Synchronous Events Research Articles

Modeling directed weighted network based on event coincidence analysis and its application on spatial propagation characteristics.

The problem of synchronicity quantification, based on event occurrence time, has become the research focus in different fields. Methods of synchrony measurement provide an effective way to explore spatial propagation characteristics of extreme events. Using the synchrony measurement method of event coincidence analysis, we construct a directed weighted network and innovatively explore the direction of correlations between event sequences. Based on trigger event coincidence, the synchrony of traffic extreme events of base stations is measured. Analyzing topology characteristics of the network, we study the spatial propagation characteristics of traffic extreme events in the communication system, including the propagation area, propagation influence, and spatial aggregation. This study provides a framework of network modeling to quantify the propagation characteristics of extreme events, which is helpful for further research on the prediction of extreme events. In particular, our framework is effective for events that occurred in time aggregation. In addition, from the perspective of a directed network, we analyze differences between the precursor event coincidence and the trigger event coincidence and the impact of event aggregation on the synchrony measurement methods. The precursor event coincidence and the trigger event coincidence are consistent when identifying event synchronization, while there are differences when measuring the event synchronization extent. Our study can provide a reference for the analysis of extreme climatic events such as rainstorms, droughts, and others in the climate field.

Memory-Efficient Fixed-Length Representation of Synchronous Event Frames for Very-Low-Power Chip Integration

The new event cameras are now widely used in many computer vision applications. Their high raw data bitrate levels require a more efficient fixed-length representation for low-bandwidth transmission from the event sensor to the processing chip. A novel low-complexity lossless compression framework is proposed for encoding the synchronous event frames (EFs) by introducing a novel memory-efficient fixed-length representation suitable for hardware implementation in the very-low-power (VLP) event-processing chip. A first contribution proposes an improved representation of the ternary frames using pixel-group frame partitioning and symbol remapping. Another contribution proposes a novel low-complexity memory-efficient fixed-length representation using multi-level lookup tables (LUTs). Complex experimental analysis is performed using a set of group-size configurations. For very-large group-size configurations, an improved representation is proposed using a mask-LUT structure. The experimental evaluation on a public dataset demonstrates that the proposed fixed-length coding framework provides at least two times the compression ratio relative to the raw EF representation and a close performance compared with variable-length video coding standards and variable-length state-of-the-art image codecs for lossless compression of ternary EFs generated at frequencies bellow one KHz. To our knowledge, the paper is the first to introduce a low-complexity memory-efficient fixed-length representation for lossless compression of synchronous EFs, suitable for integration into a VLP event-processing chip.

Two forms of asynchronous release with distinctive spatiotemporal dynamics in central synapses.

Asynchronous release is a ubiquitous form of neurotransmitter release that persists for tens to hundreds of milliseconds after an action potential. How asynchronous release is organized and regulated at the synaptic active zone (AZ) remains debatable. Using nanoscale-precision imaging of individual release events in rat hippocampal synapses, we observed two spatially distinct subpopulations of asynchronous events, ~75% of which occurred inside the AZ and with a bias towards the AZ center, while ~25% occurred outside of the functionally defined AZ, that is, ectopically. The two asynchronous event subpopulations also differed from each other in temporal properties, with ectopic events occurring at significantly longer time intervals from synchronous events than the asynchronous events inside the AZ. Both forms of asynchronous release did not, to a large extent, utilize the same release sites as synchronous events. The two asynchronous event subpopulations also differ from synchronous events in some aspects of exo-endocytosis coupling, particularly in the contribution from the fast calcium-dependent endocytosis. These results identify two subpopulations of asynchronous release events with distinctive organization and spatiotemporal dynamics.

