1,720,961 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Design, synthesis, and evaluation of thiodisaccharides mimetics of lactose. Inhibition of a β-galactosidase
No full textLa búsqueda de nuevos inhibidores de enzimas involucradas en procesos biológicos claves es un área en auge que ha promovido avances sustanciales en glicobiología. Entre los glicomiméticos desarrollados para investigar estos procesos, los tiodisacáridos, obtenidos mediante reemplazo por azufre del átomo de oxígeno del enlace interglicosídico, se han posicionado como buenos targets. Dada la similitud estructural con sus análogos naturales, suelen ser reconocidos por las enzimas, pero generalmente son más resistentes a la hidrólisis y a los procesos metabólicos que sus contrapartes naturales y, en muchos casos, actúan como inhibidores de las mismas. Por estos motivos, la síntesis de tiodisacáridos ha atraído considerable atención y, en los últimos años, se han desarrollado procedimientos sintéticos novedosos para obtenerlos mediante secuencias eficientes y altamente diastereoselectivas. Considerando la relevancia biológica y el potencial terapéutico de estos compuestos como inhibidores enzimáticos y herramientas en glicobiología, se planteó como objetivo de esta Tesis el diseño y síntesis de bencil 3-desoxi-4-tiodisacáridos con construcción estereoselectiva del enlace tioglicosídico. Estas moléculas se diseñaron con modificaciones específicas basadas en estudios previos del laboratorio, en particular, en la estructura del anillo piranosídico del extremo reductor e introduciendo sustituyentes en el anillo aromático del bencilo anomérico. Para la construcción del enlace tioglicosídico se emplearon enonas de azúcares (2-benciloxi- dihidropiranonas quirales) como precursoras del extremo reductor de los tiodisacáridos y que portaban grupos electrodonores o electroatractores en el bencilo. También, con el fin de introducir un grupo acetamido en el C-2, en reemplazo del HO-2, se sintetizaron las oximas derivadas de las enonas. Estos sistemas α,β-insaturados (enonas y oximas) se emplearon como aceptores en la adición conjugada de la 1-tiogalactosa, en la cual se lograba la construcción del enlace tioglicosídico regio- y diastereoselectivamente. Uno de los pasos de la secuencia sintética completa, que lleva desde las enonas hasta los tiodisacáridos libres, involucraba la reducción de un grupo carbonilo (u oxima), reacción que generaba dos tiodisacáridos con configuración opuesta en C-2. Esto permitió estudiar la influencia de dicho estereocentro en la inhibición. En el caso de la oxima, su reducción producía un grupo amino en C-2, obteniéndose 2-amino-2,3- didesoxi-4-tiodisacáridos. Este procedimiento constituye una metodología novedosa para sintetizar este tipo de tiodisacáridos. Todos los compuestos libres obtenidos se evaluaron como inhibidores de la β-galactosidasa de E. coli, una enzima paradigmática de amplio uso en glicobiología. Se llevaron a cabo estudios de cinética enzimática y se determinó la constante de inhibición (Ki) y el tipo de inhibidor. Se obtuvieron inhibidores competitivos, no competitivos y mixtos con valores de Ki en el rango de 14-180 μM. Cabe destacar que, entre los tiodisacáridos descriptos en literatura, algunos de estos resultaron ser los inhibidores más potentes. Se lograron correlacionar las modificaciones estructurales con el potencial inhibidor de los tiodisacáridos.The search for inhibitors of enzymes, which are involved in key biological processes, is an expanding area that has promoted substantial progress in glycobiology. Among the most common glycomimetics developed to study these processes, the thiodisaccharides have raised as useful targets. These compounds result from the replacement of the interglycosidic oxygen atom by sulfur. Due to their structural resemblance with the natural counterpart, they are commonly recognized by the enzymes. However, they usually show resistance to hydrolysis and to metabolic degradation, and act, in many cases, as enzyme inhibitors. Therefore, the synthesis of thiodisaccharides has attracted great attention, and novel highly diastereoselective and efficient synthetic procedures have been developed. In light of the biological relevance and therapeutic potential of thiodisaccharides and their use as enzyme inhibitors and useful tools in