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Physical Review A 2020年第5期101卷 053814-053814页

作者： C. L. Zhong B. Qiao X. R. Xu Y. X. Zhang X. B. Li Y. Zhang C. T. Zhou S. P. Zhu X. T. He Center for Applied Physics and Technology HEDPS and SKLNPT School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of IFSA (CICIFSA) Shanghai Jiao Tong University Shanghai 200240 China Center for Advanced Material Diagnostic Technology Shenzhen Technology University Shenzhen 518118 China Department of Physics National University of Defense Technology Changsha 410073 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China Graduate School of China Academy of Engineering Physics P.O. Box 2101 Beijing 100088 China

A method for the production of intense circularly polarized (CP) attosecond pulses from relativistic laser-solid interactions is proposed, where a two-color linearly polarized (LP) laser is used. The polarization, photon frequency, and other properties of the obtained attosecond pulse can be controlled by adjusting the ratio of the dichromatic driving LP field in different harmonics, which is much easier and more efficient than those previously using CP driving lasers. Both one- and two-dimensional particle-in-cell simulations show that a CP attosecond extreme-ultraviolet pulse with an intensity of 1.4×1019W/cm2 and a duration of about 120 as is obtained by a two-color LP laser at intensities in the fundamental and second harmonics of, respectively, 1.5×1022 and 6.4×1021W/cm2, which can be applied for the detection of the magnetic and chiral properties of materials.

关键词： High-order harmonic generation Ultrafast optics X-ray beams & optics X-ray generation in plasmas

Pattern change of precipitation extremes in Bear Island

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arXiv 2023年

作者： Ray, Arnob Chakraborty, Tanujit Radhakrishnan, Athulya Hens, Chittaranjan Dana, Syamal K. Ghosh, Dibakar Murukesh, Nuncio Physics and Applied Mathematics Unit Indian Statistical Institute Kolkata700108 India Roux Institute Northeastern University Portland04101 United States Institute for Experiential AI Northeastern University Boston02115 United States Department of Science and Engineering Sorbonne University Abu Dhabi United Arab Emirates Sorbonne Center for Artificial Intelligence Sorbonne University Paris75005 France Ocean Atmospheric Studies National Centre for Antarctic and Ocean Research Vasco Da Gama403804 India Center for Computational Natural Science and Bioinformatics International Institute of Informational Technology Hyderabad500032 India Division of Dynamics Lodz University of Technology postcode Lodz90-924 Poland

Extreme precipitation in the Arctic region plays a crucial role in global weather and climate patterns. Bear Island (Bjørnøya) is located in the Norwegian Svalbard archipelago, which is, therefore, selected for our study on extreme precipitation. The island occupies a unique geographic position at the intersection of the high and low Arctic, characterized by a flat and lake-filled northern region contrasting with mountainous terrain along its southern shores. Its maritime-polar climate is influenced by North Atlantic currents, resulting in relatively mild winter temperatures. An increase in precipitation level in Bear Island is a significant concern linked to climate change and has global implications. We have collected the amount of daily precipitation as well as daily maximum temperatures from the meteorological station of Bjørnøya located on the island, operated by the Norwegian Centre for Climate Services in Svalbard for a period spanning from January 1, 1960 to December 31, 2021. We observe that the trend of yearly mean precipitation during this period linearly increases. Also, the number of extreme precipitation events is also increasing. Motivating from this observation, we analyze the recorded data to investigate the changing pattern of precipitation extremes over the climate scales. We employ the generalized extreme value distribution to model yearly and seasonal maxima of daily precipitation amount and determine the return levels and return period of precipitation extremes. We compare the variability of precipitation extremes between the two time periods: (i) 1960-1990 and (ii) 1991-2021. Our analysis reveals an increase in the frequency of precipitation extremes occurrences between 1991 and 2021. A relationship between temperature and precipitation in the area is discerned using wavelet transform coherence. Our findings establish a better understanding of precipitation extremes in Bear Island from a statistical viewpoint, with an observation of seasonal a

关键词： Wavelet transforms

Controlling Rydberg excitation process with shaped intense ultrashort laser pulses

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Chinese physics B 2019年第8期28卷 79-83页

