A note on the geodesic deviation equation for null geodesics in the Schwarzschild black-hole

We use the Hamiltonian formulation of the geodesic equation in the Schwarzschild space-time so as to get the variational equation as the counterpart of the Jacobi equation in this approach. In this context we are able to apply the Morales-Ramis theorem to link the integrability of the geodesic equation to the integrability, in the sense of differential Galois theory, of the variational equation. This link is strong enough to hold even on geodesics for which the usual conserved quantities fail to be independent, as is the case of circular geodesics. We show explicitly the particular cases of some null geodesics and their variational equations.Comment: 12 page

Right to die with dignity?

El derecho a morir con dignidad es un concepto vago y que recibe múltiples interpretaciones, muchas de ellas inapropiadas. Se propone la necesidad de que sea el médico quien se haga responsable de proteger los derechos del paciente, de garantizar el uso racional de los recursos y de velar porque las decisiones sean apropiadas y proporcionadas a la situación del paciente, a su pronóstico, expectativas y deseos, pero también, a la utilidad esperada y a la relación costo-beneficio. Se enfatiza que la dignidad puede ser entendida de muchas maneras y que, a veces, en su nombre se somete al paciente, o lo hace él mismo, a sufrimientos, dolor y complicaciones que podrían haberse evitado, no necesariamente en busca de prolongar la vida. Se hace énfasis en que, cuando no hay probabilidades razonables de supervivencia o cuando no puede ya buscarse mejorar la calidad de vida, deben enfocarse los esfuerzos en procurar calidad de muerte.Q4Q3Ensayo191-194The right to die with dignity is an ill-defined concept, with multiple, often inappropriate, interpretations. The current proposition is that the physician take full responsibility for protecting the patient’s rights, for ensuring a rational use of resources and for overseeing the decision- making process such that the information is adequate and the steps proportioned. This responsibility extends not only to the health status of the patient situation, to the patient’s prognosis, and to his/her expectations and wishes, but also to the benefits foreseen and to the cost-benefit ratio. Emphasis is placed on two aspects of this relationship. First, dignity can be interpreted in many ways and sometimes, in the name of dignity, the patient is exposed (or exposes him/herself) to suffering, pain and complications that can be avoided. Second, when no reasonable probability of survival is present and a better “quality of life” is impossible, efforts are better redirected to offering a better quality of death

Systematic reviews for the evaluation of interventions that include non-randomized studies

Las revisiones sistemáticas para evaluar intervenciones que incluyan la evidencia aportada por los estudios no aleatorizados (ENA), pueden ser muy útiles para soportar decisiones clínicas en temas que no estén bien cubiertos por experimentos clínicos aleatorizados (ECA), como la evaluación de los efectos de un tratamiento a largo plazo, sus efectos adversos o la evaluación de intervenciones en salud pública u organizacionales. El desarrollo de estas RSL requiere una serie de ajustes meto-dológicos para la búsqueda y selección de los estudios primarios, la evaluación de la calidad de los mismos y la combinación de la evidencia. Especial cuidado debe tenerse para identificar y manejar adecuadamente el mayor riesgo de sesgos, en especial los derivados de un inadecuado control de los factores de confusión. El presente artículo presenta las particularidades a tener en cuenta a la hora de realizar RSL para evaluar intervenciones que incluyan ENA, las herramientas que se han desarrollado para facilitar su desarrollo, y las consideraciones importantes para reportar y discutir los hallazgos. El desarrollo de este tipo de RSL requiere un alto nivel de experiencia por parte del grupo desarrollador y una mayor cantidad de recursos económicos y de tiempo. Sin embargo, cuando han sido bien diseñadas, conducidas y analizadas, pueden ser de gran utilidad en la toma de decisiones clínicas, y pueden ser integradas en el desarrollo de las recomendaciones presentadas en las guías de práctica clínica.100-106Systematic reviews to evaluate interventions including the evidence provided by non-randomized studies (NRS), can be very useful to support clinical decisions in subjects that are not well covered by randomized clinical trials (RCTs), such as the evaluation of the effects of long-term treatment, its adverse effects or the evaluation of public health or organizational interventions. The develop-ment of these RSLs requires a series of methodological adjustments for the search and selection of the primary studies, the evaluation of their quality and the combination of the evidence. Special care must be taken to identify and appropriately manage the increased risk of bias, especially those derived from inadequate control of confounding factors. This article presents the particularities to take into account when performing RSL to evaluate interventions that include NRS, the tools that have been developed to facilitate their development, and the important considerations to report and discuss the findings. The development of this type of RSL requires a high level of experience by the developer group and a greater amount of economic resources and time. However, when they have been well designed, conducted and analyzed, they can be very useful in clinical decision-making, and can be integrated into the development of the recommendations presented in the clinical practice guidelines

