1,984 research outputs found
Equivalence of -bosons using the exponential phase operator
Various forms of the -boson are explained and their hidden symmetry
revealed by transformations using the exponential phase operator. Both the
one-component and the multicomponent -bosons are discussed. As a byproduct,
we obtain a new boson algebra having a shifted vacuum structure and define a
global operatal gauge transformation.Comment: 18 pages, LaTex(run twice), To appear in J. PHys.
ALMA Observations of Warm Molecular Gas and Cold Dust in NGC 34
We present ALMA Cycle-0 observations of the CO (6-5) line emission
(rest-frame frequency = 691.473 GHz) and of the 435 dust continuum
emission in the nuclear region of NGC 34, a local luminous infrared galaxy
(LIRG) at a distance of 84 Mpc (1" = 407 pc) which contains a Seyfert 2 active
galactic nucleus (AGN) and a nuclear starburst. The CO emission is well
resolved by the ALMA beam (), with an integrated flux of
. Both the morphology
and kinematics of the CO (6-5) emission are rather regular, consistent with a
compact rotating disk with a size of 200 pc. A significant emission feature is
detected on the red-shifted wing of the line profile at the frequency of the
line, with an integrated flux of . However, it cannot be ruled out
that the feature is due to an outflow of warm dense gas with a mean velocity of
. The continuum is resolved into an elongated
configuration, and the observed flux corresponds to a dust mass of . An unresolved central core () contributes of the continuum flux and of
the CO (6-5) flux, consistent with insignificant contributions of the AGN to
both emissions. Both the CO (6-5) and continuum spatial distributions suggest a
very high gas column density () in the nuclear
region at .Comment: 10 pages, 13 figures, accepted for publication in Astrophysical
Journa
ALMA Observations of Warm Dense Gas in NGC 1614 --- Breaking of Star Formation Law in the Central kpc
We present ALMA Cycle-0 observations of the CO (6-5) line emission and of the
435um dust continuum emission in the central kpc of NGC 1614, a local luminous
infrared galaxy (LIRG) at a distance of 67.8 Mpc (1 arcsec = 329 pc). The CO
emission is well resolved by the ALMA beam (0".26 x 0".20) into a
circum-nuclear ring, with an integrated flux of f_{CO(6-5)} = 898 (+-153) Jy
km/s, which is 63(+-12)% of the total CO(6-5) flux measured by Herschel. The
molecular ring, located between 100pc < r < 350pc from the nucleus, looks
clumpy and includes seven unresolved (or marginally resolved) knots with median
velocity dispersion of 40 km/s. These knots are associated with strong star
formation regions with \Sigma_{SFR} 100 M_\sun/yr/kpc^{2} and \Sigma_{Gas}
1.0E4 M_\sun/pc^{2}. The non-detections of the nucleus in both the CO (6-5)
line emission and the 435um continuum rule out, with relatively high
confidence, a Compton-thick AGN in NGC 1614. Comparisons with radio continuum
emission show a strong deviation from an expected local correlation between
\Sigma_{Gas} and \Sigma_{SFR}, indicating a breakdown of the Kennicutt-Schmidt
law on the linear scale of 100 pc.Comment: 13 pages, 10 figures; accepted by Ap
Convergence to stable laws for multidimensional stochastic recursions: the case of regular matrices
Given a sequence of i.i.d.\ random variables with
generic copy , we consider the random
difference equation (RDE) , and assume
the existence of such that \lim_{n \to \infty}(\E{\norm{M_1 ...
M_n}^\kappa})^{\frac{1}{n}} = 1 . We prove, under suitable assumptions, that
the sequence , appropriately normalized, converges in
law to a multidimensional stable distribution with index . As a
by-product, we show that the unique stationary solution of the RDE is
regularly varying with index , and give a precise description of its
tail measure. This extends the prior work http://arxiv.org/abs/1009.1728v3 .Comment: 15 page
Classes of fast and specific search mechanisms for proteins on DNA
Problems of search and recognition appear over different scales in biological
systems. In this review we focus on the challenges posed by interactions
between proteins, in particular transcription factors, and DNA and possible
mechanisms which allow for a fast and selective target location. Initially we
argue that DNA-binding proteins can be classified, broadly, into three distinct
classes which we illustrate using experimental data. Each class calls for a
different search process and we discuss the possible application of different
search mechanisms proposed over the years to each class. The main thrust of
this review is a new mechanism which is based on barrier discrimination. We
introduce the model and analyze in detail its consequences. It is shown that
this mechanism applies to all classes of transcription factors and can lead to
a fast and specific search. Moreover, it is shown that the mechanism has
interesting transient features which allow for stability at the target despite
rapid binding and unbinding of the transcription factor from the target.Comment: 65 pages, 23 figure
Is there a vortex-glass transition in high-temperature superconductors?
