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Search Results: 1 - 10 of 473585 matches for " Miguel A. Marquina Carmona "
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Relativity and the Tunneling Problem in a “Reduced” Waveguide
Eckehard W. Mielke,Miguel A. Marquina Carmona
International Journal of Optics , 2013, DOI: 10.1155/2013/947068
Abstract: Wave packets are considered as solutions of the Maxwell equations in a reduced waveguide exhibiting tunneling due to a stepwise change of the index of refraction. We discuss several concepts of “tunneling time” during the propagation of an electromagnetic pulse and analyze their compatibility with standard relativity. 1. Introduction Tunneling is often regarded as a quantum effect. Among the many recent applications is the scanning tunneling microscope exhibiting also phonon tunneling [1]. However, in optics, it was discovered already by Newton as frustrated total reflection of light, compare [2]. In physics, it is largely accepted that there is some time scale [3] associated with the duration of any tunneling process [4]. In fact, it has been directly measured, for instance, with microwaves [5–8]. However, there is a lack of consensus what is the exact nature of this “tunneling time,” and a unique and simple expression [9] is still missing. Here, we will recapitulate some introductional material about its classical aspects and discuss the consequences for propagating electromagnetic waves in undersized waveguides. Our main objective is to confront them with standard relativity [10]. Recently, modern versions [11] of the Michelson-Morley experiment have provided the bound of for the isotropy of the velocity of light in vacuum, one of the most stringent experimental limits in physics. The wave operator of Jean-Baptiste le Rond d’Alembert is invariant under the general Lorentz transformations where is the radius vector of an event and the Lorentz factor. It is quite remarkable that Riemann [12] proposed already in 1858 an invariant wave equation for the electromagnetic potential in an attempt to accommodate—within his scalar electrodynamics—the 1855 experiments of Kohlrausch and Weber [13]. He estimated correctly the velocity of light in vaccum from the then known values the electromagnetic units. In 1886, Voigt [14] anticipated to some extent the invariance of the d’Alembertian (1) under what is now called a Lorentz boost (2). 2. Electromagnetic Plane Waves Let us consider the electromagnetic field in a waveguide [15, 16]. To this end, we depart from the Maxwell equations of the Appendix which imply the wave equations for the electric and magnetic field. The refractive index is given in terms of the relative permittivity or dielectric constant and permeability of a medium. Let us restrict ourselves first to a plane wave solution written in the complex form where is the wave vector determining the direction of the wave propagation and the amplitudes and
Sellos documentales
José Miguel Alva Marquina
Contribuciones desde Coatepec , 2002,
An Analysis of a New Foliar Architecture of the Permian Period in Mexico and Its Ecological Interactions  [PDF]
Maria P. Velasco-de León, Miguel A. Flores-Barragan, Diego E. Lozano-Carmona
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.65066
Abstract: The Paleozoic flora of the state of Puebla is characterized by the presence of ancient and conservative lineages; we focus this study on the taxonomical Annularia, Bjuvia and the new morphotype. These groups are found in carbonaceous lutite, where paleosoils, small roots and trunks in situ are abundant, and have been associated with swampy environments. In this paper, we discuss the presence of a new architectural form of megaphyll size that has not been registered in other Permian locations. These lutite imprints are the second most abundant in this location and their degree of preservation supports their autochthonous nature. The large size of its funnel-shaped blade and its extremely long petiole support the idea that its size was a response to a competition for biotic resources and to the hydric stress to which communities of this region were exposed, as consequence of the environmental conditions prevailing at the end of the Paleozoic era. It is proposed that they lived in environments with seasonal humidity and this hypothesis is supported by both the abundance of fossil groups and lithology.
