8,321 research outputs found
Determination of the strong coupling from semi-leptonic decay
According to heavy-meson chiral perturbation theory, the vector form factor
of exclusive semi-leptonic decay is closely
related, at least in the soft-pion region (i.e., ),
to the strong coupling or the normalized coupling .
Combining the precisely measured spectrum of decay by
the BaBar and Belle collaborations with several parametrizations of the form
factor , we can extract these couplings from the residue of the form
factor at the pole, which relies on an extrapolation of the form factor
from the semi-leptonic region to the unphysical point .
Comparing the extracted values with the other experimental and theoretical
estimates, we can test these various form-factor parametrizations, which differ
from each other by the amount of physical information embedded in. It is found
that the extracted values based on the BK, BZ and BCL parametrizations are
consistent with each other and roughly in agreement with the other theoretical
and lattice estimates, while the BGL ansatz, featured by a spurious, unwanted
pole at the threshold of the cut, gives a neatly larger value.Comment: 19 pages, no figure. Revise
Determination and pharmacokinetic study of catechin in rat plasma by HPLC
AbstractA high performance liquid chromatographic method was developed and validated for the quantitative determination of catechin in rat plasma and its pharmacokinetic study after intragastric administration of Catechu and Xiongdanjiangre Wan into SD rats. Plasma samples were prepared by protein precipitation using methanol–5% aqueous zinc sulfate (70:30, v/v) as precipitant. Chromatographic separation was achieved on Hypersil C18 column (250mm×4.6mm, 10μm) with acetonitrile–water–triethylamine (6:94:0.3, v/v/v, pH 4.0±0.1, adjusted with phosphoric acid) as mobile phase, followed by a UV detection at 207nm. Good linearity was obtained over the range of 0.143–7.15mg/L of catechin, with correlation coefficient of 0.9992. The method was simple, sensitive, accurate and reproducible and has been successfully applied to the pharmacokinetic study of catechin in rat plasma
Experimental high-intensity three-photon entangled source
We experimentally realize a high-intensity three-photon
Greenberger-Horne-Zeilinger (GHZ) entanglement source directly following the
proposal by Rarity and Tapster [J. G. Rarity and P. R. Tapster, Phys. Rev. A
59, R35 (1999)]. The threefold coincidence rate can be more than 200 Hz with a
fidelity of 0.811, and the intensity can be further improved with moderate
fidelity degradation. The GHZ entanglement is characterized by testing the
Bell-Mermin inequality and using an entanglement witness operator. To optimize
the polarization-entangled source, we theoretically analyze the relationship
between the mean photon number of the single-photon source and the probability
of parametric down-conversion.Comment: 4 pages, 4 figure
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