Distinct Regimes Research Articles

Spin pumping effect in non-Fermi liquid metals

Spin pumping effect is a sensitive and well-established experimental method in two-dimensional (2D) magnetic materials. We propose that spin pumping effect can be a valuable probe for non-Fermi liquid (NFL) behaviors at the 2D interface of magnetic heterostructures. We show that the modulations of ferromagnetic resonance exhibit power-law scalings in frequency and temperature for NFL metals induced near a quantum critical point (QCP). At the Ising nematic QCP, we demonstrate that the enhanced Gilbert damping coefficient δα acquires negative power-law exponents in distinct frequency regimes. The exponents convey universal parameters inherited from the QCP and reflect the non-quasiparticle nature of the spin carriers in the NFL metal. At finite temperature, we show that the Gilbert damping mechanism is restored in the quantum critical regime and δα measures the temperature dependence of the correlation length. Our theoretical proposal has the potential to stimulate the development of an interdisciplinary research domain where insights from non-equilibrium spin physics in spintronics are integrated into strongly correlated matter.

Revisiting the FJH Hypothesis: New Data and New Measure for an Old Question on Social Mobility

Abstract This paper attempts to update one of the most entrenched controversies in the field of social mobility: the idea, as maintained by Featherman, Jones & Hauser (1974) in their well-known FJH hypothesis, that societies exhibit a fundamental similarity in social mobility rates. To do that, we exploit the main historical international database that allows a large degree of quality in the comparison due to standardization procedures. To achieve this goal, we utilize the main international historical databases (ISSP, EVS and ESS), enabling extensive cross-national comparisons. We use an alternative nonparametric approach based on the average of the global odds ratios (without requiring any statistical assumptions (as difference uniform). Our results confirm that there is no clear presence of distinct regimes of social mobility; rather, there is only a continuum with two breaking points above or below the threshold that includes the majority of countries. Those outside this threshold are few and are consistently recurrent.

How spatiotemporal dynamics can enhance ecosystem resilience

We study how self-organization in systems showing complex spatiotemporal dynamics can increase ecosystem resilience. We consider a general simple model that includes positive feedback as well as negative feedback mediated by an inhibitor. We apply this model to Posidonia oceanica meadows, where positive and negative feedbacks are well documented, and there is empirical evidence of the role of sulfide accumulation, toxic for the plant, in driving complex spatiotemporal dynamics. We describe a progressive transition from homogeneous meadows to extinction through dynamical regimes that allow the ecosystem to avoid the typical ecological tipping points of homogeneous vegetation covers. A predictable sequence of distinct dynamical regimes is observed as mortality is continuously increased: turbulent regimes, formation of spirals and wave trains, and isolated traveling pulses or expanding rings, the latter being a harbinger of ecosystem collapse, however far beyond the tipping point of the homogeneous cover. The model used in this paper is general, and the results can be applied to other plant-soil spatially extended systems, regardless of the mechanisms behind negative and positive feedbacks.

Non-Newtonian Solute Mixing via Protonic Exchange of a Polyelectrolyte Layer: Unveiling Formation of Electroosmotic Vortices.

Biochemical and medical diagnostics are two main fields in which vortex generation in microfluidic devices has several applications. Therefore, the aim of the present endeavor is to investigate the characteristics of a non-Newtonian vortex under the influence of a pH-sensitive polyelectrolyte layer (PEL)-modulated electroosmotic effect in a microchannel. Additionally, it is considered that the bulk solution pH (pHb0) and ionic concentration of the solution influence the zeta potential. Accordingly, the corresponding mathematical framework is constructed by using a numerical solver based on the finite element method and is subsequently verified against available experimental data in limiting conditions. Within the range of pHb0 and rheological parameters─Carreau number and flow behavior index─we critically analyze the PEL space charge density, net body force, and flow pattern. The current findings indicate that the existence of discrete net electrical body force patterns yields specific flow structures that enable substantial variation in the flow rate and mixing efficiency. The dominance of the basic PEL group protonic exchange at lower pHb0 and acidic PEL group protonic exchange at higher pHb0, respectively, permits positive and negative PEL space charge densities. Consequently, it is evident that the net electrical body force in PEL is extremely pHb0-dependent. Therefore, with smaller pHb0, the anticlockwise vortex with a negative flow rate is identified, whereas the clockwise vortex with a positive flow rate is predicted for larger pHb0. In turn, five distinct flow pattern regimes appear when the bulk solution pH pivots from 3 to 11. Remarkably, mixing efficiency exceeds 90% for greater diffusive Peclet numbers in highly acidic liquids. Overall, the outcomes of this study may significantly impact the design of microfluidic devices that mix and transport non-Newtonian liquids at particular pHb0 values.

