bluuebunny/crossref_metadata_2025 huggingface dataset:
Concentración por flotación de menas de oro-cobre con bajas recuperaciones de arsénico
Authors: Chacón L. , Ruiz F. , Zapico R.
Published: December 2010

El objetivo del presente trabajo es definir los reactivos y las condiciones apropiadas para obtener concentrados con alta ley de cobre y baja recuperación de arsénico, a partir de muestras de una mezcla con 80 % en peso de una mena de oro, cobre y bismuto, y 20 % en peso de otra mena rica en oro y cobre, pero con alta ley de arsénico, provenientes de los yacimientos El Valle y Carlés, ubicados en Asturias-España, y procesados en una planta de concentración. La presencia de arsénico en el concentrado flotado es penalizada por sus compradores. La principal conclusión del trabajo es que un ditiofosfato como único reactivo colector es el que logra alcanzar el objetivo planteado, lo que se comprobó con pruebas en la planta de concentración.
Tecnología romana utilizada en la fabricación de una esquila
Authors: Gómez de Salazar J. M. , Barrena M. I. , Soria A.
Published: December 2010

A principios de los años 70 fueron excavados los restos arqueológicos de una villa tardorromana en la provincia de Palencia. Es conocida como La Olmeda y tiene como mayor atractivo sus mosaicos y los numerosos bienes encontrados. Una de las piezas estudiadas es la denominada esquila o campano de ganado. Se trata de un objeto constituido por hierro y bronce, en su sección hueca y únicamente por hierro en el asa y el badajo. Los estudios de caracterización química, microestructural y de propiedades mecánicas (dureza) han permitido establecer la tecnología utilizada en la fabricación de esta esquila. Este tipo de estudios arqueometalúrgicos permitirán aproximarnos al conocimiento de los procesos tecnológicos llevados a cabo en época romana, en la provincia de Palencia.
Generación de capas de conversión con elementos de tierras raras sobre acero galvanizado
Authors: Arenas M. A. , Damborenea J. J.
Published: December 2010

En el presente trabajo, se desarrollan capas de conversión de cerio sobre un acero galvanizado comercial, proponiéndose un mecanismo de formación de las mismas. Las condiciones óptimas de generación de la capa se consiguieron empleando una disolución de 10.000 ppm de CeCl3·7H2O + 0,3 % vol. de H2O2 ajustando el pH a 1,3. A su vez, para mejorar la adherencia y reducir el tiempo de tratamiento se realizó, durante los 10 min del tratamiento, una activación potenciostática a -100 mV respecto al potencial de corrosión, manteniéndose la temperatura a 43 °C. El estudio del corte transversal de las muestras mediante microscopía electrónica de barrido reveló que las capas de cerio poseen un espesor no uniforme de 1-2 μm. Los resultados electroquímicos indicaron que las capas de cerio generadas ofrecían porcentajes de inhibición del orden del 94 % en cloruro sódico. Un posible mecanismo de formación de la capa de conversión sería que los iones de cerio (III) en solución se oxidan a Ce (IV) por la adición de peróxido de hidrógeno, para precipitar, posteriormente, en forma de óxido de cerio (IV). El potencial catódico aplicado durante la generación de la misma podría originar un proceso de electroreducción de cerio (IV) a cerio (III) en la película de óxido. Por tanto, la capa estaría mayoritariamente compuesta por Ce (III) encontrándose en menor proporción la presencia de Ce (IV) en la misma.
Reducción de óxidos de cromo contenidos en las escorias
Authors: Gutiérrez-Paredes J. , Romero-Serrano A. , Hernández M. A. , Chávez-Alcalá F. , Zeifert B.
Published: December 2010

En el presente trabajo se realiza un estudio teórico y experimental para determinar el efecto de la basicidad de la escoria y la cantidad de agentes reductores sobre la reducción de óxidos de cromo contenidos en la escoria, la cual está en contacto con acero líquido a 1.600 °C. La escoria se prepara con los reactivos CaO, MgO, SiO2, CaF2 y ferroaleaciones (Fe-Si y Fe-Si-Mg). Los contenidos de CaF2 y MgO en la escoria son de 10 %, cada uno, y el de Cr2O3 es 25 %. La cantidad de la ferroaleación varía de 12,5 a 50 g por cada 100 g de escoria. La relación (CaO+MgO)/SiO2 tiene los valores de 1 y 2. Se determina la eficiencia de recuperación de cromo empleando los dos tipos de ferroaleaciones. Se realizaron cálculos para determinar el efecto teórico de la temperatura, la basicidad de la escoria, (CaO+MgO)/SiO2, y la cantidad de agentes reductores sobre la reducción de los óxidos de cromo. El sistema de cómputo FACT (Instalación para el Análisis de Termodinámica Química) se empleó para determinar el equilibrio entre la escoria y el acero líquido.
Resistencia a la corrosión y desgaste de recubrinnientos deTiN obtenidos por PVD
Authors: Conde A. , Navas C. , Damborenea J. J.
Published: December 2010

Los tratamientos de endurecimiento superficial de aleaciones metálicas se utilizan para lograr capas de muy elevada dureza, resistencia a la corrosión y desgaste. En este trabajo, se estudia el comportamiento de recubrimientos de TiN obtenidos mediante PVD sobre aceros de herramientas. Las capas obtenidas se caracterizan mediante microscopía electrónica de barrido, difracción de rayos X y XPS. Se analiza el comportamiento frente a la corrosión de las capas protectoras, así como la influencia del substrato en su comportamiento en soluciones de NaCl. Finalmente, se realizan ensayos de desgaste por deslizamiento en seco mediante la técnica de pin-on-disk, comprobándose la mayor resistencia de estas capas.
Modelización global del proceso de colada continua
Authors: Barco J. , Palacios J. , Ojeda C. , Ojanguren M.
Published: December 2010

