Theoretical–Experimental Study of the Action of Trace Amounts of Formaldehyde, Propionaldehyde, and Butyraldehyde as Inhibitors of the Ziegler–Natta Catalyst and the Synthesis of an Ethylene–Propylene Copolymer

The copolymer synthesis process can be affected by failures in the production process or by contaminating compounds such as ketones, thiols, and gases, among others. These impurities act as an inhibiting agent of the Ziegler–Natta (ZN) catalyst affecting its productivity and disturbing the polymerization reaction. In this work, the effect of formaldehyde, propionaldehyde,and butyraldehyde on the ZN catalyst and the way in which it affects the final properties of the ethylene-propylene copolymer is presented by analyzing 30 samples with different concentrations of the mentioned aldehydes along with three control samples. It was determined that the presence of formaldehyde 26 ppm, propionaldehyde 65.2 ppm, and butyraldehyde 181.2 ppm considerably affect the productivity levels of the ZN catalyst; this effect increases as the concentration of aldehydes is higher in the process; likewise, these impurities affect the properties of the final product, such as the fluidity index (MFI), thermogravimetric analysis (TGA), bending, tension, and impact, which leads to a polymer with low-quality standards and less resistance to breakage. The computational analysis showed that the complexes formed by formaldehyde, propionaldehyde, and butyraldehyde with the active center of the catalyst are more stable than those obtained by the ethylene-Ti and propylene-Ti complexes, presenting values of −40.5, −47.22, −47.5, −5.2 and −1.3 kcal mol−1 respectively

Learning Skills And Achievements: A Comparative Analysis In Public Accounting And Business Administration Careers

The objective was to provide an analysis of the self-efficacy of business science students belonging to a Colombian university and make a comparison according to careers and gender. Methodologically, the research was descriptive, correlational and field design with quantitative methods. The sample was made with 198 students. The instrument used was an adaptation of the self-efficacy scale in academic life. In the results, it was found that the self-efficacy of the students in independent (individual) work has a statistically significant positive relationship with the academic self-efficacy in terms of confidence to carry out any academic work assigned by the teacher or to collaborate with any of their peers. in teamwork activities. It was concluded that different areas of student self-efficacy are interrelated to achieve success in a specific area

Skills And Abilities Acquired By Accounting Professionals During The Training Period In A University In Colombia

The objective of this work is to know the skills and abilities acquired by public accounting professionals in their academic training process. To this end, a research was carried out with  a quantitative approach, with a descriptive field design;  The sample corresponds to 149 accounting professionals.  The main result obtained is the  following: in general, on average of every 10 professionals, 8 consider having acquired the skills  and abilities necessary to carry out their professional activities, this under an ethical and social responsibility approach.  Therefore, it was concluded that the education provided to these professionals is relevant

Post-Graduate Education. An Analysis From The Perceptions Of Graduate Students In Public Accounting

The objective was to analyze the perceptions of the graduates of the Public Accounting program of the Faculty of Business Sciences belonging to the Colombian university on postgraduate education. Methodologically, the research was carried out under a quantitative approach, the type was descriptive and field design. The sample consisted of 134 public accounting graduate students. The instrument used was a questionnaire with several alternatives. The results show that this group of graduates could be seeking to obtain the academic capacity to adapt to the changing requirements of the organizational environment, since to be dynamic it is necessary to adapt to the constantly changing market environment. It was concluded that the development of society requires the continuous expansion of postgraduate education together with the strengthening of continuous development in the training and cultivation of basic skills of graduates in any area of ​​knowledge and social, economic, of science, technology, among others, where the accumulation of practices and experience is the basis for innovation in postgraduate education

