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571.
572.
Toma? Skapin Zoran Mazej Adolf Jesih Sven L.M. Schroeder Norbert Weiher John M. Winfield 《Journal of fluorine chemistry》2011,132(10):703-712
Decomposition of hydrazinium pentafluoroaluminate under oxidative (F2) conditions leads to aluminium(III) fluoride whose properties are highly dependent on the conditions used for synthesis. In the presence of anhydrous HF, which probably acts as a heat exchange agent, samples have high BET areas, whereas BET areas of samples prepared under gas-solid conditions are small. XPS data are consistent with the presence of Lewis acid centres but, more importantly, emphasise the importance of surface hydroxyl groups, particularly in high surface area compounds. Catalytic behaviour towards isomerisation of 1,1,2-trichlorotrifluoroethane and subsequent dismutations at moderate temperatures and towards room temperature dehydrochlorination of tert-butyl chloride has been demonstrated for some high BET samples; both reactions indicate that surface Lewis sites exist. Catalytic ability is inhibited by surface hydroxyl groups but is improved by prior fluorination of the surface with CCl2F2. Catalysis is inhibited also by the presence of ammonium fluoroaluminate, a by-product of the decomposition process. The [NH4]+ salt level can be reduced by washing with anhydrous HF. 相似文献
573.
Hg(AuF6)2 crystallizes at 200 K in the orthorhombic space group Pbcn (No. 60) with a = 917.67(7) pm, b = 971.59(8) pm, c = 962.04(8) pm, and Z = 4. Mercury atoms are coordinated by eight fluorine atoms with six short and two long Hg-F contacts. HgF8 polyhedra share their four vertices and two edges with six AuF6 units forming a tridimensional framework.The results of X-ray diffraction analysis on single crystals of AgFAuF6 are in agreement with previously known powder X-ray diffraction data (Casteel et al, J. Solid State Chem. 96 (1992) 84-96). AgFAuF6 crystallizes orthorhombic in the space group Pnma (No. 62), a = 717.06(7) pm, b = 761.67(7) pm, c = 1013.61(10) pm at 200 K, Z = 4. 相似文献
574.
We present a computational study of a visualization method for invariant sets based on ergodic partition theory, first proposed by Mezic? (Ph.D. thesis, Caltech, 1994) and Mezic? and Wiggins [Chaos 9, 213 (1999)]. The algorithms for computation of the time averages of observables on phase space are developed and used to provide an approximation of the ergodic partition of the phase space. We term the graphical representation of this approximation--based on time averages of observables--a mesochronic plot (from Greek: meso--mean, chronos--time). The method is useful for identifying low-dimensional projections (e.g., two-dimensional slices) of invariant structures in phase spaces of dimensionality bigger than two. We also introduce the concept of the ergodic quotient space, obtained by assigning a point to every ergodic set, and provide an embedding method whose graphical representation we call the mesochronic scatter plot. We use the Chirikov standard map as a well-known and dynamically rich example in order to illustrate the implementation of our methods. In addition, we expose applications to other higher dimensional maps such as the Froe?schle map for which we utilize our methods to analyze merging of resonances and, the three-dimensional extended standard map for which we study the conjecture on its ergodicity [I. Mezic?, Physica D 154, 51 (2001)]. We extend the study in our next paper [Z. Levnajic? and I. Mezic?, e-print arXiv:0808.2182] by investigating the visualization of periodic sets using harmonic time averages. Both of these methods are related to eigenspace structure of the Koopman operator [I. Mezic? and A. Banaszuk, Physica D 197, 101 (2004)]. 相似文献
575.
We design a computational experiment in which a quantum particle tunnels into a billiard of variable shape and scatters out of it through a double-slit opening on the billiard's base. The interference patterns produced by the scattered probability currents for a range of energies are investigated in relation to the billiard's geometry which is connected to its classical integrability. Four billiards with hierarchical integrability levels are considered: integrable, pseudointegrable, weak-mixing, and strongly chaotic. In agreement with the earlier result by Casati and Prosen [Phys. Rev. A 72, 032111 (2005)], we find the billiard's integrability to have a crucial influence on the properties of the interference patterns. In the integrable case, most experiment outcomes are found to be consistent with the constructive interference occurring in the usual double-slit experiment. In contrast to this, nonintegrable billiards typically display asymmetric interference patterns of smaller visibility characterized by weakly correlated wave function values at the two slits. Our findings indicate an intrinsic connection between the classical integrability and the quantum dephasing, which is responsible for the destruction of interference. 相似文献
576.
Slavica Ristic Suzana Polic-Radovanovic Boris Katavic Marina Kutin Zoran Nikolic Mirjana Puharic 《Journal of Russian Laser Research》2010,31(4):380-389
Preventive care, research, and restoration of cultural heritage objects requires multidisciplinary research and the involvement
of experts of different profiles, using high technology equipment. Nondestructive methods dominate in the diagnosis of the
situation and protection of cultural heritage objects. The application of lasers has opened many possibilities for research
in the field of protection, conservation, restoration, and/or assessment of artifacts. We present the results of the interaction
of ruby-laser light with the surfaces of Neolithic ceramics (Obrenovac, Serbia) and samples of copper of unknown age. The
investigation was conducted in order to determine the maximum energy density of the laser light that can be applied in nondestructive
testing and encrustation cleaning of these ceramic and metal cultural heritage objects. We investigate the laser-light interactions
using a scanning electron microscope (SEM) with energy-dispersal unit for the analysis of X-rays (EDX). 相似文献
577.
Aleksandar Radivojac Oskar Bera Zoran Zekovi Nemanja Tesli
ivan Mrkonji Danijela Bursa Kova
evi Predrag Putnik Branimir Pavli 《Molecules (Basel, Switzerland)》2021,26(10)
Consumers are becoming more mindful of their well-being. Increasing awareness of the many beneficial properties of peppermint essential oil (EO) has significantly increased product sales in recent years. Hydrodistillation (HD), a proven conventional method, and a possible alternative in the form of microwave-assisted hydrodistillation (MWHD) have been used to isolate peppermint EO. Standard Soxhlet and alternatively supercritical fluid (SFE), microwave-assisted, and ultrasound-assisted extraction separated the lipid extracts. The distillations employed various power settings, and the EO yield varied from 0.15 to 0.80%. The estimated environmental impact in terms of electricity consumption and CO2 emissions suggested that MWHD is an energy efficient way to reduce CO2 emissions. Different extraction methods and solvent properties affected the lipid extract yield, which ranged from 2.55 to 5.36%. According to the corresponding values of statistical parameters, empiric mathematical models were successfully applied to model the kinetics of MWHD and SFE processes. 相似文献
578.
Micro‐Raman spectroscopy has been used to investigate the chemical micro‐heterogeneity of multiphase‐separated poly(ether urethanes) (PETU). Analysis of PETU cross‐sections by means of micro‐Raman spectroscopy revealed the nearly complete absence of soft segments in AI aggregates (called globules). These aggregates are in the order of a few micrometers in size. The composition of the matrix and the AII aggregates (spherulites) was comparable.
579.
580.
The title compounds are prepared according to the literature and used for single crystal growth in a T‐shaped fluoroethylene‐hexafluoropropylene crystallization apparatus. 相似文献