Phosphate sorption and desorption by two contrasting volcanic soils of equatorial Africa

Volcanic soils cover 1% of the Earth's surface but support 10% of the world's population. They are among the most fertile soils in the world, due to their excellent physical properties and richness in available nutrients. The major limiting factor for plant growth in volcanic soils is phosphate fixation, which is mainly attributable to active species of aluminium and iron. The sorption and desorption of phosphate is studied on the surface horizons of two African agricultural soils, a silandic Andosol (Rwanda) and a vitric Andosol (São Tomé and Principe). Both soils are slightly acid. The silandic Andosol is rich in active aluminium forms, while the vitric Andosol has high amounts of crystalline iron and aluminium oxides. Sorption isotherms were determined by equilibrating at 293K soil samples with phosphate solutions of concentrations between 0 and 100 mg P L-1 in NaNO3; phosphate was determined by visible spectrophotometry in the equilibrium solution. To study desorption, the soil samples from the sorption experiment were equilibrated with 0.02 M NaNO3. The isotherms were adjusted to mathematical models. In almost all the concentration range, the adsorption of phosphate by the silandic Andosol was greater than 90% of the amount added, being lower in the vitric Andosol but always higher than 65%. The high sorption by the silandic Andosol is attributed to its richness in non-crystalline Fe and Al, while in the vitric Andosol crystalline iron species seem to play a relevant role in the adsorption. The sorption isotherms of both soils fitted to the Temkin model, the adjustment to the Langmuir or Freundlich models being unsatisfactory; throughout the range studied, the sorption increases with increasing phosphorus concentration, a maximum sorption is not predictable (as occurs when the sorption is adjusted to the Langmuir model). For an added P concentration of 100 mg L-1 (3.2 mmol L-1), the sorption is 47.7 mmol P g-1 in the silandic Andosol and 41.6 mmol P g-1 in the vitric Andosol. The desorption is low and the comparison of the sorption and desorption isotherms reveals a pronounced hysteresis, that is, the irreversibility of the sorption. The high phosphate sorption and its irreversibility are comparable to those published for other volcanic soils with high contents of allophane, active aluminium and free iron. The strong phosphate adsorption is a serious limiting factor for plant growth, which requires a careful management of phosphorus fertilization.S

Sorption and Desorption of Vanadate, Arsenate and Chromate by Two Volcanic Soils of Equatorial Africa

Sorption of oxyanions by soils and mineral surfaces is of interest due to their role as nutrients or pollutants. Volcanic soils are variable charge soils, rich in active forms of aluminum and iron, and capable of sorbing anions. Sorption and desorption of vanadate, arsenate, and chromate by two African andosols was studied in laboratory experiments. Sorption isotherms were determined by equilibrating at 293 K soil samples with oxyanion solutions of concentrations between 0 and 100 mg L−1 V, As, or Cr, equivalent to 0−2.0 mmol V L−1, 0−1.3 mmol As L−1, and 0−1.9 mmol Cr L−1, in NaNO3; V, As, or Cr were determined by ICP-mass spectrometry in the equilibrium solution. After sorption, the soil samples were equilibrated with 0.02 M NaNO3 to study desorption. The isotherms were adjusted to mathematical models. After desorption with NaNO3, desorption experiments were carried out with a 1 mM phosphate. The sorption of vanadate and arsenate was greater than 90% of the amount added, while the chromate sorption was much lower (19–97%). The sorption by the Silandic Andosol is attributed to non-crystalline Fe and Al, while in the Vitric Andosol, crystalline iron species play a relevant role. The V and Cr sorption isotherms fitted to the Freundlich model, while the As sorption isotherms conformed to the Temkin model. For the highest concentrations of oxyanions in the equilibrating solution, the sorbed concentrations were 37–38 mmol V kg−1, 25 mmol As kg−1, and 7.2–8.8 mmol Cr kg−1. The desorption was low for V and As and high for Cr. The comparison of the sorption and desorption isotherms reveals a pronounced hysteresis for V in both andosols and for Cr in the Silandic Andosol. Phosphate induced almost no V desorption, moderate As desorption, and considerable Cr desorptionS

Aprendizaje léxico de una lengua extranjera mediante una metodología basada en la adquisición de contenidos

