A Dual Stimuli Responsive Supramolecular Gel Provides Insulin Hydrolysis Protection and Redox-Controlled Release of Actives

Two supramolecular hydrogelators containing a central disulfide moiety and terminal carboxylic acid groups are studied. On the one hand, the hydrogels are responsive to a reductive environment, which transforms the disulfide unit to the corresponding thiols. On the other hand, the hydrogels show pH response associated with the presence of carboxylic acid units. Gels are formed at pH below ≈4 while at higher pH values, ionization of the gela-tors provokes gel disassembly. The properties of the gel are exploited for the release, as a proof of concept, of Bromophenol Blue in the presence of the reducing species tris(2-carboxyethyl)phosphine hydrochloride. Additionally, insulin is loaded into the hydrogels and protected from hydrolysis with simu-lated gastric fluid containing pepsin. Quantitative release of unaltered insulin, checked with an enzyme-linked immunosorbent assay colorimetric assay, is observed upon treatment with pH 7.4 buffer. This behavior would permit the use of the new hydrogels for oral insulin deliver

Set-up analysis and Optimization of CFD Simulations for Radial Turbines

[EN] This paper proposes a CFD method for simulating radial turbocharger turbine flows. A review is presented of the computational model in terms of meshing, mesh movement strategy, and computational algorithm in turbomachinery CFD simulations. A novel local mesh independence analysis is developed for this purpose. This procedure is aimed at distributing the cells more efficiently by selecting suitable cell sizes for the different regions of the domain to optimize the use of the available computational resources. Pressure- and density-based solvers are compared. The influence of the moving-mesh strategy was analyzed, and small differences were observed in the region near the maximum efficiency point, while these differences increased when off-design conditions were considered. Finally, a comparison of the results with data from an experimental test bench shows that the proposed computational methodology can be used to characterize radial turbomachinery. The objective of the analysis and the optimization of the case configuration was to establish some general guidelines for CFD turbomachinery simulations.The authors are indebted to the Spanish Ministerio de Econom a y Competitividad through Project TRA 2010-16205.Galindo, J.; Hoyas, S.; Fajardo, P.; Navarro, R. (2013). Set-up analysis and Optimization of CFD Simulations for Radial Turbines. Engineering Applications of Computational Fluid Mechanics. 7(4):441-460. doi:10.1080/19942060.2013.11015484S44146074ANSYS (2009).Ansys Fluent 12.0 User’s Guide. Canonsburg, PA: ANSYS Inc.ANSYS (2011).ANSYS FLUENT Theory Guide. ANSYS Inc.Aymanns R, Scharf J, Uhlmann T, Lückmann D (2011). A revision of quasi steady modelling of turbocharger turbines in the simulation of pulse charged engines.16th Supercharging Conference.Hellström F (2010).Numerical Computations of the Unsteady Flow in Turbochargers. PhD thesis, Royal Institute of Technology KTH Fluid Physics.Hiereth H, Prenninger P (2007).Charging the Internal Combustion Engine. Springer Verlag.Japikse D, Baines NC (1997).Introduction to Turbomachinery. Oxford University Press.Liu Z, Hill DL (2000). Issues surrounding multiple frames of reference models for turbo compressor applications.Fifteenth International Compressor Engineering Conference, Purdue University, USA

Lead levels in retail samples of spanish infant formulae and their contribution to dietary intake of infants

Lead concentrations in a total of 82 different types of infant formulae (cow’s milk and soy based) marked in Spain were analysed by acid-microwave decomposition and anodic stripping voltammetry. Dietary lead intake from infant formula and tap water used for powder formula reconstitution were estimated in comparison with the provisional tolerable weekly intake (PTWI). Additionally, the influence of physical state (powder and ready to use formulae), the type of container used and the impact of industrial process from different manufacturers on lead levels were evaluated. According to our results, lead exposure from drinking water was negligible with respect to formulae investigated; where soya formulae contributed the highest intake (58 – 73 % PTWI), non adapted starter and specialised formulae gave an moderate intake (31 – 42 and 26 – 37 % PTWI, respectively) and, finally, pre-term, adapted starter and follow up formulae provided the lowest lead intake (22 – 25, 22 – 26 and 16 – 22 % PTWI, respectively). Based on the current state of knowledge about lead toxicity, manufacturers are called to make an additional effort in order to keep a maximum lead level at 20 g l-1 for all infant formulae, although it is recommendable that these formulations supply the upper limit (5 g l-1) of “normal” human milk

