1,313 research outputs found
Validity of single-channel model for a spin-orbit coupled atomic Fermi gas near Feshbach resonances
We theoretically investigate a Rashba spin-orbit coupled Fermi gas near
Feshbach resonances, by using mean-field theory and a two-channel model that
takes into account explicitly Feshbach molecules in the close channel. In the
absence of spin-orbit coupling, when the channel coupling between the
closed and open channels is strong, it is widely accepted that the two-channel
model is equivalent to a single-channel model that excludes Feshbach molecules.
This is the so-called broad resonance limit, which is well-satisfied by
ultracold atomic Fermi gases of Li atoms and K atoms in current
experiments. Here, with Rashba spin-orbit coupling we find that the condition
for equivalence becomes much more stringent. As a result, the single-channel
model may already be insufficient to describe properly an atomic Fermi gas of
K atoms at a moderate spin-orbit coupling. We determine a characteristic
channel coupling strength as a function of the spin-orbit coupling
strength, above which the single-channel and two-channel models are
approximately equivalent. We also find that for narrow resonance with small
channel coupling, the pairing gap and molecular fraction is strongly suppressed
by SO coupling. Our results can be readily tested in K atoms by using
optical molecular spectroscopy.Comment: 6 pages, 6 figure
Whole-Chain Recommendations
With the recent prevalence of Reinforcement Learning (RL), there have been
tremendous interests in developing RL-based recommender systems. In practical
recommendation sessions, users will sequentially access multiple scenarios,
such as the entrance pages and the item detail pages, and each scenario has its
specific characteristics. However, the majority of existing RL-based
recommender systems focus on optimizing one strategy for all scenarios or
separately optimizing each strategy, which could lead to sub-optimal overall
performance. In this paper, we study the recommendation problem with multiple
(consecutive) scenarios, i.e., whole-chain recommendations. We propose a
multi-agent RL-based approach (DeepChain), which can capture the sequential
correlation among different scenarios and jointly optimize multiple
recommendation strategies. To be specific, all recommender agents (RAs) share
the same memory of users' historical behaviors, and they work collaboratively
to maximize the overall reward of a session. Note that optimizing multiple
recommendation strategies jointly faces two challenges in the existing
model-free RL model - (i) it requires huge amounts of user behavior data, and
(ii) the distribution of reward (users' feedback) are extremely unbalanced. In
this paper, we introduce model-based RL techniques to reduce the training data
requirement and execute more accurate strategy updates. The experimental
results based on a real e-commerce platform demonstrate the effectiveness of
the proposed framework.Comment: 29th ACM International Conference on Information and Knowledge
Managemen
Superfluid density and Berezinskii-Kosterlitz-Thouless transition of a spin-orbit coupled Fulde-Ferrell superfluid
We theoretically investigate the superfluid density and
Berezinskii-Kosterlitz-Thouless (BKT) transition of a two-dimensional Rashba
spin-orbit coupled atomic Fermi gas with both in-plane and out-of-plane Zeeman
fields. It was recently predicted that, by tuning the two Zeeman fields, the
system may exhibit different exotic Fulde-Ferrell (FF) superfluid phases,
including the gapped FF, gapless FF, gapless topological FF and gapped
topological FF states. Due to the FF paring, we show that the superfluid
density (tensor) of the system becomes anisotropic. When an in-plane Zeeman
field is applied along the \textit{x}-direction, the tensor component along the
\textit{y}-direction is generally larger than in most
parameter space. At zero temperature, there is always a discontinuity jump in
as the system evolves from a gapped FF into a gapless FF state. With
increasing temperature, such a jump is gradually washed out. The critical BKT
temperature has been calculated as functions of the spin-orbit coupling
strength, interatomic interaction strength, in-plane and out-of-plane Zeeman
fields. We predict that the novel FF superfluid phases have a significant
critical BKT temperature, typically at the order of , where
is the Fermi degenerate temperature. Therefore, their observation is within the
reach of current experimental techniques in cold-atom laboratories.Comment: 11 pages, 7 figure
Gapless topological Fulde-Ferrell superfluidity in spin-orbit coupled Fermi gases
Topological superfluids usually refer to a superfluid state which is gapped
in the bulk but metallic at the boundary. Here we report that a gapless,
topologically non-trivial superfluid with inhomogeneous Fulde-Ferrell pairing
order parameter can emerge in a two-dimensional spin-orbit coupled Fermi gas,
