593 research outputs found
Panoramic optical and near-infrared SETI instrument: prototype design and testing
The Pulsed All-sky Near-infrared Optical Search for ExtraTerrestrial
Intelligence (PANOSETI) is an instrument program that aims to search for fast
transient signals (nano-second to seconds) of artificial or astrophysical
origin. The PANOSETI instrument objective is to sample the entire observable
sky during all observable time at optical and near-infrared wavelengths over
300 - 1650 nm. The PANOSETI instrument is designed with a number of modular
telescope units using Fresnel lenses (0.5m) arranged on two geodesic
domes in order to maximize sky coverage. We present the prototype design
and tests of these modular Fresnel telescope units. This consists of the design
of mechanical components such as the lens mounting and module frame. One of the
most important goals of the modules is to maintain the characteristics of the
Fresnel lens under a variety of operating conditions. We discuss how we account
for a range of operating temperatures, humidity, and module orientations in our
design in order to minimize undesirable changes to our focal length or angular
resolution.Comment: 12 pages, 8 figures, 1 tabl
Identifying Factors to Improve Oral Cancer Screening Uptake: A Qualitative Study
Aims: To engage with high risk groups to identify knowledge and awareness of oral cancer signs and symptoms and the factors likely to contribute to improved screening uptake. Methods: Focus group discussions were undertaken with 18 males; 40+ years of age; smokers and/or drinkers (15+ cigarettes per day and/or 15+ units of alcohol per week), irregular dental attenders living in economically deprived areas of Teesside. Results: There was a striking reported lack of knowledge and awareness of oral cancer and its signs and symptoms among the participants. When oral/mouth cancer leaflets produced by Cancer Research UK were presented to the participants, they claimed that they would seek help on noticing such a condition. There was a preference to seek help from their general practitioner rather than their dentist due to perceptions that a dentist is ‘inaccessible ’ on a physical and psychological level, costly, a ‘tooth specialist ’ not a ‘mouth specialist’, and also not able to prescribe medication and make referrals to specialists. Interestingly, none of the 18 participants who were offered a free oral cancer examination at a dental practice took up this offer. Conclusions: The uptake of oral cancer screening may be improved by increasing knowledge of the existence and signs and symptoms of oral cancer. Other factors that may increase uptake are increased awareness of the role of dentists in diagnosing oral cancer, promotion of oral cancer screening by health professionals during routine health checks, and the use of a ‘‘health’ ’ screening setting as opposed to a ‘‘dental’ ’ setting for such checks
Angular momentum and an invariant quasilocal energy in general relativity
Owing to its transformation property under local boosts, the Brown-York
quasilocal energy surface density is the analogue of E in the special
relativity formula: E^2-p^2=m^2. In this paper I will motivate the general
relativistic version of this formula, and thereby arrive at a geometrically
natural definition of an `invariant quasilocal energy', or IQE. In analogy with
the invariant mass m, the IQE is invariant under local boosts of the set of
observers on a given two-surface S in spacetime. A reference energy subtraction
procedure is required, but in contrast to the Brown-York procedure, S is
isometrically embedded into a four-dimensional reference spacetime. This
virtually eliminates the embeddability problem inherent in the use of a
three-dimensional reference space, but introduces a new one: such embeddings
are not unique, leading to an ambiguity in the reference IQE. However, in this
codimension-two setting there are two curvatures associated with S: the
curvatures of its tangent and normal bundles. Taking advantage of this fact, I
will suggest a possible way to resolve the embedding ambiguity, which at the
same time will be seen to incorporate angular momentum into the energy at the
quasilocal level. I will analyze the IQE in the following cases: both the
spatial and future null infinity limits of a large sphere in asymptotically
flat spacetimes; a small sphere shrinking toward a point along either spatial
or null directions; and finally, in asymptotically anti-de Sitter spacetimes.
