4,162 research outputs found

    Optimum training programme during pregnancy to prevent gestational hypertension and preeclampsia: a systematic review

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    Gestational hypertension and pre-eclampsia are hypertensive disorders which are the world’s leading cause of maternal and perinatal mortality. Currently, evidences support the benefit of moderate physical exercise (PE) during uncomplicated pregnancies in the prevention of HTG and pre-eclampsia. However, there is no evidence on which kind of training is more effective for its prevention. The aim of this study was to analyze which kind of exercise, duration of the intervention and session, frequency and intensity produce the greatest benefits in the prevention of gestational hypertension and pre-eclampsia in women with uncomplicated pregnancies. An exhaustive search of PubMed and Web of Science was carried out until October 21, 2020. From 705 studies found, we analyzed 14 original full-text intervention articles in English or Spanish, with a PE program in pregnant women without complications, evaluating BP and including in their methodology, at least, frequency, duration, intensity, or kind of exercise. Exercise training in healthy women with uncomplicated pregnancies reduces the incidence of HTG and preeclampsia. The program with most benefits is concurrent training combined with flexibility, with a minimum duration of 29 weeks, from the 8th-9th gestational week to 36, but can be extended until the end of pregnancy. It’s recommended to get to a training frequency equal to or greater than 3 days a week, with sessions at 50-70% of the maximum heart rate and 10-14 on the Borg Scale, and a duration of 45 and 60 minutes per session

    High Vapor Transport Deposition: A Novel Process to Develop Cu2ZnSn(SxSe1–x)4 Thin Film Solar Cells

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    Kesterite thin film solar cells are known to be a promising cost-effective solution because they are based on earth-abundant and environmental compounds. However, it is known that their best efficiency (12.6%) has not been improved since 2013, meanwhile other thin-film solar cells have demonstrated that their performance has been enhanced continuously. The main drawbacks to explain this situation is the narrow process window of this compound and simultaneously, the high composition and thermal control needed to avoid intrinsic defects in the p-type layer. The high vapor transport deposition process has not been explored yet by kesterite thin film solar cell developers. Herein, we present the results obtained using a design of a new vacuum deposition method similar to close space sublimation, which reported excellent results in CdTe. The main advantages of this novel process are: 1) to achieve a high deposition rate; 2) to be able to deposit precursor materials and to carry out the sulfur-selenization in the same process chamber, avoiding the two steps used in the sequential process; 3) to provide a high accuracy in the chemical composition control; and 4) simple design using commercial components to facilitate its scalability for large production

    Angular Dependence of Photonic Crystal Coupled to Photovoltaic Solar Cell

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    Photonic crystals have the advantage of minimizing thermal losses from solar cells, reflecting the solar radiation that is not absorbed by the photovoltaic device. To optimize this optical response, photonic crystals are designed considering the relative position of the Bragg peak and the bandgap of the solar cell, under normal incident irradiation conditions. The aim of this research article was to determine experimentally the optical limits of a solar cell coupled to a photonic crystal acting as beam splitter. For that purpose, the photovoltaic system was characterized under indoor and outdoor conditions; angular dependence of the irradiation source was determined in each case, and both results were compared with good agreement. Moreover, other parameters such as irradiation spectrum and polarization of the light were investigated. The main conclusion is that photovoltaic performance is highly affected by the Bragg peak shifting and the profile is distorted, due to the angular dependence with the sun. These experimental limits must be considered at the early design stage to avoid performance losses

    Mitigating energy poverty: Potential contributions of combining PV and building thermal mass storage in low-income households

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    The issue of energy poverty has devastating implications for the society, and it has been aggravated in the past years due to the economic crisis and the increase of energy prices. Among the most affected are those with low incomes and living in inefficient buildings. Unfortunately, the bitter reality is that sometimes this part of the population are facing the next question: Heating, or eating? The declining prices of distributed energy technologies such as photovoltaics provides an opportunity for positive social change. Although their use does not address energy poverty directly, substantial contributions may be made. Measurements of indoor temperatures in a social housing district of southern Spain in 2017 have revealed the unbearable temperatures that the occupants have to endure, both in summer and winter. Using this district as a case study, the present work aims to evaluate the benefits of exploiting its rooftop PV potential to cover part of the electricity consumption of the district (reducing the energy bills), and use the surplus electricity to supply power for the heat pumps in the district. Optimal alternatives regarding maximum PV production, maximum self-sufficiency ratio and minimum investment costs have been found, considering as well different options when sharing the available electricity surplus to improve the thermal comfort of the occupants. As far as the authors know, no previous study has followed an approach aimed at energy poverty alleviation such as the one presented in this work. The results show that using the surplus electricity to heat or cool the whole dwellings would improve the thermal comfort of the occupants in average up to 11% in winter and 26% in summer. If all the PV generation was used or more buildings in the area were employed to install PV modules, improvements up to 33% in winter and 67% in summer could be obtained, reducing at the same time the thermal comfort differences among the dwellings of the district

