8,514 research outputs found
Automata Minimization: a Functorial Approach
In this paper we regard languages and their acceptors - such as deterministic
or weighted automata, transducers, or monoids - as functors from input
categories that specify the type of the languages and of the machines to
categories that specify the type of outputs. Our results are as follows:
A) We provide sufficient conditions on the output category so that
minimization of the corresponding automata is guaranteed.
B) We show how to lift adjunctions between the categories for output values
to adjunctions between categories of automata.
C) We show how this framework can be instantiated to unify several phenomena
in automata theory, starting with determinization, minimization and syntactic
algebras. We provide explanations of Choffrut's minimization algorithm for
subsequential transducers and of Brzozowski's minimization algorithm in this
setting.Comment: journal version of the CALCO 2017 paper arXiv:1711.0306
Starting Sick Leave on Part-Time as a Treatment Method?
This paper analyzes the effects of starting the sick leave on part-time compared to fulltime on the probability to recover (i.e., return to work with full recovery of lost work capacity). Using a discrete choice one-factor model, we estimate mean treatment parameters and distributional treatment parameters from a common set of structural parameters. Our results indicate that part-time sick leave is not an intensive treatment and should not to be used for all from the very beginning of a case. However, when the output is analyzed for time spans longer than three months, the average probability to recover is higher for those who started on part time sick leave. Besides, the share of individuals who are positive indifferent between the two states is large (above 50%), which suggests that there is potential for increasing the sharepart-time sick leave; selection; unobserved heterogeneity; treatment effects
Zero forcing in iterated line digraphs
Zero forcing is a propagation process on a graph, or digraph, defined in
linear algebra to provide a bound for the minimum rank problem. Independently,
zero forcing was introduced in physics, computer science and network science,
areas where line digraphs are frequently used as models. Zero forcing is also
related to power domination, a propagation process that models the monitoring
of electrical power networks.
In this paper we study zero forcing in iterated line digraphs and provide a
relationship between zero forcing and power domination in line digraphs. In
particular, for regular iterated line digraphs we determine the minimum
rank/maximum nullity, zero forcing number and power domination number, and
provide constructions to attain them. We conclude that regular iterated line
digraphs present optimal minimum rank/maximum nullity, zero forcing number and
power domination number, and apply our results to determine those parameters on
some families of digraphs often used in applications
Gravitational entropy of black holes and wormholes
Pure thermodynamical considerations to describe the entropic evolution of the
universe seem to violate the Second Law of Thermodynamics. This suggests that
the gravitational field itself has entropy. In this paper we expand recent work
done by Rudjord, Gr{\O}n and Sigbj{\O}rn where they suggested a method to
calculate the gravitational entropy in black holes based on the so-called `Weyl
curvature conjecture'. We study the formulation of an estimator for the
gravitational entropy of Reissner-Nordstr\"om, Kerr, Kerr-Newman black holes,
and a simple case of wormhole. We calculate in each case the entropy for both
horizons and the interior entropy density. Then, we analyse whether the
functions obtained have the expected behaviour for an appropriate description
of the gravitational entropy density.Comment: 11 pages, 11 figures, accepted for publication in International
Journal of Theoretical Physic
Minimum rank and zero forcing number for butterfly networks
The minimum rank of a simple graph is the smallest possible rank over all
symmetric real matrices whose nonzero off-diagonal entries correspond to
the edges of . Using the zero forcing number, we prove that the minimum rank
of the butterfly network is and
that this is equal to the rank of its adjacency matrix
M@TE - Monitoring at TeV Energies
Blazars are extremely variable objects emitting radiation across the
electromagnetic spectrum and showing variability on time scales from minutes to
years. For the understanding of the emission mechanisms, simultaneous
multi-wavelength observations are crucial. Various models for flares predict
simultaneous flux increases in the X-ray and gamma-ray band or more complex
variability patterns, depending on the dominant process responsible for the
gamma-ray emission. Monitoring at TeV energies is providing important
information to distinguish between different models. To study duty cycle and
variability time scales of an object, an unbiased data sample is essential, and
good sensitivity and continuous monitoring are needed to resolve smaller time
scales. A dedicated long-term monitoring program at TeV energies has been
started by the FACT project. Its success clearly illustrated that the usage of
silicon based photo sensors (SIPMs) is ideal for long-term monitoring. They
provide not only an excellent and stable detector performance, but also allow
for observations during bright ambient light minimizing observational gaps and
increasing the instrument's duty cycle. The observation time in a single
