Femtosecond laser-induced filamentation typically exhibits pronounced spectral broadening, featuring a bright central white core encircled by concentric colored rings that span from the ultraviolet to the visible range and extend into the infrared. While ionization, self-steepening and self-phase modulation are widely accepted as explanations for the white spot, the underlying physics of colored rings remain inadequately understood by current models, such as Cherenkov radiation and four-wave mixing. In this study, inspired by the observation of similar discrete colored rings produced by cascaded four-wave mixing (CFWM) of intersecting beams, we systematically investigated the relationship between the colored rings in the white-light supercontinuum and CFWM. The CFWM model accurately predicted the correlation between color and divergence angles, thereby enhancing our understanding of spectral broadening in filamentation and providing guidance for optimizing the conversion efficiency and configuration of multi-wavelength ultrashort optical pulses in both spatial and spectral domains.

Path planning, as a critical component of mobile robotic systems, significantly impacts operational efficiency and energy consumption ratios. State-of-the-art algorithms often suffer from inadequate real-time adjustment capability, insufficient dynamic environment adaptation, and suboptimal computational efficiency. To resolve these limitations, we propose a bidirectionally optimized path planning algorithm named Bidirectional Q-learning LPA* (BQ-LPA*), which incorporates three key innovations. Specifically, to enhance the global search capability of the LPA* framework, we replace fixed heuristic functions with a Q-learning-driven adaptive heuristic mechanism, which improves path quality through dynamic heuristic weighting and update strategies. Additionally, to improve the convergence rate and sample efficiency of Q-learning in complex environments, we propose integrating the LPA* framework to provide prior knowledge guidance, which can effectively minimize redundant exploration attempts by informed pathfinding initialization. Moreover, the Q-learning method inherently faces dimensionality challenges in high-dimensional continuous spaces, which manifest as action space congestion, storage bottlenecks, and computational inefficiency. To mitigate these risks, we devise an LPA*-based space discretization strategy that can reduce action space dimensionality and preserve the path feasibility. Experimental results show that, compared with mainstream path planning algorithms, BQ-LPA* achieves higher accuracy and faster convergence in mobile robot path planning.

Although co-production between the government and society can improve service outcomes, the two parties may lack the willingness and the capacity to cooperate. Can nonprofit organizations play an active role in facilitating government–citizen co-production? If so, how? The role of nonprofits in social services co-production has received increasing attention, but studies on developing countries are limited. Therefore, this study conducts an in-depth case study of a rural social work institute in Z village, Beijing, China. Using on-site observations, semi-structured interviews, and secondhand materials, we found that social workers adopted four strategies to engage community officials and rural residents in service co-production. They established trustworthy relationships, facilitated effective communication, fostered shared motivation, and built co-productive capacity. The results showed that nonprofit organizations use third-party roles and professional skills to shape government-citizen interactions through service co-production. These findings can improve rural service provision in developing countries.

Menopausal age represents the endpoint of the entire reproductive cycle of women, and it is a biological marker that indicates the overall health and ageing status of women. Flavonoids are the most common polyphenolic compounds in the daily diet, and their intake is related to reduced risks of certain diseases. Our study aimed to analyse the relationships between the intake of flavonoids and menopausal age. We selected 29 940 participants from National Health and Nutrition Examination Survey database from 2007–2008, 2009–2010 to 2017–2018. A total of 680 participants were included in our analysis after screening. Multiple logistic regression was used to explore the association between dietary flavonoid subclasses intake and menopausal delay (≥ 55 years old). Restricted cubic splines plots were generated to reveal the nonlinear relationships between the subclasses of flavonoids intake and menopausal age. According to the adjusted multiple factor logistic regression analysis, the top quartile intake (compared with bottom intake) of anthocyanidins was positively associated with delayed menopause (OR = 4·123; 95 % CI: 1·130, 15·041; Ptrend = 0·036), whereas the moderate intake of flavonols was negatively associated with delayed menopause (Q2 v. Q1, OR = 0·081 (95 % CI: 0·025, 0·261), Ptrend = 0·001; Q3 v. Q1, OR = 0·271 (95 % CI: 0·093, 0·791), Ptrend = 0·023). The restricted cubic splines revealed that non-linear association was observed between the intake of isoflavones, flavan-3-ols, flavonols and later menopause (P value for non-linearity < 0·05). Our findings suggest that specific dietary flavonoids intake may have potential roles in regulating menopausal timing.

