The frequency of mouse plagues in grain-growing areas of Australia has increased since the advent of conservation farming practices. The increase bas been particularly marked on the Darling Downs in Queensland where the frequency has trebled. Broadscale monitoring is undertaken by the government to provide a general forewarning of plague. However, the authors found, from a questionnaire to farmers, that the incidence and timing of plagues is highly variable across the Downs. It is apparent that farmers need to monitor the numbers of mice on their properties at regular intervals if they are to undertake preventive management. Bait cards (pieces of paper soaked in canola oil) were tested as a method for on-farm monitoring. The average amount of each card eaten was significantly correlated with the density of mice, but because of the scatter of the data the authors recommend that the cards be used in conjunction with other signs of mice such as evidence of crop damage or of active holes and runways in stubble. Zinc phosphide bait was found to be a highly effective rodenticide if used at a time when food was scarce. If the bait receives registration, it would be a valuable tool to control mice in crops, especially prior to flowering . On the basis of these results, it was concluded that effective management of mice could best be achieved by minimizing food supply in stubble by efficient harvesting, regular monitoring, and by strategic baiting and stubble management when necessary.

This investigation evaluated target fabrication and beam parameters for scale-up production of high specific activity (186)Re using deuteron irradiation of enriched (186)W via the (186)W(d,2n)(186)Re reaction. Thick W and WO3 targets were prepared, characterized and evaluated in deuteron irradiations. Full-thickness targets, as determined using SRIM, were prepared by uniaxially pressing powdered natural abundance W and WO3, or 96.86% enriched (186)W, into Al target supports. Alternatively, thick targets were prepared by pressing (186)W between two layers of graphite powder or by placing pre-sintered (1105°C, 12h) natural abundance WO3 pellets into an Al target support. Assessments of structural integrity were made on each target prepared. Prior to irradiation, material composition analyses were conducted using SEM, XRD, and Raman spectroscopy. Within a minimum of 24h post irradiation, gamma-ray spectroscopy was performed on all targets to assess production yields and radionuclidic byproducts. Problems were encountered with the structural integrity of some pressed W and WO3 pellets before and during irradiation, and target material characterization results could be correlated with the structural integrity of the pressed target pellets. Under the conditions studied, the findings suggest that all WO3 targets prepared and studied were unacceptable. By contrast, (186)W metal was found to be a viable target material for (186)Re production. Thick targets prepared with powdered (186)W pressed between layers of graphite provided a particularly robust target configuration.

Quasi‐static Weibull strength‐size scaling of hot‐pressed silicon carbide is described. Two surface conditions (uniaxial ground and uniaxial ground followed by grit blasting) were explored. Strength test coupons sampled effective areas from the very small (4 × 10−3 mm2) to the very large (4 × 104 mm2). Equibiaxial flexure and Hertzian ring crack initiation were used for the strength tests, and characteristic strengths for several different specimen geometries were analyzed as a function of effective area. Characteristic strength was found to substantially increase with decreased effective area for both surface conditions. Weibull moduli of 9.4‐ and 11.7 well‐represented strength‐size scaling for the two ground conditions between an effective area range of 10−1 and 4 × 104 mm2. Machining damage was observed to be the dominant flaw type over this range. However, for effective areas <10−1 mm2, the characteristic strength increased rapidly for both ground surface conditions as the effective area decreased, and one or more of the inherent assumptions behind the classical Weibull strength‐size scaling were in violation in this range. The selections of a ceramic strength to account for ballistically induced tile deflection and expanding cavity modeling are considered in context with the measured strength‐size scaling. The observed size‐scaling is briefly discussed with reference to dynamic strength.

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Hertzian ring cracking in two SiCs was studied as a function of elastic property mismatch between indenter and target. Ring crack initiation forces (RCIF) were measured using ZrO 2 , steel, Si 3 N 4 , Al 2 O 3 , and WC balls. The SiCs were similar; however, B20% of the grains in one were larger than the largest grains in the other. Decreasing indenter stiffness resulted in lower RCIFs and initiation occurred at lower forces in the SiC containing larger grains. Using a spherical indenter with similar elastic properties as the target provides a simpler interpretation and useful and confident estimates of ring crack initiation stresses.