The last case reveals a striking similarity between the reference IQE and a
certain counterterm energy recently proposed in the context of the conjectured
AdS/CFT correspondence.Comment: 54 pages LaTeX, no figures, includes brief summary of results,
submitted to Physical Review
Pre-eclampsia, soluble fms-like tyrosine kinase 1, and the risk of reduced thyroid function: nested case-control and population based study
Objective To determine if pre-eclampsia is associated with reduced thyroid function during and after pregnancy
Isospin breaking corrections to nucleon form factors in the constituent quark model
We examine isospin breaking in the nucleon wave functions due to the
quark mass difference and the Coulomb interaction among the quarks, and their
consequences on the nucleon electroweak form factors in a nonrelativistic
constituent quark model. The mechanically induced isospin breaking in the
nucleon wave functions and electroweak form factors are exactly evaluated in
this model. We calculate the electromagnetically induced isospin admixtures by
using first-order perturbation theory, including the lowest-lying resonance
with nucleon quantum numbers but isospin 3/2. We find a small (), but
finite correction to the anomalous magnetic moments of the nucleon stemming
almost entirely from the quark mass difference, while the static nucleon axial
coupling remains uncorrected. Corrections of the same order of magnitude appear
in charge, magnetic, and axial radii of the nucleon. The correction to the
charge radius in this model is primarily isoscalar, and may be of some
significance for the extraction of the strangeness radius from e.g. elastic
forward angle parity violating electron-proton asymmetries, or elastic
experiments.Comment: 15 pp(22 as preprint), revtex, 3 uuencoded figs at end of this fil
Panoramic SETI: on-sky results from prototype telescopes and instrumental design
The Panoramic SETI (Search for Extraterrestrial Intelligence) experiment (PANOSETI) aims to detect and quantify optical transients from nanosecond to second precision over a large field-of-view (∼4,450 square-degrees). To meet these challenging timing and wide-field requirements, the PANOSETI experiment will use two assemblies of ∼45 telescopes to reject spurious signals by coincidence detection, each one comprising custom-made fast photon-counting hardware combined with (f/1.32) focusing optics. Preliminary on-sky results from pairs of PANOSETI prototype telescopes (100 sq.deg.) are presented in terms of instrument performance and false alarm rates. We found that a separation of >1 km between telescopes surveying the same field-of-view significantly reduces the number of false positives due to nearby sources (e.g., Cherenkov showers) in comparison to a side- by-side configuration of telescopes. Design considerations on the all-sky PANOSETI instrument and expected field-of-views are reported
Model Channel Ion Currents in NaCl - SPC/E Solution with Applied-Field Molecular Dynamics
Using periodic boundary conditions and a constant applied field, we have
simulated current flow through an 8.125 Angstrom internal diameter, rigid,
atomistic channel with polar walls in a rigid membrane using explicit ions and
SPC/E water. Channel and bath currents were computed from ten 10-ns
trajectories for each of 10 different conditions of concentration and applied
voltage. An electric field was applied uniformly throughout the system to all
mobile atoms. On average, the resultant net electric field falls primarily
across the membrane channel, as expected for two conductive baths separated by
a membrane capacitance. The channel is rarely occupied by more than one ion.
Current-voltage relations are concentration-dependent and superlinear at high
concentrations.Comment: Accepted for publication in Biophysical Journa
Predictive modeling for determination of microscopic residual disease at primary cytoreduction: An NRG Oncology/Gynecologic Oncology Group 182 Study
Microscopic residual disease following complete cytoreduction (R0) is associated with a significant survival benefit for patients with advanced epithelial ovarian cancer (EOC). Our objective was to develop a prediction model for R0 to support surgeons in their clinical care decisions.Demographic, pathologic, surgical, and CA125 data were collected from GOG 182 records. Patients enrolled prior to September 1, 2003 were used for the training model while those enrolled after constituted the validation data set. Univariate analysis was performed to identify significant predictors of R0 and these variables were subsequently analyzed using multivariable regression. The regression model was reduced using backward selection and predictive accuracy was quantified using area under the receiver operating characteristic area under the curve (AUC) in both the training and the validation data sets.Of the 3882 patients enrolled in GOG 182, 1480 had complete clinical data available for the analysis. The training data set consisted of 1007 patients (234 with R0) while the validation set was comprised of 473 patients (122 with R0). The reduced multivariable regression model demonstrated several variables predictive of R0 at cytoreduction: Disease Score (DS) ( < 0.001), stage ( = 0.009), CA125 ( < 0.001), ascites ( < 0.001), and stage-age interaction ( = 0.01). Applying the prediction model to the validation data resulted in an AUC of 0.73 (0.67 to 0.78, 95% CI). Inclusion of DS enhanced the model performance to an AUC of 0.83 (0.79 to 0.88, 95% CI).We developed and validated a prediction model for R0 that offers improved performance over previously reported models for prediction of residual disease. The performance of the prediction model suggests additional factors (i.e. imaging, molecular profiling, etc.) should be explored in the future for a more clinically actionable tool
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