Local Electronic Structure and High Temperature Superconductivity

It is argued that a new mechanism and many-body theory of superconductivity are required for doped correlated insulators. Here we review the essential features of and the experimental support for such a theory, in which the physics is driven by the kinetic energy.Comment: 8 Pages Latex. For the Proceedings of HTS99, Miami, FL, Jan. 199

Enhancement of pairing in a boson-fermion model for coupled ladders

Motivated by the presence of various charge inhomogeneities in strongly correlated systems of coupled ladders, a model of spatially separated bosonic and fermionic degrees of freedom is numerically studied. In this model, bosonic chains are connected to fermionic chains by two types of generalized Andreev couplings. It is shown that for both types of couplings the long-distance pairing correlations are enhanced. Near quarter filling, this effect is much larger for the splitting of a pair in electrons which go to the two neighboring fermionic chains than for a pair hopping process. It is argued that the pairing enhancement is a result of the nearest neighbor Coulomb repulsion which tunes the competition between pairing and charge ordering.Comment: 7 pages, 7 eps figures, enlarged version accpeted in Phys. Rev.

Stripe phases in high-temperature superconductors

Stripe phases are predicted and observed to occur in a class of strongly-correlated materials describable as doped antiferromagnets, of which the copper-oxide superconductors are the most prominent representative. The existence of stripe correlations necessitates the development of new principles for describing charge transport, and especially superconductivity, in these materials.Comment: 5 pp, 1 color eps fig., to appear as a Perspective in Proc. Natl. Acad. Sci. US

Exact Results for 1D Kondo Lattice from Bosonization

We find a solvable limit to the problem of the 1D electron gas interacting with a lattice of Kondo scattering centers. In this limit, we present exact results for the problems of incommensurate filling, commensurate filling, impurity vacancy states, and the commensurate-incommensurate transition.Comment: 4 pages, two columns, Latex fil

Sea surface velocities from visible and infrared multispectral atmospheric mapping sensor imagery

High resolution (100 m), sequential Multispectral Atmospheric Mapping Sensor (MAMS) images were used in a study to calculate advective surface velocities using the Maximum Cross Correlation (MCC) technique. Radiance and brightness temperature gradient magnitude images were formed from visible (0.48 microns) and infrared (11.12 microns) image pairs, respectively, of Chandeleur Sound, which is a shallow body of water northeast of the Mississippi delta, at 145546 GMT and 170701 GMT on 30 Mar. 1989. The gradient magnitude images enhanced the surface water feature boundaries, and a lower cutoff on the gradient magnitudes calculated allowed the undesirable sunglare and backscatter gradients in the visible images, and the water vapor absorption gradients in the infrared images, to be reduced in strength. Requiring high (greater than 0.4) maximum cross correlation coefficients and spatial coherence of the vector field aided in the selection of an optimal template size of 10 x 10 pixels (first image) and search limit of 20 pixels (second image) to use in the MCC technique. Use of these optimum input parameters to the MCC algorithm, and high correlation and spatial coherence filtering of the resulting velocity field from the MCC calculation yielded a clustered velocity distribution over the visible and infrared gradient images. The velocity field calculated from the visible gradient image pair agreed well with a subjective analysis of the motion, but the velocity field from the infrared gradient image pair did not. This was attributed to the changing shapes of the gradient features, their nonuniqueness, and large displacements relative to the mean distance between them. These problems implied a lower repeat time for the imagery was needed in order to improve the velocity field derived from gradient imagery. Suggestions are given for optimizing the repeat time of sequential imagery when using the MCC method for motion studies. Applying the MCC method to the infrared brightness temperature imagery yielded a velocity field which did agree with the subjective analysis of the motion and that derived from the visible gradient imagery. Differences between the visible and infrared derived velocities were 14.9 cm/s in speed and 56.7 degrees in direction. Both of these velocity fields also agreed well with the motion expected from considerations of the ocean bottom topography and wind and tidal forcing in the study area during the 2.175 hour time interval

Experimental study of acoustic displays of flight parameters in a simulated aerospace vehicle

Evaluating acoustic displays of target location in target detection and of flight parameters in simulated aerospace vehicle

Detection of early osteogenic commitment in primary cells using Raman spectroscopy

Major challenges in the development of novel implant surfaces for artificial joints include osteoblast heterogeneity and the lack of a simple and sensitive in vitro assay to measure early osteogenic responses. Raman spectroscopy is a label-free, non-invasive and non-destructive vibrational fingerprinting optical technique that is increasingly being applied to detect biochemical changes in cells. In this study Raman spectroscopy has been used to obtain bone cell-specific spectral signatures and to identify any changes therein during osteoblast commitment and differentiation of primary cells in culture. Murine calvarial osteoblasts (COBs) were extracted and cultured and studied by Raman spectroscopy over a 14 day culture period. Distinct osteogenic Raman spectra were identified after 3 days of culture with strong bands detected for mineral: phosphate ν3 (1030 cm−1) and B-type carbonate (1072 cm−1), DNA (782 cm−1) and collagen matrix (CH2 deformation at 1450 cm−1) and weaker phosphate bands (948 and 970 cm−1). Early changes were detected by Raman spectroscopy compared to a standard enzymatic alkaline phosphatase (ALP) assay and gene expression analyses over this period. Proliferation of COBs was confirmed by fluorescence intensity measurements using the Picogreen dsDNA reagent. Changes in ALP levels were evident only after 14 days of culture and mRNA expression levels for ALP, Col1a1 and Sclerostin remained constant during the culture period. Sirius red staining for collagen deposition also revealed little change until day 14. In contrast Raman spectroscopy revealed the presence of amorphous calcium phosphate (945–952 cm−1) and carbonated apatite (957–962 cm−1) after only 3 days in culture and octacalcium phosphate (970 cm−1) considered a transient mineral phase, was detected after 5 days of COBs culture. PCA analysis confirmed clear separation between time-points. This study highlights the potential of Raman spectroscopy to be utilised for the early and specific detection of proliferation and differentiation changes in primary cultures of bone cells