1,202 research outputs found
Regulation of mitochondrial biogenesis in erythropoiesis by mTORC1-mediated protein translation.
Advances in genomic profiling present new challenges of explaining how changes in DNA and RNA are translated into proteins linking genotype to phenotype. Here we compare the genome-scale proteomic and transcriptomic changes in human primary haematopoietic stem/progenitor cells and erythroid progenitors, and uncover pathways related to mitochondrial biogenesis enhanced through post-transcriptional regulation. Mitochondrial factors including TFAM and PHB2 are selectively regulated through protein translation during erythroid specification. Depletion of TFAM in erythroid cells alters intracellular metabolism, leading to elevated histone acetylation, deregulated gene expression, and defective mitochondria and erythropoiesis. Mechanistically, mTORC1 signalling is enhanced to promote translation of mitochondria-associated transcripts through TOP-like motifs. Genetic and pharmacological perturbation of mitochondria or mTORC1 specifically impairs erythropoiesis in vitro and in vivo. Our studies support a mechanism for post-transcriptional control of erythroid mitochondria and may have direct relevance to haematologic defects associated with mitochondrial diseases and ageing
Probing Anomalous Wtb Coupling via Single Top Production at TeV Energy e Colliders
Results of complete tree level calculations of the single top production
reaction at the Next Linear Collider, including
the contribution of anomalous operators to the Wtb coupling are presented. The
sensitivity for probing the structure of the Wtb coupling in a model
independent way is analyzed and found to be significantly higher than for
comparable measurements at the Tevatron.Comment: 10 Latex pages including 1 ps-figure and 3 eps-figure
1+1 dimensional QCD with fundamental bosons and fermions
We analyze the properties of mesons in 1+1 dimensional QCD with bosonic and
fermionic ``quarks'' in the large \nc limit. We study the spectrum in detail
and show that it is impossible to obtain massless mesons including boson
constituents in this model. We quantitatively show how the QCD mass inequality
is realized in two dimensional QCD. We find that the mass inequality is close
to being an equality even when the quarks are light. Methods for obtaining the
properties of ``mesons'' formed from boson and/or fermion constituents are
formulated in an explicit manner convenient for further study. We also analyze
how the physical properties of the mesons such as confinement and asymptotic
freedom are realized.Comment: 20 pages, harvmac, 5 figure
Structure formation constraints on the Jordan-Brans-Dicke theory
We use cosmic microwave background data from WMAP, ACBAR, VSA and CBI, and
galaxy power spectrum data from 2dF, to constrain flat cosmologies based on the
Jordan-Brans-Dicke theory, using a Markov Chain Monte Carlo approach. Using a
parametrization based on \xi=1/4\omega, and performing an exploration in the
range \ln\xi \in [-9,3], we obtain a 95% marginalized probability bound of
\ln\xi < -6.2, corresponding to a 95% marginalized probability lower bound on
the Brans-Dicke parameter \omega>120.Comment: 6 pages, 5 figures, RevTeX. Updated to match version accepted by PRD.
Significant updates. Headline constraint tightened to omega > 120 (95% conf)
by improved statistical analysi
A Strong-Coupling Analysis of the Lattice Models in the Presence of a Term
A term, which couples to topological charge, is added to the lattice
model. The strong-coupling character expansion is developed. The
series for the free energy and mass gap are respectively computed to tenth
order and fourth order. Several features of the strong-coupling analysis
emerge. One is the loss of superconfinement. Another is that in the
intermediate coupling constant region, there are indications of a transition to
a deconfining phase when is sufficiently large. The transition is like
the one which has been observed in Monte Carlo simulations of a similar lattice
action.Comment: Latex file, 19 pages plus a postscript file of 4 figures, to appear
in Physical Review
Screening of the topological charge in a correlated instanton vacuum
Screening of the topological charge due to he fermion-induced interactions is
an important phenomenon, closely related with the resolution of the strong CP
and U(1) problems. We study the mechanism of such screening in a 'correlated
instanton vacuum', as opposed to the 'random' one. Both scalar and pseudoscalar
gluonic correlators are analyzed by means of an observable that minimizes
finite size effects. Screening of the topological charge is established. This
allows us to calculate the mass without having to invert the Dirac
operator. We suggest that this method might be used in lattice QCD calculations
as well. Our results for the screening of the topological charge are in
agreement with the chiral Ward identities, and the scalar gluonic correlator
satisfies a low energy theorem first derived by Novikov et al.
