| 1. |
- Bridel, Claire, et al.
(author)
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Diagnostic Value of Cerebrospinal Fluid Neurofilament Light Protein in Neurology : A Systematic Review and Meta-analysis
- 2019
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In: JAMA Neurology. - : American Medical Association (AMA). - 2168-6149 .- 2168-6157. ; 76:9, s. 1035-1048
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Research review (peer-reviewed)abstract
- Importance Neurofilament light protein (NfL) is elevated in cerebrospinal fluid (CSF) of a number of neurological conditions compared with healthy controls (HC) and is a candidate biomarker for neuroaxonal damage. The influence of age and sex is largely unknown, and levels across neurological disorders have not been compared systematically to date.Objectives To assess the associations of age, sex, and diagnosis with NfL in CSF (cNfL) and to evaluate its potential in discriminating clinically similar conditions.Data Sources PubMed was searched for studies published between January 1, 2006, and January 1, 2016, reporting cNfL levels (using the search terms neurofilament light and cerebrospinal fluid) in neurological or psychiatric conditions and/or in HC.Study Selection Studies reporting NfL levels measured in lumbar CSF using a commercially available immunoassay, as well as age and sex.Data Extraction and Synthesis Individual-level data were requested from study authors. Generalized linear mixed-effects models were used to estimate the fixed effects of age, sex, and diagnosis on log-transformed NfL levels, with cohort of origin modeled as a random intercept.Main Outcome and Measure The cNfL levels adjusted for age and sex across diagnoses.Results Data were collected for 10 059 individuals (mean [SD] age, 59.7 [18.8] years; 54.1% female). Thirty-five diagnoses were identified, including inflammatory diseases of the central nervous system (n = 2795), dementias and predementia stages (n = 4284), parkinsonian disorders (n = 984), and HC (n = 1332). The cNfL was elevated compared with HC in a majority of neurological conditions studied. Highest levels were observed in cognitively impaired HIV-positive individuals (iHIV), amyotrophic lateral sclerosis, frontotemporal dementia (FTD), and Huntington disease. In 33.3% of diagnoses, including HC, multiple sclerosis, Alzheimer disease (AD), and Parkinson disease (PD), cNfL was higher in men than women. The cNfL increased with age in HC and a majority of neurological conditions, although the association was strongest in HC. The cNfL overlapped in most clinically similar diagnoses except for FTD and iHIV, which segregated from other dementias, and PD, which segregated from atypical parkinsonian syndromes.Conclusions and Relevance These data support the use of cNfL as a biomarker of neuroaxonal damage and indicate that age-specific and sex-specific (and in some cases disease-specific) reference values may be needed. The cNfL has potential to assist the differentiation of FTD from AD and PD from atypical parkinsonian syndromes.
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| 2. |
- Böhmer, Jens, 1981, et al.
(author)
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Absolute Quantification of Donor-Derived Cell-Free DNA in Pediatric and Adult Patients After Heart Transplantation: A Prospective Study.
- 2023
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In: Transplant international : official journal of the European Society for Organ Transplantation. - 0934-0874 .- 1432-2277. ; 36
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Journal article (peer-reviewed)abstract
- In this prospective study we investigated a cohort after heart transplantation with a novel PCR-based approach with focus on treated rejection. Blood samples were collected coincidentally to biopsies, and both absolute levels of dd-cfDNA and donor fraction were reported using digital PCR. 52 patients (11 children and 41 adults) were enrolled (NCT03477383, clinicaltrials.gov), and 557 plasma samples were analyzed. 13 treated rejection episodes >14days after transplantation were observed in 7 patients. Donor fraction showed a median of 0.08% in the cohort and was significantly elevated during rejection (median 0.19%, p < 0.0001), using a cut-off of 0.1%, the sensitivity/specificity were 92%/56% (AUC ROC-curve: 0.78). Absolute levels of dd-cfDNA showed a median of 8.8 copies/mL and were significantly elevated during rejection (median 23, p = 0.0001). Using a cut-off of 7.5 copies/mL, the sensitivity/specificity were 92%/43% for donor fraction (AUC ROC-curve: 0.75). The results support the feasibility of this approach in analyzing dd-cfDNA after heart transplantation. The obtained values are well aligned with results from other trials. The possibility to quantify absolute levels adds important value to the differentiation between ongoing graft damage and quiescent situations.
