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1.
We report six-dimensional quantum dynamics calculations of the dissociative scattering of molecular hydrogen from the copper111 surface. Two potential energy surfaces are investigated and the results are compared with experiment. Our study completes the preliminary work of Somers et al. [Chem. Phys. Lett. 360, 390 (2002)] and focuses on the role of initial vibrational excitation and on isotopic effects. None of the two investigated potential energy surfaces is found satisfactory: the use of neither potential yields reaction and vibrational excitation probabilities and vibrational efficacies that are in close agreement with experiment. In addition to showing the shortcomings of existing potential energy surfaces we point out an inconsistency in the experimental fits for D2. 相似文献
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The effects of lattice motion and reconstruction on the dissociation of methane on Ni(111) are explored, using both electronic structure theory and quantum dynamical calculations. We show that during the reaction, the Ni lattice reconstructs, effectively lowering the barrier to reaction, in contrast with earlier models of this process. 相似文献
4.
We describe a simple real space renormalization group technique for two-dimensional classical lattice models. The approach is similar in spirit to block spin methods, but at the same time it is fundamentally based on the theory of quantum entanglement. In this sense, the technique can be thought of as a classical analogue of the density matrix renormalization group method. We demonstrate the method - which we call the tensor renormalization group method - by computing the magnetization of the triangular lattice Ising model. 相似文献
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Xianhong Feng Anthony East Willis Hammond Zohar Ophir Yi Zhang Michael Jaffe 《Journal of Thermal Analysis and Calorimetry》2012,109(3):1267-1275
Sugar-based new monomers, polymers, and low molar mass additives have emerged as an exciting topic on green chemistry research, due to the worldwide focus on sustainable material. Isosorbide and its isomers, as ??Generally Recognized as Safe?? GRAS materials, possess unique stereochemistry and molecular geometry suitable for making cost-effective chemicals and polymers. With growing awareness of bisphenol A (BPA) as a xenoestrogen, isosorbide and its isomers holding the remarkable chemical properties and attractive price can be attached to glycidyl ether to make crosslinkable epoxy resin monomers with similar properties to BPA diglycidyl ether. By adding the hydrophobic functional group into the backbone of isosorbide epoxy or adjusting the amount and type of crosslinker, the mechanical properties and the water uptake ratios (from <1 to >50?wt%) of the isosorbide-derived epoxies could be optimized for different applications. The high water uptake epoxy with controllable biodegradation rate could be used as a drug delivery system or extracellular matrix for biomedical applications while the low water uptake epoxy with strong mechanical properties could be used for can coatings, bone cements, and other industrial additives and adhesives. The chemical structures and properties of the synthesized epoxy monomers and polymers were characterized by DSC, TG, and 1H NMR. 相似文献
6.
Continuous time random walks (CTRWs) on finite arbitrarily inhomogeneous chains are studied. By introducing a technique of counting all possible trajectories, we derive closed-form solutions in Laplace space for the Green's function (propagator) and for the first passage time probability density function (PDF) for nearest neighbor CTRWs in terms of the input waiting time PDFs. These solutions are also the Laplace space solutions of the generalized master equation. Moreover, based on our counting technique, we introduce the adaptor function for expressing higher order propagators (joint PDFs of time-position variables) for CTRWs in terms of Green's functions. Using the derived formula, an escape problem from a biased chain is considered. 相似文献
7.
Elastography typically measures and images the normal strain component along the insonification/compression axis, i.e., in the axial direction. We have recently shown that, by using interpolation and cross-correlation methods of transversely displaced RF echo segments, it is possible to measure and image displacement and strain transversely to the beam with good precision. This enables the estimation and imaging of all three principal normal strain components. Generally, motion in a direction other than that in which strain is estimated may result in decorrelation noise, severely corrupting the estimates. Therefore, a correction method is applied to correct the displacement and strain estimates for decorrelating motion. In this paper, we show how corrected displacement estimates can also be used to estimate and image the shear strain components. This may allow us to identify regions of decorrelation noise in the normal strain measurement that are due to shear strain. Shear strain estimates provide supplementary information, which can characterize different tissue elements based on their mobility. In the case of breast lesions, low mobility is related to malignancy. Following an in vivo case, we show with 2D simulations how assessment of tumor mobility can be achieved with shear strain estimation. 相似文献
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Y. Nagasoe N. Ichiyanagi H. Okabayashi S. Nave J. Eastoe C. J. O'Connor 《Colloid and polymer science》1999,277(10):947-956
A homologous series of sodium dialkylsulfosuccinates (SDAS) has been synthesized with various chain lengths (dibutyl, dihexyl,
diheptyl, dioctyl, dinonyl, didecyl, diundecyl and didodecyl). These compounds are straight-chain analogues for Aerosol-OT.
Raman scattering spectra have been recordered for these SDAS compounds, both in the solid state and in aqueous solutions.
These spectra are analyzed in detail in the CH stretch and CH2 deformation regions, and the results depend specifically on the length of the hydrocarbon chain. In particular, the longitudinal
accordion-like vibrational modes coming from the all-trans n-alkyl chains have been investigated. For the SDAS dihydrates, all hydrocarbon chains take up an extended form, whereas for
the monohydrates the tails tend to become disordered at the CH2-CH2 single bond close to the terminal methyl groups. It has also been confirmed that for the concentrated aqueous SDAS (sodium
dibutylsulfosuccinate – sodium dioctylsulfosuccinate) samples preferential stabilization of the extended conformation of the
hydrocarbon chain may occur.
Received: 23 February 1999 Accepted: 10 May 1999 相似文献
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