Enhancing lifetime, forecasting, and economic benefits of photovoltaic technologies undergoing UV-induced degradation with optical filtering

Abstract Ultraviolet-induced degradation (UV-ID) of various PV cell types was analyzed under optical UV filters with different cutoff wavelengths. Cell types studied included interdigitated back contact (IBC), passivated emitter and rear totally diffused (PERT), and heterojunction technology (HJT) based on crystalline Si (c-Si), and metal halide perovskite (MHP) cells. Analyzing degradation rates in two distinct regimes proved beneficial for all cell types. We used empirical linearizing functions ln(t) for c-Si technologies and ²√t for MHP samples where t is time. These were applied to extrapolate UV-induced degradation over the lifetime of PV modules under various levels of optical UV filtering and used to predict the relative economic benefits for PV power plants. Degradation rates for all technologies were generally faster under the long pass optical filters having shorter cutoff wavelengths transmitting more UV irradiation and at elevated temperatures when testing MHP samples in the range between 60 °C and 90 °C.

Theoretical insights into 1:2 and 1:3 internal resonance for frequency stabilization in nonlinear micromechanical resonators

Abstract Micromechanical resonators are essential components in time-keeping and sensing devices due to their high frequency, high quality factor, and sensitivity. However, their extremely low damping can lead to various nonlinear phenomena that can compromise frequency stability. A major limiting factor is the Duffing hardening effect, which causes frequency drift through amplitude variations, known as the amplitude-frequency effect. Recently, internal resonance (InRes) has emerged as an effective approach to mitigate this issue and enhance frequency stabilization. In this study, we investigate the frequency stabilization mechanisms of 1:2 and 1:3 InRes using a generalized two-mode reduced-order model that includes Duffing nonlinearity and nonlinear modal coupling. By analyzing the frequency response curves and $$\pi /2$$ π / 2 –backbone curves, we demonstrate how different parameters affect the effectiveness of frequency stabilization. Our results identify two distinct regimes depending on the coupling strength relative to the stiffening effect as a key factor in determining the stabilization mechanism. For the regime of weak coupling, both 1:2 and 1:3 InRes achieve frequency stabilization through amplitude and frequency saturation over a range of forcing amplitudes. In contrast, strong coupling reduces the amplitude-frequency effect by forming an asymptote line for 1:2 InRes or a zero-dispersion point for 1:3 InRes. These insights offer valuable guidelines for designing micromechanical resonators with high-frequency stability, highlighting InRes as a robust tool for enhancing performance in practical applications.

Between Centralism and Localism: Dual Mobility Regimes in the Chinese Bureaucracy

ABSTRACT There is an inherent tension between centralism and localism in the state-making processes in the authoritarian state of China, with its centralization of authority over diverse localities. We investigate the organizational response to this tension through the lens of personnel flow patterns in the Chinese bureaucracy. We propose a model of dual-mobility regimes that highlights the bifurcation of spatial mobility and local mobility as two distinct mobility regimes, with their distinctive network structures, thereby providing the organizational basis for variable coupling between central control and local agency. We illustrate our arguments in an empirical study of personnel flow patterns in a large bureaucracy in Jiangsu Province of China, from 1990 to 2012.

Aerodynamic investigation and modeling of dynamic variable sweep wing at low Reynolds number

This study investigates the unsteady aerodynamic characteristics of a dynamic variable sweep wing at low Reynolds numbers of 104, with a focus on the effects of variable sweep reduced frequency k on lift generation and flow structures. Numerical simulations reveal two distinct regimes: (1) when k < 0.2, the average lift of dynamic variable sweep cases closely matches with static values, and the flow structure is dominated by the tip vortices and unsteady leading-edge vortices (LEVs) shedding; (2) when k > 0.2, the average lift exceeds the static counterpart and increases rapidly, the LEVs develop into an arch vortex or vortex ring due to the high reduced frequency. Vorticity transport analysis further demonstrates the critical influence of spanwise vorticity transport on LEVs stability and lift generation, providing insights into the aerodynamic mechanisms underlying variable sweep motions. Additionally, a lift predictive model combining Greenberg and Atassi's theories with a correction term shows strong consistency with computational fluid dynamics results within certain frequency ranges. These findings underscore the significant impact of LEVs on lift dynamics and provide valuable insights for the development of bio-inspired aircraft designs.

