4,151 research outputs found
Radial and vertical angular momentum transport in protostellar discs
Angular momentum in protostellar discs can be transported either radially,
through turbulence induced by the magnetorotational instability (MRI), or
vertically, through the torque exerted by a large-scale magnetic field. We
present a model of steady-state discs where these two mechanisms operate at the
same radius and derive approximate criteria for their occurrence in an
ambipolar diffusion dominated disc. We obtain "weak field'' solutions - which
we associate with the MRI channel modes in a stratified disc - and transform
them into accretion solutions with predominantly radial angular-momentum
transport by implementing a turbulent-stress prescription based on published
results of numerical simulations. We also analyze "intermediate field
strength'' solutions in which both radial and vertical transport operate at the
same radial location. Our results suggest, however, that this overlap is
unlikely to occur in real discs.Comment: 5 pages, 2 figures, 1 table, aastex.cls. Accepted for publication in
Astrophysics & Space Scienc
Lymph node removal enhances corneal graft survival in mice at high risk of rejection
Peer reviewedPublisher PD
Superconductivity in a Two-Orbital Hubbard Model with Electron and Hole Fermi Pockets: Application in Iron Oxypnictide Superconductors
We investigate the electronic states of a one-dimensional two-orbital Hubbard
model with band splitting by the exact diagonalization method. The Luttinger
liquid parameter is calculated to obtain superconducting (SC) phase
diagram as a function of on-site interactions: the intra- and inter-orbital
Coulomb and , the Hund coupling , and the pair transfer . In
this model, electron and hole Fermi pockets are produced when the Fermi level
crosses both the upper and lower orbital bands. We find that the system shows
two types of SC phases, the SC \Roman{u'-large} for and the SC
\Roman{u-large} for , in the wide parameter region including both weak
and strong correlation regimes. Pairing correlation functions indicate that the
most dominant pairing for the SC \Roman{u'-large} (SC \Roman{u-large}) is the
intersite (on-site) intraorbital spin-singlet with (without) sign reversal of
the order parameters between two Fermi pockets. The result of the SC
\Roman{u'-large} is consistent with the sign-reversing s-wave pairing that has
recently been proposed for iron oxypnictide superconductors.Comment: 5 pages, 8 figures, to appear in J. Phys. Soc. Jpn., Vol.78, No.12,
p.12470
Non-Gaussian Distributions in Extended Dynamical Systems
We propose a novel mechanism for the origin of non-Gaussian tails in the
probability distribution functions (PDFs) of local variables in nonlinear,
diffusive, dynamical systems including passive scalars advected by chaotic
velocity fields. Intermittent fluctuations on appropriate time scales in the
amplitude of the (chaotic) noise can lead to exponential tails. We provide
numerical evidence for such behavior in deterministic, discrete-time passive
scalar models. Different possibilities for PDFs are also outlined.Comment: 12 pages and 6 figs obtainable from the authors, LaTex file,
OSU-preprint-
Equivalent birational embeddings II: divisors
Two divisors in are said to be Cremona equivalent if there is a
Cremona modification sending one to the other. We produce infinitely many non
equivalent divisorial embeddings of any variety of dimension at most 14. Then
we study the special case of plane curves and rational hypersurfaces. For the
latter we characterise surfaces Cremona equivalent to a plane.Comment: v2 Exposition improved, thanks to referee, unconditional
characterization of surfaces Cremona equivalent to a plan
Discovery of a molecular cloud possibly associated with the youngest Galactic SNR G1.9+0.3
The youngest known Galactic supernova remnant (SNR) G1.9+0.3 has
high-velocity supernova shock beyond 10000 km s-1, and it is considered to be
one of the major candidates of a PeVatron. Despite these outstanding
properties, the surrounding interstellar matter of this object is poorly
understood. We investigated the interstellar gas toward G1.9+0.3 using the
12CO(J=3-2) data with the angular resolution of 15" obtained by the CHIMPS2
survey by the James Clerk Maxwell Telescope, and discovered three individual
clouds at -1, 7, and 45 km s-1. From its morphological and velocity structures,
the -1 km s-1 cloud, having the largest velocity width >20 km s-1 and located
at the distance of the Galactic Center, is possibly associated with the SNR.
