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151.
Park T Nussinov Z Hazzard KR Sidorov VA Balatsky AV Sarrao JL Cheong SW Hundley MF Lee JS Jia QX Thompson JD 《Physical review letters》2005,94(1):017002
The low-frequency dielectric response of hole-doped insulators La(2)Cu(1-x)Li(x)O(4) and La(2-x)Sr(x)NiO(4) shows a large dielectric constant epsilon(') at high temperature and a steplike drop by a factor of 100 at a material-dependent low temperature T(f). T(f) increases with frequency, and the dielectric response shows universal scaling in a Cole-Cole plot, suggesting that a charge-glass state is realized both in the cuprates and in the nickelates. 相似文献
152.
S. Jha D. Suyanto S. Yehia Gleen M. Julian R. A. Dunlap Amer Lahamer S -W. Cheong Z. Fisk J. D. Thompson 《Hyperfine Interactions》1990,55(1-4):1323-1326
Mössbauer spectra of57Co-doped polycrystalline or single-crystal samples of layered perovskites La2Mo4 (M=Cu, Co, Ni) and R2CuO4 (R=Nd, Eu, Gd) were recorded at room temperature and below. Of the samples studied, only La2CuO4 shows a widely separated doublet at room temperature and a single clearly resolved sextet well belowT N. 相似文献
153.
A Hamiltonian coupling identification (HCI) technique is introduced to reveal the independent and cooperative roles of Hamiltonian matrix elements in determining the bound-state energies of quantum systems. The HCI technique operates by encoding each Hamiltonian matrix element with a unique modulation signal, producing a nonlinear signature in the energy eigenvalues that may be decoded to reveal the contributing coupling structure in the Hamiltonian. The HCI technique is capable of exploring the roles of Hamiltonian coupling structure within and beyond the convergence limits of standard perturbation theory expansions. The flexibility residing in the encoding and decoding processes may be exploited to tailor the analysis to meet the desired degree of sought-after information about the Hamiltonian coupling structure. HCI, based on a Fourier encoding and decoding scheme, is illustrated by extracting information on the role of coupling interactions in the potential matrix elements of several simple model systems. 相似文献
154.
Sharma PA Ahn JS Hur N Park S Kim SB Lee S Park JG Guha S Cheong SW 《Physical review letters》2004,93(17):177202
The thermal conductivity of the magnetically frustrated, ferroelectric YMnO3 exhibits an isotropic suppression in the cooperative paramagnetic state, followed by a sudden increase upon magnetic ordering. This unprecedented behavior without an associated static structural distortion probably originates from the strong dynamic coupling between acoustic phonons and low-energy spin fluctuations in geometrically frustrated magnets. The replacement of magnetic Ho for Y at the ferroelectrically active site results in an even larger effect, suggestive of the strong influence of multiferroicity. 相似文献
155.
Linear stability analysis of capillary instabilities in a thin nematic liquid crystalline cylindrical fiber embedded in an
immiscible viscous matrix is performed by formulating and solving the governing nemato-capillary equations, that include the
effect of temperature on the nematic ordering as well as the effect of the nematic orientation. A representative axial nematic
orientation texture with the planar easy axis at the fiber surface is studied. The surface disturbance is expressed in normal
modes, which include the azimuthal wave number m to take into account non-axisymmetric modes. Capillary instabilities in nematic fibers reflect the anisotropic nature of
liquid crystals, such as the ordering and orientation contributions to the surface elasticity and surface normal and bending
stresses. Surface gradients of normal and bending stresses provide additional anisotropic contributions to the capillary pressure
that may renormalize the classical displacement and curvature forces that exist in any fluid fiber. The exact nature (stabilizing
and destabilizing) and magnitude of the renormalization of the displacement and curvature forces depend on the nematic ordering
and orientation, i.e. the anisotropic contribution to the surface energy, and accordingly capillary instabilities may be axisymmetric or non-axisymmetric.
In addition, when the interface curvature effects are accounted for as contributions of the work of interfacial bending and
torsion to the total energy of the system, the higher-order bending moment contribution to the surface stress tensor is critical
in stabilizing the fiber instabilities. For the planar easy axis, the nematic ordering contribution to the surface energy,
which renormalizes the effect of the fiber shape, plays a crucial role to determine the instability mechanisms. Moreover,
the unstable modes, which are most likely observed, can be driven by the dependence of surface energy on the surface area.
Low-ordering fibers display the classical axisymmetric mode, since the surface energy decreases by decreasing the surface
area. Decreasing temperature gives rise to the encounter with a local maximum or to monotonic increase of the characteristic
length of the axisymmetric mode. Meanwhile, in the presence of high surface ordering, non-axisymmetric finite wavelength instabilities
emerge, with higher modes growing faster since the surface energy decreases by increasing the surface area. As temperature
decreases, the pitches of the chiral microstructures become smaller. However, this non-axisymmetric instability mechanism
can be regulated by taking account of the surface bending moment, which contains higher order variations in the interface
curvatures. More and more non-axisymmetric modes emerge as temperature decreases, but, at constant temperature, only a finite
number of non-axisymmetric modes are unstable and a single fastest growing mode emerges with lower and higher unstable modes
growing slower. For nematic fibers, the classical fiber-to-droplet transformation is one of several possible instability pathways,
while others include chiral microstructures. The capillary instabilities' growth rate of a thin nematic fiber in a viscous
matrix is suppressed by increasing either the fiber or matrix viscosity, but the estimated droplet sizes after fiber breakup
in axisymmetric instabilities decrease with increasing the matrix viscosity.
