Direct observation of high-speed plasma outflows produced by magnetic reconnection in solar impulsive events

Spectroscopic observations of a solar limb flare recorded by SUMER on SOHO reveal, for the first time, hot fast magnetic reconnection outflows in the corona. As the reconnection site rises across the SUMER spectrometer slit, significant blue- and red-shift signatures are observed in sequence in the Fe XIX line, reflecting upflows and downflows of hot plasma jets, respectively. With the projection effect corrected, the measured outflow speed is between 900-3500 km/s, consistent with theoretical predictions of the Alfvenic outflows in magnetic reconnection region in solar impulsive events. Based on theoretic models, the magnetic field strength near the reconnection region is estimated to be 19-37 Gauss.Comment: 5 pages, 6 color figures, 1 animation onlin

The impact of external plant carbon sources on nitrogen removal and microbial community structure in vertical flow constructed wetlands

The present study was developed to explore nitrogen removal performance and associated microbial mechanisms of action in vertical flow constructed wetlands (VFCWs) when using external carbon sources. These analyses ultimately revealed that alkali-soaked Phragmites australis (P. australis) could serve as an effective plant carbon source, exhibiting the lower levels of total nitrogen (TN) release and the highest chemical oxygen demand (COD) of all tested carbon sources. Nitrogen removal efficiency improved following the addition of plant carbon sources, and under carbon/nitrogen (C/N) rations of 2, 4, 5, and 7, the VFCW system was able to remove 43.69%–75.76% TN, with the highest removal rate being observed at a C/N of 5. The abundance of denitrifying microorganisms such as Thiobaillus and Halomonas were also more enriched in VFCW1 than VFCW0, with stronger correlations in the microbial network community. A qPCR approach was used to analyze functional genes involved in denitrification, revealing that the addition of plant carbon sources was associated with increases in total gene abundance and the abundance of the denitrifying gene nirS, whereas no corresponding increase in amoA or nxrA abundance was observed. Higher total gene, amoA, and nxrA abundance were observed in the upper levels of these VFCW systems as compared to the lower layers, whereas nirS exhibited the opposite abundance pattern. Overall, these findings suggested that short-range denitrification is likely to be the primary denitrification process active in this VFCW system

SgVA-CLIP: Semantic-guided Visual Adapting of Vision-Language Models for Few-shot Image Classification

Although significant progress has been made in few-shot learning, most of existing few-shot image classification methods require supervised pre-training on a large amount of samples of base classes, which limits their generalization ability in real world application. Recently, large-scale Vision-Language Pre-trained models (VLPs) have been gaining increasing attention in few-shot learning because they can provide a new paradigm for transferable visual representation learning with easily available text on the Web. However, the VLPs may neglect detailed visual information that is difficult to describe by language sentences, but important for learning an effective classifier to distinguish different images. To address the above problem, we propose a new framework, named Semantic-guided Visual Adapting (SgVA), which can effectively extend vision-language pre-trained models to produce discriminative adapted visual features by comprehensively using an implicit knowledge distillation, a vision-specific contrastive loss, and a cross-modal contrastive loss. The implicit knowledge distillation is designed to transfer the fine-grained cross-modal knowledge to guide the updating of the vision adapter. State-of-the-art results on 13 datasets demonstrate that the adapted visual features can well complement the cross-modal features to improve few-shot image classification

A DNA aptamer for binding and inhibition of DNA methyltransferase 1.

DNA methyltransferases (DNMTs) are enzymes responsible for establishing and maintaining DNA methylation in cells. DNMT inhibition is actively pursued in cancer treatment, dominantly through the formation of irreversible covalent complexes between small molecular compounds and DNMTs that suffers from low efficacy and high cytotoxicity, as well as no selectivity towards different DNMTs. Herein, we discover aptamers against the maintenance DNA methyltransferase, DNMT1, by coupling Asymmetrical Flow Field-Flow Fractionation (AF4) with Systematic Evolution of Ligands by EXponential enrichment (SELEX). One of the identified aptamers, Apt. #9, contains a stem-loop structure, and can displace the hemi-methylated DNA duplex, the native substrate of DNMT1, off the protein on sub-micromolar scale, leading for effective enzymatic inhibition. Apt. #9 shows no inhibition nor binding activity towards two de novo DNMTs, DNMT3A and DNMT3B. Intriguingly, it can enter cancer cells with over-expression of DNMT1, colocalize with DNMT1 inside the nuclei, and inhibit the activity of DNMT1 in cells. This study opens the possibility of exploring the aptameric DNMT inhibitors being a new cancer therapeutic approach, by modulating DNMT activity selectively through reversible interaction. The aptamers could also be valuable tools for study of the functions of DNMTs and the related epigenetic mechanisms

