Asymmetry gap in the electronic band structure of bilayer graphene.

A tight binding model is used to calculate the band structure of bilayer graphene in the presence of a potential difference between the layers that opens a gap U between the conduction and valence bands. In particular, a self consistent Hartree approximation is used to describe imperfect screening of an external gate, employed primarily to control the density n of electrons on the bilayer, resulting in a potential difference between the layers and a density dependent gap U(n). We discuss the influence of a finite asymmetry gap U(0) at zero excess density, caused by the screening of an additional transverse electric field, on observations of the quantum Hall effect

Legality of Age Restrictions in the NBA and NFL

This essay examines age eligibility rules in the National Football League (NFL) and the National Basketball Association (NBA), offers analysis of related antitrust and labor law issues, and shares perspective on underlying policies. As a matter of background, the NFL and the NBA are the only major sports organizations that prohibit players from entrance until a prescribed period after high school graduation. Major League Baseball, the National Hockey League, NASCAR, professional tennis, professional golf, and professional boxing have no such rules. Individuals can also partake in professional acting, theater, music, and other entertainment professions without satisfying a period after high school graduation. The same is true of those who enlist in the U.S. armed forces and in various occupations that require maturity and discipline. Such an employment landscape raises inquiry as to why NFL and NBA teams, unlike so many other employers, would agree to boycott any candidate, regardless of talent or skill, until a prescribed period after high school graduation. This inquiry enjoys heightened interest when considering that NFL and NBA teams are incomparable employers, as players may not play in other leagues for similar compensation

Distributed Optimization in Energy Harvesting Sensor Networks with Dynamic In-network Data Processing

Energy Harvesting Wireless Sensor Networks (EH- WSNs) have been attracting increasing interest in recent years. Most current EH-WSN approaches focus on sensing and net- working algorithm design, and therefore only consider the energy consumed by sensors and wireless transceivers for sensing and data transmissions respectively. In this paper, we incorporate CPU-intensive edge operations that constitute in-network data processing (e.g. data aggregation/fusion/compression) with sens- ing and networking; to jointly optimize their performance, while ensuring sustainable network operation (i.e. no sensor node runs out of energy). Based on realistic energy and network models, we formulate a stochastic optimization problem, and propose a lightweight on-line algorithm, namely Recycling Wasted Energy (RWE), to solve it. Through rigorous theoretical analysis, we prove that RWE achieves asymptotical optimality, bounded data queue size, and sustainable network operation. We implement RWE on a popular IoT operating system, Contiki OS, and eval- uate its performance using both real-world experiments based on the FIT IoT-LAB testbed, and extensive trace-driven simulations using Cooja. The evaluation results verify our theoretical analysis, and demonstrate that RWE can recycle more than 90% wasted energy caused by battery overflow, and achieve around 300% network utility gain in practical EH-WSNs

On orbit validation of solar sailing control laws with thin-film spacecraft

Many innovative approaches to solar sail mission and trajectory design have been proposed over the years, but very few ever have the opportunity to be validated on orbit with real spacecraft. Thin- Film Spacecraft/Lander/Rovers (TF-SL Rs) are a new class of very low cost, low mass space vehicle which are ideal for inexpensively and quickly testing in flight new approaches to solar sailing. This paper describes using TF- SLR based micro solar sails to implement a generic solar sail test bed on orbit. TF -SLRs are high area- to-mass ratio (A/m) spacecraft developed for very low cost consumer and scientific deep space missions. Typically based on a 5 μm or thinner metalised substrate, they include an integrated avionics and payload system -on-chip (SoC) die bonded to the substrate with passive components and solar cells printed or deposited by Metal Organic Chemical Vapour Deposition (MOCVD). The avionics include UHF/S- band transceivers, processors, storage, sensors and attitude control provided by integrated magnetorquers and reflectivity control devices. Resulting spacecraft have a typical thickness of less than 50 μm, are 80 mm in diameter, and have a mass of less than 100 mg resulting in sail loads of less than 20 g/m 2 . TF -SLRs are currently designed for direct dispensing in swarms from free flying 0.5U Interplanetary CubeSats or dispensers attached to launch vehicles. Larger 160 mm, 320 mm and 640 mm diameter TF -SLRs utilizing a CubeSat compatible TWIST deployment mechanism that maintains the high A/m ratio are also under development. We are developing a mission to demonstrate the utility of these devices as a test bed for experimenting with a variety of mission designs and control laws. Batches of up to one hundred TF- SLRs will be released on earth escape trajectories, with each batch executing a heterogeneous or homogenous mixture of control laws and experiments. Up to four releases at different points in orbit are currently envisaged with experiments currently being studied in MATLAB and GMA T including managing the rate of separation of individual spacecraft, station keeping and single deployment/substantially divergent trajectory development. It is also hoped to be able to demonstrate uploading new experiment designs while in orbit and to make this capability available to researchers around the world. A suitable earth escape mission is currently being sought and it is hoped the test bed could be on orbit in 2017/18

