Medición del impacto de la convexidad en la curva de rendimientos del mercado de bonos

La inversión en renta fija tiene una participación mayor al 80% en el mercado de Valores Colombiano, y aunque este instrumento es caracterizado por su bajo nivel de riesgo, es importante para el inversionista realizar una adecuada medición de este, así, el objetivo principal del presente trabajo es determinar el impacto que tiene la convexidad de la curva de rendimiento e identificar en qué momento es conveniente tener en cuenta la convexidad como método de valoración del bono, teniendo presente que actualmente el cálculo de la duración es suficiente. El desarrollo de la investigación comienza con la selección de algunos títulos de deuda pública con tasa fija de la Bolsa de Valores de Colombia, a partir de los cuales se realizará la construcción de las curvas de rendimientos mediante el Método de Nelson y Siegel y Esplines Cúbicos, de los que según los resultados obtenidos se seleccionará el más adecuado. El siguiente paso consistirá en calcular las variables de valoración de cada uno de los bonos seleccionados, mediante la medición del precio y del riesgo de los títulos a través los métodos de duración, duración modificada, convexidad y VAR. Una vez realizados estos cálculos se aplicará el método de Análisis de Componentes Principales (ACP) al estudio de bonos con finalidad de analizar la incidencia de las variables que dan explicación al comportamiento de la curva de rendimientos. Finalmente, se valoraran los portafolios de inversión por el Método de mapeo de posiciones haciendo uso de la Geometría Euclidiana y se determinará el margen del precio del bono excluido en el cálculo para diferentes momentos de la curva y así lograr resolver los objetivo del proyecto

Interface chemistry effects in nanofluids: Experimental and computational study of oil-based nanofluids with gold nanoplates

The chemistry of interfaces and its relation with energy storage at and transport through solid-liquid interfaces in heat transfer nanofluids is a very unexplored terrain. Here we discuss how the magnitude of the changes in specific heat and thermal conductivity of the base fluid, upon dispersion of a nanoma-terial, depends on the surface chemistry of that nanomaterial. We focus on nanofluids with Au nanoplates from an integrated experimental and theoretical perspective, and compared our findings with those pre-viously reported for nanofluids with Pd nanoplates in the same base fluid. Pd and Au are known to have different surface chemistry, and so are the structures of the solid-liquid interfaces and the thermal prop-erties of these nanofluids. It was experimentally found that for mass fractions in the order of 0.01 wt%, Pd and Au nanoplates provide enhancements of 5.9% and 1.6% in specific heat, and enhancements of 12.5% and 17.9% in thermal conductivity, at 373 K. It was verified using density functional theory and classical molecular dynamics simulations that base fluid molecules can chemisorb on Pd surfaces, but not on Au surfaces. This work suggests that the stronger interactions between species at solid-liquid interfaces, the higher the specific heat enhancements and the lower the thermal conductivity enhancements at high temperature.(c) 2022 The Author(s). Published by Elsevier B.V

Grado de conocimiento, tratamiento y control de la hipertensión arterial, hipercolesterolemia y diabetes mellitus en la población general adulta

ObjetivosEstimar la prevalencia de los principales factores de riesgo cardiovascular (FRCV) tras la confirmación diagnóstica con el criterio clínico. Analizar el grado de su conocimiento y control, y evaluar la asociación de los FRCV entre sí, estimando qué población es susceptible de intervención.DiseñoEstudio observacional, descriptivo,transversal.EmplazamientoEstudio poblacional realizado en el Área de Salud número 20 de la Comunidad Valenciana (comarca de la Vega Baja del río Segura)PacientesPersonas con ≥ 20 años residentes en dicha área. Muestreo aleatorio polietápico proporcional con definición de cuotas muestrales según el tipo de residencia. Tamaño muestral: 2.550 personas (falta de respuesta en la primera fase en el 26%). Segunda fase del estudio: se realiza la confirmación clínica de los 374 casos detectados de hipertensión arterial (HTA), los 126 de hipercolesterolemia (HCOL) y los 33 de diabetes mellitus (DM).MedicionesSe realiza una entrevista a los pacientes detectados para las tomas de presión arterial a los hipertensos y para practicar la extracción sanguínea a hipercolesterolémicos y diabéticos. Se han utilizado los criterios diagnósticos preconizados por los últimos consensos.ResultadosParticipan 1.886 personas (78,1%). Prevalencias halladas: HTA total, 42 ± 2,2%; diagnosticada, 11,7 ± 1,4%; HCOL total, 26,6 ± 2%; DM total, 9,5 ± 1,3%; tabaquismo: 33,6 ± 2,1% y obesidad: 31,6 ± 2,1%. Grado de control: HTA, 8,6%; HCOL, 21,7%; DM, 56,1%. Asociación de FRCV: el 25,5% no presenta hipertensión, hipercolesterolemia ni fuma.ConclusionesElevada prevalencia FRCV en nuestra área frente a los resultados publicados de ámbito nacional. El tabaquismo resulta menos frecuente que en el resto del país. El grado de control es escaso y la asociación de los FRCV principales para cardiopatía isquémica reflejan que cerca del 75% de la población debe ser intervenida.ObjectivesTo calculate the prevalence of the main cardiovascular risk factors (CVRF) after diagnostic confirmation using clinical criteria. To analyse the degree of understanding and monitoring of these factors and to evaluate the association of CVRF with each other, so estimating who is susceptible to intervention.DesignCross-sectional, descriptive, observational study.SettingPopulation study conducted in Health Area 20 of the Community of Valencia (county of the Low Plain of the River Segura). Patients. People who had lived in this Area for ³20 years. Proportional, multi-stage randomised sampling with definition of sample quotas according to type of residence. Sample size: 2550 people (no reply in first stage: 26%). The second stage involved the clinical confirmation of those identified as suffering from hypertension (HT) (374), hypercholesterolaemia (HCOL) (126), and diabetes (DM) (33).MeasurementsPatients identified were interviewed for taking blood pressure in the case of those with HT, and blood samples in the case of those with HCOL and DM. The diagnostic criteria recommended by the latest consensus were used.Results1886 people (78.1%) took part. Prevalences found: total HT 42±2.2%, diagnosed: 11.7±1.4; total HCOL 26.6±2%; total DM 9.5±1.3%.Tobacco dependency was 33.6±2.1% and Obesity: 31.6±2.1%. Degree of control: HT, 8.6%; HCOL, 21.7%; DM, 56.1%. Association of CVR factors with each other: 25.5% had neither HT nor HCOL and did not smoke.ConclusionsHigh prevalence of CVRF in our area, compared with published national findings.Tobacco dependency is less common than at national level. The degree of control is very low and the association of the main CVRF factors for ischaemic cardiopathy reflect that nearly 75% of the population requires a preventive intervention

