Selection indexes using principal component analysis for reproductive, beef and milk traits in Simmental cattle.

Selection indexes in dual-purpose cattle should include beef, milk and reproductive traits. The principal component analysis is a multivariate technique that allows researchers to explore relationships between explanatory variables and traits of interest. The objective of this study was to construct selection indexes for tropical dual-purpose Simmental cattle based on principal components. The evaluated traits were weight at 8 months of age; age at first calving; cumulative first-lactation milk yield at 60, 150, 210 and 305 days; and first calving interval. The selection indexes were estimated as the sum of the products of the estimated breeding values for the seven traits times their respective eigenvectors for the first three principal components. The three selection indexes from principal components analysis generated favourable expected genetic progress for all the traits. However, a selection index with a high expected genetic progress for all traits could not be obtained. The principal component analysis allows breeders to have a selection index that simultaneously improves milk, beef and reproductive traits in dual-purpose Simmental cattle. Because a selection index yielding high expected genetic progress for all traits could not be achieved, the decision to use a specific selection index will depend on the specific conditions of the market, the local needs and the farmer preference.

Catalytic assessment of solid materials for the pyrolytic conversion of low-density polyethylene into fuels.

Pyrolysis techniques provide an interesting way of recycling plastic wastes (PW) by transforming them into liquid fuels with high calorific values. Catalysts are employed in PW pyrolysis in order to favor cracking reactions; in that regard, cheap and abundant natural resources are being investigated as potential catalyst precursors. This article explores the pyrolysis of low-density polyethylene (LDPE) in a semibatch reactor under a reduced pressure of 300 torr and temperatures in the range of 370 °C-430 °C. Three different solid materials, an activated carbon (AC1), a commercial Fluid cracking catalyst (FCC) and an aluminum- pillared clay (Al-PILC), were tested as catalysts for the pyrolysis process. Thermogravimetric analyzes were previously performed to select the most catalytically active materials. AC1 displayed very low catalytic activity while FCC and Al-PILC displayed high activity and conversion to liquid products. Hydrocarbons ranging from C5 to C28 were identified in the liquid products as well as significant changes in their composition when FCC and Al-PILC catalyst were used. Differences in the catalytic activity of the 3 solid materials are ascribed mainly to differences in their acid properties.

Population structure and genetic diversity in Colombian Simmental cattle.

A vital requirement to design and implement a breeding program is to know the structure and genetic diversity of a population. The aim of this study was to characterize population structure and genetic diversity of the Colombian Simmental cattle. The pedigree file included 27,985 animals born from 1975 to 2017. The level of genetic diversity and breed structure was evaluated through probabilities of gene origin expressed via effective number of founders, ancestors and founders genomes. The inbreeding rates and the degree of genetic connectivity were estimated using a regression analysis and a genetic drift variance analysis, respectively. The lowest effective number of founders and ancestors were 50 and 38 by year, respectively. The average inbreeding by year of birth decreased from 5.06% in 1980 to 2.25% in 2017. The dairy line genetic contributions in the overall population increased significantly in the last 37 years, and the beef line contribution decreased. Regarding the genetic connectivity, Colombian regions (administrative divisions) with the largest cattle population had higher values. The results indicate that the availability of European and North American bulls contributes to genetic diversity by increasing the effective number of founders over time in the Colombian Simmental cattle population. However, the intensive use of relatively few founders causes an unbalanced genetic contribution and the loss of genetic diversity by gene pool erosion.

Activated carbon briquettes from biomass materials.

Disposal of biomass wastes, produced in different agricultural activities, is frequently an environmental problem. A solution for such situation is the recycling of these residues for the production of activated carbon, an adsorbent which has several applications, for instance in the elimination of contaminants. For some uses, high mechanical strength and good adsorption characteristics are required. To achieve this, carbonaceous materials are conformed as pellets or briquettes, in a process that involves mixing and pressing of char with adhesive materials prior to activation. In this work, the influence of the operation conditions on the mechanical and surface properties of briquettes was studied. Eucalyptus wood and rice husk from Uruguay were used as lignocellulosic raw materials, and concentrated grape must from Cuyo Region-Argentina, as a binder. Different wood:rice and solid:binder ratios were used to prepare briquettes in order to study their influence on mechanical and surface properties of the final products.

Propiedades psicométricas de un cuestionario de opinión estudiantil para la evaluación del desempeño de docentes universitarios / Psychometric properties of a questionaire for evaluation of University teachers' perfomance through students' opinions

Uno de los instrumentos empleados para evaluar el desempeño de los profesores de la Facultad de Química (FQ), Universidad de la República (Uruguay), es un cuestionario de opinión estudiantil. El mismo consta de 16 preguntas tipo Likert, con cinco categorías de respuesta. Una de las preguntas corresponde a la evaluación global del desempeño docente y se emplea como criterio interno de validez. El instrumento se implementó con carácter piloto entre unos 500 estudiantes del primer semestre. Los análisis factoriales exploratorio y confirmatorio muestran una estructura unidimensional subyacente a las medidas. La fiabilidad (a y ?) y la validez de criterio son elevadas, por lo que se puede concluir que esta escala presenta muy buenas características métricas, resultando válida y confiable para conocer la opinión de los estudiantes de la FQ con respecto a los aspectos del desempeño docente que son considerados más relevantes para dicha Facultad.

Propiedades psicométricas de un cuestionario de opinión estudiantil para la evaluación del desempeño de docentes universitarios / Psychometric properties of a questionaire for evaluation of University teachers perfomance through students opinions

Uno de los instrumentos empleados para evaluar el desempeño de los profesores de la Facultad de Química (FQ), Universidad de la República (Uruguay), es un cuestionario de opinión estudiantil. El mismo consta de 16 preguntas tipo Likert, con cinco categorías de respuesta. Una de las preguntas corresponde a la evaluación global del desempeño docente y se emplea como criterio interno de validez. El instrumento se implementó con carácter piloto entre unos 500 estudiantes del primer semestre. Los análisis factoriales exploratorio y confirmatorio muestran una estructura unidimensional subyacente a las medidas. La fiabilidad (a y ?) y la validez de criterio son elevadas, por lo que se puede concluir que esta escala presenta muy buenas características métricas, resultando válida y confiable para conocer la opinión de los estudiantes de la FQ con respecto a los aspectos del desempeño docente que son considerados más relevantes para dicha Facultad.(AU)