10,414 research outputs found
Checking the internal pedagogical consistency of a game learning situation: the Leclercq’s triple consistency triangle
Leclercq’s triangle is a conceptual tool used for securing the pedagogical validity of learning situations. It materializes the sound pedagogy principle which commands to establish a triple consistency between objectives, methods and evaluation in any given learning situation. The ELEKTRA adventure game provides a practical illustration of its relevance.Peer reviewe
A MiMeS analysis of the magnetic field and circumstellar environment of the weak-wind O9 sub-giant star HD 57682
I will review our recent analysis of the magnetic properties of the O9IV star
HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the
Canada-France-Hawaii telescope within the context of the Magnetism in Massive
Stars (MiMeS) Large Program. I discuss our most recent determination of the
rotational period from longitudinal magnetic field measurements and Halpha
variability - the latter obtained from over a decade's worth of professional
and amateur spectroscopic observations. Lastly, I will report on our
investigation of the magnetic field geometry and the effects of the field on
the circumstellar environment.Comment: 2 pages, 2 figures, IAUS272 - Active OB Stars: Structure, Evolution,
Mass Loss and Critical Limit
Spin dynamics in the ordered spin ice TbSnO
Geometrical frustration is a central challenge in contemporary condensed
matter physics, a crucible favourable to the emergence of novel physics. The
pyrochlore magnets, with rare earth magnetic moments localized at the vertices
of corner-sharing tetrahedra, play a prominent role in this field, with a rich
variety of exotic ground states ranging from the "spin ices" \hoti\ and \dyti\
to the "spin liquid" and "ordered spin ice" ground states in \tbti\ and \tbsn.
Inelastic neutron scattering provides valuable information for understanding
the nature of these ground states, shedding light on the crystal electric field
(CEF) level scheme and on the interactions between magnetic moments. We have
performed such measurements with unprecedented neutron flux and energy
resolution, in the "ordered spin ice" \tbsn. We argue that a new interaction,
which involves the spin lattice coupling through a low temperature distortion
of the trigonal crystal field, is necessary to account for the data
The effects of donepezil in Alzheimer's disease - Results from a multinational trial
Donepezil has been shown to be well tolerated and to improve cognition and global function in patients with mild to moderately severe Alzheimer's disease (AD). The current trial was undertaken to investigate further the efficacy and safety of donepezil, in a multinational setting, in patients with mild to moderately severe AD. This 30-week, placebo-controlled, parallel-group study consisted of a 24-week, double-blind treatment phase followed by a 6-week, single-blind, placebo washout. Eight hundred and eighteen patients with mild to moderately severe AD were randomly allocated to treatment with single, daily doses of 5 or 10 mg donepezil, or placebo. The two primary efficacy measures were: a cognitive performance test, the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) and a global evaluation, the Clinician's Interview-Based Impression of Change with caregiver input (CIBIC plus). Secondary outcome measures included the Sum of the Boxes of the Clinical Dementia Rating Scale (CDR-SB), a modified Interview for Deterioration in Daily living activities in Dementia (IDDD) and a patient-rated quality of life assessment. Statistically significant improvements in cognitive and global function were observed, as evaluated by ADAS-cog and CIBIC plus, respectively, in both the 5 and 10 mg/day donepezil groups, compared with placebo. Treatment-associated changes were also observed in functional skills, as shown by improved scores on the CDR-SB and the complex-tasks component of the IDDD. A dose-response effect was evident, with the 10 mg/day donepezil group demonstrating greater benefits in all outcome measures than the 5 mg/day group. Donepezil was well tolerated by this patient population and did not produce any clinically significant laboratory test abnormalities. The results of this study confirm that donepezil is effective and well tolerated in treating the symptoms of mild to moderately severe AD
Magnetostrictive hysteresis of TbCo/CoFe multilayers and magnetic domains
Magnetic and magnetostrictive hysteresis loops of TbCo/CoFe multilayers under
field applied along the hard magnetization axis are studied using vectorial
magnetization measurements, optical deflectometry and magneto optical Kerr
microscopy. Even a very small angle misalignment between hard axis and magnetic
field direction is shown to drastically change the shape of magnetization and
magnetostrictive torsion hysteresis loops. Two kinds of magnetic domains are
revealed during the magnetization: big regions with opposite rotation of
spontaneous magnetization vector and spontaneous magnetic domains which appear
in a narrow field interval and provide an inversion of this rotation.
We show that the details of the hysteresis loops of our exchange-coupled
films can be described using the classical model of homogeneous magnetization
rotation of single uniaxial films and the configuration of observed domains.
The understanding of these features is crucial for applications (for MEMS or
microactuators) which benefit from the greatly enhanced sensitivity near the
point of magnetic saturation at the transverse applied field.Comment: 10 pages, 11 figure
The Kuiper Belt Luminosity Function from m(R)=21 to 26
We have performed an ecliptic imaging survey of the Kuiper belt with our
deepest and widest field achieving a limiting flux of m(g') = 26.4, with a sky
coverage of 3.0 square-degrees. This is the largest coverage of any other
Kuiper belt survey to this depth. We detect 72 objects, two of which have been
previously observed. We have improved the Bayesian maximum likelihood fitting
technique presented in Gladman et al. (1998) to account for calibration and sky
density variations and have used this to determine the luminosity function of
the Kuiper belt. Combining our detections with previous surveys, we find the
luminosity function is well represented by a single power-law with slope alpha
= 0.65 +/- 0.05 and an on ecliptic sky density of 1 object per square-degree
brighter than m(R)=23.42 +/- 0.13. Assuming constant albedos, this slope
suggests a differential size-distribution slope of 4.25 +/- 0.25, which is
steeper than the Dohnanyi slope of 3.5 expected if the belt is in a state of
collisional equilibrium. We find no evidence for a roll-over or knee in the
luminosity function and reject such models brightward of m(R) ~ 24.6.Comment: 50 Pages, 8 Figure
Magnetic topology and surface differential rotation on the K1 subgiant of the RS CVn system HR 1099
We present here spectropolarimetric observations of the RS CVn system HR 1099
(V711 Tau) secured from 1998 February to 2002 January with the
spectropolarimeter MuSiCoS at the Telescope Bernard Lyot (Observatoire du Pic
du Midi, France). We apply Zeeman-Doppler Imaging and reconstruct brightness
and magnetic surface topologies of the K1 primary subgiant of the system, at
five different epochs. We confirm the presence of large, axisymmetric regions
where the magnetic field is mainly azimuthal, providing further support to the
hypothesis that dynamo processes may be distributed throughout the whole
convective zone in this star. We study the short-term evolution of surface
structures from a comparison of our images with observations secured at
close-by epochs by Donati et al. (2003) at the Anglo-Australian Telescope. We
conclude that the small-scale brightness and magnetic patterns undergo major
changes within a timescale of 4 to 6 weeks, while the largest structures remain
stable over several years. We report the detection of a weak surface
differential rotation (both from brightness and magnetic tracers) indicating
that the equator rotates faster than the pole with a difference in rotation
rate between the pole and the equator about 4 times smaller than that of the
Sun. This result suggests that tidal forces also impact the global dynamic
equilibrium of convective zones in cool active stars.Comment: accepted by MNRA
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