Reachability Analysis of Communicating Pushdown Systems

The reachability analysis of recursive programs that communicate asynchronously over reliable FIFO channels calls for restrictions to ensure decidability. Our first result characterizes communication topologies with a decidable reachability problem restricted to eager runs (i.e., runs where messages are either received immediately after being sent, or never received). The problem is EXPTIME-complete in the decidable case. The second result is a doubly exponential time algorithm for bounded context analysis in this setting, together with a matching lower bound. Both results extend and improve previous work from La Torre et al

Multiparty compatibility in communicating automata: characterisation and synthesis of global session types

Multiparty session types are a type system that can ensure the safety and liveness of distributed peers via the global specification of their interactions. To construct a global specification from a set of distributed uncontrolled behaviours, this paper explores the problem of fully characterising multiparty session types in terms of communicating automata. We equip global and local session types with labelled transition systems (LTSs) that faithfully represent asynchronous communications through unbounded buffered channels. Using the equivalence between the two LTSs, we identify a class of communicating automata that exactly correspond to the projected local types. We exhibit an algorithm to synthesise a global type from a collection of communicating automata. The key property of our findings is the notion of multiparty compatibility which non-trivially extends the duality condition for binary session types

Reports of accomplishments of planetology programs, 1975 - 1976

Abstracts of reports which summarize work conducted by Planetology Program Principal Investigators are presented. Full reports of selected abstracts were presented to the annual meeting of Planetology Program Principal Investigators at the Center for Astrogeology, U.S. Geological Survey, Flagstaff, Arizona, March 8, 9, 19, 1976

Modeling riparian vegetation responses to flow alteration by dams and and climate change

2013 Fall.Includes bibliographical references.As the interface between freshwater and terrestrial ecosystems, riparian vegetation is a critical influence on biodiversity maintenance and ecosystem service production along river corridors. Understanding how altered environmental drivers will affect this vegetation is therefore central to sound watershed management. A river's flow regime exerts a primary control on the type and abundance of riparian vegetation, as differing adaptations to changing discharge levels mediate plant recruitment and persistence. Models of the relationships between flow and vegetation, generalized across species in terms of flow response traits such as flood tolerance, provide a means to explore the consequences of hydrologic alteration resulting from dams and climate change. I addressed these issues through development of a stage-structured model of woody riparian vegetation driven by variation in annual high flows. Simulation experiments offered insight into the potential trajectories of competing vegetation trait types relative to scenarios of dam construction, re-operation and removal. Modifying the size and frequency of the floods responsible for both disturbance mortality and establishment opportunities altered the relative abundance of pioneer and upland cover. Yet, qualitative differences in simulated outcomes resulted from alternative assumptions regarding seed limitation and floodplain stabilization, illustrating the need to carefully consider how these factors may shape estimated and actual vegetation responses to river regulation. In addition, I linked this simulation approach with an integrated watershed-modeling framework to assess the relative risk of invasion by the introduced plant Tamarix under multiple climate change scenarios. Though warming may increase the potential for Tamarix range expansion by weakening thermal constraints, the results of this work supported the expectation that hydrogeomorphic variation will control how this potential is realized. With simulated invasion risk strongly dependent on shifts in both the magnitude and timing of high flows, model outcomes underscored the importance of accounting for multiple, interacting flow regime attributes when evaluating the spread of introduced species in river networks. This research suggested the utility of simplified but process-based simulations of riparian flow-ecology relationships, demonstrating that such models can establish a first approximation of the potential consequences of management decisions and can highlight key questions for additional research, particularly where data are scarce and uncertainty is high

Thermodynamics and Inflammation: Insights into Quantum Biology and Ageing

Inflammation as a biological concept has been around a long time and derives from the Latin “to set on fire” and refers to the redness and heat, and usually swelling, which accompanies injury and infection. Chronic inflammation is also associated with ageing and is described by the term “inflammaging”. Likewise, the biological concept of hormesis, in the guise of what “does not kill you, makes you stronger”, has long been recognized, but in contrast, seems to have anti-inflammatory and age-slowing characteristics. As both phenomena act to restore homeostasis, they may share some common underlying principles. Thermodynamics describes the relationship between heat and energy, but is also intimately related to quantum mechanics. Life can be viewed as a series of self-renewing dissipative structures existing far from equilibrium as vortexes of “negentropy” that ages and dies; but, through reproduction and speciation, new robust structures are created, enabling life to adapt and continue in response to ever changing environments. In short, life can be viewed as a natural consequence of thermodynamics to dissipate energy to restore equilibrium; each component of this system is replaceable. However, at the molecular level, there is perhaps a deeper question: is life dependent on, or has it enhanced, quantum effects in space and time beyond those normally expected at the atomistic scale and temperatures that life operates at? There is some evidence it has. Certainly, the dissipative adaptive mechanism described by thermodynamics is now being extended into the quantum realm. Fascinating though this topic is, does exploring the relationship between quantum mechanics, thermodynamics, and biology give us a greater insight into ageing and, thus, medicine? It could be said that hormesis and inflammation are expressions of thermodynamic and quantum principles that control ageing via natural selection that could operate at all scales of life. Inflammation could be viewed as a mechanism to remove inefficient systems in response to stress to enable rebuilding of more functional dissipative structures, and hormesis as the process describing the ability to adapt; underlying this is the manipulation of fundamental quantum principles. Defining what “quantum biological normality” is has been a long-term problem, but perhaps we do not need to, as it is simply an expression of one end of the normal quantum mechanical spectrum, implying that biology could inform us as to how we can define the quantum world

