5,312 research outputs found
Cover Picture: Towards Organo‐Click Chemistry: Development of Organocatalytic Multicomponent Reactions Through Combinations of Aldol, Wittig, Knoevenagel, Michael, Diels–Alder and Huisgen Cycloaddition Reactions (Chem. Eur. J. 21/2004)
No full textThe cover picture shows a perspective of organo-click chemistry depicting the bringing together of simple reagents, and amino acid and copper/copper sulfate catalysts to produce spirotriones, which are antioxidant compounds. Unlike conventional methods, organo-click chemistry produces stereospecific products with very good yields in a single operation. Multicomponent reactions catalyzed by amino acids and copper sulfate together with simple reagents depicted here support the potential of a rich variety of chemistries available to the prebiotic world and beyond. For more information see the article by D. B. Ramachary and C. F. Barbas III on p. 5323 ff. The picture was designed by Michael Pique at the Scripps Research Institute
Six Overtures Composed by C. F. Abel. Adapted for the Harpsichord or Piano Forte : being Opera First / By the Author
No full textSIX OVERTURES COMPOSED BY C. F. ABEL. ADAPTED FOR THE HARPSICHORD OR PIANO FORTE : BEING OPERA FIRST / BY THE AUTHOR
Six Overtures Composed by C. F. Abel. Adapted for the Harpsichord or Piano Forte : being Opera First / By the Author (1)
Cover (1)
Titelseite (2)
Overture I. (3)
Overture II. (8)
Overture III. (12)
Overture IV. (16)
Overture V. (20)
Overture VI. (24
Zinc finger recombinases with adaptable DNA sequence specificity
No full textSite-specific recombinases have become essential tools in genetics and molecular biology for the precise excision or integration of DNA sequences. However, their utility is currently limited to circumstances where the sites recognized by the recombinase enzyme have been introduced into the DNA being manipulated, or natural 'pseudosites' are already present. Many new applications would become feasible if recombinase activity could be targeted to chosen sequences in natural genomic DNA. Here we demonstrate efficient site-specific recombination at several sequences taken from a 1.9 kilobasepair locus of biotechnological interest (in the bovine beta-casein gene), mediated by zinc finger recombinases (ZFRs), chimaeric enzymes with linked zinc finger (DNA recognition) and recombinase (catalytic) domains. In the "Z-sites" tested here, 22 bp casein gene sequences are flanked by 9 bp motifs recognized by zinc finger domains. Asymmetric Z-sites were recombined by the concomitant action of two ZFRs with different zinc finger DNA-binding specificities, and could be recombined with a heterologous site in the presence of a third recombinase. Our results show that engineered ZFRs may be designed to promote site-specific recombination at many natural DNA sequence
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Influence of diluent alkyl substitution on the extraction of Am(III) and Eu(III) by a 6,6’-bis(1,2,4-triazin-3-yl)-2,2’-bipyridine ligand dissolved in alkylated cyclohexanone Diluents
No full textSeveral alkylated cyclohexanones were investigated as potential diluents for the selective extraction of Am(III) from Eu(III) from nitric acid solutions by the CyMe4-BTBP ligand. No significant extraction of either of the metal ions was observed for these diluents themselves. In the extractions from 1 M HNO3, 3-methylcyclohexanone and 4-methylcyclohexanone gave comparable results to cyclohexanone whereas in the extractions from 4 M HNO3, 2-methylcyclohexanone, 3-methylcyclohexanone and 4-methylcyclohexanone all gave superior results. For the monomethylated diluents, DAm and SFAm/Eu decreased in the order of alkyl substitution 2 > 4 ~ 3. However, alkyl substitution of cyclohexanone significantly slows down the extraction kinetics compared to cyclohexanone, and the position of alkyl substitution was found to play an important role in the solvents properties. 3-Methylcyclohexanone was identified as the most promising of the diluent
Estudo comparativo entre hidróxido de sódio e hexametafosfato de sódio atuando como dispersantes químicos de argila
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Físicas e Matemáticas. Curso de Química.A determinação do teor de argila em amostras de solo é de grande interesse para a agricultura. Em laboratórios de análise de solo, onde o volume de amostras a serem analisadas por dia é muito grande, é comum utilizar métodos simplificados, calibrados com base em um método padronizado. Uma técnica bastante utilizada se baseia na medida da densidade da suspensão obtida com a dispersão da amostra de solo em uma solução dispersante adequada. Para que essa técnica tenha resultados satisfatórios é necessário que se use um dispersante eficaz, ou seja, capaz de dispersar o máximo possível da argila presente na amostra. O presente trabalho, realizado no laboratório de análise de solo da CIDASC (Companhia Integrada de Desenvolvimento Agrícola de Santa Catarina) no período de agosto a dezembro de 2004, se trata de uma comparação entre os dispersantes químicos hexametafosfato de sódio e hidróxido de sódio na eficácia da dispersão de 26 amostras de solo de SC. Foram construídas curvas de calibração do tipo % de argila em função da variação de densidade para cada uma dos dezesseis soluções dispersantes empregadas. Foram utilizadas soluções somente com hidróxido de sódio, somente com