Systematic reviews for the evaluation of interventions that include non-randomized studies : methodological considerations

Las revisiones sistemáticas para evaluar intervenciones que incluyan la evidencia aportada por los estudios no aleatorizados (ENA), pueden ser muy útiles para soportar decisiones clínicas en temas que no estén bien cubiertos por experimentos clínicos aleatorizados (ECA), como la evaluación de los efectos de un tratamiento a largo plazo, sus efectos adversos o la evaluación de intervenciones en salud pública u organizacionales. El desarrollo de estas RSL requiere una serie de ajustes metodológicos para la búsqueda y selección de los estudios primarios, la evaluación de la calidad de los mismos y la combinación de la evidencia. Especial cuidado debe tenerse para identificar y manejar adecuadamente el mayor riesgo de sesgos, en especial los derivados de un inadecuado control de los factores de confusión. El presente artículo presenta las particularidades a tener en cuenta a la hora de realizar RSL para evaluar intervenciones que incluyan ENA, las herramientas que se han desarrollado para facilitar su desarrollo, y las consideraciones importantes para reportar y discutir los hallazgos. El desarrollo de este tipo de RSL requiere un alto nivel de experiencia por parte del grupo desarrollador y una mayor cantidad de recursos económicos y de tiempo. Sin embargo, cuando han sido bien diseñadas, conducidas y analizadas, pueden ser de gran utilidad en la toma de decisiones clínicas, y pueden ser integradas en el desarrollo de las recomendaciones presentadas en las guías de práctica clínica.100-106Systematic reviews to evaluate interventions including the evidence provided by non-randomized studies (NRS), can be very useful to support clinical decisions in subjects that are not well covered by randomized clinical trials (RCTs), such as the evaluation of the effects of long-term treatment, its adverse effects or the evaluation of public health or organizational interventions. The develop-ment of these RSLs requires a series of methodological adjustments for the search and selection of the primary studies, the evaluation of their quality and the combination of the evidence. Special care must be taken to identify and appropriately manage the increased risk of bias, especially those derived from inadequate control of confounding factors. This article presents the particularities to take into account when performing RSL to evaluate interventions that include NRS, the tools that have been developed to facilitate their development, and the important considerations to report and discuss the findings. The development of this type of RSL requires a high level of experience by the developer group and a greater amount of economic resources and time. However, when they have been well designed, conducted and analyzed, they can be very useful in clinical decision-making, and can be integrated into the development of the recommendations presented in the clinical practice guidelines

