X-ViT: High Performance Linear Vision Transformer without Softmax

Vision transformers have become one of the most important models for computer vision tasks. Although they outperform prior works, they require heavy computational resources on a scale that is quadratic to the number of tokens, $N$. This is a major drawback of the traditional self-attention (SA) algorithm. Here, we propose the X-ViT, ViT with a novel SA mechanism that has linear complexity. The main approach of this work is to eliminate nonlinearity from the original SA. We factorize the matrix multiplication of the SA mechanism without complicated linear approximation. By modifying only a few lines of code from the original SA, the proposed models outperform most transformer-based models on image classification and dense prediction tasks on most capacity regimes

SNR enhanced high-speed two-photon microscopy using a pulse picker and time gating detection

Abstract Two-photon microscopy (TPM) is an attractive biomedical imaging method due to its large penetration depth and optical sectioning capability. In particular, label-free autofluorescence imaging offers various advantages for imaging biological samples. However, relatively low intensity of autofluorescence leads to low signal-to-noise ratio (SNR), causing practical challenges for imaging biological samples. In this study, we present TPM using a pulse picker to utilize low pulse repetition rate of femtosecond pulsed laser to increase the pulse peak power of the excitation source leading to higher emission of two-photon fluorescence with the same average illumination power. Stronger autofluorescence emission allowed us to obtain higher SNR images of arterial and liver tissues. In addition, by applying the time gating detection method to the pulse signals obtained by TPM, we were able to significantly reduce the background noise of two-photon images. As a result, our TPM system using the pulsed light source with a 19 times lower repetition rate allowed us to obtain the same SNR image more than 19 times faster with the same average power. Although high pulse energy can increase the photobleaching, we also observed that high-speed imaging with low total illumination energy can mitigate the photobleaching effect to a level similar to that of conventional illumination with a high repetition rate. We anticipate that this simple approach will provide guidance for SNR enhancement with high-speed imaging in TPM as well as other nonlinear microscopy

Ginsenoside Rf inhibits cyclooxygenase-2 induction via peroxisome proliferator–activated receptor gamma in A549 cells

Background: Ginsenoside Rf is a ginseng saponin found only in Panax ginseng that affects lipid metabolism. It also has neuroprotective and antiinflammatory properties. We previously showed that Korean Red Ginseng (KRG) inhibited the expression of cyclooxygenase-2 (COX-2) by hypoxia via peroxisome proliferator–activated receptor gamma (PPARγ). The aim of the current study was to evaluate the possibility of ginsenoside Rf as an active ingredient of KRG in the inhibition of hypoxia-induced COX-2 via PPARγ. Methods: The effects of ginsenoside Rf on the upregulation of COX-2 by hypoxia and its antimigration effects were evaluated in A549 cells. Docking of ginsenoside Rf was performed with the PPARγ structure using Surflex-Dock in Sybyl-X 2.1.1. Results: PPARγ protein levels and peroxisome proliferator response element promoter activities were promoted by ginsenoside Rf. Inhibition of COX-2 expression by ginsenoside Rf was blocked by the PPARγ-specific inhibitor, T0070907. The PPARγ inhibitor also blocked the ability of ginsenoside Rf to suppress cell migration under hypoxia. The docking simulation results indicate that ginsenoside Rf binds to the active site of PPARγ. Conclusions: Our results demonstrate that ginsenoside Rf inhibits hypoxia induced-COX-2 expression and cellular migration, which are dependent on PPARγ activation. These results suggest that ginsenoside Rf has an antiinflammatory effect under hypoxic conditions. Moreover, docking analysis of ginsenoside Rf into the active site of PPARγ suggests that the compound binds to PPARγ in a position similar to that of known agonists. Keywords: COX-2, ginsenoside Rf, hypoxia, PPAR

Co₃V₂O₈ Sponge Network Morphology Derived from Metal–Organic Framework as an Excellent Lithium Storage Anode Material

