Derivation of Green's Function of Spin Calogero-Sutherland Model by Uglov's Method

Hole propagator of spin 1/2 Calogero-Sutherland model is derived using Uglov's method, which maps the exact eigenfunctions of the model, called Yangian Gelfand-Zetlin basis, to a limit of Macdonald polynomials (gl_2-Jack polynomials). To apply this mapping method to the calculation of 1-particle Green's function, we confirm that the sum of the field annihilation operator on Yangian Gelfand-Zetlin basis is transformed to the field annihilation operator on gl_2-Jack polynomials by the mapping. The resultant expression for hole propagator for finite-size system is written in terms of renormalized momenta and spin of quasi-holes and the expression in the thermodynamic limit coincides with the earlier result derived by another method. We also discuss the singularity of the spectral function for a specific coupling parameter where the hole propagator of spin Calogero-Sutherland model becomes equivalent to dynamical colour correlation function of SU(3) Haldane-Shastry model.Comment: 36 pages, 8 figure

NMR spectra of PB2 627, the RNA-binding domain in influenza A virus RNA polymerase that contains the pathogenicity factor lysine 627, and improvement of the spectra by small osmolytes

The influenza A virus, which has an RNA genome, requires RNA-dependent RNA polymerase for transcription and replication. The polymerase is comprised of the subunits PA, PB1, and PB2. The C-terminal RNA-binding domain in PB2 contains lysine 627 (PB2 627), which is associated with pathogenicity and host range. However, the structure and molecular mechanism of PB2 627 in solution remain obscure. Here, we investigated PB2 627 in solution by nuclear magnetic resonance (NMR) and detected inhomogeneity in the intensities of backbone amide proton signals due to local fluctuations in structure. To characterize the effects of chemical chaperones on spectral data and improve the data quality, we tested 20 different additives, including L-arginine L-glutamate salt, (L-arginine)2SO4, glycerol, β-octylglucoside, 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate, Na2SO4, 1,5-diaminopentane, 1,4-diaminobutane, trehalose, sucrose, glycine, trimethylamine N-oxide, β-alanine, L-α-alanine, hydroxyectoine, betaine, L-proline, and non-detergent sulfobetaine 195, 201, and 256. We evaluated the quality of the resulting spectra by calculating the standard deviation and average of the ratio of signal intensities to noise level of amide peaks, as well as the ratio of the standard deviation to the average. NMR-profile analysis revealed diverse effects of additives on the dynamic properties of PB2 627. Based on such criteria, we found that small osmolytes such as glycine and L-α-alanine reduced structural fluctuations and improved the quality of spectral data, which is likely to facilitate a detailed NMR-based structural analysis. The methodology developed here may also be more generally useful for evaluating the effects of chemical chaperones on the structural integrity of proteins

Transmission and Reflection of Collective Modes in Spin-1 Bose-Einstein Condensate

We study tunneling properties of collective excitations in spin-1 Bose-Einstein condensates. In the absence of magnetic fields, the total transmission in the long wavelength limit occurs in all kinds of excitations but the quadrupolar spin mode in the ferromagnetic state. The quadrupolar spin mode alone shows the total reflection. A difference between those excitations comes from whether the wavefunction of an excitation corresponds to that of the condensate in the long wavelength limit. The correspondence results in the total transmission as in the spinless BEC.Comment: 6 pages, 5 figure

Mechanism of a Mutation in Non-Structural Protein 1 Including High Pathogenicity of Avian Influenza Virus H5N1

Avian influenza H5N1 has shown high mortality rate in human. Non-structural protein 1 (NS1) is a virulence factor of H5N1. Mutation at the 42nd residue within the RNA-binding domain (RBD) of NS1 dramatically changes the degree of pathogenicity of H5N1 in mice. We here studied the impact of this mutation on the function of RBD, and found that RBD with serine at the 42th residue binds doublestranded RNA (dsRNA), whereas that with proline at the 42th residue does not. Analysis of structural models of the RBD proteins with S42 and P42 suggested remarkable difference in the structure of the dsRNA-binding interface, whereas structural analysis by analytical gel filtration and CD measurements did not indicate difference between those RBD proteins. Our results suggest that the single amino acid replacement induces a minor, but global structural change leading to the loss of function of NS1 thereby the change in the degree of pathogenicity

Structural basis for potent inhibition of d-amino acid oxidase by thiophene carboxylic acids

