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101.
A. Gold 《Zeitschrift für Physik B Condensed Matter》1994,95(3):341-355
We calculate the local-field correctionsG(q, q
z) f electron superlattices with interlayer distanced in order to describe many-body effects. A generalized Hubbard expression for the local-field correction is derived. The sum-rule version of the self-consistent approach for the local-field correction is developed and used to discuss the effects of exchange and correlation. The RPA-parameterr
s and the ratiod/a
* determine the many-body effects.a
* is the effective Bohr radius. The stability region for the Fermi liquid behavior of the layered electron gas is discussed: (i) forda
* the critical RPA-parameterr
sc1 is determined by exchange andintraplane correlation effects, (ii) forda
* withr
sc1 correlation effects are small and the instability point is mainly determined by exchange effects, (iii) forda
* withr
sc<1 exchange andinterplane correlation effects are both important for the instability point. Our results are important for high-T
c superconductors, organic superconductors and semiconductor superlattices. 相似文献
102.
F. R. Aussenegg A. Leitner H. Gold 《Applied Physics A: Materials Science & Processing》1995,60(2):97-101
In metal-island films consisting of nanometer particles on a transparent substrate irradiated light fields can be locally enhanced by electron-plasma resonances. Therefore, nonlinear optical processes should be enhanced dramatically. However, second-order nonlinear processes as second-harmonic generation occuring in the surface are strongly reduced by the centrosymmetric shape of the metal particles. It is found that this surface-specific contribution to second-harmonic generation is less enhanced, as is expected from the field enhancement. The bulk contribution, at smooth metal surfaces known to be much weaker than the contribution from the real surface, is strongly enhanced by the plasma resonances without symmetry restrictions and becomes comparably important.Paper presented at the 129th WE-Heraeus-Seminar on Surface Studies by Nonlinear Laser Spectroscopies, Kassel, Germany, May 30 to June 1, 1994. 相似文献
103.
A new method is described for the determination of Ni based on the cathodic adsorptive stripping of Ni(II) complexed with hydroxynaphthol blue (HNB) at a static mercury drop electrode. Optimal conditions were found to be: accumulation potential -0.50 V (vs. Ag/AgCl); final potential -1.10 V; accumulation time 50 sec; scan rate 200 mV/sec; linear scan mode; filter 0.1 sec; supporting electrolyte acetic acid/acetate (0.25M, pH = 6.0) and concentration of HNB 3.3 x 10(-5)M. The response of the system was found to be linear in a range of Ni concentrations from 25 ppb to the detection limit. The detection limit was found to be 1.7 nM (0.10 ppb) with 2 mins of accumulation time. The effect of various potential interferences (including a variety of cations, anions and organic surfactants) were also studied. With the exception of Co, at less than equimolar concentrations no significant interferences were observed. Al was found to interfere at high concentrations with respect to Ni, but Al concentrations up to 1000 ppb may be masked by sodium citrate or sodium fluoride. The utility of the method is demonstrated by the recovery of Ni in a doped sample of commercial mineral water. 相似文献
104.
P. Steiner S. Hüfner V. Kinsinger I. Sander B. Siegwart H. Schmitt R. Schulz S. Junk G. Schwitzgebel A. Gold C. Politis H. P. Müller R. Hoppe S. Kemmler-Sack C. Kunz 《Zeitschrift für Physik B Condensed Matter》1988,69(4):449-458
From XPS core level spectroscopy the average copper charge on the Cu sites in the high temperature superconductor Y1Ba2Cu3O7–x
is determined as function of the oxygen vacancy concentrationx. Analysis of these data leads to the suggestion that there are holes on the oxygen sites in the basal plane of the crystal structure. The probability for holes on these oxygen ions is rather constant for 0x0.3 with a value of 0.64 and decreases to zero forx=0.5. The dependence of the superconducting transition temperature on the hole concentration is discussed. An energy level diagram for Cu2+ and Cu3+ in YBa2Cu3O7–x
is constructed. 相似文献
105.
Li JS Chen FX Shikiya R Marky LA Gold B 《Journal of the American Chemical Society》2005,127(36):12657-12665
Stable DNA triple-helical structures are normally restricted to homopurine sequences. We have described a system of four heterocyclic bases (TRIPsides) that, when incorporated into oligomers (oligoTRIPs), can recognize and bind in the major groove to any native sequence of DNA [Li et al., J. Am. Chem. Soc. 2003, 125, 2084]. To date, we have reported on triplex-forming oligomers composed of two of these TRIPsides, i.e., antiTA and antiGC, and their ability to form intramolecular triplexes at mixed purine/pyrimidine sequences. In the present study, we describe the synthesis and characterization of the antiCG TRIPside and its use in conjunction with antiTA and antiGC to form sequence-specific intra- and/or intermolecular triplex structures at mixed purine/pyrimidine sequences that require as many as four major groove crossovers. 相似文献
106.
107.
108.
109.
110.
Riles K Perl ML Barklow T Boyarski A Burchat PR Burke DL Dorfan JM Feldman GJ Gladney L Hanson G Hayes K Hollebeek RJ Innes WR Jaros JA Karlen D Klein SR Lankford AJ Larsen RR LeClaire BW Lockyer NS Lüth V Ong RA Richter B Yelton JM Abrams G Amidei D Baden AR Boyer J Butler F Gidal G Gold MS Goldhaber G Golding L Haggerty J Herrup D Juricic I Kadyk JA Levi ME Nelson ME Rowson PC Schellman H Schmidke WB Sheldon PD Trilling GH Wood DR Schaad T 《Physical review D: Particles and fields》1990,42(1):1-9