O lodo de curtume é frequentemente usado na agricultura como fonte de nutrientes e para controlar a acidez do solo. No entanto, o uso dessa substância pode promover a contaminação do solo com cromo. O objetivo deste estudo foi determinar as isotermas de sorção e dessorção do cromo proveniente de lodo de curtume em um experimento de laboratório. A sorção e dessorção do cromo foram determinadas em amostras de um Latossolo sob pastagem e vegetação nativa de Cerrado. As amostras de solo foram misturadas com lodo de curtume e sulfato de cromo. As amostras de solo contendo cromo em diferentes concentrações foram agitadas por 72 h, alternando ciclos de 12 h de agitação e 12 h de repouso. As amostras foram centrifugadas, e o solo separado do sobrenadante foi submetido a extrações de dessorção seletiva com soluções de CaCl2, NaOH, e Na2EDTA para determinar diferentes frações de cromo. Os resultados mostraram que a retenção de cromo no solo foi fortemente influenciada pela matéria orgânica do solo. O cromo proveniente tanto do lodo de curtume como do sulfato foi fortemente sorvido no solo. A dessorção de cromo foi maior nas amostras tratadas com NaOH no lodo de curtume e com outros extratores no tratamento com sulfato.

Tannery sludge is often used in agriculture as a source of nutrients and for controlling soil acidity. However, the use of this substance can promote soil contamination by chromium. The objectives of this research were to determine the sorption and desorption isotherms of chromium from tannery sludge in a laboratory experiment. The sorption and desorption of chromium were determined in samples of an Oxisol under pasture and native vegetation (Cerrado). Soil samples were mixed with tannery sludge and a solution of chromium sulfate. The soil samples containing chromium at different concentrations were shaken for 72 hours in cycles of 12 hours of shaking and 12 hours of rest. The samples were then centrifuged, and the soil separated from the supernatant and were subjected to selective desorption with CaCl2, NaOH, and Na2EDTA solutions to determine the different fractions of chromium. Results showed of the chromium retention in the soil was strongly influenced by the soil organic matter and the organic matter from tannery sludge. That chromium presented in both tannery sludge and sulfate was strongly sorbed on soil. Chromium desorption was higher for samples treated with NaOH in the tannery sludge and with others extractors in the sulfate treatment.

Crop production is traversing expansion and intensification processes all over the planet and in consequence the large scale cattle production is being displaced to marginal lands with lower stocking capacity. The objective of this work was to assess the seasonality of vegetation in La Pampa province located in a semiarid region in Argentina and to explore if the variations in seasonality are related to the stocking rate. The hypothesis is the changes in stocking rate of rangelands and its grazing pressure alter the proportion of different vegetation functional groups and so the vegetation seasonality. It is predicted that overgrazing of seasonal grasses will alter the proportion of woody species having consequences over spectral indices. It was analyzed satellite data, particularly the MODIS Enhanced Vegetation Index (EVI) and related it to stocking rate records from SENASA. This work evidences the relationship between the stocking rate and the spectral index EVI, indicator of the primary productivity of vegetation, at departmental scale in the natural areas of Monte and Espinal of La Pampa. Results indicate that in western region (Monte) there was an increment in the stocking rate at department level and a decrease in vegetation seasonality. It is posed that the higher grazing pressure led to the overgrazing of the most palatable herbaceous species, increasing the shrub proportion in landscape.

La producción de cultivos está atravesando procesos de expansión e intensificación alrededor de todo el planeta. En consecuencia, la producción ganadera está siendo desplazada hacia tierras marginales de menor capacidad de carga. El objetivo de este trabajo es evaluar la estacionalidad de la vegetación en la provincia de La Pampa, ubicada en la región semiárida argentina; y explorar si las variaciones en la estacionalidad están relacionadas con la carga de ganado vacuno. Se plantea como hipótesis que los cambios en la carga animal y la presión de pastoreo alteran la proporción de diferentes grupos funcionales de vegetación, y de esta manera, su estacionalidad. Se predice que el sobrepastoreo de los pastos más estacionales alterará la proporción de especies leñosas, y ello repercutirá sobre los índices espectrales. Se analizó la información satelital, particularmente el Índice de Vegetación Mejorado (EVI) de MODIS y se lo relacionó con los registros de carga animal de SENASA. Este trabajo evidencia la relación entre la carga animal y el EVI, indicador de la productividad primaria de la vegetación, a la escala de departamento en las áreas naturales del Monte y el Espinal de La Pampa. Los resultados indican que al oeste de la provincia (Monte) hubo un aumento de la carga animal y una disminución de la estacionalidad de la vegetación a escala de departamento. La mayor presión de pastoreo habría conducido al sobrepastoreo de las especies herbáceas más palatables aumentando la proporción de arbustos en el paisaje.

