Influence of additives on the charactaristics of stone matrix asphalt

The increase in traffic growth and maintenance expenditures demands the urgent need for building better, long-lasting, and more efficient roads preventing or minimizing bituminous pavement distresses. Many of the principal distresses in pavements initiate or increase in severity due to the presence of water. In Kerala highways, where traditional dense graded mixtures are used for the surface courses, major distress is due to moisture induced damages. The Stone Matrix Asphalt (SMA) mixtures provide a durable surface course. Proven field performance of test track at Delhi recommends Stone Matrix Asphalt as a right choice to sustain severe climatic and heavy traffic conditions. But the concept of SMA in India is not so popularized and its application is very limited mainly due to the lack of proper specifications. This research is an attempt to study the influence of additives on the characteristics of SMA mixtures and to propose an ideal surface course for the pavements. The additives used for this investigation are coir, sisal, banana fibres (natural fibres), waste plastics (waste material) and polypropylene (polymer). A preliminary investigation is conducted to characterize the materials used in this study. Marshall test is conducted for optimizing the SMA mixtures (Control mixture-without additives and Stabilized mixtures with additives). Indirect tensile strength tests, compression strength tests, triaxial strength tests and drain down sensitivity tests are conducted to study the engineering properties of stabilized mixtures. The comparison of the performance of all stabilized mixtures with the control mixture and among themselves are carried out. A statistical analysis (SPSS package Ver.16) is performed to establish the findings of this study

Immunostimulatory effect of a marine yeast Candida sake S165 in Fenneropenaeus indicus

The efficacy of a marine yeast Candida sake as source of immunostimulant to Indian white shrimp Fenneropenaeus indicus was estimated. Biomass of C. sake was prepared using malt extract agar and incorporated at graded levels into a standard diet to prepare yeast diets of varying biomass concentrations (1%, 10% and 20%). F. indicus were fed on these diets for a period of 28 days and challenged orally with white spot syndrome virus (WSSV) and immune parameters such as total haemocyte count, phenoloxidase and nitroblue tetrazolium reduction (NBT) were determined. Ten per cent C. sake in the diet was found to support an optimum immune response in the animals in general and their enhancement could be observed on the second and third day following challenge with the virus. The study has demonstrated that marine yeast C. sake at 10% in diet (w/w) may be used as an effective source of immunostimulants in F. indicus

Influence Of Additives On The Drain Down Characteristics Of Stone Matrix Asphalt Mixtures

In Kerala highways, where traditional dense graded mixtures are used for the surface courses, major distress is due to moisture induced damages. Development of stabilized Stone Matrix Asphalt (SMA) mixtures for improved pavement performance has been the focus of research all over the world for the past few decades. Many successful attempts are made to stabilize SMA mixtures with synthetic fibres and polymers. India, being an agricultural economy produces fairly huge quantity of natural fibres such as coconut, sisal, banana, sugar cane, jute etc.. Now- a -days the disposal of waste plastics is a major concern for an eco- friendly sustainable environment. This paper focuses on the influence of additives like coir, sisal, banana fibres (natural fibres), waste plastics (waste material) and polypropylene (polymer) on the drain down characteristics of SMA mixtures. A preliminary investigation is conducted to characterize the materials used in this study. Drain down sensitivity tests are conducted to study the bleeding phenomena and drain down of SMA mixtures. Based on the drain down characteristics of the various stabilized mixtures it is inferred that the optimum fibre content is 0.3% by weight of mixture for all fibre mixtures irrespective of the type of fibre. For waste plastics and polypropylene stabilized SMA mixtures, the optimum additive contents are respectively 7% and 5% by weight of mixture. Due to the absorptive nature of fibres, fibre stabilizers are found to be more effective in reducing the drain down of the SMA mixture. The drain values for the waste plastics mix is within the required specification range. The coir fibre additive is the best among the fibres investigated. Sisal and banana fibre mixtures showed almost the same characteristics on stabilization.