China accounts for over 90% of global alveolar echinococcosis (AE) cases caused primarily by Echinococcus multilocularis. If left untreated, AE can have a 10-year mortality rate of 94%. Understanding its epidemiological patterns is essential for targeted control strategies. Surveillance data from 2006 to 2020 were obtained from the Public Health Scientific Data Center, and spatial and temporal trends were analyzed using spatial autocorrelation, hot spot analysis, and centroid migration techniques. A total of 51,403 echinococcosis cases were reported from 2006 to 2020, with an average annual incidence of 0.25 per 100,000. Most cases (71.33%) occurred in individuals aged 20–60 years. High-incidence areas centred in western/northwestern provinces, including Qinghai, Xinjiang, Xizang, Gansu, and Ningxia. Incidence and cases increased until 2017, then declined steadily. Spatial autocorrelation revealed persistent High-High clusters in Gansu and Ningxia (2008–2018) and Xizang (2010–2020), while Low-Low clusters persisted in central/eastern China. Hotspot analysis confirmed sustained high-risk zones in western/northwestern regions. Trend surface and centroid migration showed a southward disease shift within Qinghai. Echinococcosis remains endemic in western/northwestern China, with a trend of southward expansion. Strengthened, tailored interventions are urgently needed, particularly in high-burden areas like Xizang and Qinghai.

Unlike existing studies on labour and income in the digital era, this paper argues not only that the impact of the digital economy’s intervention in the labour process is fragmented rather than comprehensive, but also that the transformation of job demand and labour supply behaviours is simultaneous and related to the attributes of the industries in which they operate. Drawing on the conventional biased technological progress hypothesis and labour process theory, we argue that the digital economy has generally increased the labour income inequality for migrant workers in China. Using geospatially matched China Labour Dynamics Survey 2018 microdata and provincial digitalisation indices, we uncover a digital ‘upgrading trap’: the development of the digital economy hides the process of inequality formation in the hedging relationship between objective labour demand ‘upgrading’ and subjective labour supply ‘expanding’. The former can be summarised as the risk of ‘no job’ and the latter as the risk of ‘no way back’. Counterintuitively, consumer Internet development demonstrates a greater role in both reducing workers’ inequality in secondary labour markets and promoting a fair primary distribution. These findings reconceptualise digital inequality as coevolutionary outcomes, and offer a tripartite governance way for inclusive growth through portable skill certification, algorithmic accountability mechanisms, and interoperable social security systems.

Asymptotic flow states with limiting drag modification are explored via direct numerical simulations in a moderate-curvature viscoelastic Taylor–Couette flow of the FENE-P fluid. We show that asymptotic drag modification (ADM) states are achieved at different solvent-to-total viscosity ratios ($\beta$) by gradually increasing the Weissenberg number from 10 to 150. As $\beta$ decreases from 0.99 to 0.90, for the first time, a continuous transition pathway is realised from the maximum drag reduction to the maximum drag enhancement, revealing a complete phase diagram of the ADM states. This transition originates from the competition between Reynolds stress reduction and polymer stress development, namely, a mechanistic change in angular momentum transport. Reduced $\beta$ has been found to effectively enhance elastic instability, suppressing large-scale Taylor vortices while promoting the formation of small-scale elastic Görtler vortices. The enhancement and in turn dominance of small-scale structures result in stronger incoherent transport, facilitating efficient mixing and substantial polymer stress development that ultimately drives the AMD state transition. Further analysis of the scale-decomposed transport equation of turbulent kinetic energy reveals an inverse energy cascade in the gap centre, which is attributed to the polymer-induced energy redistribution: polymers extract more energy from large scales than they can dissipate, with the excess energy redirected to smaller scales. However, the energy accumulating at smaller scales cannot be dissipated immediately and is consequently transferred back to larger scales via nonlinear interactions, thereby unravelling a novel polymer-mediated cycle for the reverse energy cascade. Overall, this study unravels the challenging puzzle of the existence of distinct dynamically connected ADM states and paves the way for coordinated experimental, simulation and theoretical studies of transition pathways to desired ADM states.

