2,260 research outputs found
Streptococcal pharyngitis and systemic lupus erythematosus
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Weakly Nonlinear Analysis of Electroconvection in a Suspended Fluid Film
It has been experimentally observed that weakly conducting suspended films of
smectic liquid crystals undergo electroconvection when subjected to a large
enough potential difference. The resulting counter-rotating vortices form a
very simple convection pattern and exhibit a variety of interesting nonlinear
effects. The linear stability problem for this system has recently been solved.
The convection mechanism, which involves charge separation at the free surfaces
of the film, is applicable to any sufficiently two-dimensional fluid. In this
paper, we derive an amplitude equation which describes the weakly nonlinear
regime, by starting from the basic electrohydrodynamic equations. This regime
has been the subject of several recent experimental studies. The lowest order
amplitude equation we derive is of the Ginzburg-Landau form, and describes a
forward bifurcation as is observed experimentally. The coefficients of the
amplitude equation are calculated and compared with the values independently
deduced from the linear stability calculation.Comment: 26 pages, 2 included eps figures, submitted to Phys Rev E. For more
information, see http://mobydick.physics.utoronto.c
Ellipsometric measurements of the refractive indices of linear alkylbenzene and EJ-301 scintillators from 210 to 1000 nm
We report on ellipsometric measurements of the refractive indices of LAB-PPO,
Nd-doped LAB-PPO and EJ-301 scintillators to the nearest +/-0.005, in the
wavelength range 210-1000 nm.Comment: 7 pages, 4 figure
Biochar from microwave pyrolysis of selected feedstocks
This is a brief summary of work carried out by a team of researchers to produce biochar using microwave pyrolysis system developed at Bioenergy, Bioproducts Research Lab (BBRL), at UNB. Various feedstocks such as corn stalk, spruce, maple, switchgrass, and wood pellets were used to produce biochar. A batch type microwave reactor with a frequency of 2.45 GHz and a power generator of 3 kW was used in the pyrolysis experiments. The amount of biochar obtained depends on the microwave pyrolysis conditions and type of feedstock. For corn stalk briquettes, the yield of biochar ranged from 30.9 to 41.1 wt%. The average biochar yield for spruce, maple, and switchgrass was found to be 22.2 wt%, 22.0 wt%, and 24.4 wt% respectively.
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UV Degradation of the Optical Properties of Acrylic for Neutrino and Dark Matter Experiments
UV-transmitting (UVT) acrylic is a commonly used light-propagating material
in neutrino and dark matter detectors as it has low intrinsic radioactivity and
exhibits low absorption in the detectors' light producing regions, from 350 nm
to 500 nm. Degradation of optical transmittance in this region lowers light
yields in the detector, which can affect energy reconstruction, resolution, and
experimental sensitivities. We examine transmittance loss as a result of short-
and long-term UV exposure for a variety of UVT acrylic samples from a number of
acrylic manufacturers. Significant degradation peaking at 343 nm was observed
in some UVT acrylics with as little as three hours of direct sunlight, while
others exhibited softer degradation peaking at 310 nm over many days of
exposure to sunlight. Based on their measured degradation results, safe time
limits for indoor and outdoor UV exposure of UVT acrylic are formulated.Comment: 13 pages, 6 figures, 3 tables; To be submitted to Journal of
Instrumentatio
Target Mass Monitoring and Instrumentation in the Daya Bay Antineutrino Detectors
The Daya Bay experiment measures sin^2 2{\theta}_13 using functionally
identical antineutrino detectors located at distances of 300 to 2000 meters
from the Daya Bay nuclear power complex. Each detector consists of three nested
fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to
overflow tanks on top of the detector to allow for thermal expansion of the
liquid. Antineutrinos are detected through the inverse beta decay reaction on
the proton-rich scintillator target. A precise and continuous measurement of
the detector's central target mass is achieved by monitoring the the fluid
level in the overflow tanks with cameras and ultrasonic and capacitive sensors.
In addition, the monitoring system records detector temperature and levelness
at multiple positions. This monitoring information allows the precise
determination of the detectors' effective number of target protons during data
taking. We present the design, calibration, installation and in-situ tests of
the Daya Bay real-time antineutrino detector monitoring sensors and readout
electronics.Comment: 22 pages, 20 figures; accepted by JINST. Changes in v2: minor
revisions to incorporate editorial feedback from JINS
Characteristics and Enablers of Transparency in Product Development Organizations
Risks in product development lead to schedule and cost overruns and poor product quality. While many risk management frameworks have been published and research on specific practices has been conducted, little is understood of key characteristics of successful risk management in product development and how they manifest in real development projects.
This research consists of two phases. The first phase is a survey on 171 best practices in risk management. Analysis of over 200 responses from industry practitioners identified transparency as a key characteristic of successful risk management in product development. Due to the limited exploration of the concept of transparency in the literature, the second phase of this work consisted of a qualitative investigation of transparency through interviews with 15 industry practitioners. Analysis of the interview results suggests a hierarchical structure which decomposes transparency into several characteristics and identifies enablers for each of these characteristics.
We propose that transparency can be a valuable lever for product developers and managers. Future work is needed to validate the generalizability of the observations provided
Annular electroconvection with shear
We report experiments on convection driven by a radial electrical force in
suspended annular smectic A liquid crystal films. In the absence of an
externally imposed azimuthal shear, a stationary one-dimensional (1D) pattern
consisting of symmetric vortex pairs is formed via a supercritical transition
at the onset of convection. Shearing reduces the symmetries of the base state
and produces a traveling 1D pattern whose basic periodic unit is a pair of
asymmetric vortices. For a sufficiently large shear, the primary bifurcation
changes from supercritical to subcritical. We describe measurements of the
resulting hysteresis as a function of the shear at radius ratio . This simple pattern forming system has an unusual combination of
symmetries and control parameters and should be amenable to quantitative
theoretical analysis.Comment: 12 preprint pages, 3 figures in 2 parts each. For more info, see
http://mobydick.physics.utoronto.c
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