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71.
We compare the low bias conductance of a series of alkanes terminated on their ends with dimethyl phosphines, methyl sulfides, and amines and find that junctions formed with dimethyl phosphine terminated alkanes have the highest conductance. We see unambiguous conductance signatures with these link groups, indicating that the binding is well-defined and electronically selective. This allows a detailed analysis of the single-molecule junction elongation properties which correlate well with calculations based on density functional theory.  相似文献   
72.
73.
Four asymmetric cobalt(III) complexes, [Co(bpy)2(aip)]3+, [Co(bpy)2(pyip)]3+, [Co(phen)2(aip)]3+, and [Co(phen)2(pyip)]3+ (bpy = 2,2,bipyridine, phen = 1,10-phenathroline), (pyip = 2-(1-pyrenyl)-1H-imidazo[4,5-f][phen], (aip = 2-(9-anthryl)-1H-imidazo[4,5,-f][phen], have been synthesized and characterized. Their interaction with calf thymus DNA (CT-DNA) was investigated by physico-chemical methods and photocleavage. The size and shape of the ligands have a marked effect on the DNA-binding affinity of the complexes. Irradiation of pBR322 DNA with these novel cobalt(III) complexes results in nicking of the plasmid DNA. Toxicity and induced cell death investigations revealed that the complexes of pyip had higher toxicity than those of aip. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
74.
本文根据内燃机缸内流动的LDA测量数据的特点,讨论了低通滤波过程、数据预处理过程、截止频率的选择、数据处理误差等,论述了在目前LDA测量数据率还不够高的情况下,如何较好地用低通滤波法对LDA测量数据进行单一循环分析处理,最大限度地减少数据处理误差.  相似文献   
75.
Temperature and frequency dependence of dielectric constant and conductivity properties of Pb0.77K0.26Li0.2Ti0.25Nb1.8O6 (PKLTN) ceramics are modelled through the universal dielectric response (UDR). Partial substitution of Ti4+ for Nb5+ was compensated by charge and the creation of oxygen vacancies according to the Kroger-Vink notation. The electrons released by this reaction are captured by Nb5+ and Ti4+ to generate Nb3+ and/or Ti3+. The hopping of electrons between Nb5+–Nb3+ and Ti4+–Ti3+ are believed to participate in conductivity. Characterization of the dielectric constant has been performed from room temperature to 590°C in the frequency range from 45 Hz to 5 MHz. The measured dielectric constant obeyed Jonscher's dielectric dispersion relations: ε l = ε + sin(n(T)π/2)(a(T)/ε 0)(ωn ( T )?1) and ε ll = σ/ 0 ω + cos(n(T)π/2)(a(T)/ε 0)(ωn ( T )?1). Cole-Cole plots inclined at an angle (1 ? n(T))π/2 and followed the trend of universal material behavior ε + A(T)(ωn ( T )?1). The exponent n(T) and coefficient A(T) = (a(T)S/L) exhibited a minimum and maximum at T c = 425°C, respectively. The conductivity studies show the contribution of the hopping of bound charge carriers to conduction in PKLTN.  相似文献   
76.
Sodium hydrogen succinate, an alkali metallo-organic third-order nonlinear optical crystal, had been grown successfully using aqueous solution by slow evaporation technique at room temperature. Transparent single crystals were selected and subjected to single-crystal X-ray diffraction analysis to identify lattice parameters, space group and morphology. The grown crystal was further subjected to powder X-ray diffraction to analyze the crystalline quality, UV–Vis–NIR spectral analysis to reveal optical transparency, FTIR spectroscopy for confirmation of the functional group analysis and TG–DTG/DSC analysis to determine the thermal stability. The dielectric constant and dielectric loss were studied as a function of frequency at different temperatures, and the results were discussed. The mechanical properties were calculated by Vickers microhardness test, and the third-order nonlinear optical parameters such as nonlinear refractive index, nonlinear absorption coefficient and real and imaginary parts of the third-order nonlinear optical susceptibility were determined by Z-scan technique.  相似文献   
77.
78.
Let G = (V, E) be a connected graph. A set D ? V is a set-dominating set (sd-set) if for every set T ? V ? D, there exists a nonempty set S ? D such that the subgraph 〈ST〉 induced by ST is connected. The set-domination number γs(G) of G is the minimum cardinality of a sd-set. In this paper we develop properties of this new parameter and relate it to some other known domination parameters.  相似文献   
79.
Three symmetric ligands 7-methyl dipyrido-[3,2-a;2′,3′-c]phenazine (dppz-CH3), 7-nitro dipyrido-[3,2-a;2′,3′-c]phenazine (dppz-NO2) and benzo[i]dipyrido-[3,2-a;2′,3′-c]phenazine (dppn) and their ruthenium(II) complexes [Ru(en)2(L)][ClO4]2 (en= ethylenediamine), L= dppz-CH3, dppz-NO2 and dppn have been synthesized and characterized by IR, 1H, 13C NMR and Mass spectra. The interactions of these complexes with calf thymus DNA have been investigated by spectrophotometric, spectrofluorimetric, circular dichroism, viscosity and thermal denaturation studies. As the planar extension of the intercalative ligand increases, the interaction of the complex with DNA increases, indicating that the size and shape of the intercalalative ligand has a marked effect on the strength of interaction. The plot of log K versus log [Na+] yield a slope of -1.26, -1.53, -1.60 for the complexes 1, 2 and 3 respectively. These three complexes have been found to promote the cleavage of plasmid pBR 322 DNA upon irradiation.  相似文献   
80.
In this paper,we establish a new algorithm to the non-overlapping Schwarz domain decomposition methods with changing transmission conditions for solving one dimensional advection reaction diffusion problem.More precisely,we first describe the new algorithm and prove the convergence results under several natural assumptions on the sequences of parameters which determine the transmission conditions.Then we give a simple method to estimate the new value of parameters in each iteration.The interesti...  相似文献   
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