2,256 research outputs found
Restos subfósiles en el sedimento superficial de las lagunas de la cuenca del Duero: empleo en la definición de condiciones ambientales. Aplicación en la predicción de condiciones ambientales pasadas a partir del sedimento profundo de las lagunas Enmedio y Sentiz
271 p.En las últimas tres décadas, el desarrollo de la industria, de las prácticas agrÃcolas y la urbanización han conducido al progresivo deterioro de los humedales. Las lagunas mediterráneas son someras, éstas son más sensibles a los cambios hidrológicos que las lagunas profundas ya que, incluso, pequeños cambios pueden influir en las concentraciones de los principales iones
Hydrochemistry of northwest Spain ponds and its relationships to groundwaters
We built a classification system for lentic ecosystems and groundwaters in South-East León based on degree of mineralization and composition of major ions. In the ponds with the softest water (< 5 mEq/L), chlorides and bicarbonates were the main mineralizing anions. In contrast, in more highly mineralized ponds (> 5 mEq/L), all major ions were at comparable proportions. In these more mineralized shallow lakes, more sulphates could be found compared to less mineralized waters in the region. Independently of the level of mineralization, calcium was the predominant cation, although shallow lakes with lower mineral content favoured sodium over magnesium. The intense summer evaporation and the filling in autumn of ponds which had completely dried out and remained dry during the summer triggered changes not only in the mineral content, but also in the ionic composition of the water, with an increase in the concentrations of all ions in autumn. Overall mineralization and alkalinization were the two chief factors shaping the chemical variability of groundwater in our region. The length of flows discharging into groundwater-influenced areas shaped the general features of the wetlands studied, so that the degree of mineralization of the water in any given lake was determined in large measure by the geographical position. Thus, the greater length of flows in southerly areas of the study zone led to an increase in the more highly mineralized shallow lakes of the salinity of groundwater and of surfacing groundwater. Nonetheless, a substantial number of the ponds investigated are apparently linked to the aquifers under the "raña" formations. The chemical make-up of the water in these bodies is to some extent related to precipitation in the form of rain or in other forms and is apparently little influenced by groundwater. Hence the ponds are made up of slightly mineralized sheets of water, and can be tracked to discharges from brief surfacing groundwater flows. A link to deeper regional flows can be identified by the presence of comparatively more mineralized water bodies. Overall, outflows do not correspond to the chemical pattern of groundwaters, suggesting a more complex explanation for the hydrology of the study area.Se realizó una tipificación de los sistemas lenÃticos y del agua subterránea en el sureste de la provincia de León basada en su grado de mineralización y composicón iónica mayoritaria. En las lagunas más dulces (<5 mEq/L) cloruro y bicarbonato fueron los aniones con mayor peso en la mineralización. Por el contrario, en las lagunas más mineralizadas (>5 mEq/L) las proporciones de los aniones mayoritarios fueron muy semejantes, con un incremento de sulfato respecto a las aguas menos mineralizadas. Con independencia del nivel de mineralización, el calcio fue el catión predominante, aunque la disminución del contenido mineral favoreció al sodio sobre el magnesio. La intensa evaporación producida durante el verano y el llenado en otoño de las lagunas que permanecieron secas en el periodo anterior provocaron cambios no sólo en el contenido mineral, sino también en la composición iónica del agua, con aumento de las concentraciones de todos los iones en otoño. La mineralización global y la alcalinización fueron los dos procesos más importantes que marcaron la varibilidad hidroquÃmica del agua subterránea. La longitud del flujo de descarga en las áreas bajo la influencia del agua subterránea ha condicionado las caracterÃsticas de los humedales estudiados, de modo que el nivel de mineralización del agua ha estado determinado en buena medida por su posición geográfica. Es asà que el aumento de la longitud de flujo hacia el sur del área de estudio ha determinado un incremento de la concentración salina del agua subterránea y de su manifestación en superficie, en