Keypoint-Augmented Self-Supervised Learning for Medical Image Segmentation with Limited Annotation

Pretraining CNN models (i.e., UNet) through self-supervision has become a powerful approach to facilitate medical image segmentation under low annotation regimes. Recent contrastive learning methods encourage similar global representations when the same image undergoes different transformations, or enforce invariance across different image/patch features that are intrinsically correlated. However, CNN-extracted global and local features are limited in capturing long-range spatial dependencies that are essential in biological anatomy. To this end, we present a keypoint-augmented fusion layer that extracts representations preserving both short- and long-range self-attention. In particular, we augment the CNN feature map at multiple scales by incorporating an additional input that learns long-range spatial self-attention among localized keypoint features. Further, we introduce both global and local self-supervised pretraining for the framework. At the global scale, we obtain global representations from both the bottleneck of the UNet, and by aggregating multiscale keypoint features. These global features are subsequently regularized through image-level contrastive objectives. At the local scale, we define a distance-based criterion to first establish correspondences among keypoints and encourage similarity between their features. Through extensive experiments on both MRI and CT segmentation tasks, we demonstrate the architectural advantages of our proposed method in comparison to both CNN and Transformer-based UNets, when all architectures are trained with randomly initialized weights. With our proposed pretraining strategy, our method further outperforms existing SSL methods by producing more robust self-attention and achieving state-of-the-art segmentation results. The code is available at https://github.com/zshyang/kaf.git.Comment: Camera ready for NeurIPS 2023. Code available at https://github.com/zshyang/kaf.gi

EFFECT OF NANOCRYSTALLIZATION-ASSISTED NITRIDING ON THE CORROSION BEHAVIOR OF AISI 4140 STEEL

ABSTRACT In this study, an innovative process called nanocrystallizationassisted nitriding was used to process 4140 steels. First, a nanocrystalline surface layer was induced in 4140 steel by ultrasonic nanocrystal surface modification (UNSM). The abundant nanoscale grain boundaries provide micro-channels for efficient nitrogen diffusion during nitriding at relatively low temperature (450 °C) and short duration (4 hours). The samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The hardness and corrosion resistance were examined and compared for samples after different processing conditions. It has been demonstrated that the sample processed by nanocrystallization-assisted nitriding has much higher hardness and corrosion resistance compared with the samples processed by nitriding only. INTRODUCTION As a widely used material in engineering applications, 4140 steel can be easily fabricated to gear, pinion, bolt and other machine tool components while maintaining a good mechanical and chemical propertie

Butterfly Community Diversity in the Qinling Mountains

The Qinling Mountains are one of the oldest mountain ranges in China and a global biodiversity research and conservation hotspot. However, there is a lack of systematic research and survey of butterfly diversity in this region. Based on the butterfly taxa, combined with the changes in natural climate, altitude gradient and season in the Qinling Mountains, the butterfly diversity and community structure changes in 12 counties in the middle Qinling Mountains were analyzed by transect surveys and platform data analyses. A total of 9626 butterflies were observed, belonging to 427 species across 175 genera and 5 families. The species richness on the southern slope of the Qinling Mountains was higher than on the northern slope. We also studied the variation in alpha and beta diversity of butterflies. The results show that butterfly species were abundant and the highest diversity was found at the middle altitudes (1000–2000 m). Moreover, there were obvious seasonal differences in both species and number of butterflies. The community similarity in spring, summer and autumn was low, with limited species co-existing. The butterflies in the Qinling Mountains reserve area were the most abundant, exhibiting no significant difference with those in the ecotone and the farm area. Finally, we did an assessment of butterflies as endangered and protected species. In conclusion, our long-term butterfly survey data show that human disturbance and climate and environmental changes jointly shape the butterfly diversity in the middle of the Qinling Mountains

Energy Availability Factors Drive the Geographical Pattern of Tenebrionidae (Coleoptera) in the Arid and Semiarid Areas of China

Species richness is regarded as the core index of biogeography. Estimating the correlation between species richness and modern environmental factors will be of great significance for species conservation. The arid and semiarid areas of China present serious desertification, but there are rich biodiversity resources of high value. In this study, we evaluated species diversity, species richness, and the correlation between species richness and modern environmental factors using the species of Tenebrionidae in arid and semiarid areas of China, which will provide basic data for species conservation. The species richness was measured using 1° × 1° grid cells, and its determinants were explored based on generalized linear models (GLMs) and random forest models. A total of 696 species, belonging to 125 genera of 38 tribes and 7 subfamilies, were recorded in the study area. The non-uniform species richness pattern was presented, with more species in Altai, Tianshan, Nyenchen Thanglha and Helan Mountains. The species richness was affected by a variety of environmental factors. The variables representing energy availability and climate stability had stronger explanatory power, especially the annual mean temperature (BIO1) and the mean temperature of warmest quarter (BIO10). In contrast, water availability and habitat heterogeneity have relatively little correlation with species richness

Transcriptional Memory in Taraxacum mongolicum in Response to Long-Term Different Grazing Intensities

