News on China's scientific and technological development.

China successfully runs the world's first electromagnetic sled, with a magnetic levitation speed exceeding 1000 km/h​

近日，南京农业大学宿州研究院组织安徽省农科院、宿州市农科院、宿州市植保站、埇桥区农业局等单位的专家对大豆新品种“南农47”进行测产。经测定，“南农47”平均种植密度为1.311万株/亩，按审定百粒重18.9克计算，亩产可达306.5公斤。

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南京农业大学国家大豆改良中心王吴彬副教授介绍，示范品种为南京农业大学国家大豆改良中心选育的大豆新品种“南农47”，该品种2019年通过江苏省审定，2021年通过国家黄淮海南片和河南省审定。“南农47”具有三大特性，一是产量高，其产量在六次区域试验中，五次排名第一，产量较对照增产9.5%-15.4%；二是产量稳，50余次试点中，48次表现增产，增产点率高达96%；三是品质优，蛋白质含量高达44.44%，接近高蛋白大豆标准。

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中新网北京10月15日电 (记者 孙自法)中国耐盐大豆育种研究和示范推广工作获得重大进展——中国科学院遗传与发育生物学所(中科院遗传发育所)田志喜研究团队成功选育的耐盐高产优质大豆新品系“科豆35”，在山东省东营市黄河入海口的典型盐碱地上采用完全天然雨养方式进行示范种植，10月15日通过田间实收测产显示亩产为270公斤以上。

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据了解，中国大豆产量长期不足，近年来大豆进口量一直持续在9000万吨以上，对外依存度高达85%，提高大豆生产能力是中国粮食安全的重大急需。而增加大豆种植面积是缓解中国大豆危机的有效途径，但单纯地在现有耕地基础上通过减少主粮作物种植以增加大豆种植面积并不符合中国人多地少的实际国情。除18多亿亩红线耕地外，中国还有11.7亿亩的边际土地，其中包括5亿亩左右的盐碱地，而拥有各类具有农业利用前景的盐碱地总面积1.85亿亩，对这些盐碱地的有效开发利用，是提升中国大豆产能的重要新方向。2021年12月，农业农村部印发《“十四五”全国种植业发展规划》提出，要开发盐碱地种大豆。(完)

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Ytterbium optical lattice clock with instability of order 10-18​

Abstract​

We have built an ytterbium optical lattice clock with improvements over our previous version. An in-vacuum blackbody radiation (BBR) shield is employed to provide a well characterized BBR environment. The effective temperature felt by the atoms can be determined at an accuracy level of 13 mK, leading to a total BBR frequency shift uncertainty of 9.5×10-19. We have also built an ultra-stable optical cavity system to pre-stabilize the clock laser, achieving a flicker frequency instability of ∽3×10-16. Rabi spectroscopy of the lattice-trapped atoms can achieve sub-Hertz linewidth spectra. Two ytterbium clocks have been operated in an antisynchronized configuration, with real-time BBR-Stark-shift corrections applied to both of them. By comparing the two clocks, we demonstrate a single-clock instability of 5.4×10-18 in 4500 s. This clock will be applied for frequency comparisons to other optical clocks of different atomic species in the future.

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中科院精密测量院研制出稳定度达E-18量级的镱原子光钟​

中国科学院精密测量科学与技术创新研究院吕宝龙研究团队与华东师范大学马龙生团队合作，成功研制出一种高精度镱原子光钟，该光钟的频率稳定度达到E-18量级。相关成果近日发表在Metrologia上。

研究团队突破了镱原子光钟的多项关键技术，在黑体辐射频移的精准控制、直流Stark频移与原子碰撞频移的抑制、钟激光频率稳定度的改善等方面采取了系列创新措施，实现了光钟稳定度的大幅度提升，特别是采用了量子化轴方向与环境干扰磁场矢量相垂直的方案，大幅度地降低了钟跃迁对相关干扰的敏感度，使得该光钟能够在地铁干扰环境下仍然能够正常工作。钟跃迁的Rabi探询能够得到亚赫兹线宽的谱线。团队通过同类光钟之间的反同步频率比对，测得该光钟的在4500秒内的频率稳定度达到5.4E-18。频率噪声分析表明，频率稳定度主要受限于Dick效应。

镱原子光钟是一种以囚禁于光晶格中的超冷镱原子为工作介质的原子钟，具有能够达到E-20量级稳定度的巨大潜力。基于其本身的优势，该光钟已成为竞争下一代秒定义的候选光钟之一，将会在基本物理规律检验、基本物理常数变化测量、暗物质及引力波探测、相对论大地重力测量等前沿科学研究和重大应用中发挥重要作用。

