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The BaBar Electromagnetic Calorimeter: Status and Performance Improvements (open access)

The BaBar Electromagnetic Calorimeter: Status and Performance Improvements

The electromagnetic calorimeter at the BABAR detector, part of the asymmetric B Factory at SLAC, measures photons in the energy range from 20 MeV to 8 GeV with high resolution. The current status of the calorimeter, now in its seventh year of operation, is being presented, as well as details on improvements made to the analysis code during the last years.
Date: January 20, 2006
Creator: Bauer, Johannes M.
System: The UNT Digital Library
Beam Delivery WG Summary: Optics, Collimation & Background (open access)

Beam Delivery WG Summary: Optics, Collimation & Background

The presented paper partially summarizes the work of the Beam Delivery working group (WG4) at Snowmass, concentrating on status of optics, layout, collimation, and background. The strawman layout with 2 interaction regions was recommended at the first ILC workshop at KEK in November 2004. Two crossing-angle designs were included in this layout. The design of the ILC BDS has evolved since the first ILC workshop. The progress on the BDS design and extraction line design has been reviewed and the design issues were discussed during the optics and layout session at the Snowmass.
Date: January 20, 2006
Creator: Angal-Kalinin, D.; Jackson, F.; Mokhov, N. V.; Kuroda, S. & Seryi, A. A.
System: The UNT Digital Library
The complete chloroplast genome sequence of Pelargonium xhortorum: Or ganization and evolution of the largest and most highlyrearranged chloroplast genome of land plants (open access)

The complete chloroplast genome sequence of Pelargonium xhortorum: Or ganization and evolution of the largest and most highlyrearranged chloroplast genome of land plants

The chloroplast genome of Pelargonium e hortorum has beencompletely sequenced. It maps as a circular molecule of 217,942 bp, andis both the largest and most rearranged land plant chloroplast genome yetsequenced. It features two copies of a greatly expanded inverted repeat(IR) of 75,741 bp each, and consequently diminished single copy regionsof 59,710 bp and 6,750 bp. It also contains two different associations ofrepeated elements that contribute about 10 percent to the overall sizeand account for the majority of repeats found in the genome. Theyrepresent hotspots for rearrangements and gene duplications and include alarge number of pseudogenes. We propose simple models that account forthe major rearrangements with a minimum of eight IR boundary changes and12 inversions in addition to a several insertions of duplicated sequence.The major processes at work (duplication, IR expansion, and inversion)have disrupted at least one and possibly two or three transcriptionaloperons, and the genes involved in these disruptions form the core of thetwo major repeat associations. Despite the vast increase in size andcomplexity of the genome, the gene content is similar to that of otherangiosperms, with the exceptions of a large number of pseudogenes as partof the repeat associations, the recognition of two open reading frames(ORF56 and ORF42) …
Date: January 20, 2006
Creator: Chumley, Timothy W.; Palmer, Jeffrey D.; Mower, Jeffrey P.; Fourcade, H. Matthew; Calie, Patrick J.; Boore, Jeffrey L. et al.
System: The UNT Digital Library
DAPHNE Operation And Plans for DAPHNE2 (open access)

DAPHNE Operation And Plans for DAPHNE2

The e{sup +}e{sup -} collider DA{Phi}NE, a 1.02 GeV c.m. {Phi}-factory, has reached a peak luminosity of about 1.4 x 10{sup 32} cm{sup -2} s{sup -1} and a peak integrated luminosity in one day of about 8.6 pb{sup -1}. With the current rates the physics program of the three main experiments DEAR, FINUDA and KLOE will be completed by the end of 2007. In this paper we describe in detail the steps which have led to the luminosity improvement and the options for the upgrade of the collider towards higher energy and/or luminosity.
Date: January 20, 2006
Creator: Zobov, M.; Alesini, D.; Benedetti, G.; Biagini, M. E.; Biscari, C.; Boni, R. et al.
System: The UNT Digital Library
A Mountain-Scale Monitoring Network for Yucca Mountain PerformanceConfirmation (open access)

