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Using tremendous photon statistics gained with the stray light aperture of the NuSTAR telescope over 11 years of operation, we set strong limits on the emission of close to monochromatic photons from the radiative decays of putative dark matter sterile neutrinos in the Milky Way. In the energy range of 3-20 keV covered by the NuSTAR, the obtained limits reach the bottom edge of theoretical predictions of realistic models where sterile neutrinos are produced in the early Universe. Only a small region is left to explore, if the sterile neutrinos form the entire dark matter component.
View Article and Find Full Text PDFThe time-resolved backlight imaging of plasma is crucial for diagnosing density-dependent plasma information. It requires a high-intensity X-ray source and efficient optics. We propose a quasi-coaxial, multi-channel Kirkpatrick-Baez (KB) structure that realizes high-brightness illumination.
View Article and Find Full Text PDFWe demonstrate PaCMAN, a ptychography algorithm that can reconstruct high quality images with broadband illumination sources while being robust to shot, detector, and parasitic noise. We extend prior monochromatization work to improve accuracy, especially for discrete spectra, and also demonstrate how PaCMAN can be converted into Ms. PaCMAN, a multi-spectral variant that outperforms multi-spectral ePIE.
View Article and Find Full Text PDFChem Asian J
January 2025
University of Macau, Institute of Applied Physics and Materials Engineering, MACAO.
In recent years, carbon dots (CDs) with fluorescence imaging function have been widely used in biomedicine, electronic manufacturing and environmental monitoring. However, monochromatic fluorescence is often limited by the application environment and loses its effectiveness. Here, we carefully designed white fluorescent CDs (WF-CDs) by solvothermal method, which is used for fluorescence imaging applications under different environmental conditions.
View Article and Find Full Text PDFJ Appl Crystallogr
January 2024
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, USA.
Neutron reflectometry (NR) is a powerful technique for interrogating the structure of thin films at interfaces. Because NR measurements are slow and instrument availability is limited, measurement efficiency is paramount. One approach to improving measurement efficiency is active learning (AL), in which the next measurement configurations are selected on the basis of information gained from the partial data collected so far.
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