2,159 research outputs found
Low temperature acoustic properties of amorphous silica and the Tunneling Model
Internal friction and speed of sound of a-SiO(2) was measured above 6 mK
using a torsional oscillator at 90 kHz, controlling for thermal decoupling,
non-linear effects, and clamping losses. Strain amplitudes e(A) = 10^{-8} mark
the transition between the linear and non-linear regime. In the linear regime,
excellent agreement with the Tunneling Model was observed for both the internal
friction and speed of sound, with a cut-off energy of E(min) = 6.6 mK. In the
non-linear regime, two different behaviors were observed. Above 10 mK the
behavior was typical for non-linear harmonic oscillators, while below 10 mK a
different behavior was found. Its origin is not understood.Comment: 1 tex file, 6 figure
Feature Nets: behavioural modelling of software product lines
Software product lines (SPL) are diverse systems that are developed using a dual engineering process: (a)family engineering defines the commonality and variability among all members of the SPL, and (b) application engineering derives specific products based on the common foundation combined with a variable selection of features. The number of derivable products in an SPL can thus be exponential in the number of features. This inherent complexity poses two main challenges when it comes to modelling: Firstly, the formalism used for modelling SPLs needs to be modular and scalable. Secondly, it should ensure that all products behave correctly by providing the ability to analyse and verify complex models efficiently. In this paper we propose to integrate an established modelling formalism (Petri nets) with the domain of software product line engineering. To this end we extend Petri nets to Feature Nets. While Petri nets provide a framework for formally modelling and verifying single software systems, Feature Nets offer the same sort of benefits for software product lines. We show how SPLs can be modelled in an incremental, modular fashion using Feature Nets, provide a Feature Nets variant that supports modelling dynamic SPLs, and propose an analysis method for SPL modelled as Feature Nets. By facilitating the construction of a single model that includes the various behaviours exhibited by the products in an SPL, we make a significant step towards efficient and practical quality assurance methods for software product lines
Characterisation of detachment in the MAST-U Super-X divertor using multi-wavelength imaging of 2D atomic and molecular emission processes
In this work, we provide the first 2D spatially resolved description of radiative detachment in MAST-U Super-X L-mode divertor plasmas. The Super-X magnetic configuration was designed to achieve reduced heat- and particle loads at the divertor target compared to conventional exhaust solutions. We use filtered camera imaging to reconstruct 2D emissivity profiles in the poloidal plane for multiple atomic and molecular emission lines and bands. A set of deuterium fuelling scans is discussed that, together, span attached to deeply detached divertor states observed in MAST-U. Emissivity profiles facilitate separate analysis of locked-mode induced split branches of the scrape-off layer. Molecular deuterium Fulcher band emission front tracking reveals that the deuterium electron-impact ionisation front, for which it serves a proxy, detaches at different upstream electron densities in the split branches. Upon detachment of this ionisation front, Balmer emission attributed to molecular activated recombination appears near-target. We report a simultaneous radial broadening of the emission leg, consistent with previous SOLPS-ITER modelling. With increased fuelling this emission region detaches, implying electron temperatures below ∼ 1 eV. In this phase, 2D Balmer line ratio reconstruction indicates an onset of volumetric direct electron-ion recombination near-target. At the highest fuelling rates this emission region moves off-target, suggesting a drop in near-wall electron density accompanying the low temperatures.</p
Developing more environmentally friendly and nutritious pea varieties
Non-Peer ReviewedPhytate is the major storage form of phosphorus in crop seeds, but is not well digested by humans
and non-ruminant animals. In addition, phytate chelates several essential micronutrients which are also
excreted contributing to phosphorus pollution in the environment. Environmental and nutritional concerns
led to the development of cultivars with the low phytate trait. The present study is aimed at biochemical
and molecular characterization of two low phytate pea mutant lines, 1-150-81 and 1-2347-144 developed
at the Crop Development Centre, University of Saskatchewan in collaboration with Dr. Victor Raboy,
USDA, Idaho. Biochemical characterization is in progress for the two low phytate lines, their progenitor,
CDC Bronco and CDC Meadow that were grown in replicated field trials at Saskatoon and Rosthern, SK
in 2010 and 2011. Samples of developing seeds were collected 7 days after pollination and at weekly
intervals thereafter until maturity. The concentration of phytate-phosphorus, isomeric forms of phytatephosphorus and inorganic phosphorus in these developing cotyledons and seed coats will be assessed
using colorimetric and HPLC methods. In this way, the pattern of phytate-phosphorus and inorganic
phosphorus accumulation will be determined in developing seeds.
