8,363 research outputs found
Transformation of UML Behavioral Diagrams to Support Software Model Checking
Unified Modeling Language (UML) is currently accepted as the standard for
modeling (object-oriented) software, and its use is increasing in the aerospace
industry. Verification and Validation of complex software developed according
to UML is not trivial due to complexity of the software itself, and the several
different UML models/diagrams that can be used to model behavior and structure
of the software. This paper presents an approach to transform up to three
different UML behavioral diagrams (sequence, behavioral state machines, and
activity) into a single Transition System to support Model Checking of software
developed in accordance with UML. In our approach, properties are formalized
based on use case descriptions. The transformation is done for the NuSMV model
checker, but we see the possibility in using other model checkers, such as
SPIN. The main contribution of our work is the transformation of a non-formal
language (UML) to a formal language (language of the NuSMV model checker)
towards a greater adoption in practice of formal methods in software
development.Comment: In Proceedings FESCA 2014, arXiv:1404.043
Descriptive Complexity of Deterministic Polylogarithmic Time and Space
We propose logical characterizations of problems solvable in deterministic
polylogarithmic time (PolylogTime) and polylogarithmic space (PolylogSpace). We
introduce a novel two-sorted logic that separates the elements of the input
domain from the bit positions needed to address these elements. We prove that
the inflationary and partial fixed point vartiants of this logic capture
PolylogTime and PolylogSpace, respectively. In the course of proving that our
logic indeed captures PolylogTime on finite ordered structures, we introduce a
variant of random-access Turing machines that can access the relations and
functions of a structure directly. We investigate whether an explicit predicate
for the ordering of the domain is needed in our PolylogTime logic. Finally, we
present the open problem of finding an exact characterization of
order-invariant queries in PolylogTime.Comment: Submitted to the Journal of Computer and System Science
Stimulus-responsive Injectable Polysaccharide Scaffolds for Soft Tissue Engineering Prepared by O/W High Internal Phase Emulsion
This thesis describes work on the development of several novel stimuli-responsive
porous hydrogels prepared from oil-in-water (o/w) high internal phase emulsion
(HIPE) as injectable scaffolds for soft tissue engineering. Firstly, by copolymerising
glycidyl methacrylate (GMA) derivatised dextran and N-isopropylacrylamide
(NIPAAm) in the aqueous phase of a toluene-in-water HIPE, thermo-responsive
polyHIPE hydrogels were obtained. The temperature depended modulus of these
porous hydrogels, as revealed by oscillatory mechanical measurements, indicated
improvements of the mechanical properties of these hydrogels when heated from
room temperature to human body temperature, as the polyNIPAAm copolymer
segments starts to phase separate from the aqueous phase and causes the hydrogel to
form a more compact structure within the aqueous phase of the polyHIPE. Secondly
ion responsive methacrylate modified alginate polyHIPE hydrogels were prepared.
The physical dimensions, pore and pore throat sizes as well as water uptakes of these
ion responsive hydrogels can be controllably decreased in the presence of Ca2+ ions
and are fully recovered after disruption of the ionic crosslinking using a chelating
agent (sodium citrate). These ion-responsive polyHIPE hydrogels also possess good
mechanical properties (modulus up to 20 kPa). Both of these polyHIPE hydrogels
could be easily extruded through a hypodermic needle while breaking into small
fragments (about 0.5 to 3.0 mm in diameter), but the interconnected porous morphology was maintained after injection as revealed by SEM characterisation.
Furthermore, the hydrogel fragments produced during injection can be crosslinked
into a coherent scaffold under very mild condition using Ca2+ salts and alginate
aqueous solution as the ionically crosslinkable adhesive.
In order to increase the pore size of these covalently crosslinked polyHIPE hydrogels
and also find a biocompatible nontoxic emulsifier as substitution to traditional
surfactants, methyl myristate-in-water and soybean oil-in-water HIPEs solely
stabilised by hydroxyapatite (HAp) nanoparticle were prepared. These Pickering-
HIPEs were used as template to prepare polyHIPE hydrogels. Dextran-GMA, a water
soluble monomer, was polymerised in the continuous phase of the HAp Pickering
HIPEs leading to porous hydrogels with a tunable pore size varying from 1.5 μm to
41.0 μm. HAp is a nontoxic biocompatible emulsifier, which potentially provides
extra functions, such as promoting hard tissue cell proliferation.
HIPE-templated materials whose porous structure is maintained solely by the
reversible physical aggregation between thermo-responsive dextran-b-polyNIPAAm
block polymer chains in an aqueous environment (for this type of HIPE templated
material we coined the name thermo-HIPEs) were prepared. No chemical reaction is
required for the solidification of this porous material. This particular feature should
provide a safer route to injectable scaffolds as issues of polymerisation/crosslinking
chemistry or residual initiator fragments or monomers potentially being cytotoxic do not arise in our case, as all components are purified polymers prior to HIPE formation.
