The degradation of luminescence in phenylenevinylene polymers is due to exciton diffusion to quenching defects. The microscopic structure of these defects is identified by in-situ vibrational spectroscopy. The authors present evidence that the defect quenching is due to charge transfer by studies on model phenylenevinylene oligomer. In the absence of defect quenchers, the authors have achieved nearly exponential photoluminescence decay with observed lifetimes > 1 ns and a fourfold increase in electroluminescence. They have also utilized picosecond laser spectroscopy to study the formation yield of emissive excitons in the polymer PPVs with different morphology. They have found that increasing polymer chain separation would greatly increases the luminescent efficiency due to avoiding the interchain excitons (exciplexes). Clarification of the nature of photophysics of conjugated polymers suggests avenues for improvement in fabrication of emissive polymers and electroluminescent polymers devices.

Water Rocket is the collective name for an integrated set of technologies that offer new options for spacecraft propulsion, power, energy storage, and structure. Low pressure water stored on the spacecraft is electrolyzed to generate, separate, and pressurize gaseous hydrogen and oxygen. These gases, stored in lightweight pressure tanks, can be burned to generate thrust or recombined to produce electric power. As a rocket propulsion system, Water Rocket provides the highest feasible chemical specific impulse (-400 seconds). Even higher specific impulse propulsion can be achieved by combining Water Rocket with other advanced propulsion technologies, such as arcjet or electric thrusters. With innovative pressure tank technology, Water Rocket's specific energy [Wh/kg] can exceed that of the best foreseeable batteries by an order of magnitude, and the tanks can often serve as vehicle structural elements. For pulsed power applications, Water Rocket propellants can be used to drive very high power density generators, such as MHD devices or detonation-driven pulse generators. A space vehicle using Water Rocket propulsion can be totally inert and non-hazardous during assembly and launch. These features are particularly important for the timely development and flight qualification of new classes of spacecraft, such as microsats, nanosats, and refuelable spacecraft.

The All-Russian Scientific Research Institute of Inorganic Materials (VNIINM) performs research in nuclear power reactor fuel, spent fuel reprocessing and waste management, materials science of fissionable and reactor structural materials, metallurgy, superconducting materials, and analytical sciences. VNIINM supports the Ministry of Atomic Energy of the Russian Federation (MINATOM) in technologies for fabrication and processing of nuclear fuel. As a participant in the US/Russian Lab-to-Lab nuclear materials protection, control and accounting (MPC and A) program, VNIINM is providing support for measurements of nuclear materials in bulk forms by developing specifications, test and evaluation, certification, and implementation of measurement methods for such materials. In 1996, VNIINM will be working with Brookhaven staff in developing and documenting material control and accounting requirements for nuclear materials in bulk form, Livermore and Los Alamos staff in testing and evaluating gamma-ray spectrometry methods for bulk materials, Los Alamos staff in test and evaluation of neutron-coincidence counting techniques, Oak Ridge staff in accounting of bulk materials with process instrumentation, and Pacific Northwest staff on automating VNIINM`s coulometric titration system. In addition, VNIINM will develop a computerized accounting system for nuclear material within VNIINM and their storage facility. The paper will describe the status of this work and …

The evaluation of the disposition of plutonium using light water reactors is receiving increased attention. However, mixed-oxide (MOX) fuel assemblies possess much higher absorption and fission cross- sections when compared to standard UO2 assemblies. Those properties yield very high thermal flux gradients at the interfaces between MOX and UO2 assemblies. It has already been reported that standard flux reconstruction methods (that recover the homogeneous intranodal flux shape using the converged nodal solution) yield large errors in the presence of MOX assemblies. In an accompanying paper, we compare diffusion and simplified PN calculations of a mixed-oxide benchmark problem to a reference transport calculation. In this paper, we examine the errors associated with standard nodal diffusion methods when applied to the same benchmark problem. Our results show that a large portion of the error is associated with the quadratic leakage approximation (QLA) that is commonly used in the standard nodal codes.

Structural proteins such as collagen and elastin are known to generate second harmonic at high laser intensities. Second and third harmonic generations (SHG, THG) of 0.4 ps Ti-Sapphire laser radiation at 800 nm were observed in various biological tissues. Dependence of SHG on laser pulse energy and pulse width was investigated. Reflected second harmonic yield was measured for animal tissue <i>in vitro</i> and human skin <i>in vivo</i>. The yield varies about a factor of 20 for various areas of the skin while the scattered laser radiation (diffuse reflectance) varies only by a factor of 2. In some cases the THG efficiency was comparable to the SHG. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed.

