2,258 research outputs found
Tap: A Novel Cellular Protein That Interacts with Tip of Herpesvirus Saimiri and Induces Lymphocyte Aggregation
AbstractTip of herpesvirus saimiri associates with Lck and down-regulates Lck-mediated activation. We identified a novel cellular Tip-associated protein (Tap) by a yeast two-hybrid screen. Tap associated with Tip following transient expression in COS-1 cells and stable expression in human Jurkat-T cells. Expression of Tip and Tap in Jurkat-T cells induced dramatic cell aggregation. Aggregation was likely caused by the up-regulated surface expression of adhesion molecules including integrin α, L-selectin, ICAM-3, and H-CAM. Furthermore, NF-κB transcriptional factor of aggregated cells had approximately 40-fold higher activity than that of parental cells. Thus, Tap is likely to be an important cellular mediator of Tip function in T cell transformation by herpesvirus saimiri
The Glueball in a Chiral Linear Sigma Model with Vector Mesons
We present a two-flavour linear sigma model with global chiral symmetry and
(axial-)vector mesons as well as an additional glueball degree of freedom. We
study the structure of the well-established scalar resonances f0(1370) and
f0(1500): by a fit to experimentally known decay widths we find that f0(1370)
is predominantly a \bar{q}q state and f0(1500) is predominantly a glueball
state. The overall phenomenology of these two resonances can be well described.
Other assignments for our mixed quarkonium-glueball states are also tested, but
turn out to be in worse agreement with the phenomenology. As a by-product of
our analysis, the gluon condensate is determined.Comment: 8 page
Surface charge transfer doping a quantum confined silver monolayer beneath epitaxial graphene
Recently the graphene/SiC interface has emerged as a versatile platform for
the epitaxy of otherwise unstable, monoelemental, two-dimensional (2D) layers
via intercalation. Intrinsically capped into a van der Waals heterostructure
with overhead graphene, they compose a new class of quantum materials with
striking properties contrasting their parent bulk crystals. Intercalated silver
presents a prototypical example where 2D quantum confinement and inversion
symmetry breaking entail a metal-to-semiconductor transition. However, little
is known about the associated unoccupied states, and control of the Fermi level
position across the bandgap would be desirable. Here, we n-type dope a
graphene/2D-Ag/SiC heterostack via in situ potassium deposition and probe its
band structure by means of synchrotron-based angle-resolved photoelectron
spectroscopy. While the induced carrier densities on the order of
cm are not yet sufficient to reach the onset of the silver conduction
band, the band alignment of graphene changes relative to the rigidly shifting
Ag valence band and substrate core levels. We further demonstrate an ordered
potassium adlayer ( relative to graphene) with free-electron-like
dispersion, suppressing plasmaron quasiparticles in graphene via enhanced
metalization of the heterostack. Our results establish surface charge-transfer
doping as an efficient handle to modify band alignment and electronic
properties of a van der Waals heterostructure assembled from graphene and a
novel type of monolayered quantum material.Comment: 12 pages, 6 figures; minor changes, accepted in journa
Overdoping Graphene Beyond the van Hove Singularity
At very high doping levels the van Hove singularity in the band of
graphene becomes occupied and exotic ground states possibly emerge, driven by
many-body interactions. Employing a combination of ytterbium intercalation and
potassium adsorption, we dope epitaxial graphene on silicon carbide past
the van Hove singularity, up to a charge carrier density of
5.510 cm. This regime marks the unambiguous completion of
a Lifshitz transition in which the Fermi surface topology has evolved from two
electron pockets into a giant hole pocket. Angle-resolved photoelectron
spectroscopy confirms these changes to be driven by electronic structure
renormalizations rather than a rigid band shift. Our results open up the
previously unreachable beyond-van-Hove regime in the phase diagram of epitaxial
graphene, thereby accessing an unexplored landscape of potential exotic phases
in this prototype two-dimensional material.Comment: 6 pages, 2 figure
Novel role for the innate immune receptor toll-like receptor 4 (TLR4) in the regulation of the wnt signaling pathway and photoreceptor apoptosis
Recent evidence has implicated innate immunity in regulating neuronal survival in the brain during stroke and other neurodegenerations. Photoreceptors are specialized light-detecting neurons in the retina that are essential for vision. In this study, we investigated the role of the innate immunity receptor TLR4 in photoreceptors. TLR4 activation by lipopolysaccharide (LPS) significantly reduced the survival of cultured mouse photoreceptors exposed to oxidative stress. With respect to mechanism, TLR4 suppressed Wnt signaling, decreased phosphorylation and activation of the Wnt receptor LRP6, and blocked the protective effect of the Wnt3a ligand. Paradoxically, TLR4 activation prior to oxidative injury protected photoreceptors, in a phenomenon known as preconditioning. Expression of TNFα and its receptors TNFR1 and TNFR2 decreased during preconditioning, and preconditioning was mimicked by TNFα antagonists, but was independent of Wnt signaling. Therefore, TLR4 is a novel regulator of photoreceptor survival that acts through the Wnt and TNFα pathways. © 2012 Yi et al
