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Ward identities under the frame transformations in curved space-time

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Communications in Theoretical physics 2024年第9期76卷 109-119页

作者： Susobhan Mandal department of physics Indian Institute of Technology Bombay

Scalar-tensor theories of gravity are considered to be competitors to Einstein's theory of general relativity for the description of classical gravity, as they are used to build feasible models for cosmic inflation. These theories can be formulated both in the Jordan and Einstein frame, which are related by a Weyl transformation with a field transformation, known together as a frame transformation. These theories formulated in the above two frames are often considered to be equivalent from the point of view of classical theory. However, this is no longer true from the quantum field theoretical perspective. In the present article, we show that the Ward identities derived in the above two frames are not connected through the frame transformation. This shows that the quantum field theories formulated in these two frames are not equivalent to each ***, this inequivalence is also shown by comparing the effective actions derived in these two frames.

关键词： curved spacetime frame transformations ward identities

Highly sensitive flexible strain sensor based on the two-dimensional semiconductor tellurium with a negative gauge factor

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Science China(Information Sciences) 2024年第7期67卷 295-304页

作者： Jiarui HE Yusong QU Shengyao CHEN Cong WANG Lena DU Xiaoshan DU Yuanyuan ZHENG Guozhong ZHAO He TIAN College of Mathematics and physics Beijing University of Chemical Technology School of Integrated Circuits Tsinghua University Beijing China & The Beijing National Research Center for Information Science and Technology (BNRist)Tsinghua University CAS Center for Excellence in nanoscience National Center for Nanoscience and Technology &University of Chinese Academy of Sciences Beijing Key Lab of Terahertz Spectroscopy and Imaging Key Lab of Terahertz OptoelectronicsMinistry of Education Department of Physics Capital Normal University

Research on flexible strain sensors has advanced rapidly in recent years, with particular attention being devoted to two-dimensional(2D) semiconductor materials owing to their exceptional mechanical and electrical properties that are conducive to sophisticated sensing performance. However, resistive strain sensors based on 2D semiconductor materials typically exhibit positive gauge factors(GF), while materials for strain sensors with a negative GF remain elusive. We have identified a trend of reduction in the band gap of the emerging 2D semiconductor material tellurium(Te) under strain in simulations reported in past research,and have observed a negative GF in the Te-based strain sensor. In this study, we combined Te with a flexible polyethylene terephthalate(PET) substrate to manufacture a flexible strain sensor with a significantly negative GF. The results of tests revealed that the Te-based strain sensor achieved an impressive maximum sensitivity of-139.7 within a small range of bending-induced strain(< 1%). Furthermore, it exhibited excellent linearity and good cyclic stability, and was successfully applied to monitor limb movements. The work here verifies the significant potential for the use of Te-based strain sensors in next-generation flexible electronics.

关键词： 2D semiconductor materials 2D tellurium flexibleelectronics strain sensors negative gauge factor high sensitivity

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Assembly of functional carboxymethyl cellulose/polyethylene oxide/anatase TiO_(2) nanocomposites and tuning the dielectric relaxation, optical, and photoluminescence performances

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Journal of Semiconductors 2024年第7期45卷 26-38页

作者： Asmaa M.Ismail Abeer A.Reffaee Fawzy G.El Desouky Spectroscopy department Physics Research InstituteNational Research CentreGizaCairo 12622Egypt Microwave physics and Dielectrics department National Research CentreDokkiCairoEgypt Solid State physics department Physics Research InstituteNational Research CentreGizaCairo 12622Egypt

Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting ***2 nanocrystals were effectively incorporated into CMC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-FTIR)*** roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CMC/*** differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO *** increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as *** electrical properties of the CMC/PEO/TO nanocomposite undergo significant *** nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer *** decline in the energy gap is readily apparent as the weight percentage of TO NCs *** photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO *** nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.

关键词： anatase TiO_(2) CMC/PEO nanocomposites optical photoluminescent electrical optoelectronics

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Recent progress in MnBi2nTe3n+1 intrinsic magnetic topological insulators: crystal growth, magnetism and chemical disorder

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National Science Review 2024年第2期11卷 65-80页

作者： Chaowei Hu Tiema Qian Ni Ni department of physics and Astronomy and California Nano Systems institute University of California-Los Angeles

The search for magnetic topological materials has been at the forefront of condensed matter research for their potential to host exotic states such as axion insulators, magnetic Weyl semimetals, Chern insulators,etc. To date, the MnBi2nTe3n+1family is the only group of materials showcasing van der Waals-layered structures, intrinsic magnetism and non-trivial band topology without trivial bands at the Fermi level. The interplay between magnetism and band topology in this family has led to the proposal of various topological phenomena, including the quantum anomalous Hall effect, quantum spin Hall effect and quantum magnetoelectric effect. Among these, the quantum anomalous Hall effect has been experimentally observed at record-high temperatures, highlighting the unprecedented potential of this family of materials in fundamental science and technological innovation. In this paper, we provide a comprehensive review of the research progress in this intrinsic magnetic topological insulator family, with a focus on single-crystal growth, characterization of chemical disorder, manipulation of magnetism through chemical substitution and external pressure, and important questions that remain to be conclusively answered.

