Critical exponents of the degenerate Hubbard model

We study the critical behaviour of the \SUN{} generalization of the one-dimensional Hubbard model with arbitrary degeneracy $N$. Using the integrability of this model by Bethe Ansatz we are able to compute the spectrum of the low-lying excitations in a large but finite box for arbitrary values of the electron density and of the Coulomb interaction. This information is used to determine the asymptotic behaviour of correlation functions at zero temperature in the presence of external fields lifting the degeneracy. The critical exponents depend on the system parameters through a $N\times N$ dressed charge matrix implying the relevance of the interaction of charge- and spin-density waves.Comment: 18 page

The Van der Waals interaction of the hydrogen molecule - an exact local energy density functional

We verify that the van der Waals interaction and hence all dispersion interactions for the hydrogen molecule given by: W"= -{A/R^6}-{B/R^8}-{C/R^10}- ..., in which R is the internuclear separation, are exactly soluble. The constants A=6.4990267..., B=124.3990835 ... and C=1135.2140398... (in Hartree units) first obtained approximately by Pauling and Beach (PB) [1] using a linear variational method, can be shown to be obtainable to any desired accuracy via our exact solution. In addition we shall show that a local energy density functional can be obtained, whose variational solution rederives the exact solution for this problem. This demonstrates explicitly that a static local density functional theory exists for this system. We conclude with remarks about generalising the method to other hydrogenic systems and also to helium.Comment: 11 pages, 13 figures and 28 reference

Dielectric relaxation and electrical properties of 0.94Pb(Fe[sub ½]Nb[sub ½])O₃-0.06PbTiO₃ single crystals

Author name used in this publication: X. G. Tang2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Tissue microarray immunohistochemical detection of brachyury is not a prognostic indicator in chordoma.

Brachyury is a marker for notochord-derived tissues and neoplasms, such as chordoma. However, the prognostic relevance of brachyury expression in chordoma is still unknown. The improvement of tissue microarray technology has provided the opportunity to perform analyses of tumor tissues on a large scale in a uniform and consistent manner. This study was designed with the use of tissue microarray to determine the expression of brachyury. Brachyury expression in chordoma tissues from 78 chordoma patients was analyzed by immunohistochemical staining of tissue microarray. The clinicopathologic parameters, including gender, age, location of tumor and metastatic status were evaluated. Fifty-nine of 78 (75.64%) tumors showed nuclear staining for brachyury, and among them, 29 tumors (49.15%) showed 1+ (<30% positive cells) staining, 15 tumors (25.42%) had 2+ (31% to 60% positive cells) staining, and 15 tumors (25.42%) demonstrated 3+ (61% to 100% positive cells) staining. Brachyury nuclear staining was detected more frequently in sacral chordomas than in chordomas of the mobile spine. However, there was no significant relationship between brachyury expression and other clinical variables. By Kaplan-Meier analysis, brachyury expression failed to produce any significant relationship with the overall survival rate. In conclusion, brachyury expression is not a prognostic indicator in chordoma

Growth and pyroelectric property of 0.2 mol % Fe-doped Pb(Mg[sub ⅓]Nb[sub ⅔])O₃-0.38PbTiO₃ single crystals measured by a dynamic technique

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Synthesis, vacuum ultraviolet and near ultraviolet-excited luminescent properties of GdCaAl3O7: RE3+ (RE=Eu, Tb)

Vacuum ultraviolet (VUV) excitation and photoluminescent (PL) properties of Eu3+ and Tb3+ ion-doped aluminate phosphors, GdCaAl 3O7:Eu3+ and GdCaAl3O 7:Tb3+ have been investigated. X-ray diffraction (XRD) patterns indicate that the phosphor GdCaAl3O7 forms without impurity phase at 900 °C. Field emission scanning electron microscopy (FE-SEM) images show that the particle size of the phosphor is less than 3 μm. Upon excitation with VUV irradiation, the phosphors show a strong emission at around 619 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu 3+, and at around 545 nm corresponding to the 5D 4→7F5 transition of Tb3+. The results reveal that both GdCaAl3O7:RE3+ (RE=Eu, Tb) are potential candidates as red and green phosphors, respectively, for use in plasma display panel (PDP). © 2005 Elsevier Inc. All rights reserved.postprin

Granitoid rocks and associated coper skarn, Whycocomagh Mountain, Cape Breton Island, Nova Scotia

