6,153 research outputs found
Interdot Coulomb repulsion effect on the charge transport of parallel double single electron transistors
The charge transport behaviors of parallel double single electron transistors
(SETs) are investigated by the Anderson model with two impurity levels. The
nonequilibrium Keldysh Green's technique is used to calculate the
current-voltage characteristics of system. For SETs implemented by quantum dots
(QDs) embedded into a thin layer, the interdot Coulomb repulsion is
more important than the interdot electron hopping as a result of high potential
barrier height between QDs and . We found that the interdot Coulomb
repulsion not onlyleads to new resonant levels, but also creates negative
differential conductances.Comment: 12 pages, 7 figure
Solar Neutrinos with Three Flavor Mixings
The recent 71Ga solar neutrino observation is combined with the 37Cl and
Kamiokande-II observations in an analysis for neutrino masses and mixings. The
allowed parameter region is found for matter enhanced mixings among all three
neutrino flavors. Distortions of the solar neutrino spectrum unique to three
flavors are possible and may be observed in continuing and next generation
experiments.Comment: August 1992 (Revised) PURD-TH-92-
Bistability in the Tunnelling Current through a Ring of Coupled Quantum Dots
We study bistability in the electron transport through a ring of N coupled
quantum dots with two orbitals in each dot. One orbital is localized (called b
orbital) and coupling of the b orbitals in any two dots is negligible; the
other is delocalized in the plane of the ring (called d orbital), due to
coupling of the d orbitals in the neighboring dots, as described by a
tight-binding model. The d orbitals thereby form a band with finite width. The
b and d orbitals are connected to the source and drain electrodes with a
voltage bias V, allowing the electron tunnelling. Tunnelling current is
calculated by using a nonequilibrium Green function method recently developed
to treat nanostructures with multiple energy levels. We find a bistable effect
in the tunnelling current as a function of bias V, when the size N>50; this
effect scales with the size N and becomes sizable at N~100. The temperature
effect on bistability is also discussed. In comparison, mean-field treatment
tends to overestimate the bistable effect.Comment: Published in JPSJ; minor typos correcte
Effects of interdot hopping and Coulomb blockade on the thermoelectric properties of serially coupled quantum dots
We have theoretically studied the thermoelectric properties of serially
coupled quantum dots (SCQD) embedded in an insulator matrix connected to
metallic electrodes. In the framework of Keldysh Green's function technique,
the Landauer formula of transmission factor is obtained by using the equation
of motion method. Based on such analytical expressions of charge and heat
currents, we calculate the electrical conductance, Seebeck coefficient,
electron thermal conductance and figure of merit (ZT) of SCQD in the linear
response regime. The effects of electron Coulomb interactions on the reduction
and enhancement of ZT are analyzed. We demonstrate that ZT is not a monotonic
increasing function of interdot electron hopping strength (). We also show
that in the absence of phonon thermal conductance, SCQD can reach the Carnot
efficiency as approaches zero.Comment: corrected some argumenet
Editorial: on the road towards treatment of gastroparesisâaccelerating, but do we get closer? Authors' reply
LINKED CONTENTThis article is linked to Kuo et al and Wuestenberghs & Gourcerol papers. To view these articles, visit https://doi.org/10.1111/apt.16344 and https://doi.org/10.1111/apt.1637
Style-Aware Radiology Report Generation with RadGraph and Few-Shot Prompting
Automatically generated reports from medical images promise to improve the
workflow of radiologists. Existing methods consider an image-to-report modeling
task by directly generating a fully-fledged report from an image. However, this
conflates the content of the report (e.g., findings and their attributes) with
its style (e.g., format and choice of words), which can lead to clinically
inaccurate reports. To address this, we propose a two-step approach for
radiology report generation. First, we extract the content from an image; then,
we verbalize the extracted content into a report that matches the style of a
specific radiologist. For this, we leverage RadGraph -- a graph representation
of reports -- together with large language models (LLMs). In our quantitative
evaluations, we find that our approach leads to beneficial performance. Our
human evaluation with clinical raters highlights that the AI-generated reports
are indistinguishably tailored to the style of individual radiologist despite
leveraging only a few examples as context.Comment: Accepted to Findings of EMNLP 202
Is Large Lepton Mixing Excluded?
The original \bnum -(or -) energy spectrum from the
gravitational collapse of a star has a larger average energy than the spectrum
for \bnue since the opacity of \bnue exeeds that of \bnum (or ).
