Variety Of Time Scales Research Articles

Pace and shape of senescence in three species of duckweed.

Senescence is progressive bodily deterioration associated with declines in survival and fecundity in older age classes. There is great diversity in patterns of senescence across species, but these patterns can be difficult to compare formally due to variation in the absolute time scales in which species live and die: members of some species live for a matter of days, others for millennia. To address this issue, the “pace‐shape” approach was developed to decouple absolute time from analyses and instead standardize life history traits in terms of average life expectancy, facilitating intra‐ and interspecific comparisons. Here, we use this approach to distinguish the generic form of demographic trajectories (shape) from the time scale on which the trajectories occurred (pace) in three species of tiny, free‐floating aquatic plants known as duckweeds (Lemna gibba L., L. minor L., and L. turionifera Landolt), which have mean lifespans of less than a month under typical lab conditions, and exhibit age‐related declines in survivorship and reproduction. Using a randomized block design in which we tracked a final total of 430 individuals, we report differences in pace and shape among the three species. Specifically, the largest, least‐fecund, and typically longest‐lived species, L. gibba, tended to exhibit more rapid decreases in time‐standardized survivorship and fecundity compared with the other two species. This study emphasizes variation in aging patterns that can be found among plant species, including those in the same genus, and provides further validation for the utility of applying the pace and shape approach in interspecific comparisons.

Time scale and influencing factor variations of water and heat fluxes in sandy land

Abstract The transfer process and variation characteristics of water and heat fluxes play an important role in both the ecosystem function and the climatic patterns of arid and semi-arid areas. However, both water (latent heat flux, Fe) and heat (sensible heat flux, Fh) fluxes, and the factors impacting each, operate on different time scales. Therefore, the wavelet transformation was used to reconstruct water and heat flux data measured by an eddy covariance system installed in Horqin sandy land, China. The distribution and response regularity of water and heat fluxes in response to control factors were then analysed across different time scales. The results indicated that the responses of Fe and Fh to controlling factors were similar on 30 min and daily scales, to which the energy terms of net radiation (Fn) and available energy (Fa) showed an extremely significant positive contribution. Removing the interference of the energy terms, Fe and Fh are strongly correlated with the vapour pressure deficit (VPD) and air temperature (Ta) at the daily scale. The water conditions of VPD and relative humidity (RH) were the main influencing factors at the monthly scale. At the seasonal scale, Fe was positively correlated with Fa and Fn but negatively correlated with soil heat flux (Fg), RH and wind speed (WS). On the contrary, Fh was positively correlated with RH but negatively correlated with Fn. At the annual scale, Fe and Fh showed a significant positive correlation with all factors. By the increasing time scale, the cross-correlations between various hydroclimatic processes become better. Generally, at the daily and annual scales, there is a high correlation between Fe, Fh and the control factors, and a pronounced periodicity is exhibited. Another factor that is known to cause such effects is the so-called long-term persistence (or else long-range dependence or the Hurst phenomenon). These results suggest that the time scales of flux and impacting factors should be considered when undertaking water and heat flux analyses of sandy land and other ecosystems.

Two Classes of Gamma-ray Bursts Distinguished within the First Second of Their Prompt Emission

Studies of Gamma-Ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes, beyond the short/hard and long/soft prototypes, using model-dependent methods. In this paper, a model-independent approach was used to analyse the gamma-ray light curves of large samples of GRBs detected by BATSE, Swift/BAT and Fermi/GBM. All the features were extracted from the GRB time profiles in four energy bands using the Stationary Wavelet Transform and Principal Component Analysis. t-distributed Stochastic Neighbourhood Embedding (t-SNE) visualisation of the features revealed two distinct groups of Swift/BAT bursts using the T100 interval with 64 ms resolution data. When the same analysis was applied to 4 ms resolution data, two groups were seen to emerge within the first second (T1) post-trigger. These two groups primarily consisted of short/hard (Group 1) and long/soft (Group 2) bursts, and were 95% consistent with the groups identified using the T100 64 ms resolution data. Kilonova candidates, arising from compact object mergers, were found to belong to Group 1, while those events with associated supernovae fell into Group 2. Differences in cumulative counts between the two groups in the first second, and in the minimum variability timescale, identifiable only with the 4 ms resolution data, may account for this result. Short GRBs have particular significance for multi-messenger science as a distinctive EM signature of a binary merger, which may be discovered by its gravitational wave emissions. Incorporating the T1 interval into classification algorithms may support the rapid classification of GRBs, allowing for an improved prioritisation of targets for follow-up observations.

