Consider an asynchronous network in a shared-memory environment consisting of n nodes. Assume that up to f of the nodes might be Byzantine (n > 12f), where the adversary is full-information and ...dynamic (sometimes called adaptive). In addition, the non-Byzantine nodes may undergo transient failures. Nodes advance in atomic steps, which consist of reading all registers, performing some calculation and writing to all registers. This paper contains three main contributions. First, the clock-function problem is defined, which is a generalization of the clock synchronization problem. This generalization encapsulates previous clock synchronization problem definitions while extending them to the current paper's model. Second, a randomized asynchronous self-stabilizing Byzantine tolerant clock synchronization algorithm is presented. In the construction of the clock synchronization algorithm, a building block that ensures different nodes advance at similar rates is developed. This feature is the third contribution of the paper. It is self-stabilizing and Byzantine tolerant and can be used as a building block for different algorithms that operate in an asynchronous self-stabilizing Byzantine model. The convergence time of the presented algorithm is exponential. Observe that in the asynchronous setting the best known full-information dynamic Byzantine agreement also has expected exponential convergence time, even though currently there is no known reduction between the two.
One of the main challenges in building a large scale publish-subscribe infrastructure in an enterprise network, is to provide the subscribers with the required information, while minimizing the ...consumed host and network resources. Typically, previous approaches utilize either IP multicast or point-to-point unicast for efficient dissemination of the information. In this work, we propose a novel hybrid framework, which is a combination of both multicast and unicast data dissemination. Our hybrid framework allows us to take the advantages of both multicast and unicast, while avoiding their drawbacks. We investigate several algorithms for computing the best mapping of publishers' transmissions into multicast and unicast transport. Using extensive simulations, we show that our hybrid framework reduces consumed host and network resources, outperforming traditional solutions. To insure the subscribers interests closely resemble those of real-world settings, our simulations are based on stock market data and on recorded IBM WebShpere subscriptions.
Many challenging tasks in sensor networks, including sensor calibration, ranking of nodes, monitoring, event region detection, collaborative filtering, collaborative signal processing, {\em etc.}, ...can be formulated as a problem of solving a linear system of equations. Several recent works propose different distributed algorithms for solving these problems, usually by using linear iterative numerical methods. The main problem with previous approaches is that once the problem inputs change during the process of computation, the computation may output unexpected results. In real life settings, sensor measurements are subject to varying environmental conditions and to measurement noise. We present a simple iterative scheme called SS-Iterative for solving systems of linear equations, and examine its properties in the self-stabilizing perspective. We analyze the behavior of the proposed scheme under changing input sequences using two different assumptions on the input: a box bound, and a probabilistic distribution. As a case study, we discuss the sensor calibration problem and provide simulation results to support the applicability of our approach.
Soft real-time applications require timely delivery of messages conforming to the soft real-time constraints. Satisfying such requirements is a complex task both due to the volatile nature of ...distributed environments, as well as due to numerous domain-specific factors that affect message latency. Prompt detection of the root-cause of excessive message delay allows a distributed system to react accordingly. This may significantly improve compliance with the required timeliness constraints. In this work, we present a novel approach for distributed performance monitoring of soft-real time distributed systems. We propose to employ recent distributed algorithms from the statistical signal processing and learning domains, and to utilize them in a different context of online performance monitoring and root-cause analysis, for pinpointing the reasons for violation of performance requirements. Our approach is general and can be used for monitoring of any distributed system, and is not limited to the soft real-time domain. We have implemented the proposed framework in TransFab, an IBM prototype of soft real-time messaging fabric. In addition to root-cause analysis, the framework includes facilities to resolve resource allocation problems, such as memory and bandwidth deficiency. The experiments demonstrate that the system can identify and resolve latency problems in a timely fashion.
A comprehensive systematic literature review of the health-related quality-of-life (HRQOL) differences among individuals with chronic ankle instability (CAI), ankle-sprain copers, and healthy control ...participants has not been conducted. It could provide a better indication of the self-reported deficits that may be present in individuals with CAI.
To systematically summarize the extent to which HRQOL deficits are present in individuals with CAI.
We searched for articles in the electronic databases of EBSCO Host and PubMed Central using key words chronic, functional, mechanical, coper, instability, sprains, and patient-assessed. We also performed a hand search of reference lists, authors, and patient-reported outcomes (PROs) of the articles screened for inclusion.
Studies were included if they (1) incorporated a PRO as a participant descriptor or as a study outcome to compare adults with CAI to ankle-sprain copers or healthy controls, (2) were written in English, and (3) were published in peer-reviewed journals.