On the coherence of synthetic turbulence generation methods

Synthetic turbulence generation methods have been extensively used by engineers and scientists in the past ten years in order to impose initial conditions in a wide range of turbulent flow problems. The interest in synthetic methods relies in the fact that reliability of methodologies such as large eddy simulation (LES) or direct numerical simulation (DNS) strongly depends on how well the developed turbulence is characterized, which generally leads to computationally expensive simulations. In this work the methodology known as “modified discretizing and synthesizing random flow generation” (MDSRFG) jointly with a LES method is analyzed for its use in the study of bluff body aerodynamics. A comparison with other generation techniques, that are closely related by their features and their conceptual origins, is presented with particular emphasis on the correct representation of the coherence of the velocity field. The resulting wind loads on the model, along with the statistical characteristics of the flow, show that the MDSRFG technique allows to represent a field of spatially correlated velocities correctly.Publicado en: Mecánica Computacional vol. XXXV, no. 18Facultad de Ingenierí

On the coherence of synthetic turbulence generation methods

Synthetic turbulence generation methods have been extensively used by engineers and scientists in the past ten years in order to impose initial conditions in a wide range of turbulent flow problems. The interest in synthetic methods relies in the fact that reliability of methodologies such as large eddy simulation (LES) or direct numerical simulation (DNS) strongly depends on how well the developed turbulence is characterized, which generally leads to computationally expensive simulations. In this work the methodology known as “modified discretizing and synthesizing random flow generation” (MDSRFG) jointly with a LES method is analyzed for its use in the study of bluff body aerodynamics. A comparison with other generation techniques, that are closely related by their features and their conceptual origins, is presented with particular emphasis on the correct representation of the coherence of the velocity field. The resulting wind loads on the model, along with the statistical characteristics of the flow, show that the MDSRFG technique allows to represent a field of spatially correlated velocities correctly.Publicado en: Mecánica Computacional vol. XXXV, no. 18Facultad de Ingenierí

Estimation of Molecular Pairwise Relatedness in Autopolyploid Crops

A suitable pairwise relatedness estimation is key to genetic studies. Several methods are proposed to compute relatedness in autopolyploids based on molecular data. However, unlike diploids, autopolyploids still need further studies considering scenarios with many linked molecular markers with known dosage. In this study, we provide guidelines for plant geneticists and breeders to access trustworthy pairwise relatedness estimates. To this end, we simulated populations considering different ploidy levels, meiotic pairings patterns, number of loci and alleles, and inbreeding levels. Analysis were performed to access the accuracy of distinct methods and to demonstrate the usefulness of molecular marker in practical situations. Overall, our results suggest that at least 100 effective biallelic molecular markers are required to have good pairwise relatedness estimation if methods based on correlation is used. For this number of loci, current methods based on multiallelic markers show lower performance than biallelic ones. To estimate relatedness in cases of inbreeding or close relationships (as parent-offspring, full-sibs, or half-sibs) is more challenging. Methods to estimate pairwise relatedness based on molecular markers, for different ploidy levels or pedigrees were implemented in the AGHmatrix R package

Molecular and functional characterization of a fads2 orthologue in the Amazonian teleost, Arapaima gigas

The Brazilian teleost Arapaima gigas is an iconic species of the Amazon. In recent years a significant effort has been put into the farming of arapaima to mitigate overfishing threats. However, little is known regarding the nutritional requirements of A. gigas in particular those for essential fatty acids including the long-chain polyunsaturated fatty acids (LC-PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The ability to biosynthesize LC-PUFA is dependent upon the gene repertoire of fatty acyl desaturases (Fads) and elongases (Elovl), as well as their fatty acid specificities. In the present study we characterized both molecularly and functionally an orthologue of the desaturase fatty acid desaturase 2 (fads2) from A. gigas. The isolated sequence displayed the typical desaturase features, a cytochrome b5-domain with the heme-binding motif, two transmembrane domains and three histidine-rich regions. Functional characterization of A. gigas fads2 showed that, similar to other teleosts, the A. gigas fads2 exhibited a predominant Δ6 activity complemented with some capacity for Δ8 desaturation. Given that A. gigas belongs to one of the oldest teleostei lineages, the Osteoglossomorpha, these findings offer a significant insight into the evolution LC-PUFA biosynthesis in teleosts

