Atomistic simulations of graphene origami:Dynamics and kinetics

Origami offers two-dimensional(2D)materials with great potential for applications in flexible electronics,sensors,and smart devices.However,the dynamic process,which is crucial to construct origami,is too fast to be characterized by using state-of-the-art experimental techniques.Here,to understand the dynamics and kinetics at the atomic level,we explore the edge effects,structural and energy evolution during the origami process of an elliptical graphene nano-island(GNI)on a highly ordered pyrolytic graphite(HOPG)substrate by employing steered molecular dynamics simulations.The results reveal that a sharper armchair edge is much easier to be lifted up and realize origami than a blunt zigzag edge.The potential energy of the GNI increases at the lifting-up stage,reaches the maximum at the beginning of the bending stage,decreases with the formation of van der Waals overlap,and finally reaches an energy minimum at a half-folded configuration.The unfolding barriers of elliptical GNIs with different lengths of major axis show that the major axis should be larger than 242 A to achieve a stable single-folded structure at room temperature.These findings pave the way for pursuing other 2D material origami and preparing origami-based nanodevices.

Fabrication of honeycomb AuTe monolayer with Dirac nodal line fermions

Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate.Low energy electron diffraction measurements reveal that it is(2×2)AuTe layer stacked onto(3×3)Au(111)substrate.Moreover,scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure.Scanning transmission electron microscopy reveals that it is a single-atom layer.In addition,first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry,which is validated by angle-resolved photoemission spectra.Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.

Prediction of a monolayer spin-spiral semiconductor:CoO with a honeycomb lattice

The recent successful fabrication of two-dimensional(2D)CoO with nanometer-thickness motivates us to investigate monolayer CoO due to possible magnetic properties induced by Co atoms.Here,we employ first-principles calculations to show that monolayer CoO is a 2D spin-spiral semiconductor with a honeycomb lattice.The calculated phonon dispersion reveals the monolayer's dynamical stability.Monolayer CoO exhibits a type-I spin-spiral magnetic ground state.The spinspiral state and the direct bandgap character are both robust under biaxial compressive strain(-5%)to tensile strain(5%).The bandgap varies only slightly under either compressive or tensile strain up to 5%.These results suggest a potential for applications in spintronic devices and offer a new platform to explore magnetism in the 2D limit.

Transition of photoconductive and photovoltaic operation modes in amorphous Ga_2O_3-based solar-blind detectors tuned by oxygen vacancies

We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga_2O_3-based solar-blind photodetectors in metal–semiconductor–metal(MSM) configurations. The conversion from Ohmic to Schottky contacts at Ti/Ga_2O_3 interface is realized by tuning the conductivity of amorphous Ga_2O_3 films with delicate control of oxygen flux in the sputtering process. The abundant donor-like oxygen vacancies distributed near the Ti/Ga_2O_3 interface fascinate the tunneling process across the barrier and result in the formation of Ohmic contacts. As a consequence, the serious sub-gap absorption and persistent photoconductivity(PPC) effect degrades the performance of the photoconductive detectors. In contrast, the photovoltaic device with a Schottky contact exhibits an ultra-low dark current less than 1 pA,a high detectivity of 9.82×10^(12) cm·Hz^(1/2)·W^(-1), a fast response time of 243.9 μs, and a high ultraviolet C(UVC)-toultraviolet A(UVA) rejection ratio of 103. The promoting performance is attributed primarily to the reduction of the subgap states and the resultant suppression of PPC effect. With simple architecture, low fabrication cost, and easy fusion with modern high-speed integrated circuitry, these results provide a cost-effective way to realize high performance solar-blind photodetectors towards versatile practical applications.

