Breadboard linear array scan imager using LSI solid-state technology

The performance of large scale integration photodiode arrays in a linear array scan (pushbroom) breadboard was evaluated for application to multispectral remote sensing of the earth's resources. The technical approach, implementation, and test results of the program are described. Several self scanned linear array visible photodetector focal plane arrays were fabricated and evaluated in an optical bench configuration. A 1728-detector array operating in four bands (0.5 - 1.1 micrometer) was evaluated for noise, spectral response, dynamic range, crosstalk, MTF, noise equivalent irradiance, linearity, and image quality. Other results include image artifact data, temporal characteristics, radiometric accuracy, calibration experience, chip alignment, and array fabrication experience. Special studies and experimentation were included in long array fabrication and real-time image processing for low-cost ground stations, including the use of computer image processing. High quality images were produced and all objectives of the program were attained

Redox Reactivity of Bacterial and Mammalian Ferritin: Is Reductant Entry Into the Ferritin Interior a Necessary Step for Iron Release?

Both mammalian and bacterial ferritin undergo rapid reaction with small-molecule reductants, in the absence of Fe2+ chelators, to form ferritins with reduced (Fe2+) mineral cores. Large, low-potential reductants (flavoproteins and ferredoxins) similarly react anaerobically with both ferritin types to quantitatively produce Fe2+ in the ferritin cores. The oxidation of Fe2+ ferritin by large protein oxidants [cytochrome c and Cu(II) proteins] also occurs readily, yielding reduced heme and Cu(I) proteins and ferritins with Fe3+ in their cores. These latter oxidants also convert enthetically added Fe2+, bound in mammalian or bacterial apo- or holo-ferritin, to the corresponding Fe3+ state in the core of each ferritin type. Because the protein reductants and oxidants are much larger than the channels leading into the mineral core attached to the ferritin interior, we conclude that redox reactions involving the Fe2+/Fe3+\u3e components of the ferritin core can occur without direct interaction of the redox reagent at the mineral core surface. Our results also suggest that the oxo, hydroxy species of the core, composed essentially of Fe(O)OH, arise exclusively from solvent deprotonation. The long-distance ferritin-protein electron transfer observed in this study may occur by electron tunneling

A New Approach for the Study of Chemical Mechanical Polishing

The process of chemical mechanical polishing (CMP) can be studied using in situ atomic force microscopy (AFM) by intentionally using a high tip/sample interaction force. The nominal removal rate ofAl during AFM scratching is studied under a range of conditions including varying tip/sample force, solution pH, and electrode potential. This approach should be useful for CMP process development and furthering the fundamental understanding of CMP mechanisms

Pitting in Aluminum Thin Films Supersaturation and Effects of Dichromate Ions

The growth of pits in 209 nm thick Al films in chloride solutions with and without dichromate ions was examined using image analysis of the growing pits to determine pit current density. In pure chloride solutions, the pit current density decreased at high potentials after reaching a maximum value, and then was almost independent of applied potential. A hysteresis in the pit current density-potential behavior was observed during downward stepping of the potential from high values. This is a result of a combination of supersaturation of the pit electrolyte followed by salt film formation, and changes in mass transport from hydrogen bubbles that increase convection and lift the remnant passive film away from the dissolving surface. In solutions containing dichromate ions, the corrosion and repassivation potentials shifted in the noble direction, and rather large metastable pits formed at the open circuit. A large concentration of dichromate ions was needed to inhibit pit growth. In dichromate solutions, subsequent pit growth at higher potentials often initiated at the edge of the open-circuit pits. The rate of pit growth was lower for these pits because the remnant passive film layer was not easily lifted up at these sites, and thus created a barrier for mass transport away from the dissolving pit edge.This work was supported by Major H. DeLong at the United States Air Force Office of Scientific Research under contract F49620-96-0042

