Time Scale Of Response Research Articles

Ih block reveals separation of timescales in pyloric rhythm response to temperature changes in Cancer borealis.

Motor systems operate over a range of frequencies and relative timing (phase). We studied the role of the hyperpolarization-activated inward current (Ih) in regulating these features in the pyloric rhythm of the stomatogastric ganglion (STG) of the crab, Cancer borealis, as temperature was altered from 11°C to 21°C. Under control conditions, rhythm frequency increased monotonically with temperature, while the phases of the pyloric dilator (PD), lateral pyloric (LP), and pyloric (PY) neurons remained constant. Blocking Ih with cesium (Cs+) phase advanced PD offset, LP onset, and LP offset at 11°C, and the latter two further advanced as temperature increased. In Cs+ the frequency increase with temperature diminished and the Q10 of the frequency dropped from ~1.75 to ~1.35. Unexpectedly in Cs+, the frequency dynamics became non-monotonic during temperature transitions; frequency initially dropped as temperature increased, then rose once temperature stabilized, creating a characteristic 'jag'. Interestingly, these jags persisted during temperature transitions in Cs+ when the pacemaker was isolated by picrotoxin, although the temperature-induced change in frequency recovered to control levels. Overall, these data suggest that Ih plays an important role in maintaining smooth transitory responses and persistent frequency increases by different mechanisms in the pyloric circuitry during temperature fluctuations.

Ih block reveals separation of timescales in pyloric rhythm response to temperature changes in Cancer borealis

Motor systems operate over a range of frequencies and relative timing (phase). We studied the role of the hyperpolarization-activated inward current (Ih) in regulating these features in the pyloric rhythm of the stomatogastric ganglion (STG) of the crab, Cancer borealis, as temperature was altered from 11°C to 21°C. Under control conditions, rhythm frequency increased monotonically with temperature, while the phases of the pyloric dilator (PD), lateral pyloric (LP), and pyloric (PY) neurons remained constant. Blocking Ih with cesium (Cs+) phase advanced PD offset, LP onset, and LP offset at 11°C, and the latter two further advanced as temperature increased. In Cs+ the frequency increase with temperature diminished and the Q10 of the frequency dropped from ~1.75 to ~1.35. Unexpectedly in Cs+, the frequency dynamics became non-monotonic during temperature transitions; frequency initially dropped as temperature increased, then rose once temperature stabilized, creating a characteristic ‘jag’. Interestingly, these jags persisted during temperature transitions in Cs+ when the pacemaker was isolated by picrotoxin, although the temperature-induced change in frequency recovered to control levels. Overall, these data suggest that Ih plays an important role in maintaining smooth transitory responses and persistent frequency increases by different mechanisms in the pyloric circuitry during temperature fluctuations.

Quantifying the internal and external drivers of Southeast Asian rainfall extremes on decadal timescales

Rainfall over mainland Southeast Asia experiences variability on seasonal to decadal timescales in response to a multitude of climate phenomena. Historical records and paleoclimate archives that span the last millennium reveal extreme multi-year rainfall variations that significantly affected the societies of mainland Southeast Asia. Here we utilize the Community Earth System Model Last Millennium Ensemble (CESM-LME) to quantify the contributions of internal and external drivers to decadal-scale rainfall extremes in the Southeast Asia region. We find that internal variability was dominant in driving both Southeast Asian drought and pluvial extremes on decadal timescales although external forcing impacts are also detectable. Specifically, rainfall extremes are more sensitive to Pacific Ocean internal variability than the state of the Indian Ocean. This discrepancy is greater for droughts than pluvials which we suggest is attributable to external forcing impacts that counteract the forced Indian Ocean teleconnections to Southeast Asia. Volcanic aerosols, the most effective radiative forcing during the last millennium, contributed to both the Ming Dynasty Drought (1637–1643) and the Strange Parallels Drought (1756–1768). From the Medieval Climate Anomaly to the Little Ice Age, we observe a shift in Indo-Pacific teleconnection strength to Southeast Asia consistent with enhanced volcanism during the latter interval. This work not only highlights asymmetries in the drivers of rainfall extremes but also presents a framework for quantifying multivariate drivers of decadal-scale variability and hydroclimatic extremes.

