39,901 research outputs found
High-Energy Forward Scattering and the Pomeron: Simple Pole versus Unitarized Models
Using the largest data set available, we determine the best values that the
data at t=0 (total cross sections and real parts of the hadronic amplitudes)
give for the intercepts and couplings of the soft pomeron and of the rho/omega
and a/f trajectories. We show that these data cannot discriminate between a
simple-pole fit and asymptotic log square s and log s fits, and hence are not
sufficient to reveal the ultimate nature of the pomeron. However, we evaluate
the existing evidence (factorization, universality, quark counting) favouring
the simple-pole hypothesis. We also examine the range of validity in energy of
the fits, and show that one cannot rely on such fits in the region sqrt(s)<9
GeV. We also establish bounds on the odderon and the hard pomeron.Comment: 20 pages, 10 figures. Predictions of Table 4 corrected and
acknowledgements adde
Theory of Fano-Kondo effect in quantum dot systems: temperature dependence of the Fano line shapes
The Fano-Kondo effect in zero-bias conductance is studied based on a
theoretical model for the T-shaped quantum dot by the finite temperature
density matrix renormalization group method. The modification of the two Fano
line shapes at much higher temperatures than the Kondo temperature is also
investigated by the effective Fano parameter estimated as a fitting parameter.Comment: 2 pages, 2 figures, the proceeding of SCES'0
Triple sign reversal of Hall effect in HgBa_{2}CaCu_{2}O_{6} thin films after heavy-ion irradiations
Triple sign reversal in the mixed-state Hall effect has been observed for the
first time in ion-irradiated HgBa_{2}CaCu_{2}O_{6} thin films. The negative dip
at the third sign reversal is more pronounced for higher fields, which is
opposite to the case of the first sign reversal near T_c in most high-T_c
superconductors. These observations can be explained by a recent prediction in
which the third sign reversal is attributed to the energy derivative of the
density of states and to a temperature-dependent function related to the
superconducting energy gap. These contributions prominently appear in cases
where the mean free path is significantly decreased, such as our case of
ion-irradiated thin films.Comment: 4 pages, 3 eps figures, submitted Phys. Rev. Let
Cascade of Quantum Phase Transitions in Tunnel-Coupled Edge States
We report on the cascade of quantum phase transitions exhibited by
tunnel-coupled edge states across a quantum Hall line junction. We identify a
series of quantum critical points between successive strong and weak tunneling
regimes in the zero-bias conductance. Scaling analysis shows that the
conductance near the critical magnetic fields is a function of a single
scaling argument , where the exponent .
This puzzling resemblance to a quantum Hall-insulator transition points to
importance of interedge correlation between the coupled edge states.Comment: 4 pages, 3 figure
Metabolic Impacts of Using Nitrogen and Copper-Regulated Promoters to Regulate Gene Expression in Neurospora crassa.
The filamentous fungus Neurospora crassa is a long-studied eukaryotic microbial system amenable to heterologous expression of native and foreign proteins. However, relatively few highly tunable promoters have been developed for this species. In this study, we compare the tcu-1 and nit-6 promoters for controlled expression of a GFP reporter gene in N. crassa. Although the copper-regulated tcu-1 has been previously characterized, this is the first investigation exploring nitrogen-controlled nit-6 for expression of heterologous genes in N. crassa. We determined that fragments corresponding to 1.5-kb fragments upstream of the tcu-1 and nit-6 open reading frames are needed for optimal repression and expression of GFP mRNA and protein. nit-6 was repressed using concentrations of glutamine from 2 to 20 mM and induced in medium containing 0.5-20 mM nitrate as the nitrogen source. Highest levels of expression were achieved within 3 hr of induction for each promoter and GFP mRNA could not be detected within 1 hr after transfer to repressing conditions using the nit-6 promoter. We also performed metabolic profiling experiments using proton NMR to identify changes in metabolite levels under inducing and repressing conditions for each promoter. The results demonstrate that conditions used to regulate tcu-1 do not significantly change the primary metabolome and that the differences between inducing and repressing conditions for nit-6 can be accounted for by growth under nitrate or glutamine as a nitrogen source. Our findings demonstrate that nit-6 is a tunable promoter that joins tcu-1 as a choice for regulation of gene expression in N. crassa
Soft Pomeron and Lower-Trajectory Intercepts
We present a preliminary report on the determination of the intercepts and
couplings of the soft pomeron and of the rho/omega and f/a trajectories from
the largest data set available for all total cross sections and real parts of
the hadronic amplitudes. Factorization is reasonably satisfied by the pomeron
couplings, which allows us to make predictions on gamma gamma and gamma p total
cross sections. In addition we show that these data cannot discriminate between
fits based on a simple Regge pomeron-pole and on an asymptotic log^2s-type
behaviour, implying that the effect of unitarisation is negligible. Also we
examine the range of validity in energy of the fit, and the bounds that these
data place on the odderon and on the hard pomeron.Comment: 13 pages, LaTeX, 14 figures. Presented by K. Kang at a 4th Workshop
on Quantum Chromodynamics, June 1 - 6, 1998, The American University of
Paris, Paris, France, and at the 4th Workshop on Small-x and Diffractive
Physics, September 17 - 20, 1998, Fermi National Accelerator Laboratory,
Batavia, I
Characterization of a novel reassortant H5N6 highly pathogenic avian influenza virus clade 2.3.4.4 in Korea, 2017
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