Este trabajo se propone refl exionar sobre una serie de aspectos relacionados con las últimas investigaciones centradas en el aprendizaje léxico en una lengua extranjera y analizar cómo todos estos aspectos pueden ser integrados mediante la aplicación de la metodología basada en contenidos con la fi nalidad de incrementar el repertorio léxico de los alumnos de forma natural, signifi cativa y duradera. The aim of this paper is to refocus attention on some aspects connected to the latest research on lexical learning in a foreign language and to analyze how all those basic and fundamental aspects can be integrated by using Content-based Instruction in order to improve our students’ lexicon in a natural, meaningful way

Novel Findings about Double-Loaded Curcumin-in-HPβcyclodextrin-in Liposomes: Effects on the Lipid Bilayer and Drug Release

In this study, the encapsulation of curcumin (Cur) in “drug-in-cyclodextrin-in-liposomes (DCL)” by following the double-loading technique (DL) was proposed, giving rise to DCL–DL. The aim was to analyze the effect of cyclodextrin (CD) on the physicochemical, stability, and drug-release properties of liposomes. After selecting didodecyldimethylammonium bromide (DDAB) as the cationic lipid, DCL–DL was formulated by adding 2-hydroxypropyl-α/β/γ-CD (HPβCD)–Cur complexes into the aqueous phase. A competitive effect of cholesterol (Cho) for the CD cavity was found, so cholesteryl hemisuccinate (Chems) was used. The optimal composition of the DCL–DL bilayer was obtained by applying Taguchi methodology and regression analysis. Vesicles showed a lower drug encapsulation efficiency compared to conventional liposomes (CL) and CL containing HPβCD in the aqueous phase. However, the presence of HPβCD significantly increased vesicle deformability and Cur antioxidant activity over time. In addition, drug release profiles showed a sustained release after an initial burst effect, fitting to the Korsmeyer-Peppas kinetic model. Moreover, a direct correlation between the area under the curve (AUC) of dissolution profiles and flexibility of liposomes was obtained. It can be concluded that these “drug-in-cyclodextrin-in-deformable” liposomes in the presence of HPβCD may be a promising carrier for increasing the entrapment efficiency and stability of Cur without compromising the integrity of the liposome bilayer

Mexican Women’s Parliament: Is it the way to reach gender equity

One of the most important decisions taken by the Mexican Assembly is to approve the annual budget of the country. Beijing Agreements in 1995 change the perception in the parliament which was merely for men. So, the few Mexican women in the parliament from the different parties organized the “Women’s Parliament” to reach gender equity not only in the different parties but in political, economic and social life. This year the women deputies and senators divided the country in five regions and had meetings outside of the central parliament office. at San Lázaro in Mexico City. These meetings tried to include the rich diversity demands from the different states, municipals and NGOs that participate during three weeks between February and March 2005. At the end of the regional meetings all the agreements were approved in the federal parliament. After Beijing Agreements + 10 not only the government but politicians are aware of improving empowerment women which has been a goal in a “machista” and traditional societ

Fucoxanthin-Containing Cream Prevents Epidermal Hyperplasia and UVB-Induced Skin Erythema in Mice

Microalgae represent a source of bio-active compounds such as carotenoids with potent anti-inflammatory and antioxidant properties. We aimed to investigate the effects of fucoxanthin (FX) in both in vitro and in vivo skin models. Firstly, its anti-inflammatory activity was evaluated in LPS-stimulated THP-1 macrophages and TNF-α-stimulated HaCaT keratinocytes, and its antioxidant activity in UVB-irradiated HaCaT cells. Next, in vitro and ex vivo permeation studies were developed to determine the most suitable formulation for in vivo FX topical application. Then, we evaluated the effects of a FX-containing cream on TPA-induced epidermal hyperplasia in mice, as well as on UVB-induced acute erythema in hairless mice. Our results confirmed the in vitro reduction of TNF-α, IL-6, ROS and LDH production. Since the permeation results showed that cream was the most favourable vehicle, FX-cream was elaborated. This formulation effectively ameliorated TPA-induced hyperplasia, by reducing skin edema, epidermal thickness, MPO activity and COX-2 expression. Moreover, FX-cream reduced UVB-induced erythema through down-regulation of COX-2 and iNOS as well as up-regulation of HO-1 protein via Nrf-2 pathway. In conclusion, FX, administered in a topical formulation, could be a novel natural adjuvant for preventing exacerbations associated with skin inflammatory pathologies as well as protecting skin against UV radiation

