Remanent Magnetization in Portland-Cement-Based Materials

The purpose of this research is to demonstrate the possibility of applying one geophysical method to studying untraditional systems as is the case with Portland-cement-based materials. The research demonstrates how conventional paleomagnetic methodology can be employed in studying the mode of magnetic recording in present-day industrial materials. Portland-cement admixtures such as fly ashes and furnace slags should be discriminated, because those particles interact in soils and sediments in nature. Moreover, a better undertanding of magnetic remanent acquisition in model materials can serve to improve the interpretation of magnetic remanent acquisition in natural rocks formed a long time ago. The magnetic constituents of Portland-cement paste and mortar acquire a magnetic remanence due to their alignment with the earth's magnetic field at the casting place. This magnetization can be measured using ordinary paleomagnetic techniques. The alignment of the individual magnetic particles accounts for the intensity of the magnetic remanence, which can be increased by adding water and by vibration before setting and hardening. Blast furnace slag admixtures also add to the enhancement of the intensity of remanence. The magnetization of Portland-cement-based materials shows a near linear relationship with the water /cement (w/c) ratios employed in the experimental work; the w/c ratios range between 0.2 – 0.6 in pastes and 0.3 – 0.6 in mortar. Stable remanent magnetization was obtained during the first seven days of setting and hardening, a period necessary for magnetic particles to become locked parallel to the earth's magnetic field. The stability of magnetic remanence predicts the usefulness of the methodology in studying the properties of Portland cement and particularly in the control of iron-bearing admixtures.Laboratorio de Entrenamiento Multidisciplinario para la Investigación TecnológicaFacultad de Ciencias Astronómicas y Geofísica

Strip Till, No-Till and Conventional Tillage Comparisons - Does Planting Date Affect Results?

Numerous tillage studies have been conducted in Iowa, the Midwest, and throughout the U.S. with a wide range of results. The tillage system that results in the highest yield depends on several factors including soil type and weather during the study Generally, systems with little soil disturbance are favored on coarser textured soils and/or in drier years (Eckert 1987; Beyaert et al 2002). For soil and water conservation purposes, as well as for economic reasons, extending successful use of no-till or similar systems to finer textured soils seems advantageous

Marine Infectious Disease Dynamics and Outbreak Thresholds: Contact Transmission, Pandemic Infection, and the Potential Role of Filter Feeders

Disease-causing organisms can have significant impacts on marine species and communities. However, the dynamics that underlie the emergence of disease outbreaks in marine ecosystems still lack the equivalent level of description, conceptual understanding, and modeling context routinely present in the terrestrial systems. Here, we propose a theoretical basis for modeling the transmission of marine infectious diseases (MIDs) developed from simple models of the spread of infectious disease. The models represent the dynamics of a variety of host-pathogen systems including those unique to marine systems where transmission of disease is by contact with waterborne pathogens both directly and through filter-feeding processes. Overall, the analysis of the epizootiological models focused on the most relevant processes that interact to drive the initiation and termination of epizootics. A priori, systems with multi-step disease infections (e.g., infection-death-particle release-filtration-transmission) reduced dependence on individual parameters resulting in inherently slower transmissions rates. This is demonstrably not the case; thus, these alternative transmission pathways must also considerably increase the rates of processes involved in transmission. Scavengers removing dead infected animals may inhibit disease spread in both contact-based and waterborne pathogen-based diseases. The capacity of highly infected animals, both alive and dead, to release a substantial number of infective elements into the water column, making them available to suspension feeders results in such diseases being highly infective with a very small low-abundance refuge . In these systems, the body burden of pathogens and the relative importance between the release and the removal rate of pathogens in the host tissue or water column becomes paramount. Two processes are of potential consequence inhibiting epizootics. First, large water volumes above the benthic susceptible populations can function as a sink for pathogens. Second, unlike contact-based disease models in which an increase in the number of susceptible individuals in the population increases the likelihood of transmission and epizootic development, large populations of filter feeders can reduce this likelihood through the overfiltration of infective particles