Wall pressure fluctuations (WPFs) over aerodynamic surfaces contribute to the physical origin of noise generation and vibrational loading. Understanding the generation mechanism of WPFs, especially those exhibiting extremely high amplitudes, is important for advancing design and control in practical applications. In this work, we systematically investigate extreme events of WPFs in turbulent boundary layers and the compressibility effects thereon. The compressibility effects, encompassing extrinsic and intrinsic ones, ranging from weak to strong, are achieved by varying Mach numbers and wall temperatures. A series of datasets at moderate Reynolds numbers obtained from direct numerical simulation are analysed. It is found that the intermittency of WPFs depends weakly on extrinsic compressibility effects, whereas intrinsic compressibility effects significantly enhance intermittency at small scales. Coherent structures related to extreme events are identified using volumetric conditional average. Under extrinsic compressibility effects, extreme events are associated with the weak dilatation structures induced by interactions of high- and low-speed motions. When intrinsic compressibility effects dominate, these events are associated with the strong alternating positive and negative dilatation structures embedded in low-speed streaks. Furthermore, Poisson-equation-based pressure decomposition is performed to partition pressure fluctuations into components governed by distinct physical mechanisms. By analysing the proportion of each pressure component in extreme events, it is found that the contributions of the slow pressure and viscous pressure exhibit weak dependence on the compressibility effects, especially the extrinsic ones, and the varying trend of contributions of the rapid pressure with compressibility effects is opposite to that of the compressible pressure component.

Accurate 3D deformation control of deformable soft tissues is of paramount importance in robotic-assisted surgeries. Selecting optimal grasping points is a fundamental challenge, as the deformation behavior is highly dependent on the applied forces and their locations. This paper presents an efficient grasping point selection algorithm using optimization-based inverse finite element method for tissue manipulation tasks. We propose a method for the automatic identification of optimal grasping points that minimize feature or shape errors during deformation tasks. Specifically, we formulate the grasping task as a quadratic programming problem while considering the complex mechanical coupling within the tissue structure. Our method effectively accommodates both discrete key points and point clouds as input, and can simultaneously determine multiple optimal grasping points in one optimization process. We validate the proposed method in simulation on a tissue and liver model, demonstrating its feasibility and efficiency in various scenarios. Real-world experiments are conducted on a silicone liver phantom to further validate the effectiveness of our proposed method.

Non-suicidal self-injury (NSSI) among adolescents severely jeopardizes their well-being and has emerged as a significant global public health challenge. However, research on the trends in NSSI among adolescents remains scarce. This study sought to uncover the evolving patterns in the severity of NSSI among adolescents and the factors that influence these patterns. The Deliberate Self-Harm Inventory was employed to measure the severity of NSSI among adolescents. Relevant studies were retrieved from both Chinese databases (CNKI, Wanfang, and VIP) and English databases (Web of Science, PubMed, Scopus, ProQuest, and Wiley). A total of 70 articles (71 studies; N = 96,382) were included in this review. The data spanned from 2007 to 2023. The analysis revealed the following: (1) Although the severity of NSSI showed a small to moderate upward trend from 2007 to 2023, this increase did not reach statistical significance. (2) No significant differences in trends were observed among Asia, Europe, and the America. (3) Adolescents with clinical samples exhibited a more pronounced upward trajectory in NSSI severity compared to those with non-clinical samples. (4) Social development indicators (GDP per capita, Human Development Index, and Internet penetration rate) and social well-being (happiness index) exhibited significant positive correlations with NSSI among adolescents. Conversely, lower social equity (higher Gini coefficient) was associated with reduced NSSI among adolescents. This study elucidated the changing trends in NSSI among adolescents and offered novel insights for the early prevention and individualized intervention of NSSI among adolescents.

The emergence, on the Loess Plateau of Central China, of settlements enclosed by circular ditches has engendered lively debate about the function of these (often extensive) ditch systems. Here, the authors report on a suite of new dates and sedimentological analyses from the late Yangshao (5300–4800 BP) triple-ditch system at the Shuanghuaishu site, Henan Province. Exploitation of natural topographic variations, and evidence for ditch maintenance and varied water flows, suggests a key function in hydrological management, while temporal overlap in the use of these three ditches reveals the large scale of this endeavour to adapt to the pressures of the natural environment.