A Mountain-Scale Monitoring Network for Yucca Mountain PerformanceConfirmation

Confirmation of the performance of Yucca Mountain is required by 10 CFR Part 63.131 to indicate, where practicable, that the natural system acts as a barrier, as intended. Hence, performance confirmation monitoring and testing would provide data for continued assessment during the pre-closure period. In general, to carry out testing at a relevant scale is always important, and in the case of performance confirmation, it is particularly important to be able to test at the scale of the repository. We view the large perturbation caused by construction of the repository at Yucca Mountain as a unique opportunity to study the large-scale behavior of the natural barrier system. Repository construction would necessarily introduce traced fluids and result in the creation of leachates. A program to monitor traced fluids and construction leachates permits evaluation of transport through the unsaturated zone and potentially downgradient through the saturated zone. A robust sampling and monitoring network for continuous measurement of important parameters, and for periodic collection of agrochemical samples, is proposed to observe thermo-hydrogeochemical changes near the repository horizon and down to the water table. The sampling and monitoring network can be used to provide data to (1) assess subsurface conditions encountered and changes in …
Date: January 20, 2006
Creator: Freifeld, Barry & Tsang, Yvonne
System: The UNT Digital Library
NIF: Path to Ignition in the Laboratory (open access)

NIF: Path to Ignition in the Laboratory

The National Ignition Facility (NIF) is a 192 beam laser facility presently under construction at LLNL. When completed NIF will be a 1.8 MJ, 500 TW ultraviolet laser system. Its missions are to obtain fusion ignition and to perform high energy density experiments in support of the US nuclear weapons stockpile. Four of the NIF beams have been commissioned to demonstrate laser performance and to commission the target area including target and beam alignment and laser timing. During this time, NIF demonstrated on a single beam basis that it will meet its performance goals and demonstrated its precision and flexibility for pulse shaping, pointing, timing and beam conditioning. It also performed four important experimental campaigns for Inertial Confinement Fusion and High Energy Density Science. Presently, the project is installing production hardware to complete the project in 2009 with the goal to begin ignition experiments in 2010. An integrated plan has been developed including the NIF operations, user equipment such as diagnostics and cryogenic target capability, and experiments and calculations to meet this goal. This talk will provide NIF status, the plan to complete NIF, and the path to ignition.
Date: January 20, 2006
Creator: Moses, E; Bonanno, G; Haynam, C; Kauffman, B; MacGowan, B; Sawicki, R et al.
System: The UNT Digital Library
Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle (open access)

Phonon Density of States and Sound Velocities of Magnesiow?stite in Earth's Lower Mantle

The partial phonon densities of states of iron in magnesiowuestite [(Mg{sub 0.75},Fe{sub 0.25})O] have been measured by nuclear inelastic X-ray scattering up to 109 GPa. Compressional and shear wave velocities, shear moduli, and their pressure derivatives increase significantly across the spin-pairing transition of iron in (Mg{sub 0.75},Fe{sub 0.25})O at approximately 50 GPa. The effects of the transition on the elastic properties of (Mg,Fe)O at lower-mantle pressures are in contrast to what was predicted by studying MgO and high-spin magnesiowuestite, and need to be considered in future geophysical modeling of the lower mantle. The transition also affects other thermodynamic properties of magnesiowuestite under high pressures.
Date: January 20, 2006
Creator: Lin, J.; Jacosben, S. D.; Sturhahn, W.; Jackson, J.; Zhao, J. & Yoo, C.
System: The UNT Digital Library
Proposal of An Experiment on Bunch Length Modulation in DAFNE (open access)

Proposal of An Experiment on Bunch Length Modulation in DAFNE

Obtaining very short bunches is an issue especially for colliders but also for CSR sources. The modulation of the bunch length in a strong rf focusing regime had been proposed, corresponding to a high value of the synchrotron tune. A ring structure where the function R56 along the ring oscillates between large positive and negative values will produce bunch length modulation. The synchrotron frequency can be tuned both by the rf power and by the integral of the function R56, up to the limit of zero value corresponding to the isochronicity condition. The proposal of a bunch length modulation along the ring in DA{Phi}NE is here described. DA{Phi}NE lattice can be tuned to positive or negative momentum compaction values, or to structures in which the two arcs are respectively set to positive/negative integrals of the R56 function. With the installation of an extra rf system at 1.3 GHz, experiments on bunch length modulation both in the regime of high and low synchrotron tune can be realized.
Date: January 20, 2006
Creator: Biscari, C.; Alesini, D.; Benedetti, G.; Biagini, M. E.; Boni, R.; Boscolo, M. et al.
System: The UNT Digital Library
Recent Observations on a Horizontal Instability in the DAFNE Positron Ring (open access)