作者： Xiao-Yun Zhao Chun-Cheng Wang Shi-Lin Hu Wei-Dong Li Jing Chen Xiao-Lei Hao Institute of Theoretical Physics and Department of Physics State Key Laboratory of Quantum Optics and Quantum Optics DevicesCollaborative Innovation Center of Extreme OpticsShanxi UniversityTaiyuan 030006China Institute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China Laboratory of Quantum Engineering and Quantum Metrology School of Physics and AstronomySun Yat-Sen University (Zhuhai Campus)Zhuhai 519082China CAPT HEDPSand IFSA Collaborative Innovation Center of MoECollege of EngineeringPeking UniversityBeijing 100084China Institute of Applied Physics and Computational Mathematics Beijing 100088China

We perform a theoretical investigation on the control over the atomic excitation of Rydberg states with shaped intense ultrashort laser pulses. By numerically solving the time-dependent Schr?dinger equation（TDSE）, we systematically study the dependence of the population of the Rydberg states on the π phase step position in the frequency spectra of the laser pulse for different intensities, central wavelengths and pulse durations. Our results show that the Rydberg excitation process can be effectively modulated using shaped intense laser pulses with the laser intensity as high as 1 × 1014 W/cm2. Our work also have benefit to the future investigation to find out the dominant mechanism behind the excitation of Rydberg states in strong laser fields.

关键词： shaped laser pulse Rydberg states excitation intense field

Reducing bias and variance for CTF estimation in single particle cryo-EM

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arXiv 2019年

作者： Heimowitz, Ayelet Andén, Joakim Singer, Amit Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Center for Computational Mathematics Flatiron Institute New YorkNY10010 United States Program in Applied and Computational Mathematics Department of Mathematics Princeton University PrincetonNJ08544 United States

When using an electron microscope for imaging of particles embedded in vitreous ice, the recorded image, or micrograph, is a significantly degraded version of the tomographic projection of the sample. Apart from noise, the image is affected by the optical configuration of the microscope. This transformation is typically modeled as a convolution with a point spread function. The Fourier transform of this function, known as the contrast transfer function (CTF), is oscillatory, attenuating and amplifying different frequency bands, and sometimes flipping their signs. High-resolution reconstruction requires this CTF to be accounted for, but as its form depends on experimental parameters, it must first be estimated from the micrograph. We present a new method for CTF estimation based on multitaper methods, which reduces bias and variance in the estimate. We also use known properties of the CTF and the background noise power spectrum to further reduce the variance through background subtraction and steerable basis projection. We show that the resulting power spectrum estimates better capture the zero-crossings of the CTF and yield accurate CTF estimates on several experimental micrographs. Copyright © 2019, The Authors. All rights reserved.

关键词： Linear programming

Discrete scale invariance of the quasi-bound states at atomic vacancies in a topological material

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arXiv 2022年

作者： Shao, Zhibin Li, Shaojian Liu, Yanzhao Li, Zi Wang, Huichao Bian, Qi Yan, Jiaqiang Mandrus, David Liu, Haiwen Zhang, Ping Xie, X.C. Wang, Jian Pan, Minghu School of Physics and Information Technology Shaanxi Normal University Xi’an710119 China School of Physics Huazhong University of Science and Technology Wuhan430074 China International Center for Quantum Materials School of Physics Peking University Beijing100871 China Institute of Applied Physics and Computational Mathematics Beijing100088 China School of Physics Sun Yat-sen University Guangzhou510275 China Materials Science and Technology Division Oak Ridge National Laboratory Oak RidgeTN37831 United States Department of Materials Science and Engineering University of Tennessee KnoxvilleTN37996 United States Center for Advanced Quantum Studies Department of Physics Beijing Normal University Beijing100875 China School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Collaborative Innovation Center of Quantum Matter Beijing100871 China Cas Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China Beijing Academy of Quantum Information Sciences Beijing100193 China

Recently, log-periodic quantum oscillations have been detected in topological materials zirconium pentatelluride (ZrTe5) and hafnium pentatelluride (HfTe5), displaying intriguing discrete scale invariance (DSI) characteristic. In condensed materials, the DSI is considered to be related to the quasi-bound states formed by massless Dirac fermions with strong Coulomb attraction, offering a feasible platform to study the long-pursued atomic-collapse phenomenon. Here, we demonstrate that a variety of atomic vacancies in the topological material HfTe5can host the geometric quasi-bound states with DSI feature, resembling the artificial supercritical atom collapse. The density of states of these quasi-bound states are enhanced and the quasi-bound states are spatially distributed in the "orbitals" surrounding the vacancy sites, which are detected and visualized by low-temperature scanning tunneling microscope/spectroscopy (STM/S). By applying the perpendicular magnetic fields, the quasi-bound states at lower energies become wider and eventually invisible, meanwhile the energies of quasi-bound states move gradually towards the Fermi energy (EF). These features are consistent with the theoretical prediction of a magnetic-field-induced transition from supercritical to subcritical states. The direct observation of geometric quasi-bound states sheds light on the deep understanding of the DSI in quantum materials. © 2022, CC BY.