    Fitness, body composition, and metabolic risk scores in children and adolescents: the UP&DOWN study

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    We aimed to analyse the longitudinal association between physical fitness (PF) and body composition (BC) with a metabolic risk score (Met4) in children and adolescents and to elucidate whether the association between PF and Met4 differs when using relativized or absolute fitness variables. A total of 188 children (86 females) and 195 adolescents (97 females) were included. Cardiorespiratory fitness (CRF) was determined by the 20-m shuttle run test, and muscular fitness (MF) was determined by hand grip and standing long jump tests. Height and weight were measured, and the body mass index (Kg/ m2) was calculated. Triceps and subscapular skinfolds were assessed to compute body fat percentage. Met4 was computed from systolic blood pressure, triglycerides, high-density lipoprotein cholesterol, and glucose levels. Relative CRF was longitudinally and negatively associated with Met4 in female children (β = −0.031, p = 0.025), while absolute CRF was positively associated with Met4 in male children and adolescents (β = 0.000, p < 0.05). Relative upper and lower-body MF were longitudinally and negatively associated with Met4 in female adolescents (β = −1.347, β = −0.005, p < 0.05), while absolute lower-body MF was positively associated with Met4 in male children (β = 0.000, p = 0.019). BC was longitudinally and positively associated with Met4 in male children (β-ranging from 0.011 to 0.055, all p < 0.05) and male adolescents (β-ranging from 0.011 to 0.046, all p < 0.05). Conclusion: BC is more strongly associated with Met4 than PF in children and adolescents. An optimal body weight status should be considered the main objective of health-promoting programs at childhood and adolescence. Furthermore, the way of expressing the fitness variables determines the direction of the association with Met4.CRUE-CSICNational Plan for Research, Development, and Innovation (R + D + i) from the Spanish Ministry of Science and Innovation DEP 201021662-C04-00 DEP 2010-21662-C04-01 DEP 2010-21662-C04-02 DEP 2010-21662-C04-03 DEP 2010-21662-C04-0

    Coherent structures and bubble-particle velocity in 2-D fluidized beds

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    This work presents an experimental study to characterize ascending bubbles and granular velocity in the dense phase of a 2-D fluidized bed. Three different non-intrusive techniques based on images obtained with a high speed camera are developed, and applied to the images. First the bubble paths are characterized with time-average concentration maps and the bubble velocities are obtained, using a tracking algorithm over the mass centers of the bubbles. Finally, a PIV (particle image velocimetry) method is used to characterize the particle velocity vectors. This procedure is repeated for different bed aspect ratios, and different superficial gas velocities. This study analyzes the superficial gas velocity influence on the bed behavior, and how the bubble path configuration depends on the bed aspect ratio. The PIV measurements give us information on the location of the recirculation regions and the influence of the superficial gas velocity.Publicad

    Influence of Degradation Processes in Lead–Acid Batteries on the Technoeconomic Analysis of Photovoltaic Systems

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    Most technoeconomic feasibility studies of photovoltaic (PV) systems with batteries are mainly focused on the load demand, PV system profiles, total system costs, electricity price, and the remuneration rate. Nevertheless, most do not emphasise the influence degradation process such as corrosion, sulphation, stratification, active material seeding, and gassing on battery lifetime, efficiency, and capacity. In this paper, it is analysed the influence of the degradation processes in lead–acid batteries on the technoeconomic analysis of PV systems with and without battery. Results show that Net Present Value (NPV), Payback Period (PBP), and Discounted PayBack Period (DPBP) have a heavy dependence on the assumptions about the value of the battery performance parameters according to its degradation processes. Results show NPV differences in the range from −307% to 740%, PBP differences in the range from 9% to 188%, and DPBP differences in the range from 0% to 211%

    Estudio comparativo de empatía médica, sensibilidad emocional y características psicodemográficas entre estudiantes de Medicina y médicos especialistas docentes en Venezuela

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    Tesis doctoral inédita realizada en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Psiquiatría. Fecha de lectura: 29 de Junio de 2010

    On split Leibniz algebras

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    Con intención de acometer la estructura de álgebras de Leibniz arbitrarias (sin restricciones ni en su dimensión ni en su cuerpo base), definimos las álgebras de Leibniz split como la generalización natural de las álgebras de Lie split. Desarrollando técnicas de conexiones de raíces para estas álgebras, mostramso que son suma de una subespacio de una subálgebra abeliana e ideales bien definidos, tales que estos ideales tienen producto nulo cuando se multiplican dos distintos. En caso de que una álgebra de Leibniz split sea de longitud máxima caracterizamos su simplicidad en términos de conexiones de raíces
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