Molecular characterization will include cloning, sequencing and mapping of the gene(s) associated
with the low phytate trait. Molecular markers will be developed based on the gene sequences.
Recombinant inbred lines (RILs) were developed from crosses between the two low phytate lines and
CDC Meadow. One set of RILs was evaluated in a field trial in Saskatchewan in 2011, and will be
evaluated again in 2012. The RILs will be genotyped using available microsatellite markers or SNP
markers and phenotyped using colorimetric and HPLC assays. These data will then be used to identify
the molecular marker(s) for the trait. The study will aid us to understand the nature of the low phytate
mutation(s). Significant potential benefits that we could expect out of the project include improved
bioavailability of phosphorus, iron and zinc in foods and feeds, less phosphorus excretion and
environmental pollution and a substantial saving in feed costs
“What smell?” Temporarily loading visual attention induces a prolonged loss of olfactory awareness
The human sense of smell is highly sensitive, often conveying important biological signals. Yet, anecdotal evidence suggests that we commonly fail to notice supra-threshold environmental olfactory stimuli. The determinants of olfactory awareness are, as yet, unknown. Here, we adapted the ‘inattentional blindness’ paradigm, to test whether olfactory awareness is dependent on attention. Across three experiments, participants performed a visual search task with either a high or low perceptual load (a well-established attentional manipulation) while exposed to an ambient coffee aroma. Consistent with our hypothesis, task load modulated olfactory awareness: 42.5% fewer participants in the high (vs. low) load condition reported noticing the coffee aroma. Our final experiment demonstrates that, due to unique characteristics of olfactory habituation, the consequences of inattentional anosmia can persist even once attention becomes available. These findings establish the phenomenon of inattentional anosmia, and have applied implications for predicting when people may miss potentially important olfactory information
Elastic response of [111]-tunneling impurities
We study the dynamic response of a [111] quantum impurity, such as lithium or
cyanide in alkali halides, with respect to an external field coupling to the
elastic quadrupole moment. Because of the particular level structure of a
eight-state system on a cubic site, the elastic response function shows a
biexponential relaxation feature and a van Vleck type contribution with a
resonance frequency that is twice the tunnel frequency . This
basically differs from the dielectric response that does not show relaxation.
Moreover, we show that the elastic response of a [111] impurity cannot be
reduced to that of a two-level system. In the experimental part, we report on
recent sound velocity and internal friction measurements on KCl doped with
cyanide at various concentrations. At low doping (45 ppm) we find the dynamics
of a single [111] impurity, whereas at higher concentrations (4700 ppm) the
elastic response rather indicates strongly correlated defects. Our theoretical
model provides a good description of the temperature dependence of
and at low doping, in particular the relaxation peaks, the absolute
values of the amplitude, and the resonant contributions. From our fits we
obtain the value of the elastic deformation potential eV.Comment: 19 pages, 5 figure
Cavitation of Electrons Bubbles in Liquid Helium Below saturation Pressure
We have used a Hartree-type electron-helium potential together with a density
functional description of liquid He and He to study the explosion of
electron bubbles submitted to a negative pressure. The critical pressure at
which bubbles explode has been determined as a function of temperature. It has
been found that this critical pressure is very close to the pressure at which
liquid helium becomes globally unstable in the presence of electrons. It is
shown that at high temperatures the capillary model overestimates the critical
pressures. We have checked that a commonly used and rather simple
electron-helium interaction yields results very similar to those obtained using
the more accurate Hartree-type interaction. We have estimated that the
crossover temperature for thermal to quantum nucleation of electron bubbles is
very low, of the order of 6 mK for He.Comment: 22 pages, 9 figure
The effect of pressure on statics, dynamics and stability of multielectron bubbles
The effect of pressure and negative pressure on the modes of oscillation of a
multi-electron bubble in liquid helium is calculated. Already at low pressures
of the order of 10-100 mbar, these effects are found to significantly modify
the frequencies of oscillation of the bubble. Stabilization of the bubble is
shown to occur in the presence of a small negative pressure, which expands the
bubble radius. Above a threshold negative pressure, the bubble is unstable.Comment: 4 pages, 2 figures, accepted for publication in Physical Review
Letter
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