Spatial-temporal response and precursor characteristics of tensile failure on disc coal samples of different sizes combining AE, EMR and DIC techniques

Tensile fractures in deep coal and rock mass can readily trigger dynamic calamities like rock bursts, significantly impacting the safety of coal mining. To enhance our understanding of coal’s tensile failure mechanism, Brazilian splitting failure experiments were conducted on coal samples with prefabricated cracks of different sizes. Acoustic emission (AE), electromagnetic radiation (EMR) and digital image correlation (DIC) techniques were used to analyze the instability failure process and precursor characteristics of coal samples. The results showed that, for coal samples of the same thickness, the tensile strength and peak strain gradually decreased with the increase of coal sample size, whereas the elastic modulus increased gradually, highlighting more pronounced brittleness characteristics and revealing a noticeable size effect. The time-varying evolution of AE energy, EMR energy and VE (virtual extensometer) elongation during the tensile failure process of coal samples is closely correlated to the stress evolution trend, exhibiting distinct characteristics at various loading stages. The failure modes of coal samples of varying sizes exhibited a strong correlation with the spatial distribution of AE events, as well as the strain and displacement field measured by DIC. With the coal sample’s growing size, the percentage of AE high energy events rose while the total number of AE positioning events fell, the proportion of DIC strain concentration area decreased, displacement zoning characteristics became more obvious, and the critical opening displacement of cracks increased. The variance of AE, EMR and DIC related parameters in coal samples showed significant critical slowing down characteristics. Based on their response timescales, EMR energy was identified as an “Early warning”, AE energy as a “Medium warning”, and VE elongation as a “Short-imminent warning”. A comprehensive analysis of multi-parameter monitoring information proved beneficial in accurately pinpointing precursory response points of coal mine dynamic disasters, thereby enhancing monitoring precision.

Ih Block Reveals Separation of Timescales in Pyloric Rhythm Response to Temperature Changes in Cancer borealis.

Motor systems operate over a range of frequencies and relative timing (phase). We studied the contribution of the hyperpolarization-activated inward current (Ih) to frequency and phase in the pyloric rhythm of the stomatogastric ganglion (STG) of the crab, Cancer borealis as temperature was altered from 11°C to 21°C. Under control conditions, the frequency of the rhythm increased monotonically with temperature, while the phases of the pyloric dilator (PD), lateral pyloric (LP), and pyloric (PY) neurons remained constant. When we blocked Ih with cesium (Cs+) PD offset, LP onset, and LP offset were all phase advanced in Cs+ at 11°C, and the latter two further advanced as temperature increased. In Cs+ the steady state increase in pyloric frequency with temperature diminished and the Q10 of the pyloric frequency dropped from ~1.75 to ~1.35. Unexpectedly in Cs+, the frequency displayed non-monotonic dynamics during temperature transitions; the frequency initially dropped as temperature increased, then rose once temperature stabilized, creating a characteristic "jag". Interestingly, these jags were still present during temperature transitions in Cs+ when the pacemaker was isolated by picrotoxin, although the temperature-induced change in frequency recovered to control levels. Overall, these data suggest that Ih plays an important role in the ability of this circuit to produce smooth transitory responses and persistent frequency increases by different mechanisms during temperature fluctuations.

