Analytical description of high-aperture STED resolution with 0-2π\pi vortex phase modulation

Stimulated emission depletion (STED) can achieve optical super-resolution, with the optical diffraction limit broken by the suppression on the periphery of the fluorescent focal spot. Previously, it is generally experimentally accepted that there exists an inverse square root relationship with the STED power and the resolution, yet without strict analytical description. In this paper, we have analytically verified the relationship between the STED power and the achievable resolution from vector optical theory for the widely used 0-2$\pi$ vortex phase modulation. Electromagnetic fields of the focal region of a high numerical aperture objective are calculated and approximated into polynomials, and analytical expression of resolution as a function of the STED intensity has been derived. As a result, the resolution can be estimated directly from the measurement of the saturation power of the dye and the STED power applied.Comment: (19 pages

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

A Mode-Sum Prescription for Vacuum Polarization in Even Dimensions

We present a mode-sum regularization prescription for computing the vacuum polarization of a scalar field in static spherically-symmetric black hole spacetimes in even dimensions. This is the first general and systematic approach to regularized vacuum polarization in higher even dimensions, building upon a previous scheme we developed for odd dimensions. Things are more complicated here since the even-dimensional propagator possesses logarithmic singularities which must be regularized. However, in spite of this complication, the regularization parameters can be computed in closed form in arbitrary even dimensions and for arbitrary metric function $f(r)$. As an explicit example of our method, we show plots for vacuum polarization of a massless scalar field in the Schwarzschild-Tangherlini spacetime for even $d=4,...,10$. However, the method presented applies straightforwardly to massive fields or to nonvacuum spacetimes.Comment: arXiv admin note: text overlap with arXiv:1609.0816

Development of a Novel Electromagnetic Rewarming Technology for the Cryopreservation of Stem Cells with Large Volume

Applications of stem cells have been playing significant roles in scientific and clinical settings in the last few decades. The foundation of these approaches is successful cryopreservation of stem cells for future use. However, so far we can only cryopreserve stem cell suspension of small volumes in the order of 1 mL mostly due to the lack of an effective rewarming technique. Rapid and uniform rewarming has been approved to be beneficial, and sometimes, indispensable for the survival of cryopreserved stem cells, inhibiting ice recrystallization or devitrification. Unfortunately, the conventional water bath thawing method failed in providing the rapid and uniform rewarming. The conversion of electromagnetic (EM) energy into heat provides a possible solution to this problem. This chapter will focus on (1) analysis of the combined EM and heat transfer phenomenon in the rewarming of a biospecimen, (2) numerical investigation of the rewarming system, (3) practical setup of an EM resonance system, and (4) test of heating performance with large volume of cells

Strain rate sensitivities of deformation mechanisms in magnesium alloys

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.ijplas.2018.04.005 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Strain rate sensitivity (SRS) is an important material property that governs the rate dependent mechanical behaviors associated with deformation rate changes, creep, stress relaxation, formability, etc. The variety of activated deformation mechanisms of magnesium alloys under different loading paths, e.g. tension vs. compression, implies that SRS of magnesium alloys obviously depends on loading paths, and each deformation mechanism has its own SRS. However, a single SRS scheme is commonly employed in numerical modeling to describe the rate dependent behaviors of magnesium alloys, which disregards the distinction of SRSs among different deformation mechanisms. The implementation of the constitutive model that works for a wide range of values of SRSs has been a challenge to crystal plasticity modeling for metals with multiple deformation mechanisms like magnesium. Especially, very small values of SRS, corresponding to low rate-sensitivity, generally lead to high nonlinearity involved in the governing equations, and then computational failure. In this paper, the elasto-viscoplastic self-consistent (EVPSC) crystal plasticity model is improved to enhance its numerical robustness for very small SRS values. Taking advantage of this improvement, different SRSs for various deformation mechanisms are employed to investigate the strain rate dependent behaviors of magnesium alloys at room temperature. First, the SRSs for various deformation mechanisms are determined based on the compressive stress relaxation tests on an AZ31 alloy plate; secondly, the obtained SRSs are applied to interpret internal elastic strain evolution of the same magnesium alloy under in-plane compression; finally, the determined SRSs are applied to investigate the deformation of another AZ31 alloy under various deformation paths and strain rates. The present work is the first effort on studying effects of strain rate-sensitivity on mechanical behavior of Mg alloys under wide range of applied strain rates by using an improved self-consistent polycrystal plasticity model. Good agreement between the experiments and simulations reveals the importance and necessity of using different SRSs for the deformation mechanisms involved. The rate dependent behaviors of magnesium alloys can be better described by using multiple SRSs associated to each operative deformation mechanism.Natural Sciences and Engineering Research Council of CanadaMinistry of Research, Innovation and ScienceNational Natural Science Foundation of China [51575346, 51675331]Shanghai Jiao Tong UniversityAutomotive Partnerships CanadaCanada Research Chairs Secretaria

