Efectos de vacancias y adsorción de H en g-GaN

En esta tesis de maestría se muestra el estudio de las propiedades estructurales y electrónicas de la monocapa hexagonal de g-GaN al introducir vacancias de galio y nitrógeno con diferentes estados de carga: también la adsorción de átomos de hidrógeno con diferentes concentraciones sobre las posiciones de galio y nitrógeno. Todo lo anterior se realizó utilizando cálculo de primeros principios dentro del formalismo de la Teoría Funcional de Densidad y la aproximación de pseudopotenciales. Las propiedades del sistemas g-GaN al introducirle vacancias y adsorciones es importante hoy día, por las excelentes propiedades de los sistemas 2-D como el grafeno y las aplicaciones en la industria electrónica por parte del sistema 3-D de GaN (w-GaN). Sumado a lo anterior, se tiene el descubrimiento de un método de crecimiento de materiales 2-D en el 2016, al igual que el aumento de estudio teóricos a materiales bidimensionales, donde se demuestra que este tipo de estudio contribuye en la consecución de nuevos materiales que se puedan emplear principalmente en la construcción de dispositivos electrónicos de bajos consumo y alta eficiencia. Iniciamos este estudio con la caracterización de la celda limpia del g-GaN, obteniendo sus propiedades estructurales y electrónicas mediante el análisis de las constantes de red, energía de cohesión, análisis de transferencia de carga y estructuras de bandas. Posteriormente se introducen las vacancias (Ga-N) con diferentes estados de carga y la adsorción de hidrógeno para diferentes concentraciones utilizando el método de la supercelda y así calcular la energía total y estabilidad del sistema

WSIA: web ontological search engine based on smart agents applied to scientific articles

The Semantic Web proposed by the W3C (Word Wide Web Consortium), aims to make the automation of the information contained in the current web through semantic processing based on ontologies that define what must be the rules used for the representation knowledge. This article resulting from the research project “Model for the representation of knowledge based on Web ontologies and intelligent search agents, if required: Scientific articles WSIA” proposes an architecture for finding information through intelligent agents and ontologies Web of scientific articles. This paper shows the architecture, implementation and comparing these with traditional applications

Stereological Evaluation of Precipitates within Ferrite Grains in Heat-Treated 1.25Cr0.5Mo Steel Previously Exposed to Service

The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters (size, quantity and volume fraction) of precipitates within ferrite grains of a creep-resistant 1.25Cr0.5Mo steel after long-term operation. The heat treatment was similar to the treatment that is carried out in industrial steam pipelines after welding (post weld heat treatment - PWHT) during installation and/or repairing. The operation aging corresponds to a subsequent long in-service operation after repairing. To determine the stereological parameters, SEM digital images were taken from samples of this material after conditions of in-service-aged (after long-term operation), in-service-aged and heat-treated (simulating repairing) and in-service-aged, heat-treated and in-laboratory aged (simulating subsequent long-term operation after repairing). The results indicate that the changes in the stereological parameters of the precipitates within ferrite grains after PWHT is associated with the coarsening process of the within-ferrite-grain precipitates as well as stabilizing the microstructure, since the material aging after PWHT of an in-serviced aged material would not change the stereological parameters

Improvements of Fire Fuels Attributes Maps by Integrating Field Inventories, Low Density ALS, and Satellite Data in Complex Mediterranean Forests

One of the most determining factors in forest fire behaviour is to characterize forest fuel attributes. We investigated a complex Mediterranean forest type—mountainous Abies pinsapo–Pinus–Quercus–Juniperus with distinct structures, such as broadleaf and needleleaf forests—to integrate field data, low density Airborne Laser Scanning (ALS), and multispectral satellite data for estimating forest fuel attributes. The three-step procedure consisted of: (i) estimating three key forest fuel attributes (biomass, structural complexity and hygroscopicity), (ii) proposing a synthetic index that encompasses the three attributes to quantify the potential capacity for fire propagation, and (iii) generating a cartograph of potential propagation capacity. Our main findings showed that Biomass–ALS calibration models performed well for Abies pinsapo (R2 = 0.69), Juniperus spp. (R2 = 0.70), Pinus halepensis (R2 = 0.59), Pinus spp. mixed (R2 = 0.80), and Pinus spp.–Juniperus spp. (R2 = 0.59) forests. The highest values of biomass were obtained for Pinus halepensis forests (190.43 Mg ha−1). The structural complexity of forest fuels was assessed by calculating the LiDAR Height Diversity Index (LHDI) with regard to the distribution and vertical diversity of the vegetation with the highest values of LHDI, which corresponded to Pinus spp.–evergreen (2.56), Quercus suber (2.54), and Pinus mixed (2.49) forests, with the minimum being obtained for Juniperus (1.37) and shrubs (1.11). High values of the Fuel Desiccation Index (IDM) were obtained for those areas dominated by shrubs (−396.71). Potential Behaviour Biomass Index (ICB) values were high or very high for 11.86% of the area and low or very low for 77.07%. The Potential Behaviour Structural Complexity Index (ICE) was high or very high for 37.23% of the area, and low or very low for 46.35%, and the Potential Behaviour Fuel Desiccation Index (ICD) was opposite to the ICB and ICE, with high or very high values for areas with low biomass and low structural complexity. Potential Fire Behaviour Index (ICP) values were high or very high for 38.25% of the area, and low or very low values for 45.96%. High or very high values of ICP were related to Pinus halepensis and Pinus pinaster forests. Remote sensing has been applied to improve fuel attribute characterisation and cartography, highlighting the utility of integrating multispectral and ALS data to estimate those attributes that are more closely related to the spatial organisation of vegetation