Solar Irradiance Variability Monitor for the Galileo Solar Space Telescope Mission: Concept and Challenges

Long and reliable total solar irradiance (TSI) time series is one of the essential parameters for understanding solar contributions to climate change. The minor fluctuations of TSI in long timescales could impact the energy balance. Despite the improvement of accurate measurements provided by the instruments, at the time, long-term TSI variability and its effects had not been established. The space-borne radiometer era provided observations in short timescales from minutes to years. Therefore, this study presents an overview of irradiance observations, highlighting the importance of following its variability in different time scales. In this context, the Galileo Solar Space Telescope that has been developed by the Institute for Space Research (INPE), Brazil, includes the Irradiance Monitor Module with a radiometer cavity like the classical design and a next-generation compact radiometer.

Relationship between southern hemispheric jet variability and forced response: the role of the stratosphere

Abstract. Climate models show a wide range of southern hemispheric jet responses to greenhouse gas forcing. One approach to constrain the future jet response is by utilising the fluctuation–dissipation theorem (FDT) which links the forced response to internal variability timescales, with the Southern Annular Mode (SAM) the most dominant mode of variability of the southern hemispheric jet. We show that interannual stratospheric variability approximately doubles the SAM timescale during austral summer in both re-analysis data and models from the Coupled Model Intercomparison Project, Phases 5 (CMIP5) and 6 (CMIP6). Using a simple barotropic model, we demonstrate how the enhanced SAM timescale subsequently leads to an overestimate of the forced jet response based on the FDT, and we introduce a method to correct for the stratospheric influence. This result helps to resolve a previously identified discrepancy between the seasonality of jet response and the internal variability timescale. However, even after accounting for this influence, the SAM timescale cannot explain inter-model differences in the forced jet shift across CMIP models during austral summer.

Multi-scale variability of hydrothermal regime based on wavelet analysis - The middle reaches of the Yangtze River, China

Water temperature is a major driver of riverine ecosystems and has an extremely significant impact on them. Understanding the multi-scale water temperature dynamics in a river basin is critical to analyze the water temperature status of rivers. In this study, the intra-annual and inter-annual time series of water temperature (WT) at Yichang station in the middle reaches of the Yangtze River over the past 62 years was analyzed using complex Morlet wavelet functions to reveal the complex structure of water temperature variation at multiple time scales. The ecological impact of water temperature changes on the reproduction of the “Four Major Chinese Carp” under the influence of the Three Gorges Dam (TGD). The results showed that the water temperature at Yichang Station has a multi-level time scale structure, with an increasing trend at the inter-annual scale from 1956 to 2017, but different variations at the seasonal scale, and the water temperature cycles at both the inter-annual and seasonal scales have time scale variations of about 8–14 years and 4–7 years, with obvious characteristics of WT variation stages. The inter-annual and summer scales will have low WT in 2017–2022 and high WT in 2023–2027, while the other seasonal scales will have high WT in the next few years, either in the short or medium term. The correlation between air temperature and WT is the most significant among the three drivers of air temperature, flow and rainfall, and the correlation between WT and the air temperature is the most significant in winter scale under the influence of the Three Gorges Dam construction. Since the completion of TGD in 2003, the summer drainage temperature has decreased and the breeding period of the “Four Major Chinese Carp” has been shortened by 30–40 days compared to that before the construction of TGD. The results of this study can be used as a basis for further exploration of the formation mechanism of river water temperature and provide a scientific basis for river ecological protection.