"DOCENTE-NANO”: UNA ALTERNATIVA PARA LA DIVULGACIÓN DEL CONCEPTO DE NANOMATERIALES EN LA EDUCACIÓN MEDIA

La enseñanza de la Nanociencia y la Nanotecnología en la educación secundaria aún es muy incipiente en Colombia, ya que los estándares de competencias curriculares del Ministerio de educación Nacional MEN aún no contemplan el llevar estas temáticas a las aulas en estos niveles educativos.“Docente-Nano” es una propuesta educativa dirigida a docentes de Ciencias Naturales de Educación Media (Ciclo V) para la divulgación y enseñanza del concepto de Nanomateriales, a partir de las dimensiones de la Alfabetización Científica y Tecnológica.La investigación es de tipo cualitativo y la metodología comprende cinco etapas. La selección de conceptos, la definición de elementos y estructura, la elaboración, la implementación y evaluación. Los resultados y análisis se realizan en términos de tres etapas importantes tales como la convocatoria, la selección y la ejecución. En la convocatoria se contó con la inscripción de 72 personas, luego se realizó el proceso de selección y finalmente en la implementación se llevaron a cabo trece sesiones de trabajo de dos horas cada una en las cuales se abordaron temáticas como: introducción a la nanociencia y nanotecnología, nanoescala, nanomateriales, métodos de observación, nanomateriales de Carbono, nanotoxicologia, entre otros. Los resultados fueron favorables, ya que ratifican que sí es posible e importante abordar temáticas de Nanotecnología desde la educación secundaria y que los docentes son conscientes de la necesidad de formarse en estos contenidos que abren un mar de posibilidades para lograr generar impacto, curiosidad, motivación y así despertar el interés de los estudiantes por el aprendizaje de las ciencias.La enseñanza de la Nanociencia y la Nanotecnología en la educación secundaria aún es muy incipiente en Colombia, ya que los estándares de competencias curriculares del Ministerio de educación Nacional (MEN) aún no contemplan el llevar estas temáticas a las aulas en estos niveles educativos.“Docente-Nano” es una propuesta educativa dirigida a docentes de Ciencias Naturales de Educación Media (Ciclo V) para la divulgación y enseñanza del concepto de Nanomateriales, a partir de las dimensiones de la Alfabetización Científica y Tecnológica.La investigación es de tipo cualitativo y la metodología comprende cinco etapas. : La selección de conceptos, la definición de elementos y estructura, la elaboración, la implementación y evaluación. Los resultados y análisis se realizan en términos de tres etapas importantes tales como: la convocatoria, la selección y la ejecución. En la convocatoria se contó con la inscripción de 72 personas, luego se realizó el proceso de selección y finalmente en la implementación se llevaron a cabo trece sesiones de trabajo de dos horas cada una. en En las estas cuales se abordaron temáticas como: introducción a la nanociencia y nanotecnología, nanoescala, nanomateriales, métodos de observación, nanomateriales de Carbono, nanotoxicologiananotoxicología, entre otros. Los resultados fueron favorables, ya que ratifican que sí es posible e importante abordar temáticas de Nanotecnología desde la educación secundaria y que los docentes son conscientes de la necesidad de formarse en estos contenidos que abren un mar de posibilidades para lograr generar impacto, curiosidad, motivación y así despertar el interés de los estudiantes por el aprendizaje de las ciencias.The teaching of Nanoscience and Nanotechnology in secondary education is still in its formative stages in Colombia, since the standards of curricular competences for the Ministry of National Education do not contemplate the introduction of these subjects into the classroom at these educational levels.“Nano- Teacher" is an educational proposal addressed to teachers of Natural Sciences of Middle Education (Cycle V) for the divulgation of knowledge regarding the teaching of the concepts of Nanomaterials, based on the dimensions of Scientific and Technological Literacy.The research is qualitative and the methodology comprises of five stages: The selection of concepts, the definition of elements and structure, elaboration, implementation and evaluation. The results and analysis are performed in terms of three important stages such: As the call, selection and execution. In the call, 72 people were registered, then the selection process, finally in the implementation thirteen work sessions in which topics such as: Introduction to Nanoscience and Nanotechnology, Nanoscale, Nanomaterials, methods of observation, Carbon Nanomaterials, Nanotoxicology, among others, were covered. The results were favorable since they confirmed that if it is possible and important to approach nanotechnology topics throughout secondary education and that teachers are aware of the need to be informed of these contents that will open a sea of possibilities to achieve an impact, inspiring motivation and curiosity towards nanomaterials, further arousing the students' interest in learning science

Prevalence of metabolic syndrome in scholars from Bucaramanga, Colombia: a population-based study

Background: Obesity and metabolic syndrome are strongly associated with type 2 diabetes mellitus and cardiovascular diseases, thus the increasing trend in their prevalence among children and adolescents from developing countries requires a further understanding of their epidemiology and determinants. Methods and design: A cross-sectional study was designed to determine the prevalence of metabolic syndrome among 6–10 year-old children from Bucaramanga, Colombia. A two-stage random-cluster (neighborhoods, houses) sampling process was performed based on local city maps and local statistics. The study involves a domiciliary survey; including a comprehensive sociodemographic, nutritional and physical activity characterization of the children that participated in the study, followed by a complete clinical examination; including blood pressure, anthropometry, lipid profile determination, fasting glucose and insulin levels. The prevalence of metabolic syndrome will be determined using definitions and specific percentile cut-off points for this population. Finally, the association between components of metabolic syndrome and higher degrees of insulin resistance will be analyzed through a multivariable logistic regression model. This study protocol was designed in compliance with the Helsinki declaration and approved by the local ethics board. Consent was obtained from the children and their parents/guardians. Discussion: A complete description of the environmental and non-environmental factors underlying the burden of metabolic syndrome in children from a developing country like Colombia will provide policy makers, health care providers and educators from similar settings with an opportunity to guide primary and secondary preventive initiatives at both individual and community levels. Moreover, this description may give an insight into the pathophysiological mechanisms mediating the development of cardio-metabolic diseases early in life