Recent Observations on a Horizontal Instability in the DAFNE Positron Ring

A strong horizontal instability limits the maximum positron current storable in the DAFNE Phi-Factory. A powerful feedback system makes it possible to store and put in collision more than 1300 mA of positron current in 105-109 bunches. Nevertheless, a much higher current (>2.4A) has been successfully stored in the twin electron ring. Measurements have been carried out to understand the positron current limit and to characterize the behavior of the horizontal instability at high current with different bunch patterns. Grow/damp turn-by-turn data obtained by turning off the horizontal feedback have been acquired and analyzed. Spectral analysis and growth rates of the instability are shown. In particular, the -1 mode has strong evidence and fast growth rate. Its growth rate behavior is analyzed at different beam currents and bunch patterns.
Date: January 20, 2006
Creator: Drago, A.; Zobov, M. & Teytelman, D.
System: The UNT Digital Library
RETRIEVAL & TREATMENT OF HANFORD TANK WASTE (open access)

RETRIEVAL & TREATMENT OF HANFORD TANK WASTE

The Hanford Tank Farms contain 53 million gal of radioactive waste accumulated during over 50 years of operations. The waste is stored in 177 single-shell and double-shell tanks in the Hanford 200 Areas. The single-shell tanks were put into operation from the early 1940s through the 1960s with wastes received from several generations of processing facilities for the recovery of plutonium and uranium, and from laboratories and other ancillary facilities. The overall hanford Tank Farm system represents one of the largest nuclear legacies in the world driving towards completion of retrieval and treatment in 2028 and the associated closure activity completion by 2035. Remote operations, significant radiation/contamination levels, limited access, and old facilities are just some of the challenges faced by retrieval and treatment systems. These systems also need to be able to successfully remove 99% or more of the waste, and support waste treatment, and tank closure. The Tank Farm retrieval program has ramped up dramatically in the past three years with design, fabrication, installation, testing, and operations ongoing on over 20 of the 149 single-shell tanks. A variety of technologies are currently being pursued to retrieve different waste types, applications, and to help establish a baseline for recovery/operational …
Date: January 20, 2006
Creator: EACKER, J. A.; SPEARS, J. A.; STURGES, M. H. & MAUSS, B. M.
System: The UNT Digital Library
Analytic model of bunched beams for harmonic generation in thelow-gain free electron laser regime (open access)

Analytic model of bunched beams for harmonic generation in thelow-gain free electron laser regime

One scheme for harmonic generation employs free electron lasers (FELs) with two undulators: the first uses a seed laser to modulate the energy of the electron beam; following a dispersive element which acts to bunch the beam, the second undulator radiates at a higher harmonic. These processes are currently evaluated using extensive calculations or simulation codes which can be slow to evaluate and difficult to set up. We describe a simple algorithm to predict the output of a harmonic generation beamline in the low-gain FEL regime, based on trial functions for the output radiation. Full three-dimensional effects are included. This method has been implemented as a Mathematica package, named CAMPANILE, which runs rapidly and can be generalized to include effects such as asymmetric beams and misalignments. This method is compared with simulation results using the FEL code GENESIS, both for single stages of harmonic generation and for the LUX project, a design concept for an ultrafast X-ray facility, where multiple stages upshift the input laser frequency by factors of up to 200.
Date: February 20, 2006
Creator: Penn, G.; Reinsch, M. & Wurtele, J.S.
System: The UNT Digital Library
Quantum Interactive Dualism: The Libet and Einstein-Podolsky-RosenCausal Anomalies (open access)

Quantum Interactive Dualism: The Libet and Einstein-Podolsky-RosenCausal Anomalies

The "free will" data of Benjamin Libet and the predictionsof quantum theory considered by Einstein, Podolsky,and Rosen, both posepuzzles within aconceptual framework that, simultaneously, is compatiblewith the theory of relativity and allows human subjects to freely choosehow they will act. The quantum theoretic resolutions of these puzzles aredescribed.
Date: February 20, 2006
Creator: Stapp, Henry P.
System: The UNT Digital Library
A Directed Energy System for Defeat of Improvised Explosive Devices and Landmines (open access)

A Directed Energy System for Defeat of Improvised Explosive Devices and Landmines

We describe a laser system, built in our laboratory at LLNL, that has near-term, effective applications in exposing and neutralizing improvised explosive devices and landmines. We discuss experiments with this laser, demonstrating excavation capabilities and relevant material interactions. Model results are also described.
Date: March 20, 2006
Creator: Boley, C.; Fochs, S.; Parker, J.; Rotter, M.; Rubenchik, A. & Yamamoto, R.
System: The UNT Digital Library
Functional Nanostructured Platforms for Chemical and Biological Sensing (open access)

