Dissolution of minor sulphides present in a pyritic sludge at pH 3 and 25º C

The steady-state dissolution rates of galena, sphalerite and chalcopyrite at pH 3 under oxygen saturated atmosphere and at 25ºC are obtained by means of non-stirred flow-through experiments. These dissolution rates are compared with those estimated by dissolving pyritic sludge from the Aznalcollar mining tailings composed of pyrite and minor sulphides galena, sphalerite and chalcopyrite.Based on the respective release of Fe, Pb, Zn and Cu, the steady-state dissolution rates of pyrite (RateFe), galena (RatePb), sphalerite (RateZn) and chalcopyrite (RateCu) are 6.33 ± 0.95 x 10-11, 1.2 ± 0.18x10-10, 1.3 ± 0.20x10-11 and 1.71 ± 0.25x10-11 mol m-2 s-1, respectively, yielding RatePb > RateFe > RateZn = RateCu. Based on the release of metal and sulphur to solution, the stoichiometric ratios Pb/S, Zn/S and Cu/S are 4 ± 0.25, 1.2 ± 0.1 and 0.90 ± 0.05 for the respective dissolution reactions of galena, sphalerite and chalcopyrite, which are higher than the ideal ones. These high values result from a sulphur deficit in the output solutions attributed to the loss of H2S(aq) via gasification by which H2S(aq) partially converts to H2S(g). Nevertheless, the Cu/Fe ratio is 0.95 ± 0.05 during chalcopyrite dissolution at steady state, suggesting that chalcopyrite dissolves stoichiometrically

Rocks under the microscope: an approach to the study of thin sections of minerals and rocks

En este trabajo se presenta una propuesta didáctica destinada a favorecer el acercamiento de los alumnos a una de las técnicas más habituales empleadas para el estudio de las rocas, sedimentos y minerales: la microscopía de luz polarizada. Para conseguir este objetivo, se proporciona a los alumnos un mínimo de conocimientos teóricos que les permite trabajar en grupos notablemente autónomos e identificar algunos de los componentes más frecuentes en distintos tipos de rocas y sedimentos. Con esta actividad, se familiariza a los estudiantes con algunas de las propiedades empleadas en microscopía óptica y con las propiedades de los propios componentes rocosos, y se proporcionan unas herramientas que facilitan el acercamiento a esta faceta del trabajo científico.In this work, a didactic proposal is presented, aimed at favoring the contact of the students with one of the most usual techniques for the study of rocks, sediments and minerals: polarized light microscopy. With this purpose, a minimal set of theoretical basis is presented to the students, which allows them to work fairly autonomously and to identify some of the most frequent components in different rock and sediment types. By means of this activity, the students become familiar with some of the light properties and also with some of the mineral properties currently used in microscopy, encouraging their contact with this type of scientific work.7 página

Rocas bajo el microscopio: acercamiento al estudio en lámina delgada de minerales y rocas

En este trabajo se presenta una propuesta didáctica destinada a favorecer el acercamiento de los alumnos a una de las técnicas más habituales empleadas para el estudio de las rocas, sedimentos y minerales: la microscopía de luz polarizada. Para conseguir este objetivo, se proporciona a los alumnos un mínimo de conocimientos teóricos que les permite trabajar en grupos notablemente autónomos e identificar algunos de los componentes más frecuentes en distintos tipos de rocas y sedimentos. Con esta actividad, se familiariza a los estudiantes con algunas de las propiedades empleadas en microscopía óptica y con las propiedades de los propios componentes rocosos, y se proporcionan unas herramientas que facilitan el acercamiento a esta faceta del trabajo científico

Rocas bajo el microscopio: acercamiento al estudio en lámina delgada de minerales y rocas

In this work, a didactic proposal is presented, aimed at favoring the contact of the students with one of the most usual techniques for the study of rocks, sediments and minerals: polarized light microscopy. With this purpose, a minimal set of theoretical basis is presented to the students, which allows them to work fairly autonomously and to identify some of the most frequent components in different rock and sediment types. By means of this activity, the students become familiar with some of the light properties and also with some of the mineral properties currently used in microscopy, encouraging their contact with this type of scientific work.En este trabajo se presenta una propuesta didáctica destinada a favorecer el acercamiento de los alumnos a una de las técnicas más habituales empleadas para el estudio de las rocas, sedimentos y minerales: la microscopía de luz polarizada. Para conseguir este objetivo, se proporciona a los alumnos un mínimo de conocimientos teóricos que les permite trabajar en grupos notablemente autónomos e identificar algunos de los componentes más frecuentes en distintos tipos de rocas y sedimentos. Con esta actividad, se familiariza a los estudiantes con algunas de las propiedades empleadas en microscopía óptica y con las propiedades de los propios componentes rocosos, y se proporcionan unas herramientas que facilitan el acercamiento a esta faceta del trabajo científico.Palabras clave: Microscopía de luz polarizada; Rocas; Minerales, Lámina delgada.Rocks under the microscope: an approach to the study of thin sections of minerals and rocksIn this work, a didactic proposal is presented, aimed at favoring the contact of the students with one of the most usual techniques for the study of rocks, sediments and minerals: polarized light microscopy. With this purpose, a minimal set of theoretical basis is presented to the students, which allows them to work fairly autonomously and to identify some of the most frequent components in different rock and sediment types. By means of this activity, the students become familiar with some of the light properties and also with some of the mineral properties currently used in microscopy, encouraging their contact with this type of scientific work.Keywords: Polarized light microscopy; rocks; minerals; thin sections