Two authors independently assessed methodologic quality using the modified Downs and Black Index. Articles were filtered into 3 categories based on between-groups comparisons: CAI and copers, CAI and healthy control participants, copers and healthy participants. We calculated Hedges g effect sizes and 95% confidence intervals to examine PRO group differences.
Of the 124 studies assessed for eligibility, 27 were included. A total of 24 articles compared PROs in individuals with CAI and healthy controls, 7 compared individuals with CAI and copers, and 4 compared copers and healthy controls. Quality scores on the modified Downs and Black Index ranged from 52.9% to 88.2%, with 8 high-, 16 moderate-, and 3 low-quality studies. Overall, we observed moderate to strong evidence that individuals with CAI displayed deficits on generic and region-specific PROs compared with copers and healthy controls. However, evidence that differences exist between copers and healthy controls was conflicting. In addition, for dimension-specific outcomes, evidence to suggest that fear of reinjury is heightened in individuals with CAI was limited.
The evidence suggested that CAI is associated with functional and HRQOL deficits, particularly when examined with region-specific PROs. However, PROs do not appear to differ between copers and healthy controls.
In this Letter we study a system consisting of two nearly degenerate mechanical modes that couple to a single mode of an optical cavity. We show that this coupling leads to nearly complete (99.5%) ...hybridization of the two mechanical modes into a bright mode that experiences strong optomechanical interactions and a dark mode that experiences almost no optomechanical interactions. We use this hybridization to transfer energy between the mechanical modes with 40% efficiency.
Assessment of health-related quality of life (HRQOL) after injury is important. Differences in HRQOL between nonathletes and athletes and between injured and uninjured athletes have been ...demonstrated; however, the evidence has not been synthesized.
To answer the following questions: (1) Does HRQOL differ among adolescent and collegiate athletes and nonathletes? (2) Does HRQOL differ between injured adolescent and collegiate athletes or between athletes with a history of injury and uninjured athletes or those without a history of injury?
We systematically searched CINAHL, MEDLINE, SPORTDiscus, and PubMed. A hand search of references was also conducted.
Studies were included if they used generic instruments to compare HRQOL outcomes between athletes and nonathletes and between uninjured and injured athletes. Studies were excluded if they did not use a generic instrument, pertained to instrument development, or included retired athletes or athletes with a chronic disease.
We assessed study quality using the modified Downs and Black Index Tool. Bias-corrected Hedges g effect sizes and 95% confidence intervals (CIs) were calculated. The Strength of Recommendation Taxonomy (SORT) was used to determine the overall strength of the recommendation. A random-effects meta-analysis was performed for all studies using the composite or total score.
Eight studies with modified Downs and Black scores ranging from 70.6% to 88.4% were included. For question 1, the overall random-effects meta-analysis was weak (effect size = 0.27, 95% confidence interval = 0.14, 0.40; P < .001). For question 2, the overall random-effects meta-analysis was moderate (effect size = 0.68, 95% confidence interval = 0.42, 0.95; P < .001).
Grade A evidence indicates that athletes reported better HRQOL than nonathletes and that uninjured athletes reported better HRQOL than injured athletes. However, the overall effect for question 1 was weak, suggesting that the differences between athletes and nonathletes may not be clinically meaningful. Clinicians should monitor HRQOL after injury to ensure that all dimensions of health are appropriately treated.
The mammalian telencephalon plays critical roles in cognition, motor function, and emotion. Though many of the genes required for its development have been identified, the distant-acting regulatory ...sequences orchestrating their in vivo expression are mostly unknown. Here, we describe a digital atlas of in vivo enhancers active in subregions of the developing telencephalon. We identified more than 4,600 candidate embryonic forebrain enhancers and studied the in vivo activity of 329 of these sequences in transgenic mouse embryos. We generated serial sets of histological brain sections for 145 reproducible forebrain enhancers, resulting in a publicly accessible web-based data collection comprising more than 32,000 sections. We also used epigenomic analysis of human and mouse cortex tissue to directly compare the genome-wide enhancer architecture in these species. These data provide a primary resource for investigating gene regulatory mechanisms of telencephalon development and enable studies of the role of distant-acting enhancers in neurodevelopmental disorders.
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► Genome-wide screen identifies distant-acting enhancers in the developing forebrain ► High-resolution mapping shows in vivo enhancer activities in transgenic mice ► Computational analysis provides sequence classifiers for telencephalon subregions ► Comparison of human and mouse cortex reveals differences in enhancer architecture
A genome-wide screen combined with high-resolution histological analysis in transgenic mouse embryos has identified a large number of distant-acting enhancers that are active in specific subregions of the forebrain during development. Information about these enhancers is available in a publicly accessible database.
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