Hamilton-Jacobi framework for Regge-Teitelboim gravity

We discuss the Hamilton-Jacobi formalism for brane gravity described by the Regge-Teitelboim model, in higher co-dimension. Being originally a second-order in derivatives singular theory, we analyzed its constraint structure by identifying the complete set of Hamilton-Jacobi equations, under the Carath\'eodory's equivalent Lagrangians method, which goes hand by hand with the study of the integrability for this type of gravity. Besides, we calculate the characteristic equations including the one that satisfy the Hamilton principal function $S$. We find the presence of involutive and non-involutive constraints so that by properly defining a generalized bracket, the non-involutive constraints that originally arise in our framework, are removed while the set of parameters related to the time evolution and the gauge transformations, are identified. A detailed comparison with a recent Ostrogradsky-Hamilton approach for constrained systems, developed for this brane gravity, is also made. Some remarks on the gauge symmetries behind this theory are commented upon.Comment: 16 pages, no figure

Investigation on thermostatic expansion valves

In der vorliegenden Arbeit wird das thermostatische Expansionsprinzip in einem automobilen Kompressionskältekreislauf experimentell und theoretisch untersucht. Sein Einfluss auf den gesamten R134a-Kältekreislauf wird beleuchtet, und die potenziellen Vorteile seiner Anwendung im R744-Kältekreislauf werden in Aussicht gestellt. Hierfür wird eine Methode zur transienten Modellierung von thermostatischen Expansionsventilen (TXV) mit physikalisch interpretierbaren Parametern, die anhand von Herstellerangaben oder durch einfache Messungen am TXV-Prüfling bestimmt werden können, entwickelt. Diese Methode wurde angewandt, um ein Serien-TXV mit der Simulationssprache Modelica abzubilden. Das erhaltene Modell wurde mittels der Simulationssoftware Dymola in einer Umgebung zur transienten Kältekreislaufsimulation integriert. Hiermit wurden Parametervariationen und Nachrechnung von Fahrzeugversuchen durchgeführt. Außerdem diente diese Modellierungsmethode dazu, eine neue Darstellungsform für den stationären Regelbereich eines TXV abzuleiten, die darauf basiert, Gleichgewichtszustände des TXV, sogenannte Iso-Hubkennlinien, im p-h-Diagramm des jeweiligen Betriebskältemittels abzubilden. Mit Hilfe dieser neuen Darstellungsform konnte erstens ein Optimierungspotenzial in der Auslegung eines automobilen TXV aufgedeckt werden, wodurch eine Ansammlung von flüssigem Kältemittel im Kältemittelverdichter bei ausgeschalteter Kälteanlage vermieden werden kann; zweitens ließ sich ein neuartiges TXV-Konzept zur Hochdruckregelung anhand der Temperatur am Ventileintritt einer R744-Kälteanlage entwickeln, das eine COP-optimierende Arbeitsweise mit einer Überdruckfunktion autark kombiniert. Dieses Ventilkonzept wurde in Form eines Prototyps umgesetzt, mit welchem sich dessen funktionelle Eignung zur optimalen Hochdruckregelung einer automobilen Kälteanlage zeigen ließ.The purpose of the following investigation is to describe the thermostatic expansion principle in an automobile A/C system in a theoretical and experimental way. Its influence on the complete R134a A/C system will be described and a perspective of the potential advantages of its usage on the R744 A/C system will be given. In order to accomplish this, a transient modelling method was developed. This type of modelling method is based on physical interpreted parameters that can be obtained from the specifications of a thermostatic expansion valve (TXV) or through simple measurements on TXV samples. This method was applied in order to represent a series TXV using the Modelica simulation language. The obtained model was integrated into a transient A/C simulation envi-ronment. This approach allowed the realization of parameter variations, the recalculation of automobile experiments and the development of a new way to visualize the stationary control range of a TXV based on the conditions of equilibrium (also called iso-stroke characteristic lines) in a p-h diagram for every refrigerant. Using this new visualization way the following was achieved: a. The optimization potential during the dimensioning of an automobile TXV was discovered, in which the accumulation of refrigerant in a compressor of a switched-off A/C system can be avoided. b. A new concept for the high-pressure control, based on the temperature at the valve’s inlet in an R744 A/C system was developed. This concept combines the COP optimization function with a high pressure safety function. This valve concept was implemented in a new prototype, with which the functional adequacy for the optimal high pressure control could be shown

Characterization of k-carrageenan/Locust bean gumbased films with b-carotene emulsion

New bio-based materials have been exploited to develop biodegradable and edible films as an effort to extend shelf life and improve quality of food while reducing packaging waste. The objective of this study was to investigate physicochemical properties of k-carrageenan/locust bean gum (k-car/LBG) films with different bcarotene emulsion concentrations. To prepare oil-in-water emulsions, b-carotene (0.03% v/v) was dissolved in mediumchain triglycerides (MCTs), and the solution was mixed (1:9 v/v) with a pectin solution (3% w/v) as emulsifier. Film forming solutions were prepared by adding b-carotene emulsion (0-3% w/w) into the k-car/LBG solution (40/60% w/w) with 0.3% (w/v) of glycerol. Films with different b-carotene concentrations were characterized in terms of optical, mechanical and barrier properties and compared with control films without bcarotene. The results suggested that mechanical, physical and barrier properties of k-car/LBG films were influenced by the presence of b-carotene. Results showed that addition of b-carotene to the k-car/LBG films studied resulted in significant decrease (p<0.05) in water vapour transmission rate values. Film opacity values (ranging from 4.9 to 12.5 %) increased when b-carotene was incorporated to the film. Therefore, b-carotene emulsions have potential to be used as a natural additive on kcar/LBG films, particularly in the food packaging industry