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Abstract​

A supramolecular approach was applied to the construction of adhesive materials with excellent temperature resistance and strong adhesion capacity. Supramolecular hot-molten glues were prepared from two small compounds,

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(A) and

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chloride (C), using a combination of molecular recognition (formation of supramonomers) and supramolecular polymerization (formation of cross-linked polymers). The coexistence of covalent poly(A) backbones and non-covalent crosslinker C units enabled the poly(A-C)s to display tough adhesion effects with long-term stability at high (150 °C, 5.18 MPa) and low temperatures (–196 °C, 9.52 MPa) without any additives. Real-time and quantitative monitoring of the adhesion behavior of poly(A-C)s was successfully realized over a wide temperature range of −80 to 150 °C, using a customized device that allowed for easy monitoring of the adhesion duration, attenuation, and failure. Importantly, adhesion failure was visualized and wirelessly alarmed.

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Abstract​

Inspired by the bottom-up assembly in nature, an artificial self-assembly pattern is introduced into 3D-fused deposition modeling (FDM) printing to achieve additive manufacturing on the macroscopic scale. Thermally activated polymerization of thioctic acid (TA) enabled the bulk construction of poly(TA), and yielded unique time-dependent self-assembly. Freshly prepared poly(TA) can spontaneously and continuously transfer into higher-molecular-weight species and low-molecular-weight TA monomers. Poly(TA) and the newly formed TA further assembled into self-reinforcing materials via microscopic-phase separation. Bottom-up self-assembly patterns on different scales are fully realized by 3D FDM printing of poly(TA): thermally induced polymerization of TA (microscopic-scale assembly) to poly(TA) and 3D printing (macroscopic-scale assembly) of poly(TA) are simultaneously achieved in the 3D-printing process; after 3D printing, the poly(TA) modes show mechanically enhanced features over time, arising from the microscopic self-assembly of poly(TA) and TA. This study clearly demonstrates that micro- and macroscopic bottom-up self-assembly can be applied in 3D additive manufacturing.

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近日，中国农业科学院麻类研究所可降解材料开发与利用团队联合湖南大学、中南大学在环保型可降解粘合剂开发与利用方面取得重要进展。他们利用超分子聚合的方法从小分子出发制备出了一系列粘附性能好，使用范围大的粘合材料，并利用其粘性效果，将其作为3D打印材料。这些超分子聚合物基可降解粘合材料不仅粘附效果高于同类型材料，而且在应用上提供了一种新思路。相关研究成果在线发表于《化学工程杂志》(chemical engineering journal )和《先进科学》 (advanced science )，并获得国家发明专利授权。

粘合剂在日常生活、医疗卫生、汽车工业、航天航空等领域有着普遍应用，随着环保意识的提升，开发环保型可生物降解粘附材料已成为一项重要的研究课题。现有粘合剂存在粘附效果不佳，特别是在极端环境下效果更差。更重要的是这些粘附材料无法进行增材制造，无法使其应用更广泛。

研究人员利用分子识别和超分子聚合的策略合成一系列具有同时耐高低温的粘合剂，这些粘合剂在高温150°C达到了5.18MPa ，在低温-196°C达到了9.52MPa。在较宽的温度范围内(-80℃至150°C) 成功实现了对粘附行为的实时和定量监测，使用定制设备，可轻松监测粘附持续时间、衰减和失效。这项工作制备了一系列可同时耐高低温的、粘附效果好的粘附材料，同时也为粘附效果的监测提供了新思路。

针对以往的粘附材料缺乏进一步增材使用的问题，研究人员进一步利用天然小分子硫辛酸的热响应开环聚合形成聚硫辛酸，制备了新型粘合剂。基于此粘合剂的时间依赖自增强效应，将其应用在增材制造的热熔沉积3D打印中。

通过聚硫辛酸的3D打印，完全实现了不同尺度上的模型形成。3D打印后，聚硫辛酸打印的模型随着时间的推移表现出机械增强的特征。这是由聚硫辛酸和硫辛酸的微观自组装引起的。

这项工作实现了微观层面的自组装和宏观层面的自组装有机结合。该研究也为粘合材料的可控制造和机械增强提供了一种可行的方法，为下一代功能粘合材料的应用开辟了道路。

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olalavn said:

China successfully runs the world's first electromagnetic sled, with a magnetic levitation speed exceeding 1000 km/h​

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olalavn said:

China successfully runs the world's first electromagnetic sled, with a magnetic levitation speed exceeding 1000 km/h​

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