Validation of the detected Dry–Wet Abrupt Alternation by developing a weighting analysis method

AbstractThe phenomenon of sudden drought after pluvial (or heavy pluvial after drought) is known as the Dry–Wet Abrupt Alternation (DWAA). This kind of disaster has been evaluated globally based on various DWAA indices. However, few validations have been performed to compare the various DWAA indices. Given that directly validating the identified DWAA events remains difficult because of the limited historical records of DWAA events, in this study, we developed a simple weighting analysis method to cross‐validate the detected DWAA events using three widely‐used indices. The weighting analysis method can be used to estimate the effectiveness of the DWAA indices by calculating the ratio of the synchronous DWAA events (the DWAA events could be synchronously detected by different indices) to the total number of the detected DWAA events. Results suggest that the standard weighted average of precipitation (SWAP) index has better performance for detecting DWAA events in the Pearl River Basin (PRB) compared to other indices. The soil moisture synchronization, meteorological concentration and real DWAA records further testify that the SWAP is more capable of detecting the DWAA events in the PRB. Based on the validation, the SWAP‐derived DWAA events show that both dry–wet (D–W) events and wet–dry events are severe in the upstream sub‐basins in the PRB, while D–W events are more frequent in the downstream PRB. Our study provides a simple but effective method to validate the detected DWAA. The finding underscores the need to validate DWAA detection generated from multiple indicators before further research, and it could help develop adaptation strategies to improve resilience to combined extremes under changing climate.

Magnetotelluric constraints on the tectonic evolution beneath the Luotian dome in the North Dabie complex zone, Central China

The Dabie orogen, formed by a Triassic continent-continent collision between the Yangtze and the North China craton, contains one of the largest ultrahigh-pressure (UHP) metamorphic terranes in the world. However, compared to the widespread UHP metamorphic rocks in the Central Dabie, little evidence shows the North Dabie Zone (NDZ) has experienced UHP metamorphism. To understand the cause of these variances and constrain the post-collision evolution of the NDZ, we conducted a magnetotelluric profile across the Luotian dome, southwestern NDZ. Our electrical resistivity model exhibits intriguing post-collision evolution-related characteristics. On both sides of the profile, the resistive features extend to ∼10 km, suggesting the UHP metamorphic or magmatic rocks are mainly concentrated in the upper crust; the underlying crustal high conductive features are interpreted to be the graphite from the mantle-derived or related magma, which were interconnected by the shearing. The middle resistive features extend deeper to ∼20 km, which may represent the magmatic rocks that contributed to the formation of the Luotian dome during the early Cretaceous. The lithosphere mantle generally behaves as high conductive features related to graphite, indicating a fertile mantle. Combining geological and geophysical observations previously, we suggest the Luotian region experienced doming in response to the hot asthenosphere upwelling resulting from the delamination of the lithospheric keel of the Dabie orogen during the early Cretaceous as triggered by synchronous tectonic events like the development of the Tan-Lu fault. These processes may fertilize the lithosphere, uplift and erode the Luotian or the NDZ, resulting in the observed resistivity structures and the lack of UHP metamorphic rocks.

Biotic homogenisation and differentiation as directional change in beta diversity: synthesising driver-response relationships to develop conceptual models across ecosystems.

Biotic homogenisation is defined as decreasing dissimilarity among ecological assemblages sampled within a given spatial area over time. Biotic differentiation, in turn, is defined as increasing dissimilarity over time. Overall, changes in the spatial dissimilarities among assemblages (termed 'beta diversity') is an increasingly recognised feature of broader biodiversity change in the Anthropocene. Empirical evidence of biotic homogenisation and biotic differentiation remains scattered across different ecosystems. Most meta-analyses quantify the prevalence and direction of change in beta diversity, rather than attempting to identify underlying ecological drivers of such changes. By conceptualising the mechanisms that contribute to decreasing or increasing dissimilarity in the composition of ecological assemblages across space, environmental managers and conservation practitioners can make informed decisions about what interventions may be required to sustain biodiversity and can predict potential biodiversity outcomes of future disturbances. We systematically reviewed and synthesised published empirical evidence for ecological drivers of biotic homogenisation and differentiation across terrestrial, marine, and freshwater realms to derive conceptual models that explain changes in spatial beta diversity. We pursued five key themes in our review: (i) temporal environmental change; (ii) disturbance regime; (iii) connectivity alteration and species redistribution; (iv) habitat change; and (v) biotic and trophic interactions. Our first conceptual model highlights how biotic homogenisation and differentiation can occur as a function of changes in local (alpha) diversity or regional (gamma) diversity, independently of species invasions and losses due to changes in species occurrence among assemblages. Second, the direction and magnitude of change in beta diversity depends on the interaction between spatial variation (patchiness) and temporal variation (synchronicity) of disturbance events. Third, in the context of connectivity and species redistribution, divergent beta diversity outcomes occur as different species have different dispersal characteristics, and the magnitude of beta diversity change associated with species invasions also depends strongly on alpha and gamma diversity prior to species invasion. Fourth, beta diversity is positively linked with spatial environmental variability, such that biotic homogenisation and differentiation occur when environmental heterogeneity decreases or increases, respectively. Fifth, species interactions can influence beta diversity via habitat modification, disease, consumption (trophic dynamics), competition, and by altering ecosystem productivity. Our synthesis highlights the multitude of mechanisms that cause assemblages to be more or less spatially similar in composition (taxonomically, functionally, phylogenetically) through time. We consider that future studies should aim to enhance our collective understanding of ecological systems by clarifying the underlying mechanisms driving homogenisation or differentiation, rather than focusing only on reporting the prevalence and direction of change in beta diversity, per se.

Differential ripple propagation along the hippocampal longitudinal axis.

Hippocampal ripples are highly synchronous neural events critical for memory consolidation and retrieval. A minority of strong ripples has been shown to be of particular importance in situations of increased memory demands. The propagation dynamics of strong ripples inside the hippocampal formation are, however, still opaque. We analyzed ripple propagation within the hippocampal formation in a large open-access dataset comprising 267 Neuropixel recordings in 49 awake, head-fixed mice. Surprisingly, strong ripples (top 10% in ripple strength) propagate differentially depending on their generation point along the hippocampal longitudinal axis. The septal hippocampal pole is able to generate longer ripples that engage more neurons and elicit spiking activity for an extended time even at considerable distances. Accordingly, a substantial portion of the variance in strong ripple duration (R² = 0.463) is explained by the ripple generation location on the longitudinal axis, in agreement with a possible distinctive role of the hippocampal septal pole in conditions of high-memory demand. Moreover, we observed that the location of the ripple generation has a significant impact on the spiking rate modulation of different hippocampal subfields, even before the onset of the ripple. This finding suggests that ripple generation location plays a crucial role in shaping the neural activity across the hippocampus.

Same, same but different: Exploring Plasmodium cell division during liver stage development.

Plasmodium parasites have a complex life cycle alternating between a mosquito and a vertebrate host. Following the bite of an Anopheles female mosquito, Plasmodium sporozoites are transmitted from the skin to the liver; their first place of replication within the host. Successfully invaded sporozoites undergo a massive replication and growth involving asynchronous DNA replication and division that results in the generation of tens of thousands or even hundreds of thousands of merozoites depending on the Plasmodium species. The generation of a high number of daughter parasites requires biogenesis and segregation of organelles to finally reach a relatively synchronous cytokinesis event. At the end of liver stage (LS) development, merozoites are packed into merosomes and released into the bloodstream. They are then liberated and infect red blood cells to again produce merozoites by schizogony for the erythrocytic stage of the life cycle. Although parasite LS and asexual blood stage (ABS) differ in many respects, important similarities exist between the two. This review focuses on the cell division of Plasmodium parasite LS in comparison with other life cycle stages especially the parasite blood stage.

Multiscale phenological niches of seed fall in diverse Amazonian plant communities.

