MODIFIED BOROHYDRIDES FOR REVERSIBLE HYDROGEN STORAGE (open access)

MODIFIED BOROHYDRIDES FOR REVERSIBLE HYDROGEN STORAGE

This paper reports the results in the effort to destabilize lithium borohydride for reversible hydrogen storage. A number of metals, metal hydrides, metal chlorides and complex hydrides were selected and evaluated as the destabilization agents for reducing dehydriding temperature and generating dehydriding-rehydriding reversibility. It is found that some additives are effective. The Raman spectroscopic analysis shows the change of B-H binding nature.
Date: May 10, 2006
Creator: Au, Ming
System: The UNT Digital Library
REVIEW OF FORWARD PHYSICS AT RHIC. (open access)

REVIEW OF FORWARD PHYSICS AT RHIC.

None
Date: May 10, 2006
Creator: DEBBE, R. & COLLABORATION), (FOR THE BRAHMS
System: The UNT Digital Library
Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: III. Emission Line Diagnostics of Ensembles of H II Regions (open access)

Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: III. Emission Line Diagnostics of Ensembles of H II Regions

We have built, as far as possible, fully self-consistent models of H II regions around aging clusters of stars. These produce strong emission line diagnostics applicable to either individual H II regions in galaxies, or to the integrated emission line spectra of disk or starburst galaxies. The models assume that the expansion and internal pressure of individual H II regions is driven by the net input of mechanical energy from the central cluster, be it through winds or supernova events. This eliminates the ionization parameter as a free variable, replacing it with a parameter which depends on the ratio of the cluster mass to the pressure in the surrounding interstellar medium. These models explain why H II regions with low abundances have high excitation, and demonstrate that at least part of the warm ionized medium is the result of overlapping faint, old, large, and low pressure H II regions. We present a number of line ratios (at both optical and IR wavelengths) that provide reliable abundance diagnostics for either single H II regions or for integrated galaxy spectra, and others that are sensitive to the age of the cluster stars exciting individual H II regions.
Date: May 10, 2006
Creator: Dopita, M A; Fischera, J; Sutherland, R S; Kewley, L J; Leitherer, C; Tuffs, R J et al.
System: The UNT Digital Library
Energetic feedback in galaxies: Processing of interstellar silicate grains by cosmic rays (open access)

Energetic feedback in galaxies: Processing of interstellar silicate grains by cosmic rays

The formation and evolution of stars and galaxies is a complex process that involves the cooling and collapse of dense interstellar clouds as well as energetic feedback on these clouds. Interstellar dust grains are central to the radiative transfer, thermal balance, and molecular processes in these clouds and can provide an important diagnostic. Hence, the effects of energetic processing of interstellar dust may have significant consequences. r This may be studied in our own Galaxy, where observations have shown that an appreciable fraction of silicates formed in the outflows from red giants and supergiants have a crystalline structure. Yet, the fraction of crystalline silicates in the interstellar medium is very small, pointing towards an efficient crystalline crystalline-to to-amorphous conversion process. Here we report experimental and modeling results that show that relatively ''low'' energy (0.1 - 5.0 GeV) heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium. The implications of this are briefly discussed. We also examine the effects of cosmic ray processing of silicates in the solar system and in stellar debris disks. In the latter systems, cosmic ray processing may play a role for grains trapped in resonance …
Date: May 10, 2006
Creator: Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G W M; Dai, Z R et al.
System: The UNT Digital Library
Electron Beam-induced Light Emission and Transport in GaN Nanowires (open access)

Electron Beam-induced Light Emission and Transport in GaN Nanowires

We report observations of electron beam-induced light from GaN nanowires grown by chemical vapor deposition. GaN nanowires were modified in-situ with deposited opaque platinum coatings to estimate the extent to which light is channeled to the ends of nanowires. Some evidence of light channeling was found, but wire microstructure and defects play an important role in light scattering and transport, limiting the extent to which light is confined. Optical interconnects are powerful components presently applied for high bandwidth communications among high-performance processors. Future circuits based on nanometer-scale components could similarly benefit from optical information transfer among processing blocks. Strong light channeling (and even lasing) has been observed in GaN nanowires, suggesting that these structures could be useful building blocks in a future networked electro-optical processor. However, the extent to which defects and microstructure control optical performance in nanowire waveguides has not been measured. In this study, we use electron microscopy and in-situ modification of individual nanowires to begin to correlate wire structure with light transport efficiency through GaN nanowires tens of microns long.
Date: May 10, 2006
Creator: Tringe, J W; MoberlyChan, W J; Stevens, C G; Davydov, A V & Motayed, A
System: The UNT Digital Library
Physical controls on directed virus assembly at nanoscale chemical templates (open access)

