Experimental Analysis of a Flat Plate Solar Collector with Integrated Latent Heat Thermal Storage

In the present paper, an experimental analysis of a solar water heating collector with an integrated latent heat storage unit is presented. With the purpose to determine the performance of a device on a lab scale, but with commercial features, a flat plate solar collector with phase change material (PCM) containers under the absorber plate was constructed and tested. PCM used was a commercial semi-refined light paraffin with a melting point of 60°C. Tests were carried out in outdoor conditions from October 2016 to March 2017 starting at 7:00 AM until the collector does not transfer heat to the water after sunset. Performance variables as water inlet temperature, outlet temperature, mass flow and solar radiation were measured in order to determine a useful heat and the collector efficiency. Furthermore, operating temperatures of the glass cover, air gap, absorber plate, and PCM containers are presented. Other external variables as ambient temperature, humidity and wind speed were measured with a weather station located next to the collector. The developed prototype reached an average thermal efficiency of 24.11% and a maximum outlet temperature of 50°C. Results indicate that the absorber plate reached the PCM melting point in few cases, this suggests that the use of a PCM with a lower melting point could be a potential strategy to increase thermal storage. A thermal analysis and conclusions of the device performance are discussed

Pandemic effects in the Solow growth model

We show how diseases can affect economic growth in a Solow growth model, with population growth and no technical progress, but modified to include a saving rate that depends on the individual health status. We successively insert this model into the SIS (susceptible–infected–susceptible) and SIR (susceptible–infected–recovered) models of disease spreading. In these two models, the spread of the infection proceeds according to the so-called basic reproductive number. This number determines in which of the two possible equilibria, the disease-free or the pandemic equilibrium, the economy ends. We show that output per capita is always lower in the pandemic steady state, which implies a contraction in the economy's production possibilities frontier.Julio Carmona acknowledges the financial support from the Spanish Ministerio de Economía y Competitividad, through the project ECO2016-77200-P. Ángel León acknowledges the financial support from the Spanish Ministerio de Economía y Competitividad, through grant PID2021-124860NB-I00

Investment option under CIR interest rates

We analyze extensively the characteristics of the solution to an irreversible investment decision when the only source of uncertainty comes from interest rates. They are assumed to be driven by the popular Cox–Ingersoll–Ross (CIR) stochastic process. Particular attention is paid to the impact that both CIR parameters and risk aversion have on the threshold rate.Financial support from the Spanish Ministry of Education and Science through the grant SEJ 2005-09372 (Leon) and SEJ 2004-05815 (Carmona) is gratefully acknowledged

Characterization of thermophysical properties of phase change materials using unconventional experimental technologies

The growing interest in developing applications for the storage of thermal energy (TES) is highly linked to the knowledge of the properties of the materials that will be used for that purpose. Likewise, the validity of representing processes through numerical simulations will depend on the accuracy of the thermal properties of the materials. The most relevant properties in the characterization of phase change materials (PCM) are the phase change enthalpy, thermal conductivity, heat capacity and density. Differential scanning calorimetry (DSC) is the most widely used technique for determining thermophysical properties. However, several unconventional methods have been proposed in the literature, mainly due to overcome the limitations of DSC, namely, the small sample required which is unsuitable for studying inhomogeneous materials. This paper presents the characterization of two commercial paraffins commonly used in TES applications, using methods such as T-history and T-melting, which were selected due to their simplicity, high reproducibility, and low cost of implementation. In order to evaluate the reliability of the methods, values calculated with the proposed alternative methods are compared with the results obtained by DSC measurements and with the manufacturer’s technical datasheet. Results obtained show that these non-conventional techniques can be used for the accurate estimation of selected thermal properties. A detailed discussion of the advantage and disadvantage of each method is given

Pricing executive stock optons under employment shocks

We obtain explicit expressions for the subjective, objective and market value of perpetual executive stock options (ESOs) under exogenous employment shocks driven by an independent Poisson process. Previously, we obtain the executive's optimal exercise policy from the subjective valuation that is necessary for the objective one, or fair value. The perpetual ESO is compared with the true finite maturity ESO finding that the approximation is reasonably good. To illustrate the usefulness of the objective valuation for accounting purposes, we analyze the statistical distribution of the fair value when there is uncertainty about the employment shock intensity. Finally, the role of ESOs in the design of executives’ incentives is also discussed.Spanish Ministry for Science and Innovation through the Grant SEJ 2004-05815; Spanish Ministry for Science and Innovation through the Grant ECO2008-02599/ECO; Spanish Ministry for Science and Innovation through the Grant ECO2010-18567

Does stock return predictability affect ESO fair value?

