Electrically-driven ultrafast out-of-equilibrium light emission from hot electrons in suspended graphene/hBN heterostructures

Nanoscale light sources with high speed of electrical modulation and low energy consumption are key components for nanophotonics and optoelectronics.The record-high carrier mobility and ultrafast carrier dynamics of graphene make it promising as an atomically thin light emitter which can be further integrated into arbitrary platforms by van der Waals forces.However,due to the zero bandgap,graphene is difficult to emit light through the interband recombination of carriers like conventional semiconductors.Here,we demonstrate ultrafast thermal light emitters based on suspended graphene/hexagonal boron nitride(Gr/hBN)heterostructures.Electrons in biased graphene are significantly heated up to 2800 K at modest electric fields,emitting bright photons from the near-infrared to the visible spectral range.By eliminating the heat dissipation channel of the substrate,the radiation efficiency of the suspended Gr/hBN device is about two orders of magnitude greater than that of graphene devices supported on SiO2or hBN.Wefurther demonstrate that hot electrons and low-energy acoustic phonons in graphene are weakly coupled to each other and are not in full thermal equilibrium.Direct cooling ofhigh-temperature hot electrons to low-temperature acoustic phonons is enabled by the significant near-field heat transfer at the highly localized Gr/hBN interface,resulting in ultrafast thermal emission with up to 1 GHz bandwidth under electrical excitation.It is found thatsuspending the Gr/hBN heterostructures on the SiO2trenches significantly modifies the light emission due to the formation of the optical cavity and showed a~440%enhancement inintensity at the peak wavelength of 940 nm compared to the black-body thermal radiation.The demonstration of electrically driven ultrafast light emission from suspended Gr/hBNheterostructures sheds the light on applications of graphene heterostructures in photonicintegrated circuits,such as broadband light sources and ultrafast thermo-optic phase modulators.

Perspectives on exfoliated two-dimensional spintronics

Magnetic orderings, i.e., the spontaneous alignment of electron spins below a critical temperature, have been playing key roles in modern science and technologies for both the wide applications of magnetic recording for information storage and the vibrant potential of solid state electronic spin devices (also known as spintronics) for logic operations. In the past decades, thanks to the development of thin film technologies, magnetic thin films via sputtering or epitaxial growth have made the spintronic devices possible at the industrial scale. Yet thinner materials at lower costs with more versatile functionalities are highly desirable for advancing future spintronics. Recently, van der Waals magnetic materials, a family of magnets that can in principle be exfoliated down to the monolayer limit, seem to have brought tremendous opportunities: new generation van der Waals spintronic devices can be seamlessly assembled with possible applications such as optoelectronics, flexible electronics, and etc. Moreover, those exfoliated spintronic devices can potentially be compatible with the famed metal-oxide field effect transistor architectures, allowing the harness of spin performances through the knob of an electrostatic field.

Overexpression of estrogen receptor beta alleviates the toxic effects of beta-amyloid protein on PC12 cells via non-hormonal ligands

After binding to the estrogen receptor, estrogen can alleviate the toxic effects of beta-amyloid protein, and thereby exert a therapeutic effect on Alzheimer＇s disease patients. Estrogen can increase the incidence of breast carcinoma and endometrial cancer in post-menopausal women, so it is not suitable for clinical treatment of Alzheimer＇s disease. There is recent evidence that the estrogen receptor can exert its neuroprotective effects without estrogen dependence. Real-time quantitative PCR and flow cytometry results showed that, compared with non-transfected PC12 cells, adenovirus-mediated estrogen receptor β gene-transfected PC12 cells exhibited lower expression of tumor necrosis factor a and interleukin 1β under stimulation with beta-amyloid protein and stronger protection from apoptosis. The Akt-specific inhibitor Abi-2 decreased the anti-inflammatory and anti-apoptotic effects of estrogen receptor β gene-transfection. These findings suggest that overexpression of estrogen receptor β can alleviate the toxic effect of beta-amyloid protein on PC12 cells, without estrogen dependence. The Akt pathway is one of the potential means for the anti-inflammatory and anti-apoptotic effects of the estrogen receptor.

