2,979 research outputs found
Limitations in Predicting Radiation-Induced Pharmaceutical Instability during Long-Duration Spaceflight
As human spaceflight seeks to expand beyond low-Earth orbit, NASA and its
international partners face numerous challenges related to ensuring the safety
of their astronauts, including the need to provide a safe and effective
pharmacy for long-duration spaceflight. Historical missions have relied upon
frequent resupply of onboard pharmaceuticals; as a result, there has been
little study into the effects of long-term exposure of pharmaceuticals to the
space environment. Of particular concern are the long-term effects of space
radiation on drug stability, especially as missions venture away from the
protective proximity of the Earth. Here we highlight the risk of space
radiation to pharmaceuticals during exploration spaceflight, identifying the
limitations of current understanding. We further seek to identify ways in which
these limitations could be addressed through dedicated research efforts aimed
towards the rapid development of an effective pharmacy for future spaceflight
endeavors.Comment: in press, Nature Microgravit
Physical Activity Belief Scales for Diabetes Risk: Development and Psychometric Testing
This article describes the development and psychometric evaluation of behavioral belief, normative belief, and
control belief scales, derived from the theory of planned behavior to predict physical activity intentions of persons at risk for diabetes. In Study 1, belief statements from interviews were categorized, ranked, and evaluated for item construction. Content validity was established by 96. 1 % agreement among a five-member expert panel. In Study 2, items developed from the belief statements were administered to 106 adults at risk for diabetes. Psychometric analyses provided evidence of construct validity and reliability of the three scales. Internal consistency was sufficient (α = .76-.95), and test-retest evaluations indicated scale stability (r = .79-
.91). Factor analyses and confirmatory factor analysis using structural equation modeling provided evidence that the items were appropriately grouped under each construct. Researchers and practitioners can use these measures to assess behavioral, normative, and control beliefs about physical activity among persons at risk for diabetes
Preliminary results of fast neutron treatments in carcinoma of the pancreas
A group of 30 patients with adenocarcinoma of the pancreas including some patients with very advanced disease, were treated with the so-called mixed beam modality employing photon treatments three times per week and neutron treatments twice a week. Two hundred Rads or equivalent Rads (RBE 3.3) were given in daily fractions aiming at a total dose of 6000 Rads in 6 to 8 weeks. The treatments were well tolerated and significant palliation was achieved in 26 to 30 cases. Twelve months survival was 33 percent with a median survival of 7 months or 210 days. Treatment techniques and localization procedures are discussed
Platform for enhanced detection efficiency in luminescence-based sensors
Luminescence-based biochip measurement platforms are employed in a wide range of biological applications, such as biomedical diagnostics. Based on an understanding of the anisotropic emission properties of luminescence emitters close to a dielectric interface, a simple strategy for producing a better than 25-fold enhancement of the detected luminescence is presented. This strategy is demonstrated for low cost polymer platforms compatible with mass-production
Eleven years of monitoring the Seyfert 1 Mrk 335 with Swift: Characterizing the X-ray and UV/optical variability
The narrow-line Seyfert 1 galaxy (NLS1) Mrk 335 has been continuously
monitored with Swift since May 2007 when it fell into a long-lasting, X-ray
low-flux interval. Results from the nearly 11 years of monitoring are presented
here. Structure functions are used to measure the UV-optical and X-ray power
spectra. The X-ray structure function measured between 10-100 days is
consistent with the flat, low-frequency part of the power spectrum measured
previously in Mrk 335. The UV-optical structure functions of Mrk 335 are
comparable with those of other Seyfert 1 galaxies and of Mrk 335 itself when it
was in a normal bright state. There is no indication that the current X-ray
low-flux state is attributed to changes in the accretion disc structure of Mrk
335. The characteristic timescales measured in the structure functions can be
attributed to thermal (for the UV) and dynamic (for the optical) timescales in
a standard accretion disc. The high-quality UVW2 (~1800 A in the source frame)
structure function appears to have two breaks and two different slopes between
10-160 days. Correlations between the X-ray and other bands are not highly
significant when considering the entire 11-year light curves, but more
significant behaviour is present when considering segments of the light curves.
A correlation between the X-ray and UVW2 in 2014 (Year-8) may be predominately
caused by an giant X-ray flare that was interpreted as jet-like emission. In
2008 (Year-2), possible lags between the UVW2 emission and other UV-optical
waveband may be consistent with reprocessing of X-ray or UV emission in the
accretion disc.Comment: Figure 8b has been corrected. 12 pages. Accepted for publication in
MNRA
Linearized gravity and gauge conditions
In this paper we consider the field equations for linearized gravity and
other integer spin fields on the Kerr spacetime, and more generally on
spacetimes of Petrov type D. We give a derivation, using the GHP formalism, of
decoupled field equations for the linearized Weyl scalars for all spin weights
and identify the gauge source functions occuring in these. For the spin weight
0 Weyl scalar, imposing a generalized harmonic coordinate gauge yields a
generalization of the Regge-Wheeler equation. Specializing to the Schwarzschild
case, we derive the gauge invariant Regge-Wheeler and Zerilli equation directly
from the equation for the spin 0 scalar.Comment: 24 pages, corresponds to published versio
Edge pixel response studies of edgeless silicon sensor technology for pixellated imaging detectors
Silicon sensor technologies with reduced dead area at the sensor's perimeter are under development at a number of institutes. Several fabrication methods for sensors which are sensitive close to the physical edge of the device are under investigation utilising techniques such as active-edges, passivated edges and current-terminating rings. Such technologies offer the goal of a seamlessly tiled detection surface with minimum dead space between the individual modules. In order to quantify the performance of different geometries and different bulk and implant types, characterisation of several sensors fabricated using active-edge technology were performed at the B16 beam line of the Diamond Light Source. The sensors were fabricated by VTT and bump-bonded to Timepix ROICs. They were 100 and 200 μ m thick sensors, with the last pixel-to-edge distance of either 50 or 100 μ m. The sensors were fabricated as either n-on-n or n-on-p type devices. Using 15 keV monochromatic X-rays with a beam spot of 2.5 μ m, the performance at the outer edge and corners pixels of the sensors was evaluated at three bias voltages. The results indicate a significant change in the charge collection properties between the edge and 5th (up to 275 μ m) from edge pixel for the 200 μ m thick n-on-n sensor. The edge pixel performance of the 100 μ m thick n-on-p sensors is affected only for the last two pixels (up to 110 μ m) subject to biasing conditions. Imaging characteristics of all sensor types investigated are stable over time and the non-uniformities can be minimised by flat-field corrections. The results from the synchrotron tests combined with lab measurements are presented along with an explanation of the observed effects
Strichartz estimates on Schwarzschild black hole backgrounds
We study dispersive properties for the wave equation in the Schwarzschild
space-time. The first result we obtain is a local energy estimate. This is then
used, following the spirit of earlier work of Metcalfe-Tataru, in order to
establish global-in-time Strichartz estimates. A considerable part of the paper
is devoted to a precise analysis of solutions near the trapping region, namely
the photon sphere.Comment: 44 pages; typos fixed, minor modifications in several place
Erratum: Leakage current measurements of a pixelated polycrystalline CVD diamond detector
This is an erratum for the article 2013 JINST 8 C0105
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