. Here, we describe four pieces of ca. 99-million-year-old (early Cenomanian) Myanmar amber from Kachin containing four closely related genera of shortwinged flower beetles (Coleoptera: Kateretidae) associated with abundant pollen grains identified as three distinct palynomorphotypes of the gymnosperm Cycadopites and Praenymphaeapollenites cenomaniensis gen. and sp. nov., a form-taxon of pollen from a basal angiosperm lineage of water lilies (Nymphaeales: Nymphaeaceae).We demonstrate how a gymnosperm to angiosperm plant-host shift occurred during the mid-Cretaceous, from a generalist pollen-feeding family of beetles, which served as a driving mechanism for the subsequent success of flowering plants

The point spread function of electrons in a magnetic field, and the decay of the free neutron

Experiments in nuclear and particle physics often use magnetic fields to guide charged reaction products to a detector. Due to their gyration in the guide field, the particles hit the detector within an area that can be considerably larger than the diameter of the source where the particles are produced. This blurring of the image of the particle source on the detector surface is described by a suitable point spread function (PSF), which is defined as the image of a point source. We derive simple analytical expressions for such magnetic PSFs, valid for any angular distribution of the emitted particles that can be developed in Legendre polynomials. We investigate this rather general problem in the context of neutron beta decay spectrometers and study the effect of limited detector size on measured neutron decay correlation parameters. To our surprise, insufficient detector size does not affect much the accuracy of such measurements, even for rather large radii of gyration. This finding can considerably simplify the layout of the respective spectrometers.Comment: 24 pages, 12 figure

Unbiased Global Optimization of Lennard-Jones Clusters for N <= 201 by Conformational Space Annealing Method

We apply the conformational space annealing (CSA) method to the Lennard-Jones clusters and find all known lowest energy configurations up to 201 atoms, without using extra information of the problem such as the structures of the known global energy minima. In addition, the robustness of the algorithm with respect to the randomness of initial conditions of the problem is demonstrated by ten successful independent runs up to 183 atoms. Our results indicate that the CSA method is a general and yet efficient global optimization algorithm applicable to many systems.Comment: revtex, 4 pages, 2 figures. Physical Review Letters, in pres

Paleogene succession underlying the La Espina Thrust (boundary between the Cantabrian and West-asturianleonese zones). Tectonic implications

Este artículo da a conocer la existencia de una sucesión paleógena, datada mediante su contenido polínico, bajo el cabalgamiento que separa las zonas Cantábrica y Asturoccidental-leonesa. Esta sucesión paleógena se apoya sobre arenas y arcillas con facies similares a unidades cretácicas como la Formación Utrillas. El cobijamiento de dicha sucesión por el cabalgamiento varisco antes mencionado, implica que éste fue reactivado durante la deformación AlpinaThis paper describes the stratigraphy and structural setting of a new outcrop of Paleogene sediments, whose age has been determined from their pollen content. These sediments overlie sands and clays of presumed Cretaceous age and underlie the La Espina Thrust, that is the boundary between two Variscan geological domains: the Cantabrian and Westasturian-leonese zones. The Alpine deformation caused reactivation of the La Espina Variscan Thrust as a reverse faul

PREVALENCE OF HUMAN ECHINOCOCCOSIS USING IMAGING TECHNIQUES IN YANAHUANCA, PASCO

El objetivo del estudio fue determinar la prevalencia de hidatidosis humana en nueve comunidades rurales del distrito de Yanahuanca, Pasco, empleando como técnicas de diagnóstico la ecografía abdominal y la radiografía de tórax. Además, se evaluó la asociación entre las variables edad, género y comunidad de procedencia y la presencia de pobladores positivos a quistes hidatídicos. La ecografía se realizó a 949 personas (52% de la población mayor de 5 años) y el examen radiográfico a 829 (45.6%). La prevalencia general de hidatidosis fue de 5.5% (52/949) con un intervalo de confianza al 95% de 4.1 a 7.1%. Se halló asociación estadística (p&lt;0.05) entre edad con el resultado positivo al examen ecográfico, siendo las personas mayores de 40 años las que presentaron un mayor porcentaje. La relación de quistes hidatídicos hepáticos / pulmonares fue de 5.1. El 56% (25/45) de los quistes detectados por ecografía presentaron parcial o completa calcificación. La prevalencia obtenida es una de las más altas en Latinoamérica, posiblemente por la convivencia del poblador andino con el perro, dado su uso en el cuidado y pastoreo del ganado ovino, además de las deficientes condiciones higiénico-sanitarias, y bajos niveles socioeconómicos y culturales.The objective of this study was to determine the prevalence of human echinococcosis in nine communities of the district of Yanahuanca, Pasco, through abdominal echography and thorax radiography. In addition, the association between age, gender, and community with the disease was evaluated. Echographic examination was conducted in 949 persons (52% of the population over 5 years of age) and X ray test was performed in 829 (45.6%). The overall prevalence of human cystic echinococcosis was 5.5% (52/949) and the 95% confidence interval varied from 4.1 to 7.1%. There was statistical association (p&lt;0.05) between age with positive results when using the ultrasound exam. The liver / lung hydatid cyst ratio was 5:1. Partial or total calcified cysts were detected by echographical examination (56%, 25/45). The prevalence of human hydatidosis in this endemic area of Peru is one of the highest in Latin America, possibly due to the close interaction with dogs, as they shepherd the flocks, plus poor sanitation and hygiene conditions in the area

New measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many body physics. Unfortunately, the pair correlation function $g(r)$ inferred from neutron scattering measurements of the differential cross section $d\sigma \over d\Omega$ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43~meV and 16.1~meV on liquid hydrogen at 15.6~K (which is dominated by the parahydrogen component) using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1~meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra non-equilibrium component of orthohydrogen. Liquid parahydrogen is also a widely-used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. We describe our measurements and compare them with previous work.Comment: Edited for submission to Physical Review

High-Efficiency Resonant RF Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams

We have developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beam with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to RF neutron spin flippers based on adiabatic fast passage. The spin rotator does not change the kinetic energy of the neutrons and leaves the neutron beam phase space unchanged to high precision. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically-polarized 3He neutron spin filters. The efficiency of the spin rotator was measured to be 98.0+/-0.8% on resonance for neutron energies from 3.3 to 18.4 meV over the full phase space of the beam. As an example of the application of this device to an experiment we describe the integration of the RF spin rotator into an apparatus to search for the small parity-violating asymmetry A_gamma in polarized cold neutron capture on para-hydrogen by the NPDGamma collaboration at LANSCE