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931.
C.E. Allmond V.P. Oleshko J.M. Howe J.M. Fitz-Gerald 《Applied Physics A: Materials Science & Processing》2006,82(4):675-678
Nanostructured powders have shown great promise for a variety of applications including chemical gas sensors, high surface
area supports for catalysis, tribology, chemical mechanical polishing, and optoelectronics. In this report, highly dispersed
Pd nanoparticles with a narrow size distribution, and mean diameter of 2±0.2 nm, were deposited at room temperature onto amorphous
carbon and oxide supports (TiO2, Al2O3) by pulsed-laser ablation of a Pd sputtering target. Depositions were performed in Ar at a back-fill pressure of 3 mTorr
after reaching a base pressure of 10-7 Torr. Populations of uniformly dispersed particles with an interparticle spacing of 3 to 10 nm were observed by high-resolution
transmission electron microscopy with little evidence of nanoparticle aggregation. The chemical compositions of individual
nanoparticles were confirmed by high spatial resolution energy-dispersive X-ray spectroscopy. 相似文献
932.
Intramolecular electron spin exchange as a function of temperature and solvent viscosity and polarity has been studied by
X-band electron paramagnetic resonance (EPR) spectroscopy in two rigid nitroxide biradicals existing in one spatial conformation
only. Temperature variations of the isotropic hyperfine splitting constanta and exchange integral value |J/a| were measured from EPR spectra and subsequently analyzed. The interaction of polar solvent molecules with >N-O fragments
of nitroxide groups led to a slight decrease of the |J/a| value with the increase of temperatureT. In contrast, the interaction of polar solvent molecules with functional groups inside the bridge resulted in a noticeable
increase of |J/a| vs.T. In the last case, a coverse relationship between the values of |J/a| and the hyperfine splitting constanta has been observed for solvents with different polarity. 相似文献
933.
Within the perturbative-recombination model, the charge asymmetries in the D* +–D* ?, D* 0–D* 0, and D + s –D ? s yields are estimated under the kinematical conditions of the COMPASS experiment. Corrections that arise owing to the mass of a light quark in a charmed meson are taken into account. The yield of D + s meaons is predicted to be large in relation to the yield of D ? s mesons. 相似文献
934.
J. Łukasik G. Auger M. L. Begemann-Blaich N. Bellaize R. Bittiger F. Bocage B. Borderie R. Bougault B. Bouriquet J. L. Charvet A. Chbihi R. Dayras D. Durand J. D. Frankland E. Galichet D. Gourio D. Guinet S. Hudan P. Lautesse F. Lavaud A. Le Fèvre R. Legrain O. Lopez U. Lynen W. F. J. Müller L. Nalpas H. Orth E. Plagnol E. Rosato A. Saija C. Schwarz C. Sfienti B. Tamain W. Trautmann A. Trzciński K. Turzó E. Vient M. Vigilante C. Volant B. Zwiegliński 《Acta Physica Hungarica A》2006,25(2-4):229-239
Directed and elliptic flow for the 197Au+197Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4π multi-detector. For semi-central collisions, the excitation function of elliptic flow shows a transition from in-plane to out-of-plane emission at around 100 MeV per nucleon. The directed flow changes sign at a bombarding energy between 50 and 60 MeV per nucleon and remains negative at lower energies. Molecular dynamics calculations (CHIMERA) indicate sensitivity of the global squeeze-out transition on the σ NN and demonstrate the importance of angular momentum conservation in transport codes at low energies. 相似文献
935.
P. Kavouras Th. Kehagias K. Chrissafis Ph. Komninou Th. Karakostas 《Journal of Thermal Analysis and Calorimetry》2006,86(3):715-719
Three batch compositions of pure oxides (SiO2,
Fe2O3, PbO, Na2O)
with equivalent SiO2, Fe2O3
and PbO contents and a gradually increased Na2O content
were vitrified through heating in a high temperature electric furnace and
subsequent quenching. The resulting vitreous products were thermally treated
in order to study the devitrification behaviour, under conditions designated
from differential thermal analysis experiments. Depending on the Na2O
content, crystal phase separation gave rise to the growth of acmite and hematite
or maghemite. A uniformly phase separated glass-ceramic material, with crystallites
of similar size and population density, was produced from devitrification
of the vitreous product with the higher Na2O content. 相似文献
936.