A series of thiophene-2-carboxylic acids and thiophene-3-carboxylic acids were identified as a new class of DAO inhibitors. Structure-activity relationship (SAR) studies revealed that small substituents are well-tolerated on the thiophene ring of both the 2-carboxylic acid and 3-carboxylic acid scaffolds. Crystal structures of human DAO in complex with potent thiophene carboxylic acids revealed that Tyr224 was tightly stacked with the thiophene ring of the inhibitors, resulting in the disappearance of the secondary pocket observed with other DAO inhibitors. Molecular dynamics simulations of the complex revealed that Tyr224 preferred the stacked conformation irrespective of whether Tyr224 was stacked or not in the initial state of the simulations. MM/GBSA indicated a substantial hydrophobic interaction between Tyr244 and the thiophene-based inhibitor. In addition, the active site was tightly closed with an extensive network of hydrogen bonds including those from Tyr224 in the stacked conformation. The introduction of a large branched side chain to the thiophene ring markedly decreased potency. These results are in marked contrast to other DAO inhibitors that can gain potency with a branched side chain extending to the secondary pocket due to Tyr224 repositioning. These insights should be of particular importance in future efforts to optimize DAO inhibitors with novel scaffolds

Two-Dimensional Vortex Lattice Melting

We report on a Monte-Carlo study of two-dimensional Ginzburg-Landau superconductors in a magnetic field which finds clear evidence for a first-order phase transition characterized by broken translational symmetry of the superfluid density. A key aspect of our study is the introduction of a quantity proportional to the Fourier transform of the superfluid density which can be sampled efficiently in Landau gauge Monte-Carlo simulations and which satisfies a useful sum rule. We estimate the latent heat per vortex of the melting transition to be $\sim 0.38 k_B T_M$ where $T_M$ is the melting temperature.Comment: 10 pages (4 figures available on request), RevTex 3.0, IUCM93-00

Correlations in Two-Dimensional Vortex Liquids

We report on a high temperature perturbation expansion study of the superfluid-density spatial correlation function of a Ginzburg-Landau-model superconducting film in a magnetic field. We have derived a closed form which expresses the contribution to the correlation function from each graph of the perturbation theory in terms of the number of Euler paths around appropriate subgraphs. We have enumerated all graphs appearing out to 10-th order in the expansion and have evaluated their contributions to the correlation function. Low temperature correlation functions, obtained using Pad\'{e} approximants, are in good agreement with Monte Carlo simulation results and show that the vortex-liquid becomes strongly correlated at temperatures well above the vortex solidification temperature.Comment: 18 pages (RevTeX 3.0) and 4 figures, available upon request, IUCM93-01

Impurity Effect on Kramer-Pesch Core Shrinkage in s-Wave Vortex and Chiral p-Wave Vortex

The low-temperature shrinking of the vortex core (Kramer-Pesch effect) is studied for an isolated single vortex for chiral p-wave and s-wave superconducting phases. The effect of nonmagnetic impurities on the vortex core radius is numerically investigated in the Born limit by means of a quasiclassical approach. It is shown that in the chiral p-wave phase the Kramer-Pesch effect displays a certain robustness against impurities owing to a specific quantum effect, while the s-wave phase reacts more sensitively to impurity scattering. This suggests chiral p-wave superconductors as promising candidates for the experimental observation of the Kramer-Pesch effect.Comment: 18 pages, 4 figures; to be published in J. Low Temp. Phys.; Proc. of NATO ARW: VORTEX 2004, Yalta (Uknaine

Supranormal orientation selectivity of visual neurons in orientation-restricted animals

Altered sensory experience in early life often leads to remarkable adaptations so that humans and animals can make the best use of the available information in a particular environment. By restricting visual input to a limited range of orientations in young animals, this investigation shows that stimulus selectivity, e.g., the sharpness of tuning of single neurons in the primary visual cortex, is modified to match a particular environment. Specifically, neurons tuned to an experienced orientation in orientation-restricted animals show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. This sharpened tuning appears to be due to elongated receptive fields. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of single neurons tailored for a particular environment. The above findings, in addition to the minimal population response to orientations close to the experienced one, agree with the predictions of a sparse coding hypothesis in which information is represented efficiently by a small number of activated neurons. This suggests that early brain areas adopt an efficient strategy for coding information even when animals are raised in a severely limited visual environment where sensory inputs have an unnatural statistical structure

Efimov effect in quantum magnets

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. Here we employ an anisotropic Heisenberg model to show that collective excitations in quantum magnets (magnons) also exhibit the Efimov effect. We locate anisotropy-induced two-magnon resonances, compute binding energies of three magnons and find that they fit into the universal scaling law. We propose several approaches to experimentally realize the Efimov effect in quantum magnets, where the emergent Efimov states of magnons can be observed with commonly used spectroscopic measurements. Our study thus opens up new avenues for universal few-body physics in condensed matter systems.Comment: 7 pages, 5 figures; published versio