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31.
We give an example of an exact, stably finite, simple, separable C*-algebra D which is not isomorphic to its opposite algebra. Moreover, D has the following additional properties. It is stably finite, approximately divisible, has real rank zero and stable rank one, has a unique tracial state, and the order on projections over D is determined by traces. It also absorbs the Jiang-Su algebra Z, and in fact absorbs the 3∞ UHF algebra. We can also explicitly compute the K-theory of D, namely ${K_0 (D) \cong {\mathbb{Z}} [ \tfrac{1}{3}]}$ with the standard order, and K 1 (D) = 0, as well as the Cuntz semigroup of D, namely ${W (D) \cong {\mathbb{Z}} [ \tfrac{1}{3} ]_{+} \sqcup (0, \infty).}$ 相似文献
32.
33.
Alessandro Marzani Erasmo Viola Francesco Lanza di Scalea 《Journal of sound and vibration》2008,318(3):488-505
A semi-analytical finite element (SAFE) method is presented for analyzing the wave propagation in viscoelastic axisymmetric waveguides. The approach extends a recent study presented by the authors, in which the general SAFE method was extended to account for material damping. The formulation presented in this paper uses the cylindrical coordinates to reduce the finite element discretization over the waveguide cross-section to a mono-dimensional mesh. The algorithm is validated by comparing the dispersion results with viscoelastic cases for which a Superposition of Partial Bulk Waves solution is known. The formulation accurately predicts dispersion properties and does not show any missing root. Applications to viscoelastic axisymmetric waveguides with varying mechanical and geometrical properties are presented. 相似文献
34.
We introduce a general operational characterization of information-preserving structures-encompassing noiseless subsystems, decoherence-free subspaces, pointer bases, and error-correcting codes-by demonstrating that they are isometric to fixed points of unital quantum processes. Using this, we show that every information-preserving structure is a matrix algebra. We further establish a structure theorem for the fixed states and observables of an arbitrary process, which unifies the Schr?dinger and Heisenberg pictures, places restrictions on physically allowed kinds of information, and provides an efficient algorithm for finding all noiseless and unitarily noiseless subsystems of the process. 相似文献
35.
Viola Francke Hans Joachim Rder Yves Geerts Klaus Müllen 《Macromolecular rapid communications》1998,19(6):275-281
The synthesis of the poly(para-phenyleneethynylene)-block-poly(ethylene oxide) block copolymer (PPE-b-PEO) ( 1 ) via condensation of endfunctionalized poly(para-phenyleneethynylene) (PPE) ( 5 ) and poly(ethylene oxide) monomethyl ether (PEO) is reported. This is achieved by the initial synthesis of a PPE homopolymer with quantitative terminal functionalization, as proven by 1H NMR and field desorption mass spectrometry (FD-MS). Reaction of the latter with PEO affords the block copolymer 1 , which was characterized by 1H NMR spectroscopy, FD-MS and gel permeation chromatography (GPC). Furthermore it is shown that matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) is a suitable method to investigate PPE-b-PEO with respect to molecular weights and copolymer composition. 相似文献
36.
Péter Baracskay Viola Kiglics Katalin A Kékesi Gábor Juhász András Czurkó 《BMC neuroscience》2009,10(1):133
Background
The impairment of the pontine reticular formation (PRF) has recently been revealed to be histopathologically connected with focal-cortical seizure induced generalized convulsive status epilepticus. To elucidate whether the impairment of the PRF is a general phenomenon during status epilepticus, the focal-cortical 4-aminopyridine (4-AP) application was compared with other epilepsy models. The presence of "dark" neurons in the PRF was investigated by the sensitive silver method of Gallyas in rats sacrificed at 3 h after focal 4-AP crystal or systemic 4-AP, pilocarpine, or kainic acid application. The behavioral signs of the developing epileptic seizures were scored in all rats. The EEG activity was recorded in eight rats. 相似文献37.