formaciones palustres más mineralizadas. No obstante, una parte importante de las lagunas estudiadas aparecen ligadas a los acuÃferos de rañas y el carácter hidroquÃmico de sus aguas está relacionado, en parte, con el agua meteórica y aparece poco influenciado por el agua subterránea. Constituyen, por tanto, láminas de agua poco mineralizada, identÃficándose como descargas de flujos subterráneos cortos. La conexión con flujos regionales más profundos se reconocen como lagunas que comparativamente son altamente mineralizadas. Sin embargo, estas descargas no tienen correspondencia con el quimismo de las aguas subterráneas, lo que otorga una cierta complejidad al comportamiento hidrológico observado en el área de estudio
Preparation and characterization of hydrogels with potential for use as biomaterials
Hydrogels have been extensively explored for biomedical applications due to their ability to absorb high water content in its structure, which gives excellent biocompatibility. This work aims at obtaining biocompatible hydrogels with potential for use in increasing the mechanical strength of bone substitutes, or controlled drug release. Poly (N-vinyl-2-pyrrolidone) hydrogels were prepared by free radical polymerization with and without the addition of acrylic acid. Azobisisobutyronitrile and ammonium persulfate were used as initiator and N,N-methylenebisacrylamide was used as the crosslinking agent. The characterization of the hydrogels was performed by thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy and swelling properties. The results obtained demonstrate different degrees of crosslinking and swelling of up to 490 ± 30%. The different properties of the hydrogels suggest different applications
Sprouting suppression and mushroom production after inoculation of Juglans x intermedia stumps with edible fungi species
Removal of stumps and suppression of sprouts after harvesting by conventional methods, such as using heavy machinery or herbicides, alters the physico-chemical characteristics of soil, may cause environmental damage and can be very costly. In this study, the performance of inoculation with edible fungi as a biological alternative for stump degradation, has been examined in walnut plantations of five Spanish provinces. Stumps were inoculated with two species of edible fungi: Pleurotus ostreatus (Jacq. Ex Fr.) P. Kumm and Lentinula edodes (Berk) Pené. Compared with untreated controls, the two biological treatments resulted in a significant and evident reduction of the sprouting probability, which was stronger than the result obtained with chemical treatments. Inoculated stumps also produced edible sporocarps, averaging 15.58 g per stump during the first year. This article constitutes the basis for the development of a sustainable, environmentally friendly and cost-effective product, which is a bioeconomy-based solution for stump degradation in intensive plantations
Creación de una empresa para la prestación del servicio de rutas gastronómicas en la ciudad de Cartagena D. T. y C.: estudio de prefactibilidad
El Turismo Gastronómico es una forma de hacer turismo en la que la gastronomÃa
del paÃs visitado es parte de la actividad preponderante durante su visita. Es asÃ
que la gastronomÃa se convierte en un recurso cultural intangible que debe ser
explotado por los actores del turismo en las ciudades turÃsticas de Colombia,
debido a que su finalidad más importante es la preservación de la cultura y la
biodiversidad.
El trabajo realizado consiste en un estudio de Pre factibilidad para la creación de
una empresa para la prestación del servicio de Rutas Gastronómicas en la ciudad
de Cartagena D.T y C, el cual comprende el análisis del entorno, el estudio de
mercado, el estudio técnico, el estudio legal y el estudio financiero. Asà mismo
incluye el desarrollo de un análisis de riesgos y la elaboración de un plan de
gestión atendiendo los lineamientos de PMBOK (Cuerpo de Conocimiento de la
Gestión de Proyectos).
La necesidad de realizar este estudio surgió luego de analizar las tendencias
actuales del turismo, en donde cada vez cobran mayor importancia y aumentan los
viajes especializados para el disfrute de lÃneas de productos tales como circuitos
culturales, gastronómicos, turismo activo y golf, siendo las ciudades de Bogotá,
Cartagena, MedellÃn, Cali y San Andrés las que gozan de mayor preferencia por
parte de los turistas para ser visitadas y demandar estos servicios.
El método empleado en la investigación fue descriptivo y se emplearon fuentes de
información tanto primarias como secundarias.