glycobiology, the main goal of this Thesis was the design and synthesis of benzyl 3-deoxy-4-thiodisaccharides with stereoselective construction of the thioglycosidic linkage. These molecules were designed including specific modifications, based on previous studies from our laboratory, in the structure of the pyranoside reducing end and in the substitution of the aromatic ring of the benzyl group. For the construction of the thioglycosidic linkage, sugar enones (chiral 2-benzyloxy-dihydropyranones) were employed as precursor for the reducing end of the thiodisaccharides. The benzyloxy substituent of the enone carried electron withdrawing or electron donating groups. Additionally, to introduce an acetamide group at C-2, in replacement of HO-2, the oximes derived from the enones were synthesized. These α,β-unsaturated systems (enones and oximes) were employed as acceptors in the conjugate addition of 1-thiogalactose, achieving regio- and stereoselective construction of the thioglycosidic bond. One of the steps in the full synthetic sequence, from the enones to the free thiodisaccharides, involved the carbonyl (or oxime) reduction, thus, generating two diastereoisomers with opposite configuration at C-2. This way the influence of the C-2 stereocenter on the inhibition could be studied. The reduction of the oxime led to an amino group at C-2, thus obtaining 2-amino-2,3- dideoxy-4-thiodisaccharides. This procedure turned out to be a novel methodology for the synthesis of this type of molecules. All free compounds were evaluated as inhibitors of the E. coli β-galactosidase, a paradigmatic enzyme widely used in glycobiology. Enzyme kinetics were conducted and for each individual compound have been determined the inhibition constant (Ki) and the type of inhibitor. Competitive, non-competitive, and mixed inhibitors were obtained with Ki values in the range of 14-180 μM. Some of these thiodisaccharides were found to be, so far, the more powerful inhibitors of this kind. A correlation between the structural modifications and the inhibitory potential of the thiodisaccharides was established.Fil: Dada, Lucas. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Design, synthesis, and evaluation of thiodisaccharides mimetics of lactose. Inhibition of a β-galactosidase
Full text linkLa búsqueda de nuevos inhibidores de enzimas involucradas en procesos biológicos claves es un área en auge que ha promovido avances sustanciales en glicobiología. Entre los glicomiméticos desarrollados para investigar estos procesos, los tiodisacáridos, obtenidos mediante reemplazo por azufre del átomo de oxígeno del enlace interglicosídico, se han posicionado como buenos targets. Dada la similitud estructural con sus análogos naturales, suelen ser reconocidos por las enzimas, pero generalmente son más resistentes a la hidrólisis y a los procesos metabólicos que sus contrapartes naturales y, en muchos casos, actúan como inhibidores de las mismas. Por estos motivos, la síntesis de tiodisacáridos ha atraído considerable atención y, en los últimos años, se han desarrollado procedimientos sintéticos novedosos para obtenerlos mediante secuencias eficientes y altamente diastereoselectivas. Considerando la relevancia biológica y el potencial terapéutico de estos compuestos como inhibidores enzimáticos y herramientas en glicobiología, se planteó como objetivo de esta Tesis el diseño y síntesis de bencil 3-desoxi-4-tiodisacáridos con construcción estereoselectiva del enlace tioglicosídico. Estas moléculas se diseñaron con modificaciones específicas basadas en estudios previos del laboratorio, en particular, en la estructura del anillo piranosídico del extremo reductor e introduciendo sustituyentes en el anillo aromático del bencilo anomérico. Para la construcción del enlace tioglicosídico se emplearon enonas de azúcares (2-benciloxi- dihidropiranonas quirales) como precursoras del extremo reductor de los tiodisacáridos y que portaban grupos electrodonores o electroatractores en el bencilo. También, con el fin de introducir un grupo acetamido en el C-2, en reemplazo del HO-2, se sintetizaron las oximas derivadas de las enonas. Estos sistemas α,β-insaturados (enonas y oximas) se emplearon como aceptores en la adición conjugada de la 1-tiogalactosa, en la cual se lograba la construcción del enlace tioglicosídico regio- y