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71.
F. J. Barros‐García Avaro Bernalte‐García A. M. Lozano‐Vila F. Luna‐Giles 《无机化学与普通化学杂志》2005,631(5):947-951
The copper(II) complex [Cu(NO3)(PyTz)2](NO3) has been previously characterized means X‐ray powder diffraction and now studied by IR spectroscopy, UV‐Vis‐NIR diffuse reflectance, magnetic susceptibility measurement, electronic spin resonance (ESR) and thermal analysis. The results are correlated with a distorted square pyramidal coordination around copper(II) ion rather than the cis‐distorted octahedral stereochemistry of a CuN4OO′ chromophore in good concordance with their structure. Likewise, in order to indicate towards what square pyramidal isomer the complex is distorted, the method proposed by Carugo and Bisi has been applied to the structural data of [Cu(NO3)(PyTz)2](NO3). It is deduced that there is a large distortion from the trigonal bipyramid geometry, close to a square pyramid geometry, being produced almost exclusively through the B route of the Berry mechanism. 相似文献
72.
F.R.T. Luna G.H. Cavalcanti 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,75(5):559-587
We are presenting a complete list of wavelengths for all classified lines of Rb I. The data are based mainly on the observations and analysis of this spectrum by many authors. The tabulated data include 615 observed lines in the spectral range 103-, classified as transitions among 22 even-parity and 414 odd-parity levels. Vacuum wavelengths are given for all the lines, and wavelengths in air are also included for the region above . We also present the results of the doppler-free two-photon absorption spectrum for the transition n2S←52S and n2D←52S of atomic rubidium. 相似文献
73.
Concepción Gómez-Vaamonde Amparo Alvarez-Valdés María del Carmen Navarro-Ranninger José R. Masaguer 《Transition Metal Chemistry》1984,9(2):52-54
Summary The synthesis and identification of the compoundstrans-bis(2-aminopyridine)dichloropalladium(II) and tetrakis(2-aminopyridine)palladium(II) chloride are described. The infrared spectra are discussed, particularly the metal-halogen and metal-ligand vibrations. Thermal decomposition was studied by differential thermal analysis (DTA) and thermogravimetry (TG). 相似文献
74.
This article is devoted to the problem of improving the frequency resolution inherent in a parallel acousto-optical spectrum analysis via involving an additional nonlinear phenomenon into the data processing. In so doing, we examine possible application of the wave heterodyning to the real-time scale acousto-optical analysis of the frequency spectrum belonging to ultra-high-frequency radio-wave signals peculiar, for example, for radio-astronomy. The nonlinear process of wave heterodyning is realized through providing a co-directional collinear interaction of the longitudinal acoustic waves of finite amplitudes. This process, which is beforehand studied theoretically and investigated experimentally via the acousto-optical technique as well, allows us either to improve the frequency resolution of spectrum analysis at a given frequency range or to increase by a few times the current frequencies of radio-wave signals under processing. The first step along this way is connected with the experimental modeling of the acoustic wave heterodyning in solids via exploitation of the specific acousto-optical cell based on a liquid, which allows the simplest realization of a cell with the needed properties. Then, these theoretical and practical findings are used in our experimental studies aimed at creating a new type of acousto-optical cells, which are able to improve the resolution inherent in acousto-optical spectrum analyzer operating over ultra-high-frequency radio-wave signals. In particular, the possibility of upgrading the frequency resolution through the acoustic wave heterodyning is experimentally demonstrated using the cell made of lead molybdate crystal. The obtained results demonstrate practical efficiency of the novel approach presented. 相似文献
75.
Marco C. Goldbarg Elizabeth F. G. Goldbarg Henrique P. L. Luna Matheus S. Menezes Lucas Corrales 《Optimization Letters》2018,12(4):743-761
The traveling car renter problem (CaRS) is an extension of the classical traveling salesman problem (TSP) where different cars are available for use during the salesman’s tour. In this study we present three integer programming formulations for CaRS, of which two have quadratic objective functions and the other has quadratic constraints. The first model with a quadratic objective function is grounded on the TSP interpreted as a special case of the quadratic assignment problem in which the assignment variables refer to visitation orders. The second model with a quadratic objective function is based on the Gavish and Grave’s formulation for the TSP. The model with quadratic constraints is based on the Dantzig–Fulkerson–Johnson’s formulation for the TSP. The formulations are linearized and implemented in two solvers. An experiment with 50 instances is reported. 相似文献
76.