hexametafosfato de sódio e com misturas entre eles. O melhor dispersante foi escolhido em função do melhor coeficiente de correlação (e conseqüentemente menor desvio padrão). As porcentagens de argila das amostras foram obtidas segundo o método da pipeta, considerado padrão para tal determinação. As melhores soluções dispersantes foram NaOH 6,68 g L-1 + (NaPO3)6 40,0 g L-1 (R2 = 0,966 e SD = 3,43), NaOH 6,68 g L-1 + (NaPO3)6 20,0 g L-1 (R2 = 0,961 e SD = 3,71) e NaOH 20,0 g L-1 + (NaPO3)6 40,0 g L-1 (R2 = 0,960 e SD = 3,72). Além da comparação entre os dispersantes, correlações entre propriedades físico-químicas e o grau de floculação das amostras dispersas em água foram realizadas. Correlações negativas foram encontradas com os teores (Na + K), (Al + Ca + Mg), P e pH em água. Correlação positiva foi encontrada com o teor de matéria orgânica
El perfil metabólico de los pacientes puede definir el pronóstico de la COVID-19
No full textNota de prensa y noticia publicada el 03/08/2022Un estudio liderado desde el Centro Nacional de Microbiología del ISCIII, publicado en la revista Frontiers in Immunology, identifica diversas rutas metabólicas que marcan diferentes patrones en la evolución de la COVID-19, y sugiere que su análisis en pacientes ingresados facilitaría la identificación de quiénes evolucionarán hacia una enfermedad grave o moderada. Puede consultar el artículo: Ceballos FC, Virseda-Berdices A, Resino S, Ryan P, Martínez-González O, Peréz-García F, Martin-Vicente M, Brochado-Kith O, Blancas R, Bartolome-Sánchez S, Vidal-Alcántara EJ, Albóniga-Díez OE, Cuadros-González J, Blanca-López N, Martínez I, Martinez-Acitores IR, Barbas C, Fernández-Rodríguez A and Jiménez-Sousa MÁ (2022) Metabolic Profiling at COVID-19 Onset Shows Disease Severity and Sex-Specific Dysregulation. Front. Immunol. 13:925558. doi: 10.3389/fimmu.2022.925558.N
Research in economics in Spain: rankings of institutions and authors
No full textIn this paper we analyse the research in Economics in Spain during the 1990s considering the contributions of both Spanish and foreign economist who have worked in Spain during that period. To do so, we use different bibliometric indicators in order to elaborate rankings for both institutions and researchers. These rankings can be useful for several potentials users such as: a) Evaluation Agencies and Funding Bodies to help them in grant-allocation decisions; b) Graduate students who whish to choose the right institution to complete their postgraduate education, and c) Young Ph Ds who have entered the academic job market and need information about the research perfomance of different institutions
Producción científica y visibilidad de los investigadores de la Universidad Carlos III de Madrid en las bases de datos del ISI, 1997-2003
No full textLos objetivos planteados en esta tesis son conocer los hábitos de publicación de los investigadores adscritos a un conjunto de áreas/departamentos de la UC3M, durante el período 1997-2003, en las bases de datos del Institute for Scientific Information (ISI), identificando la calidad de las publicaciones recogidas (documentos propios y citas recibidas), medida ésta en términos de impacto y visibilidad, y relacionando esta calidad con los hábitos de publicación obtenidos.
La metodología utilizada en el trabajo ha requerido la aplicación conjunta de técnicas estadísticas (univariantes, bivariantes y multivariantes), y del análisis de redes sociales, para la construcción de indicadores bibliométricos unidimensionales y multidimensionales, tanto de la producción científica identificada como de las citas recibidas por la misma.
Entre las conclusiones del estudio destaca que tanto la producción como las citas recibidas en todas las áreas/departamentos analizados tienen una tendencia ascendente, que los trabajos se realizan habitualmente en colaboración, así como que las temáticas con mayor producción son Física y Matemáticas, que gran parte de la investigación se publica en revistas situadas en el primer cuartil del Journal Citation Reports (JCR), y que esta actividad investigadora recibe normalmente citas de revistas con igual o mejor posición en el JCR en función de su Factor de Impacto
Organocatalysis Reactions With Chiral Amines. Mechanistic Aspects And Use On Organic Synthesis [reações De Organocatálise Com Aminas Quirais. Aspectos Mecanísticos E Aplicações Em Síntese Orgânica]
No full textThe philosophy of organocatalysis is based on the utilization of organic compounds to catalyze organic transformations without the intervention of metals. This area has attracted much attention of the synthetic chemistry community on the last years, which can be confirmed by the explosion of published papers dealing with this subject. Phosphorus compounds, urea and thiourea derivatives, alkaloids, guanidine derivatives, for example, have already been used as organocatalysts. In this review we have focused on the use of chiral amines as organocatalyst. We have also chosen some outstanding examples to demonstrate the potentiality of this strategy in the synthesis of natural products and biologically active compounds.322469481Alexakis, A., (2007) Chimia, 61, p. 212Hajos, Z.G., Parrish, D.R., (1974) J. Org. Chem, 39, p. 1615Hajos, Z. G.Parrish, D. R.Patente Alemã DE 2,102,623,1978 (CA, 1978, 88, 62529)Eder, U., Sauer, G., Wiechert, R., (1971) Angew. Chem., Int. 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