Unpolarized inelastic neutron scattering is used to study the temperature and wave vector dependence of the dynamical magnetic susceptibility, {xi}`` (q,{omega}), of a well characterized single crystal YBa{sub 2}Cu{sub 3}O{sub 6.6} (T{sub c} = 62.7 K). We find that a pseudogap opens in the spin fluctuation spectrum at temperatures well above T{sub c}. We speculate that the appearance of the low frequency incommensurate fluctuations is associated with the opening of the pseudogap. To within the error of the measurements, a gap in the spin fluctuation spectrum is found in the superconducting state.

The authors compare the polarized optical spectra of the organic metal {beta}{double_prime}-(ET){sub 2}SF{sub 5}CHFSO{sub 3} and the {beta}{double_prime}-ET{sub 2}SF{sub 5}CHFCF{sub 2}SO{sub 3} metal/insulator material with those of the first fully organic superconductor {beta}{double_prime}-ET{sub 2}SF{sub 5}CH{sub 2}SO{sub 3}. The small chemical modification of the counterion has a dramatic effect on the spectral and charge transport properties of these materials, and they discuss their electronic structure in terms of band structure, many-body effects, and disorder. Based on structural differences in the anion pocket of the three salts, they conclude that the unusual electronic excitations observed in the {beta}{double_prime}-(ET){sub 2}SF{sub 5}CHFCF{sub 2}SO{sub 3} metal/insulator material are caused by disorder-related localization.

A high-precision cryogenically-cooled crystal monochromator has been developed for the APS diagnostics beamline. The design permits simultaneous measurements of the particle beam size and divergence. It provides for a large rotation angle, {minus}15{degree} to 180{degree}, with a resolution of 0.0005{degree}. The roll angle of the crystal can be adjusted by up to {+-}3{degree} with a resolution of 0.0001{degree}. A vertical translational stage, with a stroke of {+-}25 mm and resolution of 8 {micro}m, is provided to enable using different parts of the same crystal or to retract the crystal from the beam path. The modular design will allow optimization of cooling schemes to minimize thermal distortions of the crystal under high heat loads.

Argonne National Laboratory is developing a process to convert hydrocarbon fuels to clean hydrogen feeds for a polymer electrolyte fuel cell. The process incorporates an autothermal reforming catalyst that can process hydrocarbon feeds at lower temperatures than existing commercial catalysts. The authors have tested the catalyst with three diesel-type fuels: hexadecane, certified low-sulfur grade 1 diesel, and a standard grade 2 diesel. Hexadecane yielded products containing 60% hydrogen on a dry, nitrogen-free basis at 850 C, while maximum hydrogen product yields for the two diesel fuels were near 50%. Residual products in all cases included CO, CO{sub 2}, ethane, and methane. Further studies with grade 1 diesel showed improved conversion as the water:fuel ratio was increased from 1 to 2 at 850 C. Soot formation was reduced when the oxygen:carbon ratio was maintained at 1 at 850 C. There were no significant changes in hydrogen yield as the space velocity and the oxygen:fuel ratio were varied. Tests with a microchannel monolithic catalyst yielded similar or improved hydrogen levels at higher space velocities than with extruded pellets in a packed bed.

The authors carry out a comparative study of the energetic and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its rocking motion, observed in STM, actually reflects a 180{degree} rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.

Simulations of granular packings in 2-D by throwing disks in a rectangular die are performed. Different size distributions as bimodal, uniform and gaussian are used. Once the array of particles is done, a relaxation process is carried on using a large-amplitude, low-frequency vertical shaking. This relaxation is performed a number N of times. Then, the authors measure the density of the package, contact distribution, coordination number distribution, entropy and also the disks size distribution vs. height. The dependence of all these magnitudes on the number N of shakings used to relax the packing and on the size distribution parameters are explored and discussed.

Each year, about five (5) million ton of shredder residues are landfilled in the US. Similar quantities are landfilled in Europe and the Pacific Rim. Landfilling of these residues results in a cost to the existing recycling industry and also represents a loss of material resources that are otherwise recyclable. In this paper, the authors outline the resources recoverable from typical shredder residues and describe technology that they have developed to recover these resources.

The inverse deuterium isotope effect, previously found in K-(BEDT-TTF){sub 2}CU(NCS){sub 2}, is also found in two other BEDT-TTF-based superconductors with different packing motifs and different types of anions. Remarkably, the magnitude of the isotope shift is essentially identical in all three superconductors, ca. +0.26 {+-} 0.06 K. These results, when taken together with the recent results of Lang et al. on the uniaxial pressure derivatives of T{sub c}, suggest that the inverse isotope effect may not have a direct relationship to the pairing mechanism but instead is a reflection of the change in the internal lattice pressure.