Received 15 April 2002 and Received in final form 3 October 2002
RID="a"
ID="a"e-mail: alejandro.rey@mcgill.ca 相似文献
156.
Sharma PA Hur N Horibe Y Chen CH Kim BG Guha S Cieplak MZ Cheong SW 《Physical review letters》2002,89(16):167003
Our results from various transport experiments on Mg1-xB2 indicate a surprising effect associated with the presence of a Mg deficiency in MgB2: the phase separation between Mg-vacancy rich and Mg-vacancy poor phases. The Mg-vacancy poor phase is superconducting, but the insulating nature of the Mg-vacancy rich phase probably originates from the Anderson (disorder-induced) localization of itinerant carriers. Furthermore, electron diffraction measurements indicate that within vacancy-rich regions these defects tend to order with intriguing patterns. This electronic phase separation in Mg1-xB2 shows similar, but also distinct characteristics compared with that observed in La(2)CuO(4+delta). 相似文献
157.
Smolyaninov II Smolyaninova VN Davis CC Kim BG Cheong SW Greene RL 《Physical review letters》2001,87(12):127204
We report near-field and far-field optical microscopic studies of photoinduced effects in charge-ordered Bi(0.3)Ca(0.7)MnO(3). Unlike previously reported transient photoinduced effects in manganites, we have observed permanent reflectivity changes following local sample illumination with 488 nm light. High-resolution images of exposed regions reveal optical contrast on a submicrometer scale. This observation indicates that photonic band-gap structures may be created using holographic recording in manganites. We also present images of photoinduced charge-order domain switching in Bi(0.3)Ca(0.7)MnO(3). 相似文献
158.
Dr. Priyankar Paira Mun Juinn Chow Gopalakrishnan Venkatesan Vamsi Krishna Kosaraju Dr. Siew Lee Cheong Karl‐Norbert Klotz Dr. Wee Han Ang Assoc.Prof. Giorgia Pastorin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8321-8330
Human A3 adenosine receptor (hA3AR) is a membrane‐bound G protein‐coupled receptor implicated in a number of severe pathological conditions, including cancer, in which it acts as a potential therapeutic target. To derive structure–activity relationships on pyrazolo–triazolo–pyrimidine (PTP)‐based A3AR antagonists, we developed a new class of organometallic inhibitors through replacement of the triazolo moiety with an organoruthenium fragment. The objective was to introduce by design structural diversity into the PTP scaffold in order to tune their binding efficacy toward the target receptor. These novel organoruthenium antagonists displayed good aquatic stability and moderate binding affinity toward the hA3 receptor in the low micromolar range. The assembly of these complexes through a template‐driven approach with selective ligand replacement at the metal center to control their steric and receptor‐binding properties is discussed. 相似文献
159.
Two-phase flow over tube bundles is commonly observed in shell and tube-type heat exchangers. However, only limited amount
of data concerning flow pattern and void fraction exists due to the flow complexity and the difficulties in measurement. The
detailed flow structure in tube bundles needs to be understood for reliable and effective design. Therefore, the objective
of this study was to clarify the two-phase structure of cross-flow in tube bundles by PIV. Experiments were conducted using
two types of models, namely in-line and staggered arrays with a pitch-to-diameter ratio of 1.5. Each test section contains
20 rows of five 15 mm O.D. tubes in each row. The experiment’s data were obtained under very low void fraction (α<0.02). Liquid
and gas velocity data in the whole flow field were measured successfully by optical filtering and image processing. The structures
of bubbly flow in the two different configurations of tube bundles were described in terms of the velocity vector field, turbulence
intensity and void fraction. 相似文献
160.
Two nonlinear models are proposed to investigate the focused acoustic waves that the nonlinear effects will be important inside the liquid around the scatterer. Firstly, the one dimensional solutions for the widely used Westervelt equation with different coordinates are obtained based on the perturbation method with the second order nonlinear terms. Then, by introducing the small parameter (Mach number), a dimensionless formulation and asymptotic perturbation expansion via the compressible potential flow theory is applied. This model permits the decoupling between the velocity potential and enthalpy to second order, with the first potential solutions satisfying the linear wave equation (Helmholtz equation), whereas the second order solutions are associated with the linear non-homogeneous equation. Based on the model, the local nonlinear effects of focused acoustic waves on certain volume are studied in which the findings may have important implications for bubble cavitation/initiation via focused ultrasound called HIFU (High Intensity Focused Ultrasound). The calculated results show that for the domain encompassing less than ten times the radius away from the center of the scatterer, the non-linear effect exerts a significant influence on the focused high intensity acoustic wave. Moreover, at the comparatively higher frequencies, for the model of spherical wave, a lower Mach number may result in stronger nonlinear effects. 相似文献