2,534 research outputs found
X-ray absorption spectroscopy and X-ray magnetic circular dichroism studies of transition-metal-co-doped ZnO nano-particles
We report on x-ray absorption spectroscopy (XAS) and x-ray magnetic circular
dichroism (XMCD) studies of the paramagnetic (Mn,Co)-co-doped ZnO and
ferromagnetic (Fe,Co)-co-doped ZnO nano-particles. Both the surface-sensitive
total-electron-yield mode and the bulk-sensitive total-fluorescence-yield mode
have been employed to extract the valence and spin states of the surface and
inner core regions of the nano-particles. XAS spectra reveal that significant
part of the doped Mn and Co atoms are found in the trivalent and tetravalent
state in particular in the surface region while majority of Fe atoms are found
in the trivalent state both in the inner core region and surface region. The
XMCD spectra show that the Fe ions in the surface region give rise to
the ferromagnetism while both the Co and Mn ions in the surface region show
only paramagnetic behaviors. The transition-metal atoms in the inner core
region do not show magnetic signals, meaning that they are
antiferromagnetically coupled. The present result combined with the previous
results on transition-metal-doped ZnO nano-particles and nano-wires suggest
that doped holes, probably due to Zn vacancy formation at the surfaces of the
nano-particles and nano-wires, rather than doped electrons are involved in the
occurrence of ferromagnetism in these systems.Comment: Proceedings of "XAFS theory and nanoparticles
Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nano-particles
We have studied the electronic structure of ZnFeO
nano-particles, which have been reported to show ferromagnetism at room
temperature, by x-ray photoemission spectroscopy (XPS), resonant photoemission
spectroscopy (RPES), x-ray absorption spectroscopy (XAS) and x-ray magnetic
circular dichroism (XMCD). From the experimental and cluster-model calculation
results, we find that Fe atoms are predominantly in the Fe ionic state
with mixture of a small amount of Fe and that Fe ions are
dominant in the surface region of the nano-particles. It is shown that the room
temperature ferromagnetism in the ZnFeO nano-particles is
primarily originated from the antiferromagnetic coupling between unequal
amounts of Fe ions occupying two sets of nonequivalent positions in the
region of the XMCD probing depth of 2-3 nm.Comment: Single column, 12 pages, 8 figures, 1 tabl
Extended states in 1D lattices: application to quasiperiodic copper-mean chain
The question of the conditions under which 1D systems support extended
electronic eigenstates is addressed in a very general context. Using real space
renormalisation group arguments we discuss the precise criteria for determining
the entire spertrum of extended eigenstates and the corresponding
eigenfunctions in disordered as well as quasiperiodic systems. For purposes of
illustration we calculate a few selected eigenvalues and the corresponding
extended eigenfunctions for the quasiperiodic copper-mean chain. So far, for
the infinite copper-mean chain, only a single energy has been numerically shown
to support an extended eigenstate [ You et al. (1991)] : we show analytically
that there is in fact an infinite number of extended eigenstates in this
lattice which form fragmented minibands.Comment: 10 pages + 2 figures available on request; LaTeX version 2.0
Exchange bias effect in alloys and compounds
The phenomenology of exchange bias effects observed in structurally
single-phase alloys and compounds but composed of a variety of coexisting
magnetic phases such as ferromagnetic, antiferromagnetic, ferrimagnetic,
spin-glass, cluster-glass and disordered magnetic states are reviewed. The
investigations on exchange bias effects are discussed in diverse types of
alloys and compounds where qualitative and quantitative aspects of magnetism
are focused based on macroscopic experimental tools such as magnetization and
magnetoresistance measurements. Here, we focus on improvement of fundamental
issues of the exchange bias effects rather than on their technological
importance
THE SPLICEOSOMAL PROTEIN SnRNP F BINDS TO BOTH U3 AND U14 CLASS OF snoRNA IN Giardia lamblia