Selenium Content of Spanish Infant Formulae and Human Milk: Influence of Protein Matrix, Interactions with Other Trace Elements and Estimation of Dietary Intake by Infants

The Selenium content of infant formulae varies as a result of differences in the amount of intrinsic selenium compounds. Manufacturers have been gradually changing the protein profile of infant formula to reflect human milk contents more closely. Because of these variations in infant formula composition and their potential impact on selenium content, this trace element was analysed with regard to the different protein sources. The aims of this study were to determine the selenium content in infant formulae sold commercially in Spain, to estimate a daily dietary intake for infants fed on formulae and to compare with the selenium provided by Spanish breast milk samples used as a reference. We have also identified certain trace elements added to formulae which interact with selenium according to type and protein matrix of infant formula. Selenium concentration was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) with a hydride generator. The selenium concentrations in human milk and infant formula determined in this study are similar to those found by other researchers in different countries. Daily intake of studied formulae was estimated according to recommended doses from manufacturers. Theoretical intake of lactating infants has been studied in relation to the Recommended Dietary Allowance (RDA: 10 μg Se/day) and the specific recommendations for infant formula nutrient contents (10 – 35 μg/L) set by Expert Panel of Life Sciences Research Office (LSRO) of the American Society for Nutritional Sciences. According to our results, on an overall view, infants fed on the studied infant formulae have an intake between the basal and normative requirements. This might be considered to provide an adequate selenium intake. However, several formulae included in this research could provide an intake of selenium that does not reach the RDA for the first month of neonate life

Assessment of the numerical and experimental methodology to predict EGR cylinder-to-cylinder dispersion and pollutant emissions

This is the author¿s version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087420972544[EN] EGR cylinder-to-cylinder dispersion poses an important issue for piston engines, since it increases NOx and particulate matter (PM) emissions. In this work, the EGR distribution on a 6-cylinder intake manifold is analyzed by means of experiments, 0D/ID engine modeling and 3D CFD simulations at three different working points. Using a comprehensive set of measurements, statistical regressions for NOx and PM emissions are developed and employed to quantify the sensitivity of numerical configuration to EGR dispersion and subsequent increase of pollutants. CFD mesh and time-step size independence studies are conducted, taking into account their interrelation through the Courant number. The obtained numerical configuration is validated against experimental measurements, considering different unsteady RANS turbulence submodels (k - epsilon and SSTk - omega) as well as the inviscid case. The agreement of the different approaches is quite sensitive to the operating conditions, obtaining root mean square errors for the average cylinder-to-cylinder EGR distribution between 1% and 17% and for the transient CO2 traces between 8% and 29%. However, for the worst-case scenario, the error in NOx and PM emissions prediction is below 2%. The regressions are employed to find a greater EGR distribution impact on pollutants when EGR rate or dispersion are increased. Flow investigation reveals the underlying reasons for the discrepancies and similarities between the predictions of the different turbulence submodels. A statistical analysis shows the significant errors that average CO2 probes make when assessing EGR cylinder-to-cylinder distribution, which is explain by the flow heterogeneity at some operating conditions.The authors of this paper wish to thank Francisco Moya for his invaluable work during the test cell setup and the experimental campaign. Guillermo Garcia is partially supported through contract FPI-S2-2018 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.Galindo, J.; Climent, H.; Navarro, R.; García-Olivas, G. (2021). Assessment of the numerical and experimental methodology to predict EGR cylinder-to-cylinder dispersion and pollutant emissions. International Journal of Engine Research. 22(10):3128-3146. https://doi.org/10.1177/146808742097254431283146221