Candelilla wax edible coating with Flourensia cernua bioactives to prolong the quality of tomato fruits

The improvement of the postharvest quality of tomato fruits was evaluated using an edible coating functionalized with an Flourensia cernua extract evaluating the antifungal, structural, barrier, and optical properties. The formulation and evaluation of an edible coating and its application on tomato was evaluated using a response surface methodology to determine the ideal concentrations of candelilla wax, whey protein, and glycerol. Edible films showed good barrier properties, with water vapor permeability varying from 0.4350.404 g mm/m2 day kPa. The addition o F. cernua extract showed significant improvement in the transparency of films. The edible coating applied to tomato reduced weight and firmness loss. The sensory evaluation proved that the product obtained is acceptable for consumers. The edible coating added with F. cernua extract was the most effective in inhibiting the growth of pathogenic fungi and the visual appearance at the end of storage confirmed the beneficial effect of the edible coating.(undefined)info:eu-repo/semantics/publishedVersio

Impact of Implementing a Dyslipidemia Management Guideline on Cholesterol Control for Secondary Prevention of Ischemic Heart Disease in Primary Care

Cardiovascular diseases (CVD) are the main cause of death worldwide. The control of CVD risk factors, such as dyslipidemia, reduces their mortality rate. Nonetheless, fewer than 50% of patients with ischemic heart disease (IHD) have good cholesterol control. Our objective is to assess whether the level of participation of general practitioners (GPs) in activities to implement a dyslipidemia management guideline, and the characteristics of the patient and physician are associated with cholesterol control in IHD patients. We undertook a quasi-experimental, uncontrolled, before-and-after study of 1151 patients. The intervention was carried out during 2010 and 2011, and consisted of a face-to-face training and online course phase (Phase 1), and another of face-to-face feedback (Phase 2). The main outcome variable was the low-density lipoprotein cholesterol (LDL-C) control, whereby values of <100 mg/dL (2.6 mmol/L) were set as a good level of control, according to the recommendations of the guidelines in force in 2009. After Phase 1, 6.7% more patients demonstrated good cholesterol control. With respect to patient characteristics, being female and being older were found to be risk factors of poor control. Being diabetic and having suffered a stroke were protective factors. Of the GPs' characteristics, being tutor in a teaching center for GP residents and having completed the online course were found to be protective factors. We concluded that cholesterol control in IHD patients was influenced by the type of training activity undertook by physicians during the implementation of the GPC, and patient and physician characteristics. We highlight that if we apply the recent targets of the European guideline, which establish a lower level of LDL-C control, the percentage of good control could be worse than the observed in this study

Evaluation of silicon, calcium and magnesium in liquid fertilizers on sorghum growth in the greenhouse.

Se evaluó el uso de fertilizantes líquidos con Si, Ca o Mg sobre el crecimiento del sorgo (Sorghum bicolor) en un Ultisol bajo invernadero. Se utilizaron 2 silicatos de potasio, carbonato de calcio y óxido de magnesio, todos en líquidos aplicados al suelo en dosis de 2 y 4 ml.pote-1, y un testigo, en un diseño irrestricto al azar con 9 tratamientos y 4 repeticiones. Las variables de crecimiento, evaluadas 45 días después de siembra, fueron peso seco de raíz y de parte aérea. Se realizó un análisis de suelos y de planta al final del ensayo. Las aplicaciones de Ca y de Mg incrementaron de manera significativa el crecimiento y la absorción de nutrimentos del sorgo. El carbonato de calcio promovió los valores más altos de biomasa seca y de absorción de N, P, Ca, S, Cu, Zn, Mn y B. Las fuentes de Si no tuvieron efectos significativos sobre la biomasa del sorgo, a excepción del silicato de K con Ca y Mg en dosis de 4 ml.pote-1, que además produjo un incremento significativo en la absorción de K. El carbonato de calcio y el óxido de magnesio incrementaron significativamente el pH, disminuyeron la acidez y el Al intercambiable, y aumentaron los contenidos de Ca o Mg en el suelo.The effect of liquid fertilizers with Si, Ca or Mg on the growth of sorghum (Sorghum bicolor) was evaluated in an Ultisol under greenhouse conditions. Four liquid fertilizers (two potassium silicates, calcium carbonate and magnesium oxide) were applied into the soil in liquids at doses of 2 and 4 ml.pot-1, plus a control, in a randomized unrestricted design with 9 treatments and 4 replicates. Growth variables, assessed 45 days after sowing, were dry weight of root and aerial parts. Analysis of soil and plant at the end of the test was performed. The application of Ca and Mg significantly increased growth and nutrient uptake of sorghum. Liquid calcium carbonate promoted the highest values of dry biomass and absorption of N, P, Ca, S, Cu, Zn, Mn and B. Si sources had no significant effects on biomass, except for K silicate with Ca and Mg at the dose of 4 ml.pot-1, which also produced a significant increase in K absorption. Calcium carbonate and magnesium oxide significantly increased soil pH and decreased exchangeable acidity and Al, and also increased Ca or Mg content in the soil.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro de Investigaciones Agronómicas (CIA