520 research outputs found
Is it Round? Spectropolarimetry of the Type II-P Supernova 1999em
We present the first multi-epoch spectropolarimetry of a type II plateau
supernova (SN II-P), with optical observations of SN 1999em on days 7, 40, 49,
159, and 163 after discovery. These data are used to probe the geometry of the
electron-scattering atmosphere before, during, and after the plateau phase,
which ended roughly 90 days after discovery. Weak continuum polarization with
an unchanging polarization angle (theta ~ 160 deg) is detected at all epochs,
with p ~ 0.2% on day 7, p ~ 0.3% on days 40 and 49, and p ~ 0.5% in the final
observations. Distinct polarization modulations across strong line features are
present on days 40, 49, 159, and 163. Uncorrected for interstellar polarization
(which is believed to be quite small), polarization peaks are associated with
strong P Cygni absorption troughs and nearly complete depolarization is seen
across the H-alpha emission profile. The temporal evolution of the continuum
polarization and sharp changes across lines indicate polarization intrinsic to
SN 1999em. When modeled in terms of the oblate, electron-scattering atmospheres
of Hoeflich, the observed polarization implies anasphericity of at least 7%
during the period studied. The temporal polarization increase may indicate
greater asphericity deeper into the ejecta. We discuss the implications of
asphericity on the use of type II-P supernovae as primary extragalactic
distance indicators through the expanding photosphere method (EPM). If
asphericity produces directionally dependant flux and peculiar galaxy motions
are characterized by sigma_v_rec = 300 km/s, it is shown that the agreement
between previous EPM measurements of SNe II and distances to the host galaxies
predicted by a linear Hubble law restrict mean SN II asphericity to values less
than 30% (3-sigma) during the photospheric phase.Comment: 65 pages (29 Figures, 4 Tables), Accepted for publication in the June
1, 2001 edition of ApJ. Revised statistical analysis of scatter in Hubble
diagram of previous EPM distances and the implications for mean SN II
asphericit
Chemotherapy-Response Monitoring of Breast Cancer Patients Using Quantitative Ultrasound-Based Intra-Tumour Heterogeneities
© 2017 The Author(s). Anti-cancer therapies including chemotherapy aim to induce tumour cell death. Cell death introduces alterations in cell morphology and tissue micro-structures that cause measurable changes in tissue echogenicity. This study investigated the effectiveness of quantitative ultrasound (QUS) parametric imaging to characterize intra-tumour heterogeneity and monitor the pathological response of breast cancer to chemotherapy in a large cohort of patients (n = 100). Results demonstrated that QUS imaging can non-invasively monitor pathological response and outcome of breast cancer patients to chemotherapy early following treatment initiation. Specifically, QUS biomarkers quantifying spatial heterogeneities in size, concentration and spacing of acoustic scatterers could predict treatment responses of patients with cross-validated accuracies of 82 ± 0.7%, 86 ± 0.7% and 85 ± 0.9% and areas under the receiver operating characteristic (ROC) curve of 0.75 ± 0.1, 0.80 ± 0.1 and 0.89 ± 0.1 at 1, 4 and 8 weeks after the start of treatment, respectively. The patients classified as responders and non-responders using QUS biomarkers demonstrated significantly different survivals, in good agreement with clinical and pathological endpoints. The results form a basis for using early predictive information on survival-linked patient response to facilitate adapting standard anti-cancer treatments on an individual patient basis
Cosmological Constraints on Lorentz Violation in Electrodynamics
Infrared, optical, and ultraviolet spectropolarimetry of cosmological sources
is used to constrain the pure electromagnetic sector of a general
Lorentz-violating standard-model extension. The coefficients for Lorentz
violation are bounded to less than 3x10^{-32}.Comment: 4 pages, accepted for publication in Physical Review Letter
Effectiveness and meaningful use of paediatric surgical safety checklists and their implementation strategies: a systematic review with narrative synthesis
Objective: To examine the effectiveness and meaningful use of paediatric surgical safety checklists (SSCs) and their implementation strategies through a systematic review with narrative synthesis. Summary background data Since the launch of the WHO SSC, checklists have been integrated into surgical systems worldwide. Information is sparse on how SSCs have been integrated into the paediatric surgical environment. Methods: A broad search strategy was created using Pubmed, Embase, CINAHL, Cochrane Central, Web of Science, Science Citation Index and Conference Proceedings Citation Index. Abstracts and full texts were screened independently, in duplicate for inclusion. Extracted study characteristic and outcomes generated themes explored through subgroup analyses and idea webbing. Results: 1826 of 1921 studies were excluded after title and abstract review (kappa 0.77) and 47 after full-text review (kappa 0.86). 20 studies were of sufficient quality for narrative synthesis. Clinical outcomes were not affected by SSC introduction in studies without implementation strategies. A comprehensive SSC implementation strategy in developing countries demonstrated improved outcomes in high-risk surgeries. Narrative synthesis suggests that meaningful compliance is inconsistently measured and rarely achieved. Strategies involving feedback improved compliance. Stakeholder-developed implementation strategies, including team-based education, achieved greater acceptance. Three studies suggest that parental involvement in the SSC is valued by parents, nurses and physicians and may improve patient safety. Conclusions: A SSC implementation strategy focused on paediatric patients and their families can achieve high acceptability and good compliance. SSCs’ role in improving measures of paediatric surgical outcome is not well established, but they may be effective when used within a comprehensive implementation strategy especially for high-risk patients in low-resource settings