Resumo O objetivo deste trabalho foi determinar a movimentação vertical do íon potássio em perfil de Neossolo Quartzarênico cultivado com cana-de-açúcar. Foram realizados dois experimentos, em campo. O primeiro consistiu de uma avaliação da movimentação do íon no perfil do solo até 1,80 m de profundidade, por dois anos, em uma área cultivada com cana-de-açúcar e em outra sob cerrado. O segundo consistiu da avaliação do movimento do íon até a profundidade de 1,00 m, sob dois regimes hídricos: natural e controlado. No experimento sob condições controladas, as avaliações foram feitas em parcelas de 0,5 m2, delimitadas por chapas galvanizadas, com adição de 80 kg ha-1 de K2O seguida da adição de 1.200 mm de água. A área sob lavoura apresentou maior conteúdo de matéria orgânica do solo, maior pH e, consequentemente, maior capacidade de retenção do K+ nas camada superficiais do perfil do que a área de cerrado. Além disso, na área sob lavoura, a avaliação da disponibilidade de K+ ao longo do perfil do Neossolo avaliado foi influenciada pelo tipo de regime hídrico adotado (chuva natural ou controlada). Independentemente do uso do solo, o K+ apresenta rápida movimentação no perfil do solo.

Abstract The objective of this work was to determine the vertical movement of the potassium ion in the profile of Quartzipsamment Entisols cultivated with sugarcane. Two experiments were conducted in field conditions. The first one consisted of an assessment of ion movement in the soil profile, down to 1.80-m depth, for two years, in an area cultivated with sugarcane and in another one under cerrado. The second one consisted of the evaluation of ion movement to a depth of 1.00 m, under two water regimes: natural and controlled. In the experiment under controlled conditions, evaluations were done with 0.5-m2 plots, delimited by galvanized sheets, receiving 80 kg ha-1 K2O followed by the addition of 1,200 mm of water. The area cropped with sugarcane showed greater soil organic matter content, greater pH, and, consequently, greater retention capacity of K+ in the superficial layers of the soil profile than the cerrado area. Moreover, in the area with sugarcane crop, the evaluation of K+ availability in the profile of the Quartzipsamment Entisol profile was affected by the adopted water regime (natural or controlled rainfall). Regardless of soil use, K+ moves rapidly through the soil profile.

En esta investigación, se pretendió averiguar la influencia de la mnemotecnia de la palabra clave en el recuerdo y en los juicios metamnemónicos: juicios de facilidad de aprendizaje (EOL), juicios de aprendizaje (JOL) y juicios de confianza (CL), tanto en una lista corta de 16 palabras latinas (Experimento 1) como en una lista larga de 32 palabras latinas (Experimento 2). Tanto en el Experimento 1 como en el Experimento 2 se efectuó un diseño experimental de dos grupos independientes. En el Experimento 1 participaron 88 mujeres, con una media de edad de 74.34 años. En el 2, participó un grupo de 84 mujeres, de una edad similar al anterior. En ambos experimentos se realizó una prueba t de Student para muestras independientes. En el Experimento 1, se encontró que el método de la palabra clave fue superior al método de repetición en el recuerdo y en los juicios de confianza en la respuesta (CL). En el Experimento 2, se halló que el método de la palabra clave fue significativamente superior al método de repetición en el recuerdo y en todos los juicios metamnemónicos estudiados. El método de la palabra clave fue más eficaz que el método de repetición.

This study consisted of two experiments designed to assess the efficacy of the keyword mnemonic technique on recall and the following mnemonic judgments: ease of learning (EOL), judgments of learning (JOL), and confidence level (CL) using a short word list i.e., 16 Latin words (Experiment 1), or a long word list, 32 Latin words (Experiment 2). In Experiment 1 an experimental design with two independent groups was performed, involving 88 women, mean age 74.34 years, a Student's t-test for independent groups was performed and the keyword method was found to be more efficacious than the rote learning method on recall and confidence level judgments (CL). In Experiment 2 an experimental design with two independent groups was performed, involving 84 women of similar age, a Student's t-test for independent groups was performed, and the keyword method was significantly more efficacious than the rote learning method on recall and all of the mnemonic judgments under study. The keyword method was more effective than the rote learning method.