Concordancia entre los modelos de SCORE y Framingham y las ecuaciones AHA/ACC como evaluadores de riesgo cardiovascular

ResumenObjetivoDiferentes modelos de evaluación de riesgo cardiovascular están actualmente en uso en Colombia. El objetivo de este estudio es analizar la concordancia entre las ecuaciones AHA/ACC 2013, SCORE y Framingham ajustado, así como el impacto de usar una u otra en la cantidad de pacientes clasificados como de alto riesgo y en la cantidad de pacientes que requerirían manejo farmacológico.MétodosSe evaluaron 800 pacientes entre 40 y 74 años, de la clínica de prevención primaria del Hospital militar Central en Bogotá (Colombia), libres de eventos cardiovasculares. Se estimaron el riesgo a 10 años de enfermedad arterioesclerótica cardiovascular según las ecuaciones propuestas por las guías AHA/ACC 2013, el riesgo de muerte cardiovascular según la función SCORE de la guía europea y el riesgo coronario según la función de Framingham ajustada, recomendada por la guía colombiana. Se consideró como indicación de manejo farmacológico un cálculo de riesgo AHA/ACC o Framingham ajustado>7,5%. Un riesgo de Framingham>20% o SCORE>5% definía el riesgo alto.ResultadosSegún el Framingham había un 5,9% de pacientes de alto riesgo, según las ecuaciones de SCORE para países de bajo riesgo un 18,7% y según las ecuaciones de SCORE para países de alto riesgo, un 31,2%. El coeficiente Kappa mostró baja concordancia entre Framingham ajustado y cada una de las ecuaciones de SCORE (0,28 y 0,22 respectivamente). Según las recomendaciones de la guía AHA/ACC, el tratamiento hipolipemiante estaría indicado en un 40,8% de los pacientes, frente a un 50,6% según la guía colombiana (Framingham ajustado). El coeficiente kappa fue de 0,5735.ConclusionesEn la actualidad existe pobre acuerdo entre las diferentes escalas de evaluación del riesgo cardiovascular usadas en Colombia, hecho que conlleva incertidumbre para la toma de decisiones terapéuticas. Los datos de este estudio demuestran la necesidad de validar los modelos de SCORE y AHA/ACC en Colombia y Latinoamérica.AbstractMotivationIn Colombia, different models of cardiovascular risk assessment are currently being used. The motivation of this study is to analyse the concordance between the ACC/AHA 2013 equation, SCORE and adjusted Framingham, as well as the impact of using one or another in the amount of patients classified as high risk and the amount of patients requiring pharmacological management.Methods800 patients between 40 and 74 years old were assessed, from the primary prevention clinic of the Hospital Militar Central in Bogotá (Colombia), who were free of cardiovascular events. 10-year risk for atherosclerotic vascular disease was estimated according to the equations proposed by ACC/AHA 2013 guides, the risk of cardiovascular death according to the SCORE function of the European guide and the coronary risk according to the adjusted Framingham function recommended by the Colombian guide. The indication of pharmacological management was considered with an ACC/AHA or adjusted Framingham risk of>7.5%. A >20% Framingham or a >5% SCORE risk were considered high risk.ResultsAccording to Framingham there was a 5.9% of high-risk patients, according to SCORE equations for low-risk countries an 18.7% and according to SCORE equations for high-risk countries, a 31.2%. The Kappa coefficient showed a low concordance between adjusted Framingham and each of the SCORE equations (0.28 and 0.22 respectively). According to the ACC/AHA guide recommendations, hypolipidemic treatment would be indicated in 40.8% of patients, versus a 50.6% following the Colombian guide indications (adjusted Framingham). Kappa coefficient was 0.5735.ConclusionsNowadays there is a poor agreement between the different cardiovascular risk assessment scales used in Colombia, thus generating uncertainty when it comes to making therapeutic choices. Data from this study show the need to validate the validate the SCORE and ACC/AHA models in Colombia and Latin America

