425 research outputs found
Simulation method of urban evacuation based on mesoscopic cellular automata
This study integrates pedestrian flow characteristics to formulate a
mesoscopic cellular automata model tailored for simulating evacuations in
large-scale scenarios. Departing from the conventional planar grid cell
division, the model employs road cell segmentation, thereby physically
enlarging the dimensions of individual cells. This augmentation accommodates an
increased occupancy of individuals per cell, representing pedestrian flow
parameters within each cell through state variables. The source loading cell
facilitates the simulation of pedestrian behavior transitioning from buildings
to roads during an actual evacuation event, while the unloading cell situated
at the exit removes evacuees from the system. The continuity equation for state
transitions comprehensively encapsulates the dynamics of pedestrians throughout
the evacuation process. Potential challenges in actual evacuation processes are
identified through the simulation, offering valuable insights for improvement.
This research aims to contribute to a more effective and informed approach to
evacuation planning and management.Comment: 13 pages, 14figure
Exploring crowd persistent dynamism from pedestrian crossing perspective: An empirical study
Crowd studies have gained increasing relevance due to the recurring incidents
of crowd crush accidents. In addressing the issue of the crowd's persistent
dynamism, this paper explored the macroscopic and microscopic features of
pedestrians crossing in static and dynamic contexts, employing a series of
systematic experiments. Firstly, empirical evidence has confirmed the existence
of crowd's persistent dynamism. Subsequently, the research delves into two
aspects, qualitative and quantitative, to address the following questions:(1)
Cross pedestrians tend to avoid high-density areas when crossing static crowds
and particularly evade pedestrians in front to avoid deceleration, thus
inducing the formation of cross-channels, a self-organization phenomenon.(2) In
dynamic crowds, when pedestrian suffers spatial constrained, two patterns
emerge: decelerate or detour. Research results indicate the differences in
pedestrian crossing behaviors between static and dynamic crowds, such as the
formation of crossing channels, backward detours, and spiral turning. However,
the strategy of pedestrian crossing remains consistent: utilizing detours to
overcome spatial constraints. Finally, the empirical results of this study
address the final question: pedestrians detouring causes crowds' persistent
collective dynamism. These findings contribute to an enhanced understanding of
pedestrian dynamics in extreme conditions and provide empirical support for
research on individual movement patterns and crowd behavior prediction.Comment: 31pages, 17figure
Clustering Analysis of User Loyalty Based on K-means
In recent years, the rise of machine learning has made it possible to further explore large data in various fields. In order to explore the attributes of loyalty of public transport travelers and divide these people into different clustering clusters, this paper uses K-means clustering algorithm (K-means) to cluster the holding time, recharge amount and swiping frequency of bus travelers. Then we use Kernel Density Estimation Algorithms (KDE) to analyze the density distribution of the data of holding time, recharge amount and swipe frequency, and display the results of the two algorithms in the way of data visualization. Finally, according to the results of data visualization, the loyalty of users is classified, which provides theoretical and data support for public transport companies to determine the development potential of users
Multi-View Vertebra Localization and Identification from CT Images
Accurately localizing and identifying vertebrae from CT images is crucial for
various clinical applications. However, most existing efforts are performed on
3D with cropping patch operation, suffering from the large computation costs
and limited global information. In this paper, we propose a multi-view vertebra
localization and identification from CT images, converting the 3D problem into
a 2D localization and identification task on different views. Without the
limitation of the 3D cropped patch, our method can learn the multi-view global
information naturally. Moreover, to better capture the anatomical structure
information from different view perspectives, a multi-view contrastive learning
strategy is developed to pre-train the backbone. Additionally, we further
propose a Sequence Loss to maintain the sequential structure embedded along the
vertebrae. Evaluation results demonstrate that, with only two 2D networks, our
method can localize and identify vertebrae in CT images accurately, and
outperforms the state-of-the-art methods consistently. Our code is available at
https://github.com/ShanghaiTech-IMPACT/Multi-View-Vertebra-Localization-and-Identification-from-CT-Images.Comment: MICCAI 202
Exosomes from embryonic mesenchymal stem cells alleviate osteoarthritis through balancing synthesis and degradation of cartilage extracellular matrix
Abstract
Background
Mesenchymal stem cell therapy for osteoarthritis (OA) has been widely investigated, but the mechanisms are still unclear. Exosomes that serve as carriers of genetic information have been implicated in many diseases and are known to participate in many physiological processes. Here, we investigate the therapeutic potential of exosomes from human embryonic stem cell-induced mesenchymal stem cells (ESC-MSCs) in alleviating osteoarthritis (OA).
Methods
Exosomes were harvested from conditioned culture media of ESC-MSCs by a sequential centrifugation process. Primary mouse chondrocytes treated with interleukin 1 beta (IL-1β) were used as an in vitro model to evaluate the effects of the conditioned medium with or without exosomes and titrated doses of isolated exosomes for 48 hours, prior to immunocytochemistry or western blot analysis. Destabilization of the medial meniscus (DMM) surgery was performed on the knee joints of C57BL/6 J mice as an OA model. This was followed by intra-articular injection of either ESC-MSCs or their exosomes. Cartilage destruction and matrix degradation were evaluated with histological staining and OARSI scores at the post-surgery 8 weeks.
Results
We found that intra-articular injection of ESC-MSCs alleviated cartilage destruction and matrix degradation in the DMM model. Further in vitro studies illustrated that this effect was exerted through ESC-MSC-derived exosomes. These exosomes maintained the chondrocyte phenotype by increasing collagen type II synthesis and decreasing ADAMTS5 expression in the presence of IL-1β. Immunocytochemistry revealed colocalization of the exosomes and collagen type II-positive chondrocytes. Subsequent intra-articular injection of exosomes derived from ESC-MSCs successfully impeded cartilage destruction in the DMM model.
Conclusions
The exosomes from ESC-MSCs exert a beneficial therapeutic effect on OA by balancing the synthesis and degradation of chondrocyte extracellular matrix (ECM), which in turn provides a new target for OA drug and drug-delivery system development
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