Recoverable, Abortable, and Adaptive Mutual Exclusion with Sublogarithmic RMR Complexity

We present the first recoverable mutual exclusion (RME) algorithm that is simultaneously abortable, adaptive to point contention, and with sublogarithmic RMR complexity. Our algorithm has O(min(K,log_W N)) RMR passage complexity and O(F + min(K,log_W N)) RMR super-passage complexity, where K is the number of concurrent processes (point contention), W is the size (in bits) of registers, and F is the number of crashes in a super-passage. Under the standard assumption that W = ?(log N), these bounds translate to worst-case O((log N)/(log log N)) passage complexity and O(F + (log N)/(log log N)) super-passage complexity. Our key building blocks are: - A D-process abortable RME algorithm, for D ? W, with O(1) passage complexity and O(1+F) super-passage complexity. We obtain this algorithm by using the Fetch-And-Add (FAA) primitive, unlike prior work on RME that uses Fetch-And-Store (FAS/SWAP). - A generic transformation that transforms any abortable RME algorithm with passage complexity of B < W, into an abortable RME lock with passage complexity of O(min(K,B))

Formalization and confirmation of the Boyd-Epley operating system model

An approach to operating system modelling is described in which the simultaneous and synergistic application of tractable queueing theory models and their simulatable refinements is essential. Cross checking of these models against each other and against the real system results in a degree of confirmation not achievable by relying on either analytic or simulation models alone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23006/1/0000574.pd

Evacetrapib and Cardiovascular Outcomes in High-Risk Vascular Disease

BACKGROUND: The cholesteryl ester transfer protein inhibitor evacetrapib substantially raises the high-density lipoprotein (HDL) cholesterol level, reduces the low-density lipoprotein (LDL) cholesterol level, and enhances cellular cholesterol efflux capacity. We sought to determine the effect of evacetrapib on major adverse cardiovascular outcomes in patients with high-risk vascular disease. METHODS: In a multicenter, randomized, double-blind, placebo-controlled phase 3 trial, we enrolled 12,092 patients who had at least one of the following conditions: an acute coronary syndrome within the previous 30 to 365 days, cerebrovascular atherosclerotic disease, peripheral vascular arterial disease, or diabetes mellitus with coronary artery disease. Patients were randomly assigned to receive either evacetrapib at a dose of 130 mg or matching placebo, administered daily, in addition to standard medical therapy. The primary efficacy end point was the first occurrence of any component of the composite of death from cardiovascular causes, myocardial infarction, stroke, coronary revascularization, or hospitalization for unstable angina. RESULTS: At 3 months, a 31.1% decrease in the mean LDL cholesterol level was observed with evacetrapib versus a 6.0% increase with placebo, and a 133.2% increase in the mean HDL cholesterol level was seen with evacetrapib versus a 1.6% increase with placebo. After 1363 of the planned 1670 primary end-point events had occurred, the data and safety monitoring board recommended that the trial be terminated early because of a lack of efficacy. After a median of 26 months of evacetrapib or placebo, a primary end-point event occurred in 12.9% of the patients in the evacetrapib group and in 12.8% of those in the placebo group (hazard ratio, 1.01; 95% confidence interval, 0.91 to 1.11; P=0.91). CONCLUSIONS: Although the cholesteryl ester transfer protein inhibitor evacetrapib had favorable effects on established lipid biomarkers, treatment with evacetrapib did not result in a lower rate of cardiovascular events than placebo among patients with high-risk vascular disease. (Funded by Eli Lilly; ACCELERATE ClinicalTrials.gov number, NCT01687998 .)

Chronic Stroke Outcome Measures for Motor Function Intervention Trials: Expert Panel Recommendations.

BackgroundAbout half of survivors with stroke experience severe and significant long-term disability. The purpose of this article is to review the state of the science and to make recommendations for measuring patient-centric outcomes in interventions for motor improvement in the chronic stroke phase.Methods and resultsA 9-member expert panel reviewed evidence to identify measures of upper and lower extremity function used to date as outcomes in trials with patients who experienced a stroke ≥6 months before assessment. Outcome measures were screened using StrokEDGE consensus panel recommendations, and evaluated for availability of a published minimal clinically important difference. Measures meeting these criteria were further evaluated with regard to their level of measurement, psychometric properties, and ability of minimal clinically important difference to capture gains associated with improved function and clinical relevance to patients, to arrive at recommendations. A systematic literature review yielded 115 clinical trials of upper and lower extremity function in chronic stroke that used a total of 34 outcome measures. Seven of these had published minimal clinically important differences and were recommended or highly recommended by StrokEDGE. Those are the Fugl-Meyer Upper Extremity and Lower Extremity scales, Wolf Motor Function Test, Action Research Arm Test, Ten-Meter and Six-Minute Walk Tests, and the Stroke Impact Scale. All had evidence for their psychometric performance, although the strength of evidence for validity varied, especially in populations with chronic stroke Fugl-Meyer Upper and Lower Extremity scales showing the strongest evidence for validity.ConclusionsThe panel recommends that the Fugl-Meyer Upper and Lower Extremity scales be used as primary outcomes in intervention trials targeting motor function in populations with chronic stroke. The other 6 measures are recommended as secondary outcomes