3,914 research outputs found
Equilibrium topology of the intermediate state in type-I superconductors of different shapes
High-resolution magneto-optical technique was used to analyze flux patterns
in the intermediate state of bulk Pb samples of various shapes - cones,
hemispheres and discs. Combined with the measurements of macroscopic
magnetization these results allowed studying the effect of bulk pinning and
geometric barrier on the equilibrium structure of the intermediate state.
Zero-bulk pinning discs and slabs show hysteretic behavior due to geometric
barrier that results in a topological hysteresis -- flux tubes on penetration
and lamellae on flux exit. (Hemi)spheres and cones do not have geometric
barrier and show no hysteresis with flux tubes dominating the intermediate
field region. It is concluded that flux tubes represent the equilibrium
topology of the intermediate state in reversible samples, whereas laminar
structure appears in samples with magnetic hysteresis (either bulk or
geometric). Real-time video is available in
http://www.cmpgroup.ameslab.gov/supermaglab/video/Pb.html
NOTE: the submitted images were severely downsampled due to Arxiv's
limitations of 1 Mb total size
Fiscal year 1981 US corn and soybeans pilot preliminary experiment plan, phase 1
A draft of the preliminary experiment plan for the foreign commodity production forecasting project fiscal year 1981 is presented. This draft plan includes: definition of the phase 1 and 2 U.S. pilot objectives; the proposed experiment design to evaluate crop calendar, area estimation, and area aggregation components for corn and soybean technologies using 1978/1979 crop-year data; a description of individual sensitivity evaluations of the baseline corn and soybean segment classification procedure; and technology and data assessment in support of the corn and soybean estimation technology for use in the U.S. central corn belt
Topological Hysteresis in the Intermediate State of Type-I Superconductors
Magneto-optical imaging of thick stress-free lead samples reveals two
distinct topologies of the intermediate state. Flux tubes are formed upon
magnetic field penetration (closed topology) and laminar patterns appear upon
flux exit (open topology). Two-dimensional distributions of shielding currents
were obtained by applying an efficient inversion scheme. Quantitative analysis
of the magnetic induction distribution and correlation with magnetization
measurements indicate that observed topological differences between the two
phases are responsible for experimentally observable magnetic hysteresis.Comment: 4 pages, RevTex
Dynamic Formation of Metastable Intermediate State Patterns in Type-I Superconductors
Structure of the intermediate state in type-I superconducting lead (Pb) is
shown to be very sensitive to the ramp rate of an applied magnetic field. The
configurations of resulting static patterns depend sensitively on the shape of
the specimen. In particular, geometric barrier, present in the samples with
rectangular cross-section, plays an important role in determining the sharp
boundary between the phases of different topology. We propose that seemingly
laminar (stripe) pattern obtained as a result of the fast field ramp is simply
an imprint left behind by the fast-moving flux tubes. Our results confirm that
flux tube phase is topologically favorable.Comment: to be presented at LT-25 (Amsterdam, 2008
Full scale visualization of the wing tip vortices generated by a typical agricultural aircraft
The trajectories of the wing tip vortices of a typical agricultural aircraft were experimentally determined by flight test. A flow visualization method, similar to the vapor screen method used in wind tunnels, was used to obtain trajectory data for a range of flight speeds, airplane configurations, and wing loadings. Detailed measurements of the spanwise surface pressure distribution were made for all test points. Further, a powered 1/8 scale model of the aircraft was designed, built, and used to obtain tip vortex trajectory data under conditions similar to that of the full scale test. The effects of light wind on the vortices were demonstrated, and the interaction of the flap vortex and the tip vortex was clearly shown in photographs and plotted trajectory data
The photospheric solar oxygen project: IV. 3D-NLTE investigation of the 777 nm triplet lines
The solar photospheric oxygen abundance is still widely debated. Adopting the
solar chemical composition based on the "low" oxygen abundance, as determined
with the use of three-dimensional (3D) hydrodynamical model atmospheres,
results in a well-known mismatch between theoretical solar models and
helioseismic measurements that is so far unresolved. We carry out an
independent redetermination of the solar oxygen abundance by investigating the
center-to-limb variation of the OI IR triplet lines at 777 nm in different sets
of spectra with the help of detailed synthetic line profiles based on 3D
hydrodynamical CO5BOLD model atmospheres and 3D non-LTE line formation
calculations with NLTETD. The idea is to simultaneously derive the oxygen
abundance,A(O), and the scaling factor SH that describes the cross-sections for
inelastic collisions with neutral hydrogen relative the classical Drawin
formula. The best fit of the center-to-limb variation of the triplet lines
achieved with the CO5BOLD 3D solar model is clearly of superior quality
compared to the line profile fits obtained with standard 1D model atmospheres.
