Level correlations in integrable systems

We derive a simple analytical expression for the level correlation function of an integrable system. It accounts for both the lack of correlations at smaller energy scales and for global rigidity (level number conservation) at larger scales. We apply our results to a rectangle with incommensurate sides and show that they are in excellent agreement with the limiting cases established in the semiclassical theory of level rigidity.Comment: 5 page

Prevalence of Occupational Stress among Secondary School Teachers in Public Schools in the District of Colombo, Sri Lanka

Teacher occupational stress is increasing globally. We aimed to determine the prevalence of occupational stress among secondary teachers, to advocate policies for prevention of occupational stress among teachers in Sri Lanka. A cross-sectional study included 1426 secondary teachers, selected using multistage cluster sampling from public schools of Colombo, Sri Lanka. Validated Teacher Stress Inventory-Sinhala (TSI-Sinhala) assessed occupational stress. Prevalence of high [15.9% (95% CI: 14.0%-17.8%)] and moderate [67.5% (95% CI: 65.1%-69.9%)] occupational stress among secondary teachers, resulted an overall high prevalence of 83.4% (95%CI: 81.4%-85.3%). Moderate occupational stress among female teachers (68.6%, 95% CI: 65.7-71.5%) was significantly higher than males (61.9%. 95% CI: 58.9-64.9%). Urgent attention to preventative interventions for occupational stress among teachers in Sri Lanka is recommended

Could Edge-Lit Type Ia Supernovae be Standard Candles

The progenitors of Type Ia supernovae (SNe Ia) have not been identified. Though they are no longer fashionable we investigate the consequences if a significant number of SNe Ia were edge-lit detonations (ELDs) of carbon/oxygen white dwarfs that have accreted a critical mass of helium. Our best understanding of the Phillips relation between light curve speed and peak luminosity assigns both these phenomena to the amount of $^{56}$Ni produced. In ELDs there are two sites of $^{56}$Ni synthesis. If the peak luminosity is determined primarily by the C/O ratio in the core it is primarily a function of its progenitor's initial mass. If the light curve decay speed is determined by the total mass of iron group elements ejected this is a function of the total mass of the ELD at the time of explosion. In general these two masses are correlated and an empirical relation between peak luminosity and light curve shape can be expected. However when we perform population synthesis for progenitors of different metallicities we find a systematic shift in this relation that would make distant SNe Ia fainter than those nearby. The abundances of alpha-rich isotopes, such as $^{44}$Ca, in the solar system indicate that only about 40 per cent of SNe Ia are edge-lit so any systematic effect that could be present would be correspondingly diluted. If we examine only the small subset of ELDs that accrete from a naked helium star, rather than a He white dwarf, the systematic effect disappears.Comment: 14 pages, 3figure

Scanned Imaging Techniques for Surface NDE

A phase sensitive laser probe in which the focussed spot is small, as compared with the acoustic wavelength, is capable of measuring the complex distributions of a SAW field along prescribed scan lines. Using the probe, it is possible, on a defect free sample, to measure the SAW velocity surface with an accuracy of a few parts in 105. Such accuracy suggests that the technique is sufficiently sensitive to detect small changes in surface characteristics; the presence of a defect is revealed by perturbations in the relationship between various scans. The scattered radiation patterns from a surface crack irradiated by acoustic surface waves can be utilised to determine the defect size and location with improved accuracy. Results on deliberate and real cracks are presented