Greenland's firn responds more to warming than to cooling

Abstract. The porous layer of snow and firn on the Greenland Ice Sheet stores meltwater and limits the rate at which the ice sheet contributes to sea level rise. This buffer is threatened in a warming climate. To better understand the nature and timescales of firn's response to air temperature change on the Greenland Ice Sheet, we use a physics-based model to assess the effects of atmospheric warming and cooling on Greenland's firn air content in idealized climate experiments. We identify an asymmetric response of Greenland's firn to air temperature: firn loses more air content due to warming compared to the amount gained from commensurate cooling. 100 years after a 1 °C temperature perturbation, warming decreases the spatially integrated air content by 9.7 %, and cooling increases it by 8.3 %. In dry firn, this asymmetry is driven by the highly nonlinear relationship between temperature and firn compaction, as well as the dependence of thermal conductivity on the composition of the firn. The influence of liquid water accentuates this asymmetry. In wet firn areas, melt increases nonlinearly with atmospheric warming, thus enhancing firn refreezing and further warming the snowpack through increased latent heat release. Our results highlight the vulnerability of Greenland firn to temperature change and demonstrate that firn air content is more efficiently depleted than generated. This asymmetry in the temperature–firn relationship may contribute to the overall temporally asymmetric mass change of the Greenland Ice Sheet in a changing climate across many timescales.

Timescales of Benthic Macrofaunal Response to Diel and Episodic Low Oxygen in a Subtropical Estuary

Timescales of Benthic Macrofaunal Response to Diel and Episodic Low Oxygen in a Subtropical Estuary

Task switch costs scale with dissimilarity between task rules.

Cognitive flexibility enables humans to voluntarily switch tasks. Task switching requires replacing the previously active task representation with a new one, an operation that typically results in a switch cost. Thus, understanding cognitive flexibility requires understanding how tasks are represented in the brain. We hypothesize that task representations are cognitive map-like, such that the magnitude of the difference between task representations reflects their conceptual differences: The greater the distinction between the two task representations, the more updating is required. This hypothesis predicts that switch costs should increase with between task dissimilarity. To test this hypothesis, we use an experimental design that parametrically manipulates the similarity between task rules. We observe that response time scales with the dissimilarity between the task rules. The findings shed light on the organizational principles of task representations and extend the conventional binary task-switch effect (task repeat vs. switch) to a theoretical framework with parametric task switches. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Energy inputs imprint seasonality and fractal structure on river metabolic regimes

AbstractThe temporal structures of gross primary production (GPP) and ecosystem respiration (ER) vary across time scales in response to complex interactions among dynamic drivers (e.g., flow, light, temperature, organic matter supply). To explore emergent patterns of river metabolic variation, we applied frequency‐domain analysis to multiyear records of metabolism across 87 US rivers. We observed a dominant annual periodicity in metabolic variation and universal fractal scaling (i.e., power spectral density inversely correlated with frequency) at subannual frequencies, suggesting these are foundational temporal structures of river metabolic regimes. Frequency‐domain patterns of river metabolism aligned best with drivers related to energy inputs: benthic light for GPP and GPP for ER. Simple river metabolism models captured frequency‐domain patterns when parameterized with appropriate energy inputs but neglecting temperature controls. These results imply that temporal variation of energy supply imprints directly on metabolic signals and that frequency‐domain patterns provide benchmark properties to predict river metabolic regimes.

Event-Driven Day-Ahead and Intra-Day Optimal Dispatch Strategy for Sustainable Operation of Power Systems Considering Major Weather Events

As the proportion of renewable energy installations in modern power systems increases, major weather events can easily trigger significant fluctuations in new energy generation and electricity load, presenting the system with the dual challenges of ensuring power supply and renewable energy consumption. Traditional dispatch models need more coordination and optimization of flexible resources under major weather events and risk management of system operations. This study focuses on provincial-level transmission systems, aiming to achieve the coordinated and optimized dispatch of flexible resources across multiple time scales in response to the complex and variable environments faced by the system. Firstly, by profoundly analyzing the response mechanisms of power systems during major weather events, this study innovatively proposes an event-driven day-ahead and intra-day optimal dispatch strategy for power systems. This strategy can sense and respond to major weather events in the day-ahead phase and adjust dispatch decisions in real time during the intra-day phase, thereby comprehensively enhancing the adaptability of power systems to sudden weather changes. Secondly, by considering the variability of renewable energy sources and electricity demand in the day-ahead and intra-day dispatch plans, the strategy ensures efficient and reliable power system operation under normal and major weather event scenarios. Finally, the method’s effectiveness is validated using actual data from a provincial-level power grid in China. The proposed dispatch strategy enhances the resilience and adaptability of power systems to major weather events, which are becoming increasingly frequent and severe due to climate change. The research demonstrates that an event-driven day-ahead and intra-day optimal dispatch strategy can enhance the economic efficiency and robustness of power system operations through the coordinated dispatch of flexible resources during major weather events, thereby supporting the transition toward sustainable energy systems that are resilient against the challenges of a changing climate.