longitude is limited to 6 hours. To study typical variability time scales of
few hours to one day, the ultimate goal is 24/7 monitoring with a network of
small telescopes around the globe (DWARF project). The installation of an
Imaging Air Cherenkov Telescope is planned in San Pedro Martir, Mexico. For the
M@TE (Monitoring at TeV energies) telescope, a mount from a previous experiment
is being refurbished to be equipped with a camera using the new generation of
SiPMs. In the presentation, the status of the M@TE project will be reported
outlining the scientific potential, including the possibility to extend
monitoring campaigns to 12 hours by coordinated observations together with
FACT.Comment: 5 pages, 1 figure. Contribution to the 6th International Symposium on
High Energy Gamma-Ray Astronomy (Gamma2016), Heidelberg, Germany. To be
published in the AIP Conference Proceeding
Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe
We investigate the interactions of photoexcited carriers with lattice
vibrations in thin films of the layered transition metal dichalcogenide (TMDC)
WSe. Employing femtosecond electron diffraction with monocrystalline
samples and first principle density functional theory calculations, we obtain a
momentum-resolved picture of the energy-transfer from excited electrons to
phonons. The measured momentum-dependent phonon population dynamics are
compared to first principle calculations of the phonon linewidth and can be
rationalized in terms of electronic phase-space arguments. The relaxation of
excited states in the conduction band is dominated by intervalley scattering
between valleys and the emission of zone-boundary phonons.
Transiently, the momentum-dependent electron-phonon coupling leads to a
non-thermal phonon distribution, which, on longer timescales, relaxes to a
thermal distribution via electron-phonon and phonon-phonon collisions. Our
results constitute a basis for monitoring and predicting out of equilibrium
electrical and thermal transport properties for nanoscale applications of
TMDCs
Descriptive Cost-Effectiveness Analysis of a Counseling and Coordination Model in Psychosocial Care. Integration of Health Care and Social Rehabilitation
Introduction: A psychosocial outreach clinic was established to offer counseling and coordination of healthcare and complementary services for persons with psychosocial and mental problems. The cost-effectiveness of these services was measured based on a pre-post comparison.
Methods: A prospective observational study was conducted with clients of the outreach clinic. Data on resource consumption and quality of life were collected at baseline and follow-up after 3, 6, and 12 months using the Client Sociodemographic and Service Receipt Inventory to assess service utilization, and the 12-Item Short Form Health Survey to assess quality of life. The objective of the present analysis was to estimate the relation between monetary expenditure and QALYs (quality-adjusted life-years), before and after the outreach clinic was established, descriptively. The analysis was constructed from payer’s perspective and was supplemented by a sensitivity analysis.
Results: A total of 85 participants were included. Total annual expenditures before the intervention were 5,832 € per client for all service segments. During the 12-months study duration expenditures decreased to 4,350 € including the costs associated with outreach clinic services. QALYs for the 12-month study period were 0.6618 and increased about 0.0568 compared to the period before.
Discussion: Despite methodological limitations due to small sample size, a pre-post comparison and the retrospective cost data collection, this study suggests acceptability of the outreach clinic as cost-effective.
Conclusion: The activities of the outreach clinic as an integrated care model seem to be cost-effective regarding the relation between monetary expenditures and clients’ quality of life
Preliminary Evidence of Increased Hippocampal Myelin Content in Veterans with Posttraumatic Stress Disorder.
Recent findings suggest the formation of myelin in the central nervous system by oligodendrocytes is a continuous process that can be modified with experience. For example, a recent study showed that immobilization stress increased oligodendrogensis in the dentate gyrus of adult rat hippocampus. Because changes in myelination represents an adaptive form of brain plasticity that has a greater reach in the adult brain than other forms of plasticity (e.g., neurogenesis), the objective of this "proof of concept" study was to examine whether there are differences in myelination in the hippocampi of humans with and without post-traumatic stress disorder (PTSD). We used the ratio of T1-weighted/T2-weighted magnetic resonance image (MRI) intensity to estimate the degree of hippocampal myelination in 19 male veterans with PTSD and 19 matched trauma-exposed male veterans without PTSD (mean age: 43 ± 12 years). We found that veterans with PTSD had significantly more hippocampal myelin than trauma-exposed controls. There was also found a positive correlation between estimates of hippocampal myelination and PTSD and depressive symptom severity. To our knowledge, this is the first study to examine hippocampal myelination in humans with PTSD. These results provide preliminary evidence for stress-induced hippocampal myelin formation as a potential mechanism underlying the brain abnormalities associated with vulnerability to stress
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