Mixed insulating and conducting thermal boundary conditions in Rayleigh-B\'enard convection

A series of direct numerical simulations of Rayleigh-B\'enard convection, the flow in a fluid layer heated from below and cooled from above, were conducted to investigate the effect of mixed insulating and conducting boundary conditions on convective flows. Rayleigh numbers between $\text{Ra}=10^7$ and $\text{Ra}=10^9$ were considered, for Prandtl numbers $\text{Pr}=1$ and $\text{Pr}=10$. The bottom plate was divided into patterns of conducting and insulating stripes. The size ratio between these stripes was fixed to unity and the total number of stripes was varied. Global quantities such as the heat transport and average bulk temperature and local quantities such as the temperature just below the insulating boundary wall were investigated. For the case with the top boundary divided into two halves, one conducting and one insulating, the heat transfer was found to be approximately two thirds of the fully conducting case. Increasing the pattern frequency increased the heat transfer which asymptotically approached the fully conducting case, even if only half of the surface is conducting. Fourier analysis of the temperature field revealed that the imprinted pattern of the plates is diffused in the thermal boundary layers, and cannot be detected in the bulk. With conducting-insulating patterns on both plates, the trends previously described were similar, however, the half-and-half division led to a heat transfer of about a half of the fully conducting case instead of two-thirds. The effect of the ratio of conducting and insulating areas was also analyzed, and it was found that even for systems with a top plate with only $25\%$ conducting surface, heat-transport of $60\%$ of the fully conducting case can be seen. Changing the 1D stripe pattern to 2D checkerboard tessellations does not result in a significantly different response of the system.Comment: Submitted to JF

Tratamiento farmacológico y deterioro de la función pulmonar en pacientes con diabetes de tipo 2: Un estudio de corte transversal

Introduction: There is no clear relationship between type 2 diabetes mellitus and lung function decline; it is also unclear whether the type of treatment can modify spirometric variables and levels of inflammatory biomarkers. Objectives: To compare pulmonary function in patients with type 2 diabetes treated with an insulin-sensitizing agent (metformin) and in those treated with secretagogues, as well as combined with insulin, and to evaluate differences in inflammatory biomarkers between treatment groups. Material and methods: We conducted a cross-sectional analytic study in 196 diabetic patients with type 2 diabetic mellitus. Spirometric variables and levels of inflammatory biomarkers (ferritin, fibrinogen, C-reactive protein, interleukin 6, tumor necrosis factor-alpha), were obtained. Residual values (observed minus expected) for forced vital capacity and for forced expiratory volume were calculated and compared between treatment types. Differences in median levels of biomarkers were also compared. Results: After adjustment by known determinants of lung function, and by the control and duration of type 2 diabetes, patients treated with the insulin-sensitizing agent had statistically significant lower differences against expected values for forced vital capacity compared with secretagogues (-212.1 ml vs 270.2 ml, p=0.039), as well as for forced expiratory volume, but without statistical significance (-133.2 mL vs -174.8 mL, p>0.05). In the group of patients treated with the insulin-sensitizing agent, ferritin and tumor necrosis factor-alpha levels were lower (p less than 0.01). Conclusion: This study supports the hypothesis that insulin-sensitizing agents appear to be associated with less deterioration of lung function and less systemic inflammation in type 2 diabetes. The present study serves to formulate new hypothesis and research projects

Costos económicos de neumonía adquirida en comunidad, meningitis y bacteriemia por Streptococcus pneumoniae en una población adulta que requirió hospitalización en Bogotá, Colombia

