379 research outputs found
Effect of mesenchymal stem cell-incorporated hydroxyapatite-collagen scaffold on tissue repair in acute spinal cord injury, and the mechanism involved
Purpose: To study the effect of hydroxyapatite-collagen (HC) scaffold with mesenchymal stem cells (MSCs) on tissue repair in acute spinal cord injury (SCI).Method: Adult female Sprague-Dawley rats weighing 200 - 230 g were randomly divided into two groups implanted either with bone marrow-MSCs (experimental group) or HC scaffold alone (control group). Spinal cord injury was induced using laminectomy, resulting in a 2.0-mm gap at T10 of the spinal cord. The gap was filled in both groups with 2-mm HC scaffold at day 10 of culture. Cellular development, viability, and proliferation inside the scaffold were determined. Angiogenesis was determined by measuring fibronectin (FN) immunofluorescence, von Willebrand factor (vWF), hypoxiainducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF).Results: HC scaffold strengthened MSCs. Bone marrow MSCs exhibited no statistically significant difference when compared with cells in culture at day 10 (47.03 ± 3.135 %, p > 0.05). Moreover, on days 5 and 10, FN deposition was higher in MSCs with scaffold than in scaffold-free MSCs. The expressions of FN, vWF, HIF-1α and VEGF were positively correlated, indicating that incorporation of HC scaffold into MSCs significantly improved tissue repair by improving angiogenesis via a differentiation process (p < 0.001).Conclusion: These findings suggest that HC scaffold with MSCs is a potential therapeutic procedure for spinal cord injury.
Keywords: Mesenchymal stem cells, Hydroxyapatite-collagen, Spinal cord injury, HC scaffol
Fidelity of a Bose-Einstein Condensate
We investigate fidelity, the Loschmidt echo, for a Bose-Einstein Condensate.
It is found that the fidelity decays with time in various ways (exponential,
Gaussian, and power-law), depending on the choice of initial coherent state as
well as the parameters that determine properties of the underlying classical
dynamics. Moreover, high fidelity is found for initial states lying in the
regular region of a mixed-type phase space. A possible experimental scheme is
suggested.Comment: 5 pages and 6 figure
MedDG: An Entity-Centric Medical Consultation Dataset for Entity-Aware Medical Dialogue Generation
Developing conversational agents to interact with patients and provide
primary clinical advice has attracted increasing attention due to its huge
application potential, especially in the time of COVID-19 Pandemic. However,
the training of end-to-end neural-based medical dialogue system is restricted
by an insufficient quantity of medical dialogue corpus. In this work, we make
the first attempt to build and release a large-scale high-quality Medical
Dialogue dataset related to 12 types of common Gastrointestinal diseases named
MedDG, with more than 17K conversations collected from the online health
consultation community. Five different categories of entities, including
diseases, symptoms, attributes, tests, and medicines, are annotated in each
conversation of MedDG as additional labels. To push forward the future research
on building expert-sensitive medical dialogue system, we proposes two kinds of
medical dialogue tasks based on MedDG dataset. One is the next entity
prediction and the other is the doctor response generation. To acquire a clear
comprehension on these two medical dialogue tasks, we implement several
state-of-the-art benchmarks, as well as design two dialogue models with a
further consideration on the predicted entities. Experimental results show that
the pre-train language models and other baselines struggle on both tasks with
poor performance in our dataset, and the response quality can be enhanced with
the help of auxiliary entity information. From human evaluation, the simple
retrieval model outperforms several state-of-the-art generative models,
indicating that there still remains a large room for improvement on generating
medically meaningful responses.Comment: Data and code are available at https://github.com/lwgkzl/MedD
Identifying the orbital angular momentum of light based on atomic ensembles
We propose a scheme to distinguish the orbital angular momentum state of the
Laguerre-Gaussian (LG) beam based on the electromagnetically induced
transparency modulated by a microwave field in atomic ensembles. We show that
the transverse phase variation of a probe beam with the LG mode can be mapped
into the spatial intensity distribution due to the change of atomic coherence
caused by the microwave. The proposal may provide a useful tool for studying
higher-dimensional quantum information based on atomic ensembles.Comment: 4 pages, 4 figure
Magnetic properties of Er-doped ZnO films prepared by reactive magnetron sputtering
All Zn1−x
Er
x
O (x=0.04, 0.05, and 0.17) films deposited on glass substrates by radio-frequency reactive magnetron sputtering exhibit the mixture of ferromagnetic and paramagnetic phases at room temperature. The estimated magnetic moment per Er ion decreases with the increase of Er concentration. The temperature dependence of the magnetization indicates that there is no intermetallic ErZn buried in the films. The ferromagnetism is attributed to the Er ions substitution for Zn2+ in ZnO lattices, and it can be interpreted by the bound-magnetic-polaron model
Improving Multi-turn Emotional Support Dialogue Generation with Lookahead Strategy Planning
Providing Emotional Support (ES) to soothe people in emotional distress is an
essential capability in social interactions. Most existing researches on
building ES conversation systems only considered single-turn interactions with
users, which was over-simplified. In comparison, multi-turn ES conversation
systems can provide ES more effectively, but face several new technical
challenges, including: (1) how to adopt appropriate support strategies to
achieve the long-term dialogue goal of comforting the user's emotion; (2) how
to dynamically model the user's state. In this paper, we propose a novel system
MultiESC to address these issues. For strategy planning, drawing inspiration
from the A* search algorithm, we propose lookahead heuristics to estimate the
future user feedback after using particular strategies, which helps to select
strategies that can lead to the best long-term effects. For user state
modeling, MultiESC focuses on capturing users' subtle emotional expressions and
understanding their emotion causes. Extensive experiments show that MultiESC
significantly outperforms competitive baselines in both dialogue generation and
strategy planning. Our codes are available at
https://github.com/lwgkzl/MultiESC.Comment: Accepted by the main conference of EMNLP 202
Manipulating droplet jumping behaviors on hot substrates with surface topography by controlling vapor bubble growth: from vibration to explosion
A major challenge in surface science is rapid removal of sessile liquid
droplets from a substrate with complex three-dimensional structures. However,
our understanding of interfacial phenomena including droplet wetting dynamics
and phase changes on engineered surfaces remains elusive, impeding dexterous
designs for agile droplet purging. Here we present a surface topography
strategy to modulate droplet jumping behaviors on micropillared substrates at
moderate superheat of 20-30 {\deg}C. Specifically, sessile droplets usually
dwell in the Wenzel state and therefore the micropillar matrix functions as fin
array for heat transfer enhancement. By tuning the feature sizes of
micropillars, one can adjust the vapor bubble growth at the droplet base from
the heat-transfer-controlled mode to the inertia-controlled mode. As opposed to
the relatively slow vibration jumping in seconds, the vapor bubble growth in
the inertia-controlled mode on tall-micropillared surface leads to droplet
out-of-plane jumping in milliseconds. Such rapid droplet detachment stems from
the swift Wenzel-to Cassie transition incurred by vapor bubble burst
(explosion), during which the bubble expanding velocity can reach as fast as ~4
m/s. Vapor bubble growth in a droplet and bubble-burst-induced droplet jumping
have been less explored. This study unveils the underpinning mechanisms of
versatile jumping behaviors of boiling droplets from a hot micro-structured
surface and opens up further possibilities for the design of engineered
surfaces that mitigate potential damage of vapor explosion or alleviate
condensate flooding
Experimental and theoretical analysis of microstructural evolution and deformation behaviors of CuW composites during equal channel angular pressing
CuW composites were synthesized using an equal channel angular pressing (ECAP) technique. Microstructural evolution during sintering process was investigated using both optical microscopy and transmission electron microscopy (TEM), and their deformation mechanisms were studied using finite element analysis (FEA). Results showed severe plastic deformation of the CuW composites and effective refinement of W grains after the ECAP process. TEM observation revealed that the ECAP process resulted in lamellar bands with high densities dislocations inside the composites. Effects of extrusion temperature and extrusion angles on stress-strain relationship and sizes of deformation zones after the ECAP process were investigated both theoretically and experimentally. When the extrusion angle was 90°, a maximum equivalent stress of ~1001 MPa was obtained when the extrusion test was done at room temperature of 22 °C, and this value was lower than compression strength of the CuW composites (1105.43 MPa). The maximum equivalent strains were varied between 0.5 and 0.7. However, when the extrusion temperature was increased to 550 °C and further to 900 °C, the maximum equivalent stresses were decreased sharply, with readings of 311 MPa and 68 MPa, respectively. When the extrusion angle was increased to 135°, the maximum equivalent stresses were found to be 716.9 MPa, 208 MPa, and 32 MPa for the samples extruded at temperatures of 22 °C, 550 °C and 900 °C, respectively. Simultaneously, the maximum equivalent strains were decreased to 0.2–0.4. Furthermore, results showed that the maximum equivalent stress was located on the sample's external surface and the stress values were gradually decreased from the surface to the center of samples, and the magnitudes of plastic deformation zones at the surface were much larger than those at the central part of the sintered samples. FEA simulation results were in good agreements with experimentally measured ones
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