Large-scale circulation (LSC) dynamics have been studied in thermal convection driven by heat-releasing particles via the four-way coupled Euler–Lagrange approach. We consider a wide range of Rayleigh–Robert number (${\textit{Rr}}=4.97\times 10^{5} - 4.97 \times 10^{8}$) and density ratio ($\hat {\rho }_r=1- 1000$) that characterize the thermal buoyancy and the particle inertia, respectively. An intriguing flow transition has been found as $\hat {\rho }_r$ continuously increases, involving in sequence three typical LSC regimes, i.e. the bulk-flow-up regime, the marginal regime and the bulk-flow-down (BFD) regime. The comprehensive influence of the LSC regime transition is demonstrated by examining the key flow statistics. As integral flow responses, the heat transfer efficiency and flow intensity change substantially when the LSC regime transition happens, and the thermal boundary layer thicknesses at the top and bottom walls exhibit similar alterations. Significant local accumulation of particles occurs as $\hat {\rho }_r$ increases to a sufficiently high value, resulting in a great modification in the flow dynamics. Specifically, particles aggregate near the sidewalls and heat the local surrounding fluid to generate rising warmer plumes that drive the LSC regime transition. Of interest, well-patterned cellular structures of particles take place near the top wall and obtain notable deviation from the thermal convection cells for the BFD regimes. A mechanical interpretation is proposed and substantiated based on a conceptual vortex–particle model, namely, the centrifugal motion of heat-releasing particles that is confirmed to play a driving role for the LSC regime transition.

Lake-terminating glaciers retreat and thin faster than land-terminating glaciers, yet their long-term dynamics remain underexplored. Using multi source–remote sensing data combined with glacier velocity and elevation change datasets, we investigated their distribution and evolution in the Himalaya and Southeastern Tibet from 1990 to 2020. By 2020, 577 lake-terminating glaciers (2561.5 ± 11.8 km2) had been identified, representing ∼2% of all glaciers by number and ∼10% by area. Of these, 246 glaciers maintained contact with proglacial lakes (Type 1 change), while 331 developed new lakes (Type 2 change). Additionally, 173 glaciers detached from lakes (Type 3 change). Variations in glacier–lake contact strongly modulate glacier dynamics. Type 1 change glaciers experienced the largest area loss (73.8 ± 13.1 km2), whereas Type 2 change glaciers showed the greatest average retreat distance (1.06 ± 0.05 km). Among Type 1 change glaciers (>5 km2) with significant velocity trends, 22% accelerated and 78% decelerated, while all Type 3 change glaciers with significant velocity trends consistently decelerated. These findings underscore the pivotal influence of proglacial lake evolution on glacier dynamics, advancing our understanding of glacier–lake interactions on the Tibetan Plateau and beyond.

An experimental study of the equation of state for metallic powders under impact loading was carried out at a high-energy laser facility. A laser-ablatable micro-target was obtained to satisfy the laser equation of state for experimental study, and the precise characterization of the initial density was realized. The technique boosts the pressure of copper powder to 1400 GPa. The data consistency can effectively distinguish the data trends under different initial densities (~4.05 and 4.50 g/cm3). Experimental data can effectively distinguish the differences between the high-pressure Thomas–Fermi model and the Thomas–Fermi–Kirzhnits model, providing strong support for the WEOS-Pα model of the Institute of Applied Physics and Computational Mathematics, which is more in line with the actual state description of the material. This experimental technique can be extended to study the high-pressure physical properties of other powder particles.

The evolution of the mixing layer in rotation-driven Rayleigh–Taylor (RT) turbulence is investigated theoretically and numerically. It is found that the evolution of the turbulent mixing layer in rotation-driven RT turbulence is self-similar, but the width of the mixing layer does not follow the classical quadratic growth observed in planar RT turbulence induced by constant external acceleration. Based on the approach used in cylindrical RT turbulence without rotation (Zhao et al. 2021, Phys. Rev. E, vol. 104, 055104), a theoretical model is established to predict the growth of mixing widths in rotation-driven RT turbulence, and the model’s excellent agreement with direct numerical simulations (DNS) serves to validate its reliability. The model proposes a rescaled time that allows for the unification of the evolutions of the mixing layers in rotation-driven RT turbulence with various Atwood numbers and rotation numbers. It is further identified that the growth law described by the model of rotation-driven RT turbulence can be recovered to quadratic growth when the effects of geometrical curvature, radial inhomogeneity of the centrifugal force, and Coriolis force become negligible. Moreover, based on the DNS results, we find that turbulent mixing layers in rotation-driven RT turbulence cover a wide range of length scales. The strong rotation at the same Atwood number enhances the generation of fine-scale structures but is not conducive to overall fluid mixing within the mixing layer.