2,747 research outputs found
How have MOOCs been portrayed in the New Zealand public media?
Reports of Massive Open Online Courses (MOOCs) hit the news media from 2012 with messages of disruption to existing higher education systems. However, several years on their role is still evolving. Given the power of media to influence acceptance of new ideas, this research investigates New Zealand news media representations of MOOCs to the public. A document analysis of twenty seven newspaper articles published in New Zealand mainstream media between January, 2012 and December, 2016 revealed similar results to overseas research, in that MOOCs are predominantly reported as a catalyst for necessary change to higher education, with higher education commonly discussed in commodified terms. Previously published research focuses on the association of MOOCs and elite universities, whereas this research reveals that MOOCs are considered experimental within New Zealand’s higher education system. While New Zealand media present a more balanced perspective than previous research, dominant themes of MOOCs as revolutionising are likely to foster the public’s acceptance of radical changes to existing higher education structures.fals
Thermal noise in half infinite mirrors with non-uniform loss: a slab of excess loss in a half infinite mirror
We calculate the thermal noise in half-infinite mirrors containing a layer of
arbitrary thickness and depth made of excessively lossy material but with the
same elastic material properties as the substrate. For the special case of a
thin lossy layer on the surface of the mirror, the excess noise scales as the
ratio of the coating loss to the substrate loss and as the ratio of the coating
thickness to the laser beam spot size. Assuming a silica substrate with a loss
function of 3x10-8 the coating loss must be less than 3x10-5 for a 6 cm spot
size and a 7 micrometers thick coating to avoid increasing the spectral density
of displacement noise by more than 10%. A similar number is obtained for
sapphire test masses.Comment: Passed LSC (internal) review. Submitted to Phys. Rev. D. (5/2001)
Replacement: Minor typo in Eq. 17 correcte
A Chandra Snapshot Survey of IR-bright LINERs: A Possible Link Between Star Formation, AGN Fueling, and Mass Accretion
We present results from a high resolution X-ray imaging study of nearby
LINERs observed by Chandra. This study complements and extends previous X-ray
studies of LINERs, focusing on the under-explored population of nearby
dust-enshrouded infrared-bright LINERs. The sample consists of 15 IR-bright
LINERs (L_FIR/L_B > 3), with distances that range from 11 to 26 Mpc. Combining
our sample with previous Chandra studies we find that ~ 51% (28/55) of the
LINERs display compact hard X-ray cores. The nuclear 2-10 keV luminosities of
the galaxies in this expanded sample range from ~ 2 X 10^38 ergs s^-1 to ~ 2 X
10^44 ergs s^-1. We find an intriguing trend in the Eddington ratio vs. L_FIR
and L_FIR/L_B for the AGN-LINERs in the expanded sample that extends over seven
orders of magnitude in L/L_Edd. This correlation may imply a link between black
hole growth, as measured by the Eddington ratio, and the star formation rate
(SFR), as measured by the far-IR luminosity and IR-brightness ratio. If the
far-IR luminosity is an indicator of the molecular gas content in our sample of
LINERs, our results may further indicate that the mass accretion rate scales
with the host galaxy's fuel supply. We discuss the potential implications of
our results in the framework of black hole growth and AGN fueling in low
luminosity AGN. (Abridged)Comment: Accepted for publication by ApJ 14 pages, 13 figure
Cytotoxic T lymphocyte lysis of HTLV-1 infected cells is limited by weak HBZ protein expression, but non-specifically enhanced on induction of Tax expression
BACKGROUND: Immunogenetic evidence indicates that cytotoxic T lymphocytes (CTLs) specific for the weak CTL antigen HBZ limit HTLV-1 proviral load in vivo, whereas there is no clear relationship between the proviral load and the frequency of CTLs specific for the immunodominant antigen Tax. In vivo, circulating HTLV-1-infected cells express HBZ mRNA in contrast, Tax expression is typically low or undetectable. To elucidate the virus-suppressing potential of CTLs targeting HBZ, we compared the ability of HBZ- and Tax-specific CTLs to lyse naturally-infected cells, by co-incubating HBZ- and Tax-specific CTL clones with primary CD4(+) T cells from HLA-matched HTLV-1-infected donors. We quantified lysis of infected cells, and tested whether specific virus-induced host cell surface molecules determine the susceptibility of infected cells to CTL-mediated lysis. RESULTS: Primary infected cells upregulated HLA-A*02, ICAM-1, Fas and TRAIL-R1/2 in concert with Tax expression, forming efficient targets for both HTLV-1-specific CTLs and CTLs specific for an unrelated virus. We detected expression of HBZ mRNA (spliced isoform) in both Tax-expressing and non-expressing infected cells, and the HBZ(26–34) epitope was processed and presented by cells transfected with an HBZ expression plasmid. However, when coincubated with primary cells, a high-avidity HBZ-specific CTL clone killed significantly fewer infected cells than were killed by a Tax-specific CTL clone. Finally, incubation with Tax- or HBZ-specific CTLs resulted in a significant decrease in the frequency of cells expressing high levels of HLA-A*02. CONCLUSIONS: HTLV-1 gene expression in primary CD4(+) T cells non-specifically increases susceptibility to CTL lysis. Despite the presence of HBZ spliced-isoform mRNA, HBZ epitope presentation by primary cells is significantly less efficient than that of Tax. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12977-014-0116-6) contains supplementary material, which is available to authorized users
Modelling the evolution of dusty starburst galaxies in multi-band deep surveys
We model the constraints set on the evolution of dusty starburst galaxies by
the current deep extragalactic surveys performed in the far-infrared with , and at radio wavelengths with the VLA. Our models fit the number
counts in all the available spectral bands well, and also provide a reasonably
close match to the redshift distribution of the detections. We
find: 1.) dusty starburst galaxies with infrared burst phases triggered by
galactic interactions at redshift are good candidates to fit the
results at , and , assuming
plausible strengths for the PAH features for the infrared luminous sources. An
