128 research outputs found
Conditional Transition Systems with Upgrades
We introduce a variant of transition systems, where activation of transitions
depends on conditions of the environment and upgrades during runtime
potentially create additional transitions. Using a cornerstone result in
lattice theory, we show that such transition systems can be modelled in two
ways: as conditional transition systems (CTS) with a partial order on
conditions, or as lattice transition systems (LaTS), where transitions are
labelled with the elements from a distributive lattice. We define equivalent
notions of bisimilarity for both variants and characterise them via a
bisimulation game.
We explain how conditional transition systems are related to featured
transition systems for the modelling of software product lines. Furthermore, we
show how to compute bisimilarity symbolically via BDDs by defining an operation
on BDDs that approximates an element of a Boolean algebra into a lattice. We
have implemented our procedure and provide runtime results
Electron gun for diffraction experiments off controlled molecules
A dc electron gun, generating picosecond pulses with up to
electrons per pulse, was developed. Its applicability for future
time-resolved-diffraction experiments on state- and conformer-selected
laser-aligned or oriented gaseous samples was characterized. The focusing
electrodes were arranged in a velocity-map imaging spectrometer configuration.
This allowed to directly measure the spatial and velocity distributions of the
electron pulses emitted from the cathode. The coherence length and pulse
duration of the electron beam were characterized by these measurements combined
with electron trajectory simulations. Electron diffraction data off a thin
aluminum foil illustrated the coherence and resolution of the electron-gun
setup
Spatially-controlled complex molecules and their applications
The understanding of molecular structure and function is at the very heart of
the chemical and molecular sciences. Experiments that allow for the creation of
structurally pure samples and the investigation of their molecular dynamics and
chemical function have developed tremendously over the last few decades,
although "there's plenty of room at the bottom" for better control as well as
further applications.
Here, we describe the use of inhomogeneous electric fields for the
manipulation of neutral molecules in the gas-phase, \ie, for the separation of
complex molecules according to size, structural isomer, and quantum state. For
these complex molecules, all quantum states are strong-field seeking, requiring
dynamic fields for their confinement. Current applications of these controlled
samples are summarised and interesting future applications discussed.Comment: Accepted by Int. Rev. Phys. Che
Ultrafast light-induced dynamics in solvated biomolecules: The indole chromophore with water
Interactions between proteins and their solvent environment can be studied in
a bottom-up approach using hydrogen-bonded chromophore-solvent clusters. The
ultrafast dynamics following UV-light-induced electronic excitation of the
chromophores, potential radiation-damage, and their dependence on solvation are
important open questions. The microsolvation effect is challenging to study due
to the inherent mix of the produced gas-phase aggregates. We used the deflector
to spatially separate different molecular species in combination with
pump-probe velocity-map-imaging experiments. We demonstrated that this powerful
experimental approach reveals intimate details of the UV-induced dynamics in
the near-UV-absorbing prototypical biomolecular indole-water system. We
determined the time-dependent appearance of the different reaction products and
disentangled the occurring ultrafast processes. This novel approach ensures
that the reactants are well-known and that detailed characteristics of the
specific reaction products are accessible -- paving the way for the complete
chemical-reactivity experiment
Concatenation and other Closure Properties of Recognizable Languages in Adhesive Categories
We consider recognizable languages of cospans in adhesive categories, ofwhich recognizable graph languages are a special case. We show that such languages are closed under concatenation, i.e. under cospan composition, by providing a con-crete construction that creates a concatenation automaton from two given automata.The construction is considerably more complex than the corresponding construction for finite automata. We conclude by showing negative closure properties for Kleene star and substitution
Strongly aligned and oriented molecular samples at a kHz repetition rate
We demonstrate strong adiabatic laser alignment and mixed-field orientation
at kHz repetition rates. We observe degrees of alignment as large as
cos\Theta=0.94 at 1 kHz operation for iodobenzene. The experimental setup
consist of a kHz laser system simultaneously producing pulses of 30 fs (1.3 mJ)
and 450 ps (9 mJ). A cold 1 K state-selected molecular beam is produced at the
same rate by appropriate operation of an Even-Lavie valve. Quantum state
selection has been obtained using an electrostatic deflector. A camera and data
acquisition system records and analyzes the images on a single-shot basis. The
system is capable of producing, controlling (translation and rotation) and
analyzing cold molecular beams at kHz repetition rates and is, therefore,
ideally suited for the recording of ultrafast dynamics in so-called "molecular
movies".Comment: 6 pages, 4 figures, in press in Mol. Phys., accepted in February
2013, in final production (galley proofs done) since March 8, 2013, v3 only
adds publication dat
Conditional Bisimilarity for Reactive Systems
Reactive systems \`a la Leifer and Milner, an abstract categorical framework
for rewriting, provide a suitable framework for deriving bisimulation
congruences. This is done by synthesizing interactions with the environment in
order to obtain a compositional semantics. We enrich the notion of reactive
systems by conditions on two levels: first, as in earlier work, we consider
rules enriched with application conditions and second, we investigate the
notion of conditional bisimilarity. Conditional bisimilarity allows us to say
that two system states are bisimilar provided that the environment satisfies a
given condition. We present several equivalent definitions of conditional
bisimilarity, including one that is useful for concrete proofs and that employs
an up-to-context technique, and we compare with related behavioural
equivalences. We instantiate reactive systems in order to obtain DPO graph
rewriting and consider a case study in this setting
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