Functional Nanostructured Platforms for Chemical and Biological Sensing

The central goal of our work is to combine semiconductor nanotechnology and surface functionalization in order to build platforms for the selective detection of bio-organisms ranging in size from bacteria (micron range) down to viruses, as well as for the detection of chemical agents (nanometer range). We will show on three porous silicon platforms how pore geometry and pore wall chemistry can be combined and optimized to capture and detect specific targets. We developed a synthetic route allowing to directly anchor proteins on silicon surfaces and illustrated the relevance of this technique by immobilizing live enzymes onto electrochemically etched luminescent nano-porous silicon. The powerful association of the specific enzymes with the transducing matrix led to a selective hybrid platform for chemical sensing. We also used light-assisted electrochemistry to produce periodic arrays of through pores on pre-patterned silicon membranes with controlled diameters ranging from many microns down to tens of nanometers. We demonstrated the first covalently functionalized silicon membranes and illustrated their selective capture abilities with antibody-coated micro-beads. These engineered membranes are extremely versatile and could be adapted to specifically recognize the external fingerprints (size and coat composition) of target bio-organisms. Finally, we fabricated locally functionalized single nanopores using a combination …
Date: March 20, 2006
Creator: Letant, S E
System: The UNT Digital Library
A Kalman-filter bias correction of ozone deterministic, ensemble-averaged, and probabilistic forecasts (open access)

A Kalman-filter bias correction of ozone deterministic, ensemble-averaged, and probabilistic forecasts

Kalman filtering (KF) is used to postprocess numerical-model output to estimate systematic errors in surface ozone forecasts. It is implemented with a recursive algorithm that updates its estimate of future ozone-concentration bias by using past forecasts and observations. KF performance is tested for three types of ozone forecasts: deterministic, ensemble-averaged, and probabilistic forecasts. Eight photochemical models were run for 56 days during summer 2004 over northeastern USA and southern Canada as part of the International Consortium for Atmospheric Research on Transport and Transformation New England Air Quality (AQ) Study. The raw and KF-corrected predictions are compared with ozone measurements from the Aerometric Information Retrieval Now data set, which includes roughly 360 surface stations. The completeness of the data set allowed a thorough sensitivity test of key KF parameters. It is found that the KF improves forecasts of ozone-concentration magnitude and the ability to predict rare events, both for deterministic and ensemble-averaged forecasts. It also improves the ability to predict the daily maximum ozone concentration, and reduces the time lag between the forecast and observed maxima. For this case study, KF considerably improves the predictive skill of probabilistic forecasts of ozone concentration greater than thresholds of 10 to 50 ppbv, but …
Date: March 20, 2006
Creator: Monache, L D; Grell, G A; McKeen, S; Wilczak, J; Pagowski, M O; Peckham, S et al.
System: The UNT Digital Library
LNAPLs do not Always Float: An Example Case of a Viscous LNAPL under Variable Water Table Conditions (open access)

LNAPLs do not Always Float: An Example Case of a Viscous LNAPL under Variable Water Table Conditions

An intermediate-scale experiment was conducted to investigate the behavior of a viscous LNAPL under variable water table conditions. Two LNAPL volumes were released from a small source zone on top of the flow cell into a partly saturated, homogeneously packed porous medium. Following a 30-day redistribution period, the water table was increased 0.5 m in 50 minutes. After the water table rise, LNAPL behavior was monitored for an additional 45 days. Fluid saturation scans were obtained periodically with a fully automated dual-energy gamma radiation system. Results show that both spills follow similar paths downwards. LNAPL drainage from the unsaturated zone was relatively slow and a considerable residual LNAPL saturation was observed after 30 days of drainage. Most of the mobile LNAPL moved into the capillary fringe during this period. After the water table rise, LNAPL moved up in a delayed fashion. After 45 days, the LNAPL has moved up only approximately 0.2 m. Since the LNAPL has only moved up a limited amount, nonwetting fluid entrapment was also limited. The experiment was simulated using the STOMP multifluid flow simulator. A comparison indicates that the simulator is able to predict the observed phenomena well, including residual saturation formation in the vadose …
Date: March 20, 2006
Creator: Oostrom, Mart; Hofstee , C & Wietsma, Thomas W.
System: The UNT Digital Library
MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY (open access)

MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY

The purpose of this study is to design, fabricate and optimize microfluidic mixers to investigate the kinetics of protein secondary structure formation with Synchrotron Radiation Circular Dichroism (SRCD) spectroscopy. The mixers are designed to rapidly initiate protein folding reaction through the dilution of denaturant. The devices are fabricated out of fused silica, so that they are transparent in the UV. We present characterization of mixing in the fabricated devices, as well as the initial SRCD data on proteins inside the mixers.
Date: March 20, 2006
Creator: Kane, A; Hertzog, D; Baumgartel, P; Lengefeld, J; Horsley, D; Schuler, B et al.
System: The UNT Digital Library
Micron-Size Zero-Valent Iron Emplacement in Porous Media Using Polymer Additives: Column and Flow Cell Ex-periments (open access)

Micron-Size Zero-Valent Iron Emplacement in Porous Media Using Polymer Additives: Column and Flow Cell Ex-periments

At the Hanford Site, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. Laboratory experiments have been conducted to investigate whether barrier reductive capacity can be enhanced by adding micron-scale zero-valent iron to the high-permeability zones within the aquifer using shear-thinning fluids containing polymers. Porous media were packed in a wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone between two low-permeability zones or a high-permeability channel sur-rounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments. The flow cell experiments indicated that iron concentration enhancements of at least 0.6% (w/w) could be obtained using moderate flow rates and injection of 30 pore volumes. The 0.6% amended Fe0 concentration would provide approximately 20 times the average reductive capacity that is provided by the dithionite-reduced iron in the ISRM barrier. Calculations show that a 1-m-long Fe0 amended zone with an average concentration of 0.6% w/w iron subject to a groundwater velocity …
Date: March 20, 2006
Creator: Oostrom, Mart; Wietsma, Thomas W.; Covert, Matthew A. & Vermeul, Vince R.
System: The UNT Digital Library
Multiple ordered phases in the filled skutterudite compound PrOs4As12 (open access)

Multiple ordered phases in the filled skutterudite compound PrOs4As12

Magnetization, specific heat, and electrical resistivity measurements were made on single crystals of the filled skutterudite compound PrOs{sub 4}As{sub 12}. Specific heat measurements indicate an electronic specific heat coefficient {gamma} {approx} 50-200 mJ/mol K{sup 2} at temperatures 10 K {le} T {le} 18 K, and {approx} 1 J/mol K{sup 2} for t {le} 1.6 K. Magnetization, specific heat, and electrical resistivity measurements reveal the presence of two, or possibly three, ordered phases at temperatures below {approx} 2.3 K and in fields below {approx} 3 T. The low temperature phase displays antiferromagnetic characteristics, while the nature of the ordering in the other phase(s) has yet to be determined.
Date: March 20, 2006
Creator: Yuhasz, W M; Butch, N P; Sayles, T A; Ho, P; Jeffries, J R; Yanagisawa, T et al.
System: The UNT Digital Library
Probabilistic aspects of meteorological and ozone regional ensemble forecasts (open access)

Probabilistic aspects of meteorological and ozone regional ensemble forecasts

This study investigates whether probabilistic ozone forecasts from an ensemble can be made with skill; i.e., high verification resolution and reliability. Twenty-eight ozone forecasts were generated over the Lower Fraser Valley, British Columbia, Canada, for the 5-day period 11-15 August 2004, and compared with 1-hour averaged measurements of ozone concentrations at five stations. The forecasts were obtained by driving the CMAQ model with four meteorological forecasts and seven emission scenarios: a control run, {+-} 50% NO{sub x}, {+-} 50% VOC, and {+-} 50% NO{sub x} combined with VOC. Probabilistic forecast quality is verified using relative operating characteristic curves, Talagrand diagrams, and a new reliability index. Results show that both meteorology and emission perturbations are needed to have a skillful probabilistic forecast system--the meteorology perturbation is important to capture the ozone temporal and spatial distribution, and the emission perturbation is needed to span the range of ozone-concentration magnitudes. Emission perturbations are more important than meteorology perturbations for capturing the likelihood of high ozone concentrations. Perturbations involving NO{sub x} resulted in a more skillful probabilistic forecast for the episode analyzed, and therefore the 50% perturbation values appears to span much of the emission uncertainty for this case. All of the ensembles analyzed …
Date: March 20, 2006
Creator: Monache, L D; Hacker, J; Zhou, Y; Deng, X & Stull, R
System: The UNT Digital Library
Simultaneous interferometric optical-figure characterizations for two optical elements in series: Proposition of an unconventional numerical integration scheme (open access)

Simultaneous interferometric optical-figure characterizations for two optical elements in series: Proposition of an unconventional numerical integration scheme