Introduction: Streptococcus pneumoniae infection in adults is related to pneumonia, meningitis and bacteremia. Its care costs in adults are not well documented in Colombia and it has a greater impact in people over 45 years old.Objectives: The aims of this study were to analyze the associated costs of pneumonia, bacteremia and meningitis in invasive S. pneumoniae infection in Colombia among hospitalized adults and to estimate outpatient costs for community-acquired pneumonia. Additionally, we wanted to serve as a starting point for future economic evaluations.Materials and methods: We performed a direct cost study associated with S. pneumoniae outpatient community-acquired pneumonia, bacteremia and meningitis costs confirmed by cultures. A cohort of hospitalized adults treated between January 2010 and June 2011 in three third level hospitals in Bogotá was analyzed. We evaluated 107 records and 60 bills charged to the payer. The data were classified according to care and treatment costs. We performed an estimate of direct costs for community-acquired pneumonia for outpatient cases through Delphi methodology using expert clinicians.Results: The average direct costs associated with pneumococcal disease were US$6,283, US$ 3,886, and US$4,768 for pneumonia, meningitis and bacteremia, respectively (exchange rate 1 US$ = Col$1,938.34; average variation between 2010 and 2011). Pneumonia cases were 70$ 82.2 (Col$159,280) in adults. For special cases, direct cost increased to US$ 142 (Col$274,427).Conclusions: The management of S. pneumoniae infection in people over 45 years old represents a high cost due to the use of drugs and hospitalization, which has a direct impact on health resources. Prevention and early treatment for pneumonia can reduce the cost and the burden of the disease.Introducción. Las infecciones por Streptococcus pneumoniae en adultos se relacionan con neumonía, meningitis y bacteriemia. El costo de la atención en personas adultas no está bien documentado en Colombia, pero puede ser significativo.Objetivo. Analizar los costos asociados con la neumonía adquirida en comunidad, meningitis y bacteriemia por S. pneumoniae en adultos hospitalizados en Colombia y estimar el costo de la atención ambulatoria de esta neumonía. Servir de base para futuras evaluaciones económicas.Materiales y métodos. Se realizó un estudio de costos directos asociados a neumonía adquirida en comunidad, meningitis y bacteriemia por S. pneumoniae confirmado por cultivos. Se tomó una muestra de conveniencia de adultos hospitalizados entre enero de 2010 y junio de 2011 en tres hospitales de tercer nivel de Bogotá. Se analizaron 107 registros y se obtuvieron 60 facturas cobradas al pagador. La información se clasificó por costos de atención y tratamiento. Para los casos ambulatorios de neumonía, el estimativo de costos se hizo utilizando metodología Delphi con expertos clínicos.Resultados. El promedio de los costos directos totales asociados con neumonía fue de Col$ 12’178.949, Col$7’533.187 para meningitis y Col$ 9’242.806 para bacteriemia. La neumonía se presentó en 70 % de los hombres y 30 % de las mujeres; la meningitis se distribuyó igual en ambos sexos (50 %) y la bacteriemia se presentó en 67 % de los hombres y 33 % de las mujeres. El costo por adulto de la atención ambulatoria de la neumonía adquirida en la comunidad se estimó en Col$106.174. Para casos especiales se incrementó a Col$ 164.695.Conclusión. La enfermedad neumocócica en adultos, especialmente mayores de 45 años, representa un alto costo por el empleo de medicamentos y la estancia hospitalaria, que causan un impacto en los recursos del sistema. La prevención y el tratamiento temprano de las neumonías pueden disminuir costos y reducir la carga de enfermedad

Optimal Taylor-Couette flow: Radius ratio dependence

Taylor-Couette flow with independently rotating inner (i) and outer (o) cylinders is explored numerically and experimentally to determine the effects of the radius ratio {\eta} on the system response. Numerical simulations reach Reynolds numbers of up to Re_i=9.5 x 10^3 and Re_o=5x10^3, corresponding to Taylor numbers of up to Ta=10^8 for four different radius ratios {\eta}=r_i/r_o between 0.5 and 0.909. The experiments, performed in the Twente Turbulent Taylor-Couette (T^3C) setup, reach Reynolds numbers of up to Re_i=2x10^6$ and Re_o=1.5x10^6, corresponding to Ta=5x10^{12} for {\eta}=0.714-0.909. Effective scaling laws for the torque J^{\omega}(Ta) are found, which for sufficiently large driving Ta are independent of the radius ratio {\eta}. As previously reported for {\eta}=0.714, optimum transport at a non-zero Rossby number Ro=r_i|{\omega}_i-{\omega}_o|/[2(r_o-r_i){\omega}_o] is found in both experiments and numerics. Ro_opt is found to depend on the radius ratio and the driving of the system. At a driving in the range between {Ta\sim3\cdot10^8} and {Ta\sim10^{10}}, Ro_opt saturates to an asymptotic {\eta}-dependent value. Theoretical predictions for the asymptotic value of Ro_{opt} are compared to the experimental results, and found to differ notably. Furthermore, the local angular velocity profiles from experiments and numerics are compared, and a link between a flat bulk profile and optimum transport for all radius ratios is reported.Comment: Submitted to JFM, 28 pages, 17 figure

