Measurement-device-independent quantum key distribution (MDI-QKD), based on two-photon interference, is immune to all attacks against the detection system and allows a QKD network with untrusted ...relays. Since the MDI-QKD protocol was proposed, fiber-based implementations aimed at longer distance, higher key rates, and network verification have been rapidly developed. However, owing to the effect of atmospheric turbulence, MDI-QKD over a free-space channel remains experimentally challenging. Herein, by developing a robust adaptive optics system, high-precision time synchronization and frequency locking between independent photon sources located far apart, we realized the first free-space MDI-QKD over a 19.2-km urban atmospheric channel, which well exceeds the effective atmospheric thickness. Our experiment takes the first step toward satellite-based MDI-QKD. Moreover, the technology developed herein opens the way to quantum experiments in free space involving long-distance interference of independent single photons.
The filamentous cyanobacterium Anabaena sp. PCC 7120 is able to form heterocysts for nitrogen fixation. Heterocyst differentiation is initiated by combined-nitrogen deprivation, followed by the ...commitment step during which the developmental process becomes irreversible. Mature heterocysts are terminally differentiated cells unable to divide, and cell division is required for heterocyst differentiation. Previously, we have shown that the HetF protease regulates cell division and heterocyst differentiation by cleaving PatU3, which is an inhibitor for both events. When hetF is required during the developmental program remains unknown. Here, by controlling the timing of hetF expression during heterocyst differentiation, we provide evidence that hetF is required just before the beginning of heterocyst morphogenesis. Consistent with this finding, transcriptome data show that most of the genes known to be involved in the early step (such as hetR and ntcA) or the commitment step (such as hetP and hetZ) of heterocyst development could be expressed in the ΔhetF mutant. In contrast, most of the genes involved in heterocyst morphogenesis and nitrogen fixation remain repressed in the mutant. These results indicated that in the absence of hetF, heterocyst differentiation is able to be initiated and proceeds to the stage just before heterocyst envelope formation.
Benzoxepane derivatives were designed and synthesized, and one hit compound emerged as being effective in vitro with low toxicity. In vivo, this hit compound ameliorated both sickness behavior ...through anti‐inflammation in LPS‐induced neuroinflammatory mice model and cerebral ischemic injury through anti‐neuroinflammation in rats subjected to transient middle cerebral artery occlusion. Target fishing for the hit compound using photoaffinity probes led to identification of PKM2 as the target protein responsible for anti‐inflammatory effect of the hit compound. Furthermore, the hit exhibited an anti‐neuroinflammatory effect in vitro and in vivo by inhibiting PKM2‐mediated glycolysis and NLRP3 activation, indicating PKM2 as a novel target for neuroinflammation and its related brain disorders. This hit compound has a better safety profile compared to shikonin, a reported PKM2 inhibitor, identifying it as a lead compound in targeting PKM2 for the treatment of inflammation‐related diseases.
Fishing around: The benzoxepane derivative A was effective in vivo, ameliorating both sickness behavior through anti‐inflammation in LPS‐induced neuroinflammatory mice model and cerebral ischemic injury through anti‐neuroinflammation in rats subjected to transient middle cerebral artery occlusion. Target fishing identified PKM2 as the target protein for A. Furthermore, A exhibited an anti‐neuroinflammatory effect in vitro and in vivo by inhibiting PKM2‐mediated glycolysis and NLRP3 activation.
We report on entanglement-based quantum key distribution between a low-Earth-orbit satellite equipped with a space borne entangled-photon source and a ground observatory. One of the entangled photons ...is measured locally at the satellite, and the other one is sent via a down link to the receiver in the Delingha ground station. The link attenuation is measured to vary from 29 dB at 530 km to 36 dB at 1000 km. We observe that the two-photon entanglement survives after being distributed between the satellite and the ground, with a measured state fidelity of ≥0.86. We then perform the entanglement-based quantum key distribution protocol and obtain an average final key rate of 3.5 bits/s at the distance range of 530-1000 km.
Quantized impact of rod on plate Peng, Qing; Liu, Xiaoming; Wei, Yue-Guang
Journal of the mechanics and physics of solids,
July 2024, 2024-07-00, Letnik:
188
Journal Article
Recenzirano
•We proposed a new model for the impact of a rod on a plate, consolidating classical bead-on-wall, bead-on-plate, and rod-on-wall theories.•We provided a universal loading history for the impact ...contact of a rod on a plate.•The unloading force is quantized and the duration of contact has a band structure as the flexibility of plate increases.
In this work, we attacked the problem of elastic impact of a rod on a plate. By considering wave propagation on the plate and along the rod, we established a mathematic model with delay differential equation that governs such impact. The proposed model could consolidate classical impact problems from bead-on-wall, bead-on-plate, to rod-on-wall impact. Solving the governing equation, we obtained a universal loading and unloading history of such impact: the unloading history exhibits quantized plateaus, the values of which are quantitatively provided in the present study. Also, the contact duration also shows a band structure while tuning the compliance of plate. In addition, we analyzed the overshoots leading the plateaus during unloading, which cause the final detachment between the rod and the plate.
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Abstract
Quantum key distribution (QKD) enables secure key exchanges between two remote users. The ultimate goal of secure communication is to establish a global quantum network. The existing field ...tests suggest that quantum networks are feasible. To achieve a practical quantum network, we need to overcome several challenges including realizing versatile topologies for large scales, simple network maintenance, extendable configuration and robustness to node failures. To this end, we present a field operation of a quantum metropolitan-area network with 46 nodes and show that all these challenges can be overcome with cutting-edge quantum technologies. In particular, we realize different topological structures and continuously run the network for 31 months, by employing standard equipment for network maintenance with an extendable configuration. We realize QKD pairing and key management with a sophisticated key control centre. In this implementation, the final keys have been used for secure communication such as real-time voice telephone, text messaging and file transmission with one-time pad encryption, which can support 11 pairs of users to make audio calls simultaneously. Combined with intercity quantum backbone and ground–satellite links, our metropolitan implementation paves the way toward a global quantum network.
Perovskite structure compounds are significant candidates for designing new optical function materials due to their structural variability. Here, an inorganic tetravalent cerium fluoride, Na2CeF6, is ...derived from the perovskite structure through double‐site cation co‐substitution. Na2CeF6 crystalizes in the non‐centrosymmetric space group P6¯2m${P}^{\bar{6}}2m$. Edge‐sharing connected NaF9 and CeF9 polyhedra build the whole 3D structure of Na2CeF6. Importantly, it represents the first Ce(IV) fluoride nonlinear optical (NLO) crystal and can produce a strong and phase‐matchable second‐harmonic generation (SHG) effect of ≈2.1 times that of KH2PO4 (KDP), making it the strongest among non‐lone pair electron metal fluoride system. Further, it exhibits a high laser‐induced damage threshold (LIDT) of 74.65–76.25 MW cm−2, which is over 20 times that of AgGaS2. It also exhibits a wide transparent region (0.5−14.3 µm). This work provides a facile route for exploring high‐performance halide NLO materials.
Here, an inorganic tetravalent cerium fluoride, Na2CeF6, is derived from the perovskite structure by double site cation substitution. It represents the first Ce(IV) fluoride nonlinear optical crystal and demonstrates a strong and phase‐matchable second‐harmonic generation effect (2.1 × KH2PO4). It also exhibits large laser‐induced damage threshold (over 20 × AgGaS2).
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