diastereoselectivamente. Uno de los pasos de la secuencia sintética completa, que lleva desde las enonas hasta los tiodisacáridos libres, involucraba la reducción de un grupo carbonilo (u oxima), reacción que generaba dos tiodisacáridos con configuración opuesta en C-2. Esto permitió estudiar la influencia de dicho estereocentro en la inhibición. En el caso de la oxima, su reducción producía un grupo amino en C-2, obteniéndose 2-amino-2,3- didesoxi-4-tiodisacáridos. Este procedimiento constituye una metodología novedosa para sintetizar este tipo de tiodisacáridos. Todos los compuestos libres obtenidos se evaluaron como inhibidores de la β-galactosidasa de E. coli, una enzima paradigmática de amplio uso en glicobiología. Se llevaron a cabo estudios de cinética enzimática y se determinó la constante de inhibición (Ki) y el tipo de inhibidor. Se obtuvieron inhibidores competitivos, no competitivos y mixtos con valores de Ki en el rango de 14-180 μM. Cabe destacar que, entre los tiodisacáridos descriptos en literatura, algunos de estos resultaron ser los inhibidores más potentes. Se lograron correlacionar las modificaciones estructurales con el potencial inhibidor de los tiodisacáridos.The search for inhibitors of enzymes, which are involved in key biological processes, is an expanding area that has promoted substantial progress in glycobiology. Among the most common glycomimetics developed to study these processes, the thiodisaccharides have raised as useful targets. These compounds result from the replacement of the interglycosidic oxygen atom by sulfur. Due to their structural resemblance with the natural counterpart, they are commonly recognized by the enzymes. However, they usually show resistance to hydrolysis and to metabolic degradation, and act, in many cases, as enzyme inhibitors. Therefore, the synthesis of thiodisaccharides has attracted great attention, and novel highly diastereoselective and efficient synthetic procedures have been developed. In light of the biological relevance and therapeutic potential of thiodisaccharides and their use as enzyme inhibitors and useful tools in glycobiology, the main goal of this Thesis was the design and synthesis of benzyl 3-deoxy-4-thiodisaccharides with stereoselective construction of the thioglycosidic linkage. These molecules were designed including specific modifications, based on previous studies from our laboratory, in the structure of the pyranoside reducing end and in the substitution of the aromatic ring of the benzyl group. For the construction of the thioglycosidic linkage, sugar enones (chiral 2-benzyloxy-dihydropyranones) were employed as precursor for the reducing end of the thiodisaccharides. The benzyloxy substituent of the enone carried electron withdrawing or electron donating groups. Additionally, to introduce an acetamide group at C-2, in replacement of HO-2, the oximes derived from the enones were synthesized. These α,β-unsaturated systems (enones and oximes) were employed as acceptors in the conjugate addition of 1-thiogalactose, achieving regio- and stereoselective construction of the thioglycosidic bond. One of the steps in the full synthetic sequence, from the enones to the free thiodisaccharides, involved the carbonyl (or oxime) reduction, thus, generating two diastereoisomers with opposite configuration at C-2. This way the influence of the C-2 stereocenter on the inhibition could be studied. The reduction of the oxime led to an amino group at C-2, thus obtaining 2-amino-2,3- dideoxy-4-thiodisaccharides. This procedure turned out to be a novel methodology for the synthesis of this type of molecules. All free compounds were evaluated as inhibitors of the E. coli β-galactosidase, a paradigmatic enzyme widely used in glycobiology. Enzyme kinetics were conducted and for each individual compound have been determined the inhibition constant (Ki) and the type of inhibitor. Competitive, non-competitive, and mixed inhibitors were obtained with Ki values in the range of 14-180 μM. Some of these thiodisaccharides were found to be, so far, the more powerful inhibitors of this kind. A correlation between the structural modifications and the inhibitory potential of the thiodisaccharides was established.Fil: Dada, Lucas. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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