On the Limits of Analogy Between Self-Avoidance and Topology-Driven Swelling of Polymer Loops

The work addresses the analogy between trivial knotting and excluded volume in looped polymer chains of moderate length, $N<N_0$, where the effects of knotting are small. A simple expression for the swelling seen in trivially knotted loops is described and shown to agree with simulation data. Contrast between this expression and the well known expression for excluded volume polymers leads to a graphical mapping of excluded volume to trivial knots, which may be useful for understanding where the analogy between the two physical forms is valid. The work also includes description of a new method for the computational generation of polymer loops via conditional probability. Although computationally intensive, this method generates loops without statistical bias, and thus is preferable to other loop generation routines in the region $N<N_0$.Comment: 10 pages, 5 figures, supplementary tex file and datafil

Concert recording 2012-11-05

[Track 01]. Danse macabre / Camille Saint-Saens -- [Track 02]. Mazurka / Francis Poulenc -- [Track 03]. Now sleeps the crimson petal / Roger Quilter -- [Track 04]. O cessate di piagarmi / Alessandro Scarlatti -- [Track 05]. Widmung / Robert Schumann -- [Track 06]. Pique dame. Pauline\u27s aria / Peter IIlyich Tchaikovsky -- [Track 07]. Don Giovanni. Deh vieni alla finestra / Wolfgang Amadeus Mozart -- [Track 08]. Manon. Epouse quelque brave fille / Jules Massenet -- Die tote Stadt. Tanzlied des pierrot / Erick Wolfgang Korngold -- [Track 09]. Die Forelle / Franz Schubert -- [Track 10]. Ici-bas / Gabriel Faure -- [Track 11]. Un ballo in maschera. Saper vorreste / Guiseppe Verdi -- [Track 12]. Il Floriodo. Per pieta / Alessandro Stradella -- [Track 13]. Mein schoner stern/ Robert Schumann -- [Track 14]. Fleur jetee / Gabriel Faure -- [Track 15]. A view from the bridge. New York lights / William Bolcom -- [Track 16]. Les nuits d\u27ete. Vilanelle / Hector Berlioz -- [Track 17]. Ständchen / Joseph Marx -- Will there really be a morning? / Andre Previn -- The trees on the mountain / Carlisle Floyd

Local Charge of the nu=5/2 Fractional Quantum Hall State

Electrons in two dimensions and strong magnetic fields effectively lose their kinetic energy and display exotic behavior dominated by Coulomb forces. When the ratio of electrons to magnetic flux quanta in the system is near 5/2, the unique correlated phase that emerges is predicted to be gapped with fractionally charged quasiparticles and a ground state degeneracy that grows exponentially as these quasiparticles are introduced. Interestingly, the only way to transform between the many ground states would be to braid the fractional excitations around each other, a property with applications in quantum information processing. Here we present the first observation of localized quasiparticles at nu=5/2, confined to puddles by disorder. Using a local electrometer to compare how quasiparticles at nu=5/2 and nu=7/3 charge these puddles, we are able to extract the ratio of local charges for these states. Averaged over several disorder configurations and samples, we find the ratio to be 4/3, suggesting that the local charges are e/3 at seven thirds and e/4 at five halves, in agreement with theoretical predictions. This confirmation of localized e/4 quasiparticles is necessary for proposed interferometry experiments to test statistics and computational ability of the state at nu=5/2.Comment: 6 pages, 4 figures corrected titl

Understanding why primary care doctors leave direct patient care: a systematic review of qualitative research

This is the final version. Available on open access from BMJ Publishing Group via the DOI in this recordData availability statement: All data relevant to the study are included in the article or uploaded as supplementary information. No additional data available.Background UK general practitioners (GPs) are leaving direct patient care in significant numbers. We undertook a systematic review of qualitative research to identify factors affecting GPs’ leaving behaviour in the workforce as part of a wider mixed methods study (ReGROUP). Objective To identify factors that affect GPs’ decisions to leave direct patient care. Methods Qualitative interview-based studies were identified and their quality was assessed. A thematic analysis was performed and an explanatory model was constructed providing an overview of factors affecting UK GPs. Non-UK studies were considered separately. Results Six UK interview-based studies and one Australian interview-based study were identified. Three central dynamics that are key to understanding UK GP leaving behaviour were identified: factors associated with low job satisfaction, high job satisfaction and those linked to the doctor–patient relationship. The importance of contextual influence on job satisfaction emerged. GPs with high job satisfaction described feeling supported by good practice relationships, while GPs with poor job satisfaction described feeling overworked and unsupported with negatively impacted doctor–patient relationships. Conclusions Many GPs report that job satisfaction directly relates to the quality of the doctor–patient relationship. Combined with changing relationships with patients and interfaces with secondary care, and the gradual sense of loss of autonomy within the workplace, many GPs report a reduction in job satisfaction. Once job satisfaction has become negatively impacted, the combined pressure of increased patient demand and workload, together with other stress factors, has left many feeling unsupported and vulnerable to burn-out and ill health, and ultimately to the decision to leave general practice

The Geographically Contiguous and Expanding Coastal Range of the Northern Curlytail Lizard (Leiocephalus carinatus armouri ) in Florida

We surveyed for the presence of the Northern Curlytail Lizard, Leiocephalus carinatus armouri, from Port Salerno, Martin County, FL, northward to the Indian River-Brevard county line to determine the extent to which this species occurs along the Florida East Coast. The geographic range of L. c. armouri appears to be uninterrupted along the coast from northern Broward County through Palm Beach County. The heavily modified coastal habitat provided this species with the open sunny conditions and cement analogues to the rocky substratum to which it is adapted. Its ubiquity, rate of geographic expansion, combined with its carnivorous habits and large body size, have long since set the stage for an extensive restructuring of the indigenous and exotic lizard fauna in a way that has not been seen since its initial establishment in Palm Beach County almost one-half century ago. Urban heat island effects notwithstanding, frost isotherms predict instability of populations north of Fort Pierce and just below Sarasota on the West Coast

Negative refraction in hyperbolic hetero-bicrystals

We visualized negative refraction of phonon-polaritons in hetero-bicrystals of two hyperbolic van der Waals materials: molybdenum oxide (MoO3) and isotopically pure hexagonal boron nitride (h11BN). The polaritons - hybrids of infrared photons and lattice vibrations - form collimated rays that display negative refraction when passing through a planar interface between the h11BN and MoO3 crystals. At a special frequency ω0, these rays can circulate along closed diamond-shaped trajectories. We show that polariton eigenmodes display regions of both positive and negative dispersion interrupted by multiple gaps resulting from polaritonic level repulsion

Abundance of unknots in various models of polymer loops

A veritable zoo of different knots is seen in the ensemble of looped polymer chains, whether created computationally or observed in vitro. At short loop lengths, the spectrum of knots is dominated by the trivial knot (unknot). The fractional abundance of this topological state in the ensemble of all conformations of the loop of $N$ segments follows a decaying exponential form, $\sim \exp (-N/N_0)$, where $N_0$ marks the crossover from a mostly unknotted (ie topologically simple) to a mostly knotted (ie topologically complex) ensemble. In the present work we use computational simulation to look closer into the variation of $N_0$ for a variety of polymer models. Among models examined, $N_0$ is smallest (about 240) for the model with all segments of the same length, it is somewhat larger (305) for Gaussian distributed segments, and can be very large (up to many thousands) when the segment length distribution has a fat power law tail.Comment: 13 pages, 6 color figure