9,823 research outputs found
Generating ring currents, solitons, and svortices by stirring a Bose-Einstein condensate in a toroidal trap
We propose a simple stirring experiment to generate quantized ring currents
and solitary excitations in Bose-Einstein condensates in a toroidal trap
geometry. Simulations of the 3D Gross-Pitaevskii equation show that pure ring
current states can be generated efficiently by adiabatic manipulation of the
condensate, which can be realized on experimental time scales. This is
illustrated by simulated generation of a ring current with winding number two.
While solitons can be generated in quasi-1D tori, we show the even more robust
generation of hybrid, solitonic vortices (svortices) in a regime of wider
confinement. Svortices are vortices confined to essentially one-dimensional
dynamics, which obey a similar phase-offset--velocity relationship as solitons.
Marking the transition between solitons and vortices, svortices are a distinct
class of symmetry-breaking stationary and uniformly rotating excited solutions
of the 2D and 3D Gross-Pitaevskii equation in a toroidal trapping potential.
Svortices should be observable in dilute-gas experiments.Comment: 8 pages, 4 figures; accepted for publication in J. Phys. B (Letters
COVID-19:a unique learning opportunity if the well-being of learners and frontline workers is adequately supported
Spontaneous soliton formation and modulational instability in Bose-Einstein condensates
The dynamics of an elongated attractive Bose-Einstein condensate in an
axisymmetric harmonic trap is studied. It is shown that density fringes caused
by self-interference of the condensate order parameter seed modulational
instability. The latter has novel features in contradistinction to the usual
homogeneous case known from nonlinear fiber optics. Several open questions in
the interpretation of the recent creation of the first matter-wave bright
soliton train [Strecker {\it et al.} Nature {\bf 417} 150 (2002)] are
addressed. It is shown that primary transverse collapse, followed by secondary
collapse induced by soliton--soliton interactions, produce bursts of hot atoms
at different time scales.Comment: 4 pages, 3 figures. Phys. Rev. Lett. in pres
Timed Multiparty Session Types
We propose a typing theory, based on multiparty session types, for modular verification of real-time choreographic interactions. To model real-time implementations, we introduce a simple calculus with delays and a decidable static proof system. The proof system ensures type safety and time-error freedom, namely processes respect the prescribed timing and causalities between interactions. A decidable condition on timed global types guarantees time-progress for validated processes with delays, and gives a sound and complete characterisation of a new class of CTAs with general topologies that enjoys progress and liveness
Evaluation of Northern Illinois Residential Retrofit Delivery Practices
Using a detailed BEopt analysis, PARR has developed packages of measures following a 'loading order' appropriate for cold climates at increasing levels of savings. Packages of measures to provide 'good, better, best' energy savings were determined based on predicted source energy savings, safety issues, program costs and simple payback for customers
The physiology of learning:strategies clinical teachers can adopt to facilitate learning
Almost all pediatricians working in a hospital or office environment have teaching responsibilities to learners such as medical students and residents. Although teaching and supporting learning in a busy work environment imposes challenges to clinical teachers, these clinical settings provide an ideal setup for experiential learning, learning from daily experiences with patients. Advances in the science of learning derived from various fields have informed us how adults learn best. Many techniques and strategies based on this “physiology of learning” have shown their educational values in everyday pediatric practice. This article outlines how clinical teachers can create the conditions to optimize experiential learning for individual or a group of learners. We highlight practical implications of educational theories and evidence-based educational practices for clinical teachers seeking to enhance their teaching effectiveness. These include promoting active learning and engaging learners in deliberate practice; retrieval of knowledge and prior experiences to enhance motivation; supporting a psychologically safe learning environment; helping learners to set goals; fostering collaborative learning; structuring teaching to link it to authentic roles and tasks; and customizing content to individual learners. Conclusion: Applying adult learning principles in everyday teaching activities will support busy pediatricians to be successful in their tasks as clinical teachers, and contribute to work satisfaction
The Arecibo Methanol Maser Galactic Plane Survey - II: Statistical and Multi-wavelength Counterpart Analysis
We present an analysis of the properties of the 6.7 GHz methanol maser sample
detected in the Arecibo Methanol Maser Galactic Plane Survey. The distribution
of the masers in the Galaxy, and statistics of their multi-wavelength
counterparts is consistent with the hypothesis of 6.7 GHz maser emission being
associated with massive young stellar objects. Using the detection statistics
of our survey, we estimate the minimum number of methanol masers in the Galaxy
to be 1275. The l-v diagram of the sample shows the tangent point of the
Carina-Sagittarius spiral arm to be around 49.6 degrees, and suggests
occurrence of massive star formation along the extension of the Crux-Scutum
arm. A Gaussian component analysis of the maser spectra shows the mean
line-width to be 0.38 km/s which is more than a factor of two larger than what
has been reported in the literature. We also find no evidence that faint
methanol masers have different properties than those of their bright
counterparts.Comment: Accepted by ApJ; Revised footnote number 3 on page 8 based on private
communicatio
Severe episodic viral wheeze in preschool children: High risk of asthma at age 5–10 years
In population studies, most children with episodic viral wheeze (EVW) become symptom free by 6 years. We studied the outcome of children with severe EVW, treated and followed up in hospital. We followed up 78 children <4 years, managed by paediatricians for severe EVW, to the age of 5–10 years. We recorded respiratory symptoms, spirometry and exhaled nitric oxide (FeNO). At follow-up, 42 children (54%) had current wheeze or dyspnoea, and 52 (67%) had current asthma. There was no significant difference between children with and without current asthma in FEV1 (p = 0.420), but FeNO was higher in children with current asthma (median (interquartile range) 14.5 (11.25–21.50) ppb) than in those without (12.0 (10.0–13.8) ppb, p = 0.020). Positive family history of asthma was the only factor associated with current asthma (odds ratio 8.77, 95% CI 2.88–26.69, p < 0.001). This remained significant after adjustment for duration of follow-up, gender and parental smoking. Conclusion. Severe EVW at preschool age has a high risk of asthma at age 5–10 years, and this is reinforced by a positive family history of asthma and to elevated FeNO levels
High resolution sub-millimetre mapping of starburst galaxies: Comparison with CO emission
Researchers present first results from a program of submillimeter continuum mapping of starburst galaxies, and comparison of their dust and CO emission. This project was prompted by surprising results from the first target, the nearby starburst M82, which shows in the dust continuum a morphology quite unlike that of its CO emission, in contrast to what might be expected if both CO and dust are accurately tracing the molecular hydrogen. Possible explanations for this striking difference are discussed. In the light of these results, the program has been extended to include sub-mm mapping of the nearby, vigorously star forming spirals, M83 and Maffei 2. The latter were also observed extensively in CO, in order to study excitation conditions in its central regions. The James Clerk Maxwell Telescope was used in these studies
The decay and collisions of dark solitons in superfluid Fermi gases
We study soliton collisions and the decay of solitons into sound in
superfluid Fermi gases across the Bose-Einstein condensate to
Bardeen-Cooper-Schrieffer (BEC-BCS) crossover by performing numerical
simulations of the time-dependent Bogoliubov-de Gennes equations. This decay
process occurs when the solitons are accelerated to the bulk pair-breaking
speed by an external potential. A similar decay process may occur when solitons
are accelerated by an inelastic collision with another soliton. We find that
soliton collisions become increasingly inelastic as we move from the BEC to BCS
regimes, and the excess energy is converted into sound. We interpret this
effect as being due to evolution of Andreev bound states localized within the
soliton.Comment: 9 pages, 5 figure
- …