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1.
Perturbed γ-angular correlation measurements as function of the measuring temperature and the Sn-content have been performed in Sn-doped cubic In2O3 using 111In(EC)111Cd and 111m Cd probes. By comparing the spectra of both isotopes, electronic relaxation phenomena, socalled decay after-effects, following the electron capture radioactive decay of 111In, were established. A time independent loss of the static quadrupole interaction amplitudes was found to be characteristic for the electronic relaxation, and its temperature and doping dependence were measured. The high statistical accuracy of the PAC-data allowed a separation between structural and dynamic effects and the observation of each lattice site’s behaviour. Relaxation rates were extracted from numerical simulations based on Blume’s theory and related to the predominant electron transport mechanisms in In2O3, especially, with rising Sn-content, to the transition to metallic conduction.  相似文献   
2.
High resolution γ-ray studies have shown the decay patterns of isomers of 85Y to be very complex. A level scheme of 85Sr is proposed from the results of γ-γ coincidence measurements. Spin and parity assignments to the levels of 85Sr were made on the basis of log ft values, nuclear reaction data and γ-ray branchings. The level scheme is discussed within the theoretical framework of n(g92)?3 cluster properties.  相似文献   
3.
4.
The electric hyperfine interaction of ion beam implanted 111In and 111Cd probe atoms in sapphire (Al2O3) single crystals has been investigated using perturbed angular correlation spectroscopy. For both probe atoms the same distinctive electric field gradient was found, indicating that nearly all the implanted probe atoms form a stable substitutional configuration in the temperature range between 77 K and 873 K on the aluminum sublattice. A comparative study between 111In and 111Cd-measurements points to a dynamic interaction initiated by the electron-capture of 111In(EC)111Cd similar to In2O3 and La2O3. Size and orientation of the EFG are discussed in comparison to experimental results in Cr2O3 single crystals. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
5.

Background  

We describe the database ExplorEnz, which is the primary repository for EC numbers and enzyme data that are being curated on behalf of the IUBMB. The enzyme nomenclature is incorporated into many other resources, including the ExPASy-ENZYME, BRENDA and KEGG bioinformatics databases.  相似文献   
6.
The implementation of fewest-switches surface-hopping (FSSH) within time-dependent Kohn-Sham (TDKS) theory [Phys. Rev. Lett. 95, 163001 (2005)] has allowed us to study successfully excited state dynamics involving many electronic states in a variety of molecular and nanoscale systems, including chromophore-semiconductor interfaces, semiconductor and metallic quantum dots, carbon nanotubes and graphene nanoribbons, etc. At the same time, a concern has been raised that the KS orbital basis used in the calculation provides only approximate potential energy surfaces [J. Chem. Phys. 125, 014110 (2006)]. While this approximation does exist in our method, we show here that FSSH-TDKS is a viable option for computationally efficient calculations in large systems with straightforward excited state dynamics. We demonstrate that the potential energy surfaces and nonadiabatic transition probabilities obtained within the TDKS and linear response (LR) time-dependent density functional theories (TDDFT) agree semiquantitatively for three different systems, including an organic chromophore ligating a transition metal, a quantum dot, and a small molecule. Further, in the latter case the FSSH-TDKS procedure generates results that are in line with FSSH implemented within LR-TDDFT. The FSSH-TDKS approach is successful for several reasons. First, single-particle KS excitations often give a good representation of LR excitations. In this regard, DFT compares favorably with the Hartree-Fock theory, for which LR excitations are typically combinations of multiple single-particle excitations. Second, the majority of the FSSH-TDKS applications have been performed with large systems involving simple excitations types. Excitation of a single electron in such systems creates a relatively small perturbation to the total electron density summed over all electrons, and it has a small effect on the nuclear dynamics compared, for instance, with thermal nuclear fluctuations. In such cases an additional, classical-path approximation can be made. Third, typical observables measured in time-resolved experiments involve averaging over many initial conditions. Such averaging tends to cancel out random errors that may be encountered in individual simulated trajectories. Finally, if the flow of energy between electronic and nuclear subsystems is insignificant, the ad hoc FSSH procedure is not required, and a straightforward mean-field, Ehrenfest approach is sufficient. Then, the KS representation provides rigorously a convenient and efficient basis for numerically solving the TDDFT equations of motion.  相似文献   
7.
We report on the first fabrication of nanostructures with exactly resonant light revealing the quantum character of the atom-light interaction. Classically the formation of nanostructures is not expected; thus, the observed formation of complex periodic line patterns can be explained only by treating atom-light interaction and propagation of the atoms quantum mechanically. Our numerical quantum calculations are in quantitative agreement with this experimental finding. Moreover, the theory predicts that for small detunings nanostructures with lambda/4 period can be produced, which beats the standard nanofabrication limit of lambda/2. Our experiments confirm this prediction.  相似文献   
8.

Background  

Cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN) has been used successfully to induce immune responses against viral and intracellular organisms in mammals. The main objective of this study was to test the effect of CpG-ODN on antigen presenting cells of young foals.  相似文献   
9.
Two isomers of bis(carbomethoxybenzo)-24-crown-8 (cis-BCMB24C8, 1, and trans-BCMB24C8, 2) were synthesized regiospecifically with acceptable to excellent yields. Cyclization in the presence of a template reagent, KPF(6), led to an essentially quantitative yield of the potassium complex of the crown ether 1; the isolated cyclization yield of pure was a remarkable 89%! The methods not only avoid the very difficult separation of the isomers, but also greatly shorten the synthesis time by eliminating syringe pump usage during cyclization. The complexations of the isomeric BCMB24C8 with dibenzylammonium hexafluorophosphate (10) were studied by NMR; association constants (Ka) for 1 and 2 with the dibenzylammonium cation are 190 and 312 M(-1), respectively. The X-ray crystal structures of crown ether and the complexes 1.KPF(6), 2.KPF(6) and pseudorotaxane 2.10 were determined.  相似文献   
10.
The electron and hole relaxation in the (7, 0) zigzag carbon nanotube is simulated in time domain using a surface-hopping Kohn-Sham density functional theory. Following a photoexcitation between the second van Hove singularities, the electrons and holes decay to the Fermi level on characteristic subpicosecond time scales. Surprisingly, despite a lower density of states, the electrons relax faster than the holes. The relaxation is primarily mediated by the high-frequency longitudinal optical (LO) phonons. Hole dynamics are more complex than the electron dynamics: in addition to the LO phonons, holes couple to lower frequency breathing modes and decay over multiple time scales.  相似文献   
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