Mecanismos de hidratación del yeso

There is an hypothesis that the mechanism o f gypsum hydration and dehydration is performed through two simultaneous phenomena. In this study we try to clear up this phenomenon using chlorides as accelerators or a mixture of ethanol-methanol as retarders to carry out the gypsum setting. Natural Mexican gypsum samples and a hemihydrate prepared in the laboratory are used. The following analytical techniques are used: MO, DRX, DTA, TG and DTG. In agreement with the obtained results, it can be concluded: that colloid formation depends on the action of accelerators or retarders and the crystals are a consequence of the quantity of hemihydrate formed.En el mecanismo de hidratación y deshidratación del yeso existe la hipótesis de que éste se efectúa por dos fenómenos simultáneos. Este estudio intenta esclarecer estos fenómenos, empleando: cloruros como aceleradores o mezcla etanol-metanol como retardadores para efectuar el fraguado del yeso. Se emplean muestras de yeso de origen natural mexicano y hemihydrate preparado en laboratorio; se utilizan técnicas analíticas: MO, DRX, DTA, TG y DTG. De acuerdo a los resultados obtenidos se puede deducir: que la formación del coloide depende de la acción de los agentes aceleradores o retardadores y que los cristales son consecuencia de la cantidad de hemihidrato formado

Flight path analysis in sounding rocket “Libertador I” with computational simulation on three degrees of freedom

This paper presents obtained results from computer simulations in order to analyze the flight path of the sounding rocket Libertador I, developed in 2012 at the Fundación Universitaria Los Libertadores. The main aspects that affect the motion of a rocket are propulsion and aerodynamics effects. Numerical algorithms were implemented to value the thrust provided by the rocket motor as well as aerodynamic loads. Then, the differential equations of the motion are solved using the Runge-Kutta method, RK9. Trajectory and other numerical results are calculated from a code developed in FORTRAN. Finally, graphs of the flight path, curves of the vehicle velocity as function of time are presented. Also, the algorithm permits to determine the maximum altitude and possible impact sites.Facultad de Ingenierí

Flight path analysis in sounding rocket “Libertador I” with computational simulation on three degrees of freedom

This paper presents obtained results from computer simulations in order to analyze the flight path of the sounding rocket Libertador I, developed in 2012 at the Fundación Universitaria Los Libertadores. The main aspects that affect the motion of a rocket are propulsion and aerodynamics effects. Numerical algorithms were implemented to value the thrust provided by the rocket motor as well as aerodynamic loads. Then, the differential equations of the motion are solved using the Runge-Kutta method, RK9. Trajectory and other numerical results are calculated from a code developed in FORTRAN. Finally, graphs of the flight path, curves of the vehicle velocity as function of time are presented. Also, the algorithm permits to determine the maximum altitude and possible impact sites.Facultad de Ingenierí

Banking Efficiency in Chile: a Profit Frontier Approach

This paper characterizes the evolution of the efficiency X in the Chilean banking industry over 1987 to 2007, based on a profit frontier approach. Our results suggest that over this period the Chilean banking sector has attained just a 15% over its maximum profits. This inefficiency basically arises from a technical source rather than an assignative one, and mainly affects domestic and small banks. Nevertheless, the level of efficiency X of the industry as a whole has dramatically improved since the late 1990’s, which is consistent with important economic, technological and regulatory transformations.

The integration of surgical and dermatological techniques in the treatment of cutaneous aging: multidisciplinary approaches and clinical outcomes - a comprehensive systematic review of current literature

This comprehensive review explores the integration of surgical and dermatological techniques in treating cutaneous aging, highlighting the evolution of anti-aging strategies towards more refined and less invasive methods. As aging skin results from a combination of intrinsic and extrinsic factors, leading to structural and physiological changes, dermatology has advanced to offer multifaceted treatment approaches. We aimed to review advances and evolution in surgical interventions such as facelifts and blepharoplasty. We will discuss noninvasive and minimally invasive techniques, such as Ultherapy and fat grafting, which are widely used and are the best alternatives to traditional surgery. Other techniques, such as thread lifts and novel materials like polydioxanone (PDO) and polylactic acid (PLA) threads, are also reliable techniques for minimally invasive facial rejuvenation

Construção e validação de um questionário para identificação de fatores associados ao desempenho escolar (FADE)

Se construyó una prueba psicológica para medir los Factores Asociados al Desempeño Escolar (FADE), siguiendo lineamientos de la Teoría Clásica de los Test y aspectos de medición y evaluación desde una estrategia multi-informante aplicada a los contextos escolares. La finalidad de la prueba es la identificación de debilidades y fortalezas asociadas al desempeño escolar en niños de primer grado de primaria del municipio de Pasto. La muestra utilizada fue de 277 participantes pertenecientes a instituciones públicas de carácter urbano y rural. La confiabilidad calculada a través del coeficiente KR20 fue de .92 para la prueba total. Se obtuvieron evidencias favorables para validez de contenido, criterio y constructo. Se establecieron normas de estandarización para la aplicación y calificación de la prueba. La evidencia encontrada da cuenta de que la prueba resulta útil para su aplicación práctica como herramienta en la evaluación clínica y su uso en investigación.Construiu-se um teste psicológico para medir os Fatores Associados ao Desempenho Escolar (FADE), seguindo as diretrizes da Teoría Clássica dos Testes e aspectos de medição e avaliação desde uma estratégia multi-informante aplicada aos contextos escolares. A finalidade do teste é a identificação de pontos fortes e pontos fracos associados ao desempenho escolar em crianças do primeiro ano do primário do município de Pasto. A mostra utilizada foi de 277 participantes pertencentes a instituições públicas de caráter urbano e rural. A confiabilidade calculada através do coeficiente KR20 foi de ,92 para a prova total. Obtiveram-se evidências favoráveis para validade de conteúdo, critério e constructo. Estabeleceram-se normas de padronização para a aplicação e qualificação da prova. A evidência encontrada mostra que a prova é útil para sua aplicação prática como ferramenta na avaliação clínica e seu uso em pesquisa.A psychological test was constructed to measure School Performance Associated Factors (FADE, by its Spanish acronym), following the guidelines of the Classical Theory of Tests and aspects of measuring and assessment from a multiple informant strategy applied to school settings. The purpose of the test is to identify weaknesses and strengths associated with school performance in first grade primary school children from the municipality of Pasto. The sample consisted of 277 participants from public institutions of urban and rural character. The reliability calculated by KR20 coefficient was 0.92 for the total test. Favorable evidence was obtained for content, criteria and construct validity. Standardized rules were established for the test administration and scoring. The evidence found shows that the test is useful for its practical application as a tool for clinical assessment and research

