1,229 research outputs found
Concurrent constraint programming with process mobility
We propose an extension of concurrent constraint programming with primitives for process migration within a hierarchical network, and we study its semantics. To this purpose, we first investigate a "pure " paradigm for process migration, namely a paradigm where the only actions are those dealing with transmissions of processes. Our goal is to give a structural definition of the semantics of migration; namely, we want to describe the behaviour of the system, during the transmission of a process, in terms of the behaviour of the components. We achieve this goal by using a labeled transition system where the effects of sending a process, and requesting a process, are modeled by symmetric rules (similar to handshaking-rules for synchronous communication) between the two partner nodes in the network. Next, we extend our paradigm with the primitives of concurrent constraint programming, and we show how to enrich the semantics to cope with the notions of environment and constraint store. Finally, we show how the operational semantics can be used to define an interpreter for the basic calculus.
Syntactic Markovian Bisimulation for Chemical Reaction Networks
In chemical reaction networks (CRNs) with stochastic semantics based on
continuous-time Markov chains (CTMCs), the typically large populations of
species cause combinatorially large state spaces. This makes the analysis very
difficult in practice and represents the major bottleneck for the applicability
of minimization techniques based, for instance, on lumpability. In this paper
we present syntactic Markovian bisimulation (SMB), a notion of bisimulation
developed in the Larsen-Skou style of probabilistic bisimulation, defined over
the structure of a CRN rather than over its underlying CTMC. SMB identifies a
lumpable partition of the CTMC state space a priori, in the sense that it is an
equivalence relation over species implying that two CTMC states are lumpable
when they are invariant with respect to the total population of species within
the same equivalence class. We develop an efficient partition-refinement
algorithm which computes the largest SMB of a CRN in polynomial time in the
number of species and reactions. We also provide an algorithm for obtaining a
quotient network from an SMB that induces the lumped CTMC directly, thus
avoiding the generation of the state space of the original CRN altogether. In
practice, we show that SMB allows significant reductions in a number of models
from the literature. Finally, we study SMB with respect to the deterministic
semantics of CRNs based on ordinary differential equations (ODEs), where each
equation gives the time-course evolution of the concentration of a species. SMB
implies forward CRN bisimulation, a recently developed behavioral notion of
equivalence for the ODE semantics, in an analogous sense: it yields a smaller
ODE system that keeps track of the sums of the solutions for equivalent
species.Comment: Extended version (with proofs), of the corresponding paper published
at KimFest 2017 (http://kimfest.cs.aau.dk/
Graphical Encoding of a Spatial Logic for the pi-Calculus
This paper extends our graph-based approach to the verification of spatial properties of π-calculus specifications. The mechanism is based on an encoding for mobile calculi where each process is mapped into a graph (with interfaces) such that the denotation is fully abstract with respect to the usual structural congruence, i.e., two processes are equivalent exactly when the corresponding encodings yield isomorphic graphs. Behavioral and structural properties of π-calculus processes expressed in a spatial logic can then be verified on the graphical encoding of a process rather than on its textual representation. In this paper we introduce a modal logic for graphs and define a translation of spatial formulae such that a process verifies a spatial formula exactly when its graphical representation verifies the translated modal graph formula
Process algebra modelling styles for biomolecular processes
We investigate how biomolecular processes are modelled in process algebras, focussing on chemical reactions. We consider various modelling styles and how design decisions made in the definition of the process algebra have an impact on how a modelling style can be applied. Our goal is to highlight the often implicit choices that modellers make in choosing a formalism, and illustrate, through the use of examples, how this can affect expressability as well as the type and complexity of the analysis that can be performed
Biochar impact on the estimation of the colorimetric-based enzymatic assays of soil
This study was carried out in order to assess the influence of biochar applications on
the estimation of colorimetric-based
enzymatic assays and to verify the effectiveness
of the most common methods. Since most methods used to determine enzymatic
activities in the soil are based on colorimetry, biochar may absorb substrates and/
or coloured products thereby distorting the analytical result. Biochar was added to
two soils, with different textures and cation exchangeable capacities, at a rate of
2% (w/w), and seven enzyme activities were determined following standard methods.
The biochar amendment lowered the spectrophotometer reading of the activity
of FDAase and dehydrogenase in the sandy soil. In the three enzymatic activities
based on p-nitrophenol
production (β-glucosidase,
phosphatase and arylsulphatase),
the addition of biochar did not change the enzyme assays. The biochar led to an
overestimation in terms of the protease and urease activities in the sandy soil. In the
clay loamy soil, biochar did not change the response of any of the enzyme activities
tested. A biochar dose of up to 2% only guarantees the effectiveness of the most common
spectrophotometric methods for not excessively sandy soils
The Extinction Towards the GRB970228 Field
We determine the local galactic extinction towards the field of gamma-ray
burst GRB970228 using a variety of methods. We develop a maximum likelihood
method for measuring the extinction by comparing galaxy counts in the field of
interest to those in a field of known extinction, and apply this method to the
GRB970228 field. We also measure the extinction by comparing the observed
stellar spectral energy distributions of stars in the GRB970228 field to the
spectral energy distribution of library spectra of the same spectral type.
Finally we estimate the extinction using the Balmer emission line ratios of a
galaxy in the GRB970228 field, and the neutral hydrogen column density and
amount of infrared dust emission toward this field. Combining the results of
these methods, we find a best-fit galactic extinction in the optical of
, which implies a a substantial dimming and change of
the spectral slope of the intrinsic GRB970228 afterglow.Comment: 22 pages, including 7 figures. Submitted to Ap
Typing in Model Management
International audienceModel management is essential for coping with the complexity introduced by the increasing number and varied nature of artifacts involved in MDE-based projects. Global Model Management (GMM) addresses this issue enabling the representation of artifacts, particularly transformation composition and execution, by a model called a megamodel. Typing information about artifacts can be used for preventing type errors during execution. In this work, we present a type system for GMM that improves its current typing approach and enables formal reasoning about the type of artifacts within a megamodel. This type system is able to capture non-trivial situations such as the use of higher order transformations
A Photometric Investigation of the GRB970228 Afterglow and the Associated Nebulosity
We carefully analyze the WFPC2 and STIS images of GRB970228. We measure
magnitudes for the GRB970228 point source component in the WFPC2 images of
, and
, on March 26 and April 7,
respectively; and on September 4 in the STIS image.
For the extended component, we measure magnitudes of
in the combined WFPC2 images and
in the STIS image, which are consistent with no
variation. This value is fainter than previously reported (Galama et al. 98)
and modifies the previously assumed magnitudes for the optical transient when
it faded to a level where the extended source component contribution was not
negligible, alleviating the discrepancy to a power-law temporal behavior. We
also measure a color of for the
extended source component. Taking into account the extinction measured in this
field (Castander & Lamb 1998), this color implies that the extended source is
most likely a galaxy with ongoing star formation.Comment: 21 pages, including 8 figures. Submitted to Ap
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