Search Results - (Author, Cooperation:C. S. Oliveira)

2014-01-28

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Arginine/chemistry/metabolism ; Binding Sites ; Cellular Reprogramming/genetics ; Chromatin/chemistry/*metabolism ; *Chromatin Assembly and Disassembly ; Citrulline/*metabolism ; DNA/metabolism ; Embryo, Mammalian/cytology/metabolism ; Gene Expression Regulation ; Histones/*chemistry/*metabolism ; Hydrolases/metabolism ; Mice ; Pluripotent Stem Cells/cytology/*metabolism ; Protein Binding ; *Protein Processing, Post-Translational ; Proteomics ; Substrate Specificity ; Transcription, Genetic

1573-0840

Hazard analysis ; recurrence ; probability of exceedence ; zoning ; uncertainties ; time-space interdependence

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Geography

Geosciences

Abstract The Azores Islands are located in the mid-Atlantic region near the triple junction where the Euro-Asiatic-African-American plates join together. Seismic activity in the area is very high, as can be observed either from historical events since the fifteenth century, from present day microseismicity, and from direct and indirect measurements of recent tectonic deformation. Volcanic activity is also present throughout the region. All available information, even data exhibiting low quality, was used to develop hazard models of São Miguel Island. Source zones were established based on both the global tectonic behaviour of the region and on the local active fault structures. Recurrence laws for São Miguel Island, for which historical information seemed quite incomplete, were obtained from the large events in the entire archipelago and from their remarkable pattern of time and space dependence, and complimented by information on long-term fault deformation (for the longer recurrence periods) and on high precision instrumental network (for the very short recurrence periods). Attenuation laws were derived from data on events felt and/or recorded in the Island. Hazard maps were obtained through a modified version of McGuire's algorithm for several geometries of source areas and results compared with the maximum observed intensity of historical events.

Electronic Resource

1573-0840

seismic hazard ; geological conditions ; attenuation laws ; statistical analyses ; Portugal

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Geography

Geosciences

Abstract The object of this study is to consider directly the influence of regional geological conditions on the assessment of seismic hazard. It is assumed that macroseismic data at individual locations contain, in an average way, the influence of geological conditions. A Data Base referring to 199 historical (5) and instrumental (194, in the 1947–1993 period) events with macroseismic information in 1195 locations of Portugal was built. For any given seismic event, whenever macroseismic information was available at a location (town, village, etc.), an EMS-92 intensity value was estimated. To each one of those locations a geological unit, representing the most common type of soil, was assigned, based on the Geological Portuguese Map at a scale 1:500 000; the geological units were grouped into three categories: soft, intermediate and hard soils. The Data Base was used to determine the attenuation laws in terms of macroseismic intensity for the three different geological site conditions, using multiple linear regression analysis. The reasonability of the laws was tested by (i) checking residual distributions and (ii) comparing the map of isoseismals of important earthquakes with the isoseismals generated by the attenuation curves derived for each one of the three different soil classes, taking into consideration the soil class of each site. The main results of attenuation modeling are: high dispersion on macroseismic intensity data; all the models predict intensity values, for short hypocentral distances, lower than the ones observed; and for some important analyzed earthquakes and for the observed range of distances, the models confirm the expectancy that macroseismic intensity increases from hard to soft soil. The approach to obtain the hazard assessment at each location consisted in the use of the attenuation law specifically derived for the class of soil of that particular location. This method, which considers the influence of the regional geology, was illustrated with the mapping of hazard for the country for several return periods. Comparison with previous maps not taking into consideration the regional geological conditions emphasizes the importance of this new parameter. It can be concluded that (i) soil segmentation is clearly the cause for hazard increase in the region to the north of Lisbon, especially at sites with soft and intermediate soils as the ones in lower Tagus valley; the maximum increase on hazard is, in any case, less than one degree; (ii) when geological conditions are disregarded in the attenuation regression analysis, hazard pattern is similar to the one obtained for the case of hard soil everywhere.

Electronic Resource

1573-0840

acceleration ; attenuation ; digital recording ; dispersion ; displacement ; frequencies ; path ; ratios ; site ; source ; velocity

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Geography

Geosciences

Abstract During experiments with digital stations in the period 1985–1987, twenty five earthquakes with magnitudes m b in the range 2.9 to 4.8 and epicentres located within the area 36°–42.3° (N) and 4.5°–13.6° (W) were recorded at Montemor (MOE) and Montachique (MTH). The three-component recordings were obtained by Geotech S13 instruments with 1 second period. A preliminary analysis of the recordings consisted in the determination of amplitudes and spectral contents of P and S waves, and led to the following observations: (1) The attenuation of waves is expressed by the equation V = exp(C 2).R C 1. exp(C 3.M), where V stands for acceleration, velocity or displacement; M-magnitude; R-focal distance; C 1, C 2 and C 3 are constants to be obtained by least square fitting. The application of this equation led to C 1 of the order 1.7 for displacement, 1.8 for velocity and 2.0 for acceleration, with an average mean square error σ ≈ 0.8. (2) The ratios L/T (longitudinal/transversal amplitudes), for velocity and displacement, showed a tendency to reduce with increasing focal distance, being 2 for short distances (〈50 km) and 1 for long distances (≈400 km). (3) The ratios S/P (S-wave/P-wave amplitudes), although with a large dispersion, showed a slight tendency for increasing with focal distance. (4) The predominant frequencies also showed a slight tendency to decrease with increasing focal distance and with magnitude. (5) The dependence of C 1 with frequency (3 to 12 Hz) is well behaved from 0.95 to 1.75 (for the velocity trace).

Electronic Resource