Statistical model for intergranular corrosion growth kinetics

A statistical model has been developed to predict the anisotropy of intergranular corrosion (IGC) kinetics and effect of microstructure on IGC kinetics in high strength AA2024-T3 alloys. The methodology is to estimate the statistical distribution of minimum IGC path length that will be found through the thickness of a given thickness ST sample using the principle of order statistics. A brick-wall model is adopted for wrought Al alloy microstructure and different distributions of grain dimension are assumed for the purpose of the estimation of total IGC path length. Numerical stimulation using a gamma distribution model stimulated the anisotropy of localized corrosion in AA2024-T3 alloys, which quite agrees with the growth rate anisotropy experimentally determined by the foil penetration technique. Some limitations regarding the statistical model are discussed. The statistical model provides a new approach to predicting and quantifying localized corrosion kinetics on basis of the alloy microstructure.This work was supported by the United States Air Force Office of Scientific Research through Grant no. F49620-99-1-0103

Eigenvalue Separation in Some Random Matrix Models

The eigenvalue density for members of the Gaussian orthogonal and unitary ensembles follows the Wigner semi-circle law. If the Gaussian entries are all shifted by a constant amount c/Sqrt(2N), where N is the size of the matrix, in the large N limit a single eigenvalue will separate from the support of the Wigner semi-circle provided c > 1. In this study, using an asymptotic analysis of the secular equation for the eigenvalue condition, we compare this effect to analogous effects occurring in general variance Wishart matrices and matrices from the shifted mean chiral ensemble. We undertake an analogous comparative study of eigenvalue separation properties when the size of the matrices are fixed and c goes to infinity, and higher rank analogues of this setting. This is done using exact expressions for eigenvalue probability densities in terms of generalized hypergeometric functions, and using the interpretation of the latter as a Green function in the Dyson Brownian motion model. For the shifted mean Gaussian unitary ensemble and its analogues an alternative approach is to use exact expressions for the correlation functions in terms of classical orthogonal polynomials and associated multiple generalizations. By using these exact expressions to compute and plot the eigenvalue density, illustrations of the various eigenvalue separation effects are obtained.Comment: 25 pages, 9 figures include

Geometrical approach to the proton spin decomposition

We discuss in detail and from the geometrical point of view the issues of gauge invariance and Lorentz covariance raised by the approach proposed recently by Chen et al. to the proton spin decomposition. We show that the gauge invariance of this approach follows from a mechanism similar to the one used in the famous Stueckelberg trick. Stressing the fact that the Lorentz symmetry does not force the gauge potential to transform as a Lorentz four-vector, we show that the Chen et al. approach is Lorentz covariant provided that one uses the suitable Lorentz transformation law. We also make an attempt to summarize the present situation concerning the proton spin decomposition. We argue that the ongoing debates concern essentially the physical interpretation and are due to the plurality of the adopted pictures. We discuss these different pictures and propose a pragmatic point of view.Comment: 39 pages, 1 figure, updated version to appear in PRD (2013

Nonlinear equation for curved stationary flames

A nonlinear equation describing curved stationary flames with arbitrary gas expansion $\theta = \rho_{{\rm fuel}}/\rho_{{\rm burnt}}$, subject to the Landau-Darrieus instability, is obtained in a closed form without an assumption of weak nonlinearity. It is proved that in the scope of the asymptotic expansion for $\theta \to 1,$ the new equation gives the true solution to the problem of stationary flame propagation with the accuracy of the sixth order in $\theta - 1.$ In particular, it reproduces the stationary version of the well-known Sivashinsky equation at the second order corresponding to the approximation of zero vorticity production. At higher orders, the new equation describes influence of the vorticity drift behind the flame front on the front structure. Its asymptotic expansion is carried out explicitly, and the resulting equation is solved analytically at the third order. For arbitrary values of $\theta,$ the highly nonlinear regime of fast flow burning is investigated, for which case a large flame velocity expansion of the nonlinear equation is proposed.Comment: 29 pages 4 figures LaTe