Remanent Magnetization in Portland-Cement-Based Materials

The purpose of this research is to demonstrate the possibility of applying one geophysical method to studying untraditional systems as is the case with Portland-cement-based materials. The research demonstrates how conventional paleomagnetic methodology can be employed in studying the mode of magnetic recording in present-day industrial materials. Portland-cement admixtures such as fly ashes and furnace slags should be discriminated, because those particles interact in soils and sediments in nature. Moreover, a better undertanding of magnetic remanent acquisition in model materials can serve to improve the interpretation of magnetic remanent acquisition in natural rocks formed a long time ago. The magnetic constituents of Portland-cement paste and mortar acquire a magnetic remanence due to their alignment with the earth's magnetic field at the casting place. This magnetization can be measured using ordinary paleomagnetic techniques. The alignment of the individual magnetic particles accounts for the intensity of the magnetic remanence, which can be increased by adding water and by vibration before setting and hardening. Blast furnace slag admixtures also add to the enhancement of the intensity of remanence. The magnetization of Portland-cement-based materials shows a near linear relationship with the water /cement (w/c) ratios employed in the experimental work; the w/c ratios range between 0.2 – 0.6 in pastes and 0.3 – 0.6 in mortar. Stable remanent magnetization was obtained during the first seven days of setting and hardening, a period necessary for magnetic particles to become locked parallel to the earth's magnetic field. The stability of magnetic remanence predicts the usefulness of the methodology in studying the properties of Portland cement and particularly in the control of iron-bearing admixtures.Laboratorio de Entrenamiento Multidisciplinario para la Investigación TecnológicaFacultad de Ciencias Astronómicas y Geofísica

Biomechanical proposal as a cause of incomplete seed and pericarp development of the sunflower (Helianthus annuus L.) fruits

Absence or underdevelopment of sunflower fruits come usually from failure in fertilization, stresses as well as physiological and morphological defects in the ovary. Thigmomorphogenesis has never been included as a possible cause. We have previously shown that a 2-3 day fertilization shift can occur between neighboring florets in the sunflower capitulum. It is proposed here that those ovaries with advanced fertilization can generate a significant radial and axial compressive stress on ovaries with delayed fertilization. This mechanical stimulus could be strong enough to trigger a thigmo response that affects further ovary development. In vivo tests were performed, isolating ovaries by removing the adjacent flowers and rubbing them several times using a micromanipulator applying a force of 1 to 3 N. Total peroxidases in treated and untreated ovaries, isolated and not isolated were measured 24 h after treatments. Ovary development was studied in control and isolated flowers, both rubbed and not rubbed. Also a mechanical a model was made to simulate the mechanical behavior of an ovary surrounded by advanced growing neighboring ovaries. A meshed 3-D model of a young ovary was constructed and a computer simulation was performed using finite element analysis. Shear stresses generated by the friction of neighboring ovaries in contact with the model, fertilized three days later, were then estimated. After rubbing, isolated ovaries in planta showed a thigmo response that resulted in empty or incompletely developed fruits. Total peroxidase levels (ΔAbs470 min-1.g fresh weight-1) rose from 22 in control ovaries to 72 in rubbed ones. The number of ovaries that did not develop any seed from these incompletely developed fruits rose from 16.2 to 20.0% in the control non-isolated flowers to 61.1 to 86.7% in the rubbed ovaries, but dropped to 6.7 to 7.3% in the non-rubbed but isolated ovaries. From the simulation it was found that the area of contact with the receptacle was prone to show a higher magnitude of stress after deformation induced by shear forces generated by neighboring ovaries. Thigmomorphogenesis can also explain the failures observed at early stages of the sunflower ovary development. The ovary tissue sensitivity at this stage could contribute to the rapid response of the mechanically generated stimulus between neighbouring ovaries.La ausencia o el escaso desarrollo de los frutos del girasol proviene generalmente de fallas en la fertilización, condiciones de estrés y defectos fisiológicos y morfológicos en el ovario. La tigmomorfogénesis nunca ha sido considerada como una posible causa. Hemos demostrado previamente que, en el capítulo de girasol, puede producirse un retraso de 2 a 3 días en la fertilización entre flores vecinas. En este trabajo se propone que los ovarios con fertilización avanzada pueden generar un significativo estrés compresivo radial y axial en los ovarios con fertilización retrasada. Este estímulo mecánico podría ser lo suficientemente importante como para desencadenar una tigmo respuesta que afecte el desarrollo de los ovarios. Se realizaron pruebas in vivo, aislando ovarios, eliminando las flores adyacentes y, usando un micromanipulador, frotándolas aplicando una fuerza de 1 a 3 N. Se midieron las peroxidasas totales en los ovarios tratados y no tratados, aislados y no aislados 24 h después de los tratamientos. El desarrollo de los ovarios se estudió en flores control y aisladas, tanto frotadas como no frotadas. También se simuló el comportamiento mecánico de un ovario rodeado por ovarios vecinos en crecimiento avanzado. Para ello se construyó un modelo tridimensional mallado de un ovario joven y se realizó una simulación computacional utilizando el método de elementos finitos. Se estimaron las tensiones de corte generadas por la fricción de los ovarios vecinos fertilizados tres días antes y en contacto con el ovario con fertilización retrasada. En los tratamientos de fricción in planta, los ovarios aislados mostraron un desarrollo anómalo del embrión, resultando en frutos vacíos o incompletamente desarrollados. Los niveles totales de peroxidasas (ΔAbs470 min-1.g peso fresco-1) aumentaron de 22 en los ovarios control a 72 en los frotados. El número de ovarios que no desarrollaron semilla aumentó de 16.2 a 20.0% en las flores control no aisladas a 61.1 a 86.7% en las flores con ovarios frotados, pero disminuyó de 6.7 a 7.3% en las no flores no frotadas pero con ovarios aislados. A partir de la simulación se encontró que la región de unión del ovario con el receptáculo era proclive a mostrar una mayor magnitud de estrés después de la deformación inducida por las fuerzas de fricción generadas por los ovarios vecinos. Se conclutye que la tigmomorfogénesis puede también explicar en algunos casos las fallas observadas en las primeras etapas del desarrollo de los ovarios de girasol. La sensibilidad del tejido ovárico en esta etapa podría contribuir a la respuesta rápida del estímulo mecánico generado por fricción natural entre ovarios vecinos

