Relating L-Resilience and Wait-Freedom via Hitting Sets

The condition of t-resilience stipulates that an n-process program is only obliged to make progress when at least n-t processes are correct. Put another way, the live sets, the collection of process sets such that progress is required if all the processes in one of these sets are correct, are all sets with at least n-t processes. We show that the ability of arbitrary collection of live sets L to solve distributed tasks is tightly related to the minimum hitting set of L, a minimum cardinality subset of processes that has a non-empty intersection with every live set. Thus, finding the computing power of L is NP-complete. For the special case of colorless tasks that allow participating processes to adopt input or output values of each other, we use a simple simulation to show that a task can be solved L-resiliently if and only if it can be solved (h-1)-resiliently, where h is the size of the minimum hitting set of L. For general tasks, we characterize L-resilient solvability of tasks with respect to a limited notion of weak solvability: in every execution where all processes in some set in L are correct, outputs must be produced for every process in some (possibly different) participating set in L. Given a task T, we construct another task T_L such that T is solvable weakly L-resiliently if and only if T_L is solvable weakly wait-free

An Exploratory Analysis of the Psychological Dimensions of Airline Security and Correlates of Perceived Terrorism Threats: A Study of Active American Airlines Pilots.

The September 11, 2001, terrorist attack resulted in a myriad of new policies designed to enhance aviation security. These policies ostensibly considered the origins of the exact threat facing the United States. Missing, however, were the inputs from rank and file pilots of the airlines that policy makers were attempting to protect. This exploratory study distributed a 50-question survey designed to measure pilot perceptions of security risk and threats. Univariate descriptives were used to examine the extent to which sample data approximated the population of interest. Factor and reliability analysis were used to document the multidimensionality of the constructs and assess the appropriateness of the linear combination of variables used to construct the scales. Finally, correlation analysis was used to better understand which areas of airline security might be targeted by policymakers to enhance existing structures and practices. Results revealed statistically significant differences in the perceptions of pilot security concerns and the focus of current U.S. aviation security policy

Port-site metastasis following robotic-assisted radical hysterectomy for squamous cell cervical cancer

► Port-site metastases can occur following treatment for cervical cancer. ► Port-site metastases can occur following robotic assisted laparoscopic surgery. ► The pathogenesis of port-site metastases is poorly understood

A predictive hazard perception paradigm differentiates driving experience cross-culturally

Hazard perception (HP) tests are used in several developed countries as part of the driver licensing process, where they are believed to have improved road safety; however, relatively little HP research has been conducted in developing countries, which account for 80% of the world’s road fatalities. Previous research suggests that drivers in these countries may be desensitized to hazardous road situations and thus have increased response latencies to hazards, creating validity issues with the typical HP reaction time paradigm. The present study compared Malaysian and UK drivers’ HP skills when watching video clips filmed in both countries, using a predictive paradigm where hazard criterion could not affect performance. Clips filmed in the UK successfully differentiated experience in participants from both countries, however there was no such differentiation in the Malaysian set of videos. Malaysian drivers also predicted hazards less accurately overall, indicating that exposure to a greater number of hazards on Malaysian roads did not have a positive effect on participants’ predictive hazard perception skill. Nonetheless the experiential discrimination noted in this predictive paradigm may provide a practical alternative for hazard perception testing in developing countries