9,200 research outputs found
Deuteron photodisintegration with polarized photons at astrophysical energies
Following precise experimental studies at the Duke Free-Electron Laser
Laboratory, we discuss photodisintegration of deuterons with 100% linearly
polarized photons using a model independent theoretical approach taking
together and amplitudes simultaneously. The isoscalar
contribution is also taken exactly into account. From the existing experimental
measurement on doubly polarized thermal neutron capture, it is seen that the
isoscalar contribution could be of the same order of magnitude as the
experimentally measured cross sections at energies relevant to Big Bang
Nucleosynthesis (BBN). Therefore appropriate measurements on deuteron
photodisintegration are suggested to empirically determine the
contribution at astrophysical energies.Comment: 5 Pages, Latex-2
Loss and reappearance of gap junctions in regenerating liver
Changes in intercellular junctional morphology associated with rat liver regeneration were examined in a freeze-fracture study. After a two-thirds partial hepatectomy, both gap junctions and zonulae occludentes were drastically altered. Between 0 and 20 h after partial hepatectomy, the junctions appeared virtually unchanged. 28 h after partial hepatectomy, however, the large gap junctions usually located close to the bile canaliculi and the small gap junctions enmeshed within the strands of the zonulae occudentes completely disappeared. Although the zonulae occludentes bordering the bile canaliculi apparently remained intact, numerous strands could now be found oriented perpendicular to the canaliculi. In some instances, the membrane outside the canaliculi was extensively filled with isolated junctional strands, often forming very complex configurations. About 40 h after partial hepatectomy, very many small gap junctions reappeared in close association with the zonulae occludentes. Subsequently, gap junctions increased in size and decreased in number until about 48 h after partial hepatectomy when gap junctions were indistinguishable in size and number from those of control animals. The zonulae occludentes were again predominantly located around the canalicular margins. These studies provide further evidence for the growth of gap junctions by the accretion of particles and of small gap junctions to form large maculae
Chiral Electronics
We consider the properties of electric circuits involving Weyl semimetals.
The existence of the anomaly-induced chiral magnetic current in a Weyl
semimetal subjected to magnetic field causes an interesting and unusual
behavior of such circuits. We consider two explicit examples: i) a circuit
involving the "chiral battery" and ii) a circuit that can be used as a "quantum
amplifier" of magnetic field. The unique properties of these circuits stem from
the chiral anomaly and may be utilized for creating "chiral electronic"
devices.Comment: 5 pages, 2 figures; final version to appear in Physical Review
Nonlinear soil-structure interaction calculations simulating the SIMQUAKE experiment using STEALTH 2D
Transient, nonlinear soil-structure interaction simulations of an Electric Power Research Institute, SIMQUAKE experiment were performed using the large strain, time domain STEALTH 2D code and a cyclic, kinematically hardening cap soil model. Results from the STEALTH simulations were compared to identical simulations performed with the TRANAL code and indicate relatively good agreement between all the STEALTH and TRANAL calculations. The differences that are seen can probably be attributed to: (1) large (STEALTH) vs. small (TRANAL) strain formulation and/or (2) grid discretization differences
Nucleon Form Factors and Hidden Symmetry in Holographic QCD
The vector dominance of the electromagnetic form factors both for mesons and
baryons arises naturally in holographic QCD, where both the number of colors
and the 't Hooft coupling are taken to be very large, offering a bona-fide
derivation of the notion of vector dominance. The crucial ingredient for this
is the infinite tower of vector mesons in the approximations made which share
features that are characteristic of the quenched approximation in lattice QCD.
We approximate the infinite sum by contributions from the lowest four vector
mesons of the tower which turn out to saturate the charge and magnetic moment
sum rules within a few percent and compute them totally free of unknown
parameters for momentum transfers Q^2 less than 1GeV^2. We identify certain
observables that can be reliably computed within the approximations and others
that are not, and discuss how the improvement of the latter can enable one to
bring holographic QCD closer to QCD proper.Comment: 18 pages, 4 figures, revtex4; one reference added, final version to
appear in Phys. Rev.
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