Phenology has long been hypothesized as an avenue for niche partitioning or interspecific facilitation, both promoting species coexistence. Tropical plant communities exhibit striking diversity in reproductive phenology, but many are also noted for large synchronous reproductive events. Here we study whether the phenology of seed fall in such communities is nonrandom, the temporal scales of phenological patterns, and ecological factors that drive reproductive phenology. We applied multivariate wavelet analysis to test for phenological synchrony versus compensatory dynamics (i.e., antisynchronous patterns where one species' decline is compensated by the rise of another) among species and across temporal scales. We used data from long-term seed rain monitoring of hyperdiverse plant communities in the western Amazon. We found significant synchronous whole-community phenology at multiple timescales, consistent with shared environmental responses or positive interactions among species. We also observed both compensatory and synchronous phenology within groups of species (confamilials) likely to share traits and seed dispersal mechanisms. Wind-dispersed species exhibited significant synchrony at ~6-month scales, suggesting these species might share phenological niches to match the seasonality of wind. Our results suggest that community phenology is shaped by shared environmental responses but that the diversity of tropical plant phenology may partly result from temporal niche partitioning. The scale-specificity and time-localized nature of community phenology patterns highlights the importance of multiple and shifting drivers of phenology.

Nocturnal emergence facilitated by thermally-induced hatching in the Chinese softshell turtle, Pelodiscus sinensis.

The coincidence of hatching and emergence events with favorable conditions is crucial for turtle survival. Nocturnal emergence has been widely documented across marine and freshwater turtles, and has long been suggested as an adaptive behavior that reduces risks of heat stress and predation. To our knowledge, however, studies related to nocturnal emergence have mainly focused on the post-hatching behaviors of turtles, and very few experimental studies have been performed to investigate the effects of hatching time on the distribution of emergence times over the course of a day. Here, we visually monitored the activity of the Chinese softshell turtle (Pelodiscus sinensis)-a shallow-nesting freshwater turtle-from hatching to emergence. Our study provides evidence for the novel finding that (i) the timing of synchronous hatching events in P.sinensis coincides with the time of day when nest temperatures decrease, (ii) the synchrony between hatching and emergence may further facilitate their nocturnal emergence, and (iii) synchronous behaviors of hatchlings in the nest may be effective in reducing the risk of hatchling predation, and predation is more likely to occur in the asynchronous hatching groups. This study suggests that the hatching of shallow-nesting P.sinensis in response to temperature changes in the nest might be an adaptive nocturnal emergence strategy.

Ganz entspannt im hier und jetzt: Fostering social presence in communicative language instruction—Before, during, and after the pandemic

Ganz entspannt im hier und jetzt: Fostering social presence in communicative language instruction—Before, during, and after the pandemic

Social Robots Privacy Enhancement Using Colored Petri Net (CPN) for Behavior Modeling: A Case Study of Asus Zenbo Robot

The interactions between a social robot and the user consist of continuous communication and behavior involving different data types that can be subject to cybersecurity attacks and prone to user privacy concerns. In this paper, we use Colored Petri Net (CPN) to develop two graphical models that illustrate different patterned behavior of a robot during such interaction. Using CPN, we model and analyze complicated robot system interactions considering synchronization and concurrency of events that can be subject to privacy violations. We focus on two specific scenarios involving user registration and medication reminder to provide an efficient illustration of the objects and events collaborated to carry out the intended tasks of the robot pertaining to privacy issues. The results show that CPN modeling simulation can capture and represent the robot's behavior, provide a better understanding of the task execution, and highlight users' privacy gaps requiring immediate controls.

Astronomically forced climate variability across the Eocene−Oligocene transition from a low latitude terrestrial record (Lühe Basin, South China)

Across the late Eocene to early Oligocene, Earth’s climate underwent a dramatic shift from Greenhouse to Icehouse, known as the Eocene−Oligocene transition (EOT). This globally synchronous climatic event is well-documented in marine records. However, there is a relative paucity of terrestrial records, particularly at low latitudes. In this study, we present a continuous and high-resolution terrestrial record across the EOT from the low-latitude Lühe Basin, Yunnan Province, South China. Combined with published magnetostratigraphy and 40Ar/39Ar dating of volcanic ashes in the Lühe Basin, we have constrained this record with a robust astronomical timescale. Our results, combined with previously published data from the region, reveal that the Lühe Basin experienced significant environmental and climate changes, from humid/warm to semi-humid/cool conditions, across the EOT. Cyclostratigraphic analysis of high-resolution elemental data reveal a significant switch in orbital forcing, from dominant eccentricity before ca. 34 Ma to combined eccentricity-obliquity-precession cycles after ca. 34 Ma. Atmospheric CO2 decline and subsequent Antarctic glaciation may have been a contributing factor in driving this orbital transition.

