Nutrients Export by Rivers to the Coastal Waters of Africa: Past and Future trends

We analyze past and future trends in nitrogen (N), phosphorus (P), and carbon (C) export by rivers to the coastal waters of Africa as calculated by the Global Nutrient Export to WaterShed (NEWS) models for the period 1970–2050. Between 1970 and 2000 the total nutrient export by African rivers increased by 10–80%. For future years (2000–2050) we calculate an increase in the total loads of dissolved forms of N and P, but decreasing trends for dissolved organic C and particulate forms of N and P. There are large regions that deviate from these pan-African trends. We explore the regional patterns and the underlying processes, in particular for the Nile, Zaire, Niger, and Zambezi. In the future, anthropogenic sources may, in large parts of Africa, become larger contributors to riverine nutrient loads than natural source

Millennium Ecosystem Assessment Scenario drivers (1970-2050): Climate and hydrological alterations

This study was carried out to support and enhance a series of global studies assessing contemporary and future changes in nutrient export from watersheds (Global Nutrient Export from Watersheds (NEWS)). Because hydrography is one of the most important drivers in nutrient transport, it was essential to establish how climatic changes and direct human activities (primarily irrigation and reservoir operations) affect the hydrological cycle. Contemporary and future hydrography was established by applying a modified version of a global water balance and transport model (WBMplus) driven by present and future climate forcing, as described in the Millennium Ecosystem Assessment scenarios (1970-2050). WBMplus represents a major upgrade to previous WBM implementations by incorporating irrigational water uptake and reservoir operations in a single modeling framework. Contemporary simulations were carried out by using both observed climate forcings from the Climate Research Unit of East Anglia (CRU) data sets and from Global Circulation Model (GCM) simulations that are comparable to the future simulations from the same GCM forcings. Future trends in three key human activities (land use, irrigation, and reservoirs operation for hydropower) were taken from the Integrated Model to Assess the Global Environment (IMAGE). The reservoir operation required establishing a realistic distribution of future reservoirs since the IMAGE model provided only the hydropower potentials for the different future scenarios

Cabri II Plus como herramienta para la enseñanza de las isometrías

La incorporación en la vida cotidiana de las nuevas tecnologías de la información y la comunicación ha significado un cambio radical en la forma de desarrollar el proceso de enseñanza y aprendizaje en las diferentes disciplinas y niveles escolares. En este sentido, el software de geometría dinámica “Cabri Géomètre II Plus” es un programa computacional de fácil manipulación, amigable y de rápido aprendizaje, que permite a los estudiantes visualizar, descubrir, conjeturar y/o comprobar propiedades que se deseen trabajar. El presente artículo tiene como finalidad mostrar actividades en el tema de transformaciones isométricas y que se pueden desarrollar con el uso de Cabri II Plus, y que permiten el desarrollo del pensamiento geométrico

Aplicación de la estadística en temáticas de administración de empresas

El presente artículo da cuenta de una experiencia de aula desarrollada en el Instituto de Educación Continua de la Universidad de Los Lagos de Osorno – Chile con alumnos y alumnas del primer año de la carrera Técnico Universitario en Administración de Empresas, quienes en el módulo de Estadística desarrollaron investigaciones en sus lugares de trabajo sobre temas propios de su profesión. Los estudiantes formaron equipos de trabajo y eligieron problemáticas relacionadas a sus carreras, luego aplicaron cuestionarios para recolectar información, presentaron los datos recopilados en tablas y gráficos de los cuales obtuvieron estadígrafos que permitieron establecer conclusiones. Para la descripción y análisis de los resultados, cada equipo realizó un informe escrito sobre la investigación. Como resultado de la experiencia se logró que los estudiantes se introdujeran en una problemática propia de su área laboral, investigaran y recopilaran información sobre el tema y pudieran visualizar a la estadística como una disciplina potencialmente útil para su formación profesional y futura vida laboral

How much dark matter is there inside early-type galaxies?

We study the luminous mass as a function of the dynamical mass inside the effective radius (r_e) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. We use several samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC) simulations of galaxy samples and compare them with real samples. The main results are: i) MC simulations show that the distribution of the dynamical vs. luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is approximately 7% +- 22%. iii) This amount of dark matter is lower than the minimum estimate (10%) found in the literature and four times lower than the average (30%) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.Comment: 24 pages, 12 figures. MNRAS accepte