Antenas reconfigurables en frecuencia para sistemas de radio cognitiva

This article briefly presents the background of the study of cognitive radio systems (RC), as well as the use of reconfigurable antennas for this type of system, in particular the electrically frequency reconfigurable antennas and the most used reconfiguration methods highlighting their advantages and disadvantages. In addition, some hardware and software tools such as SDR (Software Defined Radio) and GNU Radio are presented and described, with increasing popularity in the field of research for evaluating the performance of these antennas, since they are low-cost and reconfigurables allow simple implementation of different communication schemes in which the system parameters can vary from the software.En este artículo se presentan brevemente los antecedentes del estudio de los sistemas de radio cognitiva (CR, por sus siglas en inglés) así como del uso de antenas reconfigurables para este tipo de sistemas, en particular las antenas eléctricamente reconfigurables en frecuencia y los métodos de reconfiguración más utilizados resaltando sus ventajas y desventajas. Adicionalmente, se presentan y describen algunas herramientas de hardware y software como lo son los SDR (Software Defined Radio) y GNU Radio, con creciente popularidad en el ámbito de la investigación para la evaluación del desempeño de estas antenas dado que al ser de bajo costo y reconfigurables permiten la fácil implementación de diferentes esquemas de comunicaciones en los cuales pueden variarse desde software los parámetros del sistema

Evolution in the Genus Rhinella: A Total Evidence Phylogenetic Analysis of Neotropical True Toads (Anura: Bufonidae)

True toads of the genus Rhinella are among the most common and diverse group of Neotropical anurans. These toads are widely distributed throughout South America, inhabiting a great diversity of environments and ecoregions. Currently, however, the genus is defined solely on the basis of molecular characters, and it lacks a proper diagnosis. Although some phenetic species groups have traditionally been recognized within Rhinella, the monophyly of some of them have been rejected in previous phylogenetic analyses, and many species remain unassigned to these poorly defined groups. Additionally, the identity and taxonomy of several species are problematic and hinder the specific recognition and description of undescribed taxa. In this work, we first perform phylogenetic analyses of separate mitochondrial and nuclear datasets to test the possible occurrence of hybridiza-tion and/or genetic introgression in the genus. The comparative analysis of both datasets revealed unidirectional mitochondrial introgressions of an unknown parental species into R . horribilis (“ghost introgression”) and of R . dorbignyi into R . bernardoi; therefore, the mitochondrial and nuclear data-sets of these species were considered separately in subsequent analyses. We performed total-evidence phylogenetic analyses that included revised molecular (four mitochondrial and five nuclear genes) and phenotypic (90 characters) datasets for 83 nominal species of Rhinella, plus several undescribed and problematic species and multiple outgroups. Results demonstrate that Rhinella was nonmono-phyletic due to the position of R . ceratophrys, which was recovered as the sister taxon of Rhaebo nasicus with strong support. Among our outgroups, the strongly supported Anaxyrus + Incilius is the sister clade of all other species of Rhinella. Once R . ceratophrys is excluded, the genus Rhinellais monophyletic, well supported, and composed of two major clades. One of these is moderately supported and includes species of the former R . spinulosa Group (including R . gallardoi); the mono-phyletic R . granulosa, R . crucifer, and R . marina Groups; and a clade composed of the mitochondrial sequences of R . horribilis. The other major clade is strongly supported and composed of all the spe-cies from the non-monophyletic R . veraguensis and R . margaritifera Groups, the former R . acrolophaGroup, and R . sternosignata. Consistent with these results, we define eight species groups of Rhinella that are mostly diagnosed by phenotypic synapomorphies in addition to a combination of morpho-logical character states. Rhinella sternosignata is the only species that remains unassigned to any group. We also synonymize nine species, treat three former subspecies as full species, and suggest that 15 lineages represent putative undescribed species. Lastly, we discuss the apparently frequent occurrence of hybridization, deep mitochondrial divergence, and “ghost introgression”; the incomplete phenotypic evidence (including putative character systems that could be used for future phy-logenetic analyses); and the validity of the known fossil record of Rhinella as a source of calibration points for divergence dating analyses.Peer reviewe

Desarrollo y validación de un método ambientalmente amigable para determinación de metales pesados en pastos

