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- Henriksson, Roger
(författare)
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Scheduling Garbage Collection in Embedded Systems
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The complexity of systems for automatic control and other safety-critical applications grows rapidly. Computer software represents an increasing part of the complexity. As larger systems are developed, we need to find scalable techniques to manage the complexity in order to guarantee high product quality. Memory management is a key quality factor for these systems. Automatic memory management, or garbage collection, is a technique that significantly reduces the complex problem of correct memory management. The risk of software errors decreases and development time is reduced. Garbage collection techniques suitable for interactive and soft real-time systems exist, but few approaches are suitable for systems with hard real-time requirements, such as control systems (embedded systems). One part of the problem is solved by incremental garbage collection algorithms, which have been presented before. We focus on the scheduling problem which forms the second part of the problem, i.e. how the work of a garbage collector should be scheduled in order to disturb the application program as little as possible. It is studied how a priori scheduling analysis of systems with automatic memory management can be made. The field of garbage collection research is thus joined with the field of scheduling analysis in order to produce a practical synthesis of the two fields. A scheduling strategy is presented that employs the properties of control systems to ensure that no garbage collection work is performed during the execution of critical processes. The hard real-time part of the system is thus never disturbed by garbage collection work. Existing incremental garbage collection algorithms are adapted to the presented strategy. Necessary modifications of the algorithms and the real-time kernel are discussed. A standard scheduling analysis technique, rate monotonic analysis, is extended in order to make a priori analysis of the schedulability of the garbage collector possible. The scheduling algorithm has been implemented in an industrially relevant real-time environment in order to show that the strategy is feasible in practice. The experimental evaluation shows that predictable behaviour and sub-millisecond worst-case delays can be achieved on standard hardware even by a non-optimized prototype garbage collector.
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| 2. |
- Johansson, Mikael, et al.
(författare)
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Tumor blood flow and the cytotoxic effects of estramustine and its constituents in a rat glioma model
- 1997
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Ingår i: Neurosurgery. - : Oxford University Press. - 0148-396X .- 1524-4040. ; 41:1, s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Estramustine (EaM) is a conjugate of nor-nitrogen mustard (NNM) and 17 beta-estradiol (E2) that has cytotoxic and radiosensitizing effects on experimental malignant glioma. Its mechanism of action is only partly understood. To further investigate the mechanism in vivo, the effects on tumor blood flow (TBF) and tumor growth were analyzed.METHODS: TBF was measured by radioactive microspheres, and tumor growth was measured by weight. Apoptosis was evaluated by in situ end labeling and gel electrophoresis. The effects of the constituents NNM and E2 were also evaluated.RESULTS: EaM increased TBF to 153.8 ml/100 g/min after 3 days and to 153.9 ml/100 g/min after 10 days of treatment, compared with 94.0 ml/100 g/min in untreated controls. Cerebral blood flow did not change after EaM treatment. NNM increased TBF but also showed a tendency to increase cerebral blood flow. E2 increased TBF, whereas cerebral blood flow was unchanged. EaM resulted in a rapid reduction in tumor weight from 230 mg in untreated animals to 146 mg after 3 days of treatment. EaM induced an early transient fragmentation of deoxyribonucleic acid in glioma but not in the normal brain. Neither NNM nor E2 affected tumor weight.CONCLUSION: EaM increases TBF in the BT4C rat glioma model with a concomitant rapid antitumoral effect. The increase in TBF could partially be induced by an estrogen-like action of EaM, but the rapid cytotoxic effect of the drug is obviously attributed to the intact EaM compound. This cytotoxic effect might be attributable to the induction of programmed cell death.
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- Salander, Pär, 1948-
(författare)
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Qualities in the short life : psychological studies relevant to patient and spouse in malignant glioma
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with psychological issues concerning patients with malignant gliomas, and their spouses. There is no known medical cure, and the patients have a limited survival expectancy. Therefore studies evaluating new treatment modes, an overall supportive atmosphere, and attempts to avoid imposing unnessesary strain are necessary.Thirty consecutive patients with astrocytomas, grade III-IV, were included in a clinical trial with estramustine phosphate in addition to conventional treatment with surgery and radiotherapy. Both the patients and their spouses participated in the present study which aimed at a deeper understanding of the psychological processes relevant to their situation. By means of repeated thematically structured interviews, patients and spouses were followed separately during the entire course of the disease process. In addition to these interviews, all patients were assessed with a mini-mental examination, and five-month survivors were tested with a comprehensive neuropsychological battery. Questionnaires on reaction to the diagnosis and assessing psychosocial well-being were also administered to the patients.The interviews were analysed with grounded theory methodology and the findings were juxtaposed to concepts in psychoanalysis and coping theory. The main finding was that the patients, despite or owing to their severe medical situations, showed a marked capacity to create protection and hope. By means of biased perception they created an 'illusion' that palliated their strain. This finding is related to object-relational psychoanalysis with obvious implications for the crucial discussion on telling bad news. Another finding was that the spouses displayed different crisis trajectories depending on the overall status of their partners. Different senses of the relationship were related to different modes of coping. Especially spouses to patients with personality changes were put under severe strain and ought to be acknowledged by medical staff. Patients with no obvious deficits five months after termination of primary treatment nevertheless evidenced, at neuropsychological testing, a pronounced deficiancy in long-term memory, but no clear impairment in global intellectual capacities. Estramustine phosphate was found to have a negative impact on sexuality and might be one causative agent behind the decline in long-term memory, but these adversive effects did not seem to affect psychosocial well-being. The selective reminding technique proved to be sensitive in detecting deficits and is recommended in future clinical trials affecting the CNS.
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