“可控自组装体系及其功能化”重大研究计划取得系列重要研究成果

2005年美国科学(Science)杂志在纪念该刊创办125周年之际,把"我们能推动化学自组装走多远?"列为未来最具挑战性的25个科学问题之一,受到世界各国科学家的广泛关注和重视。"十一五"期间,国家自然科学基金委员会组织多领域的科学家充分讨论和酝酿从而提出了"可控自组装体系及其功能化"重大研究计划。计划实施以来,我国科学家开拓和认识了多种新型弱相互作用力,发展了多种具有"中国标签"的新组装基元,建立了类似于有机"人名反应"的组装新方法,实现了多组分、多层次组装体的功能,构建了一批有重要科学意义和潜在实用价值的可控自组装体系,实现了从跟随到原创的跨越式发展,全面推动了我国化学可控自组装研究走向国际舞台的中心。本文介绍了"可控自组装体系及其功能化"重大研究计划的总体科学目标、总体布局和实施思路,以及该重大研究计划资助下取得的系列重要研究成果。

3D biofabrication for tubular tissue engineering

The therapeutic replacement of diseased tubular tissue is hindered by the availability and suitability of current donor, autologous and synthetically derived protheses. Artificially created, tissue engineered, constructs have the potential to alleviate these concerns with reduced autoimmune response, high anatomical accuracy, long-term patency and growth potential. The advent of 3D bioprinting technology has further supplemented the technological toolbox, opening up new biofabrication research opportunities and expanding the therapeutic potential of the field. In this review, we highlight the challenges facing those seeking to create artificial tubular tissue with its associated complex macro- and microscopic architecture. Current biofabrication approaches, including 3D printing techniques, are reviewed and future directions suggested.

Sonic hedgehog elevates N-myc gene expression in neural stem cells

Proliferation of neural stem cells is regulated by the secreted signaling molecule sonic hedgehog. In this study, neural stem cells were infected with recombinant adeno-associated virus expressing sonic hedgehog-N-enhanced green fluorescent protein. The results showed that overexpression of sonic hedgehog in neural stem cells induced the increased expression of Gill and N-myc, a target gene of sonic hedgehog. These findings suggest that N-myc is a direct downstream target of the sonic hedgehog signal pathway in neural stem cells. Sonic hedgehog and N-myc are important mediators of sonic hedgehog-induced proliferation of neural stem cells.

A Recommendation Approach Based on Bayesian Networks for Clone Refactor

Reusing code fragments by copying and pasting them with or without minor adaptation is a common activity in software development.As a result,software systems often contain sections of code that are very similar,called code clones.Code clones are beneficial in reducing software development costs and development risks.However,recent studies have indicated some negative impacts as a result.In order to effectively manage and utilize the clones,we design an approach for recommending refactoring clones based on a Bayesian network.Firstly,clone codes are detected from the source code.Secondly,the clones that need to be refactored are identified,and the static and evolutions features are extracted to build the feature database.Finally,the Bayesian network classifier is used for training and evaluating the classification results.Based on more than 640 refactor examples of five open source software developed in C,we observe a considerable enhancement.The results show that the accuracy of the approach is larger than 90%.We believe our approach will provide a more accurate and reasonable code refactoring and maintenance advice for software developers.

Trichoderma viride F7 improves peanut performances while remediating cadmium-contaminated soil with microplastics

Microplastics(MPs)and cadmium(Cd)in soil have serious negative impacts on plant growth.As a bioremediator,Trichoderma viride may modulate the impacts of MPs and/or Cd on plant growth and heavy metal uptake.In this study,T.viride F7 was used to treat Cd-contaminated soil with and without the presence of polylactic acid MPs to investigate its effects on peanut growth,Cd uptake efficiency,and soil properties.Results showed that F7 increased soil pH,dissolved organic carbon,cation exchange capacity,microbial biomass nitrogen,and microbial biomass carbon,which resulted in increases of 2.10%-19.83%in peanut biomass and mitigated the negative effects of MPs and Cd on peanut growth.Trichoderma viride F7 reduced the soil bioavailable Cd and plant Cd concentrations by 16.68%-34.20%and 5.37%-25.84%,respectively.Regression path analysis showed that F7 could improve peanut performances by altering soil properties and reducing peanut Cd concentrations in MP-Cd-contaminated soil.Soil fungal community analysis indicated that the microbial community was altered via F7 inoculation,which antagonized Fusarium and promoted peanut growth.This study reveals the mechanisms of F7 in mitigating Cd contamination in the soil with the presence of MPs,which provides new ideas for managing MP-heavy metal-contaminated soil and improving soil health.

The noise spectral characteristics and noise reduction schemes of screw air-source heat pump:A case study

The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in this research.The measurements revealed that the compressor is the main noise source of the heat pump,and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions,with multiple peaks at 63,250,and 1000 Hz.Then,a compressor sound insulation cover with broadband absorption was proposed,and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA.Third,we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation.The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump.The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ALa exhibit a U-shaped relation.For buildings of different heights,the optimal heights of noise barrier are proposed.The 5.5-meter is the optimal height of the sound barrier for single-story buildings.The conclusions can be applied to other building projects for heat pump noise reduction.

DNA-based nanostructures for RNA delivery

RNA-based therapeutics have emerged as a promising approach for the treatment of various diseases,including cancer,genetic disorders,and infectious diseases.However,the delivery of RNA molecules into target cells has been a major challenge due to their susceptibility to degradation and inefficient cellular uptake.To overcome these hurdles,DNA-based nano technology offers an unprecedented opportunity as a potential delivery platform for RNA therapeutics.Due to its excellent characteristics such as programmability and biocompatibility,these DNA-based nanostructures,composed of DNA molecules assembled into precise and programmable structures,have garnered significant attention as ideal building materials for protecting and delivering RNA payloads to the desired cellular destinations.In this review,we highlight the current progress in the design and application of three DNA-based nanostructures:DNA origami,lipid-nanoparticle(LNP)technology related to frame guided assembly(FGA),and DNA hydrogel for the delivery of RNA molecules.Their biomedical applications are briefly discussed and the challenges and future perspectives in this field are also highlighted.

Reinforcing DNA Supramolecular Hydrogel with Polymeric Multiple-Unit Linker

While supramolecular hydrogels have received growing interest due to their unique dynamic features,their relatively weak mechanical properties have largely limited their biomedical applications.In this study,we propose and demonstrate a strategy to reinforce the mechanical properties of supramolecular hydrogel by introducing polymeric multiple-unit linker(PMUL),which incorporates multiple supramolecular units into a polymeric backbone to crosslink supramolecular hydrogel.We demonstrated that PMUL can effectively improve the kinetic stability of supramolecular crosslinkers through multiple-unit interaction in a DNA supramolecular hydrogel model system,thus leading to higher mechanical strength.Meanwhile,the dynamic features of the supramolecular hydrogels have been well preserved,including shear-thinning,self-healing properties,and reversible thermal responsiveness.This strategy offers a simple but effective way for mechanical reinforcement of supramolecular hydrogels to construct novel biomaterials.

Nucleic Acid-Backboned Chimeric Polymers with Designable Physics and Chemistry

Comprehensive Summary The chain effect of polymer is the kernel of the precise synthesis of complex polymer compounds and the development of polymer science.Nucleic acids,a special type of polyester,can form supramolecular polymers via hydrogen bonds among corresponding bases.We focused on the precise control of polymer chains and proposed the concept of“nucleic acid-backboned chimeric polymers”(NCPs).There are three important elements of NCPs,namely nucleic acid backbone,side group and intra-/inter-chain weak interactions.In this review,we expound how to realize the construction of intelligent DNA structures through the regulation of these three elements and the applications of NCPs in various fields.

Long and Covalently Conjugated Branched DNA Structures for in Situ Gelation in Vivo

DNA nanotechnology has been widely employed for biomedical applications.However,most DNA nanomaterials rely on noncovalent complementary base pairing of short single-stranded DNA oligonucleotides.Herein,we describe a general strategy to construct a long and covalently conjugated branched DNA structure for fast and in situ gelation in vivo.In our design,a short and covalently conjugated branched DNA structure can normally be employed as the DNA primer in the terminal deoxynucleotidyl transferase-dependent enzymatic polymerization system.After enzymatic extension,the DNA aptamer-modified branched DNA structures with the sequences of poly T or poly A can immediately coassemble for in situ encapsulation of the target protein and tumor cell.The fast and in situ gelation system can function in a murine model of local tumor recurrence for targeting residual tumor cells to achieve long-term drug release for efficient tumor inhibition in vivo.This rationally developed DNA self-assembly strategy provides a new avenue for the development of multifunctional DNA nanomaterials.

Chemical strategies and biomedical applications of DNA hydrogels

1.Introduction Deoxyribonucleic acid(DNA)is a digital polymer that,in addition to being the carrier of genetic information in biological systems,can also act as building blocks for the fabrication of nanostructures.In accordance with the rapid development of DNA synthesis technologies,DNA has also been utilized as a fantastic type of brick for the construction of sophisticated supramolecular materials,especially DNA hydrogels.Due to its favorable biocompatibility and designable responsiveness,there have been emerging efforts to demonstrate the application of DNA hydrogels in biomedicine,with encouraging results.Here,we highlight the recent advances of chemical strategies and biomedical applications of DNA hydrogels.

Robot Application and Labor Force Employment:Substitution or Complementation?——An Empirical Analysis Based on the Data from 22 Economies

The rise of robotics has brought great uncertainty to the labor market.Based on the sectoral data from 22 economies during 2008-2019,this paper explores the impact of robot application on employment.The results show that,on the whole,robot application will have complementary effects on labor force employment,and the grouped regression by economic development level and demographic characteristics supports this conclusion,while the effect of robot application on labor force employment is significantly different by industry.Further research shows that the degree of robot use is the key factor that determines the effect of robots on employment,and the complementary effect is dominant in economies with low degree of robot application,and the subtitution effect is dominant in economies with high degree of robot application.In addition,obvious spillover effects are observed in robotic application.On the one hand,robot application will have a forward crowdingout effect and a reverse siphon effect,which drive the labor force moving from the primary industry to the secondary and tertiary industries.On the other hand,robot application will also have heterogeneous effects on the labor force employment of economies in the upstream and downstream position along the value chain through the transmission effect of the Global Value Chains(GVC).The conclusions of this paper provide some practical implications for the rational formulation of artificial intelligence plans in the context of“stabilizing employment”.

Improving pixel-based regional landslide susceptibility mapping

Regional landslide susceptibility mapping(LSM)is essential for risk mitigation.While deep learning algorithms are increasingly used in LSM,their extensive parameters and scarce labels(limited landslide records)pose training challenges.In contrast,classical statistical algorithms,with typically fewer parameters,are less likely to overfit,easier to train,and offer greater interpretability.Additionally,integrating physics-based and data-driven approaches can potentially improve LSM.This paper makes several contributions to enhance the practicality,interpretability,and cross-regional generalization ability of regional LSM models:(1)Two new hybrid models,composed of data-driven and physics-based modules,are proposed and compared.Hybrid ModelⅠcombines the infinite slope stability analysis(ISSA)with logistic regression,a classical statistical algorithm.Hybrid ModelⅡintegrates ISSA with a convolutional neural network,a representative of deep learning techniques.The physics-based module constructs a new explanatory factor with higher nonlinearity and reduces prediction uncertainty caused by incomplete landslide inventory by pre-selecting non-landslide samples.The data-driven module captures the rela-tion between explanatory factors and landslide inventory.(2)A step-wise deletion process is proposed to assess the importance of explanatory factors and identify the minimum necessary factors required to maintain satisfactory model performance.(3)Single-pixel and local-area samples are compared to understand the effect of pixel spatial neighborhood.(4)The impact of nonlinearity in data-driven algorithms on hybrid model performance is explored.Typical landslide-prone regions in the Three Gorges Reservoir,China,are used as the study area.The results show that,in the testing region,by using local-area samples to account for pixel spatial neighborhoods,Hybrid ModelⅠachieves roughly a 4.2%increase in the AUC.Furthermore,models with 30 m resolution land-cover data surpass those using 1000 m resolution data,showing a 5.5%improvement in AUC.The optimal set of explanatory factors includes elevation,land-cover type,and safety factor.These findings reveal the key elements to enhance regional LSM,offering valuable insights for LSM practices.

基于深度相机的特殊表面定位与修复

由于成像原理限制,深度相机无法获得非朗伯体高反射面和透明物质的真实深度值,造成模型缺失甚至重建失败。针对特殊表面的三维重建问题,提出一种定位特殊表面并优化位姿追踪的方法。通过累计零深度区和时序一致性约束优化对特殊表面进行定位。对深度数据置信度进行评估,并采用空间、时间两个维度上非平均的位姿计算方法来减小透明物质对位姿计算的影响。实验结果表明,在自然场景中,所提方法能够仅通过消费级相机采集的深度数据完成包含特殊表面的三维模型重建与修复,位姿追踪更加准确,模型精度更高。

Bioptical microcycles of laminated speleothems from China and their chronological significance

Interfaces of microlayers, in most stalagmites from China, consist of opaque and organic materials. Observed with microscope, the interfaces seem dark under transmitted light and luminiferous under reflected fluorescent light. Stalagmites in which the two optical characters are unified spatially would be most suitable for cross-dating use, and can play an important role in the study on speleochronology and speleoclimatology.

Stepwise advance of the Mu Us Desert since late Pliocene:Evidence from a red clay-loess record

Analyses of paleomagnetic polarity reversals, magnetic susceptibility and grain size on the red clay-loess sequence, about 280 m thick, at Jingbian show that this sequence contains most of the stratigraphic units recorded in the standard red clay-loess sections of the Loess Plateau over the past 3.5 Ma. Using sand particle percentage ( 】 63 μm%) of the eolian sequence as a proxy indicator of desert extent and aridity in the dust source regions, it is found that during the past 3.5 Ma, there are three important climatic events indicating the advance of the Mu Us Desert. The events occurred at about 2.6, 1.1 and 0.6 MaBP, respectively. The stepwise advance of the Mu Us Desert may be linked closely to increase in global ice volume and uplift of the Tibetan Plateau in the late Cenozoic.

Discrimination of two kinds of sedimentary laminae in maar lakes of China

Varved lacustrine sediments have been found from high latitude to low latitude, even in tropical area. Paleoenvironmental and paleoclimatic research has increasingly relied on the use of varved sediments to provide high-resolution geochronologies and climatic reconstructions. However, a special depositional environment is necessary for varve formation and preservation. Generally, varves can be found in the sediments of maar lakes because of their special geological and hydrological environment. The preliminary research showed that a few carbonate laminations are developed in the Huguangyan maar lake, south China. They are poorly developed and not annual laminations, and may be related to periodically drought. Diatomaceous laminations are found in the maar lakes in northeast China. Diatomaceous laminations with cyclic nature corresponding with seasonal diatom blooming are the credible natural clock.

Magnetic susceptibility properties of polluted soils

An investigation of magnetic properties using magnetic susceptibility ( x) andfrequency-dependent susceptibility (xfd) was conducted on representative modern pollutants, which include smelted slag dust, automobile exhaust dust and coal ash. Their magnetic susceptibility values are more than 500×108 m3/kg, and frequency-dependent susceptibility values less than 3%, indicating that ample ferrimagnetic and scanty superparamagnetic grains occurred in the studied pollutants. Similar to the artificially synthetic polluted soils, the industrially-polluted soils display a negative relationship between magnetic susceptibility and frequency-dependent susceptibility. However, the unpolluted soils, e.g. the Quaternary loess in the Chinese Loess Plateau, show a positive relationship between them. In this note, we propose a convenient and effective approach for identifying the polluted soils.

Climatic instability recorded by the mollusk assemblages from the late glacial loess deposits in China

The loess-paleosol sequence in China records abundant and valuable information on the global and regional climate changes. Biological record from the loess sequence is the most direct evidence on variation in pattern of paleo-atmospheric circulation and changes in winter and summer monsoon. A new record of climatic instability, which occurred in the Loess Plateau during the late glacial period, is presented. Through the study of terrestrial mollusks from three loess sequences, the authors intend to characterize the biological response process to rapid climate change and to learn the mechanisms driving the instable climate changes and the possible linkage in different regions. The result shows the striking consistent variability in the ratio records of three mollusk sequences of the late glacial, indicating apparent rapid climate fluctuations. Correlation of our three mollusk records with the oxygen isotopic records from Greenland ice cores and foraminiferal records from the Northeast Pacific Ocean

The worm-shaped veins in the red earth of South China——Pedological evidence for root traces of past forest

Field observation of the macromorphology and analyses of micromorphology and geochemistry were conducted to the worm-shaped veins (WSVs) in the red earth of South China. The WSVs exhibit outward features of root traces and contain the traces of stele that can be used as the definite evidence of root traces. Surrounding the worm-shaped veins there are some micro-features pressed by past root growth. Geochemical analyses indicate that the white part in the WSV was depleted in Fe content. These lines of evidence suggest the WSVs in the red earth of South China are the root traces of past forest.