Numerical and experimental evaluation of dielectric properties of thermally aged insulating paper used in power transformers

Due to the relevant role of the cellulosic insulation in the dielectric system of a power transformer, it is necessary to know its dielectric properties and its evolution as insulating material. The dependence of the dielectric properties of solid insulation on the moisture content, temperature, or pressure is well-defined. However, it is not clear the effect of the paper degradation on its insulating capacity. To study the impact of ageing on the dielectric properties, samples of Kraft paper were subjected to an accelerated hygrothermal ageing. Degree of polymerization (DP) value was reduced from 1000 to 200, with intermediate study points. All samples were conditioned to the same moisture content in order to only evaluate the effect of the paper degradation. Different dielectric properties, such as loss factor (tanδ) and complex permittivity (ε) were measured using the dielectric spectroscopy technique. These experimental results were used to develop a numerical model with the finite element-based tool Comsol Multiphysics. This model provided some extra information about the material properties, such as the electric field distribution. Results showed that the degradation of Kraft paper modifies its dielectric response.We acknowledge the support of the Spanish Ministry of Science and Innovation by means of the National Research Project Asset management of biodegradable-fluid-based transformers (PID2019-107126RB-C22/AEI/ 10.13039/501100011033). The authors also wish to thank “Fundación Iberdrola” for its financial support for the research project: S090 “Análisis de las Propiedades Dieléctricas de Aislamientos Sólidos Impregnados con Líquidos Dieléctricos”. C. Méndez also wants to acknowledge the Spanish Ministry of Science, Innovation and Universities for the financial support for the FPU grant (FPU19/01849)

Titania nanofluids based on natural ester: cooling and insulation properties assessment

The assessment of a TiO2 vegetal-based dielectric nanofluid has been carried out, and its characteristics and behavior have been tested and compared with a previously tested maghemite nanofluid. The results obtained reflect a similar affectation of the main properties, with a maximal improvement of the breakdown voltage of 33% at 0.5 kg/m3, keeping the thermal conductivity and the viscosity almost constant, especially the first one. This thermal characterization agrees with the results obtained when applying the TiO2 optimal nanofluid in the cooling of an experimental setup, with a slightly worse performance than the base fluid. Nevertheless, this performance is the opposite to that noticed with the ferrofluid, which was capable of improving the cooling of the transformer and decreasing its temperature. The similarities between the characterizations of both nanofluids, the differences in their cooling performances and their different magnetic natures seem to point out the presence of additional thermomagnetic buoyancy forces to support the improvement of the cooling.This research is under BIOTRAFO project—“Raising Knowledge and Developing Technology for the Design and Deployment of High Performance Power Transformers Immersed in Biodegradable Fluids,” which has received funding from the European Union Commission’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement H2020-MSCARISE-2018- 823969; 2019-21. The authors of this research wish to thank the Spanish Ministry of Economy for its financial support for the National Research Project: “Improvement of Insulation Systems of Transformers through Dielectric Nanofluids: Thermodynamic Characterizations and Modelling” (DPI2015-71219-C2 1-R). Additionally, they want to thank the Regional Government of Cantabria; more precisely, the Department of Universities, Research, Environment and Social Policy, for its financial support for the Project “Fluidos Biodegradables en Transformadores Eléctricos de Potencia: Impregnación de Dieléctricos Sólidos y Modelado Térmico con THNM.” Mr. Olmo would like to acknowledge to the University of Cantabria and the Government of Cantabria for the financial support for the Ph. D. scholarship (CVE-2016-6626)

Maghemite nanofluid based on natural ester: cooling and insulation properties assessment

The objective of this work is to study the effect that the addition of magnetic nanoparticles to a natural ester has on its properties and its cooling capacity. Some samples of ferrofluid (natural ester with maghemite) have been prepared using different concentrations. These have been characterized by measuring their thermo-hydraulic and dielectric properties, to find an optimal concentration. Then, the cooling capacities of the optimal nanofluid and the base fluid have been tested in a transformer immersed in these liquids. The experimental platform allowed the measurement of temperatures in different locations at different load levels. Parallel simulations of these tests have been carried out with a Computational Fluid Dynamics model of the experimental platform. The results show an improvement of the insulating capacity of the base fluid with the addition of maghemite nanoparticles, and an enhanced cooling capacity.This work was supported in part by the European Union’s Horizon 2020 Research and Innovation Programme through the Marie Sklodowska-Curie under Grant 823969, and in part by the Ministry of Economy through the National Research Project: Improvement of Insulation Systems of Transformers through Dielectric Nanofluids under Grant DPI2015-71219-C2 1-R. The work of C. Olmo was supported by the University of Cantabria and the Government of Cantabria through Ph.D. Scholarship under Grant CVE-2016-6626