Executive Stock Options (ESOs) are modified American options that cannot be valued using standard methods. With a few exceptions, the literature has discussed the ESO fair value by assuming unpredictable stock returns which are not supported by the available empirical evidence. In this paper we obtain the fair value of American ESOs when stock returns are predictable and, specifically, driven by the trending Ornstein–Uhlenbeck process of Lo and Wang (1995). We solve the executive’s portfolio allocation problem for a simple buy-and-hold strategy when his wealth can be distributed between a risk-free asset and a market portfolio. This problem is jointly solved with the executive’s optimal exercise policy. We find that executives tend to wait longer the higher the predictability, independently of the composition of executive’s asset menu. We have also analyzed the implications under the FAS123R proposals for the ESO fair value and found that, even for low autocorrelations, there is a meaningful mispricing when unpredictable returns are erroneously assumed.Angel León and Antoni Vaello-Sebastiá acknowledge the financial support from the Spanish Ministry for Science and Innovation through the Grants ECO2011-29751 and ECO2010-18567 respectively

Estilo de vida y control metabólico en pacientes con diabetes mellitus tipo 2. Validación por constructo del IMEVID

ObjetivoEvaluar la validez de constructo de un instrumento para medir el estilo de vida en los pacientes con diabetes mellitus tipo 2 (cuestionario IMEVID)DiseñoEstudio observacional transversal comparativoEmplazamientoSeis unidades de medicina familiar (atención primaria)ParticipantesUn total de 412 adultos con diabetes mellitus tipo 2Mediciones principalesSe aplicó el IMEVID por autoadministración y se midió el índice de masa corporal (IMC), índice cintura/cadera (ICC), hemoglobina glucosilada (HbA1C), colesterol total (CT), triglicéridos (TG), presión arterial (PA) y glucemia en ayunas (GA). El constructo hipotético de prueba fue que las mayores calificaciones totales en el IMEVID (mejor estilo de vida) estarían asociadas a valores menores de estas variables clínicas. Se dividió a los sujetos en tres grupos según su calificación total: grupo uno (< cuartil 25), grupo dos (cuartil 25-75), grupo tres (> cuartil 75) y se buscaron diferencias intergrupo en los valores de los parámetros medidosResultadosCompletaron el estudio 389 sujetos, y un 69,2% eran mujeres. Siete dimensiones del IMEVID tuvieron correlaciones débiles al menos con dos de los ocho parámetros (r, –0,22 a 0,16; p≤0,05). La calificación total se correlacionó con seis de ocho parámetros (r, –0,18 a 0,10; p≤0,05). Los sujetos del grupo tres tuvieron valores menores de IMC, ICC, HbA1C, GA, CT y TGL que los del grupo 1 (p<0,05)ConclusionesEl IMEVID tiene validez de constructo para medir el estilo de vida en los sujetos con diabetes tipo 2. Su calificación total discrimina las características clínicamente relevantesObjectiveTo evaluate construct validity of an instrument to measure lifestyle in patients with type 2 diabetes mellitus (IMEVID questionnaire)DesignComparative cross-sectional studySettingSix family medicine units (primary care)Patients412 adults with type 2 diabetesMeasurementsThe IMEVID was applied by self-administration and the following metabolic control parameters values were measured: body mass index (BMI), waist/hip index (WHI), hemoglobin A1C (HbA1C), total cholesterol (TC), triglycerides (TG), systolic blood pressure (SBP), diastolic blood pressure (DBP), and the average of fasting plasma glucose in the last three months (FG). The test hypothetic construct was that higher total scores in the IMEVID (better lifestyle) would be associated with lower values in the metabolic control parameters. Three groups of subjects were formed based on the total score: group one (<cuartil 25), group two (among cuartil 25 and 75) and group three (>cuartil 75). Differences on these parameters between groups were researchedResults389 subjects completed the study, 69,2% were women. Seven IMEVID domains had weak correlations at least with two of eight parameters (r between –0.22 and 0.16; P≤.05). The total score had correlation with six of eight parameter (r between –0.18 and 0.10; P≤.05). The group three subjects had lower levels of BMI,WHI, HbA1C, FG,TC and TGL than group one subjects (P≤.05)ConclusionsIMEVID has construct validity to measure the lifestyle in subjects with DM2. Its total score discriminates outstanding clinical characteristics in these patient

High resolution transmission electron microscopy: A key tool to understand drug release from mesoporous matrices

This work demonstrates that high resolution transmission electron microscopy (HRTEM) is an essential tool to understand drug delivery performance of mesoporous silica materials, mainly those submitted to functionalization processes involving harsh conditions that may affect the mesostructure. Herein an SBA-15-type mesoporous material bearing Si(CH2)(2)P(O)(OCH2CH3)(2) groups was synthesized following the co-condensation route. Then, the resulting material was treated with 37 wt% HCl to convert ethylphosphonate groups to ethylphosphonic acid groups. The proper dealkylation of ethoxy groups following acid treatment was confirmed by FTIR and CP-MAS H-1 -> C-13 solid state NMR, which indicated the presence of Si(CH2)(2)P(O)(OH)(2) functionalities in the treated sample. Characterization of mesoporous materials by XRD diffraction and N-2 adsorption points to well-ordered SBA-15 structures in both untreated and acid-treated samples. Nonetheless, a deep study by HRTEM reveals that the acid-treatment provokes noticeable loss of mesostructural order, only remaining small crystalline domains. This structural damage does not influence cargo loading but it severely affects the release of molecules confined into the mesopores, as concluded from in vitro delivery tests using cephalexin as model drug. Thus, whereas untreated sample showed a sustained diffusion-controlled drug release during more than 2 weeks, 100% of the loaded drug was released only after 10 h from treated sample. This abrupt burst effect cannot be explained on the basis of the existing matrix-drug interactions, whose nature and extension is quite similar under the release conditions for both samples. Thus, it can be only understood on the basis of the mesostructural damage revealed by HRTEM studies. (C) 2016 Elsevier Inc. All rights reserved

