2,587 research outputs found
The immediate upstream region of the 5 '-UTR from the AUG start codon has a pronounced effect on the translational efficiency in Arabidopsis thaliana
The nucleotide sequence around the translational initiation site is an important cis-acting element for post-transcriptional regulation. However, it has not been fully understood how the sequence context at the 5'-untranslated region (5'-UTR) affects the translational efficiency of individual mRNAs. In this study, we provide evidence that the 5'-UTRs of Arabidopsis genes showing a great difference in the nucleotide sequence vary greatly in translational efficiency with more than a 200-fold difference. Of the four types of nucleotides, the A residue was the most favourable nucleotide from positions -1 to -21 of the 5'-UTRs in Arabidopsis genes. In particular, the A residue in the 5'-UTR from positions -1 to -5 was required for a high-level translational efficiency. In contrast, the T residue in the 5'-UTR from positions -1 to -5 was the least favourable nucleotide in translational efficiency. Furthermore, the effect of the sequence context in the -1 to -21 region of the 5'-UTR was conserved in different plant species. Based on these observations, we propose that the sequence context immediately upstream of the AUG initiation codon plays a crucial role in determining the translational efficiency of plant genes.ope
The relationship between labour unionsā bargaining power and firmsā operating flexibility: New evidence from emerging markets
This study analyses the relevance between the bargaining power of labour unions and the operating flexibility on firmsā capital costs by using non-financial firms listed on the Korean stock exchange from 1999 to 2013. Under the assumption that constraints in business activities attributed to the collective bargaining power of labour unions lead to reduced operating flexibility and increased capital costs, we test this notion empirically; the main test results are as follows: First, we find from portfolio analysis that the cost of capital is higher for firms in more unionized industries. Second, we find that union coverage positively affects the cost of capital at a significant level. Third, we confirm through robustness tests that the industry adjusted union coverage (IAUC) also has a positive effect on the cost of capital at a significant level. As a result, the effect holds after controlling for a host of industry- and firm-level characteristics, and is stronger when unions have more favourable bargaining power. Thus, our findings are consistent with the hypothesis that the increase of labour unionsā bargaining power leads to raise firmsā capital costs by decreasing operating flexibility in the Korean firms
Notes on Supersymmetry Enhancement of ABJM Theory
We study the supersymmetry enhancement of ABJM theory. Starting from a supersymmetric Chern-Simons matter theory with gauge group
U(2)U(2) which is a truncated version of the ABJM theory, we find by
using the monopole operator that there is additional supersymmetry
related to the gauge group. We show this additional supersymmetry can combine
with supersymmetry of the original ABJM theory to an enhanced
SUSY with gauge group U(2)U(2) in the case . We
also discuss the supersymmetry enhancement of the ABJM theory with
U()U() gauge group and find a condition which should be satisfied
by the monopole operator.Comment: 23 pages, no figure, minor corrections, version to appear in JHE
Linear Kondo conductance in a quantum dot
In a tunneling experiment across a quantum dot it is possible to change the
coupling between the dot and the contacts at will, by properly tuning the
trasparency of the barriers and the temperature. Gate voltages allow for
changes of the relative position of the dot addition energies and the Fermi
level of the leads. Here we discuss the two limiting cases: weak and strong
coupling in the tunneling Hamiltonian. In the latter case Kondo resonant
conductance can emerge at low temperature in a Coulomb blockade valley. We give
a pedagogical approach to the single-channel Kondo physics at equilibrium and
review the Nozieres scattering picture of the correlated fixed point. We
emphasize the effect of an applied magnetic field and show how an orbital Kondo
effect can take place in vertical quantum dots tuned both to an even and to an
odd number of electrons at a level crossing. We extend the approach to the
two-channel overscreened Kondo case and discuss recent proposals for detecting
the non-Fermi liquid fixed point which could be reached at strong coupling.Comment: 31 pages, invited review articl
On the helium content of Galactic globular clusters via the R parameter
We estimate the empirical R parameter in 26 Galactic Globular Clusters
covering a wide metallicity range, imaged by WFPC2 on board the HST. The
