Showing 1–32 of 32 results for author: Lei, L

Centimeter-scale fully suspended metal and metal oxide thin films by one-step transfer-free liquid metal capillary forming

Authors: Chunlei Song, Zhenqi Guo, Yuanting Su, Changren Tian, Yeqi Zhu, Liang Lei, Jianbo Tang

Abstract: Fully suspended thin films can decouple substrate effects and provide additional tuning degrees of freedom compared with their substrate-supported counterparts, making them unique platforms for next-generation thin film devices. Here we report one-step, transfer-free and substrate-free fabrication of centimeter-scale ultrathin fully suspended metal and metal oxide film structures via liquid metal… ▽ More Fully suspended thin films can decouple substrate effects and provide additional tuning degrees of freedom compared with their substrate-supported counterparts, making them unique platforms for next-generation thin film devices. Here we report one-step, transfer-free and substrate-free fabrication of centimeter-scale ultrathin fully suspended metal and metal oxide film structures via liquid metal capillary forming. We show that, analogous to soap film formation, the instantaneously developed few-nanometer-thick native surface oxide can laminate various liquid metals into micrometer-thick metallic films. Surprisingly, the surfactant-like metal oxide bilayer can survive dewetting-induced liquid metal drainage, forming suspended two-dimensional films featuring an enormous lateral size-to-thickness ratio on the order of 10^7. We further demonstrate rapid prototyping of metallic minimal-surface thin-walled structures and ultra-sensitive acoustic wave detection with these suspended thin film platforms. △ Less

Submitted 31 July, 2026; originally announced August 2026.

Self-Driven Atomic Dispersion in Graphitic Layers

Authors: Zhaoxi Chen, Yulu He, Zhuoran Yao, Jian Liu, Jun Cai, Ziyi Fan, Wenjun Zhang, Lei Lei, Zupeng Chen, Bo Yang, Zhi Liu, Zhu-Jun Wang

Abstract: Carbon-supported single-atom catalysts maximize metal utilization, but how metal nanoparticles transform into isolated atoms within carbon remains unclear. We show that metal nanoparticles can undergo a self-driven dispersion process under hydrocarbon oxidation conditions, transforming into single atoms that are confined in carbon matrix. Using Pt-catalysed hydrocarbon oxidation as a model, we com… ▽ More Carbon-supported single-atom catalysts maximize metal utilization, but how metal nanoparticles transform into isolated atoms within carbon remains unclear. We show that metal nanoparticles can undergo a self-driven dispersion process under hydrocarbon oxidation conditions, transforming into single atoms that are confined in carbon matrix. Using Pt-catalysed hydrocarbon oxidation as a model, we combine operando electron microscopy, near-ambient-pressure X-ray photoelectron spectroscopy and mass spectrometry to track coupled structural and chemical evolution. Graphitic carbon grows at step edges of Pt nanoparticle, continuously reconstructing Pt surface and generating undercoordinated sites for atom release. In-situ generated CO accumulates at the metal-carbon interface, weakening bonding and facilitating self-amplified atom release and migration. Defective carbon overlayers then trap, stabilize and transport liberated atoms, while oxidative etching preserves interfacial access of reaction-gas. Similar behaviour across other metals suggests a general atomization pathway for single-atom catalyst synthesis, yielding products with electrocatalytic hydrogen production activity beyond standard commercial benchmarks. △ Less

Submitted 3 July, 2026; originally announced July 2026.

Comments: 30 pages, 5 figures

How is Water released in Hydrogen-Based Metal Oxide Reduction? Unraveling the Kinetic Bottleneck in Sustainable Metal Production

Authors: Zhaoxi Chen, Yulu He, Zhuoran Yao, Chunwen Wang, Lei Lei, Jun Cai, Martin Aaskov Karlsen, Claudio Pistidda, Wu Zhou, Marc-Georg Willinger, Yan Ma, Dierk Raabe, Zhi Liu, Zhu-Jun Wang

Abstract: Hydrogen-based direct reduction of metal oxides is a ubiquitous solid-gas redox process central to geophysics, sustainable metallurgy, redox energy cycles and catalysis. During this process, hydrogen removes lattice oxygen to form water, yet product water has long been regarded as a passive exhaust, and its nanoscale formation, trapping and removal remain poorly understood. Here, we directly obser… ▽ More Hydrogen-based direct reduction of metal oxides is a ubiquitous solid-gas redox process central to geophysics, sustainable metallurgy, redox energy cycles and catalysis. During this process, hydrogen removes lattice oxygen to form water, yet product water has long been regarded as a passive exhaust, and its nanoscale formation, trapping and removal remain poorly understood. Here, we directly observe redox-product water release from iron oxide during hydrogen-based direct reduction. Because water removal emerges from coupled structural, chemical and crystallographic evolution across multiple length-scales under realistic non-equilibrium reaction-conditions, we establish a correlative multiscale in-situ approach that links pore evolution, molecular water signatures, phase transformation and chemical-state evolution during hematite reduction. We uncover a mechanism in which oxygen removal induces closed nanopores spatially delocalized from reaction surfaces, causing transient trapping of water vapor. Water is released only when these pores coalesce into a percolating network connected to the surface, coinciding with and accelerating the onset of the hematite-to-magnetite transformation. These findings show that dynamically evolving pore topology governs mass transport and redox kinetics in solid-gas reactions, closing a critical mechanistic gap in product-water removal and providing nanoscale guidance for hydrogen-based metal extraction, reactor design, and sustainable redox energy technologies under practical conditions. △ Less

Submitted 29 June, 2026; originally announced June 2026.

Comments: 17 pages, 5 figures

Physics-embedded neural computational electron microscopy for quantitative 4D nanometrology

Authors: Hao-Jin Wang, Liqun Shen, Xin-Ning Tian, Lei Lei, Kexin Wang, Grigore Moldovan, Marc-Georg Willinger, Zhu-Jun Wang

Abstract: The fusion of rigorous physical laws with flexible data-driven learning represents a new frontier in scientific simulation, yet bridging the gap between physical interpretability and computational efficiency remains a grand challenge. In electron microscopy, this divide limits the ability to quantify three-dimensional topography from two-dimensional projections, fundamentally constraining our unde… ▽ More The fusion of rigorous physical laws with flexible data-driven learning represents a new frontier in scientific simulation, yet bridging the gap between physical interpretability and computational efficiency remains a grand challenge. In electron microscopy, this divide limits the ability to quantify three-dimensional topography from two-dimensional projections, fundamentally constraining our understanding of nanoscale structure-function relationships. Here, we present a physics-embedded neural computational microscopy framework that achieves metrological three-dimensional reconstruction by deeply coupling a differentiable electron-optical forward model with deep learning. By introducing a Vision Field Transformer as a high-speed, differentiable surrogate for physical process analysis simulations, we establish an end-to-end, self-supervised optimization loop that enforces strict physical consistency with hardware geometry. This synergy enables single-shot, quantitative three-dimensional nanometrology with precision comparable to atomic force microscopy but at orders of magnitude higher throughput. Furthermore, we demonstrate the capability for four-dimensional (3D real space plus time) in situ characterization by tracking the dynamic evolution of surface nanostructure during copper redox, revealing hidden crystallographic kinetics invisible to conventional imaging. Our work not only redefines the limits of scanning electron microscopy but also establishes a generalizable archetype for solving ill-posed inverse problems across physical sciences, unlocking the full potential of simulation as a third pillar of discovery. △ Less

Submitted 12 January, 2026; originally announced January 2026.

