1,721,042 research outputs found
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
A wind-tunnel study on saltation and PM10 emission from agricultural soils
No full textPM10 emission depends on the texture and the aggregation state of a soil. A decisive but less studied factor is the saltation fraction of the soil (fraction between 100 and 500 μm). Six soils of contrasting textures were selected, and a wind tunnel study was carried out under three different saltation conditions: increased saltation, in which a sample of the saltation fraction was added to the air stream prior to the soil bed; no saltation added, in which the soil bed eroded without the addition of extra saltation fraction; and only saltation, in which the saltation fraction was injected into the air stream in the absence of the soil bed. Results indicated that the saltation efficiency for PM10 emission increased with the fine fraction content of the soil and decreased with the sand content, but this process showed a complex behavior depending on the cohesion and stability of the aggregates. An index for describing the saltation efficiency of the studied soils was proposed based on the combination of three parameters: the PM10 content, the amount of saltation fraction available in the soil surface, and an aggregation parameter (clay × organic matter content). Increasing the saltation rate increased the PM10 emission from the eroding soil bed, except for the sandy soil. Results suggest that the main mechanisms of PM10 emission under saltation conditions differ according to the soil texture: detachment of the PM10 adhered to the grains of sand predominates on sandy soils and fragmentation on finer soils, but both processes occur together on high-emitting soils of intermediate textures.EEA AnguilFil: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina.Fil: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Buschiazzo, Daniel Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin
A study on the fragmentation of saltating particles along the fetch distance during wind erosion
No full textPM10 emission largely depends on the characteristics of the saltation process, which involves the movement of aggregate and isolated particles. Studies analyzing the relationship between the fragmentation of saltating aggregates and the dust emission along the fetch distance are very scarce. The objective of the present study was to analyze, on a loamy texture soil, the changes in the size distribution of the eroded sediment along the fetch distance under field conditions. Changes in the particle size distribution of the transported material were measured at four different heights above the soil surface every 25 m on a 200 m plot, during three strong wind erosion events. Statistically significant differences were found both for particle size distribution and aggregation when comparing the eroded sediment at the windward and leeward sides of the experimental plot. A greater proportion of coarser particles was found as the distance traveled by the eroded sediment increased. From the change in average particle size distribution at the beginning and at the end of the 200 m experimental plot, it was estimated that around 12% of the particles smaller than 62.5 μm were lost by vertical transport (dust plume) producing an average concentration of 48 µg m−3 at 2 m height and 200 m fetch. Under the conditions of this experiment, a soil aggregate transported by saltation was fragmented at a rate of 38% every 100 m traveled (R2 = 0.88; p < 0.001). Particle size analysis of the eroded sediment and open-air PM10 concentration measurements indicated that the fragmentation of aggregates during saltation can be considered as the main mechanism of dust emission on this soil.EEA AnguilFil: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Buschiazzo, Daniel Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin
Variable effects of saltation and soil properties on wind erosion of different textured soils
Get PDFWind erosion largely depends on saltation. Nevertheless, the effect of the composition of the saltation fraction of different textured soils is poorly understood, as is the relative influence of both saltation and soil properties on wind erosion. In order to answer these questions, wind erosion of six differently textured soils were simulated with a wind tunnel. The following saltation conditions were considered: injected saltation, in which the saltation fraction of each soil was added to the soil bed; no saltation, in which the soil eroded naturally, without injection of its saltation fraction; and only saltation, in which the saltation fraction was injected in absence of the soil bed. Results indicated that total erosion amounts increased as a function of the abrasion energy of the saltating particles but also with decreasing aggregation rate of the saltation fraction. The aforementioned agrees with a lower aggregate stability and higher amounts of the erodible fraction of sandy soils. Though saltation of individual sand grains produced impacts of higher kinetic energy on the soil surface of sandy soils than of fine textured soils, the relative erosion (quotient between the erosion occurred with and without saltation) was higher in finest soils, indicating a larger effect of saltation, probably due to the larger fragmentation of aggregates in these soils. Results of this study indicated that both the composition of the saltating fraction and also the intrinsic properties of the soil determined wind erosion.Fil: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Buschiazzo, Daniel Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Síntesis, caracterización y comportamiento biológico de hidrazonas derivadas de piridoxal y de sus complejos de vanadio
Get PDF[Resumen]
El vanadio como metal es micronutriente esencial con una concentración de 0,3μM en el cuerpo humano. La similitud que presenta el vanadato con el fosfato lleva a estudiar el vanadio frente a dolencias como el cáncer. En este trabajo se buscó conse-guir metalofármacos de vanadio con baja toxicidad y estables. Para ello se han sinteti-zado cuatro compuestos de vanadio con ligandos hidrazona derivados de piridoxal.
