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Many acoustic surveys have been initiated to monitor anuran populations in North America. We used the Ontario Backyard Frog Survey to examine temporal and spatial trends, from 1994 to 2001. Our data suggest that there have been no consistent trends in site occupancy during this time period, but there were some differences among years. Both American toads and northern leopard frogs were more prevalent in 1995 than in 1994. Similarly, species richness was higher in 1995 and 1996 compared to most other years. Individual populations of species, however, often were not stable. Extinction and colonization rates varied among species, and ranged from 1.5 to 19.5% per year, and site occupancy was negatively correlated with extinction rates. Daily detection probabilities were often quite low, and were primarily driven by the perceived calling intensity. We recommend: (i) that monitoring programs attempt to preserve common survey routes, despite heavy turnover of volunteers, (ii) calling surveys be timed to maximize detection probabilities, and (iii) analyses based upon landscape features and GIS approaches should be used to determine localized changes in site occupancy or species richness. [ABSTRACT FROM AUTHOR]

The correctness of a component-based specification is not guaranteed by the correctness of its components alone; on the contrary, integration analysis is needed to observe their conjoint behavior. Existing approaches often leave the results of the analysis at the level of the integrated system, without tracing them onto the corresponding components. This effectively results in loss of architecture, as it is no longer possible to reason over those components and evolve their specification while keeping the results of integration analysis. This paper presents a formal approach to automatically translate changes on the integrated system into revisions of the components and the architecture initially defined by the developers. Several architectural alternatives are provided that, besides allowing developers to reason about the system from different points of view, promote its correct modularization in two overlapping perspectives: the encapsulation of crosscutting concerns and the elaboration of the architecture desired for the final implementation. [ABSTRACT FROM AUTHOR]

In this paper we introduce TCTL, a dense-time extension of the multi-valued Computation Tree Logic ( CTL) in [1]. Alternatively, TCTL is a multi-valued extension of TCTL [2] over quasi-boolean algebras. A multi-valued quotient is defined which enables to reduce dense-time TCTL model checking to the untimed case. Keywords: formal methods, model checking, multi-valued logic, dense real-time. [ABSTRACT FROM AUTHOR]

We study the way in which the properties of spin glasses and associative memory networks are changed when the interactions between the units are not symmetrical. Our models are analog networks subject to thermal noise (Langevin models). In an approximation which becomes exact in the limit of large spin dimensionality, we find that spin glass phases are suppressed, even for arbitrarily small asymmetry. However, in the associative networks, memory states are not seriously degraded; their critical temperature is simply lowered from its value in the corresponding symmetric model. The effect of making the number of memories a finite fraction of the number of units in the system is also qualitatively the same as in the symmetric case. We suggest that asymmetric couplings may make retrieval of the desired memory states faster, since the system will not get trapped in spin glass states. [ABSTRACT FROM AUTHOR]