Jurassic Flora in Southern Mexico: Anomozamites Schimper, 1870 Emend. Pott et McLoughlin, 2009 from Mixteco Terrane, Phytogeographical Implications of Williamsoniaceae Family (Bennettitales)  [PDF]
Diego Enrique Lozano-Carmona, María Patricia Velasco-de León, Miguel Angel Flores-Barragan
Open Journal of Geology (OJG) , 2019, DOI: 10.4236/ojg.2019.93010
Abstract: Anomozamites is a fossil-genus of leaf attributed to the Bennettitales, with a distribution mainly in the Kingdom of Laurasia and a stratigraphic range of the Upper Triassic to the Lower Cretaceous. In Mexico there were only reports of some specimens until the 1980s and later of four fossil-species at the beginning of the 21st century, all of them from the Jurassic in the Mixteco Terrane. In this review, three fossil-species of Anomozamites are identified: A. angustifolium is the first of them, which is a fossil-taxon with a range of the Rhaetian to Bajocian and Euramerican distribution; the second one is A. cf. triangularis, of which the geographic and stratigraphic extension of fossil-taxon is proposed; finally, we propose the existence of the A. sp.1, informally named, but with morphological characters that do not match the descriptions of Triassic/Jurassic fossil-taxa. These identifications were made based on macromorphology of the foliar organs and on the review of the diagnostic characters of both the fossil-genus and the fossil-species of taxonomic validity. Then, with this study, the taxonomic and phytogeographic knowledge of Anomozamites during the Jurassic period is increased and this allows reconsidering the amplitude of the Wielandiella distribution, a fossil-genus related to Anomozamites due to the existence of two fossil-taxa in organic connection.
Miocardiopatía periparto con trombosis biventricular
Sánchez-Rubio Lezcano,J.; Galache Osuna,J. G.; Marquina Barcos,A.; Calvo Cebollero,I.; Diarte de Miguel,J. A.; Placer Peralta,L. J.;
Anales de Medicina Interna , 2004, DOI: 10.4321/S0212-71992004001000008
Abstract: peripartum cardiomyopathy is a rare cause of congestive heart failure which developes in the last month of pregnancy or during five months postpartum in women without previously known cardiac disease. intraventricular thrombi are no unusual and can be identified by echocardiography. we report the case of a woman with peripartum cardiomyopathy whose echocardiographic study showed the presence of biventricular thrombi. this is a quite rare finding with only two cases reported in the literature. diagnosis, treatment and special situations that could predispose to intracardiac thrombi formation are discussed.
Using RFID to Enhance Security in Off-Site Data Storage
Miguel A. Lopez-Carmona,Ivan Marsa-Maestre,Enrique De la Hoz,Juan R. Velasco
Sensors , 2010, DOI: 10.3390/s100908010
Abstract: Off-site data storage is one of the most widely used strategies in enterprises of all sizes to improve business continuity. In medium-to-large size enterprises, the off-site data storage processes are usually outsourced to specialized providers. However, outsourcing the storage of critical business information assets raises serious security considerations, some of which are usually either disregarded or incorrectly addressed by service providers. This article reviews these security considerations and presents a radio frequency identification (RFID)-based, off-site, data storage management system specifically designed to address security issues. The system relies on a set of security mechanisms or controls that are arranged in security layers or tiers to balance security requirements with usability and costs. The system has been successfully implemented, deployed and put into production. In addition, an experimental comparison with classical bar-code-based systems is provided, demonstrating the system’s benefits in terms of efficiency and failure prevention.
Valores profesionales en la formación universitaria
Casares García, Pilar M.;Carmona Orantes, Gabriel;Martínez-Rodríguez, Francisco Miguel;
Revista electrónica de investigación educativa , 2010,
Abstract: one of the key functions of universities is professional training. performing professional tasks properly calls for not only acquisition of the appropriate technical competences, but also the development of ethical values. in order to adjust to the needs of society and students, university education should offer an integrated development model, which, in addition to technical and cognitive competences, also plans for the inclusion of personal and moral growth.
Mobile Agents for Service Personalization in Smart Environments
Iván Marsá-Maestre,Miguel A. López-Carmona,Juan R. Velasco,Andrés Navarro
Journal of Networks , 2008, DOI: 10.4304/jnw.3.5.30-41
Abstract: Service personalization is an important goal for any smart environment. Comfort systems may be adjusted in an automatic way when a given user is present, and multimedia devices may offer a music or movie catalog with favorite contents or may even pick one of them for the user. To achieve this goal, we propose a Service Oriented Architecture implementation based on multiagent systems. We specially take advantage of the mobility features of software agents. In particular, we have developed a hierarchical, agent-based solution intended to be applicable to different smart space scenarios, ranging from small environments, like smart homes or smart offices, to large smart spaces like cities. In this paper we describe the global architecture and focus on our approach to service personalization using mobile agents that follow the users as they move through different smart spaces.
