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Exploring social-ecological system resilience in South China Karst:Quantification,interaction and policy implication
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作者 tiantian chen Yuxi Wang Li Peng 《Geography and Sustainability》 CSCD 2024年第2期289-301,共13页
China’s Grain to Green Program(GTGP),which is one of the largest payments for ecosystem services(PES)in the world,has made significant ecological improvements to the environment.However,current understanding of its o... China’s Grain to Green Program(GTGP),which is one of the largest payments for ecosystem services(PES)in the world,has made significant ecological improvements to the environment.However,current understanding of its outcomes on the social-ecological system(SES)remains limited.Therefore,taking the South China Karst as an example,a SES resilience evaluation index system was constructed followed by an exploratory spatial analysis,root mean square error,and Self-Organizing Feature Map to clarify the spatiotemporal changes and relationship of SES resilience,achieve the zoning of SES resilience and provide restoration measures.The results showed an upward trend in social resilience from 2000 to 2020,especially its subsystem of social development.Regional ecological resilience was stable,owing to a slightly declined ecosystem services and increased landscape pattern.Spatially,nearly half of the counties exhibited a distribution mismatch in SES resilience.There was an obvious inverted U-shaped relationship of SES resilience,indicating a clear threshold effect,and the constraint relation-ship of SES resilience eased over time,demonstrating the effectiveness of the ecological restoration program.GTGP played a positive role in reducing regional SES trade-off,but this positive effect was limited,reflecting the limitations of overemphasizing the conversion from farmland to forest and grassland.Regional SES resilience can be divided into four clusters,which were the key optimization zone for social system,the SES resilience safety zone,the key restoration zone for SES resilience,and the key optimization zone for ecological system.Adaptive adjustments for the GTGP in these zones should be taken to achieve maximum SES benefits in the future. 展开更多
关键词 SES resilience Trade-off CLUSTERING GTGP South China Karst
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A Review of Artificial Waterfalls in Gardens
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作者 Ni Lan tiantian chen +1 位作者 Qiushuang Fan Shiyu Mi 《Journal of World Architecture》 2024年第1期31-34,共4页
When artificial waterfalls are built in gardens,leaves from trees or vegetation often fall into the water storage pool and block the pipelines,requiring regular cleaning of pipelines.This not only increases the manpow... When artificial waterfalls are built in gardens,leaves from trees or vegetation often fall into the water storage pool and block the pipelines,requiring regular cleaning of pipelines.This not only increases the manpower needed for maintenance but also disrupts the use of the waterfalls.Therefore,it is necessary to design a new type of artificial waterfall that is suitable for gardens.The waterfall should incorporate features that make cleaning easier,including filter plates and water funnels to prevent clogging caused by fallen leaves and debris. 展开更多
关键词 INTELLIGENCE Efficiency improvement Transportation pipeline Technical artificial waterfall
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Increased artemisinin production by promoting glandular secretory trichome formation and reconstructing the artemisinin biosynthetic pathway in Artemisia annua 被引量:1
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作者 Yongpeng Li Wei Qin +10 位作者 Hang Liu tiantian chen Xin Yan Weizhi He Bowen Peng Jin Shao Xueqing Fu Ling Li Xiaolong Hao Guoyin Kai Kexuan Tang 《Horticulture Research》 SCIE CSCD 2023年第5期275-277,共3页
Dear Editor,Artemisinin,which has potent antimalarial properties,is a sesquiterpene endoperoxide originally isolated from the traditional Chinese medicinal plant Artemisia annua.However,the artemisinin content in wild... Dear Editor,Artemisinin,which has potent antimalarial properties,is a sesquiterpene endoperoxide originally isolated from the traditional Chinese medicinal plant Artemisia annua.However,the artemisinin content in wild-type(WT)A.annua is low(1-10 mg/g dry weight),leading to its erratic supply and price fluctuations[1]. 展开更多
关键词 PRICE annua originally
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QTL mapping for pre-harvest sprouting in a recombinant inbred line population of elite wheat varieties Zhongmai 578 and Jimai 22