Statefinder diagnosis and the interacting ghost model of dark energy
A new model of dark energy namely "ghost dark energy model" has recently been
suggested to interpret the positive acceleration of cosmic expansion. The
energy density of ghost dark energy is proportional to the hubble parameter. In
this paper we perform the statefinder diagnostic tool for this model both in
flat and non-flat universe. We discuss the dependency of the evolutionary
trajectories in and planes on the interaction parameter between
dark matter and dark energy as well as the spatial curvature parameter of the
universe. Eventually, in the light of SNe+BAO+OHD+CMB observational data, we
plot the evolutionary trajectories in and planes for the best fit
values of the cosmological parameters and compare the interacting ghost model
with other dynamical dark energy models. We show that the evolutionary
trajectory of ghost dark energy in statefinder diagram is similar to
holographic dark energy model. It has been shown that the statefinder location
of CDM is in good agreement with observation and therefore the dark
energy models whose current statefinder values are far from the CDM
point can be ruled out.Comment: 23 pages, 6 figure
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An Ultra-High Gradient Cherenkov Wakefield Acceleration Experiment at SLAC FFTB
The creation of ultra-high current, ultra-short pulse beams Q=3 nC, {sigma}{sub z} = 20{micro}m at the SLAC FFTB has opened the way for very high gradient plasma wakefield acceleration experiments. We study here the use of these beams in a proposed Cherenkov wakefield experiment, where one may excite electromagnetic wakes in a simple dielectric tube with inner diameter of few 100 microns that exceed the GV/m level. We discuss the scaling of the fields with design geometric design parameters, and choice of dielectric. We also examine measurable aspects of the experiment, such as the total coherent Cerenkov radiation energy one may collect, and the expected aspects of dielectric breakdown at high fields
Combinatorial nuclear level density by a Monte Carlo method
We present a new combinatorial method for the calculation of the nuclear
level density. It is based on a Monte Carlo technique, in order to avoid a
direct counting procedure which is generally impracticable for high-A nuclei.
The Monte Carlo simulation, making use of the Metropolis sampling scheme,
allows a computationally fast estimate of the level density for many fermion
systems in large shell model spaces. We emphasize the advantages of this Monte
Carlo approach, particularly concerning the prediction of the spin and parity
distributions of the excited states, and compare our results with those derived
from a traditional combinatorial or a statistical method. Such a Monte Carlo
technique seems very promising to determine accurate level densities in a large
energy range for nuclear reaction calculations.Comment: 30 pages, LaTex, 7 figures (6 Postscript figures included). Fig. 6
upon request to the autho
Interacting Ghost Dark Energy in Non-Flat Universe
A new dark energy model called "ghost dark energy" was recently suggested to
explain the observed accelerating expansion of the universe. This model
originates from the Veneziano ghost of QCD. The dark energy density is
proportional to Hubble parameter, , where is a
constant of order and is
QCD mass scale. In this paper, we extend the ghost dark energy model to the
universe with spatial curvature in the presence of interaction between dark
matter and dark energy. We study cosmological implications of this model in
detail. In the absence of interaction the equation of state parameter of ghost
dark energy is always and mimics a cosmological constant in the
late time, while it is possible to have provided the interaction is
taken into account. When , all previous results of ghost dark energy in
flat universe are recovered. To check the observational consistency, we use
Supernova type Ia (SNIa) Gold sample, shift parameter of Cosmic Microwave
Background radiation (CMB) and the Baryonic Acoustic Oscillation peak from
Sloan Digital Sky Survey (SDSS). The best fit values of free parameter at
confidence interval are: ,
and . Consequently
the total energy density of universe at present time in this model at 68% level
equates to .Comment: 19 pages, 9 figures. V2: Added comments, observational consequences,
references, figures and major corrections. Accepted for publication in
General Relativity and Gravitatio
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