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707 Matching Results

Start Over Decade 2000-2009 Year 2007 Day 9th

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Results: 1 - 24 of 707 next

(open access)

Thermodynamic ground states of platinum metal nitrides

We have systematically studied the thermodynamic stabilities of various phases of the nitrides of the platinum metal elements using density functional theory. We show that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability can extend up to 17 GPa for PtN{sub 2}. Furthermore, we show that according to calculations using the local density approximation, these new compounds are also thermodynamically stable at ambient pressure and thus may be the ground state phases for these materials. We further discuss the fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures.

Date: October 9, 2007

Creator: Aberg, D; Sadigh, B; Crowhurst, J & Goncharov, A

Object Type: Article

System: The UNT Digital Library

(open access)

PILOT-SCALE HYDRAULIC TESTING OF RESORCINOL FORMALDEHYDE ION EXCHANGE RESIN

Savannah River National Laboratory (SRNL) performed pilot-scale hydraulic/chemical testing of spherical resorcinol formaldehyde (RF) ion exchange (IX) resin for the River Protection Project Hanford Tank Waste Treatment & Immobilization Plant (WTP) Project. The RF resin cycle testing was conducted in two pilot-scale IX columns, 1/4 and 1/2 scale. A total of twenty-three hydraulic/chemical cycles were successfully completed on the spherical RF resin. Seven of the cycles were completed in the 12-inch IX Column and sixteen cycles were completed in the 24-inch IX Column. Hydraulic testing showed that the permeability of the RF resin remained essentially constant, with no observed trend in the reduction of the permeability as the number of cycles increased. The permeability during the pilot-scale testing was 2 1/2 times better than the design requirements of the WTP full-scale system. The permeability of the resin bed was uniform with respect to changes in bed depth. Upflow Regeneration and Simulant Introduction in the IX columns revealed another RF resin benefit; negligible radial pressures to the column walls from the swelling of resin beads. In downflow of the Regeneration and Simulant Introduction steps, the resin bed particles pack tightly together and produce higher hydraulic pressures than that found in upflow. …

Date: January 9, 2007

Creator: Adamson, D

Object Type: Article

System: The UNT Digital Library

(open access)

On macromolecular refinement at subatomic resolution withinteratomic scatterers

A study of the accurate electron density distribution in molecular crystals at subatomic resolution, better than {approx} 1.0 {angstrom}, requires more detailed models than those based on independent spherical atoms. A tool conventionally used in small-molecule crystallography is the multipolar model. Even at upper resolution limits of 0.8-1.0 {angstrom}, the number of experimental data is insufficient for the full multipolar model refinement. As an alternative, a simpler model composed of conventional independent spherical atoms augmented by additional scatterers to model bonding effects has been proposed. Refinement of these mixed models for several benchmark datasets gave results comparable in quality with results of multipolar refinement and superior of those for conventional models. Applications to several datasets of both small- and macro-molecules are shown. These refinements were performed using the general-purpose macromolecular refinement module phenix.refine of the PHENIX package.

Date: November 9, 2007

Creator: Afonine, Pavel V.; Grosse-Kunstleve, Ralf W.; Adams, Paul D.; Lunin, Vladimir Y. & Urzhumtsev, Alexandre

Object Type: Article

System: The UNT Digital Library

(open access)

Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4

The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray …

Date: May 9, 2007

Creator: Ahn, Kyunghan

Object Type: Thesis or Dissertation

System: The UNT Digital Library

(open access)

Timpson & Tenaha News (Timpson, Tex.), Vol. 25, No. 32, Ed. 1 Thursday, August 9, 2007

Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.

Date: August 9, 2007

Creator: Alexander, Nancy

Object Type: Newspaper

System: The Portal to Texas History

(open access)

Measurement of the Hadronic Form factor in D0 to K- e+ nu_e Decays

The shape of the hadronic form factor f{sub +} (q{sup 2}) in the decay D{sup 0} {yields} K{sup -} e{sup +}{nu}{sub e} has been measured in a model independent analysis and compared with theoretical calculations. They use 75 fb{sup -1} of data recorded by the BABAR detector at the PEPII electron-positron collider. The corresponding decay branching fraction, relative to the decay D{sup 0} {yields} K{sup -} {pi}{sup +}, has also been measured to be R{sub D} = BR(D{sup 0} {yields} K{sup -}e{sup +}{nu}{sub e})/BR(D{sup 0} {yields} K{sup -}{pi}{sup +}) = 0.927 {+-} 0.007 {+-} 0.012. From these results, and using the present world average value for BR(D{sup 0} {yields} K{sup -}{pi}{sup +}), the normalization of the form factor at q{sup 2} = 0 is determined to be f{sub +}(0) = 0.727 {+-} 0.007 {+-} 0.005 {+-} 0.007 where the uncertainties are statistical, systematic, and from external inputs, respectively.

