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21.
A systematic theoretical study of the equilibrium geometries and total energies of Cr encapsulated in Si clusters reveals that Cr@Si(12) is more stable than its neighbors. The origin of this enhanced stability is consistent with the 18-electron sum rule commonly used in the synthesis of stable chemical complexes, and may provide a criterion for a systematic search of magic numbers in metalloinorganic clusters. The 6 mu(B) magnetic moment of the caged Cr atom, the largest among the 3d transition metal atoms, is completely quenched. This effect of caging on the properties of transition metal atoms may lead to the synthesis of novel cluster based materials. 相似文献
22.
The thermal instability of a horizontal layer of micropolar fluid which loses heat throughout its volume at a constant rate has been considered. The influence of the various micropolar fluid parameters on the onset of convection have been analysed. It is found that heat source and heat sink have the same destabilising effect in micropolar fluid. It is observed that the horizontal dimension of the cells remains insensitive to the changes in the micropolar fluid parameters and also to the heat source parameterQ except forQ values near zero, where the change is drastic. Further, it is observed that though the vertical component of velocity and the curl of microrotation do not vanish anywhere between the two boundaries forQ=0, they vanish at a point nearer to the lower boundary even for a small change in theQ value. 相似文献
23.
A relativistic model of independent quarks based on Dirac equation with an equally mixed scalar-vector square root confining
potential is used to compute the quark core contributions to the static properties like magnetic moments, charge radii and
axial vector coupling constant ratios of the baryon octet. The results obtained with appropriate corrections due to centre-of-mass
motion agree fairly well with experimental values. The model is also extended to the study of magnetic moments of the quark
core of baryons in the charmed andb-flavoured sectors and the overall predictions so obtained compare well with other model predictions. 相似文献
24.
P. Jena 《Solid State Communications》1978,27(11):1249-1253
A self-consistent calculation based on the density functional formalism yields the spin density at a muon in a vacant lattice site, which is significantly different from that at a muon in an interstitial site. It is argued that a precision μ+ spin rotation experiment should be able to detect the difference in spin density. 相似文献
25.
A coupled-channel treatment of the two-baryon system is carried out in order to study the effects of baryon-resonance components in nuclear states. The coupling potentials are derived in a static one-pion-exchange model, and a one-boson-exchange interaction is used in the two-nucleon channel. For the deuteron, the wave function of the Δ(1236)-Δ(1236) component is calculated and found to have high Fourier components. For N-N scattering the Δ(1236) components are shown to account for much of the intermediate range attraction for which scalar mesons are introduced in one-boson-exchange models. 相似文献
26.
Prevalent visualization tools exploit gray value distribution in images through modified histogram equalization and matching technique, referred to as the window width/window level-based method, to improve visibility and enhance diagnostic value. The window width/window level tool is extensively used in magnetic resonance (MR) images to highlight tissue boundaries during image interpretation. However, the identification of different regions and distinct boundaries between them based on gray-level distribution and displayed intensity levels is extremely difficult because of the large dynamic range of tissue intensities inherent in MR images. We propose a soft-segmentation visualization scheme to generate pixel partitions from the histogram of MR image data using a connectionist approach and then generate selective visual depictions of pixel partitions using pseudo color based on an appropriate fuzzy membership function. By applying the display scheme in clinical examples in this study, we could demonstrate additional overlapping regions between distinct tissue types in healthy and diseased areas (in the brain) that could help improve the tissue characterization ability of MR images. 相似文献
27.
28.
Stolcic D Fischer M Ganteför G Kim YD Sun Q Jena P 《Journal of the American Chemical Society》2003,125(10):2848-2849
Using ultraviolet photoelectron spectroscopy, we provide direct experimental evidence that di-oxygen species are stable on anionic gold dimer and tetramer clusters at room temperature. The stabilization of molecular oxygen is crucial for the high activities of the low-temperature reactions on gold catalysts. 相似文献
29.
Bimal P. Singh Jayadev Jena Laxmidhar Besra Sarama Bhattacharjee 《Journal of nanoparticle research》2007,9(5):797-806
The dispersion characteristics of nanosize silicon carbide (SiC) suspension were investigated in terms of surface charge,
particle size, rheological measurement and adsorption study. Ammonium polycarboxylate has been used as dispersant to stabilize
the suspension. It was found that the isoelectric point (iep) of SiC powder was pHiep (4.9). The surface charge of powder changed significantly in presence of the ammonium polycarboxylate dispersant and iep
shifted significantly towards lower acidic pH (3.6). The shift in iep has been quantified in terms of ΔG
0
SP, the specific free energy of adsorption between the surface sites and the adsorbing polyelectrolyte (APC). The values of
ΔG
0
SP (−10.85 RT unit) estimated by the electro kinetic data compare well with those obtained from adsorption isotherms (−9.521 RT unit). The experimentally determined optimum concentration of dispersant required for maximizing the dispersion was found
to be 2.4 mg/g of SiC (corresponding to an adsorbed amount of 1.10 mg/g), at pH 7.5. This is much below the full monolayer
coverage (corresponding to adsorbed amount of 1.75 mg/g) of the particles surface by the dispersant. The surface charge quantity,
rheological, pH, electro kinetic and adsorption isotherm results were used to explain and correlate the stability of the nanosize
silicon carbide in aqueous media. At pH 7.5, where both SiC surface and APC are negatively charged, the adsorption of APC
was low because of limited availability of favourable adsorption sites. In addition, the brush-like configuration of the adsorbed
polymer prevented close approach of any additional dispersant; hence stabilization of the slurry happens at a comparatively
lower concentration than the monolayer coverage. 相似文献
30.
In an attempt to study the scope of a theorem due to Pati, the authors have established that φ(t) logK|t∈B
u
V in (0,π)⟹ΣA
n
(x) is |C, 0,β| forβ>1, at the pointt = x. 相似文献