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991.
992.
The thermal properties of perfluorocarbonsulfonic acid ionomer films cast from solution and their temperature-dependent far infrared spectra have been investigated. In addition to the endotherms and spectral changes associated with the loss of solvent as the films were heated, a significant exotherm has been observed and assigned to the relaxation associated with rearrangements resulting in partially crystallized phases in insoluble thermally treated membranes. © 1993 John Wiley & Sons, Inc. 相似文献
993.
Demin D. L. Dzhelepov V. P. Filchenkov V. V. Grafov N. N. Grebinnik V. G. Migachev D. V. Konin A. D. Rudenko A. I. Sidorov V. T. Zhestkov Yu. G. Zinov V. G. Davies J. D. Bom V. R. van Eijk C. W. E. 《Hyperfine Interactions》1996,101(1):13-19
The ddµ molecule formation rate is experimentally measured for the two hyperfine states of the dµ-atom in the temperature range of 5–30 K. Results are consistent with a preliminary measurement by the TRIUMF group and contradict theoretical predictions. The work has been performed on the JINR phasotron (Dubna). 相似文献
994.
995.
996.
997.
998.
J. Telser H. -I. Lee E. T. Smith H. Huang P. Brereton M. W. W. Adams R. C. Conover M. K. Johnson B. M. Hoffman 《Applied magnetic resonance》1998,14(2-3):305-321
The hyperthermophilic archaeonPyrococcus furiosus contains a four-Fe ferredoxin (Pf- Fd) that differs from most other 4Fe-Fd’s in that its [Fe4S4] cluster is anchored to protein by only three cysteinyl residues.Pf- Fd also is of interest because in its reduced form, [Fe4S4]+, the cluster exhibits bothS = 1/2 andS = 3/2 spin states. Addition of excess cyanide ion converts the cluster exclusively to anS = 1/2 state (g1 = 2.09, g2 = 1.95, g3 = 1.92), however dialysis restores the EPR signal of native reduced protein indicating that the cluster is not irreversibly altered by cyanide. Both the native protein and protein in the presence of excess cyanide ion (Pf- Fd 4Fe-CN) were investigated here using the techniques of electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy. In particular,Pf- Fd 4Fe-CN was investigated using13CN? and C15N? ligands.13C and15N ENDOR indicated that a single cyanide ion bound directly, with the cluster showing an unusually small contact interaction (aiso(13C)~ ?3 MHz, aiso(15N) ~ 0). This is in contrast to cyanide bound to monomeric low-spin Fe(III)-containing proteins such as transferrin and myoglobin, for which the13C hyperfine coupling has a large isotropic component (aiso(13C) ≈ ?30 MHz). This small contact interaction is not due to low spin density of Fe, as57Fe ENDOR of the singly and triply labeledPf- Fd 4FeCN isotopologs, [57FeFe3S4]+ and [Fe57Fe3S4]+, show hyperfine coupling characteristic for [Fe4S4]+ clusters, particularly for the Fe to which cyanide binds. Thus, the low spin density on13C is not due to low spin density on the Fe ion to which it binds. Further theoretical work is needed to explain the contrast between the strong electronic effect of cyanide ion binding with the low spin density on the ligand. 相似文献
999.
Davis J. Clark R.W. Giuliani J.L. Jr. Thornhill J.W. Deeney C. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(4):1192-1201
In this paper, we study the dynamics of a massive aluminum Z-pinch plasma load and evaluate its performance as a soft X-ray radiator. A radiation hydrodynamic model self-consistently driven by a circuit describes the dynamics. Comparisons are made for the K- and L-shell soft X-ray emission as a function of the ionization dynamic model. The ionization dynamic models are represented by: 1) a time-dependent nonequilibrium (NEQ) model, 2) a collisional radiative equilibrium (CRE) model, and 3) a local thermodynamic equilibrium (LTE) model. For all three scenarios the radiation is treated 1) in the free streaming optically thin approximation where the plasma is treated as a volume emitter and 2) in the optically thick regime where the opacity for the lines and continuum is self-consistently calculated online and the radiation is transported through the plasma. Each simulation is carried out independently to determine the sensitivity of the implosion dynamics to the ionization and radiation model, i.e., how the ionization dynamic model affects the radiative yield and emission spectra. Results are presented for the L- and K-shell radiation yields and emission spectra as a function of photon energy from 10 eV to 10 keV. Also, departure coefficients from LTE are presented for selected levels and ionization stages 相似文献
1000.
N. V. Gaponenko A. V. Mudryi O. V. Sergeev M. Stepikhova L. Palmetshofer W. Jantsch J. C. Pivin B. Hamilton A. S. Baran A. I. Rat''ko 《Journal of luminescence》1998,80(1-4):399-403
Sol–gel derived Fe2O3 films containing about 10 wt% of Er2O3 were deposited on porous silicon by dipping or by a spin-on technique followed by thermal processing at 1073 K for 15 min. The samples were characterized by means of PL, SEM and X-ray diffraction analyses. They exhibit strong room-temperature luminescence at 1.5 μm related to erbium in the sol–gel derived host. The luminescence intensity increases by a factor of 1000 when the samples are cooled from 300 to 4.2 K. After complete removal of the erbium-doped film by etching and partial etching the porous silicon, the erbium-related luminescence disappears. Following this, luminescence at 1.5 μm originating from optically active dislocations (“D-lines”) in porous silicon was detected. The influence of the conditions of synthesis on luminescence at 1.5 μm is discussed. 相似文献