Mineralized (Fe-Cu-W-Mo) skarn in the Whycocomagh Mountain area is associated with a small pluton of Devonian (402±20 Ma) age, which intruded predominantly metasedimentary rocks of the Hadrynian George River Group. The pluton consists largely of granite porphyry with a marginal granodiorite to diorite zone, and minor porphyritlc granodiorite to monzodiorite dykes and pegmatite. The suite is calc-alkalic with I-type characteristics. Although weakly mineralized, the Whycocomagh Mountain pluton has features typical of plutons associated with porphyry-type Cu-Mo deposits. Calc-silicate rocks derived from marbles of the George River Group are the chief hosts for magnetlte ± chalcopyrlte ± scheelite ± molybdenite ± pyrite which occur in veinlets along fractures and as disseminated grains In adjacent alteration envelopes. Characteristics of the pluton and the skarn minerals suggest that the deposit is a copper skarn. RÉSUMÉ Un skarn minéralise (Fe-Cu-W-Mo), situe dans la région de la montagne Whycocomagh, est associé à une petite intrusion ignée d'âge Dévonien (402±20 m.a.) qui pénétre des roches, principalement des métasédiments, du groupe George River (Hadrynien). Le pluton consiste surtout en un granite porphyrique accompagne d'une zone marginale (granodiorite à diorite), de dykes mineurs (granodiorite à monzodiorite porphyrique) et de pegmatite. L'ensemble est calco-alcalln et de "type 1". Blen que faiblement minéralise, le pluton Whycocomagh Mountain possède lea caractérlstiques typiques des plutons associés aux dépôts porphyrlques de type Cu-Mo. Les calco-sflicates dérives des marbres du groupe George River sont les notes principaux du cortege for magnétite ± chalcopyrlte ± scheelite ± molybdenite ± pyrite que L’on retrouve dans des veinules le long des fractures et disséminés dans les enveloppes d'alteratlon volsines. Les caractérlstiques du pluton ainsi que la minéralogle du skarn font croire qu'il s'agit d'un dépôt de skarn cuprifère. (Tradult par le Journal

Electrokinetic behavior of two touching inhomogeneous biological cells and colloidal particles: Effects of multipolar interactions

We present a theory to investigate electro-kinetic behavior, namely, electrorotation and dielectrophoresis under alternating current (AC) applied fields for a pair of touching inhomogeneous colloidal particles and biological cells. These inhomogeneous particles are treated as graded ones with physically motivated model dielectric and conductivity profiles. The mutual polarization interaction between the particles yields a change in their respective dipole moments, and hence in the AC electrokinetic spectra. The multipolar interactions between polarized particles are accurately captured by the multiple images method. In the point-dipole limit, our theory reproduces the known results. We find that the multipolar interactions as well as the spatial fluctuations inside the particles can affect the AC electrokinetic spectra significantly.Comment: Revised version with minor changes: References added and discussion extende

NMR studies of Successive Phase Transitions in Na0.5CoO2 and K0.5CoO2

59Co- and 23Na-NMR measurements have been carried out on polycrystalline and c-axis aligned samples of Na0.5CoO2, which exhibits successive transitions at temperatures T = 87 K (= Tc1) and T = 53 K (= Tc2). 59Co-NMR has also been carried out on c-axis aligned crystallites of K0.5CoO2 with similar successive transitions at Tc1 ~ 60 K and Tc2 ~ 20 K. For Na0.5CoO2, two sets of three NMR lines of 23Na nuclei explained by considering the quadrupolar frequencies nuQ ~1.32 and 1.40 MHz have been observed above Tc1, as is expected from the crystalline structure. Rather complicated but characteristic variation of the 23Na-NMR spectra has been observed with varying T through the transition temperatures, and the internal fields at two crystallographically distinct Na sites are discussed on the basis of the magnetic structures reported previously. The internal fields at two distinct Co sites observed below Tc1 and the 591/T1-T curves of Na0.5CoO2 and K0.5CoO2 are also discussed in a comparative way.Comment: 7 pages, 10 figures, submitted to J. Phys. Soc. Jpn, correction is made in right colum of p6 (35th line) as K0.5CoO2-->Na0.5CoO

Effect of dc bias on the Curie-Weiss exponent in 0.76Pb(Mg[sub ⅓]Nb[sub ⅔]) O₃-0.24PbTiO₃ ferroelectric single crystal

2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe