H2O: An Autonomic, Resource-Aware Distributed Database System

This paper presents the design of an autonomic, resource-aware distributed database which enables data to be backed up and shared without complex manual administration. The database, H2O, is designed to make use of unused resources on workstation machines. Creating and maintaining highly-available, replicated database systems can be difficult for untrained users, and costly for IT departments. H2O reduces the need for manual administration by autonomically replicating data and load-balancing across machines in an enterprise. Provisioning hardware to run a database system can be unnecessarily costly as most organizations already possess large quantities of idle resources in workstation machines. H2O is designed to utilize this unused capacity by using resource availability information to place data and plan queries over workstation machines that are already being used for other tasks. This paper discusses the requirements for such a system and presents the design and implementation of H2O.Comment: Presented at SICSA PhD Conference 2010 (http://www.sicsaconf.org/

Letter

"Angus MacDonald was Chief Trader at Fort Colville (originally spelled Colvile) and this letter was to his son-in-law, James McKenzie, a former Hudson's Bay Company clerk at the same fort.

Aspects of colonic motility in idiopathic slow transit constipation

This thesis sets out to examine the hypothesis that some patients with idiopathic constipation, notably those who develop their symptoms following childbirth or hysterectomy, have regional as opposed to total colonic dysmotility. Such a group may be amenable to segmental rather than total colonic resection. Several clinical studies are presented which establish postchildbirth/hysterectomy constipation as a distinct subgroup of idiopathic constipation. Studies of gastric emptying demonstrate that patients with postchildbirth/hysterectomy constipation have normal motility in the proximal gastrointestinal tract. In contrast, patients with idiopathic constipation have prolonged gastric emptying indicating that proximal GI dysmotility may form a significant component of the presenting symptoms. Having identified that the proximal GI tract appears normal in patients with postchildbirth/hysterectomy constipation the next task was to identify in which region of the colon the dysmotility was most severe. Segmental colonic transit studies, using radio-opaque markers, identify delayed transit in the left colon, while dynamic radio-isotope studies localise the area of abnormality to the sigmoid colon. Colonic manometry studies, using a water-perfusion catheter point to a region of hindgut dysmotility which manifests as an excess of low pressure waves at rest and a specific failure to generate high pressure propagative waves. The usefulness of prostigmine provocation testing is examined critically in this group of patients and the pitfalls of this technique are presented

An Approach to Ad hoc Cloud Computing

We consider how underused computing resources within an enterprise may be harnessed to improve utilization and create an elastic computing infrastructure. Most current cloud provision involves a data center model, in which clusters of machines are dedicated to running cloud infrastructure software. We propose an additional model, the ad hoc cloud, in which infrastructure software is distributed over resources harvested from machines already in existence within an enterprise. In contrast to the data center cloud model, resource levels are not established a priori, nor are resources dedicated exclusively to the cloud while in use. A participating machine is not dedicated to the cloud, but has some other primary purpose such as running interactive processes for a particular user. We outline the major implementation challenges and one approach to tackling them

Study in epidemiology: illustrated by a diphtheria epidemic

The consideration of Epidemic disease here set out, while illustrated by the study of a Diphtheria Epidemic, represents rather the conclusions arrived at after some twenty years experience of disease in general gained in the practice of Medicine and Surgery, amplified by two years recently devoted to the study of Preventive Medicine and Bacteriology in particular. Little of originality is claimed ; but the exceptional advantage of being able to discuss an epidemic from personal investigation thereof, from the clinical and epidemiological at the same time as from the Bacteriological standpoint is undoubted. Personal experience would stand for little, unless it had been aided by the study of the recent and current literature on the subject of Diphtheria and Epidemics in general. Contributions to the various Medical Journals, `Public Health,' Journal of Hygiene, and different publications and text books have all been taken advantage of ; and amongst others contributing to these may be mentioned the names of Loeffler, Newsholme, Newman, Theobald Smith, Cobbett, Graham Smith, Delépine, Woodhead. I may add that I owe much to Professor Delépine of Manchester, under whom I spent various periods of study from 1908 to 1910 ; for no one can come in contact with him without being infected with his enthusiasm in the cause of Preventive Medicine and trying to emulate in some degree his extraordinary precision and thoroughness and attempting to adopt his breadth of outlook. The personal friendship as well as continuous help and suggestion of Dr. Buckley, Medical Officer of Health for Crewe, greatly assisted my work at Crewe