High performance PtRuIr catalysts supported on carbon nanotubes for the anodic oxidation of methanol 总被引:1,自引:0,他引:1
Liao S Holmes KA Tsaprailis H Birss VI 《Journal of the American Chemical Society》2006,128(11):3504-3505
We report the formation of a new PtRuIr catalyst using an organic colloid synthesis method, involving acetone as the solvent, ethylene glycol as the reducing agent, citrate as a complexing agent and stabilizer, and multiwall carbon nanotubes (CNT, diameter 8-10 nm) as the support. This catalyst has a very high real surface area and is highly active toward the oxidation of methanol, relevant to fuel cell applications. The Ir component appears to act as a promoter, and the splitting of the Pt(111) XRD feature into four peaks and the shift to larger d spacing reflect the high dispersion of the metallic components. 相似文献
38.
Stadler F Oeckler O Höppe HA Möller MH Pöttgen R Mosel BD Schmidt P Duppel V Simon A Schnick W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(26):6984-6990
The new layered oxonitridosilicate EuSi2O2N2 has been synthesized in a radio‐frequency furnace at temperatures of about 1400 °C starting from europium(III ) oxide (Eu2O3) and silicon diimide (Si(NH)2). The structure of the yellow material has been determined by single‐crystal X‐ray diffraction analysis (space group P1 (no. 1), a=709.5(1), b=724.6(1), c=725.6(1) pm, α=88.69(2), β=84.77(2), γ=75.84(2)°,V=360.19(9)×106 pm3, Z=4, R1=0.0631, 4551 independent reflections, 175 parameters). Its anionic Si2O2N22? layers consist of corner‐sharing SiON3 tetrahedra with threefold connecting nitrogen and terminal oxygen atoms. High‐resolution transmission electron micrographs indicate both ordered and disordered crystallites as well as twinning. Magnetic susceptibility measurements of EuSi2O2N2 exhibit Curie–Weiss behavior above 20 K with an effective magnetic moment of 7.80(5) μB Eu?1, indicating divalent europium. Antiferromagnetic ordering is detected at 4.5(2) K. EuSi2O2N2 shows a field‐induced transition with a critical field of 0.50(5) T. The four crystallographically different europium sites cannot be distinguished by 151Eu Mössbauer spectroscopy. The room‐temperature spectrum is fitted by one signal at an isomer shift of δ=?12.3(1) mm s?1 subject to quadrupole splitting of ΔEQ=?2.3(1) mm s?1 and an asymmetry parameter of 0.46(3). Luminescence measurements show a narrow emission band with regard to the four crystallographic europium sites with an emission maximum at λ=575 nm. 相似文献
39.
Liu X Bordunov A Tracy M Slingsby R Avdalovic N Pohl C 《Journal of chromatography. A》2006,1119(1-2):120-127
This paper describes a new polar-embedded stationary phase that contains an internal sulfonamide functional group coupled with an ether linkage. The synthesis involves functionalization of spherical silica particles with ligands prepared in a multi-step synthesis. The resulting material contains 16.5% carbon, corresponding to a ligand coverage of 2.4mumol/m(2). Chromatographic evaluations indicates that the new stationary phase exhibits lower polarity than any other polar-embedded packings investigated, with additional features such as low silanol activity, excellent compatibility with 100% aqueous mobile phases, higher shape selectivity for polycyclic aromatic hydrocarbons, and strong affinity to nitro-containing compounds. 相似文献
40.
Dall'Acqua S Viola G Giorgetti M Loi MC Innocenti G 《Chemical & pharmaceutical bulletin》2006,54(8):1187-1189
As a part of our ongoing interest in new bioactive compounds from natural sources, we studied Laurus nobilis (Lauraceae). This plant is widespread in the Mediterranean area and is used for medicinal and economic purposes. Chromatographic separations on active extracts led to the isolation of two new sesquiterpene lactones, 5a,9-dimethyl-3-methylene-3,3a,4,5,5a,6,7,8-octahydro-1-oxacyclopenta[c]azulen-2-one (1) and 3beta-chlorodehydrocostuslactone (2). The structures of the new compounds were identified by 1D and 2D NMR experiments, as well as high resolution mass spectrometry. The cytotoxic activity was also evaluated against three different tumor cell lines of human origin. 相似文献