Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Rare events in generalized Levy Walks and the Big Jump principle.

ABSTRACT: The prediction and control of rare events is an important task in disciplines that range from physics and biology, to economics and social science. The Big Jump principle deals with a peculiar aspect of the mechanism that drives rare events. According to the principle, in heavy-tailed processes a rare huge fluctuation is caused by a single event and not by the usual coherent accumulation of small deviations. We consider generalized Lévy walks, a class of stochastic processes with power law distributed step durations and with complex microscopic dynamics in the single stretch. We derive the bulk of the probability distribution and using the big jump principle, the exact form of the tails that describes rare events. We show that the tails of the distribution present non-universal and non-analytic behaviors, which depend crucially on the dynamics of the single step. The big jump estimate also provides a physical explanation of the processes driving the rare events, opening new possibilities for their correct prediction.

SUBMITTER: Vezzani A

PROVIDER: S-EPMC7026067 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Rare events in generalized Lévy Walks and the Big Jump principle.

Vezzani Alessandro A Barkai Eli E Burioni Raffaella R

Scientific reports 20200217 1

The prediction and control of rare events is an important task in disciplines that range from physics and biology, to economics and social science. The Big Jump principle deals with a peculiar aspect of the mechanism that drives rare events. According to the principle, in heavy-tailed processes a rare huge fluctuation is caused by a single event and not by the usual coherent accumulation of small deviations. We consider generalized Lévy walks, a class of stochastic processes with power law distr ...[more]

PMID: 32066775

Similar Datasets

Generalized Levy walks and the role of chemokines in migration of effector CD8+ T cells.

Project description:Chemokines have a central role in regulating processes essential to the immune function of T cells, such as their migration within lymphoid tissues and targeting of pathogens in sites of inflammation. Here we track T cells using multi-photon microscopy to demonstrate that the chemokine CXCL10 enhances the ability of CD8+ T cells to control the pathogen Toxoplasma gondii in the brains of chronically infected mice. This chemokine boosts T-cell function in two different ways: it maintains the effector T-cell population in the brain and speeds up the average migration speed without changing the nature of the walk statistics. Notably, these statistics are not Brownian; rather, CD8+ T-cell motility in the brain is well described by a generalized Lévy walk. According to our model, this unexpected feature enables T cells to find rare targets with more than an order of magnitude more efficiency than Brownian random walkers. Thus, CD8+ T-cell behaviour is similar to Lévy strategies reported in organisms ranging from mussels to marine predators and monkeys, and CXCL10 aids T cells in shortening the average time taken to find rare targets.

| S-EPMC3387349 | biostudies-literature

Levy Walks Suboptimal under Predation Risk.

Project description:A key challenge in movement ecology is to understand how animals move in nature. Previous studies have predicted that animals should perform a special class of random walks, called Lévy walk, to obtain more targets. However, some empirical studies did not support this hypothesis, and the relationship between search strategy and ecological factors is still unclear. We focused on ecological factors, such as predation risk, and analyzed whether Lévy walk may not be favored. It was remarkable that the ecological factors often altered an optimal search strategy from Lévy walk to Brownian walk, depending on the speed of the predator's movement, density of predators, etc. This occurred because higher target encounter rates simultaneously led searchers to higher predation risks. Our findings indicate that animals may not perform Lévy walks often, and we suggest that it is crucial to consider the ecological context for evaluating the search strategy performed by animals in the field.

| S-EPMC4636162 | biostudies-literature

Efficient Levy walks in virtual human foraging.

Project description:Efficient foraging depends on decisions that account for the costs and benefits of various activities like movement, perception, and planning. We conducted a virtual foraging experiment set in the foothills of the Himalayas to examine how time and energy are expended to forage efficiently, and how foraging changes when constrained to a home range. Two hundred players foraged the human-scale landscape with simulated energy expenditure in search of naturally distributed resources. Results showed that efficient foragers produced periods of locomotion interleaved with perception and planning that approached theoretical expectations for Lévy walks, regardless of the home-range constraint. Despite this constancy, efficient home-range foraging trajectories were less diffusive by virtue of restricting locomotive search and spending more time instead scanning the environment to plan movement and detect far-away resources. Altogether, results demonstrate that humans can forage efficiently by arranging and adjusting Lévy-distributed search activities in response to environmental and task constraints.

| S-EPMC7933158 | biostudies-literature

Mussels realize Weierstrassian Levy walks as composite correlated random walks.

Project description:Composite correlated random walks (CCRW) have been posited as a potential replacement for Lévy walks and it has also been suggested that CCRWs have been mistaken for Lévy walks. Here I test an alternative, emerging hypothesis: namely that some organisms approximate Lévy walks as an innate CCRW. It is shown that the tri-modal CCRW found to describe accurately the movement patterns of mussels (Mytilus edulis) during spatial pattern formation in mussel beds can be regarded as being the first three levels in a hierarchy of nested movement patterns which if extended indefinitely would correspond to a Lévy walk whose characteristic (power-law) exponent is tuned to nearly minimize the time required to form patterned beds. The mussels realise this Lévy walk to good approximation across a biologically meaningful range of scales. This demonstrates that the CCRW not only describes mussel movement patterns, it explains them.

| S-EPMC3957148 | biostudies-other

Functional advantages of Levy walks emerging near a critical point.