En el proceso de colada continua contribuyen complicados fenómenos físicos con un marcado efecto en la calidad final del producto y en la productividad del proceso. Además, los distintos fenómenos físicos no aparecen de forma aislada, sino que interactúan unos con otros de manera acoplada, afectando a la calidad del semiproducto. El correcto diseño y ajuste es, por lo tanto, una tarea que requiere un gran conocimiento tanto de los distintos fenómenos que intervienen como de sus interacciones. En este trabajo se presenta un novedoso método de simulación que resuelve el proceso en su conjunto, siendo las variables del proceso las únicas condiciones de contorno. Mediante la utilización conjunta de herramientas comerciales (FLUENT y ABAQUS) y una serie de modelos de desarrollo propio se resuelven las interacciones entre los distintos fenómenos.
Mejora en la producción de recubrimientos de NiAl obtenidos por síntesis autopropagada a alta temperatura mediante energía solar concentrada
Authors: Sierra C. , Michie E. , Vázquez A. J.
Published: December 2010

Se presenta un procedimiento para la obtención de recubrimientos de NiAl sobre acero, de forma rápida, barata y limpia desde el punto de vista medioambiental. Todas estas ventajas son posibles mediante el empleo combinado de la Energía Solar Concentrada (CSE) y la Síntesis Autopropagada a Alta Temperatura (SHS) aplicada a la producción de intermetálicos. Las reacciones SHS permiten la obtención de NiAl en procesos de corta duración, prácticamente instantáneos, aprovechando la elevada exotermicidad de la propia reacción. El aporte energético inicial se realiza concentrando radiación solar con una lente de Fresnel. El objetivo del trabajo presentado era mejorar la adherencia del recubrimiento de NiAl al acero base; se comparan los resultados de los ensayos entre probetas con una capa intermedia de polvo de níquel y probetas con níquel electrodepositado.
Separación selectiva de hierro y cromo de las lejías agotadas del decapado de acero inoxidable
Authors: Gálvez J. L. , Dufour J. , Negro C. , López-Mateos F.
Published: December 2010

Los baños ácidos agotados del decapado de acero inoxidable son disoluciones muy complejas debido al alto contenido de metales y ácidos (HNO3 y HF), por lo que constituyen un grave problema medioambiental. Existen tratamientos comerciales para la recuperación del ácido (libre o complejado) que se basan en técnicas de retardo ácido, extracción con disolventes, evaporación o membranas. En estos procesos el contenido metálico es precipitado y tratado como un residuo. El grupo de investigación formado por los autores del presente trabajo ha desarrollado un procedimiento que permite el aprovechamiento de dichos metales mediante su recuperación selectiva con una técnica de precipitación modificada inducida por fluoruro libre. Se consigue la precipitación de hierro (Fe) y cromo (Cr) como pentafluoruros (pH 3-4,5) dejando el níquel en disolución. Posteriormente, los fluoruros complejos son hidrolizados con álcali dando lugar a hidróxidos de hierro y cromo, mientras que el fluoruro es redisuelto.
Vida, durante el mecanizado, del filo de herramientas de corte obtenidas mediante recubrimientos de c-BN+h-BN con diferentes estructuras
Authors: Kupczyk M. , Misiak W.
Published: December 2010

En este trabajo se describen los resultados experimentales referentes a la calidad funcional (durabilidad durante el mecanizado del acero) de recubrimientos delgados, de elevada dureza del filo de corte. Las diferencias en las propiedades de los recubrimientos se deben, principalmente, a la estructura del recubrimiento. No obstante, la estructura del recubrimiento está relacionada con los parámetros de la deposición. Recubrimientos de nitruro de boro de elevada dureza se depositaron sobre filos de corte insertados, fabricados con carburos cementados mediante el método de pulsos de plasma aplicando diferentes valores de voltaje de descarga. Las investigaciones comparativas de los mencionados recubrimientos han relacionado la vida del filo de la herramienta durante el mecanizado del material (acero nitrurado endurecido en aceite). En estas investigaciones se aplicaron capas interfaciales para aumentar la adherencia del recubrimiento.
Influencia del carbono y el cromo en el comportamiento tribológico de aleaciones férreas
Authors: García A. , Rico C. , Varela Á. , Naya S. , Losada R. , García L.
Published: December 2010

En este estudio se analiza la influencia, en las propiedades tribológicas, del contenido en carbono para distintas aleaciones férreas con similares contenidos en cromo, así como la influencia del cromo cuando el contenido en carbono es semejante. También, se analizó la influencia de estos elementos en propiedades como la dureza y en la microestructura de las aleaciones. Para el estudio tribológico se llevaron a cabo dos ensayos, el ensayo descrito en la norma ASTM G105: Standard Test Method for Conducting Wet Sand/Rubber Wheel Abrasion Test y ensayos de chorreo.
Intermetálicos: pasado, presente y futuro
Authors: Morris D. G. , Muñoz-Morris M. A.
Published: December 2010