关键词： Atoms

Differential gene expression in trabecular bone osteocytes is related to the local strain and strain gradient

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Scientific reports 2025年第1期15卷 18501页

作者： Meghana Machireddy Sarah Nano Lucas Debiase Jonathan Lewis Sara Cole Jun Li Glen L Niebur University of Notre Dame Bioengineering Graduate Program Notre Dame IN USA. Department of Aerospace and Mechanical Engineering Notre Dame IN USA. Notre Dame Integrated Imaging Facility Notre Dame IN USA. Department of Applied and Computational Mathematics and Statistics University of Notre Dame Notre Dame IN USA. University of Notre Dame Bioengineering Graduate Program Notre Dame IN USA. gniebur@nd.edu. Department of Aerospace and Mechanical Engineering Notre Dame IN USA. gniebur@nd.edu.

Osteocytes regulate the response of osteoclasts and osteoblasts to mechanical loading through signaling molecules, the levels of which are controlled by post-translational modification or degradation and by differential gene transcription and translation. The magnitude and mode of bone tissue deformation that elicits a transcriptional response in individual osteocytes in situ has been difficult to quantify. We measured SOST, Wnt11, TNF, and FRZB gene expression in osteocytes within loaded and unloaded control porcine trabecular bone explants using RNAScope® and compared the local tissue level strain and strain gradient-which we used as an indicator of potential poroelastic fluid flow-in the tissue surrounding osteocytes with high vs. low gene expression. The measured expression of all four genes differed between loaded and unloaded explants, on average, with the mean SOST expression level decreasing by 45%. In the loaded explants, gene expression was altered from baseline in about 30% of the osteocytes, and they were surrounded by tissue with higher strain and strain gradient than the 20 to 25% of osteocytes that remained near baseline expression. Both deviatoric strain and hydrostatic strain gradient were sensitive and specific predictors of the mechanobiological response for individual genes as well as combinations. SOST expression was highly related to elevated strain gradient, providing evidence that osteocytes respond to fluid flow in the lacunar-canalicular system.

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Chiral quasi-bound states in the continuum

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arXiv 2020年

作者： Overvig, Adam Yu, Nanfang Alù, Andrea Photonics Initiative Advanced Science Research Center The Graduate Center The City University of New York United States Department of Applied Physics and Applied Mathematics Columbia University United States Physics Program Graduate Center City University of New York United States

Quasi-bound states in the continuum (q-BICs) are resonant states of suitably tailored nanostructures with long optical lifetimes controlled by symmetry-breaking perturbations. While in planarized ultrathin devices the resulting Fano resonance is limited to linear polarization, we show here that chiral perturbations extend q-BIC concepts to arbitrary elliptical polarizations. Using geometric phase engineering, we realize metasurfaces with ultrasharp Fano spectral features that can shape the impinging wavefront with near-unity efficiency, while at the same time precisely filtering their spectral content. Copyright © 2020, The Authors. All rights reserved.

关键词： Polarization

LtU-ILI: AN ALL-IN-ONE FRAMEWORK FOR IMPLICIT INFERENCE IN ASTROphysics AND COSMOLOGY

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arXiv 2024年

作者： Ho, Matthew Bartlett, Deaglan J. Chartier, Nicolas Cuesta-Lazaro, Carolina Ding, Simon Lapel, Axel Lemos, Pablo Lovell, Christopher C. Makinen, T. Lucas Modi, Chirag Pandya, Viraj Pandey, Shivam Perez, Lucia A. Wandelt, Benjamin Bryan, Greg L. UMR 7095 98 bis bd Arago ParisF-75014 France Center for the Gravitational-Wave Universe Astronomy Program Department of Physics and Astronomy Seoul National University Seoul08826 Korea Republic of Center for Astrophysics Harvard & Smithsonian 60 Garden St CambridgeMA02138 United States The NSF AI Institute for Artificial Intelligence and Fundamental Interactions United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics Université de Montréal Montréal Canada Mila - Quebec Artificial Intelligence Institute Montréal Canada Ciela - Montreal Institute for Astrophysical Data Analysis and Machine Learning Montréal Canada Center for Computational Astrophysics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Institute of Cosmology and Gravitation University of Portsmouth Burnaby Road PortsmouthPO1 3FX United Kingdom & Astrophysics Group Imperial College London Blackett Laboratory Prince Consort Road LondonSW7 2AZ United Kingdom Center for Computational Mathematics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Columbia Astrophysics Laboratory Columbia University 550 West 120th Street New YorkNY10027 United States 4 place Jussieu ParisF-75252 Cedex 5 France