Deficiency of Tfh Cells and Germinal Center in Deceased COVID-19 Patients

Summary:The COVID-19 pandemic caused by SARS-CoV2 is characterized by a remarkable variation in clinical severity ranging from a mild illness to a fatal multi-organ disease.Understanding the dysregulated human immune responses in the fatal subjects is critical for management of COVID-19 patients and the pandemic.In this study,we examined the immune cell compositions in the lung tissues and hilar lymph nodes using immunohistochemistry on 6 deceased COVID-19 patients and 4 focal organizing pneumonia(FOP)patients who underwent lung surgery and served as controls.We found a dominant presence of macrophages and a general deficiency of T cells and B cells in the lung tissues from deceased COVID-19 patients.In contrast to the FOP patients,Tfh cells and germinal center formation were largely absent in the draining hilar lymph nodes in the deceased COVID-19 patients.This was correlated with reduced IgM and IgG levels compared to convalescent COVID-19 patients.In summary,our data highlight a defect of germinal center structure in deceased COVID-19 patients leading to an impaired humoral immunity.Understanding the mechanisms of this deficiency will be one of the key points for the management of this epidemic.

Effects of BN content on the mechanical properties of nanocrystalline 3Y-TZP/Al_(2)O_(3)/BN dental ceramics

3Y-TZP/3wt%Al_(2)O_(3) powder was coated with varying amounts of BN using the urea and borate reaction sintering method,and then multiphase ceramics were prepared by hot pressing sintering.The micro-topography and the compositional analysis of synthesized ceramics were conducted through scanning electron microscopy,transmission electron microscopy and X-ray diffraction.A mechanical tester was used to analyze the Vickers hardness,fracture toughness,and bending strength of the synthesized ceramics.The results showed that the ceramic with a BN content of 12wt%showed the best processability,but had diminished mechanical properties(such as fracture toughness and bending strength).The ceramic with a BN content of 9wt%showed better processability than those with 3wt%and 6wt%BN.However,the fracture toughness was affected by the addition of 9wt%BN,making this ceramic only usable as a base material for a three-unit fixed bridge.In contrast,the ceramics with a BN content of 3wt%or 6wt%fulfilled the criteria for use in multi-unit restoration,but their low processability made them unsuitable for milling after sintering.

Synergisms of cardiovascular effects between iptakalim and amlodipine, hydrochlorothiazide or propranolol in anesthetized rats

The primary object of this fundamental research was to survey the synergistic cardiovascular effects of iptakalim, a novel ATP–sensitive potassium channel(KATP) opener, and clinical first-line antihypertensive drugs, such as calcium antagonists, thiazide diuretics and β receptor blockers by a 2×2 factorial-design experiment. It would provide a theoretical basis for the development of new combined antihypertensive therapy program after iptakalim is applied to the clinic. Amlodipine besylate, hydrochlorothiazide and propranolol were chosen as clinical first-line antihypertensive drugs. Blood pressure, heart rate(HR) and cardiac functions were observed in anesthetized normal rats by an eightchannel physiological recorder. The results showed that iptakalim monotherapy in a low dose could produce significant antihypertensive effect. There was no interaction between iptakalim and amlodipine on the maximal changes of systolic blood pressure(SBP), diastolic blood pressure(DBP), mean arterial blood pressure(MABP), the left ventricular systolic pressure(LVSP), and the left ventricular end-diastolic pressure(LVEDP)(P>0.05). However, the effects of combination iptakalim/amlodipine on the maximal changes of SBP, DBP, MABP, LVSP and LVEDP were more obvious than those of iptakalim or amlodipine monotherapy. And there was strong positive interaction between iptakalim and amlodipine on the maximal changes of HR(P>0.05). According to the maximal changes of DBP, MABP, LVSP and LVEDP(P<0.05) of combination iptakalim with hydrochlorothiazide, there was strong positive interaction between them. But there was no interaction between iptakalim and hydrochlorothiazide on the maximal drop of SBP and HR(P>0.05). According to the maximal drops of DBP, MABP of combination iptakalim with propranolol, there was strong positive interaction between them(P<0.05). But there was no interaction between iptakalim and propranolol on the maximal changes of SBP, LVSP,LVEDP and HR(P>0.05). In conclusion, it was the first time to study the effects of amlodipine, hydrochlorothiazide or propranolol, which had different mechanisms of action from iptakalim, on cardiovascular effects of iptakalim in anesthetized normal rats. This study proved that the combination of iptakalim with hydrochlorothiazide or propranolol respectively had significant synergism on lowering blood pressure, while the combination of iptakalim/amlodipine had additive action on lowering blood pressure. Meanwhile the antihypertensive effect was explicit, stable and long-lasting. Iptakalim thus appears suitable for the clinical treatment of hypertensive people who need two or more kinds of antihypertensive agents.