Project description:A special class of random walks, so-called Lévy walks, has been observed in a variety of organisms ranging from cells, insects, fishes, and birds to mammals, including humans. Although their prevalence is considered to be a consequence of natural selection for higher search efficiency, some findings suggest that Lévy walks might also be epiphenomena that arise from interactions with the environment. Therefore, why they are common in biological movements remains an open question. Based on some evidence that Lévy walks are spontaneously generated in the brain and the fact that power-law distributions in Lévy walks can emerge at a critical point, we hypothesized that the advantages of Lévy walks might be enhanced by criticality. However, the functional advantages of Lévy walks are poorly understood. Here, we modeled nonlinear systems for the generation of locomotion and showed that Lévy walks emerging near a critical point had optimal dynamic ranges for coding information. This discovery suggested that Lévy walks could change movement trajectories based on the magnitude of environmental stimuli. We then showed that the high flexibility of Lévy walks enabled switching exploitation/exploration based on the nature of external cues. Finally, we analyzed the movement trajectories of freely moving Drosophila larvae and showed empirically that the Lévy walks may emerge near a critical point and have large dynamic range and high flexibility. Our results suggest that the commonly observed Lévy walks emerge near a critical point and could be explained on the basis of these functional advantages.

| S-EPMC7533831 | biostudies-literature

Delay time of waves performing Levy walks in 1D random media.

Project description:The time that waves spend inside 1D random media with the possibility of performing Lévy walks is experimentally and theoretically studied. The dynamics of quantum and classical wave diffusion has been investigated in canonical disordered systems via the delay time. We show that a wide class of disorder-Lévy disorder-leads to strong random fluctuations of the delay time; nevertheless, some statistical properties such as the tail of the distribution and the average of the delay time are insensitive to Lévy walks. Our results reveal a universal character of wave propagation that goes beyond standard Brownian wave-diffusion.

| S-EPMC7705700 | biostudies-literature

A stochastic SIR epidemic model with Levy jump and media coverage.

Project description:A stochastic susceptible-infectious-recovered epidemic model with temporary immunity and media coverage is proposed. The effects of Lévy jumps on the dynamics of the model are considered. A unique global positive solution for the epidemic model is obtained. Sufficient conditions are derived to guarantee that the epidemic disease is extinct and persistent in the mean. The threshold behavior is discussed. Numerical simulations are given to verify our theoretical results.

| S-EPMC7224063 | biostudies-literature

Zigzag Generalized Levy Walk: the In Vivo Search Strategy of Immunocytes.

Project description:Immune responses are based on the coordinated searching behaviors of immunocytes that are aimed at tracking down specific targets. The search efficiency of immunocytes significantly affects the speed of initiation and development of immune responses. Previous studies have shown that not only the intermittent walk but also the zigzag turning preference of immunocytes contributes to the search efficiency. However, among existing models describing immunocytes' search strategy, none has captured both features. Here we propose a zigzag generalized Lévy walk model to describe the search strategy of immunocytes more accurately and comprehensively by considering both the intermittent and the zigzag-turning walk features. Based on the analysis of the searching behaviors of typical immune cell types, dendritic cells and leukocytes, in their native physiological environment, we demonstrate that the model can describe the in vivo search strategy of immunocytes well. Furthermore, by analyzing the search efficiency, we find that this type of search strategy enables immunocytes to capture rare targets in approximately half the time than the previously proposed generalized Lévy walk. This study sheds new light on the fundamental mechanisms that drive the efficient initiation and development of immune responses and in turn may lead to the development of novel therapeutic approaches for diseases ranging from infection to cancer.

| S-EPMC4568454 | biostudies-other

Big smile, small self: Awe walks promote prosocial positive emotions in older adults.

Project description:Aging into later life is often accompanied by social disconnection, anxiety, and sadness. Negative emotions are self-focused states with detrimental effects on aging and longevity. Awe-a positive emotion elicited when in the presence of vast things not immediately understood-reduces self-focus, promotes social connection, and fosters prosocial actions by encouraging a "small self." We investigated the emotional benefits of a novel "awe walk" intervention in healthy older adults. Sixty participants took weekly 15-min outdoor walks for 8 weeks; participants were randomly assigned to an awe walk group, which oriented them to experience awe during their walks, or to a control walk group. Participants took photographs of themselves during each walk and rated their emotional experience. Each day, they reported on their daily emotional experience outside of the walk context. Participants also completed pre- and postintervention measures of anxiety, depression, and life satisfaction. Compared with participants who took control walks, those who took awe walks experienced greater awe during their walks and exhibited an increasingly "small self" in their photographs over time. They reported greater joy and prosocial positive emotions during their walks and displayed increasing smile intensity over the study. Outside of the walk context, participants who took awe walks reported greater increases in daily prosocial positive emotions and greater decreases in daily distress over time. Postintervention anxiety, depression, and life satisfaction did not change from baseline in either group. These results suggest cultivating awe enhances positive emotions that foster social connection and diminishes negative emotions that hasten decline. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

| S-EPMC8034841 | biostudies-literature

Rare presentation of botulism with generalized fasciculations.

Project description:Botulism is a dreadful, life-threatening, neuroparalytic disease caused by gram positive bacteria Clostridium botulinum. Food borne botulism has been described following ingestion of preformed toxins in canned food or food products that have not been preserved properly. Botulinum toxin acts on neuromuscular junction and manifests as ophthalmoplegia, bulbar and limb weakness, and autonomic features along with respiratory compromise. The literature and case reports regarding neuroparalytic botulism in India are sparse. Generalized fasciculations have been rarely reported in literature as manifestation of food borne botulism. We present a 35-year-male presenting with usual features described, but with prominent generalized fasciculations which are rare, and which rapidly responded to treatment.

| S-EPMC3931218 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data