Durante los últimos décadas ha habido un desarrollo de los intermetálicos, sobre todo por aplicaciones estructurales a alta temperatura en aplicaciones aeroespaciales, donde, por su rigidez alta, en combinación con una resistencia mecánica y ductilidad razonable, su buena estabilidad estructural y resistencia a la oxidación, han sido vistos como versiones avanzadas y mejoradas de las aleaciones metálicas como, por ejemplo, las superaleaciones a base de nitrógeno y las aleaciones de titanio. Se discute el desarrollo importante durante las últimas décadas, y también los nuevos desarrollos probables durante los próximos años. Se podrían ver los intermetálicos como versiones mejoradas de los cerámicos.
Evaluación del comportamiento frente a la corrosión de recubrimientos procesados con láser de alta potencia
Authors: Rodríguez G. P. , Checa M. , Damborenea J. J.
Published: December 2010

Los aceros inoxidables presentan altas resistencias a la corrosión pero cuando trabajan en determinados medios a elevadas temperaturas aparecen problemas de oxidación. Una solución a este problema consiste en aplicar recubrimientos utilizando láseres de alta potencia. Los recubrimientos objeto de estudio en este proyecto han sido procesados con un láser de CO2 a partir de polvos compuestos de NiCrAl y ZrO2/Y2O3. Se ha estudiado la influencia de las condiciones de procesado de los recubrimientos en la calidad de los cordones, microestructura obtenida, resistencia a la oxidación y resistencia a la corrosión electroquímica. Las condiciones de procesado estudiadas han sido la velocidad de desplazamiento del láser respecto de la muestra y el caudal de los polvos formadores del recubrimiento.
Aceros para embutido profundo: fabricación, caracterización, microestructura y texturas
Authors: Sipos K. , Martínez J. , Burgos N. , Pesenti H.
Published: December 2010

El conocimiento de las características de formabilidad de las chapas metálicas es de gran interés tecnológico para la industria del conformado de planchas de acero. En el presente trabajo se muestra cómo se evalúan las chapas en su aptitud a la embutición a través de variados parámetros de propiedades mecánicas, y cómo éstas se relacionan con su fabricación en la industria siderúrgica. Durante este proceso, el conocimiento de los fenómenos metalúrgicos en las distintas etapas permiten el correcto control de las texturas cristalográficas, las cuales, finalmente, permiten el desarrollo de buenos índices de anisotropía normal y planar. Se muestra, a través de ejemplos industriales, la relación entre los parámetros operativos y los resultados obtenidos, ilustrándose éstos no solo a través de valores de los índices de anisotropía sino que también a través de las texturas obtenidas. La caracterización del producto a través de las curvas de deformación límite permite a las empresas que producen piezas de diseños particulares evaluar sus diseños y la conveniencia o no del uso de diferentes tipos de aceros para su fabricación. Se muestra como ejemplo el caso de cubiertas de enceradoras.
La lengua del Carmen Campidoctoris
Authors: Escobar Ángel
Published: December 2010

Nuestra contribución se ocupa de la lengua del Carmen Campidoctoris, no tanto desde una perspectiva descriptiva como en su dimensión específicamente literaria, sobre todo en cuanto posible indicio de utilidad para intentar esclarecer la personalidad de su anónimo autor e, indirectamente, la cronología y procedencia del poema (cuya composición debe situarse, en nuestra opinión, hacia el tercer cuarto del siglo XII, y quizá en un ámbito navarro-riojano). Se extraen seguidamente algunas consecuencias de carácter general referentes a la edición de textos latinos medievales, aplicables, muy en particular, cuando éstos se atestiguan –como en el caso del Carmen– en un codex unicus.
El primer testimonio cristiano sobre la toma de Valencia (1098)
Authors: Martin Georges
Published: December 2010

La charte de la donation faite en 1098 par Rodrigue Diaz à Jérôme, évêque de Valence, nous permet de nous faire une idée de l’organisation de la seigneurie valencienne (au moins dans ses structures de tutelle), de ses relations avec la Castille et de l’imaginaire qui se forgea autour de Rodrigue pour interpréter son aventure et soutenir ses aspirations.
Gesta Roderici: El Cid en la historiografía latina medieval del siglo XII
Authors: PEÑA PÉREZ Francisco Javier
Published: December 2010

La memoria histórica de Rodrigo Díaz estuvo a punto de perderse tras la pérdida de Valencia a manos de los almorávides y el declive posterior del imperio levantado por éstos. Pero la llegada a la Península Ibérica de los almohades y su agresividad progresiva contra los cristianos del norte hispano desde medidos del siglo xii reavivó los recuerdos del pasado almorávide y de su verdugo más exitoso: el Cid Campeador, creando con ello las condiciones para que la memoria cidiana resurgiera de sus cenizas con renovado brío, aunque sensiblemente estilizada. Dadas las condiciones, los cronistas se ponen manos a la obra, allí donde los recuerdos del caballero castellano pudieron guardarse con más esmero: la corte Navarra, a finales del xii, y el monasterio de Cardeña, en el siglo siguiente.
Hilando un reinado. Alfonso VI y las mujeres
Authors: Martin Georges
Published: December 2010

