An experimental method for calibration of the plasmon mean free path.

Transmission electron microscopy specimens in the form of elongated, conical needles were made using a dual-beam focused ion beam system, allowing the specimen thickness to be geometrically determined for a range of thickness values. From the same samples electron energy loss maps were acquired and the plasmon mean free path (lambda) for inelastic scattering was determined experimentally from the measured values of specimen thickness. To test the method lambda was determined for Ni (174 +/- 17 nm), alpha-Al(2)O(3) (143 +/- 14 nm), Si (199 +/- 20 nm) and amorphous SiO(2) (238 +/- 12 nm), and compared both to experimental values of lambda taken from the literature and to calculated values. The calculated values of lambda significantly underestimate the true sample thickness for high accelerating voltages (300 kV) and large collection angles. A linear dependence of lambda on thickness was confirmed for t/lambda < 0.5-0.6, but this method also provides an approach for calibrating lambda at sample thicknesses for which multiple scattering occurs, thus expanding the thickness range over which electron energy loss spectroscopy can be used to determine the absolute sample thickness (t/lambda > 0.6). The experimental method proposed in this contribution offers a means to calibrate lambda for any type of material or phase that can be milled using a focused ion beam system.

Quantitative HRTEM analysis of FIB prepared specimens.

The preparation of good transmission electron microscopy specimens with minimum milling damage can be very complicated, especially from a specific area in a sample. Therefore, a novel approach for transmission electron microscopy specimen preparation using a focused ion beam system is proposed, based on the use of low energy (5 kV)Ga ions and a low incident ion angle (approximately 1 degree ) from a thickness of approximately 500 nm until the sample is electron transparent. Transmission electron microscopy specimens prepared by this method have significantly less irradiation damage, demonstrated by successful quantitative high-resolution transmission electron microscopy conducted on sapphire from data acquired using an aberration-corrected field emission gun transmission electron microscopy. Quantitative analysis was conducted by iterative digital image matching. The accuracy and sensitivity of the matching process is discussed.

Risky business.

In prior studies by high-level commissions, emphasis was given to improving the scientific basis and institutional procedures for risk assessment and risk regulation within existing statutory frameworks. Recommendations have led to slow but steady progress. This study is considerably different. It emphasizes a public health approach for efficient use of resources in a new flexible framework for risk management, reductionist approaches to risk assessment and characterization, increased public involvement, and various methods for managing such public involvement. It provides a mix of aspirations and concepts, procedures, and "shop floor rules" for putting the new system of risk management into practice. Concerns remain, however, that bright lines and other rules are at odds with the report's professed aspirations for meaningful public involvement; that ad hoc institutional arrangements for putting each risk in a situational context may not be an efficient use of public and private resources; that techniques for managing stakeholder involvement will be seen as manipulative and may even increase public mistrust and anxieties about risk; and that reductionism by the regulatory clients of risk assessment could diminish progress in the environmental health sciences. Says Lucier, "The goal of risk assessment should be to prevent environmentally or occupationally mediated diseases or injury. This point is not made sufficiently clear in the commission's report. Nevertheless, the report does an admirable job of attempting to merge science, common sense, public perception, public health, economics, and stakeholder interests into a regulatory policy strategy." He continues, "The merging of these diverse inputs will never be easy and should never be overly prescriptive. The complete integration of all relevant information into the risk assessment and risk management process will require greater reliance on expert judgment to make decisions that are timely, that are based on appropriate peer review, that are consistent with public health priorities, that do not create unnecessary regulatory burdens, and that are understandable by the public." The commission's report provides an alternative vision of risk management that incorporates popular political and social trends. Thorough evaluation of the report's recommendations will, at the very least, focus scrutiny on current risk assessment and risk management practices and perhaps produce better solutions.

Screening and monitoring data as evidence in legal proceedings.

The greatest legal impact of medical screening and biological monitoring may be in proceedings to compensate workers for occupational disease. In workers' compensation, failure to demonstrate a disease's work-relatedness has often barred compensation. Screening and monitoring data can add a new causal link by demonstrating longitudinally a worker's reaction to a toxic exposure. Employers may also use the data to rebut claims. In tort suits, the data can help establish causation and aid the admissibility of expert testimony. Of most significance, it may create a higher legal standard of care for employers based on increased knowledge of their workers' health status, which may open up new grounds for suits. These legal implications of greater liability may make employers reluctant to collect medical test data. On the other hand, testing programs may aid them in legal proceedings by demonstrating good faith efforts to reduce disease risks.

The right to know and the duty to disclose hazard information.

KIE: In late 1983, the Occupational Safety and Health Administration (OSHA) promulgated its final rule on "hazard communication," establishing the right of workers in manufacturing industries to information about chemical hazards, and the duty of importers and manufacturers to disclose such information. Baram reviews areas where the new, limited OSHA regulation conflicts with existing local, state, and federal laws, many of which are more stringent and more protective of worker and community health. He suggests steps that could be taken to avoid the extensive litigation that might result from the potential preemptive effect of the new OSHA rule.^ieng