Modulated
DSC for gas hydrates analysis 总被引:1,自引:0,他引:1
C. Giavarini F. Maccioni Maria Laura Santarelli 《Journal of Thermal Analysis and Calorimetry》2006,84(2):419-424
Modulated DSC has been applied to the study of methane,
ethane and propane hydrates at different hydrate and ice concentrations. The
reversing component of the TMDSC curves, makes it possible to characterize
such hydrates.
Methane and ethane hydrates show the melting-decomposition
peak at a temperatures higher than the ice contained in the sample, while
propane hydrate melts and decomposes at lower temperature than the ice present
in the sample. The hydrate peaks tend to disappear if the hydrate is stored
at atmospheric pressure. Guest size and cavity occupation fix the heat of
dissociation and stability of the hydrates, as confirmed by parallel tests
on tetrahydrofurane hydrates. 相似文献
937.
Composite optical thin-film materials have received a significant amount of interest in order to relieve the material constraints on refractive indices as well as reducing the number of layers required in optical coating design. Amongst others binary zirconia-silica composite thin films have attracted considerable attentions due to their several favorable opto-mechanical properties. In the present studies such a composite system under certain compositional mixings displayed both refractive index and band gap supremacy over pure zirconia films violating the most popular Moss rule. This unexpected evolution has several practical applications one of which can be directly employed in extending the range of tunability of the refractive index. Besides, the probing of such a novel evolution through the analysis of ellipsometric refractive index modeling and morphological correlation functions has revealed several novel as well as superior microstructural properties in the composite thin film systems. All these characterization and analysis techniques distinctly indicate a strong interrelation between the microstructural ordering and superior optical properties of the present zirconia-silica codeposited composites. 相似文献
938.
S.A. Masti A.K. Sharma P.N. Vasambekar A.S. Vaingankar 《Journal of magnetism and magnetic materials》2006
Magnetization and permeability of polycrystalline ferrites with general formula CdxMg1−xFe2−yCryO4 (x=0, 0.2, 0.4, 0.6, 0.8, 1.0; y=0, 0.05 and 0.10) were studied. Study of saturation magnetization reveals that the Neel's two-sublattice model exists upto x=0.4, for y=0, 0.05 and 0.1 and a three-sublattice model (YK-model) is predominant for x>0.4 and y=0, 0.05 and 0.10. The saturation magnetization and magnetic moment were found to decrease with the increase in Cr3+ contents, which is attributed to the dilution of B–B site interaction. Variation of initial permeability with temperature revealed the long-range ferromagnetic ordering in the compounds with x=0.4. The sample with x?0.4 and y=0, 0.05 and 0.10 showed peaking behavior near Curie temperature, which is attributed to the decrease of anisotropy constant K1 to zero. Low-frequency dispersion of initial permeability suggests domain wall displacement. Addition of Cd2+ resulted in a sharp decrease in Curie temperature. With the addition of Cr3+, initial permeability was found to decrease. 相似文献
939.
We show that the tenure lengths for managers of sport teams follow a power law distribution with an exponent between 2 and 3. We develop a simple theoretical model which replicates this result. The model demonstrates that the empirical phenomenon can be understood as the macroscopic outcome of pairwise interactions among managers in a league, threshold effects in managerial performance evaluation, competitive market forces, and luck at the microscopic level. 相似文献
940.
J. C. Spehner 《Semigroup Forum》1989,39(1):323-334
The main results about automatas and the languages they accept are easily extended to automatas which recognize a family of
languages (Li)iεI of a free monoid, that is to automatas which recognize simultaneously all the languages Li. This generalization enhances the notion of automata of type (p,r) introduced by S. Eilenberg [4].
In a similar way the notion of syntactic monoid of a family of languages extends the notion of syntactic monoid of a language.
This extension is far from being trivial since we show that every finite monoid is the syntactic monoid of a recognizable
partition of a free monoid, though this is false for the syntactic monoids of languages.
相似文献