Methodische Grundlagen zur Bewahrung und Wiederherstellung großräumig funktionsfähiger ökologischer Beziehungen in der räumlichen Umweltplanung

Mit der Verwirklichung ,Ökologischer Netzwerke‘ werden Hoffnungen zum Stopp des Verlustes der biologischen Vielfalt verknüpft. Sowohl auf gesamteuropäischer Ebene (Pan-European Ecological Network - PEEN) als auch in den einzelnen Staaten entstehen Pläne zum Aufbau von Verbundsystemen. Im föderalen Deutschland werden kleinmaßstäbliche Biotopverbundplanungen auf Landesebene aufgestellt; zum nationalen Biotopverbund bestehen erste Konzepte. Die vorliegende Arbeit ist auf diese überörtlichen, strategisch vorbereitenden Planungsebenen ausgerichtet. Ziele des Verbunds sind der Erhalt von Populationen insbesondere der gefährdeten Arten sowie die Ermöglichung von Ausbreitung und Wanderung. Aufgrund fehlender Datengrundlagen zu den Arten und Populationen ist es nicht ohne weiteres möglich, die Konzepte und Modelle der Populationsökologie in die überörtlichen Planungsebenen zu übertragen. Gemäß der o.g. Zielstellungen sollte sich aber die Planung von Verbundsystemen an den Ansprüchen der auf Verbund angewiesenen Arten orientieren. Ziel der Arbeit war die Entwicklung einer praktikablen GIS-gestützten Planungshilfe zur größtmöglichen Integration ökologischen Wissens unter der Bedingung eingeschränkter Informationsverfügbarkeit. Als Grundlagen dazu werden in Übersichtsform zunächst die globalen, europäisch-internationalen und nationalen Rahmenbedingungen und Anforderungen bezüglich des Aufbaus von Verbundsystemen zusammengestellt. Hier sind die Strategien zum PEEN hervorzuheben, die eine Integration ökologischer Inhalte insbesondere durch die Berücksichtigung räumlich-funktionaler Beziehungen fordern. Eine umfassende Analyse der landesweiten Biotopverbundplanungen der BRD zeigte die teilweise erheblichen Unterschiede zwischen den Länderplanungen auf, die es aktuell nicht ermöglichen, ein schlüssiges nationales Konzept zusammenzufügen. Nicht alle Länder haben landesweite Biotopverbundplanungen und Landeskonzepte, bei denen dem geplanten Verbund die Ansprüche von Arten zugrunde gelegt werden, gibt es nur ansatzweise. Weiterhin wurde eine zielgerichtete Eignungsprüfung bestehender GIS-basierter Modelle und Konzepte zum Verbund unter Berücksichtigung der regelmäßig in Deutschland verfügbaren Datengrundlagen durchgeführt. Da keine integrativen regelorientierten Ansätze vorhanden waren, wurde der vektorbasierte Algorithmus HABITAT-NET entwickelt. Er arbeitet mit ,Anspruchstypen‘ hinsichtlich des Habitatverbunds, die stellvertretend für unterschiedliche ökologische Gruppen von (Ziel-) Arten mit terrestrischer Ausbreitung stehen. Kombiniert wird die Fähigkeit zur Ausbreitung mit einer Grobtypisierung der Biotopbindung. Die wichtigsten Grundlagendaten bilden die jeweiligen (potenziellen) Habitate von Arten eines Anspruchstyps sowie die umgebende Landnutzung. Bei der Bildung von ,Lebensraumnetzwerken‘ (Teil I) werden gestufte ,Funktions- und Verbindungsräume‘ generiert, die zu einem räumlichen System verknüpft sind. Anschließend kann die aktuelle Zerschneidung der Netzwerke durch Verkehrstrassen aufgezeigt werden, um darauf aufbauend prioritäre Abschnitte zur Wiedervernetzung zu ermitteln (Teil II). Begleitend wird das Konzept der unzerschnittenen Funktionsräume (UFR) entworfen, mit dem die Indikation von Habitatzerschneidung auf Landschaftsebene möglich ist. Diskutiert werden schließlich die Eignung der Ergebnisse als kleinmaßstäblicher Zielrahmen, Tests zur Validierung, Vergleiche mit Verbundplanungen und verschiedene Setzungen im GIS-Algorithmus. Erläuterungen zu den Einsatzmöglichkeiten erfolgen beispielsweise für die Bereiche Biotopverbund- und Landschaftsplanung, Raumordnung, Strategische Umweltprüfung, Verkehrswegeplanung, Unterstützung des Konzeptes der Lebensraumkorridore, Kohärenz im Schutzgebietssystem NATURA 2000 und Aufbau von Umweltinformationssystemen. Schließlich wird ein Rück- und Ausblick mit der Formulierung des weiteren Forschungsbedarfs verknüpft.