Physical controls on directed virus assembly at nanoscale chemical templates

Viruses are attractive building blocks for nanoscale heterostructures, but little is understood about the physical principles governing their directed assembly. In-situ force microscopy was used to investigate organization of Cowpea Mosaic Virus engineered to bind specifically and reversibly at nanoscale chemical templates with sub-30nm features. Morphological evolution and assembly kinetics were measured as virus flux and inter-viral potential were varied. The resulting morphologies were similar to those of atomic-scale epitaxial systems, but the underlying thermodynamics was analogous to that of colloidal systems in confined geometries. The 1D templates biased the location of initial cluster formation, introduced asymmetric sticking probabilities, and drove 1D and 2D condensation at subcritical volume fractions. The growth kinetics followed a t{sup 1/2} law controlled by the slow diffusion of viruses. The lateral expansion of virus clusters that initially form on the 1D templates following introduction of polyethylene glycol (PEG) into the solution suggests a significant role for weak interaction.
Date: May 10, 2006
Creator: Cheung, C. L.; Chung, S.; Chatterji, A.; Lin, T.; Johnson, J. E.; Hok, S. et al.
System: The UNT Digital Library
THRESHOLD RESUMMATION FOR HIGGS PRODUCTION IN EFFECTIVE FIELD THEORY. (open access)

THRESHOLD RESUMMATION FOR HIGGS PRODUCTION IN EFFECTIVE FIELD THEORY.

None
Date: May 10, 2006
Creator: YUAN, F.
System: The UNT Digital Library
Solid Target Studies for Muon Colliders And Neutrino Beams (open access)

Solid Target Studies for Muon Colliders And Neutrino Beams

This paper presents preliminary results from an ongoing post-irradiation analysis of materials that have been irradiated at the Brookhaven National Laboratory (BNL) Isotope facility. The effort is part of an experimental study that focuses on how prone to irradiation damage these materials are and thus what is their potential in playing the role of high power targets in the neutrino superbeam and the muon collider initiatives.
Date: May 10, 2006
Creator: Simos, N.; Kirk, H.; Ludewig, H.; Thieberger, P.; Weng, W. T.; Trung, P. T. et al.
System: The UNT Digital Library
Charge Identification of Highly Ionizing Particles in Desensitized Nuclear Emulsion Using High Speed Read-Out System (open access)

Charge Identification of Highly Ionizing Particles in Desensitized Nuclear Emulsion Using High Speed Read-Out System

We performed an experimental study of charge identification of heavy ions from helium to carbon having energy of about 290 MeV/u using an emulsion chamber. Emulsion was desensitized by means of forced fading (refreshing) to expand a dynamic range of response to highly charged particles. For the track reconstruction and charge identification, the fully automated high speed emulsion read-out system, which was originally developed for identifying minimum ionizing particles, was used without any modification. Clear track by track charge identification up to Z=6 was demonstrated. The refreshing technique has proved to be a powerful technique to expand response of emulsion film to highly ionizing particles.
Date: May 10, 2006
Creator: Toshito, T.; Kodama, K.; Yusa, K.; Ozaki, M.; Amako, K.; Kameoka, S. et al.
System: The UNT Digital Library
UNIFYING THE MECHANISMS FOR SINGLE SPIN ASYMMETRIES IN HARD PROCESSES. (open access)

UNIFYING THE MECHANISMS FOR SINGLE SPIN ASYMMETRIES IN HARD PROCESSES.

None
Date: May 10, 2006
Creator: YUAN, F.
System: The UNT Digital Library
Two Paths to Transforming Markets through Public Sector Energy Efficiency: Bottom Up versus Top Down (open access)

Two Paths to Transforming Markets through Public Sector Energy Efficiency: Bottom Up versus Top Down

The evolution of government purchasing initiatives in Mexicoand China, part of the PEPS (Promoting an Energy-efficient Public Sector)program, demonstrates the need for flexibility in designingenergy-efficiency strategies in the public sector. Several years ofpursuing a top-down (federally led) strategy in Mexico produced fewresults, and it was not until the program was restructured in 2004 tofocus on municipal-level purchasing that the program gained momentum.Today, a new partnership with the Mexican federal government is leadingto an intergovernmental initiative with strong support at the federallevel. By contrast, the PEPS purchasing initiative in China wassuccessfully initiated and led at the central government level withstrategic support from international experts. The very different successtrajectories in these two countries provide valuable lessons fordesigning country-specific public sector energy-efficiency initiatives.Enabling conditions for any successful public sector purchasinginitiative include the existence of mandatory energy-efficiencyperformance standards, an effective energy-efficiency endorsementlabeling program, an immediate need for energy conservation, a simplepilot phase (focusing on a limited number of strategically chosenproducts), and specialized technical assistance. Top-down purchasingprograms are likely to be more successful where there is high-levelpolitical endorsement and a national procurement law in place, supportedby a network of trained purchasers. Bottom-up (municipally led)purchasing programs require that municipalities have the authority to settheir own purchasing …
Date: May 10, 2006
Creator: Van Wie McGrory, Laura; Coleman, Philip; Fridley, David; Harris,Jeffrey & Villasenor Franco, Edgar
System: The UNT Digital Library
The use of bulk states to accelerate the band edge statecalculation of a semiconductor quantum dot (open access)

