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 population’s 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 $10^{21}$ to $10^{24} \mathrm{cm^{-3}}$ 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