5,521 research outputs found
Search for synchrotron emission from secondary leptons in dense cold starless cores
We report radio continuum observations with the Australia Telescope Compact
Array of two molecular clouds. The impetus for these observations is a search
for synchrotron radiation by cosmic ray secondary electrons/positrons in a
region of enhanced density and possibly high magnetic field. We present
modelling which shows that there should be an appreciable flux of synchrotron
above the more diffuse, galactic synchrotron background.
The starless core G333.125-0.562 and infrared source IRAS 15596-5301 were
observed at 1384 and 2368 MHz. For G333.125-0.562, we find no significant
levels of radio emission from this source at either frequency, nor any
appreciable polarisation: we place an upper limit on the radio continuum flux
from this source of 0.5 mJy per beam at both 1384 and 2368 MHz. Due to the
higher than expected flux density limits, we also obtained archival ATCA data
at 8640 MHz for this cloud and place an upper limit on the flux density of 50
micro-Jy per beam. Assuming the cosmic ray spectrum is similar to that near the
Sun, and given the cloud's molecular density and mass, we place an upper limit
on the magnetic field of 500 micro-G. IRAS 15596-5301, with an RMS of 50
micro-Jy per beam at 1384 MHz, shows an HII region consistent with optically
thin free-free emission already detected at 4800 MHz. We use the same
prescription as G333 to constrain the magnetic field from this cloud to be less
than 500 micro-G. We find that these values are not inconsistent with the view
that magnetic field values scale with the average density of the molecular
cloud.Comment: 6 pages, 5 pdf figures, accepted for publication in PAS
Some integration formulae which simplify the evaluation of certain integrals in common use by engineers
Integration formulas to simplify evaluation of certain commonly used integral
Preliminary analysis of the effects of pressure space correlations on the vibrations of Apollo flight structure
Vibration response of Apollo skin structure to convected boundary layer turbulenc
Acoustic prediction methods for rocket engines, including the effects of clustered engines and deflected exhaust flow
Acoustic prediction methods for rocket engine
Neutrinos from the Galactic Center in the Light of its Gamma-Ray Detection at TeV Energy
We re-evaluate the event rate expected in km^3-scale detectors for neutrinos
from the direction of the Galactic Center (GC) in light of recent spectral
measurements obtained by the HESS instrument for ~TeV gamma-radiation from this
direction. In the most plausible scenario the re-evaluated event rate is
smaller than that previously calculated--and here re-calculated--on the basis
of EGRET data. However, the GC TeV gamma-ray detections by the Whipple,
CANGAROO, and HESS instruments, together with the strong indications for an
overabundance of cosmic rays coming from the GC at EeV energies, strengthen the
expectation for a detectable, TeV-PeV GC neutrino signal from proton-proton
interactions in that region. If the TeV gamma-ray--EeV cosmic ray anisotropy
connection is correct, this signal will be detectable within a year and half
for km^3-scale neutrino detectors in the Northern Hemisphere at super-TeV
energies and, significantly, should also be detectable in 1.6 years by the
South Polar IceCube detector at energies > 10^14 eV. The GC neutrino signal
should also produce a detectable signal from neutrino showering and resonant
W^- production by anti-electron-neutrinos in the volume of a km^3-scale
detector.Comment: 12 pages, 1 figure. Version accepted to ApJ Letters. Minor amendment
Measurement of long-range steric repulsions between microspheres due to an adsorbed polymer
We have measured the interparticle potential between pairs of micron-sized silica spheres induced by adsorbed polyethylene oxide polymer using a line-scanned optical tweezer. We found this long-range steric repulsion to be exponential over the range of energies (0.1kBT–5kBT) and polymer molecular weights (452 000–1 580 000) studied, and that the potential scaled with the polymer’s radius of gyration RG. The potential’s exponential decay length was about 0.6RG and its range was about 4RG, although both parameters varied significantly from one pair of spheres to another. The potential’s exponential prefactor was greater than mean-field predictions
Maximal oscillations, Borexino and smoking guns
We examine the maximal and
oscillation solutions to the solar neutrino problem. These solutions lead to
roughly a 50% solar flux reduction for the large parameter range . It is known that the earth regeneration
effect may cause a potentially large night-day asymmetry even for maximal
neutrino oscillations. We investigate the night-day asymmetry predictions for
the forthcoming Borexino measurement of the ^7Be neutrinos for both maximal
and oscillations. If case and y = 1 for case) then the maximal
neutrino oscillations will lead to observable night-day asymmetries in Borexino
and/or superKamiokande. With Kamland covering the high mass range, and Borexino/superK covering the low mass range,
("just so" region),
essentially all of the parameter space will soon be scrutinized.Comment: Various improvements...still about 6 pages with some fig
How to Drink from a Firehose: Systemic Supports for Polytechnic Chairs
This Organizational Improvement Plan (OIP) is centred on the Problem of Practice of the inadequate institutional supports for academic Chairs at Prairie Polytechnic (a pseudonym), a large public higher education institution in Western Canada. Chairs are pivotal for higher education institutions because they impact student, departmental, and institutional outcomes; however, the leadership development needs of Chairs are overlooked, and the limited training available for Chairs is primarily ad hoc, episodic, short-term, and self-guided. The objective of this OIP is to determine how Prairie Polytechnic can provide more effective systemic supports for Chairs. Postmodernism is used to explore the relationships between knowledge and positional power, and Critical Theory highlights the inequities Chairs face. Four potential solutions are explored and compared: increased release time from teaching, increased role clarity, Chair learning communities, and a Chair life cycle strategy. The Chair life cycle strategy is selected as the most feasible, efficacious, and ethical solution, and a change plan is detailed for how the strategy will be implemented at Prairie Polytechnic. The change plan is mapped to the stages of change from the ADKAR change model (awareness; desire; knowledge; ability; reinforcement) and guided by Adaptive Leadership behaviours. A communication plan identifies how collaborators will be engaged in the change process, and a monitoring and evaluation plan identifies how the change plan will be assessed. Successful implementation of the change plan will provide the systemic infrastructure needed to support academic leadership development at Prairie Polytechnic
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