NONLINEAR STATIONARY OSCILLATIONS OF BEAM GIRDER STRUCTURES FROM THE ACTION OF PERIODIC PULSES

Purpose. The aim of this work is to construct an approximate solution of stationary oscillations of a nonlinear equation with a cubic characteristic. The design scheme under consideration best corresponds to the operating conditions of the girder structure in the event of defects of the supporting parts. In this case, longitudinal forces may appear in the girder of the girder structure. Methods. The paper investigates nonlinear oscillations of girder structures of small bridges. The undamped oscillations of the beam resting on hinged fixed support parts on both sides from the action of periodic unilateral impulse loading are considered. The design scheme differs from the statically defined beam scheme, which takes into account defective support parts. In the article, the possible transition to the beam system on moving support parts is considered. To solve the nonlinear equation of the second order of a single-span beam taking into account the longitudinal force, a method of variable time scale used, developed by Academician of the Academy of Sciences of the USSR, professor Bondar M. G. The method of variable scale gives fairly approximate solutions to this class of problems. Results. An approximate analytical solution is performed by the method of variable time scale of stationary nonlinear oscillations of the girder structure taking into account the longitudinal force caused by one-sided pulses that are periodically repeated. According to the obtained formulas of the solution of the nonlinear equation with cubic characteristic it is easy to construct amplitude-frequency characteristics and forms of oscillations. Originality. For the first time the solution of the equation of oscillations of a beam taking into account longitudinal force is executed. The criteria of impact resonance for the system without friction, as well as taking into account the viscous friction. An expression for the amplitude-frequency characteristic of the system under consideration is obtained. Practical meaning. Studies of beam structure oscillations taking into account the longitudinal force gave practical value in the possibility of analytical calculation of oscillation forms, shock resonance criteria and amplitude-frequency characteristics of the system from the action of periodic unilateral impulse loads. The system of girder beams takes into account defective supporting parts (jamming of movable supporting parts) of girder structures of small and medium railway bridgesd.

Exploring γ-Ray Flares in the Long-term Light Curves of CTA 102 at GeV Energies

Blazar CTA 102 experienced an intense multiwavelength activity phase from 2015 to 2018; in particular, an unprecedented outburst was observed from 2016 October to 2017 February. In this work, we extract a 7 day binned γ-ray light curve from 2008 August to 2018 March in the energy range 0.1–300 GeV and identify three main outbursts. We study in detail the short-timescale variability of these three outbursts via an exponential function with parameterized rise and decay timescales. The obtained shortest rise and decay timescales are 0.70 ± 0.05 hr and 0.79 ± 0.27 hr, respectively. Based on these variability timescales, the physical parameters of the flaring region (e.g., the minimum Doppler factor and the emission region size) are constrained. The short-timescale flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the light-crossing timescale or by disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that the best-fitting form of the γ-ray spectra during the flare period is a power law with an exponential cutoff. The derived jet parameters from the spectral behavior and the temporal characteristics of the individual flares suggest that the γ-ray emission region is located upstream of the radio core. The extreme γ-ray flare of CTA 102 is likely to have been caused by magnetic reconnection.

A mixing timescale model for differential mixing in transported probability density function simulations of turbulent non-premixed flames

The modeling of scalar mixing timescale remains a primary challenge in the transported probability density function (TPDF) method. The variation of scalar mixing timescale among species, i.e., differential mixing, results from the difference in molecular diffusivity and reaction-induced scalar gradient. Nevertheless, the vast majority of TPDF studies on turbulent non-premixed flames simply apply a single mixing timescale determined by the mixture fraction. In this work, a reaction-induced differential mixing timescale (RIDM) model for the mixing timescale of individual species in turbulent non-premixed flames is proposed. The key idea of the RIDM model is to approximate the relative magnitude of the species dissipation rates by using their values in laminar flamelets. A direct numerical simulation dataset of a temporally evolving non-premixed ethylene flame is employed to thoroughly evaluate the model performance via a priori and a posteriori tests. Results show that specifying a single mixing timescale for all species results in a poor prediction of the species dissipation rate and thus the failure to predict the overall combustion process. By accounting for the difference in molecular diffusivity, a slightly better prediction can be obtained, but the improvement is very limited, illustrating that simply modeling the difference due to molecular diffusivities for differential mixing is not sufficient. In comparison, the RIDM model exhibits superior performance in both a priori and a posteriori tests. Moreover, all the components of the RIDM model are readily available in the TPDF method, making the RIDM model a promising candidate employed in practice.

Multiple variability time-scales of the early nitrogen-rich Wolf–Rayet star WR 7

ABSTRACT We present the analysis of the optical variability of the early, nitrogen-rich Wolf–Rayet (WR) star WR 7. The analysis of multisector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multiperiodic variability that is modulated on time-scales of years. We detect a dominant period of 2.6433 ± 0.0005 d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR 7, including pulsations, binarity, co-rotating interaction regions (CIRs), and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR 7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR 7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short (≲1 d) and long (≳1000 d) variability time-scales.

