An electric-field representation of the harmonic XY model

The two-dimensional harmonic XY (HXY) model is a spin model in which the classical spins interact via a piecewise parabolic potential. We argue that the HXY model should be regarded as the canonical classical lattice spin model of phase fluctuations in two-dimensional condensates, as it is the simplest model that guarantees the modular symmetry of the experimental systems. Here we formulate a lattice electric-field representation of the HXY model and contrast this with an analogous representation of the Villain model and the two-dimensional Coulomb gas with a purely rotational auxiliary field. We find that the HXY model is a spin-model analogue of a lattice electric-field model of the Coulomb gas with an auxiliary field, but with a temperature-dependent vacuum (electric) permittivity that encodes the coupling of the spin vortices to their background spin-wave medium. The spin vortices map to the Coulomb charges, while the spin-wave fluctuations correspond to auxiliary-field fluctuations. The coupling explains the striking differences in the high-temperature asymptotes of the specific heats of the HXY model and the Coulomb gas with an auxiliary field. Our results elucidate the propagation of effective long-range interactions throughout the HXY model (whose interactions are purely local) by the lattice electric fields. They also imply that global spin-twist excitations (topological-sector fluctuations) generated by local spin dynamics are ergodically excluded in the low-temperature phase. We discuss the relevance of these results to condensate physics.Comment: 13 pages, 10 figure

Topological-sector fluctuations and ergodicity breaking at the Berezinskii-Kosterlitz-Thouless transition

The Berezinskii-Kosterlitz-Thouless (BKT) phase transition drives the unbinding of topological defects in many two-dimensional systems. In the two-dimensional Coulomb gas, it corresponds to an insulator-conductor transition driven by charge deconfinement. We investigate the global topological properties of this transition, both analytically and by numerical simulation, using a lattice-field description of the two-dimensional Coulomb gas on a torus. The BKT transition is shown to be an ergodicity breaking between the topological sectors of the electric field, which implies a definition of topological order in terms of broken ergodicity. The breakdown of local topological order at the BKT transition leads to the excitation of global topological defects in the electric field, corresponding to different topological sectors. The quantized nature of these classical excitations, and their strict suppression by ergodicity breaking in the low-temperature phase, afford striking global signatures of topological-sector fluctuations at the BKT transition. We discuss how these signatures could be detected in experiments on, for example, magnetic films and cold-atom systems.Comment: 11 pages, 6 figure

Phase order in superfluid helium films

Classic experimental data on helium films are transformed to estimate a finite-size phase order parameter that measures the thermal degradation of the condensate fraction in the two-dimensional superfluid. The order parameter is found to evolve thermally with the exponent $\beta = 3 \pi^2/128$, a characteristic, in analogous magnetic systems, of the Berezinskii-Kosterlitz-Thouless (BKT) phase transition. Universal scaling near the BKT fixed point generates a collapse of experimental data on helium and ferromagnetic films, and implies new experiments and theoretical protocols to explore the phase order. These results give a striking example of experimental finite-size scaling in a critical system that is broadly relevant to two-dimensional Bose fluids.Comment: 6 pages, 2 figure

Guidelines for data management and scientific integrity in ethnography

New protocols for scientific integrity and data management issued by universities, journals, and transnational social science funding agencies are often modelled on medical or psychological research, and do not take account of the specific characteristics of the processes of ethnographic research. These guidelines provide ethnographers with some of the most basic principles of doing such research. They show that the primary response of ethnographers to requests to share research materials with third parties should be to remain aware of the fact that these research materials have been coproduced with their research participants; that the collaborative ethnographic research process resists turning these materials into commodified, impersonal ‘data’ that can be owned and shared publicly; and that therefore the primary response of ethnographers should be to retain custody of research materials

OFDM time and frequency synchronization by spread spectrum pilot technique

Correct time and frequency synchronization is important for the performance of orthogonal frequency division multiplex (OFDM) systems. We evaluate a system where a pseudonoise sequence (PN-sequence) is used for estimation of these synchronization parameters. The PN-sequence is superimposed on the OFDM signal. The system is evaluated by means of the variance of the frequency estimation error and the probability for correct timing synchronization. Both theoretical and simulated results are presented. The proposed technique is very flexible and works also at low signal to noise ratios. The frequency offset range has been significantly increased compared to conventional OFDM synchronizer scheme

