10,355 research outputs found
Library Research Instruction for Doctor of Ministry Students: Outcomes of Instruction Provided by a Theological Librarian and by a Program Faculty Member
At some seminaries the question of who is more effective teaching library research is an open question. There are two camps of thought: (1) that the program faculty member is more effective in providing library research instruction as he or she is intimately engaged in the subject of the course(s), or 2) that the theological librarian is more effective in providing library research instruction as he or she is more familiar with the scope of resources that are available, as well as how to obtain âhard to getâ resources
On the fine structure of medium energy electron fluxes in the auroral zone and related effects in the ionospheric D-region
This study is based on measurements of trapped and precipitated electrons of energy >30 keV and >100 keV observed by
polar orbiting environmental satellites during overpasses of the imaging riometer at KilpisjÀrvi, Finland.
The satellites are in sun-synchronous orbits of about 850 km altitude, recording the electron fluxes at 2-s time resolution.
The riometer measures the radiowave absorption at 38.2 MHz, showing the spatial pattern within a 240 km field of view.
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The analysis has focussed on two areas.
Having found a close correlation between the radiowave absorption and the medium-energy electron fluxes during satellite overpasses,
empirical relationships are derived, enabling one quantity to be predicted from the other for three sectors of local time.
It is shown that small-scale variations observed during a pass are essentially spatial rather than temporal.
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Other properties, such as the spectra and the relation between precipitated and trapped components, are also considered in the light of the theory
of pitch angle scattering by VLF waves.
It is found that the properties and behaviour depend strongly on the time of day.
In the noon sector, the precipitated and trapped fluxes are highly correlated through a square law relationship
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Possible immunoenhancement of persistent viremia by feline leukemia virus envelope glycoprotein vaccines in challenge-exposure situations where whole inactivated virus vaccines were protective.
Kittens immunized with purified native FeLV-gp70 or -gp85 envelope proteins developed ELISA, but not virus neutralizing, antibodies in their serum to both whole FeLV and FeLV-gp70. Kittens vaccinated with envelope proteins and infected with feline sarcoma virus (FeSV) developed smaller tumors than nonvaccinates, but a greater incidence of persistent retroviremia. Similarly, FeLV-gp70 and -gp85 vaccinated kittens were more apt to become persistently retroviremic following virulent FeLV challenge exposure than nonvaccinates. Kittens vaccinated with inactivated whole FeLV developed smaller tumors after FeSV inoculation and had a lower incidence of persistent retroviremia than nonvaccinates. The protective effect of inactivated whole FeLV vaccine against persistent retroviremia was also seen with FeLV challenge-exposed cats. Protection afforded by inactivated whole FeLV vaccine was not associated with virus neutralizing antibodies, although ELISA antibodies to both whole FeLV and FeLV-gp70 were induced by vaccination
Mean flow field and surface heating produced by unequal shock interactions at hypersonic speeds
Mean velocity profiles were measured in a free shear layer produced by the interaction of two unequal strength shock waves at hypersonic free-stream Mach numbers. Measurements were made over a unit Reynolds number range of 3,770,000 per meter to 17,400,000 per meter based on the flow on the high velocity side of the shear layer. The variation in measured spreading parameters with Mach number for the fully developed flows is consistent with the trend of the available zero velocity ratio data when the Mach numbers for the data given in this study are taken to be characteristic Mach numbers based on the velocity difference across the mixing layer. Surface measurements in the shear-layer attachment region of the blunt-body model indicate peak local heating and static pressure consistent with other published data. Transition Reynolds numbers were found to be significantly lower than those found in previous data
Numerical simulations of multiple scattering of the mode by flux tubes
We use numerial simulations to study the absorption and phase shift of
surface-gravity waves caused by groups of magnetic flux tubes. The dependence
of the scattering coefficients with the distance between the tubes and their
positions is analyzed for several cases with two or three flux tubes embedded
in a quiet Sun atmosphere. The results are compared with those obtained
neglecting completely or partially multiple scattering effects. We show that
multiple scattering has a significant impact on the absorption measurements and
tends to reduce the phase shift. We also consider more general cases of