Lithological controls on the timing of strath terrace staircase formation in a collisional mountain belt

AbstractIn mountain belts, strath terrace staircases serve as markers for deriving river incision rates and erosional patterns. Distinguishing between terrace patterns influenced by external perturbations like changes in climate and tectonics and those driven by internal dynamics including feedbacks between topography, erosion and sediment transport remains challenging. We demonstrate that in a collisional mountain belt, lithology can act as a first‐order control on the spatial and temporal scales of strath terrace formation. Here, we investigate the role of lithology in modulating internal dynamics and the formation of strath terraces in the Mgoun River catchment of the High Atlas in Morocco, a region characterised by constant low‐rate rock uplift, a cyclical cool‐warm/arid‐humid Quaternary climate history and contrasting bedrock lithologies. By collecting (1) modern river and terrace clast data, (2) bedrock strath and strath‐top sediment elevations of four terrace levels, (3) terrace sedimentology and (4) integration with published terrace chronology, we found a dominance of local sediment input from hillslopes, mostly from recycled bedrock conglomerates. Additionally, we found valley width, controlled by the stratigraphic and structural configuration of lithological erodibility, significantly impacts sediment connectivity. The isolation between valleys with varying widths results in varied timescales of river channel response to hillslope coupling, with hillslope‐derived stochastic sediment gravity flows preserved in fluvial terraces in some river reaches and not in others. Furthermore, asynchronous terrace formation and abandonment ages result from the low longitudinal river connectivity between multiple valleys formed in erodible rock separated by gorges in high‐strength rock. These gorges limit knickpoint migration rates, inhibiting the ability of terraces formed in one valley to spread through the catchment. These findings can inform future research distinguishing between autogenic and external signals in erosional landscapes and help carefully derive river incision rates and climate insights from terraces.

Cutaneous Evaporative Water Loss in Lizards Changes Immediately with Temperature.

AbstractCutaneous evaporative water loss (CEWL) makes up a significant portion of total evaporative water loss in many terrestrial vertebrates. CEWL changes on evolutionary and acclimatory timescales in response to temperature and humidity. However, the lability of CEWL on acute timescales is unknown. To examine this, we increased or decreased body temperatures of western fence lizards (Sceloporus occidentalis) over a 15-min period while continuously recording CEWL with a handheld evaporimeter. CEWL increased in response to heating and decreased in response to cooling on the order of seconds. However, CEWL was different between heating and cooling groups at a common body temperature. We observed the same positive relationship between CEWL and body temperature, as well as the difference in CEWL between treatments, for deceased lizards that we opportunistically measured. However, deceased lizards had more extreme CEWL values for any given body temperature and treatment. Overall, our results suggest that both structural traits and active physiological processes likely influence the rates and plasticity of CEWL.

Real-time in situ monitoring of dust particle growth in a low-pressure nanodusty plasma based on laser-induced photodetachment

Particulate matter air pollution in the form of ultrafine dust is a growing global concern. In this Letter, we will use a nanodusty Ar/HMDSO plasma as a model system for a heavily contaminated gas and we present the development of a technique for real-time in situ measurements of the dust particle size. The method is based on laser-induced photodetachment of bound electrons from the surface of dust particles. These photo-released electrons are measured as an increase in the free electron density of the plasma using microwave cavity resonance spectroscopy. We show that instead of reconstructing the entire resonance profile, the temporal response of a single microwave frequency was enough to perform the measurements. More specifically, the decay timescale of the cavity response can be interpreted as the re-charging timescale of the dust particles. Then, using a stochastic model, this timescale can be modeled, which eventually retrieves the dust particle size. We found good agreement between the predicted dust particle size and the average dust particle size obtained from ex situ scanning electron microscopy measurements. This method allows for the real-time monitoring of the dust particle size and a controlled production of nanometer-scale dust particles, which gives opportunities both for fundamental dusty plasma physics and models, as well as for applications in monitoring ultrafine dust air pollution.

