Bioblanqueo de lino mediante el sistema lacasa mediador a presión atmosférica

En este trabajo se estudia el bioblanqueo de pasta de lino basado en el sistema lacasa mediador (L) a presión atmosférica, en concreto, la influencia de la adición de oxigeno y del tiempo de tratamiento en las propiedades de pastas. Los resultados obtenidos muestran que la adición de oxigeno al sistema influye en las propiedades de la pasta tanto después de aplicar la etapa enzimática como después de la posterior realización de una etapa de extraccional calina (E). En la evolución de la blancura de la pasta, se observan diferentes comportamientos después de la etapa L y después de la secuencia LE. A partir de los resultados del estudio de las coordenadas cromáticas CIEL*C*h y las curvas espectrofotométricas, se puede deducir que la etapa de tratamiento enzimático produce una modificación de la estructura de la lignina que lleva a la formación de grupos cromoforos que aportan color a la pasta. Los valores de numero kappa indican que se producen dos fases diferenciadas en el biotratamiento, una primera fase de deslignificacion rápida y una segunda de deslignificación lenta

Are the motives for food choices different in orthorexia nervosa and healthy orthorexia?

Recent research points to the bidimensional nature of orthorexia, with one dimension related to interest in healthy eating (healthy orthorexia) and another dimension related to a pathological preoccupation with eating healthily (orthorexia nervosa). Research was needed to provide further support for this differentiation. We examined the food-choice motives related to both aspects of orthorexia. Participants were 460 students from a Spanish university who completed the Teruel Orthorexia Scale and the Food Choice Questionnaire. By means of structural equation modeling, we analyzed the relationship between orthorexia, food-choice motives, gender, body mass index, and age. The motives predicting food choices in orthorexia nervosa and healthy orthorexia were quite different. In the case of orthorexia nervosa, the main motive was weight control, with sensorial appeal and affect regulation also showing significant associations. For healthy orthorexia, the main motive was health content, with sensorial appeal and price also showing significant associations. This supports the hypothesis that orthorexia nervosa is associated with maladaptive eating behavior motived more by weight control than by health concerns

Effect of Diesel injection pressures up to 450MPa on in-nozzle flow using realistic multicomponent surrogates

Investigations with 300MPa injection pressures show significant soot reduction, but the effect of such extremepressures on the in-nozzle flow has not been closely examined. The study of the in-nozzle flow is important becauseit dominates primary break-up characteristics and therefore the combustion efficiency. Moreover, the characteristicpressure drops in Diesel injectors may cause the fuel to cavitate, which leads to enhancements in the nozzleoutlet velocity, the spray cone angle and the fuel atomisation. In this work, the fuel property database is modelledusing the molecular-based PC-SAFT EoS with an eight-components surrogate based on a grade no. 2 Dieselemissions-certification fuel. The composition for the surrogate is (in mole fration): 2.7% n-hexadecane, 20.2% n-octadecane, 29.2% heptamethylnonane, 5.1% n-butylcyclohexane, 5.5% trans-decalin, 7.5% trimethylbenzene and15.4% tetralin. Then, this surrogate is utilised in simulations for a common rail 5-hole tip injector tapered nozzle.The needle is assumed to be still at a lift of 100μm, which is representative of the lift reached during pilot injection.The injector operating pressures start from 180MPa and reach 450MPa. The collector back pressure is 5MPa. Thedensity of the bulk fluid is assumed to vary according to a barotropic-like scheme, following an isentropic expansion.Results show an increase in the mass flow rate, following the square root of the pressure difference law and alsoin the outlet velocity, both as expected. Surprisingly, the cavitation is significantly reduced as the injection pressureincreases. A focused study on this particular phenomenon shows a significant decrease in the Reynolds numberin the sac, therefore the flow is found to be more stable and the pressure drop along the nozzle is smaller. Thereason for the lower Reynolds number is found on the heavy nature of Diesel fuels. While the sac average velocityincreases 15% between an injection pressure of 180MPa and 450MPa, the kinematic viscosity increases close to a70%

On the effect of realistic multicomponent diesel surrogates on cavitation and in-nozzle flow

Cavitation and cavitation-induced erosion highly depends on the thermodynamic properties of the fluid, which in turn affect the in-nozzle flow. However, many predictive models used today rely on constant properties or very simplified diesel surrogates. In this work, the diesel properties are predicted using a realistic four-component diesel surrogate, named J1D, which is compared with the traditionally used n-dodecane and then additised with n-hexane in amounts of 1% and 10%, named 1C6 and 10C6 respectively. The fuel property variation as function of pressure is modelled using the PC-SAFT EoS. The fluids are then used in simulations for a common rail 5-hole tip injector nozzle. The needle is assumed to be still at a lift of 105µm, which is representative of the lift reached during pilot injection. The injector operating pressure is 180MPa and the collector back pressure is 5MPa. The density of the bulk fluid is assumed to vary according to a barotropic-like scheme, following an isentropic expansion. Regarding the results from the simulations, the value of mass flow rate was proportional to the liquid density of the fluids. From the results, it appears that for substances with similar viscosity and density, such as J1D, 1C6 and 10C6 the vapour pressure is dominant in the cavitation production, as the greater the vapour pressure the greater the cavitation obtained. However, when the vapour pressure is comparable, such as that for J1D and n-dodecane, the difference in density and viscosity of the fluids seems to provide the cause for a greater vaporisation the lighter the fluid is. Despite its exploratory nature, this study offers some insight into the use of complex EoS and surrogate mixtures and their effect on cavitation and preferential vaporisation in diesel

