Simulation of a solar funnel cooker using MATLAB

A software for the calculation of the radiation heat transfer in solar funnel cookers by means of the radiosity method has been developed in Matlab. The software has been used to study a folding solar cooker. The cooker geometry is discretized using a triangular mesh where a piecewise constant approximation is assumed for the radiosity function. Form factors, including self-occlusions, are calculated by properly refining the triangular mesh. The concentration factor of the solar cooker is estimated as a function of its position and orientation with respect to that of the Sun.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Metals, environment and life interference of vanadium in living systems and their contextualization in teaching experimental sciences

The ammonium metavanadate (V + 5), widely used in chemical industry is a toxic compound which is involved in several cases of enzyme inhibition. The alkaline phosphatase (ALP) a zincglycoenzyme implicated in cell growth and apoptosis can be affected by the presence of metals like vanadium. The main objective of this study was to interest young students to the toxicity of metals, exploring the effects of vanadium on the ALP activity, using Saccharomyces cerevisiae as biological model. This activity was developed by a pilot group of students from Dom Manuel Martins high school of Setúbal, Portugal, which follow the yeast growth at 640nm and obtained cell extracts from S. cerevisiae growing at 28 ◦C in YPD medium (glucose 2% (w / v)) in absence and presence of 25 or 75mM NH4VO3, for the quantification of proteins at 720nm by Lowry’s method and ALP activity determination at 405 nm, using pNPP as substrate. The young people observed a growth inhibition of yeast cells exposed to vanadium as well as a decrease of total proteins and ALP activity level, facts which put in evidence a sharp toxicological effect of vanadium in eukaryotic cell. The average score obtained before and after the experimental activity (41%) and (63%), respectively, using the same set of questionsproblem, revealed an overall positive performance of skills developed by students, in the scope of metals toxicological effects in eukaryote cells. In more detail, it was also observed a positive and significant effect in each experimental phase (p < 0.05), before and after the development of the action. The assessment of skills developed by students showed an improvement of their compliance level, thereby acquiring a significant learning. The results for the opinion survey showed that most respondents classified the activity and its difficulty degree as good

On the error of calculation of heat gains through walls by methods using constant decrement factor and time lag values

A transient heat transfer model was developed to numerically predict the thermal behaviour of the external walls of a room under realistic outdoor conditions. The excitation is not simply sinusoidal even though it is considered to have daily periodicity. The numerical model is based on the finite difference method and handles one-dimensional heat conduction through multilayered walls. The boundary condition at the outer surface of the wall is described with the sol-air temperature concept. The temperatures of indoor air and of other internal surfaces in the room are assumed to be equal and constant. The numerical results were used to calculate values of the decrement factor and time lag of several walls. The calculation followed two methods found in literature, in which these parameters are assumed constant, distinguished by the temperature evolution used: the sol-air or the wall's outer surface. Additionally, the inner surface temperature is used in both methods. The walls investigated range from low to high mass construction, face towards various directions and have light or dark coloured sunlit outer surfaces. The heat fluxes at the inner surface of the walls predicted by numerical modelling and estimated by the simplified methods are compared in detail to conclude on the validity of these simplified methods. As a by-product it is also possible to conclude on the dependence of the decrement factor and of the time lag on the outer surface colour and on the orientation of different types of walls. The results show that both simplified methods have poor accuracy in a significant number of cases. Also, it was found that the wall's azimuth significantly affects the time lag

Seroprevalence of antibodies against SARS-CoV-2 among health care workers in a Portuguese hospital

"Background: Health care workers (HCW) are presumably exposed to a higher risk of infection by SARS-CoV-2 and could possibly represent a source of transmission to susceptible patients. Thus, characterization of SARS-CoV-2 infection among HCW is necessary to better understand the determinants of viral transmission and properly implement strategies to prevent dissemination and protect HCW and vulnerable patients. The aim of this study was to estimate the seroprevalence of antibodies against SARS-CoV-2 in a Portuguese tertiary hospital, in the period of July 2020 to March 2021, before the generalized use of the SARS-CoV-2 vaccine, characterize its evolution over time, and identify risk factors associated with seroconversion. Methods: HCW were approached to collect serum samples for qualitative SARS-CoV-2 antibody testing and completion of an online survey capturing demographics, previous symptoms, and details of health care and community exposure. Odds ratio with bivariable and multivariable logistic regression was used to assess characteristics associated with seroprevalence. Results: One thousand HCW were included for analysis. Two hundred nineteen HCW (22%) were seropositive for immunoglobulin G against SARS-CoV-2, and 166 (17%) were seropositive for immunoglobulin M, most of whom reported a previous diagnosis of SARS-CoV-2 infection. The risk factors associated with seroconversion included a previous COVID-19 diagnosis, contact with patients, occupational contact with colleagues, and outside contact. However, in a multivariate logistic regression analysis, only a previous diagnosis and outside contact were associated with seroconversion. Seropositivity decreased over time, especially 28 weeks after infection. Conclusion: HCWs have a high seroprevalence for SARS-CoV-2 infection, probably due to a combination of health care and community exposure. Seropositivity decreases over time, but further studies are needed to better understand our adaptive immune response.

Two photon decay of π0\pi^0 and η\eta at finite temperature and density

A comparative study of the anomalous decays $\pi^0, \eta \to\gamma\gamma$, at finite temperature and at finite density, is performed in the framework of the three--flavor Nambu--Jona-Lasinio. The similarities and differences between both scenarios are discussed. In both cases the lifetimes of these mesons decrease significantly at the critical point, although this might not be sufficient to observe enhancement of these decays in heavy-ion collisions.Comment: 5 pages, 1 figure. Talk given at Strange Quark Matter 2004, Cape Town, South Africa, 15-20 September, 200

Influence of the rainfall in the content of nutrients in litter in agroforestry systems managed with burning and without burning in Amazon.

