Anomalous quantum reflection of Bose-Einstein condensates from a silicon surface: the role of dynamical excitations

We investigate the effect of inter-atomic interactions on the quantum-mechanical reflection of Bose-Einstein condensates from regions of rapid potential variation. The reflection process depends critically on the density and incident velocity of the condensate. For low densities and high velocities, the atom cloud has almost the same form before and after reflection. Conversely, at high densities and low velocities, the reflection process generates solitons and vortex rings that fragment the condensate. We show that this fragmentation can explain the anomalously low reflection probabilities recently measured for low-velocity condensates incident on a silicon surface.Comment: 5 figures, 5 pages, references correcte

Creation of solitons and vortices by Bragg reflection of Bose-Einstein condensates in an optical lattice

We study the dynamics of Bose-Einstein condensates in an optical lattice and harmonic trap. The condensates are set in motion by displacing the trap and initially follow simple semiclassical paths, shaped by the lowest energy band. Above a critical displacement, the condensate undergoes Bragg reflection. For high atom densities, the first Bragg reflection generates a train of solitons and vortices, which destabilize the condensate and trigger explosive expansion. At lower densities, soliton and vortex formation requires multiple Bragg reflections, and damps the center-of-mass motion.Comment: 5 pages including 5 figures (for higher resolution figures please email the authors

Nonlinear resonant tunneling in systems coupled to quantum reservoirs

An adiabatic approximation in terms of instantaneous resonances is developed to study the steady-state and time-dependent transport of interacting electrons in biased resonant tunneling heterostructures. The resulting model consists of quantum reservoirs coupled to regions where the system is described by nonlinear ordinary differential equations and has a general conceptual interest.Comment: 4 pages, 3 postscript figure

The Lexis of Maths Lectures: The Creation of a Pedagogic Corpus and Wordlist from a Series of Maths Lectures

Researchers have investigated discipline-specific and academic vocabulary in multiple academic disciplines through the creation of word lists (Dang, 2018; Gilmore and Millar, 2018; Watson Todd, 2017; Valipouri and Nassajii, 2013). However, there are currently no mathematics wordlists based on spoken corpora that are suitable for the context in question. The present study involved the creation of a context-specific corpus to investigate the frequency of technical and sub-technical vocabulary in a series of mathematics lectures through the creation of a keyword list. The keyword list was created using Sketch Engine from a 152,443-word corpus of 46 mathematics lectures. The final wordlist comprised 202 lemmas, covering 12.89% of the corpus. The benefit of creating a context-specific wordlist was clear. The New Academic Word List (NAWL) (Browne et al., 2013a) provided just 4.51% coverage of the corpus. Assuming students have knowledge of the first 2000 word families of the New General Service List (NGSL) (Browne et al., 2013b), which provided 84% coverage, total coverage was nearly 97% with the mathematics wordlist, compared to 88.67% with the general academic list. Of the 202 lemmas in the mathematics wordlist, 116 were sub-technical, meaning that they are polysemous, with both a general meaning and a mathematical meaning. This is a feature of the language of mathematics and may be an added challenge for students

The Dynamic Characteristics of a High Pressure Turbine Stage in a Transient Wind Tunnel

ABSTRACT A new transient facility for the study of time averaged and unsteady aerodynamics and heat transfer in a high pressure turbine was recently commissioned. During the facility design a high priority was placed on ease of access to the turbine blading to facilitate the development of blade mounted instrumentation. The turbine disc was cantilevered on a shaft by a thin annular link, with the shaft passing back through the disc to a single row and matched pair of relatively closely spaced bearings. The bearings were originally designed for use in a marine gas turbine. Due to the facility's novel mode of operation the bearings were working well beyond some of their original design limits, primarily due to the high turbine acceleration and the high speed/low load condition at the end of facility operation. During the facility design a programme of work was undertaken to predict its dynamic performance. This was continued during commissioning to measure actual facility performance. In this paper the predicted dynamic performance of the disc/shaft assembly and its bearing system are presented. The programme of work undertaken during the facility commissioning phase to ascertain actual dynamic performance is described, and the results discussed. Finally, the technique developed to field balance the rotating assembly following changes to blade instrumentation is described

Perturbative matching of staggered four-fermion operators with hypercubic fat links

We calculate the one-loop matching coefficients between continuum and lattice four-fermion operators for lattice operators constructed using staggered fermions and improved by the use of fattened links. In particular, we consider hypercubic fat links and SU(3) projected Fat-7 links, and their mean-field improved versions. We calculate only current-current diagrams, so that our results apply for operators whose flavor structure does not allow ``eye-diagrams''. We present general formulae, based on two independent approaches, and give numerical results for the cases in which the operators have the taste (staggered flavor) of the pseudo-Goldstone pion. We find that the one-loop corrections are reduced down to the 10-20% level, resolving the problem of large perturbative corrections for staggered fermion calculations of matrix elements.Comment: 37 pages, no figure, 20 table

