1,720,960 research outputs found
Soil quality indicators related to pasture degradation and forage yield of kikuyu grass Cenchrus clandestinus (Hochst. ex Chiov.) Morrone
Get PDFilustraciones, diagramas, mapasEl manejo inadecuado de las praderas ha conllevado a la degradación de extensas áreas y a la pérdida de productividad y de sostenibilidad de muchas de ellas, convirtiéndose, en una realidad a la que se enfrentan comúnmente los ganaderos del Colombia. Por ello, en la Estación Agraria Paysandú de la Universidad Nacional de Colombia, Sede Medellín, localizada en el corregimiento de Santa Elena, se desarrolló una investigación que permitió determinar un índice de calidad de suelo, al evaluar los indicadores físicos y químicos que más se relacionaron con la degradación y producción de materia seca del pasto kikuyu (Cenchrus clandestinus). Se estableció el set mínimo de datos (SMD) para los indicadores más sensibles, elegidos mediante el análisis de componentes principales PCA, y se utilizó una función de puntuación no lineal para desarrollar el índice de calidad del suelo (SQI). Se encontró diferencia estadística entre todos los tratamientos y la producción de materia seca (p porosidad total OP > macroporos MAC > microporos MIC > resistencia a la penetración PR > capacidad efectiva de intercambio catiónico CECE > pH. Como resultado se obtuvo el índice de calidad del suelo y la ecuación fue = (0,225×BD) + (0,224×OP) + (0,220×MAC) + (0,218×MIC) + (0,113×PR) + (0,0879×CECE) + (0,0877×pH). Es necesario probar el índice a escala regional en sistemas de lechería bajo pastoreo ubicados en el trópico alto andino colombiano, especialmente en praderas con dominio de pasto kikuyu. (Texto tomado de la fuente)The inadequate management of pastures has led to the degradation of extensive areas and to the loss of productivity and sustainability of many of them, becoming a reality commonly faced by cattle ranchers in Colombia. For this reason, at the Paysandú Agricultural Station of the National University of Colombia, Medellín, located in the town of Santa Elena, an investigation was carried out to determine a soil quality index by evaluating the physical and chemical indicators that were most related to the degradation and dry matter production of kikuyu grass (Cenchrus clandestinus). The minimum data set (MDS) was established for the most sensitive indicators, chosen by principal component analysis PCA, and a nonlinear scoring function was used to develop the soil quality index (InCS). Statistical difference was found between all treatments and dry matter production (p total porosity OP > macropores MAC > micropores MIC > penetration resistance PR > effective cation exchange capacity CECE > pH. As a result, the soil quality index was obtained and the equation was = (0.225×BD) + (0.224×OP) + (0.220×MAC) + (0.218×MIC) + (0.113×PR) + (0.0879×CECE) + (0.0877×pH). It is necessary to test the index at a regional scale in grazing dairy systems located in the Colombian high Andean tropics, especially in Kikuyu grass-dominated pastures.MaestríaMagister en Ciencias AgrariasFísica y química de suelosÁrea Curricular en Producción Agraria Sostenibl
Microbial transformation of low rank coal to enhance changes in soil properties
Get PDFilustraciones, fotografías, gráficas, tablasComo subproducto de la extracción de carbón en la mina “El Cerrejón” se genera carbón de bajo rango (CBR), este es un material rico en sustancias húmicas (SH) y susceptible a la transformación microbiana. En la presente investigación se evaluó la biotransformación de un CBR tipo lignito, mediante actividad de bacterias solubilizadoras de carbón (BSC) y se determinó el efecto del CBR sobre algunas propiedades de materiales edáficos (ME) empleados en la rehabilitación de tierras post-minería. Se encontraron BSC nativas que transforman hasta el 38% del CBR bajo condiciones in vitro, produciendo hasta 3100 mgL-1de SH. La caracterización supramolecular de la fracción de ácidos húmicos (AH) producidos por BSC reveló modificaciones estructurales en comparación con AH obtenidos por el método clásico de extracción alcalina. La mezcla de CBR al 1% con ME en condiciones de invernadero incrementa la capacidad de intercambio catiónico, estimula la actividad microbiana y promueve el crecimiento en plantas de Zea mays en condiciones de campo a razón de 2,5 ton.ha-1; adicionalmente induce cambios sobre el perfil metabólico de la comunidad microbiana y modifica la distribución de poros del ME. Los resultados sugieren la posibilidad de integración del CBR al subciclo edáfico del carbono y su aprovechamiento como fuente de materia orgánica humificada para la rehabilitación de suelos en el área de influencia de la minería de carbón en el Caribe seco colombiano. (Texto tomado de la fuente).As a product of coal extraction from the “Cerrejón” mine, low rank coal (LRC), is generated. This is a material rich in humic substances and it is susceptible to microbial transformation. On the current research, biotransformation of a lignite type LRC was evaluated through the activity of coal solubilizing bacteria (CSB), and the LRC effect was determined on some properties of edaphic materials (EM), utilized on post- mining land reclamation. Native CSB which transform up to a 38% of the CBR under in vitro conditions were found, producing up to 3100 mgL-1of SH. The supramolecular characterization of the humic acids fraction (HA) produced by CSB, revealed structural modifications compared to HA obtained through the classic method of alkaline extraction. The addition of 1% of LRC to EM in greenhouse conditions increases the cationic exchange capacity, stimulates microbial activity and promotes growth of Zea Mays plants; in field conditions at a ratio of a 2,5 ton.ha-1, additionally induces changes on the metabolic profile of microbial community and modifies EM pore distribution. Results suggest the possibility of LRC integration to the carbon edaphic subcicle and its useful disposition as humified organic matter for the land reclamation in the coal mining affected areas in the Colombian dry Caribbean.DoctoradoDoctor en Ciencias AgrariasÁrea agrariaCiencias Agronómica
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
Gold phytoextraction and mining-degraded soil reclamation
Get PDFGold phytoextraction is a technology used to obtain this metal (Au) throughout plants. Some of the benefits of this technology are the mitigation of the environmental impact, the fact that it does not imply the constant use of pollutants, and has the ability to promote soil reclamation. The aim of this research was to determine if Brachiaria decumbens has the potential to improve soil physical properties while had achieved a gold extraction. For this purpose, Helianthus annuus and Brachiaria decumbens, were used in a completely randomized design with four replicates. To induce gold uptake, ammonium thiocyanate was applied to plants. The statistical analysis was performed using the R-Studio software. Finally, it became evident that B. decumbens is a gold extractor plant, which also improves the soil physical qualities and compared to H. annuus and present higher concentrations of gold than the latter (P<0.05). The dose and mode of application of ammonium thiocyanate, modulates the gold absorption process since it causes toxicity in plants
- …
