672 research outputs found
Simulation of changes in some soil properties as affected by water level fluctuation in an inland salt marsh
AbstractAn 87-day simulation experiment was conducted to test the effects of water level fluctuation on soil properties of an inland salt marsh. The simulated wetland was periodically flooded for 15 days with consistent water levels of 10cm above the wetland surface soil and then drained to 0cm for 9 days. Soil samples were collected from the 0 to 30cm depth with 10cm intervals at days of 0, 39 and 72 after a 15-day pre-incubation. Total nitrogen (TN), total phosphorus (TP), soil organic matter (SOM) and pH were determined during the experimental period. Results showed that TN content was much higher in surface soils than other soil layers during the whole incubation period, especially at the second inundation period (54 days), and TN greatly increased in the soil layers above 20cm with increasing incubation time. However, the SOM content in each soil layer showed a consistent tendency of âdecreasing followed increasingâ with increasing incubation time. Compared to other soil layers, SOM content in surface soils were generally higher during the simulation periods. TP content in upper soils (0-20cm) consistently increased over the course of incubation time, while those in deeper soils (20-30cm) decreased. Soil pH values showed similar changing tendencies to SOM content over the incubation experiment, while they generally increased with depth
Finite-Temperature Transition into a Power-Law Spin Phase with an Extensive Zero-Point Entropy
We introduce an generalization of the frustrated Ising model on a
triangular lattice. The presence of continuous degrees of freedom stabilizes a
{\em finite-temperature} spin state with {\em power-law} discrete spin
correlations and an extensive zero-point entropy. In this phase, the unquenched
degrees of freedom can be described by a fluctuating surface with logarithmic
height correlations. Finite-size Monte Carlo simulations have been used to
characterize the exponents of the transition and the dynamics of the
low-temperature phase
Anomalous c-axis charge dynamics in copper oxide materials
Within the t-J model, the c-axis charge dynamics of the copper oxide
materials in the underdoped and optimally doped regimes is studied by
considering the incoherent interlayer hopping. It is shown that the c-axis
charge dynamics is mainly governed by the scattering from the in-plane
fluctuation. In the optimally doped regime, the c-axis resistivity is a linear
in temperatures, and shows the metallic-like behavior for all temperatures,
while the c-axis resistivity in the underdoped regime is characterized by a
crossover from the high temperature metallic-like behavior to the low
temperature semiconducting-like behavior, which are consistent with experiments
and numerical simulations.Comment: 6 pages, Latex, Three figures are adde
Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD
approach. It is found that form factors and branching ratios are sensitive to
the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of
the charmonium wave functions for Coulomb potential and harmonic oscillator
potential, respectively, f_J/psi and f_etac are the decay constants of the
J/psi and etac mesons, respectively. The large branching ratios and the clear
signals of the final states make the Bc --> J/psi pi, etac pi decays to be the
prospective channels for measurements at the hadron collidersComment: 21 pages, revtex
Distributed phase-covariant cloning with atomic ensembles via quantum Zeno dynamics
We propose an interesting scheme for distributed orbital state quantum
cloning with atomic ensembles based on the quantum Zeno dynamics. These atomic
ensembles which consist of identical three-level atoms are trapped in distant
cavities connected by a single-mode integrated optical star coupler. These
qubits can be manipulated through appropriate modulation of the coupling
constants between atomic ensemble and classical field, and the cavity decay can
be largely suppressed as the number of atoms in the ensemble qubits increases.
The fidelity of each cloned qubit can be obtained with analytic result. The
present scheme provides a new way to construct the quantum communication
network.Comment: 5 pages, 4 figure
Interplay of Electron-Phonon Interaction and Electron Correlation in High Temperature Superconductivity
We study the electron-phonon interaction in the strongly correlated
superconducting cuprates. Two types of the electron-phonon interactions are
introduced in the model; the diagonal and off-diagonal interactions which
modify the formation energy of the Zhang-Rice singlet and its transfer
integral, respectively. The characteristic phonon-momentum and
electron-momentum dependence resulted from the off-diagonal coupling
can explain a variety of experiments. The vertex correction for the
electron-phonon interaction is formulated in the SU(2) slave-boson theory by
taking into account the collective modes in the superconducting ground states.
It is shown that the vertex correction enhances the attractive potential for
the d-wave paring mediated by phonon with around
which corresponds to the half-breathing mode of the oxygen
motion.Comment: 14 pages, 13 figure
Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models
In the framework of general two-Higgs-doublet models, we calculate the
branching ratios of various inclusive charmless b decays by using the low
energy effective Hamiltonian including next-to-leading order QCD corrections,
and examine the current status and the new physics effects on the determination
of the charm multiplicity and semileptonic branching ratio .
Within the considered parameter space, the enhancement to the ratio due to the charged-Higgs penguins can be as large as a factor of 8 (3) in
the model III (II), while the ratio can be increased from
the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II).
Consequently, the value of and can be decreased simultaneously
in the model III. The central value of will be lowered slightly by
about 0.003, but the ratio can be reduced significantly from the
theoretical prediction of in the SM to , for GeV, respectively. We find that
the predicted and the measured now agree within roughly one
standard deviation after taking into account the effects of gluonic charged
Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be
published in Phys.Rev.
The energy spectrum of tau leptons induced by the high energy Earth-skimming neutrinos
We present a semi-analytic calculation of the tau-lepton flux emerging from
the Earth, induced by the incident high energy neutrinos interacting inside the
Earth for . We obtain results for
the energy dependence of the tau-lepton flux coming from the Earth-skimming
neutrinos, because of the neutrino-nucleon charged-current scattering as well
as the resonant scattering. We illustrate our results for
several anticipated high energy astrophysical neutrino sources such as the
AGNs, the GRBs, and the GZK neutrino fluxes. The tau lepton fluxes resulting
from rock-skimming and ocean-skimming neutrinos are compared. Such comparisons
can render useful information for the spectral indices of incident neutrino
fluxes.Comment: 23 pages, 6 figure
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