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891.
892.
893.
Using γ-γ(θ), γ(θ) (nuclear orientation) and ek-γ(θ) directional correlation techniques, we have determined the multipole character of some transitions connecting the quadrupole and octupole quasi-vibrational bands to the ground state quasi-rotational band in 152Gd following the decay of 152Tb. For the γ-γ directional correlation measurements a high-energy resolution system employing a Ge(Li) and a NaI(Tl) detector was used while for the ek-γ correlation we used a NaI(Tl) and magnetic lens spectrometer system. The nuclear orientation measurements were carried out at low temperatures obtained with a 3He-4He dilution refrigerator. The results show that the 2+ → 2+ transition between the β-vibrational and the ground state bands contains ≈ 10% Ml admixture, δ = − 3.05 ± 0.14, and a large E0 contribution while the similar transition from the γ-vibrational band has δ = 4.3 ± 0.7. These results are compared with Kumar's predictions for similar transitions in 152Sm. Three other mixing ratios were also determined. 相似文献
894.
An oligopyridine foldamer, whose structure is dictated by bifurcated hydrogen bonds, was designed to recognize the surface of calcite through three carboxylates, projected from one face of the molecule. At low concentrations of the trimer, elongated calcite crystals with angular, teeth-like growths, identified as {0l} faces, were exclusively formed. In the presence of a related monomer, only calcite rhombohedra are formed, indicating that it is the ordered array of carboxylates that causes the morphological changes, via a specific interaction between the foldamer and the newly expressed faces of the growing calcite crystals. 相似文献
895.
Emelianov SY Hamilton MF Ilinskii YA Zabolotskaya EA 《The Journal of the Acoustical Society of America》2004,115(2):581-588
A nonlinear model in the form of the Rayleigh-Plesset equation is developed for a gas bubble in an essentially incompressible elastic medium such as a tissue or rubberlike medium. Two constitutive laws for the elastic medium are considered: the Mooney potential, and Landau's expansion of the strain energy density. These two constitutive laws are compared at quadratic order to obtain a relation between their respective elastic constants. Attention is devoted to the relative importance of shear stress on the bubble dynamics, allowing for the equilibrium gas pressure in the bubble to differ substantially from the pressure at infinity. The model for the bubble motion is approximated to quadratic order to assess the importance of shear stress in the surrounding medium relative to that of the gas pressure in the bubble. Relations are derived for the value of the shear wave speed at which the two contributions are comparable, which provide an assessment of when shear stress in the surrounding medium must be taken into account when modeling bubble dynamics. 相似文献
896.
We report time-resolved small angle neutron scattering (t-SANS) measurements of the topological relaxation of Couette shear-induced stacked L(alpha) lamellar states to their multiconnected isotropic L3 sponge equilibrium phases in a surfactant bilayer membrane system. Comparison of this structural relaxation time to the interval between diffusive membrane contacts, as determined from dynamic light scattering or estimated from the shear rates required for L(alpha) saturation, allows us to determine the activation energy barrier to the membrane fusion process reestablishing the solution channel handles that characterize the sponge phase. 相似文献
897.
Varela M Findlay SD Lupini AR Christen HM Borisevich AY Dellby N Krivanek OL Nellist PD Oxley MP Allen LJ Pennycook SJ 《Physical review letters》2004,92(9):095502
The ability to localize, identify, and measure the electronic environment of individual atoms will provide fundamental insights into many issues in materials science, physics, and nanotechnology. We demonstrate, using an aberration-corrected scanning transmission electron microscope, the spectroscopic imaging of single La atoms inside CaTiO3. Dynamical simulations confirm that the spectroscopic information is spatially confined around the scattering atom. Furthermore, we show how the depth of the atom within the crystal may be estimated. 相似文献
898.
Ling WL de la Figuera J Bartelt NC Hwang RQ Schmid AK Thayer GE Hamilton JC 《Physical review letters》2004,92(11):116102
We report an experimental (scanning tunneling microscopy) and theoretical (embedded atom method) study of a heterophase interface reconstruction between Ag(111) and Ru(0001). Despite the large 7% mismatch, the second layer of Ag from the Ru exhibits a hexagonal structure with Ag bulk spacing, providing a close match to bulk Ag. The first layer of Ag (next to Ru) is reconstructed in a highly symmetrical and regular structure containing monolayer long threading dislocations. We argue that this structure may generally occur to relieve strain in a certain class of heterophase interfaces. 相似文献
899.
F.M.?Pontes D.S.L.?Pontes E.R.?LeiteEmail author E.?Longo A.J.?Chiquito M.A.C.?Machado P.S.?Pizani J.A.?Varela 《Applied Physics A: Materials Science & Processing》2004,78(3):349-354
Dielectric and Raman scattering experiments were performed on polycrystalline Pb1-xCaxTiO3 thin films (x=0.10, 0.20, 0.30, and 0.40) as a function of temperature. The results showed no shift in the dielectric constant (K) maxima, a broadening with frequency, and a linear dependence of the transition temperature on increasing Ca2+ content. On the other hand, a diffuse-type phase transition was observed upon transforming from the cubic paraelectric to the tetragonal ferroelectric phase in all thin films. The temperature dependence of Raman scattering spectra was investigated through the ferroelectric phase transition. The temperature dependence of the phonon frequencies was used to characterize the phase transitions. Raman modes persisted above the tetragonal to cubic phase transition temperature, although all optical modes should be Raman inactive. The origin of these modes was interpreted in terms of a breakdown of the local cubic symmetry due to chemical disorder. The lack of a well-defined transition temperature and the presence of broad bands in some temperature interval above the FE–PE phase transition temperature suggested a diffuse-type phase transition. This result corroborates the dielectric constant versus temperature data, which showed a broad ferroelectric phase transition in these thin films. PACS 77.80.Bh; 77.55.+f; 78.30.-j; 77.80.-e; 68.55.-a 相似文献
900.
The rearrangement of the 2-methyl-2-phenylpropyl (or neophyl) radical 1 to the 1-methyl-1-benzylethyl radical 2 is observed by ESR. spectroscopy during photolysis of di-t-butylperoxide in t-butylbenzene at 270–360 K. The energy of activation of the rearrangement is determined to be (43 ± 9) kJ mol?1. 相似文献