Neutron-image intensifier

Electronic intensifier tube with a demagnification ratio of 9-1 enhances the usefulness of neutron-radiographic techniques. A television signal can be obtained by optical coupling of a small-output phosphor-light image to a television camera

Microscopic Determinations of Fission Barriers, (MEAN-Field and Beyond)

With a help of the selfconsistent Hartree-Fock-Bogoliubov (HFB) approach with the D1S effective Gogny interaction and the Generator Coordinate Method (GCM) we incorporate the transverse collective vibrations to the one-dimensional model of the fission-barrier penetrability based on the traditional WKB method. The average fission barrier corresponding to the least-energy path in the two-dimensional potential energy landscape as function of quadrupole and octupole degrees of freedom is modified by the influence of the transverse collective vibrations along the nuclear path to fission. The set of transverse vibrational states built in the fission valley corresponding to a successively increasing nuclear elongation produces the new energy barrier which is compared with the least-energy barrier. These collective states are given as the eigensolutions of the GCM purely vibrational Hamiltonian. In addition, the influence of the collective inertia on the fission properties is displayed, and it turns out to be the decisive condition for the possible transitions between different fission valleys.Comment: 12 pages, 5 figures, presented at XIII Workshop of Nuclear Physics, Kazimierz Dolny, 2006 (Poland

Bayesian Nonparametric Shrinkage Applied to Cepheid Star Oscillations

Bayesian nonparametric regression with dependent wavelets has dual shrinkage properties: there is shrinkage through a dependent prior put on functional differences, and shrinkage through the setting of most of the wavelet coefficients to zero through Bayesian variable selection methods. The methodology can deal with unequally spaced data and is efficient because of the existence of fast moves in model space for the MCMC computation. The methodology is illustrated on the problem of modeling the oscillations of Cepheid variable stars; these are a class of pulsating variable stars with the useful property that their periods of variability are strongly correlated with their absolute luminosity. Once this relationship has been calibrated, knowledge of the period gives knowledge of the luminosity. This makes these stars useful as "standard candles" for estimating distances in the universe.Comment: Published in at http://dx.doi.org/10.1214/11-STS384 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Femtosecond "snapshots "of gap-forming charge-density-wave correlations in quasi-two-dimensional dichalcogenides 1T-TaS2 and 2H-TaSe2

Time-resolved optical spectroscopy of collective and single-particle excitations of 1T-TaS2 and 2H-TaSe2 reveals the presence of a large gap in the excitation spectrum on the femtosecond timescale, associated with the formation of various degrees of CDW order. In common with superconducting cuprates, excitations with energies less than the full gap show much slower relaxation. This separation of timescales cannot be explained in a quasi-2D Fermi-Liquid picture with an anisotropic gap but rather suggests the formation of a fluctuating spatially inhomogeneous state eventually forming a long-range ordered state at low temperatures.Comment: to appear in Phys. Rev.B Rapid Com

Thermal neutron image intensifier tube provides brightly visible radiographic pattern

Vacuum-type neutron image intensifier tube improves image detection in thermal neutron radiographic inspection. This system converts images to an electron image, and with electron acceleration and demagnification between the input target and output screen, produces a bright image viewed through a closed circuit television system

New camera tube improves ultrasonic inspection system

Electron multiplier, incorporated into the camera tube of an ultrasonic imaging system, improves resolution, effectively shields low level circuits, and provides a high level signal input to the television camera. It is effective for inspection of metallic materials for bonds, voids, and homogeneity

Persistence of singlet fluctuations in the coupled spin tetrahedra system Cu2Te2O5Br2 revealed by high-field magnetization and 79Br NQR - 125Te NMR

We present high-field magnetization and $^{79}$Br nuclear quadrupole resonance (NQR) and $^{125}$Te nuclear magnetic resonance (NMR) studies in the weakly coupled Cu$^{2+}$ ($S=1/2$) tetrahedral system Cu$_2$Te$_2$O$_5$Br$_2$. The field-induced level crossing effects were observed by the magnetization measurements in a long-ranged magnetically ordered state which was confirmed by a strong divergence of the spin-lattice relaxation rate 1/T1 at T0=13.5 K. In the paramagnetic state, 1/T1 reveals an effective singlet-triplet spin gap much larger than that observed by static bulk measurements. Our results imply that the inter- and the intra-tetrahedral interactions compete, but at the same time they cooperate strengthening effectively the local intratetrahedral exchange couplings. We discuss that the unusual feature originates from the frustrated intertetrahedral interactions.Comment: 5 pages, 4 figures, accepted in Phys. Rev. B as a Rapid Communication

A Modified Version of the Waxman Algorithm

The iterative algorithm recently proposed by Waxman for solving eigenvalue problems, which relies on the method of moments, has been modified to improve its convergence considerably without sacrificing its benefits or elegance. The suggested modification is based on methods to calculate low-lying eigenpairs of large bounded hermitian operators or matrices