Unsteady free surface flow induced by a line sink in a fluid of finite depth

The unsteady withdrawal of fluid from a reservoir of finite depth with a free surface through a line sink is considered. A numerical method is used to investigate the evolution of a free surface in several different geometric and initial configurations, and it is shown that there are some critical flow parameters at which the flow changes its nature. The existence of steady states is also considered. Results both with and without surface tension are included and placed in context with previous work. Inclusion of surface tension reveals that solutions either evolve to a steady state or drawdown. As the sink is moved off the base, the behaviour becomes consistent with flows in a fluid of infinite depth, and consequently flows can be classified as either “shallow” or “deep” depending on their drawdown behaviour.     

Non-peptidic HIV protease inhibitors: C2-symmetry-based design of bis-sulfonamide dihydropyrones

Potent, non-peptidic, dihydropyrone sulfonamide HIV protease inhibitors have been previously described. Crystallographic analysis of dihydropyrone sulfonamide inhibitor/HIV protease complexes suggested incorporation of a second, C2 symmetry-related sulfonamide group. Selected bis-sulfonamide dihydropyrone analogues display high HIV protease inhibitory activity.     

Transmission-based scatter correction of 180 degrees myocardial single-photon emission tomographic studies

Meaningful comparison of single-photon emission tomographic (SPET) reconstructions for data acquired over 180 degrees or 360 degrees can only be performed if both attenuation and scatter correction are applied. Convolution subtraction has appeal as a practical method for scatter correction; however, it is limited to data acquired over 360 degrees. A new algorithm is proposed which can be applied equally well to data acquired over 180 degrees or 360 degrees. The method involves estimating scatter based on knowledge of reconstructed transmission data in combination with a reconstructed estimate of the activity distribution, obtained using attenuation correction with broad beam attenuation coefficients. Processing is implemented for planes of activity parallel to the projection images for which a simplified model for the scatter distribution may be applied, based on the measured attenuation. The appropriate broad beam (effective) attenuation coefficients were determined by considering the scatter buildup equation. It was demonstrated that narrow beam attenuation coefficients should be scaled by 0.75 and 0.65 to provide broad beam attenuation coefficients for technetium-99m and thallium-201 respectively. Using a thorax phantom, quantitative accuracy of the new algorithm was compared with conventional transmission-based convolution subtraction (TDCS) for 360 degrees data. Similar heart to lung contrasts were achieved and correction of 180 degrees data yielded a 10.4% error for cardiac activity compared to 5.2% for TDCS. Contrast for myocardium to ventricular cavity was similarly good for scatter-corrected 180 degrees and 360 degrees data, in contrast to attenuation-corrected data, where contrast was significantly reduced. The new algorithm provides a practical method for correction of scatter applicable to 180 degrees myocardial SPET.     

Premature separation of centromere and aneuploidy: an indicator of high risk in unaffected individuals from familial breast cancer families?

OBJECTIVES: Injury is the leading cause of death in the male working population of Brazil. An important fraction of these deaths are work related. Very few cohort studies of steel workers, and none from developing countries, have reported on mortality from injuries. This paper analyses mortality from work and non-work related injuries among Brazilian steel workers. METHODS: Deaths during employment from 1 January 1977 to 30 November 1992 were analysed in a cohort of 21,816 male steel workers. Mortality rates specific for age and calendar year among the workers were compared with those of the male population of the state where the plant is located. Work related injuries were analysed by comparing the mortality rates for different subgroups of the cohort. RESULTS: The number of deaths (391) was less than half that expected based on death rates of the general population. Over 60% (242) of deaths were due to injuries. Mortality from most causes was substantially below that in the general population, but that from unintentional injury, was 50% above that of the general population. Standardised mortality ratios (SMRs) were highest for the youngest and the oldest employees and for labourers and clerical workers. Mortality from motor vehicle injury was twice that expected from population rates (SMR = 209, 95% confidence interval (95% CI) 176-244). There was a 67% fall in the age adjusted mortality from occupational injuries in the study period. CONCLUSION: The healthy worker effect in this cohort was greater than that commonly found in studies of occupational groups in developed countries, probably because of a greater socioeconomic gap between employed and unemployed populations in Brazil, and unequal distribution of health care resources. Mortality was especially high for motor vehicle injuries. The fall in mortality from occupational injuries during the study period was probably due to improvement in safety standards, increased automation, and better medical care. There is a need to investigate risk factors for unintentional injuries among steel workers, especially those due to motor vehicle injuries. Prevention of occupational and nonoccupational injuries should be a main priority in Brazil.     

OPTIMUM-AIV: A planning and scheduling system for spacecraft AIV

This paper presents a project undertaken for the European Space Agency (ESA). The project is developing a knowledge based system for planning and scheduling of activities for spacecraft assembly, integration and verification (AIV). The system extends to the monitoring of plan execution and the plan repair phases.

The objectives of the contract are to develop an operational kernel of a planning, scheduling and plan repair tool, called OPTIMUM-AIV, and to provide facilities which will allow individual projects to customize the kernel to suit its specific needs. The kernel shall consist of a set of software functionalities for assistance in the initial specification of the AIV plan, in the verification and generation of valid plans and schedules for the AIV activities, and in interactive monitoring and execution problem recovery for the detailed AIV plans. Embedded in OPTIMUM-AIV are external interfaces which allow integration with alternative scheduling systems and project databases.

The current status of the OPTIMUM-AIV project, as of May 1991, is that the architectural design of the system has been agreed on by ESTEC/ESA and detailed design and implementation is now underway, expecting a final delivery in October of 1991.