Los resultados de los estudios realizados, indican que el presente proyecto es
viable desde el punto de vista jurÃdico, ambiental, técnico y financiero, asà mismo
indican que de acuerdo a la estructura fÃsica, organizacional y financiera esta
propuesta empresarial es rentableIncluye bibliografÃ
Evidence from Cochrane systematic reviews for the dissemination control of the COVID-19 infection
Introduction: The COVID-19 infection has high transmissibility and several measures have been adopted for dissemination control. Objective: To identify and summarize the evidence from the Cochrane systematic reviews (SR) on measures to control the dissemination of the COVID-19 infection. Study design: This review of Cochrane SR has carried out in the Division of Vascular and Endovascular Surgery and in the Division of Emergency Medicine and Evidence-Based Medicine of the Universidade Federal de São Paulo, Brazil. Methods: A comprehensive search in the Cochrane Database of Systematic Reviews retrieved all Cochrane SR directly related to control measures for the COVID-19 dissemination. The main characteristics and results of all included SR were summarized and discussed. Results: Three Cochrane SRs were included in the qualitative synthesis and they evaluated populational and individual measures to control the dissemination of COVID-19. Conclusion: Low-certainty evidence show that quarantine of people exposed to those confirmed or suspected COVID-19 cases prevented 44% - 81% of incident cases and 31% - 63% of deaths compared to no measures and as sooner the quarantine measures are implemented, greater costs are saved. High-confidence evidence showed that clear communication about infection control and prevention guidelines was vital to its implementation. Low-certainty evidence showed that people with a long gown had less contamination than those with a coverall, and the coverall was more difficult to doff. Other SRs are desirable for controlling the dissemination of the COVID-19 infection
Estudio de atributos de calidad en sitios de E-commerce argentinos
Este paper, como replicación del primer estudio realizado en el 2000 [Lafuente et al 00], analiza y evalúa atributos de calidad a ser considerados en proyectos Web operativos o en fase de desarrollo, principalmente para la caracterÃstica de funcionalidad de sitios o aplicaciones con comercio electrónico. Se parte de un modelo de calidad representado por un árbol de caracterÃsticas y atributos. Con el fin de ilustrar dicha caracterÃstica, realizamos un nuevo estudio de sitios ecommerce de Argentina sobre una muestra de 71 sitios, interviniendo los mismos 17 atributos directamente mensurables, que en el estudio previo. El mismo arroja información útil para determinar el grado de disponibilidad de atributos y caracterÃsticas de calidad, en consideración del visitante general, y que potencialmente influencian al tráfico y a las ventas. Presentamos un análisis detallado del presente estudio y una discusión que compara ambos. Técnicas estadÃsticas fueron aplicadas al primer estudio [Loranca et al 03], y nuevos estudios estadÃsticos exploratorios se realizarán para determinar categorÃas y tendencias.Eje: I - Workshop de IngenierÃa de Software y Base de DatosRed de Universidades con Carreras en Informática (RedUNCI
Estudio de atributos de calidad en sitios de E-commerce argentinos
Este paper, como replicación del primer estudio realizado en el 2000 [Lafuente et al 00], analiza y evalúa atributos de calidad a ser considerados en proyectos Web operativos o en fase de desarrollo, principalmente para la caracterÃstica de funcionalidad de sitios o aplicaciones con comercio electrónico. Se parte de un modelo de calidad representado por un árbol de caracterÃsticas y atributos. Con el fin de ilustrar dicha caracterÃstica, realizamos un nuevo estudio de sitios ecommerce de Argentina sobre una muestra de 71 sitios, interviniendo los mismos 17 atributos directamente mensurables, que en el estudio previo. El mismo arroja información útil para determinar el grado de disponibilidad de atributos y caracterÃsticas de calidad, en consideración del visitante general, y que potencialmente influencian al tráfico y a las ventas. Presentamos un análisis detallado del presente estudio y una discusión que compara ambos. Técnicas estadÃsticas fueron aplicadas al primer estudio [Loranca et al 03], y nuevos estudios estadÃsticos exploratorios se realizarán para determinar categorÃas y tendencias.Eje: I - Workshop de IngenierÃa de Software y Base de DatosRed de Universidades con Carreras en Informática (RedUNCI