Centrifugal compressor influence on condensation due to Long Route-Exhaust Gas Recirculation mixing

[EN] State of the art techniques for reducing pollutant emission in internal combustion engines often require local flow assessment, specially in the air management field. This work addresses the interaction between a turbo- charger compressor and the 3-way long-route EGR joint, where exhaust gases of the combustion are mixed with fresh air. A validated methodology for compressor simulation is combined with a validated condensation model for this work. Numerical simulations of two different working points with three flap positions are conducted. The influence of these operating conditions on the flow field is evaluated. Particularly, there is a connection between the mixing of both steams and the generation of water condensates, responsible for the erosion of the impeller and the loss of compressor efficiency. Moreover, neglecting the impact of the compressor presence on the condensation production is shown to be of low magnitude, so that simulations without the compressor are regarded as accurate, thus reducing the computational effort by two orders of magnitude.Daniel Taxi is partially supported through contract FPI-S2-2015-1095 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.Galindo, J.; Navarro, R.; Tarí, D.; García -Olivas, G. (2018). Centrifugal compressor influence on condensation due to Long Route-Exhaust Gas Recirculation mixing. Applied Thermal Engineering. 144:901-909. https://doi.org/10.1016/j.applthermaleng.2018.09.005S90190914

Development of an experimental test bench and a psychrometric model for assessing condensation on a low-pressure exhaust gas recirculation cooler

This is the author¿s version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087420909735[EN] A test bench has been designed to assess condensation formation produced on the interior of a low-pressure exhaust gas recirculation cooler working with hot stream of humid air representing an engine warm-up stage, when its coolant starts from very cold conditions. An experimental campaign has been conducted with three different exhaust gas recir- culation mass flow rates, four exhaust gas recirculation inlet temperatures and three different coolant initial tempera- tures, covering common conditions found in the low-pressure exhaust gas recirculation system of internal combustion engines under cold starts. The transient experimental results are analyzed and compared with a simple psychrometric condensation model, obtaining a good correlation and reproducing the trends of the condensation, even though an over- prediction of the condensates of around 20%¿40% exists due to the strong hypotheses assumed. The warm-up tests are most sensitive to the initial coolant temperature. For example, an engine starting at ¿10 °C ambient temperature could require 10 min to stop producing water in the low-pressure exhaust gas recirculation cooler, with an accumulated quan- tity during the warm-up of about 100 mL of condensates.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Francisco Moya is partially supported through a FPI-GVA-ACIF-2019 grant of the Government of Generalitat Valenciana and the European Social Fund.Galindo, J.; Navarro, R.; Tarí, D.; Moya-Torres, F. (2021). Development of an experimental test bench and a psychrometric model for assessing condensation on a low-pressure exhaust gas recirculation cooler. International Journal of Engine Research. 22(5):1540-1550. https://doi.org/10.1177/1468087420909735S1540155022

Analysis of the impact of the geometry on the performance of an automotive centrifugal compressor using CFD simulations

[EN] During the latest years, downsizing in internal combustion engines has moved the operating conditions of the compressor closer the surge limit. Surge onset depends on the geometry of the compressor inlet and is difficult to predict. Unfortunately, the determination of the surge line is essential for engine design and calibration, since surge is an oscillating phenomenon that endangers the turbocharger integrity. This work is addressed to study the impact of placing different geometries, namely a tapered duct, a convergent-divergent nozzle and a divergent nozzle in the compressor inlet on different compressor parameters such as stability, efficiency and noise emission. 3D-CFD simulations are performed using the commercial code STAR-CCM+ at both near-surge conditions and high mass flow rate, focusing on the flow structures generated by each configuration. The results are compared with corresponding experimental tests and show a meaningful sensitivity of geometry to the performance, indicating potential benefits of using some of these geometries in turbocharger configurations.Daniel Tarí is partially supported through contract FPI-S2-2015- 1095 of Programa de Apoyo para la Investigación y Desarrollo (PAID) of Universitat Politècnica de València.Galindo, J.; Gil Megías, A.; Navarro, R.; Tarí, D. (2019). Analysis of the impact of the geometry on the performance of an automotive centrifugal compressor using CFD simulations. Applied Thermal Engineering. 148:1324-1333. https://doi.org/10.1016/j.applthermaleng.2018.12.018S1324133314

