98 research outputs found
Generalized quantization condition in topological insulator
The topological magnetoelectric effect (TME) is the fundamental quantization
effect for topological insulators in units of the fine structure constant
. In [Phys. Rev. Lett. 105, 166803(2010)], a topological quantization
condition of the TME is given under orthogonal incidence of the optical beam,
in which the wave length of the light or the thickness of the TI film must be
tuned to some commensurate values. This fine tuning is difficult to realize
experimentally. In this article, we give manifestly
covariant expressions for Kerr and Faraday angles at oblique incidence at a
topological insulator thick film. We obtain a generalized quantization
condition independent of material details, and propose a more easily realizable
optical experiment, in which only the incidence angle is tuned, to directly
measure the topological quantization associated with the TME.Comment: 3 figure
Membrane Potential Batch Normalization for Spiking Neural Networks
As one of the energy-efficient alternatives of conventional neural networks
(CNNs), spiking neural networks (SNNs) have gained more and more interest
recently. To train the deep models, some effective batch normalization (BN)
techniques are proposed in SNNs. All these BNs are suggested to be used after
the convolution layer as usually doing in CNNs. However, the spiking neuron is
much more complex with the spatio-temporal dynamics. The regulated data flow
after the BN layer will be disturbed again by the membrane potential updating
operation before the firing function, i.e., the nonlinear activation.
Therefore, we advocate adding another BN layer before the firing function to
normalize the membrane potential again, called MPBN. To eliminate the induced
time cost of MPBN, we also propose a training-inference-decoupled
re-parameterization technique to fold the trained MPBN into the firing
threshold. With the re-parameterization technique, the MPBN will not introduce
any extra time burden in the inference. Furthermore, the MPBN can also adopt
the element-wised form, while these BNs after the convolution layer can only
use the channel-wised form. Experimental results show that the proposed MPBN
performs well on both popular non-spiking static and neuromorphic datasets. Our
code is open-sourced at \href{https://github.com/yfguo91/MPBN}{MPBN}.Comment: Accepted by ICCV202
Spiking PointNet: Spiking Neural Networks for Point Clouds
Recently, Spiking Neural Networks (SNNs), enjoying extreme energy efficiency,
have drawn much research attention on 2D visual recognition and shown gradually
increasing application potential. However, it still remains underexplored
whether SNNs can be generalized to 3D recognition. To this end, we present
Spiking PointNet in the paper, the first spiking neural model for efficient
deep learning on point clouds. We discover that the two huge obstacles limiting
the application of SNNs in point clouds are: the intrinsic optimization
obstacle of SNNs that impedes the training of a big spiking model with large
time steps, and the expensive memory and computation cost of PointNet that
makes training a big spiking point model unrealistic. To solve the problems
simultaneously, we present a trained-less but learning-more paradigm for
Spiking PointNet with theoretical justifications and in-depth experimental
analysis. In specific, our Spiking PointNet is trained with only a single time
step but can obtain better performance with multiple time steps inference,
compared to the one trained directly with multiple time steps. We conduct
various experiments on ModelNet10, ModelNet40 to demonstrate the effectiveness
of Spiking PointNet. Notably, our Spiking PointNet even can outperform its ANN
counterpart, which is rare in the SNN field thus providing a potential research
direction for the following work. Moreover, Spiking PointNet shows impressive
speedup and storage saving in the training phase.Comment: Accepted by NeurIP
Multifunctional targeting micelle nanocarriers with both imaging and therapeutic potential for bladder cancer.