The use of bulk states to accelerate the band edge statecalculation of a semiconductor quantum dot

We present a new technique to accelerate the convergence of the folded spectrum method in empirical pseudopotential band edge state calculations for colloidal quantum dots. We use bulk band states of the materials constituent of the quantum dot to construct initial vectors and a preconditioner. We apply these to accelerate the convergence of the folded spectrum method for the interior states at the top of the valence and the bottom of the conduction band. For large CdSe quantum dots, the number of iteration steps until convergence decreases by about a factor of 4 compared to previous calculations.
Date: May 10, 2006
Creator: Vomel, Christof; Tomov, Stanimire Z.; Wang, Lin-Wang; Marques,Osni A. & Dongarra, Jack J.
System: The UNT Digital Library
Bottom-up, decision support system development : a wetlandsalinity management application in California's San Joaquin Valley (open access)

Bottom-up, decision support system development : a wetlandsalinity management application in California's San Joaquin Valley

Seasonally managed wetlands in the Grasslands Basin ofCalifornia's San Joaquin Valley provide food and shelter for migratorywildfowl during winter months and sport for waterfowl hunters during theannual duck season. Surface water supply to these wetland contain saltwhich, when drained to the San Joaquin River during the annual drawdownperiod, negatively impacts downstream agricultural riparian waterdiverters. Recent environmental regulation, limiting discharges salinityto the San Joaquin River and primarily targeting agricultural non-pointsources, now addresses return flows from seasonally managed wetlands.Real-time water quality management has been advocated as a means ofmatching wetland return flows to the assimilative capacity of the SanJoaquin River. Past attempts to build environmental monitoring anddecision support systems to implement this concept have failed forreasons that are discussed in this paper. These reasons are discussed inthe context of more general challenges facing the successfulimplementation of environmental monitoring, modelling and decisionsupport systems. The paper then provides details of a current researchand development project which will ultimately provide wetland managerswith the means of matching salt exports with the available assimilativecapacity of the San Joaquin River, when fully implemented. Manipulationof the traditional wetland drawdown comes at a potential cost to thesustainability of optimal wetland moist soil plant habitat in thesewetlands - hence the project …
Date: May 10, 2006
Creator: Quinn, Nigel W.T.
System: The UNT Digital Library
Multiple-code benchmark simulation study of coupled THMC processesin the excavation disturbed zone associated with geological nuclear wasterepositories (open access)

Multiple-code benchmark simulation study of coupled THMC processesin the excavation disturbed zone associated with geological nuclear wasterepositories

An international, multiple-code benchmark test (BMT) studyis being conducted within the international DECOVALEX project to analysecoupled thermal, hydrological, mechanical and chemical (THMC) processesin the excavation disturbed zone (EDZ) around emplacement drifts of anuclear waste repository. This BMT focuses on mechanical responses andlong-term chemo-mechanical effects that may lead to changes in mechanicaland hydrological properties in the EDZ. This includes time-de-pendentprocesses such as creep, and subcritical crack, or healing of fracturesthat might cause "weakening" or "hardening" of the rock over the longterm. Five research teams are studying this BMT using a wide range ofmodel approaches, including boundary element, finite element, and finitedifference, particle mechanics, and elasto-plastic cellular automatamethods. This paper describes the definition of the problem andpreliminary simulation results for the initial model inception part, inwhich time dependent effects are not yet included.
Date: May 10, 2006
Creator: Rutqvist, J.; Feng, X. T.; Hudson, J.; Jing, L.; Kobayashi, A.; Koyama, T. et al.
System: The UNT Digital Library
Comparative simulation study of coupled THM processes nearback-filled and open-drift nuclear waste repositories in Task D of theInternational DECOVALEX Project (open access)

Comparative simulation study of coupled THM processes nearback-filled and open-drift nuclear waste repositories in Task D of theInternational DECOVALEX Project

As part of the ongoing international DECOVALEX project, fourresearch teams used five different models to simulate coupled thermal,hydrological, and mechanical (THM) processes near underground wasteemplacement drifts. The simulations were conducted for two genericrepository types, one with open and the other with back-filled repositorydrifts, under higher and lower post-closure temperature, respectively. Inthe completed first model inception phase of the project, a goodagreement was achieved between the research teams in calculating THMresponses for both repository types, although some disagreement inhydrological responses are currently being resolved. Good agreement inthe basic thermal-mechanical responses was also achieved for bothrepository types, even though some teams used relatively simplifiedthermal-elastic heat-conduction models that neglect complex near-fieldthermal-hydrological processes. The good agreement between the complexand simplified process models indicates that the basic thermal-mechanicalresponses can be predicted with a relatively high confidencelevel.
Date: May 10, 2006
Creator: Rutqvist, J.; Birkholzer, J.T.; Chijimatsu, M.; Kolditz, O.; Liu,Quan-Sheng; Oda, Y. et al.
System: The UNT Digital Library