CLIP-VG: Self-paced Curriculum Adapting of CLIP for Visual Grounding

Visual Grounding (VG) is a crucial topic in the field of vision and language, which involves locating a specific region described by expressions within an image. To reduce the reliance on manually labeled data, unsupervised methods have been developed to locate regions using pseudo-labels. However, the performance of existing unsupervised methods is highly dependent on the quality of pseudo-labels and these methods always encounter issues with limited diversity. In order to utilize vision and language pre-trained models to address the grounding problem, and reasonably take advantage of pseudo-labels, we propose CLIP-VG, a novel method that can conduct self-paced curriculum adapting of CLIP with pseudo-language labels. We propose a simple yet efficient end-to-end network architecture to realize the transfer of CLIP to the visual grounding. Based on the CLIP-based architecture, we further propose single-source and multi-source curriculum adapting algorithms, which can progressively find more reliable pseudo-labels to learn an optimal model, thereby achieving a balance between reliability and diversity for the pseudo-language labels. Our method outperforms the current state-of-the-art unsupervised method by a significant margin on RefCOCO/+/g datasets in both single-source and multi-source scenarios, with improvements ranging from 6.78% to 10.67% and 11.39% to 14.87%, respectively. Furthermore, our approach even outperforms existing weakly supervised methods. The code and models are available at https://github.com/linhuixiao/CLIP-VG.Comment: Accepted by IEEE Transaction on Multimedia (2023), Paper page: https://ieeexplore.ieee.org/abstract/document/10269126. Code will be released at https://github.com/linhuixiao/CLIP-V

Evolution of magnetic field of the Quasar 1604+159 at pc scale

We have analyzed the total intensity, spectral index, linear polarization, and RM distributions at pc scale for the quasar 1604+159. The source was observed in 2002 and 2020 with the VLBA. Combining the MOJAVE results, we studied the evolution of the magnetic field. We detected a core-jet structure. The jet extends to a distance of ~25 mas. The jet shape varies slightly with time. We divided the source structure into the central region and the jet region. In the jet region, we find the polarized emission varies with time. The flatter spectral index values and EVPA direction indicate the possible existence of shocks, contributing to the variation. In the central region, the derived core shift index k_r values indicate that the core in 2002 is close to the equipartition case while deviating from it in 2020. The measured magnetic field strength in 2020 is two orders of magnitude lower than that in 2002. We detected transverse RM gradients, evidence of a helical magnetic field, in the core. At 15 GHz, in the place close to the jet base, the polarization direction changes significantly with time from perpendicular to parallel to the jet direction. The evolution of RM and magnetic field structure are potential reasons for the observed polarization change. The core |RM| in 2020 increases with frequency following a power law with index a = 2.7, suggesting a fast electron density fall-off in the medium with distance from the jet base.Comment: 24 pages, 14 figures, accepted for publication in Ap

Analytical solution of the nitracline with the evolution of subsurface chlorophyll maximum in stratified water columns

In a stratified water column, the nitracline is a layer where the nitrate concentration increases below the nutrient-depleted upper layer, exhibiting a strong vertical gradient in the euphotic zone. The subsurface chlorophyll maximum layer (SCML) forms near the bottom of the euphotic zone, acting as a trap to diminish the upward nutrient supply. Depth and steepness of the nitracline are important measurable parameters related to the vertical transport of nitrate into the euphotic zone. The correlation between the SCML and the nitracline has been widely reported in the literature, but the analytic solution for the relationship between them is not well established. By incorporating a piecewise function for the approximate Gaussian vertical profile of chlorophyll, we derive analytical solutions of a specified nutrient-phytoplankton model. The model is well suited to explain basic dependencies between a nitracline and an SCML. The analytical solution shows that the nitracline depth is deeper than the depth of the SCML, shoaling with an increase in the light attenuation coefficient and with a decrease in surface light intensity. The inverse proportional relationship between the light level at the nitracline depth and the maximum rate of new primary production is derived. Analytic solutions also show that a thinner SCML corresponds to a steeper nitracline. The nitracline steepness is positively related to the light attenuation coefficient but independent of surface light intensity. The derived equations of the nitracline in relation to the SCML provide further insight into the important role of the nitracline in marine pelagic ecosystems