Cooling performance of different dielectric fluids containing nanoparticles in a transformer winding

This work presents a study where the thermal performance of different nanofluids is tested in a transformer winding model. A 2D axisymmetric non-isothermal CFD model has been used to compare temperature and velocity distribution of the proposed fluids. The fluids tested consists of eight different mixtures manufactured from two different nanoparticles and two different concentrations, using a mineral oil and a natural ester as base liquids. The comparison has been carried out between each nanofluid and their base fluid to observe the thermal impact of nanoparticles. The temperature dependent properties have been determined to include them in the simulation model. Two different inlet velocities were selected as inlet conditions, representing Oil Natural and Oil Directed Cooling. The analysis has been carried out using ANSYS Fluent ® in a two pass winding model. The average and maximum disc temperatures and mass flow distributions are obtained for all the cases. The results obtained show that the temperature in the seven discs of the considered winding increases when the nanoparticles are added to the natural ester, between 3 and 7%. On the other hand, in the case of mineral oil, the addition of nanoparticles reduces the temperature in the discs between 0.3 and 3%.The authors of this research wish to thank the Ministry of Economy for financial support to the National Research Project: Improvement of Insulation Systems of Transformers through Dielectric Nanofluids (DPI2015-71219-C2 1-R)

Imatinib therapy of chronic myeloid leukemia restores the expression levels of key genes for DNA damage and cell-cycle progression

[EN] Background Chronic myeloid leukemia (CML) is a malignant clonal disorder of the hematopoietic system caused by the expression of the BCR/ABL fusion oncogene. It is well known that CML cells are genetically unstable. However, the mechanisms by which these cells acquire genetic alterations are poorly understood. Imatinib mesylate is the standard therapy for newly diagnosed CML patients. Imatinib mesylate targets the oncogenic kinase activity of BCR-ABL. Objective To study the gene expression profile of bone marrow hematopoietic cells in the same patients with CML before and 1 month after imatinib therapy. Methods Samples from patients with CML were analyzed using Affymetrix GeneChip Expression Arrays. Results A total of 594 differentially expressed genes, most of which (393 genes) were downregulated, as a result of imatinib therapy were observed. Conclusion The blockade of oncoprotein Bcr-Abl by imatinib could cause a decrease in the expression of key DNA repair genes and substantially modify the expression profile of the bone marrow cells in the first days of therapy

Investigation of the degradation of a wood pulp-cotton presspaper in different biodegradable oils

New insulating materials, as biodegradable oils and upgraded paper, need to be investigated. In this paper, the ageing of a wood pulp - cotton presspaper is studied. Solid insulation is impregnated and aged with three different fluids: a mineral oil and two vegetable oils, from sunflower and soybean. Both oils and paper were dried before the ageing process, which was carried out at 150°C for 732 hours in iron vessels. Degradation of oils is analysed through the measurement of their breakdown voltage, dielectric dissipation factor (tan δ), resistivity, moisture content and acidity. Deterioration of presspaper is quantified by its polymerization degree (DP), moisture content and dielectric dissipation factor. Results showed that the dielectric properties of oils are negatively affected by the ageing, since the breakdown voltage and resistivity were reduced, whereas the dissipation factor increased. Also, acidity increased, especially in the vegetable oils. In the case of the solid insulation, its tanδ increased with the ageing, despite the reduction of its moisture content. DP was reduced, reaching the end-of-life criteria (DP<200) in the ageing with mineral oil (134) whereas it remained at higher values for the sunflower (206) and soybean (216) oils.This research is under BIOTRAFO project, which has received funding from the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Action-Research and Innovation Staff Exchange (MSCA-RISE) grant agreement No 823969. The authors of this research wish to thank the Ministry of Economy for its financial support for the National Research Project: Gestión del Ciclo de Vida de Transformadores Aislados con Fluidos Biodegradables (PID 2019-107126RBC22). Cristina Méndez also wants to acknowledge the Spanish Ministry of Science, Innovation and Universities for the financial support for the FPU grant (FPU19/01849)

Cost-effectiveness of breast cancer control strategies in Central America: The cases of Costa Rica and Mexico