NiO nanowire-containing heat transfer nanofluids for CSP plants: Experiments and simulations to promote their application

Concentrating solar power (CSP) is considered a clean, renewable and sustainable energy with a significant potential to become an alternative to polluting fossil fuel-based technologies. Among CSP collectors, parabolic-trough collectors (PTC) are the most mature technology, representing nearly 90% of the currently installed collectors in CSP plants worldwide. In this technology, a heat transfer fluid (HTF) carries the thermal energy absorbed to a power block to produce electricity. Improving the thermal properties of the conventional HTF could lead to an improvement of the efficiency of CSP plants. In this sense, the use of nanofluids as the HTF in these plants can be a promising choice. Here, polycrystalline NiO nanowirecontaining nanofluids have been prepared using the conventional HTF used in CSP plants as the base fluid; that is, the eutectic and azeotropic mixture of biphenyl (26.5%) and diphenyl oxide (73.5%). The stability, rheological and thermal properties have been characterized, and an analysis of the performance of the nanofluids prepared in standard and volumetric absorbers have been carried out. The overall CSP system performance can be increased up to 34.8% using the nanofluid in a surface collector or up to 34.3% using the nanofluid in a volumetric collector, which are better than the predicted 28.5% using the conventional HTF in a standard surface collector, thanks to the improvements in thermal properties, both specific heat and thermal conductivity. Finally, from molecular dynamics simulations we determined that the mean free path of thermal vibrations is longer for monocrystalline NiO nanowires. Thus, the development of strategies for obtaining this kind of nanostructures is of great interest because they can further improve the efficiency of these nanofluids

Recensiones [Revista de Historia Económica Año VII Otoño 1989 n. 3 pp. 727-757]

Antoni Segura i Mas (coord.). El Catastro en España, vol. I (1714-1906) (Por Francisco Comín).-- Antonia Heredia Herrera. Sevilla y los hombres del Comercio (1700-1800) (Por Andrés J. Moreno Mengíbar).-- Pedro Tedde de Lorca. El Banco de San Carlos (1782-1829 (Por Javier Cuenca Esteban).-- José Ramón García López. El Banco de Oviedo, 1864-1874 (Por José Luis García Ruiz).-- Enrique Prieto. Agricultura y atraso en la España contemporánea. Estudio sobre el desarrollo del Capitalismo (Por Carlos Barciela López).-- Mª Asunción Sivera Tejerina. Los cambios técnicos de la agricultura en el término rural de Málaga: siglos XVIII-XX (Por Juan Francisco Zambrana Pineda).-- Pablo Martín Aceña. La política monetaria en España, 1919-1935 (Por M. Cruz Manzano Frias).-- Carles Sudria i Triay. Una societat plenament industrial, vol. 4 de Historia Económica de la Catalunya Contemporánia (Por Gabriel Tortella).-- CH. S. Maier. La refundación de la Europa burguesa. Estabilización en Francia, Alemania e Italia en la década posterior a la Primera Guerra Mundial y In Search of Stability Explorations in Historical Political Economy (Por Mercedes Cabrera).-- Michael Sandersona. Eductttional Opportunity and Social Change in England (Por Clara Eugenia Núñez)Publicad