Uno de los aspectos más llamativos de Alfonso VI como figura histórica es el papel que desempeñaron, tanto en su destino como en su gobierno, las mujeres. Entre una Urraca, su hermana, que protagonizó su restauración en el trono, y otra Urraca, su hija, que le sucedió en éste, están las siete esposas y concubinas, alguna de las cuales contribuyó a orientar su política, así como una nutrida prole femenina que decidió de diversos e importantes aspectos de su posteridad. Este círculo de mujeres forma como una rueca en la que se hiló una parte no desdeñable del reinado de Alfonso VI.
Los usos del pasado. Historia, derecho y narración en la Crónica de Pedro I y Enrique II de Pero López de Ayala y una colección de fazañas castellanas
Authors: SOLER BISTUE Maximiliano
Published: December 2010

El trabajo analiza los procedimientos discursivos mediante los cuales se legitima el discurso histórico y el discurso jurídico en la Castilla de mediados del siglo XIV en el marco de la contienda político-cultural entre la nobleza y el poder regio. Para el primer caso, se centra en algunos pasajes de la Crónica del Rey Don Pedro y del Rey Don Enrique de Pero López de Ayala; para el segundo, en ciertos pasajes del manuscrito 431 de la Biblioteca Nacional de Madrid, códice que reúne textos legislativos paradigmáticos del derecho señorial castellano. En ambos, tanto el discurso jurídico como el historiográfico explotan la riqueza y potencialidad semiótica de la estructura narrativa de los exempla y las fazañas. Se trata, en definitiva, de observar en detalle de qué modo particular se están articulando en Castilla y en el contexto de la crisis del siglo XIV, la historia, el derecho y la narración.
THE ORIGINS OF AGRISCIENCE: OR WHERE DID ALL THAT SCIENTIFIC AGRICULTURE COME FROM?
Authors: Hillison John
Published: December 2010

The Hatch Act was passed as part of the scientific revolution that occurred in agriculture during the late 1800s. What started as a need to have more accurate fertilizer analyses ended with a revolutionary federal act that started experiment stations. The preamble to the Act used the words agricultural science. Following passage o the Act agricultural education was defined as being primarily academic and having a strong scientific base. Higher education institutions emphasized a strong science content in teacher training curriculum. Secondary Congressional District agricultural schools also emphasized a great deal of science in their curricula. Federal leadership came from the United States Department of Agriculture with, among other things, scientific agricultural bulletins being regularly made available to agricultural education department. However, with passage of the Smith-Hughes Act in 1917 agricultural education joined with other areas and became vocational in nature. National leadership shifted to the Federal Board for Vocational Education. Currently the agricultural education profession is debating how much science should be included in its curriculum. The profession’s history has a great deal to say about the subject and should be examined closely.
TOWARD A SCIENTIFIC BASIS FOR THE CRAFT OF TEACHING
Authors: Buriak Philip , McNurlen Brian , Harper Joe G.
Published: December 2010

This study develops a hard systems model for learning that differs from traditional or intuitive models. Research in educational psychology and cognitive science provides the basis for the model. The paper also presents a traditional soft system view of the craft of teaching. Perception, memory, and concept formation are presented as the essential ingredients for effective learning. The systems models for learning and teaching are defined and contrasted, and instructional implications are discussed. Agricultural educators teach; they train prospective teachers, and they offer inservice to practicing teachers. This is education. These educators have historically spent the majority of their research and instructional time studying and teaching the craft of teaching. University professors, who may or may not have had any formal teacher training, practice the craft of teaching. This paper presents a review that moves toward a scientific basis for the craft of teaching.
Agricultural Education At A Distance: Attitudes And Perceptions Of Secondary Teachers
Authors: Miller Greg
Published: December 2010

As the variety and sophistication of educational technologies continues to grow, the need to know more about the incentives and obstacles to technology adoption becomes more important. The purpose of this study was to investigate the usefulness of an interactive communications network (ICN) for agricultural education at the secondary level. The ICN is a state-wide two-way full-motion fiber optics telecommunications system that connects students and teachers who are separated by distance and allows them to share in real-time video, data, and voice instruction. The primary objectives of the study were to: (1) describe obstacles that may inhibit use of the ICN as perceived by secondary agriculture teachers; (2) describe secondary agriculture teachers' attitude toward using the ICN for delivering agricultural instruction; and (3) describe relationships between teachers' attitude, perceived obstacles, and selected variables. Results indicate that teachers were most concerned about obstacles related to scheduling problems and difficulties associated with managing laboratory and SAE experiences. Data related to teacher attitudes indicate that teachers were undecided about using the ICN to teach agriculture. Recommendations included the development of planned experiences with ICN technology, the development of demonstrations for using the system, andfollow-up research to assess changes in attitude over time.
Block Scheduling's Impact On Instruction, FFA, And SAE In Agricultural Education
Authors: Morre Gary , Kirby Barbara , Becton Linda Kay
Published: December 2010

The purpose of this study was to examine the impact of block scheduling on teachers and agricultural education programs in North Carolina. Questionnaires were sent to the senior agricultural instructor in each department in the state. Responses were obtainedfrom 68 percent. Approximately 75% of the NC schools are on block scheduling. Teachers generally have a positive attitude toward block scheduling. Block scheduling has resulted in an substantial increase in the number of agriculture students while the number of students in the FFA has remained the same. Block scheduling has had little impact on the quality of the instruction a slight negative impact on SAE, and a substantial negative impact on the FFA program. A variety of instructional techniques are needed and each class period needs to be broken up into segments. The communications, the entire structure and operating procedures for the FFA may need to be re-examined.
Motivational Needs Of Students Enrolled In Agricultural Education Programs In Georgia
Authors: Turner Jeff , Herren Ray V.
Published: December 2010