Karst collapse and gypsum-filled veins in Eocene outcrops, Dammam Dome, Saudi Arabia: Causes and implications

• Differential weathering of Dammam Dome through uplift and erosion. • Factors affecting Dammam Dome geomorphology. • Gypsum-filled veins on the Dammam Dome due to karst collapse. • Results from this study can be related with water and hydrocarbon reservoirs. A recent road cut through Dammam Formation outcrop on the Dammam Dome in Dhahran, Saudi Arabia exposed an array of open fractures and gypsum-filled veins. The widespread array of fractures in the road cut was mostly contained within Saila Shale member and consisted of horizontal, vertical, and oblique extensional fractures, most were filled with gypsum. The gypsum veins are of varying thickness with the largest exceeding 2.5 inches. Vertical gypsum veins, similar to those encountered at the road cut, were found in adjacent areas. Thin layer of gypsum (about 1 inch) was also observed in the Rus Formation. The open fractures, in the Saila and Midra Shales members, were devoid of gypsum fill. Most of the open vertical and horizontal fractures were interpreted to be recent with indications of triggered by the excavation work. The open fractures and filled veins cover a stretch of about 250 ft. across the road cut that also exposed what was interpreted as a local karst collapse. Horizontally-layered and continuous rocks overlying the collapse indicated that it was a paleo structure. The causal mechanism for fracture formation and subsequent fill was associated with deformations accompanying post-karst collapse. Here, natural fracturing and fluid transport were not synchronous events. Insights from this interpretation offered an explanation for widespread surface structures with major and subtle morphologies on the Dammam Dome. These insights also highlighted the significance of collapse in the modification of the Dammam Dome over a geological timescale. The unstable nature of gypsum, prevalent in Dammam Formation in the Dammam Dome, has potential implications for integrity of anthropogenic structures such as roads and building foundations.

A modified extreme event-based synchronicity measure for climate time series.

Extreme event-based synchronicity is a specific measure of similarity of extreme event-like time series. It is capable to capture the nonlinear interactions between climatic extreme events. In this study, we proposed a modified extreme event-based synchronicity measure that incorporates two types of extreme events (positive and negative) simultaneously in climate anomalies to characterize the synchronization and time delays. Statistical significance of the modified extreme event synchronization measure is tested by Monte-Carlo simulations. The applications of the modified extreme event-based synchronicity measure on synthetic time series verified that it was superior to the traditional event synchronicity measure. Both synchronous and antisynchronous features between climate time series could be captured by the modified measure. It is potentially applied in investigating the interrelationship between climate extremes and climate index or constructing complex networks of climate variables. In addition, this modified extreme event-based synchronicity measure could be easily applied to other types of time series just by identifying the extreme events properly.

Ripples in macaque V1 and V4 are modulated by top-down visual attention

Sharp-wave ripples (SWRs) are highly synchronous neuronal activity events. They have been predominantly observed in the hippocampus during offline states such as pause in exploration, slow-wave sleep, and quiescent wakefulness. SWRs have been linked to memory consolidation, spatial navigation, and spatial decision-making. Recently, SWRs have been reported during visual search, a form of remote spatial exploration, in macaque hippocampus. However, the association between SWRs and multiple forms of awake conscious and goal-directed behavior is unknown. We report that ripple activity occurs in macaque visual areas V1 and V4 during focused spatial attention. The occurrence of ripples is modulated by stimulus characteristics, increased by attention toward the receptive field, and by the size of the attentional focus. During attention cued to the receptive field, the monkey's reaction time in detecting behaviorally relevant events was reduced by ripples. These results show that ripple activity is not limited to hippocampal activity during offline states, rather they occur in the neocortex during active attentive states and vigilance behaviors.

