Articles you may be interested inA study on density functional theory of the effect of pressure on the formation and migration enthalpies of intrinsic point defects in growing single crystal Si Comment on "Assessment of complete basis set methods for calculation of enthalpies of formation" [J. Chem.A comprehensive set of 600 experimental standard enthalpies of formation (⌬H f 0 ) is presented. With its diverse species, many possessing less usual geometries and bonding situations, this compilation is capable of uncovering deficiencies in approaches of quantum chemistry that are not detectable with smaller sets of ⌬H f 0 values. Its usefulness in benchmarking, calibration, and parametrization of new electronic structure methods is illustrated with the development of the B3LYP/6-311ϩϩG** bond density functional scheme. This scheme, which is sufficiently inexpensive in terms of computer time and memory to allow predictions even for molecules as large as the C 60 fullerene, requires only single point calculations at optimized geometries. It yields values of ⌬H f 0 with the average absolute error of 3.3 kcal/mol, rivaling more expensive methods in accuracy ͑especially for larger systems͒. A list of species that are poorly handled by a typical hybrid density functional used in conjunction with a moderate-size basis set is given. This list is intended for rigorous testing of new density functionals.

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Evidence has indicated that plasma ghrelin was elevated in chronic heart failure (CHF) patients with cachexia. The present report studied whether pathophysiologic increment of endogenous ghrelin levels was existed in the progression of adriamycin (ADR)-induced CHF, then the possible compensatory mechanism by which the changes were induced and the relationship between active ghrelin, cardiac function and energy reserve in heart failure (HF) rats were explored. Cardiac function, high energy phosphates (HEP) content, and ghrelin levels in plasma and myocardium were measured at 4 days, 1, 2 and 3 weeks after the last injection of ADR, after which correlation analysis was performed between these markers in HF rats. Results showed that cardiac function decreased early, then was significantly restored and worsened at 3 weeks accompanied by the decrease of myocardial ATP content. Plasma ghrelin level increased significantly at each time point while myocardial ghrelin level increased transiently, then was restored followed by increased oxidative stress status and apoptosis in the weakening heart. Moreover, correlation analysis indicated that the markers of cardiac function and HEP were positively correlated to the endogenous ghrelin levels at the HF stage. This study indicated that the increase of endogenous ghrelin levels during the progression of the HF induced by ADR represent a compensatory self-protective effect by improving cardiac function and retaining myocardial energy reserve; this may be closely linked to anti-oxidative and anti-apoptosis mechanisms through regulating myocardial mitochondria function by ghrelin; but further investigations are necessary.

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Quasi-periodic responses can appear in a wide variety of nonlinear dynamical systems. To the best of our knowledge, it has been a tough job for years to solve quasi-periodic solutions, even by numerical algorithms. Here in this paper, we will present effective and accurate algorithms for quasi-periodic solutions by improving Wilson-θ and Newmark-β methods, respectively. In both the two methods, routinely, the considered equations are re-arranged in the form of incremental equilibrium equations with the coefficient matrixes being updated in each time step. In this study, the two methods are improved via a predictor-corrector algorithm without updating the coefficient matrixes, in which the predicted solution at one time point can be corrected to the true one at the next. Numerical examples show that, both the improved Wilson-θ and Newmark-β methods can provide much more accurate quasi-periodic solutions with a smaller amount of computational resources. With a simple way to adjust the convergence of the iterations, the improved methods can even solve some quasi-periodic systems effectively, for which the original methods cease to be valid.