__Abstract__ This paper reports the most cost-effective policy options to support and improve breast cancer control in Costa Rica and Mexico. Total costs and effects of breast cancer interventions were estimated using the health care perspective and WHO-CHOICE methodology. Effects were measured in disability-adjusted life years (DALYs) averted. Costs were assessed in 2009 United States Dollars (US$). To the extent available, analyses were based on locally obtained data. In Costa Rica, the current strategy of treating breast cancer in stages I to IV at a 80$4,739 per DALY averted. At a coverage level of 95%, biennial clinical breast examination (CBE) screening could improve Costa Rica's population health twofold, and can still be considered very cost-effective (ICER US$5,964/DALY). For Mexico, our results indicate that at 95$5,021/DALY). If more resources are available in Mexico, biennial mammography screening for women 50-70 yrs (ICER US$12,718/DALY), adding trastuzumab (ICER US$13,994/DALY) or screening women 40-70 yrs biennially plus trastuzumab (ICER US$17,115/DALY) are less cost-effective options. We recommend both Costa Rica and Mexico to engage in MAR, CBE or mammography screening programs, depending on their budget. The results of this study should be interpreted with caution however, as the evidence on the intervention effectiveness is uncertain. Also, these programs require several organizational, budgetary and human resources, and the accessibility of breast cancer diagnostic, referral, treatment and palliative care facilities should be improved simultaneously. A gradual implementation of early detection programs should give the respective Ministries of Health the time to negotiate the required budget, train the required human resources and understand possible socioeconomic barriers

Effect of magnetic and non-magnetic nanoparticles on insulation and cooling behaviour of a natural ester for power transformers

This paper analyses and compares the impact that maghemite and titania nanoparticles have in the electrical and thermal performance of a commercial natural ester used in power transformers. Vegetal-oil-based nanofluids have been prepared at different concentrations. Once the nanofluids were obtained, the breakdown voltage of the oil samples with and without nanoparticles was measured. It was found that the concentration of nanoparticles influences the breakdown voltage of natural ester. The existence of optimal concentrations has been noticed, and these nanofluids were selected for the upcoming tests. The cooling capacity of these liquids and the base fluid was measured through a thermal analysis in an experimental platform. The experiment developed is based on a 1-phase transformer (800 VA, 230/115 V) immersed in a stainless-steel fulfilled with insulating liquid. The temperatures inside the tank were monitored at the bottom and at the top of the tub to measure the oil temperature. Other sensor measured the hotspot winding temperature, defined as the hottest temperature of winding conductors in contact with solid insulation or insulating liquid. This sensor was located at the top of the winding as the most probable hot-spot location. Ambient temperature was also measured as a reference. A microcontroller (Arduino) and an Integrated Development Environment (IDE) was utilized to record the measurements of the sensors. The results of the thermal study showed that only maghemite based nanofluids exhibited improved heat transfer characteristics in comparison with the natural ester oil.This research is under BIOTRAFO project which has received funding from the European Union Commission’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement H2020-MSCARISE-2018- 823969; 2019-21. Also it has received financial support from the Spanish National Research Project: “Improvement of Insulation Systems of Transformers through Dielectric Nanofluids: Thermodynamic Characterizations and Modelling” (DPI2015-71219-C2 1-R) and from the Regional Government of Cantabria, Project “Fluidos Biodegradables en Transformadores Eléctricos de Potencia: Impregnación de Dieléctricos Sólidos y Modelado Térmico con THNM.

Comportamiento de algunos factores de riesgo del bajo peso al nacer. Policlínico Docente Luis Enrique de la Paz Reyna, 2008-2010