We show that DC voltage versus current measurements of a YBCO micro-bridge in
a magnetic field can be collapsed onto scaling functions proposed by Fisher,
Fisher, and Huse, as is widely reported in the literature. We find, however,
that good data collapse is achieved for a wide range of critical exponents and
temperatures. These results strongly suggest that agreement with scaling alone
does not prove the existence of a phase transition. We propose a criterion to
determine if the data collapse is valid, and thus if a phase transition occurs.
To our knowledge, none of the data reported in the literature meet our
criterion.Comment: 4 pages, 4 figure
Expression quantitative trait loci are highly sensitive to cellular differentiation state
Blood cell development from multipotent hematopoietic stem cells to specialized blood cells is accompanied by drastic changes in gene expression for which the triggers remain mostly unknown. Genetical genomics is an approach linking natural genetic variation to gene expression variation, thereby allowing the identification of genomic loci containing gene expression modulators (eQTLs). In this paper, we used a genetical genomics approach to analyze gene expression across four developmentally close blood cell types collected from a large number of genetically different but related mouse strains. We found that, while a significant number of eQTLs (365) had a consistent âstaticâ regulatory effect on gene expression, an even larger number were found to be very sensitive to cell stage. As many as 1,283 eQTLs exhibited a âdynamicâ behavior across cell types. By looking more closely at these dynamic eQTLs, we show that the sensitivity of eQTLs to cell stage is largely associated with gene expression changes in target genes. These results stress the importance of studying gene expression variation in well-defined cell populations. Only such studies will be able to reveal the important differences in gene regulation between different ce
A population of luminous accreting black holes with hidden mergers
Major galaxy mergers are thought to play an important part in fuelling the
growth of supermassive black holes. However, observational support for this
hypothesis is mixed, with some studies showing a correlation between merging
galaxies and luminous quasars and others showing no such association. Recent
observations have shown that a black hole is likely to become heavily obscured
behind merger-driven gas and dust, even in the early stages of the merger, when
the galaxies are well separated (5 to 40 kiloparsecs). Merger simulations
further suggest that such obscuration and black-hole accretion peaks in the
final merger stage, when the two galactic nuclei are closely separated (less
than 3 kiloparsecs). Resolving this final stage requires a combination of
high-spatial-resolution infrared imaging and high-sensitivity hard-X-ray
observations to detect highly obscured sources. However, large numbers of
obscured luminous accreting supermassive black holes have been recently
detected nearby (distances below 250 megaparsecs) in X-ray observations. Here
we report high-resolution infrared observations of hard-X-ray-selected black
holes and the discovery of obscured nuclear mergers, the parent populations of
supermassive-black-hole mergers. We find that obscured luminous black holes
(bolometric luminosity higher than 2x10^44 ergs per second) show a significant
(P<0.001) excess of late-stage nuclear mergers (17.6 per cent) compared to a
sample of inactive galaxies with matching stellar masses and star formation
rates (1.1 per cent), in agreement with theoretical predictions. Using
hydrodynamic simulations, we confirm that the excess of nuclear mergers is
indeed strongest for gas-rich major-merger hosts of obscured luminous black
holes in this final stage.Comment: To appear in the 8 November 2018 issue of Nature. This is the
authors' version of the wor
Consistency of cosmic microwave background temperature measurements in three frequency bands in the 2500-square-degree SPT-SZ survey
We present an internal consistency test of South Pole Telescope (SPT)
measurements of the cosmic microwave background (CMB) temperature anisotropy
using three-band data from the SPT-SZ survey. These measurements are made from
observations of ~2500 deg^2 of sky in three frequency bands centered at 95,
150, and 220 GHz. We combine the information from these three bands into six
semi-independent estimates of the CMB power spectrum (three single-frequency
power spectra and three cross-frequency spectra) over the multipole range 650 <
l < 3000. We subtract an estimate of foreground power from each power spectrum
and evaluate the consistency among the resulting CMB-only spectra. We determine
that the six foreground-cleaned power spectra are consistent with the null
hypothesis, in which the six cleaned spectra contain only CMB power and noise.
A fit of the data to this model results in a chi-squared value of 236.3 for 235
degrees of freedom, and the probability to exceed this chi-squared value is
46%.Comment: 21 pages, 4 figures, current version matches version published in
JCA
âBuilding for the Future?â Government and Industry Responses to the Challenges of Talent Management in China Following the GFC
China suffered minimal fallout from the global financial crisis due to its burgeoning economy and âsocialism with Chinese characteristicsâ political strategy. However, despite this, its industries face enormous human resource management (HRM) challenges associated with the country's rapid economic growth. Principal amongst these HRM challenges is the need to attract and retain crucial talent. It is likely that if Chinese industry is unsuccessful in these endeavours, the future economic growth of China may be stalled, resulting in more serious long-term outcomes. This paper explores these challenges together with some possible solutions and future research directions
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