1435 research outputs found
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Hard life with weak binders
No full textWe introduce weak binders, a lightweight construct to deal with fresh names in nominal calculi. Weak binders do not define the scope of names as precisely as the standard nu-binders, yet they enjoy strong semantic properties.We provide them with a denotational semantics, an equational theory, and a trace inclusion preorder. Furthermore, we present a trace-preserving mapping between weak binders and nu-binders
Preliminary proceedings of WADT 2008
No full textAfter having joined forces with the International Workshop on Coalgebraic Methods in Computer Science (CMCS) for the Second International Conference on Algebra and Coalgebra in Computer Science (CALCO 2007), the Nineteenth International Workshop on Algebraic Development Techniques (WADT 2008) was held as an individual workshop and in its traditional form in Pisa, Italy, from the 13th to the 16th of June 2008. This report contains the thirtythree abstracts presented during the workshop: they were selected by the Steering Committee on the basis of the submitted abstracts according to originality, significance, and general interest. In addition to the presentations of ongoing research results, the programme included three invited lectures by Egon Boerger (Dipartimento di Informatica, Pisa), Luca Cardelli (Microsoft Research, Cambridge) and Stephen Gilmore (Laboratory for Foundations of Computer Science, Edinburgh)
An Approximation Algorithm for Generalized EXOR Projected Sum of Products
No full textFast minimization time, compact area and low delay are important issues in logic circuit design. In order to orchestrate these main goals, in this paper we propose a new four level logic form ({\em Generalized EXOR-Projected Sum of Products}, in short {\em GEP-SOP}) with low delay and compact area. Even if the problem of finding an optimal GEP-SOPs is computationally hard, we propose an efficient approximation algorithm that gives guaranteed near optimal solutions. A wide set of experimental results confirms that the GEP-SOP forms are often more compact than the SOP forms, and their synthesis is always a very fast reoptimization phase after SOP minimization
A new stereoselective approach to a selectively protected derivative of D-pinitol and its evaluation as a-L-rhamnopyranose mimetic
No full textSUMMARY The synthesis of 3,5-di-O-benzyl-D-pinitol has been stereoselectively accomplished through intramolecular aldolization of 2,6-di-O-benzyl-4-O-methyl-L-lyxo-hexos-5-ulose followed by reduction with NaBH( OAc)3. Computational analysis [DFT calculations at the B3LYP/6-31G(d) level] suggests that D-pinitol in water largely prefers the conformation corresponding to the 1C4 one of a a-L-rhamnopyranoside unit, being thus a good candidate for its mimicking
Prototype Implementation Of A Demand Driven Network Monitoring Architecture
No full textSUMMARY - The capability of dynamically monitoring the perfomance of the communication infrastructure is one of the emerging requirements for a Grid. We claim that such a capability is in fact orthogonal to the more popular collection of data for scheduling and diagnosis, which needs large storage and indexing capabilities, but may disregard real-time performance issues. We discuss such claim analyzing the gLite NPM architecture, and we describe a novel network monitoring infrastructure specifically designed for demand driven monitoring, named gd2, that can be potentially integrated in the gLite framework. We describe a Java implementation of gd2 on a virtual testbed
Coherent control of dressed matter waves
No full textBy moving the pivot of a pendulum rapidly up and down one can create a stable
position with the pendulum's bob above the pivot rather than below it. This\ud
surprising and counterintuitive phenomenon is a widespread feature of driven
systems and carries over into the quantum world. Even when the static
properties of a quantum system are known, its response to an explicitly
time-dependent variation of its parameters may be highly nontrivial, and
qualitatively new states can appear that were absent in the original system. In
quantum mechanics the archetype for this kind of behaviour is an atom in a
radiation field, which exhibits a number of fundamental phenomena such as the
modification of its g-factor in a radio-frequency field and the dipole force
acting on an atom moving in a spatially varying light field. These effects can
be successfully described in the so-called dressed atom picture. Here we show
that the concept of dressing can also be applied to macroscopic matter waves,
and that the quantum states of "dressed matter waves" can be coherently
controlled. In our experiments we use Bose-Einstein condensates in driven
optical lattices and demonstrate that the many-body state of this system can be
adiabatically and reversibly changed between a superfluid and a Mott insulating
state by varying the amplitude of the driving. Our setup represents a versatile
testing ground for driven quantum systems, and our results indicate the
direction towards new quantum control schemes for matter waves
Compositional Specification of Web Services via Behavioural Equivalence of Nets: A Case Study
No full textWeb services represent a promising technology for the development of distributed heterogeneous software systems. In this setting, a major issue is to establish whether two services can be used interchangeably in any context. This paper illustrates - through a concrete scenario from banking systems - how a suitable notion of behavioural equivalence over Petri nets can be effectively employed for checking the correctness of service specifications and the replaceability of (sub)services
Model checking usage policies
No full textWe propose a model for specifying, analysing and enforcing safe usage of resources.Our usage policies allow for parametricity over resources, and they can be enforced through finite state automata. The patterns of resource access and creation are described through a basic calculus of usages. In spite of the augmented flexibility given by resource creation and by policy parametrization, we devise an efficient (polynomial-time)model-checking technique for deciding when a usage is resource-safe,i.e. when it complies with all the relevant usage policies
Global Coordination Policies for Services
No full textAn important issue of the service oriented approach is the possibility to aggregate, through programmable coordination patterns, the activities involved by service interactions. Two different approaches can be adopted to tackle service coordination: orchestration and choreography. In this paper, we introduce a formal methodology for the with the aim of handling coordinationamong services from the perspective of a global observer in the spirit of choreography models. In particular, we address the problem of verifying compliance and consistency between the design of service interactions and the choreography constraints
Pattern of wing moult and its relationship to breeding in the Eurasian Stone-curlew Burhinus oedicnemus
No full textSUMMARY: The timing, duration and pattern of the poorly documented wing moultin the Eurasian Stone-curlew Burhinus oedicnemus were described and related to the breeding cycle. Between 1998 and 2007, 141 birds were trapped in the Taro River Regional Park (Parma, Italy) both while incubating and during the post-breeding season. The timing of primary moult was estimated according to the method of Underhill & Zucchini (1988) and Underhill et al. (1990). Primary moult was very slow and overlapped most of the breeding season, beginning in early May and ending in October. Secondary moult was much more irregular and was not completed within a single moult cycle. Innermost and outermost secondaries were more likely to be shed than those at the centre of this tract. Juvenile secondaries were not shed during the first winter. The study provides the first detailed analysis of wing moult in the Eurasian Stone-curlew and suggests some useful ageing criteria based on the pattern of secondary moult. The extensive overlap between breeding and moulting is relatively uncommon compared to other waders. This could be interpreted as a way to maximize breeding success through renesting potential (up to 4 attempts), i.e. by spreading the cost of moult over a prolonged time period. A between-species comparison using independent contrasts was consistent with this hypothesis: species with a prolonged breeding season also showed considerable overlap in the timing of primary moult and breeding activitie