Stimulation of endothelial non-neuronal muscarinic receptor attenuates the progression of atherosclerosis via inhibiting endothelial cells activation

Objective To investigate the effects of non-neuronal muscarinic receptors(NNMR) stimulation on atherosclerosis and endothelial cells activation.Methods Atherosclerosis model was established in ApoE^(-/-)mice by a high fat diet for 7 weeks.During the experimental periods,animals were received a low(7 mg/kg/d) or a high(21 mg/kg/d) dose of arecoline by gavage.At the termination of the treatments,serum total cholesterol and NO levels were measured,and the aorta morphology was analyzed by hematoxylin and eosin staining.The gene expression of monocyte chemoattractant protein-1(MCP-1) and adhesion molecules in the thoracic aortas was determined by RT-PCR,and the MCP-1 protein expression and NFkB activity were detected by Western blot analysis.NO production,MCP-1 secretion in cultured rat aortic endothelial cells(RAECs),and monocyte-endothelium adhesion assay were also performed after arecoline treatments.Results Arecoline efficiently decreased atherosclerotic plaque areas,increased serum nitric oxide(NO) content,suppressed the mRNA and protein expression of MCP-1,and modulated the IκB-αdegradation and P65 phosphorylation in the aortae of ApoE^(-/-) mice.Furthermore,arecoline promoted NO production and suppressed MCP-1 secretion in cultured RAECs after ox-LDL exposure,and either atropine or NG-nitro-L-arginine methylester could abrogate these effects.Arecoline also significantly inhibited the adherence of U937 monocytes to the ox-LDL injured human umbilical vein endothelial cells,which could be abolished by atropine.Conclusion Our results indicate that arecoline attenuates the progression of atherosclerosis and inhibits endothelial cells activation and adherence by stimulating endothelial NNMR.These effects,at least in part,are due to its modulation on NF-kB activity.

Ultra-low Young’s modulus and high super-exchange interactions in monolayer CrN: A promising candidate for flexible spintronic applications

Monolayer CrN has been predicted to be half-metallic ferromagnet with high Curie temperature.Due to bulk CrN’s biocompatibility,the monolayer is a promising candidate for bio-related devices.Here,using first-principles calculations based on density functional theory,we find that the formation energy of the bulk CrN stacking from layers with square lattice is only 68 meV/atom above the convex hull,suggesting a great potential to fabricate the monolayer CrN in a square lattice by using molecular beam epitaxy method.The monolayer CrN is then proved to be a soft material with an ultra-low Young’s modulus and can sustain very large strains.Moreover,the analysis of the projected density of states demonstrates that the ferromagnetic half-metallicity originates from the splitting of Cr-d orbitals in the CrN square crystal field,the bonding interaction between Cr-N,and that between Cr-Cr atoms.It is worth noting that the super-exchange interaction is much larger than the direct-exchange interaction and contributes to the ultra-high Curie temperature,which is obtained from Monte Carlo simulations based on Heisenberg model.Our findings suggest that the monolayer CrN can be an indispensable candidate for nanoscale flexible spintronic applications with good biocompatibility and is considerable appealing to be realized in experiment.

