745 research outputs found
Recoil Order Chiral Corrections to Baryon Octet Axial Currents
We calculate chiral corrections to the octet axial currents through using baryon chiral perturbation theory (BCPT). The relativistic BCPT
framework allows one to sum an infinite series of recoil corrections at a given
order in the chiral expansion. We also include SU(3)-breaking operators
occuring at not previously considered. We determine the
corresponding low-energy constants (LEC's) from hyperon semileptonic decay data
using a variety of infrared regularization schemes. We find that the chiral
expansion of the axial currents does not display the proper convergence
behavior, regardless of which scheme is chosen. We explore the implications of
our analysis for determinations of the strange quark contribution to the
nucleon spin, .Comment: RevTex, 19 pages + 2 PS figure
Time-Dependent Density-Functional Theory for Trapped Strongly-Interacting Fermionic Atoms
The dynamics of strongly interacting trapped dilute Fermi gases (dilute in
the sense that the range of interatomic potential is small compared with
inter-particle spacing) is investigated in a single-equation approach to the
time-dependent density-functional theory. Our results are in good agreement
with recent experimental data in the BCS-BEC crossover regime. It is also shown
that the calculated corrections to the hydrodynamic approximation may be
important even for systems with a rather large number of atoms.Comment: Resubmitted to PRA in response to referee's comments. Abstract is
changed. Added new figure
A small protein is involved in tryptophan biosynthesis and morpho-physiological differentiation in Streptomyces coelicolor
A small protein is involved in tryptophan biosynthesis and morpho-physiological differentiation in Streptomyces coelicolo
Baryon Octet magnetic moments in PT: More on the importance of the Decuplet
We address the impact of treating the decuplet of spin-3/2 baryons as an
explicit degree of freedom in the chiral expansion of the magnetic moments of
the octet of spin-1/2 baryons. We carry out a complete calculation of the octet
moments to O(1/\lamchic), including decuplet contributions to the chiral loops.
In contrast to results of previous analyses, we find that inclusion of the
decuplet preserves the convergence behavior of the chiral expansion implied by
power counting arguments.Comment: 17 pages, 2 figures. Includes axodraw.sty needed for figures Minor
typos correcte
Baryon magnetic moments and sigma terms in lattice-regularized chiral perturbation theory
An SU(3) chiral Lagrangian for the lightest decuplet of baryons is
constructed on a discrete lattice of spacetime points, and is added to an
existing lattice Lagrangian for the lightest octets of mesons and baryons. A
nonzero lattice spacing renders all loop integrations finite, and the continuum
limit of any physical observable is identical to the result obtained from
dimensional regularization. Chiral symmetry and gauge invariance are preserved
even at nonzero lattice spacing. Specific calculations discussed here include
the non-renormalization of a conserved vector current, the magnetic moments of
octet baryons, and the pi N and KN sigma terms that relate to the nucleon's
strangeness content. The quantitative difference between physics at a nonzero
lattice spacing and physics in the continuum limit is easily computed, and it
represents an expectation for the size of discretization errors in
corresponding lattice QCD simulations.Comment: 19 pages, 5 figures, one paragraph added to introduction, to appear
in Phys Rev
Measurement of the 20 and 90 keV resonances in the N reaction via THM
The reaction is of primary importance in
several astrophysical scenarios, including fluorine nucleosynthesis inside AGB
stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus
the indirect measurement of the low energy region of the reaction has been performed to reduce the nuclear
uncertainty on theoretical predictions. In particular the strength of the 20
and 90 keV resonances have been deduced and the change in the reaction rate
evaluated.Comment: 4 pages, 4 figures, submitted to PR
Multiple detection and spread of novel strains of the SARS-CoV-2 B.1.177 (B.1.177.75) lineage that test negative by a commercially available nucleocapsid gene real-time RT-PCR
Several lineages of SARS-CoV-2 are currently circulating worldwide. During SARS-CoV-2 diagnostic activities performed in Abruzzo region (central Italy) several strains belonging to the B.1.177.75 lineage tested negative for the N gene but positive for the ORF1ab and S genes (+/+/- pattern) by the TaqPath COVID-19 CE-IVD RT-PCR Kit manufactured by Thermofisher. By sequencing, a unique mutation, synonymous 28948C > T, was found in the N-negative B.1.177.75 strains. Although we do not have any knowledge upon the nucleotide sequences of the primers and probe adopted by this kit, it is likely that N gene dropout only occurs when 28948C > T is coupled with 28932C > T, this latter present, in turn, in all B.1.177.75 sequences available on public databases. Furthermore, epidemiological analysis was also performed. The majority of the N-negative B.1.177.75 cases belonged to two clusters apparently unrelated to each other and both clusters involved young people. However, the phylogeny for sequences containing the +/+/- pattern strongly supports a genetic connection and one common source for both clusters. Though, genetic comparison suggests a connection rather than indicating the independent emergence of the same mutation in two apparently unrelated clusters. This study highlights once more the importance of sharing genomic data to link apparently unrelated epidemiological clusters and to, remarkably, update molecular tests
m-MTDATA on Au(111): Spectroscopic Evidence of Molecule-Substrate Interactions
The starburst π-conjugated molecule based on triphenylamine (TPA) building blocks, 4,4′,4″-tris(N-3-ethylphenyl-N-phenylamino)triphenylamine (C57H48N4, m-MTDATA), is widely used in optoelectronic devices due to its electron-donating properties. The electronic structure of m-MTDATA adsorbed on an Au(111) surface was investigated by means of photoelectron spectroscopy (PES) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results were further compared to gas-phase measurements and DFT calculations. Our results clearly indicate a significant molecule-substrate interaction that induces considerable modifications on the electronic structure of the adsorbate compared to the isolated molecule. The energy level alignment analysis shows that the HOMO-LUMO gap is filled by new interface states
Long distance regularization in chiral perturbation theory with decuplet
We investigate the use of long distance regularization in SU(3) baryon chiral
perturbation theory with decuplet fields. The one-loop decuplet contributions
to the octet baryon masses, axial couplings, S-wave nonleptonic hyperon decays
and magnetic moments are evaluated in a chirally consistent fashion by
employing a cutoff to implement long distance regularization. The convergence
of the chiral expansions of these quantities is improved compared to the
dimensionally regularized version which indicates that the propagation of
Goldstone bosons over distances smaller than a typical hadronic size, which is
beyond the regime of chiral perturbation theory but included by dimensional
regularization, is removed by use of a cutoff.Comment: 31 page
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