1,142 research outputs found
El Programa de Investigación en Maíz: objetivos, resultados y proyecciones.
En el presente documento los autores reseñan lo que ha sido el Programa de Maíz en el ICA teniendo en cuenta los objetivos planteados, los resultados y las proyecciones propuestas. Para ello inicialmente, se muestra la importancia del maíz como alimento, el área cultivada, la producción y productividad a nivel nacional basandose en tablas que muestran series históricas desde 1950 hasta 1983 del área en producción y rendimiento en Colombia. Con el objeto de elevar los niveles de productividad de maíz, el ICA elaboró el Plan Nacional de Investigación en el Cultivo de Maíz, el cual hace parte del Plan Nacional de Investigación Agropecuaria del ICA(PLANIA) para 1981 a 1986 los objetivos del primer plan eran: obtener información básica y detectar los factores limitantes en la producción del maíz, determinar el grado de tecnología disponible, establecer prioriddades de investigación y formular los proyectos de investigación para los 5 años siguientes. Se realizaron investigacioes en fitomejoramiento, suelos, fisiología, fitopatología, entomología, recursos de agua y tierra, maquinaria agrícola, procesos agrícolas y todos los factaores socioeconómicos involucrados en el proceso de producción. Los resultados de este plan para 1983 muestran la producción de 73 diferentes tipos mejorados de maíz y el programa ha autorizado la comercialización de 9 genotipos de maíz. Se enumeran las empresas que también se dedican a la multiplicación, distribución y venta de semillas de maíz en Colombia Finalmente se enumeran los proyectos contemplados por el PLANIA en maíz, los cuales son los señalados anteriormente de los que se espera una respuesta efectia a los factores tecnológicos limitantes de la producción del cultivo de maízMaíz-Zea may
Oxygen mobility in A_(2)Ti_(2y)Zr_(y)O_(7) (A: Y, Gd) ionic conductors
© Sociedad Española de Cerámica y Vidrio. Los autores del CINVESTAV-IPN agradecen a CONACYT el apoyo económico prestado para la realización de este trabajo (Proyecto 31198U). K. J. Moreno agradece al CINVESTAV-IPN el apoyo económico concedido para su estancia en la Universidad Complutense. Los autores de la Universidad Complutense agradecen el apoyo económico del MCYT (MAT 2001-3713-C04).Presentamos un estudio de la conductividad iónica en las series Y_(2)Ti_(2-y)Zr_(y)O_(7) y Gd_(2)Ti_(2-y)Zr_(y)O_(7) (0≤y≤2) obtenidas por síntesis mecanoquímica. Se presenta un estudio de la dinámica de iones oxígeno en estos materiales mediante la técnica de Espectroscopia de Admitancias. La variación con el contenido en Zr de la conductividad dc y de su energía de activación se interpreta en términos del aumento tanto del número de vacantes de oxígeno como del desorden en la estructura al aumentar el contenido en Zr.We report a study of ionic conductivity in the series Y_(2)Ti_(2-y)Zr_(y)O_(7) and Gd_(2)Ti_(2-y)Zr_(y)O_(7) (0≤y≤2) obtained by mechanochemical synthesis. We present
a study of oxygen ion dynamics in these materials by Impedance Spectroscopy. The change in dc conductivity and activation energy with Zr content is interpreted in terms of the increase in the number of oxygen vacancies and of structural disorder when increasing Zr content.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUECONACYTCINVESTAV-IPNMCYTpu
Electron energy loss and induced photon emission in photonic crystals
The interaction of a fast electron with a photonic crystal is investigated by
solving the Maxwell equations exactly for the external field provided by the
electron in the presence of the crystal. The energy loss is obtained from the
retarding force exerted on the electron by the induced electric field. The
features of the energy loss spectra are shown to be related to the photonic
band structure of the crystal. Two different regimes are discussed: for small
lattice constants relative to the wavelength of the associated electron
excitations , an effective medium theory can be used to describe the
material; however, for the photonic band structure plays an
important role. Special attention is paid to the frequency gap regions in the
latter case.Comment: 12 pages, 7 figure
Evaluation of Natural Language Processing for the Identification of Crohn Disease-Related Variables in Spanish Electronic Health Records:A Validation Study for the PREMONITION-CD Project
Background: The exploration of clinically relevant information in the free text of electronic health records (EHRs) holds the potential to positively impact clinical practice as well as knowledge regarding Crohn disease (CD), an inflammatory bowel disease that may affect any segment of the gastrointestinal tract. The EHRead technology, a clinical natural language processing (cNLP) system, was designed to detect and extract clinical information from narratives in the clinical notes contained in EHRs. Objective: The aim of this study is to validate the performance of the EHRead technology in identifying information of patients with CD. Methods: We used the EHRead technology to explore and extract CD-related clinical information from EHRs. To validate this tool, we compared the output of the EHRead technology with a manually curated gold standard to assess the quality of our cNLP system in detecting records containing any reference to CD and its related variables. Results: The validation metrics for the main variable (CD) were a precision of 0.88, a recall of 0.98, and an F1 score of 0.93. Regarding the secondary variables, we obtained a precision of 0.91, a recall of 0.71, and an F1 score of 0.80 for CD flare, while for the variable vedolizumab (treatment), a precision, recall, and F1 score of 0.86, 0.94, and 0.90 were obtained, respectively. Conclusions: This evaluation demonstrates the ability of the EHRead technology to identify patients with CD and their related variables from the free text of EHRs. To the best of our knowledge, this study is the first to use a cNLP system for the identification of CD in EHRs written in Spanish. © 2022 JMIR Medical Informatics. All rights reserved
The Palomar Testbed Interferometer Calibrator Catalog
The Palomar Testbed Interferometer (PTI) archive of observations between 1998
and 2005 is examined for objects appropriate for calibration of optical
long-baseline interferometer observations - stars that are predictably
point-like and single. Approximately 1,400 nights of data on 1,800 objects were
examined for this investigation. We compare those observations to an
intensively studied object that is a suitable calibrator, HD217014, and
statistically compare each candidate calibrator to that object by computing
both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis
is that the frequency distribution of visibility data associated with
calibrator stars differs from non-calibrator stars such as binary stars.
