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921.
Cristina M. Belfiore Mauro F. La Russa Antonino Pezzino Elisa Campani Antonella Casoli 《Applied Physics A: Materials Science & Processing》2010,100(3):835-844
The Baroque monuments of several cities in eastern Sicily, built of local calcarenitic stone, are often subjected to conservation
treatments, since they undergo many forms of alteration and degradation which can cause significant damage. However, a recent
study of these building materials (Barone et al. in Environ. Geol. 54:1501, 2008) has demonstrated that some protective products, once applied, cause irreversible chromatic alterations. 相似文献
922.
B. Gonzalo J. L. Vilas T. Breczewski M. A. Pérez‐Jubindo M. R. De La Fuente M. Rodriguez L. M. León 《Journal of polymer science. Part A, Polymer chemistry》2009,47(3):722-730
Three amorphous piezoelectric polyimides have been synthesized and characterized to analyze their utility for high‐temperature applications. The studied polyimides have been prepared from 4,4′‐oxydiphthalic anhydride and the diamines 2,4‐di(3‐aminophenoxy)benzonitrile (poly2‐4), 2,6‐bis(3‐aminophenoxy)benzonitrile (poly2‐6), and 1,3‐bis‐2‐cyano‐3‐(3‐aminophenoxy)phenoxybenzene (poly2CN). These polyimides differ in the position of the dipolar groups ? CN in the aromatic ring (poly2‐4 and poly2‐6) and in the number of these groups in the repetitive unit (poly2‐6 and poly2CN). The imidization degree has been studied by Fourier transform infrared (FTIR) and thermogravimetry‐mass spectrometry (TG‐MS) and thermal properties by differential scanning calorimetry (DSC) and thermogravimetry (TG). The piezoelectric behavior has been analyzed from remnant polarization measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 722–730, 2009 相似文献
923.
Low and high frequency dielectric spectroscopy on a liquid crystal with the phase sequence N*-SA-S*c
M. R. De La Fuente M. A. Pérez Jubindo J. Zubia T. Pérez Iglesias A. Seoane 《Liquid crystals》2013,40(6):1051-1063
Abstract Broadband dielectric measurements on a multicomponent ferroelectric liquid crystal mixture have been performed. The alignment was homeotropic and the cell and sample holder were the same in the whole frequency range. Two relaxation processes have been observed in all liquid crystal phases with shapes given by the Havriliak-Negami and inverted Havriliak-Negami functions. Strengths and frequencies of both modes have been obtained for the different phases. The values of the latter and their activation energies allowed us to assign the low and high frequency mechanism to the molecular reorientation around the transversal axis and around the longitudinal axis, respectively. The behaviour of this high frequency mode does not show any jump in the SA-S*c phase transition, neither in the amplitude nor in the frequency, indicating that the appearance of the spontaneous polarization in the S*c phase is not the consequence of the freezing of this mode. 相似文献
924.
Ornella Abollino Maurizio Aceto Sandro Buoso Carmela La Gioia Corrado Sarzanini Edoardo Mentasti 《International journal of environmental analytical chemistry》2013,93(6-7):471-492
The composition of seawater in the Ross Sea (Antarctica) was investigated. The distribution of heavy metals (Cd, Cu, Fe, Mn, Ni), minor and trace (B, Ba, Li, Sr, Si) and major (Na, K, Ca, Mg) elements in coastal and offshore sites was determined. The samples were collected during the XIII Campaign of the Italian “National Programme of Research in Antarctica”, PNRA, at different depths and different stages of the Antarctic summer. In the subsequent campaign the concentrations in the water top micro-layer, and just below it, were compared. Results are also given for the data treatment by pattern recognition. 相似文献
925.
Antonio Stocco Vincenzo La Carrubba Stefano Piccarolo Valerio Brucato 《Journal of Polymer Science.Polymer Physics》2009,47(8):799-810
In recent years, much attention has been paid to the development of high‐performance polyester blends, among which blends of polybutylene terephthalate/polyethylene terephthalate (PBT/PET) are expected to exhibit remarkable properties as far as their crystallization behavior is concerned. Through trial and error, appropriate commercial compositions have been chosen which could not be otherwise explained by a suitable interpretation of the mechanisms determining their solidification behavior. The solidification behavior of a 60/40 w/w PBT/PET blend was studied in a wide range of cooling conditions, according to a continuous cooling transformation (CCT) procedure developed previously, aiming at emulating the typical conditions encountered in polymer processing. Several samples characterized by a homogeneous structure were solidified from the melt at various cooling rates and the resulting structure and properties were subsequently evaluated by analyzing the density, microhardness (MH), and wide angle x‐ray diffraction (WAXD). The resulting solidification behavior was then compared to that exhibited by the individual constituents of the blend (i.e., PBT and PET). The blend displayed a unique solidification behavior, conversely to those of the pure components which showed characteristics not recognized in the blend except at certain restricted cooling rates ranges. The cooling rate dependence observed in the blend does not bring similarities to the crystallization behavior of individual constituents since the fall down of density with cooling rate should be related to the rate controlling demixing stage of the two moieties just before crystallization occurs. The kinetics observed is thus a measure of the kinetics of demixing. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 799–810, 2009 相似文献
926.
927.
A. La Cognata D. Valenti B. Spagnolo A. A. Dubkov 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(2):273-279
The dynamics of two competing species within the framework
of the generalized Lotka-Volterra equations, in the presence of
multiplicative α-stable Lévy noise sources and a random
time dependent interaction parameter, is studied. The species
dynamics is characterized by two different dynamical regimes,
exclusion of one species and coexistence of both, depending on the
values of the interaction parameter, which obeys a Langevin equation
with a periodically fluctuating bistable potential and an additive
α-stable Lévy noise. The stochastic resonance phenomenon
is analyzed for noise sources asymmetrically distributed. Finally,
the effects of statistical dependence between multiplicative noise
and additive noise on the dynamics of the two species are studied. 相似文献
928.
M. F. La Russa S. A. Ruffolo M. Malagodi D. Barca R. Cirrincione A. Pezzino G. M. Crisci D. Miriello 《Applied Physics A: Materials Science & Processing》2010,100(3):865-872
In this multidisciplinary contribution, several diagnostic tests were carried out in order to characterize the stone materials,
forms of alteration, and protective products applied in the past to two monumental tombs located in the Protestant Cemetery
of Rome (Italy). 相似文献
929.
Dr. Fabio Morana Dr. Andrea Basso Prof. Dr. Renata Riva Valeria Rocca Prof. Luca Banfi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(14):4563-4569
A straightforward and fully stereoselective synthesis of a new class of peptidomimetics, that is α‐oxo‐γ‐acylaminoamides, was achieved starting from various benzaldehydes by a sequence of 1) an asymmetric organocatalytic Mannich reaction, 2) a Passerini multicomponent reaction, 3) an amine deprotection–acyl migration protocol, and 4) a final oxidation. The whole sequence can be performed without purification of the intermediates and represents the first example of a homo‐Passerini–amine deprotection–acyl migration (PADAM) strategy. Highly stereoselective reduction of the α‐oxo‐γ‐acylaminoamides afforded α‐hydroxy‐γ‐acylaminoamides as well. In some cases both diastereomers were obtained by simply changing the reducing agent. Finally, starting from protected salicylaldehyde, the same sequence, followed by a Mitsunobu cyclization, afforded highly substituted chromanes. 相似文献
930.