1,321 research outputs found
Alleviating the Long-Tail Problem in Conversational Recommender Systems
Conversational recommender systems (CRS) aim to provide the recommendation
service via natural language conversations. To develop an effective CRS,
high-quality CRS datasets are very crucial. However, existing CRS datasets
suffer from the long-tail issue, \ie a large proportion of items are rarely (or
even never) mentioned in the conversations, which are called long-tail items.
As a result, the CRSs trained on these datasets tend to recommend frequent
items, and the diversity of the recommended items would be largely reduced,
making users easier to get bored.
To address this issue, this paper presents \textbf{LOT-CRS}, a novel
framework that focuses on simulating and utilizing a balanced CRS dataset (\ie
covering all the items evenly) for improving \textbf{LO}ng-\textbf{T}ail
recommendation performance of CRSs. In our approach, we design two pre-training
tasks to enhance the understanding of simulated conversation for long-tail
items, and adopt retrieval-augmented fine-tuning with label smoothness strategy
to further improve the recommendation of long-tail items. Extensive experiments
on two public CRS datasets have demonstrated the effectiveness and
extensibility of our approach, especially on long-tail recommendation.Comment: work in progres
Improving Conversational Recommendation Systems via Counterfactual Data Simulation
Conversational recommender systems (CRSs) aim to provide recommendation
services via natural language conversations. Although a number of approaches
have been proposed for developing capable CRSs, they typically rely on
sufficient training data for training. Since it is difficult to annotate
recommendation-oriented dialogue datasets, existing CRS approaches often suffer
from the issue of insufficient training due to the scarcity of training data.
To address this issue, in this paper, we propose a CounterFactual data
simulation approach for CRS, named CFCRS, to alleviate the issue of data
scarcity in CRSs. Our approach is developed based on the framework of
counterfactual data augmentation, which gradually incorporates the rewriting to
the user preference from a real dialogue without interfering with the entire
conversation flow. To develop our approach, we characterize user preference and
organize the conversation flow by the entities involved in the dialogue, and
design a multi-stage recommendation dialogue simulator based on a conversation
flow language model. Under the guidance of the learned user preference and
dialogue schema, the flow language model can produce reasonable, coherent
conversation flows, which can be further realized into complete dialogues.
Based on the simulator, we perform the intervention at the representations of
the interacted entities of target users, and design an adversarial training
method with a curriculum schedule that can gradually optimize the data
augmentation strategy. Extensive experiments show that our approach can
consistently boost the performance of several competitive CRSs, and outperform
other data augmentation methods, especially when the training data is limited.
Our code is publicly available at https://github.com/RUCAIBox/CFCRS.Comment: Accepted by KDD 2023. Code: https://github.com/RUCAIBox/CFCR
Assessment of mitochondrial dysfunction and implications in cardiovascular disorders
Mitochondria play a pivotal role in cellular function, not only acting as the powerhouse of the cell, but also regulating ATP synthesis, reactive oxygen species (ROS) production, intracellular Ca2+ cycling, and apoptosis. During the past decade, extensive progress has been made in the technology to assess mitochondrial functions and accumulating evidences have shown that mitochondrial dysfunction is a key pathophysiological mechanism for many diseases including cardiovascular disorders, such as ischemic heart disease, cardiomyopathy, hypertension, atherosclerosis, and hemorrhagic shock. The advances in methodology have been accelerating our understanding of mitochondrial molecular structure and function, biogenesis and ROS and energy production, which facilitates new drug target identification and therapeutic strategy development for mitochondrial dysfunction-related disorders. This review will focus on the assessment of methodologies currently used for mitochondrial research and discuss their advantages, limitations and the implications of mitochondrial dysfunction in cardiovascular disorders
6-Amino-3-methyl-4-(4-nitrophenyl)-1-phenylpyrazolo[3,4-b]pyridine-5-carbonitrile
The title compound, C20H14N6O2, contains four rings. The dihedral angle between the pyridine ring and the pyrazole ring is 1.9 (1)°, i.e. almost coplanar, which gives rise to a conjugated structure. The dihedral angle between the nitro-substituted phenyl ring and the pyridine ring is 76.3 (1)° and that between the pyrazole ring and the non-substituted phenyl ring is 40.5 (1)°. In the crystal structure, symmetry-related molecules are linked by N—H⋯O and C—H⋯N hydrogen bonds
Tanshinone IIA Inhibits Growth of Keratinocytes through Cell Cycle Arrest and Apoptosis: Underlying Treatment Mechanism of Psoriasis