improved spatial resolution permits a large fraction of the evolved stars to be
measured and permits accurate assessment of radial populaton gradients and
completeness corrections. In order to evaluate both the He abundance and the He
to metal enrichment ratio, we construct a large set of evolutionary models by
adopting similar metallicities and different He contents. We find an absolute
He abundance which is lower than that estimated from spectroscopic measurements
in HII regions and from primordial nucleosynthesis models. This discrepancy
could be removed by adopting a C12O16 nuclear cross section about a factor of
two smaller than the canonical value, although also different assumptions for
mixing processes can introduce systematical effects. The trend in the R
parameter toward solar metallicity is consistent with an upper limit to the He
to metal enrichment ratio of the order of 2.5.Comment: accepted for pubblication on Ap
Enhanced Supersymmetry of Nonrelativistic ABJM Theory
We study the supersymmetry enhancement of nonrelativistic limits of the ABJM
theory for Chern-Simons level . The special attention is paid to the
nonrelativistic limit (known as `PAAP' case) containing both particles and
antiparticles. Using supersymmetry transformations generated by the monopole
operators, we find additional 2 kinematical, 2 dynamical, and 2 conformal
supercharges for this case. Combining with the original 8 kinematical
supercharges, the total number of supercharges becomes maximal: 14
supercharges, like in the well-known PPPP limit. We obtain the corresponding
super Schr\"odinger algebra which appears to be isomorphic to the one of the
PPPP case. We also discuss the role of monopole operators in supersymmetry
enhancement and partial breaking of supersymmetry in nonrelativistic limit of
the ABJM theory.Comment: 22 pages, references added, version to appear in JHE
The Far-Infrared Properties of Spatially Resolved AKARI Observations
We present the spatially resolved observations of IRAS sources from the
Japanese infrared astronomy satellite AKARI All-Sky Survey during the
performance verification (PV) phase of the mission. We extracted reliable point
sources matched with IRAS point source catalogue. By comparing IRAS and AKARI
fluxes, we found that the flux measurements of some IRAS sources could have
been over or underestimated and affected by the local background rather than
the global background. We also found possible candidates for new AKARI sources
and confirmed that AKARI observations resolved IRAS sources into multiple
sources. All-Sky Survey observations are expected to verify the accuracies of
IRAS flux measurements and to find new extragalactic point sources.Comment: 11 pages, 7 figures, accepted publication in PASJ AKARI special issu
Observation of Collective Excitations of the Dilute 2D Electron System
We report inelastic light scattering measurements of dispersive spin and
charge density excitations in dilute 2D electron systems reaching densities
less than 10^{10} cm^{-2}. In the quantum Hall state at nu=2, roton critical
points in the spin inter--Landau level mode show a pronounced softening as r_s
is increased. Instead of a soft mode instability predicted by Hartree--Fock
calculations for r_s ~ 3.3, we find evidence of multiple rotons in the
dispersion of the softening spin excitations. Extrapolation of the data
indicates the possibility of an instability for r_s >~ 11.Comment: Submitted to Physical Review Letter
Robust test method for time-course microarray experiments
<p>Abstract</p> <p>Background</p> <p>In a time-course microarray experiment, the expression level for each gene is observed across a number of time-points in order to characterize the temporal trajectories of the gene-expression profiles. For many of these experiments, the scientific aim is the identification of genes for which the trajectories depend on an experimental or phenotypic factor. There is an extensive recent body of literature on statistical methodology for addressing this analytical problem. Most of the existing methods are based on estimating the time-course trajectories using parametric or non-parametric mean regression methods. The sensitivity of these regression methods to outliers, an issue that is well documented in the statistical literature, should be of concern when analyzing microarray data.</p> <p>Results</p> <p>In this paper, we propose a robust testing method for identifying genes whose expression time profiles depend on a factor. Furthermore, we propose a multiple testing procedure to adjust for multiplicity.</p> <p>Conclusions</p> <p>Through an extensive simulation study, we will illustrate the performance of our method. Finally, we will report the results from applying our method to a case study and discussing potential extensions.</p
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