Compositional nonblocking verification with always enabled and selfloop-only events

This report proposes to improve compositional nonblocking verification through the use of two special event types: always enabled and selfloop-only events. Compositional verification involves abstraction to simplify parts of a system during verification. Normally, this abstraction is based on the set of events not used in the remainder of the system. Here, it is proposed to exploit more knowledge about the system and abstract events even though they are used in the remainder of the system. This can lead to more simplification than was previously possible. Abstraction rules from previous work are extended to respect the new special events and proofs show these rules still preserve nonblocking. The rules have been implemented in Waters and experimental results demonstrate that these extended simplification rules help verify several industrial-scale discrete event system models while achieving better state-space reduction than before

Using state machines for the visualisation of specifications via refinement

We talk in this paper about using state machines and refinement to characterise the visualisation of a computation. We use Z specifications to give examples of systems in the usual way, and then use Z schemas to also represent states and transitions in state machines, which we consider to be a particular kind of visualisation of a specified system. We have investigated the principle of substitutivity and the idea of downward simulation to check whether or not a refinement relation exists between the specification and the state machine. We are looking at this because we believe that the soundness of the visualisation can be captured by such a refinement relationship

An algorithm for compositional nonblocking verification using special events

This paper proposes to improve compositional nonblocking verification of discrete event systems through the use of special events. Compositional verification involves abstraction to simplify parts of a system during verification. Normally, this abstraction is based on the set of events not used in the remainder of the system, i.e., in the part of the system not being simplified. Here, it is proposed to exploit more knowledge about the remainder of the system and check how events are being used. Always enabled events, selfloop-only events, failing events, and blocked events are easy to detect and often help with simplification even though they are used in the remainder of the system. Abstraction rules from previous work are generalised, and experimental results demonstrate the applicability of the resulting algorithm to verify several industrial-scale discrete event system models, while achieving better state-space reduction than before

Association of Factor V Leiden with Subsequent Atherothrombotic Events:A GENIUS-CHD Study of Individual Participant Data

BACKGROUND: Studies examining the role of factor V Leiden among patients at higher risk of atherothrombotic events, such as those with established coronary heart disease (CHD), are lacking. Given that coagulation is involved in the thrombus formation stage on atherosclerotic plaque rupture, we hypothesized that factor V Leiden may be a stronger risk factor for atherothrombotic events in patients with established CHD. METHODS: We performed an individual-level meta-analysis including 25 prospective studies (18 cohorts, 3 case-cohorts, 4 randomized trials) from the GENIUS-CHD (Genetics of Subsequent Coronary Heart Disease) consortium involving patients with established CHD at baseline. Participating studies genotyped factor V Leiden status and shared risk estimates for the outcomes of interest using a centrally developed statistical code with harmonized definitions across studies. Cox proportional hazards regression models were used to obtain age- and sex-adjusted estimates. The obtained estimates were pooled using fixed-effect meta-analysis. The primary outcome was composite of myocardial infarction and CHD death. Secondary outcomes included any stroke, ischemic stroke, coronary revascularization, cardiovascular mortality, and all-cause mortality. RESULTS: The studies included 69 681 individuals of whom 3190 (4.6%) were either heterozygous or homozygous (n=47) carriers of factor V Leiden. Median follow-up per study ranged from 1.0 to 10.6 years. A total of 20 studies with 61 147 participants and 6849 events contributed to analyses of the primary outcome. Factor V Leiden was not associated with the combined outcome of myocardial infarction and CHD death (hazard ratio, 1.03 [95% CI, 0.92-1.16]; I2=28%; P-heterogeneity=0.12). Subgroup analysis according to baseline characteristics or strata of traditional cardiovascular risk factors did not show relevant differences. Similarly, risk estimates for the secondary outcomes including stroke, coronary revascularization, cardiovascular mortality, and all-cause mortality were also close to identity. CONCLUSIONS: Factor V Leiden was not associated with increased risk of subsequent atherothrombotic events and mortality in high-risk participants with established and treated CHD. Routine assessment of factor V Leiden status is unlikely to improve atherothrombotic events risk stratification in this population

Subsequent Event Risk in Individuals with Established Coronary Heart Disease:Design and Rationale of the GENIUS-CHD Consortium

BACKGROUND: The "GENetIcs of sUbSequent Coronary Heart Disease" (GENIUS-CHD) consortium was established to facilitate discovery and validation of genetic variants and biomarkers for risk of subsequent CHD events, in individuals with established CHD. METHODS: The consortium currently includes 57 studies from 18 countries, recruiting 185,614 participants with either acute coronary syndrome, stable CHD or a mixture of both at baseline. All studies collected biological samples and followed-up study participants prospectively for subsequent events. RESULTS: Enrollment into the individual studies took place between 1985 to present day with duration of follow up ranging from 9 months to 15 years. Within each study, participants with CHD are predominantly of self-reported European descent (38%-100%), mostly male (44%-91%) with mean ages at recruitment ranging from 40 to 75 years. Initial feasibility analyses, using a federated analysis approach, yielded expected associations between age (HR 1.15 95% CI 1.14-1.16) per 5-year increase, male sex (HR 1.17, 95% CI 1.13-1.21) and smoking (HR 1.43, 95% CI 1.35-1.51) with risk of subsequent CHD death or myocardial infarction, and differing associations with other individual and composite cardiovascular endpoints. CONCLUSIONS: GENIUS-CHD is a global collaboration seeking to elucidate genetic and non-genetic determinants of subsequent event risk in individuals with established CHD, in order to improve residual risk prediction and identify novel drug targets for secondary prevention. Initial analyses demonstrate the feasibility and reliability of a federated analysis approach. The consortium now plans to initiate and test novel hypotheses as well as supporting replication and validation analyses for other investigators

Characterising sound visualisations of specifications using refinement

Visualisations can be used to help analyse, explore, and validate Z specifications. However, if visualisations contain errors or are used incorrectly then they can be misleading and harmful. The aim of this work is to characterise the soundness of visualisations of Z specifications. We achieve this by using refinement. We look for a refinement relation between a Z specification and its (claimed sound) visualisation. If the relation does not hold, then the visualisation is not sound. The main type of visualisation we investigate is state diagrams. These diagrams are useful for visualising the state and operations of Z specifications. We look at a variety of state diagrams styles before widening the scope to include μ-Chart visualisations and animated visualisations. We find that existing refinement methods should not be used for all types of visualisations. To characterise the soundness of partial visualisations we extend the standard rules to include unexamined states and restricted specifications. Finally, we include examples of the refinement rules being used on our visualisations. This lets us formally show whether each individual visualisation is sound or not

Evidence for Divergence in Populations of Bonobos (Pan paniscus) in the Lomami-Lualaba and Kasai-Sankuru Regions Based on Preliminary Analysis of Craniodental Variation

Historical climatic events and riverine barriers influence the distribution of primates. The River Congo exerts the most significant influence on primate distribution in equatorial Africa, but the extent to which the inner basin of the Congo provided a r

Characterising Sound Visualisations of Specifications using Micro-charts and Refinement

For validation or for communication with a client, it is useful to create a visualisation of a specification. It is important that the visualisation does not mislead the user. In this work we look at how to characterise the conditions for a micro-chart visualisation to be sound. This is done by introducing a new operator to the micro-chart semantics, allowing us to use Z data refinement to find a refinement relation between a Z specification and its (claimed sound) micro-chart visualisation. If the relation does not hold, then the visualisation is not sound