82,427 research outputs found
Abstracting Asynchronous Multi-Valued Networks: An Initial Investigation
Multi-valued networks provide a simple yet expressive qualitative state based
modelling approach for biological systems. In this paper we develop an
abstraction theory for asynchronous multi-valued network models that allows the
state space of a model to be reduced while preserving key properties of the
model. The abstraction theory therefore provides a mechanism for coping with
the state space explosion problem and supports the analysis and comparison of
multi-valued networks. We take as our starting point the abstraction theory for
synchronous multi-valued networks which is based on the finite set of traces
that represent the behaviour of such a model. The problem with extending this
approach to the asynchronous case is that we can now have an infinite set of
traces associated with a model making a simple trace inclusion test infeasible.
To address this we develop a decision procedure for checking asynchronous
abstractions based on using the finite state graph of an asynchronous
multi-valued network to reason about its trace semantics. We illustrate the
abstraction techniques developed by considering a detailed case study based on
a multi-valued network model of the regulation of tryptophan biosynthesis in
Escherichia coli.Comment: Presented at MeCBIC 201
Abstracting Asynchronous Multi-Valued Networks
Multi-valued networks (MVNs) provide a simple yet expressive qualitative state based modelling approach for biological systems. In this paper we develop an abstraction theory for asynchronous MVNs that allows the state space of a model to be reduced while preserving key properties. The abstraction theory therefore provides a mechanism for coping with the state space explosion problem and supports the analysis and comparison of MVNs. We take as our starting point the abstraction theory for synchronous MVNs which uses the under- approximation approach of trace set inclusion. We show this definition of asynchronous abstraction allows the sound inference of analysis properties and preserves other interesting model properties. One problem that arises in the asynchronous case is that the trace set of an MVN can be infinite making a simple trace set inclusion check infeasible. To address this we develop a decision procedure for checking asynchronous abstractions based on using the finite state graph of an asynchronous MVN to reason about its trace semantics and formally show that this decision procedure is correct. We illustrate the abstraction techniques developed by considering two detailed case studies in which asynchronous abstractions are identified and validated for existing asynchronous MVN models taken from the literature
Explosive Formation and Dynamics of Vapor Nanobubbles around a Continuously Heated Gold Nanosphere
We form sub-micrometer-sized vapor bubbles around a single laser heating gold
nanoparticle in a liquid and monitor them through optical scattering of a probe
laser. The fast, inertia-governed expansion is followed by a slower contraction
and disappearance after some tens of nanoseconds. In a narrow range of
illumination powers, bubble time traces show a clear echo signature. We
attribute it to sound waves released upon the initial explosion and reflected
by flat interfaces, hundreds of microns away from the particle. Echoes can
trigger new explosions. A steady state of nanobubble with a vapor shell
surrounding the heated nanoparticle can be reached by a proper time profile of
the heating intensity. Stable nanobubbles could have original applications for
light modulation and for enhanced optical-acoustic coupling in photoacoustic
microscopy
The Paradoxes of the Interaction-Free Measurement
Interaction-free measurements introduced by Elitzur and Vaidman [Found. Phys.
23, 987 (1993)] allow finding infinitely fragile objects without destroying
them. Paradoxical features of these and related measurements are discussed. The
resolution of the paradoxes in the framework of the Many-Worlds Interpretation
is proposed.Comment: 8 pages, 7 eps figures. Contribution to the "Mysteries and Paradoxes
in Quantum Mechanics", Garda Lake 200
Are Interaction-free Measurements Interaction Free?
In 1993 Elitzur and Vaidman introduced the concept of interaction-free
measurements which allowed finding objects without ``touching'' them. In the
proposed method, since the objects were not touched even by photons, thus, the
interaction-free measurements can be called as ``seeing in the dark''. Since
then several experiments have been successfully performed and various
modifications were suggested. Recently, however, the validity of the term
``interaction-free'' has been questioned. The criticism of the name is briefly
reviewed and the meaning of the interaction-free measurements is clarified.Comment: 11 pages, 3 eps figures. Contribution to the ICQO 2000, Raubichi,
Belaru
- …