283 research outputs found
Distributed sampled-data control of nonholonomic multi-robot systems with proximity networks
This paper considers the distributed sampled-data control problem of a group
of mobile robots connected via distance-induced proximity networks. A dwell
time is assumed in order to avoid chattering in the neighbor relations that may
be caused by abrupt changes of positions when updating information from
neighbors. Distributed sampled-data control laws are designed based on nearest
neighbour rules, which in conjunction with continuous-time dynamics results in
hybrid closed-loop systems. For uniformly and independently initial states, a
sufficient condition is provided to guarantee synchronization for the system
without leaders. In order to steer all robots to move with the desired
orientation and speed, we then introduce a number of leaders into the system,
and quantitatively establish the proportion of leaders needed to track either
constant or time-varying signals. All these conditions depend only on the
neighborhood radius, the maximum initial moving speed and the dwell time,
without assuming a prior properties of the neighbor graphs as are used in most
of the existing literature.Comment: 15 pages, 3 figure
Subgraph Networks Based Contrastive Learning
Graph contrastive learning (GCL), as a self-supervised learning method, can
solve the problem of annotated data scarcity. It mines explicit features in
unannotated graphs to generate favorable graph representations for downstream
tasks. Most existing GCL methods focus on the design of graph augmentation
strategies and mutual information estimation operations. Graph augmentation
produces augmented views by graph perturbations. These views preserve a locally
similar structure and exploit explicit features. However, these methods have
not considered the interaction existing in subgraphs. To explore the impact of
substructure interactions on graph representations, we propose a novel
framework called subgraph network-based contrastive learning (SGNCL). SGNCL
applies a subgraph network generation strategy to produce augmented views. This
strategy converts the original graph into an Edge-to-Node mapping network with
both topological and attribute features. The single-shot augmented view is a
first-order subgraph network that mines the interaction between nodes,
node-edge, and edges. In addition, we also investigate the impact of the
second-order subgraph augmentation on mining graph structure interactions, and
further, propose a contrastive objective that fuses the first-order and
second-order subgraph information. We compare SGNCL with classical and
state-of-the-art graph contrastive learning methods on multiple benchmark
datasets of different domains. Extensive experiments show that SGNCL achieves
competitive or better performance (top three) on all datasets in unsupervised
learning settings. Furthermore, SGNCL achieves the best average gain of 6.9\%
in transfer learning compared to the best method. Finally, experiments also
demonstrate that mining substructure interactions have positive implications
for graph contrastive learning.Comment: 12 pages, 6 figure
Adenovirus-mediated delivery of bFGF small interfering RNA reduces STAT3 phosphorylation and induces the depolarization of mitochondria and apoptosis in glioma cells U251
Glioblastoma multiforme (GBM) carries a dismal prognosis primarily due to its aggressive proliferation in the brain regulated by complex molecular mechanisms. One promising molecular target in GBM is over-expressed basic fibroblast growth factor (bFGF), which has been correlated with growth, progression, and vascularity of human malignant gliomas. Previously, we reported significant antitumor effects of an adenovirus-vector carrying bFGF small interfering RNA (Ad-bFGF-siRNA) in glioma in vivo and in vitro. However, its mechanisms are unknown. Signal transducer and activator of transcription 3 (STAT3) is constitutively active in GBM and correlates positively with the glioma grades. In addition, as a specific transcription factor, STAT3 serves as the convergent point of various signaling pathways activated by multiple growth factors and/or cytokines. Therefore, we hypothesized that the proliferation inhibition and apoptosis induction by Ad-bFGF-siRNA may result from the interruption of STAT3 phosphorylation. In the current study, we found that in glioma cells U251, Ad-bFGF-siRNA impedes the activation of ERK1/2 and JAK2, but not Src, decreases IL-6 secretion, reduces STAT3 phosphorylation, decreases the levels of downstream molecules CyclinD1 and Bcl-xl, and ultimately results in the collapse of mitochondrial membrane potentials as well as the induction of mitochondrial-related apoptosis. Our results offer a potential mechanism for using Ad-bFGF-siRNA as a gene therapy for glioma. To our knowledge, it is the first time that the bFGF knockdown using adenovirus-mediated delivery of bFGF siRNA and its potential underlying mechanisms are reported. Therefore, this finding may open new avenues for developing novel treatments against GBM
- …