Procesos cognitivos distorsionados en la conducta agresiva y antisocial en adolescentes

ResumenEn el presente trabajo se realiza una revisión de diferentes aportaciones teóricas y empíricas que abordan la relación entre las conductas agresivas y antisociales en la adolescencia y un conjunto de procesos cognitivos distorsionados que interfieren en la percepción y comprensión de los eventos o experiencias sociales. A partir de las diferentes aproximaciones teóricas, en esta revisión se sugiere la necesidad de contar con una perspectiva más integradora que permita una mejor conceptualización y tipificación de estos procesos cognitivos distorsionados, a fin de clarificar la naturaleza y la función específica que cada uno de ellos desempeña en la explicación del comportamiento agresivo y antisocial en adolescentes.AbstractA review of different theoretical and empirical contributions about the relationship between antisocial behavior in adolescence and distorted cognitive processes, which interfere with the perception and understanding of social events or experiences, is presented in this study. According to different theoretical approaches, it is necessary to take into account a more comprehensive perspective that allows a better conceptualization and characterization of these distorted cognitive processes and, therefore, that clarifies the nature and specific function they play in the explanation of aggressive and antisocial behavior in adolescents

Effect of realistic multicomponent diesel surrogates on predicted in-nozzle flow and cavitation

In-nozzle flow dominates primary break-up characteristics and therefore the combustion efficiency. However, predictive methods of the internal nozzle flow and its link with the spray characteristics have traditionally used constant fuel properties, which may lead to large inaccuracies. Surprisingly enough, neither the effects of using realistic surrogates have been closely examined. In this work, the fuel property variation as function of pressure and temperature of three diesel surrogates are modelled using the PC-SAFT state-of-the-art EoS; these include n-dodecane and two mixtures comprising four and eight components, named V0 and V1 respectively, based on a grade no. 2 diesel emissions-certification fuel. Then, the surrogates used in simulations for a common rail 5-hole tip injector. The needle is assumed to be still at a lift of 105µm, similar to that used for pilot injections. The injector operating pressure is 180MPa and the collector back pressure is 5MPa. Heat effects are omitted and no turbulence model is used. The bulk fluid is considered to be a single phase whose density varies according to a barotropic-like scheme, following an isentropic line. Results show that the mixture surrogates V0 and V1 have a greater vapour pressure than that of n-dodecane, although they are significantly heavier both in density and viscosity. Predicted cavitation clouds occupied a ∼14% larger volume for V1 than that for n-dodecane. Slight differences were observed on mass flux, where V1 gave an increase of ∼7% with respect to n-dodecane. Interestingly, the amount of vaporised components which appear simultaneously in the two mixtures were not the same, which may show that there exists an interaction between the components during the vaporisation process. Despite its exploratory nature, this study offers some insight for the first time into the use of complex EoS and surrogate mixtures, which may be worth to capture the particular properties of diesel fuel during high pressure injections

Supercritical and transcritical real-fluid mixing using the PC-SAFT EOS

A numerical framework has been developed to simulate the mixing of supercritical and transcritical fluids using an equation of state based on statistical associating fluid theory. In a Diesel engine the liquid fuel is injected into supercritical air. After the injection, the Diesel is heated over its critical temperature reaching a supercritical state. Modelling real-fluid effects is critical in order to properly characterize the air/fuel mixing in the combustion chamber. By using the PC-SAFT EoS (Perturbed Chain Statistical Association Fluid Theory Equation of State) real fluids effects can be taken into account in a CFD simulation. The PC-SAFT EoS shows best results than cubic EoS computing liquid density, compressibility, speed of sound, vapor pressures and density derivatives. Unlike cubic EoS, this model accounts for the shape and size of the molecules. Gas, liquid, supercritical and vapor-liquid equilibrium states can be simulated. PT FLASH (Isothermal Multiphase Flash Calculation) is applied to compute the phase diagram used by the code. Shock tube problems were conducted in a wide range of pressures and densities using n-dodecane to show the capability of the developed algorithm. The results were compared with the solution of an exact Riemann solver which has the PC-SAFT EoS implemented showing a high degree of agreement. In addition, a two-dimensional simulation of supercritical nitrogen jet mixing was carried out to check the multidimensional capability of the code

