6,363 research outputs found
Automotive Object Detection via Learning Sparse Events by Temporal Dynamics of Spiking Neurons
Event-based sensors, with their high temporal resolution (1us) and dynamical
range (120dB), have the potential to be deployed in high-speed platforms such
as vehicles and drones. However, the highly sparse and fluctuating nature of
events poses challenges for conventional object detection techniques based on
Artificial Neural Networks (ANNs). In contrast, Spiking Neural Networks (SNNs)
are well-suited for representing event-based data due to their inherent
temporal dynamics. In particular, we demonstrate that the membrane potential
dynamics can modulate network activity upon fluctuating events and strengthen
features of sparse input. In addition, the spike-triggered adaptive threshold
can stabilize training which further improves network performance. Based on
this, we develop an efficient spiking feature pyramid network for event-based
object detection. Our proposed SNN outperforms previous SNNs and sophisticated
ANNs with attention mechanisms, achieving a mean average precision (map50) of
47.7% on the Gen1 benchmark dataset. This result significantly surpasses the
previous best SNN by 9.7% and demonstrates the potential of SNNs for
event-based vision. Our model has a concise architecture while maintaining high
accuracy and much lower computation cost as a result of sparse computation. Our
code will be publicly available
Optical and Gamma-Ray Variability Behaviors of 3C 454.3 from 2006 to 2011
We present our photometric monitoring of a flat spectrum radio quasar (FSRQ)
3C 454.3 at Yunnan observatories from 2006 to 2011. We find that the optical
color of 3C 454.3 shows obvious redder-when-brighter trend, which reaches a
saturation stage when the source is brighter than 15.15 mag at V band. We
perform a simulation with multiple values of disk luminosity and spectral index
to reproduce the magnitude-color diagram. The results show that the
contamination caused by the disk radiation alone is difficult to produce the
observed color variability. The variability properties during the outburst in
December 2009 are also compared with -ray data derived from Fermi
-ray space telescope. The flux variation of these two bands follow a
linear relation with , which provides an
observational evidence for external Compton process in 3C 454.3. Meanwhile,
this flux correlation indicates that electron injection is the main mechanism
for variability origin. We also explore the variation of the flux ratio
and the detailed structures in the lightcurves, and discuss
some possible origins for the detailed variability behaviors.Comment: accepted for publication in The Astrophysical Journal, 5 figures, 2
table
The decay rate of to in SM and beyond
With rapid growth of the database of the BES III and the proposed super
flavor factory, measurement on the rare decays may be feasible,
especially the weak decays into baryon final states. In this work we study the
decay rate of to in the SM and
physics beyond the SM (here we use the unparticle model as an example). The QPC
model is employed to describe the creation of a pair of from vacuum.
We find that the rate of is
at order of in the SM, whereas the contribution of the unparticle is
too small to be substantial. Therefore if a large branching ratio is observed,
it must be due to new physics beyond SM, but by no means the unparticle.Comment: 9 pages, 1 figure
Recommended from our members
In Situ TEM Study of the Degradation of PbSe Nanocrystals in Air
PbSe
nanocrystals have attracted widespread attention due to a
variety of potential applications. However, the practical utility
of these nanocrystals has been hindered by their poor air stability,
which induces undesired changes in the optical and electronic properties.
An understanding of the degradation of PbSe nanocrystals when they
are exposed to air is critical for improving the stability and enhancing
their applications. Here, we use in situ transmission electron microscopy
(TEM) with an environmental cell connected to air to study PbSe nanocrystal
degradation triggered by air exposure. We have also conducted a series
of complementary studies, including in situ environmental TEM study
of PbSe nanocrystals exposed to pure oxygen and PbSe nanocrystals
in H2O using a liquid cell, and ex situ experiments, such
as O2 plasma treatment and thermal heating of PbSe nanocrystals
under different air exposure. Our in situ observations reveal that
when PbSe nanocrystals are exposed to air (or oxygen) under electron
beam irradiation, they experience a series of changes, including shape
evolution of individual nanocrystals with the cuboid intermediates,
coalescence between nanocrystals, and formation of PbSe thin films
through drastic solid-state fusion. Further studies show that the
PbSe thin films transform into an amorphous Pb rich phase or eventually
pure Pb, which suggest that Se reacts with oxygen and can be evaporated
under electron beam illumination. These various in situ and ex situ
experimental results indicate that PbSe nanocrystal degradation in
air is initiated by the dissociation and removal of ligands from the
PbSe nanocrystal surface
Dysfunction of cortical GABAergic neurons leads to sensory hyper-reactivity in a Shank3 mouse model of ASD.
Hyper-reactivity to sensory input is a common and debilitating symptom in individuals with autism spectrum disorders (ASD), but the neural basis underlying sensory abnormality is not completely understood. Here we examined the neural representations of sensory perception in the neocortex of a Shank3B-/- mouse model of ASD. Male and female Shank3B-/- mice were more sensitive to relatively weak tactile stimulation in a vibrissa motion detection task. In vivo population calcium imaging in vibrissa primary somatosensory cortex (vS1) revealed increased spontaneous and stimulus-evoked firing in pyramidal neurons but reduced activity in interneurons. Preferential deletion of Shank3 in vS1 inhibitory interneurons led to pyramidal neuron hyperactivity and increased stimulus sensitivity in the vibrissa motion detection task. These findings provide evidence that cortical GABAergic interneuron dysfunction plays a key role in sensory hyper-reactivity in a Shank3 mouse model of ASD and identify a potential cellular target for exploring therapeutic interventions
Partially impaired functional connectivity states between right anterior insula and default mode network in autism spectrum disorder.