The aim of the present investigation was to elucidate the cellular mechanisms whereby Tanshinone IIA (Tan IIA) leads to cell cycle arrest and apoptosis in vitro in keratinocytes, the target cells in psoriasis. Tan IIA inhibited proliferation of mouse keratinocytes in a dose- and time-dependent manner and induced apoptosis, resulting in S phase arrest accompanied by down-regulation of pCdk2 and cyclin A protein expression. Furthermore, Tan IIA-induced apoptosis and mitochondrial membrane potential changes were also further demonstrated by DNA fragmentation, single-cell gel electrophoresis assay (SCGE), and flow cytometry methods. Apoptosis was partially blocked by the caspase-3 inhibitor Ac-DEVD-CHO. Mitochondrial regulation of apoptosis further downstream was investigated, showing changes in the mitochondrial membrane potential, cytochrome c release into the cytoplasm, and enhanced activation of cleaved caspase-3 and Poly ADP-ribose polymerase (PARP). There was also no translocation of apoptosis-inducing factor (AIF) from mitochondria to the nucleus in apoptotic keratinocytes, indicating Tan IIA-induced apoptosis occurs mainly through the caspase pathway. Our findings provide the molecular mechanisms by which Tan IIA can be used to treat psoriasis and support the traditional use of Salvia miltiorrhiza Bungee (Labiatae) for psoriasis and related skin diseases
Astragaloside IV Downregulates β-Catenin in Rat Keratinocytes to Counter LiCl-Induced Inhibition of Proliferation and Migration
Re-epithelialization is a crucial step towards wound healing. The traditional Chinese medicine, Astragalus membranaceus (Fisch) Bge, has been used for hundreds of years for many kinds of ulcerated wounds. Recent research has identified the active compound in this drug as astragaloside IV (AS-IV), but the underlying molecular mechanisms of its therapeutic action on keratinocytes remain poorly understood. In this study, we used an in vitro model of ulcer-like wound processes, lithium chloride (LiCl)-induced cultured mouse keratinocytes, to investigate the effects of AS-IV treatment. The effects on cell proliferation were evaluated by the MTS/PMS colorimetric assay, effects on cell migration were determined by a wound-healing scratch experiment, effects on the cell cycle were analyzed by flow cytometry, and effects on protein expression were analyzed by immunoblotting and immunofluorescence. LiCl strongly inhibited cell proliferation and migration, up-regulated β-catenin expression, and down-regulated proliferating cell nuclear antigen (PCNA) expression. AS-IV treatment attenuat the inhibition of proliferation and migration, significantly reducing the enhanced β-catenin expression, and recovering PCNA and β-tubulin expression. Thus, AS-IV mediates mouse keratinocyte proliferation and migration via regulation of the Wnt signaling pathway. Down-regulating β-catenin to increase keratinocyte migration and proliferation is one mechanism by which AS-IV can promote ulcerated wound healing
Symmetry and -Enhanced Quantum Sensing in a Spin-Boson System
Open systems, governed by non-Hermitian Hamiltonians, evolve fundamentally
differently from their Hermitian counterparts and facilitate many unusual
applications. Although non-Hermitian but parity-time () symmetric
dynamics has been realized in a variety of classical or semiclassical systems,
its fully quantum-mechanical demonstration is still lacking. Here we
ingeniously engineer a highly controllable anti-Hermitian spin-boson model in a
circuit quantum-electrodynamical structure composed of a decaying artificial
atom (pseudospin) interacting with a bosonic mode stored in a microwave
resonator. Besides observing abrupt changes in the spin-boson entanglement
evolution and bifurcation transition in quantum Rabi splitting, we demonstrate
super-sensitive quantum sensing by mapping the observable of interest to a
hitherto unobserved -manifested entanglement evolution. These
results pave the way for exploring non-Hermitian entanglement dynamics and
-enhanced quantum sensing empowered by nonclassical correlations.Comment: 25 pages, 19 figure
Measuring topological invariants for higher-order exceptional points in quantum multipartite systems
Owing to the presence of exceptional points (EPs), non-Hermitian (NH) systems
can display intriguing topological phenomena without Hermitian analogs.
However, experimental characteristics of exceptional topological invariants
have been restricted to second-order EPs (EP2s) in classical or semiclassical
systems. We here propose an NH multi-qubit model with higher-order EPs, each of
which is underlain by a multifold-degenerate multipartite entangled eigenstate.
We implement the three-qubit model by controllably coupling a superconducting
qubit to two microwave resonators, one serving as a Hermitian photonic qubit
while the other as an NH qubit. We experimentally quantify the topological
invariant for an EP3, by mapping out the complex eigenspectra along a loop
surrounding this EP3 in the parameter space. The nonclassicality of the
realized topology is manifested by the observed quantum correlations in the
corresponding eigenstates. Our results extend research of exceptional topology
to fully quantum-mechanical models with multi-partite entangled eigenstates. We
further demonstrate the non-reciprocal transmission of a single photon, during
which the photon is nonlocally shared by three individual elements
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