MEDICAL ISOTOPE PRODUCTION

Nearly 95 percent of the world demand for molybdenum-99 (Mo-99)—perhaps the world's most important medical isotope—is met by just four manufacturers, all of whom use highly enriched uranium (HEU) targets in their isotope production programs. Research and development on the use of low-enriched uranium targets and gel generators to produce Mo-99 began in the 1980s; some success has been achieved, but Mo-99 is still mainly produced by irradiating HEU targets in a reactor. Fission-produced Mo-99 has a high specific activity, but activation methods provide low specific activity Mo-99, which is unsuitable for the generators routinely used in most of the world's medical centers. This article evaluates the use of enriched Mo-98 to produce Mo-99 by activation methods; the use of medium specific activity Mo-99 for the preparation of alumina-based generators is also discussed. This article concludes that if support is provided for the production of enriched Mo-98, it may replace to a significant extent the use of HEU and LEU for the production of Mo-99.     

Response of masonry systems against blast loading

In this paper eight successive experimental blast tests with an increasing TNT equivalent charge weights ranging from 0.56 kg to 17.78 kg were conducted on unreinforced, ferrocemented overlay masonry and confined masonry walls. The pressure-time history caused by the blast was recorded by pressure sensors installed on the test specimen. The resulting damage pattern was observed during each test. Weak zones in the three systems of masonry were identified. Scaled distances for different damage levels in the three masonry systems were experimentally obtained. The results provide a basis for determining the response of each masonry system against blast loading. Consequently, efficiency of ferrocemented overlay ma-sonry and confined masonry was found established in mitigation against blast loads.     

Optimal accelerated life test designs for Burr type XII distributions under periodic inspection and type I censoring

This article develops optimal accelerated life test designs for Burr Type XII distributions under periodic inspection and Type I censoring. It is assumed that the mean lifetime (the Burr XII scale parameter) is a log-linear function of stress and that the shape parameters are independent of stress. For given shape parameters, design stress and high test stress, the test design is optimized with respect to the low test stress and the proportion of test units allocated to the low stress. The optimality criterion is the asymptotic variance of the maximum-likelihood estimator of log mean life at the design stress with the use of equally spaced inspection times. Computational results for various values of the shape parameters show that this criterion is insensitive to the number of inspection times and to misspecification of imputed failure probabilities at the design and high test stresses. Procedures for planning an accelerated life test, including selection of sample size, are also discussed. It is shown that optimal designs previously obtained for exponential and Weibull distributions are similar to those obtained here for the appropriate special cases of the Burr XII distribution. Thus the Burr XII distribution is a useful and widely applicable family of reliability models for ALT design. © 1996 John Wiley & Sons, Inc.     

The legality of unmanned aerial vehicles outside the combat zone: a case study of the Federally Administered Tribal Areas of Pakistan

The drone is the latest tool to promote interests of a nation-state. It is clear that USA as well as other major powers anticipate that robotics will play a key role in future warfare. Today, more than 70 countries have already acquired drone technology and many others are desperate to join the ranks. This urge for drone technology will ultimately lead to a “boundless and borderless war without end.” In the case of Pakistan, the US drone campaign has raised some important issues regarding how their use could, or should, be regulated in the future. This article analyses the legal issues raised by the US's use of drone technology in non-combat zones, such as Pakistan. It is argued that a reckless disrespect of Pakistan's sovereignty has had adverse implications and consequences for the legitimacy of the Pakistani government. Drone strikes have prompted instinctive opposition among the Pakistani population, hurt their feelings and estranged them from the government. This in turn has added to Pakistan's instability and stimulated a ground-swell of animosity toward the USA.