316 research outputs found
Deterministic soliton automata with at most one cycle
AbstractSoliton valves have been proposed as molecular switching elements. Their mathematical model is the soliton graph and the soliton automaton (Dassow and Jürgensen, J. Comput. System Sci.40 (1990), 154–181). In this paper we continue the study of the logic aspects of soliton switching. There are two cases of special importance: those of deterministic and those of strongly deterministic soliton automata. The former have deterministic state transitions in the usual sense of automaton theory. The latter do not only have deterministic state transitions, but also deterministic soliton paths—a much stronger property, as it turns out. In op cit. a characterization of indecomposable, strongly deterministic soliton automata was proved and it was shown that their transition monoids are primitive groups of permutations. Roughly speaking, the main difference between deterministic and strongly deterministic soliton automata is that in the former the underlying soliton graphs may contain cycles of odd lengths while such cycles are not permitted in the soliton graphs belonging to strongly deterministic soliton automata. In the present paper, we focus on a special class of deterministic soliton automata, that of deterministic soliton automata whose underlying graphs contain at most one cycle. For this class we derive structural descriptions. Our main results concern the elimination of certain types of loops, the treatment of soliton paths with repeated edges, the structure of cycles of odd length, and the transition monoid. As an application we show that the memory element proposed in the literature (Carter, in Bioelectronics, edited by Aizawa, Research and Development Report 50, CMC Press, Denver, CO, 1984) can be transformed in into a soliton tree, thus turning a deterministic device into a logically equivalent strongly deterministic device
Decision Problems For Convex Languages
In this paper we examine decision problems associated with various classes of
convex languages, studied by Ang and Brzozowski (under the name "continuous
languages"). We show that we can decide whether a given language L is prefix-,
suffix-, factor-, or subword-convex in polynomial time if L is represented by a
DFA, but that the problem is PSPACE-hard if L is represented by an NFA. In the
case that a regular language is not convex, we prove tight upper bounds on the
length of the shortest words demonstrating this fact, in terms of the number of
states of an accepting DFA. Similar results are proved for some subclasses of
convex languages: the prefix-, suffix-, factor-, and subword-closed languages,
and the prefix-, suffix-, factor-, and subword-free languages.Comment: preliminary version. This version corrected one typo in Section
2.1.1, line
A Fast Algorithm Finding the Shortest Reset Words
In this paper we present a new fast algorithm finding minimal reset words for
finite synchronizing automata. The problem is know to be computationally hard,
and our algorithm is exponential. Yet, it is faster than the algorithms used so
far and it works well in practice. The main idea is to use a bidirectional BFS
and radix (Patricia) tries to store and compare resulted subsets. We give both
theoretical and practical arguments showing that the branching factor is
reduced efficiently. As a practical test we perform an experimental study of
the length of the shortest reset word for random automata with states and 2
input letters. We follow Skvorsov and Tipikin, who have performed such a study
using a SAT solver and considering automata up to states. With our
algorithm we are able to consider much larger sample of automata with up to
states. In particular, we obtain a new more precise estimation of the
expected length of the shortest reset word .Comment: COCOON 2013. The final publication is available at
http://link.springer.com/chapter/10.1007%2F978-3-642-38768-5_1
Gastrointestinal Tract As Entry Route for Hantavirus Infection
Background: Hantaviruses are zoonotic agents that cause hemorrhagic fevers and
are thought to be transmitted to humans by exposure to aerosolized excreta of
infected rodents. Puumala virus (PUUV) is the predominant endemic hantavirus
in Europe. A large proportion of PUUV-infected patients suffer from
gastrointestinal symptoms of unclear origin. In this study we demonstrate that
PUUV infection can occur via the alimentary tract. Methods: We investigated
susceptibility of the human small intestinal epithelium for PUUV infection and
analyzed the resistance of virions to gastric juice. As model for intestinal
virus translocation we performed infection experiments with human intestinal
Caco-2 monolayers. In animal experiments we infected Syrian hamsters with PUUV
via the intragastric route and tested seroconversion and protective immunity
against subsequent Andes virus challenge. Results: PUUV retained infectivity
in gastric juice at pH >3. The virus invaded Caco-2 monolayers in association
with endosomal antigen EEA1, followed by virus replication and loss of
epithelial barrier function with basolateral virus occurrence. Cellular
disturbance and depletion of the tight junction protein ZO-1 appeared after
prolonged infection, leading to paracellular leakage (leak flux diarrhea).