BackgroundWe previously developed a bladder cancer-specific ligand (PLZ4) that can specifically bind to both human and dog bladder cancer cells in vitro and in vivo. We have also developed a micelle nanocarrier drug-delivery system. Here, we assessed whether the targeting micelles decorated with PLZ4 on the surface could specifically target dog bladder cancer cells.Materials and methodsMicelle-building monomers (ie, telodendrimers) were synthesized through conjugation of polyethylene glycol with a cholic acid cluster at one end and PLZ4 at the other, which then self-assembled in an aqueous solution to form micelles. Dog bladder cancer cell lines were used for in vitro and in vivo drug delivery studies.ResultsCompared to nontargeting micelles, targeting PLZ4 micelles (23.2 Β± 8.1 nm in diameter) loaded with the imaging agent DiD and the chemotherapeutic drug paclitaxel or daunorubicin were more efficient in targeted drug delivery and more effective in cell killing in vitro. PLZ4 facilitated the uptake of micelles together with the cargo load into the target cells. We also developed an orthotopic invasive dog bladder cancer xenograft model in mice. In vivo studies with this model showed the targeting micelles were more efficient in targeted drug delivery than the free dye (14.3Γ; P < 0.01) and nontargeting micelles (1.5Γ; P < 0.05).ConclusionTargeting micelles decorated with PLZ4 can selectively target dog bladder cancer cells and potentially be developed as imaging and therapeutic agents in a clinical setting. Preclinical studies of targeting micelles can be performed in dogs with spontaneous bladder cancer before proceeding with studies using human patients
RMP-Loss: Regularizing Membrane Potential Distribution for Spiking Neural Networks
Spiking Neural Networks (SNNs) as one of the biology-inspired models have
received much attention recently. It can significantly reduce energy
consumption since they quantize the real-valued membrane potentials to 0/1
spikes to transmit information thus the multiplications of activations and
weights can be replaced by additions when implemented on hardware. However,
this quantization mechanism will inevitably introduce quantization error, thus
causing catastrophic information loss. To address the quantization error
problem, we propose a regularizing membrane potential loss (RMP-Loss) to adjust
the distribution which is directly related to quantization error to a range
close to the spikes. Our method is extremely simple to implement and
straightforward to train an SNN. Furthermore, it is shown to consistently
outperform previous state-of-the-art methods over different network
architectures and datasets.Comment: Accepted by ICCV202
On the Circular Polarisation of Repeating Fast Radio Bursts
Fast spinning (e.g., sub-second) neutron star with ultra-strong magnetic
fields (or so-called magnetar) is one of the promising origins of repeating
fast radio bursts (FRBs). Here we discuss circularly polarised emissions
produced by propagation effects in the magnetosphere of fast spinning
magnetars. We argue that the polarisation-limiting region is well beyond the
light cylinder, suggesting that wave mode coupling effects are unlikely to
produce strong circular polarisation for fast spinning magnetars. Cyclotron
absorption could be significant if the secondary plasma density is high.
However, high degrees of circular polarisation can only be produced with large
asymmetries in electrons and positrons. We draw attention to the non-detection
of circular polarisation in current observations of known repeating FRBs. We
suggest that the circular polarisation of FRBs could provide key information on
their origins and help distinguish different radiation mechanisms.Comment: ApJ accepte
Novel theranostic nanoporphyrins for photodynamic diagnosis and trimodal therapy for bladder cancer
The overall prognosis of bladder cancer has not been improved over the last 30 years and therefore, there is a great medical need to develop novel diagnosis and therapy approaches for bladder cancer. We developed a multifunctional nanoporphyrin platform that was coated with a bladder cancer-specific ligand named PLZ4. PLZ4-nanoporphyrin (PNP) integrates photodynamic diagnosis, image-guided photodynamic therapy, photothermal therapy and targeted chemotherapy in a single procedure. PNPs are spherical, relatively small (around 23 nm), and have the ability to preferably emit fluorescence/heat/reactive oxygen species upon illumination with near infrared light. Doxorubicin (DOX) loaded PNPs possess slower drug release and dramatically longer systemic circulation time compared to free DOX. The fluorescence signal of PNPs efficiently and selectively increased in bladder cancer cells but not normal urothelial cells in vitro and in an orthotopic patient derived bladder cancer xenograft (PDX) models, indicating their great potential for photodynamic diagnosis. Photodynamic therapy with PNPs was significantly more potent than 5-aminolevulinic acid, and eliminated orthotopic PDX bladder cancers after intravesical treatment. Image-guided photodynamic and photothermal therapies synergized with targeted chemotherapy of DOX and significantly prolonged overall survival of mice carrying PDXs. In conclusion, this uniquely engineered targeting PNP selectively targeted tumor cells for photodynamic diagnosis, and served as effective triple-modality (photodynamic/photothermal/chemo) therapeutic agents against bladder cancers. This platform can be easily adapted to individualized medicine in a clinical setting and has tremendous potential to improve the management of bladder cancer in the clinic
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