Optically pure heterobimetallic helicates from self-assembly and click strategies

Single diastereomer, diamagnetic, octahedral Fe(II) tris chelate complexes are synthesised that contain three pendant pyridine proligands pre-organised for coordination to a second metal. They bind Cu(I) and Ag(I) with coordination geometry depending on the identity of the metal and the detail of the ligand structure, but for example homohelical (ΔFe,ΔCu) configured systems with unusual trigonal planar Cu cations are formed exclusively in solution as shown by VT-NMR and supported by DFT calculations. Similar heterobimetallic tris(triazole) complexes are synthesised via clean CuAAC reactions at a tris(alkynyl) complex, although here the configurations of the two metals differ (ΔFe,ΛCu), leading to the first optically pure heterohelicates. A second series of Fe complexes perform less well in either strategy as a result of lack of preorganisation

Protein synthesis in skeletal muscle following acute exhaustive exercise

Cell-free and whole-tissue protein synthesis was studied in skeletal muscle of untrained male guinea pigs that had undergone a treadmill run to exhaustion. Experiments using explants from the gastrocnemius muscle maintained in organ culture demonstrated that the ability of the acutely exercised muscle to incorporate amino acids into protein had increased. Compared to polyribosomes prepared from several lower hind limb muscles of nonexercised guinea pigs, polyribosomes from the same muscle in exhausted guinea pigs had incorporated almost 50% more radioactive leucine into protein. However, the polysome profiles of control and exercised muscle were identical, and no difference in the total polysome RNA content could be detected. The efficiency of in-vitro protein synthesis using washed membrane-bound polyribosomes (microsomes) isolated from acutely exercised skeletal muscle was 50% greater than with microsomes from rested control muscle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50128/1/880020403_ftp.pd

Simulation-based training for increasing health service board members' effectiveness : protocol for a cluster-randomised controlled trial

Introduction Research indicates that health service boards can influence quality of care. However, government reviews have indicated that board members may not be as effective as possible in attaining this goal. Simulation-based training may help to increase board members' ability to effectively communicate and hold hospital staff to account during board meetings. Methods and analysis To test effectiveness and feasibility, a prospective, cluster-randomised controlled trial will be used to compare simulation-based training with no training. Primary outcome variables will include board members' perceived skill and confidence in communicating effectively during board meetings, and board members' perceptions of board meeting processes. These measures will be collected both immediately before training, and 3 months post-training, with boards randomly assigned to intervention or control arms. Primary analyses will comprise generalised estimating equations examining training effects on each of the primary outcomes. Secondary analyses will examine participants' feedback on the training. Ethics and dissemination Research ethics approval has been granted by Monash University (reference number: 2018-12076). We aim to disseminate results through peer-reviewed journal publication, conference presentation and social media. Trial registration number Open Science Framework: http://osf.io/jaxt6/; Pre-results. © 2019 Author(s). **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Jane Boag” is provided in this record*

Channel Capacity Limits of Cognitive Radio in Asymmetric Fading Environments

Cognitive radio technology is an innovative radio design concept which aims to increase spectrum utilization by exploiting unused spectrum in dynamically changing environments. By extending previous results, we investigate the capacity gains achievable with this dynamic spectrum approach in asymmetric fading channels. More specifically, we allow the secondary-to-primary and secondary-to-secondary user channels to undergo Rayleigh or Rician fading, with arbitrary link power. In order to compute the capacity, we derive the distributions of ratios of Rayleigh and Rician variables. Compared to the symmetric fading scenario, our results indicate several interesting features of the capacity behaviour under both average and peak received power constraints. Finally, the impact of multiple primary users on the capacity under asymmetric fading has also been studied.Comment: 6 pages, 8 figures, in Proceedings of IEEE International Conference on Communications (ICC 2008), Beijing, China, May 19-23, 200