Relationship between vitamin B12 levels and insulin resistance in postmenopausal women from Colombia Caribbean

Introdução: A alta prevalência de baixos níveis séricos de vitamina B12 foi reconhecida como um problema de saúde pública na América Latina, mas a magnitude atual dessa deficiência na Colômbia é incerta. Baixos níveis de vitamina B12 podem induzir distúrbios hematológicos e neurológicos clínicos e subclínicos. Na verdade, estudos epidemiológicos demonstram uma relação entre deficiência de vitamina B12 e doenças cardiovasculares (DCVs). No entanto, o papel da vitamina B12 na resistência à insulina tem sido pouco estudado. Objetivo: O objetivo deste estudo foi avaliar a relação entre os níveis séricos de vitamina B12 e marcadores bioquímicos e antropométricos relacionados com doenças cardiovasculares e resistência à insulina em mulheres pós-menopáusicas da Colômbia Caribe. Métodos: Estudo correlacional, descritivo. Por amostragem de conveniência, foram vinculadas 182 mulheres na pós-menopausa do serviço de consulta médica de uma instituição de saúde. Níveis séricos de vitamina B12, variáveis ​​antropométricas (índice de massa corporal, perímetro abdominal) e variáveis ​​bioquímicas (glicemia, insulina, perfil lipídico, HOMA IR) foram avaliadas. Resultados: O valor médio do nível sérico de vitamina B12 foi de 312,5 ± 122,5 pg/mL (230,6 ± 90,4 pmol/L); 46,7% das mulheres tinham níveis abaixo do adequado de 300 pg/mL (> 221 pmol/L), e 9,9% eram deficientes, com níveis abaixo de 200 pg/mL (148 pmol/L). As mulheres com síndrome metabólica foram 63,7% e, segundo o HOMA IR, 52,7% apresentavam resistência à insulina. Uma relação inversa significativa entre os níveis séricos de vitamina B12 com glicemia basal (P = 0,002) e HOMA-IR (P = 0,040) foi mostrada. Conclusões: Foi observada uma relação inversa significativa entre os níveis de vitamina B12 e glicemia basal e HOMA-IR. Esses achados destacam a deficiência de vitamina B12 em mulheres na pós-menopausa e sugerem suplementação nutricional.Introduction: The high prevalence of low vitamin B12 serum levels has been recognized as a public health problem in Latin America; however, the current magnitude of this deficiency in Colombia is uncertain. Low levels of vitamin B12 can induce clinical and subclinical hematological and neurological disorders. Epidemiological studies have demonstrated a relationship between vitamin B12 deficiency and cardiovascular diseases (CVDs). However, the role of vitamin B12 in insulin resistance has been poorly studied. Objective: This study aimed to evaluate the relationship between vitamin B12 serum levels and biochemical and anthropometric markers related to CVDs and insulin resistance in postmenopausal women from Colombia Caribbean. Methods: Correlational, descriptive study. By convenience sampling, 182 postmenopausal women from the medical consultation service of a health institution were linked. Serum vitamin B12 levels, anthropometric variables (body mass index, abdominal perimeter), and biochemical variables (glycemia, insulin, lipid profile, HOMA IR) were evaluated. Results: The average value of the vitamin B12 serum level was 312.5 ± 122.5 pg/mL (230.6 ± 90.4 pmol/L); 46.7% of the women had less than adequate levels of 300 pg/mL (> 221 pmol/L), and 9. 9% were deficient, with levels of less than 200 pg/mL (148 pmol/L). The women with metabolic syndrome were 63.7%, and according to HOMA IR, 52.7 % had insulin resistance. A significant inverse relationship was shown between serum vitamin B12 levels with basal glycemic (P =0.002) and HOMA-IR (P =0.040). Conclusions: A significant inverse relationship between vitamin B12 levels and basal glycemia and HOMA-IR was observed. These findings highlight vitamin B12 deficiency in postmenopausal women and suggest nutritional supplementation.Introducción: La deficiencia de vitamina B12 ha sido reconocida como un problema de salud pública en América Latina, pero la magnitud actual de esta deficiencia en Colombia es incierta. Bajos niveles de vitamina B12 pueden inducir trastornos hematológicos y neurológicos clínicos y subclínicos. Estudios epidemiológicos han demostrado una relación entre la deficiencia de vitamina B12 y las enfermedades cardiovasculares (ECV). Sin embargo, el papel de la B12 en la resistencia a la insulina ha sido poco estudiado. Objetivo: Evaluar la relación entre los niveles séricos de vitamina B12 y los marcadores bioquímicos y antropométricos relacionados con ECV y la resistencia a la insulina. Métodos: Estudio descriptivo correlacional.  Por muestreo de conveniencia se vincularon 182 mujeres posmenopáusicas del servicio de consulta médica de una institución de salud. Se evaluaron los niveles séricos de vitamina, variables antropométricas (índice de masa corporal, perímetro abdominal) y bioquímicas (glucemia, insulina, perfil lipídico, HOMA IR). Resultados: El valor promedio del nivel sérico de vitamina B12 fue de 312,5±122,5 pg/mL (230,6±90,4 pmol/L); El 46,7% de las mujeres tenían niveles inferiores a los adecuados de 300 pg/mL (>221 pmol/L), y el 9,9% eran deficientes, con niveles inferiores a 200 pg/mL (148 pmol/L). Las mujeres con síndrome metabólico fueron el 63,7 %, y según el HOMA IR, el 52,7 % presentó resistencia a la insulina. Se mostró una relación inversa significativa entre los niveles séricos de vitamina B12 con la glucemia basal (P=0,002) y HOMA-IR (P=0,040). Conclusiones: Se observó una relación inversa significativa entre los niveles séricos de vitamina B12 y la glucemia basal y HOMA-IR. Estos hallazgos muestran la importancia de estudiar la deficiencia de vitamina B12 en mujeres posmenopáusicas y sugieren la necesidad de suplementación nutricional

