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Long-term temporal correlations observed in event sequences of natural and social phenomena have been characterized by algebraically decaying autocorrelation functions. Such temporal correlations can be understood not only by heterogeneous interevent times (IETs) but also by correlations between IETs. In contrast to the role of heterogeneous IETs on the autocorrelation function, little is known about the effects due to the correlations between IETs. To rigorously study these effects, we derive an analytical form of the autocorrelation function for the arbitrary IET distribution in the case with weakly correlated IETs, where the Farlie-Gumbel-Morgenstern copula is adopted for modeling the joint probability distribution function of two consecutive IETs. Our analytical results are confirmed by numerical simulations for exponential and power-law IET distributions. For the power-law case, we find a tendency of the steeper decay of the autocorrelation function for the stronger correlation between IETs. Our analytical approach enables us to better understand long-term temporal correlations induced by the correlations between IETs.
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http://dx.doi.org/10.1103/PhysRevE.100.012306 | DOI Listing |
Phys Chem Chem Phys
September 2025
Department of Physics, Indian Institute of Technology Jodhpur, N.H. 62, Nagaur Road, Karwar, Jodhpur, Rajasthan, 342030, India.
We report an anomalous temperature-induced transition in thermal conductivity in the germanene monolayer around a critical temperature = 350 K. Equilibrium molecular dynamics simulations reveal a transition from ∼ scaling below the to ∼ above, contrasting with conventional ∼ behavior. This anomalous scaling correlates with the long-scale characteristic timescale obtained from double exponential fitting of the heat current autocorrelation function.
View Article and Find Full Text PDFAdv Sci (Weinh)
September 2025
Research Institute of Intelligent Complex Systems, Fudan University, Shanghai, 200433, China.
Early-warning signals of delicate design are used to predict critical transitions in complex systems, which makes it possible to render the systems far away from the catastrophic state by introducing timely interventions. Traditional signals including the dynamical network biomarker (DNB), based on statistical properties such as variance and autocorrelation of nodal dynamics, overlook directional interactions and thus have limitations in capturing underlying mechanisms and simultaneously sustaining robustness against noise perturbations. This study therefore introduces a framework of causal network markers (CNMs) by incorporating causality indicators, which reflect the directional influence between variables.
View Article and Find Full Text PDFNpj Nanophoton
September 2025
Chair in Hybrid Nanosystems, Nanoinstitute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, Munich, Germany.
Second-order nonlinear optical processes are fundamental to photonics, spectroscopy, and information technologies, with material platforms playing a pivotal role in advancing these applications. Here, we demonstrate the exceptional nonlinear optical properties of the van der Waals crystal 3R-MoS, a rhombohedral polymorph exhibiting high second-order optical susceptibility ( ) and remarkable second-harmonic generation (SHG) capabilities. By designing high quality factor resonances in 3R-MoS metasurfaces supporting quasi-bound states in the continuum (qBIC), we first demonstrate SHG efficiency enhancement exceeding 10.
View Article and Find Full Text PDFEye Vis (Lond)
September 2025
Faculty of Medicine, Coimbra Institute for Clinical and Biomedical Research (iCBR), University of Coimbra, Coimbra, Portugal.
Background: Diabetic retinopathy (DR) is often diagnosed many years after diabetes onset, highlighting the need for early diagnosis. The current study aimed to assess whether texture analysis of computed optical coherence tomography (OCT) retinal images can identify (very) early retinal changes. We previously reported retinal texture changes in a type 1 diabetes animal model.
View Article and Find Full Text PDFFront Public Health
September 2025
School of Architecture and Urban Planning, Shandong Jianzhu University, Jinan, China.
To address the pressure of emissions reduction in urban residential blocks (RBs), this study takes 99 micro-scale RBs in Hongqiao District, Tianjin as the objects, aiming to reveal the driving mechanism of built environmental factors (BEF) on residential blocks carbon emissions (RBCE) and explore planning strategies that balance carbon reduction and health benefits. By integrating spatial statistical analysis and high-precision machine learning models, the system has systematically revealed the spatio-temporal evolution laws, spatial differentiation characteristics and driving mechanisms of BEF on RBCE. Key findings include: (1) From 2021 to 2023, both the RBCE, residential blocks carbon emissions intensity (RBCEI), and average household carbon emissions (RBCE-AH) showed a "first rise then fall" fluctuation, with an overall 5.
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