Reachability in Cooperating Systems with Architectural Constraints is PSPACE-Complete

The reachability problem in cooperating systems is known to be PSPACE-complete. We show here that this problem remains PSPACE-complete when we restrict the communication structure between the subsystems in various ways. For this purpose we introduce two basic and incomparable subclasses of cooperating systems that occur often in practice and provide respective reductions. The subclasses we consider consist of cooperating systems the communication structure of which forms a line respectively a star.Comment: In Proceedings GRAPHITE 2013, arXiv:1312.706

Reachability in tree-like component systems is PSPACE-complete

The reachability problem in component systems is PSPACE-complete. We show here that even the reachability problem in the subclass of component systems with "tree-like'' communication is PSPACE-complete. For this purpose we reduce the question if a Quantified Boolean Formula (QBF) is true to the reachability problem in "tree-like'' component systems

Complexity Results for Reachability in Cooperating Systems and Approximated Reachability by Abstract Over-Approximations

This work deals with theoretic aspects of cooperating systems, i.e., systems that consists of cooperating subsystems. Our main focus lies on the complexity theoretic classification of deciding the reachability problem and on efficiently establishing deadlock-freedom in models of cooperating systems. The formal verification of system properties is an active field of research, first attempts of which go back to the late 60's. The behavior of cooperating systems suffers from the state space explosion problem and can become very large. This is, techniques that are based on an analysis of the reachable state space have a runtime exponential in the number of subsystems. The consequence is that even modern techniques that decide whether or not a system property holds in a system can become unfeasible. We use interaction systems, introduced by Sifakis et al. in 2003, as a formalism to model cooperating systems. The reachability problem and deciding deadlock-freedom in interaction systems was proved to be PSPACE-complete. An approach to deal with this issue is to investigate subclasses of systems in which these problems can be treated efficiently. We show here that the reachability problem remains PSPACE-complete in subclasses of interaction systems with a restricted communication structure. We consider structures that from trees, stars and linear arrangements of subsystems. Our result motivates the research of techniques that treat the reachability problem in these subclasses based on sufficient conditions which exploit characteristics of the structural restrictions. In a second part of this work we investigate an approach to efficiently establish the reachability of states and deadlock-freedom in general interaction systems. We introduce abstract over-approximations -- a concept of compact representations of over-approximations of the reachable behavior of interaction systems. Families of abstract over-approximations are the basis for our approach to establish deadlock-freedom in interaction systems in polynomial time in the size of the underlying interaction system. We introduce an operator called Edge-Match for refining abstract over-approximations. The strength of our approach is illustrated on various parametrized instances of interaction systems. Furthermore, we establish a link between our refinement approach and the field of relational database theory and use this link in order to make a preciseness statement about our refinement approach

The Cost of Defection: The Consequences of Quitting Al-Shabaab

This study investigates defections from the Al-Shabaab insurgency in Somalia. Thirty-two disengaged Al-Shabaab combatants were interviewed about their motivations, grievances, needs, and challenges in relation to the recruitment, defection, and post-defection phases. This paper focuses on post-defection challenges, where we found the primary concern to be lack of personal security. Without adequate security, disengaged combatants are vulnerable to being hunted and killed by Al-Shabaab. This significant threat discourages further mass and individual defections. We also found that disengaged combatants joined and defected out of religious zeal, to fight for what they believed to be a holy Islamic cause. This same zeal led them to defect, as they came to believe Al-Shabaab was not obeying the true Islamic faith. Indiscriminate killing by Al-Shabaab disenchants its religiously pious members, creating an opportunity to encourage mass and individual defections. However, if disengaged combatants are not protected from retribution, defection will lose its appeal

Reproducibility in Machine Learning-Driven Research

Research is facing a reproducibility crisis, in which the results and findings of many studies are difficult or even impossible to reproduce. This is also the case in machine learning (ML) and artificial intelligence (AI) research. Often, this is the case due to unpublished data and/or source-code, and due to sensitivity to ML training conditions. Although different solutions to address this issue are discussed in the research community such as using ML platforms, the level of reproducibility in ML-driven research is not increasing substantially. Therefore, in this mini survey, we review the literature on reproducibility in ML-driven research with three main aims: (i) reflect on the current situation of ML reproducibility in various research fields, (ii) identify reproducibility issues and barriers that exist in these research fields applying ML, and (iii) identify potential drivers such as tools, practices, and interventions that support ML reproducibility. With this, we hope to contribute to decisions on the viability of different solutions for supporting ML reproducibility.Comment: This research is supported by the Horizon Europe project TIER2 under grant agreement No 10109481

Circulating miRNAs in bone health and disease

microRNAs have evolved as important regulators of multiple biological pathways essential for bone homeostasis, and microRNA research has furthered our understanding of the mechanisms underlying bone health and disease. This knowledge, together with the finding that active or passive release of microRNAs from cells into the extracellular space enables minimal-invasive detection in biofluids (circulating miRNAs), motivated researchers to explore microRNAs as biomarkers in several pathologic conditions, including bone diseases. Thus, exploratory studies in cohorts representing different types of bone diseases have been performed. In this review, we first summarize important molecular basics of microRNA function and release and provide recommendations for best (pre-)analytical practices and documentation standards for circulating microRNA research required for generating high quality data and ensuring reproducibility of results. Secondly, we review how the genesis of bone-derived circulating microRNAs via release from osteoblasts and osteoclasts could contribute to the communication between these cells. Lastly, we summarize evidence from clinical research studies that have investigated the clinical utility of microRNAs as biomarkers in musculoskeletal disorders. While previous reviews have mainly focused on diagnosis of primary osteoporosis, we have also included studies exploring the utility of circulating microRNAs in monitoring anti-osteoporotic treatment and for diagnosis of other types of bone diseases, such as diabetic osteopathy, bone degradation in inflammatory diseases, and monogenetic bone diseases.Peer reviewe

SPATIAL AND SEASONAL DISTRIBUTION OF BIOCLIMATIC INDICES IN THE STATE OF STYRIA AS A BASIS FOR HOLIDAY PLANNING

In the period between 1991. and 2000., bioclimatic data were collected from 34 meteorological stations in the Austrian State of Styria. The equivalent temperature served as an indicator for the thermal action complex; during the winter months, wind-chill temperatures were used (thermal action complex). Finally, the geographic and seasonal distribution of weatherbiotropic intensity was studied (neurotropic action complex). The mean values and frequency distributions of the equivalent temperature show that with the exception of mid-summer, cool conditions predominate. Comfortable conditions prevail only between June and August, below 500 meters. However, during that period, the heat-stress situations are more noticeable, although they are clearly less frequent than comfortable conditions. The results for wind-chill temperatures show that during the winter months, up to an altitude of 1500 meters, the extremes of "bitter cold" and ,,very cold" are very infrequent, at least during daylight hours. In the open alpine region, however, cold stress clearly predominates. For the calculation of the weather-biotropy, only 12 stations could be used as there was no air pressure available at the rest of the stations (compare with Figure 1). On the average, biotropic assessments show a predominance of biologically favourable days throughout Styria. No regional differences appear in meteorotropic stimuli, but seasonal differences do exist. Thus, there are clearly more biologically stressed days in the months of winter than in summer, whereas the maximum number of days with favourable biotropic conditions is in summer