1,721,078 research outputs found
Campos locales en cristales líquidos termotrópicos : su influencia en estudios por RMN
Get PDFTesis (Doctor en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2002.Fil: Acosta, Rodolfo Héctor. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.En esta tesis se presenta un análisis de la influencia de las interacciones dipolares en diabaticidad del proceso de demagnetización en un experimento por ciclado de campo magnético. Esta técnica ha sido utilizada para discernir los movimientos colectivos particularmente en fluídos complejos. Enlos cristales líquidos termotrópicos, se observan discrepancias en las mediciones para frecuencias de Larmor muy bajas en estudios presentados por diversos autores. Proponemos la utilización de una secuencia multipulso para evaluar la intensisdad de los acoples dipolares de una manera rápida como también, un experimento novedoso para evaluar el desorden que las fluctuaciones térmicas introducen en un cristal líquido a campo cero.Fil: Acosta, Rodolfo Héctor. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina
Water state/structure inside nanopores modulates hydrolytic enzymatic catalysis
Get PDFFil: Burgos, Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina.Fil: Burgos, Inés. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química Industrial y Aplicada. Cátedra de Química Biológica; Argentina.Fil: Velasco, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Velasco, Manuel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Acosta, Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Acosta, Rodolfo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Ochoa, A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; Argentina.Fil: Perillo, M. A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; Argentina.In the present work we studied the catalytic activity of E.coli β-Gal confined in a nanoporous silicate matrix (Eβ-Gal) at different times after the beginning of the sol-gel polymerization process. The use of two substrates (ONPG and PNPG) differing in the rate-limiting steps of their hydrolysis reaction mechanisms, in conjunction with data from transverse relaxation
1H-NMR (T2), and scanning electron microscopy analysis of the nanostructure of gels,
provided evidence that water availability is crucial for the modulation observed in the catalytic activity of β-Gal provided water participates in the rate limiting step of the reaction (only with ONPG). In this case, a biphasic rate vs. substrate concentration is obtained exhibiting one phase with catalytic rate constant (kcA) similar to that obtained in solution and another phase with a higher and aging-dependent catalytic rate constant (kcB). More structured water populations (lower T2) correlates with higher catalytic rate constants (kcB). A T2-kcB negative correlation is maintained along gels agingwithin the 15 days period assayed.https://intranet.biofisica.org.ar/media/libro/libro_final_2019.pdfFil: Burgos, Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina.Fil: Burgos, Inés. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química Industrial y Aplicada. Cátedra de Química Biológica; Argentina.Fil: Velasco, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Velasco, Manuel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Acosta, Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Acosta, Rodolfo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Ochoa, A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; Argentina.Fil: Perillo, M. A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; Argentina.Otras Ciencias Química
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
High-resolution hyperpolarized J-Spectra with Parahydrogen discrimination
Get PDFParahydrogen-induced polarization (PHIP) has become a powerful tool not only to overcome the low intrinsic sensitivity of nuclear magnetic resonance (NMR) but also as a probe for catalytic reactions, as a contrast agent in magnetic resonance imaging (MRI), or in analytic chemistry. In complex systems, the antiphase signals coming from parahydrogen in a PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) experiment can be partially canceled by the presence of large thermally polarized signals. In the present work, we present a simple method to separate the thermal and hyperpolrized contributions by taking advantage of their very different evolution during a modified CPMG sequence. The separation is obtained in combination with a property of the fast Fourier transform algorithm (FFT). The technique is experimentally demonstrated for a mixture of hyperpolarized 1-hexene and a large amount of CH2Cl2.Fil: Prina, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin
Combination of OPSY and PhD-PHIP results in enhanced sensitivity in PHIP
No full textDespite the large degree of polarization in PHIP experiments compared to the Boltzmann factor, the presence of a large amount of non-reacted molecules with thermal polarization is an important obstacle when dealing with very diluted samples. The feasibility of enhancing both sensitivity and resolution in a single experiment by combining two well established pulse sequences, OPSY and PHD-PHIP is presented. OPSY is used as a block for filtering the signals originated from thermally polarized protons. PhD-PHIP, on the other hand, is used as an acquisition block, increasing the resolution and further improving the sensitivity by preventing signal canceling in the presence of magnetic field inhomogeneities. Experiments in a complex sample with very low hyperpolarization levels are presented showing the excellent performance of the method.Fil: Bussandri Mattia, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin
Diffusion measurements with continuous hydrogenation in PHIP
No full textDOSY is a powerful spectroscopic NMR technique that resolves components in mixtures through the evaluation of different diffusion coefficients. The application of DOSY to dilute mixtures is hampered by the low signal to noise ratios (SNR), leading to long acquisition times. The use of PHIP may resolve this issue as long as reproducible signals are obtained in order to perform 2D experiments. Here we show that the use of hollow membranes and adequate gas flow produce constant polarization for a time-span that enables the acquisition of 2D experiments. A pressure gradient is evidenced by the presence of convection, which is accounted for by using a DPGSE sequence. The influence of J-coupling evolution during the sequence is studied both numerically and experimentally, to determine the optimum echo-time. The applicability of the method for samples with poor SNR is explored by setting the reaction rate to achieve a low intensity of polarized signals.Fil: Bussandri Mattia, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Buljubasich Gentiletti, Lisandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Acosta, Rodolfo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin
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