Numerical and theoretical models to predict fatigue life in aggressive environments from experimental data

Corrosion fatigue produce sensible effects in the fracture mechanics of structural materials. Aggressive environments in presence of dynamic fatigue load are indeed responsible of multiple effects, regarding crack nucleation and propagation rates. Considering Ti-6Al-4V in air, inert paraffin oil and 3.5 wt.% NaCl mixture, environmental effects are sensible in terms of acceleration of Fatigue Crack Growth Rate – i.e. da/dN vs. stress intensity factor ΔK. Several literature studies dealt with the topic in the past years. However, research has been focused mainly on the FCGR description, and the prediction of number of cycles to failure in aggressive environments is not addressed. In the presented poster, a methodology to obtain a numeric model which reconstruct da/dN vs ΔK from experimental results, including crack length and applied stress, is presented and compared against literature data. Results are related to R = 0.1 axial test involving smooth and notched flat dogbone specimens, with varying notch radius. The proposed model is used to reconstruct the number of cycles to failure of the tested specimens, resulting in a satisfactory correlation with experimental data. Comparison with other literature models highlights the necessity to develop a proper numerical model with each test case. Please click Additional Files below to see the full abstract

The role of sodium phosphate cotransporters in ectopic calcification

Phosphate plays a critical role in many vital cellular processes. Deviations from normal serum phosphate levels, including alterations in the extracellular phosphate/pyrophosphate ratio, can cause severe consequences, such as ectopic calcification. Cellular phosphate levels are tightly controlled by sodium phosphate cotransporters, underscoring their importance in cellular physiology. The role of sodium phosphate cotransporters in ectopic calcification requires further elucidation, taking into account their important role in the control of intracellular phosphate levels and the synthesis of ATP, the main source of extracellular pyrophosphate (a potent endogenous inhibitor of calcification). In this review, we discuss the roles of phosphate and pyrophosphate homeostasis in ectopic calcification, with a specific focus on phosphate transporters. We concentrate on the five known sodium-dependent phosphate transporters and review their localisation and regulation by external factors, and the effects observed in knockout studies and in naturally occurring mutations

On the "CRISPR" of the wave: Development of a new CRISPR-Cas9 application.

The recent emergence of the prokaryotic CRISPR-Cas9 system provides the opportunity for efficient genome engineering in eukaryotic cells by simply specifying a 20-nt targeting sequence within its guide RNA (1). Apart from its use in genome editing, CRISPR-Cas9 system can be used as a programmable RNA-dependent DNA-binding protein by using a catalytically inactive Cas9 protein (dCas9) (2). Precisely recruiting of dCas9 to desired regions of the genome offers numerous applications such as fusion of dCas9 to transcriptional effector or repressor domains, upregulating or downregulating the transcription of endogenous target genes (3). On the other hand, dCas9 can be fused to a fluorescent protein allowing the visualization of endogenous genomic elements in living cells (4). Recently, this system has been implemented in the fission yeast Schizosaccharomyces pombe, a potent genetic model organism. Genome editing in S. pombe with CRISPR/Cas9 involves the manual identification of unique PAM and spacer sequences (sgRNA) and cloning of these sequences into an expression plasmid (5).This project proposes the validation of a novel idea that can represent a valuable tool in the study of the location and dynamics of genomic regions of interest. To achieve that, the new-fangled system combines the Cas9 nuclease with the bi-molecular fluorescent complementation technique (BiMFC) in the yeast Schizosaccharomyces pombe. The catalytically inactive Cas9 nuclease (dCas9 from S. pyogenes harbouring D10A and A840A substitutions; Addgene #46920) is fused to the yellow fluorescent protein (YFP), both the whole protein and the N-terminal and C-terminal ends. The resulting protein is directed to the centromeric regions of S. pombe through the introduction of sgRNAs specific to those regions into plasmids derivate from the S. pombe plasmid pMZ376 (Addgene #74213). On the other hand, the protein Cnp1, a variant of the H3 histone that binds to the centromeres, is fused to the cherry protein and the two halves of the YFP. As a result, we will be able to determine if there is a colocalization between the YFP signal of dCas9 and the red signal of the cherry protein fused to Cnp1. In the case of YFP halves, the colocalization of the dCas9 and Cnp1 will allow to recover the full structure of the yellow fluorescent protein, resulting in the emission of yellow fluorescence. The development of this system allows an accurate study of the DNA-protein interactions at cell level

A numerical model to assess the role of crack-tip hydrostatic stress and plastic deformation in Environmental Assisted Fatigue Cracking

