The deployment of unmanned aerial vehicle (UAV) for surveillance and monitoring gives rise to the confidential information leakage challenge in both civilian and military environments. The security ...and covert communication problems for a pair of terrestrial nodes against UAV surveillance are considered in this paper. To overcome the information leakage and increase the transmission reliability, a multi-hop relaying strategy is deployed. We aim to optimize the throughput by carefully designing the parameters of the multi-hop network, including the coding rates, transmit power, and required number of hops. In the secure transmission scenario, the expressions of the connection probability and secrecy outage probability of an end-to-end path are derived and the closed-form expressions of the optimal transmit power, transmission and secrecy rates under a fixed number of hops are obtained. In the covert communication problem, under the constraints of the detection error rate and aggregate power, the sub-problem of transmit power allocation is a convex problem and can be solved numerically. Simulation shows the impact of network settings on the transmission performance. The trade-off between secrecy/covertness and efficiency of the multi-hop transmission is discussed which leads to the existence of the optimal number of hops.
Nanoreactors with hollow structures have attracted great interest in catalysis research due to their void‐confinement effects. However, the challenge in unambiguously unraveling these confinement ...effects is to decouple them from other factors affecting catalysis. Here, we synthesize a pair of hollow carbon sphere (HCS) nanoreactors with presynthesized PdCu nanoparticles encapsulated inside of HCS (PdCu@HCS) and supported outside of HCS (PdCu/HCS), respectively, while keeping other structural features the same. Based on the two comparative nanoreactors, void‐confinement effects in liquid‐phase hydrogenation are investigated in a two‐chamber reactor. It is found that hydrogenations over PdCu@HCS are shape‐selective catalysis, can be accelerated (accumulation of reactants), decelerated (mass transfer limitation), and even inhibited (molecular‐sieving effect); conversion of the intermediate in the void space can be further promoted. Using this principle, a specific imine is selectively produced. This work provides a proof of concept for fundamental catalytic action of the hollow nanoreactors.
A pair of hollow carbon sphere (HCS) nanoreactors with PdCu nanoparticles encapsulated inside the HCS (PdCu@HCS) and supported outside the HCS (PdCu/HCS) have been prepared. Based on the two comparable systems, the void‐confinement effects of hollow nanoreactors in liquid‐phase hydrogenation have been extensively investigated in a two‐chamber reactor.
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In this Information Age, computers and mobile phones are important carriers of data transmission and many scientists work hard to speed up that process. Professor Peter Delfyett of the University of ...Central Florida has done just that. A member of the US National Academy of Engineering, he developed the world's fastest and most powerful mode-locked semiconductor laser. I have known Professor Delfyett since 2011, when he took part in the CIOMP-OSA International Summer Session. His sincere and friendly attitude, humorous and optimistic nature and excellent academic style left a deep impression. Driven by curiosity, human beings are constantly exploring the unknown, and asking questions. Einstein once suggested, defining what the problem is can be more important than solving it. And this is what Professor Delfyett has been advocating: pursue the ultimate academic goal, ask questions, believe in yourself and never give up. In addition, he has been striving to integrate industry and scientific research, so that scientific research results can truly benefit mankind. And now, please follow Light People to the latest cutting-edge progress in optics.
Under global warming, a novel category of extreme events has become increasingly apparent, where flood and hot extremes occur in rapid succession, causing significant damages to infrastructure and ...ecosystems. However, these bivariate compound flood‐hot extreme (CFH) hazards have not been comprehensively examined at the global scale, and their evolution under climate warming remains unstudied. Here, we present the first global picture of projected changes in CFH hazards by using a cascade modeling chain of CMIP6 models, satellite and reanalysis data sets, bias correction, and hydrological models. We find an increasing percentage of floods will be accompanied by hot extremes under climate change; the joint return periods of CFHs are projected to decrease globally, particularly in the tropics. These decreasing joint return periods are largely driven by changes in hot extremes and indicate a likely increase of CFH hazards, and ultimately highlight the urgent need to conduct adaptation planning for future risks.
