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171.
172.
173.
It is conceivable that the high-T
c
superconducting perovskites are conventional electronphonon superconductors. In this case one expects significant strong-coupling effects because of the unusually high ratiok
B
T
c
/ of the order 0.1 and greater. We use a set of reasonable models for the Eliashberg function 2
F() (which takes into account available information on the phonon spectra and which fit the measuredT
c
's) and calculate strong-coupling effects in the specific heatc
s
(T)/T
c
, the ratio 0/k
B
T
c
, the critical fieldsH
c
(T) andH
c2
(T) including Pauli limiting, and other measurable quantities. Strongcoupling corrections turn out to be in the range of 0 to about 100%, depending on the quantity of interest. We discuss the perspectives of using strong-coupling effects as indicators for conventional electron-phonon superconductivity in the new materials. 相似文献
174.
175.
176.
J. P. Osleeb S. J. Ratick P. Buckley K. Lee M. Kuby 《Annals of Operations Research》1986,6(6):161-180
The formulation and use of a mixed integer mathematical programming location-allocation model, the Coal Logistics System (COLS), is presented in this study. COLS is used to evaluate the potential for reducing water-borne coal transportation costs, and concomitantly the costs of delivering coal to European markets. This cost reduction is accomplished through the use of supercolliers which would require the dredging of channels at selected ports or the use of offshore loading sites at East and Gulf Coast ports or both. The model developed and the analysis presented in this paper are intended to aid in the determination of the location and extent of these activities, and to indicate the size of the potential reduction in the costs of U.S. export coal. In order to be able to accommodate these deeper draft vessels at East and Gulf Coast ports, expensive improvements would need to be undertaken which may include the deepening of harbor channels to the depths required for 120 000 dead weight ton (dwt) or larger supercolliers. Since dredging requires large initial investments and has significant long-term maintenance costs, excess capacity could represent an inefficient use of both U.S. revenues and the ports' own funds. The use of offshore loading moorings to permit the topping off of supercolliers by self-unloading colliers at the deepwater sections of harbor channels has been proposed as a way of reducing trans-ocean transportation costs and avoiding the large investments and time delays associated with dredging activities. The Coal Logistics System was modified and extended to enable the evaluation of these two port improvement options to be undertaken in a consistent and realistic manner. 相似文献
177.
An experimental investigation on shortening of travelling-wave ASE employing a transversal pumping is presented. A N2 laser with =337.1 nm, pulsewidth: 700 ps is used as a pump source. An ASE pulse with duration of 45, 55 and 45 ps from dye solution of Rh 6G, Rh B and C311, respectively, is obtained. Pulse shapes of output signals generated from these solutions in three different pumping schemes are compared. 相似文献
178.
Treatment of (thd)H (thd=2,2,6,6-tetramethyl-3,5-heptandionate) with excess Os3(CO)12 in an autoclave at 180°C gives the formation of a brown metal chain complex [Os2(CO)5(thd)2]2 (1) and a yellow CO2 cluster complex [Os4(-H)(-CO2)(thd)(CO)13] (2) in low yields. Complex 2 was fully identified by a combination of spectroscopic methods and X-ray diffraction study, showing a unique CO2 ligand bridging a triosmium metal fragment, Os3(-H)(CO)10 and a monometallic osmium fragment, Os(CO)3(thd). Upon treatment of 1 with Me3NO at an elevated temperature, oxidation of the CO ligand occurred at the position trans to the unique CO2 ligand on the Os(CO)3(thd) fragment, giving the formation of a second CO2 cluster [Os4(-H)(-CO2)(thd)(CO)12(NCMe)] (3), which is stabilized by a weakly coordinated acetonitrile molecule. 相似文献
179.
Lin CS Zhang RQ Lee ST Elstner M Frauenheim T Wan LJ 《The journal of physical chemistry. B》2005,109(29):14183-14188
The assembly of small water clusters (H2O)n, n = 1-6, on a graphite surface is studied using a density functional tight-binding method complemented with an empirical van der Waals force correction, with confirmation using second-order M?ller-Plesset perturbation theory. It is shown that the optimized geometry of the water hexamer may change its original structure to an isoenergy one when interacting with a graphite surface in some specific orientation, while the smaller water cluster will maintain its cyclic or linear configurations (for the water dimer). The binding energy of water clusters interacting with graphite is dependent on the number of water molecules that form hydrogen bonds, but is independent of the water cluster size. These physically adsorbed water clusters show little change in their IR peak position and leave an almost perfect graphite surface. 相似文献
180.
Biosynthesis of polyhydroxyalkanoates (PHAs) consisting of 3-hydroxyalkanoates (3HAs) of 4 to 10 carbon atoms was examined
in metabolically engineered Escherichia coli strains. When the fadA and/or fadB mutant E. coli strains harboring the plasmid containing the Pseudomonas sp. 61-3 phaC2 gene and the Ralstonia eutropha phaAB genes were cultured in Luria-Bertani (LB) medium supplemented with 2 g/L of sodium decanoate, all the recombinant E. coli strains synthesized PHAs consisting of C4, C6, C8, and C10 monomer units. The monomer composition of PHA was dependent on
the E. coli strain used. When the fadA mutant E. coli was employed, PHA containing up to 63 mol% of 3-hydroyhexanoate was produced. In fadB and fadAB mutant E. coli strains, 3-hydroxybutyrate (3HB) was efficiently incorporated into PHA up to 86 mol%. Cultivation of recombinant fadA and/or fadB mutant E. coli strains in LB medium containing 10 g/L of sodium gluconate and 2 g/L of sodium decanoate resulted in the production of PHA
copolymer containing a very high fraction of 3HB up to 95 mol%. Since the material properties of PHA copolymer consisting
of a large fraction of 3HB and a small fraction of medium-chain-length 3HA are similar to those of low-density polyethylene,
recombinant E. coli strains constructed in this study should be useful for the production of PHAs suitable for various commercial applications. 相似文献