La susceptibilidad magnética como indicadora de temperaturas de calcinación de suelos

Este artículo constituye la continuación de un trabajo reciente, donde se reportó la influencia del carbonato de calcio (CaCO3) inicial en las propiedades magnéticas de suelos calcinados a 1000ºC en atmósfera de aire. Estos suelos están compuestos principalmente por silicatos y aluminosilicatos, con cantidades variables de CaCO3. Los estudios realizados evidenciaron que tras la calcinación, el calcio (Ca) promueve la formación de partículas ferrimagnéticas (tipo magnetita), en cambio, cuando el Ca está en bajas concentraciones, domina la señal de sustancias antiferromagnéticas como la hematita. Los materiales tratados en el presente trabajo corresponden a suelos con un amplio rango en el contenido de CaCO3, calcinados a temperaturas crecientes, desde 20º hasta 1050ºC, en atmósfera de aire. Se realizaron determinaciones de elementos químicos mayoritarios, análisis gravimétricos y de susceptibilidad magnética (SM), con la finalidad de establecer con mayor claridad las temperaturas de aparición-desaparición de fases magnéticas en relación con el contenido de Ca. Frente a la calcinación y el posterior enfriamiento, la SM varió con relativa independencia del contenido de Ca hasta la aplicación de temperaturas de 900ºC. A partir de esa temperatura los suelos más ricos en Ca se diferenciaron, adquiriendo los valores más elevados de SM. Las curvas gravimétricas no evidenciaron perdidas de masa para temperaturas mayores a 800ºC, de manera que los elevados valores de SM en las muestras con más Ca corresponden a transformaciones que no necesariamente implican reacciones de volatilización. Como una primera aproximación, planteamos que la presencia de calcio favorecería la incorporación de hierro en espinelas, del tipo magnetita-hercinita, formadas entre los 900 y los 1000ºC. Se considera que el presente trabajo será de utilidad para el desarrollo de técnicas para la estimación de temperaturas de cocción de ladrillos y cerámicas, potencialmente aplicable a estudios arqueológicos y de patrimonio histórico-arquitectónico; también para la investigación de los efectos del fuego en los suelos y para la identificación de fases minerales vinculadas a procesos pirometamórficos.This article corresponds to an extension of a recent work which reported the influence of initial calcium carbonate (CaCO3) on magnetic properties of calcined sediments at 1000°C under air atmosphere. These sediments were mainly composed of silicates and silicoaluminates, with varying amounts of calcium (Ca). It was evidenced that the Ca promotes the formation of ferrimagnetic particles after the calcination, whereas when the amount of Ca are low, the signal of antiferromagnetic substances (as hematite) dominates. The analyzed materials in the present paper correspond to soils with a wide range of Ca content, calcined by increasing temperatures (from 20° to 1050° C) in air atmosphere. Chemical and gravimetric determinations as well as magnetic susceptibility (MS) measurement were performed in order to establish the presence of magnetic phases in relation with temperature variations and Ca content. MS varies regardless of Ca content until the application of temperatures of 900ºC. From this temperature, the Ca-rich soils were differentiated, acquiring the highest values of MS. The thermogravimetric curves did not show mass losses for temperatures higher than 800ºC, so that the high values of MS in the Ca-rich samples correspond to transformations that do not involve devolatilization reactions. As a first approach, we propose that the presence of Ca would facilitate the iron incorporation in spinel of magnetite-hercynite type, formed between 900 and 1000ºC. We consider that the present investigation should be useful for studying bricks and ceramics calcination temperatures, as well for archaeological and historical-architectural heritage studies. In addition, it may be useful for investigating the effects of fire on soils and the mineral phases identification associated with pyrometamorphic processes

Tamanho amostral na identificação de subpopulações espermáticas em carneiros Santa Inês.

