EFFECTS OF ANGLE OF INCIDENCE OF SH-WAVE AT THE BASIN-EDGE ON THE CHARACTRISTICS OF BASIN-EDGE INDUCED LOVE WAVE

This paper presents the effects of angle of incidence of SH-wave at the basin-edge on the characteristics of basin-edge induced Love waves and associated strain and aggravation factor (aggravation factor is simply the extra spectral amplification due to complex 2D site effects over the 1D response of the soil column). The linear seismic responses of basin-edge model with various edge-slopes were computed using SH-wave finite difference algorithm with second-order accuracy in time and fourth-order accuracy in space. The analysis of simulated results revealed an increase of amplitude of induced Love waves, differential ground motion (strain), and aggravation factor with decrease of basin-edge slope and increase of angle of incidence of SH-wave at the basin-edge. Maximum strain of the order of 9.23 × 10-4 (for 1.0 cm peak ground displacement at the bedrock) was obtained at an offset of 60.0 m (0.47λF0, where λF0 is the fundamental wavelength), in case of 84.4° angle of incidence of SH-wave. Further, the percentage increase of strain with respect to the strain in case of normal incidence of SH-wave was almost equal to the angle of incidence of SH-wave at the basin-edge.

Reinfections with strains of Trypanosoma cruzi, of different biodemes as a factor of aggravation of myocarditis and myositis in mice

Reinfections with Trypanosoma cruzi in patients from endemic areas have been claimed to be an aggravation factor of cardiac manifestations in Chagas' disease. In the present study, the influence of triple infections with strains of different biodemes, on cardiac and skeletal muscle lesions was experimentally tested. Fifty eight mice chronically infected with the Colombian strain (Biodeme Type III) were successively reinfected as follows: 1st group - reinfected with 21 SF strain (Type II) followed by Y strain (Type I ); 2nd - group reinfections with Y strain followed by 21SF strain. Isoenzyme analysis of parasites from hemocultures obtained from triple infected mice, revealed the patterns of three distinct zymodemes in the same animal. Each Trypanosoma cruzi strain was reisolated after four passages in mice on either the 7th, 14th or 30th day after inoculation with the blood of triple infected mice. Histopathology results demonstrated a significant exacerbation of cardiac and skeletal muscle inflammatory lesions, confirmed by morphometric evaluation, in mice with triple infection. No aggravation of parasitism was detected. The possibility of an enhancement of cellular response in the triple infected mice is suggested.

Soil-Dependent Topographic Effects: A Case Study from the 1999 Athens Earthquake

In the Ms 5.9 Athens, Greece, earthquake, surprisingly heavy damage occurred on the eastern bank of the Kifissos River canyon. To explore whether the particular topographic relief and/or the local soil conditions have contributed to the observed concentration and non-uniform damage distribution within a 300-m zone from the canyon crest, we conduct finite-element analyses in one and two dimensions, using Ricker wavelets and six realistic accelerograms as excitation. The nonlinear soil response is simulated in the time-domain using a hyperbolic stress-strain model, and also approximated using a modified equivalent-linear algorithm; results obtained by means of the two methods are discussed in detail. Our simulations show that topographic effects are substantial only within about 50 m from the canyon ridge, materializing primarily because of the presence of relatively soft soil layers near the surface of the profile. We then introduce the concept of two-dimensional/one-dimensional response spectral ratio to describe the effects of topography as a function of local soil conditions, and suggest a frequency- and location-dependent topographic aggravation factor to be introduced for the modification of design spectra in a seismic code.