1,251 research outputs found
Doping driven magnetic instabilities and quantum criticality of NbFe
Using density functional theory we investigate the evolution of the magnetic
ground state of NbFe due to doping by Nb-excess and Fe-excess. We find
that non-rigid-band effects, due to the contribution of Fe-\textit{d} states to
the density of states at the Fermi level are crucial to the evolution of the
magnetic phase diagram. Furthermore, the influence of disorder is important to
the development of ferromagnetism upon Nb doping. These findings give a
framework in which to understand the evolution of the magnetic ground state in
the temperature-doping phase diagram. We investigate the magnetic instabilities
in NbFe. We find that explicit calculation of the Lindhard function,
, indicates that the primary instability is to finite
antiferromagnetism driven by Fermi surface nesting. Total energy
calculations indicate that antiferromagnetism is the ground
state. We discuss the influence of competing and finite
instabilities on the presence of the non-Fermi liquid behavior in
this material.Comment: 8 pages, 7 figure
Magnetic ordering above room temperature in the sigma-phase of Fe66V34
Magnetic properties of four sigma-phase Fe_(100-x)V_x samples with
34.4<x<55.1 were investigated by Mossbauer spectroscopy and magnetic
measurements in the temperature interval 5-300 K. Four magnetic quantities viz.
hyperfine field, Curie temperature, magnetic moment and susceptibility were
determined. The sample containing 34.4 at% V was revealed to exhibit the
largest values found up to now for the sigma-phase for average hyperfine field,
B = 12.1 T, average magnetic moment per Fe atom, m = 0.89 mB, and Curie
temperature, TC = 315.5 K. The quantities were shown to be strongly correlated
with each other. In particular, TC is linearly correlated with m with a slope
of 406.5 K/mB, as well as B is so correlated with m yielding 14.3 T/mB for the
hyperfine coupling constant.Comment: 15 pages, 11 figures, 1 tabl
Influences of state anxiety on gaze behavior and stepping accuracy in older adults during adaptive locomotion
This article is available open access through the publisher’s website at the link below. Copyright © The Authors 2011.OBJECTIVES: Older adults deemed to be at a high risk of falling transfer their gaze from a stepping target earlier than their low-risk counterparts. The extent of premature gaze transfer increases with task complexity and is associated with a decline in stepping accuracy. This study tests the hypothesis that increased anxiety about upcoming obstacles is associated with (a) premature transfers of gaze toward obstacles (i.e., looking away from a target box prior to completing the step on it in order to fixate future constraints in the walkway) and (b) reduced stepping accuracy on the target in older adults. METHODS: High-risk (9) and low-risk (8) older adult participants walked a 10-m pathway containing a stepping target area followed by various arrangements of obstacles, which varied with each trial. Anxiety, eye movements, and movement kinematics were measured. RESULTS: Progressively increasing task complexity resulted in associated statistically significant increases in measures of anxiety, extent of early gaze transfer, and stepping inaccuracies in the high-risk group. DISCUSSION: These results provide evidence that increased anxiety about environmental hazards is related to suboptimal visual sampling behavior which, in turn, negatively influences stepping performance, potentially contributing to increased falls risk in older adults.Biotechnology and Biological Sciences Research Counci
Site Occupancy and Lattice Parameters in Sigma-Phase Co-Cr alloys
Neutron diffraction technique was used to study distribution of Co and Cr
atoms over different lattice sites as well as lattice paramaters in sigma-phase
Co100-xCrx compounds with x = 57.0, 62.7 and 65.8. From the diffractograms
recorded in the temperature range of 4.2 - 300 K it was found that all five
sites A, B, C, D and E are populated by both kinds of atoms. Sites A and D are
predominantly occupied by Co atoms while sites B, C and E by Cr atoms. The unit
cell parameters a and c, hence the unit cell volume, increase with x, the
increase being characteristic of the lattice paramater and temperature. Both a
and c show a non-linear increase with temperature.Comment: 5 figure
Association of blood pressure with knee cartilage composition and structural knee abnormalities: data from the osteoarthritis initiative.
ObjectiveTo investigate the associations of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with changes in knee cartilage composition and joint structure over 48 months, using magnetic resonance imaging (MRI) data from the Osteoarthritis Initiative (OAI).Materials and methodsA total of 1126 participants with right knee Kellgren-Lawrence (KL) score 0-2 at baseline, no history of rheumatoid arthritis, blood pressure measurements at baseline, and cartilage T2 measurements at baseline and 48 months were selected from the OAI. Cartilage composition was assessed using MRI T2 measurements, including laminar and gray-level co-occurrence matrix texture analyses. Structural knee abnormalities were graded using the whole-organ magnetic resonance imaging score (WORMS). We performed linear regression, adjusting for age, sex, body mass index, physical activity, smoking status, alcohol use, KL score, number of anti-hypertensive medications, and number of nonsteroidal anti-inflammatory drugs.ResultsHigher baseline DBP was associated with greater increases in global T2 (coefficient 0.22 (95% CI 0.09, 0.34), P = 0.004), global superficial layer T2 (coefficient 0.39 (95% CI 0.20, 0.58), P = 0.001), global contrast (coefficient 15.67 (95% CI 8.81, 22.53), P < 0.001), global entropy (coefficient 0.02 (95% CI 0.01, 0.03) P = 0.011), and global variance (coefficient 9.14 (95% CI 5.18, 13.09), P < 0.001). Compared with DBP, the associations of SBP with change in cartilage T2 parameters and WORMS subscores showed estimates of smaller magnitude.ConclusionHigher baseline DBP was associated with higher and more heterogenous cartilage T2 values over 48 months, indicating increased cartilage matrix degenerative changes
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