Fundamental estimation bounds for polarimetric imagery.

Precise channel-to-channel registration is a prerequisite for effective exploitation of passive polarimetric imagery. In this paper, the Cramer-Rao bound is employed to determine the limits of registration precision in the presence of scene polarization diversity, channel noise, and random translational registration errors between channels. The effects of misregistration on Stokes image estimation are also explored in depth.

Use of tandem circulation wells to measure hydraulic conductivity without groundwater extraction.

Conventional methods to measure the hydraulic conductivity of an aquifer on a relatively large scale (10-100 m) require extraction of significant quantities of groundwater. This can be expensive, and otherwise problematic, when investigating a contaminated aquifer. In this study, innovative approaches that make use of tandem circulation wells to measure hydraulic conductivity are proposed.

Phase analysis of stimulated Brillouin scattering in long, graded-index optical fiber.

A continuous-wave beam was wavefront-split by a prism and propagated through separate paths before being coupled into a long, graded-index fiber. Stimulated Brillouin scattering (SBS) was generated in the fiber and the phase of the reflection was compared to that of the pump using lateral shearing interferometers immediately after reflection and also after propagating back through the separate paths. To analyze the phase conjugating properties of SBS in the fiber, one of the paths included a pathlength oscillation.

Stimulated Brillouin scattering continuous wave phase conjugation in step-index fiber optics.

Continuous wave (CW) stimulated Brillouin scattering (SBS) phase conjugation in step-index optical fibers was studied experimentally and modeled as a function of fiber length. A phase conjugate fidelity over 80% was measured from SBS in a 40 m fiber using a pinhole technique. Fidelity decreases with fiber length, and a fiber with a numerical aperture (NA) of 0.

Anisoplanatism in airborne laser communication.

Airborne laser-communication systems require special considerations in size, complexity, power, and weight. We reduce the variability of the received signal by implementing optimized multiple-transmitter systems to average out the deleterious effects of turbulence. We derive the angular laser-beam separation for various isoplanatic and uncorrelated (anisoplanatic) conditions for the phase and amplitude effects.

Optical phase unwrapping in the presence of branch points.

Strong turbulence causes phase discontinuities known as branch points in an optical field. These discontinuities complicate the phase unwrapping necessary to apply phase corrections onto a deformable mirror in an adaptive optics (AO) system. This paper proposes a non-optimal but effective and implementable phase unwrapping method for optical fields containing branch points.

Surface stress influences on nanopatterns formed in polystyrene films using a force-modulated nanohammer.

Two-dimensional lattices of nanodots can be reproducibly produced on polymer surfaces by a biaxial stress field generated using a force-modulated atomic force microscope tip as a nanohammer. Molecular sized super-lattice nanostructures were previously formed by a combination of fundamental and harmonic modulation of surface stress waves in different scanning directions. We find that similar super-lattice structures can be formed in polystyrene films using only fundamental force modulation by taking advantage of elastic interactions between nearby nanoridges.

Nonlinear wavelet transforms for image coding via lifting.

We investigate central issues such as invertibility, stability, synchronization, and frequency characteristics for nonlinear wavelet transforms built using the lifting framework. The nonlinearity comes from adaptively choosing between a class of linear predictors within the lifting framework. We also describe how earlier families of nonlinear filter banks can be extended through the use of prediction functions operating on a causal neighborhood of pixels.

Modeling positrons in molecular electronic structure calculations with the nuclear-electronic orbital method.

The nuclear-electronic orbital (NEO) method was modified and extended to positron systems for studying mixed positronic-electronic wavefunctions, replacing the mass of the proton with the mass of the positron. Within the modified NEO framework, the NEO-HF (Hartree-Fock) method provides the energy corresponding to the single-configuration mixed positronic-electronic wavefunction, minimized with respect to the molecular orbitals expressed as linear combinations of Gaussian basis functions. The electron-electron and electron-positron correlation can be treated in the NEO framework with second-order perturbation theory (NEO-MP2) or multiconfigurational methods such as the full configuration interaction (NEO-FCI) and complete active space self-consistent-field (NEO-CASSCF) methods.

An explanation of SRS beam cleanup in graded-index fibers and the absence of SRS beam cleanup in step-index fibers.

Beam cleanup via stimulated Raman scattering in multimode fibers is modeled by numerically considering the competition between the Stokes modes of graded-index and step-index fibers. The relative gain of each Stokes mode is calculated by considering the overlap the various pump and Stokes modes of the fibers. Mode competition in a graded-index fiber favors the LP(01) Stokes mode while mode competition in a step-index fiber does not favor the LP(01) Stokes mode.

Multiframe phase-diversity algorithm for active imaging.

A multiframe phase-diversity algorithm for imaging through the turbulent atmosphere tailored to the statistics of coherent light is developed and presented. The problem is posed as a maximum likelihood estimation where pupil-plane intensity data and atmospheric statistics are used to regularize the inverse problem. Reconstruction results characterized by residual mean square error are presented for varying detection parameters.

Effects of cross-sectional partitioning on active noise control in round ducts.

Active noise control (ANC) is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control. Basic acoustic principles dictate that the cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional diameter of the duct.

Cardinal interpolation.