Band engineering of honeycomb monolayer CuSe via atomic modification

Two-dimensional monolayer copper selenide(CuSe)has been epitaxially grown and predicted to host the Dirac nodal line fermion(DNLF).However,the metallic state of monolayer CuSe inhibits the potential application of nanoelectronic devices in which a band gap is needed to realize on/off properties.Here,we engineer the band structure of monolayer CuSe which is an analogue of a p-doped system via external atomic modification in an effort to realize the semiconducting state.We find that the H and Li modified monolayer CuSe shifts the energy band and opens an energy gap around the Fermi level.Interestingly,both the atomic and electronic structures of monolayer CuHSe and CuLiSe are very different.The H atoms bind on top of Se atoms of monolayer CuSe with Se-H polar covalent bonds,annihilating the DNLF band of monolayer CuSe dominated by Se orbitals.In contrast,Li atoms prefer to adsorb at the hexagonal center of CuSe,preserving the DNLF band of monolayer CuSe dominated by Se orbitals,but opening band gaps due to a slight buckling of the CuSe layer.The realization of metal-to-semiconductor transition from monolayer CuSe to CuXSe(X=H,Li)as revealed by first-principles calculations makes it possible to use CuSe in future electronic devices.

Database Construction for Two-Dimensional Material-Substrate Interfaces

Interfacial structures and interactions of two-dimensional(2D)materials on solid substrates are of fundamental importance for fabrications and applications of 2D materials.However,selection of a suitable solid substrate to grow a 2D material,determination and control of 2D material-substrate interface remain a big challenge due to the large diversity of possible configurations.Here,we propose a computational framework to select an appropriate substrate for epitaxial growth of 2D material and to predict possible 2D material-substrate interface structures and orientations using density functional theory calculations performed for all non-equivalent atomic structures satisfying the symmetry constraints.The approach is validated by the correct prediction of three experimentally reported 2D material-substrate interface systems with only the given information of two parent materials.Several possible interface configurations are also proposed based on this approach.We therefore construct a database that contains these interface systems and has been continuously expanding.This database serves as preliminary guidance for epitaxial growth and stabilization of new materials in experiments.

非化学计量比的Hf(Zr)_(1+x)O_(2)稳定性和铁电性的起源

铪基氧化物(Hf(Zr)O_(2))因其优异的铁电性质而成为计算机存储等应用中备受青睐的材料.然而,化学计量比的铪基氧化物基态是非铁电的单斜相.在密度泛函理论计算中,我们发现插入铪或锆原子将随着插入浓度的增加,将Hf(Zr)O_(2)的基态从单斜相转变为三方相.声子色散和态密度投影揭示了插入的Hf(Zr)原子消除了已有的非等效Hf(Zr)原子之间的竞争,从而稳定了r相.此外,Hf/Zr插层原子的有序分布进一步降低了形成能和铁电转换势垒,导致高耐久性和超低的矫顽场.能带结构显示,Hf/Zr插层原子引起的局域平带对漏电流的贡献最小.最后,我们证明了ZrO_(2)对于形成非化学计量比的Hf(Zr)_(1+x)O_(2)至关重要.

Designing two-dimensional ferroelectric materials from phosphorus-analogue structures

Two-dimensional(2D)ferroelectric(FE)materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory devices.Herein,we screen out 39 new 2D ferroelectric materials,MX(M:Group III-V elements;X:Group V-VII elements),in three phosphorus-analogue phases including black phosphorene-likeα-phase,blue phosphorus-likeβ-phase,and GeSe-likeγ-phase using high-throughput calculations.Seven materials(α-SbP,γ-AsP,etc.)exhibit FE switching barriers lower than 0.3 eV/f.u.,ferroelectric polarization larger than 2×10^(−10)C/m,and high thermodynamic stability with energy above hull smaller than 0.2 eV/atom.We find that the larger the electronegativity difference between M and X,the larger the ferroelectric polarization.Moreover,larger electronegativity differences result in lower in-plane piezoelectric stress tensor(e11)for MX consisting of Group IV and VI elements and larger e11 for those consisting of Group V elements.Further calculations predict a giant tunneling electroresistance in ferroelectric tunnel junctionα-Sb(Sn)P/α-SbP/α-Sb(Te)P(1.26×104%)and large piezoelectric strain coefficient inα-SnTe(396 pm/V),providing great opportunities to the design of non-volatile resistive memories,and high-performance piezoelectric devices.