Thermionic electron emission in the 1D edge-to-edge limit

Thermionic emission is a tunneling phenomenon,which depicts that electrons on the surface of a conductor can be pulled out into the vacuum when they are subjected to high electrical tensions while being heated hot enough to overtake their work functions.This principle has led to the great success of the so-called vacuum tubes in the early 20 th century.To date,major challenges still remain in the miniaturization of a vacuum channel transistor for on-chip integration in modern solid-state integrated circuits.Here,by introducing nano-sized vacuum gaps(~200 nm)in a van der Waals heterostructure,we successfully fabricated a one-dimensional(1 D)edge-to-edge thermionic emission vacuum tube using graphene as the filament.With the increasing collector voltage,the emitted current exhibits a typical rectifying behavior,with the maximum emission current reaching 200 p A and an ON-OFF ratio of 10;.In addition,it is found that the maximum emission current is proportional to the number of the layers of graphene.Our results expand the research of nano-sized vacuum tubes to an unexplored physical limit of 1 D edge-to-edge emission,and hold great promise for future nano-electronic systems based on it.

Surface plasmon assisted high-performance photodetectors based on hybrid TiO_(2)@GaO_(x)N_(y)-Ag heterostructure

In this work,we reported a high-performance-based ultraviolet-visible(UV-VIS)photodetector based on a TiO_(2)@GaO_(x)N_(y)-Ag heterostructure.Ag particles were introduced into TiO_(2)@GaO_(x)N_(y)to enhance the visible light detection perfor-mance of the heterojunction device.At 380 nm,the responsivity and detectivity of TiO_(2)@GaO_(x)N_(y)-Ag were 0.94 A/W and 4.79×109 Jones,respectively,and they increased to 2.86 A/W and 7.96×1010 Jones at 580 nm.The rise and fall times of the response were 0.19/0.23 and 0.50/0.57 s,respectively.Uniquely,at 580 nm,the responsivity of fabricated devices is one to four orders of magnitude higher than that of the photodetectors based on TiO_(2),Ga_(2)O_(3),and other heterojunctions.The excellent optoelectronic characteristics of the TiO_(2)@GaO_(x)N_(y)-Ag heterojunction device could be mainly attributed to the synergistic effect of the type-Ⅱband structure of the metal-semiconductor-metal heterojunction and the plasmon resonance effect of Ag,which not only effectively promotes the separation of photogenerated carriers but also reduces the recombination rate.It is fur-ther illuminated by finite difference time domain method(FDTD)simulation and photoelectric measurements.The TiO_(2)@GaO_(x)N_(y)-Ag arrays with high-efficiency detection are suitable candidates for applications in energy-saving communica-tion,imaging,and sensing networks.

Solid-State Hydrogen Storage Properties of Ti-V-Nb-Cr High-Entropy Alloys and the Associated Effects of Transitional Metals(M=Mn,Fe,Ni)

Recently,high-entropy alloys(HEAs)designed by the concepts of unique entropy-stabilized mechanisms,started to attract widespread interests for their hydrogen storage properties.HEAs with body-centered cubic(BCC)structures present a high potential for hydrogen storage due to the high hydrogen-to-metal ratio(up to H/M=2)and vastness of compositions.Although many studies reported rapid absorption kinetics,the investigation of hydrogen desorption is missing,especially in BCC HEAs.We have investigated the crystal structure,microstructure and hydrogen storage performance of a series of HEAs in the Ti-V-Nb-Cr system.Three types of TiVCrNb HEAs(Ti_(4)V_(3)NbCr_(2),Ti_(3)V_(3)Nb2Cr_(2),Ti_(2)V_(3)Nb_(3)Cr_(2))with close atomic radii and different valence electron concentrations(VECs)were designed with single BCC phase by CALPHAD method.The three alloys with fast hydrogen absorption kinetics reach the H/M ratio up to 2.Particularly,Ti_(4)V_(3)NbCr_(2)alloy shows the hydrogen storage capacity of 3.7 wt%,higher than other HEAs ever reported.The dehydrogenation activation energy of HEAs’hydride has been proved to decrease with decreasing VEC,which may be due to the weakening of alloy atom and H atom.Moreover,Ti_(4)V_(3)NbCr_(2)M(M=Mn,Fe,Ni)alloys were also synthesized to destabilize hydrides.The addition of Mn,Fe and Ni lead to precipitation of Laves phase,however,the kinetics did not improve further because of their own excellent hydrogen absorption.With increasing the content of Laves phase,there appear more pathways for hydrogen desorption so that the hydrides are more easily dissociated,which may provide new insights into how to achieve hydrogen desorption in BCC HEAs at room temperature.

Metal–insulator transition in few-layered GaTe transistors

Two-dimensional(2D)materials have triggered enormous interest thanks to their interesting properties and potential applications,ranging from nanoelectronics to energy catalysis and biomedicals.In addition to other widely investigated 2D materials,GaTe,a layered material with a direct band gap of^1.7 e V,is of importance for applications such as optoelectronics.However,detailed information on the transport properties of GaTe is yet to be explored,especially at low temperatures.Here,we report on electrical transport measurements on few-layered GaTe field effect transistors(FETs)encapsulated by h-BN at different temperatures.We find that by tuning the carrier density,ambipolar transport was realized in GaTe devices,and an electrical-field-induced metal to insulator transition(MIT)was observed when it was hole doped.The mobilities of GaTe devices show a clear dependence on temperature and increase with the decrease of temperature,reaching^1200 cm2 V-1s-1 at 3 K.Our findings may inspire further electronic studies in devices based on GaTe.

粤港澳大湾区健康管理高质量发展的思考

建设粤港澳大湾区是党和国家政府重要部署的发展战略之一。发展融合创新的高质量健康管理是粤港澳大湾区大健康产业领域的重要议题。随着大湾区居民对健康医疗的诉求日益上升,健康管理的创新融合发展势在必行。但目前香港地区、澳门地区与内地在融合发展仍面临许多挑战,本文通过介绍香港地区、澳门地区两地的健康管理现状,比较和概括三地面临的融合发展的挑战,结合粤港澳大湾区的特点,从政策、经贸、教育人才、学术科研、文化观念等方面对健全大湾区健康管理的融合发展提出建议。

A monolithically sculpted van der Waals nano-opto-electro-mechanical coupler

The nano-opto-electro-mechanical systems(NOEMS)are a class of hybrid solid devices that hold promises in both classical and quantum manipulations of the interplay between one or more degrees of freedom in optical,electrical and mechanical modes.To date,studies of NOEMS using van der Waals(vdW)heterostructures are very limited,although vdW materials are known for emerging phenomena such as spin,valley,and topological physics.Here,we devise a universal method to easily and robustly fabricate vdW heterostructures into an architecture that hosts opto-electro-mechanical couplings in one single device.We demonstrated several functionalities,including nano-mechanical resonator,vacuum channel diodes,and ultrafast thermo-radiator,using monolithically sculpted graphene NOEMS as a platform.Optical readout of electric and magnetic field tuning of mechanical resonance in a CrOCl/graphene vdW NOEMS is further demonstrated.Our results suggest that the introduction of the vdW heterostructure into the NOEMS family will be of particular potential for the development of novel lab-on-a-chip systems.

Nuclear Aurora kinase A triggers programmed death-ligand 1-mediated immune suppression by activating MYC transcription in triple-negative breast cancer

Background:Increasing studies have reported that oncogenes regulate components of the immune system,suggesting that this is a mechanism for tumorigenesis.Aurora kinase A(AURKA),a serine/threonine kinase,is involved in cell mitosis and is essential for tumor cell proliferation,metastasis,and drug resistance.However,the mechanism by which AURKA is involved in immune response regulation is unclear.Therefore,this study aimed to investigate the role of AURKA in immune regulation in triple-negative breast cancer(TNBC).Methods:Peripheral blood mononuclear cells(PBMCs)were co-cultured with TNBC cells.The xCELLigence Real-Time Cell Analyzer-MP system was used to detect the killing efficiency of immune cells on TNBC cells.The expression of immune effector molecules was tested by quantitative real-time polymerase chain reaction(qRT-PCR)to evaluate immune function.Furthermore,to validate AURKA-regulated immune response in vivo,4T1 murine breast cancer cell line with AURKA overexpression or downregulation was engrafted into BALB/c mice.The distribution and proportion of immune cells in tumors were further evaluated by immunohistochemistry and flow cytometry.Results:Downregulation of AURKA in TNBC cells increased immune response by activating CD8^(+)T cell proliferation and activity.Nuclear rather than cytoplasmic AURKA-derived programmed death-ligand 1(PD-L1)expression was independent of its kinase activity.Mechanistic investigations showed that nuclear AURKA increased PD-L1 expression via an MYC-dependent pathway.PD-L1 overexpression mostly reversed AURKA silencing-induced expression of immune effector molecules,including interleukin-(IL-2),interferon-γ(IFN-γ),and perforin.Moreover,AURKA expression was negatively correlated with the enrichment and activity of tumor-infiltrating CD8^(+)T cells in 4T1 engrafted BALB/c mouse model.Conclusions:Nuclear AURKA elevated PD-L1 expression via an MYCdependent pathway and contributed to immune evasion in TNBC.Therapies targeting nuclear AURKA may restore immune responses against tumors.

Pledgee competition, strategic disclosure, and future crash risk

We investigate whether pledgee competition affects the disclosure choice of firms whose controlling shareholders pledge their shares.We find that pledgee competition is positively related to pledge firms’ annual report tone management.This positive relationship is stronger for pledge firms with lower credit quality and non-state-owned enterprise pledge firms.Further corroborating our results, higher pledgee competition increases the future crash risk of pledge firms.Collectively, our results suggest that competition pressure induces pledgees to lower their monitoring incentives to remain competitive in the marketplace, thus leading to pledge firms’ bad news hoarding behavior.

Nanoparticles targeting at methylases with high correlation to N^(6)-methyladenosine-related lncRNA signatures as potential therapy of kidney clear cell carcinoma

Clear cell renal cell carcinoma(ccRCC)is a heterogeneous malignancy with poor prognosis.Methylation of the N^(6) position of adenosine(m^(6)A),the most common epigenetic modification in both messenger RNAs and noncoding RNAs,has been reported to regulate the initiation and progression of ccRCC.However,whether and how m^(6)A-related long noncoding RNAs(m^(6)ArlncRNAs)signify the progression of ccRCC remain unclear.We found m^(6)ArlncRNAs are effective signatures illustrating immune landscape and risk stratification in ccRCC.We identified two differently expressed m^(6)ArlncRNAs(DEm^(6)ArlncRNAs),AC008870.2 and EMX2OS,as independent risk factors for overall survival of ccRCC patients,by applying stringent variable selection procedure to data from the Cancer Genome Atlas Kidney Renal Clear Cell Carcinoma project.The risk score generated from the DEm^(6)ArlncRNA expression categorizes patients into either high or low-risk groups,between which,enrichment analysis indicated an enrichment in immune-related pathways.Under different DEm^(6)ArlncRNA transcription pattern,the two risk groups differ in immune cell population composition and expression levels of therapy targeting genes.Nanoparticle is satisfactory strategy to delivering therapeutic drugs.For further clinical translation,we designed a novel nanoparticle delivery system packaged STM2457(STM@8P4 NPs),which selectively inhibits AC008870.2-correlated m^(6)A writer.STM@8P4 NPs loaded drug successfully with uniform particle size,long-term stability and high release efficiency.STM@8P4 NPs can easily enter ccRCC cells and showed a highly efficient ccRCC killing activity in vitro.Our results therefore indicate that m^(6)ArlncRNAs expression can depict tumor microenvironment,predict prognosis for ccRCC patient and give hint to therapeutic strategies in ccRCC.

Down-Regulation of TLR9 Expression Affects the Maturation and Function of Murine Bone Marrow-Derived Dendritic Cells Induced by CpG

Toll-like receptor 9 （TLR9） is expressed intracellularly by dendritic cells （DCs） and specifically recognizes unmethylated CpG motif. Recognition of TLR9 to CpG DNA can induce DC maturation followed by the subsequent immune responses. Here, RNA interference （RNAi） was used to identify the effect of CpG DNA signaling on DC function. The results showed that transfection of DCs with siRNA specific for TLR9 gene significantly down-regulated TLR9 expression. Immature DCs transfected with TLR9 siRNA did not differentiate into mature DCs with exposure to CpG. TLR9 siRNA-treated DCs expressed low levels of MHC II and CD40 without reducing endocytosis. Furthermore, TLR9 siRNA-transfected DCs exhibited a decreased allostimulatory capacity in a lymphocyte proliferation assay and attenuated Thl responses by decreasing IL-12p70 production. Our findings indicate that siRNA in silencing TLR9 gene in DCs may offer a potential tool to study the TLR9-CpG pathway.