Comments: 26 pages, 6 figures

Initial performance results of the JUNO detector

Authors: Angel Abusleme, Thomas Adam, Kai Adamowicz, David Adey, Shakeel Ahmad, Rizwan Ahmed, Timo Ahola, Sebastiano Aiello, Fengpeng An, Guangpeng An, Costas Andreopoulos, Giuseppe Andronico, João Pedro Athayde Marcondes de André, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, Didier Auguste, Margherita Buizza Avanzini, Andrej Babic, Jingzhi Bai, Weidong Bai, Nikita Balashov, Roberto Barbera, Andrea Barresi , et al. (1114 additional authors not shown)

Abstract: The Jiangmen Underground Neutrino Observatory (JUNO) started physics data taking on 26 August 2025. JUNO consists of a 20-kton liquid scintillator central detector, surrounded by a 35 kton water pool serving as a Cherenkov veto, and almost 1000 m$^2$ of plastic scintillator veto on top. The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e. This paper present… ▽ More The Jiangmen Underground Neutrino Observatory (JUNO) started physics data taking on 26 August 2025. JUNO consists of a 20-kton liquid scintillator central detector, surrounded by a 35 kton water pool serving as a Cherenkov veto, and almost 1000 m$^2$ of plastic scintillator veto on top. The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e. This paper presents the performance results of the detector, extensively studied during the commissioning of the water phase, the subsequent liquid scintillator filling phase, and the first physics runs. The liquid scintillator achieved an attenuation length of 20.6 m at 430 nm, while the high coverage PMT system and scintillator together yielded about 1785 photoelectrons per MeV of energy deposit at the detector centre, measured using the 2.223 MeV $γ$ from neutron captures on hydrogen with an Am-C calibration source. The reconstructed energy resolution is 3.4% for two 0.511 MeV $γ$ at the detector centre and 2.9% for the 0.93 MeV quenched Po-214 alpha decays from natural radioactive sources. The energy nonlinearity is calibrated to better than 1%. Intrinsic contaminations of U-238 and Th-232 in the liquid scintillator are below 10$^{-16}$ g/g, assuming secular equilibrium. The water Cherenkov detector achieves a muon detection efficiency better than 99.9% for muons traversing the liquid scintillator volume. During the initial science runs, the data acquisition duty cycle exceeded 97.8%, demonstrating the excellent stability and readiness of JUNO for high-precision neutrino physics. △ Less

Submitted 18 November, 2025; originally announced November 2025.

Comments: 38 pages, 23 figures

Moire-enabled optical vortex with tunable topological charge in twisted bilayer photonic crystals

Authors: Tiancheng Zhang, Li Lei, Changhao Ding, Fanhao Meng, Qicheng Jiang, Lijie Li, Scott Dhuey, Jingze Yuan, Zhengyan Cai, Yi Li, Jingang Li, Costas P. Grigoropoulos, Haoning Tang, Jie Yao

Abstract: The orbital angular momentum (OAM) of light is a versatile degree of freedom with transformative impact across optical communication, imaging, and micromanipulation. These applications have motivated a growing demand for compact, reconfigurable vortex arrays with tunable topological charge, yet integrating these functionalities into nanophotonic platforms remains elusive. Among possible strategies… ▽ More The orbital angular momentum (OAM) of light is a versatile degree of freedom with transformative impact across optical communication, imaging, and micromanipulation. These applications have motivated a growing demand for compact, reconfigurable vortex arrays with tunable topological charge, yet integrating these functionalities into nanophotonic platforms remains elusive. Among possible strategies to meet this challenge is exploiting the twist degree of freedom in layered structures, which enables both emerging moire physics and unprecedented reconfigurability of photonic and electronic properties. Here, we harness these capabilities in twisted bilayer moire photonic crystals (TBMPCs) to realize vortex array generation with tunable OAM, demonstrated both analytically and experimentally. Central to this advancement is a new class of quasi-bound state in the continuum: Bessel-type modes emerging from moire-induced interlayer coupling, which generate vortex beams with tailored spiral phase distributions. We experimentally demonstrate vortex beams spanning eight OAM orders, from -3 to 4, and achieve selective excitation of distinct topological charges at a fixed telecommunication wavelength by tuning the interlayer separation and twist angle. Furthermore, localized Bessel-type modes at AA stacking regions can be excited nonlocally across the moire superlattice, enabling vortex array generation. Our work offers new insights into moire physics and introduces an innovative approach for future multiplexing technology integrating OAM, wavelength, and spatial division. △ Less

Submitted 29 October, 2025; originally announced October 2025.

Local Proton Disorder Induced Intermolecular H-H Coupling in Ionization of Dense Ammonia

Authors: Yu Tao, Li Lei, Jingyi Liu, Binbin Wu

Abstract: Under cold compression, hydrogen bonding was considered to dominate intermolecular interaction during the ionization of ammonia. Here, we provide experimental and theoretical evidence of intermolecular HH coupling in dense ammonia. Ab initio molecular dynamics simulations (AIMD) reveal an increasing degree of proton disorder in ammonia with increasing pressure, which promotes intermolecular H-H co… ▽ More Under cold compression, hydrogen bonding was considered to dominate intermolecular interaction during the ionization of ammonia. Here, we provide experimental and theoretical evidence of intermolecular HH coupling in dense ammonia. Ab initio molecular dynamics simulations (AIMD) reveal an increasing degree of proton disorder in ammonia with increasing pressure, which promotes intermolecular H-H coupling. At pressure below the ionization phase transition pressure (135 GPa), intermolecular HH coupling gives rise to a unique dissociation pathway in ammonia. Sporadic molecular hydrogen was observed without laser heating, accompanied by the absence of molecular nitrogen. At pressure above 135 GPa, intermolecular HH coupling serves as an intermediate state in the ionization of ammonia. Two fingerprint Raman modes previously assigned to the ionic phase disappear upon further compression or heating. Together with proton transfer based on hydrogen bond, a dual path mechanism exists in the ionization of ammonia. Our results demonstrate a case of hydrides phase transition pathway that occurs independently of hydrogen bonding under high pressure. △ Less

Submitted 20 October, 2025; originally announced October 2025.