The associated cloud shows a cavity structure both in space and velocity and
coincides well with the SNR. We found that the associated cloud has higher
column densities toward three bright, radio synchrotron-emitted rims where the
radial expansion velocity of the supernova shock is decelerated, and the cloud
is faint in the other parts of the SNR. This is the first direct evidence
indicating that the highly anisotropic expansion of G1.9+0.3 observed by
previous studies results from the deceleration by the interaction between the
supernova shock and surrounding dense interstellar medium.Comment: 17 pages, 10 figures, accepted by PAS
Impact Ionization in ZnS
The impact ionization rate and its orientation dependence in k space is
calculated for ZnS. The numerical results indicate a strong correlation to the
band structure. The use of a q-dependent screening function for the Coulomb
interaction between conduction and valence electrons is found to be essential.
A simple fit formula is presented for easy calculation of the energy dependent
transition rate.Comment: 9 pages LaTeX file, 3 EPS-figures (use psfig.sty), accepted for
publication in PRB as brief Report (LaTeX source replaces raw-postscript
file
Physiological level Production of Antigen-Specific Human Immunoglobulin in Cloned Transchromosomic Cattle
Therapeutic human polyclonal antibodies (hpAbs) derived from pooled plasma from human donors are Food and Drug Administration approved biologics used in the treatment of a variety of human diseases. Powered by the natural diversity of immune response, hpAbs are effective in treating diseases caused by complex or quickly-evolving antigens such as viruses. We previously showed that transchromosomic (Tc) cattle carrying a human artificial chromosome (HAC) comprising the entire unrearranged human immunoglobulin heavy-chain (hIGH) and kappa-chain (hIGK) germline loci (named as κHAC) are capable of producing functional hpAbs when both of the bovine immunoglobulin mu heavy-chains, bIGHM and bIGHML1, are homozygously inactivated (double knockouts or DKO). However, B lymphocyte development in these Tc cattle is compromised, and the overall production of hpAbs is low. Here, we report the construction of an improved HAC, designated as cKSL-HACΔ, by incorporating all of the human immunoglobulin germline loci into the HAC. Furthermore, for avoiding the possible human-bovine interspecies incompatibility between the human immunoglobulin mu chain protein (hIgM) and bovine transmembrane α and β immunoglobulins (bIgα and bIgβ) in the pre-B cell receptor (pre-BCR) complex, we partially replaced (bovinized) the hIgM constant domain with the counterpart of bovine IgM (bIgM) that is involved in the interaction between bIgM and bIgα/Igβ; human IgM bovinization would also improve the functionality of hIgM in supporting B cell activation and proliferation. We also report the successful production of DKO Tc cattle carrying the cKSL-HACΔ (cKSL-HACΔ/DKO), the dramatic improvement of B cell development in these cattle and the high level production of hpAbs (as measured for the human IgG isotype) in the plasma. We further demonstrate that, upon immunization by tumor immunogens, high titer tumor immunogen-specific human IgG (hIgG) can be produced from such Tc cattle
Numerical solution to the hermitian Yang-Mills equation on the Fermat quintic
We develop an iterative method for finding solutions to the hermitian
Yang-Mills equation on stable holomorphic vector bundles, following ideas
recently developed by Donaldson. As illustrations, we construct numerically the
hermitian Einstein metrics on the tangent bundle and a rank three vector bundle
on P^2. In addition, we find a hermitian Yang-Mills connection on a stable rank
three vector bundle on the Fermat quintic.Comment: 25 pages, 2 figure
A Symmetry Property of Momentum Distribution Functions in the Nonequilibrium Steady State of Lattice Thermal Conduction
We study a symmetry property of momentum distribution functions in the steady
state of heat conduction. When the equation of motion is symmetric under change
of signs for all dynamical variables, the distribution function is also
symmetric. This symmetry can be broken by introduction of an asymmetric term in
the interaction potential or the on-site potential, or employing the thermal
walls as heat reservoirs. We numerically find differences of behavior of the
models with and without the on-site potential.Comment: 13 pages. submitted to JPS
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