Towards Adaptable and Adaptive Policy-Free Middleware

We believe that to fully support adaptive distributed applications, middleware must itself be adaptable, adaptive and policy-free. In this paper we present a new language-independent adaptable and adaptive policy framework suitable for integration in a wide variety of middleware systems. This framework facilitates the construction of adaptive distributed applications. The framework addresses adaptability through its ability to represent a wide range of specific middleware policies. Adaptiveness is supported by a rich contextual model, through which an application programmer may control precisely how policies should be selected for any particular interaction with the middleware. A contextual pattern mechanism facilitates the succinct expression of both coarse- and fine-grain policy contexts. Policies may be specified and altered dynamically, and may themselves take account of dynamic conditions. The framework contains no hard-wired policies; instead, all policies can be configured.Comment: Submitted to Dependable and Adaptive Distributed Systems Track, ACM SAC 200

Insurance loss coverage and social welfare

Restrictions on insurance risk classification may induce adverse selection, which is usually perceived as a bad outcome, both for insurers and for society. However, a social benefit of modest adverse selection is that it can lead to an increase in `loss coverage', defined as expected losses compensated by insurance for the whole population. We reconcile the concept of loss coverage to a utilitarian concept of social welfare commonly found in economic literature on risk classification. For iso-elastic insurance demand, ranking risk classification schemes by (observable) loss coverage always gives the same ordering as ranking by (unobservable) social welfare

Conservation implications of the invasion of southern Africa by alien organisms

Bibliography: pages 792-808.Alien species known to be invading untransformed ecosystems in southern Africa, and, more particularly, those inside nature reserves, were identified. The extent and ecological impacts of these invasions were assessed. Their control within reserves was also evaluated. Research approaches used were; literature review (which included an international review), a detailed questionnaire survey of alien plant invasions in 307 reserves, rapid field surveys of 60 reserves, intensive case studies of four reserves (Cape of Good Hope Nature Reserve, Hluhluwe-Umfolozi Game Reserve, Kruger National Park, Pella Fynbos Research Site), international comparison with case-study reserves in other savanna and Mediterranean-type biomes, and field evaluation of control methods for alien plants in the two fynbos reserves. Ecological impacts of alien invasions throughout the subcontinent were determined from historical changes in vertebrate populations, including detailed studies of three native birds (Bostrychia hagedash, Lybius leucomelas, Ploceus velatus) expanding their ranges, partly in response to the spread of invasive alien trees. The results are presented in eight chapters, comprising 26 published (or submitted) papers, an introduction and a concluding summary. One chapter covers contributions to the theoretical understanding of invasion processes, including a prediction of their interaction with rapid global environmental change. The conclusion is reached that alien invasions pose a serious challenge to nature conservation in the region. Mostly this comes from alien woody plants but the importance of herbaceous plants has possibly been underestimated regionally. Introduced mammalian pathogens and predatory fishes have also had important effects. Alien invertebrates have been poorly studied (the ant lridomyrmex humilis poses a significant threat). Alien terrestrial vertebrates have generally had only localized effects. Alien plant invasions affect all biomes, with riparian ecosystems being regionally threatened. Mesic biomes and habitats are usually more invaded by alien plants than xeric equivalents. 281 alien vascular plant species were recorded invading vegetation within nature reserves (an average of 12 species per reserve) with an additional 200 species being possibly present but unrecorded (an average of 18 species per reserve). By 1984, the 54 plant taxa recorded invading reserves most frequently were estimated, on average, to be present in 30% of the 11cm x 11cm grid cells of the reserves they were invading. The average potential future extent of these invasions was estimated to be 51%. Control had, on average, been initiated for two plant species in each reserve and 18% of these operations had already resulted in complete eradication. Reported control costs were particularly high for the woody plants which pose a serious threat to the highly endemic flora of the fynbos biome, on average R48 284/reserve (R1,8/ha = US Dollar 1,2/ha) in 1983. These high costs were validated experimentally. A computerized optimization model, aimed at minimizing the costs of controlling the most intractable shrub invader of fynbos, Acacia saligna, was developed from the results of a field experiment at the Pella site. Practical field- scale control of these invasions was assessed to be feasible, using the results of repeated monitoring of permanent plots in the Cape of Good Hope Nature Reserve. Control strategies and regional priorities, based on the theoretical and practical insights gained from this study, are proposed. Even though the intensity of invasions is likely to increase in the foreseeable future, in part as a result of rapid man-induced changes in global climate, it is predicted that these invasions can be controlled if the correct approaches are adopted timeously. Failure to control them, will ensure that the extinction rate of native species will markedly increase and that ecosystem functioning will be altered significantly at a local scale and, conceivably also, at a regional scale