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作者 Rabiu Sani Shawai Dan Liu +7 位作者 Lingli Li tiantian chen Ming Li Shuanghe Cao Xianchun Xia Jindong Liu Zhonghu He Yong Zhang 《The Crop Journal》 SCIE CSCD 2023年第3期863-869,共7页
Pre-harvest sprouting(PHS)is one of the serious global issues in wheat production.Identification of quantitative trait loci(QTL)and closely-linked markers is greatly helpful for wheat improvement.In the present study,... Pre-harvest sprouting(PHS)is one of the serious global issues in wheat production.Identification of quantitative trait loci(QTL)and closely-linked markers is greatly helpful for wheat improvement.In the present study,a recombinant inbred line(RIL)population derived from the cross of Zhongmai 578(ZM578)/Jimai 22(JM22)and parents were phenotyped in five environments and genotyped by the wheat 50 K single-nucleotide polymorphism(SNP)array.Two QTL of germination index(GI),QGI.caas-3A and QGI.caas-5A,were detected,explaining 4.33%–5.58%and 4.43%–8.02%of the phenotypic variances,respectively.The resistant effect of QGI.caas-3A was contributed by JM22,whereas that of QGI.caas.5A was from ZM578.The two QTL did not correspond to any previously identified genes or genetic loci for PHSrelated traits according to their locations in the Chinese Spring reference genome,indicating that they are likely to be new loci for PHS resistance.Four kompetitive allele-specific PCR(KASP)markers K_AX-109605367and K_AX-179559687 flanking QGI.caas-3A,and K_AX-111258240 and K_AX-109402944flanking QGI.caas-5A,were developed and validated in a natural population of 100 wheat cultivars.The distribution frequency of resistance alleles at Qphs.caas-3A and Qphs.caas-5A loci were 82.7%and57.1%,respectively,in the natural population.These findings provide new QTL and tightly linked KASP markers for improvement of PHS resistance in wheat. 展开更多
关键词 Pre-harvest sprouting Germination index Quantitative trait loci KASP marker Triticum aestivum L.
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AaWRKY17, a positive regulator of artemisinin biosynthesis, is involved in resistance to Pseudomonas syringae in Artemisia annua 被引量:4
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作者 tiantian chen Yongpeng Li +12 位作者 Lihui Xie Xiaolong Hao Hang Liu Wei Qin chen Wang Xin Yan Kuanyu Wu-Zhang Xinghao Yao Bowen Peng Yaojie Zhang Xueqing Fu Ling Li Kexuan Tang 《Horticulture Research》 SCIE 2021年第1期2926-2936,共11页
Artemisia annua,a traditional Chinese medicinal plant,remains the only plant source for artemisinin production,yet few genes have been identified to be involved in both the response to biotic stresses,such as pathogen... Artemisia annua,a traditional Chinese medicinal plant,remains the only plant source for artemisinin production,yet few genes have been identified to be involved in both the response to biotic stresses,such as pathogens,and artemisinin biosynthesis.Here,we isolated and identified the WRKY transcription factor(TF)AaWRKY17,which could significantly increase the artemisinin content and resistance to Pseudomonas syringae in A.annua.Yeast one-hybrid(Y1H),dual-luciferase(dual-LUC),and electrophoretic mobility shift assay(EMSA)results showed that AaWRKY17 directly bound to the W-box motifs in the promoter region of the artemisinin biosynthetic pathway gene amorpha-4,11-diene synthase(ADS)and promoted its expression.Real-time quantitative PCR(RT-qPCR)analysis revealed that the transcript levels of two defense marker genes,Pathogenesis-Related 5(PR5)and NDR1/HIN1-LIKE 10(NHL10),were greatly increased in AaWRKY17-overexpressing transgenic A.annua plants.Additionally,overexpression of AaWRKY17 in A.annua resulted in decreased susceptibility to P.syringae.These results indicated that AaWRKY17 acted as a positive regulator in response to P.syringae infection.Together,our findings demonstrated that the novel WRKY transcription factor AaWRKY17 could potentially be used in transgenic breeding to improve the content of artemisinin and pathogen tolerance in A.annua. 展开更多
关键词 EXPRESSION AaW RESISTANCE
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Diversity and seasonal variation of marine phytoplankton in Jiaozhou Bay, China revealed by morphological observation and metabarcoding 被引量:1
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作者 tiantian chen Yingxin ZHANG +3 位作者 Shuqun SONG Yun LIU Xiaoxia SUN Caiwen LI 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2022年第2期577-591,共15页
Phytoplankton are central components of marine environments,and are major players in the production and respiration budgeting.However,their diversity and distribution patterns are still poorly understood due largely t... Phytoplankton are central components of marine environments,and are major players in the production and respiration budgeting.However,their diversity and distribution patterns are still poorly understood due largely to their small sizes and inconspicuous morphology that have been determined via the application of traditional morphology methods over the past two decades.To better understand the composition and diversity of phytoplankton in Jiaozhou Bay,China,seasonal sampling was carried out in 2019 and samples were analyzed with morphological observations and high-throughput sequencing,from which obvious seasonal variations in phytoplankton composition and proportional abundances were uncovered.Metabarcoding revealed far more diversity and species richness of phytoplankton than morphological observations,especially with respect to dinofl agellates.Diatoms were the most dominant phytoplankton group throughout the year,of which Thalassionema and Skeletonema were co-dominant in the bay.Parasitic dinofl agellates(e.g.Amoebophrya),which is often overlooked in the morphological observations,were in dominance and high diversity in the metabarcoding dataset,thus more attention should be paid to exploring the potential role of parasitic dinofl agellates.Temperature,chlorophyll a,and nutrient levels were the main infl uential factors on the distribution of phytoplankton.This study provided a comprehensive morphological and molecular description of phytoplankton and clearly demonstrated the importance of molecular technology in exploring phytoplankton communities.More-widespread use of molecular technology will facilitate deeper understanding of the ecological importance of the diff erent species. 展开更多
关键词 PHYTOPLANKTON high-throughput sequencing DIVERSITY morphological observation Jiaozhou Bay
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Specular Detection and Removal for a Grayscale Image Based on the Markov Random Field
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作者 Fang Yin tiantian chen +2 位作者 Rui Wu Ziru Fu Xiaoyang Yu 《国际计算机前沿大会会议论文集》 2016年第1期165-167,共3页
Specular detection and removal has been a hot topic in the field of computer vision. Most of the existing methods are mainly for color images, but grayscale images are widely used. For a single grayscale image with on... Specular detection and removal has been a hot topic in the field of computer vision. Most of the existing methods are mainly for color images, but grayscale images are widely used. For a single grayscale image with only intensity information, highlight detection and removal becomes a difficult issue. To solve this problem, the single grayscale image highlight detection and removal method based on Markov random field is presented. Each reflection component modeling is estimated by geometric relation of surface normal in diffuse and specular reflection component in the framework of Markov random field. Their maximum a posteriori estimation is calculated under Bayesian formula and highlight area is detected. Finally, image inpainting method based on the BSCB model removes highlights. Experiment reveals that this method can effectively detect grayscale image specular reflection area, improve highlight areas the repair rate. 展开更多
关键词 COMPUTER VISION Specular DETECTION MARKOV RANDOM field
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Chemotactic nanomotor for multimodal combined therapy of glioblastoma
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作者 Ting Li Lin chen +8 位作者 Yunxin Xue Xiangyu Xiao Wenjun Dai Kaiyuan Tan tiantian chen Yingfang Tao Chun Mao Jian Shen Mimi Wan 《Science China Chemistry》 SCIE EI CAS CSCD 2024年第4期1277-1288,共12页
Glioblastoma(GBM) is the most aggressive malignant brain tumor. Due to the infiltration and heterogeneity of GBM, the obstruction of the blood-brain barrier(BBB) and the unique immunosuppressive mechanism, it is hard ... Glioblastoma(GBM) is the most aggressive malignant brain tumor. Due to the infiltration and heterogeneity of GBM, the obstruction of the blood-brain barrier(BBB) and the unique immunosuppressive mechanism, it is hard to achieve significant effects of GBM treatment. Here, a kind of chemotactic nanomotor that loaded with glucose oxidase(GOx) and carboxylated cisplatin(Pt(IV)) prodrug on the L-arginine-derived polymer is proposed. The nanomotors are driven by catalysis of glucose decomposition and the positive chemotaxis towards the GBM microenvironment where inducible nitric oxide synthase and reactive oxygen species are highly expressed. This facilitates the BBB crossing and GBM targeting of the nanomotors. In addition, the released nitric oxide(NO) during propulsion as well as the loaded GOx and Pt(IV) can exert combined NO/starvation/chemotherapy. Meanwhile, it is able to induce and enhance the immune response through multiple pathways, thus better coping with the complexities of GBM treatment. 展开更多
关键词 CHEMOTAXIS combined therapy GLIOBLASTOMA NANOMOTORS
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产前超声诊断持续性卵黄动脉一例 被引量:1
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作者 龚菁菁 周毓青 +2 位作者 陈田田 何碧媛 孙红 《中华医学超声杂志(电子版)》 CSCD 北大核心 2023年第1期136-138,共3页
患者女性,29岁,孕4产1,2019年7月因异位妊娠行左侧输卵管切除手术。本次受孕末次月经时间为2021年1月15日,停经40d自测尿人绒毛膜促性腺激素阳性。2021年4月20日行早孕筛查检查,估测孕周12周0天,颈项透明层厚度1.7mm,股骨长6.3mm(图1);2... 患者女性,29岁,孕4产1,2019年7月因异位妊娠行左侧输卵管切除手术。本次受孕末次月经时间为2021年1月15日,停经40d自测尿人绒毛膜促性腺激素阳性。2021年4月20日行早孕筛查检查,估测孕周12周0天,颈项透明层厚度1.7mm,股骨长6.3mm(图1);2021年5月19日孕16周行常规超声检查时发现胎儿膀胱横断面双侧脐动脉未显示,股骨长15mm(图2) 展开更多
关键词 产前超声诊断 末次月经时间 颈项透明层厚度 常规超声检查 人绒毛膜促性腺激素 股骨长 脐动脉 异位妊娠
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Time-lagged and cumulative effects of drought and anthropogenic activities on China's vegetation greening from 1990 to 2018 被引量:3
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作者 Yuxi Wang tiantian chen +1 位作者 Qiang Wang Li Peng 《International Journal of Digital Earth》 SCIE EI 2023年第1期2233-2258,共26页
Previous studies have confirmed the time-lagged and cumulative effects of drought and anthropogenic activities on vegetation growth,but these studies focus on the time-lagged effect of drought and are poorly known how... Previous studies have confirmed the time-lagged and cumulative effects of drought and anthropogenic activities on vegetation growth,but these studies focus on the time-lagged effect of drought and are poorly known how vegetation productivity responds to anthropogenic activities.Here,based on the reconstructed Normalized Difference Vegetation Index,the Standardized Precipitation Evapotranspiration Index and land use degree comprehensive index,we diagnosed the spatiotemporal pattern of vegetation and drought,investigated time-lagged and cumulative effects of drought and anthropogenic activities over China through the month where the maximum correlation coefficient occurred.It revealed that the browning trend of 32.21%of vegetated lands was covered by overall greening,especially northwestern China.Drought intensified with a rate of 0.0014/year.in 66.41%and 54.57%of the vegetated lands had time-lagged and cumulative response to drought,with a shorter timescales of 1–4 months,indicating the higher sensitivity of vegetation growth to drought.There was a U-shaped relationship between moisture conditions and vegetation response time.49.9%of China’s vegetation showed time-lagged effects to anthropogenic activities,with a longer timescales of 6–10 years,demonstrating that anthropogenic activities triggered ecological changes but vegetation ecosystems cannot keep pace.The accumulated and time-lagged years declined with increased land use intensity. 展开更多
关键词 Vegetation greening time-lagged effect cumulative effect DROUGHT anthropogenic activities
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Conductive Ni3(HITP)2 MOFs thin films for flexible transparent supercapacitors with high rate capability 被引量:4
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作者 Weiwei Zhao tiantian chen +7 位作者 Weikang Wang Beibei Jin Jiali Peng Shuaihang Bi Mengyue Jiang Shujuan Liu Qiang Zhao Wei Huang 《Science Bulletin》 SCIE EI CAS CSCD 2020年第21期1803-1811,M0003,M0004,共11页
The flexible transparent supercapacitors have been considered as one of the key energy-storage components to power the smart portable electronic devices.However,it is still a challenge to explore flexible transparent ... The flexible transparent supercapacitors have been considered as one of the key energy-storage components to power the smart portable electronic devices.However,it is still a challenge to explore flexible transparent capacitive electrodes with high rate capability.Herein,conductive Ni3(HITP)2(HITP=2,3,6,7,10,11-hexaiminotriphenylene)thin films are adopted as capacitive electrodes in flexible transparent supercapacitors.The Ni3(HITP)2 electrode possesses the excellent optoelectronic property with optical transmittance(T)of 78.4%and sheet resistance(Rs)of 51.3Ωsq-1,remarkable areal capacitance(CA)of 1.63 mF cm^-2and highest scan rate up to 5000 mV s-1.The asymmetric Ni3(HITP)2//PEDOT:PSS supercapacitor(T=61%)yields a high CA of 1.06 mF cm^-2at 3μA cm-2,which maintains 77.4%as the current density increases by 50 folds.The remarkable rate capability is ascribed to the collaborative advantages of low diffusion resistance and high ion accessibility,resulting from the intrinsic conductivity,short oriented pores and large specific areas of Ni3(HITP)2 films. 展开更多
关键词 Conductive film Metal-organic frameworks Collaborative advantages Flexible transparent supercapacitors High rate capability
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Influences of Sense of Place on Farming Households' Relocation Willingness in Areas Threatened by Geological Disasters:Evidence from China 被引量:3
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作者 Dingde Xu Li Peng +3 位作者 Shaoquan Liu Chunjiang Su Xuxi Wang tiantian chen 《International Journal of Disaster Risk Science》 SCIE CSCD 2017年第1期16-32,共17页
Scholars from environmental psychology,geography, disaster science, and sociology have recently focused attention on evacuation and relocation behaviors and influencing factors in hazard-threatened areas. However, exi... Scholars from environmental psychology,geography, disaster science, and sociology have recently focused attention on evacuation and relocation behaviors and influencing factors in hazard-threatened areas. However, existing studies are mainly focused on developed countries and the influence of individual characteristics,household characteristics, and the perception of risk of urban households on evacuation and relocation behaviors.Few studies examine developing countries and the influence of farmers' sense of place in geological hazardthreatened areas. Using statistics of farming households in an area threatened by landslides, this is a pilot study to explore the relationship of sense of place to the relocation willingness of farming households while controlling for other variables. The results show that:(1) Households with higher scores of place identity and place dependence are less willing to relocate, whereas place attachment has no significant relationship to household relocation willingness;(2) Risk perception dimensions, including probability,threat, and controllability have a significant relationship to household relocation willingness, while worry and fear of the unknown have no significant relationship;(3) Household characteristics, including income, whether a household has experienced economic loss from landslides, and social support are significantly correlated with household relocation willingness, while gender, age, experience, distance to hazard sites, size of household, children, older people, and housing material are not. The results for information and education are not robust. This study contributes to the current literature by improving the understanding of the relationship of sense of place to the relocation willingness of farming households in villages threatened by geological disasters in rural China. 展开更多
关键词 China Farming households Relocation willingness Risk perception Sense of place Three Gorges Reservoir area
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Ultrathin Ti_(3)C_(2) nanowires derived from multi-layered bulks for high-performance hydrogen evolution reaction 被引量:2
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作者 Weiwei Zhao Beibei Jin +6 位作者 Longlu Wang chengbo Ding Mengyue Jiang tiantian chen Shuaihang Bi Shujuan Liu Qiang Zhao 《Chinese Chemical Letters》 SCIE CAS CSCD 2022年第1期557-561,共5页
One-dimensional ultrathin nanowires(NWs)offer a great deal of promising properties for electrochemical energy storage and conversion due to their nanoscale confinement effect and high surface-to-volume ratios.It is hi... One-dimensional ultrathin nanowires(NWs)offer a great deal of promising properties for electrochemical energy storage and conversion due to their nanoscale confinement effect and high surface-to-volume ratios.It is highly desirable to precisely design and synthesize ultrathin Ti_(3)C_(2)NWs in the aspect of size,crystalline structure and composition.Here,we report a simple alkalization strategy to design the ultrathin Ti_(3)C_(2)NWs for hydrogen evolution reaction(HER)by modulating the surface-active sites.The design principle can well improve the amount of the defect sites and ion accessibility to increase the interactions between Ti_(3)C_(2)NWs and H^(*).The optimized Ti_(3)C_(2)NWs achieve an overpotential of 476 mV at the current density of 10 mA/cm^(2)and a Tafel slope of 129 mV/dec for HER catalysis,which are superior to that of Ti_(3)C_(2)nanosheets and m-Ti_(3)C_(2).It paves an avenue for the rational transformation of MXene bulks to one-dimensional NWs catalysts for HER. 展开更多
关键词 MXene Ti_(3)C_(2)nanowires Ultrathin films Chemical transformation Hydrogen evolution reaction
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Development and testing of an image transformer for explainable autonomous driving systems 被引量:2
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作者 Jiqian Dong Sikai chen +2 位作者 Mohammad Miralinaghi tiantian chen Samuel Labi 《Journal of Intelligent and Connected Vehicles》 EI 2022年第3期235-249,共15页
Purpose–Perception has been identified as the main cause underlying most autonomous vehicle related accidents.As the key technology in perception,deep learning(DL)based computer vision models are generally considered... Purpose–Perception has been identified as the main cause underlying most autonomous vehicle related accidents.As the key technology in perception,deep learning(DL)based computer vision models are generally considered to be black boxes due to poor interpretability.These have exacerbated user distrust and further forestalled their widespread deployment in practical usage.This paper aims to develop explainable DL models for autonomous driving by jointly predicting potential driving actions with corresponding explanations.The explainable DL models can not only boost user trust in autonomy but also serve as a diagnostic approach to identify any model deficiencies or limitations during the system development phase.Design/methodology/approach–This paper proposes an explainable end-to-end autonomous driving system based on“Transformer,”a state-ofthe-art self-attention(SA)based model.The model maps visual features from images collected by onboard cameras to guide potential driving actions with corresponding explanations,and aims to achieve soft attention over the image’s global features.Findings–The results demonstrate the efficacy of the proposed model as it exhibits superior performance(in terms of correct prediction of actions and explanations)compared to the benchmark model by a significant margin with much lower computational cost on a public data set(BDD-OIA).From the ablation studies,the proposed SA module also outperforms other attention mechanisms in feature fusion and can generate meaningful representations for downstream prediction.Originality/value–In the contexts of situational awareness and driver assistance,the proposed model can perform as a driving alarm system for both human-driven vehicles and autonomous vehicles because it is capable of quickly understanding/characterizing the environment and identifying any infeasible driving actions.In addition,the extra explanation head of the proposed model provides an extra channel for sanity checks to guarantee that the model learns the ideal causal relationships.This provision is critical in the development of autonomous systems. 展开更多
关键词 Explainable deep learning Computer vision TRANSFORMER Autonomous driving
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A mitochondria-targeted fluorescent probe for ratiometric detection of hypochlorite in living cells 被引量:1
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作者 Yahui chen Tingwen Wei +6 位作者 Zhijie Zhang Wei Zhang Jing Lv tiantian chen Bo Chi Fang Wang Xiaoqiang chen 《Chinese Chemical Letters》 SCIE CAS CSCD 2017年第10期1957-1960,共4页
Hypochlorous acid(HOCl) plays a vital role in many physiological and pathological processes as one of reactive oxygen species(ROS). Developing highly sensitive and selective methods for HOCl detection is of signif... Hypochlorous acid(HOCl) plays a vital role in many physiological and pathological processes as one of reactive oxygen species(ROS). Developing highly sensitive and selective methods for HOCl detection is of significant interest. In this work, we developed a benzothiazole based probe 1 for ratiometric fluorescence detection of hypochlorite in living cells. The probe can detect HOCl with high selectivity, fast response(within 30 s) as well as low detection limit(0.18 mmol/L). Fluorescence co-localization studies demonstrated that probe 1 was a mitochondria-targeted fluorescent probe. Furthermore, confocal fluorescence images of He La cell indicated that probe 1 could be used for monitoring intracellular HOCl in living cells. Finally, test strips experiment suggests that the probe 1 can detect the hypochlorous acid in tap water accompanied by remarkable color change. 展开更多
关键词 Fluorescent probe Mitochondria-targeted Ratiometric detection Hypochlorous acid ROS
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Earth’s thermal cycles and major geological events 被引量:1
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作者 Chun’an TANG tiantian chen Bin GONG 《Science China Earth Sciences》 SCIE EI CSCD 2021年第10期1821-1824,共4页
In the study of global change since the 1980s,a new field of Earth system science has been established(Wang et al.,2019).However,compared with the rapid development of geoscience technology and the numerous associated... In the study of global change since the 1980s,a new field of Earth system science has been established(Wang et al.,2019).However,compared with the rapid development of geoscience technology and the numerous associated achievements,the theoretical progress and breakthrough of core issues in geosciences have not advanced as much as expected.In the 1960s,based on the continental drift hypothesis of an individual scientist named Alfred L.Wegener and the seafloor spreading hypothesis based on the crude trench exploration by the US Navy,the theory of plate tectonics was proposed and has come to be regarded as a revolution in Earth sciences.Since then,despite major technological advances,massive investment of human effort and equipment all over the world,and the implementation of numerous geoscientist teams and international cooperation projects,the development of geotectonic science in recent decades has remained in a phase of careful verification based on the theory of plate tectonics.In other words,most studies are still being performed to verify the models and hypotheses proposed by predecessors,mainly focusing on local and regional geology and lacking high-level and universal theoretical innovation and newly proposed major scientific problems(Ren et al.,2021).Earth sciences,now armed with new technology,should attempt to explore deeper basic issues,such as the origin of the Earth,the origin of life,the development and decline of ice ages,climate change,and the relationship between life,climate and the Earth’s interior. 展开更多
关键词 EARTH GEOLOGY BREAKTHROUGH
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Numerical analysis of dynamic stability of falling maple samaras
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作者 tiantian chen Shilong Lan 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2022年第12期45-57,共13页
Due to autorotation,samaras can fly efficiently and stably to be dispersed over a great distance under various weather conditions.Here,we provide a quantitative analysis of the dynamic stability of free-falling maple ... Due to autorotation,samaras can fly efficiently and stably to be dispersed over a great distance under various weather conditions.Here,we provide a quantitative analysis of the dynamic stability of free-falling maple samara(Acer grosseri Pax)and verify whether they are dynamically stable as observed.Morphological and kinematic parameters were obtained based on the existing experimental data of the maple seed.Then the linearized equations of motion were derived,and the stability derivatives were calculated by a computational fluid dynamics method.The techniques of eigenvalue and eigenvector analysis were also used to examine the stability characteristics.It is found that there are five natural modes of motion of the maple seed:one stable oscillatory mode,one fast subsidence mode,one slow subsidence mode,and two neutral stable modes.The two neutral modes are manifested as the seed moving horizontally at a low speed under disturbance.Results show that the maple seed has dynamic stability in sustaining the steady autorotation and descent,exhibiting a minor horizontal motion when disturbed.These findings can beapplied to biomimetic aircraft. 展开更多
关键词 Dynamic stability Maple samara Numerical simulation Natural modes of motion
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Construction of quaternary carbon centers by KOtBu-catalyzed α-homoallylic alkylation of lactams with 1,3-dienes
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作者 Shang Wang Yunfei Xiang +2 位作者 tiantian chen Xiang Wu Dong Xing 《Organic Chemistry Frontiers》 SCIE EI 2022年第6期1642-1648,共7页
We report a KOtBu-catalyzed α-homoallylic alkylation of lactams with 1,3-dienes. With this transitionmetal-free and atom-economical protocol, a variety of α-homoallylic alkylated lactams bearingα-quaternary carbon ... We report a KOtBu-catalyzed α-homoallylic alkylation of lactams with 1,3-dienes. With this transitionmetal-free and atom-economical protocol, a variety of α-homoallylic alkylated lactams bearingα-quaternary carbon centers were formed in a 2,1-addition manner with excellent regioselectivity. Acation–π interaction between the in situ-generated potassium enolate and the diene is proposed to play akey role in accelerating this transformation. 展开更多
关键词 QUATERNARY CENTERS CATALYZED
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