492 research outputs found
Non-local Correlations are Generic in Infinite-Dimensional Bipartite Systems
It was recently shown that the nonseparable density operators for a bipartite
system are trace norm dense if either factor space has infinite dimension. We
show here that non-local states -- i.e., states whose correlations cannot be
reproduced by any local hidden variable model -- are also dense. Our
constructions distinguish between the cases where both factor spaces are
infinite-dimensional, where we show that states violating the CHSH inequality
are dense, and the case where only one factor space is infinite-dimensional,
where we identify open neighborhoods of nonseparable states that do not violate
the CHSH inequality but show that states with a subtler form of non-locality
(often called "hidden" non-locality) remain dense.Comment: 8 pages, RevTe
Mixed State Entanglement: Manipulating Polarisation-Entangled Photons
There has been much discussion recently regarding entanglement
transformations in terms of local filtering operations and whether the optimal
entanglement for an arbitrary two-qubit state could be realised. We introduce
an experimentally realisable scheme for manipulating the entanglement of an
arbitrary state of two polarisation entangled qubits. This scheme is then used
to provide some perspective to the mathematical concepts inherent in this field
with respect to a laboratory environment. Specifically, we look at how to
extract enhanced entanglement from systems with a fixed rank and in the case
where the rank of the density operator for the state can be reduced, show how
the state can be made arbitrarily close to a maximally entangled pure state. In
this context we also discuss bounds on entanglement in mixed states.Comment: 12 pages, 10 figure
Distillability and partial transposition in bipartite systems
We study the distillability of a certain class of bipartite density operators
which can be obtained via depolarization starting from an arbitrary one. Our
results suggest that non-positivity of the partial transpose of a density
operator is not a sufficient condition for distillability, when the dimension
of both subsystems is higher than two.Comment: 8 pages, 1 figur
Absolute Flux Calibration of the IRAC Instrument on the Spitzer Space Telescope using Hubble Space Telescope Flux Standards
The absolute flux calibration of the James Webb Space Telescope will be based
on a set of stars observed by the Hubble and Spitzer Space Telescopes. In order
to cross-calibrate the two facilities, several A, G, and white dwarf (WD) stars
are observed with both Spitzer and Hubble and are the prototypes for a set of
JWST calibration standards. The flux calibration constants for the four Spitzer
IRAC bands 1-4 are derived from these stars and are 2.3, 1.9, 2.0, and 0.5%
lower than the official cold-mission IRAC calibration of Reach et al. (2005),
i.e. in agreement within their estimated errors of ~2%. The causes of these
differences lie primarily in the IRAC data reduction and secondarily in the
SEDs of our standard stars. The independent IRAC 8 micron band-4 fluxes of
Rieke et al. (2008) are about 1.5 +/- 2% higher than those of Reach et al. and
are also in agreement with our 8 micron result.Comment: 16 pages, 6 figure
The COPE LBP trial: Cognitive Patient Education for Low Back Pain - a cluster randomized controlled trial in primary care
<p>Abstract</p> <p>Background</p> <p>Non-specific low back pain (LBP) is usually self-limiting within 4-6 weeks. Longstanding pain and disability are not predictable from clinical signs or pathoanatomical findings. Pain cognition and physical performance have been shown to improve patients with chronic LBP following neurophysiological education. The primary aim of this study is to evaluate whether a specific cognitive based education programme for patients with LBP in primary care is more effective than normal care in terms of increased function. The secondary aims of the study are to evaluate whether this intervention also results in earlier return to work, decreased pain, increased patient satisfaction, increased quality-of-life, and cost utility.</p> <p>Methods/Design</p> <p>Cluster randomised controlled trial with 20 general practitioners and 20 physiotherapists in primary care as the unit of randomisation. Each practitioner will recruit up to 10 patients, aged 20 to 55 years, with non-specific sub-acute/chronic LBP of more than four weeks but less than 1 year's duration. Practitioners in the intervention arm will provide cognitive patient education intervention in up to four weekly sessions, each lasting 30 minutes. Practitioners in the control arm will provide normal treatment, but have to make four appointments for the patients. Patients, outcome assessors, and study statistician will be blinded to group allocation.</p> <p>Discussion</p> <p>We present the rationale and design of an ongoing RCT study that potentially offers an easily implemented treatment strategy for LBP patients in primary care. The results will be available in 2012.</p> <p>Trial registration</p> <p>ISRCTN04323845</p
High-velocity neon line emission from the ULIRG IRAS F00183-7111: revealing the optically obscured base of a nuclear outflow
We report the first mid-IR detection of highly disturbed ionized gas in the
ultraluminous infrared galaxy IRAS F00183-7111. The gas, traced by the 12.81um
[NeII] and 15.56um [NeIII] lines, spans a velocity range of-3500 to 3000 km/s
with respect to systemic velocity. Optical and near-IR spectroscopic studies
show no evidence for similarly high velocity gas components in forbidden lines
at shorter wavelengths. We interpret this as the result of strong extinction
(Av=10-50) on the high-velocity gas, which identifies the base of the outflow
traced in 5007A [OIII] as a plausible origin. Unusual excitation conditions are
implied by a comparison of the mid-infrared low-excitation neon line emission
and the PAH emission for a sample of 56 ULIRGs. For IRAS F00183, the neon/PAH
ratio is 8 times higher than the average ratio. Similar mid-infrared kinematic
and excitation characteristics are found for only 2 other ULIRGs in our sample:
IRAS 12127-1412NE and IRAS 13451+1232. Both sources have an elevated neon/PAH
ratio and exhibit pronounced blue wings in their 15.56um [NeIII] line profiles.
