Entropic and enthalpic effects of 4-methoxy substitution in phenoxyl radicals

Values of ΔH_3=(–12.4 ± 1.6) kJ mol^(–1), ΔS_3=(–18.5 ± 5.6) J K^(–1) mol^(–1) for reaction (3) (see text), corresponding to an O–H bond energy of 322.2 kJ mol^(–1) in 1, and to a 14.5 J K^(–1) mol^(–1) entropy loss for the CH_3O–Ar (Ar = aromatic) libration in 2 relative to 1, are derived from the temperature dependence of the equilibrium constant K_3, determined by EPR spectrometry in benzene–toluene media, between 251 and 304 K. These results allow, for the first time, discrimination between enthalpic and entropic effects on the rates of (O)H-atom abstraction by peroxyl radicals from 4-methoxyphenols and related species

Dynamics of ignition of stoichiometric hydrogen-air mixtures by moving heated particles

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work, two-dimensional simulations with detailed chemistry are used to study the reaction pathways of the transient flow and ignition of a stoichiometric hydrogen/air mixture by moving hot spheres. For temperatures above the ignition threshold, ignition takes place after a short time between the front stagnation point and separation location depending upon the sphere's surface temperature. Closer to the threshold, the volume of gas adjacent to the separation region ignites homogeneously after a longer time. These results demonstrate the importance of boundary layer development and flow separation in the ignition process

Effects of differential diffusion on ignition of stoichiometric hydrogen-air by moving hot spheres

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work, two-dimensional simulations with detailed chemistry are used to study the effect of differential diffusion on the prediction of ignition thresholds of a stoichiometric hydrogen-air mixture by moving hot spheres. Numerical experiments showed an increase of 40 K in the minimum ignition temperature required for ignition when diffusion of species at different rates is taken into account. Detailed analysis of the species profiles at the ignition location and a sensitivity study of the system to the diffusivity of H_2 and H revealed the key role played by the diffusion of H atoms in preventing ignition to take place at temperatures below 1000 K

Dynamics of ignition of stoichiometric hydrogen-air mixtures by moving heated particles

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work, two-dimensional simulations with detailed chemistry are used to study the reaction pathways of the transient flow and ignition of a stoichiometric hydrogen/air mixture by moving hot spheres. For temperatures above the ignition threshold, ignition takes place after a short time between the front stagnation point and separation location depending upon the sphere's surface temperature. Closer to the threshold, the volume of gas adjacent to the separation region ignites homogeneously after a longer time. These results demonstrate the importance of boundary layer development and flow separation in the ignition process

Effects of differential diffusion on ignition of stoichiometric hydrogen-air by moving hot spheres

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work, two-dimensional simulations with detailed chemistry are used to study the effect of differential diffusion on the prediction of ignition thresholds of a stoichiometric hydrogen-air mixture by moving hot spheres. Numerical experiments showed an increase of 40 K in the minimum ignition temperature required for ignition when diffusion of species at different rates is taken into account. Detailed analysis of the species profiles at the ignition location and a sensitivity study of the system to the diffusivity of H_2 and H revealed the key role played by the diffusion of H atoms in preventing ignition to take place at temperatures below 1000 K

Flame burning speeds and combustion characteristics of undiluted and nitrogen-diluted hydrogen-nitrous oxide mixtures

In the present study, some explosive properties of undiluted and nitrogen-diluted H_2–N_2O mixtures were characterized. Laminar burning speeds and the explosion-induced pressure rises were determined experimentally for a range of mixture equivalence ratios (ϕ=0.15−1.0), dilutions (0-55%N_2) and initial pressures (20-80kPa). The measured burning speeds were used to validate laminar burning speed computations using a detailed chemical kinetic mechanism. The computations were then used to estimate burning speeds at high initial pressure and low dilution conditions that could not be measured experimentally. The results demonstrate that hydrogen–nitrous oxide mixtures exhibit laminar burning speeds as large as 350 cm/s and pressure rise coefficients (K_g) as large as 35 MPa m/s. Also, flames in lean mixtures are shown to be highly unstable which can lead to flame acceleration and possible deflagration-to-detonation transition

In silico ischaemia-induced reentry at the Purkinjeventricle interface

This computational modelling work illustrates the influence of hyperkalaemia and electrical uncoupling induced by defined ischaemia on action potential (AP) propagation and the incidence of reentry at the Purkinjeventricle interface in mammalian hearts. Unidimensional and bidimensional models of the Purkinjeventricle subsystem, including ischaemic conditions (defined as phase 1B) in the ventricle and an ischaemic border zone, were developed by altering several important electrophysiological parameters of the LuoRudy AP model of the ventricular myocyte. Purkinje electrical activity was modelled using the equations of DiFrancesco and Noble. Our study suggests that an extracellular potassium concentration [K](o) 14 mM and a slight decrease in intercellular coupling induced by ischaemia in ventricle can cause conduction block from Purkinje to ventricle. Under these conditions, propagation from ventricle to Purkinje is possible. Thus, unidirectional block (UDB) and reentry can result. When conditions of UDB are met, retrograde propagation with a long delay (320 ms) may re-excite Purkinje cells, and give rise to a reentrant pathway. This induced reentry may be the origin of arrhythmias observed in phase 1B ischaemia. In a defined setting of ischaemia (phase 1B), a small amount of uncoupling between ventricular cells, as well as between Purkinje and ventricular tissue, may induce UDBs and reentry. Hyperkalaemia is also confirmed to be an important factor in the genesis of reentrant rhythms, since it regulates the range of coupling in which UDBs may be induced.This work was supported: (i) by the European Commission preDiCT grant (DG-INFSO-224381), (ii) by the 'VI Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica' from the Ministerio de Economia y Competitividad of Spain (grant number TIN2012-37546-C03-01) and the European Commission (European Regional Development Funds - ERDF - FEDER), and (iii) by the Programa de Apoyo a la Investigacioon y Desarrollo (PAID-06-11-2002) de la Universidad Politecnica de Valencia, Programa Prometeo (PROMETEO/2012/030) de la Conselleria d'Educacio Formacio I Ocupacio, Generalitat Valenciana, and (iv) Direccion General de Politica Cientifica de la Generalitat Valenciana (GV/2013/119).Esteban Ramírez, J.; Saiz Rodríguez, FJ.; Romero Pérez, L.; Ferrero De Loma-Osorio, JM.; Trénor Gomis, BA. (2014). In silico ischaemia-induced reentry at the Purkinjeventricle interface. EP-Europace. 16(3):444-451. https://doi.org/10.1093/europace/eut386S44445116

Empirical Study Between Compiled, Interpreted, and Dynamic Programming Languages Applying Stable Ordering Algorithms (Case Study: Java, Python, Jython, Jpype and Py4J)

This article allows to investigate benchmark between programming languages, with the objective of identifying the performance between the execution time and the memory use between the Java and Python languages, as well as, in three implementations of dynamic languages that combine the two aforementioned languages: Jython, Jpype, Py4J. According to the results, it is concluded that the language that obtains the best performance is Py4J.   Keywords: programming languages, benchmark, algorithms, compiler