A cinética espermática é importante por estar correlacionada positivamente com a fertilidade do sêmen. Estudos de cinética utilizam ferramentas estatísticas multivariadas para incrementar a acurácia na identificação de subpopulações espermáticas em ovinos; assim o tamanho amostral é importante na variabilidade do agrupamento de células. Objetivou-se estudar a influência do n amostral aleatório na identificação de subpopulações espermáticas. Foi utilizado o banco de informações digitais da análise seminal feita em 35 carneiros adultos no Laboratório de Biotecnologia da Reprodução Animal ? Embrapa Tabuleiros Costeiros; constituindo um total de 77070 observações espermáticas contendo dados de velocidades curvilínea (VCL), em linha reta (VSL) e do percurso médio (VAP), linearidade (LIN), retilinearidade (STR), índice de oscilação (WOB), deslocamento lateral da cabeça (ALH) e batimento flagelar Cruzado (BCF) dos espermatozoides. Foi utilizada a metodologia estatística de análise dos componentes principais sendo testados diferentes n amostrais: 10, 50, 100, 250, 500, 750, 1000, 1500, 2000, 3000, 5000 e 15000. A influência do n amostral na identificação de subpopulações espermáticas em carneiros Santa Inês, considerando cinco parâmetros cinéticos espermáticos foi significativa (p<0,05), onde o n amostral abaixo de 50 espermatozoides avaliados mostrou uma maior variabilidade numérica comparada aos outros tamanhos amostrais. Conclui-se que para identificar subpopulações espermáticas homogêneas, pode ser simulado o n amostral igual ou maior de 50 espermatozoides selecionados aleatoriamente e com pelo menos 10 repetições

Optimización de la producción del hongo medicinal Reishi (Ganoderma lucidum) para el desarrollo de nutracéuticos y fitoterápicos

En los últimos años, el mercado de los nutra y nutricéuticos ha tenido un marcado crecimiento, sobre todo a partir de la toma de conciencia de los consumidores de la eficacia de los mismos en la prevención y tratamiento de enfermedades. Ganoderma lucidum es un Basidiomycete conocido desde hace 2.000 años por sus propiedades medicinales. Este hongo produce numerosos compuestos bioactivos, que han sido extensamente estudiados y aplicados en la elaboración de alimentos funcionales, suplementos dietarios y fitoterápicos. Actualmente, la producción mundial de este hongo es aproximadamente de 6.000 toneladas y las últimas estimaciones disponibles colocan el valor anual de los productos de G. lucidum en más de US$ 2.500 millones. Sin embargo, en Argentina no existe producción industrial, comercialización, ni desarrollo de productos a base de Reishi. Este hongo puede ser cultivado en sustratos sólidos sintéticos formulados a base de diferentes residuos agroindustriales. Usualmente, su cultivo produce rendimientos menores comparado con otros hongos comestibles cultivables. Los altos costos asociados a su producción y su alto valor en el mercado hacen que cualquier mejora en los rendimientos redunde en un beneficio económico. En el marco de un proyecto PICT modalidad Start Up, fue posible trasladar los resultados de varios años de investigación a una escala piloto de producción, a fin de considerar la generación de una empresa de base tecnológica para el cultivo ecológico y normalizado del hongo Reishi. Este desarrollo continúa en el manejo post-cosecha, para la obtención de productos a partir del fruto seco del hongo para uso como fitoterápico o bien como suplemento dietario. La selección del sustrato, de los aditivos y el manejo de las condiciones de cultivo, resultaron estrategias eficientes para aumentar los rendimientos de la producción. Se ha desarrollado una tecnología de bajo costo de producción de Glucidum utilizando como sustrato base cáscara de girasol, un residuo abundante de la industria aceitera. Se ha logrado incrementar los rendimientos en un 43% y acortar significativamente el tiempo de producción, con respecto a los datos reportados por otros autores, sin afectar la obtención de los principios activos. El manejo optimizado de la tecnología de producción de Glucidum permitirá obtener mejores precios y asegurar calidad, cantidad y continuidad en el suministro; por lo cual es factible su transferencia al ámbito productivo.publishedVersio

Sedatives and Analgesics Given to Infants in Neonatal Intensive Care Units at the End of Life

To describe the administration of sedatives and analgesics at the end of life in a large cohort of infants in North American neonatal intensive care units (NICUs)

Association between positive urine cultures and necrotizing enterocolitis in a large cohort of hospitalized infants

We used a large research database to examine the association between urinary tract infections and necrotizing enterocolitis (NEC) in premature infants