Strained Silicon on Silicon by Wafer Bonding and Layer Transfer from Relaxed SiGe Buffer

We report the creation of strained silicon on silicon (SSOS) substrate technology. The method uses a relaxed SiGe buffer as a template for inducing tensile strain in a Si layer, which is then bonded to another Si handle wafer. The original Si wafer and the relaxed SiGe buffer are subsequently removed, thereby transferring a strained-Si layer directly to Si substrate without intermediate SiGe or oxide layers. Complete removal of Ge from the structure was confirmed by cross-sectional transmission electron microscopy as well as secondary ion mass spectrometry. A plan-view transmission electron microscopy study of the strained-Si/Si interface reveals that the lattice-mismatch between the layers is accommodated by an orthogonal array of edge dislocations. This misfit dislocation array, which forms upon bonding, is geometrically necessary and has an average spacing of approximately 40nm, in excellent agreement with established dislocation theory. To our knowledge, this is the first study of a chemically homogeneous, yet lattice-mismatched, interface.

Factores determinantes del margen entre la deuda corporativa y la deuda pública en Colombia

Este trabajo hace una estimación explicita de los factores en los cuales está compuesto el margen corporativo, entendido este como la diferencia entre la tasa spot de deuda pública y la tasa spot de deuda corporativa con calificación AAA y AA. La metodología implementada, es la propuesta por Elton et al (2001), y de esta manera se establece el margen corporativo como la suma de tres factores: factor por riesgo de emisor, factor por costos de emisión y factor por riesgo sistémico. La muestra analizada contiene los datos diarios de negociación observados en el Mercado Electrónico Colombiano (MEC) desde enero de 2005 hasta noviembre de 2009, las probabilidades de incumplimiento son estimadas a partir de las matrices de transición calculadas por las dos principales calificadoras de valores del mercado colombiano.

Resultados en reducción abierta de cadera por via interna: necrosis avascular y concordancia interobservador

Introducción: la luxación típica de la cadera es una patología con alta incidencia, de ahí la necesidad de métodos efectivos para lograr una reducción de esta. Han surgido varios métodos de reducción, uno de estos métodos es la reducción abierta por vía interna. Metodología Estudió descriptivo retrospectivo, incluyo los casos operados de reducción abierta por vía interna en el Instituto de Ortopedia Infantil Roosevelt y Clínica Jorge Piñeros Corpas por uno de los tutores, desde enero de 2006 hasta junio de 2011, valorando estas caderas según los criterios de Salter de necrosis avascular (NAV), con un seguimiento mínimo de 18 meses. Se evaluó la concordancia interobservador para la clasificación de Salter en tres ortopedistas infantiles. Resultados Se evaluaron 20 caderas en 16 pacientes a los que se realizo reducción abierta de luxación típica de cadera por vía interna. El 40 % de las caderas presentaron NAV, el 75% de estas caderas presentan NAV tipo I según la clasificación de Kalamchi. El índice Kappa para la clasificación de Salter en tres ortopedistas infantiles fue 0.6. Discusión El abordaje por vía interna para la reducción de luxación de cadera típica en niños menores de 18 meses es una alternativa más para el manejo de estos pacientes, que puede producir NAV en la cadera, pero esta NAV es tipo I de Kalamchi en la mayoría de casos. La reproducibilidad de la radiografía para la evaluación de NAV, realizada por personas expertas es buena, medida con índice kappa de 0.6.

Planificación de la enseñanza del Inglés.

