行波：数学推理的元极导航

本书是《剑桥理论计算科学专论》丛书的第56卷。自从20世纪50年代起，自动化理论证明成为一个活跃的研究领域。在该领域中的研究人员开始着手处理类似人类的自动化推理。在20世纪60年代和70年代，人们对自动化理论证明的兴趣增加了，这是由于理论进展的驱动。例如归纳的开发以及对程序验证的兴趣增加。     

OPTIMAL MAINTENANCE AND REPLACEMENT OF EXTRACTION MACHINERY

This paper considers a problem of optimal preventive maintenance and replacement schedule of equipment devoted to extracting resources from known deposits. Typical examples are oil drills, mine shovels, etc. At most one replacement of the existing machinery by a new one is allowed. The problem is formulated as an optimal control problem subject to the state constraint that the remaining deposit at any given time is nonnegative. We show that the optimal preventive maintenance, production rates, and the replacement and salvage times of the existing machinery and the new one, if required, can be obtained by solving sequentially a series of free-end-point optimal control problems. Moreover, an algorithm based on this result is developed and used to solve two illustrative examples.     

Stream temperatures and the elevational distribution of redband trout in southwestern Idaho

During July to September 1994-1995, I examined water temperatures at the lower end of the elevational distribution of redband trout ( Oncorhynchus mykiss gairdneri ) in 4 streams in the Owyhee Mountains in southwestern Idaho. Maximum water temperatures in Castle, Shoofly, Little Jacks, and Big Jacks creeks during low flows during a drought in 1994 ranged from 26.7° C to 29.0° C. Water temperatures fluctuated 9.5-11° C during the 24-h period maximum temperatures were observed. Stream flows at the lower end of Big Jacks and Little Jacks creeks in 1994 were 3 s -1 and subsided underground 50-130 m downstream pools inhabited by trout. Trout were distributed to lower elevations where drainage basin area was larger in 2 of 3 yr ( P 5 km downstream of the lowest pool inhabited by trout in 1995-1996.     

Stinger utilization and predation in the scorpion Paruroctonus boreus

The utilization of the stinger and the predatory technique of the scorpion, Paruroctonus boreus, was studied under laboratory conditions. During the study, 83 feedings were observed. Age of the scorpions and the percentage of prey stung by them were used to classify the scorpions into groups. The scorpions aged 13–61 days always stung prey. After 62 days the scorpions began to selectively utilize the stinger. Utilization declined until it reached 30 percent in the adult stage. The stinger is apparently necessary for prey capture only in the early life stages.       

Anti-apoptotic mechanisms of HIV: lessons and novel approaches to curing HIV

Past efforts at curing infection with the human immunodeficiency virus (HIV) have been blocked by the resistance of some infected cells to viral cytopathic effects and the associated development of a latent viral reservoir. Furthermore, current efforts to clear the viral reservoir by means of reactivating latent virus are hampered by the lack of cell death in the newly productively infected cells. The purpose of this review is to describe the many anti-apoptotic mechanisms of HIV, as well as the current limitations in the field. Only by understanding how infected cells avoid HIV-induced cell death can an effective strategy to kill infected cells be developed.     

Book reviews

This paper traces the relationship between the food committees of the Royal Society and government during the First World War, concentrating on the period up to the resignation of Lord Devonport as first Food Controller. It argues that, in the context of a radical public science discourse emanating from some sections of the scientific community and greatly increased contacts between scientists and government, the food scientists of the committees were moved to press for a formalization of the committees' role in food policy. The members constantly manoeuvred to achieve this aim, but also used a network of alternative channels into the heart of the policy process to get their findings translated into hard policy. In doing so, they explicitly rehearsed characteristic 'public science' arguments. In the institutional blur of wartime state-science relations, scientists often got close to the policy-making process. Post-War, the state swiftly moved to clarify the position: science was to be given more money, but was to be specifically blocked by new administrative arrangements embodied in the Haldane Report on the Machinery of Government from having any say in the core areas of general policy, the expert domain of the generalist policy-maker.     

Environmental sustainability and information systems: The similarity

Application of information technology and environmental planning share two very important characteristics: they are both concerned with planning, evaluating, and directing human activity in a wider context, and this activity is multiaspectual, multimodal, and multidisciplinary in scope. Further, the ideal in both cases is sustainable, long-term activity that brings overall good rather than harm. This paper discusses the multiaspectual nature of environmental sustainability and shows briefly how this understanding can be translated to the field of information systems.