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JOURNAL ARTICLE
Xiaoyan Zhou, Hongtao Wang, Shuxi Liu, Hao Wang, John You En Chan, Cheng-Feng Pan, Daomu Zhao, Joel K W Yang, Cheng-Wei Qiu
Caustics occur in diverse physical systems, spanning the nano-scale in electron microscopy to astronomical-scale in gravitational lensing. As envelopes of rays, optical caustics result in sharp edges or extended networks. Caustics in structured light, characterized by complex-amplitude distributions, have innovated numerous applications including particle manipulation, high-resolution imaging techniques, and optical communication. However, these applications have encountered limitations due to a major challenge in engineering caustic fields with customizable propagation trajectories and in-plane intensity profiles...
May 2, 2024: Nature Communications
#2
JOURNAL ARTICLE
Jinfa Liu, Yawen Yu, Weixin Qi, Xin Ma, Yan Han
This study aims to investigate the influence of pre-entrepreneurial career mobility frequency and job changes among returning migrant workers (RMWs) on the innovation level of enterprises, with a particular focus on the mediating role of urban social capital accumulated by RMWs. Using data from the "current entrepreneurial status of RMWs", we applied an ordered probit model to validate our hypotheses. To address endogeneity, a recursive bivariate probit model was used, and stepwise regression combined with bootstrap methods was employed to ascertain the mediating influence of urban social capital...
May 15, 2024: Heliyon
#3
JOURNAL ARTICLE
Alyssa O Vanderlinden, Masood Nevisipour, Thomas Sugar, Hyunglae Lee
Older adults have a decreased trunk movement control which is linked to their higher fall risk. While motor/cognitive dual-tasking deteriorates balance and walking in older adults, there is limited understanding on how trunk kinematics and kinetics are affected by dual-tasking in scenarios where falls can occur. Therefore, the purpose of the study was to determine the impacts of a challenging motor dual-task, specifically obstacle avoidance during walking, on trunk and lower-body kinematics and kinetics of older adults compared to young adults...
April 30, 2024: Human Movement Science
#4
JOURNAL ARTICLE
Manon Laget, Laetitia Drago, Thelma Panaïotis, Rainer Kiko, Lars Stemmann, Andreas Rogge, Natalia Llopis-Monferrer, Aude Leynaert, Jean-Olivier Irisson, Tristan Biard
Thriving in both epipelagic and mesopelagic layers, Rhizaria are biomineralizing protists, mixotrophs or flux-feeders, often reaching gigantic sizes. In situ imaging showed their contribution to oceanic carbon stock, but left their contribution to element cycling unquantified. Here, we compile a global dataset of 167,551 Underwater Vision Profiler 5 Rhizaria images, and apply machine learning models to predict their organic carbon and biogenic silica biomasses in the uppermost 1000 m. We estimate that Rhizaria represent up to 1...
April 29, 2024: Nature Communications
#5
JOURNAL ARTICLE
Gia Dvali, Oleg Kaikov, Florian Kühnel, Juan Sebastián Valbuena-Bermúdez, Michael Zantedeschi
Vorticity has recently been suggested to be a property of highly spinning black holes. The connection between vorticity and limiting spin represents a universal feature shared by objects of maximal microstate entropy, so-called saturons. Using Q-ball-like saturons as a laboratory for black holes, we study the collision of two such objects and find that vorticity can have a large impact on the emitted radiation as well as on the charge and angular momentum of the final configuration. As black holes belong to the class of saturons, we expect that the formation of vortices can cause similar effects in black hole mergers, leading to macroscopic deviations in gravitational radiation...
April 12, 2024: Physical Review Letters
#6
REVIEW
Antoine Bédard
White dwarfs are the dense, burnt-out remnants of the vast majority of stars, condemned to cool over billions of years as they steadily radiate away their residual thermal energy. To first order, their atmosphere is expected to be made purely of hydrogen due to the efficient gravitational settling of heavier elements. However, observations reveal a much more complex situation, as the surface of a white dwarf (1) can be dominated by helium rather than hydrogen, (2) can be polluted by trace chemical species, and (3) can undergo significant composition changes with time...
2024: Astrophysics and Space Science
#7
JOURNAL ARTICLE
Vyacheslav S Lukin, Elena Khomenko, Beatrice Popescu Braileanu
This study explores nonlinear development of the magnetized Rayleigh-Taylor instability (RTI) in a prominence-corona transition region. Using a two-fluid model of a partially ionized plasma, we compare RTI simulations for several different magnetic field configurations. We follow prior descriptions of the numerical prominence model (Popescu Braileanu et al. 2021 Astron. Astrophys. 646 , A93 (doi:10.1051/0004-6361/202039053), Popescu Braileanu et al. 2021 Astron. Astrophys. 650 , A181 (doi:10.1051/0004-6361/202140425) and Popescu Braileanu et al...