Plain Language Summary
Climate change alters the Earth's energy budget and accelerates the hydrological cycle, bringing new hazards such as temporally compounding flood and hot extremes. Rapid transitions from devastating floods to deadly heat, or vice versa, which used to be rare, are already occurring under the present climate and bring new threats to infrastructure and the public. However, these bivariate CFH hazards have been poorly understood at the global scale, and their future evolution in the context of climate change has not yet been assessed. Here, we provide the first systematic assessment of projected changes and attributions in the multivariate hazards of global flood‐hot extremes. We find that the fraction of flooding accompanied by hot extremes could rise markedly under global warming. Changes in hot extremes dominate the exacerbation of global CFH hazards, especially in tropical climate zones. Our study identifies the tropics as the new global hotspot of flood‐hot extreme events in a warming future, and reveals an increasing global risk of unexpected sequential wet‐hot extremes, highlighting the need to better prepare adaptation and mitigation solutions.
Key Points
We present the first global assessment of projected changes in compound river flood‐hot extremes
Future flood‐hot extremes are mainly driven by changes in hot extremes
Substantial increases in compound flood‐hot extremes are projected in tropical regions
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PURPOSE OF REVIEWDue to the stringent measures including quarantine of infected individuals and social distancing, the COVID-19 pandemic has posted great challenges for HIV-1 care in China. In this ...mini-review, I will discuss the situation in Shenzhen city as a window of China to reflect our strategies in fighting the concurrent HIV/AIDS and COVID-19 pandemics.
RECENT FINDINGSPrevention of nosocomial infection, minimizing the follow-up visits to the hospital, maintaining the delivery of PreP/PEP services and testing for SARS-Cov-2 and HIV when someone have fever or respiratory symptoms were the four major approaches to maintain uninterrupted HIV care in Shenzhen. None of 15 000 PLWH seeking HIV care at Shenzhen were diagnosed with COVID-19 during this pandemic.
SUMMARYThis article share the experience unprecedented from Shenzhen. We have to adapt our care and service to continue to engage PLWH to avoid poor outcomes. More research is needed to know the long-term implications of pandemic for the health of PLWH.
The Nobel Prize in Physics 2022 was awarded to French physicist Alain Aspect, American physicist John F. Clauser, and Austrian physicist Anton Zeilinger, in recognition of their contributions to the ...research of quantum information, a clear indication that we are entering the era of quantum information.In China, a scientist has played herald in quantum research since as early as the 1980s. He introduced quantum optics and quantum informatics to China, a virgin land in terms of quantum research back then. That scientist is Academician Guangcan Guo.Out of personal interests and his good sense as a scientist, Prof. Guo took it upon himself to take on quantum optics when little was known about it in China. He trained many students and launched China's first academic conference on quantum optics, which helped to accelerate the development of quantum optics in China.In the early 1990s, he took on another challenge, shifting his research focus to the emerging subject of quantum informatics. His work helped to establish China's current leading position in this interdisciplinary field. Today, China leads the world in quantum USB drives and quantum chips.Now in his 1980s, Prof. Guo is still working tirelessly at the front line of scientific research, doing science popularization, and teaching students. He is ready for the third big challenge of his life-to reveal the mysteries of the classical world and the quantum world.Next, please follow "Light People" into the mysterious "quantum world", and feel the beauty of science.
In applications of the Internet of Things (IoT), the use of short packets is expected to meet the stringent latency requirement in ultra-reliable low-latency communications; however, the incurred ...security issues and the impact of finite blocklength coding on the physical-layer security are not well understood. This paper investigates the performance of secure short-packet communications in a mission-critical IoT system with an external multi-antenna eavesdropper. An analytical framework is proposed to approximate the average achievable secrecy throughput of the system with finite blocklength coding. To gain more insight, a simple case with a single-antenna access point (AP) is considered first, in which the secrecy throughput is approximated in a closed form. Based on that result, the optimal blocklengths to maximize the secrecy throughput with and without the reliability and latency constraints, respectively, are derived. For the case with a multi-antenna AP, following the proposed analytical framework, closed-form approximations for the secrecy throughput are obtained under both beamforming and artificial-noise-aided transmission schemes. The numerical results verify the accuracy of the proposed approximations and illustrate the impact of the system parameters on the tradeoff between transmission latency and reliability under a secrecy constraint.