The article proposes a scheme to break a catch-22 loop in an optical-figure/wavefont measurement. For instance, to measure the tilt-independent optical-figure of a nominal optical flat at cryogenic temperatures, it requires a cryogenic dewar-window system for a Fizeau interferometer outside the dewar to see through. The issue is: how to calibrate in situ the window system using the yet-to-be-calibrated nominal optical flat, and vice versa, in only one cryogenic cooldown? The proposition includes: (a) interferometric phase-map measurements with the test piece slightly offset in different transverse directions, and (b) for synthesizing the 2-dimensional WDF, an unconventional numerical scheme starting with 1-dimensional bi-direction integration. The numerical scheme helps minimize the non-uniformity in integrated noise-power distribution that results from integrating data, and thus the associated uncorrelated random noise, from raw phase-maps. The numerical scheme represents a new concept specifically for integrating noise-carrying experimental data.
Date: March 20, 2006
Creator: Gwo, D.
System: The UNT Digital Library
Towards a Cosmological Hubble Diagram for Type II-PSupernovae (open access)

Towards a Cosmological Hubble Diagram for Type II-PSupernovae

We present the first high-redshift Hubble diagram for Type II-P supernovae (SNe II-P) based upon five events at redshift upto z {approx}0.3. This diagram was constructed using photometry from the Canada-France-Hawaii Telescope Supernova Legacy Survey and absorption line spectroscopy from the Keck observatory. The method used to measure distances to these supernovae is based on recent work by Hamuy&Pinto (2002) and exploits a correlation between the absolute brightness of SNeII-P and the expansion velocities derived from the minimum of the Fe II 516.9 nm P-Cygni feature observed during the plateau phases. We present three refinements to this method which significantly improve the practicality of measuring the distances of SNe II-P at cosmologically interesting redshifts. These are an extinction correction measurement based on the V-I colors at day 50, across-correlation measurement for the expansion velocity and the ability to extrapolate such velocities accurately over almost the entire plateau phase. We apply this revised method to our dataset of high-redshift SNe II-P and find that the resulting Hubble diagram has a scatter of only 0.26 magnitudes, thus demonstrating the feasibility of measuring the expansion history, with present facilities, using a method independent of that based upon supernovae of Type Ia.
Date: March 20, 2006
Creator: Nugent, Peter; Sullivan, Mark; Ellis, Richard; Gal-Yam, Avishay; Leonard, Douglas C.; Howell, D. Andrew et al.
System: The UNT Digital Library
Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28GPa at 300 K (open access)

Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28GPa at 300 K

We report Raman and infrared absorption spectroscopy alongwith X-ray diffraction for brucite-type beta-Cd(OH)2 to 28 GPa at 300 K.The OH-stretching modes soften with pressure and disappear at 21 GPa withtheir widths increasing rapidly above 5 GPa, consistent with a gradualdisordering of the H sublattice at 5 20 GPa similar to that previouslyobserved for Co(OH)2.Asymmetry in the peak shapes of the OH-stretchingmodes suggests the existence of diverse disordered sitesfor H atoms inCd(OH)2 under pressure. Above 15 GPa, the A1g(T) lattice mode showsnon-linear behavior and softens to 21 GPa, at which pressure significantchanges are observed: new Raman modes appear, two Raman-active latticemodes and the OH-stretching modes of the low-pressure phase disappears,and the positions of some X-ray diffraction lines change abruptly withthe appearance of weak new diffraction features. These observationssuggest that amorphization of the H sublattice is accompanied by acrystalline-to-crystalline transition at 21 GPa in Cd(OH)2, which has notbeen previously observed in the brucite-type hydroxides. The Ramanspectra of the high-pressure phase of Cd(OH)2 is similar to those of thehigh-pressure phase of single-crystal Ca(OH)2 of which structure has beententatively assigned to the Sr(OH)2 type.
Date: March 20, 2006
Creator: Shim, Sang-Heon; Rekhi, Sandeep; Martin, Michael C. & Jeanloz,Raymond
System: The UNT Digital Library
Air to Muscle and Blood/Plasma to Muscle Distribution of Volatile Organic Compounds and Drugs: Linear Free Energy Analyses (open access)

Air to Muscle and Blood/Plasma to Muscle Distribution of Volatile Organic Compounds and Drugs: Linear Free Energy Analyses

Article on air to muscle and blood/plasma to muscle distribution of volatile organic compounds and drugs and linear free energy analyses.
Date: April 20, 2006
Creator: Abraham, M. H. (Michael H.); Ibrahim, Adam & Acree, William E. (William Eugene)
System: The UNT Digital Library