Comments: 14 pages, 4 figures

Observation of Iron Oxide to Nitride Conversion via Liquid Liquid Phase Separation in High pressure Borate Melt

Authors: Yu Tao, Depu Liu, Chunyin Zhou, Xu Jia, Jingyi Liu, Xue Chang, Yangbin Wang, Yipeng Wang, Duanwei He, Li Lei

Abstract: High pressure chemistry provides a powerful route to materials that are inaccessible or difficult to synthesize under ambient conditions. However, high pressure chemical reaction processes and mechanisms remain largely unexplored because of the challenges associated with in situ characterization under high pressure and high temperature, particularly within the deeply enclosed sample environment of… ▽ More High pressure chemistry provides a powerful route to materials that are inaccessible or difficult to synthesize under ambient conditions. However, high pressure chemical reaction processes and mechanisms remain largely unexplored because of the challenges associated with in situ characterization under high pressure and high temperature, particularly within the deeply enclosed sample environment of a large volume press. Here, we employ the state of the art real time synchrotron X ray radiography to image a high pressure chemical reaction at 5.4 GPa and 1700 K within a large volume press. Using Fe2O3 and BN as precursors, we capture the complete dynamic metal oxide to nitride conversion and show that it differs fundamentally from conventional solid state diffusion controlled nitridation. Synchrotron X ray radiography clearly revealed that this conversion involves a two stage liquid liquid separation process (LLPS), including fluid nitrogen and fluid Fe N alloy. On the basis of these observations, we propose a nitrogen driven mechanism for LLPS in borate melts. Specifically, nitrogen reduces metal cations in the borate network, altering their coordination environments and triggering a substantial reorganization of the melt structure. This coordination induced restructuring destabilizes the borate melt and promotes the LLPS of fluid Fe N alloy. Our in-situ observations suggest a general pathway for high pressure metal oxide to nitride conversion. This study provides a direct visualization of a pres-sure-enabled chemical reaction that is inaccessible under ambient conditions, offering fundamental in-sight into how high pressure reshapes chemical reaction pathways and enables the synthesis of metal nitrides. △ Less

Submitted 8 August, 2026; v1 submitted 29 September, 2025; originally announced September 2025.

Comments: 13 pages, 5 figures

AI-Driven Reinvention of Hydrological Modeling for Accurate Predictions and Interpretation to Transform Earth System Modeling

Authors: Cuihui Xia, Lei Yue, Deliang Chen, Yuyang Li, Hongqiang Yang, Ancheng Xue, Zhiqiang Li, Qing He, Guoqing Zhang, Dambaru Ballab Kattel, Lei Lei, Ming Zhou

Abstract: Traditional equation-driven hydrological models often struggle to accurately predict streamflow in challenging regional Earth systems like the Tibetan Plateau, while hybrid and existing algorithm-driven models face difficulties in interpreting hydrological behaviors. This work introduces HydroTrace, an algorithm-driven, data-agnostic model that substantially outperforms these approaches, achieving… ▽ More Traditional equation-driven hydrological models often struggle to accurately predict streamflow in challenging regional Earth systems like the Tibetan Plateau, while hybrid and existing algorithm-driven models face difficulties in interpreting hydrological behaviors. This work introduces HydroTrace, an algorithm-driven, data-agnostic model that substantially outperforms these approaches, achieving a Nash-Sutcliffe Efficiency of 98% and demonstrating strong generalization on unseen data. Moreover, HydroTrace leverages advanced attention mechanisms to capture spatial-temporal variations and feature-specific impacts, enabling the quantification and spatial resolution of streamflow partitioning as well as the interpretation of hydrological behaviors such as glacier-snow-streamflow interactions and monsoon dynamics. Additionally, a large language model (LLM)-based application allows users to easily understand and apply HydroTrace's insights for practical purposes. These advancements position HydroTrace as a transformative tool in hydrological and broader Earth system modeling, offering enhanced prediction accuracy and interpretability. △ Less

Submitted 7 January, 2025; originally announced January 2025.

Sublayers Editing of Covalent MAX Phase for Nanolaminated Early Transition Metal Compounds

Authors: Ziqian Li, Ke Chen, Xudong Wang, Kan Luo, Lei Lei, Mian Li, Kun Liang, Degao Wang, Shiyu Du, Zhifang Chai, Qing Huang

Abstract: Two-dimensional transition metal carbides and nitrides (MXenes) have gained popularity in fields such as energy storage, catalysis, and electromagnetic interference due to their diverse elemental compositions and variable surface terminations (T). Generally, the synthesis of MXene materials involves etching the weak M-A metallic bonds in the ternary layered transition metal carbides and nitrides (… ▽ More Two-dimensional transition metal carbides and nitrides (MXenes) have gained popularity in fields such as energy storage, catalysis, and electromagnetic interference due to their diverse elemental compositions and variable surface terminations (T). Generally, the synthesis of MXene materials involves etching the weak M-A metallic bonds in the ternary layered transition metal carbides and nitrides (MAX phase) using HF acid or Lewis acid molten salts, while the strong M-X covalent bonds preserve the two-dimensional framework structure of MXenes. On the other hand, the MAX phase material family also includes a significant class of members where the A site is occupied by non-metal main group elements (such as sulfur and phosphorus), in which both M-A and M-X are covalent bond-type sublayers. The aforementioned etching methods cannot be used to synthesize MXene materials from these parent phases. In this work, we discovered that the covalent bond-type M-A and M-X sublayers exhibit different reactivity with some inorganic materials in a high-temperature molten state. By utilizing this difference in reactivity, we can structurally modify these covalent sublayers, allowing for the substitution of elements at the X site (from B to Se, S, P, C) and converting non-metal A site atoms in non-van der Waals (non-vdW) MAX phases into surface atoms in vdW layered materials. This results in a family of early transition metal Xide chalcogenides (TMXCs) that exhibit lattice characteristics of both MXenes and transition metal chalcogenides. Using electron-donor chemical scissors, these TMXC layered materials can be further exfoliated into monolayer nanosheets. The atomic configurations of each atom in these monolayer TMXCs are the same as those of conventional MXenes, but the oxidation states of the M-site atoms can be regulated by both X-site atoms and intercalated cations. △ Less

Submitted 2 December, 2024; originally announced December 2024.

Compton Edge Convolutional Model and Algorithm for Energy-channel Calibration

Authors: Yanbiao Zhang, Fanjie Zeng, Dehua Kong, Lian Lei, Zhonghai Wang

Abstract: Scintillation detectors are essential tools for radiation measurement, but calibrating them accurately can be challenging, especially when full-energy peaks are not prominent. This is common in detectors like plastic scintillators. Current methods for calibrating these detectors often require manual adjustments. To address this, we propose a new method called the convolution model. This model accu… ▽ More Scintillation detectors are essential tools for radiation measurement, but calibrating them accurately can be challenging, especially when full-energy peaks are not prominent. This is common in detectors like plastic scintillators. Current methods for calibrating these detectors often require manual adjustments. To address this, we propose a new method called the convolution model. This model accurately calibrates the energy-channel relationship of the Compton edge in various detectors. We tested it with plastic scintillator BC408, NaI crystal, and LaBr$_3$ crystal. Using ${}^{137}$Cs radioactive sources, we calibrated NaI and LaBr$_3$ detectors using full-energy peaks, then applied the convolution model to fit the Compton edge. Our results show errors within 1\% when compared to full-energy peak calibration. △ Less

Submitted 3 October, 2025; v1 submitted 10 April, 2024; originally announced April 2024.

Comments: 17 pages, 8 figures. This article proposes a convolution model for accurately fitting the energy-channel relationship of the Compton edge in scintillation detectors, validated through experiments with plastic scintillator BC408, NaI crystal, and LaBr$_3$ crystal, showcasing errors within 1% when compared to full-energy peak calibration methods

Extremely intrinsic chirality in two-dimensional planar waveguide grating induced by quasi-bound states in the continuum

Authors: Dandan Zhang, Tingting Liu, Linlin Lei, Weimin Deng, Tongbiao Wang, Qinghua Liao, Wenxing Liu, Shuyuan Xiao, Tianbao Yu

Abstract: The strong chiral light-matter interaction is crucial for various important fields such as chiral optics, quantum optics, and biomedical optics, driving a quest for the extreme intrinsic chirality assisted by ultrahigh quality ($Q$-) factor resonances. In this quest, we propose a straightforward method to achieve extreme intrinsic chirality in lossless planar structures by manipulating the quasi-B… ▽ More The strong chiral light-matter interaction is crucial for various important fields such as chiral optics, quantum optics, and biomedical optics, driving a quest for the extreme intrinsic chirality assisted by ultrahigh quality ($Q$-) factor resonances. In this quest, we propose a straightforward method to achieve extreme intrinsic chirality in lossless planar structures by manipulating the quasi-BIC through in-plane perturbation. The temporal coupled-mode theory is employed to derive the conditions necessary for achieving maximal intrinsic chirality. The quasi-BIC should be excited within the transparent spectral range of the structure and couple with $x$- and $y$-polarized waves with the same intensity but a phase difference of $π$/2. For an illustration, a planar chiral dielectric dimeric waveguide grating is designed that strong interacts with left circularly polarized (LCP) light while decouples from right circularly polarized (RCP) light through in-plane symmetry engineering. Furthermore, by adjusting the magnitude of the in-plane asymmetry, we can independently manipulate the $Q$-factors of the chiral quasi-BIC while maintaining nearly unity circular dichroism. Our results provide a simple yet powerful paradigm for achieving extreme intrinsic chirality on an easily manufacturable platform, which may have potential applications in chiral emission, chiral sensing, and enantiomer separation. △ Less

Submitted 28 January, 2024; originally announced January 2024.

Journal ref: Physical Review B 109 (20), 205403 (2024)

Simultaneous manipulation of electromagnetic and elastic waves via glide symmetry phoxonic crystal waveguides

Authors: Linlin Lei, Lingjuan He, Qinghua Liao, Wenxing Liu, Tianbao Yu

Abstract: A phoxonic crystal waveguide with the glide symmetry is designed, in which both electromagnetic and elastic waves can propagate along the glide plane at the same time. Due to the band-sticking effect, super-cell bands of the waveguide degenerate in pairs at the boundary of the Brillouin zone, causing the appearance of gapless guided-modes in the bandgaps. The gapless guided-modes are single-modes… ▽ More A phoxonic crystal waveguide with the glide symmetry is designed, in which both electromagnetic and elastic waves can propagate along the glide plane at the same time. Due to the band-sticking effect, super-cell bands of the waveguide degenerate in pairs at the boundary of the Brillouin zone, causing the appearance of gapless guided-modes in the bandgaps. The gapless guided-modes are single-modes over a relatively large frequency range. By adjusting the magnitude of the glide dislocation, the edge bandgaps of the guided-modes can be further adjusted, so as to achieve photonic and phononic single-mode guided-bands with relatively flat dispersion relationship. In addition, there exists acousto-optic interaction in the cavity constructed by the glide plane. The proposed waveguide has potential applications in the design of novel optomechanical devices. △ Less

Submitted 26 October, 2023; originally announced October 2023.

Comments: 16 pages, 9 figures

Nanometer displacement measurement based on metrological self-mixing grating interferometer traceable to the pitch standard of one-dimension chromium self-traceable grating

Authors: Zhenjie Gu, Zhangning Xie, Zhikun Chang, Guangxu Xiao, Zhijun Yin, Zichao Lin, Tong Zhou, Lihua Lei, Tao Jin, Dongbai Xue, Xiao Deng, Xinbin Chen, Tongbao Li

Abstract: Traceability of precision instrument and measuring method is the core issue in metrology science. In the field of nanometer length measurement, the laser interferometers are usually used to trace the measurement value to the laser wavelength, but the laser wavelength is sensitive to the environment disturbance. Chromium self-traceable grating is an ideal nanometer length reference grating with pit… ▽ More Traceability of precision instrument and measuring method is the core issue in metrology science. In the field of nanometer length measurement, the laser interferometers are usually used to trace the measurement value to the laser wavelength, but the laser wavelength is sensitive to the environment disturbance. Chromium self-traceable grating is an ideal nanometer length reference grating with pitch traceability, fabricated by the atomic lithography technique. The new nanometer length traceability chain can be established based on the pitch traceability of chromium self-traceable grating, which is often used to calibrate the systematic error of the atomic force microscope. In this paper, the metrological self-mixing grating interferometer based on the chromium self-traceable grating (SMGI-Cr) is firstly established, whose interfere phase is traceable to the pitch of the chromium self-traceable grating directly and traceable to the chromium atomic transition frequency of energy level 7 S 3 to 7 P 4 indirectly. The nanometer displacement measurement is also achieved by the SMGI-Cr. The measurement error is no more than 0.2366%, compared to a commercial interferometer. △ Less

Submitted 25 June, 2023; originally announced June 2023.

Chromium Self-Traceable Length Standard: Investigating Geometry and Diffraction for Length Traceability Chain

Authors: Zichao Lin, Yulin Yao, Zhangning Xie, Dongbai Xue, Tong Zhou, Zhaohui Tang, Lihua Lei, Tao Jin, Xiong Dun, Xiao Deng, Xinbin Cheng, Tongbao Li

Abstract: Natural constant-based metrology methods offer an effective approach to achieving traceability in nanometric measurements. The Cr grating, fabricated by atom lithography and featuring a pitch of $d=212.7705\pm0.0049~{\rm nm}$ traceable to the Cr transition frequency $^{7}S_{3}$ $\rightarrow$ $^{7}P_{4}^{0}$, demonstrates potential as a self-traceable length standard in nano-length metrology by gra… ▽ More Natural constant-based metrology methods offer an effective approach to achieving traceability in nanometric measurements. The Cr grating, fabricated by atom lithography and featuring a pitch of $d=212.7705\pm0.0049~{\rm nm}$ traceable to the Cr transition frequency $^{7}S_{3}$ $\rightarrow$ $^{7}P_{4}^{0}$, demonstrates potential as a self-traceable length standard in nano-length metrology by grating interferometer. This research aims to analyze and engineer the diffraction characteristics that enhance the Cr grating as a self-traceable length standard within the length traceability chain based on the Cr transition frequency. Accordingly, we investigate the geometric morphology and diffraction characteristics of the Cr grating, analyzes the influence of the grating's polarization-sensitive characteristics on the Littrow configuration grating interferometer, and establishes the criteria for Cr grating fabrication. Experimentally, we fabricate an expanded Cr grating by scanning atom lithography, characterize its diffraction performance, and conduct preliminary verification of length measurement in a self-traceable grating interferometer. This work adheres to the international trend of flattened metrology development, offering a valuable reference for advancing subsequent metrological technologies throughout the new traceability chain. △ Less

Submitted 24 June, 2023; originally announced June 2023.

Comments: 14 pages, 14 figures, 1 table

Black holes as the source of dark energy: a stringent test with high-redshift JWST AGNs

Authors: Lei Lei, Lei Zu, Guan-Wen Yuan, Zhao-Qiang Shen, Yi-Ying Wang, Yuan-Zhu Wang, Zhen-Bo Su, Wen-ke Ren, Shao-Peng Tang, Hao Zhou, Chi Zhang, Zhi-Ping Jin, Lei Feng, Yi-Zhong Fan, Da-Ming Wei

Abstract: Studies have proposed that there is evidence for cosmological coupling of black holes (BHs) with an index of $k\approx 3$; hence, BHs serve as the astrophysical source of dark energy. However, the data sample is limited for the redshifts of $\leq 2.5$. In recent years, the James Webb Space Telescope (JWST) has detected many high-redshift active galactic nuclei (AGNs) and quasars. Among the JWST NI… ▽ More Studies have proposed that there is evidence for cosmological coupling of black holes (BHs) with an index of $k\approx 3$; hence, BHs serve as the astrophysical source of dark energy. However, the data sample is limited for the redshifts of $\leq 2.5$. In recent years, the James Webb Space Telescope (JWST) has detected many high-redshift active galactic nuclei (AGNs) and quasars. Among the JWST NIRSpec-/NIRCam-resolved AGNs, three are determined to be in early-type host galaxies with a redshift of $z\sim 4.5--7$. However, their $M_{\star}$ and $M_{\rm BH}$ are in tension with the predicted cosmological coupling of black holes with $k = 3$ at a confidence level of $\sim 2σ$, which challenges the hypothesis that BHs serve as the origin of dark energy. Future work on high-redshift AGNs using the JWST will further assess such a hypothesis by identifying more early-type host galaxies in the higher mass range. △ Less

Submitted 17 January, 2024; v1 submitted 5 May, 2023; originally announced May 2023.

Comments: 9 pages, 3 figures, 2 tables; Comments are welcome!

Journal ref: Sci. China-Phys. Mech. Astron. 67, 229811 (2024)

Length traceability chain based on chromium atom transition frequency

Authors: Xiao Deng, Zichao Lin, Gaoliang Dai, Zhaohui Tang, Zhangning Xie, Guangxu Xiao, Zhijun Yin, Lihua Lei, Tao Jin, Dongbai Xue, Zhenjie Gu, Xinbin Cheng, Tongbao Li

Abstract: Precise positioning measurement plays an important role in in today advanced manufacturing industry, and length traceability chain has been optimizing and enriching to fulfill the developing and various precise positioning requirement. In this paper, we propose a new length traceability chain based on chromium atom transition frequency, which is a combining utilization of fundamental physical cons… ▽ More Precise positioning measurement plays an important role in in today advanced manufacturing industry, and length traceability chain has been optimizing and enriching to fulfill the developing and various precise positioning requirement. In this paper, we propose a new length traceability chain based on chromium atom transition frequency, which is a combining utilization of fundamental physical constant accuracy and grating interferometer environmental robustness. The selftraceable grating pitch standard, the selftraceable angle standard and the selftraceable grating interferometer are promising to improve the measurement accuracy, consistency and selfcalibration ability in situ for precise positioning. △ Less

Submitted 23 February, 2023; originally announced February 2023.

Derivation and Efficient Entropy-Production-Rate-Preserving Algorithms for a Thermodynamically Consistent Nonisothermal Model of Incompressible Binary Fluids

Authors: Shouwen Sun, Liangliang Lei, Qi Wang

Abstract: We present a new hydrodynamic model for incompressible binary fluids that is thermodynamically consistent and non-isothermal. This model follows the generalized Onsager principle and Boussinesq approximation and preserves the volume of each fluid phase and the positive entropy production rate under consistent boundary conditions. To solve the governing partial differential equations in the model n… ▽ More We present a new hydrodynamic model for incompressible binary fluids that is thermodynamically consistent and non-isothermal. This model follows the generalized Onsager principle and Boussinesq approximation and preserves the volume of each fluid phase and the positive entropy production rate under consistent boundary conditions. To solve the governing partial differential equations in the model numerically, we design a set of second-order, volume and entropy-production-rate preserving numerical algorithms. Using an efficient adaptive time-stepping strategy, we conduct several numerical simulations. These simulations accurately simulate the Rayleigh-Bénard convection in binary fluids and the interfacial dynamics between two immiscible fluids under the effects of the temperature gradient, gravity, and interfacial forces. Our numerical results show roll cell patterns and thermally induced mixing of binary fluids in a rectangular computational domain with a set of specific boundary conditions: a zero-velocity boundary condition all around, the insulation boundary condition at the lateral boundaries, and an imposed temperature difference vertically. We also perform long-time simulations of interfacial dynamics, demonstrating the robustness of our new structure-preserving schemes and reveal interesting fluid mixing phenomena. △ Less

Submitted 10 August, 2023; v1 submitted 15 February, 2023; originally announced February 2023.

Characterization and Generation of 3D Realistic Geological Particles with Metaball Descriptor based on X-Ray Computed Tomography

Authors: Yifeng Zhao, Xiangbo Gao, Pei Zhang, Liang Lei, S. A. Galindo-Torres, Stan Z. Li

Abstract: The morphology of geological particles is crucial in determining its granular characteristics and assembly responses. In this paper, Metaball-function based solutions are proposed for morphological characterization and generation of three-dimensional realistic particles according to the X-ray Computed Tomography (XRCT) images. For characterization, we develop a geometric-based Metaball-Imaging alg… ▽ More The morphology of geological particles is crucial in determining its granular characteristics and assembly responses. In this paper, Metaball-function based solutions are proposed for morphological characterization and generation of three-dimensional realistic particles according to the X-ray Computed Tomography (XRCT) images. For characterization, we develop a geometric-based Metaball-Imaging algorithm. This algorithm can capture the main contour of parental particles with a series of non-overlapping spheres and refine surface-texture details through gradient search. Four types of particles, hundreds of samples, are applied for evaluations. The result shows good matches on key morphological indicators(i.e., volume, surface area, sphericity, circularity, corey-shape factor, nominal diameter and surface-equivalent-sphere diameter), confirming its characterization precision. For generation, we propose the Metaball Variational Autoencoder. Assisted by deep neural networks, this method can generate 3D particles in Metaball form, while retaining coessential morphological features with parental particles. Additionally, this method allows for control over the generated shapes through an arithmetic pattern, enabling the generation of particles with specific shapes. Two sets of XRCT images different in sample number and geometric features are chosen as parental data. On each training set, one thousand particles are generated for validations. The generation fidelity is demonstrated through comparisons of morphologies and shape-feature distributions between generated and parental particles. Examples are also provided to demonstrate controllability on the generated shapes. With Metaball-based simulations frameworks previously proposed by the authors, these methods have the potential to provide valuable insights into the properties and behavior of actual geological particles. △ Less

Submitted 5 February, 2023; originally announced February 2023.

Polarization-independent second-order photonic topological corner states

Authors: Linlin Lei, Shuyuan Xiao, Wenxing Liu, Qinghua Liao, Lingjuan He, Tianbao Yu

Abstract: Recently, much attention has been paid to second-order photonic topological insulators (SPTIs), because of their support for highly localized corner states with excellent robustness. SPTIs have been implemented in either transverse magnetic (TM) or transverse electric (TE) polarizations in two-dimensional (2D) photonic crystals (PCs), and the resultant topological corner states are polarization-de… ▽ More Recently, much attention has been paid to second-order photonic topological insulators (SPTIs), because of their support for highly localized corner states with excellent robustness. SPTIs have been implemented in either transverse magnetic (TM) or transverse electric (TE) polarizations in two-dimensional (2D) photonic crystals (PCs), and the resultant topological corner states are polarization-dependent, which limits their application in polarization-independent optics. However, to achieve polarization-independent corner states is not easy, since they are usually in-gap and the exact location in the topological bandgap is not known in advance. Here, we report on a SPTI based on a 2D square-lattice PC made of an elliptic metamaterial, and whether the bandgap is topological or trivial depends on the choice of the unit cell. It is found that locations of topological bandgaps of TM and TE polarizations in the frequency spectrum can be independently controlled by the out-of-plane permittivity $\varepsilon_\perp$ and in-plane permittivity $\varepsilon_{\varparallel}$, respectively, and more importantly, the location of in-gap corner states can also be separately manipulated by them. From this, we achieve topological corner states for both TM and TE polarizations with the same frequency in the PC by adjusting $\varepsilon_\perp$ and $\varepsilon_\varparallel$, and their robustness against disorders and defects are numerically demonstrated. The proposed SPTI provides a potential application scenario for polarization-independent topological photonic devices. △ Less

Submitted 28 January, 2023; originally announced January 2023.

Journal ref: PhysRevApplied.20.024014 (2023)

Laboratory observation of plasmoid-dominated magnetic reconnection in hybrid collisional-collisionless regime

Authors: Z. H. Zhao, H. H. An, Y. Xie, Z. Lei, W. P. Yao, W. Q. Yuan, J. Xiong, C. Wang, J. J. Ye, Z. Y. Xie, Z. H. Fang, A. L. Lei, W. B. Pei, X. T. He, W. M. Zhou, W. Wang, S. P. Zhu, B. Qiao

Abstract: Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasma particles that occurs pervasively throughout the universe. In most natural circumstances, the plasma properties on either side of the reconnection layer are asymmetric, in particular for the collision rates that are associated with a combination o… ▽ More Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasma particles that occurs pervasively throughout the universe. In most natural circumstances, the plasma properties on either side of the reconnection layer are asymmetric, in particular for the collision rates that are associated with a combination of density and temperature and critically determine the reconnection mechanism. To date, all laboratory experiments on magnetic reconnections have been limited to purely collisional or collisionless regimes. Here, we report a well-designed experimental investigation on asymmetric magnetic reconnections in a novel hybrid collisional-collisionless regime by interactions between laser-ablated Cu and CH plasmas. We show that the growth rate of the tearing instability in such a hybrid regime is still extremely large, resulting in rapid formation of multiple plasmoids, lower than that in the purely collisionless regime but much higher than the collisional case. In addition, we, for the first time, directly observe the topology evolutions of the whole process of plasmoid-dominated magnetic reconnections by using highly-resolved proton radiography. △ Less

Submitted 24 February, 2022; originally announced February 2022.

Optimization of the JUNO liquid scintillator composition using a Daya Bay antineutrino detector

Authors: Daya Bay, JUNO collaborations, :, A. Abusleme, T. Adam, S. Ahmad, S. Aiello, M. Akram, N. Ali, F. P. An, G. P. An, Q. An, G. Andronico, N. Anfimov, V. Antonelli, T. Antoshkina, B. Asavapibhop, J. P. A. M. de André, A. Babic, A. B. Balantekin, W. Baldini, M. Baldoncini, H. R. Band, A. Barresi, E. Baussan , et al. (642 additional authors not shown)

Abstract: To maximize the light yield of the liquid scintillator (LS) for the Jiangmen Underground Neutrino Observatory (JUNO), a 20 t LS sample was produced in a pilot plant at Daya Bay. The optical properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector. The concentrations of the fluor, PPO, and the wavelength shifter, bis-MSB, were… ▽ More To maximize the light yield of the liquid scintillator (LS) for the Jiangmen Underground Neutrino Observatory (JUNO), a 20 t LS sample was produced in a pilot plant at Daya Bay. The optical properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector. The concentrations of the fluor, PPO, and the wavelength shifter, bis-MSB, were increased in 12 steps from 0.5 g/L and <0.01 mg/L to 4 g/L and 13 mg/L, respectively. The numbers of total detected photoelectrons suggest that, with the optically purified solvent, the bis-MSB concentration does not need to be more than 4 mg/L. To bridge the one order of magnitude in the detector size difference between Daya Bay and JUNO, the Daya Bay data were used to tune the parameters of a newly developed optical model. Then, the model and tuned parameters were used in the JUNO simulation. This enabled to determine the optimal composition for the JUNO LS: purified solvent LAB with 2.5 g/L PPO, and 1 to 4 mg/L bis-MSB. △ Less

Submitted 1 July, 2020; originally announced July 2020.

Comments: 13 pages, 8 figures

Feasibility and physics potential of detecting $^8$B solar neutrinos at JUNO

Authors: JUNO collaboration, Angel Abusleme, Thomas Adam, Shakeel Ahmad, Sebastiano Aiello, Muhammad Akram, Nawab Ali, Fengpeng An, Guangpeng An, Qi An, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, João Pedro Athayde Marcondes de André, Didier Auguste, Andrej Babic, Wander Baldini, Andrea Barresi, Eric Baussan, Marco Bellato, Antonio Bergnoli, Enrico Bernieri, David Biare , et al. (572 additional authors not shown)

Abstract: The Jiangmen Underground Neutrino Observatory~(JUNO) features a 20~kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent experiment for $^8$B solar neutrino measurements, such as its low-energy threshold, its high energy resolution compared to water Cherenkov detectors, and its much large target mass compared to previous liquid s… ▽ More The Jiangmen Underground Neutrino Observatory~(JUNO) features a 20~kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent experiment for $^8$B solar neutrino measurements, such as its low-energy threshold, its high energy resolution compared to water Cherenkov detectors, and its much large target mass compared to previous liquid scintillator detectors. In this paper we present a comprehensive assessment of JUNO's potential for detecting $^8$B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2~MeV threshold on the recoil electron energy is found to be achievable assuming the intrinsic radioactive background $^{238}$U and $^{232}$Th in the liquid scintillator can be controlled to 10$^{-17}$~g/g. With ten years of data taking, about 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the tension between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If $Δm^{2}_{21}=4.8\times10^{-5}~(7.5\times10^{-5})$~eV$^{2}$, JUNO can provide evidence of neutrino oscillation in the Earth at the about 3$σ$~(2$σ$) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moveover, JUNO can simultaneously measure $Δm^2_{21}$ using $^8$B solar neutrinos to a precision of 20\% or better depending on the central value and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help elucidate the current tension between the value of $Δm^2_{21}$ reported by solar neutrino experiments and the KamLAND experiment. △ Less

Submitted 21 June, 2020; originally announced June 2020.

Comments: 29 pages, 14 plots, 7 tables

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

Authors: JUNO Collaboration, Angel Abusleme, Thomas Adam, Shakeel Ahmad, Sebastiano Aiello, Muhammad Akram, Nawab Ali, Fengpeng An, Guangpeng An, Qi An, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, João Pedro Athayde Marcondes de André, Didier Auguste, Andrej Babic, Wander Baldini, Andrea Barresi, Eric Baussan, Marco Bellato, Antonio Bergnoli, Enrico Bernieri, David Biare , et al. (568 additional authors not shown)

Abstract: The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future re… ▽ More The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022. △ Less

Submitted 18 May, 2020; originally announced May 2020.

Comments: 134 pages, 114 figures

Evidence for a new extended solid of nitrogen

Authors: Li Lei, Qiqi Tang, Feng Zhang, Shan Liu, Binbin Wu, Chunyin Zhou

Abstract: A new extended solid nitrogen, referred to post-layered-polymeric nitrogen (PLP-N), was observed by further heating the layered-polymeric nitrogen (LP-N) to above 2300 K at 161 GPa. The new phase is found to be very transparent and exhibits ultra-large d-spacings ranging from 2.8 to 4.9 Å at 172 GPa, suggesting a possible large-unit-cell 2D chain-like or 0D cluster-type structure with wide bandgap… ▽ More A new extended solid nitrogen, referred to post-layered-polymeric nitrogen (PLP-N), was observed by further heating the layered-polymeric nitrogen (LP-N) to above 2300 K at 161 GPa. The new phase is found to be very transparent and exhibits ultra-large d-spacings ranging from 2.8 to 4.9 Å at 172 GPa, suggesting a possible large-unit-cell 2D chain-like or 0D cluster-type structure with wide bandgap. However, the observed X-ray diffraction pattern and Raman scattering data cannot match any predicted structures in the published literature. This finding further complicates the phase diagram of nitrogen and also highlights the path dependence of the high-pressure dissociative transition in nitrogen. In addition, the forming boundary between cg-N and LP-N has been determined. △ Less

Submitted 8 February, 2020; originally announced February 2020.

Comments: 13 pages, 4 figures, 1 table

Synthesis and temperature-dependent photoluminescence of high density GeSe triangular nanoplate arrays on Si substrates

Authors: Xueyan Li, Xi Zhang, Xiaowei Lv, Jun Pang, Li Lei, Yong Liu, Yong Peng, Gang Xiang

Abstract: We have grown germanium selenide (GeSe) triangular nanoplate arrays (TNAs) with a high density (3.82E+6 / mm2) on the Si (111) substrate using a simple thermal evaporation method. The thickness and trilateral lengths of a single triangular nanoplate were statistically estimated by atomic force microscopy (AFM) as 44 nm, 365 nm, 458 nm and 605 nm, respectively. Transmission electron microscopy (TEM… ▽ More We have grown germanium selenide (GeSe) triangular nanoplate arrays (TNAs) with a high density (3.82E+6 / mm2) on the Si (111) substrate using a simple thermal evaporation method. The thickness and trilateral lengths of a single triangular nanoplate were statistically estimated by atomic force microscopy (AFM) as 44 nm, 365 nm, 458 nm and 605 nm, respectively. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) patterns show that the TNAs were composed of single crystalline GeSe phase. The Se-related defects in the lattice were also revealed by TEM images and Raman vibration modes. Unlike previously reported GeSe compounds, the GeSe TNAs exhibited temperature-dependent photoluminescence (PL). In addition, not previously reported PL peak (1.25 eV) of the 44 nm thick TNAs at 5 K was in the gaps between those of GeSe monolayers (1.5 nm) and thin films (400 nm), revealing a close relationship between the PL peak and the thickness of GeSe. The high-density structure and temperature-dependent PL of the TNAs on the Si substrate may be useful for temperature controllable semiconductor nanodevices. △ Less

Submitted 1 January, 2020; originally announced January 2020.

High-pressure isostructural transition in nitrogen

Authors: Shan Liu, Meifang Pu, Qiqi Tang, Feng Zhang, Binbin Wu, Li Lei

Abstract: Understanding high-pressure transitions in prototypical linear diatomic molecules, such as hydrogen, nitrogen, and oxygen, is an important objective in high-pressure physics. Recent ultrahigh-pressure study on hydrogen revealed that there exists a molecular-symmetry-breaking isostructural electronic transition in hydrogen. The pressure-induced symmetry breaking could also lead to a series of solid… ▽ More Understanding high-pressure transitions in prototypical linear diatomic molecules, such as hydrogen, nitrogen, and oxygen, is an important objective in high-pressure physics. Recent ultrahigh-pressure study on hydrogen revealed that there exists a molecular-symmetry-breaking isostructural electronic transition in hydrogen. The pressure-induced symmetry breaking could also lead to a series of solid molecular phases in nitrogen associated with the splitting of vibron, walking a path from fluid nitrogen to molecular solids and then to polymetric nitrogen phases. However, isostructural transition in nitrogen has not been reported so far, which may provide crucial information on the crystallographic nature of the pressure-induced dissociation transitions in nitrogen. Here we present a high-pressure Raman scattering and high-pressure angle dispersive X-ray diffraction study of the previously reported lambda-N2 and reveal an isostructural transition from the lambda-N2 to a new derivative phase, lambda-N2. Under compression, lambda-N2 remains in the monoclinic crystal lattice, accompanied by a monotonic increase in anisotropy. The pressure-dependent decrease of the unit cell parameters exhibits a discontinuity at the pressure of 54 GPa, accompany with sudden broadening and turnover of vibron. △ Less

Submitted 30 October, 2019; originally announced October 2019.

Comments: 19 pages, 5 figures

Electronic structure and bond relaxation at Na/Ta(110) interfaces and 1D-chain and 2D-ring Ta metal structures on Na(110)

Authors: Maolin Bo, Li Lei, Chuang Yao, Cheng Peng, Zhongkai Huang, Chang Q. Sun

Abstract: We investigated the mechanism of Na/Ta(110) and Ta/Na(110) interfaces using a combination of bond band barrier (BBB) and zone selective electron spectroscopy (ZES) correlation. We found that 7/9 ML and 8/9 ML Ta metal on a Na(110) surface form one dimensional (1D) chain and two dimensional (2D) ring structures, respectively. Moreover, we show that on Na(110), the Ta-induced Na(110) surface binding… ▽ More We investigated the mechanism of Na/Ta(110) and Ta/Na(110) interfaces using a combination of bond band barrier (BBB) and zone selective electron spectroscopy (ZES) correlation. We found that 7/9 ML and 8/9 ML Ta metal on a Na(110) surface form one dimensional (1D) chain and two dimensional (2D) ring structures, respectively. Moreover, we show that on Na(110), the Ta-induced Na(110) surface binding energy (BE) shifts are dominated by quantum entrapment. On the contrary, on a Ta(110) surface, the Na-induced Ta(110) surface BE shifts are dominated by polarization. Thus, the BBB and ZES strategy could potentially be used for designing 1D and 2D metals with desired structures and properties. △ Less

Submitted 8 August, 2018; v1 submitted 27 June, 2018; originally announced June 2018.

How reproducible are methods to measure the dynamic viscoelastic properties of poroelastic media?

Authors: Paolo Bonfiglio, Francesco Pompoli, Kirill V. Horoshenkov, Mahmud Iskandar B Seth A Rahim, Luc Jaouen, Julia Rodenas, Francois-Xavier Becot, Emmanuel Gourdon, Dirk Jaeger, Volker Kursch, Maurizio Tarello, Nicolaas Bernardus Roozen, Christ Glorieux, Fabrizio Ferrian, Pierre Leroy, Francesco Briatico Vangosa, Nicolas Dauchez, Felix Foucart, Lei Lei, Kevin Carillo, Olivier Doutres, Franck Sgard, Raymond Panneton, Kevin Verdiere, Claudio Bertolini1 , et al. (8 additional authors not shown)

Abstract: There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of ScienceTM (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate knowledge of the elastic properties over a broad fr… ▽ More There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of ScienceTM (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate knowledge of the elastic properties over a broad frequency range. However, the accuracy of the measurement of the dynamic elastic properties of poroelastic media has been a contentious issue. The novelty of this paper is that it studies the reproducibility of some popular experimental methods which are used routinely to measure the key elastic properties such as the dynamic Young's modulus, loss factor and Poisson ratio of poroelastic media. In this paper, fourteen independent sets of laboratory measurements were performed on specimens of the same porous materials. The results from these measurements suggest that the reproducibility of this type of experimental method is poor. This work can be helpful to suggest improvements which can be developed to harmonize the way the elastic properties of poroelastic media are measured worldwide. △ Less

Submitted 23 May, 2018; originally announced May 2018.

Journal ref: Journal of Sound & Vibration, vol. 428, pp. 26-43, 2018

JUNO Conceptual Design Report

Authors: T. Adam, F. An, G. An, Q. An, N. Anfimov, V. Antonelli, G. Baccolo, M. Baldoncini, E. Baussan, M. Bellato, L. Bezrukov, D. Bick, S. Blyth, S. Boarin, A. Brigatti, T. Brugière, R. Brugnera, M. Buizza Avanzini, J. Busto, A. Cabrera, H. Cai, X. Cai, A. Cammi, D. Cao, G. Cao , et al. (372 additional authors not shown)

Abstract: The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector. It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants in Guangdong, China. The experimental hall, spanning more than 50 meters, is under a granite mountain of over 700 m overburden. Within six years of running, the dete… ▽ More The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector. It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants in Guangdong, China. The experimental hall, spanning more than 50 meters, is under a granite mountain of over 700 m overburden. Within six years of running, the detection of reactor antineutrinos can resolve the neutrino mass hierarchy at a confidence level of 3-4$σ$, and determine neutrino oscillation parameters $\sin^2θ_{12}$, $Δm^2_{21}$, and $|Δm^2_{ee}|$ to an accuracy of better than 1%. The JUNO detector can be also used to study terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard Model. The central detector contains 20,000 tons liquid scintillator with an acrylic sphere of 35 m in diameter. $\sim$17,000 508-mm diameter PMTs with high quantum efficiency provide $\sim$75% optical coverage. The current choice of the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of detected photoelectrons per MeV is larger than 1,100 and the energy resolution is expected to be 3% at 1 MeV. The calibration system is designed to deploy multiple sources to cover the entire energy range of reactor antineutrinos, and to achieve a full-volume position coverage inside the detector. The veto system is used for muon detection, muon induced background study and reduction. It consists of a Water Cherenkov detector and a Top Tracker system. The readout system, the detector control system and the offline system insure efficient and stable data acquisition and processing. △ Less

Submitted 28 September, 2015; v1 submitted 28 August, 2015; originally announced August 2015.

Comments: 328 pages, 211 figures

A Fast local Reconstruction algorithm by selective backprojection for Low-Dose in Dental Computed Tomography

Authors: Yan Bin, Deng Lin, Han Yu, Zhang Feng, Wang Xian Chao, Li Lei

Abstract: High radiation dose in computed tomography (CT) scans increases the lifetime risk of cancer, which become a major clinical concern. The backprojection-filtration (BPF) algorithm could reduce radiation dose by reconstructing images from truncated data in a short scan. In dental CT, it could reduce radiation dose for the teeth by using the projection acquired in a short scan, and could avoid irradia… ▽ More High radiation dose in computed tomography (CT) scans increases the lifetime risk of cancer, which become a major clinical concern. The backprojection-filtration (BPF) algorithm could reduce radiation dose by reconstructing images from truncated data in a short scan. In dental CT, it could reduce radiation dose for the teeth by using the projection acquired in a short scan, and could avoid irradiation to other part by using truncated projection. However, the limit of integration for backprojection varies per PI-line, resulting in low calculation efficiency and poor parallel performance. Recently, a tent BPF (T-BPF) has been proposed to improve calculation efficiency by rearranging projection. However, the memory-consuming data rebinning process is included. Accordingly, the chose-BPF (C-BPF) algorithm is proposed in this paper. In this algorithm, the derivative of projection is backprojected to the points whose x coordinate is less than that of the source focal spot to obtain the differentiated backprojection (DBP). The finite Hilbert inverse is then applied to each PI-line segment. C-BPF avoids the influence of the variable limit of integration by selective backprojection without additional time cost or memory cost. The simulation experiment and the real experiment demonstrated the higher reconstruction efficiency of C-BPF. △ Less

Submitted 19 November, 2013; originally announced November 2013.

Comments: 18 pages,10 figures

MSC Class: 78-05

Diversity of photonic differentiators based on flexible demodulation of phase signals

Authors: Zheng Ao-ling, Dong Jian-ji, Lei Lei, Yang Ting, Zhang Xin-Liang

Abstract: We theoretically prove a multifunctional photonic differentiation (DIFF) scheme based on phase demodulation using two cascaded linear filters. The photonic DIFF has a diversity of output forms, such as 1st order intensity DIFF, 1st order field DIFF and its inversion, 2nd order field DIFF, dependent on the relative shift between the optical carrier and the filter's resonant notches. As a proof, we… ▽ More We theoretically prove a multifunctional photonic differentiation (DIFF) scheme based on phase demodulation using two cascaded linear filters. The photonic DIFF has a diversity of output forms, such as 1st order intensity DIFF, 1st order field DIFF and its inversion, 2nd order field DIFF, dependent on the relative shift between the optical carrier and the filter's resonant notches. As a proof, we also experimentally demonstrate the DIFF diversity using a phase modulator and two delay interferometers (DIs). The calculated average deviation is less than 7% for all DIFF waveforms. Our schemes show the advantages of flexible DIFF functions and forms, which may have different optical applications. For example, high order field differentiators can be used to generate complex temporal waveforms. And intensity differentiators are useful for ultra-wideband pulse generation. △ Less

Submitted 27 August, 2013; originally announced August 2013.

Comments: 12 pages, 8 figures. Chinese physics B, 2013