Note on Fundamental Physics Tests from Black Hole Imaging: Comment on “Hunting for Extra Dimensions in the Shadow of Sagittarius A*”

Several recent works have tested fundamental physics with horizon-scale black hole (BH) images, using the size r sh and deviation from circularity of the BH shadow. For the Event Horizon Telescope image of Sgr A*, limits on are not available due to the sparse interferometric coverage of the 2017 observations, alongside the short variability timescale of Sgr A* compared to M87*. We comment on the results of a recent preprint which purports to have derived new limits on extra dimensions using the deviation from circularity of Sgr A*'s shadow. The latter is quoted to be ≲10% as with M87*, based on the “similarity” of the two shadows, which however is an incorrect assumption. In the immediate future, the simplest tests of fundamental physics from Sgr A*'s image will mostly have to rely on r sh.

Stress Relaxation and Composition of Hydrazone-Crosslinked Hybrid Biopolymer-Synthetic Hydrogels Determine Spreading and Secretory Properties of MSCs.

The extracellular matrix plays a critical role in mechanosensing and thereby influences the secretory properties of bone-marrow-derived mesenchymal stem/stromal cells (MSCs). As a result, interest has grown in the development of biomaterials with tunable properties for the expansion and delivery of MSCs that are used in cell-based therapies. Herein, stress-relaxing hydrogels are synthesized as hybrid networks containing both biopolymer and synthetic macromer components. Hyaluronic acid is functionalized with either aldehyde or hydrazide groups to form covalent adaptable hydrazone networks, which are stabilized by poly(ethylene glycol) functionalized with bicyclononyne and heterobifunctional small molecule crosslinkers containing azide and benzaldehyde moieties. Tuning the composition of these gels allows for controlled variation in the characteristic timescale for stress relaxation and the amount of stress relaxed. Over this compositional space, MSCs are observed to spread in formulations with higher degrees of adaptability, with aspect ratios of 1.60± 0.18, and YAP nuclear:cytoplasm ratios of 6.5± 1.3. Finally, a maximum MSC pericellular protein thickness of 1.45± 0.38µm occurred in highly stress-relaxing gels, compared to 1.05± 0.25µm in non-adaptable controls. Collectively, this study contributes a new understanding of the role of compositionally defined stress relaxation on MSCs mechanosensing and secretion.

Versatile Modelling of Extreme Surges in Connection with Large-Scale Circulation Drivers

In this article, we investigate the dependence of extreme surges on the North Atlantic weather regime variability across different timescales using the North Atlantic Oscillation (NAO) and Scandinavian blocking (SCAND) indices. The analysis was done using time series of surges along the North French Coast, covering long time periods (43 to 172 years of data). Time series that exhibited gaps were filled using linear interpolation to allow spectral analyses to be conducted. First, a continuous wavelet analysis on monthly maxima surges in the North French Coast was conducted to identify the multi-timescale variability. Second, a wavelet coherence analysis and maximum overlap discrete wavelet transform (MODWT) were used to study the timescale-dependent relationships between maxima surges and NAO or SCAND. Finally, NAO and SCAND were tested as physical covariates for a nonstationary generalized extreme value (GEV) distribution to fit monthly maxima surge series. Specific low-frequency variabilities characterizing these indices (extracted using MODWT) were also used as covariates to determine whether such specific variabilities would allow for even better GEV fitting. The results reveal common multi-annual timescales of variability between monthly maxima surge time series along the North French coasts: ~2–3 years, ~5–7 years, and ~12–17 years. These modes of variability were found to be mainly induced by the NAO and the SCAND. We identified a greater influence of the NAO on the monthly maxima surges of the westernmost stations (Brest, Cherbourg, Le Havre), while the SCAND showed a greater influence on the northernmost station (Dunkirk). This shows that the physical climate effects at multi-annual scales are manifested differently between the Atlantic/English Channel and the North Sea regions influenced by NAO and SCAND, respectively. Finally, the introduction of these two climate indices was found to clearly enhance GEV models as well as a few timescales of these indices.

Comparison of Three Methods for Measuring Dietary Composition of Plains Hog-nosed Snakes

Wild animal diets are challenging to quantify, and the various methods for doing so have strengths and weaknesses. Combining multiple methods can allow ecologists to assess their level of confidence in particular results, increase sample size, and investigate diet over varying time scales. The biases of traditional gut content–based methods are mostly well understood. Newer methods may have important biases that can only be worked out through comparison to established ones. We collected data on the diet of wild Plains Hog-nosed Snakes (Heterodon nasicus) using multiple, fundamentally dissimilar methods, combined analytically using a Bayesian framework to describe an ontogenetic dietary shift. Gut contents were the most straightforward, but yielded a small sample size that fell below any reasonable threshold for making generalizations. Stable isotopes indicated an obvious ontogenetic dietary shift, but were labor-intensive, and conclusions are limited by multiple methodological caveats including similarity among prey groups, maternal carryover effects, and uncertainty in trophic enrichment factors. Fecal environmental DNA (eDNA) was intermediate in terms of effort, yielding results congruent with the other two methods, but the interpretation of which would likely have been confounded by contaminants had we not used all three methods in tandem. Several apparent artifacts are discussed. There are some reassuring similarities among methods. There are also several differences. The most complete picture uses data from all methods taken together. Future studies should attempt to compare the biases, expense, and potential drawbacks of these and other methods in greater detail.

