1000 resultados para Evolución-Orgánica


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Desde esta perspectiva del control, la evaluación de la calidad de los cuidados de enfermería es una"vieja idea", ya que hace más de un siglo (1860), Florence Nightingale realizó una serie de informes críticos sobre la calidad asistencial en los hospitales militares británicos. Desde entonces hasta nuestros días, la preocupación de las enfermeras para ofrecer unos cuidados de óptima calidad y poder evaluarlos, para así...

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Objetivo general: Analizar la evolución del estudio de las necesidades humanas desde los autores clásicos hasta los teóricos actuales. Metodología: Revisión bibliográfica de las necesidades humanas desde distintas perspectivas de las ciencias sociales. Resultados: En las grandes corrientes científicas que teorizan sobre las necesidades humanas, se observan distintas maneras de conceptualizarlas, aunque en su mayoría contemplan las necesidades como constructo social, que puede interpretarse vinculado al momento socio-histórico.

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Objetivo general: Analizar la evolución del estudio de las necesidades humanas desde los autores clásicos hasta los teóricos actuales. Metodología: Revisión bibliográfica de las necesidades humanas desde distintas perspectivas de las ciencias sociales. Resultados: En las grandes corrientes científicas que teorizan sobre las necesidades humanas, se observan distintas maneras de conceptualizarlas, aunque en su mayoría contemplan las necesidades como constructo social, que puede interpretarse vinculado al momento socio-histórico.

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Objetivo general: Analizar la evolución del estudio de las necesidades humanas desde los autores clásicos hasta los teóricos actuales. Metodología: Revisión bibliográfica de las necesidades humanas desde distintas perspectivas de las ciencias sociales. Resultados: En las grandes corrientes científicas que teorizan sobre las necesidades humanas, se observan distintas maneras de conceptualizarlas, aunque en su mayoría contemplan las necesidades como constructo social, que puede interpretarse vinculado al momento socio-histórico.

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Este informe pretende analizar los antecedentes de la migración internacional con la crisis económica, y de manera específica, la estructura del empleo en el Perú y cómo éste afecta y afectará la emigración. A continuación presento el contenido del informe el que tiene cuatro partes mutuamente complementarias: Primero.- Evolución de la emigración peruana en los últimos 17 años desde 1990 al2007. Para el efecto se utilizan datos oficiales para analizar las características sociodemográficas de la migración. Segundo.- Se analizan los impactos de la emigración en el mercado de trabajo y los acontecimientos que sucedieron en los dos últimos años, fecha en la que la migración empieza a ser afectada por la crisis económica, en particular en el último año. Para el efecto, acompañamos datos del censo de población y vivienda y el censo económico del 2007 elaborado por el Instituto Nacional de Estadística e Informática (INEI) del gobierno peruano. Tercero.- Se analiza la relación entre la migración y las redes sociales de los migrantes con sus familiares y las asociaciones de migrantes. Los datos para esta parte del informe están basados en entrevistas informales a familiares, a retornantes, a potenciales migrantes.; además uso datos de un estudio previo que desarrollé en el año 1998 y 1999 sobre las asociaciones de peruanos en España. Cuarto.- Presento los posibles escenarios futuros en los próximos años a la luz de los cambios, las tendencias y los hechos que sucedieron en los últimos 19 años. Se pone especial énfasis a o que puede suceder en el campo laboral, el retorno de migrantes a sus países y el comportamiento de las remesas y su impacto en la economía doméstica de las familias que los reciben.

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La actualidad y los acontecimientos de las últimas décadas han puesto de manifiesto la importancia del miedo en la vida pública. El miedo como tal y sus factores desencadenantes están presentes en la prensa, el discurso político, la neurociencia, la ciencia y la filosofía política. Entendemos que la gestión del miedo intuitivo, cognitivo y heurístico debe contemplarse como un elemento básico en la vida del ciudadano de este siglo. Tanto en la visión moderna de la nación y el contrato social, como en las visiones más futuristas de cosmopolitismo y estados supranacionales, la heurística del miedo difícilmente podrá desaparecer de los sistemas jurídicos y sociales, no solo por su utilidad intrínseca, sino también por su inmanencia y consubstancialidad genético-biológica y psico-social. El hecho de que exista miedo consideramos que es positivo puesto que nos alerta de riesgos que pueden afectar negativamente el futuro del individuo.

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A model for the construction of a simple and cheap apparatus to be used as bioreactor for reactions catalyzed by baker's yeast (Saccharomyces cerevisiae) is described. The bioconversion and separation of cells from products and residual substrates are obtained at the same time. The reactions carried out in this type of reactor are faster than those catalyzed by immobilized cells. Yeast cells can be cultivated in this bioreactor operating with cell recycling at appropriated conditions using glucose and other nutrients.

