TY - JOUR AB - Wild isolates of Caenorhabditis elegans can feed either alone or in groups1,2. This natural variation in behaviour is associated with a single residue difference in NPR-1, a predicted G-protein-coupled neuropeptide receptor related to Neuropeptide Y receptors2. Here we show that the NPR-1 isoform associated with solitary feeding acts in neurons exposed to the body fluid to inhibit social feeding. Furthermore, suppressing the activity of these neurons, called AQR, PQR and URX, using an activated K+ channel, inhibits social feeding. NPR-1 activity in AQR, PQR and URX neurons seems to suppress social feeding by antagonizing signalling through a cyclic GMP-gated ion channel encoded by tax-2 and tax-4. We show that mutations in tax-2 or tax-4 disrupt social feeding, and that tax-4 is required in several neurons for social feeding, including one or more of AQR, PQR and URX. The AQR, PQR and URX neurons are unusual in C. elegans because they are directly exposed to the pseudocoelomic body fluid3. Our data suggest a model in which these neurons integrate antagonistic signals to control the choice between social and solitary feeding behaviour. AU - Coates, Juliet C. AU - de Bono, Mario ID - 6158 IS - 6910 JF - Nature SN - 0028-0836 TI - Antagonistic pathways in neurons exposed to body fluid regulate social feeding in Caenorhabditis elegans VL - 419 ER - TY - JOUR AB - Natural Caenorhabditis elegans isolates exhibit either social or solitary feeding on bacteria. We show here that social feeding is induced by nociceptive neurons that detect adverse or stressful conditions. Ablation of the nociceptive neurons ASH and ADL transforms social animals into solitary feeders. Social feeding is probably due to the sensation of noxious chemicals by ASH and ADL neurons; it requires the genes ocr-2 and osm-9, which encode TRP-related transduction channels, and odr-4 and odr-8, which are required to localize sensory chemoreceptors to cilia. Other sensory neurons may suppress social feeding, as social feeding in ocr-2 and odr-4 mutants is restored by mutations in osm-3, a gene required for the development of 26 ciliated sensory neurons. Our data suggest a model for regulation of social feeding by opposing sensory inputs: aversive inputs to nociceptive neurons promote social feeding, whereas antagonistic inputs from neurons that express osm-3 inhibit aggregation. AU - de Bono, Mario AU - Tobin, David M. AU - Davis, M. Wayne AU - Avery, Leon AU - Bargmann, Cornelia I. ID - 6159 IS - 6910 JF - Nature SN - 0028-0836 TI - Social feeding in Caenorhabditis elegans is induced by neurons that detect aversive stimuli VL - 419 ER - TY - CONF AB - We present a theory of timed interfaces, which is capable of specifying both the timing of the inputs a component expects from the environment, and the timing of the outputs it can produce. Two timed interfaces are compatible if there is a way to use them together such that their timing expectations are met. Our theory provides algorithms for checking the compatibility between two interfaces and for deriving the composite interface; the theory can thus be viewed as a type system for real-time interaction. Technically, a timed interface is encoded as a timed game between two players, representing the inputs and outputs of the component. The algorithms for compatibility checking and interface composition are thus derived from algorithms for solving timed games. AU - De Alfaro, Luca AU - Henzinger, Thomas A AU - Stoelinga, Mariëlle ID - 4631 SN - 9783540443070 T2 - Proceedings of the 2nd International Conference on Embedded Software TI - Timed interfaces VL - 2491 ER - TY - CONF AB - We present interface models that describe both the input assumptions of a component, and its output behavior. By enabling us to check that the input assumptions of a component are met in a design, interface models provide a compatibility check for component-based design. When refining a design into an implementation, interface models require that the output behavior of a component satisfies the design specification only when the input assumptions of the specification are satisfied, yielding greater flexibility in the choice of implementations. Technically, our interface models are games between two players, Input and Output; the duality of the players accounts for the dual roles of inputs and outputs in composition and refinement. We present two interface models in detail, one for a simple synchronous form of interaction between components typical in hardware, and the other for more complex synchronous interactions on bidirectional connections. As an example, we specify the interface of a bidirectional bus, with the input assumption that at any time at most one component has write access to the bus. For these interface models, we present algorithms for compatibility and refinement checking, and we describe efficient symbolic implementations. AU - Chakrabarti, Arindam AU - De Alfaro, Luca AU - Henzinger, Thomas A AU - Mang, Freddy ID - 4562 SN - 9783540439974 T2 - Proceedings of the 14th International Conference on Computer Aided Verification TI - Synchronous and bidirectional component interfaces VL - 2404 ER - TY - CONF AB - In the literature, we find several formulations of the control problem for timed and hybrid systems. We argue that formulations where a controller can cause an action at any point in dense (rational or real) time are problematic, by presenting an example where the controller must act faster and faster, yet causes no Zeno effects (say, the control actions are at times 0, 1/2, 1, 1 1/4, 2, 2 1/8, 3, 3 1/16 ,...). Such a controller is, of course, not implementable in software. Such controllers are avoided by formulations where the controller can cause actions only at discrete (integer) points in time. While the resulting control problem is well- understood if the time unit, or “sampling rate” of the controller, is fixed a priori, we define a novel, stronger formulation: the discrete-time control problem with unknown sampling rate asks if a sampling controller exists for some sampling rate. We prove that this problem is undecidable even in the special case of timed automata. AU - Cassez, Franck AU - Henzinger, Thomas A AU - Raskin, Jean ID - 4565 SN - 9783540433217 T2 - Proceedings of the 5th International Workshop on Hybrid Systems: Computation and Control TI - A comparison of control problems for timed and hybrid systems VL - 2289 ER -