247 research outputs found
Demonstration and Operation of Quantum Harmonic Oscillators in AlGaAs/GaAs Heterostructure
The quantum harmonic oscillator (QHO), one of the most important and
ubiquitous model systems in quantum mechanics, features equally spaced energy
levels or eigenstates. Here we report on the design, demonstration and
operation of nearly perfect QHOs in AlGaAs/GaAs heterostructure. On the basis
of model calculations, we demonstrate that, when a substitutional Si donor
substitutes the Ga/Al lattice site close to AlGaAs/GaAs heterointerface, a
hydrogenic Si QHO, characterized by a restoring Coulomb force producing square
law harmonic potential, is formed. This gives rise to QHO states with energy
spacing of ~8-9 meV. We experimentally confirm this proposal by utilizing Stark
effect and measuring QHO states using an aluminum single-electron transistor
(SET). A sharp and fast oscillation with period of ~7-8 mV appears in addition
to the regular Coulomb blockade (CB) oscillation with much larger period, for
positive gate biases above 0.5 V. The observation of fast oscillation and its
behavior is qualitatively consistent with our theoretical result, manifesting
the harmonic motion of electrons from the QHO. Our results might establish a
general principle to design, construct and manipulate QHOs in semiconductor
heterostructures.Comment: 17 pages, 4 figure
Numerical Simulation Study on Propeller Slipstream Interference of High Altitude Long Endurance Unmanned Air Vehicle
AbstractIn this paper,thecontrol equation of Multiple Reference Frame(MRF) as the propeller calculation model was present and analyzed, the propeller slipstream interference on HALE UAV was studied with three-dimensional numerical simulation. It is shown that the flow field of the MRF model is good consistent with true propeller flow, and MRF can accurately simulate aerodynamic interference on the aircraft. The stream traces on the V-tail surface were deflected and shrank, pressure distribution,Cmx and Cmzon V-tail surface was changed apparently too.Butslipstream had little effect on wing. The influence of propeller slipstream on the aerodynamic performance of the UAV at the status of taking off is biggest, become weaker at status of climbing and smallest at the status of cruising. The influence of propeller slipstream is enhanced with increment of propeller thrust and basically familiar in the same thrust between the two blade attack angle. The pressure drag on aft of UAV fuselage increased rapidly by the interference of propeller slipstream, leading aerodynamic performance of UAV become badly
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Water-Soluble 3D Covalent Organic Framework that Displays an Enhanced Enrichment Effect of Photosensitizers and Catalysts for the Reduction of Protons to H2.
Covalent organic frameworks (COFs) are emerging porous polymers that have 2D or 3D long-range ordering. Currently available COFs are typically insoluble or decompose upon dissolution, which remarkably restricts their practical implementations. For 3D COFs, the achievement of noninterpenetration, which maximizes their porosity-derived applications, also remains a challenge synthetically. Here, we report the synthesis of the first highly water-soluble 3D COF (sCOF-101) from irreversible polymerization of a preorganized supramolecular organic framework through cucurbit[8]uril (CB[8])-controlled [2 + 2] photodimerization. Synchrotron X-ray scattering and diffraction analyses confirm that sCOF-101 exhibits porosity periodicity, with a channel diameter of 2.3 nm, in both water and the solid state and retains the periodicity under both strongly acidic and basic conditions. As an ordered 3D polymer, sCOF-101 can enrich [Ru(bpy)3]2+ photosensitizers and redox-active polyoxometalates in water, which leads to remarkable increase of their photocatalytic activity for proton reduction to produce H2
Topological dissipative Kerr soliton combs in a valley photonic crystal resonator
Topological phases have become an enabling role in exploiting new
applications of nonlinear optics in recent years. Here we theoretically propose
a valley photonic crystal resonator emulating topologically protected
dissipative Kerr soliton combs. It is shown that topological resonator modes
can be observed in the resonator. Moreover, we also simulate the dynamic
evolution of the topological resonator with the injection of a continuous-wave
pump laser. We find that the topological optical frequency combs evolve from
Turing rolls to chaotic states, and eventually into single soliton states. More
importantly, such dissipative Kerr soliton combs generated in the resonator are
inborn topologically protected, showing robustness against sharp bends and
structural disorders. Our design supporting topologically protected dissipative
Kerr soliton combs could be implemented experimentally in on-chip
nanofabricated photonic devices.Comment: 16 pages, 12 figure
Optical Ranging Using Coherent Kerr Soliton Dual-microcombs with Extended Ambiguity Distance
Optical ranging is a key technology in metrology. Optical frequency combs are
shown to provide several advantages in light ranging, offering high precision
with high acquisition rate. However, performance of traditional ranging systems
based on microcombs is limited by the short ambiguity distance and
non-real-time processing. Here, we show that dual-comb ranging system using
coherent Kerr soliton microcombs and optical switch realizes extended ambiguity
distance and provides a route to real-time processing. The ambguity distance is
extended to 3.28 m from about 1.5 mm and the uncertainty reaches about 1.05
times 10^-7, while the system is compatible with low-bandwidth detectors.
Combining coherent microcomb ranging systems with special FPGA could enable
comb-based real-time ranging systems for several applications such as
industrial process monitoring.Comment: 9 pages, 5 figure
Identification of BST2 Contributing to the Development of Glioblastoma Based on Bioinformatics Analysis
Rigorous molecular analysis of the immune cell environment and immune response of human tumors has led to immune checkpoint inhibitors as one of the most promising strategies for the treatment of human cancer. However, in human glioblastoma multiforme (GBM) which develops in part by attracting immune cell types intrinsic to the human brain (microglia), standard immunotherapy has yielded inconsistent results in experimental models and patients. Here, we analyzed publicly available expression datasets to identify molecules possibly associated with immune response originating from or influencing the tumor microenvironment in primary tumor samples. Using three glioma datasets (GSE16011, Rembrandt-glioma and TCGA-glioma), we first analyzed the data to distinguish between GBMs of high and low tumor cell purity, a reflection of the cellular composition of the tumor microenvironment, and second, to identify differentially expressed genes (DEGs) between these two groups using GSEA and other analyses. Tumor purity was negatively correlated with patient prognosis. The interferon gamma-related gene BST2 emerged as a DEG that was highly expressed in GBM and negatively correlated with tumor purity. BST2high tumors also tended to harbor PTEN mutations (31 vs. 9%, BST2high versus BST2low) while BST2low tumors more often had sustained TP53 mutations (8 versus 36%, BST2high versus BST2low). Prognosis of patients with BST2high tumors was also poor relative to patients with BST2low tumors. Further molecular in silico analysis demonstrated that high expression of BST2 was negatively correlated with CD8+ T cells but positively correlated with macrophages with an M2 phenotype. Further functional analysis demonstrated that BST2 was associated with multiple immune checkpoints and cytokines, and may promote tumorigenesis and progression through interferon gamma, IL6/JAK/STAT3 signaling, IL2/STAT5 signaling and the TNF-α signaling via NF-kB pathway. Finally, a series of experiments confirmed that the expression of BST2 can be significantly increased by IFN induction, and knockdown of BST2 can significantly inhibit the growth and invasion of GBM cells, and may affect the phenotype of tumor-associated macrophages. In conclusion, BST2 may promote the progression of GBM and may be a target for treatment.publishedVersio
Development and application of a three-dimensional simulation test system for directional regional grouting
Directional regional grouting to transform aquifers is one of the effective ways to prevent and control mine water hazards. In order to study the diffusion law of grouting slurry in directional areas, a three-dimensional simulation test system for directional area grouting has been independently developed. The system is mainly composed of test bench, grouting system, water injection system, data monitoring and other subsystems, which can realize directional drilling grouting simulation, three-dimensional slurry diffusion simulation, high pressure water simulation and regional grouting simulation. The system can independently control the grouting hole unit to achieve porous and multi sequence grouting. With the help of six grouting holes, the slurry flow process is simulated under various parameters such as different grouting pressure, slurry viscosity, grouting rate, and water cement ratio. It can also achieve real-time monitoring of the slurry diffusion process in dynamic/static (high) water pressure environments. The paper takes the simulated naked hole lengths of 200 mm, 250 mm, and 300 mm as the research objects, and preliminarily explores the characteristics and effects of slurry diffusion in naked hole grouting under directional grouting. The study found that: in the case where only the naked hole length is a variable, the slurry diffusion range does not synchronously increase linearly with the linear increase of naked hole length; The slurry stone body of the short open hole is cylindrical with the drilling open hole as the axis, while the slurry stone body of the long open hole is circular with the drilling open hole as the axis; Increasing the same length of the bare hole results in a larger difference in the diffusion range of the slurry at both ends of the bare hole. At the same time, the more pressure loss there is, the smaller the diffusion distance of the slurry. Comparing the diffusion radius of the slurry obtained from the experiment with that calculated by the Maag formula, the difference between the two values is only 2.8% when the length of the grouting open hole is 200 mm. The experimental results comply with the Maag spherical diffusion theory and verified the scientificity and rationality of this experimental system
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