Buprenorphine versus dihydrocodeine for opiate detoxification in primary care: a randomised controlled trial

Background Many drug users present to primary care requesting detoxification from illicit opiates. There are a number of detoxification agents but no recommended drug of choice. The purpose of this study is to compare buprenorphine with dihydrocodeine for detoxification from illicit opiates in primary care. Methods Open label randomised controlled trial in NHS Primary Care (General Practices), Leeds, UK. Sixty consenting adults using illicit opiates received either daily sublingual buprenorphine or daily oral dihydrocodeine. Reducing regimens for both interventions were at the discretion of prescribing doctor within a standard regimen of not more than 15 days. Primary outcome was abstinence from illicit opiates at final prescription as indicated by a urine sample. Secondary outcomes during detoxification period and at three and six months post detoxification were recorded. Results Only 23% completed the prescribed course of detoxification medication and gave a urine sample on collection of their final prescription. Risk of non-completion of detoxification was reduced if allocated buprenorphine (68% vs 88%, RR 0.58 CI 0.35–0.96, p = 0.065). A higher proportion of people allocated to buprenorphine provided a clean urine sample compared with those who received dihydrocodeine (21% vs 3%, RR 2.06 CI 1.33–3.21, p = 0.028). People allocated to buprenorphine had fewer visits to professional carers during detoxification and more were abstinent at three months (10 vs 4, RR 1.55 CI 0.96–2.52) and six months post detoxification (7 vs 3, RR 1.45 CI 0.84–2.49). Conclusion Informative randomised trials evaluating routine care within the primary care setting are possible amongst drug using populations. This small study generates unique data on commonly used treatment regimens

Perturbative Matching of the staggered four-fermion operators for e'/e

Using staggered fermions, we calculate the perturbative corrections to the bilinear and four-fermion operators that are used in the numerical study of weak matrix elements for $\epsilon'/\epsilon$. We present results for one-loop matching coefficients between continuum operators, calculated in the Naive Dimensional Regularization (NDR) scheme, and gauge invariant staggered fermion operators. These results, combined with existing results for penguin diagrams, provide the complete one-loop renormalization of the staggered four-fermion operators.Comment: 36 pages. will appear in physical review

One Spin Trace Formalism for BK B_K

It has been known for some time that there are two methods to calculate $B_K$ with staggered fermions: one is the two spin trace formalism and the other is the one spin trace formalism. Until now, the two spin trace formalism has been exclusively used for weak matrix element calculations with staggered fermions. Here, the one spin trace formalism to calculate $B_K$ with staggered fermions is explained. It is shown that the one spin trace operators require additional chiral partner operators in order to keep the continuum chiral behavior. The renormalization of the one spin trace operators is described and compared with the two spin trace formalism.Comment: 47 pages, latex, 4 figures are available on reques

The Leeds Evaluation of Efficacy of Detoxification Study (LEEDS) prisons project: a randomised controlled trial comparing dihydrocodeine and buprenorphine for opiate detoxification

<p>Abstract</p> <p>Background</p> <p>Many opiate users entering British prisons require prescribed medication to help them achieve abstinence. This commonly takes the form of a detoxification regime. Previously, a range of detoxification agents have been prescribed without a clear evidence base to recommend a drug of choice. There are few trials and very few in the prison setting. This study compares dihydrocodeine with buprenorphine.</p> <p>Methods</p> <p>Open label, pragmatic, randomised controlled trial in a large remand prison in the North of England. Ninety adult male prisoners requesting an opiate detoxification were randomised to receive either daily sublingual buprenorphine or daily oral dihydrocodeine, given in the context of routine care. All participants gave written, informed consent. Reducing regimens were within a standard regimen of not more than 20 days and were at the discretion of the prescribing doctor. Primary outcome was abstinence from illicit opiates as indicated by a urine test at five days post detoxification. Secondary outcomes were collected during the detoxification period and then at one, three and six months post detoxification. Analysis was undertaken using relative risk tests for categorical data and unpaired t-tests for continuous data.</p> <p>Results</p> <p>64% of those approached took part in the study. 63 men (70%) gave a urine sample at five days post detoxification. At the completion of detoxification, by intention to treat analysis, a higher proportion of people allocated to buprenorphine provided a urine sample negative for opiates (abstinent) compared with those who received dihydrocodeine (57% vs 35%, RR 1.61 CI 1.02–2.56). At the 1, 3 and 6 month follow-up points, there were no significant differences for urine samples negative for opiates between the two groups. Follow up rates were low for those participants who had subsequently been released into the community.</p> <p>Conclusion</p> <p>These findings would suggest that dihydrocodeine should not be routinely used for detoxification from opiates in the prison setting. The high relapse rate amongst those achieving abstinence would suggest the need for an increased emphasis upon opiate maintenance programmes in the prison setting.</p> <p>Trial registration</p> <p>Current Controlled Trials ISRCTN07752728</p