Dynamic Analysis of a Predator-Prey Model with Holling-II Functional Response

A predator-prey model with linear capture term Holling-II functional response was studied by using differential equation theory. The existence and the stabilities of non-negative equilibrium points of the model were discussed. The results show that under certain limited conditions, these two groups can maintain a balanced position, which provides a theoretical reference for relevant departments to make decisions on ecological protection.

近30年中国文献报道恶性淋巴瘤合并自身免疫性血细胞减少症的系统性分析

本文通过收集1989年1月至2019年12月国内学者发表在国内外期刊上的文献及参考文献,共纳入符合标准的140例恶性淋巴瘤(malignant lymphoma,ML)合并自身免疫性血细胞减少(autoimmune cytopenia,AIC)病例,包括溶血性贫血(autoimmune hemolytic anemia,AIHA)、免疫性血小板减少症(immune thrombocytopenia,ITP)、纯红细胞再生障碍性贫血(pure red cell aplasia,PRCA)及Evans综合征等。虽然各亚型淋巴瘤病例数均较少(n=1~28),但通过系统性分析仍得到部分有意义的发现。除免疫性中性粒细胞减少(autoimmune neutropenia,AIN)外,各类AIC均有报道,发生率依次为AIHA>ITP>冷凝集素综合征(cold agglutinin syndrome,CAS)>PRCA>Evans综合征。AIC见于各亚型淋巴瘤,但各类AIC在不同亚型发生率存在差异。CAS仅见于淋巴瘤B细胞非霍奇金淋巴瘤(B cell nonHodgkin′slymphoma,B-NHL)、AIHA、ITP,Evans综合征多见于B-NHL,PRCA则多见于T细胞非霍奇金淋巴瘤(T cell non Hodgkin′s lymphoma,T-NHL)。相较于糖皮质激素等常规治疗,合并ML的AIC抗肿瘤治疗对有效率更高。恶性淋巴瘤合并AIC临床情况复杂,需引起临床关注。

Ultimate dielectric scaling of 2D transistors via van der Waals metal integration

The two-dimensional transition metal dichalcogenides(TMDs)have attracted intense interest as an atomically thin semiconductor channel for the continued transistor scaling.However,with a dangling bond free surface,it has been a key challenge to reliably integrate high-quality gate dielectrics on TMDs.In particular,the atomic layer deposition of dielectrics on TMDs typically features highly non-uniform nucleation and produces a highly rough or porous dielectric film with rich pinholes that are prone to further damage during the gate integration process.Herein we report a van der Waals(vdW)integration route towards highly reliable gate metal integration on porous dielectrics.The physical lamination process employed by the vdW integration avoids the direct deposition of metal electrodes into porous dielectrics to ensure reliable gate integration and produce low gate leakage devices.The electrical measurements demonstrate the vdW integrated MoS_(2) top gate devices exhibit substantially reduced gate leakage current that is about 3-5 orders of magnitude smaller than that with deposited metal electrodes.Furthermore,we show the vdW integration process can be used to create high performance top-gated MoS_(2) transistors with ultrathin Al_(2)O_(3) dielectrics down to 1 nm,representing the ultimate dielectric scaling for TMDs transistors.This study demonstrates that vdW integration can enable highly reliable gate integration on relatively low quality dielectrics on TMDs,and opens an interesting pathway to high-performance top-gate transistors using dangling bond free two-dimensional(2D)semiconductors.

两性分子掺杂自支撑单离子传导聚合物电解质及其锂金属二次电池

制备高离子电导率的自支撑单离子传导聚合物电解质仍然面临挑战.本文中,我们通过聚[4,4’(二苯醚基)-5,5’-联苯并咪唑]侧链化学接枝丙烷磺酰(三氟甲基磺酰)亚胺锂,得到自支撑聚合物电解质(PBIg-LiPSI).PBI-g-LiPSI具有优异的成膜性能,实验发现,掺杂两性分子1-甲基-3-丙烷磺酰(三氟甲基磺酰)亚胺咪唑内盐(MeImPSI)后,离子电导率和^(7)Li核磁共振峰的化学位移都随着掺杂两性分子的质量分数呈线性递增.PBI-g-LiPSI/MeImPSI(25 wt%)凝胶自支撑单离子传导聚合物电解质的室温离子电导率是0.68 mS cm^(-1),锂离子迁移数是0.95.使用该电解质隔膜的金属锂对称电池在±0.5 mA cm^(-2)@2 mA h cm^(-2)运行2100小时未发生短路,金属锂二次电池可在1C下稳定循环500圈.本工作开发了一种用于金属锂二次电池的两性分子掺杂自支撑单离子传导聚合物电解质.

Room temperature ferromagnetism in ultra-thin van der Waals crystals of 1T-CrTe2

Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered the related practical applications.Here,we show that ferromagnetism can hold above 300 K in a metallic phase of 1T-CrTe2 down to the ultra-thin limit.It thus makes CrTe2 so far the only known exfoliated ultra-thin vdW magnets with intrinsic long-range magnetic ordering above room temperature.An in-plane room-temperature negative anisotropic magnetoresistance(AMR)was obtained in ultra-thin CrTe2 devices,with a sign change in the AMR at lower temperature,with−0.6%and+5%at 300 and 10 K,respectively.Our findings provide insights into magnetism in ultra-thin CrTe2,expanding the vdW crystals toolbox for future room-temperature spintronic applications.

A gate-tunable artificial synapse based on vertically assembled van der Waals ferroelectric heterojunction

Memtransistor,a multi-terminal device that combines both the characteristics of a memristor and a transistor,has been intensively studied in two-dimensional layered materials(2 DLM),which show potential for applications in such as neuromorphic computation.However,while often based on the migration of ions or atomic defects in the conduction channels,performances of memtransistors suffer from the poor reliability and tunability.Furthermore,those known 2 DLM-based memtransistors are mostly constructed in a lateral manner,which hinders the further increasing of the transistor densities per area.Until now,fabricating non-atomic-diffusion based memtransistors with vertical structure remains challenging.Here,we demonstrate a vertically-integrated ferroelectric memristor by hetero-integrating the 2 D ferroelectric materials CuInP_(2)S_(6)(CIPS)into a graphite/CuInP_(2)S_(6)/MoS_(2)vertical heterostructure.Memristive behaviour and multi-level resistance states were realized.Essential synaptic behaviours including excitatory postsynaptic current,paired-pulse-facilitation,and spike-amplitude-dependent plasticity are successfully mimicked.Moreover,by applying a gate potential,the memristive behaviour and synaptic features can be effectively gate tuned.Our findings pave the way for the realization of novel gate-tunable ferroelectric synaptic devices with the capability to perform complex neural functions.