7,164 research outputs found
Leading the evaluation of institutional online learning environments for quality enhancement in times of change
This paper reports on findings from a nationally funded project which aims to design and implement a quality management framework for online learning environments (OLEs). Evaluation is a key component of any quality management system and it is this aspect of the framework that is the focus of this paper. In developing the framework initial focus groups were conducted at the five participating institutions. These revealed that, although regarded as important, there did not appear to be a shared understanding of the nature and purpose of evaluation. A second series of focus groups revealed there were multiple perspectives arising from those with a vested interest in online learning. These perspectives will be outlined. Overall, how evaluation was undertaken was highly variable within and across the five institutions reflecting where they were at in relation to the development of their OLE
A Geometrical Method of Decoupling
The computation of tunes and matched beam distributions are essential steps
in the analysis of circular accelerators. If certain symmetries - like midplane
symmetrie - are present, then it is possible to treat the betatron motion in
the horizontal, the vertical plane and (under certain circumstances) the
longitudinal motion separately using the well-known Courant-Snyder theory, or
to apply transformations that have been described previously as for instance
the method of Teng and Edwards. In a preceeding paper it has been shown that
this method requires a modification for the treatment of isochronous cyclotrons
with non-negligible space charge forces. Unfortunately the modification was
numerically not as stable as desired and it was still unclear, if the extension
would work for all thinkable cases. Hence a systematic derivation of a more
general treatment seemed advisable.
In a second paper the author suggested the use of real Dirac matrices as
basic tools to coupled linear optics and gave a straightforward recipe to
decouple positive definite Hamiltonians with imaginary eigenvalues. In this
article this method is generalized and simplified in order to formulate a
straightforward method to decouple Hamiltonian matrices with eigenvalues on the
real and the imaginary axis. It is shown that this algebraic decoupling is
closely related to a geometric "decoupling" by the orthogonalization of the
vectors , and , that were introduced with the
so-called "electromechanical equivalence". We present a structure-preserving
block-diagonalization of symplectic or Hamiltonian matrices, respectively. When
used iteratively, the decoupling algorithm can also be applied to n-dimensional
systems and requires iterations to converge to a given
precision.Comment: 13 pages, 1 figur
Fast outflows in compact radio sources: evidence for AGN-induced feedback in the early stages of radio source evolution
We present intermediate resolution, wide wavelength coverage spectra for a
complete sample of 14 compact radio sources taken with the aim of investigating
the impact of the nuclear activity on the circumnuclear (ISM) in the early
stages of radio source evolution. We observe spatially extended line emission
(up to 20 kpc) in the majority of sources which is consistent with a quiescent
halo. In the nuclear apertures we observe broad, highly complex emission line
profiles. Multiple Gaussian modelling of the [O III]5007 line reveals 2-4
components which can have FWHM and blueshifts relative to the halo of up to
2000 km/s. We interpret these broad, blueshifted components as material in
outflow and discuss the kinematical evidence for jet-driven outflows.
Comparisons with samples in the literature show that compact radio sources
harbour more extreme nuclear kinematics than their extended counterparts, a
trend seen within our sample with larger velocities in the smaller sources. The
observed velocities are also likely to be influenced by source orientation with
respect to the observer's line of sight. Nine sources have associated HI
absorption. In common with the optical emission line gas, the HI profiles are
often highly complex with the majority of the detected components significantly
blueshifted, tracing outflows in the neutral gas. The sample has been tested
for stratification in the ISM (FWHM/ionisation potential/critical density) as
suggested by Holt et al. (2003) for PKS1345+12 but we find no significant
trends within the sample using a Spearman Rank analysis. This study supports
the idea that compact radio sources are young radio loud AGN observed during
the early stages of their evolution and currently shedding their natal cocoons
through extreme circumnuclear outflows.Comment: Accepted for publication in MNRAS, 24 pages, 7 figure
The central structure of Broad Absorption Line QSOs: observational characteristics in the cm-mm wavelength domain
Accounting for ~20% of the total QSO population, Broad Absorption Line QSOs
are still an unsolved problem in the AGN context. They present wide troughs in
the UV spectrum, due to material with velocities up to 0.2 c toward the
observer. The two models proposed in literature try to explain them as a
particular phase of the evolution of QSOs or as normal QSOs, but seen from a
particular line of sight.
We built a statistically complete sample of Radio-Loud BAL QSOs, and carried
out an observing campaign to piece together the whole spectrum in the cm
wavelength domain, and highlight all the possible differences with respect to a
comparison sample of Radio-Loud non-BAL QSOs. VLBI observations at high angular
resolution have been performed, to study the pc-scale morphology of these
objects. Finally, we tried to detect a possible dust component with
observations at mm-wavelengths.