Effect of Assimilating SMAP Soil Moisture on CO2 and CH4 Fluxes through Direct Insertion in a Land Surface Model

Soil moisture impacts the biosphere–atmosphere exchange of CO2 and CH4 and plays an important role in the terrestrial carbon cycle. A better representation of soil moisture would improve coupled carbon–water dynamics in terrestrial ecosystem models and could potentially improve model estimates of large-scale carbon fluxes and climate feedbacks. Here, we investigate using soil moisture observations from the Soil Moisture Active Passive (SMAP) satellite mission to inform simulated carbon fluxes in the global terrestrial ecosystem model LPJ-wsl. Results suggest that the direct insertion of SMAP reduces the bias in simulated soil moisture at in situ measurement sites by 40%, with a greater improvement at temperate sites. A wavelet analysis between the model and measurements from 26 FLUXNET sites suggests that the assimilated run modestly reduces the bias of simulated carbon fluxes for boreal and subtropical sites at 1–2-month time scales. At regional scales, SMAP soil moisture can improve the estimated responses of CO2 and CH4 fluxes to extreme events such as the 2018 European drought and the 2019 rainfall event in the Sudd (Southern Sudan) wetlands. The simulated improvements to land–surface carbon fluxes using the direct insertion of SMAP are shown across a variety of timescales, which suggests the potential of SMAP soil moisture in improving the model representation of carbon–water coupling.

The environment and constraints on the mass of FRB 190520B

ABSTRACT Recent observations of FRB 20190520B have revealed rapid (tens of s) fluctuation of its Dispersion Measure within apparently fixed bounds, as well as a reversal of its Rotation Measure. The fluctuations of Dispersion Measure are uncorrelated with the intervals between bursts, setting upper bounds $\sim 10\,$ s on any characteristic time-scale of the dispersing region; it must be very compact. Measurements of the full dependence of the dispersive time delay on frequency may determine the actual electron density and the size of this region. It is possible to set a lower bound on the mass of the FRB source from constraints on the size of the dispersing region and its time-scale of variation. Comparison of the variations of DM and RM leads to an estimate of the magnetic field $\sim 500~ \mu$G.

Metabolism and Soil Water Viscosity Control Diel Patterns of Nitrate and DOC in a Low Order Temperate Stream

AbstractWe investigated diel dissolved organic carbon (DOC) and nitrate (NO3−) dynamics in White Clay Creek, a third‐order stream in Pennsylvania, USA. High‐frequency DOC and NO3− concentrations were modeled from absorbance spectra collected with a deployable spectrophotometer. Periodicities of 24 hr in solute concentrations and streamflow were frequent throughout the year. To test potential drivers of diel oscillations, we focused on five periods with at least 5 days of clear diel changes that were not drastically influenced by high‐flow events. Maxima and minima of the diel variation in solute concentrations, and significant correlations between their daily amplitude and gross primary production (GPP) indicate that stream metabolism was the major driver diel oscillations in April (r = 0.86 and −0.87 for GPP vs. DOC and NO3−, respectively) and May (r = 0.86 and −0.90 for GPP vs. DOC and NO3−, respectively). In summer, drivers of daily oscillations of DOC and NO3− were unclear but likely influenced by stream metabolism. In winter, we observed no correlation between GPP and amplitude of daily concentration change, instead streamflow was the dominant driver via the viscosity effect (r = −0.92 and 0.89 for streamflow vs. DOC and NO3− respectively). As the hydraulic conductivity of the riparian soil increased throughout the daytime, the contribution of DOC‐rich and NO3−‐poor soil water to the stream relative to groundwater also increased. Results from this work highlight that watershed processes influence stream solutes on widely variable time scales, ranging from hours to centuries; and that underlying controls depend highly on seasonality.