Efecto alelopático de especies invasoras de ribera sobre la germinación de especies del sotobosque

9 páginas. -- Trabajo presentado en la 50ª Reunión Científica de la SEEPLa producción de sustancias alelopáticas por las especies vegetales contribuye a incrementar su éxito competitivo frente a otras especies coexistentes dentro de un mismo hábitat, pudiendo llegar incluso a eliminarlas. Las sustancias alelopáticas pueden inhibir la germinación y el crecimiento de otras especies de la comunidad. En los bosques de ribera se ha detectado la presencia de árboles exóticos con potencial invasor en otros ecosistemas pero se desconoce su efecto sobre las especies autóctonas herbáceas. Nuestra hipótesis es que las especies invasoras podrían utilizar la producción de aleloquímicos de una manera eficiente para desplazar a las especies herbáceas autóctonas, pudiendo llegar a eliminarlas. El objetivo del presente trabajo fue estudiar el efecto extractos de hojarasca de especies alóctonas arbóreas (Ulmus pumila, Robinia pseudoacacia, Ailanthus altissima) y autóctonas (Populus alba) sobre la germinación de cuatro especies herbáceas frecuentes en el sotobosque del bosque de ribera del rio Henares (Madrid). Los resultados mostraron una disminución de la velocidad de germinación de B. phoenicoides y B. sylvaticum con los extractos de las especies alóctonas y autóctonas excepto para el olmo siberiano. Chenopodium album no se vio perjudicada por los extractos de las especies alóctonas pero sí por lo de la especie autóctona. La velocidad de germinación de Dactylis glomerata fue afectada por los extractos de todas las especies alóctonas. Se concluye que no existe un efecto consistente de los extractos de las hojas de árboles exóticos sobre las herbáceas nativas, sino que éstos dependen tanto de la naturaleza del árbol donante como de la herbácea receptora.Plants produce allelopathic substances increasing their competitive success over other species coexisting within the same habitat, being able to eliminate them. Allelopathic substances inhibit germination and growth of other species in the community. In the riverside forests, it has been detected, the presence of invasive tree species with demonstrated invasive potential in other ecosystems. Our hypothesis is that invasive species could use the production of allelochemicals in an efficient way to compete against native herbaceous species. The aim of this work was to assess the effects of leaf extracts of invasive species (Ulmus pumila, Robinia pseudoacacia, Ailanthus altissima) and native (Populus alba) on the germination of four grass species frequent in the forest understory bank of the river Henares (Madrid). The results showed that extracts of alien and native species (except Siberian elm) decreased the germination speed of B. phoenicoides and B. sylvaticum. The effect of extracts in Chenopodium album was not clear. The extracts of all alien species affected the germination speed of Dactylis glomerata.Agradecemos la ayuda de la Dra. Teodora Martínez en la localización de las zonas de campo. Este trabajo ha sido financiado por los proyectos POII10-0179-4700 de la Junta de Castilla La Mancha y CGL2010-16388/BOS del Ministerio de Ciencia e Innovación.Peer reviewe

Single-blind, randomized, controlled trial of pelvic floor muscle training, electrical stimulation, vaginal cones, and no active treatment in the management of stress urinary incontinence

PURPOSE: To compare the effectiveness of pelvic floor exercises, electrical stimulation, vaginal cones, and no active treatment in women with urodynamic stress urinary incontinence. PATIENTS AND METHODS: One hundred eighteen subjects were randomly selected to recieve pelvic floor exercises (n=31), ES (n=30), vaginal cones (n=27), or no treatment (untreated control) (n=30). Women were evaluated before and after completion of six months of treatment by the pad test, quality of life questionnaire (I-QOL), urodynamic test, voiding diary, and subjective response. RESULTS: In the objective evaluation, we observed a statistically significant reduction in the pad test (p=0.003), in the number of stress urinary episodes (