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31.
32.
The specific heat of A-15 Nb3Al.83Ge.21 with a transition temperature, Tc, of 20.0 K has been measured from 6 to 25 K. Values of the parameters derived from the data are γ=35.0±2 mJ/mole-K2; the Debye temperature, θD=278±5 K; the energy gap, △, normalized as 2△/kTc, is 4.9±.3, and the thermodynamic critical field, Hc(0), is 4700±300 Gauss. 相似文献
33.
Ambrosi G Boggioni A Formica M Fusi V Giorgi L Lucarini S Micheloni M Secco F Venturini M Zappia G 《Dalton transactions (Cambridge, England : 2003)》2005,(3):485-490
The equilibria and kinetics of the binding of gallium(III) to 4-(N),10-(N)-bis[2-(3-hydroxo-2-oxo-2-H-pyridine-1-y1)acetamido]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L) were investigated in acidic medium at ionic strength 1 M (NaClO4). Spectrophotometric titrations in the UV region revealed that L is able to bind Ga3+ also at high H+ concentration. The kinetic (stopped-flow) experiments are interpreted on the basis of three parallel reaction paths (i) M3+ + H2L2+ = M(H2L)5+ where M(H2L)5+ is in a steady state, (ii) M(OH)2+ + H2L2+ = M(HL)4+ + H2O and (iii) M(OH)2+ + HL+ = ML3+ + H2O. The first-order rate constants for conversion of the outer-sphere into the inner-sphere complexes are similar to those of the Ga(III)/tropolone system which is known to react according to the dissociative Id mechanism and to the relevant rate constants for water exchange at the metal ion. The effects of pH on the UV-Vis absorption, fluorescence emission properties and NMR spectral features on the Ga(III)/L system were also investigated. Spectrophotometric titrations in the UV region reveal that, in acid medium the prevailing species is M(HL)4+ whereas the chelate ML3+ prevails for [H+] < 0.01 M. The results indicate metal coordination at the oxygen atoms of the 3-hydroxo-2-oxopyridine residues. 相似文献
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Using a perturbatively nonrenormalizable and non-perturbatively finite example(delta-function-type potential in nonrelativistic quantum mechanics), we illustratethat one can develop a perturbative approach for a nonrenormalizable theory.The key idea is the introduction of an additional expansion parameter whichallows us to eliminate infinities from the perturbative expressions. The generatedperturbative series reproduce the expansion of the exact analytical solution. 相似文献
37.
Summary Large helium-free emissions are obtained in two mini-TEA CO2 lasers, by using always a corona preionization without additives and with a maximum energy density of 900J/l in the discharge.
In general, helium-free emissions are more stable, but the best condition in efficiency, energy and peak power is observed
always with a small He content added to the laser mixture.
Riassunto L'uso di una piú efficiente preionizzazione a corona ha permesso l'operazione di un laser a CO2 senza elio a pressione atmosferica con elevate densità di energia nella scarica (900 J/l) e grande efficienza di conversione dell'energia elettrica in radiazione laser.相似文献
38.
Tiziana Giorgi Robert Smits 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2008,124(1):600-618
We consider the principal eigenvalue λ
1Ω(α) corresponding to Δu = λ (α) u in
W, \frac?u?v = au \Omega, \frac{\partial u}{\partial v} = \alpha u on ∂Ω, with α a fixed real, and W ì Rn\Omega \subset {\mathcal{R}}^n a C
0,1 bounded domain. If α > 0 and small, we derive bounds for λ
1Ω(α) in terms of a Stekloff-type eigenvalue; while for α > 0 large we study the behavior of its growth in terms of maximum curvature.
We analyze how domain monotonicity of the principal eigenvalue depends on the geometry of the domain, and prove that domains
which exhibit domain monotonicity for every α are calibrable. We conjecture that a domain has the domain monotonicity property for some α if and only if it is calibrable. 相似文献
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G.I. Japaridze S. Sarkar 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):139-144
A one-dimensional model of interacting electrons with on-site U, nearest-neighbor V, and pair-hopping interaction W is studied at half-filling using the continuum limit field theory approach. The ground state phase diagram is obtained for
a wide range of coupling constants. In addition to the insulating spin-density wave (SDW) and charge-density wave (CDW) phases
for large U and V, respectively, we identify a bond-charge-density-wave (BCDW) phase W < 0, | U - 2V| < | 2W| and a bond-spin-density-wave (BSDW) for W > 0, | U - 2V| < W. The possibility of bond-located ordering results from the site-off-diagonal nature of the pair-hopping term and is a special
feature of the half-filled band case. The BCDW phase corresponding to an enhanced Peierls instability in the system. The BdSDW
is an unconventional insulating magnetic phase, characterized by a gapless spin excitation spectrum and a staggered magnetization
located on bonds between sites. The general ground state phase diagram including insulating, metallic, and superconducting
phases is discussed. A transition to the η-superconducting phase at | U - 2V| ≪ 2t?W is briefly discussed.
Received 20 February 2002 / Received in final form 11 April 2002 Published online 19 July 2002 相似文献