Dual-modality gene reporter for in vivo imaging
The ability to track cells and their patterns of gene expression in living organisms can increase our understanding of tissue development and disease. Gene reporters for bioluminescence, fluorescence, radionuclide, and magnetic resonance imaging (MRI) have been described but these suffer variously from limited depth penetration, spatial resolution, and sensitivity. We describe here a gene reporter, based on the organic anion transporting protein Oatp1a1, which mediates uptake of a clinically approved, Gd(3+)-based, hepatotrophic contrast agent (gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid). Cells expressing the reporter showed readily reversible, intense, and positive contrast (up to 7.8-fold signal enhancement) in T1-weighted magnetic resonance images acquired in vivo. The maximum signal enhancement obtained so far is more than double that produced by MRI gene reporters described previously. Exchanging the Gd(3+) ion for the radionuclide, (111)In, also allowed detection by single-photon emission computed tomography, thus combining the spatial resolution of MRI with the sensitivity of radionuclide imaging
Enormous disc of cool gas surrounding the nearby powerful radio galaxy NGC 612 (PKS 0131-36)
We present the detection of an enormous disc of cool neutral hydrogen (HI)
gas surrounding the S0 galaxy NGC 612, which hosts one of the nearest powerful
radio sources (PKS 0131-36). Using the Australia Telescope Compact Array, we
detect M_HI = 1.8 x 10^9 M_sun of HI emission-line gas that is distributed in a
140 kpc wide disc-like structure along the optical disc and dust-lane of NGC
612. The bulk of the gas in the disc appears to be settled in regular rotation
with a total velocity range of 850 km/s, although asymmetries in this disc
indicate that perturbations are being exerted on part of the gas, possibly by a
number of nearby companions. The HI disc in NGC 612 suggests that the total
mass enclosed by the system is M_enc ~ 2.9 x 10^12 sin^-2(i) M_sun, implying
that this early-type galaxy contains a massive dark matter halo. We also
discuss an earlier study by Holt et al. that revealed the presence of a
prominent young stellar population at various locations throughout the disc of
NGC 612, indicating that this is a rare example of an extended radio source
that is hosted by a galaxy with a large-scale star-forming disc. In addition,
we map a faint HI bridge along a distance of 400 kpc in between NGC 612 and the
gas-rich (M_HI = 8.9 x 10^9 M_sun) barred galaxy NGC 619, indicating that
likely an interaction between both systems occurred. From the unusual amounts
of HI gas and young stars in this early-type galaxy, in combination with the
detection of a faint optical shell and the system's high infra-red luminosity,
we argue that either ongoing or past galaxy interactions or a major merger
event are a likely mechanism for the triggering of the radio source in NGC 612.
This paper is part of an ongoing study to map the large-scale neutral hydrogen
properties of nearby radio galaxies. --abridged--Comment: 13 pages, 9 figures. MNRAS in press. See
http://www.blackwell-synergy.com/doi/full/10.1111/j.1365-2966.2008.13142.x
for a full resolution versio
Signals for Lorentz Violation in Electrodynamics
An investigation is performed of the Lorentz-violating electrodynamics
extracted from the renormalizable sector of the general Lorentz- and
CPT-violating standard-model extension. Among the unconventional properties of
radiation arising from Lorentz violation is birefringence of the vacuum. Limits
on the dispersion of light produced by galactic and extragalactic objects
provide bounds of 3 x 10^{-16} on certain coefficients for Lorentz violation in
the photon sector. The comparative spectral polarimetry of light from
cosmologically distant sources yields stringent constraints of 2 x 10^{-32}.
All remaining coefficients in the photon sector are measurable in
high-sensitivity tests involving cavity-stabilized oscillators. Experimental
configurations in Earth- and space-based laboratories are considered that
involve optical or microwave cavities and that could be implemented using
existing technology.Comment: 23 pages REVTe
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Optoacoustic detection of early therapy-induced tumor cell death using a targeted imaging agent
Purpose: The development of new treatments and their deployment in the clinic may be assisted by imaging methods that allow an early assessment of treatment response in individual patients. The C2A domain of Synaptotagmin-I (C2Am), which binds to the phosphatidylserine (PS) exposed by apoptotic and necrotic cells, has been developed as an imaging probe for detecting cell death. Multispectral optoacoustic tomography (MSOT) is a real-time and clinically applicable imaging modality that was used here with a near infrared (NIR) fluorophore-labeled C2Am to image tumor cell death in mice treated with a TNF-related apoptosis-inducing ligand receptor 2 (TRAILR2) agonist and with 5-fluorouracil (5-FU).Experimental Design: C2Am was labeled with a near infrared (NIR) fluorophore and injected intravenously into mice bearing human colorectal TRAIL-sensitive Colo205 and TRAIL-resistant HT-29 xenografts that had been treated with a potent agonist of TRAILR2 and in Colo205 tumors treated with 5-FU.Results: Three dimensional MSOT images of probe distribution showed development of tumor contrast within 3 h of probe administration and a signal-to-background ratio in regions containing dead cells of >10 after 24 h. A site-directed mutant of C2Am that is inactive in PS binding showed negligible binding. Tumor retention of the active probe was strongly correlated (R2=0.97, P valueConclusions: The rapid development of relatively high levels of contrast suggests that NIR fluorophore-labeled C2Am could be a useful optoacoustic imaging probe for detecting early therapy-induced tumor cell death in the clinic.The work was supported by a Cancer Research UK Programme grant
(17242) and a Project grant from MedImmune to KMB and by the CRUK-EPSRC Imaging Centre in Cambridge and Manchester (16465)
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