Metal–organic framework (MOF)-based synthesis of battery electrodes has presntly become a topic of significant research interest. Considering the complications to prepare Co₃V₂O₈ due to the criticality of its stoichiometric composition, we report on a simple MOF-based solvothermal synthesis of Co₃V₂O₈ for use as potential anodes for lithium battery applications. Characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution electron microscopy, and porous studies revealed that the phase pure Co₃V₂O₈ nanoparticles are interconnected to form a sponge-like morphology with porous properties. Electrochemical measurements exposed the excellent lithium storage (∼1000 mAh g^–1 at 200 mA g^–1) and retention properties (501 mAh g^–1 at 1000 mA g^–1 after 700 cycles) of the prepared Co₃V₂O₈ electrode. A notable rate performance of 430 mAh g^–1 at 3200 mA g^–1 was also observed, and ex situ investigations confirmed the morphological and structural stability of this material. These results validate that the unique nanostructured morphology arising from the use of the ordered array of MOF networks is favorable for improving the cyclability and rate capability in battery electrodes. The synthetic strategy presented herein may provide solutions to develop phase pure mixed metal oxides for high-performance electrodes for useful energy storage applications

An Enhanced High-Rate Na₃V₂(PO₄)₃‑Ni₂P Nanocomposite Cathode with Stable Lifetime for Sodium-Ion Batteries

Herein, we report on a high-discharge-rate Na₃V₂(PO₄)₃-Ni₂P/C (NVP-NP/C) composite cathode prepared using a polyol-based pyro synthesis for Na-ion battery applications. X-ray diffraction and electron microscopy studies established the presence of Na₃V₂(PO₄)₃ and Ni₂P, respectively, in the NVP-NP/C composite. As a cathode material, the obtained NVP-NP/C composite electrode exhibits higher discharge capacities (100.8 mAhg^–1 at 10.8 C and 73.9 mAhg^–1 at 34 C) than the NVP/C counterpart electrode (62.7 mAhg^–1 at 10.8 C and 4.7 mAhg^–1 at 34 C), and the composite electrode retained 95.3% of the initial capacity even after 1500 cycles at 16 C. The enhanced performance could be attributed to the synergetic effect of the Ni₂P phase and nanoscale NVP particles, which ultimately results in noticeably enhancing the electrical conductivity of the composite. The present study thus demonstrates that the Na₃V₂(PO₄)₃-Ni₂P/C nanocomposite is a prospective candidate for NIB with a high power/energy density

Monoclinic-Orthorhombic Na_1.1Li_2.0V₂(PO₄)₃/C Composite Cathode for Na⁺/Li⁺ Hybrid-Ion Batteries

Monoclinic Li₃V₂(PO₄)₃ (LVP) has been considered a promising cathode material for lithium-ion batteries for the past decade because of its high average potential (>4.0 V) and specific capacity (197 mAh g^–1). In this paper, we report a new monoclinic-orthorhombic Na_1.1Li_2.0V₂(PO₄)₃/C (NLVP/C) composite cathode synthesized from monoclinic LVP via a soft ion-exchange reaction for use in Na⁺/Li⁺ hybrid-ion batteries. High-resolution synchrotron X-ray diffraction (XRD), thermal studies, and electrochemical data confirm room temperature stabilization of the monoclinic-orthorhombic NLVP/C composite phase. Specifically, we report the application of a monoclinic-orthorhombic NLVP/C composite as cathode material in a Na half-cell. The cathode delivered initial discharge capacities of 115 and 145 mAh g^–1 at a current density of 7.14 mA g^–1 in the 2.5–4 and 2.5–4.6 V vs Na/Na⁺ potential windows, respectively. In the lower potential window (2.5–4 V), the composite electrode demonstrated a two-step voltage plateau during the insertion and extraction of Na⁺/Li⁺ ions. Corresponding in situ synchrotron XRD patterns recorded during initial electrochemical cycling clearly indicate a series of two-phase transitions and confirm the structural stability of the NLVP/C composite cathode during insertion and extraction of the hybrid ions. Under extended cycling, excessive storage of Na ions resulted in the gradual transformation to the orthorhombic NLVP/C symmetry due to the occupancy of Na ions in the available orthorhombic sites. Moreover, the estimated average working potential and energy density at the initial cycle for the monoclinic-orthorhombic NLVP/C composite cathode (3.47 V vs Na/Na⁺ and 102.5 Wh kg^–1, respectively) are higher than those of the pyro-synthesized rhombohedral Na₃V₂(PO₄)₃ (3.36 V vs Na/Na⁺ and 88.5 Wh kg^–1) cathode. Further, the cathode performance of the composite material was significantly higher than that observed with pure monoclinic LVP under the same electrochemical measurement conditions. The present study thus showcases the feasibility of using a soft ion-exchange reaction at 150 °C to facilitate the formation of composite phases suitable for rechargeable hybrid-ion battery applications