June 9, 2024: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
#8
JOURNAL ARTICLE
Zongchao Duan, Feilong Ren, Li-E Qiang, Keqi Qi, Haoyue Zhang
Temperature fluctuations affect the performance of high-precision gravitational reference sensors. Due to the limited space and the complex interrelations among sensors, it is not feasible to directly measure the temperatures of sensor heads using temperature sensors. Hence, a high-accuracy interpolation method is essential for reconstructing the surface temperature of sensor heads. In this study, we utilized XGBoost-LSTM for sensor head temperature reconstruction, and we analyzed the performance of this method under two simulation scenarios: ground-based and on-orbit...
April 15, 2024: Sensors
#9
JOURNAL ARTICLE
Liexiao Dong, Shixu Lu, Luxiang Xu, Ning Guo, Mingshan Wu, Shengtao Liang, Jianfei Long
The critical structural parameters are optimized and studied using the numerical simulation method to improve the resolution and stability of the Micro-Thrust Measurement Platform (MTMP). Under two different ground random vibration environments, the parameters, such as pivot thickness, pendulum rod length, and pivot structure, are focused on analyzing the influence of the system's resolution and stability. The results show that when the thickness of the pivot is 0.04 mm or 0.2 mm, and the pendulum rod length is 2 m, the effect of ground random vibration on the MTMP is minimized...
April 8, 2024: Micromachines
#10
REVIEW
Konstantinos I Adamopoulos, Lauren M Sanders, Sylvain V Costes
One of the greatest challenges of humanity for deep space exploration is to fully understand how altered gravitational conditions affect human physiology. It is evident that the spaceflight environment causes multiple alterations to musculoskeletal, cardiovascular, immune and central nervous systems, to name a few known effects. To better characterize these biological effects, we compare gene expression datasets from microarray studies found in NASA GeneLab, part of the NASA Open Science Data Repository. In this review, we summarize these archived results for various tissues, emphasizing key genes which are highly reproducible in different mice or human experiments...
April 26, 2024: NPJ Microgravity
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JOURNAL ARTICLE
Scott T Anderson, Jordan R Mount, Braden C Hintze, Jacob S Hogan, Irving A Jorge, David A Etzioni, Ga-Ram Han, Justin T Brady
INTRODUCTION: Physicians have gravitated toward larger group practice arrangements in recent years. However, consolidation trends in colorectal surgery have yet to be well described. Our objective was to assess current trends in practice consolidation within colorectal surgery and evaluate underlying demographic trends including age, gender, and geography. METHODS: We performed a retrospective cross-sectional study using the Center for Medicare Services National Downloadable File from 2015 to 2022...
April 25, 2024: Journal of Surgical Research
#12
JOURNAL ARTICLE
Dong-Biao Kang
We have explored the exponential surface brightness profile (SBP) of stellar disks, a topic extensively discussed by many authors yet seldom integrated with the study of correlations between black holes, bulges, and entire disks. Building upon our prior work in the statistical mechanics of disk-shaped systems and aligning with methodologies from other research, we analyze the influence of the central body. This analysis reveals analytical relationships among black holes, bulges, and the entire stellar disk...
March 28, 2024: Entropy
#13
JOURNAL ARTICLE
Mengqi Lu, Robert B Mann
We evaluate here the quantum gravity partition function that counts the dimension of the Hilbert space of a simply connected spatial region of a fixed proper volume in the context of Lovelock gravity, generalizing the results for Einstein gravity. It is found that there are sphere saddle metrics for a partition function at a fixed spatial volume in Lovelock theory. Those stationary points take exactly the same forms as in Einstein gravity. The logarithm of Z corresponding to a zero effective cosmological constant indicates that the Bekenstein-Hawking entropy of the boundary area and that corresponding to a positive effective cosmological constant points to the Wald entropy of the boundary area...
March 27, 2024: Entropy
#14
JOURNAL ARTICLE
Rabindra N Mohapatra
Overwhelming astronomical evidence for dark matter and absence of any laboratory evidence for it despite many dedicated searches have fueled speculation that dark matter may reside in a parallel universe interacting with the familiar universe only via gravitational interactions as well as possibly via some ultra-weak forces. In this scenario, we postulate that the visible universe co-exists with a mirror world consisting of an identical duplicate of forces and matter of our world, obeying a mirror symmetry...
March 26, 2024: Entropy
#15
JOURNAL ARTICLE
Clemens Sämann, Benedict Schinnerl, Roland Steinbauer, Robert Švarc
Impulsive gravitational waves are theoretical models of short but violent bursts of gravitational radiation. They are commonly described by two distinct spacetime metrics, one of local Lipschitz regularity and the other one even distributional. These two metrics are thought to be 'physically equivalent' since they can be formally related by a 'discontinuous coordinate transformation'. In this paper we provide a mathematical analysis of this issue for the entire class of nonexpanding impulsive gravitational waves propagating in a background spacetime of constant curvature...
2024: Letters in Mathematical Physics
#16
REVIEW
Syed Shozab Ahmed, Nandu Goswami, Adam Sirek, David Andrew Green, Andrew Winnard, Leonie Fiebig, Tobias Weber
A systematic review of literature was conducted to evaluate the effectiveness of passive countermeasures in ameliorating the cardiopulmonary and musculoskeletal effects of gravitational unloading on humans during spaceflight. This systematic review is the third of a series being conducted by the European Space Agency to evaluate the effectiveness of countermeasures to physiologic deconditioning during spaceflight. With future long-duration space missions on the horizon, it is critical to understand the effectiveness of existing countermeasures to promote astronaut health and improve the probability of future mission success...
