Editors’ selection of papers from China's academic journals

The photonic spin-Hall effect is an important but intrinsically weak effect at the nanoscale. Xiangang Luo and co-workers from the Institute ofOptics andElectronics, Chinese Academy of Sciences, found that a single catenary-shaped hole can generate a near-perfect spin-Hall effect (see Fig. 1). As one of the smallest photonic devices reported so far, the curvature of the catenary acts as an effective magnetic field andmakes circularly polarized light bend in opposite directions in a broadband spectrum. It opens a door to the utilization of continuous nanostructures as miniaturized functional optical devices. [Luo X et al. Light-Sci Appl 2017; 6: e16276.]

The photonic spin-Hall effect is an important but intrinsically weak effect at the nanoscale. Xiangang Luo and co-workers from the Institute of Optics and Electronics, Chinese Academy of Sciences, found that a single catenary-shaped hole can generate a near-perfect spin-Hall effect (see Fig. 1). As one of the smallest photonic devices reported so far, the curvature of the catenary acts as an effective magnetic field and makes circularly polarized light bend in opposite directions in a broadband spectrum. It opens a door to the utilization of continuous nanostructures as miniaturized functional optical devices. [Luo X et al. Light-Sci Appl 2017;6: e16276.]

PHYSICS
Insight-HXMT contributes to understanding the binary-neutron-star merger gravitational-wave event After the 2016 announcement of the discovery of gravitational waves, the most significant breakthrough in astronomy is the discovery and multi-messenger observation of the gravitational-wave event GW170817 from the merger of two neutron stars. Insight-HXMT, China's first X-ray astronomy satellite, launched on 15 June 2017, observed the entire event, as reported by TiPei Li (Institute of High Energy Physics, CAS, Tsinghua University, and University of Chinese Academy of Sciences), Shuang-Nan Zhang (Institute of High Energy Physics, CAS, and University of Chinese Academy of Sciences) and co-workers. The short gamma-ray burst detected by Fermi/GBM and Integral/ACS was unexpectedly weak and soft and thus was not detected but tightly constrained by Insight-HXMT between 200 keV and 5 MeV, which can help in the understanding of the physical process of the binary-neutron-star merger. To our knowledge, oligosaccharide synthesis remains a huge challenge. Recently, Yufen Zhao (Xiamen University, Tsinghua University), Yan Liu (Xiamen University) and co-workers reported a novel oligomerization reaction of unprotected monosaccharides with the direction of the phosphorus reagent. It is of great significance to obtain oligosaccharides with the dominant (1→6) linkage pattern by a mild 'one-pot' method, which avoids the tedious protection and deprotection of sugar units. This research has implied that higher regioselectivity will be achieved in the future by the implementation of some chiral induction strategies, such as the application of chiral phosphorus reagents. [Yuan H et al. Sci China Chem 2018;61: 243-50.] CHEMISTRY Air-stable diradical dication with a large singlet-triplet energy gap Triplet ground state (S = 1) diradicals with large singlet-triplet energy gap over the thermal energy at room temperature ( E ST >> 300 K) have attracted great interest, as they could be used as building blocks in the design of magnetic materials and biomedical agents. However, the number of such species is limited. Recently, Wenqing Wang and Xinping Wang from Nanjing University reported an air-stable dication of tert-butyl-substituted tetraazacyclophane, which shows a discrete diradical geometry with strongly ferromagnetic interaction (2J = 535 K), demonstrating that a class of arylamine-based diradical dications with strong ferromagnetic interaction will be accessible. [Wang W et al. Sci China Chem 2018;61: 300-5.] IMMUNOLOGY RNA epigenetic modification is required for regulatory T-cell immune-suppression RNA m 6 A modification was recently found to be essential in mRNA metabolism and involved in the functions of all kind of cells in vitro, but its in vivo function in effector T cells is unknown. Hua-Bing Li of Shanghai JiaoTong University, Richard Flavell of Yale University and co-workers specifically deleted the RNA m 6 A marker 'writer' gene Mettl3, which is involved in the resolution of inflammation and immunosuppression in tumor 124 Natl Sci Rev, 2018, Vol. 5, No. 2 RESEARCH HIGHLIGHTS microenvironments, in regulatory T cells only. Deletion of the writer gene and consequent loss of the m 6 A marker led to severe whole-body autoimmune inflammation and eventually death of the animals. Mechanistic studies revealed that m 6 A targeted specific essential signaling pathways of the regulatory T cells, thus controlling their suppressive functions. This study points to the possibility that specific depletion of m 6 A in tumor-infiltrated regulatory T cells could be harnessed in combination with other forms of immunotherapy to combat tumors. [Tong J et al. Cell Res 2018;28: 253-6.] PLANT & ANIMAL SCIENCE