Grazing, as an important land use method in grassland, has a significant impact on the morphological and physiological traits of plants. However, little is known about how the molecular mechanism of plant responds to different grazing intensities. Here, we investigated the response of Taraxacum mongolicum to light grazing and heavy grazing intensities in comparison with a non-grazing control. Using de novo transcriptome assembly, T. mongolicum leaves were compared for the expression of the different genes under different grazing intensities in natural grassland. In total, 194,253 transcripts were de novo assembled and comprised in nine leaf tissues. Among them, 11,134 and 9058 genes were differentially expressed in light grazing and heavy grazing grassland separately, with 5867 genes that were identified as co-expression genes in two grazing treatments. The Nr, SwissProt, String, GO, KEGG, and COG analyses by BLASTx searches were performed to determine and further understand the biological functions of those differentially expressed genes (DEGs). Analysis of the expression patterns of 10 DEGs by quantitative real-time RT-PCR (qRT-PCR) confirmed the accuracy of the RNA-Seq results. Based on a comparative transcriptome analysis, the most significant transcriptomic changes that were observed under grazing intensity were related to plant hormone and signal transduction pathways, carbohydrate and secondary metabolism, and photosynthesis. In addition, heavy grazing resulted in a stronger transcriptomic response compared with light grazing through increasing the of the secondary metabolism- and photosynthesis-related genes. These changes in key pathways and related genes suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of T. mongolicum. Our findings provide important clues for improving grassland use and protection and understanding the molecular mechanisms of plant response to grazing

Biochar produced at high temperature mitigates N2O emission and promotes nitrogen retention in subtropical forest soils

Abstract Biochar is produced by burning biomass under oxygen‐limited conditions, and it has been widely used as a soil amendment to improve soil functions such as nutrient retention. However, whether the impact of biochar application on soil nitrogen (N) transformation and N2O emission varies with the pyrolysis temperature remains unclear, especially in different forest types in subtropical regions. In this study, a 60‐day laboratory incubation experiment was conducted to evaluate the impact of biochar with different pyrolysis temperatures (300°C [BC300], 500°C [BC500], and 800°C [BC800]) on net N transformation rates and N2O emission in soils collected from Castanopsis kawakamii dominated natural forest (NF) and Chinese fir (Cunninghamia lanceolate, CF) plantation in subtropical China. The results showed that the application of biochar significantly increased soil ammonium (NH4+) content (p < 0.001) but reduced nitrate (NO3−) content (p < 0.001) compared with the control. The soil NH4+ content of the BC800 treatment was significantly higher than that of other treatments (p < 0.001). Biochar application significantly reduced soil net N mineralization (NRmin) and nitrification (NRnit) rate (p < 0.001), but increased net ammonification (NRamm) rate (p < 0.001). The application of biochar led to a remarkable decrease in cumulative N2O emission compared to the control (p < 0.001). In particular, soils treated with high‐temperature biochar emitted significantly lower N2O compared to other treatments (p < 0.001). The partial least squares path model demonstrated that biochar influenced N2O emission through a direct effect in NF soil and an indirect effect in CF soil. This study highlights the distinct role of biochar, particularly that produced under high pyrolysis temperatures as a soil amendment to mitigate N2O emission and promote N retention in both subtropical natural and planted forests

Exploring the Species Richness Pattern and Areas of Endemism of Tenebrionidae (Coleoptera) in Xinjiang, China

Species richness and areas of endemicity (AOE) are the basis of biogeography, which is of great significance for understanding the evolution of species and making conservation plans. The present study aimed to investigate the species richness pattern and AOEs of Tenebrionidae in Xinjiang, China. We collected information on the geographical distribution of 556 species from several sources and obtained 2226 distribution records for the analyses. The AOEs were detected using the parsimony analysis of endemicity (PAE) and endemicity analysis (EA) at 0.5°, 1°, and 1.5° grid sizes, respectively. A total of six AOEs were found, including three mountain ranges (Altai Mountains, Tianshan Mountains, and Kunlun Mountains) and one basin (Junggar Basin), which was largely congruent with the species richness pattern. The results indicated that the complex terrain and stable climate in the mountainous area played an important role in the formation of tenebrionid species diversity and their endemic areas in Xinjiang

Melatonin Regulates Reactive Oxygen Species Metabolism to Induce Resistance to Black Spot of Postharvest Apricot Fruit

Xinjiang 'Saimaiti' apricot fruit were used as the material to study the inhibitory effects of postharvest treatment with melatonin on black spot and its influence on reactive oxygen species metabolism. Fruit were vacuum impregnated into different concentrations of melatonin (50, 100, 200 μmol/L) under pressure of 0.05 MPa for 2 min, then atmospheric pressure was restored, and the fruit was maintained in the same solution for 8 min. The distilled water treatment was used as blank control. After naturally drying, the fruit were refrigerated (0±1℃, RH 90%~95%) for 48 h. After that, apricot fruits were inoculated with Alternaria alternata and stored at the same conditions.The lesion diameter and disease incidence of apricot fruit inoculated with A.alternata, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and superoxide anion radical (O2−·) production rate, cell membrane permeability, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents were measured regularly. Results showed that compared with the control group, different concentrations of exogenous melatonin treatment significantly delayed the increase of apricot fruit morbidity and inhibited the increase of apricot fruit the lesion diameter. At the end of storage, the spot diameters of apricot fruit were significantly lower in the 50, 100, and 200 μmol/L melatonin-treated groups by 11.92%, 28.49%, and 19.67% (P<0.05) than in the control group. And 100 μmol/L melatonin had the best effect on black spot diseases of apricot fruits. In the early stage of storage, 100 μmol/L exogenous melatonin treatment increased the apricot fruit superoxide dismutase activity, decreased the rate of superoxide anion, inhibited catalase activity, and induced rapid accumulation of H2O2 in apricot fruit. At the end of storage, catalase and peroxidase activities in the 100 μmol/L melatonin-treated group were 39.13% and 78.91% higher than those in control, respectively (P<0.05). The H2O2 content of apricot fruit in the 100 μmol/L melatonin-treated group was significantly lower than that in the control group by 19.74% (P<0.05), which reduced the accumulation of H2O2 in apricot fruit, and delayed the rise of cell membrane permeability and malondialdehyde content. These findings suggested that melatonin could regulate reactive oxygen species metabolism to induce resistance to black spot in postharvest apricot fruit