This paper presents the Learning the Universe Implicit Likelihood Inference (LtU-ILI) pipeline, a codebase for rapid, user-friendly, and cutting-edge machine learning (ML) inference in astrophysics and cosmology. The pipeline includes software for implementing various neural architectures, training schemata, priors, and density estimators in a manner easily adaptable to any research workflow. It includes comprehensive validation metrics to assess posterior estimate coverage, enhancing the reliability of inferred results. Additionally, the pipeline is easily parallelizable and is designed for efficient exploration of modeling hyperparameters. To demonstrate its capabilities, we present real applications across a range of astrophysics and cosmology problems, such as: estimating galaxy cluster masses from X-ray photometry;inferring cosmology from matter power spectra and halo point clouds;characterizing progenitors in gravitational wave signals;capturing physical dust parameters from galaxy colors and luminosities;and establishing properties of semi-analytic models of galaxy formation. We also include exhaustive benchmarking and comparisons of all implemented methods as well as discussions about the challenges and pitfalls of ML inference in astronomical sciences. All code and examples are made publicly available at https://***/maho3/ltu-ili. © 2024, CC BY.

关键词： Cosmology

Web-Based Comprehensive Assessment for Postpartum Care using Rule-Based Algorithm 1

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Web-Based Comprehensive Assessment for Postpartum Care using...

1st International Conference on Computer, Science, Engineering and Technology, ICComSET 2018

作者： Mujahidah, S. Suryono, S. Widyawati, M.N. Department of Midwifery STIKES Karya Husada Semarang Indonesia Department of Physics Faculty of Mathematics and Natural Sciences Universitas Diponegoro Indonesia Postgraduate Program in Applied Midwifery Science Poltekkes Kemenkes Semarang Indonesia

Administration of postpartum care has been performed in line with health care standards. Unfortunately the health service medical record data is still *** results in delays in establishing a diagnosis and providing therapy which results in a worsening of the postpartum mother's *** paper proposes a web-based information system that may become one solution in solving the remaining issues in postpartum care. The system developed here is expected to improve health care quality with better data completion of postpartum mothers and access to them. The system developed here is web-based, in that it applies the rule-based artificial intelligence system. Input of the system are results of physical examination performed by medical professionals. Then processed using the rule-based algorithm to produce diagnosis and proper recommendation. This research is quasi-experimental using posttest only with control group. There were 40 were categorized into intervention group (n=20) who used the information system and control group (n=20) who used the present system endorsed by the government.. The rule-based algorithm in the information system uses validation from experts. Results show that the information system developed here is capable of solving the issue of incomprehensive data, as well as effectiveness in providing postpartum care. © 2019 IOP Publishing Ltd. All rights reserved.

关键词： Diagnosis

SQUARE FUNCTION ESTIMATES AND LOCAL SMOOTHING FOR FOURIER INTEGRAL OPERATORS

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arXiv 2020年

作者： Gao, Chuanwei Liu, Bochen Miao, Changxing Xi, Yakun School of Mathematical Sciences Capital Normal University Beijing100048 China Department of Mathematics International Center for Mathematics Southern University of Science and Technology Shenzhen518055 China Institute for Applied Physics and Computational Mathematics Beijing China School of Mathematical Sciences Zhejiang University Hangzhou310027 China

We prove a variable coefficient version of the square function estimate of Guth-Wang-Zhang. By a classical argument of Mockenhaupt-Seeger-Sogge, it implies the full range of sharp local smoothing estimates for 2 + 1 dimensional Fourier integral operators satisfying the cinematic curvature condition. In particular, the local smoothing conjecture for wave equations on compact Riemannian surfaces is *** Codes 35S30, 35L05 Copyright © 2020, The Authors. All rights reserved.

关键词： Wave equations