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

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

¿Adelantan el diagnóstico de la diabetes tipo 2 los nuevos criterios de la Asociación Americana de Diabetes?

ObjetivoAnalizar el intervalo temporal entre la primera hiperglucemia basal ocasional (HBO) y el diagnóstico de diabetes mellitus tipo 2 (DM2) al aplicar los criterios de la OMS y de la Asociación Americana de Diabetes (ADA).DiseñoEstudio observacional, retrospectivo. Ámbito del estudio. Centro de atención primaria urbano.SujetosUn total de 104 pacientes con DM2, diagnosticados entre 1991 y 1995, con antecedentes de HBO.Mediciones o intervencionesEdad, género y otros factores de riesgo, fechas de la primera HBO (glucemia basal 3 110 mg/dl), del diagnóstico según criterios OMS (2 glucemias basales 3 140 mg/dl o 3 200 mg/dl a las 2 horas de la sobrecarga oral de glucosa [SOG]) y aplicando criterios ADA (2 glucemias basales 3 126 mg/dl) y los intervalos en meses entre ellas.ResultadosDe los 222 pacientes diagnosticados, 104 (47%) presentaban antecedentes de HBO. La edad en el momento del diagnóstico fue 60,8 años (DE, 10,1), siendo un 53% mujeres. En 51 casos (49%) se realizó SOG. La mediana (rango) del intervalo entre la primera HBO y el diagnóstico fue de 16 meses (0–101) en los que se realizó la SOG y de 45 (1–104) en los que no se practicó (p = 0,003). En estos últimos, los criterios ADA lo redujeron a 31 meses (0–97) (p < 0,001) y en 27 de ellos que no cumplían ambos criterios a la vez el intervalo fue de sólo 10 meses (0–93) (p < 0,001). Conclusiones. La no realización de la SOG comporta un retraso en el diagnóstico que puede ser contrarrestado con la aplicación de los criterios de la ADA.ObjectiveTo analyze the period of time between the first occasional fasting hyperglycaemia (OFH) and the diagnosis of type 2 diabetes mellitus (DM2), using the World Health Organization (WHO) criteria or the American Diabetes Association (ADA) criteria.DesignRetrospective, observational study.SettingUrban primary care centre.Subjects104 patients with DM2 diagnosed between 1991 and 1995 who had a previous OFH.MeasurementsAge, gender and other risk factors, dates of the first OFH (fasting plasma glucose 3 110 mg/dl), the diagnosis according to WHO criteria (2 fasting plasma glucose 3 140 mg/dl or 3 200 mg/dl two hours after the oral glucose test tolerance (OGTT)) or with the ADA criteria (2 fasting plasma glucose 3 126 mg/dl), and the intervals in months between them.ResultsOf the 222 diagnosed patients, 104 (47%) had previous OFH. Age at diagnosis was 60.8 (SD 10.1) and 53% were women. OGTT was performed in 51 cases (49%). The median (range) of the interval between the first OFH and diagnosis was 16 months (0–101) for those who were undertaken an OGTT, and 45 months (1–104) for those who were not (p = 0.003). In these last ones, ADA criteria reduced the interval to 31 months (0–97) (p < 0.001). In 27 of these patients who did not satisfy both criteria at the same time, ADA criteria reduced the interval to 10 months (0–93) (p < 0.001).ConclusionsNot performing the OGTT means a delay in diagnosis which can be countered by applying the ADA criteria

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

The development, implementation and early learnings of a training program to advance interest in behavioral research careers among undergraduate BIPOC students majoring in psychology.

OBJECTIVES: Black, indigenous and people of color (BIPOC) remain underrepresented in research occupations. This report discusses a collaboration to train undergraduate BIPOC students in clinical research between a public health institute, two medical schools, and a historically Black College or University (HBCU). This nine-month program trained BIPOC undergraduates in research methodology, psychology, and addiction science, and immersed trainees in real-world research. The program included didactic seminars, experiential activities, and a mentored research project culminating in a poster and oral presentation. METHODS: Key learnings, program satisfaction survey results, and preliminary outcomes from the first three program cohorts (N = 6 students) are presented. This program addressed several barriers hypothesized to contribute to the limited number of BIPOC students pursuing research careers, including mentorship from BIPOC faculty and financial concerns. RESULTS: Students reported moderate to high satisfaction with the program and endorsed gaining new research skills. Limitations and future directions are discussed. CONCLUSION: The expansion of the BIPOC health and research workforce is an urgent priority given the importance of BIPOC professionals to the health of our nation. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04650386