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941.
942.
943.
Gleison Antonio Casagrande Ernesto Schulz Lang Prof. Dr. Bárbara Tirloni Robert Alan Burrow Gelson Manzoni de Oliveira Sebastião S. Lemos 《无机化学与普通化学杂志》2006,632(5):893-896
A three‐step one‐pot synthetic procedure to synthesize the neutral tellurium(IV) coordination compounds PhTeX3L (X = Br, I and L = ethylenethiourea) has been developed and is described in this article. Oxidative halogenation of PhTeTePh in methanol generates the tellurium(II) derivative, PhTeX, which is subsequently complexed with ethylenethiourea, and, finally, further oxidative addition of additional halogen affords the corresponding tellurium(IV) compound PhTeX3L in good yields. The final product was obtained by the slow evaporation of the reaction mixture as black crystals. The X‐ray structural analyses of the compounds show Te···X and X···X secondary interactions in the solid state and suggest a weak dependence of the formation of supramolecular assemblies on the nature of the halogen bonded to the tellurium atom. 相似文献
944.
945.
Abrahão-Neto José Infanti Patrícia Vitolo Michele 《Applied biochemistry and biotechnology》1996,57(1):407-412
Applied Biochemistry and Biotechnology - The effects of pH (4.0, 4.5, or 5.0), temperature (T) (30, 35, or 40°C) and dissolved oxygen (DO) (0.2, 2.0, 4.0, or 6.0 mg O2/L) on hexokinase and... 相似文献
946.
J. M. Garcia V.M. Castaňo M.A. Mondragón E. Ramírez F. González A. Campero V. Rentería 《Journal of Sol-Gel Science and Technology》1997,8(1-3):911-916
Silica gels prepared by the sol-gel method with TEOS as a precursor and doped with the organic dyes rhodamine B, Na fluoresceine and eosine G were exposed to UV radiation pulses from a nitrogen laser. The absorption, luminescence and IR spectra were taken as a function of the exposure time. The absorption and the luminescence curves show successive maxima and minima. The same response is observed when the exposure procedure is repeated. These results are explained in terms of the cyclic filling and depletion of the long-lived triplet excited electronic state. At short exposure times, the data can be fitted with a Lorentzian curve and the corresponding parameters are given. 相似文献
947.
Miguel A. Sierra Mamen Rodríguez-Fernández María José Mancheño Luis Casarrubios Mar Gómez-Gallego 《Tetrahedron》2008,64(40):9592-9598
A new approach to N1-C3 bridged macrocyclic β-lactams has been developed. Orthogonal functional groups' protection combined with RCM has allowed the construction of the bicyclic systems bearing a β-lactam motif. These systems could represent a structural alternative to the actual lactamic antibiotics and may be further transformed into a broad variety of compounds. 相似文献
948.
Karine L Marques Jo?o L M Santos Jo?o A Lopes José L F C Lima 《Analytical sciences》2008,24(8):985-991
An automated multi-pumping flow system is proposed for the simultaneous chemiluminometric determination of benserazide and levodopa using multivariate calibration methods. The developed methodology is based on chemiluminescence (CL) emission generated by the reaction of benserazide with luminol, and on a concurrent inhibiting effect of levodopa on this reaction. A multi-pumping flow system comprising multiple solenoid micro-pumps as the only active components was developed to implement a stopped-flow approach for signal acquisition and processing. Artificial neural networks were used to establish a relationship between the CL emission profile and the concentration of both drugs. The concentration values used to establish the experimental calibration samples were varied between 5 and 30 mg l(-1) for levodopa and between 2.5 and 20 mg l(-1) for benserazide. The proposed method was successfully applied to the simultaneous determination of levodopa and benserazide in pharmaceutical formulations combining both drugs. 相似文献
949.
950.
Paulo H Fidêncio Ronei J Poppi Jo?o C de Andrade M?nica F de Abreu 《Analytical sciences》2008,24(7):945-948
Total nitrogen has been determined by using a model developed between the conventional chemical measurements and diffuse reflectance spectra in the near-infrared region. Samples (244) from different types of soils with total nitrogen contents ranging from 0.20 to 13.60% (m/m) were modeled by partial least-squares regression (PLS), multi-layer perceptron feed-forward networks (MLP) and radial basis function networks (RBFN). The RBFN model produced a better square error of prediction (SEP) of 0.048 and R(2) = 0.93 in a procedure that is simpler, faster and less dependent on the initial conditions. 相似文献