Synthetic molecular robots can execute sophisticated molecular tasks at nanometer resolution. However, a molecular robot capable of controlling cellular behavior remains unexplored. Herein, we report ...a self‐propelled DNA robot operating on the cell membrane to control the migration of a cell. Driven by DNAzyme catalytic activity, the DNA robot could autonomously and stepwise move on the membrane‐floating cell‐surface receptors in a stochastic manner and simultaneously trigger the receptor‐dimerization to activate downstream signaling for cell motility. The cell membrane‐associated continuous motion and operation of a DNA robot allowed for the ultrasensitive regulation of MET/AKT signaling and cytoskeleton remodeling to enhance cell migration. Finally, we designed distinct conditional DNA robots to orthogonally manipulate the cell migration in a coculture of mixed cell populations. We have developed a novel strategy to engineer a cell‐driving molecular robot, representing a promising avenue for precise cell manipulation with nanoscale resolution.
A DNA molecular robot that autonomously walks on the cell membrane to drive the cell motility has been developed. The DNA robot could move stepwise on the membrane‐floating cell‐surface receptors in a stochastic manner and simultaneously trigger the receptor‐dimerization to activate downstream signal pathway regulation of desired cellular behavior.
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Editorial
“When all those around me are drunk, I alone am sober,” lamented an ancient Chinese poet on fighting a lone and helpless cause. In the world of science a few decades ago, there was also a ...lone researcher who pursued the field of optical resolution despite suspicions and derisions. Unlike those who made their names young, this scientist only succeeded thanks to his own perseverance. He developed the 4Pi microscope and successfully increased the vertical resolution of traditional optical microscopes by 3–7 times. Once he sold the patent to a company, he invested the little personal money gained from the patent in breaking the Abbe diffraction limit. Despite all his hard work, his papers kept getting rejected by respected journals, and his work was subjected to mistrust and even criticism. This scientist is Stefan Hell, someone who is never afraid of difficulties and ever determined to forge ahead.
Hell was awarded the Nobel Prize in Chemistry in 2014 for being the first to propose and demonstrate that the optical diffraction limit can be broken, and for successfully developing the STED super-resolution fluorescence microscope. Later Hell and his colleagues proposed and commercialized MINFLUX, which brought optical microscopy technology to the three-dimensional single-nanometer scale, opening the “post-superresolution era”.
Frank and sincere, persistent and humble, boldly innovative and resolute, Hell is a scientist, an entrepreneur, a mentor, and an everyday man who enjoys life.
In this interview, we will reacquaint ourselves with the Nobel laureate, Stefan Hell.
Solid/liquid interfaces are ubiquitous in nature and knowledge of their atomic-level structure is essential in elucidating many phenomena in chemistry, physics, materials science and Earth science
. ...In electrochemistry, in particular, the detailed structure of interfacial water, such as the orientation and hydrogen-bonding network in electric double layers under bias potentials, has a significant impact on the electrochemical performances of electrode materials
. To elucidate the structures of electric double layers at electrochemical interfaces, we combine in situ Raman spectroscopy and ab initio molecular dynamics and distinguish two structural transitions of interfacial water at electrified Au single-crystal electrode surfaces. Towards negative potentials, the interfacial water molecules evolve from structurally 'parallel' to 'one-H-down' and then to 'two-H-down'. Concurrently, the number of hydrogen bonds in the interfacial water also undergoes two transitions. Our findings shed light on the fundamental understanding of electric double layers and electrochemical processes at the interfaces.
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