39,135 research outputs found
Baryonic sources using irreducible representations of the double-covered octahedral group
Irreducible representations (IRs) of the double-covered octahedral group are
used to construct lattice source and sink operators for three-quark baryons.
The goal is to achieve a good coupling to higher spin states as well as ground
states. Complete sets of local and nonlocal straight-link operators are
explicitly shown for isospin 1/2 and 3/2 baryons. The orthogonality relations
of the IR operators are confirmed in a quenched lattice simulation.Comment: Talk presented at Lattice2004(heavy), Fermilab, June 21-26, 2004, 3
page
A Mammalian Homolog of Drosophila melanogaster Transcriptional Coactivator Intersex Is a Subunit of the Mammalian Mediator Complex
The multiprotein Mediator complex is a coactivator required for transcriptional activation of RNA polymerase II transcribed genes by DNA binding transcription factors. We previously partially purified a Med8-containing Mediator complex from rat liver nuclei (Brower, C. S., Sato, S., Tomomori-Sato, C., Kamura, T., Pause, A., Stearman, R., Klausner, R. D., Malik, S., Lane, W. S., Sorokina, I., Roeder, R. G., Conaway, J. W., and Conaway, R. C. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 10353–10358). Analysis of proteins present in the most highly enriched Mediator fractions by tandem mass spectrometry led to the identification of several new mammalian Mediator subunits, as well as several potential Mediator subunits. Here we identify one of these proteins, encoded by the previously uncharacterized AK000411 open reading frame, as a new subunit of the mammalian Mediator complex. The AK000411 protein, which we designate hIntersex (human Intersex), shares significant sequence similarity with the Drosophila melanogaster intersex protein, which has functional properties expected of a transcriptional coactivator specific for the Drosophila doublesex transactivator. In addition, we show that hIntersex assembles into a subcomplex with Mediator subunits p28b and TRFP. Taken together, our findings identify a new subunit of the mammalian Mediator and shed new light on the architecture of the mammalian Mediator complex
Influence of non-local exchange on RKKY interactions in III-V diluted magnetic semiconductors
The RKKY interaction between substitutional Mn local moments in GaAs is both
spin-direction-dependent and spatially anisotropic. In this Letter we address
the strength of these anisotropies using a semi-phenomenological tight-binding
model which treats the hybridization between Mn d-orbitals and As p-orbitals
perturbatively and accounts realistically for the non-local exchange
interaction between their spins. We show that exchange non-locality,
valence-band spin-orbit coupling, and band-structure anisotropy all play a role
in determining the strength of both effects. We use these results to estimate
the degree of ground-state magnetization suppression due to frustrating
interactions between randomly located Mn ions.Comment: 4 pages RevTeX, 2 figures included, v2: replacement because of font
proble
Dynamical Coupled-Channels Effects on Pion Photoproduction
The electromagnetic pion production reactions are investigated within the
dynamical coupled-channels model developed in {\bf Physics Reports, 439, 193
(2007)}. The meson-baryon channels included in this study are , , , and the , and resonant components
of the channel. With the hadronic parameters of the model determined
in a recent study of scattering, we show that the pion photoproduction
data up to the second resonance region can be described to a very large extent
by only adjusting the bare helicity amplitudes, while the
non-resonant electromagnetic couplings are taken from previous works. It is
found that the coupled-channels effects can contribute about 10 - 20 % of the
production cross sections in the (1232) resonance region, and can
drastically change the magnitude and shape of the cross sections in the second
resonance region. The importance of the off-shell effects in a dynamical
approach is also demonstrated. The meson cloud effects as well as the
coupled-channels contributions to the form factors are found
to be mainly in the low region. For the magnetic M1
(1232) form factor, the results are close to that of the Sato-Lee Model.
Necessary improvements to the model and future developments are discussed.Comment: Corrected version. 14 pages, 10 figure
A Comment on Junction and Energy Conditions in Thin Shells
This comment contains a suggestion for a slight modification of Israel's
covariant formulation of junction conditions between two spacetimes, placing
both sides on equal footing with normals having uniquely defined orientations.
The signs of mass energy densities in thin shells at the junction depend not
only on the orientations of the normals and it is useful therefore to discuss
the sign separately. Calculations gain in clarity by not choosing the
orientations in advance. Simple examples illustrate our point and complete
previous classifications of spherical thin shells in spherically symmetric
spacetimes relevant to cosmology.Comment: (Tex file + PS file with a figure) Tex errors were correcte
Interaction and Localization of One-electron Orbitals in an Organic Molecule: Fictitious Parameter Analysis for Multi-physics Simulations
We present a new methodology to analyze complicated multi-physics simulations
by introducing a fictitious parameter. Using the method, we study quantum
mechanical aspects of an organic molecule in water. The simulation is
variationally constructed from the ab initio molecular orbital method and the
classical statistical mechanics with the fictitious parameter representing the
coupling strength between solute and solvent. We obtain a number of
one-electron orbital energies of the solute molecule derived from the
Hartree-Fock approximation, and eigenvalue-statistical analysis developed in
the study of nonintegrable systems is applied to them. Based on the results, we
analyze localization properties of the electronic wavefunctions under the
influence of the solvent.Comment: 4 pages, 5 figures, the revised version will appear in J. Phys. Soc.
Jpn. Vol.76 (No.1
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