Flare echoes from relaxation shocks in perturbed relativistic jets

Context. One of the main scenarios to account for the multiwavelength flux variability observed in relativistic jets of active galactic nuclei (AGNs) is based on the diffusive shock acceleration of a population of relativistic electrons on internal shocks of various origins. Any complete AGN emission scenario has to be able to explain the wide range of observed variability timescales, which change over several orders of magnitude between the radio and gamma-ray band. In addition to observations of flux variability, constraints are also provided by very-long-baseline interferometry (VLBI), which shows a large variety of moving and standing emission zones with distinct behaviors. Aims. Combining dynamic hydrodynamic jet simulations with radiative transfer, we aim to characterize the evolution of stationary and moving emission zones in the jet and study their multiwavelength signatures through emission maps and light curves. We focus our study on flare events that occur during strong interactions between moving ejecta and stationary recollimation shocks. Such events are shown to lead to a significant perturbation of the stationary jet structure. Methods. We simulate relativistic jets with the magneto-hydrodynamic code MPI-AMRVAC and inject nonthermal particle distributions of electrons into shock regions. We follow the propagation of a moving shock and its interactions with a structure of standing recollimation shocks in the jet. Synchrotron emission and radiative transfer are calculated in the post-processing code RIPTIDE for given observation angles and frequencies, assuming a turbulent magnetic field and taking the light crossing effect into account. Results. In the case of strong shock–shock interactions, we demonstrate the appearance of trailing components behind the leading moving shock. The latter destabilizes the jet, causing the emergence of oscillating standing shocks and relaxation shocks. Emissions from these regions can dominate the overall flux or lead to “flare echoes” in the light curve. Another observational marker for the presence of relaxation shocks appears in time-distance plots of bright VLBI components of the jet. Our scenario provides a plausible explanation for radio VLBI observations of the radio galaxy 3C 111, where trailing components were observed during a radio outburst event in 1997, and may be applicable to other sources with similar features.

Characterizing the γ-Ray Variability of Active Galactic Nuclei with the Stochastic Process Method

Gamma-ray astronomy in the time domain has been by now progressed further as the variabilities of active galactic nuclei (AGNs) on different timescales have been reported a lot. We study the γ-ray variabilities of 23 jetted AGNs by applying a stochastic process method to the ∼12.7 yr long-term light curve (LC) obtained by the Fermi-Large Area Telescope (Fermi-LAT). In this method, the stochastically driven damped simple harmonic oscillator (SHO) and the damped random-walk (DRW) models are used to model the long-term LCs. Our results show that the long-term variabilities of 23 AGNs can be characterized well by both SHO and DRW models. However, the SHO model is restricted in the overdamped mode, and the parameters are poorly constrained. The SHO power spectral densities (PSDs) are the same as those of the typical DRW PSD. In the plot of the rest-frame timescale that corresponds to the broken frequency in the PSD versus black hole mass, the intrinsic, characteristic γ-ray timescales of 23 AGNs occupy almost the same space with the optical variability timescales obtained from the accretion disk emission. This suggests a connection between the jet and the accretion disk. As with the optical variability of the AGN accretion disk, the γ-ray timescale is also consistent with the thermal timescale caused by the thermal instability in the standard accretion disk of AGNs.

Local Temporal Acceleration Scheme to Couple Transport and Reaction Dynamics in Kinetic Monte Carlo Models of Electrochemical Systems.

Kinetic Monte Carlo (kMC) simulations are a well-established tool for investigating the operation of electrochemical systems. Standard kMC algorithms become unfeasible in the presence of processes on vastly different time scales. In electrochemical systems, such time scale disparities often arise between fast transport processes and slow electrochemical reactions. A promising approach to overcome time scale disparities in kMC models is given by temporal acceleration schemes. In this work, we present a local temporal acceleration scheme to bridge the time scale disparity between fast transport and slow reaction dynamics. We combine the superbasin concept with a local, particle-based criterion for the quasi-equilibrium detection and a partitioning of transitions and particles in the system into process chains. Scaling of entire quasi-equilibrated process chains considerably reduces the computational effort without disturbing the relative dynamics of transitions within a process chain. The methodology is outlined for a hybrid organic-aqueous electrolyte device which links fast electronic processes in an organic semiconductor with slow reduction reactions at its interface to the electrolyte. Our approach captures local inhomogeneities such that local physical quantities can be reproduced accurately. Additionally, we show that previous accelerated superbasin algorithms are limited by the presence of spatially varying time scale disparities. Our algorithm achieves an acceleration of several orders of magnitude providing a serious alternative to replace existing multiscale models by stand-alone kMC simulations.