El artículo analiza teóricamente como la precariedad del trabajo e del empleo no se limita al menos cualificado y se alarga progresivamente al trabajo cualificado, proponiendo un enfoque dinámico centrado en el poder. Basado en este enfoque, se presentan los resultados de un estudio sobre una profesión altamente cualificada: los profesionales de la ciencia.

O artigo analisa teoricamente como a precarização do trabalho e do emprego não se limita ao menos qualificado e se alarga, progressivamente, ao trabalho qualificado, propondo uma abordagem dinâmica centrada no poder. Seguidamente, apresenta os resultados de um estudo assente nesta abordagem, junto de uma profissão altamente qualificada, os profissionais da ciência.

L'article analyse théoriquement la façon comme la précarité du travail et de l'emploi ne se limite pas au moins qualifié et s'élargit progressivement au travail qualifié, en proposant une approche dynamique centrée sur le pouvoir. Les résultats d'une étude basée sur cette approche, sur une profession hautement qualifiée, les professions scientifiques, sont presents.

The article theoretically analyzes how precariousness of work and employment isn’t limited to unskilled labor and progressively extends to skilled work, proposing a dynamic approach centered on power. The results of a study based on this approach, among a highly skilled profession - the science professionals - are presented.

As veredas são ecossistemas úmidos, geralmente associados a solos hidromórficos e ao afloramento do lençol freático, ocorrendo com frequência nas proximidades das nascentes e cursos d'água da região do Cerrado. Este trabalho objetivou estudar os solos de veredas situadas no bioma Cerrado, em ambientes conservados e antropizados (em áreas agrícolas e de pecuária), por meio da determinação da textura e da matéria orgânica do solo. Três veredas foram selecionadas para amostragem de solo, sendo: uma conservada, circundada por vegetação natural; uma área antropizada, com pastagem em seu entorno e uma outra, também antropizada, com culturas anuais (agricultura) em seu entorno. As amostras de solo foram coletadas em diferentes profundidades, ao longo de linhas de referência dispostas segundo sua posição no relevo, nos terços superior, médio e inferior de uma das vertentes, acompanhando de modo aproximado o sentido da linha de drenagem da vereda. Verificou-se que os teores de argila na região inferior do relevo são maiores em ambientes antropizados e os teores de silte são maiores na vereda adjacente à área agrícola. No terço inferior das vertentes os teores de matéria orgânica são menores em veredas adjacentes às áreas com pastagens e agricultura.

Veredas (a type of wetland) are humid ecosystems, generally associated to hydromorphic soils and shallow water table, which occur frequently in the neighborhood of the springs and watercourses in the Cerrado region. The objective of this work was to study wetland soils located in undisturbed (native forest) and disturbed (agriculture and pasture) environments by means of determination of the soil texture and organic matter contents. Three wetlands were selected for this study: undisturbed wetland, surrounded by natural vegetation; disturbed wetland, surrounded by pasture areas; and disturbed wetland, surrounded by cultivated areas. Soil samples were collected at three different depths, following reference leveled lines defined, according to their positions in the relief, i.e., upper, middle and lower slope positions. The reference lines were approximately parallel to the direction of the wetland fluvial channel. It was verified that the clay contents in the lower portion of the slope were higher for the disturbed environments and the contents of silt were higher for the disturbed wetland surrounded by agricultural areas. The organic matter contents in the lower portion of the slope were lower for the disturbed wetlands.

This study sought to evaluate the effects of the use of imagery in immediate recollection, at the end of one day and at the end of the week, according to the type of imagery employed: no images, normal image, unusual image and mixed image. For this test, 198 subjects were selected with an average age of 14.4 years, randomly assigned to one of four experimental groups: 1) group with no mental images, 2) group which used normal mental images, 3) group which used unusual images and 4) mixed group. A set of 16 sentences was shown to the groups, each of which contained three words written in block capitals. The subjects had to indicate the relationship between the three words (in the group without any image), or the intensity of the image provoked by each sentence (groups with images). We subsequently conducted an evaluation of the recollection, recognition, false recognition, access to the sentence, the items recalled by sentence and the number of sentences completely recollected. The subjects were also questioned about their experiences in the use of the images. It was ascertained that the experience in the use of the images influenced, at the end of the day and of the week, the recollection, recognition, the number of sentences completely recalled and the access to the sentence. After a week, the groups which were shown unusual or mixed images demonstrated better results in all the dependent variables (with the exception of the items recollected by sentence) than the groups which were shown normal mental images, or no images at all.