Time-invariant resting-state functional connectivity studies have illuminated the crucial role of the right anterior insula (rAI) in prominent social impairments of autism spectrum disorder (ASD). However, a recent dynamic connectivity study demonstrated that rather than being stationary, functional connectivity patterns of the rAI vary significantly across time. The present study aimed to explore the differences in functional connectivity in dynamic states of the rAI between individuals with ASD and typically developing controls (TD). Resting-state functional magnetic resonance imaging data obtained from a publicly available database were analyzed in 209 individuals with ASD and 298 demographically matched controls. A k-means clustering algorithm was utilized to obtain five dynamic states of functional connectivity of the rAI. The temporal properties, frequency properties, and meta-analytic decoding were first identified in TD group to obtain the characteristics of each rAI dynamic state. Multivariate analysis of variance was then performed to compare the functional connectivity patterns of the rAI between ASD and TD groups in obtained states. Significantly impaired connectivity was observed in ASD in the ventral medial prefrontal cortex and posterior cingulate cortex, which are two critical hubs of the default mode network (DMN). States in which ASD showed decreased connectivity between the rAI and these regions were those more relevant to socio-cognitive processing. From a dynamic perspective, these findings demonstrate partially impaired resting-state functional connectivity patterns between the rAI and DMN across states in ASD, and provide novel insights into the neural mechanisms underlying social impairments in individuals with ASD.Fundamental Research Funds for the Central Universities. Grant Numbers: 2672018ZYGX2018J079, ZYGX2016J187
National Institute for Health Research Cambridge Biomedical Resource Centre
National Natural Science Foundation of China. Grant Numbers: 61533006, 61673089, 81771919, 81871432
Sichuan Science and Technology Program. Grant Number: 2018TJPT0016
Specialized Research Fund for the Doctoral Program of Higher Education of China. Grant Number: 2012018511002
Perfluoroarylāelemental sulfur SNAr chemistry in covalent triazine frameworks with high sulfur contents for lithiumāsulfur batteries
In order to address the challenges associated with lithiumāsulfur batteries with high energy densities, various approaches, including advanced designs of sulfur composites, electrolyte engineering, and functional separators, are lately introduced. However, most approaches are effective for sulfur cathodes with limited sulfur contents, i.e., <80 wt%, imposing a significant barrier in realizing high energy densities in practical cell settings. Here, elemental sulfur-mediated synthesis of a perfluorinated covalent triazine framework (CTF) and its simultaneous chemical impregnation with elemental sulfur via SNAr chemistry are demonstrated. SNAr chemistry facilitates the dehalogenation and nucleophilic addition reactions of perfluoroaryl units with nucleophilic sulfur chains, achieving a high sulfur content of 86 wt% in the resulting CTF. The given sulfur-impregnated CTF, named SF-CTF, exhibits a specific capacity of 1138.2 mAh gā1 at 0.05C, initial Coulombic efficiency of 93.1%, and capacity retention of 81.6% after 300 cycles, by utilizing homogeneously distributed sulfur within the micropores and nitrogen atoms of triazine units offering high binding affinity toward lithium polysulfides
Single-Cell Transcriptomics of Proliferative Phase Endometrium: Systems Analysis of CellāCell Communication Network Using CellChat
The endometrium thickness increases by which endometrial angiogenesis occurs in parallel with the rapid growth of endometrium during the proliferative phase, which is orchestrated by complex cellācell interactions and cytokine networks. However, the intercellular communication has not been fully delineated. In the present work, we studied the cellācell interactome among cells of human proliferative phase endometrium using single-cell transcriptomics. The transcriptomes of 33,240 primary endometrial cells were profiled at single-cell resolution. CellChat was used to infer the cellācell interactome by assessing the gene expression of receptorāligand pairs across cell types. In total, nine cell types and 88 functionally related signaling pathways were found. Among them, growth factors and angiogenic factor signaling pathways, including EGF, FGF, IGF, PDGF, TGFb, VEGF, ANGPT, and ANGPTL that are highly associated with endometrial growth, were further analyzed and verified. The results showed that stromal cells and proliferating stromal cells represented cellācell interaction hubs with a large number of EGF, PDGF incoming signals, and FGF outgoing signals. Endothelial cells exhibited cellācell interaction hubs with a plenty of VEGF, TGFb incoming signals, and ANGPT outgoing signals. Unciliated epithelial cells, ciliated epithelial cells, and macrophages exhibited cellācell interaction hubs with substantial EGF outgoing signals. Ciliated epithelial cells represented cellācell interaction hubs with a large number of IGF and TGFb incoming signals. Smooth muscle cells represented lots of PDGF incoming signals and ANGPT and ANGPTL outgoing signals. This study deconvoluted complex intercellular communications at the single-cell level and predicted meaningful biological discoveries, which deepened the understanding of communications among endometrial cells
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