Frans Henskens

Stability in a Persistent Store Based on a Large Virtual Memory

Persistent systems support mechanisms which allow programs to create and manipulate arbitrary data structures which outlive the execution of the program which created them. A persistent store supports mechanisms for the storage and retrieval of objects in a uniform manner regardless of their lifetime. Since all data of the system is in this repository it is important that it always be in a consistent state. This property is called integrity. The integrity of the persistent store depends in part on the store being resilient to failures. That is, when an error occurs the store can recover to a previously recorded consistent state. The mechanism for recording this state and performing recovery is called stability. This paper considers an implementation of a persistent store based on a large virtual memory and shows how stability is achieved.

Australian schizophrenia research bank: a database of comprehensive clinical, endophenotypic and genetic data for aetiological studies of schizophrenia

Objective: This article describes the establishment of the Australian Schizophrenia Research Bank (ASRB), which operates to collect, store and distribute linked clinical, cognitive, neuroimaging and genetic data from a large sample of people with schizophrenia and healthy controls. Method: Recruitment sources for the schizophrenia sample include a multi-media national advertising campaign, inpatient and community treatment services and non-government support agencies. Healthy controls have been recruited primarily through multi-media advertisements. All participants undergo an extensive diagnostic and family history assessment, neuropsychological evaluation, and blood sample donation for genetic studies. Selected individuals also complete structural MRI scans. Results: Preliminary analyses of 493 schizophrenia cases and 293 healthy controls are reported. Mean age was 39.54 years (SD = 11.1) for the schizophrenia participants and 37.38 years (SD = 13.12) for healthy controls. Compared to the controls, features of the schizophrenia sample included a higher proportion of males (cases 65.9%; controls 46.8%), fewer living in married or de facto relationships (cases 16.1%; controls 53.6%) and fewer years of education (cases 13.05, SD = 2.84; controls 15.14, SD = 3.13), as well as lower current IQ (cases 102.68, SD = 15.51; controls 118.28, SD = 10.18). These and other sample characteristics are compared to those reported in another large Australian sample (i.e. the Low Prevalence Disorders Study), revealing some differences that reflect the different sampling methods of these two studies. Conclusion: The ASRB is a valuable and accessible schizophrenia research facility for use by approved scientific investigators. As recruitment continues, the approach to sampling for both cases and controls will need to be modified to ensure that the ASRB samples are as broadly representative as possible of all cases of schizophrenia and healthy controls.

An examination of operating system support for persistent object systems

Examines operating system support for persistent systems that execute on conventional hardware architectures. The focus of the paper is to examine the inadequacies of traditional operating systems as vehicles for the construction of persistent systems. The authors concentrate on four major areas, namely addressing, stability and resilience, process management and protection. They examine the consequences of making the operating system kernel itself persistent. They conclude by outlining the requirements which must be met by future operating systems designed to support orthogonal persistence.<<ETX>>

The Australian EEG Database

The Australian EEG Database is a web-based de-identified searchable database of 18,500 EEG records recorded at a regional public hospital over an 11-year period. Patients range in age from a premature infant born at 24 weeks gestation, through to people aged over 90 years. This paper will describe the history of the database, the range of patients represented in the database, and the nature of the text-based and digital data contained in the database. Preliminary results of the first two studies undertaken using the database are presented. Plans for sharing data from the Australian EEG database with researchers are discussed. We anticipate that such data will be useful in not only helping to answer clinical questions but also in the field of mathematical modeling of the EEG.

Stability in a Network of MONADS-PC Computers

The MONADS-PC computer system implements an architecture supporting a very large persistent store based on a uniform virtual memory. We have previously shown how this virtual memory scheme can be extended to encompass a local area network of MONADS-PC computers. In this paper we examine the question of the integrity of the store in such a network. A modification to the MONADS architecture to implement stability is reviewed and extended to guarantee stability of a network-wide persistent store. The stability scheme allows for temporary interruption to the physical network without affecting the validity of exported pages owned by a node.

