1,721,067 research outputs found
Agriculture and N2O emissions in Argentinean Mollisols
No full textEl objetivo de este Capítulo es caracterizar la influencia de las principales prácticas agrícolas sobre el proceso de desnitrificación y las emisiones de N2O resultantes, determinando los factores más destacados que los regulan. Las labranzas tienen un gran efecto sobre los factores que regulan la desnitrificación y las emisiones de N2O. La labranza reducida (cero) suele mantener suelos más húmedos y con una gran acumulación de C y N en la superficie edáfica con respecto a sistemas de labranza convencional, lo que podría estimular procesos de reducción con formación de N2O por desnitrificación. Sin embargo, suelos más fríos y con menores contenidos de nitratos podrían atenuar este efecto. Existen un sinnúmero de trabajos indicando tasas de desnitrificación y emisiones de N2O crecientes ante aumentos en la dosis del fertilizante nitrogenado. Con respecto a los abonos orgánicos la información disponible indica que las fuentes orgánicas de N (como abonos animales y aguas servidas) inducen a mayores emisiones de N2O por unidad de N agregado que el fertilizante mineral. El riego aumenta el contenido de humedad del suelo y, por tanto, promueve las condiciones necesarias para que ocurran procesos desnitrificantes; este efecto es aún más acentuado cuando el riego se da en pulsos, debido a la fuerte estimulación de las emisiones de N2O ante ciclos de humedecimiento-secado. Es poco conocido el efecto de la aplicación de pesticidas comunes en las emisiones de N2O de los suelos, aunque es probable que las bajas dosis que se emplean en campo sean insuficientes para causar efectos significativos que se destaquen de la variabilidad natural de los suelos, generando sólo leves efectos transitorios. Existe un número de prácticas que se basan fundamentalmente en incrementar la eficiencia en el uso del fertilizante nitrogenado, como la aplicación fraccionada del fertilizante nitrogenado o la aplicación de ureas de liberación lenta o con inhibidores de la enzima ureasa o de la nitrificación, que son prometedoras para reducir las emisiones de N2O, aunque el uso de cada una de ellas debe ser evaluado cuidadosamente.The objective of this chapter is to characterize the influ The objective of this chapter is to characterize the infl uence of the main agricultural practices on the denitrification process and the resulting soil N2O emissions. Tillage has great effects on factors controlling denitrification and N2O emissions. Zero tillage practice often causes wetter soils with higher C and N accumulation on the soil surface, in contrast to conventional tillage systems; wetter soils could stimulate reductive processes as denitrification resulting in N2O production; however colder soils and lower nitrate concentrations could decrease these effects. There are several reports showing increasing denitrification rates and N2O emissions by increasing nitrogen fertilizer rates. With regard to organic amendments, the available information shows that organic N sources as animal manures or sewage sludge induce higher N2O emissions per unit of added N than mineral fertilizers. Irrigation increases soil moisture and consequently promotes necessary conditions for the occurrence of denitrification; this effect is stressed when irrigation has a pulse pattern, given the strong stimulation of wetting-drying cycles on N2O emissions. The effect of common pesticide applications on soil N2O emissions is poorly known, although it is probable that the small application rates used at field conditions are insufficient to cause significant effects which stand out from natural variability of soils and their analyzed populations, generating only small brief effects. There are a number of practices that fundamentally promote an increase in the efficiency of N fertilizers, for example to split the applications of N fertilizer, or to apply slow release urea or nitrification inhibitors like urease, that are promissory to reduce N2O emissions, even though the use of each one of them should be carefully evaluated.Fil: Ciarlo, Esteban Ariel. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Edafología; ArgentinaFil: Ciampitti, Ignacio Antonio. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Edafología; Argentina. International Plant Nutrition Institute; ArgentinaFil: Conti, Marta Elvira. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Edafología; Argentin
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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