Inertial dynamics of run-and-tumble particle.

We study the dynamics of a single inertial run-and-tumble particle on a straight line. The motion of this particle is characterized by two intrinsic timescales, namely, an inertial and an active timescale. We show that interplay of these two times-scales leads to the emergence of four distinct regimes, characterized by different dynamical behavior of mean-squared displacement and survival probability. We analytically compute the position distributions in these regimes when the two timescales are well separated. We show that in the large-time limit, the distribution has a large deviation form and compute the corresponding large deviation function analytically. We also find the persistence exponents in the different regimes theoretically. All our results are supported with numerical simulations.

Timing of syn-orogenic extension in the Western Alps revealed by calcite U-Pb and hematite (U-Th)/He dating

Timing of syn-orogenic extension in the Western Alps revealed by calcite U-Pb and hematite (U-Th)/He dating

Modeling capillary-driven particle agglomeration under shear in immiscible fluids using discrete multiphysics

In this study, we introduce a discrete multiphysics (DMP) model designed to simulate particulate systems where solid particles are immersed in a sheared primary fluid (water) and coated by an immiscible secondary fluid (oil). When dispersed particles come into contact with each other, the secondary fluid around the particles merges into a liquid bridge that induces particle agglomeration through capillary interaction. The model employs smoothed particle hydrodynamics to represent the primary liquid and the discrete element method for the solid particles. The secondary fluid is not explicitly modeled. Instead, we consider its impact indirectly by incorporating the attractive forces generated by the liquid bridges. These forces, arising when particles come into contact, are treated as additional attractive interactions within the DMP framework. Two liquid-bridge force models are selected for the simulations and validated against experimental observations in a granular collapse scenario. Subsequently, these validated models are integrated into the DMP framework to simulate particle agglomeration under shear, revealing three distinct agglomeration regimes based on varying Reynolds and elastocapillary numbers. These regimes are characterized by the formation of aggregates with diverse sizes and shapes, from elongated cylinders to spheroids. Results are presented in “agglomeration maps,” which facilitate the prediction of aggregate characteristics based on known Reynolds and elastocapillary numbers.

Contributions of the synoptic meteorology to the seasonal cloud condensation nuclei cycle over the Southern Ocean

Abstract. Cloud condensation nuclei (CCN) play a fundamental role in determining the microphysical properties of low-level clouds that are crucial for defining the energy budget over the Southern Ocean (SO). However, many aspects of the CCN budget over the SO remains poorly understood, including the role of the synoptic meteorology. In this study, we classify six distinct synoptic regimes over the Kennaook / Cape Grim Observatory (CGO) and examine their influence on the seasonal cycle of the CCN concentration (NCCN). Three “winter” regimes are dominant when the subtropical ridge (STR) is strong and centered at lower latitudes, while three “summer” regimes prevail when the STR shifts to higher latitudes. Distinct winter and summer “baseline” synoptic patterns contribute to the seasonal cycle of NCCN, with the winter baseline regime characterized by heavier precipitation (0.10 vs. 0.03 mm h−1), a deeper boundary layer (850 vs. 900 hPa), and lower NCCN (71 vs. 137 cm−3) than the summer one. Across these two baseline regimes, we observe a significant inverse relationship between precipitation and NCCN, underscoring the contribution of precipitation in reducing NCCN over the SO. An analysis of air mass back-trajectories, specifically at the free-troposphere level, supports this seasonal distinction, with wintertime air masses originating more frequently from higher latitudes. The summertime STR is seen as a barrier to Antarctic air masses reaching the latitude of the CGO. Conversely, the summer baseline regime is found to pass more frequently over continental Australia before reaching the CGO, consistent with enhanced radon concentrations.

Operando TEM study of a working copper catalyst during ethylene oxidation

Active catalysts are typically metastable, and their surface state depends on the gas-phase chemical potential and reaction kinetics. To gain relevant insights into structure-performance relationships, it is essential to investigate catalysts under their operational conditions. Here, we use operando TEM combining real-time observations with online mass spectrometry (MS) to study a Cu catalyst during ethylene oxidation. We identify three distinct regimes characterized by varying structures and states that show different selectivities with temperature, and elucidate the reaction pathways with the aid of theoretical calculations. Our findings reveal that quasi-static Cu2O at low temperatures is selective towards ethylene oxide (EO) and acetaldehyde (AcH) via an oxometallacycle (OMC) pathway. In the dynamic Cu0/Cu2O oscillation regime at medium temperatures, partially reduced and strained oxides decrease the activation energies associated with partial oxidation. At high temperatures, the catalyst is predominantly Cu0, partially covered by a monolayer Cu2O. While Cu0 is extremely efficient in dehydrogenation and eventual combustion, the monolayer oxide favors direct EO formation. These results challenge conclusions drawn from ultra-high vacuum studies that suggested metallic copper would be a selective epoxidation catalyst and highlight the need for operando study under realistic conditions.

