336 research outputs found
Violation of the Wiedemann-Franz Law in a Single-Electron Transistor
We study the influence of Coulomb interaction on the thermoelectric transport
coefficients for a metallic single-electron transistor. By performing a
perturbation expansion up to second order in the tunnel-barrier conductance, we
include sequential and cotunneling processes as well as quantum fluctuations
that renormalize the charging energy and the tunnel conductance. We find that
Coulomb interaction leads to a strong violation of the Wiedemann-Franz law: the
Lorenz ratio becomes gate-voltage dependent for sequential tunneling, and is
increased by a factor 9/5 in the cotunneling regime. Finally, we suggest a
measurement scheme for an experimental realization.Comment: published version, minor changes; 4 pages, 3 figure
Resonators coupled to voltage-biased Josephson junctions: From linear response to strongly driven nonlinear oscillations
Motivated by recent experiments, where a voltage biased Josephson junction is
placed in series with a resonator, the classical dynamics of the circuit is
studied in various domains of parameter space. This problem can be mapped onto
the dissipative motion of a single degree of freedom in a nonlinear
time-dependent potential, where in contrast to conventional settings the
nonlinearity appears in the driving while the static potential is purely
harmonic. For long times the system approaches steady states which are analyzed
in the underdamped regime over the full range of driving parameters including
the fundamental resonance as well as higher and sub-harmonics. Observables such
as the dc-Josephson current and the radiated microwave power give direct
information about the underlying dynamics covering phenomena as bifurcations,
irregular motion, up- and down conversion. Due to their tunability, present and
future set-ups provide versatile platforms to explore the changeover from
linear response to strongly nonlinear behavior in driven dissipative systems
under well defined conditions.Comment: 12 pages, 11 figure
Ground deposition of long-lived gamma emitters in Poland from the Chernobyl accident
Activity composition was measured for soil contaminated with the fallout from the Chernobyl accident. The soil samples were collected at various areas of Poland. A map showing the Cs deposit distribution was drawn for the most contaminated southern part of Poland
Kinetics of random sequential adsorption of two-dimensional shapes on a one-dimensional line
7 pages, 10 figuresSaturated random sequential adsorption packings built of two-dimensional ellipses, spherocylinders, rectangles, and dimers placed on a one-dimensional line are studied to check analytical prediction concerning packing growth kinetics [A. Baule, Phys. Rev. Let. 119, 028003 (2017)]. The results show that the kinetics is governed by the power-law with the exponent and for packings built of ellipses and rectangles, respectively, which is consistent with analytical predictions. However, for spherocylinders and dimers of moderate width-to-height ratio, a transition between these two values is observed. We argue that this transition is a finite size effect that arises for spherocylinders due to the properties of the contact function. In general, it appears that the kinetics of packing growth can depend on packing size even for very large packings
Online Active Learning For Sound Event Detection
Data collection and annotation is a laborious, time-consuming prerequisite
for supervised machine learning tasks. Online Active Learning (OAL) is a
paradigm that addresses this issue by simultaneously minimizing the amount of
annotation required to train a classifier and adapting to changes in the data
over the duration of the data collection process. Prior work has indicated that
fluctuating class distributions and data drift are still common problems for
OAL. This work presents new loss functions that address these challenges when
OAL is applied to Sound Event Detection (SED). Experimental results from the
SONYC dataset and two Voice-Type Discrimination (VTD) corpora indicate that OAL
can reduce the time and effort required to train SED classifiers by a factor of
5 for SONYC, and that the new methods presented here successfully resolve
issues present in existing OAL methods.Comment: Submitted to ICASSP 2024. Publication will belong to IEE
Antibunched photons emitted by a dc-biased Josephson junction
We show experimentally that a dc biased Josephson junction in series with a high-enough-impedance microwave resonator emits antibunched photons. Our resonator is made of a simple microfabricated spiral coil that resonates at 4.4 GHz and reaches a 1.97kΩ characteristic impedance. The second order correlation function of the power leaking out of the resonator drops down to 0.3 at zero delay, which demonstrates the antibunching of the photons emitted by the circuit at a rate of 6×10^7 photons per second. Results are found in quantitative agreement with our theoretical predictions. This simple scheme could offer an efficient and bright single-photon source in the microwave domain