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| 3. |
- Fan, Xing, 1975-, et al.
(author)
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Guaranteed real-time communication in packet-switched networks with FCFS queuing
- 2009
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In: Computer Networks. - Amsterdam : North Holland. - 1389-1286 .- 1872-7069. ; 53:3, s. 400-417
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Journal article (peer-reviewed)abstract
- In this paper, we propose a feasibility analysis of periodic hard real-time traffic in packet-switched networks using first come first served (FCFS) queuing but no traffic shapers. Our work constitutes a framework that can be adopted for real-time analysis of switched low-cost networks like Ethernet without modification of the standard network components. Our analysis is based on a flexible network and traffic model, e.g., variable-sized frames, arbitrary deadlines and multiple switches. The correctness of our real-time analysis and the tightness of it for network components in single-switch networks are given by theoretical proofs. The performance of the end-to-end real-time analysis is evaluated by simulations. Moreover, our conceptual and experimental comparison studies between our analysis and the commonly used Network Calculus (NC) shows that our analysis can achieve better performance than NC in many cases.
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| 4. |
- Feiertag, Nico, et al.
(author)
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A Compositional Framework for End-to-End Path Delay Calculation of Automotive Systems under Different Path Semantics
- 2008
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In: Proceedings of the IEEE Real-Time System Symposium − Workshop on Compositional Theory and Technology for Real-Time Embedded Systems, Barcelona, Spain, November 30, 2008.
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Conference paper (peer-reviewed)abstract
- While the real-time systems community has developed very valuable approaches to timing and scheduling analysis for processors and buses over the last four decades, another very relevant issue has received only limited attention: end-to-end timing. Most of the known work poses restrictions on specific task activation and communication mechanisms, e.g. unbounded FIFO queues along event-triggered paths. In automotive systems, however, register buffers and periodic sampling are far more common. In this paper, we present a formal framework for the calculation of end-to-end latencies in multi-rate, register-based systems. We show that in systems with sampling, analysis must distinguish between different "meanings" of end-to-end timing. For instance, control engineers are mostly concerned with the "maximum age of data", i.e. the worst-case timing of the latest possible signal. In body electronics, the "first reaction" is key, i.e. worst-case timing of the earliest possible signal. Because the analysis of either case can be different, a clear distinction is mandatory. This paper gives examples and introduces the notion of such end-to-end timing semantics, thereby considering the specific mechanisms and effects typically found in automotive execution platforms such as over- and under-sampling and jitter.
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| 5. |
- Abdelzaher, T., et al.
(author)
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The aperiodic multiprocessor utilization bound for liquid tasks
- 2002
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In: 8th IEEE Real-Time and Embedded Technology and Applications Symposium, 2002. Proceedings. - 1545-3421. - 0769517390 ; , s. 173-184
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Conference paper (peer-reviewed)abstract
- Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utilization bound for schedulability of periodic tasks. In 2001 this bound was generalized by Abdelzaher and Lu to the aperiodic task case. In this paper we further generalize the aperiodic bound to the case of multiprocessors, and present key new insights into schedulability, analysis of aperiodic tasks. We consider a special task model, called the liquid task model, representative of high-performance servers with aperiodic workloads, such as network routers, web servers, proxies, and real-time databases. For this model, we derive the optimal multiprocessor utilization bound, defined on a utilization-like metric we call "synthetic utilization". This bound allows developing constant-time admission control tests that provide utilization-based absolute delay, tees. We show that the real utilization of admitted tasks can be close to unity even when synthetic utilization is kept below the bound. Thus, our results lead to multiprocessor systems which combine constant-time admission control with high utilization while making no periodicity assumptions regarding the task arrival pattern.
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| 6. |
- Andersson, Björn, et al.