\cite{Novikov-etal}. We also propose to evaluate the topological susceptibility
in the Witten-Veneziano formula not in an infinite box in an world
fermions but in an infinitesimal box in a world fermions.Comment: 22 pages + 5 postscript figures, SUNY-NTG/94-25. Corrected LATEX
erro
Binary inspiral, gravitational radiation, and cosmology
Observations of binary inspiral in a single interferometric gravitational
wave detector can be cataloged according to signal-to-noise ratio and
chirp mass . The distribution of events in a catalog composed of
observations with greater than a threshold depends on the
Hubble expansion, deceleration parameter, and cosmological constant, as well as
the distribution of component masses in binary systems and evolutionary
effects. In this paper I find general expressions, valid in any homogeneous and
isotropic cosmological model, for the distribution with and of
cataloged events; I also evaluate these distributions explicitly for relevant
matter-dominated Friedmann-Robertson-Walker models and simple models of the
neutron star mass distribution. In matter dominated Friedmann-Robertson-Walker
cosmological models advanced LIGO detectors will observe binary neutron star
inspiral events with from distances not exceeding approximately
, corresponding to redshifts of (0.26) for
(), at an estimated rate of 1 per week. As the binary system mass
increases so does the distance it can be seen, up to a limit: in a matter
dominated Einstein-deSitter cosmological model with () that limit
is approximately (1.7) for binaries consisting of two
black holes. Cosmological tests based on catalogs of the
kind discussed here depend on the distribution of cataloged events with
and . The distributions found here will play a pivotal role in testing
cosmological models against our own universe and in constructing templates for
the detection of cosmological inspiraling binary neutron stars and black holes.Comment: REVTeX, 38 pages, 9 (encapsulated) postscript figures, uses epsf.st
Decay of Metastable Topological Defects
We systematically analyze the decay of metastable topological defects that
arise from the spontaneous breakdown of gauge or global symmetries.
Quantum-mechanical tunneling rates are estimated for a variety of decay
processes. The decay rate for a global string, vortex, domain wall, or kink is
typically suppressed compared to the decay rate for its gauged counterpart. We
also discuss the decay of global texture, and of semilocal and electroweak
strings.Comment: 43 pages, harvmac, HUTP-92/A018, CALT-68-178
False vacuum decay with gravity in a critical case
The vacuum decay in a de Sitter universe is studied within semiclassical
approximation for the class of effective inflaton potentials whose curvature at
the top is close to a critical value. By comparing the actions of the Hawking -
Moss instanton and the Coleman - de Luccia instanton(s) the mode of vacuum
decay is determined. The case when the fourth derivative of the effective
potential at its top is less than a critical value is discussed.Comment: 10 pages, 8 figures, minor changes don
Minimal Conformal Technicolor and Precision Electroweak Tests
We study the minimal model of conformal technicolor, an SU(2) gauge theory
near a strongly coupled conformal fixed point, with conformal symmetry softly
broken by technifermion mass terms. Conformal symmetry breaking triggers chiral
symmetry breaking in the pattern SU(4) -> Sp(4), which gives rise to a
pseudo-Nambu-Goldstone boson that can act as a composite Higgs boson. The top
quark is elementary, and the top and electroweak gauge loop contributions to
the Higgs mass are cut off entirely by Higgs compositeness. In particular, the
model requires no top partners and no "little Higgs" mechanism. A nontrivial
vacuum alignment results from the interplay of the top loop and technifermion
mass terms. The composite Higgs mass is completely determined by the top loop,
in the sense that m_h/m_t is independent of the vacuum alignment and is
computable by a strong-coupling calculation. There is an additional composite
pseudoscalar A with mass larger than m_h and suppressed direct production at
LHC. We discuss the electroweak fit in this model in detail. Corrections to Z
-> bb and the T parameter from the top sector are suppressed by the enhanced
Sp(4) custodial symmetry. Even assuming that the strong contribution to the S
parameter is positive and usuppressed, a good electroweak fit can be obtained
for v/f ~ 0.25, where v and f are the electroweak and chiral symmetry breaking
scales respectively. This requires fine tuning at the 10% level.Comment: 34 pages, 4 figures; v2: updated precision electroweak fi
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