El propósito de este trabajo es doble. Mostrar las ventajas que supone iniciar el estudio de una lengua extranjera en el tercer grado, o incluso antes. Tratar un aspecto concreto de la planificación en su doble vertiente teórico-práctica. Este trabajo se estructura de la siguiente forma. Primera parte: caracterización inicial, el problema de una segunda lengua universal; la demanda actual del inglés como 'lingua franca'; FLES (lenguas extranjeras en la Enseñanza Primaria) en la Ley General de Educación; planificación de FLES: introducción. Naturaleza, fines e implicaciones; factores; alcance de este estudio: objetivos en la enseñanza de idiomas; la fijación de contenidos; el método. Segunda parte: el movimiento FLES, argumentos; edad óptima para iniciar el estudio de una segunda lengua; algunos experimentos FLES, resultados y actitudes; el Primary French Pilot Scheme; el programa FLES ideal; el nuevo profesor de EGB. Tercera parte: bases para la fijación de contenidos; factores de orden lingüístico: dificultades en el aprendizaje del inglés, características generales del inglés; otros factores, factores sociopolíticos, factores sociobiológicos; el proceso de fijación de contenidos lingüísticos; lingüística y enseñanza de idiomas. Cuarta parte: la elección del método. Quinta parte: relación de conocimientos relevantes que ha de adquirir el alumno de inglés de la primera etapa de EGB que siga el método 'V8-a graded course for Spanish Speaking Children'. La planificación de la enseñanza de las lenguas extranjeras es absolutamente necesaria si deseamos que sea eficaz. El factor económico es uno de los que más afectan al éxito o al fracaso de la planificación. Quizá el mayor obstáculo que encontramos en la planificación sea el profesorado mismo. Se hace necesario la creación de centros de formación del personal docente, donde los futuros profesores puedan seguir cursos durante, al menos, un año académico. Es preciso que el plan vaya precedido de la oportuna experimentación. El establecimiento de objetivos de un modo operacional, no cabe duda que contribuirá a la sistematización de la enseñanza de las lenguas extranjeras. Los ocho años, parece ser la más apropiada para comenzar el estudio de una segunda lengua. La capacidad para aprender idiomas no tiene, por lo común, nada que ver con la capacidad para aprender otras materias. Un ambiente familiar favorable, así como la colaboración del personal administrativo, se consideran también factores relevantes para la obtención de buenos resultados. El profesor de EGB, es, en potencia, la persona más idónea para enseñar una segunda lengua en la escuela. En la fijación de contenidos hay que tener en cuenta factores de tipo lingüístico, sociológico y psicológico. El análisis diferencial de la lengua materna y la extranjera se considera presupuesto esencial en la preparación de materiales didácticos. Se consideran requisitos básicos que deben concurrir en todo metodo: una graduación, una presentación y una selección. El método V8-A reune los requisitos básicos exigidos.

Attitude in students of Health Sciences toward scientific knowledge

Educating health professionals implies the challenge of creating and developing an inquiring mind, ready to be in a state of permanent questioning. For this purpose, it is fundamental to generate a positive attitude toward the generation of knowledge and science. Objective: to determine the attitude toward science and the scientific method in undergraduate students of health sciences. Materials and methods: a cross-sectional study was made by applying a self-administered survey, excluding those who were transferred from other universities and repeated. The attitude toward science and the scientific method were valued using the scale validated and published by Hren, which contains three domains: value of scientific knowledge, value of scientific methodology, and value of science for health professions. Results: 362 students were included, 86,6% of them graded the attitude toward scientific knowledge above 135 points, neutral scale value. Similar scores were registered in the domains value of scientific knowlede for the human dimension of the students and value of science for health professions. 91,4% of the students graded the value of scientific methodology below 48 points. Conclusions: the favorable attitude of the students can be explained by the contact that they have with the scientific method since the beginning of their studies and its concordance with the evolution of science. The domain value of scientific methodology obtained the lowest grade on the part of the students, which could be related to the lack of knowledge about scientific methodology.

Medical Student’s Use of Time During Clinical Clerkships and the Credits Based System

Introduction: Comprehensive undergraduate education in clinical sciences is grounded on activities developed during clerkships. To implement the credits system we must know how these experiences take place. Objectives: to describe how students spend time in clerkships, how they assess the educative value of activities and the enjoyment it provides. Method: We distributed a form to a random clustered sample of a 100 students coursing clinical sciences, designed to record the time spent, and to assess the educative value and the grade of enjoyment of the activities in clerkship during a week. Data were registered and analyzed on Excel® 98 and SPSS. Results: mean time spent by students in clerkship activities on a day were 10.8 hours. Of those, 7.3 hours (69%) were spent in formal education activities. Patient care activities with teachers occupied the major proportion of time (15.4%). Of the teaching and learning activities in a week, 28 hours (56%) were spent in patient care activities and 22.4 hours (44.5%) were used in independent academic work. The time spent in teaching and learning activities correspond to 19 credits of a semester of 18 weeks. The activities assessed as having the major educational value were homework activities (4.6) and formal education activities (4.5). The graded as most enjoyable were extracurricular activities, formal educational activities and independent academic work. Conclusion: our students spend more time in activities with patients than the reported in literature. The attending workload of our students is greater than the one reported in similar studies.

Factores determinantes del margen entre la deuda corporativa y la deuda pública en Colombia

The paper makes an assessment of the factors behind corporatemargin. Corporate margin is defined as the difference between the public debt spot rate and the corporative debt spot rate graded AAA and AA. Following Elton et al (2001), in corporate margin is defined as the sum of three factors:issuer default risk, issuance costs and systemic risk. The data used contains daily trading data from the Colombian Electronic Market (MEC) since January 2005 to November 2009. The default probabilities are estimated from atransition matrix calculated by the two main risk rating agencies within the Colombian market.