关键词： MnBi2Te4 magnetic topological insulator magnetism tuning antiferromagnetism ferromagnetism pressure chemical doping

Microwave diagnostics of pulsed atmospheric discharge with electrolytic electrode and long-lived luminous formation in its afterglow

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High Voltage 2024年第1期9卷 127-136页

作者： Shixin Zhao Xingbao Lyu Aleksandr Astafiev Chengxun Yuan Lin Miao Jingfeng Yao Ying Wang Anatoly Kudryavtsev Aleksandr Chirtsov Gennadii Shabanov Zhongxiang Zhou School of physics Harbin Institute of TechnologyHarbinChina physics department Saint Petersburg Electrotechnical University“LETI”St.PetersburgRussia Heilongjiang Provincial Key Laboratory of Plasma physics and Application Technology HarbinChina physics department St.Petersburg State UniversitySt.PetersburgRussia Konstantinov Petersburg Nuclear physics institute National Research Centre“Kurchatov Institute”GatchinaRussia

The Gatchina discharge phenomenon holds significant promise as a laboratory model for simulating ball ***,crucial aspects concerning the plasma components of the resulting afterglow remain ***,the measurement of the electron density,a critical parameter,has not been fully achieved thus *** this study,microwave diagnostics and video recording were employed during a pulsed Gatchina discharge,along with synchronous measurement of discharge current and *** antennas were positioned at different heights to enable separate diagnosis of the discharge and the ensuing long-lived *** findings revealed that during the active phase of the Gatchina discharge,the plasma density was substantial enough to cause reflection of an electromagnetic wave with a frequency of 20 GHz from this highly conductive *** the afterglow,the signal experienced only a moderate weakening of 10–20 percent,facilitating the determination of the time dependence of average electron density during the afterglow's passage between the two *** measurements verified the unusually slow plasma decay in the afterglow of the Gatchina discharge,suggesting the potential significance of chemi-ionisation processes involving long-lived(metastable)particles.

关键词： holds luminous electrolytic

Epitaxial quasi-2D/3D hybrid perovskite heterojunctions for photodetector with enhanced detectivity and stability

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Nano Research 2024年第7期17卷 6594-6602页

作者： Yifu Chen Lin Zhang Xinxin Peng Weiran Qin Shiqing Li Yingwei Wang Zhihui Chen Si Xiao Bin Yang Biao Liu Junliang Yang Han Huang Yun Lin Jun He Liming Ding Yongbo Yuan Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China Hunan Key Laboratory of Nanophotonics and Devices School of PhysicsCentral South UniversityChangsha 410083China College of Materials Science and Engineering Hunan UniversityChangsha 410082China department of Photoelectric Information School of PhysicsCentral South UniversityChangsha 410083China Center for Excellence in nanoscience Key Laboratory of Nanosystem and Hierarchical FabricationNational Center for Nanoscience and TechnologyChinese Academy of ScienceBeijing 100190China

Although numerous metal halide perovskite materials have been investigated in the field of optoelectronic,the development of perovskite heterojunctions with exotic structures is still ***,we report the epitaxial growth of quasi-two-dimensional(Q-2D)perovskites on methylammonium lead iodide(MAPbI_(3))single crystals to form perovskite heterojunctions with interfacial *** MAPbI_(3)adjacent to epitaxial Q-2D perovskite shows blue shifted photoluminescence with shortened lifetime,which becomes significant with the reduced layer number of the Q-2D *** findings suggest the presence of an interfacial strain gradient leading to enhanced photocarrier ***,compared to the MAPbI_(3)single crystal detector,the BA_(2)MAPb_(2)I_(7)/MAPbI_(3)(BA:n-butylamine)heterojunction-based photodetector demonstrates a bandpass detecting property and exhibits 5 times enhanced external quantum efficiency and 83 times enhanced specific detectivity(D*=3.26×10^(11)Jones).Remarkably,the unencapsulated BA_(2)MAPb_(2)I_(7)/MAPbI_(3)heterojunction is stable in ambient condition for>300 *** Q-2D/3D heterojunction shows suppressed ion inter-diffusion due to the presence of Q-2D phase.

关键词： epitaxial growth interfacial strain quasi-two-dimensional/three-dimensional(Q-2D/3D)heterojunctions ion inter-diffusion

Praseodymium metal nanorods as a 5-fluorouracil carrier

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Journal of Rare Earths 2024年第7期42卷 1328-1336,I0005页

作者： Varnitha Manikantan Govindaraj Sri Varalakshmi Ujma Ashapak Tamboli Archana Sumohan Pillai Aleyamma Alexander Anushka Lucas Bose Allben Akash Israel V.M.V.Enoch Centre for nanoscience and Genomics Karunya Institute of Technology and Sciences(Deemed University)Coimbatore641114Tamil NaduIndia department of Applied Chemistry Karunya Institute of Technology and Sciences(Deemed University)Coimbatore641114Tamil NaduIndia

Interest in metal nanoparticles as nanoscale drug-carrying vehicles has been *** such an aspect,lanthanide metal nanoparticles are particularly ***,we report praseodymium nanoparticles as a novel anticancer therapeutic transporting *** material was made as a composite with the supramolecular host polymer,poly-β-*** praseodymium nanorods were characterized using standard analytical techniques,including X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).In addition,they were imaged using transmission electron *** nanostructures are a long rod-shaped material with 2.0±0.1μm in length and 230±10 nm in *** material shows a saturation magnetization value above 30 emu/g with a coercivity value of 130 *** nanocarrier is freighted with the drug 5-fluorouracil,and the encapsulation efficiency is 76.09%.The drug release is continuous from the nanocarrier(polymer-containing praseodymium nanoparticles)and proceeds for above 250 *** in vitro cytotoxicities of the blank nanocarrier and the 5-fluorouracil-loaded one are deduced by testing them on MCF-7 and Vero(non-cancerous)cell *** cytotoxicity on the cancerous cell lines is observed,whereas the non-cancerous cells are *** IC_(50)values on the cell lines are reported.

关键词： Metal nanoparticles Praseodymium Poly-cyclodextrin Drug delivery Anticancer activity Rare earths

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Simulation Study on Constraining Gravitational Wave Propagation Speed by Gravitational Wave and Gamma-ray Burst Joint Observation on Binary Neutron Star Mergers

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Research in Astronomy and Astrophysics 2024年第8期24卷 44-53页

作者： Jin-Hui Rao Shu-Xu Yi Lian Tao Qing-Wen Tang department of physics School of Physics and Materials ScienceNanchang University institute of High Energy physics Chinese Academy of Sciences

Theories of modified gravity suggest that the propagation speed of gravitational waves （GW） vgmay deviate from the speed of light c.A constraint can be placed on the difference between c and vgwith a simple method that uses the arrival time delay between GW and electromagnetic wave simultaneously emitted from a burst *** simulated the joint observation of GW and short gamma-ray burst signals from binary neutron star merger events in different observation campaigns,involving advanced LIGO （aLIGO） in design sensitivity and Einstein Telescope（ET） joint-detected with Fermi/*** a result,the relative precision of constraint on vgcan reach～10-17（aLIGO） and～10-18（ET）,which are one and two orders of magnitude better than that from GW170817,*** continue to obtain the bound of graviton mass mg≤7.1（3.2）×10-20eV with aLIGO （ET）.Applying the Standard-Model Extension test framework,the constraint on vgallows us to study the Lorentz violation in the nondispersive,nonbirefringent limit of the gravitational *** obtain the constraints of the dimensionless isotropic coefficients ■at mass dimension d=4,which are■for aLIGO and■for ET.

关键词： (stars:) gamma-ray burst: general gravitational waves stars: neutron

Electricity resonance-induced phase transition of water confined in nanochannels

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Communications in Theoretical physics 2024年第5期76卷 159-165页

作者： Yunqiu Ma Zhigao Zhao Shaoqian Hao Jianlong Kou Jiang-Xing Chen institute of Condensed Matter physics Zhejiang Institute of Photoelectronics&Zhejiang Institute for Advanced Light SourceZhejiang Normal UniversityJinhua 321004China department of physics Inner Mongolia UniversityHohhot 010021China department of physics Hangzhou Normal UniversityHangzhou 311121China

The phase transition of water molecules in nanochannels under varying external electric fields is studied by molecular dynamics *** is found that the phase transition of water molecules in nanochannels occurs by changing the frequency of the varying electric *** molecules maintain the ice phase when the frequency of the varying electric field is less than 16 THz or greater than 30 THz,and they completely melt when the frequency of the varying electric field is 24 *** phenomenon is attributed to the breaking of hydrogen bonds when the frequency of the varying electric field is close to their inherent resonant ***,the study demonstrates that the critical frequency varies with the confinement *** new mechanism of regulating the phase transition of water molecules in nanochannels revealed in this study provides a perspective for further understanding of the phase transition of water molecules in nanochannels,and has great application potential in preventing icing and deicing.

关键词： electricity resonance phase transition water molecules molecular dynamics simulations

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