Date: April 9, 2007

Creator: Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J. P.; Poireau, V. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Health Care and Markets

This report discusses the Invisible Hand Theorem, which states that when certain assumptions hold, market outcomes will be efficient.

Date: March 9, 2007

Creator: Austin, D. Andrew

Object Type: Report

System: The UNT Digital Library

(open access)

Hadronic Charm Decays From B Factories

The B factories, KEKB and PEPII, provide enormous samples of charmed mesons and baryons as well as B{bar B} events. The BELLE and BaBar collaborations have discovered many new particles containing charm quarks in the last few years and have measured their properties with increasing precision. The current status and most recent studies of these charm particle properties is briefly reviewed.

Date: November 9, 2007

Creator: Band, H. R.

Object Type: Article

System: The UNT Digital Library

(open access)

Farm and Food Support Under USDA’s Section 32 Program

None

Date: July 9, 2007

Creator: Becker, Geoffrey S.

Object Type: Report

System: The UNT Digital Library

(open access)

Horse Slaughter Prevention Bills and Issues

This report provides an overview of the bills and issues regarding horse slaughter prevention.

Date: August 9, 2007

Creator: Becker, Geoffrey S.

Object Type: Report

System: The UNT Digital Library

(open access)

[The International Space Station and the Space Shuttle, November 9, 2007]

This report discusses the International Space Station (ISS) and efforts to improve shuttles and space exploration after the Columbia failure in 2003. Efforts include new policy from President Bush and funding for National Aeronautics and Space Administration (NASA). Updated November 9, 2007.

Date: November 9, 2007

Creator: Behrens, Carl E.

Object Type: Report

System: The UNT Digital Library

(open access)

The Colony Courier-Leader (The Colony, Tex.), Vol. 26, No. 14, Ed. 1 Wednesday, May 9, 2007

Weekly newspaper from The Colony, Texas that includes local, state, and national news along with advertising.

Date: May 9, 2007

Creator: Bick, Jack & Crimmins, Blaine

Object Type: Newspaper

System: The Portal to Texas History

(open access)

Afghanistan: Narcotics and U.S. Policy

This report provides current statistical information, profiles the Afghanistan narcotics trade's participants, explores linkages between narcotics, insecurity, and corruption, and reviews U.S. and international policy responses since late 2001. The report also considers ongoing policy debates regarding the counternarcotics role of coalition military forces, poppy eradication, alternative livelihoods, and funding issues for Congress.

Date: March 9, 2007

Creator: Blanchard, Christopher M.

Object Type: Report

System: The UNT Digital Library

(open access)

The United Nations Human Rights Council: Issues for Congress

This report contains the issues for Congress regarding the United Nations (UN) human rights council.

Date: March 9, 2007

Creator: Blanchfield, Luisa

Object Type: Report

System: The UNT Digital Library

(open access)

Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Iron-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for container applications, though the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas atomized powders and applied as near full density, non-porous coatings with the high-velocity oxy-fuel process. This paper summarizes the performance of these coatings as corrosion-resistant barriers, and as neutron absorbers. Relevant corrosion models are also discussed, as well as a cost model to quantify the economic benefits possible with these new materials.

Date: July 9, 2007

Creator: Blink, J; Choi, J & Farmer, J

Object Type: Article

System: The UNT Digital Library

(open access)

Airborne Laser (ABL): Issues for Congress

This report examines the airborne laser (ABL) program and budget status. It also examines a variety of related issues, including the questionable maturity of ABL technologies, the number of ABL platforms the United States should acquire, and to what degree the United STates should invest in alternative technologies in the event that the ABL may not prove successful. This report does not provide a detailed technical assessment of the ABL program (see CRS Report RL30185, The Airborne Laser Anti-Missile Program).

Date: July 9, 2007

Creator: Bolkcom, Christopher & Hildreth, Steven A.

Object Type: Report

System: The UNT Digital Library