Our best estimate of the 3D non-LTE solar oxygen abundance is A(O) = 8.76 +/-
0.02, with the scaling factor SH in the range between 1.2 and 1.8. All 1D
non-LTE models give much lower oxygen abundances, by up to -0.15 dex. This is
mainly a consequence of the assumption of a -independent microturbulence.Comment: 25 pages, 17 figures, 7 tables (Accepted for publication in A&A
Knowledge, attitudes and experience associated with testing for prostate cancer: a comparison between male doctors and men in the community
Background: Debate about testing for prostate cancer using prostate-specific antigen (PSA) and digital rectal examination (DRE) continues. The evidence of benefit from screening for prostate cancer using PSA tests is inconclusive, and it is unclear how PSA can be used most effectively in the detection of prostate cancer. Given the lack of consensus, it is important that consumers understand the issues in a way that will permit them to decide whether or not to have a test and, if symptomatic, how their condition is managed.Aims: To compare prostate cancer knowledge, attitudes and testing experiences reported by male doctors and men in the community, despite the lack of evidence of a benefit.Methods : The primary method for ascertaining the attitudes of male doctors (MD) was a telephone survey, with some doctors electing to complete a written survey. Each MD was selected, at random, from a register of male practitioners aged ≥ 49 years of age. A total of 266 MD participated in the survey. The community sample (CS) was accessed using a telephone survey. Five hundred male Victorian residents aged ≥ 49 years of age participated in the study.Results:Knowledge − Overall, 55% of the CS indicated ­correctly that prostate disease is sometimes cancer, compared to 83% of MD.Attitudes − Fifty-five per cent of MD believed men should be tested for prostate disease at least every 2 years, compared to 68% of men in the CS.Testing experience − Forty-five per cent of MD had been tested for prostate cancer in the past, and 92% of those tests were reported as negative. In the CS, 56% had been tested for prostate cancer in the past, and 78% of the results were reported as negative. The ­significant independent predictors of having had a prostate test among MD were: (i) age (≥ 60 years; odds ratio (OR): 1.59; 95% confidence intervals (CI): 1.30−1.88) and (ii) positive attitudes towards regular testing for prostate cancer (OR: 2.27; 95% CI: 1.98−2.56). The significant independent predictors for the CS were: (i) age (≥ 60 years; OR: 1.65; 95% CI: 1.40−1.89), (ii) being married (OR: 1.30; 95% CI: 1.00−1.60), (iii) knowledge that prostate disease was sometimes cancer (OR: 1.46; 95% CI: 1.26−1.66) and (iv) positive attitudes towards regular testing for prostate cancer (OR: 2.12; 95% CI: 1.90−2.34).Conclusions: The results highlight that testing for prostate cancer is widespread in the community and in the medical profession. Further research should be undertaken to identify how to help men make fully informed decisions about prostate cancer testing.<br /
Confinement of knotted polymers in a slit
We investigate the effect of knot type on the properties of a ring polymer
confined to a slit. For relatively wide slits, the more complex the knot, the
more the force exerted by the polymer on the walls is decreased compared to an
unknotted polymer of the same length. For more narrow slits the opposite is
true. The crossover between these two regimes is, to first order, at smaller
slit width for more complex knots. However, knot topology can affect these
trends in subtle ways. Besides the force exerted by the polymers, we also study
other quantities such as the monomer-density distribution across the slit and
the anisotropic radius of gyration.Comment: 9 pages, 6 figures, submitted for publicatio
Performance of spiral-wound membrane modules in organic solvent nanofiltration – Fluid dynamics and mass transfer characteristics
AbstractDuring the past few decades organic solvent nanofiltration has received a great deal of attention and a growing number of studies has been reported on development and optimisation of solvent resistant membranes and their transport mechanism. However, most of these studies have used flat sheet membranes. On the other hand, many researchers studied fluid dynamics and mass transfer in spiral-wound membrane modules, almost exclusively in aqueous solutions. This paper reports the performance of four spiral-wound membrane modules tested in 0–20wt% solutions of sucrose octaacetate in ethyl acetate under various pressures and retentate flowrates. These modules were made of two different types of membranes (a commercial membrane, PuraMem® S600, and a development product, Lab-1, from Evonik Membrane Extraction Technology Limited) and covered three module sizes (1.8″×12″, 2.5″×40″ and 4.0″×40″). All modules had the same feed and permeate spacers. The classical solution diffusion model was applied to describe the transport of solute and solvent through the membrane and regress the unknown model parameters from flat sheet data. Correlations for characterising the fluid dynamics and mass transfer in the spiral-wound membrane modules, as well as the parameters describing the feed and permeate channels, were determined by performing the regression of experimental data of a 1.8″×12″ PuraMem® S600 membrane module. The classical solution–diffusion model, combined with the film theory, was then successfully applied to predict the performance of other modules of larger size (such as the 2.5″×40″ and 4.0″×40″ module sizes) and/or made of a different membrane material (such as Lab-1). The procedure proposed in this paper predicts the performance of a specific module by obtaining a limited number of experimental data for flat sheets and a 1.8″×12″ spiral-wound membrane module only (necessary to obtain the fitting parameters characteristic of the membrane and the module). Furthermore, with this procedure, it is not necessary to know a priori the spacer geometry, because the necessary information about the spacer geometry will be also obtained by regression of few experimental data
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