Enhanced energy transfer to an optomechanical piston from indistinguishable photons

Thought experiments involving gases and pistons, such as Maxwell’s demon and Gibbs’ mixing, are central to our understanding of thermodynamics. Here we present a quantum thermodynamic thought experiment in which the energy transfer from two photonic gases to a piston membrane grows quadratically with the number of photons for indistinguishable gases, while linearly for distinguishable gases. This signature of Bosonic bunching may be observed in optomechanical experiments, highlighting the potential of these systems for the realization of thermodynamic thought experiments in the quantum realm

Gibbs mixing of partially distinguishable photons with a polarising beamsplitter membrane

This is the final version. Available on open access from IOP Publishing via the DOI in this recordFor a thought experiment concerning the mixing of two classical gases, Gibbs concluded that the work that can be extracted from mixing is determined by whether or not the gases can be distinguished by a semi-permeable membrane; that is, the mixing work is a discontinuous function of how similar the gases are. Here we describe an optomechanical setup that generalises Gibbs' thought experiment to partially distinguishable quantum gases. Specifically, we model the interaction between a polarisation dependent beamsplitter, that plays the role of a semi-permeable membrane, and two photon gases of non-orthogonal polarisation. We find that the work arising from the mixing of the gases is related to the potential energy associated with the displacement of the microscopic membrane, and we derive a general quantum mixing work expression, valid for any two photon gases with the same number distribution. The quantum mixing work is found to change continuously with the distinguishability of the two polarised gases. In addition, fluctuations of the work on the microscopic membrane become important, which we calculate for Fock and thermal states of the photon gases. Our findings generalise Gibbs' mixing to the quantum regime and open the door for new quantum thermodynamic (thought) experiments with quantum gases with non-orthogonal polarisations and microscopic pistons that can distinguish orthogonal polarisations.Engineering and Physical Sciences Research Council (EPSRC)Royal Societ

Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

We report an inexpensive nanoscale patterning process for epitaxial lateral overgrowth (ELOG) in AlN layers grown by metal organic vapour phase epitaxy (MOVPE) on sapphire. The pattern was produced by an inductively coupled plasma etch using a self-assembled monolayer of silica spheres on AlN as the lithographic mask. The resulting uniform 1 [small mu ]m length rod structure across a wafer showed a massive reduction in threading dislocations (TDs) when annealed at 1100 [degree]C. Overgrowing homoepitaxial AlN on top of the nanorods, at a temperature of 1100 [degree]C, produced a crack free coalesced film with approximately 4 [small mu ]m of growth, which is formed at a much lower temperature compared to that typically required for microscale ELOG. The improved crystal quality, in terms of TD reduction, of the AlN above the rods was determined by detailed weak beam (WB) electron microscopy studies and showed that the threading dislocation density (TDD) was greatly reduced, by approximately two orders of magnitude in the case for edge-type dislocations. In situ reflectance measurements during the overgrowth allowed for thickness coalescence to be estimated along with wafer curvature changes. The in situ measurements also confirmed that tensile strain built up at a much slower rate in the ELOG AlN layer compared to that of AlN prepared directly on sapphire

Realistic boundary conditions for stochastic simulations of reaction-diffusion processes

Many cellular and subcellular biological processes can be described in terms of diffusing and chemically reacting species (e.g. enzymes). Such reaction-diffusion processes can be mathematically modelled using either deterministic partial-differential equations or stochastic simulation algorithms. The latter provide a more detailed and precise picture, and several stochastic simulation algorithms have been proposed in recent years. Such models typically give the same description of the reaction-diffusion processes far from the boundary of the simulated domain, but the behaviour close to a reactive boundary (e.g. a membrane with receptors) is unfortunately model-dependent. In this paper, we study four different approaches to stochastic modelling of reaction-diffusion problems and show the correct choice of the boundary condition for each model. The reactive boundary is treated as partially reflective, which means that some molecules hitting the boundary are adsorbed (e.g. bound to the receptor) and some molecules are reflected. The probability that the molecule is adsorbed rather than reflected depends on the reactivity of the boundary (e.g. on the rate constant of the adsorbing chemical reaction and on the number of available receptors), and on the stochastic model used. This dependence is derived for each model.Comment: 24 pages, submitted to Physical Biolog

Ultra-high-density arrays of defect-free AlN nanorods: a "space-filling" approach

Nanostructured semiconductors have a clear potential for improved optoelectronic devices, such as high-efficiency light-emitting diodes (LEDs). However, most arrays of semiconductor nanorods suffer from having relatively low densities (or “fill factors”) and a high degree of nonuniformity, especially when produced by self-organized growth. Ideally an array of nanorods for an optoelectronic emitter should have a fill factor close to 100%, with uniform rod diameter and height. In this article we present a “space-filling” approach for forming defect-free arrays of AlN nanorods, whereby the separation between each rod can be controlled to 5 nm due to a self-limiting process. These arrays of pyramidal-topped AlN nanorods formed over wafer-scale areas by metal organic chemical vapor deposition provide a defect-free semipolar top surface, for potential optoelectronic device applications with the highest reported fill factor at 98%

Quadratic Volume Preserving Maps

We study quadratic, volume preserving diffeomorphisms whose inverse is also quadratic. Such maps generalize the Henon area preserving map and the family of symplectic quadratic maps studied by Moser. In particular, we investigate a family of quadratic volume preserving maps in three space for which we find a normal form and study invariant sets. We also give an alternative proof of a theorem by Moser classifying quadratic symplectic maps.Comment: Ams LaTeX file with 4 figures (figure 2 is gif, the others are ps

