Evidence for quark-hadron duality in the proton spin asymmetry A1.

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A1. Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q2 between 1.2 and 12 GeV2 and values of W2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A1 in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q2 above 1.6 GeV2.

Q2 dependence of nuclear transparency for exclusive rho0 production.

Exclusive coherent and incoherent electroproduction of the rho(0) meson from 1H and 14N targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q2). The ratio of 14N to 1H cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q2 is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency.

Evaluation of occupational exposures: a proposed sampling method.

Occupational exposures to potentially hazardous agents may vary considerably because of worker mobility, or workplace contaminant levels that fluctuate within or between-days. In addition, individual susceptibility to adverse health effects varies among identically exposed workers. Therefore, accounting for these variables can be difficult during assessment of worker exposure for occupational health and OSHA compliance purposes. This is particularly true when there is varied and repeated exposure from day to day. A cost-effective monitoring strategy for evaluating repeated employee exposure and potential health risk that considers the foregoing exposure variables is desirable. The method this article proposes uses a well-planned sampling strategy featuring 4-hr, rather than the traditional 7 or 8-hr sampling durations. Use of 4-hr samples has been found to improve monitoring efficiency without significantly reducing sampling precision or accuracy. Statistical protocols applied during the sampling procedure and subsequent data analysis also combine to minimize the frequency and duration of samples required to reach a decision regarding the significance of a worker's exposure. The development of an Acceptable Risk Level (ARL) is another important element of the proposed method. An ARL is a variable based on risk assessment and risk management principles, which have been established by the employer for each contaminant. The ARL is dependent on the contaminant's toxicity and the time pattern and spacing of successive exposures. Ultimately, an ARL can be developed by an employer for the productive allocation of health and safety dollars to ensure worker protection.