Thermo-HIPEs with soybean oil or squalene as dispersed oil phase were prepared.
Also in this HIPE system it was possible to replace the original surfactant Triton
X405 with colloidal HAp nanoparticles or pH/thermo-responsive polyNIPAAm-co-
AA microgel particles. The pore sizes and the mechanical properties of colloidal
particles stabilised thermo-HIPEs showed improvement compared with thermo-HIPEs
stabilised by Triton X405.
In summary new injectable polyHIPEs have been prepared which retain their pore
morphology during injection and can be solidified by either a thermal or ion (Ca2+) or
chelating ion (Ca2+) stimulus. The materials used are intrinsically biocompatible and
thus makes these porous injectable scaffolds excellent candidates for soft tissue
engineering
Visual and computational analysis of structure-activity relationships in high-throughput screening data
Novel analytic methods are required to assimilate the large volumes of structural and bioassay data generated by combinatorial chemistry and high-throughput screening programmes in the pharmaceutical and agrochemical industries. This paper reviews recent work in visualisation and data mining that can be used to develop structure-activity relationships from such chemical/biological datasets
Streamability of nested word transductions
We consider the problem of evaluating in streaming (i.e., in a single
left-to-right pass) a nested word transduction with a limited amount of memory.
A transduction T is said to be height bounded memory (HBM) if it can be
evaluated with a memory that depends only on the size of T and on the height of
the input word. We show that it is decidable in coNPTime for a nested word
transduction defined by a visibly pushdown transducer (VPT), if it is HBM. In
this case, the required amount of memory may depend exponentially on the height
of the word. We exhibit a sufficient, decidable condition for a VPT to be
evaluated with a memory that depends quadratically on the height of the word.
This condition defines a class of transductions that strictly contains all
determinizable VPTs
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Using formal methods to support testing
Formal methods and testing are two important approaches that assist in the development of high quality software. While traditionally these approaches have been seen as rivals, in recent
years a new consensus has developed in which they are seen as complementary. This article reviews the state of the art regarding ways in which the presence of a formal specification can be used to assist testing
Two-way automata and transducers with planar behaviours are aperiodic
We consider a notion of planarity for two-way finite automata and
transducers, inspired by Temperley-Lieb monoids of planar diagrams. We show
that this restriction captures star-free languages and first-order
transductions.Comment: 18 pages, DMTCS submissio
05061 Abstracts Collection -- Foundations of Semistructured Data
From 06.02.05 to 11.02.05, the Dagstuhl Seminar
05061 ``Foundations of Semistructured Data\u27\u27 was held
in the International Conference and Research Center (IBFI),
Schloss Dagstuhl.
During the seminar, several participants presented their current
research, and ongoing work and open problems were discussed. Abstracts of
the presentations given during the seminar as well as abstracts of
seminar results and ideas are put together in this paper. The first section
describes the seminar topics and goals in general.
Links to extended abstracts or full papers are provided, if available
Towards Synthetic Life: Establishing a Minimal Segrosome for the Rational Design of Biomimetic Systems
DNA segregation is a fundamental life process, crucial for renewal, reproduction and propagation of all forms of life. Hence, a dedicated segregation machinery, a segrosome, must function reliably also in the context of a minimal cell. Conceptionally, the development of such a minimal cell follows a minimalistic approach, aiming at engineering a synthetic entity only consisting of the essential key elements necessary for a cell to survive. In this thesis, various prokaryotic segregation systems were explored as possible candidates for a minimal segrosome. Such a minimal segrosome could be applied for the rational design of biomimetic systems including, but not limited to, a minimal cell. DNA segregation systems of type I (ParABS) and type II (ParMRC) were compared for ensuring genetic stabilities in vivo using vectors derived from the natural secondary chromosome of Vibrio cholerae. The type II segregation system R1-ParMRC was chosen as the most promising candidate for a minimal segrosome, and it was characterized and reconstituted in vitro. This segregation system was encapsulated into biomimetic micro-compartments and its lifetime prolonged by coupling to ATP-regenerating as well as oxygen-scavenging systems. The segregation process was coupled to in vitro DNA replication using DNA nanoparticles as a mimic of the condensed state of chromosomes. Furthermore, another type II segregation system originating from the pLS20 plasmid from Bacillus subtilis (Alp7ARC) was reconstituted in vitro as a secondary orthogonal segrosome. Finally, a chimeric RNA segregation system was engineered that could be applied for an RNA-based protocell.
Overall, this work demonstrates successful bottom-up assemblies of functional molecular machines that could find applications in biomimetic systems and lead to a deeper understanding of living systems
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