MOSAIC: A Scalable reconfigurable 2D array system for NDT

This paper documents the development of a scalable 2D array system, or Mosaic that can be targeted at a wide range of NDT applications by way of a reconfigurable tile that can be tessellated to form arrays of any size and shape. Close coupling permits utilization of excitation voltages as low as +/-3.3V with insertion loss of 48dB on reflection from an aluminum back wall at 73mm achieved using 2D arrays without decoding

Arrays of Cooper Pair Boxes Coupled to a Superconducting Reservoir: `Superradiance' and `Revival.'

We consider an array of Cooper Pair Boxes, each of which is coupled to a superconducting reservoir by a capacitive tunnel junction. We discuss two effects that probe not just the quantum nature of the islands, but also of the superconducting reservoir coupled to them. These are analogues to the well-known quantum optical effects `superradiance,' and `revival.' When revival is extended to multiple systems, we find that `entanglement revival' can also be observed. In order to study the above effects, we utilise a highly simplified model for these systems in which all the single-electron energy eigenvalues are set to be the same (the strong coupling limit), as are the charging energies of the Cooper Pair Boxes, allowing the whole system to be represented by two large coupled quantum spins. Although this simplification is drastic, the model retains the main features necessary to capture the phenomena of interest. Given the progress in superconducting box experiments over recent years, it is possible that experiments to investigate both of these interesting quantum coherent phenomena could be performed in the forseeable future.Comment: 23 pages, 5 figures Clarifications made as recommended by refere

Nesting properties and anomalous band effect in MgB2

First principle FLAPW band calculations of the new superconductor MgB2 were performed and the polarization function P12(Q) between the two p-bands mainly formed of boron pz-orbital was calculated. We found that P12(Q) is substantially enhanced around Q=(0,0,p/c), which supports the two-band mechanism of superconductivity for MgB2. P12(Q) peaks at Qz ~ 0.3(2p/c) and Qz \~ 0.5(2p/c). These two peaks are related to the nesting of these Fermi surfaces, but significantly deviates from the position expected from the simplest tight-binding bands for the p-bands. From the calculations for different lattice parameters, we have found significant dependences on the isotopic species of B and on the pressure effect of the polarization function in accordance with the respective changes of Tc in the above-mentioned framework.Comment: 15 pages, 7 graphs. to be published in J. Phys. Soc. Jpn. 70_, No.

Sun-as-a-Star Spectrum Variations 1974-2006

We have observed selected Fraunhofer lines, both integrated over the Full Disk and for a small circular region near the center of the solar disk, on 1,215 days for the past 30 years. Full Disk results: Ca II K 393 nm nicely tracks the 11 year magnetic cycle based on sunspot number with a peak amplitude in central intensity of ~37%. The wavelength of the mid-line core absorption feature, called K3, referenced to nearby photospheric Fe, displays an activity cycle variation with an amplitude of 3 milli-Angstroms. Other chromospheric lines track Ca II K intensity with lower relative amplitudes. Low photosphere: Temperature sensitive CI 5380 nm appears constant in intensity to 0.2%. High photosphere: The cores of strong Fe I lines, Na D1 and D2, and the Mg I b lines, present a puzzling signal perhaps indicating a role for the 22 y Hale cycle. Solar minimum around 1985 was clearly seen, but the following minimum in 1996 was missing. This anomalous behavior is not seen in comparison atmospheric O2. Center Disk results: Both Ca II K and C I 538 nm intensities are constant, indicating that the basal quiet atmosphere is unaffected by cycle magnetism within our observational error. A lower limit to the Ca II K central intensity atmosphere is 0.040. The wavelength of Ca II K3 varies with the cycle by 6 milli-Angstroms, a factor of 2X over the full disk value. This may indicate the predominance of radial motions at Center Disk. This is not an effect of motions in plages since they are absent at Center Disk. This 11 y variation in the center of chromospheric lines could complicate the radial velocity detection of planets around solar-type stars. An appendix provides instructions for URL access to both the raw and reduced data.Comment: 38 pages with 20 figures. Accepted for publication in The Astrophysical Journa

Effective low-energy theory for correlated carbon nanotubes

The low-energy theory for single-wall carbon nanotubes including Coulomb interactions is derived and analyzed. It describes two fermion chains without interchain hopping but coupled in a specific way by the interaction. The strong-coupling properties are studied by bosonization, and consequences for experiments on single armchair nanotubes are discussed.Comment: 5 pages REVTeX, includes one figur

An Alternative Interpretation of Statistical Mechanics

In this paper I propose an interpretation of classical statistical mechanics that centers on taking seriously the idea that probability measures represent complete states of statistical mechanical systems. I show how this leads naturally to the idea that the stochasticity of statistical mechanics is associated directly with the observables of the theory rather than with the microstates (as traditional accounts would have it). The usual assumption that microstates are representationally significant in the theory is therefore dispensable, a consequence which suggests interesting possibilities for developing non-equilibrium statistical mechanics and investigating inter-theoretic answers to the foundational questions of statistical mechanics

Strong electron-phonon coupling in delta-phase stabilized Pu

Heat capacity measurements of the delta-phase stabilized alloy Pu-Al suggest that strong electron-phonon coupling is required to explain the moderate renormalization of the electronic density of states near the Fermi energy. We calculate the heat capacity contributions from the lattice and electronic degrees of freedom as well as from the electron-lattice coupling term and find good overall agreement between experiment and theory assuming a dimensionless electron-phonon coupling parameter of order unity, lambda ~ 0.8. This large electron-phonon coupling parameter is comparable to reported values in other superconducting metals with face-centered cubic crystal structure, for example, Pd (lambda ~ 0.7) and Pb (lambda ~ 1.5). Further, our analysis shows evidence of a sizable residual low-temperature entropy contribution, S_{res} ~ 0.4 k_B (per atom). We can fit the residual specific heat to a two-level system. Therefore, we speculate that the observed residual entropy originates from crystal-electric field effects of the Pu atoms or from self-irradiation induced defects frozen in at low temperatures.Comment: 9 pages, 11 figures, to appear in Phys. Rev.