Theory of the high-frequency chiral optical response in a p_x+ip_y superconductor

The optical Hall conductivity and the polar Kerr angle are calculated as functions of temperature for a two-dimensional chiral p_x+ip_y superconductor, where the time-reversal symmetry is spontaneously broken. The theoretical estimate for the polar Kerr angle agrees by the order of magnitude with the recent experimental measurement in Sr2RuO4 by Xia et al. cond-mat/0607539. The theory predicts that the Kerr angle is proportional to the square of the superconducting energy gap and is inversely proportional to the cube of frequency, which can be verified experimentally.Comment: 4 pages, no figures, RevTeX. V.2: one reference and discussion of horizontal lines of nodes added. V.3: a typo corrected, and one reference added. V.4: two references added and minor stylistic changes made, as in the published versio

The WSAVA AFSCAN Project: 5th Anniversary of a successful network in Africa

The Foundation of the World Small Animal Veterinary Association (WSAVA) began the African Small Companion Animal Network (AFSCAN) project in 2014 with the support of Zoetis and numerous other commercial and Association supporters. AFSCAN was borne of recognition of the need for  support and capacity-building for the African small companion animal veterinary community. The countries currently participating in the AFSCAN project are Ghana, Kenya, Namibia, Nigeria, Tanzania and Uganda. Small Animal Associations are now being established in the AFSCAN member  countries. AFSCAN further offers online education to member countries on small companion animal practice. Nevertheless, face-to-face continuing education is also provided by the WSAVA Continuing Education Committee. Member countries have also participated in the rabies Control activities. The clinical research and mobility awards which currently are worthy of US$ 60,000) have been provided to institutions in Kenya, Nigeria and  Tanzania, and seven undergraduate scholarships to veterinary students in Kenya, Namibia, Nigeria, Tanzania and Uganda. Four BSAVA and four NAVC AFSCAN International Scholarships have been awarded to attend the annual BSAVA and VMX congresses in the UK and Florida. A new  programme that will ‘twin’ veterinarians and veterinary practices in Africa with partners in the USA and Europe will commence shortly. With support  from Bayer Animal Health and Idexx Laboratories a major new AFSCAN research programme on canine and feline ectoparasites and arthropod-borne infectious diseases is about to commence. Key words: AFSCAN, WSAVA, companion animals, veterinary practice

Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment

Measurement of high-power proton beam-halo formation is the ongoing scientific experiment for the Low Energy Demonstration Accelerator (LEDA) facility. To attain this measurement goal, a 52-magnet beam line containing several types of beam diagnostic instrumentation is being installed. The Experimental Physics and Industrial Control System (EPICS) and commercial software applications are presently being integrated to provide a real-time, synchronous data acquisition and control system. This system is comprised of magnet control, vacuum control, motor control, data acquisition, and data analysis. Unique requirements led to the development and integration of customized software and hardware. EPICS real-time databases, Interactive Data Language (IDL) programs, LabVIEW Virtual Instruments (VI), and State Notation Language (SNL) sequences are hosted on VXI, PC, and UNIX-based platforms which interact using the EPICS Channel Access (CA) communication protocol. Acquisition and control hardware technology ranges from DSP-based diagnostic instrumentation to the PLC-controlled vacuum system. This paper describes the control system hardware and software design, and implementation.Comment: LINAC2000 Conference, 4 pg

Stability of pulse-like earthquake ruptures

Pulse-like ruptures arise spontaneously in many elastodynamic rupture simulations and seem to be the dominant rupture mode along crustal faults. Pulse-like ruptures propagating under steady-state conditions can be efficiently analysed theoretically, but it remains unclear how they can arise and how they evolve if perturbed. Using thermal pressurisation as a representative constitutive law, we conduct elastodynamic simulations of pulse-like ruptures and determine the spatio-temporal evolution of slip, slip rate and pulse width perturbations induced by infinitesimal perturbations in background stress. These simulations indicate that steady-state pulses driven by thermal pressurisation are unstable. If the initial stress perturbation is negative, ruptures stop; conversely, if the perturbation is positive, ruptures grow and transition to either self-similar pulses (at low background stress) or expanding cracks (at elevated background stress). Based on a dynamic dislocation model, we develop an elastodynamic equation of motion for slip pulses, and demonstrate that steady-state slip pulses are unstable if their accrued slip $b$ is a decreasing function of the uniform background stress $\tau_\mathrm{b}$. This condition is satisfied by slip pulses driven by thermal pressurisation. The equation of motion also predicts quantitatively the growth rate of perturbations, and provides a generic tool to analyse the propagation of slip pulses. The unstable character of steady-state slip pulses implies that this rupture mode is a key one determining the minimum stress conditions for sustainable ruptures along faults, i.e., their ``strength''. Furthermore, slip pulse instabilities can produce a remarkable complexity of rupture dynamics, even under uniform background stress conditions and material properties