Cycloreversion of azetidines via oxidative electron transfer. steady-state and time-resolved studies
Andreu I Delgado J Espinós A Pérez-Ruiz R Jiménez MC Miranda MA 《Organic letters》2008,10(22):5207-5210
Cycloreversion of cis- and trans-1,2,3-triphenylazetidine (c-2 and t-2) is achieved by electron transfer to (tris(4-bromophenyl)aminium radical cation (5 (*+)). Stepwise C-N and C-C bond cleavage of azetidine radical cations leads to cis- and trans-stilbene, together with N-benzylideneaniline, as final products. Mechanistic evidence is provided by quenching studies, using laser flash photolysis to generate 5 (*+) from its neutral precursor. 相似文献
77.
Silva SS Luna SM Gomes ME Benesch J Pashkuleva I Mano JF Reis RL 《Macromolecular bioscience》2008,8(6):568-576
Surface modification of biomaterials is a way to tailor cell responses whilst retaining the bulk properties. In this work, chitosan membranes were prepared by solvent casting and treated with nitrogen or argon plasma at 20 W for 10-40 min. AFM indicated an increase in the surface roughness as a result of the ongoing etching process. XPS and contact angle measurements showed different surface elemental compositions and higher surface free energy. The MTS test and direct contact assays with an L929 fibroblast cell line indicated that the plasma treatment improved the cell adhesion and proliferation. Overall, the results demonstrated that such plasma treatments could significantly improve the biocompatibility of chitosan membranes and thus improve their potential in wound dressings and tissue engineering applications. 相似文献
78.
Iraís A. Quintero‐Ortega Gabriel Jaramillo‐Soto Pedro R. García‐Morán M. Luz Castellanos‐Cárdenas Gabriel Luna‐Bárcenas Eduardo Vivaldo‐Lima 《大分子反应工程》2008,2(4):304-320
A comparison of kinetic models for dispersion polymerization of MMA and styrene in supercritical CO2 is presented. The limiting case of solution polymerization, as a simplified case, was also addressed. Calculation of the partition of components between the continuous and dispersed phases was emphasized. Experimental data for the solution and dispersion polymerizations of styrene and MMA, using different types of stabilizers, were used to guide the study. Although all the models analyzed can be considered as “adequate” in representing the behavior of the system, some of their strengths and drawbacks have been highlighted.
79.
Stereoselective NaN3-catalyzed halonitroaldol-type reaction of azetidine-2,3-diones in aqueous media
Azetidine-2,3-diones (alpha-oxo-beta-lactams) and bromonitromethane undergo coupling in aqueous media in the presence of catalytic amounts of sodium azide. The stereoselectivity of the process was generally good, proceeding with reasonable anti : syn ratios under substrate control. On this basis, a simple and fast protocol for the synthesis of the potentially bioactive 3-substituted 3-hydroxy-beta-lactam moiety has been developed. Besides, 2-azetidinone-tethered 1-halo-1-nitroalkan-2-ols are quite useful building blocks; for example, reactions of the above nitrobromohydrins provided spiranic and fused bicyclic-beta-lactams. 相似文献
80.
Cantó-Mirapeix A Herrero-Martínez JM Mongay-Fernández C Simó-Alfonso EF 《Electrophoresis》2008,29(18):3858-3865
Acrylate-ester-based monoliths for CEC using peroxodisulfate as a chemical initiator were prepared. The influence of two ternary porogenic solvents on the physical and chromatographic properties of butyl acrylate monolithic stationary phases was investigated. The composition and the ratio of porogenic solvent were adjusted to obtain highly permeable rigid monoliths with adequate column efficiency. Among the prepared butyl acrylate monoliths, those polymerized from a ternary porogenic solvent of acetonitrile/ethanol/water exhibited the most promising performance with a minimum plate height for naphthalene of 10.5 microm and a bed permeability of 7.3 x 10(-14) m(2). A comparison in terms of efficiency and permeability with thermal and UV initiation using alpha,alpha'-AIBN was also performed. The resulting monolithic stationary phases were evaluated in terms of reproducibility, giving RSD values below 5.1% in the electrochromatographic properties studied. 相似文献