Transitions: comparing timescales of eruption and evacuation at Volcán de Fuego (Guatemala) to understand relationships between hazard evolution and responsive action

During volcanic crisis, effective risk mitigation requires that institutions and local people respond promptly to protect lives and livelihoods. In this paper, we ask: over what timescales do explosive paroxysmal eruptions evolve? And how do these timescales relate to those of people’s past responses? We explore these questions by comparing timescales of eruptions and evacuations for several recent events at Volcán de Fuego (Guatemala) to identify lags in evacuation and determine the drivers of these lags. We use multiple geophysical datasets for explosive paroxysmal eruptions (“paroxysms”) in 2012–2018 to constrain timescales of eruptive evolution. In parallel, we determine timescales of response and the impacts of uncertainty and eruptive behaviours on decision-making through interviews with institutional and local actors. We then compare eruption and response timescales to explore the drivers for decision-making, whether volcanic, institutional, or personal. We find that eruption and response timescales are comparable. However, we also find that periods of decision-making and warning dissemination delay response until well after eruptive onset. We document how in recent eruptions, response occurs during eruptive climax when risk is at peak. We use paired timelines to elucidate the key drivers of this ‘response lag’ and show that despite the high levels of forecasting uncertainty, response times could be improved by agreed means to collaborate through shared information and agreed actions. We conclude by considering how the analysis presented here might be useful to different actors who share the goal of preserving lives and livelihoods at Fuego, focussing on how community’s needs can be met such that during an eruptive crisis the community can evacuate in time. Our analysis offers practical insights for people working to mitigate risk to populations near active volcanoes around the world.

Applications of information geometry to spiking neural network activity.

The space of possible behaviors that complex biological systems may exhibit is unimaginably vast, and these systems often appear to be stochastic, whether due to variable noisy environmental inputs or intrinsically generated chaos. The brain is a prominent example of a biological system with complex behaviors. The number of possible patterns of spikes emitted by a local brain circuit is combinatorially large, although the brain may not make use of all of them. Understanding which of these possible patterns are actually used by the brain, and how those sets of patterns change as properties of neural circuitry change is a major goal in neuroscience. Recently, tools from information geometry have been used to study embeddings of probabilistic models onto a hierarchy of model manifolds that encode how model outputs change as a function of their parameters, giving a quantitative notion of "distances" between outputs. We apply this method to a network model of excitatory and inhibitory neural populations to understand how the competition between membrane and synaptic response timescales shapes the network's information geometry. The hyperbolic embedding allows us to identify the statistical parameters to which the model behavior is most sensitive, and demonstrate how the ranking of these coordinates changes with the balance of excitation and inhibition in the network.

Timescales of response to Tonic Motor Activation (TOMAC) therapy for refractory Restless Legs Syndrome (RLS)

Timescales of response to Tonic Motor Activation (TOMAC) therapy for refractory Restless Legs Syndrome (RLS)

Mixing‐driven changes in distributions and abundances of planktonic microorganisms in a large, oligotrophic lake

AbstractTemperate lakes experience variation in mixing and stratification that affects the distributions, activities, abundances, and diversity of plankton communities. We examined temporal and vertical changes in the composition of planktonic microorganisms (including Bacteria and Archaea) in oligotrophic Flathead Lake, Montana. Using a combination of approaches that included 16S rRNA gene sequencing and flow cytometric determination of cell abundances, we found that the microbial community was responsive to variations in stratification and mixing at time scales ranging from episodic (scale of days) to seasonal. However, the impact of such physical dynamics varied among taxa, likely reflecting taxa‐specific responses to environmental changes that coincide with stratification and mixing (e.g., light availability and nutrient supply). During the early spring, periods of relatively short‐term (< 7 d) intermittency in stratification and mixing influenced the vertical distributions of specific microbial taxa, notably including the cyanobacteria. These events highlight time scales of biological responses to high‐frequency variations associated with lake stratification and mixing, particularly during the transition to the growing season in the early spring.