The application of four gas-turbine, modular helium cooled reactors and an accelerator unit (GT/AD-MHR) has been proposed for burning transuranics recycled from LWR waste. The recycled LWR discharged transuranics encapsulated in TRISO coated particles are first loaded into the outer thermal spectrum zone of the GT/AD-MHR for burning in the critical mode for about three years. Previously burned fuel is in a central fast zone. In the fourth year, the same unit is configured as an accelerator-driven system, containing a centrally located spallation target. The three-year, thermal-zone burned fuel and the inner fast-zone fuel from the critical mode operation are used in this subcritical cycle, and remain in their respective zones. At the end of this one-year subcritical irradiation, the outer thermal-zone fuel is reconstituted and used as fast-zone fuel in another critical mode operation. As the fuel in the fast-zone has reached its end of life it is discharged, with very low transuranics content. The critical mode operation is staggered, and each GT/AD-MGR unit undergoes the subcritical burn in one out of four year. The physics performance of the GT/AD-MHR has been evaluated using independent deterministic and Monte Carlo codes and the results of the study are presented in …

This paper describes a computable general equilibrium (CGE) model with considerable sector and technology detail, the ``All Modular Industry Growth Assessment'' Model (AMIGA). It is argued that a detailed model is important to capture and understand the several rolls that energy plays within the economy. Fundamental consumer and industrial demands are for the services from energy; hence, energy demand is a derived demand based on the need for heating, cooling mechanical, electrical, and transportation services. Technologies that provide energy-services more efficiently (on a life cycle basis), when adopted, result in increased future output of the economy and higher paths of household consumption. The AMIGA model can examine the effects on energy use and economic output of increases in energy prices (e.g., a carbon charge) and other incentive-based policies or energy-efficiency programs. Energy sectors and sub-sector activities included in the model involve energy extraction conversion and transportation. There are business opportunities to produce energy-efficient goods (i.e., appliances, control systems, buildings, automobiles, clean electricity). These activities are represented in the model by characterizing their likely production processes (e.g., lighter weight motor vehicles). Also, multiple industrial processes can produce the same output but with different technologies and inputs. Secondary recovery, i.e., recycling processes, …

Transportation of carbon dioxide (CO{sub 2}) for enhanced oil recovery is a mature technology, with operating experience dating from the mid-1980s. Because of this maturity, recent sequestration studies for the US Department of Energy's National Energy Technology Laboratory have been able to incorporate transportation into overall energy-cycle economics with reasonable certainty. For these studies, two different coal-fueled plants are considered; the first collects CO{sub 2} from a 456-MW integrated coal gasification combined-cycle plant, while the second employs a 353-MW pulverized-coal boiler plant retrofitted for flue-gas recycling (Doctor et al. 1999; MacDonald and Palkes 1999). The pulverized-coal plant fires a mixture of coal in a 33% O{sub 2} atmosphere, the bulk of the inert gas being made up to CO{sub 2} to the greatest extent practical. If one power plant with one pipe feeds one sequestration reservoir, projected costs for a 500-km delivery pipeline are problematic, because when supplying one reservoir both plant availability issues and useful pipeline life heavily influence capital recovery costs. The transportation system proposed here refines the sequestration scheme into a network of three distinctive pipelines: (1) 80-km collection pipelines for a 330-MW pulverized-coal power plant with 100% CO{sub 2} recovery; (2) a main CO{sub 2} transportation …

Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions. Herein the author provides a Dyson-Schwinger equation perspective, focusing on qualitative aspects of confinement and dynamical chiral symmetry breaking in cold, sparse QCD, and also elucidating consequences of the axial-vector Ward-Takahashi identity and features of the heavy-quark limit.

The de Haas-van Alphen (dHvA) signal of the organic superconductor {beta}{double_prime}-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} shows an inverse-sawtooth wave form which proves the existence of an ideal two-dimensional (2D) Fermi surface. The dHvA wave shape can almost perfectly be described by a 2D theory assuming a constant chemical potential. This either implies the existence of the predicted quasi-one-dimensional band with an exceptionally large density of states or the chemical potential may be pinned due to localized states near the Fermi energy.