Boson Pairs in a One-dimensional Split Trap

We describe the properties of a pair of ultracold bosonic atoms in a one-dimensional harmonic trapping potential with a tunable zero-ranged barrier at the trap centre. The full characterisation of the ground state is done by calculating the reduced single-particle density, the momentum distribution and the two-particle entanglement. We derive several analytical expressions in the limit of infinite repulsion (Tonks-Girardeau limit) and extend the treatment to finite interparticle interactions by numerical solution. As pair interactions in double wells form a fundamental building block for many-body systems in periodic potentials, our results have implications for a wide range of problems.Comment: 9 pages, 8 figure

Impact on maternity professionals of novel approaches to clinical audit feedback

We compared three approaches to feedback of clinical audit findings relating to miscarriage in 15 Scottish maternity services (printed report alone; report plus Action Planning Letter; report plus face-to-face Facilitated Action Planning). We surveyed clinicians to measure Theory of Planned Behaviour constructs (in the context of two audit criteria) before and after feedback (n=253) and assessed perceptions of the audit through in-depth interviews (n=17). Pre-feedback, clinicians had positive attitudes and strong subjective norms and intentions to comply, although perceived behavioural control was lower. Generally, positive attitudes, subjective norms and intentions increased after feedback but for one of the two criteria (providing a 7-day miscarriage service), perceived behavioural control decreased. No changes over time reached statistical significance and analysis of covariance (adjusting for pre-feedback scores) showed no consistent relationships between method of feedback and post-feedback construct scores. Interviews revealed positive perceptions of audit but frustration at lack of capacity to implement changes. While interventions which increased intensity of feedback proved feasible and acceptable to clinicians, we were unable to demonstrate that they increased intention to comply with audit criteria.This study was funded by NHS Quality Improvement Scotland

Tenant mix variety in regional shopping centres: some UK empirical analyses

The variety and quality of the tenant mix within a shopping centre is a key concern in shopping centre management. Tenant mix determines the extent of externalities between outlets in the centre, helps establish the image of the centre and, as a result, determines the attractiveness of the centre for consumers. This then translates into sales and rents. However, the management of tenant mix has largely been based on perceived “optimum” arrangements and industry rules of thumb. This paper attempts to model the impact of tenant mix on the rent paid by retailers in larger UK shopping centres and, hence, the returns made by shopping centre landlords. It extends work on shopping centre rent determination (see Working Paper 10/03) utilising a database of 148 regional shopping centres in the UK, with detailed data for over 1900 tenants. Econometric models test the relationship between rental levels and the levels of retail concentration and diversity, while controlling for a range of continuous and qualitative characteristics of each tenant, each retail product, and each shopping centre. Factor analysis is then used to extract the core retail and service categories from the tenant lists of the 148 shopping centres. The factor scores from these core retailer factors are then tested against rent payable. The results from the empirical analysis allow us to generate some clear analytical and empirical implications for optimal retail management

Rigid Body Constrained Motion Optimization and Control on Lie Groups and Their Tangent Bundles

