2,903 research outputs found
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
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 Zealandâs 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 publicâs acceptance of radical changes to existing higher education structures.fals
Collective excitation spectrum of a disordered Hubbard model
We study the collective excitation spectrum of a d=3 site-disordered
Anderson-Hubbard model at half-filling, via a random-phase approximation (RPA)
about broken-symmetry, inhomogeneous unrestricted Hartree-Fock (UHF) ground
states. We focus in particular on the density and character of low-frequency
collective excitations in the transverse spin channel. In the absence of
disorder, these are found to be spin-wave-like for all but very weak
interaction strengths, extending down to zero frequency and separated from a
Stoner-like band, to which there is a gap. With disorder present, a prominent
spin-wave-like band is found to persist over a wide region of the
disorder-interaction phase plane in which the mean-field ground state is a
disordered antiferromagnet, despite the closure of the UHF single-particle gap.
Site resolution of the RPA excitations leads to a microscopic rationalization
of the evolution of the spectrum with disorder and interaction strength, and
enables the observed localization properties to be interpreted in terms of the
fraction of strong local moments and their site-differential distribution.Comment: 25 pages (revtex), 9 postscript 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(26â34) 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
T cell receptor VÎČ staining identifies the malignant clone in adult T cell leukemia and reveals killing of leukemia cells by autologous CD8+ T cells
There is growing evidence that CD8+ cytotoxic T lymphocyte (CTL) responses can contribute to long-term remission of many malignancies. The etiological agent of adult T-cell leukemia/lymphoma (ATL), human T lymphotropic virus type-1 (HTLV-1), contains highly immunogenic CTL epitopes, but ATL patients typically have low frequencies of cytokine-producing HTLV-1-specific CD8+ cells in the circulation. It remains unclear whether patients with ATL possess CTLs that can kill the malignant HTLV-1 infected clone. Here we used flow cytometric staining of TCRVÎČ and cell adhesion molecule-1 (CADM1) to identify monoclonal populations of HTLV-1-infected T cells in the peripheral blood of patients with ATL. Thus, we quantified the rate of CD8+-mediated killing of the putative malignant clone in ex vivo blood samples. We observed that CD8+ cells from ATL patients were unable to lyse autologous ATL clones when tested directly ex vivo. However, short in vitro culture restored the ability of CD8+ cells to kill ex vivo ATL clones in some donors. The capacity of CD8+ cells to lyse HTLV-1 infected cells which expressed the viral sense strand gene products was significantly enhanced after in vitro culture, and donors with an ATL clone that expressed the HTLV-1 Tax gene were most likely to make a detectable lytic CD8+ response to the ATL cells. We conclude that some patients with ATL possess functional tumour-specific CTLs which could be exploited to contribute to control of the disease
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
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
ISO continuum observations of quasars at z=1-4 I.Spectral energy distributions of quasars from the UV to far-infrared
Eight luminous quasars with at z = 1.4 - 3.7 have been
observed in the mid- and far-infrared using ISO. All the quasars have been
detected in the mid-infrared bands of ISOCAM, while no far-infrared detections
have been made with ISOPHOT. Supplementing ISO observations with photometry in
the optical and near-infrared made from the ground mostly within 17 months
after the ISO observations, SEDs (Spectral Energy Distributions) from the UV to
far-infrared have been obtained. SEDs (Spectral Energy Distributions) from the
UV to far-infrared have been obtained while supplementing ISO observations with
photometry in the optical and near-infrared made from the ground within 17
months. The SEDs are compared with the MED (Mean spectral Energy Distributions)
of low-redshift quasars with . It is shown that our
far-infrared observations were limited by confusion noise due to crowded
sources.Comment: 9 pages, 3 figures: accepted for publication in Astronomy and
Astrophysic
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
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