El rol familiar en el éxito o fracaso escolar, percepción de niños y niñas del Ciclo III

92 Páginas.Los Países en vías de desarrollo han implementado políticas gubernamentales para elevar los índices de educación de las poblaciones más vulnerables. Sin embargo, a pesar de ingentes esfuerzos académicos y económicos, aún persisten altas cifras de fracaso escolar. En el seno de la Maestría en Familia de la Universidad de la Sabana, se expone la presente investigación que indaga, en el imaginario de los estudiantes, por la manera como se desarrolla la relación familia y escuela en el ciclo III de tres colegios públicos de la Localidad de Kennedy de Bogotá D.C. A partir de este punto, se pretende establecer, hasta dónde el rol familiar en el apoyo y acompañamiento estudiantil puede incidir en el éxito o fracaso escolar de sus hijos; y con base en las conclusiones obtenidas, generar alternativas de investigación y estrategias de apoyo familiar, con la participación y compromiso de la institución educativa y de la sociedad en general. Palabras clave: Relación familia escuela, Éxito y Fracaso Escolar, Apoyo y acompañamiento escolar, Estudiantes de ciclo III

Hydrogeochemical characterization of an evaporite karst area affected by sinkholes (Ebro Valley, NE Spain)

The main processes controlling the hydrochemistry of an alluvium-covered evaporite karst area with high sinkhole risk (Ebro Valley, NE Spain) are examined by means of multivariate analyses (Principal Component Analysis and Hierarchical Cluster Analysis), ion correlations and geochemical speciation-solubility calculations. The hydrogeochemistry of the studied system seems to be governed by the interaction between the groundwater from the salt-bearing evaporitic karst aquifer and from the overlying Ebro River alluvial aquifer. The observed hydrochemical features in the alluvial-karst aquifer system are mainly determined by the relative contribution of gypsum/anhydrite and halite dissolution, showing a wide spectrum from relatively fresh recharge waters (mainly irrigation waters) to highly evolved groundwater from the evaporitic aquifer. The variability of these contributions is especially evident at sinkhole ponds which, in some cases, seem to be associated with discharge areas of the karst aquifer in the valley bottom alluvium. Calculated saturation indexes suggest that, in contrast to gypsum, the amounts of halite in the sampled portions of evaporitic aquifer are not large enough to attain equilibrium, which is consistent with the predominance of gypsum/anhydrite reported for these materials. Furthermore, the observed Na:Cl and Ca:SO4 correlations and stoichiometries suggest that other possible processes, such as glauberite dissolution or Na/Ca-exchange, generally play a minor role (compared to halite and gypsum dissolution) in this system. Another important process in the system is the dissolution of carbonate minerals (dolomite and, possibly, calcite) fostered by the input of CO2(g), which is probably produced by pedogenic processes. Dolomite dissolution seems to be particularly relevant in the evaporitic materials probably due to dedolomitisation triggered by gypsum/anhydrite dissolution