Los metales pesados son peligrosos para los seres vivos y el medio ambiente, pues no pueden ser degradados y pueden llegar a los seres humanos a través la cadena trófica, por lo tanto, su determinación en diferentes matrices para consumo humano y animal, es de vital importancia. La metodología más utilizada para su extracción, es cenizas, la cual conlleva a tiempos largos de análisis y elevado consumo de energía, por esta razón, en el presente trabajo se desarrolló y validó un método ambientalmente amigable para la digestión y extracción de Cd+2 y Pb+2 en pastos, utilizando ultrasonido y espectroscopia de absorción atómica. Se evaluaron diferentes variables que afectan la digestión, como posición en el ultrasonido, peso de muestra, solvente, volumen del solvente, tiempo de sonicación y tipo de recipiente, en muestras de pastos dopadas con los metales, teniéndose como variable de respuesta, el porcentaje de recuperación. Las condiciones para extraer Cd+2 y Pb+2 en estas pasturas, fueron: 0,50g de tejido vegetal; 3,00mL de HCl:HNO3-3:1 expuestos 60min al ultrasonido, en tubos de vidrio cónicos. Este procedimiento mostró un comportamiento lineal en el rango de 0,50 - 8,00mg/Kg con R2 de 0,99 tanto para Cd como para Pb. Los límites de detección y cuantificación, fueron 0,25 y 0,43mg/Kg para Cd; 0,22 y 0,37mg/Kg para Pb. La metodología propuesta, se comparó con la técnica clásica y permitió determinar niveles trazas de estos metales tóxicos, en forraje proveniente del Magdalena medio, con porcentajes de recuperación de 97,54 y 98,62%, respectivamente

Biocompatibility of bismuth silicate coatings deposited on 316L stainless steel by sol-gel process

Películas delgadas de silicato de bismuto (BSO) se han fabricado mediante el proceso sol-gel. El sol estable se sintetizó utilizando nitrato de bismuto (III) pentahidrato y tetraetil-ortosilicato (TEOS). Las películas fueron depositadas a 1500 rpm mediante la técnica de centrifugado. Los recubrimientos se caracterizaron por microscopía de fuerza atómica (AFM), microscopía electrónica de barrido (SEM), difracción de rayos-X (DRX) y se midió el espesor de las películas. El objetivo de este estudio fue evaluar la adhesión y la proliferación en células de osteoblastos, mediante el ensayo MMT, al incubarse sobre películas BSO en sustratos de 316L. Se concluyó que el crecimiento de los osteoblastos es homogéneo en la superficie de las películas, indicando que el medio ofrecido por los recubrimientos no presenta actividad citotóxica y favorece los niveles de crecimiento celular en comparación con los resultados obtenidos para los sustratos de acero inoxidable

Residuos de metales tóxicos en suelos agrícolas de veredas cercanas a explotaciones petroleras en Tibú, norte de Santander

Soil pollution is a serious environmental problem, involving environmental impacts of human activities on air and water, affecting those places where mineral extraction and concentration activities have developed, as well as industrial processes in which they appear as raw materials and waste. In the Americas, including Colombia, the contamination of soils by heavy metals is becoming increasingly important; From the beginning of this century, the determinations of metal concentrations in soils and pastures, especially cadmium, began to rise. The objective of the present work was to determine the concentrations of heavy metals Cu, Cd and Pb collected in sidewalks close to oil farms in soils, pastures and waters. The determination of the levels of these metals was performed by atomic absorption spectroscopy. The results were compared with the regulations of the European Union, since Colombia does not have its own regulations to compare the concentrations of these metals in the soil, pasture and animal drink water. The results obtained showed that the concentrations of Cu, Cd and Pb in the Village subject of this research were found above the limits allowed by the European Union, with the exception of Pb in the samples of waters andpastures of these Villages, in which the concentrations were found according to the norm.La contaminación de los suelos debido a las actividades humanas ha tenido repercusiones ambientales graves sobre el aire y las aguas. De igual forma se ven afectados todos aquellos lugares en los que se desarrollan procesos de extracción y concentración de minerales, así como procesos industriales en donde los contaminantes aparecen como materias primas y residuos. En el continente Americano, incluyendo a Colombia, cada vez cobra mayor relevancia la contaminación de suelos por metales pesados; desde comienzos del presente siglo empezaron a tomar auge las determinaciones de las concentraciones de los metales en suelos y pastos, especialmente del cadmio. El objetivo del presente trabajo fue determinar las concentraciones de los metales pesados Cu, Cd y Pb en muestras de suelos, pastos y aguas colectados en veredas cercanas a explotaciones petroleras. La determinación de los niveles de esto metales se realizó por espectroscopia de absorción atómica. Actualmente Colombia no cuenta con una normativa que permita comparar las concentraciones de estos metales en el suelo, pastos y aguas de bebida animal, por lo tanto, en el presente estudio se utilizó la normativa de la Unión Europea como referencia. Los resultados obtenidos mostraron que las concentraciones de Cu, Cd y Pb, en las veredas objeto de esta investigación, se encontraron por encima de los límites permitidos por la Unión Europea, a excepción del Pb en las muestras de suelo y pasto de estas veredas, en las cuales las concentraciones se encontraron de acuerdo a la norma

