426 research outputs found
Surface-driven electronic structure in LaFeAsO studied by angle resolved photoemission spectroscopy
We measured the electronic structure of an iron arsenic parent compound
LaFeAsO using angle resolved photoemission spectroscopy (ARPES). By comparing
with a full-potential Linear Augmented PlaneWave calculation we show that the
extra large Gamma hole pocket measured via ARPES comes from electronic
structure at the sample surface. Based on this we discuss the strong
polarization dependence of the band structure and a temperature-dependent
hole-like band around the M point. The two phenomena give additional evidences
for the existence of the surface-driven electronic structure.Comment: 6 pages, 6 figure
Magnetism dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering
The phonon dispersion was measured at room temperature along (0,0,L) in the
tetragonal phase of LaFeAsO using inelastic x-ray scattering. Spin-polarized
first-principles calculations imposing various types of antiferromagnetic order
are in better agreement with the experimental results than nonmagnetic
calculations, although the measurements were made well above the magnetic
ordering temperature, T_N. Splitting observed between two A_{1g} phonon modes
at 22 and 26 meV is only observed in spin-polarized calculations.
Magneto-structural effects similar to those observed in the AFe_2As_2 materials
are confirmed present in LaFeAsO. The presence of Fe-spin is necessary to find
reasonable agreement of the calculations with the measured spectrum well above
T_N. On-site Fe and As force constants show significant softening compared to
nonmagnetic calculations, however an investigation of the real-space force
constants associates the magnetoelastic coupling with a complex renormalization
instead of softening of a specific pairwise force.Comment: 7 pages, 4 figure
Interpersonal emotion regulation in team sport: mechanisms and reasons to regulate teammates' emotions examined
The interpersonal dimension of emotion regulation in the field of sport has lately received a burgeoning interest. Nevertheless, how and why athletes regulate their teammates' emotions in competitive setting remains unclear. Across two studies within a team sport context, we uncovered athletes' mechanisms for, and reasons to regulate teammates' emotions during competition. In Study 1, we investigated how rugby (N = 22 males) players' emotions were self- and interpersonally regulated during games. Findings revealed the emergence of a continuum of self-involvement in the regulatory processes, wherein two forms of emotion regulation co-existed: self-regulation (total self-involvement) and interpersonal regulation, which included co-regulation (partial self-involvement; regulation with others) and extrinsic regulation (no self-involvement; regulation by/of others). In Study 2, we examined the motives that lead rugby (n = 30 males) players to use interpersonal extrinsic regulation strategies during games. Interview data indicated that players regulated teammates' emotions for altruistic reasons (to help a teammate), egoistic reasons (for one's own benefits), or both. Overall, our findings further knowledge to better understand interpersonal emotion regulation within competitive team sport contexts. From an applied perspective, findings highlight the role that both individual goals and ego involvement may play in optimising efficient interpersonal regulation during competition at team level
Electron correlation effects and magnetic ordering at the Gd(0001) surface
Effects of electron correlation on the electronic structure and magnetic
properties of the Gd(0001) surface are investigated using of the full-potential
linearized augmented plane wave implementation of correlated band theory
("LDA+U"). The use of LDA+U instead of LDA (local density approximation) total
energy calculations produces the correct ferromagnetic ground state for both
bulk Gd and the Gd surface. Surface strain relaxation leads to an 90 %
enhancement of the interlayer surface-to-bulk effective exchange coupling.
Application of a Landau-Ginzburg type theory yields a 30 % enhancement of the
Curie temperature at the surface, in very good agreement with the experiment.Comment: revised version: minor typos correcte
Pedagogical approaches for e-assessment with authentication and authorship verification in Higher Education
Checking the identity of students and authorship of their online submissions is a major concern in Higher Education due to the increasing amount of plagiarism and cheating using the Internet. The literature on the effects of e-authentication systems for teaching staff is very limited because it is a novel procedure for them. A considerable gap is to understand teaching staff’ views regarding the use of e-authentication instruments and how they impact trust in e-assessment. This mixed-method study examines the concerns and practices of 108 teaching staff who used the TeSLA - Adaptive Trust-based e-Assessment System in six countries: UK, Spain, Netherlands, Bulgaria, Finland and Turkey. The findings revealed some technological, organisational and pedagogical issues related to accessibility, security, privacy and e-assessment design and feedback. Recommendations are to provide: a FAQ and an audit report with results, to raise awareness about data security and privacy, to develop policies and guidelines about fraud detection and prevention, e-assessment best practices and course team support
Participatory Process for Implementing a Colorectal Cancer Screening Intervention: an Action Plan for Local Sustainability
Background: Rigid protocols can hamper translation of evidence-based interventions from research to real-world settings. This investigation aimed to develop procedures for modifying the study protocol of a community-based participatory research (CBPR) project and to analyze the theoretical constructs that underlie this process.
Methods: The research project is a dissemination and implementation study of the Educational Program to Increase Colorectal Cancer Screening (EPICS), an evidence-based intervention targeting African Americans in the United States. The study is being conducted in a partnership with community coalitions in 15 different cities. Each site initially presented unique issues that required modification of the study protocol.
Results: In order to honor underlying CBPR theory, it was necessary to negotiate protocol changes with the community coalition at each site, while insuring preservation of the core elements of the intervention.
Conclusions: We discuss the ways in which this represents a narrowing of the gap between CBPR and traditional research approaches
Spectral and Timing Evolution of the Black Hole X-ray Nova 4U 1543-47 During its 2002 Outburst
We present an X-ray spectral and timing analysis of 4U 1543-47 during its
2002 outburst based on 49 pointed observations obtained using the Rossi X-ray
Timing Explorer (RXTE). The outburst reached a peak intensity of 4.2 Crab in
the 2-12 keV band and declined by a factor of 32 throughout the month-long
observation. A 21.9 +- 0.6 mJy radio flare was detected at 1026.75 MHz two days
before the X-ray maximum; the radio source was also detected late in the
outburst, after the X-ray source entered the low hard state. The X-ray light
curve exhibits the classic shape of a rapid rise and an exponential decay. The
spectrum is soft and dominated by emission from the accretion disk. The
continuum is fit with a multicolor disk blackbody (kT_{max} = 1.04 keV) and a
power-law (Gamma ~ 2.7). Midway through the decay phase, a strong low-frequency
QPO (nu = 7.3-8.1 Hz) was present for several days. The spectra feature a broad
Fe K alpha line that is asymmetric, suggesting that the line is due to
relativistic broadening rather than Comptonization. Relativistic Laor models
provide much better fits to the line than non-relativistic Gaussian models,
particularly near the beginning and end of our observations. The line fits
yield estimates for the inner disk radius that are within 6 R_g; this result
and additional evidence indicates that this black hole may have a non-zero
angular momentum.Comment: Accepted for publication in ApJ, 17 pages, 10 figures, uses
emulateapj.cls and apjfonts.st
Haptic Edge Detection Through Shear
Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals
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