Moreover, animal experiments led to dose-dependent seroconversion and
protection against lethal Andes virus challenge. Conclusions: We provide
evidence that hantavirus can infect the organism via the alimentary tract and
suggest a novel aspect of hantavirus infection and pathogenesis. Significance:
Hantaviruses are zoonotic pathogens causing severe hemorrhagic fevers
worldwide. They are transmitted to humans by small mammals. To date, these
viruses were thought to infect exclusively through the airborne route by
inhalation of aerosols from infectious animal droppings or by rodent bites. In
our work we could show that the alimentary tract is an alternative path of
infection for hantaviruses, meaning a new association of virus and disease.
These findings have impact on current textbook knowledge and bring many
implications for hantavirus epidemiology and outbreak prevention measures
Extraction of 2′-O-apiosyl-6′-O-crotonic acid-betanin from the ayrampo seed (Opuntia soehrensii) cuticle and its use as an emitting layer in an organic light-emitting diode
The molecule 2′-O-apiosyl-6′-O-crotonic acid-betanin (called Achkiy) was obtained after an ecofriendly and low-cost purification process of the extract from the ayrampo seed cuticle. Results from EDS give us an idea of the organic elements present in the ayrampo cuticle layer composed of carbon, oxygen and nitrogen. Further characterization analysis of ayrampo extract by Fourier Transform Infrared Spectrophotometry (FTIR) corroborated the presence of characteristic functional groups corresponding to carboxyl, carbonyls, hydroxyls and secondary amines. On the other hand, we have confirmed by absortion peak the glucose, apiosyl, crotonic acid and betanin at 227 nm, 276 nm, 291 nm and 534 nm bands respectively. Mass Spectrometry (MS) characterization was used finally to identify the electroactive Achkiy molecule. This molecule was tested in an Organic Light Emitting Diode (OLED) achieving a luminance of 4.8 Cd m when bias voltage of 16.5 V and a current of 34.1 mA was applied. In addition, the irradiance generated by the Achkiy layer reaches a value of ≈ 113.3 μW m emitting light with a λ ≈ 390.10 nm. These preliminary results report an interesting molecule extracted from a natural pigment wich emits light in the blue region
Coherent multi-flavour spin dynamics in a fermionic quantum gas
Microscopic spin interaction processes are fundamental for global static and
dynamical magnetic properties of many-body systems. Quantum gases as pure and
well isolated systems offer intriguing possibilities to study basic magnetic
processes including non-equilibrium dynamics. Here, we report on the
realization of a well-controlled fermionic spinor gas in an optical lattice
with tunable effective spin ranging from 1/2 to 9/2. We observe long-lived
intrinsic spin oscillations and investigate the transition from two-body to
many-body dynamics. The latter results in a spin-interaction driven melting of
a band insulator. Via an external magnetic field we control the system's
dimensionality and tune the spin oscillations in and out of resonance. Our
results open new routes to study quantum magnetism of fermionic particles
beyond conventional spin 1/2 systems.Comment: 9 pages, 5 figure
Algebraic synchronization criterion and computing reset words
We refine a uniform algebraic approach for deriving upper bounds on reset
thresholds of synchronizing automata. We express the condition that an
automaton is synchronizing in terms of linear algebra, and obtain upper bounds
for the reset thresholds of automata with a short word of a small rank. The
results are applied to make several improvements in the area.
We improve the best general upper bound for reset thresholds of finite prefix
codes (Huffman codes): we show that an -state synchronizing decoder has a
reset word of length at most . In addition to that, we prove
that the expected reset threshold of a uniformly random synchronizing binary
-state decoder is at most . We also show that for any non-unary
alphabet there exist decoders whose reset threshold is in .
We prove the \v{C}ern\'{y} conjecture for -state automata with a letter of
rank at most . In another corollary, based on the recent
results of Nicaud, we show that the probability that the \v{C}ern\'y conjecture
does not hold for a random synchronizing binary automaton is exponentially
small in terms of the number of states, and also that the expected value of the
reset threshold of an -state random synchronizing binary automaton is at
most .
Moreover, reset words of lengths within all of our bounds are computable in
polynomial time. We present suitable algorithms for this task for various
classes of automata, such as (quasi-)one-cluster and (quasi-)Eulerian automata,
for which our results can be applied.Comment: 18 pages, 2 figure
Site-Directed Insertion: Decision Problems, Maximality and Minimality
Site-directed insertion is an overlapping insertion operation that can be
viewed as analogous to the overlap assembly or chop operations that concatenate
strings by overlapping a suffix and a prefix of the argument strings. We
consider decision problems and language equations involving site-directed
insertion. By relying on the tools provided by semantic shuffle on trajectories
we show that one variable equations involving site-directed insertion and
regular constants can be solved. We consider also maximal and minimal variants
of the site-directed insertion operation
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