Molecular Shells and Range of Interactions in Ionic Liquids as a Function of Temperature.

Room-temperature ionic liquids (RTILs) represent a versatile class of chemical systems composed entirely of oppositely charged species whose bulk properties can be fine-tuned by adjusting molecular structures and, consequently, intermolecular interactions. Understanding the intricate dynamics between ionic species can aid in the rational design of RTILs for specific applications in a range of fields, including catalysis and electrochemistry. Here, we investigate the temperature dependence of intermolecular interactions through magnetization transfer by means of 1H-19F heteronuclear Overhauser effect spectroscopy (HOESY) for two ionic liquids, namely, [BMIM][BF4] and [BMIM][PF6]. We find that the cross-relaxation rates vary significantly over a rather small temperature range, even changing sign. Molecular dynamics (MD) simulations on neat RTIL systems replicate this behavior well and further show that the dynamic properties rather than coordination changes of RTILs account for the observed temperature behavior. Furthermore, the investigation of different coordination shells highlights the change of interaction range with temperature even to the point where inner and outer coordination shells could be in distinct motional regimes with cross-relaxation rates of opposite sign. Since temperature changes lead primarily to dynamic changes rather than structural ones, these findings underscore the versatility and high thermal stability of ionic liquids.

Unsteady Land‐Sea Breeze Circulations in the Presence of a Synoptic Pressure Forcing

AbstractUnsteady land‐sea breezes (LSBs) that result from time‐varying surface temperature contrasts Δθ(t) are explored in the presence of a constant synoptic pressure forcing, Mg, oriented from sea to land (α = 0°) or land to sea (α = 180°). Large eddy simulations reveal the development of four distinctive regimes, depending on the joint interaction between Mg, α, and Δθ(t) in modulating the fine‐scale dynamics. Time lags, computed as the shifts that maximize correlation coefficients of the velocity between the unsteady and the corresponding steady scenarios at Δθ = Δθmax, are found to be significant and to extend 2 hr longer for α = 0° compared to α = 180°. These diurnal dynamics result in nonequilibrium conditions that are significantly affected by the flow history, and that behave differently over the two patches for the different α’s. Turbulence is found to be out of equilibrium with the mean flow, and the mean itself is found to be out of equilibrium with the thermal forcing. The sea surface heat flux is consistently more sensitive than its land counterpart to the time‐varying external forcing Δθ(t), and more so for synoptic forcing from land to sea (α = 180°). Hence, although the land reaches equilibrium faster, the sea patch is found to exert a stronger control on the turbulence‐mean flow equilibrium response. Finally, the vertical velocity profile at the shore and shore‐normal velocity transects at the first grid level are shown to encode the multiscale regimes of the LSBs evolution and can thus be used to identify these regimes using k‐means clustering.

Analyzing Cambodia Securities Exchange Index Returns using the Markov-Switching Autoregressive Model

The examination of the weekly return behavior of the Cambodia Securities Exchange (CSX) index, spanning from 2012 to 2024, was categorized into two distinct states or regimes using the Markov-Switching Autoregressive model. The research findings indicated that the MS(2)-AR(1) model, which includes two states or regimes and a first-order autoregressive component, was the most suitable model. The empirical results showed that both the first-order lag of the dependent variable and the intercept term had a significant positive effect on the return of the CSX index at a 1% significance level, applicable to both Regime 1 and Regime 2 models. In contrast, the first-order autoregressive variable in the Regime 1 model demonstrated a significant negative effect on the return of the CSX index at the same 1% significance level, a relationship not observed in the Regime 2 model. The empirical results indicated a 38.35% likelihood of the CSX index transitioning from Regime 2 to Regime 1, while the probability of exiting Regime 1 was notably lower at 17.39%, as shown by the probability transition matrix. Additionally, the volatility of the CSX index returns in Regime 2 was found to be greater than that observed in Regime 1.