Time-delayed characteristics of turbulence in pulsatile pipe flow

Direct numerical simulations are performed to study temporal variations of the wall shear stresses and flow dynamics in the turbulent pulsatile pipe flow. The mechanisms, responsible for the paradoxical phenomenon for which the amplitude of the oscillating wall shear stress in the turbulent flow is smaller than that in the laminar flow for the same pulsation conditions, are investigated. It is shown that the delayed response of turbulence in the buffer layer generates a large magnitude of the radial gradient of the Reynolds shear stress near the wall, which counteracts the effect of the oscillating pressure gradient on the change of the streamwise velocity and hence reduces the amplitude of the wall shear stress. Such a delayed response consists of two processes: the delayed development of near-wall streaks and the subsequent energy redistribution from the streamwise velocity fluctuation to the other two co-existing components. This is a dynamical manifestation of the viscoelasticity of turbulent eddies. As the frequency is reduced, the variation of the friction Reynolds number results in a phase-wise variation of the time scale and intensity of the turbulence response, causing the hysteresis of the wall shear stress. Such a phase asymmetry is amplified by the increase of the pulsation amplitude. An examination of the energy spectra reveals that the near-wall streaks are stretched in the streamwise direction during the acceleration phase, and then break up into small-scale structures in the deceleration phase, accompanied by the enhanced dissipation that transforms the turbulent kinetic energy into heat.

Robust changes in global subtropical circulation under greenhouse warming

The lower tropospheric subtropical circulation (SC) is characterized by monsoons and subtropical highs, playing an important role in global teleconnections and climate variability. The SC changes in a warmer climate are influenced by complex and region-specific mechanisms, resulting in uneven projections worldwide. Here, we present a method to quantify the overall intensity change in global SC, revealing a robust weakening across CMIP6 models. The weakening is primarily caused by global-mean surface warming, and partly counteracted by the direct CO2 effect. The direct CO2 effect is apparent in the transient response but is eventually dominated by the surface warming effect in a slow response. The distinct response timescales to global-mean warming and direct CO2 radiative forcing can well explain the time-varying SC changes in other CO2 emission scenarios. The declined SC implies a contracted monsoon range and drying at its boundary with arid regions under CO2-induced global warming.

Declining coupling between vegetation and drought over the past three decades

AbstractDroughts have been implicated as the main driver behind recent vegetation die‐off and are projected to drive greater mortality under future climate change. Understanding the coupling relationship between vegetation and drought has been of great global interest. Currently, the coupling relationship between vegetation and drought is mainly evaluated by correlation coefficients or regression slopes. However, the optimal drought timescale of vegetation response to drought, as a key indicator reflecting vegetation sensitivity to drought, has largely been ignored. Here, we apply the optimal drought timescale identification method to examine the change in coupling between vegetation and drought over the past three decades (1982–2015) with long‐term satellite‐derived Normalized Difference Vegetation Index and Standardized Precipitation‐Evapotranspiration Index data. We find substantial increasing response of vegetation to drought timescales globally, and the correlation coefficient between vegetation and drought under optimal drought timescale overall declines between 1982 and 2015. This decrease in vegetation–drought coupling is mainly observed in regions with water deficit, although its initial correlation is relatively high. However, vegetation in water‐surplus regions, with low coupling in earlier stages, is prone to show an increasing trend. The observed changes may be driven by the increasing trend of atmospheric CO2. Our findings highlight more pressing drought risk in water‐surplus regions than in water‐deficit regions, which advances our understanding of the long‐term vegetation–drought relationship and provides essential insights for mapping future vegetation sensitivity to drought under changing climate conditions.