Nonreciprocal transport in the superconducting state of the chiral crystal NbGe_(2)

Due to the lack of inversion,mirror or other roto-inversion symmetries,chiral crystals possess a well-defined handedness which,when combined with time-reversal symmetry breaking from the application of magnetic fields,can give rise to directional dichroism of the electrical transport phenomena via the magnetochiral anisotropy.In this study,we investigate the nonreciprocal magneto-transport in microdevices of NbGe_(2),a superconductor with structural chirality.A giant nonreciprocal signal from vortex motions is observed during the superconducting transition,with the ratio of nonreciprocal resistance to the normal resistanceγreaching 6×10^(5)T^(-1)·A^(-1).Interestingly,the intensity can be adjusted and even sign-reversed by varying the current,the temperature,and the crystalline orientation.Our findings illustrate intricate vortex dynamics and offer ways of manipulation on the rectification effect in superconductors with structural chirality.

Crystal growth, magnetic and electrical transport properties of the kagome magnet RCr_(6)Ge_(6)(R= Gd–Tm)

Kagome magnets have attracted considerable research attention due to the interplay between topology,magnetism and electronic correlations.In this study we report single-crystal synthesis of a series of the kagome magnets.RCr_(6)Ge_(6)(R=Gd-Tm) that possess defect-free Cr kagome lattices and systematically study their magnetic and electrical transport properties.The transition from a canted ferrimagnetic to a paramagnetic state in GdCr_(6)Ge_(6),TbCr_(6)Ge_(6),DyCr_(6)Ge_(6),HoCr_(6)Ge_(6),ErCr_(6)Ge_(6) and TmCr_(6)Ge_(6) occurs at 11.3 K,10.8 K,4.3 K,2.5 K,3.3 K and below 2 K,respectively,due to R-R interactions within the compounds.Magnetization measurements reveal highly anisotropic magnetism with canted magnetic moments in these compounds.In electrical transport,both negative and positive magnetoresistances at different magnetic fields and temperatures have been observed due to the competition between different scattering mechanisms.This work enriches our understanding of the Cr-based kagome magnets and paves the way to search for possible topological responses in this family.

Quantum Dynamics Calculations on Isotope Effects of Hydrogen Transfer Isomerization in Formic Acid Dimer

We present a quantum dynamics study on the isotope effects of hydro-gen transfer isomerization in the formic acid dimer,and this is achieved by multidimensional dy-namics calculations with an efficient quantum mechanical theoretical scheme developed by our group,on a full-dimensional neural network ab initio potential energy surface.The ground-state and fundamental tun-neling splittings for four deuterium isotopologues of formic acid dimer are considered,and the calculated results are in very good general agreement with the avail-able experimental measurements.Strong isotope effects are revealed,the mode-specific funda-mental excitation effects on the tunneling rate are evidently influenced by the deuterium sub-stitution of H atom with the substitution on the OH bond being more effective than on the CH bond.Our studies are helpful for acquiring a better understanding of isotope effects in the double-hydrogen transfer processes.

玛湖凹陷砂砾岩储层岩石力学特征与压裂对策研究

玛湖凹陷百口泉组砂砾岩油藏储量大，但储层孔渗差、单井产量低、综合开釆成本髙，“水平井+压裂”是开发该类储层的有效措施，由于对其地应力和岩石力学特征认识不清严重制约了压裂改造的有效性。通过室内声学、力学试验发现玛湖凹陷百口泉组砂砾岩储层存在两向地应力差髙、最小水平主地应力髙、岩心弹性模量小、硬度低等特点，压裂改造无法形成复杂缝网，推荐采用密切割分段体积压裂工艺增大改造体积、采用前置液挤酸预处理结合小粒径段塞方式减少压裂加砂施工难度、适当加大支撑剂铺设厚度以及近井地带使用滑溜水造长复杂缝等措施提髙改造效果。结合以上压裂施工建议，2015年底顺利完成了对试验井MaHW1325井22段体积压裂，入井压裂液23,700 m3、支撑剂1702 m3,截止到2017年8月下旬MaHW1325井累计生产528 d,累计产油12,786.8 t,平均日产油24.2 t,生产效果好，说明压裂改造方案成功，在该区块具有极髙推广价值.