Nonvolatile electrical control of spin polarization in the 2D bipolar magnetic semiconductor VSeF

Nonvolatile electrical control of spin polarization in two-dimensional(2D)magnetic semiconductors is greatly appealing toward future low-dissipation spintronic nanodevices.Here,we report a 2D material VSeF,which is an intrinsic bipolar magnetic semiconductor(BMS)featured with opposite spin-polarized valence and conduction band edges.We then propose a general nonvolatile strategy to manipulate both spin-polarized orientations in BMS materials by introducing a ferroelectric gate with proper band alignment.The spin-up/spin-down polarization of VSeF is successfully controlled by the electric dipole of ferroelectric bilayer Al_(2)Se_(3),verifying the feasibility of the design strategy.The interfacial doping effect from ferroelectric gate also plays a role in enhancing the Curie temperature of the VSeF layer.Two types of spin field effect transistors,namely multiferroic memory and spin filter,are further achieved in VSeF/Al_(2)Se_(3) and VSeF/Al_(2)Se_(3)/Al_(2)Se_(3) multiferroic heterostructures,respectively.This work will stimulate the application of 2D BMS materials in future spintronic nanodevices.

Sulfur-doped graphene nanoribbons with a sequence of distinct band gaps

Unlike graphene sheets, graphene nanoribbons （GNRs） can exhibit semiconducting band gap characteristics that can be tuned by controlling impurity doping and the GNR widths and edge structures. However, achieving such control is a major challenge in the fabrication of GNRs. Chevron-type GNRs were recently synthesized via surface-assisted polymerization of pristine or N-substituted oligophenylene monomers. In principle, GNR heterojunctions can be fabricated by mixing two different monomers. In this paper, we report the fabrication and characterization of chevron-type GNRs using sulfur-substituted oligophenylene monomers to produce GNRs and related heterostructures for the first time. First-principles calculations show that the GNR gaps can be tailored by applying different sulfur configurations from cyclodehydrogenated isomers via debromination and intramolecular cyclodehydrogenation. This feature should enable a new approach for the creation of multiple GNR heterojunctions by engineering their sulfur configurations. These predictions have been confirmed via scanning tunneling microscopy and scanning tunneling spectroscopy. For example, we have found that the S-containing GNRs contain segments with distinct band gaps, i.e., a sequence of multiple heterojunctions that results in a sequence of quantum dots. This unusual intraribbon heterojunction sequence may be useful in nanoscale optoelectronic applications that use quantum dots.

Semiconducting M_(2)X(M=Cu,Ag,Au;X=S,Se,Te)monolayers:A broad range of band gaps and high carrier mobilities

Two-dimensional semiconductors(2DSCs)with appropriate band gaps and high mobilities are highly desired for future-generation electronic and optoelectronic applications.Here,using first-principles calculations,we report a novel class of 2DSCs,group-11-chalcogenide monolayers(M_(2)X,M=Cu,Ag,Au;X=S,Se,Te),featuring with a broad range of energy band gaps and high carrier mobilities.Their energy band gaps extend from 0.49 to 3.76 eV at a hybrid density functional level,covering from ultraviolet-A,visible light to near-infrared region,which are crucial for broadband photoresponse.Significantly,the calculated room-temperature carrier mobilities of the M_(2)X monolayers are as high as thousands of cm^(2)·V^(-1)·s^(-1).Particularly,the carrier mobilities ofε-Au_(2)Se and e-Au2Te are up to 104 cm^(2)·V^(-1)·s^(-1),which is very attracitive for electronic devices.Benefitting from the broad range of energy band gaps and superior carrier mobilities,the group-11-chalcogenide M_(2)X monolayers are promising candidates for future-generation nanoelectronics and optoelectronics.

Superconductivity and topological aspects of two-dimensional transition-metal monohalides

Two-dimensional(2D)superconducting states have attracted much recent interest,especially when they coexist with nontrivial band topology which affords a promising approach towards Majorana fermions.Using first-principles calculations,we predict van der Waals monolayered transition-metal monohalides MX(M=Zr,Mo;X=F,Cl)as a class of 2D superconductors with remarkable transition temperature(5.9–12.4 K).Anisotropic Migdal-Eliashberg theory reveals that ZrCl have a single superconducting gap∆~2.14 meV,while MoCl is a two-gap superconductor with∆~1.96 and 1.37 meV.The Z_(2)band topology of 2D MX is further demonstrated that MoF and MoCl are candidates for realizing topological superconductivity.Moreover,the Dirac phonons of ZrCl and MoCl contribute w-shape phononic edge states,which are potential for an edge-enhanced electron-phonon coupling.These findings demonstrate that 2D MX offers an attractive platform for exploring the interplay between superconductivity,nontrivial electronic and phononic topology.

Quantum anomalous Hall effect in two-dimensional magnetic insulator heterojunctions

Recent years have witnessed tremendous success in the discovery of topological states of matter.Particularly,sophisticated theoretical methods in time-reversal-invariant topological phases have been developed,leading to the comprehensive search of crystal database and the prediction of thousands of topological materials.In contrast,the discovery of magnetic topological phases that break time reversal is still limited to several exemplary materials because the coexistence of magnetism and topological electronic band structure is rare in a single compound.To overcome this challenge,we propose an alternative approach to realize the quantum anomalous Hall(QAH)effect,a typical example of magnetic topological phase,via engineering two-dimensional(2D)magnetic van der Waals heterojunctions.

Auxetic two-dimensional transition metal selenides and halides

Auxetic two-dimensional(2D)materials provide a promising platform for biomedicine,sensors,and many other applications at the nanoscale.In this work,utilizing a hypothesis-based data-driven approache,we identify multiple materials with remarkable in-plane auxetic behavior in a family of buckled monolayer 2D materials.These materials are transition metal selenides and transition metal halides with the stoichiometry MX(M=V,Cr,Mn,Fe,Co,Cu,Zn,Ag,and X=Se,Cl,Br,I).First-principles calculations reveal that the desirable auxetic behavior of these 2D compounds originates from the interplay between the buckled 2D structure and the weak metal-metal interaction determined by their electronic structures.We observe that the Poisson’s ratio is sensitive to magnetic order and the amount of uniaxial stress applied.A transition from positive Poisson’s ratio(PPR)to negative Poisson’s ratio(NPR)for a subgroup of MX compounds under large uniaxial stress is predicted.The work provides a guideline for the future design of 2D auxetic materials at the nanoscale.

Neuroendocrine-Immune Regulating Mechanisms for the Anti-Inflammatory and Analgesic Actions of Acupuncture

Pain and inflammatory diseases are important clinical indications of acupuncture,which have been widely accepted in the international community.Previous studies have been focusing on rapid analgesia of acupuncture through the regulation of nervous system,but few studies on the inflammation regulatory mechanisms in which acupuncture inhibits the peripheral sensitization-induced pain.Based on studies concerning acupoint mechanisms of acupuncture actions and related researches on acupuncture regulating neuroendocrine and immune systems,we put forward the scientific hypothesis that acupuncture regulates neuroendocrine-immune(NEI)network and key response media therein,so as to achieve anti-inflammatory and analgesic effects in target organs.We have established a platform for acupuncture at ST36 to alleviate inflammatory pain in adjuvant induced arthritic rats.Based on the complex network analysis of multi-dimensional data from multi-time point and multi-site detection of NEI common signaling molecules,we have clarified the regulatory effects of acupuncture on NEI network and corresponding downstream immune network.Results indicated that monocytes/macrophages are the key targeting cells of acupuncture regulation,and acupuncture may display the anti-inflammatory and analgesic effects by regulating polarization of T cells in lymph nodes and polarization of M1/M2 macrophages in inflamed joints/paws.In addition,we have spotted a key molecule for acupuncture analgesia,CXCL1,as well as clarified the novel central analgesic mechanism of acupuncture mediated by CXCL1/CXCR2 desensitization.Thereby,we have provided novel evidence of the anti-inflammatory and analgesic actions of acupuncture through regulating NEI network and several key substances,highlighting a systemic research paradigm for investigating mechanisms of acupuncture actions.