Integrable Unsteady Motion With an Application to Ocean Eddies

Application of the Brown-Samelson theorem, which shows that particle motion is integrable in a class of vorticity-conserving, two-dimensional incompressible hows, is extended here to a class of explicit time dependent dynamically balanced flows in multilayered systems. Particle motion for nonsteady two-dimensional flows with discontinuities in the vorticity or potential vorticity fields (modon solutions) is shown to be integrable. An example of a two-layer modon solution constrained by observations of a Gulf Stream ring system is discussed

The role of double diffusive interleaving in mesoscale dynamics: An hypothesis

It is hypothesized that double diffusive interleaving can act to enhance the temperature, salinity and buoyancy signatures of some mesoscale structures. The hypothesis is founded on theoretical results showing that the fluxes produced by double diffusive interleaving can have counter-gradient components, and on the observations that isolated mesoscale rings have a long lifetime and that there is intense interleaving in the frontal zone typically surrounding the ring. Quantitative examples for a warm and a cold core ring demonstrate the feasibility of the hypothesis. Some suggestions are given for extending the hypothesis to include other mesoscale features. Also theoretical investigations and field experiments to test further the hypothesis are suggested

Surface Flow Structure of the Gulf Stream From Composite Imagery and Satellite-Tracked Drifters

A unique set of coutemporaneous satellite-tracked drifters and five-day composite Advanced Very High Resolution Radionmeter (AVHRR) satellite imagery of the North Atlantic has been analyzed to examine the surface flow structure of the Gulf Stream. The study region was divided into two sections, greater than 37 degrees N and less than 37 degrees N, in order to answer the question of geographic variability. Fractal and spectral analyses methods were applied to the data. Fractal analysis of the Lagrangian trajectories showed a fractal dimension of 1.21 +/- 0.02 with a scaling range of 83 - 343 km. The fractal dimension of the temperature fronts of the composite imagery is similar for the two regions with D = 1.11 +/- 0.01 over a scaling range of 4 - 44 km. Spectral analysis also reports a fairly consistent value for the spectral slope and its scaling range. Therefore, we conclude there is no geographic variability in the data set. A suitable scaling range for this contemporaneous data set is 80 - 200 km which is consistent with the expected physical conditions in the region. Finally, we address the idea of using five-day composite imagery to infer the surface flow of the Gulf Stream. Close analyses of the composite thermal fronts and the Lagrangian drifter trajectories show that the former is not a good indicator of the latter

Assessing Human Error Against a Benchmark of Perfection

An increasing number of domains are providing us with detailed trace data on human decisions in settings where we can evaluate the quality of these decisions via an algorithm. Motivated by this development, an emerging line of work has begun to consider whether we can characterize and predict the kinds of decisions where people are likely to make errors. To investigate what a general framework for human error prediction might look like, we focus on a model system with a rich history in the behavioral sciences: the decisions made by chess players as they select moves in a game. We carry out our analysis at a large scale, employing datasets with several million recorded games, and using chess tablebases to acquire a form of ground truth for a subset of chess positions that have been completely solved by computers but remain challenging even for the best players in the world. We organize our analysis around three categories of features that we argue are present in most settings where the analysis of human error is applicable: the skill of the decision-maker, the time available to make the decision, and the inherent difficulty of the decision. We identify rich structure in all three of these categories of features, and find strong evidence that in our domain, features describing the inherent difficulty of an instance are significantly more powerful than features based on skill or time.Comment: KDD 2016; 10 page

Extending learning opportunities: a framework for self-evaluation in study support

The Extending Learning Opportunities (ELO) framework for selfevaluation in study support is a tool to use when quality assuring learning opportunities for children and young people outside of normal lesson time. This framework is a revised edition of the ELO (2009) DCSF publication. It provides a framework for all schools, and school consortiums including Complementary Supplementary Schools, Children’s Centres, Playing for Success (PfS) centres, Higher Education Institutions (HEIs) and organisations such as libraries, museums, galleries, theatres, including youth and community/volunteer projects that offer a structured learning programmes to young people, to extend and enhance their provision and so to improve their outcomes. It is based on self–evaluation and sets out criteria against which schools, HEIs and other organisations, can review their extended provision, the planning and practices which support it and the overall ethos which supports learning. The criteria, which take the form of Key Indicators, are at three levels: Emerged, Established and Advanced

Carbon nanotube: a low-loss spin-current waveguide

We demonstrate with a quantum-mechanical approach that carbon nanotubes are excellent spin-current waveguides and are able to carry information stored in a precessing magnetic moment for long distances with very little dispersion and with tunable degrees of attenuation. Pulsed magnetic excitations are predicted to travel with the nanotube Fermi velocity and are able to induce similar excitations in remote locations. Such an efficient way of transporting magnetic information suggests that nanotubes are promising candidates for memory devices with fast magnetization switchings

Preface [to SEASAT II]

No abstract is available for this article

Time to put down the scalpel? The role of surgery in tendinopathy

No abstract available

Examining Visual Field Loss in Patients in Glaucoma Clinics During Their Predicted Remaining Lifetime

Purpose.: To evaluate the proportion of patients in glaucoma clinics progressing at rates that would result in visual disability within their expected lifetime. Methods.: This retrospective study used visual field (VF) series of at least 3 years’ duration from 3790 UK patients in glaucoma clinics calculating rates of loss for each eye using linear regression of mean deviation (MD) over time. Residual life expectancies derived from the UK Office of National Statistics actuarial tables for each patient were combined with these rates to estimate predicted MDs at end of expected lifetime. The proportion of patients projected to progress to visual impairment (MD: −14 dB or worse) or statutory blindness (MD: −22 dB or worse) in both eyes before end of expected lifetime was calculated. Results.: Only 3.0% (95% confidence interval [CI] 2.7%–3.4%) of patient eyes progressed at faster than −1.5 dB/year (n = 7149 eyes). Of those patients with both eyes followed, 5.2% (CI 4.5%–6.0%) were predicted to progress to statutory blindness, with a further 10.4% (CI 9.4%–11.4%) reaching visual impairment in their lifetime. More than 90% (CI 85.7%–94.3%) of patients predicted to progress to statutory blindness, had an MD worse than −6 dB in at least one eye at presentation. Conclusions.: This modeling exercise indicates that most patients in glaucoma clinics are not at high risk of progressing to statutory blindness. The likelihood of patients suffering impairment in their lifetimes is linked to VF loss at presentation, which illuminates the importance of reliably detecting significant VF defects in primary care