Structural Characterization of Linear Three-Dimensional Random Chains: Energetic Behaviour and Anisotropy

In this work, we will make an energetic and structural characterization of three-dimensional linear chains generated from a simple self-avoiding random walk process in a finite time, without boundary conditions, without the need to explore all possible configurations. From the analysis of the energy balance between the terms of interaction and bending (or correlation), it is shown that the chains, during their growth process, initially tend to form clusters, leading to an increase in their interaction and bending energies. Larger chains tend to “escape” from the cluster when they reach a number of “steps” N>∼1040 , resulting in a decrease in their interaction energy, however, maintaining the same behavior as flexion energy or correlation. This behavior of the bending term in the energy allows distinguishing chains with the same interaction energy that present different structures. As a complement to the energy analysis, we carry out a study based on the moments of inertia of the chains and their radius of gyration. The results show that the formation of clusters separated by “tails” leads to a final “prolate” structure for this type of chain, the same structure evident in real polymeric linear chains in a good solvent

The effect of glass ionomer and adhesive cements on substance P expression in human dental pulp

Objectives: The purpose of this study was to quantify the effect of glass ionomer and adhesive cements on SP expression in healthy human dental pulp. Study Design: Forty pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. In thirty of these premolars a Class V cavity preparation was performed and teeth were equally divided in three groups: Experimental Group I: Glass Ionomer cement was placed in the cavity. Experimental Group II: Adhesive Cement was placed in the cavity. Positive control group: Class V cavities only. The remaining ten healthy premolars where extracted without treatment and served as a negative control group. All pulp samples were processed and SP was measured by radioimmunoassay. Results: Greater SP expression was found in the adhesive cement group, followed by the glass ionomer and the positive control groups. The lower SP values were for the negative control group. ANOVA showed statistically significant differences between groups (p<0.0001). Tukey HSD post hoc tests showed statistically significant differences in SP expression between negative control group and the 3 other groups (p<0.01). Differences between the cavity-only group and the two experimental groups were also statistically significant (p<0.05 and p<0.01 respectively). There is also a statistically significant difference between the two experimental groups (p<0.01). Conclusions: These findings suggest that adhesive cements provoke a greater SP expression when compared with glass ionomer

Teleagro: iot applications for the georeferencing and detection of zeal in cattle