The purpose of this study was to examine the motivational needs of students enrolled in agricultural education classes in Georgia. The study was based on McClellands motivational needs theory. The data determined that agricultural students were motivated by the need for achievement and that FFA members had a greater need for achievement, affiliation, and power than non FFA members. The study also determined that female agricultural education students had a higher need for affiliation and power than male students, and that African-American students had a higher need for achievement and power. Freshmen had a lower need for power than students in the upper grades. Caucasians students had a higher need for affiliation: students living on a farm and in a rural setting had a higher need for power than students living in an urban setting.
Benefits Of Supervised Agricultural Experience Programs: A Sythesis Of Research
Authors: Dyer James E. , Williams David L.
Published: December 2010

This article presents a synthesis of research on benefits of supervised agricultural experience (SAE) programs during a thirty-year period 1964-1993. A library search of selected sources was used to gather data for the study. Research in this are is primarily descriptive, detailing the benefits of SAEs. Research supports the belief that SAEs are regarded as beneficial to students, and that SAEs help make agricultural education vocational. Agricultural knowledge andpositive work attitudes are among the benefits students gain from SAEs. Research supports the concept that classroom/laboratory, SAEs, and FFA complement each other in the teaching and learning process. The research is state specific, fragmented, and lacks cohesiveness. Regional and national studies are needed on the benefits of SAEs to student learning; outcomes of SAEs; ways to effectively measure benefits from SAEs; optimal scope of SAEs; and building symbiotic relationships between classroom/laboratory instruction, FFA, and SAE to further enhance student learning.
OPPORTUNITIES AND OBSTACLES FOR DISTANCE EDUCATION IN AGRICULTURAL EDUCATION
Authors: Murphy Tim H. , Terry H. Robert
Published: December 2010

A nationwide study using delphi techniques was conducted to develop consensus and provide focus and direction for future research activities concerning the adoption of electronic communication, information, and imaging technologies for instructional use in agricultural education settings. A panel of 61 distance education experts were identified The four objectives were to identify the: I)positive effects of electronic technologies designed to facilitate communication, information gathering/retrieval, and imaging for instruction; 2) major obstacles that must be overcome in their adoption; 3) most promising technologies at the secondly level; 4) most promising technologies at the post-secondary level. Panelists suggested 21 ways these technologies improve instruction; responses clustered around: 1) increased availability of educational opportunities; 2) improved informational resources; 3) more effective instructional materials; 4)more convenient delivery methods.. Panelists achieved consensus on 13 obstacles, which clustered around: 1) time constraints; 2) lack of a formalized faculty reward system; 3) lack of technical support; 4) equipment costs; 5) inadequately designed facilities. There was little difference between technologies identified as being most promising for the secondary and post-secondary levels. In general, panelists identified technologies clustered around four systems areas: I) distributed information; 2) computer-based information; 3) computer-assisted telecommunications; 4) graphical image production and display.
INFLUENCES ON ADOLESCENT JOB CHOICE: IMPLICATIONS FOR TEACHING CAREER AWARENESS IN AGRICULTURAL EDUCATION
Authors: Conroy Carol A. , Scanlon Dennis C.
Published: December 2010

This study compared students choosing agriculture as a career to those choosing other occupations. Previous research conducted by Conro y (1996) identified predictors of occupational choice among rural youth . An examination of those predictors, comparing the two groups of students, revealed that there were few differences between students whether they chose agriculture as a career option or some other career. Differences did exist, however, based on gender and father’s occupation, a variable considered to be a proxy for socioeconomic status. Findings supported prior research which suggested that family interactions are keys to vocational identity development (Steinberg, 1989; Erikson, 1963, cited in Herr, 1972). Therefore, to be effective, career awareness and educational programs must not only provide factual information about careers, they must also provide activities to reduce stereotypes commonly held about certain occupations (Steinberg, 1989; Harter, 1990). Programs that do not do this may not achieve their goals of successfully recruiting students into agriculture.
THE EFFECTS OF WORLD WIDE WEB INSTRUCTION AND TRADITIONAL INSTRUCTION AND LEARNING STYLES ON ACHIEVEMENT AND CHANGES IN STUDENT ATTITUDES IN A TECHNICAL WRITING IN AN AGRICOMMUNICATION COURSE
Authors: Day Tina M. , Raven Matt R. , Newman Michael E.
Published: December 2010

The purpose of this experimental study was to determine the effects of types of instruction and learning styles in a three-credit hour, technical writing in an agricommunication course on their achievement and attitudes towards writing, learning about writing, computers and the Internet. The two methods of instruction were traditional instruction without a laboratory and World Wide Web instruction with a laboratory. Two applications questions on the midterm examination and the major class project were used to measure students’ achievement. To measure the attitudes of the students, a semantic differenctial instrument was developed. The Group Embedded Figures Test (GEFT) was used to determine preferred learning styles. Significant differences were found to exist between type of instruction for both achievement and attitudes. WWW-dependent instruction was significantly higher for group means on achievement. The WWW-dependent class also had a higher mean gain for attitude toward writing. No significant difference was found between learning style groups on achievement and attitudes. There was no significant interaction effect between type of instruction and learning style on achievement or attitudes.
A Quantitative Analysis Of Instructor-Student Verbal Interaction In A Two-Way Audio Two-Way Vidoe Distance Education Program
Authors: Murphy Tim H.
Published: December 2010

