| 1. |
- Culverhouse, R. C., et al.
(författare)
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Collaborative meta-analysis finds no evidence of a strong interaction between stress and 5-HTTLPR genotype contributing to the development of depression
- 2018
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Ingår i: Molecular Psychiatry. - : Springer Science and Business Media LLC. - 1359-4184 .- 1476-5578. ; 23:1, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis that the S allele of the 5-HTTLPR serotonin transporter promoter region is associated with increased risk of depression, but only in individuals exposed to stressful situations, has generated much interest, research and controversy since first proposed in 2003. Multiple meta-analyses combining results from heterogeneous analyses have not settled the issue. To determine the magnitude of the interaction and the conditions under which it might be observed, we performed new analyses on 31 data sets containing 38 802 European ancestry subjects genotyped for 5-HTTLPR and assessed for depression and childhood maltreatment or other stressful life events, and meta-analysed the results. Analyses targeted two stressors (narrow, broad) and two depression outcomes (current, lifetime). All groups that published on this topic prior to the initiation of our study and met the assessment and sample size criteria were invited to participate. Additional groups, identified by consortium members or self-identified in response to our protocol (published prior to the start of analysis) with qualifying unpublished data, were also invited to participate. A uniform data analysis script implementing the protocol was executed by each of the consortium members. Our findings do not support the interaction hypothesis. We found no subgroups or variable definitions for which an interaction between stress and 5-HTTLPR genotype was statistically significant. In contrast, our findings for the main effects of life stressors (strong risk factor) and 5-HTTLPR genotype (no impact on risk) are strikingly consistent across our contributing studies, the original study reporting the interaction and subsequent meta-analyses. Our conclusion is that if an interaction exists in which the S allele of 5-HTTLPR increases risk of depression only in stressed individuals, then it is not broadly generalisable, but must be of modest effect size and only observable in limited situations.
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| 2. |
- Nemati, Farhang
(författare)
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Resource Sharing in Real-Time Systems on Multiprocessors
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years multiprocessor architectures have become mainstream, and multi-core processors are found in products ranging from small portable cell phones to large computer servers. In parallel, research on real-time systems has mainly focused on traditional single-core processors. Hence, in order for real-time systems to fully leverage on the extra capacity offered by new multi-core processors, new design techniques, scheduling approaches, and real-time analysis methods have to be developed. In the multi-core and multiprocessor domain there are mainly two scheduling approaches, global and partitioned scheduling. Under global scheduling each task can execute on any processor at any time while under partitioned scheduling tasks are statically allocated to processors and migration of tasks among processors is not allowed. Besides simplicity and efficiency of partitioned scheduling protocols, existing scheduling and synchronization techniques developed for single-core processor platforms can more easily be extended to partitioned scheduling. This also simplifies migration of existing systems to multi-cores. An important issue related to partitioned scheduling is the distribution of tasks among the processors, which is a bin-packing problem. In this thesis we propose a blocking-aware partitioning heuristic algorithm to distribute tasks onto the processors of a multi-core architecture. The objective of the proposed algorithm is to decrease the blocking overhead of tasks, which reduces the total utilization and has the potential to reduce the number of required processors. In industrial embedded software systems, large and complex systems are usually divided into several components (applications) each of which is developed independently without knowledge of each other, and potentially in parallel. However, the applications may share mutually exclusive resources when they co-execute on a multi-core platform which introduce a challenge for the techniques needed to ensure predictability. In this thesis we have proposed a new synchronization protocol for handling mutually exclusive resources shared among real-time applications on a multi-core platform. The schedulability analysis of each application is performed in isolation and parallel and the requirements of each application with respect to the resources it may share are included in an interface. The protocol did not originally consider any priorities among the applications. We have proposed an additional version of the protocol which grants access to resources based on priorities assigned to the applications. We have also proposed an optimal priority assignment algorithm to assign unique priorities to the applications sharing resources. Our evaluations confirm that the protocol together with the priority assignment algorithm outperforms existing alternatives in most cases. In the proposed synchronization protocol each application is assumed to be allocated on one dedicated core. However, in this thesis we have further extended the synchronization protocol to be applicable for applications allocated on multiple dedicated cores of a multi-core platform. Furthermore, we have shown how to efficiently calculate the resource hold times of resources for applications. The resource hold time of a resource for an application is the maximum duration of time that the application may lock the resource whenever it requests the resource. Finally, the thesis discusses and proposes directions for future work.
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| 3. |
- Ward, B. C., et al.
(författare)
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Optimizing preemption-overhead accounting in multiprocessor real-time systems
- 2014
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Ingår i: ACM International Conference Proceeding Series. - New York, NY, USA : ACM. - 9781450327275 ; , s. 235-243
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Konferensbidrag (refereegranskat)abstract
- There exist two general techniques to account for preemption-related overheads on multiprocessors. This paper presents a new preemption-related overhead-accounting technique, called analytical redistribution of preemption overheads (ARPO), which integrates the two previous techniques to minimize preemption-overhead-related utilization loss. ARPO is applicable under any job-level fixed priority (JLFP) preemptive scheduler, as well as some limited-preemption schedulers. ARPO is evaluated in a new experimentaldesign framework for overhead-aware schedulability studies that addresses unrealistic simplifying assumptions made in previous studies, and is shown to improve real-time schedulability.
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