P53 and cancer-associated sialylated glygans are surrogate markers of cancerization of the bladder associated with \u3ci\u3eSchistosoma haematobium\u3c/i\u3e infection
Background
Bladder cancer is a significant health problem in rural areas of Africa and the Middle East where Schistosoma haematobium is prevalent, supporting an association between malignant transformation and infection by this blood fluke. Nevertheless, the molecular mechanisms linking these events are poorly understood. Bladder cancers in infected populations are generally diagnosed at a late stage since there is a lack of non-invasive diagnostic tools, hence enforcing the need for early carcinogenesis markers. Methodology/Principal Findings
Forty-three formalin-fixed paraffin-embedded bladder biopsies of S. haematobium-infected patients, consisting of bladder tumours, tumour adjacent mucosa and pre-malignant/malignant urothelial lesions, were screened for bladder cancer biomarkers. These included the oncoprotein p53, the tumour proliferation rate (Ki-67\u3e17%), cell-surface cancer-associated glycan sialyl-Tn (sTn) and sialyl-Lewisa/x (sLea/sLex), involved in immune escape and metastasis. Bladder tumours of non-S. haematobium etiology and normal urothelium were used as controls. S. haematobium-associated benign/pre-malignant lesions present alterations in p53 and sLex that were also found in bladder tumors. Similar results were observed in non-S. haematobium associated tumours, irrespectively of their histological nature, denoting some common molecular pathways. In addition, most benign/pre-malignant lesions also expressed sLea. However, proliferative phenotypes were more prevalent in lesions adjacent to bladder tumors while sLea was characteristic of sole benign/pre-malignant lesions, suggesting it may be a biomarker of early carcionogenesis associated with the parasite. A correlation was observed between the frequency of the biomarkers in the tumor and adjacent mucosa, with the exception of Ki-67. Most S. haematobium eggs embedded in the urothelium were also positive for sLea and sLex. Reinforcing the pathologic nature of the studied biomarkers, none was observed in the healthy urothelium. Conclusion/Significance
This preliminary study suggests that p53 and sialylated glycans are surrogate biomarkers of bladder cancerization associated with S. haematobium, highlighting a missing link between infection and cancer development. Eggs of S. haematobium express sLea and sLex antigens in mimicry of human leukocytes glycosylation, which may play a role in the colonization and disease dissemination. These observations may help the early identification of infected patients at a higher risk of developing bladder cancer and guide the future development of non-invasive diagnostic tests
Increasing Acid Concentration, Time and Using a Two-Part Silane Potentiates Bond Strength of Lithium Disilicate-Reinforced Glass Ceramic to Resin Composite:An Exploratory Laboratory Study
There is still a lack of consensus concerning the recommended etching concentration, application time and type of silane when bonding lithium disilicate-reinforced glass ceramics manufactured by CAD/CAM. The purpose of this study was thus to conduct an in vitro study which investigates the influence of hydrofluoric acid (HF) concentration, etching time and silane type on the microtensile bond strength (μTBS) of lithium disilicate to resin composites. Thirty-nine IPS e.max CAD blocks were randomly divided between thirteen groups (n = 3). The variables were HF concentration (9.5 or 4.9%), etching time (20 or 60 s) and silane type (Bis-Silane, Monobond Plus and ESPE Sil Silane). The blocks were cut into beams, aged for 10,000 cycles in a thermocycler and submitted to tensile stress to determine μTBS. A control group featuring the Monobond Etch & Prime (MEP) agent that combines etching/silanisation into a simultaneous process was also added. This group was discarded from the analysis due to only having pre-test failures. The data were analysed using a three-way ANOVA (α = 0.05). The HF concentration, etching time and silane type significantly influenced μTBS (p < 0.001). Significant interactions between time and silane type (p = 0.004), HF concentration and silane type (p < 0.001) and among the three factors (p < 0.001) were noted. Etching lithium disilicate with 9.5% HF (60 s), followed by the application of Bis-Silane, resulted in the highest μTBS (16.6 ± 9.0 MPa). The highest concentration and etching time under study, combined with a two-part silane, resulted in the highest bond strength, while the application of MEP showed a complete pre-test failure
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