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A study of the crystallization behavior and mechanical properties of random isotactic butene–ethylene copolymers prepared with a metallocene catalyst is presented. The use of the metallocene catalysis ensures a fine control over the molecular structure with low concentration of rr stereodefects (0.8%), negligible amount of regiodefects, and random and uniform distribution of ethylene constitutional defects. This molecular characteristic has allowed evidencing the only effect of the presence of ethylene units on the polymorphic behavior and mechanical properties of isotactic polybutene (iPB). The presence of ethylene accelerates the transition of form II into form I at room temperature and at concentration of nearly 6 mol % favors the direct crystallization from the melt of the stable form I. The presence of ethylene also affects the mechanical behavior of iPB and produces increase of flexibility and ductility with increasing ethylene content. A significant modification of the properties of iPB is observed for ethylene concentration higher than 8 mol %, with development of elastomeric properties, never observed for the iPB homopolymer prepared with Ziegler–Natta catalysts and not observed in the iPB homopolymer with similar content of stereo defects. In these samples, elastomeric properties are due to the low degree of crystallinity that develops upon aging at room temperature by direct crystallization of form I′ from the amorphous phase.

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The sol-gel method is an attractive synthetic approach in the design of advanced catalytic formulations that are based on metal and metal oxide with high degree of structural and compositional homogeneity. Nowadays, though it originated with the hydrolysis and condensation of metal alkoxides, sol-gel chemistry gathers plenty of fascinating strategies to prepare materials from solution state precursors. Low temperature chemistry, reproducibility, and high surface to volume ratios of obtained products are features that add merit to this technology. The development of different and fascinating procedure was fostered by the availability of new molecular precursors, chelating agents and templates, with the great advantage of tailoring the physico-chemical properties of the materials through the manipulation of the synthesis conditions. The aim of this review is to present an overview of the “traditional” sol-gel synthesis of tailored and multifunctional inorganic materials and their application in the main domain of heterogeneous catalysis. One of the main achievements is to stress the versatility of sol-gel preparation by highlighting its advantage over other preparation methods through some specific examples of the synthesis of catalysts.

Spatial modeling of ground motion intensity measures (IMs) is required for risk assessment of spatially distributed engineering systems. For example, when a lifeline system is of concern, classical site-specific hazard tools, which treat IMs at different locations independently, may not be adequate to accurately assess the seismic risk. In fact, in this case, modeling of ground motion as a random field is required; it basically consists of assigning a correlation structure to the IM of interest. This work focuses on semiempirical estimation of the correlation coefficient, as a function of intersite separation distance, between residuals with respect to ground motion prediction equations (GMPEs) of horizontal peak ground acceleration (PGA) and peak ground velocity (PGV). In particular, subsets of the European Strong-Motion Database (ESD) and the Italian Accelerometric Archive (ITACA) were employed to evaluate the intraevent residual correlation based on multiple earthquakes, considering different GMPEs fitted to the same records. The analyses were carried out through geostatistical tools, which enabled results to be found that are generally consistent between the two datasets. Correlation for PGV appears to attenuate more gradually with respect to PGA. In order to better understand the dependency of the results on the adopted estimation approach and dataset, some aspects related to the working hypotheses are critically discussed. Finally, estimated correlation models are used to develop illustrative applications of regional probabilistic seismic-hazard analysis.

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Quantification of regional seismic risk is based on spatially correlated random fields and requires modeling of the joint distribution of ground-motion intensity measures at all sites of interest. In particular, when a portfolio of buildings or a transportation/distribution network (lifeline) is of concern, correlation models for elastic spectral acceleration (SA) may also be required in order to estimate the expected loss in case of seismic events. The presented study focuses on semi-empirical estimation of spatial correlation as a function of intersite separation distance. In fact, this paper complements, and is based on, preceding work of the authors referring to spatial correlation of peak ground acceleration and velocity (Esposito and Iervolino, 2011). The evaluation of correlation for ground-motion residuals was performed on data from multiple earthquakes, considering different ground-motion prediction equations fitted to the same records. Correlation analyses, carried out through geostatistical tools, considered two datasets: the Italian Accelerometric Archive and the European Strong-Motion Database. Results appear generally consistent with previous research on the same topic. Finally, simple relationships providing the correlation range of intraevent residuals of SA, as a function of structural period, were derived for each dataset. The developed models are useful for earthquake engineering applications where spatial correlation of peak ground motion is required.

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