IRAS 13451 even shows a strongly blue shifted and broad 14.32um [NeV] line.
While for IRAS 13451 the observed [NeIII]/[NeII] and [NeV]/[NeII] line ratios
indicate exposure of the blue shifted gas to direct radiation from the AGN, for
IRAS F00183 and 12127 the neon line ratios are consistent with an origin in
fast shocks in a high-density environment, and with an evolutionary scenario in
which strongly blue shifted [Ne II] and [Ne III] emission trace the (partial)
disruption of the obscuring medium around a buried AGN. The detection of
strongly blue shifted [Ne V] emission in IRAS 13451 would then indicate this
process to be much further advanced in this ULIRG than in IRAS F00183 and
12127, where this line is undetected.Comment: 13 pages, 10 figures, accepted for publication in the Astrophysical
Journa
Stable Isotope Analysis Can Potentially Identify Completely-Digested Bloodmeals in Mosquitoes
Background: Vertebrate bloodfeeding is a critical component of a mosquito’s ability to transmit pathogens that cause diseases such as malaria, dengue fever and viral encephalitis. Due to degradation by the digestive process, current methods to identify mosquito bloodmeal sources are only useful for approximately 36 hours post-feeding. A critical need exists for technologies to extend this window and gain a more complete picture of mosquito feeding behavior for epidemiological studies. Stable isotopes are useful for investigating organism feeding behavior because the isotopic ratio of an organism’s tissues reflects that of the material it ingests. Methodology/Principal Findings: Proof-of-principle data indicates that after bloodfeeding, Aedes albopictus mosquitoes acquire diagnostic Carbon and Nitrogen stable isotope profiles from their vertebrate hosts that can be accurately identified one week post-feeding, approximately 4 days after the entire bloodmeal has been digested. Total C/N ratio served as a biomarker marker for bloodfeeding (P,0.02), while dN was the most informative variable which could distinguish between unfed, chicken-fed and human-fed mosquitoes (P,0.01). By plotting C/N vs. dN, all feeding treatments could be identified in a double-blind analysis. Conclusions/Significance: These proof-of-principle experiments indicate that analysis of stable isotopes can be used to distinguish bloodfed from unfed mosquitoes, and also distinguish between different vertebrate bloodmeal sources eve
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
RBF-TSS: Identification of Transcription Start Site in Human Using Radial Basis Functions Network and Oligonucleotide Positional Frequencies
Accurate identification of promoter regions and transcription start sites (TSS) in genomic DNA allows for a more complete understanding of the structure of genes and gene regulation within a given genome. Many recently published methods have achieved high identification accuracy of TSS. However, models providing more accurate modeling of promoters and TSS are needed. A novel identification method for identifying transcription start sites that improves the accuracy of TSS recognition for recently published methods is proposed. This method incorporates a metric feature based on oligonucleotide positional frequencies, taking into account the nature of promoters. A radial basis function neural network for identifying transcription start sites (RBF-TSS) is proposed and employed as a classification algorithm. Using non-overlapping chunks (windows) of size 50 and 500 on the human genome, the proposed method achieves an area under the Receiver Operator Characteristic curve (auROC) of 94.75% and 95.08% respectively, providing increased performance over existing TSS prediction methods
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