Warming triggers snowfall fraction loss Thresholds in High-Mountain Asia

Global warming is accelerating climate disasters by triggering tipping points in various Earth systems. Although changes in precipitation patterns in High-Mountain Asia (HMA) have been extensively studied, the specific thresholds that trigger rapid snowfall loss remain unclear. A continuous piecewise linear regression model was employed to classify HMA into four distinct precipitation regimes: insensitive snowfall-dominated areas, sensitive snowfall-dominated areas, sensitive rainfall-dominated areas, and insensitive rainfall-dominated areas. Our results show that future warming will increase the sensitivity of winter and spring snowfall to climate change, whereas summer and autumn snowfall will become less sensitive. All four precipitation regimes exhibit an upward shift to higher elevations, with varying rates of elevation gain across regions and seasons. Temperature is the primary driver of snowfall loss, whereas relative humidity mitigates it. This study identifies high-risk areas vulnerable to snowfall loss, to help guide the development of effective mitigation strategies.

Theoretical study of mismatch-induced halo formation from an intense hadron bunch in a uniform focusing channel

Abstract A basic mechanism of halo formation in high-intensity hadron accelerators is explored theoretically. As a possible origin of halos, we focus on deviation of an initial bunch size from its ideal dimensions, in other words, spatial mismatch of the bunch shape to an accelerator lattice. Such an error is unavoidable in any machines and thus needs to be considered carefully. Assuming an axisymmetric uniform beam-focusing potential, we calculate the transverse and longitudinal wavenumbers of linear collective modes from the three-dimensional envelope equations. The obtained analytical formulas are found to explain the power spectra derived from self-consistent numerical simulations. Approximate conditions of possible resonances driven by mismatch-induced envelope oscillation are presented to estimate dangerous parameter ranges where a particularly serious halo may be developed. A simple measure to separate tail particles from the beam core is introduced, which suggests the existence of two distinct regimes of halo formation. The maximum extent of a halo as well as emittance growth rates are evaluated through systematic simulations as a function of initial mismatch factors.

Describing Seasonal Mixtures of Cloud Regimes via “Regimes of Regimes”

Abstract We propose a new type of cloud classification, relevant to monthly or longer time scales, but which inherently still encompasses cloud subgrid variability information at ∼100-km scales. Our proposed classification partitions the frequencies of occurrence over these scales of previously defined cloud regimes (CRs). We call the resulting distinct cloud entities regimes of regimes (RORs). While the CRs have been previously shown to successfully classify daily mesoscale subgrid variability via distributions of cloud fraction within distinct combinations of cloud-top pressure and cloud optical thickness, the RORs essentially represent the prevalent seasonal mixtures of these CRs. RORs thus embody the seasonal cloudiness of a mesoscale region. We show that each ROR can still be associated with more traditional cloud classifications via composites of coincident active (lidar and cloud radar) cloud views. In a first application that gauges the potential utility of RORs, we pair them with Clouds and the Earth’s Radiant Energy System Energy Balanced and Filled (CERES EBAF) radiative fluxes to gain insight into recent trends of the cloud radiative effect. The ROR corresponding to an environment of shallow convection stands out in this analysis largely because of its declining population. Our study demonstrates the potential of RORs to categorize globally mesoscale cloudiness at monthly/seasonal scales and to serve as proxies of different atmospheric states at these scales.

On the Rigidity and Mechanical Behavior of Triply Periodic Minimal Surfaces‐Based Lattices: Insights from Extensive Experiments and Simulations

Triply Periodic Minimal Surfaces (TPMS)‐based lattices are gaining attention for their multifunctional properties. Current studies have largely focused on limited cases, characterizing the mechanical properties of only a few TPMS architectures and often applying classification systems (e.g., stretching‐ or bending‐dominated behavior) developed for slender beam‐based lattices. However, TPMS structures are far frombeing slender beams, and the validity of such classifications has not been rigorously confirmed for their case. This study bridges these gaps by analyzing 36 distinct TPMS lattice architectures, covering both elastic and plastic regimes. We critically assess theapplicability of Gibson‐Ashby scaling laws, the rigidity classification, and the stretching‐bending paradigm to TPMS structures—none of which have been rigorously validated for TPMS lattices. Using experiments and numerical simulations, we investigate the strength and stiffness scaling in TPMS lattices, identifying rigid, compliant, and mixed architectures. Our findings show that TPMS rigidity depends on the alignment of surface members with load directions and the presence of solid regions that prevent rotation. We reveal that top‐performing geometries include so far unexplored TPMS such as P + CP (−), K (+), and Ss‐Yssxxx (+), further expanding the design space, challenging prior assumptions and providing critical insights for selecting the optimal TPMS‐based architecture for specific applications.