864 research outputs found
Unusual superexchange pathways in a Ni triangular lattice of NiGaS with negative charge-transfer energy
We have studied the electronic structure of the Ni triangular lattice in
NiGaS using photoemission spectroscopy and subsequent model
calculations. The cluster-model analysis of the Ni 2 core-level spectrum
shows that the S 3 to Ni 3 charge-transfer energy is -1 eV and the
ground state is dominated by the configuration ( is a S 3 hole).
Cell perturbation analysis for the NiS triangular lattice indicates that
the strong S 3 hole character of the ground state provides the enhanced
superexchange interaction between the third nearest neighbor sites.Comment: 10 pages, 5 figures, accepted to PR
Space Flight LiDARs, Navigation & Science Instrument Implementations: Lasers, Optoelectronics, Integrated Photonics, Fiber Optic Subsystems and Components
For the past 25 years, the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center's Photonics Group in the Engineering Directorate has been substantially contributing to the flight design, development, production, testing and integration of many science and navigational instruments. The Moon to Mars initiative will rely heavily upon utilizing commercial technologies for instrumentation with aggressive schedule deadlines. The group has an extensive background in screening, qualifying, development and integration of commercial components for spaceflight applications. By remaining adaptable and employing a rigorous approach to component and instrument development, they have forged and fostered relationships with industry partners. They have been willing to communicate lessons learned in packaging, part construction, materials selection, testing, and other facets of the design and production process critical to implementation for high-reliability systems. As a result, this successful collaboration with industry vendors and component suppliers has enabled a history of mission success from the Moon to Mars (and beyond) while balancing cost, schedule, and risk postures. In cases where no commercial components exist, the group works closely with other teams at Goddard Space Flight Center and other NASA field centers to fabricate and produce flight hardware for science, remote sensing, and navigation applications. Summarized here is the last ten years of instrumentation development lessons learned and data collected from the subsystems down to the optoelectronic component level
Anisotropic optical gain in m-plane InxGa1-xN/GaN multiple quantum well laser diode wafers fabricated on the low defect density freestanding GaN substrates
Crystallization behavior of iron- and boron-containing nepheline (Na2 OâAl2 O3 â2SiO2 ) based model high-level nuclear waste glasses
This study focuses on understanding the relationship between iron redox, composition, and heatâtreatment atmosphere in nephelineâbased model highâlevel nuclear waste glasses. Glasses in the Na2OâAl2O3âB2O3âFe2O3âSiO2 system with varying Al2O3/Fe2O3 and Na2O/Fe2O3 ratios have been synthesized by meltâquench technique and studied for their crystallization behavior in different heating atmospheresâair, inert (N2), and reducing (96%N2â4%H2). The compositional dependence of iron redox chemistry in glasses and the impact of heating environment and crystallization on iron coordination in glassâceramics have been investigated by Mössbauer spectroscopy and vibrating sample magnetometry. While iron coordination in glasses and glassâceramics changed as a function of glass chemistry, the heating atmosphere during crystallization exhibited minimal effect on iron redox. The change in heating atmosphere did not affect the phase assemblage but did affect the microstructural evolution. While glassâceramics produced as a result of heat treatment in air and N2 atmospheres developed a golden/brown colored ironârich layer on their surface, those produced in a reducing atmosphere did not exhibit any such phenomenon. Furthermore, while this ironârich layer was observed in glassâceramics with varying Al2O3/Fe2O3 ratio, it was absent from glassâceramics with varying Na2O/Fe2O3 ratio. An explanation of these results has been provided on the basis of kinetics of diffusion of oxygen and network modifiers in the glasses under different thermodynamic conditions. The plausible implications of the formation of ironârich layer on the surface of glassâceramics on the chemical durability of highâlevel nuclear waste glasses have been discussed
Is rs34861192 or rs1862513 a more promising variant for determining plasma resistin in an aged Japanese population?
Replication Study of Candidate Genes Associated With Type 2 Diabetes Based On Genome-Wide Screening
OBJECTIVEâThe present study was conducted to confirm possible associations between candidate genes from genome-wide association studies and type 2 diabetes in Japanese diabetic patients and a community-based general population. A total of 11 previously reported single-nucleotide polymorphisms (SNPs) from the TCF7L2, CDKAL1, HHEX, IGF2BP2, CDKN2A/B, SLC30A8, and KCNJ11 genes were analyzed
The Evolution of Data Fusion Methodologies Developed to Reconstruct Coronary Artery Geometry From Intravascular Imaging and Coronary Angiography Data: A Comprehensive Review
Understanding the mechanisms that regulate atherosclerotic plaque formation and
evolution is a crucial step for developing treatment strategies that will prevent plaque
progression and reduce cardiovascular events. Advances in signal processing and the
miniaturization of medical devices have enabled the design of multimodality intravascular
imaging catheters that allow complete and detailed assessment of plaque morphology
and biology. However, a significant limitation of these novel imaging catheters is that they
provide two-dimensional (2D) visualization of the lumen and vessel wall and thus they
cannot portray vessel geometry and 3D lesion architecture. To address this limitation
computer-based methodologies and user-friendly software have been developed. These
are able to off-line process and fuse intravascular imaging data with X-ray or computed
tomography coronary angiography (CTCA) to reconstruct coronary artery anatomy. The
aim of this review article is to summarize the evolution in the field of coronary artery
modeling; we thus present the first methodologies that were developed to model vessel
geometry, highlight the modifications introduced in revised methods to overcome the
limitations of the first approaches and discuss the challenges that need to be addressed,
so these techniques can have broad application in clinical practice and research
Improved characteristics and issues of m-plane InGaN films grown on low defect density m-plane freestanding GaN substrates by metalorganic vapor phase epitaxy
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