Space resources. Volume 4: Social concerns

Space resources must be used to support life on the Moon and exploration of Mars. This volume, Social Concerns, covers some of the most important issues which must be addressed in any major program for the human exploration of space. The volume begins with a consideration of the economics and management of large scale space activities. Then the legal aspects of these activities are discussed, particularly the interpretation of treaty law with respect to the Moon and asteroids. The social and cultural issues of moving people into space are considered in detail, and the eventual emergence of a space culture different from the existing culture is envisioned. The environmental issues raised by the development of space settlements are faced. Some innovative approaches are proposed to space communities and habitats and self-sufficiency is considered along with human safety at a lunar base or outpost

Programs with Quasi-Stable Channels are Effectively Recognizable (Extended Abstract)

) G'erard C' ec' e Alain Finkel LSV, CNRS URA 2236; ENS de Cachan, 61 av. du Pdt. Wilson 94235 Cachan Cedex, FRANCE. fGerard.CECE, [email protected] Abstract. We consider the analysis of infinite half-duplex systems which consists of finite state machines that communicate over unbounded channels. The property half-duplex for two machines and two channels (one in each direction) says that each reachable state has at least one channel empty. The contributions of this paper are (a) to give a finite description of the reachability set of such systems, which happens to be effectively recognizable; this description allows us to solve classical verification problems such as: whether a given state is reachable, whether there exist deadlock states, whether the reachability set is finite and whether a specified action is useless; (b) to propose an extension of these results for a new class, systems with quasi-stable channels, which includes systems with similar beh..

Futures Studies in the Interactive Society

This book consists of papers which were prepared within the framework of the research project (No. T 048539) entitled Futures Studies in the Interactive Society (project leader: Éva Hideg) and funded by the Hungarian Scientific Research Fund (OTKA) between 2005 and 2009. Some discuss the theoretical and methodological questions of futures studies and foresight; others present new approaches to or procedures of certain questions which are very important and topical from the perspective of forecast and foresight practice. Each study was conducted in pursuit of improvement in futures fields

Theology, science and the topos of the Logos: a stable, dynamic topology of Creation

This thesis argues that an integrated, dynamically stable theo-science may be explored by considering scientific and theological perspectives regarding stability itself, combining them in one overarching framework by embedding a scientific conception of stability within a broader theological conception thereof. Our very capacity to perceive ‘reality’ in a functionally consistent manner is dependent upon the physical cosmos presenting a particular, dynamic stability, allowing for the sustainable emergence of life in the first place. Stability is hierarchically qualified, with higher-order functional systems such as those pertaining to life being an emergent result of particular modes of interaction between lower-level degrees of stability, ultimately right down to fundamental particles or fields. Theologically, any stability inherent to ‘reality’ must furthermore be considered to derive from the fact that such reality is, at its profoundest, a manifestation of God’s revealing, Creative Activity through the Logos. The thesis considers, qualitatively, the scientific and theological ‘place’ and relevance of stability from a holistic perspective regarding our anthropological development. Scientifically this is viewed in layered, evolutionary terms. Theologically, the Incarnation is considered of central relevance to our anthropological journey, transfiguring the process of its development so as to draw human nature into its intended eschatological stability ‘at the right hand of the Father’. Since stability can be considered scientifically in topological terms, the framework is developed by means of a ‘theological topology’ centred, as the etymology suggests, on the idea of a sacramentally stable, pervasive topos indicative of God’s ‘motioning’, Creative Activity through the Logos. Such Activity becomes sense-objectified in the Incarnation, considered figuratively-speaking as a ‘phase transition’, the net effect of which is argued as a ‘drawing in’ (cf. John 12:32), reordering and enhancing all meaningful, creaturely contribution to the ‘content’ of Creation – content actively generated according to our iconic, creative capacity for conceiving (of) the Logos

Structure From Motion Methodology Captures Seasonal Influences on Coastal Bluff Erosion and Landslide Hazards in Casco Bay, ME

Shoreline erosion in response to rising sea level is a global problem. Recognizing the need for observational data on coastal bluff recession in Casco Bay, Maine, we employed Structure from Motion (SfM) photogrammetric methods in a dynamic intertidal environment. Evaluating the method as a means to measure and monitor dynamic geomorphological changes occurring at a coastal bluff shows that a spatial resolution of centimeters over an area of 10’s to 100’s of meters can be attained at relatively low cost. The efficient methodology allows for frequent surveys at an operational scale, leading to greater temporal resolution and quantification of bluff erosion activity that supports understanding of the local geohazard. With the greater temporal resolution gained from this evaluation additional inferences are made towards seasonal controls on bluff geomorphology. In the local temperate climate, the dominant erosional actor is characteristically linked to seasonal transitions. Given the urgency of coastal erosion, the lack of local records, and newfound feasibility of repeat surveys, Structure from Motion presents the opportunity to address the uncertainty of bluff instability with an approach that accounts for quantified change over time. Observations were evaluated with respect to: 1) the coastal bluff erosion cycle conceptual model; 2) local landslide hazards; and 3) preservation of a shoreline status record