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81.
Rui Yan Li Zhi Ru Li Di Wu Xi Yun Hao Ru Jiao Li Chia Chung Sun 《International journal of quantum chemistry》2005,103(2):157-166
Using four basis bets, (6‐311G(d,p), 6‐31+G(d,p), 6‐31++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for the dimers CH2O? HF, CH2O? H2O, CH2O? NH3, and CH2O? CH4. The structures of CH2O? HF, CH2O? H2O, and CH2O? NH3 are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…H? Y (Y?F, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the H atoms of CH2O and lone pair(s) on the F atom in HF, the O atom in H2O, or the N atom in NH3. In contrast with the above three dimers, for CH2O? CH4, because there is not a π‐type hydrogen bond to bend its linear hydrogen bond, the structure of CH2O? CH4 is noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD (T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
82.
The structure and stability of endohedral X@Si20H20 complexes (X = Li0/+, Na0/+, K0/+, Be0/2+, Mg0/2+, Ca0/2+) have been studied at the B3LYP/6-31G* level of density functional theory. It is found that complexes with X = Na0/+, K0/+, Mg and Ca0/2+ are energy minimum structures with X at the cage center in Ih symmetry, while those with X = Li0/+, Be0/2+, Mg2+ have off-centered structures with X towards one pentagon face in C5v symmetry. Large electron or charge transfer between the Si20H20 cage and the encapsulated X has been observed. 相似文献
83.
The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen?H2O) in absolute ethanol at 298.15 K has been determined as (-16.12 ± 0.05) kJ?mol-1 by a microcalormeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59 ± 0.29) kJ?molt-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction. 相似文献
84.
o-Dianisidine (ODA)-H2O2-horseradish peroxidase (HRP) voltammetric enzyme-linked immunoassay system has firstly been used for the detection of tobacco mosaic virus (TMV). HRP catalyzes strongly the oxidation reaction of ODA by H2O2, the product of which produces a sensitive second order derivative linear sweep voltammetric peak at potential of −0.56 V (versus SCE) in Britton–Robinson (BR) buffer. HRP activity has been measured with this voltammetric peak and TMV detected through immunoreaction. The detection limit for HRP is 9.25×10-7 mU l−1 and the linear range is 2.5×10−6–5.0×10−4 mU l−1. The detection limit for the clarified TMV is 0.25 ng ml−1 and the highest dilution ratio detected for the infected leaf sap is 1:8×105. The sensitivity for TMV detection with this method is higher than that with the enzyme-linked immunosorbent spectrophotometric assay (ELISA) using ODA-H2O2-HRP system. The processes of the enzyme-catalyzed reaction and the electro-reduction of the product of the enzyme-catalyzed reaction have been described. 相似文献
85.
Chang Xiu Han Ji Li Ren Xue Jiao Tang Bao Gui Zhang 《中国化学快报》2007,18(10):1285-1288
A new ternary Fe-based alloy catalyst FeCuP applied to decompose PH_3 was prepared with low-cost material by chemical reduction deposition method.The properties of it were characterized by XRD,ICP and SEM.Its catalytic activity on the decomposition of PH_3 and the decomposition conditions were studied.FeCuP alloy exhibits high thermal stabilities and high catalytic activity.Using it as catalyst,the decomposition temperature of phosphine decreases from over 800℃to 400-500℃.The decomposition rate of phosphine achieved 100%. 相似文献
86.
Cyanex301的纯化及其特性 总被引:7,自引:0,他引:7
研究了用Cyanex301[TM]铵盐在苯中重结晶以纯化Cyanex301的方法,该法收率62.4%,产品纯度>99%。测定了经纯化后产品的红外光谱,研究了纯化产品在-水正庚烷体系中的分配平衡及其在正庚烷中的缔合,浓度在0.2~1.0mo1/L范围,Cyanex301主要以二聚形式存在。 相似文献
87.