Circadian evening complex represses leaf senescence
Circadian clock and senescence have been shown to tightly intertwine with each other in numerous eukaryotes, but the regulation of the circadian oscillator on triggering leaf senescence in higher plants remains largely unknown. Recently, Lei Wang's group at the Institute of Botany, Chinese Academy of Sciences, discovered that evening complex (EC), a core component of the plant circadian oscillator, negatively regulates leaf senescence, by transcriptionally repressing MYC2, which encodes an essential component of the jasmonic acid (JA) signaling pathway to trigger leaf senescence in Arabidopsis (see Fig. 2). Their findings not only revealed a key underlying mechanism for circadian gated JA signaling in triggering leaf senescence,

NEUROSCIENCE
Alzheimer's-disease-related enzymes (α-and β-secretases) physically and functionally interact with each other αand β-secretases compete for amyloid precursor protein ectodomain cleavage, which is vital to Aβ pathology in Alzheimer's disease. However, whether they function separately or together remains unknown. Gang Pei's group from the Shanghai Institute of Biochemistry and Cell Biology found that ADAM10 and BACE1, the major αand β-secretases in the brain, co-localize and physically interact in neurons. ADAM10 enhances BACE1-mediated cleavage of a neuronal substrate (CHL1) and this regulation is dependent on their physical interaction. The study indicates

MATERIALS SCIENCE
Topological quantum catalyst using nodal-line semimetals Traditionally, design of catalytic materials requires highly active sites through effective control of nanoengineering, heterostructures, defects and edges or boundary states. Xing-Qiu Chen at the Shenyang National Laboratory for Materials Science, Institute of Metal Research, CAS, and co-workers have proposed a new concept of topological quantum catalyst utilizing Dirac nodalline semimetals because of the combined advantages of robust drumhead-like topologically protected surface states, high carrier density and good mobility (see Fig. 3). Moreover, the TiSi family has been suggested as a potential candidate for this functionality, catalyzing electrochemical hydrogen production from water. [Li JX et al. Sci China Mater 2018;61: 23-9.]

MATERIALS SCIENCE
Metal-organic frameworks as new materials for optical ceramics

MATERIALS SCIENCE
Effective exposure of active sites for energy conversion and storage The introduction of nitrogen heteroatoms into carbon materials renders high reactivities in energy conversion and storage. However, most heteroatoms are doped into the bulk phase of carbon, which significantly reduces the contact of feedstocks with the active dopants in a conductive scaffold. Qiang Zhang at Tsinghua University and co-workers proposed the effective exposure of nitrogen active sites on surface graphene skin in a carbon/carbon composite. More N heteroatoms are able to come into contact with the oxygen feedstocks in oxygen reduction reactions or serve as polysulfide anchoring sites in lithium−sulfur batteries. [Shi JL et al. J Energy Chem 2018;27: 167-75.]

INFORMATION SCIENCE
An efficient approach to enhance human-robot interactions with shared control Jie Chen at the Beijing Institute of Technology and co-workers proposed an optimization-based shared-control framework (see Fig. 4), where human intention is predicted as an additional cost of model predictive control (MPC) and a compromise between human intention and robots' original objectives is properly made by optimizing the blended cost. The advantages of the proposed shared-control framework are that both human and robot objectives can be achieved in the MPC system that is input-to-state stable; meanwhile, the human intervention burden can be greatly reduced. These results provide a general way to promote the safety and efficiency of human-robot systems. [Fang H et al. Sci China Inf Sci 2018;61: 014201.] Edited by Yuan Gao