Improving Access to Information and Support for Patients With Less Common Cancers: Hematologic Cancer Patients’ Views About Web-Based Approaches

Background Meeting the psychosocial needs of vulnerable groups such as cancer survivors remains an ongoing challenge. This is particularly so for those who have less access to the usual forms of medical specialist and in-person support networks. Internet-based approaches offer an opportunity to better meet patients’ information and support needs by overcoming the barrier of geographic isolation. Objective The aim of the study was to assess the reported level of access to the Internet, preferred sources of information, and preferred sources of support among survivors of hematologic cancers. Method A population-based, Australian state cancer registry invited eligible survivors to complete a survey about psychosocial needs, including items measuring Internet access and patterns of use. Of the 732 eligible survivors invited to participate, 268 (36.6%) completed and returned the pen-and-paper-based survey. Results The majority of participants (186/254, 73.2%) reported a high level of access to the Internet, with higher Internet access associated with a higher level of education, larger household, younger age, and being married or employed. A total of 62.2% (156/251) of survivors indicated they were likely to use the Internet for accessing information, with the percentage much lower (69/251, 28%) for accessing support via the Internet. Likelihood of using the Internet for support was associated with feeling anxious and being employed. Conclusions While the Internet appears to offer promise in increasing equitable access to information and support for cancer survivors for both metropolitan and regional areas, it is viewed less favorably for support and by particular subgroups (eg, older people and those without a university degree) within the survivor population. Promoting greater understanding of this mode of support may be required to achieve its potential. Information and support options other than Web-based approaches may continue to be needed by vulnerable groups of cancer survivors.

White Matter Disruptions in Schizophrenia Are Spatially Widespread and Topologically Converge on Brain Network Hubs

White matter abnormalities associated with schizophrenia have been widely reported, although the consistency of findings across studies is moderate. In this study, neuroimaging was used to investigate white matter pathology and its impact on whole-brain white matter connectivity in one of the largest samples of patients with schizophrenia. Fractional anisotropy (FA) and mean diffusivity (MD) were compared between patients with schizophrenia or schizoaffective disorder (n = 326) and age-matched healthy controls (n = 197). Between-group differences in FA and MD were assessed using voxel-based analysis and permutation testing. Automated whole-brain white matter fiber tracking and the network-based statistic were used to characterize the impact of white matter pathology on the connectome and its rich club. Significant reductions in FA associated with schizophrenia were widespread, encompassing more than 40% (234ml) of cerebral white matter by volume and involving all cerebral lobes. Significant increases in MD were also widespread and distributed similarly. The corpus callosum, cingulum, and thalamic radiations exhibited the most extensive pathology according to effect size. More than 50% of cortico-cortical and cortico-subcortical white matter fiber bundles comprising the connectome were disrupted in schizophrenia. Connections between hub regions comprising the rich club were disproportionately affected. Pathology did not differ between patients with schizophrenia and schizoaffective disorder and was not mediated by medication. In conclusion, although connectivity between cerebral hubs is most extensively disturbed in schizophrenia, white matter pathology is widespread, affecting all cerebral lobes and the cerebellum, leading to disruptions in the majority of the brains fiber bundles.

Addressing moved modules in a capability-based distributed shared memory

The MONADS distributed shared memory (DSM) consists of a single, very large, paged virtual memory space distributed across an arbitrary number of discrete nodes connected to a network. Each node acts as a server for the virtual memory pages stored at that node. The key to transparent access to the pages of the modules stored in the DSM is the use of structured addresses containing embedded location information. There is a problem with allowing modules to be moved because the location information, embedded in the addresses used to access the data in them, does not describe the correct storage location. This paper reviews an initial solution to the problem of accessing pages from moved modules. The required sequence of operations represents a significant, and usually unnecessary system overhead, since most page retrievals involve locally stored pages. An alternate solution to the problem is presented. This solution allows most page accesses, both local or remote and from moved or unmoved modules, to occur without unnecessary overheads.<<ETX>>

Qualifying Types Illustrated by Synchronisation Examples

Qualifying types represent a new approach to modifying the behaviour of instances of other types in a general way, in the form of components which can be designed and implemented without a prior knowledge of the types to be modified or their implementations. This paper illustrates the idea by showing how they can be used to program various standard synchronisation problems, including mutual exclusion, reader-writer synchronisation and several variants of the bounded buffer problem.

Automated assessment and marking of spreadsheet concepts

An academic goal of a university is to ensure that student learning outcomes are achieved to their maximum potential. Attainment of academic goals however, can often be in conflict with attempts to realise administrative or business goals, as these may be perceived as being easily achieved through rationalisation of academic costs. The modern university must find a balance in the optimisation of these goals. This was recognised by (Cranitch 1991) “...with large numbers of students with different learning styles, there is a need to develop instructional arrangements that maximise student learning, while trying to minimise the cost in terms of time, effort and money”. Practically this may mean trying to maximise individual learning outcomes within very large classes, while trying to cope with the problems associated with large classes. One method of doing this is to reduce the logistic load or the management complexity of large classes, eg the PACE system (Oliver & Mitchell, 1996) for assessment management. Another is by automating some of the tasks related to student learning outcomes, eg the provision of consistent, adequate and timely feedback.