102 research outputs found
Pressure jump interface law for the Stokes-Darcy coupling: Confirmation by direct numerical simulations
It is generally accepted that the effective velocity of a viscous flow over a
porous bed satisfies the Beavers-Joseph slip law. To the contrary, interface
law for the effective stress has been a subject of controversy. Recently, a
pressure jump interface law has been rigorously derived by Marciniak-Czochra
and Mikeli\'c. In this paper, we provide a confirmation of the analytical
result using direct numerical simulation of the flow at the microscopic level.Comment: 25 pages, preprin
Structured Population Models on Polish Spaces: A unified approach including Graphs, Riemannian Manifolds and Measure Spaces
We provide well-posedness theory of a nonlinear structured population model
on an abstract metric space which is only assumed to be separable and complete.
To this end, we leverage the structure of the space of nonnegative Radon
measures under the dual bounded Lipschitz distance (flat metric) which can be
seen as a generalization of Wasserstein distance to nonconservative problems.
Motivated by applications, the formulation of models on fairly general metric
spaces allows us to consider processes on infinite-dimensional state spaces or
on graphs combining discrete and continuous structures
Overnight pulse wave analysis to assess autonomic changes during sleep in insomnia patients and healthy sleepers
Insomnia has been associated with increased cardiovascular (CV) risk, which may be linked to sympathetic activation. Non-invasive overnight pulse wave analysis may be a useful tool to detect early signs of autonomic changes during sleep in insomniacs. Fifty-two participants (26 men, 37±13 years, BMI: 24±5 kg/m2, 26 insomniacs/ 26 controls) underwent overnight polysomnography with pulse oximetry and pulse wave analysis including pulse rate, vascular stiffness (pulse propagation time, PPT), and a composite cardiac risk index based on autonomic function and overnight hypoxia. We identified two subgroups of insomniacs, with and without objectively disturbed sleep (sleep efficiency SE≤80%, n = 14 vs. SE>80%, n = 12), and observed increased pulse rate and vascular stiffness in insomnia cases when diagnosis was based on both, subjective and objective criteria. Both insomnia groups were associated with higher overnight pulse rate than controls (median/ IQR: low-SE (low sleep efficiency): 67/ 58-70bpm; high-SE: 66/ 63-69bpm; controls: 58/ 52-63bpm; p = 0.01). Vascular stiffness was higher (reduction of PPT) in low-SE insomniacs compared with high-SE insomniacs and controls (169/ 147-232ms; 237/ 215-254ms; 244/ 180-284ms; p = 0.01). The cardiac risk index was increased in low-SE insomniacs (0.2/ 0.0–0.7; 0.0/ 0.0–0.4; 0.0/ 0.0–0.3; p = 0.05). Our results suggest a hyperarousal state in young and otherwise healthy insomniacs during sleep. The increased pulse rate and vascular stiffness in insomniacs with low SE suggest early signs of rigid vessels and potentially, an elevated CV risk. Overnight pulse wave analysis may be feasible for CV risk assessment in insomniacs and may provide a useful tool for phenotyping insomnia in order to provide individualized therapy
A compact ion-trap quantum computing demonstrator
Quantum information processing is steadily progressing from a purely academic
discipline towards applications throughout science and industry. Transitioning
from lab-based, proof-of-concept experiments to robust, integrated realizations
of quantum information processing hardware is an important step in this
process. However, the nature of traditional laboratory setups does not offer
itself readily to scaling up system sizes or allow for applications outside of
laboratory-grade environments. This transition requires overcoming challenges
in engineering and integration without sacrificing the state-of-the-art
performance of laboratory implementations. Here, we present a 19-inch rack
quantum computing demonstrator based on optical qubits in
a linear Paul trap to address many of these challenges. We outline the
mechanical, optical, and electrical subsystems. Further, we describe the
automation and remote access components of the quantum computing stack. We
conclude by describing characterization measurements relevant to digital
quantum computing including entangling operations mediated by the
Molmer-Sorenson interaction. Using this setup we produce maximally-entangled
Greenberger-Horne-Zeilinger states with up to 24 ions without the use of
post-selection or error mitigation techniques; on par with well-established
conventional laboratory setups
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