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31.
Villar AS Cruz LS Cassemiro KN Martinelli M Nussenzveig P 《Physical review letters》2005,95(24):243603
We present the first measurement of squeezed-state entanglement between the twin beams produced in an optical parametric oscillator operating above threshold. In addition to the usual squeezing in the intensity difference between the twin beams, we have measured squeezing in the sum of phase quadratures. Our scheme enables us to measure such phase anticorrelations between fields of different frequencies. In the present measurements, wavelengths differ by approximately 1 nm. Entanglement is demonstrated according to the Duan et al. criterion [Phys. Rev. Lett. 84, 2722 (2000)] Delta2p- + Delta2q+ = 1.41(2) < 2. This experiment opens the way for new potential applications such as the transfer of quantum information between different parts of the electromagnetic spectrum. 相似文献
32.
R. Jimnez M. Villar M. Cueto E. Grueso J. Illanes J. I. Cobrian F. Cantn I. Villa J. M. Snchez S. Maza J. M. Muoz C. Muoz R. Prado‐Gotor 《国际化学动力学杂志》2004,36(7):410-415
The base‐catalyzed linkage isomerization of [Co(NH3)5‐ONO]2+ to the nitro [(NH3)5Co‐NO2]2+ form is studied in various isodielectric water–cosolvent mixtures (methanol, ethanol, tert‐butyl alcohol, and 2‐propanol) at 298 K. In all cases, except for methanol–water mixtures, the rate constants increase with the proportion of cosolvent. Medium effects have been rationalized by using a multiparameter regression of solvent parameters which rationalizes the results obtained, including water–methanol mixtures. The experimental data, k2, in fact, are well correlated through the following equation: where A, B, and Gexc are the acidity parameter, the basicity parameter, and the excess Gibbs free energy of the mixture, respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 410–415, 2004 相似文献
33.
A theoretical analysis of an optical fiber photonic-bandgap-based refractometer is presented. The design is based on a quarter-wave reflector with one defect. By modifying both the real and the imaginary parts of the index of refraction of the defects we begin to change either the frequency or the amplitude of the localized optical mode. So we could fabricate a specific optical fiber refractometer by combining all the variables: index of refractive index of the defects and the rest of layers, thickness of the defect, number of layers, etc. to yield a large set of design possibilities, for example, detecting wider or thinner ranges of refractive indices, or controlling the detection accuracy. Some rules for the practical implementation of the refractometer are given. 相似文献
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36.
Konstantis F. Konidaris Giannis S. Papaefstathiou Guillem Aromi Simon J. Teat Evy Manessi-Zoupa Albert Escuer Spyros P. Perlepes 《Polyhedron》2009,28(9-10):1646-1651
The synthesis, single-crystal X-ray structure and magnetic properties of [Cu3L2Cl2(DMF)4]n (1), where L2? is the 2,3-dioxyquinoxalinate(-2) ligand, are reported. The complex was prepared by the reaction of CuCl2 and 1,4-dihydro-2,3-quinoxalinedione (H2L′) under basic conditions using either solvothermal or normal laboratory techniques. Compound 1 is a 3D coordination polymer with an (82.10)-a, lig (LiGe) topology, containing the ligand in a novel 3.1111 (Harris notation) coordination mode. Variable-temperature and variable-field magnetic studies reveal that the ligand L2? propagates weak antiferromagnetic exchange interactions through its “quinoxaline” part. IR data are discussed in terms of the structural features of 1 and the coordination mode of L2?. 相似文献
37.
Sarkar M Aromí G Cano J Bertolasi V Ray D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(46):13825-13833
A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S=3/2 ions (CN=5) with ions exhibiting strong spin-orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2-300 K) yielding parameters of g and D (for the five-coordinate Co(II) ions), of A, κ, λ, and Δ (for the metals with spin-orbit coupling) and of the exchange constants J. The agreement with results from DFT calculations, also presented here, is remarkable. 相似文献
38.
Andrea‐Nekane R. Alba Xavier Companyó Guillem Valero Albert Moyano Prof. Dr. Ramon Rios Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(18):5354-5361
A new, easy, and highly enantioselective method for the synthesis of quaternary α‐alkyl‐α‐amino acids based on organocatalysis is reported. The addition of oxazolones to 1,1‐bis(phenylsulfonyl)ethylene is efficiently catalyzed by simple chiral bases or thioureas. The reaction affords α,α‐disubstituted α‐amino acid derivatives with complete C4 regioselectivity and with excellent yields and enantioselectivities. This methodology is complementary to previously reported enantioselective approaches to quaternary α‐amino acids and allows the synthesis of α‐phenyl‐α‐alkyl‐α‐amino acids and α‐tert‐butyl‐α‐alkyl‐α‐amino acids. It has distinct advantages in terms of operational simplicity, enviromentally friendly conditions, and suitability for large‐scale reactions. 相似文献
39.
Rapid flow injection method for the determination of sulfite in wine using the permanganate-luminol luminescence system 总被引:2,自引:0,他引:2
A simple, rapid and sensitive chemiluminescence method for the determination of sulfite has been developed by combining flow-injection analysis and its sensitizing effect on the known chemiluminescence emission produced by the oxidation of luminol in alkaline medium; in this work permanganate has been proposed as oxidizing reactive. The optimum conditions for the chemiluminescence emission were established. The chemiluminescence was proportional to the sulfite concentration over the range 1.6 × 10−5 and 4.0 × 10−4 mol L−1. The detection limit was 4.7 × 10−6 mol L−1 of sulfite. The method has been satisfactorily used for the determination of free and bound sulfite in wines. 相似文献
40.
Leandro E. Roth Enrique M. Valls Marcelo A. Villar 《Journal of polymer science. Part A, Polymer chemistry》2003,41(8):1099-1106
Model silicone networks obtained by curing linear poly(dimethylsiloxane) (PDMS) chains with end‐vinyl groups, (B2), with a polyfunctional silane‐terminated crosslinker of functionality f, (Af), through a hydrosilylation reaction have been widely used. In these networks, the principal characteristics of their ultimate molecular structure are strongly affected by the final extent of reaction reached during the crosslinking reaction. This work analyzes the effect of the initial concentration of the reactive end groups on the maximum attainable extent of reaction under normal bulk crosslinking conditions. This was accomplished by examining the reaction between linear B2 PDMS chains with difunctional and trifunctional silanes. The experimental results were fitted by an exponential equation to have an empirical equation able to predict the maximum extent of reaction to be obtained as a function of the initial concentration of reactive groups. Molecular parameters relevant to this study, such as the degree of polymerization, the weight‐average molecular weight for the A2 + B2 system, or the weight fraction of solubles for the A3 + B2 system, were calculated with a mean field theory (recursive approach). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1099–1106, 2003 相似文献