3,178 research outputs found
Tautomeric mutation: A quantum spin modelling
A quantum spin model representing tautomeric mutation is proposed for any DNA
molecule. Based on this model, the quantum mechanical calculations for
mutational rate and complementarity restoring repair rate in the replication
processes are carried out. A possible application to a real biological system
is discussed.Comment: 7 pages (no figures
Electronic structure of GaCrN and Si-doping effects studied by photoemission and X-ray absorption spectroscopy
The electronic structure of the magnetic semiconductor GaCrN
and the effect of Si doping on it have been investigated by photoemission and
soft x-ray absorption spectroscopy. We have confirmed that Cr in GaN is
predominantly trivalent substituting for Ga, and that Cr 3 states appear
within the band gap of GaN just above the N 2-derived valence-band maximum.
As a result of Si doping, downward shifts of the core levels (except for Cr
2) and the formation of new states near the Fermi level were observed, which
we attribute to the upward chemical potential shift and the formation of a
small amount of Cr species caused by the electron doping. Possibility of
Cr-rich cluster growth by Si doping are discussed based on the spectroscopic
and magnetization data.Comment: 5 pages, 3 figure
Observation of in
Using a sample of events recorded with
the BESIII detector at the symmetric electron positron collider BEPCII, we
report the observation of the decay of the charmonium state
into a pair of mesons in the process
. The branching fraction is measured for the first
time to be , where the first uncertainty is
statistical, the second systematic and the third is from the uncertainty of
. The mass and width of the are
determined as MeV/ and
MeV.Comment: 13 pages, 6 figure
Observation of a charged charmoniumlike structure in at GeV
We study the process at a
center-of-mass energy of 4.26GeV using a 827pb data sample obtained with
the BESIII detector at the Beijing Electron Positron Collider. Based on a
partial reconstruction technique, the Born cross section is measured to be
pb. We observe a structure near the
threshold in the recoil mass spectrum, which we denote as the
. The measured mass and width of the structure are
MeV/c and MeV, respectively. Its
production ratio is determined to be . The first uncertainties
are statistical and the second are systematic.Comment: 7 pages, 4 figures, 1 table; version accepted to be published in PR
Measurement of proton electromagnetic form factors in in the energy region 2.00-3.08 GeV
The process of is studied at 22 center-of-mass
energy points () from 2.00 to 3.08 GeV, exploiting 688.5~pb of
data collected with the BESIII detector operating at the BEPCII collider. The
Born cross section~() of is
measured with the energy-scan technique and it is found to be consistent with
previously published data, but with much improved accuracy. In addition, the
electromagnetic form-factor ratio () and the value of the
effective (), electric () and magnetic () form
factors are measured by studying the helicity angle of the proton at 16
center-of-mass energy points. and are determined with
high accuracy, providing uncertainties comparable to data in the space-like
region, and is measured for the first time. We reach unprecedented
accuracy, and precision results in the time-like region provide information to
improve our understanding of the proton inner structure and to test theoretical
models which depend on non-perturbative Quantum Chromodynamics
First observations of hadrons
Based on events collected with
the BESIII detector, five hadronic decays are searched for via process
. Three of them, ,
, and are observed for the first
time, with statistical significances of 7.4, , and
9.1, and branching fractions of ,
, and ,
respectively, where the first uncertainties are statistical and the second
systematic. No significant signal is observed for the other two decay modes,
and the corresponding upper limits of the branching fractions are determined to
be and at 90% confidence level.Comment: 17 pages, 16 figure
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