Testing Reactive Probabilistic Processes

We define a testing equivalence in the spirit of De Nicola and Hennessy for reactive probabilistic processes, i.e. for processes where the internal nondeterminism is due to random behaviour. We characterize the testing equivalence in terms of ready-traces. From the characterization it follows that the equivalence is insensitive to the exact moment in time in which an internal probabilistic choice occurs, which is inherent from the original testing equivalence of De Nicola and Hennessy. We also show decidability of the testing equivalence for finite systems for which the complete model may not be known

Changes of Left Ventricular Systolic Function in Patients Undergoing Coronary Artery Bypass Grafting

AIM: This prospective study was designed to evaluate the changes in left ventricular (LV) systolic function after coronary artery bypass grafting (CABG) in patients with both normal and abnormal pre-operative systolic function. METHODS: During the period from October 2017 to October 2018, forty-seven consecutive patients undergoing CABG were enrolled in this prospective study. Transthoracic echocardiography was performed within 1 week before CABG as well as 4 to 6 months after surgery. All measurements were made by a single experienced investigator. RESULTS: While the mean LV ejection fraction (LVEF) showed neither improvement nor significant reduction in the whole group of patients following CABG (from 54.21 ± 15.36 to 53.66 ± 11.56%, p = 0.677), significant improvement in LVEF was detected in the subgroup of patients with pre-operative LV dysfunction (from 40.05 ± 8.65 to 45.85 ± 9.04%, p = 0.008). On the other hand, there was a significant decline in LEFT in the subgroup of patients with normal pre-operative LEFT (from 64.70 ± 9.72 to 59.44 ± 9.75%, p = 0.008). As for the other parameters of systolic function, significant decrease in LV end-diastolic volume index (LVEDVI) (p = 0.001), LV end-systolic volume index (LVESVI) (p = 0.0001), wall motion score index (WMSI) (p = 0.013) and LVmass index in male patients (p = 0.011) was shown only in patients with decreased LVEF after CABG. Patients with improved postoperative LVEF (53.2% of all patients) had significantly lower baseline LVEF (p = 0.0001), higher LVESVI (0.009) and higher WMSI (p = 0.006) vs patients with worsened postoperative LVEF (38.3% of all patients). Postoperative improvement of LVEF was correlated with stabile angina, lack of preoperative myocardial infarction and smoking, higher baseline WMSI, higher LV internal diameters and indexed volumes in diastole and systole and lower baseline LVEF. In stepwise linear regression analysis the value of baseline LVEF appeared as independent predictor of improved LVEF after CABG (B = 0,836%; 95% CI 0.655-1.017; p = 0.0001). CONCLUSION: Our study showed that LVEF, internal baseline diameters and indexed volumes of LV in diastole and systole are important determinants of postoperative change in LVEF. In patients with preoperative depressed myocardial function, there is an improvement in systolic function, whereas in patients with preserved preoperative myocardial function, the decline in postoperative LVEF was detected

NLeSC/DiVE: Dive 1.1

An interactive 3D web viewer of up to million points on one screen that represent data. Provides interaction for viewing high-dimensional data that has been previously embedded in 3D or 2D.Funded by the Netherlands eScience Cente

NLeSC/DiVE: 1.2

An interactive 3D web viewer of up to million points on one screen that represent data. Provides interaction for viewing high-dimensional data that has been previously embedded in 3D or 2D. Based on graphosaurus.js and three.js. For a Linux release of a complete embedding+visualization pipeline please visit https://github.com/sonjageorgievska/Embed-Dive

Probability and hiding in concurrent processes

Action hiding and probabilistic choice have independently established their roles in process algebraic modeling and verification of concurrent systems. While action hiding allows abstraction from unimportant details and model reduction, and the induced nondeterminism enables modeling uncertainty in the system behaviour, probabilistic choice allows quantification of the nondeterminism. However, as not all of the nondeterministic behaviour has a random nature, we are faced with the challenge to combine the above two aspects of concurrent systems, such that one can take maximal advantage of both. This thesis addresses two problems regarding concurrent processes that exhibit both hidden and probabilistic behaviour, or probabilistic processes for short. Namely, a proper reduction of a model, by elimination of the hidden actions, requires a semantical equivalence that preserves the process properties of interest and is a congruence for the process operators. For non-probabilistic processes it has been shown that such an equivalence is branching bisimilarity. However, in the presence of probabilistic choice, more concretely in the alternating model of probabilistic processes, the intuitive notion of branching bisimulation is not a congruence for parallel composition. In this thesis a new branching bisimulation for this model is defined, and it is shown that this is the coarsest congruence for parallel composition that is included in the former. To achieve the congruence result, a hidden action preceding directly a non-trivial probabilistic choice cannot be eliminated. The new branching bisimulation preserves the properties expressible in the probabilistic computation tree logic, and is decidable in polynomial time. Similar to the non-probabilistic case, a single axiom characterizes branching bisimilarity for finite probabilistic processes. The previous results imply that branching bisimilarity, although potentially useful for model reduction, may be in fact too strong to serve as an equivalence relation for probabilistic processes. Another view, taken in the may/must testing theory (as well as in the process calculus CSP), is to distinguish two processes only if they can be distinguished when interacting with their environment, i.e. with another process. However, although processes that differ only in the moment an internal (nondeterministic) choice is made are not distinguished by this theory, for probabilistic processes this is no longer valid. The problem stems from an earlier observation that the schedulers that resolve the nondeterminism in concurrent probabilistic processes are too powerful and yield unrealistic overestimations of the probabilities with which a process can pass a test. The power of the schedulers comes from the fact that they allow the same choice to be resolved in different manners in different futures. In order to restrict the schedulers and thus to obtain the right probabilities, this thesis proposes integrating the information, based on which a nondeterministic choice is resolved, in labels on the nondeterministic transitions. In this way, choices using the same information are resolved in the same way, regardless of the considered future. As a result, the new testing preorder relation can be characterized by a probabilistic ready-trace preorder, a relation that is insensitive to the moment an internal choice is made, yet sensitive to deadlock and to action priorities. In other words, it combines useful features of both the bisimulation-style and the trace-style relations. The parallel composition is also generalized here to include both interleaving and action hiding after synchronization, and it is shown that probabilistic ready-trace preorder is a precongruence with respect to it. Finally, the CSP-style axiomatic characterization shows that all the distributivity laws for nondeterministic choice from CSP are preserved and no new laws are added

FastMLC/fMLC: First release of fMLC

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