To better understand the mechanics of environmentally assisted cracking, and particularly hydrogen embrittlement, a correct description of the hydrostatic stress field is indispensable. The concentration of hydrogen in the proximity of the crack tip is indeed dependent of the hydrostatic stress effect on the microstructural lattice of the material. The overall parameters of the hydrostatic stress, including peak value, its location, gradient and distribution size are fundamental to assess the effect on hydrogen distribution near the crack tip. H concentration show indeed an exponential dependence on hydrostatic stress, so that even a moderate increase in the applied stress is traduced in a dramatic rise of hydrogen concentration. In order to investigate the mechanism beneath hydrogen embrittlement, a proper modelling of the hydrostatic stress is mandatory. Moreover, strain hardening might significantly interfere with the actual stress distribution, thus becoming a relevant parameter. The stress and strain field is also deeply affected by the presence of sharp notches. In the present work, a detailed Finite Element model, based on actual fatigue testing of notched Ti-6Al-4V specimens is proposed, providing a deeply informative tool to assess the hydrostatic stress and the plastic strain in the proximity of the crack tip. The data from the model are compared to available results and experiences in literature. Please click Additional Files below to see the full abstract

Minimum Qualitative Variables to Value Patents by Technology-Based Firms

Since the 1990’s, intangible assets such as patents have taken on importance in organizations and, as a result, several stakeholders are increasingly concerned about protecting, valuating, commercializing and negotiating technologies developed by patenting processes. This study aims to establish Minimum Qualitative Variables (MQVs) to support the valuation of patents by technology-based firms. The method to determine the MQVs was qualitative and based on a correlation matrix between MQVs identified in the literature and those suggested by experts. The results indicate that identifying such variables, especially the legal kind, is crucial to the valuation process because they suggest the possibility of producing and commercializing the technology in a given geographical context

Acompañamiento de la ciencia colombiana a las políticas públicas

Este artículo analiza el acompañamiento que la investigación científica promovida por COLCIENCIAS ha realizado a las políticas públicas en Colombia, en especial las referidas al bienestar social. A través de un doble análisis cualitativo y cuantitativo, se evalúa la distribución y la cobertura temática de algunas de las investigaciones realizadas entre 1990 y 2002, en los diversos tópicos asociados con las políticas públicas sociales. Aquí se propone un esquema básico para identificar los principales tópicos de desarrollo social alrededor de los cuales el Estado y los gobiernos nacionales proponen y aplican políticas públicas para el bienestar social. Posteriormente, se hace una clasificación de los proyectos en cada uno de los ejes temáticos, midiendo la distribución y la cobertura de las investigaciones sobre estos ejes. Por último, se presentan las conclusiones y se señalan algunos aspectos metodológicos que habría que considerar para mejorar los estudios sobre el acompañamiento e impacto de la ciencia a las políticas públicas.políticas públicas, COLCIENCIAS, acompañamiento

Estudio de la cinética de digestión de la grasa de la leche bajo distintas condiciones gastrointestinales simuladas

