335 research outputs found
Small quantum networks operating as quantum thermodynamic machines
We show that a 3-qubit system as studied for quantum information purposes can
alternatively be used as a thermodynamic machine when driven in finite time and
interfaced between two split baths. The spins are arranged in a chain where the
working spin in the middle exercises Carnot cycles the area of which defines
the exchanged work. The cycle orientation (sign of the exchanged work) flips as
the difference of bath temperatures goes through a critical value.Comment: RevTeX, 4 pages, 7 figures. Replaced by version accepted for
publication in EP
Characterization of 1D photonic crystal nanobeam cavities using curved microfiber
We investigate high-Q, small mode volume photonic crystal nanobeam cavities using a curved, tapered optical microfiber loop. The strength of the coupling between the cavity and the microfiber loop is shown to depend on the contact position on the nanobeam, angle between the nanobeam and the microfiber, and polarization of the light in the fiber. The results are compared to a resonant scattering measurement
Electric charge quantisation from gauge invariance of a Lagrangian: A catalogue of baryon number violating scalar interactions
In gauge theories like the standard model, the electric charges of the
fermions can be heavily constrained from the classical structure of the theory
and from the cancellation of anomalies. There is however mounting evidence
suggesting that these anomaly constraints are not as well motivated as the
classical constraints. In light of this we discuss possible modifications of
the minimal standard model which will give us complete electric charge
quantisation from classical constraints alone. Because these modifications to
the standard model involve the consideration of baryon number violating scalar
interactions, we present a complete catalogue of the simplest ways to modify
the standard model so as to introduce explicit baryon number violation. This
has implications for proton decay searches and baryogenesis.Comment: 15 pages, 7 Postscript figure
Large energy mode locking of an erbium-doped fiber laser with atomic layer graphene
We report on large energy pulse generation in an erbium-doped fiber laser
passively mode-locked with atomic layer graphene. Stable mode locked pulses
with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been
directly generated from the laser. Our results show that atomic layer graphene
could be a promising saturable absorber for large energy mode locking.Comment: 14 pages 4 figure
Perturbative analysis for Kaplan's lattice chiral fermions
Perturbation theory for lattice fermions with domain wall mass terms is
developed and is applied to investigate the chiral Schwinger model formulated
on the lattice by Kaplan's method. We calculate the effective action for gauge
fields to one loop, and find that it contains a longitudinal component even for
anomaly-free cases. From the effective action we obtain gauge anomalies and
Chern-Simons current without ambiguity. We also show that the current
corresponding to the fermion number has a non-zero divergence and it flows off
the wall into the extra dimension. Similar results are obtained for a proposal
by Shamir, who used a constant mass term with free boundaries instead of domain
walls.Comment: 25 page, 5 PostScript figures, [some changes in the conclusion
Venoarterial Extracorporeal Membrane Oxygenation and Implantable Cardioverter-Defibrillator Implantation in a Hemodynamically Unstable Infant with Ventricular Tachycardia from Multiple Cardiac Rhabdomyomas
Tuberous sclerosis complex (TSC) is a neurocutaneous disorder characterized by benign tissue hamartomas in multiple organ systems, including cardiac rhabdomyomas. Though prevalent in TSC, cardiac tumors are rare in children, occurring in about 0.03%–0.17%. Rhabdomyomas are the most common, accounting for 45%. When present, they are multiple and in the ventricular myocardium. Frequently, they regress and surveillance is all that is required until spontaneous regression. Intervention is necessary when life-threatening obstruction or hemodynamically significant refractory arrhythmias occur. This case highlights the course of a 6-month-old infant with TSC and cardiac rhabdomyomas who presented in refractory ventricular tachycardia (VT) with decompensation and cardiac arrest necessitating venoarterial extracorporeal membrane oxygenation (VA-ECMO), complex antiarrhythmic therapy, and ultimately implantable cardioverter-defibrillator (ICD) implantation
Kaplan-Narayanan-Neuberger lattice fermions pass a perturbative test
We test perturbatively a recent scheme for implementing chiral fermions on
the lattice, proposed by Kaplan and modified by Narayanan and Neuberger, using
as our testing ground the chiral Schwinger model. The scheme is found to
reproduce the desired form of the effective action, whose real part is gauge
invariant and whose imaginary part gives the correct anomaly in the continuum
limit, once technical problems relating to the necessary infinite extent of the
extra dimension are properly addressed. The indications from this study are
that the Kaplan--Narayanan--Neuberger (KNN) scheme has a good chance at being a
correct lattice regularization of chiral gauge theories.Comment: LaTeX 18 pages, 3 figure
Coupling an Agent-Based Model and Ensemble Kalman Filter for Real-Time Crowd Modelling
Agent-based modelling has emerged as a powerful tool for modelling systems that are driven by discrete, heterogeneous individuals and has proven particularly popular in the realm of pedestrian simulation. However, real-time agent-based simulations face the challenge that they will diverge from the real system over time. This paper addresses this challenge by integrating the Ensemble Kalman Filter (EnKF) with an agent-based crowd model to enhance its accuracy in real-time. Using the example of Grand Central Station in New York, we demonstrate how our approach can update the state of an agent-based model in real-time, aligning it with the evolution of the actual system. The findings reveal that the EnKF can substantially improve the accuracy of agent-based pedestrian simulations by assimilating data as they evolve. This approach not only offers efficiency advantages over existing methods but also presents a more realistic representation of a complex environment than most previous attempts. The potential applications of this method span the management of public spaces under ‘normality’ to exceptional circumstances such as disaster response, marking a significant advancement for real-time agent-based modelling applications
Simulating Crowds in Real Time with Agent-Based Modelling and a Particle Filter
Agent-based modelling is a valuable approach for modelling systems whose behaviour is driven by the interactions between distinct entities, such as crowds of people. However, it faces a fundamental difficulty: there are no established mechanisms for dynamically incorporating real-time data into models. This limits simulations that are inherently dynamic, such as those of pedestrian movements, to scenario testing on historic patterns rather than real-time simulation of the present. This paper demonstrates how a particle filter could be used to incorporate data into an agent-based model of pedestrian movements at run time. The experiments show that although it is possible to use a particle filter to perform online (real time) model optimisation, the number of individual particles required (and hence the computational complexity) increases exponentially with the number of agents. Furthermore, the paper assumes a one-to-one mapping between observations and individual agents, which would not be the case in reality. Therefore this paper lays some of the fundamental groundwork and highlights the key challenges that need to be addressed for the real-time simulation of crowd movements to become a reality. Such success could have implications for the management of complex environments both nationally and internationally such as transportation hubs, hospitals, shopping centres, etc
Mesenchymal Stem Cells: The Secret Children’s Weapons against the SARS-CoV-2 Lethal Infection
Due to the promising effects of mesenchymal stem cells (MSCs) in the treatment of various diseases, this commentary aimed to focus on the auxiliary role of MSCs to reduce inflammatory processes of acute respiratory infections caused by the 2019 novel coronavirus (COVID-19). Since early in 2020, COVID-19, a consequence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly affected millions of people world-wide. The SARS-CoV-2 infection in children appears to be an unusual event. Despite the high number of affected adult and elderly, children and adolescents remained low in amounts, and marginally touched. Based on the promising role of cell therapy and regenerative medicine approaches in the treatment of several life-threatening diseases, it seems that applying MSCs cell-based approaches can also be a hopeful strategy for improving subjects with severe acute respiratory infections caused by COVID-19
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