En nuestra investigación deseábamos saber si la experiencia en la utilización de imágenes mentales y el tipo de imagen utilizada: sin imagen, imagen normal, imagen rara, e imagen mixta, influía en el recuerdo inmediato, al cabo de un día y de una semana. Para ello seleccionamos a 198 sujetos, con una media de edad de 14.4 años, y los distribuimos, al azar en cuatro grupos: el grupo que no utilizó imágenes mentales, el que utilizó imágenes normales, el que utilizó imágenes raras, y el grupo mixto. A los grupos se les presentaron 16 oraciones, cada una con tres palabras en mayúsculas. Los sujetos tenían que puntuar la relación entre las tres palabras (el grupo sin imagen), o la viveza suscitada por cada oración (grupos con imagen). Posteriormente se midió el recuerdo, el reconocimiento, el falso reconocimiento, el acceso a la oración, los ítems por oración recordados, y el número de oraciones totalmente recordadas. También se preguntó a los sujetos por su experiencia en la utilización de imágenes. Encontramos que la experiencia en la utilización de imágenes influyó al cabo de un día y de una semana en el recuerdo, en el reconocimiento, en el número de oraciones totalmente recordadas, y en el acceso a la oración. Los grupos que utilizaron imágenes raras e imágenes mixtas manifestaron, después de una semana, mayor rendimiento en todas las variables dependientes (excepto en ítems por sentencia recordados), que los grupos que utilizaron imágenes normales o no utilizaron imágenes mentales.

Mining in the study area has been carried out for several centuries, causing environmental alterations, generating poor soils for plant establishment and health hazards for humans. The objective was to evaluate presence of Lead, Cadmium, Zinc and Arsenic in soil with variables: distance to the pollution source and soil depth, hence determining relations with soil physical-chemical characteristics. The study area is located south of Chihuahua State. Sampling sites were placed in the area of the mine tailing. These sites covered a lineal area of 3 km following downward directions to the dominant winds beginning from the pollution source, and taken every 300 m. Ten sites provided thirty soil samples for the analysis of metal concentrations, and for physical-chemical characteristics, from three different soil depths: 0-40, 40-60 and 60-80 cm. Metal concentrations were evaluated through ICP technique. Samples containing small concentrations were read with atomic absorption. A "Regression Analysis Model" was used. The results obtained show that the highest element concentrations were for the sites closest to the tailing deposits, and decreasing with the distances away from the main source. The two sites closest to tailing deposits had higher metal levels in lower soil layers than at the soil surface except for Cadmium. Concentration limits of these metals are higher than any limits recommended by international agencies. Distance to tailing deposits associated with the concentration of all elements. Arsenic correlated with soil texture and organic matter, Lead with texture, Zinc with distance and Cadmium with soil pH and depth.

La extracción minera en el área data del año 1600, provocando disturbios al medioambiente y generando suelos con limitaciones físicas, químicas y biológicas para el establecimiento de vegetación y riesgos a la salud. El objetivo del estudio fue evaluar la contaminación en el suelo por Plomo, Cadmio, Cinc y Arsénico a diferentes distancias y niveles de profundidad y determinar su relación con características físico-químicas. El área se encuentra en San Francisco del Oro, Chih, en el área de influencia de la presa de jales la cual es un área de confinamiento de los desechos de la industria minera, abarcó 3 km lineales en dirección de vientos dominantes a partir de la fuente de contaminación. Se extrajeron 30 muestras de suelo para análisis de concentraciones de metales y de características físico-químicas a tres diferentes profundidades: 0-40, 40-60 y 60-80 cm en 10 sitios la distancia entre sitios fue de 300 m. La concentración de metales se evaluó utilizando la técnica ICP, las muestras con pequeñas concentraciones se leyeron mediante absorción atómica. El análisis estadístico fue modelos de regresión entre características físico-químicas, distancias, profundidades y concentraciones de metales pesados. Los resultados muestran que la mayor concentración se da en sitios cercanos a los jales, disminuyendo la concentración a medida que se aleja de ellos. Todos los elementos sobrepasan los rangos establecidos por las agencias internacionales. El Arsénico se asoció con distancia a la fuente, textura y materia orgánica; el Plomo con la distancia a la fuente y textura; el Cinc con distancia a la fuente y el Cadmio con la distancia a la fuente, pH y profundidad de suelo.