A Bayesian probability density for an interpolating function is developed, and its desirable properties and practical potential are demonstrated. This density has an often needed but previously unachieved property, here called cardinal interpolation, which ensures extrapolation to the density of the least squares linear model. In particular, the mean of the cardinal interpolation density is a smooth function that intersects given (x, y) points and which extrapolates to their least squares line, and the variance of this density is a smooth function that is zero at the point x values, that increases with distance from the nearest point x value, and that extrapolates to the well-known quadratic variance function for the least squares line.

Comments on "comparison between orthogonal subspace projection and background subtraction techniques applied to remote-sensing data".

Ben-David and Ren [Appl. Opt. 44, 3846 (2005)] discussed methods of estimating the concentration of chemical vapor plumes in hyperspectral images.

Cellular interaction of different forms of aluminum nanoparticles in rat alveolar macrophages.

Nanomaterials, with dimensions in the 1-100 nm range, possess numerous potential benefits to society. However, there is little characterization of their effects on biological systems, either within the environment or on human health. The present study examines cellular interaction of aluminum oxide and aluminum nanomaterials, including their effect on cell viability and cell phagocytosis, with reference to particle size and the particle's chemical composition.

Effects of cross-sectional dimensions on active noise control in rectangular and round ducts.

Active noise control (ANC) works best to reduce low frequency noise. Because many industrial noise sources are broadband, ANC may be used more if it can be successfully applied to higher frequency ranges. This study explored one method to increase ANC effectiveness at higher frequencies.

Passive combination of multiple beams in an optical fiber via stimulated Brillouin scattering.

We demonstrate passive combination of multiple beams in an optical fiber via stimulated Brillouin scattering (SBS). Four off-axis beams are combined in a long multimode optical fiber using a novel all-optical mount. The combined beam has the high spatial coherence properties of the LP(01) mode owing to the beam cleanup properties of SBS.

Binary weighted averaging of an ensemble of coherently collected image frames.

Recent interest in the collection of remote laser radar imagery has motivated novel systems that process temporally contiguous frames of collected imagery to produce an average image that reduces laser speckle, increases image SNR, decreases the deleterious effects of atmospheric distortion, and enhances image detail. This research seeks an algorithm based on Bayesian estimation theory to select those frames from an ensemble that increases spatial resolution compared to simple unweighted averaging of all frames. The resulting binary weighted motion-compensated frame average is compared to the unweighted average using simulated and experimental data collected from a fielded laser vision system.

Predissociation of Bi2 A(0u+), v'=21-39.

Collisionless lifetimes for Bi2 A(0u+), v'=20-39, J' View Article and Find Full Text PDF

Gigahertz modulation of GaAs-based bipolar cascade vertical cavity surface-emitting lasers.

The high-frequency modulation characteristics of GaAs-based bipolar cascade vertical cavity surface-emitting lasers operating at 980 nm with GaAs tunnel junctions and p-doped Al0.98Ga0.02As oxide apertures have been measured.

Inelastic scattering matrix elements for the nonadiabatic collision B(2P1/2)+H2(1Sigmag+,j)<-->B(2P3/2)+H2(1Sigmag+,j').

Inelastic scattering matrix elements for the nonadiabatic collision B(2P1/2)+H2(1Sigmag+,j)<-->B(2P3/2)+H2(1Sigmag+,j') are calculated using the time dependent channel packet method (CPM). The calculation employs 1 2A', 2 2A', and 1 2A" adiabatic electronic potential energy surfaces determined by numerical computation at the multireference configuration-interaction level [M. H.

Antiphospholipid syndrome: an overview.

This paper reviews antiphospholipid syndrome (APS), also known as Hughes syndrome, which is a potentially life-threatening autoimmune disorder where the body produces antibodies directed toward phospholipids and phospholipid-binding proteins. Diagnosis of this syndrome relies on both clinical and laboratory criteria. Laboratory testing used for diagnosing APS includes coagulation assays for the detection of lupus anticoagulant (LA) and enzyme-linked immunosorbent assay (ELISA) for antiphospholipid antibody (APL) detection.

Flash light detection and ranging range accuracy limits for returns from single opaque surfaces via Cramer-Rao bounds.

A Cramer-Rao lower bound on the range accuracy obtainable by a Flash light detection and ranging (LADAR) system receiving a return from a single surface in the instantaneous field of view of each detector is developed and verified with experimental data. The bound is compared to the performance of a new algorithm and that of a matched filter receiver by using both simulated and measured LADAR data. The simulated data are used to show that the estimator is nearly unbiased and efficient for systems that match the negative paraboloid model used in its derivation.

Optimized phase screen modeling for optical turbulence.

An alternative method for statistical interpolation is formalized. A new theorem is proved, providing theoretical basis for optimizing statistical accuracy in successively conditioned rendering applications. The theorem is empirically validated by two simulations, each comparing two different statistical interpolators.

Atomic force microscopy of Bacillus spore surface morphology.

Bacillus spore surface morphology was imaged with atomic force microscopy (AFM) to determine if characteristic surface features could be used to distinguish between four closely related species; Bacillus anthracis Sterne strain, Bacillus thuringiensis var. kurstaki, Bacillus cereus strain 569, and Bacillus globigii var. niger.