An improved method has been developed for the determination of acrylamide in infant powdered milk and baby foods in jars, a particular class of foodstuffs which represent an important source of nutrition for young infants and babies. This method uses isotope dilution liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization and is significantly more sensitive than previous published methods with a limit of quantification estimated at 1 microg kg(-1). The new method offers effective sample preparation procedures including defatting with petroleum ether, extraction with aqueous solution of sodium chloride, further liquid-liquid extraction with ethyl acetate and clean-up by solid-phase extraction (SPE) with HLB 200 mg cartridges. The analytical method was well validated and good results were obtained with respect to repeatability (RSD < 5%) and recovery (86-97%) which fulfilled the requirements defined by European Union (EU) legislation. The acrylamide level in infant powdered milk and baby foods in jars were 3.01-9.06 microg kg(-1) and 6.80-124.93 microg kg(-1), respectively. Especially, this new method is successfully applied to the trace quantification of acrylamide in infant/baby foods, the content of which is less than 10 microg kg(-1). 相似文献
88.
The electrochemical enzyme-linked immunoassay increases the sensitivity of the detection of cucumber mosaic virus (CMV) by 5-fold compared with the spectrophotometric o-phenylenediamine (OPD) enzyme-linked immunosorbent assay (ELISA). The detection limit for the purified CMV is 1.0 ng/mL and the highest dilution ratio of the infected leaf sap is 1:5.0 x 10(4). The method is based on coupling the oxidation reaction of o-aminophenol (OAP)-H2O2 catalyzed by HRP-IgG conjugate with the electro-reduction of the enzymatic product. The enzymatic product 2-aminophenoxazine-3-one exhibits a sensitive second order derivative linear-sweep voltammetric response at the potential of -0.65 V (vs. Ag/AgCl) in pH 8.0 Britton-Robinson (B-R) buffer solution. So it can be applied to the detection of the plant virus with highly improved sensitivity. 相似文献
89.
Electrochemical studies on the interaction of heparin with crystal violet and its analytical application 总被引:1,自引:0,他引:1
In this paper, crystal violet (CV) was used to determine heparin concentration by linear sweep voltammetry on a dropping mercury
electrode (DME). In Britton-Robinson (B-R) buffer solution, pH 3.0, CV had a well-defined second-order derivative linear sweep
voltammetric reductive wave at −0.74 V (vs. SCE). After the addition of heparin to the CV solution, the reductive peak current
decreased greatly with the positive movement of the peak potential and without appearance of new peaks in the scanning potential
range. Based on the decrease in the reductive peak current, a new voltammetric method for the determination of heparin was
established. The conditions for the interaction and the electrochemical detection were optimized, and interfering substances
were investigated. Under the optimal conditions, the decrease in reductive peak currents of CV was proportional to heparin
concentration in the range 0.1–8.0 mg/L with the linear regression equation Δip″(nA) = 400.42 + 1563.11c (mg/L), (n = 14, γ = 0.993). The detection limit was 0.092 mg/L. This new method was further successfully applied to the determination of heparin
content in heparin sodium injection samples with satisfactory results. The binding ratio and binding mechanism were also studied
by the electrochemical method.
The text was submitted by the authors in English. 相似文献
90.
We compute the quantum rate constant based on two extended stationary phase approximations to the imaginary-time formulation of the quantum rate theory. The optimized stationary phase approximation to the imaginary-time flux-flux correlation function employs the optimized quadratic reference system to overcome the inaccuracy of the quadratic expansion in the standard stationary phase approximation, and yields favorable agreements with instanton results for both adiabatic and nonadiabatic processes in dissipative and nondissipative systems. The integrated stationary phase approximation to the two-dimensional barrier free energy is particularly useful for adiabatic processes and demonstrates consistent results with the imaginary-time flux-flux correlation function approach. Our stationary phase methods do not require calculation of tunneling paths or stability matrices, and work equally well in the high-temperature and the low-temperature regimes. The numerical results suggest their general applicability for calibration of imaginary-time methods and for the calculation of quantum rate constants in systems with a large number of degrees of freedom. 相似文献