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A global function for transcription factors in assisting RNA polymerase II termination.
The role of transcription factors (TFs) on nucleosome positioning, RNA polymerase recruitment, and transcription initiation has been extensively characterized. Here, we propose that a subset of TFs such as Reb1, Abf1, Rap1, and TFIIIB also serve a major function in partitioning transcription units by assisting the Nrd1p-Nab3p-Sen1p Pol II termination pathway
High-order half-integral conservative post-Newtonian coefficients in the redshift factor of black hole binaries
The post-Newtonian approximation is still the most widely used approach to
obtaining explicit solutions in general relativity, especially for the
relativistic two-body problem with arbitrary mass ratio. Within many of its
applications, it is often required to use a regularization procedure. Though
frequently misunderstood, the regularization is essential for waveform
generation without reference to the internal structure of orbiting bodies. In
recent years, direct comparison with the self-force approach, constructed
specifically for highly relativistic particles in the extreme mass ratio limit,
has enabled preliminary confirmation of the foundations of both computational
methods, including their very independent regularization procedures, with high
numerical precision. In this paper, we build upon earlier work to carry this
comparison still further, by examining next-to-next-to-leading order
contributions beyond the half integral 5.5PN conservative effect, which arise
from terms to cubic and higher orders in the metric and its multipole moments,
thus extending scrutiny of the post-Newtonian methods to one of the highest
orders yet achieved. We do this by explicitly constructing tail-of-tail terms
at 6.5PN and 7.5PN order, computing the redshift factor for compact binaries in
the small mass ratio limit, and comparing directly with numerically and
analytically computed terms in the self-force approach, obtained using
solutions for metric perturbations in the Schwarzschild space-time, and a
combination of exact series representations possibly with more typical PN
expansions. While self-force results may be relativistic but with restricted
mass ratio, our methods, valid primarily in the weak-field slowly-moving
regime, are nevertheless in principle applicable for arbitrary mass ratios.Comment: 33 pages, no figure; minor correction
Non-Parametric Direct Multi-step Estimation for Forecasting Economic Processes
We evaluate the asymptotic and finite-sample properties of direct multi-step estimation (DMS) for forecasting at several horizons. For forecast accuracy gains from DMS in finite samples, mis-specification and non-stationarity of the DGP are necessary, but when a model is well-specified, iterating the one-step ahead forecasts may not be asymptotically preferable. If a model is mis-specified for a non-stationary DGP, omitting either negative residual serial correlation or regime shifts, DMS can forecast more accurately. Monte Carlo simulations clarify the non-linear dependence of the estimation and forecast biases on the parameters of the DGP, and explain existing results.Adaptive estimation, multi-step estimation, dynamic forecasts, model mis-specification.
Half-integral conservative post-Newtonian approximations in the redshift factor of black hole binaries
Recent perturbative self-force computations (Shah, Friedman & Whiting,
submitted to Phys. Rev. {\bf D}, arXiv:1312.1952 [gr-qc]), both numerical and
analytical, have determined that half-integral post-Newtonian terms arise in
the conservative dynamics of black-hole binaries moving on exactly circular
orbits. We look at the possible origin of these terms within the post-Newtonian
approximation, find that they essentially originate from non-linear
"tail-of-tail" integrals and show that, as demonstrated in the previous paper,
their first occurrence is at the 5.5PN order. The post-Newtonian method we use
is based on a multipolar-post-Minkowskian treatment of the field outside a
general matter source, which is re-expanded in the near zone and extended
inside the source thanks to a matching argument. Applying the formula obtained
for generic sources to compact binaries, we obtain the redshift factor of
circular black hole binaries (without spins) at 5.5PN order in the extreme mass
ratio limit. Our result fully agrees with the determination of the 5.5PN
coefficient by means of perturbative self-force computations reported in the
previously cited paper.Comment: 18 pages, no figures, references updated and minor corrections
include
Exploring the reality of density substructures in the Palomar 5 stellar stream
We present an analysis of the presence of substructures in the stellar stream
of the Palomar 5 globular cluster, as derived from Sloan Digital Sky Survey
data. Using a matched filter technique, we recover the positions and sizes of
overdensities reported in previous studies. To explore the reality of these
structures, we also create an artificial model of the stream, in which we
construct a realistic background on top of which we add a perfectly smooth
stream structure, taking into account the effects of photometric completeness
and interstellar extinction. We find that the smooth artificial stream then
shows similarly-pronounced substructures as the real structure. Interestingly,
our best-fit N-body simulation does display real projected density variations
linked to stellar epicyclic motions, but these become less significant when
taking into account the SDSS star-count constraints. The substructures found
when applying our matched filter technique to the N-body particles converted
into observable stars are thus mostly unrelated to these epicyclic motions.
This analysis suggests that the majority of the previously-detected
substructures along the tidal tail of Palomar 5 are artefacts of observational
inhomogeneities.Comment: 10 pages, 9 figures, accepted for publication in MNRA
Correlation functions of one-dimensional Bose-Fermi mixtures
We calculate the asymptotic behaviour of correlation functions as a function
of the microscopic parameters for a Bose-Fermi mixture with repulsive
interaction in one dimension. For two cases, namely polarized and unpolarized
fermions the singularities of the momentum distribution functions are
characterized as a function of the coupling constant and the relative density
of bosons.Comment: RevTeX 4, 10 pages, 2 figure
Stellar streams as gravitational experiments I. The case of Sagittarius
Tidal streams of disrupting dwarf galaxies orbiting around their host galaxy
offer a unique way to constrain the shape of galactic gravitational potentials.
Such streams can be used as leaning tower gravitational experiments on galactic
scales. The most well motivated modification of gravity proposed as an
alternative to dark matter on galactic scales is Milgromian dynamics (MOND),
and we present here the first ever N-body simulations of the dynamical
evolution of the disrupting Sagittarius dwarf galaxy in this framework. Using a
realistic baryonic mass model for the Milky Way, we attempt to reproduce the
present-day spatial and kinematic structure of the Sagittarius dwarf and its
immense tidal stream that wraps around the Milky Way. With very little freedom
on the original structure of the progenitor, constrained by the total
luminosity of the Sagittarius structure and by the observed stellar mass-size
relation for isolated dwarf galaxies, we find reasonable agreement between our
simulations and observations of this system. The observed stellar velocities in
the leading arm can be reproduced if we include a massive hot gas corona around
the Milky Way that is flattened in the direction of the principal plane of its
satellites. This is the first time that tidal dissolution in MOND has been
tested rigorously at these mass and acceleration scales.Comment: 12 pages, 11 figures accepted for publication in A&A. The movie of
Fig 6 can be watched at
http://astro.unistra.fr/fileadmin/upload/DUN/observatoire/Images/GFThomas_MONDSgrstream_movie.mp
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