Empirical-Bayes and semi-Bayes approaches to occupational and environmental hazard surveillance

Depression, a complex psychobiological syndrome, has been found to be prevalent among individuals with chronic pain problems. It has been repeatedly recommended that chronic pain patients be routinely screened for depression. Many self-report questionnaires have been used to screen for depression although few have addressed potential limitations of using a self-report questionnaire to identify depressed chronic pain patients. Among the most serious problems is an over-diagnosis since typical neurovegetative symptoms of depression often resemble patients' medical/physical conditions. Some have suggested that the physical items should be replaced and others have suggested that a higher cut-off criteria for diagnosing depression should be used. In this study, the validity of the Center for Epidemiological Studies-Depression (CES-D) scale was examined to determine (a) its sensitivity, specificity, and positive, and negative predictive value with chronic pain patients, (b) the biasing effect of somatic items, and (c) the optimal cut-off score for diagnosing depression. The results support the predictive validity of the CES-D and suggest that a cut-off score of 19 should be used for diagnosing depression in chronic pain patients rather than the standard cut-off point of 16. Interestingly, the removal of the somatic items did not enhance the effectiveness of the CES-D. The discriminatory ability of somatic items with the total assessment of depression is discussed.     

A NEW METHOD FOR INFLUENCE DIAGRAM EVALUATION

As influence diagrams become a popular representational tool for decision analysis, influence diagram evaluation attracts more and more research interests. In this article, we present a new, two-phase method for influence diagram evaluation. In our method, an influence diagram is first mapped onto a decision graph and then the analysis is carried out by evaluating the decision graph. Our method is more efficient than Howard and Matheson's because, among other reasons, our method generates a much smaller decision graph for the same influence diagram. Like those most recent algorithms reported in the literature, our method also provides a clean interface between influence diagram evaluation and Bayesian net evaluation. Consequently, various well-established algorithms for Bayesian net evaluation can be used in influence diagram evaluation. Furthermore, our method has a few unique merits. First, it takes advantage of asymmetry in influence diagrams to avoid unnecessary computation. Second, by using heuristic search techniques, it provides an explicit mechanism for using heuristic information that may be available in a domain-specific form. These additional merits make our method more efficient than the current algorithms in general. Finally, by using decision graphs as an intermediate representation, the value of perfect information can be computed in a more efficient way.     

IN SITU SEM MEASUREMENTS OF CRACK CLOSURE FOR SMALL FATIGUE CRACKS IN ALUMINIUM 2024-T351

Abstract Crack closure has been measured for a range of small, self-initiated fatigue cracks using in situ SEM loading. Cracks were grown at positive R ratios in the aluminium alloy 2024-T351 and at nominal ΔK levels that extend substantially below the corresponding long crack threshold. The crack closure stress of the small cracks decreased and the K_cl level increased with increasing crack size until the long crack value near threshold was reached. For cracks of depth larger than about one grain size, a good correlation was obtained between small and long crack growth rate data in terms of ΔK_eff     

Electron microscopy of photo-oxidized polydiacetylene crystals

The photo-oxidation of toluene sulphonate polydiacetylene single crystals has been studied by scanning and transmission electron microscopy. Submicron particles were observed as reaction products on the surfaces of crystals which had been exposed to 514 nm light from an argon ion laser. Electron diffraction showed that these particles were single crystals ofparatoluene sulphonic acid. The appearance of the particles was correlated with the decrease in intensity of a Raman line associated with the presence of adsorbed oxygen on the crystal surface.     

Carrier Dynamics of Quantum-Dot, Quantum-Dash, and Quantum-Well Semiconductor Optical Amplifiers Operating at 1.55 μm

We assess the influence of the degree of quantum confinement on the carrier recovery times in semiconductor optical amplifiers (SOAs) through an experimental comparative study of three amplifiers, one InAs-InGaAsP-InP quantum dot (0-D), one InAs-InAlGaAs-InP quantum dash (1-D), and one InGaAsP-In-GaAsP-InP quantum well (2-D), all of which operate near 1.55-mum wavelengths. The short-lived (around 1 ps) and long-lived (up to 2 ns) amplitude and phase dynamics of the three devices are characterized via heterodyne pump-probe measurements. The quantum-dot device is found to have the shortest long-lived gain recovery (~80 ps) as well as gain and phase changes indicative of a smaller linewidth enhancement factor, making it the most promising for high-bit-rate applications. The quantum-dot amplifier is also found to have reduced ultrafast transients, due to a lower carrier density in the dots. The quantum-dot gain saturation characteristics and temporal dynamics also provide insight into the nature of the dot energy-level occupancy and the interactions of the dot states with the wetting layer.     

Physiological Factors Influencing Toughness in Cooked Saddletail Snapper (Lutjanus malabaricus)

Saddletail snapper (Lutjanus malabaricus) is a commercially significant tropical species in Australia and has been the subject of consumer complaints of extreme toughness in cooked fillets. Textural and biochemical analyses including collagen and hydroxylysyl pyridinoline (PYD) cross‐links concentrations were conducted on 101 commercially harvested Saddletail snapper to identify causes of toughness. Fish age was found to account for 75.6% of observed variation in cooked muscle texture (work done) of Saddletail snapper. A significant linear relationship (P < 0.001) between PYD content and cooked muscle texture was also identified accounting for 50.3% of observed variation. The concentration ratio of PYD to total collagen (TC) ranged from 0.04 to 0.38 mol PYD per mol of TC. Fish size was also found to be a poor indicator of fish age and therefore a poor indicator of the potential risk of toughness of the cooked muscle.     

Examination of precipitation in the aluminum alloy AA6111 using electrical resistivity measurements

The evolution of electrical resistivity during the aging of aluminum alloy AA6111 has been measured over a wide range of annealing temperatures. From these measurements, the solubility product for the Q phase in aluminum has been proposed and using a new approach, the contribution of precipitates to the overall resistivity is quantified.