Disorders of sex development : genetic characterization of a patient cohort

Q3Q397-106Disorders of sex development (DSDs) are congenital conditions in which the external appearance of the individual does not coincide with the chromosomal constitution or the gonadal sex. In other words, there is an ambiguous or intermediate condition between the male and female phenotypes of the anatomical sex. These atypical conditions are manifested in several ways, ranging from genital ambiguity to phenotypes that are so attenuated that they can go unnoticed or appear normal. Currently, there is a lack of understanding of the factors responsible for these outcomes; however, they are likely to be conditioned by genetic, hormonal and environmental factors during prenatal and postnatal development. The present study determined the genetic etiology of DSDs in Colombian patients by conventional cytogenetic analysis, FISH and MLPA (for SF1, DAX1, SOX9, SRY and WNT4). A cohort of 43 patients with clinical phenotypes of sex development disorder was used in the present study. Using this multistep experimental approach, a diagnostic percentage of 25.58% was obtained: 17 patients (39.53%) were classified as having gonadal development disorders, the majority of which were ovotesticular disorders with numerical and/or structural alterations of the sex chromosomes, 9 patients (20.93%) were classified as having testicular DSD with a 46,XY karyotype, and 3 patients (6.98%) as having ovarian DSD with a 46,XX karyotype. The remaining 14 patients (32.56%) were classified as ‘other’ since they could not be grouped into a specific class of gonadal development, corresponding to hypospadias and multiple congenital anomalies. These findings highlight the importance of histological and cytogenetic studies in a gonadal biopsy. In 11/43 cases, the multistep experimental protocol presented in the present study yielded etiological or histological findings that could be used to define the medical management of patients with DSDs. In conclusion, for the etiological diagnosis of DSDs, a broad‑spectrum approach that includes endocrinological tests, conventional karyotyping, molecular karyotyping by FISH and, molecular tests is required, in addition to gonadal tissue analyses, to identify genetic alterations

Gene dosage of DAX-1, determining in sexual differentiation : duplication of DAX-1 in two sisters with gonadal dysgenesis

Q3Q2Artículo original2971-2978Two sisters phenotypically normal females, presenting with tumor abdominal mass with histopathological findings of teratoma and gonadoblastoma associated to 46,XY male-to-female sex reversal syndrome, secondary to a duplication in DAX-1, possibly inherited of maternal gonadal mosaicism. Copy number variation and functional effects of the duplication were done by MLPA multiplex ligation-dependent probe amplification and real time PCR. DAX-1, also known as dosage sensitive sex reversal gene (DSS), is considered the most likely candidate gene involved in XY gonadal dysgenesis when overexpressed. The excess of DAX-1 gene disturbs testicular development by down regulation of SF-1, WT1, and SOX9. This is the first report of 46,XY sex reversal in two siblings who have a maternally inherited duplication of DAX-1 associated with reduced levels of expression of downstream genes as SOX9-SF1

Marine Biodiversity in the Caribbean: Regional Estimates and Distribution Patterns

This paper provides an analysis of the distribution patterns of marine biodiversity and summarizes the major activities of the Census of Marine Life program in the Caribbean region. The coastal Caribbean region is a large marine ecosystem (LME) characterized by coral reefs, mangroves, and seagrasses, but including other environments, such as sandy beaches and rocky shores. These tropical ecosystems incorporate a high diversity of associated flora and fauna, and the nations that border the Caribbean collectively encompass a major global marine biodiversity hot spot. We analyze the state of knowledge of marine biodiversity based on the geographic distribution of georeferenced species records and regional taxonomic lists. A total of 12,046 marine species are reported in this paper for the Caribbean region. These include representatives from 31 animal phyla, two plant phyla, one group of Chromista, and three groups of Protoctista. Sampling effort has been greatest in shallow, nearshore waters, where there is relatively good coverage of species records; offshore and deep environments have been less studied. Additionally, we found that the currently accepted classification of marine ecoregions of the Caribbean did not apply for the benthic distributions of five relatively well known taxonomic groups. Coastal species richness tends to concentrate along the Antillean arc (Cuba to the southernmost Antilles) and the northern coast of South America (Venezuela – Colombia), while no pattern can be observed in the deep sea with the available data. Several factors make it impossible to determine the extent to which these distribution patterns accurately reflect the true situation for marine biodiversity in general: (1) highly localized concentrations of collecting effort and a lack of collecting in many areas and ecosystems, (2) high variability among collecting methods, (3) limited taxonomic expertise for many groups, and (4) differing levels of activity in the study of different taxa

Experiencias en el aula: segundo encuentro de prácticas pedagógicas innovadoras

Experiencias de profesores en su quehacer en los distintos ambientes de aprendizaje presenciales y a distancia.La segunda entrega de Experiencias en el aula es una publicación anual que recoge las ponencias ganadoras presentadas en el Segundo Encuentro de Prácticas Pedagógicas Innovadoras, organizado por el Centro de Excelencia Docente aeiou, de la Vicerrectoría General Académica de la Corporación Universitaria Minuto de Dios – UNIMINUTO Todas las ponencias publicadas en la segunda entrega de Experiencias en el aula fueron seleccionadas por evaluadores externos durante la convocatoria al Segundo Encuentro de Prácticas Pedagógicas Innovadoras en el que fueron presentadas; este evento, organizado por el Centro de Excelencia Docente aeiou, y la Vicerrectoría General Académica de la Corporación Universitaria Minuto de Dios- UNIMINUTO, tuvo lugar los días 9 y 10 de octubre de 2017