Experimental quantum key distribution through free-space channels requires accurate pointing-and-tracking to co-align telescopes for efficient transmission. The hardware requirements for the sender and receiver could be drastically reduced by combining the detection of quantum bits and spatial tracking signal using two-dimensional single-photon detector arrays. Here, we apply a two-dimensional CMOS single-photon avalanche diode detector array to measure and monitor the single-photon level interference of a free-space time-bin receiver interferometer while simultaneously tracking the spatial position of the single-photon level signal. We verify an angular field-of-view of 1.28° and demonstrate a post-processing technique to reduce background noise. The experimental results show a promising future for two-dimensional single-photon detectors in low-light level free-space communications, such as quantum communications.
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http://dx.doi.org/10.1364/OE.416143 | DOI Listing |
Sci Rep
January 2025
College of Ocean and Meteorology & South China Sea Institute of Marine Meteorology, Guangdong Ocean University, 524088, Zhanjiang, Guangdong, China.
Accurate classification of tropical cyclone (TC) tracks is essential for evaluating and mitigating the potential disaster risks associated with TCs. In this study, three commonly used methods (K-means, Fuzzy C-Means, and Self-Organizing Maps) are assessed for clustering historical TC tracks that originated in the South China Sea from 1949 to 2023. The results show that the K-means method performs the best, while the Fuzzy C-Means and Self-Organizing Maps methods are also viable alternatives.
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January 2025
Department of Cognitive and Brain Sciences, Ben-Gurion University of the Negev, 1 Ben-Gurion Blvd, Beer-Sheva, Israel.
During flight, spatial disorientation (SD) commonly occurs when a pilot's perception conflicts with the aircraft's actual motion, attitude, or position. A prevalent form of SD is the somatogyral illusion, which is elicited by constant speed rotation and causes a false perception of motion in the opposite direction when the rotation ceases. This research aimed to investigate changes in brain activity that occur when experiencing a somatogyral illusion by simulating conditions closely mimicking flight conditions to gain insight into how to better manage this illusion during flight.
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January 2025
Environmental Microbiome Engineering and Biotechnology Laboratory, Center for Environmental Engineering Research, Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China; School of Public Health, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Marine Pollution, Department of Chemistry and School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China; Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macao SAR, China. Electronic address:
Rivers play an important role as reservoirs and sinks for antibiotic resistance genes (ARGs). However, it remains underexplored for the resistome and associated mobilome in river ecosystems, and hosts of riverine ARGs particularly the pathogenic ones are rarely studied. This study for the first time conducted a longitudinal metagenomic analysis to unveil the resistome, mobilome, and microbiome in river water, by collecting samples from 16 rivers in Hong Kong over a three-year period and using both short-read and long-read sequencing.
View Article and Find Full Text PDFAppl Radiat Isot
December 2024
Neutron Sciences Directorate, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN, 37831, USA.
Chemical movement through soil is an important process in agriculture and ecology. Observing the spatial and temporal dynamics of these processes using conventional chemical ecology methods requires techniques that are destructive and/or lack resolution. Neutron radiography has the capability to allow chemical motion through sand/soil to be tracked with high spatial and temporal resolution, and we show that it allows for the motion of hydrophobic and hydrophilic chemicals to be distinguished.
View Article and Find Full Text PDFSensors (Basel)
December 2024
TDA Research Inc., Golden, CO 80403, USA.
Here we describe the synthesis and evaluation of a molecular corrosion sensor that can be applied in situ in aerospace coatings, then used to detect corrosion after the coating has been applied. A pH-sensitive molecule, 4-mercaptopyridin (4-MP), is attached to a gold nanoparticle to allow surface-enhanced Raman-scattering (SERS) for signal amplification. These SERS nanoparticles, when combined with an appropriate micron-sized carrier system, are incorporated directly into an MIL-SPEC coating and used to monitor the process onset and progression of corrosion using pH changes occurring at the metal-coating interface.
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