32,975 research outputs found
Hard x-ray or gamma ray laser by a dense electron beam
A coherent x-ray or gamma ray can be created from a dense electron beam
propagating through an intense laser undulator. It is analyzed by using the
Landau damping theory which suits better than the conventional linear analysis
for the free electron laser, as the electron beam energy spread is high. The
analysis suggests that the currently available physical parameters would enable
the generation of the coherent gamma ray of up to 100 keV. The electron quantum
diffraction suppresses the FEL action, by which the maximum radiation energy to
be generated is limited
Preventing Hepatitis B-induced Liver Cancer: Implications for Eliminating Health Disparities
If the definition of eliminating of a health disparity were signified by the absence of any differences in incidence or mortality between a populationβs experiences with a health problem, then the only health disparity that has ever been eliminated is smallpox because with zero cases of smallpox in the world, no health disparities exist because of smallpox. The eradication of smallpox is perhaps the only historical example where the elimination of a health disparity has been achieved. Principles and lessons learned, particularly through the intersection of science and policy that could be applied to the elimination of other health disparities both domestically and internationally are proposed
Backward Raman compression of x-rays in metals and warm dense matters
Experimentally observed decay rate of the long wavelength Langmuir wave in
metals and dense plasmas is orders of magnitude larger than the prediction of
the prevalent Landau damping theory. The discrepancy is explored, and the
existence of a regime where the forward Raman scattering is stable and the
backward Raman scattering is unstable is examined. The amplification of an
x-ray pulse in this regime, via the backward Raman compression, is
computationally demonstrated, and the optimal pulse duration and intensity is
estimated.Comment: 4 pages, 3 figures, submitted to PR
Enhanced damping of ion acoustic waves in dense plasmas
A theory for the ion acoustic wave damping in dense plasmas and warm dense
matter, accounting for the Umklapp process, is presented. A higher decay rate
compared to the prediction from the Landau damping theory is predicted for
high-Z dense plasmas where the electron density ranges from to and the electron temperature is moderately higher
than the Fermi energy
Skyrmion mass and a new kind of the cyclotron resonance for 2DEG
The skyrmionic mass was calculated in the main order of the gradient
expansion in derivatives of the rotation matrix. The mass is proportinal to the
topological invariant which is the absolut value of the degree of the mapping.
The coefficient is defined by the exchange interaction. The charged skyrmions
in magnetic field give rise to a special branch of cyclotron resonance with the
frequency defined by the exchange interaction and have the corresponding term
in their minimal energy. The possibility of an extra bound electron and neutral
skyrmions is discussed.Comment: 4 pages, Latex (submitted to JETP lett.
Particle simulation of vibrated gas-fluidized beds of cohesive fine powders
We use three-dimensional particle dynamics simulations, coupled with
volume-averaged gas phase hydrodynamics, to study vertically vibrated
gas-fluidized beds of fine, cohesive powders. The volume-averaged interstitial
gas flow is restricted to be one-dimensional (1D). This simplified model
captures the spontaneous development of 1D traveling waves, which corresponds
to bubble formation in real fluidized beds. We use this model to probe the
manner in which vibration and gas flow combine to influence the dynamics of
cohesive particles. We find that as the gas flow rate increases, cyclic
pressure pulsation produced by vibration becomes more and more significant than
direct impact, and in a fully fluidized bed this pulsation is virtually the
only relevant mechanism. We demonstrate that vibration assists fluidization by
creating large tensile stresses during transient periods, which helps break up
the cohesive assembly into agglomerates.Comment: to appear in I&EC Research, a special issue (Oct. 2006) in honor of
Prof. William B. Russe
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