Hemoglobin and B-type natriuretic peptide preoperative values but not inflammatory markers, are associated with postoperative morbidity in cardiac surgery : A prospective cohort analytic study

Introduction: Risk stratification in cardiac surgery significantly impacts outcome. This study seeks to define whether there is an independent association between the preoperative serum level of hemoglobin (Hb), leukocyte count (LEUCO), high sensitivity C-reactive protein (hsCRP), or B-type natriuretic peptide (BNP) and postoperative morbidity and mortality in cardiac surgery.Methods: Prospective, analytic cohort study, with 554 adult patients undergoing cardiac surgery in a tertiary cardiovascular hospital and followed up for 12 months. The cohort was distributed according to preoperative values of Hb, LEUCO, hsCRP, and BNP in independent quintiles for each of these variables.Results: After adjustment for all covariates, a significant association was found between elevated preoperative BNP and the occurrence of low postoperative cardiac output (OR 3.46, 95% CI 1.53-7.80, p = 0.003) or postoperative atrial fibrillation (OR 3.8, 95% CI 1.45-10.38). For the combined outcome (death/acute coronary syndrome/rehospitalization within 12 months), we observed an OR of 1.93 (95% CI 1.00-3.74). An interaction was found between BNP level and the presence or absence of diabetes mellitus. The OR for non-diabetics was 1.26 (95% CI 0.61-2.60) and for diabetics was 18.82 (95% CI 16.2-20.5). Preoperative Hb was also significantly and independently associated with the occurrence of postoperative low cardiac output (OR 0.33, 95% CI 0.13-0.81, p = 0.016). Both Hb and BNP were significantly associated with the lengths of intensive care unit and hospital stays and the number of transfused red blood cells (p < 0.002). Inflammatory markers, although associated with adverse outcomes, lost statistical significance when adjusted for covariates.Conclusions: High preoperative BNP or low Hb shows an association of independent risk with postoperative outcomes, and their measurement could help to stratify surgical risk. The ability to predict the onset of atrial fibrillation or postoperative low cardiac output has important clinical implications. Our results open the possibility of designing studies that incorporate BNP measurement as a routine part of preoperative evaluation, and this strategy could improve upon the standard evaluation in terms of reducing adverse postoperative events. © 2013 Hernández-Leiva et al.; licensee BioMed Central Ltd

Optimización de parques de generación híbridos fotovoltaicos y eólicos conectados a la red.

Con este TFM se pretende evaluar un mejor aprovechamiento de puntos de conexión a la red existentes, mediante la hibridación eólica-fotovoltaica. Se evaluarán, para distintas localizaciones en España, distintas alternativas solo fotovoltaica, solo eólica o híbridas, optimizando el sistema. Se considerarán distintas localizaciones con datos representativos de recurso solar y eólico. Se considerarán los costes actuales de las distintas tecnologías y de la electricidad, realizando análisis de sensibilidad de las variables más importantes. Se obtendrán conclusiones acerca de la viabilidad de las distintas tecnologías dependiendo de los recursos renovables y de otras variables.<br /

Valores de referencia para parámetros de espirometría en la población adulta residente en Bogotá, D. C., Colombia