Spectroscopic binaries resolved by PTI, objects known to be unsuitable for
calibrator use, are similarly tested to establish detection limits of this
approach. From this investigation, we find more than 350 observed stars
suitable for use as calibrators (with an additional being
rejected), corresponding to sky coverage for PTI. This approach
is noteworthy in that it rigorously establishes calibration sources through a
traceable, empirical methodology, leveraging the predictions of spectral energy
distribution modeling but also verifying it with the rich body of PTI's on-sky
observations.Comment: 100 pages, 7 figures, 7 tables; to appear in the May 2008ApJS, v176n
Coastal risk mitigation by green infrastructure in Latin America
This paper aims to highlight the prevailing experiences of Latin America and to clarify what ‘green infrastructure’ entails in addition to describing seven case studies from a range of coastal ecosystems (wetlands, coastal dunes, beaches and coral reefs) at scales varying from local to regional. The case studies are categorised according to their degree of naturalness (nature-based, engineered ecosystems, soft engineering, ecologically enhanced hard infrastructure and de-engineering). Generally, the implementation of green infrastructure projects aims to increase resilience, enhance the provision of ecosystem services, recover biodiversity, reduce the negative effects of hard infrastructure and implement corrective measures. The greatest benefits of these projects relate to the creation of multi-functional spaces, which often combine the above advantages with improved opportunities for recreation and/or economic activities. It is hoped that this paper will disseminate the experience in green infrastructure among academics and practitioners and stimulate wider adoption of green infrastructure projects and good practices
VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory
VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l.
in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design,
construction techniques and data acquisition system of the HAWC observatory.
HAWC is an air-shower array currently under construction at the same site of
VAMOS with the purpose to study the TeV sky. The VAMOS setup included six water
Cherenkov detectors and two different data acquisition systems. It was in
operation between October 2011 and May 2012 with an average live time of 30%.
Besides the scientific verification purposes, the eight months of data were
used to obtain the results presented in this paper: the detector response to
the Forbush decrease of March 2012, and the analysis of possible emission, at
energies above 30 GeV, for long gamma-ray bursts GRB111016B and GRB120328B.Comment: Accepted for pubblication in Astroparticle Physics Journal (20 pages,
10 figures). Corresponding authors: A.Marinelli and D.Zaboro
The Sensitivity of HAWC to High-Mass Dark Matter Annihilations
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view
detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in
central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC
will observe gamma rays and cosmic rays with an array of water Cherenkov
detectors. The full HAWC array is scheduled to be operational in Spring 2015.
In this paper, we study the HAWC sensitivity to the gamma-ray signatures of
high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be
sensitive to diverse searches for dark matter annihilation, including
annihilation from extended dark matter sources, the diffuse gamma-ray emission
from dark matter annihilation, and gamma-ray emission from non-luminous dark
matter subhalos. Here we consider the HAWC sensitivity to a subset of these
sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the
Galactic center. We simulate the HAWC response to gamma rays from these sources
in several well-motivated dark matter annihilation channels. If no gamma-ray
excess is observed, we show the limits HAWC can place on the dark matter
cross-section from these sources. In particular, in the case of dark matter
annihilation into gauge bosons, HAWC will be able to detect a narrow range of
dark matter masses to cross-sections below thermal. HAWC should also be
sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The
constraints placed by HAWC on the dark matter cross-section from known sources
should be competitive with current limits in the mass range where HAWC has
similar sensitivity. HAWC can additionally explore higher dark matter masses
than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR
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