Extensive Mucocutaneous Histiocytic Sarcoma raised from an Acute B Lymphocytic Leukemia: A Case Report at Hospital Mexico, Costa Rica

Histiocytic sarcomas are rare neoplasms with poor prognosis originating from histiocytic or dendritic cell clones and associated with haematological malignancies such as acute or chronic leukemias and lymphomas. We describe a case of a patient who developed a disseminated and extensive mucocutaneous histiocytic sarcoma during remission.UCR::Vicerrectoría de Docencia::Salud::Facultad de Medicina::Escuela de Medicin

Efecto del cloruro de cadmio sobre la expresión del represor transcripcional REST/NRSF y su gen blanco CDH1 en tejido pulmonar de ratones ICR-CD1

REST (RE1-Silencing Transcription factor) is a transcription factor with zinc fingers that represses its transcriptional targets through its interaction with the RE1 (Restrictive Element 1) sequence. Although some metals such as cadmium can alter protein function by competing with zinc, studies at the molecular level have not been performed to determine this effect on REST. The CDH1 gene is a transcriptional target of REST that codes for the cell adhesion glycoprotein E-cadherin and the deregulation of its expression has been associated with the cancerous process. The objective of this work was to evaluate the effect of exposure to 1.3 µM/3 days with CdCl2 in ICR-CD1 mice on the levels of REST and its target gene CDH1 in lung tissue. CDH1 mRNA levels were determined by RT-PCR, while E-cadherin and REST protein levels were assessed by Western blot. After CdCl2 treatment, the levels of CDH1 and its product E-cadherin increased in relation to the loss of REST expression. In conclusion, cadmium promotes a decrease in REST at the protein level, as well as an increase in the levels of CDH1 messenger RNA and its E-cadherin product. The increase in E-cadherin is probably due to CDH1 transcriptional relaxation mediated by loss of REST expression.REST (RE1-Silencing Transcription factor) es un factor de transcripción con dedos de zinc que reprime a sus blancos transcripcionales a través de su interacción con la secuencia RE1 (Restrictive Element 1). Aunque algunos metales como el cadmio pueden alterar la función de proteínas al competir con el zinc, no se han realizado estudios a nivel molecular para para determinar dicho efecto sobre REST. El gen CDH1 es un blanco transcripcional de REST que codifica para la glicoproteína de adhesión celular E-cadherina y la desregulación de su expresión ha sido asociada al proceso canceroso. El objetivo de este trabajo fue evaluar el efecto de la exposición a 1.3 µM/3 días con CdCl2 en ratones ICR-CD1 sobre los niveles de REST y de su gen blanco CDH1 en tejido pulmonar. Los niveles del mRNA de CDH1 se determinaron por RT-PCR, mientras que los niveles de las proteínas E-cadherina y REST se evaluaron mediante Western blot. Después del tratamiento con CdCl2 los niveles de CDH1 y de su producto E-cadherina se incrementaron en relación con la pérdida de la expresión de REST. En conclusión, el cadmio promueve la disminución de REST a nivel de proteína, así como el incremento de los niveles de ARN mensajero de CDH1 y de su producto E-cadherina. El incremento de E-cadherina probablemente se debe a la relajación transcripcional de CDH1 mediado por la pérdida de la expresión de REST

Gardens as Science Learning Contexts Across Educational Stages: Learning Assessment Based on Students' Graphic Representations

The educational use of daily-life contexts is considered a valuable strategy to promote meaningful science learning, since it facilitates the establishment of connections between previous knowledge, personal interests, and new learning. The aim of this work is to provide evidence to support the presence of gardens at educational centers, by assessing key science topics whose learning is promoted at the pre-school, primary, secondary, and university stages. To this end, we analyzed the paired graphic representations of "a garden" that students drew both before and after their participation in a garden-based learning program. Firstly, we obtained the frequency of appearance of every represented element, and afterward characterized the level of change between paired graphic representations. Sample size was of 24-19-25-29 pairs per stage, respectively. Across all stages, an overall improvement in students' graphic expression was observed, which can be attributed to their experience in the space. At the pre-school stage, the garden favored the establishment of some simple cause-effect relationships which were consolidated at the primary stage, and provided a climate of motivation and affectivity that was evident in the final drawings, given the enormous quantity of details represented, the level of the finished product, and the careful combination and variety of colors. The presence of elements related to water notably increased in final graphic representations from pre-school, primary, and secondary education, thus evidencing that the use of gardens facilitates an approach to responsible water management. At the university stage, students initially demonstrated good knowledge of conventional agriculture, while the gardening experience -which was based on permaculture practices- helped evolve their ideas toward an alternative model of cultivation. The most prevalent science learning across all stages was related to plant knowledge, particularly to their anatomical traits and diversity. Finally, the role of educational gardens as models for students was evidenced, which suggests the importance of teachers and institutions carefully considering which model to offer. Overall, our results support the legitimacy of incorporating gardens to educational centers, particularly for promoting contact with live plants and plant knowledge, and potentially for promoting contact with garden fauna and activities oriented toward learning about it

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks