“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。

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.

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.

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.

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.

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”.

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.

Improving the sensitivity for DNA sensing based on doubleanchored DNA modified gold nanoparticles

DNA modified nanoparticles(Au NPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the Au NPs forming a so called double-anchored Au NP sensor, and compared it with other conventional DNA modified Au NPs. The improved design exhibited higher assembly efficiency, and consequently increased its sensitivity to target DNA.

DNA-organic molecular amphiphiles:Synthesis,self-assembly,and hierarchical aggregates

With the development of deoxyribonucleic acid(DNA)nanotechnology,various DNA nanostructures and DNA devices have been constructed,which exhibit potential applications in material science and biomedicine.Taking advantage of the programmability and biocompatibility of DNA,novel building block to chemically functionalize DNA with hydrophobic organic molecules has attracted more and more attention.Driving by amphiphilicity,DNA-organic molecular amphiphiles have been demonstrated to self-assemble or further induce hierarchically assemblies,providing novel-specific properties.In this minireview,we summarize the recent progress of DNA organic molecular amphiphiles including their synthesis,self-assembly behavior in aqueous solution,and the amphiphilic self-assembly based on hierarchical DNA nano-structures.We further briefly discuss the perspective of the application of the DNA-organic molecular amphiphiles.

A climatic reversal at the last interglacial-last glacial transition recorded in the loess section at Zhaitang, Beijing

A weakly developed paleosol was identified at S1-L1 transition of the loess section of Zhaitang, Beijing. This paleosol may represent a climatic reversal which is associated with the strengthening in summer monsoon and correlated well with the climatic regression event documented in the paleoclimate records from Greenland ice, marine sediments and European pollen at the last interglacial-last glacial transition.