Análisis del grado de degradación en diferentes agregados pétreos utilizados como materiales granulares de estructuras de pavimento en Bogotá

Trabajo de investigaciónSe analizó propiedades mecánicas como tenacidad y desgaste de materiales seleccionado en dos (2) canteras, ubicadas en la sabana de Bogotá y una (1) localizadas en el municipio de Chaparral, departamento del Tolima, mediante el ensayo de “DEGRADACIÓN DE LOS AGREGADOS PÉTREOS A CAUSA DE LA COMPACTACIÓN POR IMPACTOS, INV E – 243 – 13” y el ensayo “RESISTENCIA AL DESGASTE DE LOS AGREGADOS DE TAMAÑOS MENORES DE 37.5MM (1½”) POR MEDIO DE LA MÁQUINA DE LOS ÁNGELES INV E – 218 – 13” que se encuentra en el Manual de Normas de Ensayos de Materiales para Carretera del INVIAS en su versión 2013.INTRODUCCIÓN 1 GENERALIDADES DEL TRABAJO DE GRADO 2 MARCOS DE REFERENCIA 3 METODOLOGÍA 4 ANÁLISIS DE RESULTADOS 5 CONCLUSIONES Y RECOMENDACIONES 6 BIBLIOGRAFÍA ANEXOSEspecializaciónEspecialista en Ingeniería de Pavimento

El efecto del feedback y de la instrucción explícita de las convenciones del discurso académico sobre la producción escrita en inglés de estudiantes universitarios

Memoria ID-0025. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2014-2015

El juego como expresión desde la diversidad cultural.

Partiendo de la importancia de la diversidad cultural que surge en el juego en Educación Primaria, se ha realizado este proyecto de investigación donde se pretende visualizar el valor del juego como aportación cultural, y comprobar si existe transmisión de diversidad cultural a través de juegos culturales en el entorno escolar. Para ello, se ha realizado una primera toma de contacto con la fundamentación del trabajo, es decir, la base de este producto, teniendo en cuenta diversos términos que engloban a la cultura como son: la multiculturalidad, la interculturalidad; y su punto de vista desde el ámbito educativo. Dentro de esto, se incluyen las diferentes visiones del juego y una clasificación de su tipología que se ha realizado en base a lo investigado. Se pretende, además, dar visibilidad a la importancia que presenta la cultura en el aula, y la manera de ponerla en práctica desde la actividad lúdica de los discentes en el aula y fuera de ella. Se muestra el planteamiento de que los juegos tradicionales son una de las fuentes más relevantes de transmisión cultural, ejemplificando y encuadrando algunos de los más reconocidos en el entorno educativo en una clasificación de tipología de juegos propia. La investigación está destinada a la adquisición de datos extraídos de un cuestionario teniendo en cuenta la experiencia de docentes de tres colegios donde se imparte Educación Primaria, y los conocimientos del alumnado de un centro educativo de Tegueste, a través de una ficha de recogida de datos; en relación con el uso y el planteamiento de la transferencia cultural desde el juego. Con ello se pretende recoger información relevante, y crear una discusión y conclusión sobre el tema de la transmisión cultural en el aula desde el juego.Starting from the importance of the cultural diversity that arises in the play in Primary Education, this research project has been carried out where it is intended to visualize the value of the play as a cultural contribution, and check if there is transmission of cultural diversity through cultural play in the school environment. To do this, a first contact has been made with the foundation of the work, that is, the basis of this product, taking into account various terms that encompass culture such as: multiculturalism, interculturality; and their point of view from the educational field. Within this, the different views of the play are included and a classification of its typology that has been made based on what has been investigated. It is also intended to give visibility to the importance of culture in the classroom, and the way to put it into practice from the playful activity of students in the classroom and outside of it. The statement that traditional plays are one of the most relevant sources of cultural transmission is shown, exemplifying and framing some of the most recognized in the educational environment in a classification of their own play typology. The research is aimed at acquiring data extracted from a questionnaire, taking into account the experience of teachers from three schools where Primary Education is taught, and the knowledge of students from an educational center in Tegueste, through a data collection sheet. ; in relation to the use and approach of cultural transfer from the play. This is intended to collect relevant information, and create a discussion and conclusion on the subject of cultural transmission in the classroom from the play