[ES] La insuficiencia pancreática es una manifestación clínica que se caracteriza por la incapacidad del páncreas de liberar suficiente enzima pancreática al intestino delgado, necesaria para digerir los nutrientes intraluminares. La falta de enzimas digestivas lleva a la dificultad en la absorción de nutrientes, que conduce a la desnutrición y la falta de crecimiento y desarrollo, debido a la pérdida de calorías. El tratamiento habitual en personas que padecen esta enfermedad consiste en la administración por vía oral de enzimas pancreáticas que presentan actividades proteasa, lipasa y amilasa. No obstante, existen una serie de factores relativos al alimento (matriz, tipo de grasa, etc.), así al entorno digestivo (pH intestinal, concentración biliar entre otros), que pueden influir en la digestibilidad de los nutrientes. Por ello y debido a las limitaciones de este tratamiento en términos de eficacia, se propuso el presente trabajo con la finalidad de profundizar en el conocimiento del funcionamiento de las enzimas pancreáticas en diferentes condiciones intestinales simuladas. En un primer momento se procedió a evaluar la actividad lipolítica del suplemento enzimático de pancreatina (SEP), utilizado habitualmente en el tratamiento de la insuficiencia pancreática, en diferentes condiciones intestinales de pH (6, 7 y 8) y concentración biliar (1, 10 y 20). Los resultados obtenidos se compararon con los resultados de lipólisis obtenidos a partir de disoluciones de pancreatina porcina y lipasa: colipasa (10:1). Posteriormente, se utilizó un modelo de digestión in vitro para estudiar y caracterizar la cinética de la reacción de lipólisis de la grasa de leche. Para ello se simularon diferentes condiciones de pH (6, 7 y 8) y concentración biliar (1, 5 y 10 mM) empleando una concentración conocida de suplemento de pancreatina (8,27 UL/mL). De esta forma, a partir de la información de las constantes cinéticas calculadas, se obtuvo la relación enzima: sustrato que maximiza la eficiencia catalítica de la enzima. Los resultados mostraron la influencia del efecto del pH y la concentración biliar en la actividad de las disoluciones enzimáticas (SEP, pancreatina porcina y lipasa: colipasa). La actividad aumentó tanto al incrementar el pH de 6 a 8, como al aumentar la concentración de bilis alcanzando un máximo a 10 mM. Por otro lado, los resultados de cinética mostraron que el aumento del pH y concentración biliar tiende a aumentar la velocidad de reacción (aumenta rm) así como la afinidad de la enzima por el sustrato (disminuye km). Finalmente, las relaciones E/S que saturan a la enzima mostraron que para aquellas condiciones duodenales favorables (pH 7-8 y 10 mM), la enzima es capaz de alcanzar valores máximos de velocidad con bajas cantidades de sustrato. De esta forma, conociendo la relación E/S para la cual se alcanza la velocidad máxima, será posible calcular la dosis óptima de enzima para lograr la máxima eficiencia lipólítica.[EN] Pancreatic insufficiency is a clinical manifestation characterized by the in-ability of the pancreas to release enough pancreatic enzyme into the small intestine, necessary to digest intraluminal nutrients. The lack of digestive enzymes leads to the difficulty to absorb nutrients, which drives to malnutrition and lack of growth and development, due to the loss of calories. The habitual treatment of these patients involves oral administration of pancreatic enzymes with protease, lipase and amylase activities. However, there are a number of food related factors (matrix, type of fat, etc.) and digestive environment (intestinal pH, bile concentration, among others), which will influence the digestibility of nutrients. Therefore, and due to the limitations of this treatment in terms of efficacy, this study was proposed in order to deepen the understanding of the functioning of pancreatic enzymes under different simulated intestinal conditions. At first study was addressed to evaluate the lipolytic activity of the pancreatic enzyme supplement (PES), commonly used in the treatment of pancreatic insufficiency, under different intestinal conditions of pH (6, 7 and 8) and bile concentrations (1, 10 and 20 mM). The obtained results were compared to those obtained with solutions of porcine pancreatin and lipase: colipase (10: 1). Subsequently, an in vitro digestion model was used to study and characterize the kinetics of the lipolysis reaction of milkfat. For this, different pH conditions (6, 7 and 8) and bile concentrations (1, 5 and 10 mM) were simulated, using a fixed concentration pancreatic supplement (8.27 UL / mL). Thus, from the information of the calculated kinetic constants, it was possible to obtain the enzyme: substrate ratio that maximizes the catalytic efficiency of the enzyme. The results illustrate the influence of the pH and bile concentration in the activity of the enzyme solutions (SEP, porcine pancreatin and lipase: colipase). The activity increased by increasing both the pH from 6 to 8, as well as by increasing the bile concentration, from 1 to 10 mM. Moreover, the results showed that an increase in pH and bile concentration tends to increase the reaction rate (increases rm) as well as the affinity of the enzyme for the substrate (decreases km). Finally, relations E/S saturating the enzyme showed that, at favorable duodenal conditions (pH 7, 8 and 10 mM) the enzyme is able to reach a maximum speed with low amounts of substrate. Thus, knowing the E/S at which the maximum speed is reached, it will be possible to calculate the optimal enzyme dose to achieve the maximum lipolytic efficiency.Villa Consuegra, S. (2016). Estudio de la cinética de digestión de la grasa de la leche bajo distintas condiciones gastrointestinales simuladas. http://hdl.handle.net/10251/68953.TFG

Estrategias contra la drogodependencia

El trabajo aborda en general el contexto legal, criminológico asistencial y sanitario del mundo de la droga. De ahí se procura una descripción de cómo se aborda el problema de las adicciones (principalmente sustancias estupefacientes, pero también las nuevas tecnologías y el juego) por parte de los Organismos Públicos encargados de erradicar este tema.Grado en Criminologí

Densidad, daños y distribución de Cucullia calendulae (Noctuidae) en manchas de Calendula arvensis

Most studies on the family Noctuidae focus on very few species that cause damage to crops; however, there is little information on the biology and ecology of the remaining species of noctuid moths. This work examines the relationship of the larvae of Cucullia calendulae with their main food plant Calendula arvensis. The results showed that the larvae of this species feed on the fruiting bodies, reaching an overall incidence of ca. 30%. In addition, there was a differential distribution of larvae according to their size. Early stages were found in the reproductive structures while latter stages were found on the stems, which should be due to a defensive strategy. Furthermore, from seven characteristics of the patch taken into account, only the height of the plant explained a greater number of larvae per patch.La mayoría de los estudios sobre la Familia Noctuidae se centran en aquellas especies que causan daños a los cultivos, existiendo muy poca información sobre la biología y ecología del resto de especies de la Familia. Este trabajo examina la relación entre la larva del nóctuido Cucullia calendulae y su principal planta nutricia: Calendula arvensis. Los resultados mostraron que la larva de esta especie se alimenta de los cuerpos fructíferos de la planta, llegando a dañar hasta el 30% de los mismos. Además, existió una distribución diferencial por tamaños. Las larvas de los primeros estadios se encontraban en los órganos reproductivos, mientras las de últimos estadios se localizaban mayoritariamente en los tallos de la planta, lo que podría deberse a una estrategia defensiva. Por otro lado, de las siete variables analizadas, sólo la altura de la planta explicó un mayor número de larvas por parche