The loss of reproductive efficiency of animals and cattle rustling have become one of the main concerns of farmers. The decrease in reproductive efficiency is mainly due to the low percentage in heat detection. Reproductive efficiency is commonly measured by the interval between births, which affects the daily milk production of the cow during its productive life and the income associated with the sale of milk from its production, conditioning the profitability of the farmers. The zeal for its part consists of the theft of bovine cattle that usually is used for its commercialization, bringing considerable losses. According to figures from the Observatory of Human Rights and International Humanitarian Law of the Fundacion Colombia Ganadera, Fundagán, only during 2014 there were 164 cases of cattle rustling, resulting in the loss of 3,798 cattle throughout the country, which represents a loss for the producers of 15 billion of Colombian money. This project proposes the development of a technological platform that combines hardware, software and communications systems of the latest technology and with open standards to provide an economic and reliable solution to the Colombian and Latin American livestock industry. In Colombia, there is a history of products and prototypes that have been developed to alleviate this problem, no platforms of similar benefits have been found that are accessible to farmers in the country. In this article, the different stages developed to obtain a validated prototype with the beneficiary entity and their respective results are socialized

Formulation of a methodology for the evaluation of the competitiveness of the tourism sector

Esta investigación busca diseñar una metodología de medición que facilite a las Autoridades regionales y locales, Empresarios y Emprendedores realizar un autodiagnóstico que permita obtener una medición de los factores que afectan la competitividad del destino turístico que están evaluando, brindando un insumo para la construcción de un plan estratégico y un plan de acción que junto con el trabajo articulado con las entidades nacionales y regionales encargadas de promover la estrategia nacional de turismo, los lleve a aumentar su competitividad y a convertirse en un destino turístico de calidad.This research seeks to design a measurement methodology that facilitates regional and local Authorities, Businessmen and Entrepreneurs to carry out a self-diagnosis that allows obtaining a measurement of the factors that affect the competitiveness of the tourist destination they are evaluating, providing an input for the construction of a Strategic plan and an action plan that, together with the work coordinated with the national and regional entities in charge of promoting the national tourism strategy, will lead them to increase their competitiveness and become a quality tourist destination.Magister en Gestión Financier

Characteristics of patients undergoing robotic-assisted prostatectomy. observational study

IntroducciónLa prostatectomía es el tratamiento estándar para pacientes con cáncer de próstata localizado. Actualmente, la prostatectomía radical asistida por robot es ampliamente utilizada por sus ventajas en visualización, precisión y manipulación de los tejidos. Sin embargo, este abordaje requiere un manejo mul-tidisciplinario, pues el enfoque analgésico y anestésico es fundamental para optimizar los desenlaces. ObjetivoDescribir los primeros casos de prostatectomía radical asistida por robot realizadas en un hospital universitario de cuarto nivel en Bogotá, Colombia. MetodologíaEstudio observacional en el cual se incluyeron todos los pacientes sometidos a prostatectomía radical asistida por robot (PRAR) en el hospital Fundación Santa Fe de Bogotá entre septiembre de 2015 y diciembre de 2019. Se excluyeron los pacientes con historia clínica incompleta. Se registraron los datos demográficos y se revisaron los eventos perioperatorios importantes. ResultadosSe analizaron 301 pacientes. La edad media de pacientes sometidos a PRAR fue 61,4 ± 6,7 años. El tiempo quirúrgico promedio fue 205 ± 43 minutos y la pérdida sanguínea media fue 300 [200-400] mL. Solo 6 pacientes (2 %) requirieron transfusión. La edad y el IMC no mostraron una asociación relevante con los desenlaces clínicos.ConclusionesEl adecuado abordaje perioperatorio en PRAR es importante para minimizar las complicaciones, las cuales en este estudio y en esta institución fueron infrecuentes.Introduction: Prostatectomy is the standard treatment for patients with clinically localized prostate cancer. Currently, robot-assisted radical prostatectomy (RARP) is widely used for its advantages, as it provides better visualization, precision, and reduced tissue manipulation. However, RARP requires a multidisciplinary approach in which anesthesia and analgesia management are especially important. Objective: This study aims to describe our experience delivering anesthesia for the first cases of patients undergoing RARP in a teaching hospital in Bogotá, Colombia. Methodology: An observational study was conducted. We included all patients undergoing RARP from September 2015 to December 2019 at Fundación Santa Fe de Bogotá. All patients with incomplete data were excluded. Patient demographics were recorded, and significant perioperative events were reviewed. Results: A total of 301 patients were included. At our institution, the mean age for patients undergoing RARP was 61.4 ± 6.7 years. The mean operative time was 205 ± 43 min and mean blood loss was 300 [200-400] mL. Only 6 (2%) patients required transfusion. Age and BMI were not associated with clinical outcomes. Conclusions: An adequate perioperative approach in RARP is important to minimize complications, which in this study and in this institution were infrequent