Methodology for a Numerical Multidimensional Optimization of a Mixer Coupled to a Compressor for Its Integrationin a Hyperloop Vehicle

[EN] The current environmental concern has led both the industry and researchers to look for alternate means of transport. Amongst them, the hyperloop has become a quite promising idea. In order to overcome some of its limitations, including a compressor in its propulsive system has been investigated. In this paper, a strategy to improve the design of the mixer, which will blend the bypass and core streams coming out of the compressor, was addressed. Due to the lack of ad hoc compressors and the impossibility of experimental testing, a multidimensional optimization methodology with CFD tools was developed. A Taguchi DOE was employed for a preliminary 2D optimization from an initial geometry, whereas a numerical adjoint method was explored for the whole 3D mixer. By using this method, an initial decrease in the pressure drop of 16%16% was obtained with the 2D stage, whereas an additional 10%10% reduction was achieved in the 3D optimization. With this, the propulsive efficiency of the whole hyperloop system will be improved.Project supported by the "Agencia Valenciana de la Innovacio" and the European Regional Development Fund 2014-2020: INNEST/2021/221 and INNEST/2021/344. Borja Pallas was supported by "Conselleria de Innovacion, Universidades, Ciencia y Sociedad Digital de la Generalitat Valenciana DOCEMPR UPV program" from the regional government, Generalitat Valenciana co-funded by the European Social Fund.Galindo, J.; Dolz, V.; Navarro, R.; Pallás, B.; Torres, G. (2022). Methodology for a Numerical Multidimensional Optimization of a Mixer Coupled to a Compressor for Its Integrationin a Hyperloop Vehicle. Applied Sciences. 12(24):1-25. https://doi.org/10.3390/app122412795125122

Cinética de imbibición e isotermas de adsorción de humedad de la semilla de jamaica (Hibiscus sabdariffa L.)

La jamaica es un arbusto que se cultiva para comercializar el cáliz de sus flores, pero como subproducto se obtienen las semillas, que por su valor nutritivo y alto rendimiento representan un potencial económico considerable. El objetivo de este trabajo fue describir la cinética de imbibición y las isotermas de adsorción de humedad a 25, 35 y 45ºC en tres variedades cultivadas en México ("Criolla", "China" y "Sudán"). Los resultados mostraron que el proceso de imbibición describe una curva que se ajusta al modelo de Weibull, con coeficientes α de 12.99, 8.81 y 2.21 horas y β de 0.83, 1.70 y 0.72 para las variedades Criolla, China y Sudán, respectivamente. Los modelos de GAB, y de Chung-Pfost describieron adecuadamente las isotermas de adsorción. La humedad de la capa monomolecular (coeficiente a del modelo de GAB) resultó entre 3.97 y 5.71% b.s., lo cual representa una actividad de agua entre 0.1 y 0.30. Los calores isostéricos totales de adsorción obtenidos en el intervalo de humedades de equilibrio de 6 a 22% b.s., oscilaron entre 52.85 y 42.90 .90 kJmּol-1, 60.99 y 43.41 kJmּol-1 y 51.23 y 43.20 kJmּol-1para las variedades Criolla, China y Sudán, respectivamente. A humedades de equilibrio iguales o superiores a 12 % b.s., el calor isostérico fue similar a la entalpía de vaporización del agua, pero a humedades inferiores a 6% b.s., éste alcanzó los valores más elevados