Evaluation of the Bond-to-Concrete Properties of GFRP Rebars in Marine Environments

Increased traffic in combination with growing environmental impacts have led to the accelerated degradation of built infrastructure. In reinforced concrete structures, the corrosion of steel reinforcement is the predominant cause of deterioration. Thus, over the last years the use of glass fiber reinforced polymer (GFRP) composites as internal reinforcement bars (rebars) for concrete structures has been evaluated, and has been proved to be a viable alternative to traditional steel reinforcement mainly due to its tensile strength and non-corrosive nature. However, thus far, the GFRP rebar market is diverse and manufacturers around the world produce GFRP rebar types with different surface enhancements to improve the bond to concrete characteristics. In this study, the bond performance of three dissimilar GFRP rebar types (sand coated, helically grooved and with surface lugs) was evaluated over time in seawater environments, with a focus on the bond strength. Accordingly, specimens were exposed to seawater in circulating chambers at three different temperatures (23 °C, 40 °C and 60 °C) for multiple time periods (60 and 120 days). To evaluate the bond performance, pullout tests were conducted according to ASTM D7913. The results showed that the bond strength varied with the surface enhancement features. However, the bond strength did not vary significantly with exposure time and temperature for all three evaluated rebar types.This research was funded by the Florida Department of Transportation under the grant BDV30TW0977-18

On the energy potential of daytime radiative cooling for urban heat island mitigation

The objective of this paper is to present the potential of daytime radiative cooling materials as a strategy to mitigate the Urban Heat Island effect. To evaluate the cooling potential of daytime radiative cooling materials, 15 theoretical materials and seven existing materials were simulated: two radiative cooling materials, a coolmaterial, two white paints, a thermochromic paint and a construction material. The novelty of this study is that it shows that the optimal spectral characteristics of radiative cooling materials depending on the climate conditions and the type of application. A sensitivity analysis was performed to evaluate the impact of each wavelength emissivity on the ability to achieve sub-ambient radiative cooling. The sensitivity analysis comprised a total of 90 theoretical materials with 15 different wavelength combinations and 6 emissivity values. The heat transfer model, which includes conduction, convection, and radiation, was developed using a spectrally-selective sky model. Two conditions were considered: a very conductive surface and a highly insulated one. All the materials were simulated in two cities that suffer from the Urban Heat Island effect—Phoenix and Sydney. The mean surface temperature reduction achieved was 5.30 ◦C in Phoenix and 4.21 ◦C in Sydney. The results presented suggest that the type of application (active or passive) is a determinant factor in the design of radiative cooling materials. Modifying the spectra of the materials led to a substantial change in the cooling potential. A material that performs well in a dry climate as a passive solution could perform poorly as an active solution.Laura Carlosena would like to acknowledge the funding of the Government of Navarre for an industrial Ph.D. research grant "Doctorados industriales 2018–2020" file number 0011-1408-2017-000028 at the University of the Basque Country that takes place in the R + D department of Alonso Hernández & asociados arquitectura S.L

Calibration of semi-analytic models of galaxy formation using Particle Swarm Optimization

We present a fast and accurate method to select an optimal set of parameters in semi-analytic models of galaxy formation and evolution (SAMs). Our approach compares the results of a model against a set of observables applying a stochastic technique called Particle Swarm Optimization (PSO), a self-learning algorithm for localizing regions of maximum likelihood in multidimensional spaces that outperforms traditional sampling methods in terms of computational cost. We apply the PSO technique to the SAG semi-analytic model combined with merger trees extracted from a standard $\Lambda$CDM N-body simulation. The calibration is performed using a combination of observed galaxy properties as constraints, including the local stellar mass function and the black hole to bulge mass relation. We test the ability of the PSO algorithm to find the best set of free parameters of the model by comparing the results with those obtained using a MCMC exploration. Both methods find the same maximum likelihood region, however the PSO method requires one order of magnitude less evaluations. This new approach allows a fast estimation of the best-fitting parameter set in multidimensional spaces, providing a practical tool to test the consequences of including other astrophysical processes in SAMs.Comment: 11 pages, 4 figures, 1 table. Accepted for publication in ApJ. Comments are welcom