Introduction: low birth weight represents a world order problem in health due to serious limitations in survival and life quality.Objective: to determine some risk factors influencing in low birth weight infants.Methods: a descriptive and prospective investigation with an analytical phase, at Luis E. de la Paz polyclinic in Yara, Granma, in the period 2008 - 2010. The universe was formed by 75 low birth weights. The information was obtained through the clinical files of the mothers and their children, and the statistical analysis were made using chi square test to determine the dependence degree between the risk factor and low birth weight and then its correlation through the coefficient correlation of Pearson.Results: it was remarkable the prevalence of the low birth weights, the antecedent of underweight mothers in the beginning of the pregnancy and the ones with scarce gain of weight. Most of the pregnant were primipara with vaginal infections. The non-smokers mothers and with antecedents of BPN did not contribute to the excellent results. The pregnant under 19 years and with secondary and preuniversity school level were those that contributed a greater number of cases.Conclusions: risk factors were related to primipara pregnant women, low weight at the beginning of the pregnancy or an inadequate weight gain and the vaginal infection. There was prevalence of low birth weight in those non-smokers, having antecedents of low birth weight, less than 19 years old and from secondary and preuniversity school.Introducción: el bajo peso al nacer representa un problema de orden mundial en la  salud dado por serias limitaciones en su sobrevida y en su calidad de vida. Objetivo: determinar algunos de los factores de riesgo que influyeron en el bajo peso al nacer. Método: investigación de tipo prospectivo descriptivo con una fase analítica, policlínico Luis E. de la Paz de Yara, Granma, 2008 - 2010. El universo estuvo conformado por 75 niños con bajo peso al nacer. La información se obtuvo a través de los expedientes clínicos de madres e hijos y se procesó mediante el chi cuadrado,  para determinar el grado de dependencia entre los factores de riesgo y el bajo peso al nacer y luego su correlación a través del coeficiente de correlación de Pearson.Resultados: predominaron los recién nacidos pretérmino, el antecedente de madres con bajo peso al inicio del embarazo y con escasa ganancia de peso. La mayoría de las gestantes fueron primíparas, con infección vaginal. Las no fumadoras y con antecedentes de bajo peso al nacer no aportaron resultados relevantes. Las menores de 19 años, con nivel escolar secundario y preuniversitario aportaron mayor número de casos.Conclusiones: los factores de riesgo estuvieron relacionados con mujeres primíparas, bajo peso al inicio del embarazo o con inadecuada ganancia de peso durante el mismo y la infección vaginal, hubo predominio de bajo peso al nacer en  las pacientes que no fumaron, que  tuvieron antecedentes de bajo peso al nacer, menores de 19 años y escolaridad secundaria y preuniversitaria

Some risk factors in acute respiratory infections in less than 5 years old children. May 2014-2015

Introducción: las enfermedades agudas del aparato respiratorio se presentan en su inmensa mayoría como infecciones, por lo cual en la actualidad se prefiere referirse a ellas como infecciones respiratorias agudas.Objetivos: determinar el comportamiento de algunos factores de riesgo de infecciones respiratorias agudas en niños menores de 5 años, de mayo 2014 a mayo 2015 en los consultorios médicos del policlínico Luis E. de la Paz, municipio de Yara, Granma, Cuba.Método: se realizó una investigación epidemiológica, de tipo descriptiva y transversal, con una fase analítica. La población fue de 696 niños, que presentaron infecciones respiratorias agudas y asistieron a consulta. La información se obtuvo a través de una planilla de recogida de datos, cuestionario a las madres de los niños y entrevista a informantes clave y se procesó mediante el estadístico Chi cuadrado, para determinar el grado de dependencia y su correlación a través del estadígrafo coeficiente de correlación de Pearson.Resultados: el grupo etáreo más afectado, que fue el de 1-2 años, del sexo femenino. Los factores de riesgo más frecuentes fueron el hacinamiento, el hábito de fumar en familiares, la lactancia materna inadecuada y el nivel socioeconómico no aceptable.Conclusiones: se evidenció la alta correlación de la edad de los pacientes estudiados con el nivel socio-económico, seguido del antecedente de bajo peso al nacer, luego el hábito de fumar y la utilización de la lactancia materna. Fue mayoritario el nivel de conocimiento de las madres sobre factores de riesgo de estas enfermedades.  Introduction: acute diseases of the respiratory system appear in their vast majority as infections, which is why they are now preferred to be referred to as acute respiratory infections.Objectives: to determine the behavior of some risk factors for acute respiratory infections in children under 5 years of age, from May 2014 to May 2015 in the medical offices of the Luis E. de la Paz polyclinic, Yara municipality, Granma, Cuba. Method: an epidemiological investigation, of descriptive and transversal type, was carried out with an analytical phase. The population was 696 children, who had acute respiratory infections and attended the consultation. The information was obtained through a data collection form, questionnaire to the mothers of the children and interviewed key informants and was processed using the Chi square statistic, to determine the degree of dependence and its correlation through the statistic coefficient of Pearson correlation.Results: the most affected age group was female children from 1-2 years. The most frequent risk factors were overcrowding, family smoking, inadequate breastfeeding, and unacceptable socioeconomic status.Conclusions: the high correlation of the age of the studied patients with the socioeconomic level was evidenced, followed by the antecedent of low birth weight, then the smoking habit and the use of breastfeeding. The mothers' level of knowledge about the risk factors of these diseases was higher