To assess the effects of age on both the pituitary ACTH response to corticotropin-releasing hormone (CRH) and the secretory responses of cortisol (F) and dehydroepiandrosterone (DHEA) to endogenous rises in ACTH, we measured evening basal and ovine CRH (oCRH; 1 mu/kg)-stimulated plasma concentrations of ACTH,F, and DHEA in 49 healthy men, aged 21-86 yr. By analysis of variance, we found no change with age in either the basal concentration of ACTH or the magnitude of the peak ACTH response to oCRH. Older men had higher basal F levels (P less than 0.05), while basal plasma levels of CBG and ratios of F to CBG did not vary significantly with age (P greater than 0.1). We also found no significant increase with age in the magnitude of the peak F response to oCRH (P greater than 0.2), although peak F responses occurred significantly earlier (P less than 0.03) in the older men. Basal plasma levels of DHEA decreased significantly with age (P less than 0.001), as did the magnitude of peak DHEA responses to endogenous ACTH rises (P less than 0.01). There was no alteration in the timing of the peak DHEA response with age (P greater than 0.7). We conclude that while ACTH and F responses to evening injections of oCRH are well maintained in healthy aging men, that of DHEA is discordantly decreased. The present findings are compatible with the hypotheses that there is a diminished sensitivity of ACTH secretion to negative feedback regulation by glucocorticoids in older men, and there is an ACTH-independent age-related diminution in adrenal androgen secretion.
Article Adrenocorticotropin Hypersecretion and Pituitary Microadenoma Following Bilateral Adrenalectomy in a Patient with Classic 21-Hydroxylase Deficiency was published on January 1, 2005 in the journal Journal of Pediatric Endocrinology and Metabolism (volume 18, issue 1).
A simplified procedure is developed to consider the azimuthal orientation of buildings when estimating seismic risk. Two square‐plan reinforced concrete building models are considered as a testbed, one with similar and one with dissimilar properties along the two principal horizontal axes. The fragility of both structures is analysed using a set of ground motion records rotated to multiple incidence angles to develop orientation‐dependent fragility functions. It has been observed that, re‐orienting all records so that these structures have the same azimuth vis‐à‐vis the corresponding epicentre leads to significant differences compared to assuming random orientations. Additional results stemming from single‐degree‐of‐freedom oscillators further confirm such findings, showing a dependence to the proximity to the faults and the level of dissimilarity in the principal horizontal axes of the structure. The end results point to a non‐negligible bias in assessment studies when a structure's orientation with respect to governing rupture scenarios is not taken into account. It is shown that the median of fragility curves calculated for un‐rotated incidence angles can be bias‐corrected through shifted by an amount that depends on the azimuthal orientation and level of axes‐dissimilarity of structures.
Traditional or historic masonry structures occur in large populations throughout the world, particularly in preserved historical city clusters. Being non-engineered and aging these structures are in urgent need of assessment and seismic repair/rehabilitation. However, traditional masonry presents important challenges to computational modeling, owing to complexity of structural system, material inhomogeneity, and contact interactions that collectively can only be addressed through detailed 3D nonlinear representation. In this article, a simple performance assessment model is developed in order to address the need for preliminary assessment tools for this class of structures. The objective is to be able to rapidly identify buildings that are at higher risk in the event of a significant earthquake, potentially justifying a second round of more detailed evaluation. The proposed model defines the characteristics of a Single Degree of Freedom representation of the building, formulating consistent 3D shape functions to approximate its fundamental mode of vibration considering both in-plane and out-plane wall bending as a result of insufficient diaphragm action. Parametric expressions for the dynamic properties are derived in terms of the important geometric, material, and system characteristics, and are used to express local demand from global estimates. Acceptance criteria are established both in terms of deformation and strength indices to guide retrofit. An application example of the proposed assessment methodology is included to demonstrate the ability of the model to reproduce the essential features of traditional masonry buildings under seismic action.
No abstract is provided for this article.
Summary The selection of a scalar Intensity Measure (IM) for performing analytical vulnerability (loss) assessment across a building class is addressed. We investigate the ability of several IM choices to downgrade the effect of seismological parameters (sufficiency) as well as reduce the record‐to‐record variability (efficiency) for both highrise and lowrise sets of ‘index’ buildings. These characteristics are explored in unprecedented detail, employing comparisons and statistical significance testing at given levels of local engineering demand parameters (story drift ratios and peak floor accelerations) that relate to losses, instead of global variables such as the maximum interstory drift. Thus, a detailed limit‐state‐specific view is offered for the suitability of different scalar IMs for loss assessment. As expected, typical single‐period spectral values are found to introduce unwanted bias at high levels of scaling, both for a single as well as a class of buildings. On the other hand, the geometric mean of the spectral acceleration values estimated at several periods between the class‐average second‐mode and an elongated class‐average first‐mode period offers a practical choice that significantly reduces the spectral‐shape bias without requiring the development of new ground motion prediction equations. Given that record selection remains a site‐ and building‐specific process, such an improved IM can help achieve reliable estimates for building portfolios, as well as single structures, at no additional cost. Copyright © 2015 John Wiley & Sons, Ltd.
Wind Turbines constitute a sustainable and effective solution for the production of energy using wind power.Offshore wind turbines especially are becoming of special interest.However, their design poses great challenges, since an offshore structure is subject to combined wind and wave dynamic loading that is characteristic of the site of installation.The purpose of this paper is to provide a case study of fatigue life assessment for the cross-section at mudline (foundation) of a standard offshore wind turbine with a monopile design, under a probabilistic framework and assuming the thickness of the examined cross-section as the design variable.Two potential sites of construction in the Aegean Sea of Greece were examined.A probabilistic approach was employed in order to determine the fatigue life based on anemological data at each of the two sites of interest.At its basis is an extensive Monte Carlo simulation of wind (velocity) and wave (height, period) characteristics.The results show the dependence of fatigue life on the local wind and wave conditions, the cross-section geometry (i.e. the thickness of the foundation's pile) and the welded connection detail.All in all, the more benign conditions in the Aegean allow simpler connection details and smaller thickness of foundation pile's cross-section to still have acceptable performance.