Lawrence Livermore National Laboratory is developing a ceramic form for immobilizing excess US plutonium. The process used to produce the ceramic form is similar to the fabrication process used in the production of MOX fuel. In producing the ceramic form, the uranium and plutonium oxides are first milled to less than 20 microns. The milled actinide powder then goes through a mixing-blending step where the ceramic precursors, made from a mixture of calcined TiO₂, Ca(OH)₂, HfO₂ and Gd0₃, are blended with the milled actinides. A subsequent granulation step ensures that the powder will flow freely into the press and die set. The pressed ceramic material is then sintered. The process parameters for the ceramic fabrication steps to make the ceramic form are less demanding than equivalent processing steps for MOX fuel fabrication. As an example, the pressing pressure for MOX is in excess of 137.0 MPa, whereas the pressing pressure for the ceramic form is only 13.8 MPa. This translates into less die wear for the ceramic material pressing. Similarly, the sintering temperatures and times are also different. MOX is sintered at 1,700°C in 4% H₂ for a 24 hour cycle. The ceramic form is sintered at 1350°C in argon …

A hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer is commonly used as propellant binder material. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. The aging of these binders can be monitored by mechanical property measurements such as modulus or tensile elongation. These techniques, however, are not easily adapted to binder agents that are dispersed throughout a propellant. In this paper the authors investigated solid state NMR relaxation times as a means to predict the mechanical properties of the binder as a function of aging time. {sup 1}H spin-lattice and spin-spin relaxation times were found to be insensitive to the degree of thermal degradation of the elastomer. Apparently these relaxation times depend on localized motions that are only weakly correlated with mechanical properties. A strong correlation was found between the {sup 13}C cross-polarization (CP) NMR time constant, T{sub cp}, and the tensile elongation at break of the elastomer as a function of aging time. A ramped-amplitude CP experiment was shown to be less sensitive to imperfections in setting critical instrumental parameters for this mobile material.

There is a growing interest in the development of very high gradient ({ge} GeV/meter) accelerating structures and millimeter-wave power sources. The need for very high gradient structures to be operated in W-band or at higher frequencies poses great technical challenges and demands innovations in rf science and technology to reach this goal. Requirements for microstructure fabrication and power sources based on deep x-ray lithography techniques are examined.

The weld solidification and cracking behavior of sulfur bearing free machining austenitic stainless steel was investigated for both gas-tungsten arc (GTA) and pulsed laser beam weld processes. The GTA weld solidification was consistent with those predicted with existing solidification diagrams and the cracking response was controlled primarily by solidification mode. The solidification behavior of the pulsed laser welds was complex, and often contained regions of primary ferrite and primary austenite solidification, although in all cases the welds were found to be completely austenite at room temperature. Electron backscattered diffraction (EBSD) pattern analysis indicated that the nature of the base metal at the time of solidification plays a primary role in initial solidification. The solid state transformation of austenite to ferrite at the fusion zone boundary, and ferrite to austenite on cooling may both be massive in nature. A range of alloy compositions that exhibited good resistance to solidification cracking and was compatible with both welding processes was identified. The compositional range is bounded by laser weldability at lower Cr{sub eq}/Ni{sub eq} ratios and by the GTA weldability at higher ratios. It was found with both processes that the limiting ratios were somewhat dependent upon sulfur content.

The thermal stability of photo-imprinted Bragg gratings formed in reactive-atmosphere, RF-magnetron sputtered germanosilicate thin films was evaluated in terms of point defect modifications observed during isochronal annealing. Optical and magnetic spectroscopes were utilized to evaluate structural relaxation in these sputtered glasses on both a local and medium-range size scale. Depending upon the substrate temperature used during deposition, significant structural rearrangement was found to occur with increasing post-deposition anneal temperature to 600 C. This resulted in changes in the photobleaching response of the material itself as the identity of optically active structural defects evolved. Based on a color center model for photosensitivity in these materials and measured changes in optical absorption with annealing, the thermal stability of a photo-imprinted Bragg grating was modeled. Good qualitative agreement with experiment was observed.

Remarkable materials ordered at the nanoscale emerge when a sol-gel solution becomes co-organized with a surfactant. At sufficiently high concentration, the surfactant forms crystalline or liquid-crystalline arrays of micelles in the presence of the sol-gel, and as gelation proceeds the arrays become locked into the gel. Recent experiments demonstrate that the degree of order in the resulting mesoporous ceramic phase can be enhanced and controlled by continuous dip coating in which the solution, initially dilute, evolves through the critical micelle concentration by steady-state evaporation. The long-range order and microstructural orientation in these films suggest that the propagation of a critical-micelle-concentration transition front, with large physico-chemical gradients, promotes oriented self assembly of surfactant aggregates. This steep-gradient view is supported by results from unsteady evaporation of aerosols of similar solutions, in which internally well-ordered but complex particles are formed.