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

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

A downward revision to the distance of the 1806-20 cluster and associated magnetar from Gemini near-Infrared spectroscopy

We present H- and K-band spectroscopy of OB and Wolf-Rayet (WR) members of the Milky Way cluster 1806-20 (G10.0-0.3), to obtain a revised cluster distance of relevance to the 2004 giant flare from the SGR 1806-20 magnetar. From GNIRS spectroscopy obtained with Gemini South, four candidate OB stars are confirmed as late O/early B supergiants, while we support previous mid WN and late WC classifications for two WR stars. Based upon an absolute Ks-band magnitude calibration for B supergiants and WR stars, and near-IR photometry from NIRI at Gemini North plus archival VLT/ISAAC datasets, we obtain a cluster distance modulus of 14.7+/-0.35 mag. The known stellar content of the 1806-20 cluster suggests an age of 3-5 Myr, from which theoretical isochrone fits infer a distance modulus of 14.7+/-0.7 mag. Together, our results favour a distance modulus of 14.7+/-0.4 mag (8.7^+1.8_-1.5 kpc) to the 1806-20 cluster, which is significantly lower than the nominal 15 kpc distance to the magnetar. For our preferred distance, the peak luminosity of the December 2004 giant flare is reduced by a factor of three to 7 X 10^46 erg/s, such that the contamination of BATSE short gamma ray bursts (GRB's) from giant flares of extragalactic magnetars is reduced to a few percent. We infer a magnetar progenitor mass of ~48^+20_-8 Msun, in close agreement with that obtained recently for the magnetar in Westerlund 1.Comment: 6 pages, 4 figures, accepted for MNRAS Letter

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

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

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

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