4,584 research outputs found
Neutral gas in Lyman-alpha emitting galaxies Haro 11 and ESO 338-IG04 measured through sodium absorption
Context. The Lyman alpha emission line of galaxies is an important tool for
finding galaxies at high redshift, and thus probe the structure of the early
universe. However, the resonance nature of the line and its sensitivity to dust
and neutral gas is still not fully understood.
Aims. We present measurements of the velocity, covering fraction and optical
depth of neutral gas in front of two well known local blue compact galaxies
that show Lyman alpha in emission: ESO 338-IG 04 and Haro 11. We thus test
observationally the hypothesis that Lyman alpha can escape through neutral gas
by being Doppler shifted out of resonance.
Methods. We present integral field spectroscopy from the GIRAFFE/Argus
spectrograph at VLT/FLAMES in Paranal, Chile. The excellent wavelength
resolution allows us to accurately measure the velocity of the ionized and
neutral gas through the H-alpha emission and Na D absorption, which traces the
ionized medium and cold interstellar gas, respectively. We also present
independent measurements with the VLT/X-shooter spectrograph which confirm our
results.
Results. For ESO 338-IG04, we measure no significant shift of neutral gas.
The best fit velocity is -15 (16) km/s. For Haro 11, we see an outflow from
knot B at 44 (13) km/s and infalling gas towards knot C with 32 (12) km/s.
Based on the relative strength of the Na D absorption lines, we estimate low
covering fractions of neutral gas (down to 10%) in all three cases.
Conclusions. The Na D absorption likely occurs in dense clumps with higher
column densities than where the bulk of the Ly-alpha scattering takes place.
Still, we find no strong correlation between outflowing neutral gas and a high
Lyman alpha escape fraction. The Lyman alpha photons from these two galaxies
are therefore likely escaping due to a low column density and/or covering
fraction.Comment: 9 pages, 3 figure
Complexity of checking whether two automata are synchronized by the same language
A deterministic finite automaton is said to be synchronizing if it has a
reset word, i.e. a word that brings all states of the automaton to a particular
one. We prove that it is a PSPACE-complete problem to check whether the
language of reset words for a given automaton coincides with the language of
reset words for some particular automaton.Comment: 12 pages, 4 figure
Synchronization Problems in Automata without Non-trivial Cycles
We study the computational complexity of various problems related to
synchronization of weakly acyclic automata, a subclass of widely studied
aperiodic automata. We provide upper and lower bounds on the length of a
shortest word synchronizing a weakly acyclic automaton or, more generally, a
subset of its states, and show that the problem of approximating this length is
hard. We investigate the complexity of finding a synchronizing set of states of
maximum size. We also show inapproximability of the problem of computing the
rank of a subset of states in a binary weakly acyclic automaton and prove that
several problems related to recognizing a synchronizing subset of states in
such automata are NP-complete.Comment: Extended and corrected version, including arXiv:1608.00889.
Conference version was published at CIAA 2017, LNCS vol. 10329, pages
188-200, 201
A titanium-nitride near-infrared kinetic inductance photon-counting detector and its anomalous electrodynamics
We demonstrate single-photon counting at 1550 nm with titanium-nitride (TiN)
microwave kinetic inductance detectors. Energy resolution of 0.4 eV and
arrival-time resolution of 1.2 microseconds are achieved. 0-, 1-, 2-photon
events are resolved and shown to follow Poisson statistics. We find that the
temperature-dependent frequency shift deviates from the Mattis-Bardeen theory,
and the dissipation response shows a shorter decay time than the frequency
response at low temperatures. We suggest that the observed anomalous
electrodynamics may be related to quasiparticle traps or subgap states in the
disordered TiN films. Finally, the electron density-of-states is derived from
the pulse response.Comment: 4 pages, 3 figure
Breathlessness dimensions association with physical and mental quality of life: the population based VASCOL study of elderly men.
BackgroundBreathlessness is a multidimensional symptom prevalent in elderly affecting many aspects of life. We aimed to determine how different dimensions of breathlessness are associated with physical and mental quality of life (QoL) in elderly men.MethodsThis was a cross-sectional, population-based analysis of 672 men aged 73 years in a Swedish county. Breathlessness was assessed using Dyspnoea-12 (D-12) and Multidimensional Dyspnoea Profile (MDP), and QoL using the Short Form 12 physical and mental scores. Scores were compared as z-scores across scales and analysed using multivariable linear regression, adjusted for smoking, body mass index and the presence of respiratory and cardiovascular disease.ResultsWorse breathlessness was related to worse physical and mental QoL across all the D-12 and MDP dimension scores. Physical QoL was most strongly associated with perceptional breathlessness scores, D-12 total and physical scores (95% CI -0.45 to -0.30). Mental QoL was more strongly influenced by affective responses, MDP emotional response score (95% CI -0.61 to -0.48). Head-to-head comparison of the instruments confirmed that D-12 total and physical scores most influenced physical QoL, while mental QoL was mostly influenced by the emotional responses captured by the MDP.ConclusionBreathlessness dimensions and QoL measures are associated differently. Physical QoL was most closely associated with sensory and perceptual breathlessness dimensions, while emotional responses were most strongly associated with mental QoL in elderly men. D-12 and MDP contribute complimentary information, where affective and emotional responses may be related to function, deconditioning and QoL
The Los Alamos Trapped Ion Quantum Computer Experiment
The development and theory of an experiment to investigate quantum
computation with trapped calcium ions is described. The ion trap, laser and ion
requirements are determined, and the parameters required for quantum logic
operations as well as simple quantum factoring are described.Comment: 41 pages, 16 figures, submitted to Fortschritte der Physi
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