in the presence of both in-plane and out-of-plane Zeeman fields. The
Fulde-Ferrell pairing - induced by the spin-orbit coupling and in-plane Zeeman
field - is responsible for this gapless feature. This exotic superfluid has a
significant Berezinskii-Kosterlitz-Thouless (BKT) transition temperature and
has robust Majorana edge modes against disorder owing to its topological
nature.Comment: 5 pages, 5 figures; add the results on the critical BKT temperature
and superfluid density, as well as the discussion on the robustness of the
chiral edge states against disorde
Progress in application of peritoneal lavage fluid circulating tumor DNA to predicting peritoneal metastasis of gastrointestinal cancer
Peritoneal metastasis is one of the important causes of death in patients with gastrointestinal cancer and is also a difficult point in clinical diagnosis and treatment. How to predict the occurrence of peritoneal metastasis in patients with high-risk factors, advance the threshold of diagnosis and treatment before the occurrence of peritoneal metastasis, and improve the survival benefit of patients is an unsolved problem in clinical work. In the case of low positive rate of cytology and difficulty in diagnosing occult peritoneal metastasis, new molecular markers and detection techniques for early diagnosis of peritoneal metastasis need to be verified. Peritoneal lavage fluid has the characteristics of less leukocyte-derived cell-free DNA interference, higher concentration of circulating tumor DNA (ctDNA), and direct contact with the primary lesion or potential peritoneal metastasis at physical distance, making it a unique advantage in gastrointestinal cancer. At present, the detection methods of ctDNA in peritoneal lavage fluid include digital PCR, epigenetic-based analysis, and next-generation sequencing. With the iteration of technology, the application of next-generation sequencing and personalized panels to ctDNA detection has not only shown great potential in predicting postoperative peritoneal metastasis, but also promoted the idea of preventive escalation treatment of peritoneal metastasis. This article reviews the current application of ctDNA to peritoneal lavage fluid in predicting peritoneal metastasis of gastrointestinal cancer
Microstructure refinement by tool rotation-induced vibration in incremental sheet forming
This paper presents a study of employing tool rotation-induced vibrations in incremental sheet forming (V-ISF) to produce sheet metal parts with laminated ultrafine-grained structures. Non-axisymmetric tools were developed to generate tool vibration and surface shear deformation of sheet material during forming. Using the V-ISF process, magnesium sheets of AZ31 were formed to the hyperbolic cones and laminated ultrafine grains with higher micro hardness were obtained by tool generated low frequency vibrations with large amplitudes. To further investigate surface shear deformation induced during processing, the hole-deformation analysis of samples cut from the formed hyperbolic cones was performed. This study found that large surface shear deformation of the sheet and the tool vibration during incremental forming are the two key factors for the formation of laminated ultrafine grains. The developed V-ISF process has a great potential to produce sheet metal parts with refined grains and greater micro hardness
Adenosine A2A Receptors Mediate Anti-Inflammatory Effects of Electroacupuncture on Synovitis in Mice with Collagen-Induced Arthritis
To study the role of adenosine A2A receptor (A2AR) in mediating the anti-inflammatory effect of electroacupuncture (EA) on synovitis in collagen-induced arthritis (CIA), C57BL/6 mice were divided into five treatment groups: Sham-control, CIA-control, CIA-EA, CIA-SCH58261 (A2AR antagonist), and CIA-EA-SCH58261. All mice except those in the Sham-control group were immunized with collagen II for arthritis induction. EA treatment was administered using the stomach 36 and spleen 6 points, and stimulated with a continuous rectangular wave for 30 min daily. EA treatment and SCH58261 were administered daily from days 35 to 49 (n=10). After treatment, X-ray radiography of joint bone morphology was established at day 60 and mouse blood was collected for ELISA determination of tumor necrosis factor alpha (TNF-α) levels. Mice were sacrificed and processed for histological examination of pathological changes of joint tissue, including hematoxylin-eosin staining and immunohistochemistry of A2AR expression. EA treatment resulted in significantly reduced pathological scores, TNF-α concentrations, and bone damage X-ray scores. Importantly, the anti-inflammatory and tissue-protective effect of EA treatment was reversed by coadministration of SCH58261. Thus, EA treatment exerts an anti-inflammatory effect resulting in significant protection of cartilage by activation of A2AR in the synovial tissue of CIA
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