19,349 research outputs found
Electron transfer theory revisit: Quantum solvation effect
The effect of solvation on the electron transfer (ET) rate processes is
investigated on the basis of the exact theory constructed in J. Phys. Chem. B
Vol. 110, (2006); quant-ph/0604071. The nature of solvation is studied in a
close relation with the mechanism of ET processes. The resulting Kramers'
turnover and Marcus' inversion characteristics are analyzed accordingly. The
classical picture of solvation is found to be invalid when the solvent
longitudinal relaxation time is short compared with the inverse temperature.Comment: 5 pages, 3 figures. J. Theo. & Comput. Chem., accepte
Quantum molecular dynamics simulations of the thermophysical properties of shocked liquid ammonia for pressures up to 1.3 TPa
We investigate via quantum molecular-dynamics simulations the thermophysical
properties of shocked liquid ammonia up to the pressure 1.3 TPa and temperature
120000 K. The principal Hugoniot is predicted from wide-range equation of
state, which agrees well with available experimental measurements up to 64 GPa.
Our systematic study of the structural properties demonstrates that liquid
ammonia undergoes a gradual phase transition along the Hugoniot. At about 4800
K, the system transforms into a metallic, complex mixture state consisting of
, , ,
N, and H. Furthermore, we discuss the implications for the interiors of Uranus
and Neptune.Comment: 16 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1012.488
Constraints on the Asymptotic Baryon Fractions of Galaxy Clusters at Large Radii
While X-ray measurements have so far revealed an increase in the
volume-averaged baryon fractions of galaxy clusters with cluster radii
, should asymptotically reach a universal value ,
provided that clusters are representative of the Universe. In the framework of
hydrostatic equilibrium for intracluster gas, we have derived the necessary
conditions for : The X-ray surface brightness profile
described by the model and the temperature profile approximated by the
polytropic model should satisfy and
for , respectively, which sets
a stringent limit to the polytropic index: . In particular, a
mildly increasing temperature with radius is required if the observationally
fitted parameter is in the range . It is likely that a
reliable determination of the universal baryon fraction can be achieved in the
small clusters because the disagreement between the exact and
asymptotic baryon fractions for clusters with breaks down at rather
large radii (\ga30r_c) where hydrostatic equilibrium has probably become
inapplicable. We further explore how to obtain the asymptotic value
of baryon fraction from the X-ray measurement made primarily over
the finite central region of a cluster. We demonstrate our method using a
sample of 19 strong lensing clusters, which enables us to place a useful
constraint on : .
An optimal estimate of based on three cooling flow clusters with
or .Comment: 6 pages + 4 figures; accepted for publication in MNRA
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