Analysis of a Chemical Model System Leading to Chiral Symmetry Breaking: Implications for the Evolution of Homochirality
Explaining the evolution of a predominantly homochiral environment on the early Earth remains an outstanding challenge in chemistry. We explore here the mathematical features of a simple chemical model system that simulates chiral symmetry breaking and amplification towards homochirality. The model simulates the reaction of a prochiral molecule to yield enantiomers via interaction with an achiral surface. Kinetically, the reactions and rate constants are chosen so as to treat the two enantiomeric forms symmetrically. The system, however, incorporates a mechanism whereby a random event might trigger chiral symmetry breaking and the formation of a dominant enantiomer; the non-linear dynamics of the chemical system are such that small perturbations may be amplified to near homochirality. Mathematical analysis of the behavior of the chemical system is verified by both deterministic and stochastic numerical simulations. Kinetic description of the model system will facilitate exploration of experimental validation. Our model system also supports the notion that one dominant enantiomeric structure might be a template for other critical molecules
Accelerated Calvarial Healing in Mice Lacking Toll-Like Receptor 4
The bone and immune systems are closely interconnected. The immediate inflammatory response after fracture is known to trigger a healing cascade which plays an important role in bone repair. Toll-like receptor 4 (TLR4) is a member of a highly conserved receptor family and is a critical activator of the innate immune response after tissue injury. TLR4 signaling has been shown to regulate the systemic inflammatory response induced by exposed bone components during long-bone fracture. Here we tested the hypothesis that TLR4 activation affects the healing of calvarial defects. A 1.8 mm diameter calvarial defect was created in wild-type (WT) and TLR4 knockout (TLR4-/-) mice. Bone healing was tested using radiographic, histologic and gene expression analyses. Radiographic and histomorphometric analyses revealed that calvarial healing was accelerated in TLR4-/- mice. More bone was observed in TLR4-/- mice compared to WT mice at postoperative days 7 and 14, although comparable healing was achieved in both groups by day 21. Bone remodeling was detected in both groups on postoperative day 28. In TLR4-/- mice compared to WT mice, gene expression analysis revealed that higher expression levels of IL-1β, IL-6, TNF-α,TGF-β1, TGF-β3, PDGF and RANKL and lower expression level of RANK were detected at earlier time points (≤ postoperative 4 days); while higher expression levels of IL-1β and lower expression levels of VEGF, RANK, RANKL and OPG were detected at late time points (> postoperative 4 days). This study provides evidence of accelerated bone healing in TLR4-/- mice with earlier and higher expression of inflammatory cytokines and with increased osteoclastic activity. Further work is required to determine if this is due to inflammation driven by TLR4 activation. © 2012 Wang et al
Influence of target material impurities on physical results in relativistic heavy-ion collisions
This paper presents the studies on the influence of the target material
impurities on physical observables registered in heavy ion collisions collected
by fixed target experiments. It mainly concerns the measures of multiplicity
fluctuations which can be used to searches for critical point of strongly
interacting matter, e.g. in the {NA61/SHINE} fixed-target experiment at CERN
SPS. The elemental composition of the targets used in the NA61/SHINE experiment
was determined applying wavelength dispersive X-ray fluorescence (WDXRF)
technique. The influence of measured target impurities on multiplicity
distributions and scaled variance was estimated using simulation events. The
modification of the standard analysis was proposed to reduce this influence.Comment: 12 pages, 11 figure
Interference through quantum dots
We discuss the effect of quantum interference on transport through a quantum
dot system. We introduce an indirect coherent coupling parameter alpha, which
provides constructive/destructive interference in the transport current
depending on its phase and the magnetic flux. We estimate the current through
the quantum dot system using the non-equilibrium Green's function method as
well as the master equation method in the sequential tunneling regime. The
visibility of the Aharonov-Bohm oscillation is evaluated. For a large inter-dot
Coulomb interaction, the current is strongly suppressed by the quantum
interference effect, while the current is restored by applying an oscillating
resonance field with the frequency of twice the inter-dot tunneling energy.Comment: 10 pages, 3 figure
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