Flavor neutrino conversion, \bnue \bnum, induced by lepton
mixing results in partial permutation of the original \bnue and \bnum spectra.
An upper bound on the permutation factor, (99 CL) is derived
using the data from SN1987A and the different models of the neutrino burst. The
relation between the permutation factor and the vacuum mixing angle is
established, which leads to the upper bound on this angle. The excluded region,
, covers the regions of large mixing angle
solutions of the solar neutrino problem: ``just-so" and, partly, MSW, as well
as part of region of oscillation space which could be
responsible for the atmospheric muon neutrino deficit. These limits are
sensitive to the predicted neutrino spectrum and can be strengthened as
supernova models improve.Comment: 20 pages, TeX file. For hardcopy with figures contact
[email protected]. Institute for Advanced Study number AST 93/1
Are values at the societal-level acceptable as cross-cultural predictors in today's global economy?
Periodic interstellar scintillation variations of PSRs~J06130200 and J0636+5128 associated with the Local Bubble shell
Annual variations of interstellar scintillation can be modelled to constrain
parameters of the ionized interstellar medium. If a pulsar is in a binary
system, then investigating the orbital parameters is possible through analysis
of the orbital variation of scintillation. In observations carried out from
2011 January to 2020 August by the European Pulsar Timing Array radio
telescopes, PSRs~J06130200 and J0636+5128 show strong annual variations in
their scintillation velocity, while the former additionally exhibits an orbital
fluctuation. Bayesian theory and Markov-chain-Monte-Carlo methods are used to
interpret these periodic variations. We assume a thin and anisotropic
scattering screen model, and discuss the mildly and extremely anisotropic
scattering cases. PSR~J06130200 is best described by mildly anisotropic
scattering, while PSR~J0636+5128 exhibits extremely anisotropic scattering. We
measure the distance, velocity and degree of anisotropy of the scattering
screen for our two pulsars, finding that scattering screen distances from Earth
for PSRs~J06130200 and J0636+5128 are 316\,pc and
262\,pc, respectively. The positions of these scattering screens
are coincident with the shell of the Local Bubble towards both pulsars. These
associations add to the growing evidence of the Local Bubble shell as a
dominant region of scattering along many sightlines.Comment: Accepted by SCIENCE CHINA Physics, Mechanics & Astronomy ( SCPMA
Atlantic circulation and ice sheet influences on upper South Atlantic temperatures during the last deglaciation
Š The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Umling, N. E., Oppo, D. W., Chen, P., Yu, J., Liu, Z., Yan, M., Gebbie, G., Lund, D. C., Pietro, K. R., Jin, Z. D., Huang, K., Costa, K. B., & Toledo, F. A. L. Atlantic circulation and ice sheet influences on upper South Atlantic temperatures during the last deglaciation. Paleoceanography and Paleoclimatology, 34(6), (2019): 990-1005, doi:10.1029/2019PA003558.Atlantic Meridional Overturning Circulation (AMOC) disruption during the last deglaciation is hypothesized to have caused large subsurface ocean temperature anomalies, but records from key regions are not available to test this hypothesis, and other possible drivers of warming have not been fully considered. Here, we present the first reliable evidence for subsurface warming in the South Atlantic during Heinrich Stadial 1, confirming the link between largeâscale heat redistribution and AMOC. Warming extends across the BøllingâAllerød despite predicted cooling at this time, thus spanning intervals of both weak and strong AMOC indicating another forcing mechanism that may have been previously overlooked. Transient model simulations and quasiâconservative water mass tracers suggest that reduced northward upper ocean heat transport was responsible for the early deglacial (Heinrich Stadial 1) accumulation of heat at our shallower (~1,100 m) site. In contrast, the results suggest that warming at our deeper site (~1,900 m) site was dominated by southward advection of North Atlantic middepth heat anomalies. During the BøllingâAllerød, the demise of ice sheets resulted in oceanographic changes in the North Atlantic that reduced convective heat loss to the atmosphere, causing subsurface warming that overwhelmed the cooling expected from an AMOC reinvigoration. The data and simulations suggest that rising atmospheric CO2 did not contribute significantly to deglacial subsurface warming at our sites.We thank H. Abrams, G. Swarr, and J. Watson for technical assistance. This work was funded by the U.S. National Science Foundation grant OCE15â558341, the Investment in Science Fund at the Woods Hole Oceanographic Institution, and an Australian Research Council Future Fellowship (FT140100993). The data are included in the supporting information and are available online (https://www.ncdc.noaa.gov/paleo/study/26530)
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