Orientaciones para la revisión, fortalecimiento y actualización de los manuales de convivencia escolar hacia la incorporación del enfoque de género, enfoque diferencial por orientación sexual e identidad de género y enfoque restaurativo.

Estas orientaciones nos permitirán trascender la noción de los manuales de convivencia como una herramienta estática centrada en generar sanciones, hacia una noción multidimensional y dinámica de la convivencia escolar, explorando la potencia pedagógica de reunirnos como comunidades educativas para identificar los retos que supone construir escuelas en línea con las realidades históricas y contextuales en las que nos encontramos

Evolution in Rhinella (Anura: Bufonidae)

155 pages : illustrations (some color) ; 26 cm.True toads of the genus Rhinella are among the most common and diverse group of Neotropical anurans. These toads are widely distributed throughout South America, inhabiting a great diversity of environments and ecoregions. Currently, however, the genus is defined solely on the basis of molecular characters, and it lacks a proper diagnosis. Although some phenetic species groups have traditionally been recognized within Rhinella, the monophyly of some of them have been rejected in previous phylogenetic analyses, and many species remain unassigned to these poorly defined groups. Additionally, the identity and taxonomy of several species are problematic and hinder the specific recognition and description of undescribed taxa. In this work, we first perform phylogenetic analyses of separate mitochondrial and nuclear datasets to test the possible occurrence of hybridization and/or genetic introgression in the genus. The comparative analysis of both datasets revealed unidirectional mitochondrial introgressions of an unknown parental species into R. horribilis ("ghost introgression") and of R. dorbignyi into R. bernardoi; therefore, the mitochondrial and nuclear datasets of these species were considered separately in subsequent analyses. We performed total-evidence phylogenetic analyses that included revised molecular (four mitochondrial and five nuclear genes) and phenotypic (90 characters) datasets for 83 nominal species of Rhinella, plus several undescribed and problematic species and multiple outgroups. Results demonstrate that Rhinella was nonmonophyletic due to the position of R. ceratophrys, which was recovered as the sister taxon of Rhaebo nasicus with strong support. Among our outgroups, the strongly supported Anaxyrus + Incilius is the sister clade of all other species of Rhinella. Once R. ceratophrys is excluded, the genus Rhinella is monophyletic, well supported, and composed of two major clades. One of these is moderately supported and includes species of the former R. spinulosa Group (including R. gallardoi); the monophyletic R. granulosa, R. crucifer, and R. marina Groups; and a clade composed of the mitochondrial sequences of R. horribilis. The other major clade is strongly supported and composed of all the species from the non-monophyletic R. veraguensis and R. margaritifera Groups, the former R. acrolopha Group, and R. sternosignata. Consistent with these results, we define eight species groups of Rhinella that are mostly diagnosed by phenotypic synapomorphies in addition to a combination of morphological character states. Rhinella sternosignata is the only species that remains unassigned to any group. We also synonymize nine species, treat three former subspecies as full species, and suggest that 15 lineages represent putative undescribed species. Lastly, we discuss the apparently frequent occurrence of hybridization, deep mitochondrial divergence, and "ghost introgression"; the incomplete phenotypic evidence (including putative character systems that could be used for future phylogenetic analyses); and the validity of the known fossil record of Rhinella as a source of calibration points for divergence dating analyses

Evolution in the genus Rhinella: A total evidence analysis of Neotropical true toads (Anura: Bufonidae)

