Proposal on Non-Linear Response Analysis Method in Frequency

The objective of this report is to propose a non-linear response analysis method in frequency domain based on the stress and strain relationship of soil in frequency domain. First of all, a new model for the strain and frequency dependent characteristics between shear modulus and damping constant with respect to the complex shear modulus is proposed, considering the following two characteristics; One is the similarity of stress-strain relationship between time domain and frequency domain. The other one is a non-stationary characteristics in frequency domain caused by non-linearity of soil. A new non-linear dynamic response analysis method in frequency domain is proposed by incorporating the new model of the stress-strain relationship in frequency domain into the commonly used nonlinear response analysis method in frequency domain. The accuracy of this method is evaluated by the comparison of the analytical results obtained by two kind of non-linear dynamic response analysis codes. Hence, “YUSAYUSA2” and “SHAKE” is used as the co de in time domain, in frequency domain respectively. It is found that this proposed method is useful to take into account of nonstationary behavior caused by non-linearity of soil

Essential roles of angiotensin II in vascular endothelial growth factor expression in sleep apnea syndrome

SummaryBackgroundHypoxia-induced endothelial cell dysfunction has been implicated in increased cardiovascular disease associated with obstructive sleep apnea syndrome (OSAS). OSAS mediates hypertension by stimulating angiotensin II (Ang II) production. Hypoxia and Ang II are the major stimuli of vascular endothelial growth factor (VEGF), which is a potent angiogenic cytokine and also contributes to the atherogenic process itself.Methods & resultsWe observed serum Ang II and VEGF levels and peripheral blood mononuclear cell (PBMC) and neutrophil VEGF expression. Compared to controls, subjects with OSAS had significantly increased levels of serum Ang II and VEGF and VEGF mRNA expression in their leukocytes. To examine whether Ang II stimulates VEGF expression in OSAS, we treated PBMCs obtained from control subjects with Ang II and with an Ang II receptor type 1 (AT1) blocker, olmesartan. We observed an increased expression of VEGF in the Ang II-stimulated PBMCs and decreased in VEGF mRNA and protein expression in the PBMCs treated with olmesartan.ConclusionsThese findings suggest that the Ang II-AT1 receptors pathway potentially are involved in OSAS and VEGF-induced vascularity and that endothelial dysfunction might be linked to this change in Ang II activity within leukocytes of OSAS patients

Light Element Production in the Circumstellar Matter of Energetic Type Ic Supernovae

We investigate energetic type Ic supernovae as production sites for Li6 and Be in the early stages of the Milky Way. Recent observations have revealed that some very metal-poor stars with [Fe/H]<-2.5 possess unexpectedly high abundances of Li6. Some also exbihit enhanced abundances of Be as well as N. From a theoretical point of view, recent studies of the evolution of metal-poor massive stars show that rotation-induced mixing can enrich the outer H and He layers with C, N, and O (CNO) elements, particularly N, and at the same time cause intense mass loss of these layers. Here we consider energetic supernova explosions occurring after the progeniter star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta can interact directly with the circumstellar matter (CSM), both composed of He and CNO, and induce light element production through spallation and He-He fusion reactions. The CSM should be sufficiently thick to energetic particles so that the interactions terminate within its innermost regions. We calculate the resulting Li6/O and Be9/O ratios in the ejecta+CSM material out of which the very metal-poor stars may form. We find that they are consistent with the observed values if the mass of the He layer remaining on the pre-explosion core is 0.01-0.1 solar mass, and the mass fraction of N mixed in the He layer is about 0.01. Further observations of Li6, Be and N at low metallicity should provide critical tests of this production scenario.Comment: 12 pages, 2 figures, revised with referee suggestions, final version accepted in ApJ Letter