The purpose of this study was to establish a quantitative baseline analysis and description of the verbal interaction between instructors and students in simultaneous two-way audio and video distance education settings. Additionally, the nature of the interactions of students and instructors based upon their physical location in this distance learning environment was investigated The design was causalcomparative with data collected using observational methods, distinguished by a lack of random assignment of subjects and nonequivalent groups. The sample was purposefully drawn from classes taught over a videoconferencing network during the spring semester of 1995. The classroom observation instrument used was an expanded version of Johnson's (I986) Cognitive Interaction Analysis System. Descriptive statistics are reportedfor all IO categories in the CIAS. The levels of classroom interaction found in these settings were not fundamentally different than those found in traditional classroom settings described in the literature. Significantly different levels of both total and cognitive student talk were found The interaction between the instructor and the location of the student was significant in determining the total amount of student talk and the amount of cognitive student talk. Diff erences among instructors contributed to both amount and type of student talk at local and remote sites. Students at remote sites contributed significantly higher levels of non-cognitive student talk.
New particle formation events in semi-clean South African savannah
Authors: Vakkari V. , Laakso H. , Kulmala M. , Laaksonen A. , Mabaso D. , Molefe M. , Kgabi N. , Laakso L.
Published: December 2010

Abstract. This study is based on 18 months (20 July 2006–5 February 2008) of continuous measurements of aerosol particle size distributions, air ion size distributions, trace gas concentrations and basic meteorology in a semi-clean savannah environment in Republic of South Africa. New particle formation and growth was observed on 69% of the days and bursts of non-growing ions/sub-10 nm particles on additional 14% of the days. The new particle formation and growth rates were among the highest reported in the literature for continental boundary layer locations; median 10 nm formation rate was 2.2 cm−3s−1 and median 10–30 nm growth rate 8.9 nm h−1. The median 2 nm ion formation rate was 0.5 cm−3s−1 and the median ion growth rates were 6.2, 8.0 and 8.1 nm h−1 for size ranges 1.5–3 nm, 3–7 nm and 7–20 nm, respectively. Three different approaches were used to study the origin of the formation and growth rates: seasonal variation, air mass history analysis and estimated sulphuric acid contribution to the growth. The growth rates had a clear seasonal dependency with minimum during winter and maxima in spring and late summer and the air mass history analysis indicated the highest formation and growth rates to be associated with the area of highest VOC (Volatile Organic Compounds) emissions rather than the highest estimated sulphuric acid concentrations. The relative contribution of estimated sulphuric acid to the growth rate was decreasing with increasing particle size and could explain more than 20% of the observed growth rate only for the 1.5–3 nm size range. The implication is that the sulphuric acid alone is not enough to explain the growth, but the highest growth rates seem to originate in VOC emissions following from biological activity. The frequency of new particle formation, however, increased nearly monotonously with the estimated sulphuric acid reaching 100% at H2SO4 concentration of 4×107cm−3, which suggests the formation and growth to be independent of each other.
Influence of the variation in inflow to East Asia on surface ozone over Japan during 1996–2005
Authors: Chatani S. , Sudo K.
Published: December 2010

Abstract. Air quality simulation in which global and regional chemical transport models are coupled has been developed to investigate the influence of the variation in inflow to East Asia on the interannual variability and the long-term trend of surface ozone over Japan during 1996–2005. The simulation overestimates the concentration of surface ozone from summer to early winter. It is deduced that ozone formation around Northeast China is overestimated in the simulation. On the other hand, the simulation reproduces the interannual variability and the long-term trend of observed surface ozone over Japan well. Results of sensitivity experiments suggest that inflow to East Asia accounts for approximately 30% of the increasing trend of surface ozone, whereas it has much less influence on the interannual variability of observed surface ozone compared to meteorological processes within East Asia.
Retrieval of temperature and pressure using broadband solar occultation: SOFIE approach and results
Authors: Marshall B. T. , Deaver L. E. , Thompson R. E. , Gordley L. L. , McHugh M. J. , Hervig M. E. , Russell III J. M.
Published: December 2010

Abstract. Measurement of atmospheric temperature as a function of pressure, T(P), is key to understanding many atmospheric processes and a prerequisite for retrieving gas mixing ratios and other parameters from solar occultation measurements. This paper gives a brief overview of the solar occultation measurement technique followed by a detailed discussion of the mechanisms that make the measurement sensitive to temperature. Methods for retrieving T(P) using both broadband transmittance and refraction are discussed. Investigations using measurements of broadband transmittance in two CO2 absorption bands (the 4.3 and 2.7 μm bands) and refractive bending are then presented. These investigations include sensitivity studies, simulated retrieval studies, and examples from SOFIE.
Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization
Authors: Oschlies A. , Koeve W. , Rickels W. , Rehdanz K.
Published: December 2010

