87 research outputs found
Comment on Neutron-Proton Spin-Correlation Parameter A_{ZZ} at 68 Mev
We present two arguments indicating that the large value for the
mixing parameter at 50 MeV, which the Basel group extracted from their recent
measurement, may be incorrect. First, there are nucleon-nucleon (NN)
potentials which predict the at 50 MeV substantially below the
Basel value and reproduce the Basel data accurately. Second, the large
value for at 50 MeV proposed by the Basel group can only be
explained by a model for the NN interaction which is very unrealistic (no
-meson and essentially a point-like vertex) and overpredicts the
in the energy range where it is well determined (150--500 MeV) by
a factor of two.Comment: 6 pages text (LaTex) and 2 figures (paper, will be faxed upon
request), UI-NTH-930
3-He(p,pp)d and 3-He(p,pp)d* Reactions at 136 MeV
This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit
In-medium nucleon-nucleon potentials in configuration space
Based on the thermodynamic Green function approach two-nucleon correlations
in nuclear matter at finite temperatures are revisited. To this end, we derive
phase equivalent effective -space potentials that include the effect of the
Pauli blocking at a given temperature and density. These potentials enter into
a Schr\"odinger equation that is the -space representation of the
Galitskii-Feynman equation for two nucleons. We explore the analytical
structure of the equation in the complex -plane by means of Jost functions.
We find that despite the Mott effect the correlation with deuteron quantum
numbers are manifested as antibound states, i.e., as zeros of the Jost function
on the negative imaginary axis of the complex momentum space. The analysis
presented here is also suited for Coulombic systems.Comment: 6 pages, 1 table, 4 figure
Charge-Dependence of the Nucleon-Nucleon Interaction
Based upon the Bonn meson-exchange-model for the nucleon-nucleon ()
interaction, we calculate the charge-independence breaking (CIB) of the
interaction due to pion-mass splitting. Besides the one-pion-exchange (OPE), we
take into account the -exchange model and contributions from three and
four irreducible pion exchanges. We calculate the CIB differences in the
effective range parameters as well as phase shift differences for
partial waves up to total angular momentum J=4 and laboratory energies below
300 MeV. We find that the CIB effect from OPE dominates in all partial waves.
However, the CIB effects from the model are noticable up to D-waves and
amount to about 40% of the OPE CIB-contribution in some partial waves, at 300
MeV. The effects from 3 and 4 contributions are negligible except in
and .Comment: 12 pages, RevTex, 14 figure
Investigation of the nucleon-nucleon tensor force in the three-nucleon system
Proton-deuteron elastic scattering has been investigated at Ep =22.7 MeV by comparison of rigorous Faddeev calculations with experimental results. The observable most sensitive to the tensor force is the nucleon-nucleon polarization transfer coefficient Kyy'. The new angular distribution of Kyy' clearly favours the tensor force of the Bonn A potential, which is weaker than the one of the Paris potential.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28425/1/0000208.pd
Charge-Asymmetry of the Nucleon-Nucleon Interaction
Based upon the Bonn meson-exchange model for the nucleon-nucleon ()
interaction, we study systematically the charge-symmetry-breaking (CSB) of the
interaction due to nucleon mass splitting. Particular attention is payed
to CSB generated by the -exchange contribution to the interaction,
diagrams, and other multi-meson-exchanges. We calculate the CSB
differences in the effective range parameters as well as phase shift
differences in , and higher partial waves up to 300 MeV lab. energy. We
find a total CSB difference in the singlet scattering length of 1.6 fm which
explains the empirical value accurately. The corresponding CSB phase-shift
differences are appreciable at low energy in the state. In the other
partial waves, the CSB splitting of the phase shifts is small and increases
with energy, with typical values in the order of 0.1 deg at 300 MeV in and
waves.Comment: 11 pages, RevTex, 14 figure
Survey of attitudes, materials and methods employed in endodontic treatment by general dental practitioners in North Jordan
BACKGROUND: General dental practitioners provide the majority of endodontic treatment in Jordan. The aim of this study was to gather information on the methods, materials and attitudes employed in root canal treatment by dentists in North Jordan, in order to evaluate and improve the quality of current practice. METHODS: A questionnaire was posted to all registered general dental practitioners working in private practice in Irbid Governate in North Jordan (n = 181). The questionnaire included information on methods, materials and techniques used in endodontic treatment. RESULTS: Reply rate was 72% (n = 131). The results demonstrated that only five dentists used rubber dam occasionally and not routinely. The majority used cotton rolls for isolation solely or in combination with a high volume saliva ejector (n = 116). The most widely used irrigants were sodium hypochlorite and hydrogen peroxide, which were used by 32.9% (n = 43) and 33.6% (n = 44) of the respondents, respectively. Forty eight percent of the respondents (n = 61) used the cold lateral condensation technique for canal obturation, 31.3% (n = 41) used single cone, 9.9% (n = 13) used vertical condensation and 12.2% (n = 16) used paste or cement only for the obturation. The majority used zinc oxide eugenol as a sealer (72.5%). All, but one, respondents used hand instruments for canal preparation and the technique of choice was step back (52.7%). More than 50% (n = 70) of the dentists took one radiograph for determining the working length, whilst 22.9% (n = 30) did not take any radiograph at all. Most practitioners performed treatment in three visits for teeth with two or more root canals, and in two visits for teeth with a single root canal. CONCLUSIONS: This study indicates that dentists practicing in North Jordan do not comply with international quality standards and do not use recently introduced techniques. Many clinicians never take a radiograph for determining the working length and never used rubber dam or intra-canal medicaments
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