微液滴强化传质与化学反应的研究进展

气–液/液–液两相体系广泛存在于多种化工过程中,如精馏、吸收、萃取、多相反应等.传统宏观的两相接触方式存在接触面积小、传质效率低、反应速率慢等问题,而微液滴具有比表面积大、生成频率高、液滴系统相对独立等诸多优点,可极大强化相间传质和化学反应.将微液滴作为传质和反应的媒介,能够有效改善两相宏观接触的局限,已被广泛应用于各类化工单元操作中.本文综述了近年来关于微液滴强化相间传质与多相化学反应的研究进展,并对未来的研究方向进行了展望.

基于聚类算法的PBFT共识优化方案与验证

随着区块链技术在多个领域的广泛部署,其面临的共识机制的效率较低和计算资源的过度消耗的挑战。本研究通过对DBSCAN聚类算法进行改进,使之适应去中心化的区块链共识网络,进而对大规模的网络节点进行有效的聚类和层次化管理。通过引入了监督节点以增强共识模型的安全性。在模拟环境中进行实验,验证了通过适当的聚类可以显著优化共识过程中的耗时和通信复杂度。在拥有1,000个节点的网络环境中,相比于传统的PBFT算法,我们的方案能够将单次共识的耗时降低26.7%,并且在最佳情况下,共识通信的次数可以至少减少一个数量级。这一方案显著提高了参与共识节点的效率,使得区块链应用更加节能且高效。

Highly sensitive torsion sensor based on Mach–Zehnder interference in helical seven-core fiber taper

We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber(MHSTM).Sensors with different taper waists and helical pitches are fabricated,and their transmission spectra are obtained and analyzed.The waist and length of the sandwiched seven-core fiber are finally determined to be 68 μm and3 mm,respectively.The experimental results show that the clockwise and counterclockwise torsion sensitivities of the proposed sensor are 2.253 nm/(rad/m) and-1.123 nm/(rad/m),respectively.When tapered waist diameter reduces to48 μm,a superior torsion sensitivity of 5.391 nm/(rad/m) in the range of 0-4.24 nm/(rad/m) is obtained,which is 46 times as large as the traditional helical seven-core fiber structure.In addition,the MHSTM structure is also relatively stable to temperature variations.

Differences in pseudogene evolution contributed to the contrasting flavors of turnip and Chiifu, two Brassica rapa subspecies

Pseudogenes are important resources for investigation of genome evolution and genomic diversity because they are nonfunctional but have regulatory effects that influence plant adaptation and diversification.However,few systematic comparative analyses of pseudogenes in closely related species have been conducted.Here,we present a turnip(Brassica rapa ssp.rapa)genome sequence and characterize pseudogenes among diploid Brassica species/subspecies.The results revealed that the number of pseudogenes was greatest in Brassica oleracea(CC genome),followed by B.rapa(AA genome)and then Brassica nigra(BB genome),implying that pseudogene differences emerged after species differentiation.In Brassica AA genomes,pseudogenes were distributed asymmetrically on chromosomes because of numerous chromosomal insertions/rearrangements,which contributed to the diversity among subspecies.Pseudogene differences among subspecies were reflected in the flavor-related glucosinolate(GSL)pathway.Specifically,turnip had the highest content of pungent substances,probably because of expansion of the methylthioalkylmalate synthase-encoding gene family in turnips;these genes were converted into pseudogenes in B.rapa ssp.pekinensis(Chiifu).RNA interference-based silencing of the gene encoding 2-oxoglutarate-dependent dioxygenase 2,which is also associated with flavor and anticancer substances in the GSL pathway,resulted in increased abundance of anticancer compounds and decreased pungency of turnip and Chiifu.These findings revealed that pseudogene differences between turnip and Chiifu influenced the evolution of flavor-associated GSL metabolism-related genes,ultimately resulting in the different flavors of turnip and Chiifu.