This study evaluated the nutrient content of the litter, testing different treatments with burning and no burning, of the vegetation, to identify which one provides better efficiency in operation and production of nutrients in different seasonal conditions. The study area is located on the property of the family farmer, initially selected by a diagnosis socioeconomic, community Benjamin Constant, in northeastern Para. Litter was collected during two periods: dry season (November) and rainy (March) in 2009. For the collection of litter samples, we used collectors measuring (0.25 × 0.25 m2), which were placed directly on the soil surface. The collected material was stored in paper bags and taken to the laboratory for Chemical Analysis of the Brazilian Agricultural Research Corporation (EMBRAPA), which was determined by analyses of macronutrients (N, P, K, Ca, Mg, Na) and micronutrients (Fe, Cu, Mn, Zn). The highest concentrations of macronutrients were found in N for agroforestry systems with and without burning in two seasons (wet and dry). All macronutrients showed influence of seasonality, which was verified by the wide variation in nutritional behavior. The decreasing concentration of nutrients was presented N > Ca > Mg > Na > K > P in agroforestry system with burning, with maximum values of all nutrients in the rainy season, and N, P, K, Ca, Na in higher concentrations in agroforestry system without burning, and showed only the Mg peak in agroforestry system with burning. The behavior of the concentration of nutrients was opposite to that observed one, for all elements analyzed showed a reduction in the concentrations of nutrients in the dry season. The decreasing concentration of nutrients was presented Fe > Mn > Zn > Cu

Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in doberman pinschers with preclinical dilated cardiomyopathy (the PROTECT study)

&lt;p&gt;Background: The benefit of pimobendan in delaying the progression of preclinical dilated cardiomyopathy (DCM) in Dobermans is not reported.&lt;/p&gt; &lt;p&gt;Hypothesis: That chronic oral administration of pimobendan to Dobermans with preclinical DCM will delay the onset of CHF or sudden death and improve survival.&lt;/p&gt; &lt;p&gt;Animals: Seventy-six client-owned Dobermans recruited at 10 centers in the UK and North America.&lt;/p&gt; &lt;p&gt;Methods: The trial was a randomized, blinded, placebo-controlled, parallel group multicenter study. Dogs were allocated in a 1:1 ratio to receive pimobendan (Vetmedin capsules) or visually identical placebo.&lt;/p&gt; &lt;p&gt;The composite primary endpoint was prospectively defined as either onset of CHF or sudden death. Time to death from all causes was a secondary endpoint.&lt;/p&gt; &lt;p&gt;Results: The proportion of dogs reaching the primary endpoint was not significantly different between groups (P = .1). The median time to the primary endpoint (onset of CHF or sudden death) was significantly longer in the pimobendan (718 days, IQR 441–1152 days) versus the placebo group (441 days, IQR 151–641 days) (log-rank P = 0.0088). The median survival time was significantly longer in the pimobendan (623 days, IQR 491–1531 days) versus the placebo group (466 days, IQR 236–710 days) (log-rank P = .034).&lt;/p&gt; &lt;p&gt;Conclusion and Clinical Importance: The administration of pimobendan to Dobermans with preclinical DCM prolongs the time to the onset of clinical signs and extends survival. Treatment of dogs in the preclinical phase of this common cardiovascular disorder with pimobendan can lead to improved outcome.&lt;/p&gt

The transporters GlyT2 and VIAAT cooperate to determine the vesicular glycinergic phenotype

The mechanisms that specify the vesicular phenotype of inhibitory interneurons in vertebrates are poorly understood because the two main inhibitory transmitters, glycine and GABA, share the same vesicular inhibitory amino acid transporter (VIAAT) and are both present in neurons during postnatal development. We have expressed VIAAT and the plasmalemmal transporters for glycine and GABA in a neuroendocrine cell line and measured the quantal release of glycine and GABA using a novel double-sniffer patch-clamp technique. We found that glycine is released from vesicles when VIAAT is coexpressed with either the neuronal transporter GlyT2 or the glial transporter GlyT1. However, GlyT2 was more effective than GlyT1, probably because GlyT2 is unable to operate in the reverse mode, which gives it an advantage in maintaining the high cytosolic glycine concentration required for efficient vesicular loading by VIAAT. The vesicular inhibitory phenotype was gradually altered from glycinergic to GABAergic through mixed events when GABA is introduced into the secretory cell and competes for uptake by VIAAT. Interestingly, the VIAAT ortholog from Caenorhabditis elegans (UNC-47), a species lacking glycine transmission, also supports glycine exocytosis in the presence of GlyT2, and a point mutation of UNC-47 that abolishes GABA transmission in the worm confers glycine specificity. Together, these results suggest that an increased cytosolic availability of glycine in VIAAT-containing terminals was crucial for the emergence of glycinergic transmission in vertebrates

Raytracing optical analysis of a solar funnel cooker

Funnel type solar cookers rely on a multifaceted reflector to concentrate solar radiation on a cooking pot that is placed inside a transparent enclosure to create a greenhouse effect. This work aims to analyze the optical performance of this type of solar cooker using raytracing techniques. The open source Soltrace software tool is used to create an optical model of a solar funnel cooker. Numerous raytracing simulations are conducted in order to complete a parametric analysis of the optical performance against a set of influence variables, such as the elevation angle, sun tracking errors, optical quality of the different elements involved ( reflectors, greenhouse, cooking pot), etc.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech