2,049 research outputs found
Contribution of spin 1/2 and 3/2 resonances to two-photon exchange effects in elastic electron-proton scattering
We calculate contributions of hadron resonances to two-photon exchange
effects in electron-proton scattering. In addition to the nucleon and P33
resonance, the following heavier resonances are included as intermediate states
in the two-photon exchange diagrams: D13, D33, P11, S11 and S31. We show that
the corrections due to the heavier resonances are smaller that the dominant
nucleon and P33 contributions. We also find that there is a partial
cancellation between the contributions from the spin 1/2 and spin 3/2
resonances, which results in a further suppression of their aggregate
two-photon exchange effect.Comment: 6 pages, 1 figure; additional comparison with data, results
unchanged; to be published in Phys. Rev.
resonance contribution to two-photon exchange in electron-proton scattering
We calculate the effects on the elastic electron-proton scattering cross
section of the two-photon exchange contribution with an intermediate
resonance. The two-photon exchange contribution is found to be smaller
in magnitude than the previously evaluated nucleon contribution, with an
opposite sign at backward scattering angles. The sum of the nucleon and
two-photon exchange corrections has an angular dependence compatible
with both the polarisation transfer and the Rosenbluth methods of measuring the
nucleon electromagnetic form factors.Comment: 9 pages, 3 figures, RevTeX4; more complete discussion of results,
conclusions unchanged; to be published in Physical Review Letter
Suppression of 12-O-tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase activity by resveratrol derivatives
As demonstrated previously, resveratrol (3,4',5-trihydroxy-trans-stilbene) inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC), the key rate limiting enzyme in mammalian polyamine synthesis. Using human bladder epithelial carcinoma HTB-24 cells in culture where resveratrol inhibits induction with an IC50 of 8.8 µM, we now report potential metabolites demonstrate greater activity [tetrabutylammonium (E)-4-(3,5-dihydroxystyryl)phenyl sulfate (IC50 1.2 µM), resveratrol tripotassium 3,5,4'-trisulfate (IC50 1.8 µM), resveratrol tripotassium 3,4'-disulfate (IC50 1.8 µM), and resveratrol tripotassium 3,5-disulfate (IC50 2.3 µM)]. Based on RT-PCR studies, ODC inhibition occurs at the transcriptional level, but this was not due to direct inhibition of protein kinase C (e.g., resveratrol IC50, 79 µM; resveratrol tripotassium 3,5-disulfate IC50, 49 µM). Additional work is underway to more fully investigate this potentially important observation. [This work was supported by program project P01 CA48112 awarded by the National Cancer Institute. SL acknowledges Indo-US Science and Technology Forum (IUSSTF), New Delhi for a Research Fellowship]
Deuteron photodisintegration within the Quark-Gluon Strings Model and QCD motivated nonlinear Regge trajectories
We investigate deuteron two-body photodisintegration within the framework of
the Quark-Gluon Strings Model with nonlinear baryon Regge trajectories. Special
attention is paid to the use of QCD motivated Regge trajectories of the
logarithmic and square-root form which have been suggested recently by
Brisudov\'{a}, Burakovsky and Goldman. We find that the recent experimental
data from TJNAF in the few GeV region can reasonably be described by the model.
Angular distributions at different -energies are presented and the
effect of a forward-backward asymmetry is discussed. Predictions for the energy
dependence of at higher energies and different are
presented, too.Comment: 21 pages, LaTeX, including 6 postscript figures; submitted to Phys.
Rev.
Spin-dependent pbar-d cross sections at low and intermediate energies
Antiproton-deuteron () scattering is calculated at beam energies
below 300 MeV within the Glauber approach, utilizing the amplitudes of the
J\"ulich models. A good agreement is obtained with available
experimental data on upolarized differential and integrated cross
sections. Predictions for polarized total cross sections are
presented, obtained within the single scattering approximation including
Coulomb-nuclear interference effects. It is found that the total longitudinal
and transversal cross sections are comparable in absolute value to
those for scattering.
The kinetics of polarization buildup is considered.Comment: 8 pages, 5 figures, to appear in proceedings of the 19th
international Spin Physics Symposium, September 27 - October 2, 2010,
Juelich, German
Lecania makarevicziae, a new lichen species from Iran
A new for science species Lecania makarevicziae differing from L. pallida in having knobby to squamulose, blastidiate thallus, in having larger apothecia, in having a dark violet-brown disc, in having a plane disc, in having (1–2–)3-septate ascospores with slightly distinct constrictions at the septum, as well as in the lack of dense bluish pruina on apothecium disc, from Iran and Turkmenistan, is described, compared with closely related taxa
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