Influência das estratégias de avaliação contínua no rendimento escolar dos alunos

A avaliação contínua é um importante instrumento à disposição do professor. O presente trabalho estuda a medida em que um conjunto de conteúdos ministrados no 10º ano do ensino secundário, acompanhados de procedimentos baseados na avaliação contínua, pode contribuir para melhorar o desempenho e a aprendizagem relativamente a quatro elementos químicos da tabela periódica, nomeadamente o oxigénio, o hidrogénio, o carbono e o azoto. O trabalho será realizado em três turmas do ensino secundário. Os conteúdos programáticos relativos à “Tabela periódica-organização dos elementos químicos” a desenvolver nas três turmas serão os mesmos, mas ministrados por duas docentes distintas. Em duas das turmas, e durante quatro aulas, serão elaborados pequenos testes no início de cada aula sobre a matéria lecionada na aula anterior, que serão recolhidos e classificados pela docente por forma a averiguar uma esperada evolução. Nestas turmas as aprendizagens relativas a estes testes serão avaliadas de forma contínua. Na outra turma, turma de controlo, o programa será tratado da forma tradicional. No final proceder-se-á ao tratamento dos dados recolhidos e à elaboração das conclusões e de possíveis recomendações.

A collocation method for high frequency scattering by convex polygons

We consider the problem of scattering of a time-harmonic acoustic incident plane wave by a sound soft convex polygon. For standard boundary or finite element methods, with a piecewise polynomial approximation space, the computational cost required to achieve a prescribed level of accuracy grows linearly with respect to the frequency of the incident wave. Recently Chandler–Wilde and Langdon proposed a novel Galerkin boundary element method for this problem for which, by incorporating the products of plane wave basis functions with piecewise polynomials supported on a graded mesh into the approximation space, they were able to demonstrate that the number of degrees of freedom required to achieve a prescribed level of accuracy grows only logarithmically with respect to the frequency. Here we propose a related collocation method, using the same approximation space, for which we demonstrate via numerical experiments a convergence rate identical to that achieved with the Galerkin scheme, but with a substantially reduced computational cost.

A Galerkin boundary element method for high frequency scattering by convex polygons

In this paper we consider the problem of time-harmonic acoustic scattering in two dimensions by convex polygons. Standard boundary or finite element methods for acoustic scattering problems have a computational cost that grows at least linearly as a function of the frequency of the incident wave. Here we present a novel Galerkin boundary element method, which uses an approximation space consisting of the products of plane waves with piecewise polynomials supported on a graded mesh, with smaller elements closer to the corners of the polygon. We prove that the best approximation from the approximation space requires a number of degrees of freedom to achieve a prescribed level of accuracy that grows only logarithmically as a function of the frequency. Numerical results demonstrate the same logarithmic dependence on the frequency for the Galerkin method solution. Our boundary element method is a discretization of a well-known second kind combined-layer-potential integral equation. We provide a proof that this equation and its adjoint are well-posed and equivalent to the boundary value problem in a Sobolev space setting for general Lipschitz domains.

Annual textural banding in Holocene estuarine silts, Severn Estuary Levels (SW Britain): patterns, cause and implications

A high-resolution textural study has been made of laminated and banded estuarine silts exposed intertidally at representative localities and horizons in the Holocene deposits of the Severn Estuary Levels. The laminae, on a submillimetre to millimetre scale, are sharp-based, graded couplets formed of a lower silty part overlain by a finer-textured clayey element. The centimetre- to decimetre-scale banding is formed of laminae in alternating, gradually intergrading sets of relatively coarse and relative fine-grained examples. At outcrop in the field, the banding is recognizable because the coarse sets prove to be recessive to varying degrees under the influence of weathering and current action. Independent evidence at two localities points toward an annual origin for the banding; at a third it arose during part of what appears to have been a relatively short period. Quantified physical arguments suggest that the textural banding is a response of suspended fine sediment to marked seasonal changes in sea temperature and windiness. The banded silts occur in four distinct stratigraphical contexts and record high deposition rates (order 0.01-0.1 m/yr). Because physical factors determine their textures, the silts potentially afford insights in all contexts into aspects of changing Holocene climatic conditions. In one context, the thickness of the bands points to high (order 0.01-0.1 m/yr) but comparatively short-lived (order 10s-100s yrs) rates of relative water-level rise. In the others, however, the banding has no implications for sea-level behaviour, and simply records gross environmental disequilibrium, for example, the recovery of mudflats/marshes after an erosional episode. Similarly, because on account of their rapid accumulation the banded silts preserve animal and human tracks and trackways especially well, they provide an archive of animal and human behaviour in the area during the Holocene.