Global droughts connected by linkages between drought hubs

Quantifying the spatial and interconnected structure of regional to continental scale droughts is one of the unsolved global hydrology problems, which is important for understanding the looming risk of mega-scale droughts and the resulting water and food scarcity and their cascading impact on the worldwide economy. Using a Complex Network analysis, this study explores the topological characteristics of global drought events based on the self-calibrated Palmer Drought Severity Index. Event Synchronization is used to measure the strength of association between the onset of droughts at different spatial locations within the time lag of 1-3 months. The network coefficients derived from the synchronization network indicate a highly heterogeneous connectivity structure underlying global drought events. Drought hotspot regions such as Southern Europe, Northeast Brazil, Australia, and Northwest USA behave as drought hubs that synchronize regionally and with other hubs at inter-continental or even inter-hemispheric scale. This observed affinity among drought hubs is equivalent to the ‘rich-club phenomenon’ in Network Theory, where ‘rich’ nodes (here, drought hubs) are tightly interconnected to form a club, implicating the possibility of simultaneous large-scale droughts over multiple continents.

Extrinsic control of the early postnatal CA1 hippocampal circuits

The adult CA1 region of the hippocampus produces coordinated neuronal dynamics with minimal reliance on its extrinsic inputs. By contrast, neonatal CA1 is tightly linked to externally generated sensorimotor activity, but the circuit mechanisms underlying early synchronous activity in CA1 remain unclear. Here, using a combination of invivo and exvivo circuit mapping, calcium imaging, and electrophysiological recordings in mouse pups, we show that early dynamics in the ventro-intermediate CA1 are under the mixed influence of entorhinal (EC) and thalamic (VMT) inputs. Both VMT and EC can drive internally generated synchronous events exvivo. However, movement-related population bursts detected invivo are exclusively driven by the EC. These differential effects on synchrony reflect the different intrahippocampal targets of these inputs. Hence, cortical and subcortical pathways act differently on the neonatal CA1, implying distinct contributions to the development of the hippocampal microcircuit and related cognitive maps.

Gemini: Enabling Multi-Tenant GPU Sharing Based on Kernel Burst Estimation

Recent years have seen rapid adoption of GPUs in various types of platforms because of the tremendous throughput powered by massive parallelism. However, as the computing power of GPU continues to grow at a rapid pace, it also becomes harder to utilize these additional resources effectively with the support of GPU sharing. In this work, we designed and implemented <i>Gemini</i> , a user-space runtime scheduling framework to enable fine-grained GPU allocation control with support for multi-tenancy and elastic allocation, which are critical for cloud and resource providers. Our key idea is to introduce the concept of <i>kernel burst</i> , which refers to a group of consecutive kernels launched together without being interrupted by synchronous events. Based on the characteristics of kernel burst, we proposed a low overhead <i>event-driven monitor</i> and a <i>dynamic time-sharing scheduler</i> to achieve our goals. Our experiment evaluations using five types of GPU applications show that Gemini enabled multi-tenant and elastic GPU allocation with less than 5% performance overhead. Furthermore, compared to static scheduling, Gemini achieved 20% <inline-formula><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 30% performance improvement without requiring prior knowledge of applications.

On tick automata for distributed timed DESs with synchronisations and minimal time constraints

This paper is about the representations of distributed timed discrete event systems (DESs) with synchronisation events and minimal time constraints. A subclass of Timed Petri nets with specific time semantics is first recalled as a reference model for the considered systems. Such a model is reformulated according to modular tick automata with minimal times that behave like logical automata. A synchronous composition of such automata is then defined and the result of this composition is a new tick automaton that has the same timed language as the original Petri net, which is not the case for the earlier model of tick automata with constant (exact) times.