Optical studies of carrier and phonon dynamics in Ga_{1-x}Mn_{x}As

We present a time-resolved optical study of the dynamics of carriers and phonons in Ga_{1-x}Mn_{x}As layers for a series of Mn and hole concentrations. While band filling is the dominant effect in transient optical absorption in low-temperature-grown (LT) GaAs, band gap renormalization effects become important with increasing Mn concentration in Ga_{1-x}Mn_{x}As, as inferred from the sign of the absorption change. We also report direct observation on lattice vibrations in Ga1-xMnxAs layers via reflective electro-optic sampling technique. The data show increasingly fast dephasing of LO phonon oscillations for samples with increasing Mn and hole concentration, which can be understood in term of phonon scattering by the holes.Comment: 13 pages, 3 figures replaced Fig.1 after finding a mistake in previous versio

Detecting and quantifying insider trading and stock manipulation in Asian markets

This paper focuses on insider trading, where the perpetrators exploit market sensitive information to earn profits or avoid losses. The paper's objectives are as follows. First, we seek to examine whether we can detect possible insider trading and stock manipulation and react in almost real time, even though insider trading activity is intended to be evasive. Second, we also estimate the extent of illicit profits (or loss avoidance) that might have been earned. Finally, we analyze, if detection is possible, the appropriate response for regulators and other market participants. We do not restrict our study to cases where corporate events have materialized, as we hope to capture insider trading surrounding market rumors and failed corporate events. Because insider trading is executed with the aim of being evasive and undetected, it is impossible to conclude with certainty. Nevertheless, using a hypothesized model based on how insiders and stock manipulators trade, we detect price patterns that are consistent with their objective to maximize profits and at the same time be evasive

Collectivism, Machiavellianism, Perceived Organizational Justice and Organizational Citizenship Behavior: An Empirical Study of Chinese Employees

This study examined the relationship between perceived organizational justice and two individual differences, namely, (i) within-culture collectivism and (ii) Machiavellianism. In addition, this study also examined the influence of perceived organizational justice on organizational citizenship behavior (OCB). Previous research suggests that individual differences influence perceived organizational justice, which in turn have an effect on subsequent behaviors. However, much of the research was done in the western context. The present research seeks to examine the generalizability of findings based on the western context by investigating the relationships among within-culture collectivism, Machiavellianism, perceived organizational justice and OCB in a non-western context, specifically, among a group of employees from People’s Republic of China. Results suggested that within-culture collectivism and Machiavellianism were significantly associated with perceived organizational justice. Consistent with previous research, perceived organizational justice was positively related to OCB. Implications of the study were discusse

Lead in Kuala Lumpur Urban Dust

A preliminary survey of lead in Kuala Lumpur urban dust was carried out. Lead levels of22.9 to 6986.6 JJgg-l were obtained, depending on the locations where.the dust was collected. There is a direct relationship between lead level in dust and traffic density. The amount of lead leachable by rain water is sufficiently high to warrant further investigation

Understanding the fundamentals of freight markets volatility

We analyse empirically the drivers of freight market volatility. We use several macroeconomic and shipping-related factors that are known to affect the supply and demand for shipping and examine their impact on the term structure of freight options implied volatilities (IV). We find that the level of IVs is affected by the level of the spot rate, the slope of the forward curve, as well as by both demand and supply factors, especially the former. We demonstrate that the relation between the volatility of futures prices and the slope of the forward curve is non-monotonic and convex, that is, it has a V-shape. In general, anticipation of economic growth and of a stronger freight market reduces IV whereas higher uncertainty and anticipation of excess shipping capacity may increase IV. Panel regressions as well as a series of robustness tests produce strong validation of the results

Assessing the Impact of Internet Adoption Levels on Competitive Advantage

This paper introduces a model for Internet adoption, namely: level 0 – e-mail adoption; level 1 – Web presence; level 2 – prospecting; level 3 – business integration; and level 4 – business transformation. Two broad Web site categories can be identified: informational Web site and transactional Web site. The competitive advantages in terms of differentiation, cost reduction, innovation, growth, and alliance that are affected by Internet adoption are examined. A questionnaire survey of 553 firms was conducted, of which 159 usable responses were received, resulting in an effective response rate of 28.8%. The results show that proactive business strategy, firm size and competitive advantage are found to be positively related to Web adoption level. Implications of the results for researchers and practitioners are discussed, and directions for future research are proposed

New Measurement of the Relative Scintillation Efficiency of Xenon Nuclear Recoils Below 10 keV

Liquid xenon is an important detection medium in direct dark matter experiments, which search for low-energy nuclear recoils produced by the elastic scattering of WIMPs with quarks. The two existing measurements of the relative scintillation efficiency of nuclear recoils below 20 keV lead to inconsistent extrapolations at lower energies. This results in a different energy scale and thus sensitivity reach of liquid xenon dark matter detectors. We report a new measurement of the relative scintillation efficiency below 10 keV performed with a liquid xenon scintillation detector, optimized for maximum light collection. Greater than 95% of the interior surface of this detector was instrumented with photomultiplier tubes, giving a scintillation yield of 19.6 photoelectrons/keV electron equivalent for 122 keV gamma rays. We find that the relative scintillation efficiency for nuclear recoils of 5 keV is 0.14, staying constant around this value up to 10 keV. For higher energy recoils we measure a value around 20%, consistent with previously reported data. In light of this new measurement, the XENON10 experiment's results on spin-independent WIMP-nucleon cross section, which were calculated assuming a constant 0.19 relative scintillation efficiency, change from $8.8\times10^{-44}$ cm$^2$ to $9.9\times10^{-44}$ cm$^2$ for WIMPs of mass 100 GeV/c$^2$, and from $4.4\times10^{-44}$ cm$^2$ to $5.6\times10^{-44}$ cm$^2$ for WIMPs of mass 30 GeV/c$^2$.Comment: 8 pages, 8 figure

Influence of blade aerodynamic model on the prediction of helicopter high-frequency airloads

Brown’s vorticity transport model has been used to investigate the influence of the blade aerodynamic model on the accuracy with which the high-frequency airloads associated with helicopter blade–vortex interactions can be predicted. The model yields an accurate representation of the wake structure yet allows significant flexibility in the way that the blade loading can be represented. A simple lifting-line model and a somewhat more sophisticated liftingchord model, based on unsteady thin aerofoil theory, are compared. A marked improvement in the accuracy of the predicted high-frequency airloads of the higher harmonic control aeroacoustic rotor is obtained when the liftingchord model is used instead of the lifting-line approach, and the quality of the prediction is affected less by the computational resolution of the wake. The lifting-line model overpredicts the amplitude of the lift response to blade–vortex interactions as the computational grid is refined, exposing the fundamental deficiencies in this approach when modeling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. The airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach