Quantum key distribution (QKD) uses individual light quanta in quantum superposition states to guarantee unconditional communication security between distant parties. However, the distance over which ...QKD is achievable has been limited to a few hundred kilometres, owing to the channel loss that occurs when using optical fibres or terrestrial free space that exponentially reduces the photon transmission rate. Satellite-based QKD has the potential to help to establish a global-scale quantum network, owing to the negligible photon loss and decoherence experienced in empty space. Here we report the development and launch of a low-Earth-orbit satellite for implementing decoy-state QKD-a form of QKD that uses weak coherent pulses at high channel loss and is secure because photon-number-splitting eavesdropping can be detected. We achieve a kilohertz key rate from the satellite to the ground over a distance of up to 1,200 kilometres. This key rate is around 20 orders of magnitudes greater than that expected using an optical fibre of the same length. The establishment of a reliable and efficient space-to-ground link for quantum-state transmission paves the way to global-scale quantum networks.
Similarities in sizes, shapes, and physical properties between carbon dioxide (CO2) and acetylene (C2H2) make it a great challenge to separate the major impurity CO2 from products in C2H2 production. ...The use of porous materials is an appealing path to replace current very costly and energy‐consuming technologies, such as solvent extraction and cryogenic distillation; however, high CO2/C2H2 uptake ratio with minor adsorption of C2H2 at standard pressure was only unexpectedly observed in scarce examples in recent years although the related research started early at 1950s, and general design strategies to realize this aim are still absent. This work has successfully developed an efficient PIET strategy and obtained the second highest CO2/C2H2 adsorption ratio for porous materials in a proof‐of‐concept MOF with a photochromism‐active bipyridinium zwitterion. An unprecedented photocontrollable gate effect, owing to change of interannular dihedral after photoinduced generation of radical species, was also observed for the first time. These findings will inspire design and synthesis of porous materials for high efficient gas adsorption and separation.
Using porous materials is a promising technique but a great challenge to achieve high CO2/C2H2 uptake ratio. This work has developed a PIET strategy and obtained the second highest CO2/C2H2 adsorption ratio for porous materials. These findings will promote the development of a new generation of CO2‐selective adsorption technique in C2H2 production and inspire design and synthesis of porous materials for high efficient gas adsorption and separation.
Long-distance entanglement distribution is essential for both foundational tests of quantum physics and scalable quantum networks. Owing to channel loss, however, the previously achieved distance was ...limited to ~100 kilometers. Here we demonstrate satellite-based distribution of entangled photon pairs to two locations separated by 1203 kilometers on Earth, through two satellite-to-ground downlinks with a summed length varying from 1600 to 2400 kilometers. We observed a survival of two-photon entanglement and a violation of Bell inequality by 2.37 ± 0.09 under strict Einstein locality conditions. The obtained effective link efficiency is orders of magnitude higher than that of the direct bidirectional transmission of the two photons through telecommunication fibers.
An arbitrary unknown quantum state cannot be measured precisely or replicated perfectly. However, quantum teleportation enables unknown quantum states to be transferred reliably from one object to ...another over long distances, without physical travelling of the object itself. Long-distance teleportation is a fundamental element of protocols such as large-scale quantum networks and distributed quantum computation. But the distances over which transmission was achieved in previous teleportation experiments, which used optical fibres and terrestrial free-space channels, were limited to about 100 kilometres, owing to the photon loss of these channels. To realize a global-scale 'quantum internet' the range of quantum teleportation needs to be greatly extended. A promising way of doing so involves using satellite platforms and space-based links, which can connect two remote points on Earth with greatly reduced channel loss because most of the propagation path of the photons is in empty space. Here we report quantum teleportation of independent single-photon qubits from a ground observatory to a low-Earth-orbit satellite, through an uplink channel, over distances of up to 1,400 kilometres. To optimize the efficiency of the link and to counter the atmospheric turbulence in the uplink, we use a compact ultra-bright source of entangled photons, a narrow beam divergence and high-bandwidth and high-accuracy acquiring, pointing and tracking. We demonstrate successful quantum teleportation of six input states in mutually unbiased bases with an average fidelity of 0.80 ± 0.01, well above the optimal state-estimation fidelity on a single copy of a qubit (the classical limit). Our demonstration of a ground-to-satellite uplink for reliable and ultra-long-distance quantum teleportation is an essential step towards a global-scale quantum internet.
Nuclear power plants, working in extremely harsh environment, primarily in the form of high-speed fluid flow, circulate through complex systems. Serious tribological problems can occur when a small ...amount of nuclear energy is converted into mechanical energy in the components (e.g., fuel-rod cladding, tube of the heat exchange systems). With the increase of the service life of nuclear power equipment, a considerable number of nuclear power equipment or structure failures occur one after another. Although the influencing factors are different, fretting damage is one of the important factors. Fretting damage has strong concealment and high risk, and it is often the main cause of component failure. Thus, improving the reliability of nuclear power equipment, extending their life, and optimizing their structure are important. In recent decades, many scholars have studied fretting wear, fretting fatigue, and fretting corrosion behavior in nuclear power equipment. Accordingly, they have solved many problems, accumulated a lot of experience, and put forward many criteria. In this article, the research status of fretting damage in key equipment and structures of nuclear power plant is reviewed.
Typical positions of fretting wear in steam generator. Display omitted
•The research status of fretting method, nuclear materials damage in key equipment and structures of nuclear power plant is reviewed.•Fretting research of heat exchange materials for steam generators and fuel cladding in nuclear power systems is reviewed.•The research status of fretting wear of fuel cladding is analyzed, including the latest coating and surface strengthening technologies.
RLR-mediated type I IFN production plays a pivotal role in elevating host immunity for viral clearance and cancer immune surveillance. Here, we report that glycolysis, which is inactivated during RLR ...activation, serves as a barrier to impede type I IFN production upon RLR activation. RLR-triggered MAVS-RIG-I recognition hijacks hexokinase binding to MAVS, leading to the impairment of hexokinase mitochondria localization and activation. Lactate serves as a key metabolite responsible for glycolysis-mediated RLR signaling inhibition by directly binding to MAVS transmembrane (TM) domain and preventing MAVS aggregation. Notably, lactate restoration reverses increased IFN production caused by lactate deficiency. Using pharmacological and genetic approaches, we show that lactate reduction by lactate dehydrogenase A (LDHA) inactivation heightens type I IFN production to protect mice from viral infection. Our study establishes a critical role of glycolysis-derived lactate in limiting RLR signaling and identifies MAVS as a direct sensor of lactate, which functions to connect energy metabolism and innate immunity.
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•Lactate inhibits RLR-mediated interferon production•This regulation occurs through direct sensing of lactate by MAVS•MAVS associates with hexokinase, but this association is disrupted by RIG-I•Targeting LDHA enhances type I IFN production and viral clearance
Lactate acts as a regulator of the adaptor MAVS, allowing a cross-regulation between antiviral signaling and energy metabolism
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•The tribological behaviour of graphene nanosheets as lubricating oil additives on textured alloy cast iron surface were investigated.•A combined effect on reducing the friction and ...wear between graphene nanosheets additives and laser surface texturing was revealed.•The graphene layers form a protective film, which is closely related with the graphene structures and surface texture patterns.
Tribological properties of graphene nanosheets (GNS) as lubricating oil additives on textured surfaces were investigated using a UMT-2 tribotester. The lubricating fluids keeping a constant temperature of 100°C were applied to a GCr15 steel ball and an RTCr2 alloy cast iron plate with various texture designs (original surface, dimple density of 22.1%, 19.6% and 44.2%). The oil with GNS adding showed good tribological properties (wear reduced 50%), especially on the textured surfaces (the reduction in wear was high at over 90%). A combined effect between GNS additives and laser surface texturing (LST) was revealed, which is not a simple superposition of the two factors mentioned. A mechanism is proposed to explain for these results −the graphene layers sheared at the sliding contact interfaces, and form a protective film, which is closely related with the GNS structures and surface texture patterns.
The tight interband correlation and the lag-wavelength relation among UV/optical continua of active galactic nuclei have been firmly established. They are usually understood within the widespread ...reprocessing scenario; however, the implied interband lags are generally too small. Furthermore, it is challenged by new evidence, such as that the X-ray reprocessing yields too much high-frequency UV/optical variation and that it fails to reproduce the observed timescale-dependent color variations among the Swift light curves of NGC 5548. In a different manner, we demonstrate that an upgraded inhomogeneous accretion disk model, whose local independent temperature fluctuations are subject to a speculated common large-scale temperature fluctuation, can intrinsically generate the tight interband correlation and lag across the UV/optical and be in nice agreement with several observational properties of NGC 5548, including the timescale-dependent color variation. The emergent lag is a result of the differential regression capability of local temperature fluctuations when responding to the large-scale fluctuation. An average speed of propagations as large as 15% of the speed of light may be required by this common fluctuation. Several potential physical mechanisms for such propagations are discussed. Our interesting phenomenological scenario may shed new light on comprehending the UV/optical continuum variations of active galactic nuclei.
Micro-arc oxidation (MAO) coating with different oxidation times was prepared on aluminum alloy to improve the impact wear resistance of aluminum alloy. Surface morphology and impact wear behavior of ...the coating with different oxidation times were investigated. Results showed that the MAO coating formed on aluminum alloy had a porous and island structure comprising α-Al2O3 and γ-Al2O3. Coating thickness increased with increasing oxidation time. The coating also had a lower impact force and higher energy absorption ratio than the substrate but had a lower wear volume, which decreased with increasing oxidation time. These results indicated that MAO coating can improve the impact wear resistance of aluminum alloy. Further study revealed that the wear mechanism of aluminum alloy was oxidation wear and contact fatigue spalling, whereas that of MAO coating was contact fatigue wear.
•The characterization and impact wear behavior of the MAO coating with different oxidation times was investigated.•The wear mechanism of aluminum alloy and MAO coating was discussed.
This article focuses on a novel robust adaptive sliding mode control strategy of an electro-hydraulic force loading system with consideration of external disturbances and parameter uncertainties. To ...obtain the proposed controller, the nonlinear dynamic model of the electro-hydraulic force loading system is firstly provided, where external disturbances and system's uncertain parameters are merged. Then, with consideration of external disturbances and parameter uncertainties, a robust adaptive sliding mode controller for the force control system is proposed and designed according to Lyapunov stability theory. The proposed controller has the merit of suppressing chattering phenomenon in traditional adaptive backstepping controllers when designing sign functions. In order to verify effectiveness and feasibility of the proposed controller, experimental studies are implemented on an electro-hydraulic force loading system by xPC rapid prototyping technology. Experimental results demonstrate that the proposed controller exhibits more excellent performance on force tracking control in comparison of a traditional proportional-integral controller and an adaptive backstepping controller.
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