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extracts of the regional plants Annona squamosa and Annona muricata were analysed by silica gel thin-layer chromatography using adequate systems of solvents and spray reagents. Carbohydrates, amino acids, alkaloids, flavonoids and terpenoids were detected in both species. These data agree with those on the literature about phytochemistry of the Annonaceae.

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Lipases have been immobilized in microemulsion-based organogels (MBG's) and successfully utilized for the enantioselective esterification, diesterification and transesterification reactions, in organic solvents at 25ºC. This methodology is described as a new alternative for the use of enzymes in organic solvents. High enzymic stability has been observed. We have also used this methodology for the successful resolution of chiral secondary alcohols. This is a convenient way of using this catalyst in organic solvents which employs small amounts of the enzyme (250mg/mL).

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The generation of "cold light", visible to the human eye, by chemical reactions has attracted the attention of the scientific community since the beginning of this century. Besides the academic interest in the elucidation of the mechanisms of excited state formations, many chemiluminescence reactions have found widespread analytical applications. Moreover, the phenomenon of chemiluminescence can also be used as a tool in undergraduate and college teaching. In this article, we describe several known chemiluminescence demonstrations, which are suitable for school teaching. The main objective of this work is to produce didactic material in Portuguese to stimulate Brazilian secondary and high school teachers to use these experiments in the classroom. The demonstrations include singlet oxygen emission, the luminol reaction, oscillating chemiluminescence and the peroxyoxalate reaction.

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The herbicides are being used in huge quantities for various porpouses. Once the herbicide finds its way into the environment, a major part of it comes in contact with soil. Humic substances are major organic constituents of soil. These substances may interact with herbicides in different modes and adsorption is probably the most important one. Adsorption will control the quantity of herbicide in the soil solution, and determines its persistence, leaching, mobility and bioavailability. In this work we studied the interaction between the herbicide 2,4D and soil in the presence and absence of organic matter. The methodology utilized for the determination of 2,4D was gas chromatography with eletron capture detector. The behavior of 2,4D was evaluated through Freundlich isotherms. It was verified that the herbicide 2,4D has a large adsorption in the humic acid .

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A new approach for teaching in basic experimental organic chemistry is presented. Experimental work goes on parallel to theoretical lectures leading to an immediate application of theoretical concepts transmitted therein. One day/week is dedicated exclusively to the organic laboratory. Reactions are proposed as problems to be solved; the student has to deduce the structure of the product on the basis of his observations, the analytical data and his mechanistical knowledge. 70 different experiments, divided in 7 thematical chapters, are presented. All experiments require the analysis and discussion of 1H and 13C NMR, IR and UV spectra. Additional questions about each reaction have to be answered by the student in his written report. Laboratory safety is garanteed by the exclusion or substitution of hazardous and toxic reagents. Microscale preparations are adopted in most cases to lower the cost of materials and the amount of waste. Recycling of many reaction products as starting materials in other experiments reduces the need for commercial reagents and allows the execution of longer reaction sequences. Only unexpensive standard laboratory equipment and simple glassware are required. All experiments include instructions for the save treatment or disposal of chemical waste.

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The radiocarbon dating of the soil organic matter (SOM) is a polemic subject, due mainly to the complexity of the formation of the soils and to the variable contamination from several sources. Soil samples from 4 different Brazilian localities were submitted to physical and chemical pre-treatment for the extraction of humin fraction, which is the most stable organic compound and theoretically the oldest and representative of the age of the SOM. The radiocarbon dating obtained from the total SOM and their humin fractions are compared to the 14C ages from buried charcoals at similar depths. The radiocarbon ages obtained from such charcoals are, in most of the cases, concordant within the experimental errors of those obtained on humin fractions, or are in average 10% higher, with one exception. Thus, the ages on humin fractions could be assumed as the minimum ages for the associated soils, while the results obtained on total SOM, even at depths until 200 cm, exhibit pronounced contamination effect by modern carbon, rejuvenating their ages.

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In organic synthesis, lipases are the most frequently used biocatalysts. They are efficient stereoselective catalysts in the kinetic resolution of a wide variety of chiral compounds. The discovery that enzymes possess catalytic activity in organic solvents has made it possible to address the question of reaction medium influence on enzymatic specificity. Perhaps the most exciting and significant development in this emerging area is the discovery that enzyme specificity, in particular enantioselectivity, can be affected by changing from one organic solvent to another. This article discusses the scope and possible mechanistic models of this phenomenon in hydrolases, specially lipases, as well as directions of future research in the area.

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The Baylis-Hillman reaction has significantly advanced in the last ten years as demonstrated by a number of applications described in the literature. In this report we show some aspects of this reaction, including scope, limitations and perspectives.