Valence-state Model of Strain-dependent Mn L2,3 X-ray Magnetic Circular Dichroism from Ferromagnetic Semiconductors (open access)

Valence-state Model of Strain-dependent Mn L2,3 X-ray Magnetic Circular Dichroism from Ferromagnetic Semiconductors

We present a valence-state model to explain the characteristics of a recently observed pre-edge feature in Mn L{sub 3} x-ray magnetic circular dichroism (XMCD) of ferromagnetic (Ga,Mn)As and (Al,Ga,Mn)As thin films. The prepeak XMCD shows a uniaxial anisotropy, contrary to the cubic symmetry of the main structures induced by the crystalline electric field. Reversing the strain in the host lattice reverses the sign of the uniaxial anisotropy. With increasing carrier localization, the prepeak height increases, indicating an increasing 3d character of the hybridized holes. Hence, the feature is ascribed to transitions from the Mn 2p core level to unoccupied p-d hybridized valence states. The characteristics of the prepeak are readily reproduced by the model calculation taking into account the symmetry of the strain-, spin-orbit-, and exchange-split valence states around the zone center.
Date: March 30, 2010
Creator: van der Laan, G.; Edmonds, K. W.; Arenholz, E.; Farley, N. R. S. & Gallagher, B. L.
Object Type: Article
System: The UNT Digital Library
Determination of Natural Beryllium (Be) in Soil and Swipe Samples Utilizing Yttrium/Beryllium Ratio (open access)

Determination of Natural Beryllium (Be) in Soil and Swipe Samples Utilizing Yttrium/Beryllium Ratio

1. Objective: A method to determine whether beryllium (Be) components in surface swipe samples are from a natural source is needed. 2. Methods: Soil samples and surface swipes from area facilities were analyzed for marker elements to identify source pathways for beryllium (Be). To be useful, the natural marker element must be present at reasonably consistent levels across the site, must correlate with the Be concentration, and not have the potential to be present from non-natural sources. 3. Results: The research on marker elements used to identify source pathways for beryllium (Be) concentrations demonstrates a clear correlation between Be and yttrium (Y) in natural soils on the Nevada National Security Site. The Y/Be ratio is proposed as a method to characterize the source of Be in soil and surface swipe samples and to aid in recommendations for follow up actions. Swipe samples are analyzed using an ICP/MS method and compared with results from soil samples. Natural soil constituent levels and the Y/Be Ratio range is determined for the occupied and historical facilities and surrounding areas. Y/Be ratios within the statistical range established indicate the Be is from a natural source. Y/Be ratios lower than this range indicate the presence of …
Date: September 30, 2010
Creator: unknown
Object Type: Article
System: The UNT Digital Library
Energy Security, Innovation & Sustainability Initiative (open access)

Energy Security, Innovation & Sustainability Initiative

More than a dozen energy experts convened in Houston, Texas, on February 13, 2009, for the first in a series of four regionally-based energy summits being held by the Council on Competitiveness. The Southern Energy Summit was hosted by Marathon Oil Corporation, and participants explored the public policy, business and technological challenges to increasing the diversity and sustainability of U.S. energy supplies. There was strong consensus that no single form of energy can satisfy the projected doubling, if not tripling, of demand by the year 2050 while also meeting pressing environmental challenges, including climate change. Innovative technology such as carbon capture and storage, new mitigation techniques and alternative forms of energy must all be brought to bear. However, unlike breakthroughs in information technology, advancing broad-based energy innovation requires an enormous scale that must be factored into any equation that represents an energy solution. Further, the time frame for developing alternative forms of energy is much longer than many believe and is not understood by the general public, whose support for sustainability is critical. Some panelists estimated that it will take more than 50 years to achieve the vision of an energy system that is locally tailored and has tremendous diversity …
Date: April 30, 2010
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Marketing Strategy and Implementation (open access)

Marketing Strategy and Implementation

This report documents the preparation of materials for the marketing campaign that has been designed for middle and high school students in New Mexico to increase interest in participation in national security careers at the National Nuclear Security Administration. The materials and the marketing campaign build on the research that was previously completed, as well as the focus groups that were conducted. This work is a part of the National Nuclear Security Preparedness Project (NSPP). Previous research included outcome analysis to determine appropriate marketing strategies. The analysis was based upon focus groups with middle school and high school students, student interactions, and surveys completed by students to understand and gauge student interest in Science, Technology, Engineering, and Math (STEM) subjects, interest in careers at NNSA, future job considerations, and student desire to pursue post-secondary education. Further, through the focus groups, students were asked to attend a presentation on NNSA job opportunities and employee requirements. The feedback received from the students was utilized to develop the focus and components of a marketing campaign divided into DISCO (Discovering Intelligence and Security Career Opportunities) for the middle school age group and DISCO…..Your Way! for high school age groups. Both campaigns have an intertwined …
Date: September 30, 2010
Creator: unknown
Object Type: Text
System: The UNT Digital Library
Medicaid: The Federal Medical Assistance Percentage (FMAP) (open access)

Medicaid: The Federal Medical Assistance Percentage (FMAP)

None
Date: July 30, 2010
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Medicare Provisions in the Patient Protection and Affordable Care Act (PPACA): Summary and Timeline (open access)

Medicare Provisions in the Patient Protection and Affordable Care Act (PPACA): Summary and Timeline

None
Date: June 30, 2010
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Strategic Management Plan - Department of Defense (open access)

Strategic Management Plan - Department of Defense

This report presents the Department of Defense's business goals, objectives, measures, and initiatives for the 2011 fiscal year.
Date: December 30, 2010
Creator: unknown
Object Type: Text
System: The UNT Digital Library
Suspension of the Rules in the House: Principal Features (open access)

Suspension of the Rules in the House: Principal Features

None
Date: November 30, 2010
Creator: unknown
Object Type: Report
System: The UNT Digital Library