Rigid body motion requires formulations where rotational and translational motion are accounted for appropriately. Two Lie groups, the special orthogonal group SO(3) and the space of quaternions H, are commonly used to represent attitude. When considering rigid body pose, that is spacecraft position and attitude, the special Euclidean group SE(3) and the space of dual quaternions DH are frequently utilized. All these groups are Lie groups and Riemannian manifolds, and these identifications have profound implications for dynamics and controls. The trajectory optimization and optimal control problem on Riemannian manifolds presents significant opportunities for theoretical development. Riemannian optimization is an attractive approach to tackling these problems because it does not require the imposition of additional space-preserving constraints on the solver. Rather, these constraints are accounted for in the optimization algorithm. As such, implementing these solvers in trajectory optimization and optimal controls problems through direct transcription offers a reduction in the number of constraints imposed on the problem. The on-manifold optimization methodologies are applied to the Lie groups listed above. Then, the direct transcription of the optimal control and trajectory optimization problems on these Riemannian optimization is presented and applied. These trajectories are utilized in an unscented Kalman filter to show how these generated reference trajectories interface with state estimation. Finally, the fundamental equation of mechanics is utilized for generating initial guess trajectories which satisfy path and terminal time constraints. The results contained herein show, for the first time, that direct transcription of trajectory optimization and optimal control problems on Riemannian manifolds may be effectively conducted with on-manifold optimization techniques using relatively simple optimization algorithms

Prediction of Acute and Recurrent Ankle Sprains in Athletes

Ankle sprains are not only among the most common sport-related injuries, but also associated with a high rate of recurrence. While prevention is a favorable approach to reducing the incidence of index and recurrent ankle sprains, identifying individuals at greater risk may improve allocation of preventative resources. This dissertation aimed to accomplish the following through three aims: 1) determine the ability of baseline clinical tests to predict acute lateral ankle sprain (LAS) in an understudied athletic population, 2) describe the degree of residual impairments and activity limitations in athletes returning to play from a LAS, and 3) determine the ability of patient- and disease-oriented outcomes to predict recurrent ankle sprains in athletes returning to play in the same competitive season. In the first aim, baseline anterior star excursion balance test scores (SEBT-ANT) and isometric hip extension strength (HEXT) were not useful predictors of LAS in collegiate women’s soccer players. Participant height produced a prediction model for LAS with excellent sensitivity (0.88) and moderate specificity (0.51). The diagnostic odds ratio (DOR=7.50) and area under the receiver operating characteristic curve (AUROC=0.73) further established the predictive utility of height for injury. Taller collegiate women’s soccer players may be less able to resist external moments exerted on the body, potentially increasing LAS risk. For the second aim, athletes returning to play from a LAS reported low selfreported function based on scores from the Foot and Ankle Ability Measure activity of daily living (FAAM-ADL) and sport (FAAM-S) subscales. Additionally, participants demonstrated significantly lower ankle dorsiflexion range of motion and SEBT-ANT scores, and significantly greater ankle joint swelling and ligamentous laxity of the involved limb compared to the uninvolved limb. The residual impairments and activity limitations exhibited by athletes returning to play may offer a means of identifying individuals at increased risk for recurrent injury and chronic ankle instability. In the third aim, athletes that sustained a recurrent ankle sprain in the same competitive sport season exhibited greater height, mass, and body mass index (BMI) compared to those that did not sustain a recurrent injury. ROC curve analyses and DORs further validated the predictive utility of height (AUROC=0.71, DOR=4.93), mass (AUROC=0.75, DOR=12.21) and BMI (AUROC=0.71, DOR=9.48). A clinical evaluation of pain, ankle joint swelling, ligamentous laxity, ankle dorsiflexion range of motion, SEBT-ANT scores, FAAM-ADL scores, and FAAM-S scores at return to play (RTP) failed to predict recurrent injury status. Similar to the first study, athletes with larger stature may have decreased ability to reverse momentum in the presence of injurious forces. Athletic trainers can use information from this dissertation to determine which athletes are at elevated risk for an acute and recurrent ankle sprain, and ultimately facilitate improved allocation of resources for injury prevention