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991.
Francesca Benuzzi Fausta Lui Davide Duzzi Paolo F. Nichelli Carlo Adolfo Porro 《Magnetic resonance imaging》2009
The neural mechanisms subserving recognition of noxious stimuli and empathy for pain appear to involve at least in part the cortical regions associated with the processing of pain affect. An important issue concerns the specificity of brain networks associated with observing and representing painful conditions, in comparison with other unpleasant stimuli. Recently, we found both similarities and differences between the brain patterns of activity related to the observation of noxious or disgusting stimuli delivered to one hand or foot. Overlap regions included the perigenual anterior cingulate (pACC), whose activity was related to the perceived unpleasantness. We aimed here at revealing how pACC functional connectivity changes in relationship to the different experimental conditions, using a psychophysiological interaction model. Activity in pACC during the observation of painful stimuli was specifically and positively related to regions in the right hemisphere, including portions of the prefrontal, midcingulate and insular cortex. On the other hand, positive changes in pACC connectivity during the vision of disgusting stimuli were present in the right basal ganglia. These data suggest that pACC activity is part of different networks involved in the recognition of painful or disgusting stimuli. 相似文献
992.
Damiano Monticelli Antonino Di Iorio Elena Ciceri Alessio Castelletti Carlo Dossi 《Mikrochimica acta》2009,164(1-2):139-148
An empirical approach is presented for validating trace metal profiles in tree rings for use as environmental archives. Concentration profiles of Zn, Cd, Cu, Pb and U in tree rings and lake sediments are compared for assessing the reliability of the former as an environmental proxy. Laser ablation sampling in conjunction with inductively coupled plasma mass spectrometry (LA–ICP–MS) is used for the direct analysis of tree rings. An optimised analytical protocol is devised with particular emphasis on sample preparation and quantification strategy. Significant correlations in the two environmental archives were found for zinc, copper and uranium, while cadmium and lead temporal trends, although showing enrichment in recent years, do not agree with the concentration profiles in lacustrine sediment cores. A chemical model based on metal affinity for hard type ligands present in wood is proposed to explain these results. Moreover, spring and winter wood are analysed separately thanks to the high spatial resolution of laser ablation sampling. As a result, enhanced metal loadings are shown to lead to intraring differences in trace metal concentrations. 相似文献
993.
Hard X‐ray‐induced damage on carbon–binder matrix for in situ synchrotron transmission X‐ray microscopy tomography of Li‐ion batteries 下载免费PDF全文
Cheolwoong Lim Huixiao Kang Vincent De Andrade Francesco De Carlo Likun Zhu 《Journal of synchrotron radiation》2017,24(3):695-698
The electrode of Li‐ion batteries is required to be chemically and mechanically stable in the electrolyte environment for in situ monitoring by transmission X‐ray microscopy (TXM). Evidence has shown that continuous irradiation has an impact on the microstructure and the electrochemical performance of the electrode. To identify the root cause of the radiation damage, a wire‐shaped electrode is soaked in an electrolyte in a quartz capillary and monitored using TXM under hard X‐ray illumination. The results show that expansion of the carbon–binder matrix by the accumulated X‐ray dose is the key factor of radiation damage. For in situ TXM tomography, intermittent X‐ray exposure during image capturing can be used to avoid the morphology change caused by radiation damage on the carbon–binder matrix. 相似文献
994.
Matteo Moretti Francesca Freni Claudia Carelli Carlo Previder Pierangela Grignani Claudia Vignali Maria Cobo-Golpe Luca Morini 《Molecules (Basel, Switzerland)》2021,26(17)
Dried urine spots (DUS) represent a potential alternative sample storage for forensic toxicological analysis. The aim of the current study was to develop and validate a liquid chromatographic tandem mass spectrometric procedure for the detection and quantitative determination of cannabinoids and metabolites in DUS. A two-step extraction was performed on DUS and urine samples. An LC-MS/MS system was operated in multiple reaction monitoring and positive polarization mode. The method was checked for sensitivity, specificity, linearity, accuracy, precision, recovery, matrix effects and carryover. The method was applied to 70 urine samples collected from healthy volunteers and drug addicts undergoing withdrawal treatment. The method was successfully developed for DUS. LODs lower than 2.0 ng/mL were obtained for all the monitored substances. All the validation parameters fulfilled the acceptance criteria either for DUS or urine. Among the real samples, 45 cases provided positive results for at least one compound. A good quali-quantitative agreement was obtained between DUS and urine. A good stability of THC, THCCOOH and THCCOOH-gluc was observed after a 24 h storage, in contrast to previously published results. DUS seems to provide a good alternative storage condition for urine that should be checked for the presence of cannabinoids and metabolites. 相似文献
995.
A first-order liquid-liquid phase transition in high-pressure hydrogen between molecular and atomic fluid phases has been predicted in computer simulations using ab initio molecular dynamics approaches. However, experiments indicate that molecular dissociation may occur through a continuous crossover rather than a first-order transition. Here we study the nature of molecular dissociation in fluid hydrogen using an alternative simulation technique in which electronic correlation is computed within quantum Monte Carlo methods, the so-called coupled electron-ion Monte Carlo method. We find no evidence for a first-order liquid-liquid phase transition. 相似文献
996.
Transverse instabilities are shown to accompany counterpropagation of optical beams through reflection gratings in Kerr media. The instability threshold of continuous waves is analytically derived, and it is shown that the presence of the grating broadens and narrows the stability region of plane waves in focusing and defocusing media, respectively. Furthermore, counterpropagating soliton stability is numerically investigated and compared with the transverse modulation instability analysis, revealing an underlying physical link. 相似文献
997.
Robertson–Walker and generalized Robertson–Walker spacetimes may be characterized by the existence of a time-like unit torse-forming vector field, with other constrains. We show that Twisted manifolds may still be characterized by the existence of such (unique) vector field, with no other constrain. Twisted manifolds generalize RW and GRW spacetimes by admitting a scale function that depends both on time and space. We obtain the Ricci tensor, corresponding to the stress–energy tensor of an imperfect fluid. 相似文献
998.
Giuseppe Carlo Marano Giuseppe Quaranta 《International Journal of Solids and Structures》2008,45(11-12):3544-3557
Robust optimization is conventionally defined as the collection of the possible problem solutions that can ensure acceptable performances and sufficient immunity against the effects of uncertain parameter variability. Methods proposed until now use a probabilistic way to model uncertainty and to quantify the final sensitivity. In this work, a fuzzy uncertainty modellization is adopted for structural engineering. In particular, to define solution performance scattering, the fuzzy entropy is used as a global measure of variable dispersion. The final formulation of the problem deals with two antithetical objective functions, the fuzzy expected value of structural performance and its fuzzy entropy. This fuzzy-based approach in robust design is able to give a set of Pareto optimal solutions in terms of structural efficiency and sensitivities regarding uncertainty, and represents a suitable tool in supporting the decision maker. Finally, different applications have been developed to demonstrate the applicability of the proposed method. 相似文献
999.
1000.
We study the vanishing viscosity limit for an incompressible fluid with axial symmetry without swirl when the vorticity is sharply concentrated. 相似文献