Results do not seem to indicate a young age for all BAL QSOs. Instead a
variety of orientations and morphologies have been found, constraining the
outflows foreseen by the orientation model to have different possible angles
with respect to the jet axis
Global dynamics of three species omnivory models with Lotka-Volterra interaction
[[abstract]]In this work, we consider the community of three species food web model with Lotka-Volterra type predator-prey interaction. In the absence of other species, each species follows the traditional logistical growth model and the top predator is an omnivore which is defined as feeding on the other two species. It can be seen as a model with one basal resource and two generalist predators, and pairwise interactions of all species are predator-prey type. It is well known that the omnivory module blends the attributes of several well-studied community modules, such as food chains (food chain models), exploitative competition (two predators-one prey models), and apparent competition (one predator-two preys models). With a mild biological restriction, we completely classify all parameters. All local dynamics and most parts of global dynamics are established corresponding to the classification. Moreover, the whole system is uniformly persistent when the unique coexistence appears. Finally, we conclude by discussing the strategy of inferior species to survive and the mechanism of uniform persistence for the three species ecosystem.[[notice]]補正完
Generalized seniority scheme in light Sn isotopes
The yrast generalized seniority states are compared with the corresponding
shell model states for the case of the Sn isotopes Sn. For most of
the cases the energies agree within 100 keV and the overlaps of the wave
functions are greater than 0.7.Comment: 8 pages, revtex. Submitted to Phys. Rev.
CALING (Corpus de Accesibilidad Lingüística) Corpus : accessibility and real informants evaluation
There is strong evidence that rare copy number variants (CNVs) have a role in susceptibility to autism spectrum disorders (ASDs). Much research has focused on how CNVs mediate a phenotypic effect by altering gene expression levels. We investigated an alternative mechanism whereby CNVs combine the 5' and 3' ends of two genes, creating a 'fusion gene'. Any resulting mRNA with an open reading frame could potentially alter the phenotype via a gain-of-function mechanism. We examined 2382 and 3096 rare CNVs from 996 individuals with ASD and 1287 controls, respectively, for potential to generate fusion transcripts. There was no increased burden in individuals with ASD; 122/996 cases harbored at least one rare CNV of this type, compared with 179/1287 controls (P=0.89). There was also no difference in the overall frequency distribution between cases and controls. We examined specific examples of such CNVs nominated by case-control analysis and a candidate approach. Accordingly, a duplication involving REEP1-POLR1A (found in 3/996 cases and 0/1287 controls) and a single occurrence CNV involving KIAA0319-TDP2 were tested. However, no fusion transcripts were detected by RT-PCR. Analysis of additional samples based on cell line availability resulted in validation of a MAPKAPK5-ACAD10 fusion transcript in two probands. However, this variant was present in controls at a similar rate and is unlikely to influence ASD susceptibility. In summary, although we find no evidence that fusion-gene generating CNVs lead to ASD susceptibility, discovery of a MAPKAPK5-ACAD10 transcript with an estimated frequency of ~1/200 suggests that gain-of-function mechanisms should be considered in future CNVs studies
Solitons on the edge of a two-dimensional electron system
We present a study of the excitations of the edge of a two-dimensional
electron droplet in a magnetic field in terms of a contour dynamics formalism.
We find that, beyond the usual linear approximation, the non-linear analysis
yields soliton solutions which correspond to uniformly rotating shapes. These
modes are found from a perturbative treatment of a non-linear eigenvalue
problem, and as solutions to a modified Korteweg-de Vries equation resulting
from a local induction approximation to the nonlocal contour dynamics. We
discuss applications to the edge modes in the quantum Hall effect.Comment: 4 pages, 2 eps figures (included); to appear in Phys. Rev. Letter
Physics on the edge: contour dynamics, waves and solitons in the quantum Hall effect
We present a theoretical study of the excitations on the edge of a
two-dimensional electron system in a perpendicular magnetic field in terms of a
contour dynamics formalism. In particular, we focus on edge excitations in the
quantum Hall effect. Beyond the usual linear approximation, a non-linear
analysis of the shape deformations of an incompressible droplet yields soliton
solutions which correspond to shapes that propagate without distortion. A
perturbative analysis is used and the results are compared to analogous
systems, like vortex patches in ideal hydrodynamics. Under a local induction
approximation we find that the contour dynamics is described by a non-linear
partial differential equation for the curvature: the modified Korteweg-de Vries
equation.
PACS number(s): 73.40.Hm, 02.40.Ma, 03.40.Gc, 11.10.LmComment: 15 pages, 12 embedded figures, submitted to Phys. Rev.
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