Reliable compartmental models for double-pipe heat exchangers: An analytical study

AbstractIn this work, the analytical properties of the heat exchanger infinite-dimensional dynamic model are discussed. More importantly, those of a 2nd-order lumped-parameter model using the logarithmic mean temperature difference (LMTD) as driving force are derived and shown to agree with those of the former. Three essential aspects are focused: existence and uniqueness of solutions, equilibrium states, and stability properties. The results developed in this work are intended to supply a solid support for the reliability on the use of the kind of simple compartmental model that is treated. This is specially addressed to works where it is not the quantitative solutions but the qualitative behavior that is important, like modelling and simulation of heat exchanger networks and complex industrial processes where heat exchangers are involved

Eficacia de una técnica cognitivo-conductual en pacientes quirúrgicos

El objetivo del estudio consistió en diseñar y comprobar la eficacia de una técnica psicológica en pacientes quirúrgicos, para reducir los niveles de ansiedad y depresión, y facilitar la recuperación. La muestra estuvo compuesta por 30 mujeres que debían someterse a una histerectomía abdominal. Estas mujeres fueron repartidas al azar en dos grupos: experimental y control. La técnica se compuso de diferentes elementos: 1) información; 2) expresión de emociones; 3) respiración, relajación, visualización; 4) ejercicios para facilitar la recuperación; 5) entrega de hojas informativas. Los resultados fueron: el grupo experimental respecto al grupo control, padeció menos ansiedad y depresión postquirúrgicas, sufrió menos dolor y complicaciones después de la operación, necesitó menos analgésicos, recuperó antes sus funciones orgánicas, y se acortó su estancia hospitalaria. Por tanto podemos concluir que la técnica psicológica diseñada se mostró eficaz como facilitadora de la recuperación en pacientes quirúrgicos.The aim of this study was to design and test the efficiency of a psychological technique to reduce levels of anxiety and depression in surgery patients and to facilitate their recovery. The test group was composed of 30 women who were to have a hysterectomy. These women were divided into two groups: an experimental group and a control group . The technique involved various elements: 1) information, 2) the expression of emotions, 3) breathing, relaxation, visualitation, 4) excercises to facilitate recovery, 5) distribution of summary sheets. The results were as follows: compared to the control group, the experimental group suffered less anxiety, less post-surgical depression, less pain and fewer post-operative complications. The women needed fewer painkillers, regained their normal bodily functions and needed a shorter stay in hospital. We can thus conclude that the psychological technique designed, proved efficient in facilitating the recovery of surgical patients

Influence of emotional intelligence on sport performance in elite canoeist

Several studies support the hypothesis that emotions are linked with sport performance. However, only a few studies have addressed the direct relationship between emotional intelligence (EI) and sport performance. In order to address this question, emotional intelligence was assessed in 50 elite male canoeists from a total of fourteen countries. The sample was divided into two groups based on the number of medals achieved at world championships [Expert level Group 1, had won 1 - 3 medals (n = 33), and Expert level Group 2 had won more than 3 medals (n = 17)]. As a secondary goal, the influence of years of practice on sport performance was examined. Results indicate that the Level 2 expert athletes scored higher in empathy (p < .05), emotional recognition (p < .05), emotional control and regulation (p < .001) and years of practice invested in their preparation (p<.001) than the Level 1 expert athletes. These findings make a valuable contribution to answering some key questions regarding high performance sport and the role of EI in elite sport performance

