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181.
Stereospecific styrene enchainment at a titanium site within a helical ligand framework: evidence for the formation of homochiral polystyrene 总被引:1,自引:0,他引:1
182.
D/H exchange reactions at C2, C4 and C5 of the imidazolium cation were observed in catalytic hydrogenation reactions promoted by classical Ir(I) colloid precursors and [Ir(0)](n) nanoparticles dispersed in deuterated imidazolium ionic liquids indicating the participation of carbene species in this media. However, no D/H exchange reaction was observed in cyclohexene hydrogenation promoted by iridium bulk metal dispersed in the ionic liquid [BMI]-d(3).NTf(2). The D/H labeling experiments suggest that the ionic liquids interact with the metal centers preferentially as aggregates rather than isolated ions. 相似文献
183.
On the possibility of electric transport mediated by long living intrinsic localized solectron modes
O.G. Cantu Ros L. Cruzeiro M. G. Velarde W. Ebeling 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(4):545-554
We consider a polaron Hamiltonian in which not only the lattice and the electron-lattice interactions, but also the electron
hopping term is affected by anharmonicity. We find that the one-electron ground states of this system are localized in a wide
range of the parameter space. Furthermore, low energy excited states, generated either by additional momenta in the lattice
sites or by appropriate initial electron conditions, lead to states constituted by a localized electron density and an associated
lattice distortion, which move together through the system, at subsonic or supersonic velocities. Thus we investigate here
the localized states above the ground state which correspond to moving electrons. We show that besides the stationary localized
electron states (proper polaron states) there exist moving localized solectron states which can be easily excited. The evolution
of these localized states suggests their potential as new carriers for fast electric charge transport. 相似文献
184.
Alexander?P.?Chetverikov Werner?Ebeling Gerd?R?pke Manuel?G.?VelardeEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(7):153
The quantum statistics of electrons interacting with nonlinear excitations of a classical heated nonlinear lattice of atoms is studied. By using tight-binding approximation, Wigner momentum distributions and computer simulations we show the existence of quite fast and nearly loss-free motions of charges along crystallographic axes and estimate the range of values of transport coefficients. Using minimization of free energy we estimate the density of mobile bound states between electrons and lattice solitons (so-called solectrons). We calculate the momenta of Wigner velocity distributions and from Kubo relations the diffusivity and the electrical conductivity using the relaxation time approximation. We show that thermally excited solectrons in nonlinear media may lead to a significant transport enhancement. Our estimates and computer simulations demonstrate the existence of a temperature window, where solectrons are relatively stable and contribute strongly to transport. The electrical conductivity may be enhanced up to two orders of magnitude. 相似文献
185.
Bifunctional DNA Architectonics: Three‐Way Junctions with Sticky Perylene Bisimide Caps and a Central Metal Lock 下载免费PDF全文
M. Sc. Claudia Stubinitzky Andrea Bijeljanin Linda Antusch Dr. Daniel Ebeling Priv. Doz. Dr. Hendrik Hölscher Prof. Dr. Hans‐Achim Wagenknecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12009-12014
A new type of a bifunctional DNA architecture based on a three way junction is developed that combines the structural motif of sticky perylene bisimide caps with a tris‐bipyridyl metal ion lock in the center part. A clear stabilizing effect was observed in the presence of Fe3+, Ni2+ and Zn2+ by the formation of corresponding bipyridyl complexes in the branching part of the DNA three way junctions. The dimerization of the 5′‐terminally attached perylene diimides (PDI) chromophores by hydrophobic interactions can be followed by significant changes in the UV/Vis absorption and steady‐state fluorescence. The PDI‐mediated DNA assembly occurs at temperatures below the melting temperature and is not influenced by the metal‐ion bipyridyl locks in the central part. The corresponding AFM images revealed the formation of higher‐ordered structures as the result of DNA assemblies mediated by the PDI interactions. 相似文献
186.
We analyze the quantum statistical treatment of bound states in Hydrogen considered as a system of electrons and protons. Within this physical picture we calculate analytically isotherms of pressure for Hydrogen in a broad density region and compare to some results from the chemical picture. Our study is restricted to the range of intermediate temperatures 104K < T < 105K and not too high densities n < 1024 protons per cm3, the formation of molecules is neglected. First we resume in detail the two transitions along isotherms: (i) formation of bound states occurring by increasing the density from low to moderate values, (ii) the destruction of bound states in the high density region, modelled here by Pauli‐Fock effects. Avoiding chemical models we will show, why bound states according to a discrete part of the spectra occur only in a valley in the T‐p plane. First we study virial expansions in the canonical ensemble and then in the grand canonical ensemble. We show that in fugacity representations the population of bound states saturates at higher density and that a combination of both representations provides quickly converging equations of state. In the case of degenerate systems we calculated first the density‐dependent energy levels, and find the pressure in Hartree‐Fock‐Wigner approximation showing the prominent role of Pauli blocking and Fock effects in the selfenergy (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献