Se estudiaron los ligandos hidrazona (L1, L2, L3 y L4) y los compuestos de oxidova-nadio (L1c, L2c, L3c y L4c) por diferentes técnicas de caracterización: análisis elemental, espectrometría de masas, espectroscopia RMN 1H y espectroscopia IR con el fin de con-firmar la coordinación del metal a los ligandos y la variada especiación química del va-nadio en disolución. Además, se realizaron estudios de difracción de rayos X de mono-cristal para todos los ligandos y los complejos L2c y L3c. Destacamos la interacción de par de no enlace del átomo de cloro con la nube π del grupo piridoxal predomina en el com-puesto L3c frente a otro tipo de interacciones menos fuertes.
Los estudios de citotoxicidad in vitro de los compuestos se llevaron a cabo en la línea celular A549 (cáncer de pulmón) mediante un ensayo de MTT. Los resultados ob-tenidos se correlacionan con los obtenidos en rayos X, siendo el compuesto L3c el que mayor citotoxicidad presenta en general a las diferentes concentraciones en 48h.
Finalmente, se usó el modelo animal pez cebra para la realización de los estudios in vivo. La toxicidad detectada en los compuestos estudiados no nos permitió calcular el LC50.
Sería necesario profundizar en los estudios in vitro e in vivo para poder concluir si pueden llegar a ser o no unos buenos candidatos como posibles metalofármacos an-titumorales.[Resumo]
Este traballo céntrase na busca de meta lofármacos de vanadio con baixa toxicidade
e estables. Para elo sintetizáronse catro ligandos hidrazona derivados de piridoxal
e os seus correspondentes complexos de vanadio (L1, L2, L3, L4, L1c, L2c, L3c e L4c). Que
foron estudados mediante diferentes técnicas de caracterización: análise elemental, espectrometría
de masas, espectroscopia RMN 1H e espectroscopía IR para confirmar a
coordinación do metal aos ligandos e a variada especiación química do vanadio en disolución.
Tamén se levaron a cabo estudos de raios X de monocristal nalgúns deles. Por
outra banda, realizáronse estudos biolóxicos como o ensaio MTT para estudos in vitro,
onde se empregou a liña celular A549. Os resultados obtidos mostraron que o composto
L3c é o que ten maior citotoxicidade en xeral ás diferentes concentracións en 48h.
Finalmente, utilizouse o modelo animal de peixe cebra para realizar estudos in
vivo. A toxicidade detectada nos compostos estudados non nos permitiu calcular o LCso.[Abstract]
This work is focused on the search for vanadium metalopharmaceuticals with
low toxicity and stable. For this, four hydrazone ligands derived from pyridoxal and their
corresponding vanadium compounds have been synthesized (L', L2, L3, L4, L1c, L2c, L3c
and L 4 c). They were studied by different characterization techniques: elemental analysis,
mass spectrometry, 1H NMR spectroscopy and IR spectroscopy, in order to confirm the
coordination of the metal to the ligands and the varied chemical speciation of vanadium
in solution. Single crystal X-ray studies were also carried out on sorne of them. On the
other hand, biological studies were carried out, such as the MTT assay for in vitro studies,
where the A549 cell line was used. The results obtained showed that the L3c compound
has the highest cytotoxicity in general at the different concentrations in 48h.
Finally, the zebrafish model was u sed to carry out the in vivo studies. The toxicity
detected in the studied compounds did not allow us to calculate the LCso
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