Arp220-like spectral energy distribution (SED) for Ultraluminous Infrared
Galaxies (ULIGs) of and one like that of M82 for
Luminous Infrared Galaxies (LIGs) of give
a successful fit to the and number
counts at flux levels of ; 2.) the strong evolution of the
number density of the ULIGs from redshift to predicted by
our models is consistent with the current deep radio surveys and
accounts for the upturn in the differential counts at the sub-mJy
flux level; and 3.) comparing with number counts at near infrared bands, as
well as the background measurements using DIRBE and 2MASS, shows that only a
fraction of the stellar mass in the Universe is included in our models of dusty
starburst mergers at .Comment: 24 pages, 10 figures, accepted by Ap
Thermoelastic dissipation in inhomogeneous media: loss measurements and displacement noise in coated test masses for interferometric gravitational wave detectors
The displacement noise in the test mass mirrors of interferometric
gravitational wave detectors is proportional to their elastic dissipation at
the observation frequencies. In this paper, we analyze one fundamental source
of dissipation in thin coatings, thermoelastic damping associated with the
dissimilar thermal and elastic properties of the film and the substrate. We
obtain expressions for the thermoelastic dissipation factor necessary to
interpret resonant loss measurements, and for the spectral density of
displacement noise imposed on a Gaussian beam reflected from the face of a
coated mass. The predicted size of these effects is large enough to affect the
interpretation of loss measurements, and to influence design choices in
advanced gravitational wave detectors.Comment: 42 pages, 7 figures, uses REVTeX
Recommended from our members
Attribution of forced decadal climate change in coupled and uncoupled ocean-atmosphere model experiments
There is still no consensus about the best methodology for attributing observed changes in climate or climate events. One widely-used approach relies on experiments in which the time periods of interest are simulated using an atmospheric general circulation model (AGCM) forced by prescribed sea surface temperatures (SSTs), with and without estimated anthropogenic influences. A potential limitation of such experiments is the lack of explicit atmosphere–ocean coupling; therefore a key question is whether the attribution statements derived from such studies are in fact robust. In this research we have carried out climate model experiments to test attribution conclusions in a situation where the answer is known – a so-called “perfect model” approach. The study involves comparing attribution conclusions for decadal changes derived from experiments with a coupled climate model (specifically an AGCM coupled to an ocean mixed-layer model) with conclusions derived from parallel experiments with the same AGCM forced by SSTs derived from the coupled model simulations. Results indicate that attribution conclusions for surface air temperature changes derived from AGCM experiments are generally robust and not sensitive to air-sea coupling. However, changes in seasonal mean and extreme precipitations, and circulation in some regions show large sensitivity to air-sea coupling, notably in the summer monsoons over East Asia and Australia. Comparison with observed changes indicates that the coupled simulations generally agree better with observations. These results demonstrate that the AGCM–based attribution method has limitations and may lead to erroneous attribution conclusions in some regions for local circulation, mean and extreme precipitation. The coupled mixed–layer model used in this study offers an alternative and, in some respects, superior tool for attribution studies
Hard X-ray Luminosities of Multinuclei Infrared Luminous Galaxies Showing a Radio/Far-Infrared Excess
We report the results of hard X-ray observations of four multinuclei merging
infrared luminous galaxies (IRLGs). We selected these four sources for their
excess of radio to far-infrared luminosity ratio compared with starburst
galaxies. This excess suggests that activity associated with a supermassive
black hole (SMBH) contributes strongly to the IRLGs' bolometric luminosities.
Although we expect strong hard X-ray emission from the SMBH-driven activity,
the radio-excess multinuclei merging IRLGs show considerably smaller hard X-ray
luminosities relative to far-infrared (40500 m) and infrared (81000
m) luminosities than active galactic nuclei (AGNs) showing a similar
radio-excess. This result may demonstrate that emission in the hard X-ray
region from SMBH-driven activity in the multinuclei merging IRLGs is severely
suppressed compared to a typical spectral energy distribution of SMBH-driven
activity in AGNs. If this is a common property of merging IRLGs, without its
correction, hard X-ray observations underestimate the contribution of
SMBH-driven activity to the bolometric luminosities of merging IRLGs.Comment: 25 pages of text, 4 figures, aaspp4.sty, Astrophysical Journal, in
press (1999, Volume 527
9.7 um Silicate Features in AGNs: New Insights into Unification Models
We describe observations of 9.7 um silicate features in 97 AGNs, exhibiting a
wide range of AGN types and of X-ray extinction toward the central nuclei. We
find that the strength of the silicate feature correlates with the HI column
density estimated from fitting the X-ray data, such that low HI columns
correspond to silicate emission while high columns correspond to silicate
absorption. The behavior is generally consistent with unification models where
the large diversity in AGN properties is caused by viewing-angle-dependent
obscuration of the nucleus. Radio-loud AGNs and radio-quiet quasars follow
roughly the correlation between HI columns and the strength of the silicate
feature defined by Seyfert galaxies. The agreement among AGN types suggests a
high-level unification with similar characteristics for the structure of the
obscuring material. We demonstrate the implications for unification models
qualitatively with a conceptual disk model. The model includes an inner
accretion disk (< 0.1 pc in radius), a middle disk (0.1-10 pc in radius) with a
dense diffuse component and with embedded denser clouds, and an outer clumpy
disk (10-300 pc in radius).Comment: Accepted for publication in ApJ, 14 pages, 5 figures. The on-line
table is available at http://cztsy.as.arizona.edu/~yong/silicate_tab1.pd
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