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排序方式: 共有76条查询结果,搜索用时 15 毫秒
1.
Diane C. Rawlings Martin Gouterman Ernest R. Davidson David Feller 《International journal of quantum chemistry》1985,28(6):823-842
Ab initio CI calculations are reported on the lowest doublet, quartet, and sextet states of [FeIII(P)(NH3)2]+. The low-spin ground state is calculated as (dxy2 (dπ)3 with dxy(dπ)4 higher by 0.15 eV. The near-ir bands at ~1 eV observed in low-spin ferriheme proteins are attributed to (π → dπ) transitions. The lowest high-spin state is 6A1g, and the near-ir transitions of the high-spin ferriheme proteins observed at ~1.2 eV are attributed to higher 6[tripsextet] excited states [i.e., ring triplet, metal sextet]. The 30-ps “triplet” transient populated with low quantum yield observed in laser-flash studies on FeIII(TPP)CI [TPP = tetrapbenylporphyrin] may be an 1[tripsextet] state. 相似文献
2.
Detection of streptomycin and dihydrostreptomycin residues in milk,honey and meat samples using an optical biosensor 总被引:7,自引:0,他引:7
Immuno-biosensor inhibition assays for the detection of streptomycin and dihydrostreptomycin residues in whole cows' milk, honey, pig kidney and pig muscle are reported. The antibody showed high cross-reactivity with dihydrostreptomycin in various foodstuffs (buffer 103%, milk 96%, honey 84%, kidney extract 129% and muscle extract 98%). There was no significant cross-reaction with other aminoglycosides or commonly used antibiotics. A streptomycin derivative was used to prepare a stable, reusable sensor chip surface. The assay allowed the direct analysis of bovine whole milk (fat content approximately 3.5%). Honey samples required dilution with buffer, while kidney and muscle samples from pigs were homogenized in an aqueous extraction buffer and clarified by centrifugation. The limit of detection for each assay was determined from known streptomycin-free samples (n = 20; mean - (3 x standard deviation)) and the results were as follows: milk 30 microg kg(-1), honey 15 microg kg(-1), kidney 50 microg kg(-1) and muscle 70 microg kg(-1). Repeatability (or relative standard deviation) between runs were calculated (n = 3) at the respective Community maximum residue limits (MRL) and 0.5 x MRL with the exception of honey since no European MRL exists at present. Results were determined as 4.3% (200 microg kg(-1)) and 2.8% (100 microg kg(-1)) in milk, 13.3% (40 microg kg(-1)) and 9.5% (20 microg kg(-1)) in honey, 7.1% (1000 microg kg(-1)) and 7.6% (500 microg kg(-1)) in kidney and 7.1% (500 microg kg(-1)) and 11% (250 microg kg(-1)) in muscle. 相似文献
3.
Diane C. Rawlings Ernest R. Davidson Martin Gouterman 《International journal of quantum chemistry》1984,26(2):237-250
A new minimum basis set was developed for use in computing excitation energies of large molecules. It is particularly suited to calculating ionization potentials and Rydberg transitions. Pyrrole excitation energies and oscillator strengths calculated with this basis set are compared to larger basis set ab initio and semiempirical results. The 6-eV band in the experimental spectrum is predicted to be the result of three Rydberg absorptions, with no underlying (π, π*) absorption. The calculations also provide an explanation for the observed N? H stretch in the 6-eV region. 相似文献
4.
Jack E. Baldwin Robert M. Adlington Bernard J. Rawlings Richard H. Jones 《Tetrahedron letters》1985,26(4):485-488
Practical procedures for the resolution of racemic modification of (1, 2)-and (1, 2)-1-amino-2-ethylcyclopropane-1-carboxylic acid ,,(1, 2)- and (1, 2)-1-amino-2-methylcyclopropane-1-carboxylic acid ,, and (1, 2)- and (1, 2)-1-amino-2-methylcyclopropane-1-carboxylic acid , are described; the structures as ,, and were confirmed by X-ray-crystallographic methods. 相似文献
5.
The absorption spectra of a series of polysubstituted arenetricarbonylchromium complexes were studied. A linear correlation between the extinction coefficient of the longest wavelength band and the sum of the Hammett σp+ values was obtained. 相似文献
6.
William K. Bell Brandon M. Rawlings Brian K. Long R. Chad Webb B. Keith Keitz Lukas Häußling C. Grant Willson 《Journal of polymer science. Part A, Polymer chemistry》2014,52(19):2769-2775
A series of photocrosslinkable polymers bearing hyperpolarizable side chain chromophores was synthesized, poled and evaluated on the basis of the thermal stability of Second Harmonic Generation (SHG). Photoinitiation allowed for control of the onset of curing. Crosslinking was monitored by infrared spectroscopy and optimal conversion was achieved by applying a slow temperature ramp during exposure. The ultimate stability of the poled polymers was directly related to the number of crosslinking substituents that were attached to the chromophore pendant group. With two reactive groups per chromophore significant SHG was retained at temperatures above the initial polymer glass transition temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2769–2775 相似文献
7.
The carbonyl region infrared spectra of a large number of arenetricarbony, chromium complexes containing diverse functionality have been determined. The force constants of the CO bond calculated using the Cotton-Kraihanzel method have been correlated with Hammett, Taft and Swain-Lupton parameters. 相似文献
8.
The equilibrium segregation in the system W(100) plus two monolayers of total carbon content has been studied in the range 1600 to 2073 K. The energy of segregation is ?56(±2) kcal mole?1. The kinetics of carbon segregation at 1350 and 1420 K were observed. From a semi-empirical treatment an upper limit to the activation energy for volume diffision is deduced to be 59 (±8) kcal mole?1. 相似文献
9.
10.
Highly reactive species at small copy numbers play an important role in many biological reaction networks. We have described previously how these species can be removed from reaction networks using stochastic quasi-steady-state singular perturbation analysis (sQSPA). In this paper we apply sQSPA to three published biological models: the pap operon regulation, a biochemical oscillator, and an intracellular viral infection. These examples demonstrate three different potential benefits of sQSPA. First, rare state probabilities can be accurately estimated from simulation. Second, the method typically results in fewer and better scaled parameters that can be more readily estimated from experiments. Finally, the simulation time can be significantly reduced without sacrificing the accuracy of the solution. 相似文献