653 research outputs found
Topological Wiener-Wintner theorems for amenable operator semigroups
Inspired by topological Wiener-Wintner theorems we study the mean ergodicity
of amenable semigroups of Markov operators on and show the connection to
the convergence of strong and weak ergodic nets. The results are then used to
characterize mean ergodicity of Koopman semigroups corresponding to skew
product actions on compact group extensions.Comment: 26 pages, referee's suggestions incorporated, to appear in "Ergodic
Theory and Dynamical Systems
High-frequency cyclicity in the Mediterranean Messinian evaporites: evidence for solar-lunar climate forcing
The deposition of varved sedimentary sequences is usually controlled by
climate conditions. The study of two Late Miocene evaporite successions (one
halite and the other gypsum) consisting of annual varves has been carried out
to reconstruct the paleoclimatic and paleoenvironmental conditions existing
during the acme of the Messinian salinity crisis, ~ 6 Ma, when thick evaporite
deposits accumulated on the floor of the Mediterranean basin. Spectral analyses
of these varved evaporitic successions reveal significant periodicity peaks at
around 3-5, 9, 11-13, 20-27 and 50-100 yr. A comparison with modern
precipitation data in the western Mediterranean shows that during the acme of
the Messinian salinity crisis the climate was not in a permanent evaporitic
stage, but in a dynamic situation where evaporite deposition was controlled by
quasi-periodic climate oscillations with similarity to modern analogs including
Quasi-Biennial Oscillation, El Ni\~no Southern Oscillation, and decadal to
secular lunar- and solar-induced cycles. Particularly we found a significant
quasi-decadal oscillation with a prominent 9-year peak that is commonly found
also in modern temperature records and is present in the contemporary Atlantic
Multidecadal Oscillation (AMO) index and Pacific Decadal Oscillation (PDO)
index. These cyclicities are common to both ancient and modern climate records
because they can be associated with solar and solar-lunar tidal cycles.Comment: 13 pages, 10 figures, 1 Tabl
Traceability System’s Impact On Process Mining in Production
From the perspective of manufacturing companies, data handling is gaining more attention as it is becoming a strategic resource in digital ecosystems. Market forces such as rising amounts of product variants and decreasing batch sizes lead to higher complexity in manufacturing processes. Therefore, production management’s demand for data-based process transparency is growing continuously as well as the number of companies turning to process mining to address these challenges. The increased use of process mining has uncovered many documented data quality issues that hamper output quality. In response to data usage and quality problems, research in the field of Big Data has turned to sophisticated data value chains as a promising approach to optimize data usage. This paper presents the application of the data value chain concept on a manufacturing use case, delivering an assessment of traceability systems and their effect on data quality issues. This assessment reviews commonly known quality issues and investigates how traceability systems can influence and facilitate better data quality. The results support manufacturing companies in their use of traceability systems to improve the reliability of their process mining input data and, hence, their output performance indicators to meet the demand for more data-based process transparency
The deep record of the Messinian salinity crisis: Evidence of a non-desiccated Mediterranean Sea
This research is focused on a complete reexamination of the evaporite facies present in all the cores that cut
through the topmost deposits of the Messinian salinity crisis lying below the floor of the Mediterranean Sea
(DSDP Legs 13 and 42A, ODP Legs 107 and 161). This review suggests that the uppermost evaporite units in
both western and eastern deep Mediterranean basins consist mainly of clastic (gypsrudite, gypsarenite and
gypsiltite) and fully subaqueous deposits (laminar gypsum, selenite and cumulate halite) that are partially
affected by burial anhydritization and tectonic induced recrystallization. No unequivocal evidence of shallow
water or even supratidal (sabkha) deposition is in evidence, suggesting that at the very last phase of the salinity
crisis the Mediterranean Sea did not experience desiccation, but that deposition took place under permanent
subaqueous conditions
Comparison of the diagnostic value of a small, single channel, electrocardiogram monitoring patch with a standard 3-lead Holter system over 24 hours in dogs
Introduction/Objectives: The aim of this study was to compare a novel small event recorder device, the Carnation Ambulatory Monitor (CAM), with a standard Holter.
Animals: Nineteen adult dogs.
Material and methods: Comparative and explorative study. The two devices were simultaneously applied for approximately 24 h.
Results: Analysis time (P=0.013) and percentage of artefacts (P<0.001) were greater for the CAM (110 min [40–264]; and 9% [0–34], respectively) compared to a standard Holter (30 min [18–270]; and 0.3% [0–9], respectively). The total number of beats (P=0.017) and maximum (P=0.02) and mean (P=0.037) heart rates were lower for the CAM (113,806 ± 23,619 beats; 227 ± 35 bpm; and 88 ± 22 bpm, respectively) compared to the standard Holter (131,640 ± 40,037 beats; 260 ± 64 bpm; and 92 ± 26 bpm, respectively). The minimal heart rate (P=0.725), number of pauses (P=0.078), duration of the longest pause (P=0.087), number of ventricular ectopic complexes (P=0.55), ventricular couplets (P=0.186), ventricular triplets (P=0.203), ventricular tachycardia (P=0.05), Lown grade (P=0.233), presence or absence of ventricular bigeminy, trigeminy, supraventricular tachycardia, and atrial fibrillation (P=0.98) did not differ. The CAM missed some relevant events, like complex ventricular arrhythmias, and the Lown grade did not match in 5/19 dogs when comparing the devices.
Conclusions: Cardiac Ambulatory Monitor can be used to record ECG traces in dogs over a prolonged period, allowing to detect arrhythmias. Due to some clinically relevant limitations, including a higher percentage of artefacts, a longer reading time (which precludes quantitative counts of >300ventricular premature complexes), and underestimation of complex ventricular arrhythmias, the CAM appears not suitable for quantitative arrhythmia analysis in dogs
On the alpha formalism for the common envelope interaction
The {\alpha}-formalism is a common way to parametrize the common envelope
interaction between a giant star and a more compact companion. The {\alpha}
parameter describes the fraction of orbital energy released by the companion
that is available to eject the giant star's envelope. By using new, detailed
stellar evolutionary calculations we derive a user-friendly prescription for
the {\lambda} parameter and an improved approximation for the envelope binding
energy, thus revising the {\alpha} equation. We then determine {\alpha} both
from simulations and observations in a self consistent manner. By using our own
stellar structure models as well as population considerations to reconstruct
the primary's parameters at the time of the common envelope interaction, we
gain a deeper understanding of the uncertainties. We find that systems with
very low values of q (the ratio of the companion's mass to the mass of the
primary at the time of the common envelope interaction) have higher values of
{\alpha}. A fit to the data suggests that lower mass companions are left at
comparable or larger orbital separations to more massive companions. We
conjecture that lower mass companions take longer than a stellar dynamical time
to spiral in to the giant's core, and that this is key to allowing the giant to
use its own thermal energy to help unbind its envelope. As a result, although
systems with light companions might not have enough orbital energy to unbind
the common envelope, they might stimulate a stellar reaction that results in
the common envelope ejection.Comment: 17 pages, 8 figures. Accepted by MNRA
The Terracol and Ardouin developmental model of frontal sinus drainage pathway and surrounding spaces: a radiologic validation
The complexity of the frontal sinus drainage pathway (FSDP) can be challenging even for expert surgeons. Several classifications have been proposed to simplify the understanding of FSDP, whose anatomical variability can be simplified based on the knowledge of its developmental mechanisms
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