3,115 research outputs found
Local Manifold Augmentation for Multiview Semantic Consistency
Multiview self-supervised representation learning roots in exploring semantic
consistency across data of complex intra-class variation. Such variation is not
directly accessible and therefore simulated by data augmentations. However,
commonly adopted augmentations are handcrafted and limited to simple
geometrical and color changes, which are unable to cover the abundant
intra-class variation. In this paper, we propose to extract the underlying data
variation from datasets and construct a novel augmentation operator, named
local manifold augmentation (LMA). LMA is achieved by training an
instance-conditioned generator to fit the distribution on the local manifold of
data and sampling multiview data using it. LMA shows the ability to create an
infinite number of data views, preserve semantics, and simulate complicated
variations in object pose, viewpoint, lighting condition, background etc.
Experiments show that with LMA integrated, self-supervised learning methods
such as MoCov2 and SimSiam gain consistent improvement on prevalent benchmarks
including CIFAR10, CIFAR100, STL10, ImageNet100, and ImageNet. Furthermore, LMA
leads to representations that obtain more significant invariance to the
viewpoint, object pose, and illumination changes and stronger robustness to
various real distribution shifts reflected by ImageNet-V2, ImageNet-R, ImageNet
Sketch etc
ILSGAN: Independent Layer Synthesis for Unsupervised Foreground-Background Segmentation
Unsupervised foreground-background segmentation aims at extracting salient
objects from cluttered backgrounds, where Generative Adversarial Network (GAN)
approaches, especially layered GANs, show great promise. However, without human
annotations, they are typically prone to produce foreground and background
layers with non-negligible semantic and visual confusion, dubbed "information
leakage", resulting in notable degeneration of the generated segmentation mask.
To alleviate this issue, we propose a simple-yet-effective explicit layer
independence modeling approach, termed Independent Layer Synthesis GAN
(ILSGAN), pursuing independent foreground-background layer generation by
encouraging their discrepancy. Specifically, it targets minimizing the mutual
information between visible and invisible regions of the foreground and
background to spur interlayer independence. Through in-depth theoretical and
experimental analyses, we justify that explicit layer independence modeling is
critical to suppressing information leakage and contributes to impressive
segmentation performance gains. Also, our ILSGAN achieves strong
state-of-the-art generation quality and segmentation performance on complex
real-world data.Comment: Accepted by AAAI 202
Phenotype and functional evaluation of ex vivo generated antigen-specific immune effector cells with potential for therapeutic applications
Ex vivo activation and expansion of lymphocytes for adoptive cell therapy has demonstrated great success. To improve safety and therapeutic efficacy, increased antigen specificity and reduced non-specific response of the ex vivo generated immune cells are necessary. Here, using a complete protein-spanning pool of pentadecapeptides of the latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV), a weak viral antigen which is associated with EBV lymphoproliferative diseases, we investigated the phenotype and function of immune effector cells generated based on IFN-γ or CD137 activation marker selection and dendritic cell (DC) activation. These ex vivo prepared immune cells exhibited a donor- and antigen-dependent T cell response; the IFN-γ-selected immune cells displayed a donor-related CD4- or CD8-dominant T cell phenotype; however, the CD137-enriched cells showed an increased ratio of CD4 T cells. Importantly, the pentadecapeptide antigens accessed both class II and class I MHC antigen processing machineries and effectively activated EBV-specific CD4 and CD8 T cells. Phenotype and kinetic analyses revealed that the IFN-γ and the CD137 selections enriched more central memory T (Tcm) cells than did the DC-activation approach, and after expansion, the IFN-γ-selected effector cells showed the highest level of antigen-specificity and effector activities. While all three approaches generated immune cells with comparable antigen-specific activities, the IFN-γ selection followed by ex vivo expansion produced high quality and quantity of antigen-specific effector cells. Our studies presented the optimal approach for generating therapeutic immune cells with potential for emergency and routine clinical applications
Visualization of Photonic Band Structures via Far-field Measurements in SiNx Photonic Crystal Slabs
The band structures of the photonic crystal slabs play a significant role in
manipulating the flow of light and pre-dicting exotic physics in photonics. In
this letter, we show that the key features of photonic band structures can be
achieved experimentally by the polarization- and momentum-resolved
photoluminescence spectroscopy utilizing the light emission properties of SiNx.
The two-dimensional spectra clearly reveal the energy-momentum dispersion of
band structures which is in perfect agreement with the simulation results. The
isofrequency contours can be measured easily by adding a bandpass filter with a
desired photon energy. Furthermore, it is convenient to observe clearly and
directly the optical singularity -- the optical bound states in the continuum
featured by dark point in three-dimensional photoluminescence spectra. The
polarization-resolved isofrequency contours clearly show that this dark point
is the center of an azimuthally polarized vortex. Finally, the helical
topological edge states can be easily observed in photonic topological
insulators with deformed hexagonal lattices. Our work provides a simple and
effective approach for exploring topological photonics and other intriguing
phenomena hidden in the photonic crystal slabs.Comment: 6 pages, 5 figure
Generating axial magnetic fields via two plasmon decay driven by a twisted laser
We propose a new way of axial magnetic fields generation in a
non-relativistic laser intensity regime by using a twisted light carrying
orbital angular momentum (OAM) to stimulate two-plasmon decay (TPD) in a
plasma. The growth of TPD driven by an OAM light in a Laguerre-Gauss (LG) mode
is investigated through three dimensional fluid simulations and theory. A
theory based on the assumption that the electron plasma waves (EPWs) are
locally driven by a number of local plane-wave lasers predicts the maximum
growth rate proportional to the peak amplitude of the pump laser field and is
verified by the simulations. The OAM conservation during its transportation
from the laser to the TPD daughter EWPs is shown by both the theory and the
simulations. The theory predicts generation of ~40T axial magnetic fields
through the OAM absorption via TPD, which has perspective applications in the
field of high energy density physics.Comment: 6 pages, 3 figures
- …