Thermopower as a Possible Probe of Non-Abelian Quasiparticle Statistics in Fractional Quantum Hall Liquids

We show in this paper that thermopower is enhanced in non-Abelian quantum Hall liquids under appropriate conditions. This is because thermopower measures entropy per electron in the clean limit, while the degeneracy and entropy associated with non-Abelian quasiparticles enhance entropy when they are present. Thus thermopower can potentially probe non-Abelian nature of the quasiparticles, and measure their quantum dimension.Comment: 5 pages. Minor revisions in response to referee comments. Published versio

Preroughening, Diffusion, and Growth of An FCC(111) Surface

Preroughening of close-packed fcc(111) surfaces, found in rare gas solids, is an interesting, but poorly characterized phase transition. We introduce a restricted solid-on-solid model, named FCSOS, which describes it. Using mostly Monte Carlo, we study both statics, including critical behavior and scattering properties, and dynamics, including surface diffusion and growth. In antiphase scattering, it is shown that preroughening will generally show up at most as a dip. Surface growth is predicted to be continuous at preroughening, where surface self-diffusion should also drop. The physical mechanism leading to preroughening on rare gas surfaces is analysed, and identified in the step-step elastic repulsion.Comment: Revtex + uuencoded figures, to appear in Physical Review Letter

Association between MAPT polymorphism but not APOE promoter and elite rugby athlete status

INTRODUCTION: Incidence and outcomes of concussions have been hypothesised to be genetically influenced. The APOE Promoter G219T (rs405509) polymorphism has been associated with differential promoter activity and unfavourable outcomes after traumatic brain injury. The TT genotype is associated with a 3-fold greater risk of multiple concussions. The TT genotype of MAPT (rs10445337) has also been associated with poorer outcomes after concussion. Rugby has one of the highest incidences of concussion in sport, so it was hypothesised that APOE Promoter TT and MAPT TT genotypes would be less prevalent in elite rugby athletes because those genotypes, previously associated with increased risk, would be less compatible with achieving elite athlete status. METHODS: Participants were from the RugbyGene project, comprising elite Caucasian male rugby athletes (n = 528; mean (standard deviation) height 1.85 (0.07) m, mass 101 (14) kg, age 29 (7) yr), including 420 rugby union (RU) athletes that for some analyses were divided into forwards and backs and 108 rugby league (RL) athletes. Non-athletes were 592 Caucasian men and women (57% male, height 1.72 (0.10) m, mass 74 (14) kg, age 31 (7) yr). PCR of genomic DNA was used to determine genotypes using TaqMan probes, then groups were compared using χ2 and odds ratio (OR) statistics. RESULTS: All genotype data were in Hardy-Weinberg equilibrium. For MAPT (rs10445337), the risk genotype (TT) was underrepresented in rugby athletes (60%) compared to non-athletes (66%), CT more common in rugby athletes (34%) than non-athletes (29%) and little difference in CC genotype frequencies (χ2 = 7.092, P = 0.029; TT genotype frequency OR = 0.80, 95% confidence intervals (CI) = 0.62-1.02). There were no differences in MAPT (rs10445337) genotype frequencies between RU forwards and backs. For APOE Promoter G219T (rs405509), there were no differences in genotype frequencies between all athletes (RU and RL) and non-athletes (27% TT genotype in players and non-athletes), nor between RU forwards and backs. CONCLUSION: The MAPT (rs10445337) TT genotype is 6% less common in elite rugby athletes than non-athletes. Therefore, carrying at least one rs10445337 C allele appears to increase the probability of sustained career success in the high-risk concussion environment of elite rugby, perhaps via a greater ability to recover from concussions.Peer reviewe