Procedural Factors Associated With Percutaneous Coronary Intervention-Related Ischemic Stroke

ObjectivesThis study sought to determine whether procedural factors during percutaneous coronary intervention (PCI) are associated with the occurrence of ischemic stroke or transient ischemic attack (PCI-stroke).BackgroundStroke is a devastating complication of PCI. Demographic predictors are nonmodifiable. Whether PCI-stroke is associated with procedural factors, which may be modifiable, is unknown.MethodsWe performed a single-center retrospective study of 21,497 PCI hospitalizations between 1994 and 2008. We compared procedural factors from patients who suffered an ischemic stroke or transient ischemic attack related to PCI (n = 79) and a control group (n = 158), and matched them 2:1 based on a predicted probability of stroke developed from a logistic regression model.ResultsPCI-stroke procedures involved the use of more catheters (median: 3 [quarter (Q) 1, Q3: 3, 4] vs. 3 [Q1, Q3: 2, 3], p < 0.001), greater contrast volumes (250 ml vs. 218 ml, p = 0.006), and larger guide caliber (median: 7-F [Q1, Q3: 6, 8] vs. 6-F [Q1, Q3: 6, 8], p < 0.001). The number of lesions attempted (1.7 ± 0.8 vs. 1.5 ± 0.8, p = 0.14) and stents placed (1.4 ± 1.2 vs. 1.2 ± 1.1, p = 0.35) were similar between groups, but PCI-stroke patients were more likely to have undergone rotational atherectomy (10% vs. 3%, p = 0.029). Overall procedural success was lower in the PCI-stroke group compared with controls (71% vs. 85%, p = 0.017). Evaluation of the entire PCI population revealed no difference in the rate of PCI-stroke between radial and femoral approaches (0.4% vs. 0.4%, p = 0.78).ConclusionsIschemic stroke related to PCI is associated with potentially modifiable technical parameters. Careful procedural planning is warranted, particularly in patients at increased risk

Clinical and service implications of a cognitive analytic therapy model of psychosis

Cognitive analytic therapy (CAT) is an integrative, interpersonal model of therapy predicated on a radically social concept of self, developed over recent years in the UK by Anthony Ryle. A CAT-based model of psychotic disorder has been developed much more recently based on encouraging early experience in this area. The model describes and accounts for many psychotic experiences and symptoms in terms of distorted, amplified or muddled enactments of normal or ‘neurotic’ reciprocal role procedures (RRPs) and of damage at a meta-procedural level to the structures of the self. Reciprocal role procedures are understood in CAT to represent the outcome of the process of internalization of early, sign-mediated, interpersonal experience and to constitute the basis for all mental activity, normal or otherwise. Enactments of maladaptive RRPs generated by early interpersonal stress are seen in this model to constitute a form of ‘internal expressed emotion’. Joint description of these RRPs and their enactments (both internally and externally) and their subsequent revision is central to the practice of CAT during which they are mapped out through written and diagrammatic reformulations. This model may usefully complement and extend existing approaches, notably recent CBT-based interventions, particularly with ‘difficult’ patients, and generate meaningful and helpful understandings of these disorders for both patients and their treating teams. We suggest that use of a coherent and robust model such as CAT could have important clinical and service implications in terms of developing and researching models of these disorders as well as for the training of multidisciplinary teams in their effective treatment

Associated Production of Higgs and Weak Bosons, with H -> b\bar b, at Hadron Colliders

We consider the search for the Higgs boson at a high-luminosity Fermilab Tevatron, an upgraded Tevatron of energy 3.5 TeV, and the CERN Large Hadron Collider, via $WH/ZH$ production followed by H -> bb~ and leptonic decay of the weak vector bosons. We show that each of these colliders can potentially observe the standard Higgs boson in the intermediate-mass range, 80 GeV <m_H < 120 GeV. This mode complements the search for and the study of the intermediate-mass Higgs boson via H -> \gamma\gamma at the LHC. In addition, it can potentially be used to observe the lightest Higgs scalar of the minimal supersymmetric model in a region of parameter space not accessible to CERN LEP II or the LHC (using h -> \gamma\gamma,ZZ^*).Comment: (changed the analysis of ZH production and the figures for susy), 17 pages + 7 figures, ILL-(TH)-94-8, BNL-6034

Gendered Representations of Male and Female Social Actors in Iranian Educational Materials

This research investigates the representations of gendered social actors within the subversionary discourse of equal educational opportunities for males and females in Iranian English as a Foreign Language (EFL) books. Using critical discourse analysis (CDA) as the theoretical framework, the authors blend van Leeuwen’s (Texts and practices: Readings in critical discourse analysis, Routledge, London, 2003) ‘Social Actor Network Model’ and Sunderland’s (Gendered discourses, Palgrave Macmillan, Hampshire, 2004) ‘Gendered Discourses Model’ in order to examine the depictions of male and female social actors within this gendered discourse. The gendered discourse of equal opportunities was buttressed by such representations within a tight perspective in proportion to gender ideologies prevailing in Iran. Resorting to CDA, we can claim that resistance against such gendered discourse in Iranian EFL textbooks militates against such gender norms. These representations of male and female social actors in school books are indicative of an all-encompassing education, reinforcing that the discourse of equal opportunities is yet to be realized in the education system of Iran