Abstract. Recent suggestions to slow down the increase in atmospheric carbon dioxide have included ocean fertilization by addition of the micronutrient iron to Southern Ocean surface waters, where a number of natural and artificial iron fertilization experiments have shown that low ambient iron concentrations limit phytoplankton growth. Using a coupled carbon-climate model with the marine biology's response to iron addition calibrated against data from natural iron fertilization experiments, we examine biogeochemical side effects of a hypothetical large-scale Southern Ocean Iron Fertilization (OIF) that need to be considered when attempting to account for possible OIF-induced carbon offsets. In agreement with earlier studies our model simulates an OIF-induced increase in local air-sea CO2 fluxes by about 73 GtC over a 100-year period, which amounts to about 48% of the OIF-induced increase in organic carbon export out of the fertilized area. Offsetting CO2 return fluxes outside the region and after stopping the fertilization at 1, 7, 10, 50, and 100 years are quantified for a typical accounting period of 100 years. For continuous Southern Ocean iron fertilization, the CO2 return flux outside the fertilized area cancels about 20% of the fertilization-induced CO2 air-sea flux within the fertilized area on a 100-yr timescale. This "leakage" effect has a radiative impact more than twice as large as the simulated enhancement of marine N2O emissions. Other side effects not yet discussed in terms of accounting schemes include a decrease in Southern Ocean oxygen levels and a simultaneous shrinking of tropical suboxic areas, and accelerated ocean acidification in the entire water column in the Southern Ocean at the expense of reduced globally-averaged surface-water acidification. A prudent approach to account for the OIF-induced carbon sequestration would account for global air-sea CO2 fluxes rather than for local fluxes into the fertilized area only. However, according to our model, this would underestimate the potential for offsetting CO2 emissions by about 20% on a 100 year accounting timescale. We suggest that a fair accounting scheme applicable to both terrestrial and marine carbon sequestration has to be based on emission offsets rather than on changes in individual carbon pools.
Vrancea slab earthquakes triggered by static stress transfer
Authors: Ganas A. , Grecu B. , Batsi E. , Radulian M.
Published: December 2010

Abstract. The purpose of this paper is to study the interaction of the Vrancea seismic activity (Romania) in space as result of Coulomb, static stress transfer during M=7+ events. In this area, three large events occurred in 1977, 1986 and 1990 at mid-lower, lithospheric depths and with similar focal mechanisms. Assuming elastic rheology for the deforming rocks it is suggested that frictional sliding on pre-existing fault produced the 1986 M=7.1 event (depth 131 km), that was possibly triggered by the 1977 M=7.4 event (depth 94 km). We calculated a static stress transfer of 0.52–0.78 bar to the hypocentre of the 1986 event. On the contrary, the occurrence of the 1990 event is uncertain: it is located inside the relaxed (shadow) zone of the combined 1977 and 1986 static stress field considering an azimuth for maximum compression of N307° E. It follows that, the 1990 earthquake most likely represents an unbroken patch (asperity) of the 1977 rupture plane that failed due to loading. However, if a different compression azimuth is assumed (N323° E) then the 1990 event was also possibly triggered by static stress transfer of the 1977 and 1986 events (combined). Our modeling is a first-order approximation of the kind of earthquake interaction we might expect at intermediate lithospheric depths (80–90 to 130–140 km). It is also suggested that static stress transfer may explain the clustering of Vrancea earthquakes in space by the rupturing of two (possibly three) NW-dipping major zones of weakness (faults) which accommodate the extension (vertical elongation) of the slab.
Effectiveness of the Homeopathic Preparation Zeel Compared with Carprofen in Dogs with Osteoarthritis
Authors: Neumann Stephan , Stolt Pelle , Braun Gabriele , Hellmann Klaus , Reinhart Erich
Published: December 2010

The authors compared the symptomatic effectiveness of a complex homeopathic preparation Zeel (1–3 tablets orally per day depending on body weight) to carprofen (4 mg/kg body weight) in dogs (n=68) aged >1 yr diagnosed with osteoarthritis in a multicenter, prospective, observational open-label cohort study in 12 German veterinary clinics. The active treatment period was 56 days. Symptomatic effectiveness, lameness, stiffness of movements, and pain on palpation were evaluated by treating veterinarians and owners. Clinical signs of osteoarthritis improved significantly (P<0.05) at all time points (days 1, 28, and 56) with both therapies. At the end of the treatment period, effectiveness was comparable in both groups. Both treatment regimens were well tolerated with only three treatment-related adverse events, all in the carprofen group.
Abdominal Aortic Aneurysm Associated with Systemic Fungal Infection in a German Shepherd Dog
Authors: Gershenson Ryan T. , Melidone Raffaele , Sutherland-Smith James , Rogers Catherine L.
Published: December 2010

A 2 yr old spayed female German shepherd presented with a chief complaint of acute onset paraparesis and weight loss. At presentation, the dog was pyrexic, nonambulatory, and had generalized muscle wasting. Neurolocalization was consistent with a thoracolumbar spinal cord lesion. An abdominal ultrasound was performed and revealed a focal dilation (4 cm) of the terminal aorta with evidence of blood stasis consistent with an aortic aneurysm. The dog was euthanized shortly after admission to the hospital and a post mortem examination was performed. Fungal organisms were identified in the aortic aneurysm as well as from the thoracic vertebrae, mesenteric lymph nodes, axillary lymph nodes, spleen, kidneys, liver, lungs, and heart. Although the morphology was consistent with Candida spp., immunohistochemistry and PCR could not definitively identify the causative organism. Mycotic aortic aneurysms are a rare finding in humans and have not been previously reported in the dog. To the authors’ knowledge, this is the first known report of an aortic aneurysm associated with systemic fungal infection in a dog.
Treatment of Three Cats with Hyperviscosity Syndrome and Congestive Heart Failure Using Plasmapheresis
Authors: Boyle Tonya E. , Holowaychuk Marie K. , Adams Allison K. , Marks Steven L.
Published: December 2010