(author)
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Average-Case Performance of Static-Priority Scheduling on Multiprocessors
- 2006
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In: ARTES - A Network for Real-Time Research and Graduate Education in Sweden. - 9150618598 ; , s. 513-535
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Book chapter (other academic/artistic)abstract
- This chapter deals with the problem of scheduling a set oftasks to meet deadlines on a computer with multiple processors. Static-priority scheduling is considered,that is, a task is assigned a priority number that never changes and at every moment the highest-priority tasks that request to be executed are selected for execution.Many contemporary computers support static-priority scheduling using two different approaches: with task migration or without task migration. This chapter evaluates the performance of these approaches, using simulation of randomly-generated workloads on a range of different highly-abstracted architectural setups.
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| 7. |
- Andersson, Björn, 1974, et al.
(author)
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Fixed-Priority Preemptive Multiprocessor Scheduling: To Partition or not to Partition
- 2000
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In: Proceedings of the IEEE Conference on Real-Time Computing Systems and Applications, December 12−14, 2000, Cheju Island, South Korea. - 1530-1427. - 0769509304 ; , s. 337−346-
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Conference paper (peer-reviewed)abstract
- Traditional multiprocessor real-time scheduling partitions a task set and applies uniprocessor scheduling on each processor. For architectures where the penalty of migration is low, such as uniform-memory access shared-memory multiprocessors, the non-partitioned method becomes a viable alternative. By allowing a task to resume on another processor than the task was preempted on, some task sets can be scheduled where the partitioned method fails.We address fixed-priority scheduling of periodically arriving tasks on $m$ equally powerful processors having a non-partitioned ready queue. We propose a new priority-assignment scheme for the non-partitioned method. Using an extensive simulation study, we show that the priority-assignment scheme has equivalent performance to the best existing partitioning algorithms, and outperforms existing fixed-priority assignment schemes for the non-partitioned method. We also propose a dispatcher for the non-partitioned method which reduces the number of preemptions to levels below the best partitioning schemes.
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| 8. |
- Andersson, Björn, 1974, et al.
(author)
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Global Priority-Driven Aperiodic Scheduling on Multiprocessors
- 2003
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In: Proceedings. International Parallel and Distributed Processing Symposium, 2003. - 1530-2075. - 0769519261
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Conference paper (peer-reviewed)abstract
- This paper studies multiprocessor scheduling for aperiodic tasks where future arrivals are unknown. A previously proposed priority-driven scheduling algorithm for periodic tasks with migration capability is extended to aperiodic scheduling and is shown to have a capacity bound of 0.5. This bound is close to the best achievable for a priority-driven scheduling algorithm. With an infinite number of processors, no priority-driven scheduling algorithm can perform better. We also propose a simple admission controller which guarantees that admitted tasks meet their deadlines and for many workloads, it admits tasks so that the utilization can be kept above the capacity bound.
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| 9. |
- Andersson, Björn, 1974, et al.
(author)
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Partitioned Aperiodic Scheduling on Multiprocessors
- 2003
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In: Proceedings. International Parallel and Distributed Processing Symposium, 2003. - 1530-2075. - 0769519261
-
Conference paper (peer-reviewed)abstract
- This paper studies multiprocessor scheduling for aperiodic tasks where future arrivals are unknown. We propose an algorithm for tasks without migration capabilities and prove that it has a capacity bound of 0.31. No algorithm for tasks without migration capabilities can have a capacity bound greater than 0.50.
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| 10. |
- Andersson, Björn, 1974, et al.
(author)
-
Preemptive Multiprocessor Scheduling Anomalies
- 2002
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In: Proceedings of the IEEE International Parallel and Distributed Processing Symposium, Ft Lauderdale, Florida, April 15–19, 2002. - 0769515738 ; , s. 12-19
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Conference paper (peer-reviewed)abstract
- Preemptive scheduling of periodically arriving tasks on a multiprocessor is considered. We show that many common multiprocessor real-time scheduling algorithms suffer from scheduling anomalies, that is, deadlines are originally met, but a decrease in execution times or an increase in periods of tasks can cause deadlines to be missed. We propose a partitioned multiprocessor fixed-priority scheduling algorithm with the prominent features that (i) it does not suffer from such scheduling anomalies and (ii) if less than 41% of the capacity is used then deadlines are met.
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