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251.
Measurements of the volume magnetostriction in EuO and MnF2 confirm predictions of a model based on the volume dependence of the dominant exchange constant. No adjustable parameters are used. 相似文献
252.
F.P. Missell J.M.V. Martins C.C. Becerra N.S. Wisnik Y. Shapira 《Journal of Physics and Chemistry of Solids》1974,35(12):1599-1603
Quantum oscillations in the ultrasonic attenuation in AuSb2 were studied as a function of temperature, magnetic field and crystal orientation. The effective masses of the carriers associated with the F5 and F6 oscillations were measured in a (110) plane. For the F5 oscillations, the Dingle temperature and apparent magnetic breakdown field appear to depend strongly upon orientation. For the F6 oscillations, however, there were no signs of magnetic breakdown up to the highest magnetic fields available (70 kOe) and the Dingle temperature was roughly independent of orientation. From the acoustic velocities, the elastic constants were determined at 77 K: C11 = (14·7 ± 0·9) × 1011 dyne/cm2, C12 = (6·0 ± 0·9) × 1011 dyne/cm2, and C44 = (2·59 ± 0·06) × 1011 dyne/cm2. These elastic constants give an adiabatic compressibility Ks = (1·13 ± 0·12) × 10?12 cm2/dyne and a Debye temperature ?D = (203 ± 15) K. 相似文献
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We have optimized the method of water fluorination using the solid reagent CoF3 to produce O2. This allows isotope ratio measurements by dual-inlet mass spectrometry with very high precision of 0.01 to 0.03/1000 for both delta17O and delta18O. Using this method, delta17O and delta18O of atmospheric O2 were determined as 12.08 and 23.88/1000 vs. VSMOW, respectively. Likewise, delta17O and delta18O of GISP were -13.12 and -24.73/1000, and for SLAP they were -29.48 and -55.11/1000 vs. VSMOW, respectively. Analysis of these data in a ln(delta17O + 1) vs. ln(delta18O + 1) plot yields a line with a regression coefficient (lambda) of 0.5279 +/- 0.0001 (R2 = 0.999999). We also determined the fractionation factors 17alpha and 18alpha in liquid-vapor equilibrium, and found that the ratio ln 17alpha/ln 18alpha is constant (0.529 +/- 0.001) over the temperature range 11.4 to 41.5 degrees C. 相似文献
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We consider investments in development projects within competitive environments where the “winner takes everything”. Under stationary uncertainty, it is optimal to start investing immediately at full capacity and continue until exhausting the allocated budget. For non-stationary environments, active investment, possibly deferred, will always be at full capacity; an example demonstrates that further tractable structure may not be available. 相似文献
258.
An ELISA-based optical fiber methodology developed for the detection of anti-West Nile virus IgG antibodies in serum was compared to standard colorimetric and chemiluminescent ELISA based on microtiter plates. Colorimetric ELISA was the least sensitive, especially at high titer dilutions. The fiber-optic immunosensor based on the same ELISA immunological rationale was the most sensitive technique. 相似文献
259.
Aragonite was grown epitaxially under calcite-stable conditions by using carbonate free single-crystal substrates with a threefold axis oriented normal to the surface. 相似文献
260.
Turner B Shterenberg A Kapon M Botoshansky M Suwinska K Eichen Y 《Chemical communications (Cambridge, England)》2002,(7):726-727
meso-hexamethyl-meso-hexaphenyl calix[6]pyrrole assembles into well-defined dimeric capsules in the crystalline state; the preorganized capsule serves as an efficient host for different organic guests as well as for solvent molecules. 相似文献