ensembles of randomly distributed flux tubes, and we have evaluated the effects
on the scattering measurements of changing the number of tubes included in the
bundle and the average distance between flux tubes. We find that for the
longest wavelength incoming waves multiple scattering enhances the absorption,
and its efficiency increases with the number of flux tubes and the reduction of
the distance between them.Comment: Accepted for publication in The Astrophysical Journa
Evaluation of the capability of local helioseismology to discern between monolithic and spaghetti sunspot models
The helioseismic properties of the wave scattering generated by monolithic
and spaghetti sunspots are analyzed by means of numerical simulations. In these
computations, an incident f or p1 mode travels through the sunspot model, which
produces absorption and phase shift of the waves. The scattering is studied by
inspecting the wavefield, computing travel-time shifts, and performing
Fourier-Hankel analysis. The comparison between the results obtained for both
sunspot models reveals that the differences in the absorption coefficient can
be detected above noise level. The spaghetti model produces an steep increase
of the phase shift with the degree of the mode at short wavelengths, while
mode-mixing is more efficient for the monolithic model. These results provide a
clue for what to look for in solar observations to discern the constitution of
sunspots between the proposed monolithic and spaghetti models.Comment: Accepted for publication in The Astrophysical Journa
Helioseismic holography of simulated sunspots: magnetic and thermal contributions to travel times
Wave propagation through sunspots involves conversion between waves of
acoustic and magnetic character. In addition, the thermal structure of sunspots
is very different than that of the quiet Sun. As a consequence, the
interpretation of local helioseismic measurements of sunspots has long been a
challenge. With the aim of understanding these measurements, we carry out
numerical simulations of wave propagation through sunspots. Helioseismic
holography measurements made from the resulting simulated wavefields show
qualitative agreement with observations of real sunspots. We use additional
numerical experiments to determine, separately, the influence of the thermal
structure of the sunspot and the direct effect of the sunspot magnetic field.
We use the ray approximation to show that the travel-time shifts in the thermal
(non-magnetic) sunspot model are primarily produced by changes in the wave path
due to the Wilson depression rather than variations in the wave speed. This
shows that inversions for the subsurface structure of sunspots must account for
local changes in the density. In some ranges of horizontal phase speed and
frequency there is agreement (within the noise level in the simulations)
between the travel times measured in the full magnetic sunspot model and the
thermal model. If this conclusion proves to be robust for a wide range of
models, it would suggest a path towards inversions for sunspot structure.Comment: Accepted for publication in The Astrophysical Journa
Testing Helioseismic-Holography Inversions for Supergranular Flows Using Synthetic Data
Supergranulation is one of the most visible length scales of solar convection
and has been studied extensively by local helioseismology. We use synthetic
data computed with the Seismic Propagation through Active Regions and
Convection (SPARC) code to test regularized-least squares (RLS) inversions of
helioseismic holography measurements for a supergranulation-like flow. The code
simulates the acoustic wavefield by solving the linearized three-dimensional
Euler equations in Cartesian geometry. We model a single supergranulation cell
with a simple, axisymmetric, mass-conserving flow.
The use of simulated data provides an opportunity for direct evaluation of
the accuracy of measurement and inversion techniques. The RLS technique applied
to helioseismic-holography measurements is generally successful in reproducing
the structure of the horizontal flow field of the model supergranule cell. The
errors are significant in horizontal-flow inversions near the top and bottom of
the computational domain as well as in vertical-flow inversions throughout the
domain. We show that the errors in the vertical velocity are due largely to
cross talk from the horizontal velocity.Comment: 22 pages, 12 figues, accepted for publication in Solar Physic
Mobile integrated conditional access system
This paper presents design of a novel security architecture integrating mobile and broadcasting technologies in the Pay-TV system. The security architecture proposed herein is a state-of-the-art solution to tackle well-known problems challenging current Pay-TV systems including but not limited to interoperability amongst service providers, relatively high cost of the service deployment, the security compromise, limited interactivity and bespoken services offered to subscribers. It also proposes the Follow-me service that enables subscribers to access their entitlements via an arbitrary set-top box
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