Introduction. Reference values for pulmonary function parameters, generally applicable to most populations, have shown little validity in the correct interpretation of pulmonary function tests when applied to the adult population in Bogotá.Objective. To identify which of four prediction models generated for use in populations of a similar ethnic background to that found in Colombia is the most accurate for use in adults in Bogotá.Materials and methods. 534 subjects (male and female) between 18 and 65 years of age were recruited from a pool of workers employed by three private Bogotá companies. All subjects had resided in Bogotá for at least five years before the initiation of the study. Smokers and those with altered pulmonary function were excluded. Pulmonary function parameters were measured by flow volume curve. The results were analyzed (specifically, the difference between predicted and observed values) and the limits were calculated using the Bland &amp; Altman method. A maximum average prediction error of 5% was accepted as valid for the observed value of each parameter.Results. The models shown to be valid were as follows: Crapo for forced vital capacity (FVC) in men; Pérez-Padilla for FVC in women and for the ratio forced expiratory volume in the first second (FEV1/FVC) in both sexes, and the Hankinson model for Mexican-Americans, for all parameters in both sexes.Conclusions. The Hankinson model proved to be the most accurate in predicting all spirometry parameters. However, its poor classification average (7%) is a limitation. In the future, new models with a better predictive accuracy will be required.Introducción. Los valores de referencia para parámetros de la función pulmonar aplicables a otras poblaciones, han mostrado ser poco válidos en la interpretación de las pruebas de función pulmonar en la población adulta residente en Bogotá.Objetivo. Identificar cuál de cuatro modelos de predicción generados en poblaciones con características étnicas similares a la población colombiana, es el más adecuado para utilizar en adultos de Bogotá.Materiales y métodos. Se reclutaron 534 sujetos de ambos sexos entre los 18 y los 65 años de edad, no fumadores, libres de alteraciones pulmonares, trabajadores de tres empresas privadas y residentes en Bogotá por más de cinco años. La función pulmonar se midió por curva de flujo volumen. Se estimaron las diferencias observadas entre valores predichos y observados, y se calcularon los límites por el método de Bland y Altman. Se aceptaron como válidos los modelos que presentaron un error de predicción promedio máximo de 5% del valor observado en cada parámetro.Resultados. Demostraron ser válidos en esta población los modelos: Crapo para capacidad vital forzada (CVF) en hombres; Pérez-Padilla, para CVF en mujeres y para la relación con el volumen espiratorio forzado en el primer segundo (VEF1/CVF) en ambos grupos y los de Hankinson para mexicano-americanos para todos los parámetros en ambos sexos.Conclusiones. Los modelos de Hankinson demostraron ser los más adecuados para predecir todos los parámetros de la espirometría; sin embargo, dejan un porcentaje de mala clasificación promedio de 7%. Se requiere generar modelos propios con mayor precisión pronóstica en la población de Bogotá

Estudio sobre la automedicación en una localidad de bogotá

Objetivos Establecer la prevalencia y condicionantes asociados al uso de medicamentos por cuenta propia por parte de los habitantes de Suba en Bogotá.Métodos Aplicación de una encuesta pilotada a una muestra aleatoria.  Se midieron variables demográficas y se indagó por problemas de salud relacionados con la automedicación, motivos para no consultar al médico y medicamentos consumidos durante las dos últimas semanasResultados La automedicación fue de 27,3 % (IC 95 %, 19,2 % - 35,3 %) y la autoprescripción de 7,7 % (IC 95%, 2,8 %-12,5 %). La afiliación al Sistema de beneficiarios de la Seguridad Social en Salud (OR=2,61  IC 95 % 1,4-4,8) está asociado con ésta conducta. No se encontró asociación con otras variables. Los medicamentos más consumidos por automedicación son analgésicos (59,3 %), antigripales (13,5 %) y vitaminas (6,8 %).  Los principales problemas por los cuales las personas se automedican son dolor, fiebre y gripa.  Las principales razones que se mencionan para no asistir al médico son falta de tiempo (40 %) y recursos económicos (43 %), además de otros argumentos como la percepción de que el problema es leve y la congestión en los servicios de urgencia.Conclusiones Las cifras de automedicación aunque todavía preocupantes desde el punto de vista de salud pública, son más bajas que las encontradas en estudios similares; los medicamentos consumidos por automedicación pertenecen a la categoría de venta libre y el consumo de antibióticos por automedicación bajó, posiblemente debido a la intensa difusión que se dio a la restricción de venta de antibióticos sin fórmula médica, unos meses antes de la realización de la encuesta

Test of Time Dilation Using Stored Li+ Ions as Clocks at Relativistic Speed

We present the concluding result from an Ives-Stilwell-type time dilation experiment using 7Li+ ions confined at a velocity of beta = v/c = 0.338 in the storage ring ESR at Darmstadt. A Lambda-type three-level system within the hyperfine structure of the 7Li+ triplet S1-P2 line is driven by two laser beams aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler shifted frequencies required for resonance are measured with an accuracy of < 4 ppb using optical-optical double resonance spectroscopy. This allows us to verify the Special Relativity relation between the time dilation factor gamma and the velocity beta to within 2.3 ppb at this velocity. The result, which is singled out by a high boost velocity beta, is also interpreted within Lorentz Invariance violating test theories