895 research outputs found
Isospin symmetry breaking nucleon-nucleon potentials and nuclear structure
Modern nucleon-nucleon (NN) potentials, which accurately fit the
nucleon-nucleon scattering phase shifts, contain terms which break isospin
symmetry. The effects of these symmetry violating terms on the bulk properties
of nuclear matter are investigated. The predictions of the charge symmetry
breaking (CSB) terms are compared with the Nolen-Schiffer (NS) anomaly
regarding the energies of neighboring mirror nuclei. We find that, for a
quantitative explanation of the NS anomaly, it is crucial to include CSB in
partial waves with (besides ) as derived from a microscopic model
for CSB of the NN interaction.Comment: 14 pages, RevTex, 2 figure
Baryon-Baryon Interactions from Lattice QCD
We report on new attempt to investigate baryon-baryon interactions in lattice
QCD. From the Bethe-Salpeter (BS) wave function, we have successfully extracted
the nucleon-nucleon () potentials in quenched QCD simulations, which
reproduce qualitative features of modern potentials. The method has been
extended to obtain the tensor potential as well as the central potential and
also applied to the hyperon-nucleon () interactions, in both quenched and
full QCD.Comment: 6 pages, 10 figures, A plenary talk given at the 5-th International
Conference on Quark and Nuclear Physics, Beijing, September 21-26, 200
Rapid enzymatic test for phenotypic HIV protease drug resistance
A phenotypic resistance test based on recombinant expression of the active HIV protease in E. coli from patient blood samples was developed. The protease is purified in a rapid onestep procedure as active enzyme and tested for inhibition by five selected synthetic inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir) used presently for chemotherapy of HIVinfected patients. The HPLC system used in a previous approach was replaced by a continuous fluorogenic assay suitable for highthroughput screening on microtiter plates. This reduces significantly the total assay time and allows the determination of inhibition constants (K-i). The Michaelis constant (K-m) and the inhibition constant (K-i) of recombinant wildtype protease agree well with published data for cloned HIV protease. The enzymatic test was evaluated with recombinant HIV protease derived from eight HIVpositive patients scored from sensitive to highly resistant according to mutations detected by genotypic analysis. The measured K-i values correlate well with the genotypic resistance scores, but allow a higher degree of differentiation. The noninfectious assay enables a more rapid yet sensitive detection of HIV protease resistance than other phenotypic assays
Phaseshift equivalent NN potentials and the deuteron
Different modern phase shift equivalent NN potentials are tested by
evaluating the partial wave decomposition of the kinetic and potential energy
of the deuteron. Significant differences are found, which are traced back to
the matrix elements of the potentials at medium and large momenta. The
influence of the localisation of the one-pion-exchange contribution to these
potentials is analyzed in detail.Comment: 11 pages, LaTeX, 4 figures include
Modern nucleon-nucleon interactions and charge-symmetry breaking in nuclei
Coulomb displacement energies, i.e., the differences between the energies of
corresponding nuclear states in mirror nuclei, are evaluated using recent
models for the nucleon-nucleon (NN) interaction. These modern NN potentials
account for breaking of isospin symmetry and reproduce and phase
shifts accurately. The predictions by these new potentials for the binding of
are calculated. A particular focus of our study are effects due to
nuclear correlations and charge-symmetry breaking (CSB). We find that the CSB
terms in the modern NN interactions substantially reduce the discrepancy
between theory and experiment for the Coulomb displacement energies; however,
our calculations do not completely explain the Nolen-Schiffer anomaly.
Potential sources for the remaining discrepancies are discussed.Comment: 10 pages RevTeX, no figure
Accurate Charge-Dependent Nucleon-Nucleon Potential at Fourth Order of Chiral Perturbation Theory
We present the first nucleon-nucleon potential at
next-to-next-to-next-to-leading order (fourth order) of chiral perturbation
theory. Charge-dependence is included up to next-to-leading order of the
isospin-violation scheme. The accuracy for the reproduction of the NN data
below 290 MeV lab. energy is comparable to the one of phenomenological
high-precision potentials. Since NN potentials of order three and less are
known to be deficient in quantitative terms, the present work shows that the
fourth order is necessary and sufficient for a reliable NN potential derived
from chiral effective Lagrangians. The new potential provides a promising
starting point for exact few-body calculations and microscopic nuclear
structure theory (including chiral many-body forces derived on the same
footing).Comment: 4 pages Revtex including one figur
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