Small nuclear Ribonucleo Protein F (snRNP F) is a spliceosomal protein that binds with U1, U2, U4/U6 and U5 small nuclear RNA (snRNA) to form spliceosomal complexes responsible for pre mRNA processing. This study reports the unusual interaction of giardial snRNP F with small nucleolar RNAs (snoRNA) that are responsible for pre rRNA processing. Electrophoretic Mobility Shift Assay was used to demonstrate the interaction of this protein with U3 and U14 class snoRNA of the early branching eukaryote Giardia lamblia. It was also evident from our study that snRNP F in Giardia is evolutionary distinct from its other eukaryotic orthologues
Identification and optimization of small molecule antagonists of vasoactive intestinal peptide receptor-1 (VIPR1)
Identification, synthesis and structure-activity relationship of small-molecule VIPR1 antagonists encompassing two chemical series are described
Toe clearance and velocity profiles of young and elderly during walking on sloped surfaces
Background
Most falls in older adults are reported during locomotion and tripping has been identified as a major cause of falls. Challenging environments (e.g., walking on slopes) are potential interventions for maintaining balance and gait skills. The aims of this study were: 1) to investigate whether or not distributions of two important gait variables [minimum toe clearance (MTC) and foot velocity at MTC (VelMTC)] and locomotor control strategies are altered during walking on sloped surfaces, and 2) if altered, are they maintained at two groups (young and elderly female groups).
Methods
MTC and VelMTC data during walking on a treadmill at sloped surfaces (+3°, 0° and -3°) were analysed for 9 young (Y) and 8 elderly (E) female subjects.
Results
MTC distributions were found to be positively skewed whereas VelMTC distributions were negatively skewed for both groups on all slopes. Median MTC values increased (Y = 33%, E = 7%) at negative slope but decreased (Y = 25%, E = 15%) while walking on the positive slope surface compared to their MTC values at the flat surface (0°). Analysis of VelMTC distributions also indicated significantly (p < 0.05) lower minimum and 25th percentile (Q1) values in the elderly at all slopes.
Conclusion
The young displayed a strong positive correlation between MTC median changes and IQR (interquartile range) changes due to walking on both slopes; however, such correlation was weak in the older adults suggesting differences in control strategies being employed to minimize the risk of tripping
Inference of hidden structures in complex physical systems by multi-scale clustering
We survey the application of a relatively new branch of statistical
physics--"community detection"-- to data mining. In particular, we focus on the
diagnosis of materials and automated image segmentation. Community detection
describes the quest of partitioning a complex system involving many elements
into optimally decoupled subsets or communities of such elements. We review a
multiresolution variant which is used to ascertain structures at different
spatial and temporal scales. Significant patterns are obtained by examining the
correlations between different independent solvers. Similar to other
combinatorial optimization problems in the NP complexity class, community
detection exhibits several phases. Typically, illuminating orders are revealed
by choosing parameters that lead to extremal information theory correlations.Comment: 25 pages, 16 Figures; a review of earlier work
Effect of alloy treatment and coiling temperature on microstructure and bending performance of ultra-high strength strip steel
Two different high strength B-containing microalloyed steel strips produced in industrial processing conditions, one treated with Ti and the other treated with Al, processed by controlled rolling, accelerated cooling and coiling in two different temperatures ranges [723 K to 733 K (450 °C to 460 °C)] and [633 K to 653 K (360 °C to 380 °C)] were subjected to bend testing. The Ti treated steel coiled at the higher temperature 733 K (460 °C) showed the best bending performance. The relatively softer (tensile strength of and even {112} in the sub-surface region as well as uniformity of through thickness texture of the rolled sheet improve the bendability. In the presence of crack initiators, like coarse and brittle TiN particles found in the Ti treated steel, a harder microstructure and the presence of Cube and Goss texture in the sub-surface layer, seen for the lower coiling temperature can cause local transgranular cleavage cracking. Finally the post-uniform elongation obtained from tensile testing and bendability follow a good correlation
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