Three cats were evaluated at a veterinary teaching hospital for congestive heart failure (CHF) secondary to hyperviscosity syndrome from plasma cell neoplasia. All cats had severe hyperproteinemia due to hyperglobulinemia. Multiple myeloma or plasma cell neoplasia was diagnosed based on cytopathology and post mortem examination. The cats presented with signs of CHF including acute collapse, tachypnea, increased respiratory effort, and pulmonary crackles. All cats had heart murmurs and echocardiographic signs consistent with hypertrophic cardiomyopathy. An enlarged left atrium was found in all cats and two of three cats also had spontaneous echocardiographic contrast. Plasmapheresis (centrifugal plasma exchange) was performed on all three cats by the removal of whole blood and the infusion of a balanced electrolyte solution while the whole blood was centrifuged and separated. The RBCs were then washed before being readministered to the patient. Plasmapheresis alleviated the clinical signs of CHF (tachypnea) in all three cats. Plasmapheresis should be considered in cases of CHF secondary to hyperviscosity syndrome to rapidly alleviate clinical signs associated with heart failure while diagnosis of the underlying cause is made and appropriate therapy implemented.
Shark Skin Inspired Riblet Coatings for Aerodynamically Optimized High Temperature Applications in Aeroengines
Authors: Büttner Claudia C. , Schulz Uwe
Published: December 2010

The shark skin effect is the mechanism of wall friction reduction of a fluid due to a riblet structured surface. A new application for riblet surfaces may be jet engine blades. Riblet structured coatings on the blades would act as oxidation protection and additionally reduce the skin drag on the surface. In this study structuring surface areas of high temperature nickel‐based alloys is investigated. These alloys are used for compressor and turbine blades near the combustion chamber. Experiments are performed by depositing titanium on a nickel base alloy through particular metal grids using magnetron sputtering. For single‐digit micrometer structures, photolithography with subsequent electrodeposition of nickel as well as sputter deposition and thermal evaporation of several materials are investigated. Successfully fabricated structures are oxidized at 900–1 000 °C for up to 100 h and the resulting shape is characterized using scanning electron microscopy. The most accurate structures are obtained using photolithography and subsequent electrodeposition. The reduction of the wall shear stress was measured in an oil channel. The riblet structures prior to oxidation show a reduction of the wall shear stress of up to 4.9%.
Secular trends in height and weight for healthy Han children aged 0–7 years in China, 1975–2005
Authors: Zong Xin‐Nan , Li Hui , Zhu Zong‐Han
Published: December 2010

Objectives: To report the secular growth changes of Chinese children aged 0–7 years between 1975 and 2005.

Methods: Height and weight measurements obtained from four consecutive national surveys were used to analyze the secular trends. Urban‐rural difference and regional difference in growth were compared, respectively.

Results: A rapid positive secular trend was observed in China over the last three decades, increased by 5.3 and 5.0 cm in height for urban boys and girls at age 6–7 years, respectively. Urban–rural height difference has continuously reduced, but weight difference has gradually widened after 3‐years old which results from the excessive weight increase of urban children, 2.68 kg for rural boys aged 6–7 years but 3.26 kg for urban during the 30 years. Clear regional differences in growth are not narrowing over time. Generally, the growth level in eastern China is higher than central‐western, successively higher than southern.

Conclusions: The rapid positive secular trends will still continue with the rapid socio‐economic development in China. Urban‐rural height difference will further narrow. Currently no sufficient evidence indicates that growth difference in inter‐city has reduced. Weight increases rapidly for urban children, which does not match with height. Am. J. Hum. Biol., 2011. © 2010 Wiley‐Liss, Inc.
The serum leptin level and body mass index in Melanesian and Micronesian Solomon Islanders: Focus on genetic factors and urbanization
Authors: Furusawa Takuro , Naka Izumi , Yamauchi Taro , Natsuhara Kazumi , Kimura Ryosuke , Nakazawa Minato , Ishida Takafumi , Nishida Nao , Eddie Ricky , Ohtsuka Ryutaro , Ohashi Jun
Published: December 2010

Objectives: This study examined the association between the serum leptin level and body mass index (BMI) and the effects of urbanization and polymorphisms of leptin (LEP) or leptin receptor (LEPR) genes on the leptin level in three Solomon Islands populations.

Methods: A Melanesian population living in a remote area (participants: 106 males and 106 females, ages: 18–74 years), a Melanesian population in an urban area (89 and 94, 18–79 years), and a Micronesian population who migrated to a peri‐urban area in the 1960s (84 and 69, 18–71 years) were studied. Anthropometric and serum leptin measurements and genotyping for LEP G‐2548A and LEPR K109R and Q223R were performed.

Results: The prevalence of obesity (BMI ≥ 30 kg/m2) was the highest in the Micronesian population (30.1%), followed by the urban (18.6%) and the rural (2.4%) Melanesian population. The serum leptin concentration was the highest in the urban Melanesian, followed by the Micronesian and the rural Melanesian populations (P < 0.05). Interestingly, the parameter coefficients of the leptin concentrations on the BMIs were nearly identical in the urban and rural Melanesians after adjusting for age and gender. The LEPR 223Q/Q genotype was associated with an increased leptin level only in the Micronesian population after adjusting for BMI (P = 0.0008 and 0.0016 referenced to the Q/R and the R/R types, respectively).

Conclusions: These observations suggest that the increase in obesity in the Micronesians had a genetic component while that in Melanesians might have been related with the urbanization. Am. J. Hum. Biol., 2011. © 2010 Wiley‐Liss, Inc.