Biodiversity of Bacteriocin-Producing Lactic Acid Bacteria from Mexican Regional Cheeses and their Contribution to Milk Fermentation

The aim of this work was to examine the biodiversity of bacteriocin-producing lactic acid bacteria from homemade cheeses produced in Veracruz (México) and assess their contribution as adjunct cultures in dairy products. Ninety-three presumptive bacteriocinogenic strains were detected by direct antagonism assays and 29 of them were active against Enterococcus faecalis NRRL-B537, Listeria innocua 062 AST, or Listeria monocytogenes ATCC19115 by the well diffusion test using cell-free supernatants, adjusted to pH 6.0 to exclude inhibition by organic acids. Positive isolates were identified by partial sequencing of the 16s rDNA as Pediococcus acidilactici (four isolates), Enterococcus faecium (17 isolates), Lactobacillus plantarum (six isolates) and Lactobacillus fermentum (two isolates). RAPD-PCR discriminated seven groups with a 50% similarity and revealed the presence of the same isolates. The coding genes for the synthesis of plantaricin EF, plantaricin JK, plantaricin N, plantaricin NC8 and the inducing peptide plantaricin A were detected by PCR in L. plantarum. Similarly, enterocin P and pediocin PA-1 genes were amplified from Enterococcus and Pediococcus genomic DNA, respectively. Overall, co-culturing of bacteriocin producing Lactobacillus and Pediococcus strains with the dairy starter Lactococcus lactis IPLA947 did not interfere with milk acidification. Lactose consumption, acidification rate and production of lactic acid were unchanged. Nonetheless, higher levels of acetic acid, ethanol and succinic acid were detected depending on the strain. Our results demonstrate the diversity of bacteriocinogenic species in homemade Mexican cheeses which may be used as adjunct cultures to enhancing safety of this well-appreciated cheese while providing a richer range of metabolites.This work was supported by Tecnológico Nacional de México (5486.14.15-P), the Mexican National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnología -CONACYT) and partially by the Ministry of Economy and Competitiveness of Spain (MINECO) through grant BIO2013-46266-R. Funding by GRUPIN14-139 Plan de Ciencia, Tecnología e Innovación 2013-2017 (Principado de Asturias, Spain), supported by FEDER EU funds, is also acknowledged. S. Portilla-Vázquez held a CONACYT fellowship as well as an i-COOP mobility grant COOPA20015 funded by Consejo Superior de Investigaciones Científicas (CSIC), Spain.Peer reviewe

Description and analysis of the debris flows occurred during 2008 in the Eastern Pyrenees

Rainfall-triggered landslides taking place in the Spanish Eastern Pyrenees have usually been analysed on a regional scale. Most research focussed either on terrain susceptibility or on the characteristics of the critical rainfall, neglecting a detailed analysis of individual events. In contrast to other mountainous regions, research on debris flow has only been performed marginally and associated hazard has mostly been neglected. <br><br> In this study, five debris flows, which occurred in 2008, are selected; and site specific descriptions and analysis regarding geology, morphology, rainfall data and runout were performed. The results are compared with worldwide data and some conclusions on hazard assessment are presented. <br><br> The five events can be divided into two in-channel debris flows and three landslide-triggered debris flows. The in-channel generated debris flows exceeded 10 000 m<sup>3</sup>, which are unusually large mass movements compared to historic events which occurred in the Eastern Pyrenees. In contrast, the other events mobilised total volumes less than 2000 m<sup>3</sup>. The geomorphologic analysis showed that the studied events emphasize similar patterns when compared to published data focussing on slope angle in the initiation zone or catchment area. <br><br> Rainfall data revealed that all debris flows were triggered by high intensity-short duration rainstorms during the summer season. Unfortunately, existing rainfall thresholds in the Eastern Pyrenees consider long-lasting rainfall, usually occurring in autumn/winter. Therefore, new thresholds should be established taking into account the rainfall peak intensity in mm/h, which seems to be a much more relevant factor for summer than the event's total precipitation. <br><br> The runout analysis of the 2008 debris flows confirms the trend that larger volumes generally induce higher mobility. The numerical simulation of the Riu Runer event shows that its dynamic behaviour is well represented by Voellmy fluid rheology. A maximum front velocity of 7 m/s was back-analysed for the transit section and even on the fan velocities larger than 2 m/s were obtained. <br><br> This preliminary analysis of the major Eastern Pyrenean debris flows represents the first background for future studies. Additional research on other events is necessary to support the results presented herein, and to properly assess and reduce hazard related to debris flows