Body image and dietary habits in adolescents: a systematic review

Context: Adolescence is a critical developmental stage in which increasing concerns about body image (BI) coincide with the consolidation of dietary habits (DHs). Multiple studies have sought robust associations between BI and DHs to prevent unhealthy behaviors. Objective: The aim of this systematic review was to examine the available literature on the association between BI perception (BIP) and/or satisfaction (BIS) and DHs in adolescents. Data Sources: A search was carried out of 5 electronic databases (PubMed, SciELO, Cochrane, Embase, and PsycInfo) using a combination of keywords (and synonyms) related to adolescence, BI, and diet. Data Extraction: Data screening, extraction, and quality assessment were performed independently by 2 investigators using the PRISMA and AXIS guidelines. Data Analysis: Of 2496 articles screened, 30 articles, published in English or Spanish, that evaluated the relationship between BI and DHs in adolescents aged between 10 years and 18 years, were included. A relationship between accurate BI perception in adolescents and healthy DHs was reported in 5 articles (16.2%). A relationship between overestimation of body weight in adolescents and healthy DHs was reported in 4 articles (13.3%). A relationship between underestimation of body weight and unhealthy DHs was reported in 8 articles (26.7%). In addition, 4 articles (13.3%) reported a relationship between BIS and healthy DHs. The desire to gain weight was associated with unhealthy DHs in 3 (10%) of the articles, while the desire to lose weight was related to healthy DHs in 3 (10%) of the articles and to unhealthy DHs in 3 (10%) other articles. There were also gender differences in the relationship between BIP or BIS and DHs. Conclusion: Adolescents who underestimate their body weight tend to report less healthy DHs than body weight overestimators. Adolescents unsatisfied with their BI and with a drive for thinness frequently engage in DHs linked to losing weight. Systematic Review Registration: PROSPERO registration no. CRD42020184625

Inhibitory effects of pharmacological doses of melatonin on aromatase activity and expression in rat glioma cells

Melatonin exerts oncostatic effects on different kinds of neoplasias, especially on oestrogen-dependent tumours. Recently, it has been described that melatonin, on the basis of its antioxidant properties, inhibits the growth of glioma cells. Glioma cells express oestrogen receptors and have the ability to synthesise oestrogens from androgens. In the present study, we demonstrate that pharmacological concentrations of melatonin decreases the growth of C6 glioma cells and reduces the local biosynthesis of oestrogens, through the inhibition of aromatase, the enzyme that catalyses the conversion of androgens into oestrogens. These results are supported by three types of evidence. Firstly, melatonin counteracts the growth stimulatory effects of testosterone on glioma cells, which is dependent on the local synthesis of oestrogens from testosterone. Secondly, we found that melatonin reduces the aromatase activity of C6 cells, measured by the tritiated water release assay. Finally, by (RT)–PCR, we found that melatonin downregulates aromatase mRNA steady-state levels in these glioma cells. We conclude that melatonin inhibits the local production of oestrogens decreasing aromatase activity and expression. By analogy to the implications of aromatase in other forms of oestrogen-sensitive tumours, it is conceivable that the modulation of the aromatase by pharmacological melatonin may play a role in the growth of glioblastomas

A New Missing Data Imputation Algorithm Applied to Electrical Data Loggers

Nowadays, data collection is a key process in the study of electrical power networks when searching for harmonics and a lack of balance among phases. In this context, the lack of data of any of the main electrical variables (phase-to-neutral voltage, phase-to-phase voltage, and current in each phase and power factor) adversely affects any time series study performed. When this occurs, a data imputation process must be accomplished in order to substitute the data that is missing for estimated values. This paper presents a novel missing data imputation method based on multivariate adaptive regression splines (MARS) and compares it with the well-known technique called multivariate imputation by chained equations (MICE). The results obtained demonstrate how the proposed method outperforms the MICE algorithm.Ministerio de Economía y Competitividad; AYA2014-57648-PAsturias (Comunidad Autónoma). Consejería de Economía y Empleo; FC-15-GRUPIN14-01

CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series

Aims. The main goal of this work is to measure rotation periods of the M-type dwarf stars being observed by the CARMENES exoplanet survey to help distinguish radial-velocity signals produced by magnetic activity from those produced by exoplanets. Rotation periods are also fundamental for a detailed study of the relation between activity and rotation in late-type stars. Methods. We look for significant periodic signals in 622 photometric time series of 337 bright, nearby M dwarfs obtained by long-time baseline, automated surveys (MEarth, ASAS, SuperWASP, NSVS, Catalina, ASAS-SN, K2, and HATNet) and for 20 stars which we obtained with four 0.2-0.8 m telescopes at high geographical latitudes. Results. We present 142 rotation periods (73 new) from 0.12 d to 133 d and ten long-term activity cycles (six new) from 3.0 a to 11.5 a. We compare our determinations with those in the existing literature; we investigate the distribution of P rot in the CARMENES input catalogue,the amplitude of photometric variability, and their relation to vsin i and pEW(Halfa); and we identify three very active stars with new rotation periods between 0.34 d and 23.6 d.Comment: 34 pages, 43 figures, 2 appendix table