True toads of the genus Rhinella are among the most common and diverse group of Neotropical anurans. These toads are widely distributed throughout South America, inhabiting a great diversity of environments and ecoregions. Currently, however, the genus is defined solely on the basis of molecular characters, and it lacks a proper diagnosis. Although some phenetic species groups have traditionally been recognized within Rhinella, the monophyly of some of them have been rejected in previous phylogenetic analyses, and many species remain unassigned to these poorly defined groups. Additionally, the identity and taxonomy of several species are problematic and hinder the specific recognition and description of undescribed taxa. In this work, we first perform phylogenetic analyses of separate mitochondrial and nuclear datasets to test the possible occurrence of hybridization and/or genetic introgression in the genus. The comparative analysis of both datasets revealed unidirectional mitochondrial introgressions of an unknown parental species into R. horribilis ("ghost introgression") and of R. dorbignyi into R. bernardoi; therefore, the mitochondrial and nuclear datasets of these species were considered separately in subsequent analyses. We performed total-evidence phylogenetic analyses that included revised molecular (four mitochondrial and five nuclear genes) and phenotypic (90 characters) datasets for 83 nominal species of Rhinella, plus several undescribed and problematic species and multiple outgroups. Results demonstrate that Rhinella was nonmonophyletic due to the position of R. ceratophrys, which was recovered as the sister taxon of Rhaebo nasicus with strong support. Among our outgroups, the strongly supported Anaxyrus + Incilius is the sister clade of all other species of Rhinella. Once R. ceratophrys is excluded, the genus Rhinella is monophyletic, well supported, and composed of two major clades. One of these is moderately supported and includes species of the former R. spinulosa Group (including R. gallardoi); the monophyletic R. granulosa, R. crucifer, and R. marina Groups; and a clade composed of the mitochondrial sequences of R. horribilis. The other major clade is strongly supported and composed of all the species from the non-monophyletic R. veraguensis and R. margaritifera Groups, the former R. acrolopha Group, and R. sternosignata. Consistent with these results, we define eight species groups of Rhinella that are mostly diagnosed by phenotypic synapomorphies in addition to a combination of morphological character states. Rhinella sternosignata is the only species that remains unassigned to any group. We also synonymize nine species, treat three former subspecies as full species, and suggest that 15 lineages represent putative undescribed species. Lastly, we discuss the apparently frequent occurrence of hybridization, deep mitochondrial divergence, and "ghost introgression"; the incomplete phenotypic evidence (including putative character systems that could be used for future phylogenetic analyses); and the validity of the known fossil record of Rhinella as a source of calibration points for divergence dating analyses.Fil: Pereyra, Martín Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Blotto Acuña, Boris Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Baldo, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Universidad Nacional de Misiones. Instituto de Biología Subtropical; ArgentinaFil: Chaparro, Juan C.. Museo de Biodiversidad del Perú; PerúFil: Ron, Santiago R.. Pontificia Universidad Católica del Ecuador; EcuadorFil: Elías Costa, Agustín Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Iglesias, Patricia Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Venegas, Pablo J.. Centro de Ornitología y Biodiversidad, Lima; PerúFil: Thomé, Maria Tereza C.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Ospina Sarria, Jhon Jairo. Universidade de Sao Paulo; BrasilFil: Maciel, Natan M.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Rada, Marco. Universidade de Sao Paulo; BrasilFil: Kolenc, Francisco. Museo Nacional de Historia Natural; UruguayFil: Borteiro, Claudio. Museo Nacional de Historia Natural; UruguayFil: Rivera Correa, Mauricio. Universidad de Antioquia; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Rojas Runjaic, Fernando J. M.. Pontificia Universidade Católica do Rio Grande do Sul; BrasilFil: Moravec, Jirí. National Museum; República ChecaFil: de la Riva, Ignacio María. Consejo Superior de Investigaciones Científicas. Museo Nacional de Ciencias Naturales; EspañaFil: Wheeler, Ward C.. American Museum of Natural History; Estados UnidosFil: Castroviejo Fisher, Santiago. Pontificia Universidade Católica do Rio Grande do Sul; BrasilFil: Grant, Taran. Universidade de Sao Paulo; BrasilFil: Baptista Haddad, Célio Fernando. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Faivovich, Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin