The 1999 Athens (Greece) Earthquake: Energy and Duration- Related Response Spectral Characteristics of Different Site Conditions

An earthquake of September 7, 1999 (M5.9) has occurred in the Athens (Attika) area and was felt in almost all central Greece. The earthquake caused a lot of damage and extensive loss of life. The most damaged region is located within a distance of 10 km from the epicenter and numerous modem buildings and industrial facilities collapsed. The accelerograms, which have been recorded during the main event, are processed and compared with the empirical predictive relations proposed for Greece. For each record, the bracketed and significant duration as well as various energy-related measures are estimated. The correlation of these measures with the macroseismic intensity of the particular accelerographic site is then examined. Thus, the destructiveness of the individual records, based solely on the analysis of the ground motion process, is established. The influence of duration and frequency content on structural damage is then incorporated into the response spectral values via the adoption of novel site-dependent probabilistic 3Dspectra. Finally all the above characteristics are compared in order to select the strong-motion properties and response spectral parameters that encapsulate the damage potential of the seismic action and therefore are best suited for design purposes

Estimation of the seismic hazard parameters for various sites in Greece using a probabilistic approach

International audienceThe probabilistic approach that was recently introduced by Kijko and Graham (1998,1999) was applied for the estimation of seismic hazard for various sites in Greece in terms of peak ground acceleration (PGA) and peak ground velocity (PGV). These sites represent geographically cities of Greece among which are the capital of Greece and some others with high, intermediate and low seismicity. The approach allows the use of earthquake catalogues with incomplete reported historical and complete instrumental data, the consideration of different magnitude thresholds, and the incorporation of magnitude uncertainties. One of the advantages of the method is that it does not require any determination of seismic zones. The estimated values of PGA for return periods of 476 years were grouped in 4 categories, the same ones used in the seismic hazard map for the New Seismic Code of Greece. Comparison results were quite interesting and very encouraging concerning the reliability of this probabilistic approach

A generalized gas-liquidsolid three-phase flow analysis for airlift pump design

The object of the present study is to access the performance of an airlift pump under predetermined operating conditions. The gas-liquid-soli

Stress echocardiography in elderly patients with coronary artery disease Applicability, safety and prognostic value of dobutamine and adenosine echocardiography in elderly patients

AbstractObjectives. Our aim was to determine the applicability, safety and prognostic value of adenosine and dobutamine stress echocardiography in patients ≥70 years old.Background. These tests are sometimes mandatory because of difficulties and inaccuracies in interpreting traditional electrocardiographic stress tests. Furthermore, if these tests could be used to avoid coronary arteriography and cardiac catheterization, they would become essential in the care of the elderly, whose numbers are increasing.Methods. We performed coronary arteriography and dobutamine and adenosine stress echocardiographic tests in 120 patients (72 men) ≥70 years old who entered the hospital because of chest pain and had known or suspected coronary artery disease. The stress tests were performed on separate days, within 2 weeks of coronary arteriography. Both the arteriograms and the echocardiograms were analyzed by two experts who had no knowledge of the patients' other data or the other interpreter's report. Tests were judged to have positive or negative results, and the patients were followed up for the development of cardiac events. Univariate and multivariate analyses and other statistical modalities were applied for comparisons.Results. Documented coronary artery disease was found in 89 patients. During the 14 ± 7 months of follow-up, cardiac events developed in 50 patients, including 3 (7.9%) of 38 patients with negative dobutamine and 12 (20.7%) of 58 patients with negative adenosine test results. Demonstration of any abnormality on stress echocardiography was an independent factor for cardiac events, both for dobutamine (relative risk 7.3) and for adenosine (relative risk 3.0). Both cessation of dobutamine or adenosine tests and diagnosis of disease in two or more coronary vessels were also independent predictors. ST segment depression ≥1 mm was related to future events only with the dobutamine test.Conclusions. These echocardiographic stress tests proved safe and well tolerated. They successfully stratified this cohort of elderly patients with coronary artery disease to low or high risk subgroups for subsequent cardiac events

Spatio-temporal Models of Lymphangiogenesis in Wound Healing

Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis), very few have been proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a markedly different process from angiogenesis, occurring at different times and in response to different chemical stimuli. Two main hypotheses have been proposed: 1) lymphatic capillaries sprout from existing interrupted ones at the edge of the wound in analogy to the blood angiogenesis case; 2) lymphatic endothelial cells first pool in the wound region following the lymph flow and then, once sufficiently populated, start to form a network. Here we present two PDE models describing lymphangiogenesis according to these two different hypotheses. Further, we include the effect of advection due to interstitial flow and lymph flow coming from open capillaries. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from biological data. The models are then solved numerically and the results are compared with the available biological literature.Comment: 29 pages, 9 Figures, 6 Tables (39 figure files in total