Adenomyosis is an independent risk factor for complications in deep endometriosis laparoscopic surgery

Deep endometriosis (DE) occurs in 15-30% of patients with endometriosis and is associated with concomitant adenomyosis in around 25-49% of cases. There are no data about the effect of the presence of adenomyosis in terms of surgical outcomes and complications. Thus, the aim of the present study was to evaluate the impact of adenomyosis on surgical complications in women with deep endometriosis undergoing laparoscopic surgery. A retrospective cohort study including women referred to the endometriosis unit of a referral teaching hospital. Two expert sonographers preoperatively diagnosed DE and adenomyosis. DE was defined according to the criteria of the International Deep Endometriosis Analysis group. Adenomyosis was considered when 3 or more ultrasound criteria of the Morphological Uterus Sonographic Assessment group were present. Demographical variables, current medical treatment, symptoms, DE location, surgical time, hospital stay and difference in pre and post hemoglobin levels were collected. The Clavien-Dindo classification was used to assess surgical complications, and multivariate analysis was performed to compare patients with and without adenomyosis. 157 DE patients were included into the study; 77 (49.05%) had adenomyosis according to transvaginal ultrasound (TVS) and were classified in the A group, and 80 (50.95%) had no adenomyosis and were classified in the noA group. Adenomyosis was associated with a higher rate of surgical complications: 33.76% (A group) vs. 12.50% (noA group) (p?<?0.001). Multivariate analysis showed a 4.56-fold increased risk of presenting complications in women with adenomyosis (CI 1.90-11.30; p?=?0.001) independently of undergoing hysterectomy. There was a statistically significant association between the number of criteria of adenomyosis present in each patient and the proportion of patients presenting surgical complications (p?<?0.001). Adenomyosis is an independent preoperative risk factor for surgical complications in DE surgery after adjustment for known demographic, clinical and surgical risk factors.© 2022. The Author(s)

Intravenous immunoglobulin to prevent myasthenic crisis after thymectomy and other procedures can be omitted in patients with well-controlled myasthenia gravis

Immunoglobulin; Myasthenia; ThymectomyInmunoglobulina; Miastenia; TimectomíaImmunoglobulina; Miastènia; TimectomiaBACKGROUND: Myasthenic crisis (MC) is a potentially life-threatening complication of myasthenia gravis. Its precipitating factors include surgical procedures, particularly thymectomy. The role of preoperative intravenous immunoglobulin (IVIg) in preventing MC in patients scheduled for thymectomy and other surgery with general anaesthesia is unknown. Our objective was to test the hypothesis that preoperative IVIg is effective in preventing myasthenic crisis in patients with myasthenia gravis scheduled for surgery under general anaesthesia, including thymectomy. METHODS: A prospective, randomized, double-blind, single-centre study was conducted over a 4-year period. The treatment group received IVIg, 0.4 g/kg/day preoperatively for 5 consecutive days, and the placebo group received saline solution under the same conditions. The two groups were age-matched, with similar functional status, and Myasthenia Gravis Foundation of America class. All patients had well-controlled myasthenia gravis with minimal manifestations before surgery. The primary outcome measured was MC. Intubation times, time in the recovery room, number of postoperative complications, and days of hospitalization were the secondary outcomes measured. RESULTS: A total of 47 patients were randomized, 25 to the IVIg group and 22 to placebo. There were 19 men and 28 women, with a mean age of 58.6 years, mean body mass index of 27.8 kg/m2, and mean acetylcholine receptor antibodies of 12.9 nmol/l. The mean forced vital capacity was 84.4%. The mean quantitative myasthenia gravis sum score was 6.3. Ten patients (five in each arm) had a history of MC. Thymectomy was performed in 16 patients. Only one patient in the placebo group presented with MC requiring non-invasive ventilation (but no reintubation) for 6 days. Neither differences between groups in the univariate analysis nor risk factors for MC in the multivariate analysis were found. CONCLUSIONS: Preoperative IVIg to prevent MC does not appear to be justified in well-controlled myasthenia gravis patients. This study provides class I evidence that preparation with IVIg to prevent MC is not necessary in well-controlled myasthenia gravis patients scheduled for surgery with general anaesthesia.This work was funded by a Fondo de Investigacion Sanitaria (FIS-FEDER) (grants PI16-01673 and PI19/00593) and an Interlaken Research Award Programme (2012-12094537