April 25, 2024: NPJ Microgravity
#17
JOURNAL ARTICLE
Sandro Mereghetti, Michela Rigoselli, Ruben Salvaterra, Dominik Patryk Pacholski, James Craig Rodi, Diego Gotz, Edoardo Arrigoni, Paolo D'Avanzo, Christophe Adami, Angela Bazzano, Enrico Bozzo, Riccardo Brivio, Sergio Campana, Enrico Cappellaro, Jerome Chenevez, Fiore De Luise, Lorenzo Ducci, Paolo Esposito, Carlo Ferrigno, Matteo Ferro, Gian Luca Israel, Emeric Le Floc'h, Antonio Martin-Carrillo, Francesca Onori, Nanda Rea, Andrea Reguitti, Volodymyr Savchenko, Damya Souami, Leonardo Tartaglia, William Thuillot, Andrea Tiengo, Lina Tomasella, Martin Topinka, Damien Turpin, Pietro Ubertini
Magnetar giant flares are rare explosive events releasing up to 1047 erg in gamma rays in less than 1 second from young neutron stars with magnetic fields up to 1015-16 G (refs. 1,2 ). Only three such flares have been seen from magnetars in our Galaxy3,4 and in the Large Magellanic Cloud5 in roughly 50 years. This small sample can be enlarged by the discovery of extragalactic events, as for a fraction of a second giant flares reach luminosities above 1046 erg s-1 , which makes them visible up to a few tens of megaparsecs...
April 24, 2024: Nature
#18
JOURNAL ARTICLE
C Harvey
Avian wing morphing allows dynamic, active control of complex flight manoeuvres. Previous linear time-invariant (LTI) models have quantified the effect of varying fixed wing configurations but the time-dependent effects of morphing between different configurations is not well understood. To fill this gap, I implemented a linear parameter-varying (LPV) model for morphing wing gull flight. This approach models the wing joint angles as scheduled parameters and accounts for nonlinear kinematic and gravitational effects while interpolating between LTI models at discrete trim points...
April 2024: Journal of the Royal Society, Interface
#19
JOURNAL ARTICLE
Sushant Sharma Chaudhary, Andrew Toivonen, Gaurav Waratkar, Geoffrey Mo, Deep Chatterjee, Sarah Antier, Patrick Brockill, Michael W Coughlin, Reed Essick, Shaon Ghosh, Soichiro Morisaki, Pratyusava Baral, Amanda Baylor, Naresh Adhikari, Patrick Brady, Gareth Cabourn Davies, Tito Dal Canton, Marco Cavaglia, Jolien Creighton, Sunil Choudhary, Yu-Kuang Chu, Patrick Clearwater, Luke Davis, Thomas Dent, Marco Drago, Becca Ewing, Patrick Godwin, Weichangfeng Guo, Chad Hanna, Rachael Huxford, Ian Harry, Erik Katsavounidis, Manoj Kovalam, Alvin K Y Li, Ryan Magee, Ethan Marx, Duncan Meacher, Cody Messick, Xan Morice-Atkinson, Alexander Pace, Roberto De Pietri, Brandon Piotrzkowski, Soumen Roy, Surabhi Sachdev, Leo P Singer, Divya Singh, Marek Szczepanczyk, Daniel Tang, Max Trevor, Leo Tsukada, Verónica Villa-Ortega, Linqing Wen, Daniel Wysocki
Multimessenger searches for binary neutron star (BNS) and neutron star-black hole (NSBH) mergers are currently one of the most exciting areas of astronomy. The search for joint electromagnetic and neutrino counterparts to gravitational wave (GW)s has resumed with ALIGO's, AdVirgo's and KAGRA's fourth observing run (O4). To support this effort, public semiautomated data products are sent in near real-time and include localization and source properties to guide complementary observations. In preparation for O4, we have conducted a study using a simulated population of compact binaries and a mock data challenge (MDC) in the form of a real-time replay to optimize and profile the software infrastructure and scientific deliverables...
April 30, 2024: Proceedings of the National Academy of Sciences of the United States of America
#20
JOURNAL ARTICLE
Brandon Biggs, Hannah Agbaroji, Christopher Toth, Tony Stockman, James Coughlan, Bruce Walker
A group co-design was held in March 2021 with six blind and low-vision individuals (BLIs) from the United States. Participants were asked to discuss problems related to travel during the COVID-19 pandemic and make recommendations for possible solutions. Two probes (prototypes) of a non-visual neighborhood travel map and a non-visual COVID-19 choropleth map (a map using colors or sounds over each state to represent different values) of COVID-19 state data were shown to participants for inspiration. The participants expressed that COVID-19 had significantly increased their apprehension and discomfort associated with activities such as venturing outside, traveling, engaging with strangers, communicating, adapting to changes in familiar environments, and wearing masks...
2024: J Blind Innov Res
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