1000 resultados para Revisão de textos


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El monográfico que editamos en este quinto número de prohistoria es el resultado de una convocatoria realizada desde la revista, durante el año 2000, con la intención de confeccionar un dossier. La anchura de la respuesta está a la vista: las autoras y los autores que publican aquí sus investigaciones, comparten la voluntad de intentar dirigir la mirada a través de esta ventana indiscreta, que muestra la tela por el revés, por el bies y por sus hilos, y discute certidumbres secularmente instaladas. Ignasi Terradas, entrevistado por Dalla Corte, reflexiona, toma posición y asigna potencia al campo que se despliega, en clave de investigación y acción, detrás de la etiqueta aparentemente académica de la antropología jurídica. Un grupo de notables antropólogos e historiadores observan y analizan distintas facetas del universo de los derechos, las jurisdicciones, los cambiantes perfiles de delitos y delincuentes, o discutiendo las vías de realización de la 'ciudadanía', una cantera de fuentes que, para las historiografias hispánica y rioplatense, comienza a arrojar ya resultados sustantivos sobre los cuales edificar nuevas versiones de sociedades que transitan, sobre todo, la disolución del Antiguo Régimen.

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DDT and others organochlorine insecticides are very persistent substances. Clinical symptoms of intoxication have been reported in humans, although the main problem concerning such substances is bioaccumulation and biomagnification along throphic chains, leading to contamination of top predators and humans after them. In this review these characteristics are described, as well as some aspects of the control of vector borne diseases, like leishmaniasis and malaria, which were until recently, controlled by the health authorities using DDT.

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A brief review about the main thermochemical and spectroscopic basicity scales is presented, with a discussion about the range of reliability of them. Is concluded that, as a general trend, thermochemical basicity scales are more sensitives, and so reliable, than spectroscopic ones.

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This paper supplies a revision about the main techniques of extraction, clean-up and pre-concentration of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in water and soil samples, as well as chromatographic methods and immune assays for its identification and quantification.

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Cyclic imides consists of an important family of organic compounds with therapeutic potential. In this review, emphasis will be given to the chemical and biological aspects of several sub-classes of this family, incluing maleimides, succinimides, glutarimides, naphtalimides, etc. Additionally, will be focused the contribution of our research group in this field.

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La comunicación que presentamos nace de una investigación centrada en la descripción del gesto lector del resumen de textos narrativos por parte del alumnado que inicia la educación secundaria obligatoria. Los resultados obtenidos han permitido elaborar una rúbrica descriptiva que nos informa del estado de desarrollo de multitud de procesos relacionados con este gesto lector y, en consecuencia, pueden ser utilizados para centrar la formación del alumnado en las distintas etapas educativas. La comunicación mostrará la posibilidad de incorporar los resultados de la investigación en los libros de texto destinados al alumnado.

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This article presents a review of published literature concerning the use of computer simulations and modeling tools in Chemical Education. The findings about the possibilities of their application in the Chemistry curriculum, their effective implementation, the teaching methods involved, the research methodology and also the instruments of evaluation that were used and their results were described and analyzed. The need to develop adequate theory support to educators who want to start using this new technology in their Chemistry classes became evident along the research, as well as the lack of development of model perception among Chemistry educators and learners.

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Despite of being used as thermodynamic criterion to rank alkene stability in a number of undergraduate textbooks, the heat of hydrogenation does not describe adequately the relative stability of disubstituted alkenes. In this work, both the heat of formation and the heat of combustion were used as thermodynamic criteria to rank correctly the stability of alkenes according to the degree of alkyl substitution and also in the disubstituted series (geminal > trans > cis). An operational model based on molecular orbital and valence bond representations of hyperconjugation is proposed to show how this effect can explain the order of stability of this class of compounds.

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This paper provides a review on voltammetric and polarographic methods for the speciation analysis of inorganic and organic arsenic compounds in different matrices. A discussion on the main advantages of electroanalytical methods in comparison with other analytical methods employed for arsenic speciation is presented. The mechanistic aspects of the most relevant techniques employing cathodic and anodic stripping voltammetry as well as polarographic methods published in the last twenty five years are summarized and discussed. The bibliographic references cited in this work were selected from the Web of Science (published by the ISI) and the main journals of analytical chemistry.

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Aquest TFG és la memòria de les pràctiques de revisió i correcció de textos escrits fetes al digital de cultura 'Núvol'. En la memòria faig una presentació i una anàlisi del digital, explico les tasques desenvolupades durant les pràctiques i en faig la valoració.

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We present studies involving metallic ions and the herbicide glyphosate. The metallic complexes of Cu(II), Zn(II), Mn(II), Ni(II), Cd(II), Pb(II), Cr(III), Fe(III), Co(III), ammonium, sodium, Ag(I), alkaline earth metals and of some lanthanides ions are described. The complexes are discussed in terms of their synthesis, identification, stability and structural properties, based on data from the current literature.

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This article deals with synthesis and reactivity of complexes with triphenylstibine (SbPh3) as the ligand. A comparative study of analogous complexes of triphenylphosphine (PPh3) and triphenylarsine (AsPh3) with platinum in the oxidation states zero, two and four is included. The bibliographic revision includes publications since 1936, when the first Pt(II) complex with triphenylstibine was described.

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Gravimetric and Bailey-Andrew methods are tedious and provide inflated results. Spectrofotometry is adequate for caffeine analysis but is lengthy. Gas chromatography also is applied to the caffeine analysis but derivatization is needed. High performance liquid chromatography with ultraviolet detection (HPLC-UV) and reversed phase is simple and rapid for xanthine multianalysis. In HPLC-UV-gel permeation, organic solvents are not used. HPLC-mass spectrometry provides an unequivocal structural identification of xanthines. Capillary electrophoresis is fast and the solvent consumption is smaller than in HPLC. Chemometric methods offer an effective means for chemical data handling in multivariate analysis. Infrared spectroscopy alone or associated with chemometries could predict the caffeine content in a very accurate form. Electroanalytical methods are considered of low cost and easy application in caffeine analysis.