Ionization fraction and the enhanced sulfur chemistry in Barnard 1

Barnard B1b has revealed as one of the most interesting globules from the chemical and dynamical point of view. It presents a rich molecular chemistry characterized by large abundances of deuterated and complex molecules. Furthermore, it hosts an extremely young Class 0 object and one candidate to First Hydrostatic Core (FHSC). Our aim was to determine the cosmic ray ionization rate and the depletion factors in this extremely young star forming region. We carried out a spectral survey towards Barnard 1b as part of the IRAM Large program ASAI using the IRAM 30-m telescope at Pico Veleta (Spain). This provided a very complete inventory of neutral and ionic C-, N- and S- bearing species with, up to our knowledge, the first secure detections of the deuterated ions DCS+ and DOCO+. We used a state-of-the-art pseudo-time-dependent gas-phase chemical model to determine the value of the cosmic ray ionization rate and the depletion factors. The observational data were well fitted with $\zeta_{H_2}$ between 3E-17 s$^{-1}$ and 1E-16 s$^{-1}$. Elemental depletions were estimated to be ~10 for C and O, ~1 for N and ~25 for S. Barnard B1b presents similar depletions of C and O than those measured in pre-stellar cores. The depletion of sulfur is higher than that of C and O but not as extreme as in cold cores. In fact, it is similar to the values found in some bipolar outflows, hot cores and photon-dominated regions. Several scenarios are discussed to account for these peculiar abundances. We propose that it is the consequence of the initial conditions (important outflows and enhanced UV fields in the surroundings) and a rapid collapse (~0.1 Myr) that permits to maintain most S- and N-bearing species in gas phase to great optical depths. The interaction of the compact outflow associated with B1b-S with the surrounding material could enhance the abundances of S-bearing molecules, as well.Comment: Paper accepted in Astronomy and Astrophysics; 28 pags, 21 figure

High pressure/high temperature multiphase simulations of dodecane injection to nitrogen: Application on ECN Spray-A

The present work investigates the complex phenomena associated with pressure/high temperature dodecane injection for the Engine Combustion Network (ECN) Spray-A case, employing more elaborate thermodynamic closures, to avoid well known deficiencies concerning density and speed of sound prediction using traditional cubic models. A tabulated thermodynamic approach is proposed here, based on log10(p)-T tables, providing very high accuracy across a large range of pressures, spanning from 0 to 2500 bar, with only a small number of interpolation points. The tabulation approach is directly extensible to any thermodynamic model, existing or to be developed in the future. Here NIST REFPROP properties are used, combined with PC-SAFT Vapor-Liquid-Equilibrium to identify the liquid in mixtures penetration, hence avoiding the use of an arbitrary threshold for mass fraction. Identified liquid and vapour penetration are compared against experimental data from the ECN database showing a good agreement, within approximately 3–8% for axial penetration of liquid, 2% for vapor axial penetration and within experimental uncertainty for radial distribution of mass fraction. Analysis of the vortex evolution indicates that driving mechanisms behind the jet break-up are vortex tilting/stretching, then baroclinic torque, leading to Rayleigh-Taylor instabilities, closely followed by vortex dilation and finally viscous effects

The chemistry of H2NC in the interstellar medium and the role of the C + NH3 reaction

We carried out an observational search for the recently discovered molecule H2NC, and its more stable isomer H2CN, toward eight cold dense clouds (L1544, L134N, TMC-2, Lupus-1A, L1489, TMC-1 NH3, L1498, and L1641N) and two diffuse clouds (B0415+379 and B0355+508) in an attempt to constrain its abundance in different types of interstellar regions and shed light on its formation mechanism. We detected H2NC in most of the cold dense clouds targeted, 7 out of 8, while H2CN was only detected in 5 out of 8 clouds. The column densities derived for both H2NC and H2CN are in the range 1e11-1e12 cm-2 and the abundance ratio H2NC/H2CN varies between 0.51 and >2.7. The metastable isomer H2NC is therefore widespread in cold dense clouds where it is present with an abundance similar to that of H2CN. We did not detect either H2NC or H2CN in any of the two diffuse clouds targeted, which does not allow to shed light on how the chemistry of H2NC and H2CN varies between dense and diffuse clouds. We found that the column density of H2NC is correlated with that of NH3, which strongly suggests that these two molecules are chemically linked, most likely ammonia being a precursor of H2NC through the C + NH3 reaction. We performed electronic structure and statistical calculations which show that both H2CN and H2NC can be formed in the C + NH3 reaction through two different channels involving two different transition states which lie very close in energy. The predicted product branching ratio H2NC/H2CN is very method dependent but values between 0.5 and 0.8 are the most likely ones. Therefore, both the astronomical observations and the theoretical calculations support that the reaction C + NH3 is the main source of H2NC in interstellar clouds.Comment: Accepted for publication in A&