Free space optical communications (FSO) are beginning to provide attractive alternatives to fiber-based solutions in many situations. Currently, a handful of companies provide fiberless alternatives specifically aimed at corporate intranet and sporting event video applications. These solutions are geared toward solving the ''last mile'' connectivity issues. There exists a potential need to extend this pathlength to distances much greater than a 1 km, particularly for government and military applications. For cases of long distance optical propagation, atmospheric turbulence will ultimately limit the maximum achievable data rate. In this paper, we propose a method to improve signal quality through the use of adaptive optics. In particular, we show work in progress toward a high-speed, small footprint Adaptive Optics system for horizontal and slant path laser communications. Such a system relies heavily on recent progress in Micro-Electro-Mechanical Systems (MEMS) deformable mirrors, as well as improved communication and computational components.

The Forward Detector upgrade project at CDF is designed to enhance the capabilities for studies of diffractive physics at the Tevatron during Run II. Studies of hard diffraction and very forward physics are some of the topics that can be addressed in the next few years at the Tevatron. The program for diffractive physics, including the detectors and their commissioning, is discussed here. All the detectors have been installed and are presently collecting data.

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Block copolymers are well known to undergo micro-phase separation. Typical domain sizes range from a few to about 100 nanometers. With use of OPV{sub n-}PEG{sub m} diblock copolymers, long nanofiber, short nanorod, and lamella morphologies have been observed. OPV is oligo(phenylenevinylene) and PEG is poly(ethyleneglycol). The OPV segment is photoluminescent as well as electroluminescent. The micrometer long OPV{sub 13-}PEG{sub 45} nanofiber consists of OPV{sub 13} inner core with radius of 5.2 nm, and PEG{sub 45} outer shell with overall fiber radius of 7.9 nm. The nanorod has similar core-shell composition but with much shorter length of {approx}100 nm. Lamella morphology consists of alternating OPV and PEG layers. The structural characterization and physical properties of these nanostructured materials and their implication are summarized.

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The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions …

The RESRAD-BIOTA code was developed through a partnership among U.S. Department of Energy, the U.S. Environmental Protection Agency, and the U.S. Nuclear Regulatory Commission. RESRAD-BIOTA provides a full spectrum of analysis capabilities, from cost effective conservative screening methods (using biota concentration guides) to realistic, organism-specific dose assessment. A beta version of the RESRAD-BIOTA code is currently available for use and testing. Continued coordination and partnerships with U.S. agencies and international organizations is providing opportunities for the inclusion of additional evaluation approaches and capabilities, such as (1) development of biota concentration guides for additional radionuclides, (2) additional flexibility for specifying and expanding organism options, (3) improvements to parameter datasets of environmental transfer factors, (4) inclusion of additional ''reference organism geometries'' (e.g., dose conversion factors for ellipsoids of appropriate size and shielding properties for different sized organisms, appropriate for specific ecosystem types), and (5) the capability to perform sensitivity and uncertainty analyses for calculated dose estimates.

A novel design of a wide-angle monochromatic x-ray beam shutter is discussed. The shutter is designed as a compact unit capable of providing users with the means of shutting off the beam in secondary beamlines that are at an angle to the primary beamline and to each other. The single-unit design used the fact that all the secondary beamlines will be closed at the same time. The main challenge was to fit the shutter in the limited space of the existing Advanced Photon Source IMMW-CAT hutch. Space limitations led to the change in position of the actuator subassembly as compared to the standard shutter design. Although the actuator subassembly is placed underneath the shutter, fail-safe shutting is achieved by placing tungsten blocks above the beam while the shutter is open and using gravity to close the shutter in case of pneumatic failure. Redundancy required by safety concerns was achieved by duplicating the tungsten block/actuator subunits. Tungsten blocks of uneven length were used to counteract the increase in the center-to-center distance among secondary beamlines due to their angular offset. A special support table was designed to facilitate assembly and adjustability of the shutter position in the available space. To provide a …

D-atom atomic resonance absorption spectrometric (ARAS) detection has been used to study the thermal decomposition of C{sub 2}D{sub 5}I to give C{sub 2}D{sub 5}-radicals in {approx}70% yield (924-1370 K). C{sub 2}D{sub 5} then decomposes to give C{sub 2}D{sub 4} + D effectively instantaneously on the time scale of the bimolecular kinetics experiments. The concurrent thermal decompositions of both C{sub 2}D{sub 5}I and CH{sub 3}I can then be used to prepare well-defined initial concentrations of both D-atoms and CH{sub 3}-radicals. Experiments were performed by observing absolute [D] depletion and [H] formation. The results were initially modeled with a 33 step mechanism; however, because of the high sensitivity for H- and/or D-detection, the mechanism could be reduced to four reactions, all of which are known except the exchange reaction, D + CH{sub 3} {yields} CH{sub 2}D + H. The rate constants were found to be temperature independent with k = (2.20 {+-} 0.22) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 1294 {le} T {le} 1753 K. The present data have been combined with earlier lower temperature determinations, and the resultant database has been compared with unimolecular rate theory results. From theory, k = kk{sub {infinity}}<k{sub f{var_epsilon}}/(k{sub f{var_epsilon}} + k{sub …

The feasibility of using of a novel multi-pass absorption technique in combination with a shock tube for sensitive monitoring of free radicals for high-temperature kinetic studies was evaluated. The method was applied to study several elementary reactions of hydroxyl (OH) and methyl (CH{sub 3}) radicals.

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Background electrons are ubiquitous in high-intensity particle accelerators. Under certain operating conditions, amplification of the electron cloud can occur. The beam-cloud interaction can seriously degrade the accelerator performance with effects that range from vacuum degradation to collective beam instabilities. Although electron cloud effects (ECEs) were first observed 20 years ago in a proton ring, in recent years, they have been widely observed and intensely studied in e{sup +}/e{sup -} rings. This paper will focus on describing electron cloud diagnostics, which have led to an enhanced understanding of ECEs, especially details of beam-induced multipacting and saturation of the cloud. Such experimental results can be used to provide realistic limits on key input parameters for modeling efforts.

Analytical data and plant solution compositions are often reported in molarity units. Densities of salt solutions are needed to convert the concentrations to molal basis in order to utilize physical property data that have been established on a molal basis, for example, solution reaction equilibrium constants or activity coefficients. We report here the densities at 20.0 Degrees C of sodium tetrafluoroborate (NaBF4) solutions from 0.05 molal to 9.0 molal, near saturation of 9.2 molal.