A PRC relation for delta Scuti stars

The absolute radii of 78 Scuti variables in the Catalogue of the Geneva Observatory have been computed. A PRC relation among the period, radius and color has been obtained.     

Effects of interplanetary dust on the LISA drag-free constellation

The analysis of non-radiative sources of static or time-dependent gravitational fields in the Solar System is crucial to accurately estimate the free-fall orbits of the LISA space mission. In particular, we take into account the gravitational effects of Interplanetary Dust (ID) on the spacecraft trajectories. The perturbing gravitational field has been calculated for some ID density distributions that fit the observed zodiacal light. Then we integrated the Gauss planetary equations to get the deviations from the LISA Keplerian orbits around the Sun. This analysis can be eventually extended to Local Dark Matter (LDM), as gravitational fields are expected to be similar for ID and LDM distributions. Under some strong assumptions on the displacement noise at very low frequency, the Doppler data collected during the whole LISA mission could provide upper limits on ID and LDM densities.     

Impact of climate variability on summer fires in a Mediterranean environment (northeastern Iberian Peninsula)

We analyse the impact of climate interannual variability on summer forest fires in Catalonia (northeastern Iberian Peninsula). The study period covers 25 years, from 1983 to 2007. During this period more than 16000 fire events were recorded and the total burned area was more than 240 kha, i.e. around 7.5% of whole Catalonia. We show that the interannual variability of summer fires is significantly correlated with summer precipitation and summer maximum temperature. In addition, fires are significantly related to antecedent climate conditions, showing positive correlation with lagged precipitation and negative correlation with lagged temperatures, both with a time lag of two years, and negative correlation with the minimum temperature in the spring of the same year. The interaction between antecedent climate conditions and fire variability highlights the importance of climate not only in regulating fuel flammability, but also fuel structure. On the basis of these results, we discuss a simple regression model that explains up to 76% of the variance of the Burned Area and up to 91% of the variance of the number of fires. This simple regression model produces reliable out-of-sample predictions of the impact of climate variability on summer forest fires and it could be used to estimate fire response to different climate change scenarios, assuming that climate-vegetation-humans-fire interactions will not change significantly.     

New opacities and first overtone mode Cepheids

Some results of linear adiabatic and nonlinear pulsation models of first overtone mode Cepheids are discussed. New and augmented opacities and a nonstandard mass-luminosity relation have been taken into account. The models indicate the possible importance of the resonanceP1/P4 = 2 nearP1 = 3 days. The resonance could explain the observed characteristics of the light curve shape of first overtone mode Cepheids.     

A simplified method for predicting rainfall-induced mobility of active landslides

This paper deals with the landslides that are reactivated by a groundwater level increase owing to rainfall. These landslides are usually characterized by low displacement rate with deformations essentially concentrated within a narrow shear zone above which the unstable soil mass moves like a rigid body (i.e., with a horizontal displacement profile that is essentially constant with depth). In view of this evidence, a new method based on a simple sliding block model is proposed in the present study for a preliminary evaluation of landslide mobility. Unlike other existing methods that provide an evaluation of landslide mobility on the basis of groundwater level measurements, the present method directly relates landslide movements to rain recordings. This possibility constitutes a significant advantage from a practical viewpoint because it allows future displacement scenarios to be predicted from expected rainfall scenarios. In addition, the present method requires a limited number of parameters as input data, many of which can be obtained from conventional geotechnical tests. To evaluate the other parameters involved, an efficient calibration procedure is also proposed. Four case studies documented in the literature are analyzed to assess the capability of the present method to reproduce the main features of the slope response to rainfall. In all these case studies, both groundwater level variations and landslide displacements observed in field are well approximated by the method.     

Base isolation for retrofitting historic buildings: Evaluation of seismic performance through experimental investigation

An experimental test program on a full‐scale model representing a sub‐assemblage of the cloister facade of the Sao Vicente de Fora monastery, retrofitted through base isolation, has been recently carried out at the European Laboratory for Structural Assessment of the Joint Research Centre of the European Commission. In this paper an overview of the laboratory model and the experimental results is provided. In particular, firstly the test model is described, including the geometry and mechanical properties of the masonry specimen and the design of the isolation devices; then the testing method and the sub‐structuring of the isolation system are described and the seismic inputs adopted for the pseudo‐dynamic tests are defined. Finally, the experimental results are discussed and compared to the analogous results obtained on the ‘as is’, fixed‐base sub‐assemblage model. The implications of the test outcomes are emphasized and developments of this research line are presented. Copyright © 2001 John Wiley & Sons, Ltd.