Developments and Perspectives on Robust Nano- and Microstructured Binder-Free Electrodes for Bifunctional Water Electrolysis and Beyond

The development of robust nano- and microstructured catalysts on highly conductive substrates is an effective approach to produce highly active binder-free electrodes for energy conversion and storage applications. As a result, nanostructured electrodes with binder-free designs have abundant advantages that provide superior electrocatalytic performance; these include more exposed active sites, large surface area, strong adhesion to substrates, facile charge transfer, high conductivity, high intrinsic catalytic activity, and fine-tuning of its electronic nature through nanostructure modification. Notably, the interface chemistry of an electrocatalyst plays a significant role in their optimized electrocatalytic activity and stability. This review provides an overview of recent progress in nano- and microstructured catalysts, such as one, two, and 3D catalysts as binder-free electrodes for electrocatalytic water splitting via the hydrogen evolution reaction and oxygen evolution reaction, and beyond. Furthermore, this review focuses on the current challenges and synthesis strategies of binder-free electrodes, with a focus on the impact of nanostructure on their functional property relationships and enhanced bifunctional electrocatalytic performance. Finally, an outlook for their future advances in energy conversion and storage is provided.</p

Selective modes affect gene feature and function differentiation of tetraploid Brassica species in their evolution and domestication

The genus Brassica contains a diverse group of important vegetables and oilseed crops. Genome sequencing has been completed for the six species (B. rapa, B. oleracea, B. nigra, B. carinata, B. napus, and B. juncea) in U’s triangle model. The purpose of the study is to investigate whether positively and negatively selected genes (PSGs and NSGs) affect gene feature and function differentiation of Brassica tetraploids in their evolution and domestication. A total of 9,701 PSGs were found in the A, B and C subgenomes of the three tetraploids, of which, a higher number of PSGs were identified in the C subgenome as comparing to the A and B subgenomes. The PSGs of the three tetraploids had more tandem duplicated genes, higher single copy, lower multi-copy, shorter exon length and fewer exon number than the NSGs, suggesting that the selective modes affected the gene feature of Brassica tetraploids. The PSGs of all the three tetraploids enriched in a few common KEGG pathways relating to environmental adaption (such as Phenylpropanoid biosynthesis, Riboflavin metabolism, Isoflavonoid biosynthesis, Plant-pathogen interaction and Tropane, piperidine and pyridine alkaloid biosynthesis) and reproduction (Homologous recombination). Whereas, the NSGs of the three tetraploids significantly enriched in dozens of biologic processes and pathways without clear relationships with evolution. Moreover, the PSGs of B. carinata were found specifically enriched in lipid biosynthesis and metabolism which possibly contributed to the domestication of B. carinata as an oil crop. Our data suggest that selective modes affected the gene feature of Brassica tetraploids, and PSGs contributed in not only the evolution but also the domestication of Brassica tetraploids

Optimizing postbiotic production through solid-state fermentation with Bacillus amyloliquefaciens J and Lactiplantibacillus plantarum SN4 enhances antibacterial, antioxidant, and anti-inflammatory activities

BackgroundPostbiotics are an emerging research interest in recent years and are fairly advanced compared to prebiotics and probiotics. The composition and function of postbiotics are closely related to fermentation conditions.MethodsIn this study, we developed a solid-state fermentation preparation method for postbiotics with antimicrobial, antioxidant, and anti-inflammatory activities. The antibacterial activity was improved 3.62 times compared to initial fermentation conditions by using optimization techniques such as single factor experiments, Plackett–Burman design (PBD), steepest ascent method (SAM), and central composite design (CCD) methods. The optimized conditions were carried out with an initial water content of 50% for 8 days at 37°C and fermentation strains of Bacillus amyloliquefaciens J and Lactiplantibacillus plantarum SN4 at a ratio of 1:1 with a total inoculum size of 8%. The optimized SSF medium content ratios of peptide powder, wheat bran, corn flour, and soybean meal were 4, 37.4, 30, and 28.6%, respectively.ResultsUnder these optimized conditions, postbiotics with a concentration of 25 mg/mL showed significant broad-spectrum antibacterial capabilities against Escherichia coli, Salmonella, and Staphylococcus aureus and strong antioxidant activity against ABTS, DPPH, and OH radicals. Moreover, the optimized postbiotics exhibited good anti-inflammatory ability for reducing nitric oxide (NO) secretion in RAW 264.7 macrophage cells in response to LPS-induced inflammation. Furthermore, the postbiotics significantly improved intestinal epithelial wound healing capabilities after mechanical injury, such as cell scratches in IPEC-J2 cells (p &lt; 0.05).ConclusionIn brief, we developed postbiotics through optimized solid-state fermentation with potential benefits for gut health. Therefore, our findings suggested that the novel postbiotics could be used as potential functional food products for improving body health