Household exposure to pesticides and bladder exstrophy in a newborn baby boy: a case report and review of the literature
Marlene Martin, Kristina Rodriguez, Miguel Sánchez-Sauco, Gerardo Zambudio-Carmona, Juan Antonio Ortega-García
Journal of Medical Case Reports , 2009, DOI: 10.1186/1752-1947-3-6626
Abstract: We describe the pediatric environmental history of a newborn baby boy with isolated bladder exstrophy. In this case the pediatric environmental history includes the constitutional, genealogical, genetic and environmental factors related to bladder exstrophy, which revealed a cockroach infestation in the parents' home and the daily use of bug spray to kill them. The mother used one bottle of spray every 2 days (1000cc) and more in the summer, when the problem was worse. During gestational weeks 0-12, the mother intensively used a domestic pesticide consisting of a mixture of pyrethroids (cyfenothrin 0.5%, and tetramethrin 0.31%) and pyriproxyfen (0.01%). She described repeated episodes of mild to moderate poisoning that are associated with the use of household pesticides. The mother is a housewife and the father works as a fumigator of fruit fields and he reported gastrointestinal symptoms associated with the use of occupational pesticides. However, he did not believe he carried traces of these products into the home and his wife washed his work clothes separately. The pyrethroids and pyriproxyfen were detected in a urine sample obtained from the child 4 months after he was born. No other risk factors were identified.A detailed and carefully conducted pediatric environmental history, which includes information about home pesticide use, should be carried out for all children with bladder exstrophy. Domestic exposure to pesticides during critical developmental periods may have deleterious effects for the fetus.Bladder exstrophy (BE) is a rare urogenital abnormality present in one out of every 30 000-50 000 live births. Although its etiology is unknown, several risk factors (RFs) have been identified or studied. The following RFs are associated with BE: summer conception, white, non-Hispanic maternal race/ethnicity; male sex; and intrauterine exposure to diazepam or diphenylhydantoin [1]-[3]. BE occurs more frequently in descendents of individuals who also have the dise
SPACE: an algorithm to predict and quantify alternatively spliced isoforms using microarrays
Miguel A Anton, Dorleta Gorostiaga, Elizabeth Guruceaga, Victor Segura, Pedro Carmona-Saez, Alberto Pascual-Montano, Ruben Pio, Luis M Montuenga, Angel Rubio
Genome Biology , 2008, DOI: 10.1186/gb-2008-9-2-r46
Abstract: Alternative splicing (AS) is the process by which multiple mature mRNA sequences can be generated from the same precursor mRNA (pre-mRNA) upon the differential joining of exonic sequences limited by 5' and 3' splice sites. Through splicing mechanisms exons can be extended or shortened, skipped or included, and intronic sequences may even be retained in the mRNA sequences. AS is one of the most important sources of protein diversity in vertebrates, and at least half of human genes are alternatively spliced [1-3]. AS has been shown to be very relevant in a variety of human diseases, including cancer, and there is increasing interest in the use of AS in developing diagnostic tools and identifying new therapeutic targets [4-7].Two main strategies are pursued to identify and characterize AS events in expressed genes under both physiological and pathological conditions. On the one hand, expressed sequence tag (EST) alignment and mapping against known proteins or the whole genome may be used to identify different mRNA isoforms expressed in cell lines or tissues [8]. On the other hand, by performing analyses of splicing microarrays, the detection of new isoforms of a gene [9] and quantification of the relative concentrations for known isoforms may be obtained [10].The most important manufacturers of commercial array platforms intended for the analysis of the expression of alternatively spliced isoforms are Affymetrix, Jivan Biotechnology (based on Agilent technology) and Exonhit (which can work both with Affymetrix and Agilent technologies). The strategy for Jivan and Exonhit includes two types of probes: exon probes or junction probes. Affymetrix uses only exon probes. Exon probes are complementary sequences to each of the known transcribed exons of a given gene, while junction probes include a segment of complementary nucleotides for each of the two sides of a known exon-exon junction in the mature mRNA of the gene. When designing expression arrays, exon probes are usuall
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