64,333 research outputs found
An evaluation of auroral all-sky camera observations
From photometric, all-sky camera, and visual observations
of a moderate auroral display, it is found that the
all-sky camera compares favorably with the visual observer
in detecting and recording auroral forms. The visual
observer can make instantaneous observations and so can
detect rapid changes and auroral forms lasting only a few
seconds, whereas the poorer time resolution of the all-sky
camera prevents it from recording very short-lived phenonema.
However, the ability of the all-sky camera to accurately
record the shape and intensity of the majority of auroral
forms allows it to yield more precise and complete information
about these aspects of auroral morphology than is
normally obtained through visual observation.Ye
Theoretical mean colors for RR Lyrae variables
A hydrodynamically pulsating 0.6 solar mass model of a typical RR Lyrae variable was studied with a radiation transport-hydrodynamic computer program to predict theoretical T sub 3 and colors at many phases and to find the proper methods for getting mean colors and the consequent mean effective temperatures. The variable Eddington radiation approximation method was used with gray and with multifrequency absorption coefficients to represent the radiation flow in the outer optically thin layers. Comparison between observed and computed B-V colors indicate that these low Z population 2 models are reasonably accurate using King 1A composition opacities. The well known Oke, Giver, and Searle relation between B-V and T sub e reproduced. Mean colors were found by four different averaging methods. The method that gives a mean color and the mean T sub e closest to the nonpulsating model was the separate intensity means of B and V
Preservation of flavor in freeze dried green beans
Before freeze drying, green beans are heated to point at which their cell structure is altered. Beans freeze dried with altered cell structure have improved rehydration properties and retain color, flavor, and texture
Chiral Vortons and Cosmological Constraints on Particle Physics
We investigate the cosmological consequences of particle physics theories
that admit stable loops of current-carrying string - vortons. In particular, we
consider chiral theories where a single fermion zero mode is excited in the
string core, such as those arising in supersymmetric theories with a D-term.
The resulting vortons formed in such theories are expected to be more stable
than their non-chiral cousins. General symmetry breaking schemes are considered
in which strings formed at one symmetry breaking scale become current-carrying
at a subsequent phase transition. The vorton abundance is estimated and
constraints placed on the underlying particle physics theories from
cosmological observations. Our constraints on the chiral theory are
considerably more stringent than the previous estimates for more general
theories.Comment: minor corrections made. This version will appear in PR
What makes a 'good group'? Exploring the characteristics and performance of undergraduate student groups
Group work forms the foundation for much of student learning within higher education, and has many educational, social and professional benefits. This study aimed to explore the determinants of success or failure for undergraduate student teams and to define a ‘good group’ through considering three aspects of group success: the task, the individuals, and the team. We employed a mixed methodology, combining demographic data with qualitative observations and task and peer evaluation scores. We determined associations between group dynamic and behaviour, demographic composition, member personalities and attitudes towards one another, and task success. We also employed a cluster analysis to create a model outlining the attributes of a good small group learning team in veterinary education. This model highlights that student groups differ in measures of their effectiveness as teams, independent of their task performance. On the basis of this, we suggest that groups who achieve high marks in tasks cannot be assumed to have acquired team working skills, and therefore if these are important as a learning outcome, they must be assessed directly alongside the task output
A Killing tensor for higher dimensional Kerr-AdS black holes with NUT charge
In this paper, we study the recently discovered family of higher dimensional
Kerr-AdS black holes with an extra NUT-like parameter. We show that the inverse
metric is additively separable after multiplication by a simple function. This
allows us to separate the Hamilton-Jacobi equation, showing that geodesic
motion is integrable on this background. The separation of the Hamilton-Jacobi
equation is intimately linked to the existence of an irreducible Killing
tensor, which provides an extra constant of motion. We also demonstrate that
the Klein-Gordon equation for this background is separable.Comment: LaTeX, 14 pages. v2: Typo corrected and equation added. v3: Reference
added, introduction expanded, published versio
The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined In situ Measurements and Heliospheric Imaging
In 2010 May 23-24, SDO observed the launch of two successive coronal mass
ejections (CMEs), which were subsequently tracked by the SECCHI suite onboard
STEREO. Using the COR2 coronagraphs and the heliospheric imagers (HIs), the
initial direction of both CMEs is determined to be slightly west of the
Sun-Earth line. We derive the CME kinematics, including the evolution of the
CME expansion until 0.4 AU. We find that, during the interaction, the second
CME decelerates from a speed above 500 km/s to 380 km/s the speed of the
leading edge of the first CME. STEREO observes a complex structure composed of
two different bright tracks in HI2-A but only one bright track in HI2-B. In
situ measurements from Wind show an "isolated" ICME, with the geometry of a
flux rope preceded by a shock. Measurements in the sheath are consistent with
draping around the transient. By combining remote-sensing and in situ
measurements, we determine that this event shows a clear instance of deflection
of two CMEs after their collision, and we estimate the deflection of the first
CME to be about 10 degrees towards the Sun-Earth line. The arrival time,
arrival speed and radius at Earth of the first CME are best predicted from
remote-sensing observations taken before the collision of the CMEs. Due to the
over-expansion of the CME after the collision, there are few, if any, signs of
interaction in in situ measurements. This study illustrates that complex
interactions during the Sun-to-Earth propagation may not be revealed by in situ
measurements alone.Comment: 14 pages, 8 figures, 1 table, accepted to the Astrophysical Journa
Molecular hydrogen jets and outflows in the Serpens south filamentary cloud
We aimed to map the jets and outflows from the Serpens South star forming
region and find an empirical relationship between the magnetic field and
outflow orientation. Near-infrared H2 v=1-0 S(1) 2.122{\mu}m -line imaging of
the \sim 30'-long filamentary shaped Serpens South star forming region was
carried out. K s broadband imaging of the same region was used for continuum
subraction. Candidate driving sources of the mapped jets/outflows are
identified from the list of known protostars and young stars in this region,
which was derived from studies using recent Spitzer and Herschel telescope
observations. 14 Molecular Hydrogen emission-line objects(MHOs) are identified
using our continuum-subtracted images. They are found to constitute ten
individual flows. Out of these, nine flows are located in the
lower-half(southern) part of the Serpens South filament, and one flow is
located at the northern tip of the filament. Four flows are driven by
well-identified Class 0 protostars, while the remaining six flows are driven by
candidate protostars mostly in the Class I stage, based on the Spitzer and
Herschel observations. The orientation of the outflows is systematically
perpendicular to the direction of the near-infrared polarization vector,
recently published in the literature. No significant correlation was observed
between the orientation of the flows and the axis of the filamentary cloud.Comment: Accepted by A&A for publication. 7 pages, 5 figure
AMPS definition study on Optical Band Imager and Photometer System (OBIPS)
A study was conducted to define the characteristics of a modular optical diagnostic system (OBIPS) for AMPS, to provide input to Phase B studies, and to give information useful for experiment planning and design of other instrumentation. The system described consists of visual and UV-band imagers and visual and UV-band photometers; of these the imagers are most important because of their ability to measure intensity as a function of two spatial dimensions and time with high resolution. The various subsystems of OBIPS are in themselves modular with modules having a high degree of interchangeability for versatility, economy, and redundancy
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