10,718 research outputs found
An evaluation of the effectiveness of three types of study guides in producing immediate and delayed recall.
Thesis (Ed.M.)--Boston Universit
The Arecibo Galaxy Environments survey IV: the NGC7448 region and the HI mass function
In this paper we describe results from the Arecibo Galaxy Environments Survey
(AGES). The survey reaches column densities of ~3x10^18 cm^-2 and masses of
~10^7 M_O, over individual regions of order 10 sq deg in size, out to a maximum
velocity of 18,000 km s^-1. Each surveyed region is centred on a nearby galaxy,
group or cluster, in this instance the NGC7448 group. Galaxy interactions in
the NGC7448 group reveal themselves through the identification of tidal tails
and bridges. We find ~2.5 times more atomic gas in the inter-galactic medium
than in the group galaxies. We identify five new dwarf galaxies, two of which
appear to be members of the NGC7448 group. This is too few, by roughly an order
of magnitude, dwarf galaxies to reconcile observation with theoretical
predictions of galaxy formation models. If they had observed this region of sky
previous wide area blind HI surveys, HIPASS and ALFALFA, would have detected
only 5% and 43% respectively of the galaxies we detect, missing a large
fraction of the atomic gas in this volume. We combine the data from this paper
with that from our other AGES papers (370 galaxies) to derive a HI mass
function with the following Schechter function parameters alpha=-1.52+/-0.05,
M^*=5.1+/-0.3x10^9 h_72^-2 M_O, phi=8.6+/-1.1x10-3 h_72^3 Mpc^-3 dex-1.
Integrating the mass function leads to a cosmic mass density of atomic hydrogen
of Omega_HI=5.3+/-0.8x10^-4 h_72^-1. Our mass function is steeper than that
found by both HIPASS and ALFALFA (alpha=1.37 and 1.33 respectively), while our
cosmic mass density is consistent with ALFALFA, but 1.7 times larger than found
by HIPASS
Preparing the foundations for video-based, practice-placement support: establishing the role from a studentsâ perspective
Currently, many placement-based health programme students within the UK are supported through face-to-face visits from university staff. Whilst cited in literature as being of value, the face-to-face nature of this contact is not supported. Alternatives including video-based communications methods offer the potential for cost effective, environmentally responsible support. However, in order to establish the fitness for purpose of alternative approaches, the content and purpose of current support needs to be understood. This project aimed to investigate student perceptions of the ideal content and purpose of clinical support visits, and alternatives to the current face-to-face approach. Fifty-six Physiotherapy undergraduate students responded to questionnaires with a further nine participating in a follow-up focus group. Participants emphasised the value of the visit in guiding learning, ensuring progression and resolving arising issues, and highlighted concerns over alternative approaches. Focus group participants discussed the importance of personal and professional confidence in directing requirements for support, and went on to propose a menu of options for methods of communication.Whilst limited in some applications, video technologies may be one of the options. Overall, however, this project supports the need for consideration of individualised learning journeys within curriculum planning
Migration of Interplanetary Dust
We numerically investigate the migration of dust particles with initial
orbits close to those of the numbered asteroids, observed trans-Neptunian
objects, and Comet Encke. The fraction of silicate asteroidal particles that
collided with the Earth during their lifetime varied from 1.1% for 100 micron
particles to 0.008% for 1 micron particles. Almost all asteroidal particles
with diameter d>4 microns collided with the Sun. The peaks in the migrating
asteroidal dust particles' semi-major axis distribution at the n:(n+1)
resonances with Earth and Venus and the gaps associated with the 1:1 resonances
with these planets are more pronounced for larger particles. The probability of
collisions of cometary particles with the Earth is smaller than for asteroidal
particles, and this difference is greater for larger particles.Comment: Annals of the New York Academy of Sciences, 15 pages, 8 Figures,
submitte
JVLA overview of the bursting HO maser source G25.65+1.05
The source G25.65+1.05 (RAFGL7009S, IRAS 18316-0602) is the least studied of
the three regions of massive star formation known to show exceptionally
powerful HO maser bursts. We report spectral line observations of the
HO maser at 22 GHz, the methanol maser transitions at 6.7, 12.2 and 44 GHz,
and the continuum in these same frequency bands with The Karl G. Jansky Very
Large Array (JVLA) at the post-burst epoch of 2017. For the first time, maps of
22 GHz HO and 44 GHz CHOH maser spots are obtained and the absolute
position of the 22 GHz HO bursting feature is determined with
milliarcsecond precision. We detected four continuum components, three of which
are closely spaced in a linear orientation, suggesting a physical link between
them
Precession of a Freely Rotating Rigid Body. Inelastic Relaxation in the Vicinity of Poles
When a solid body is freely rotating at an angular velocity ,
the ellipsoid of constant angular momentum, in the space , has poles corresponding to spinning about the minimal-inertia and
maximal-inertia axes. The first pole may be considered stable if we neglect the
inner dissipation, but becomes unstable if the dissipation is taken into
account. This happens because the bodies dissipate energy when they rotate
about any axis different from principal. In the case of an oblate symmetrical
body, the angular velocity describes a circular cone about the vector of
(conserved) angular momentum. In the course of relaxation, the angle of this
cone decreases, so that both the angular velocity and the maximal-inertia axis
of the body align along the angular momentum. The generic case of an asymmetric
body is far more involved. Even the symmetrical prolate body exhibits a
sophisticated behaviour, because an infinitesimally small deviation of the
body's shape from a rotational symmetry (i.e., a small difference between the
largest and second largest moments of inertia) yields libration: the precession
trajectory is not a circle but an ellipse. In this article we show that often
the most effective internal dissipation takes place at twice the frequency of
the body's precession. Applications to precessing asteroids, cosmic-dust
alignment, and rotating satellites are discussed.Comment: 47 pages, 1 figur
A new instability of accretion disks around compact magnetic stars
Aperiodic variability and Quasi Periodic Oscillations (QPOs) are observed
from accretion disks orbiting white dwarfs, neutron stars, and black holes,
suggesting that the flow is universally broken up into discrete blobs. We
consider the interaction of these blobs with the magnetic field of a compact,
accreting star, where diamagnetic blobs suffer a drag. We show that when the
magnetic moment is not aligned with the spin axis, the resulting force is
pulsed, and this can lead to resonance with the oscillation of the blobs around
the equatorial plane; a resonance condition where energy is effectively pumped
into non--equatorial motions is then derived. We show that the same resonance
condition applies for the quadrupolar component of the magnetic field. We
discuss the conditions of applicability of this result, showing that they are
quite wide. We also show that realistic complications, such as chaotic magnetic
fields, buoyancy, radiation pressure, evaporation, Kelvin--Helmholtz
instability, and shear stresses due to differential rotation do not affect our
results. In accreting neutron stars with millisecond periods, we show that this
instability leads to Lense-Thirring precession of the blobs, and that damping
by viscosity can be neglected.Comment: Accepted for publication in the Astrophysical Journal. AASTeX LateX
needed. Two figure
Relationship between Tibial conformation, cage size and advancement achieved in TTA procedure
Previous studies have suggested that there is a theoretical discrepancy between the cage size and the resultant tibial tuberosity advancement, with the cage size consistently providing less tibial tuberosity advancement than predicted. The purpose of this study was to test and quantify this in clinical cases. The hypothesis was that the advancement of the tibial tuberosity as measured by the widening of the proximal tibia at the tibial tuberosity level after a standard TTA, will be less than the cage sized used, with no particular cage size providing a relative smaller or higher under-advancement, and that the conformation of the proximal tibia will have an influence on the amount of advancement achieved
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