scholarly journals Long-term statistics of pulsar glitches triggered by a Brownian stress accumulation process

2020 ◽  
Vol 494 (3) ◽  
pp. 3383-3391 ◽  
Author(s):  
J B Carlin ◽  
A Melatos
Keyword(s):  
Cross Correlation ◽  
Waiting Times ◽  
Rotation Frequency ◽  
Critical Threshold ◽  
Accumulation Process ◽  
Meta Model ◽  
State Dependent ◽  
Brownian Process ◽  
Stress Accumulation

ABSTRACT A microphysics-agnostic meta-model of rotational glitches in rotation-powered pulsars is developed, wherein the globally averaged internal stress accumulates as a Brownian process between glitches, and a glitch is triggered once a critical threshold is surmounted. Precise, falsifiable predictions are made regarding long-term event statistics in individual pulsars. For example, the Spearman cross-correlation coefficient between the size of a glitch and the waiting time until the next glitch should exceed 0.25 in all pulsars. Among the six pulsars with the most recorded glitches, PSR J0537−6910 and PSR J0835−4510 are consistent with the predictions of the meta-model, while PSR J1740−3015 and PSR J0631+1036 are not. PSR J0534+2200 and PSR J1341−6220 are only consistent with the meta-model, if there exists an undetected population of small glitches with small waiting times, which we do not resolve. The results are compared with a state-dependent Poisson process, another microphysics-agnostic meta-model in the literature. The results are also applied briefly to recent pulse-to-pulse observations of PSRJ0835−4510, which appear to reveal evidence for a negative fluctuation in rotation frequency just prior to the 2016 glitch.

scholarly journals Simulating pulsar glitches: an N-body solver for superfluid vortex motion in two dimensions

2020 ◽  
Vol 498 (1) ◽  
pp. 320-331
Author(s):  
G Howitt ◽  
A Melatos ◽  
B Haskell
Keyword(s):  
Waiting Times ◽  
Vortex Motion ◽  
Two Dimensions ◽  
Pitaevskii Equation ◽  
Lognormal Distributions ◽  
State Dependent ◽  
Stress Release Model ◽  
Before And After ◽  
Release Model ◽  
Stress Accumulation

ABSTRACT A rotating superfluid forms an array of quantized vortex lines that determine its angular velocity. The spasmodic evolution of the array under the influence of deceleration, dissipation, and pinning forces is thought to be responsible for the phenomenon of pulsar glitches, sudden jumps in the spin frequency of rotating neutron stars. We describe and implement an N-body method for simulating the motion of up to 5000 vortices in two dimensions and present the results of numerical experiments validating the method, including stability of a vortex ring and dissipative formation of an Abrikosov array. Vortex avalanches occur routinely in the simulations, when chains of unpinning events are triggered collectively by vortex–vortex repulsion, consistent with previous, smaller scale studies using the Gross–Pitaevskii equation. The probability density functions of the avalanche sizes and waiting times are consistent with both exponential and lognormal distributions. We find weak correlations between glitch sizes and waiting times, consistent with astronomical data and meta-models of pulsar glitch activity as a state-dependent Poisson process or a Brownian stress-accumulation process, and inconsistent with a threshold-triggered stress-release model with a single, global stress reservoir. The spatial distribution of the effective stress within the simulation volume is analysed before and after a glitch.

scholarly journals Autocorrelations in pulsar glitch waiting times and sizes

2019 ◽  
Vol 488 (4) ◽  
pp. 4890-4896 ◽  
Author(s):  
J B Carlin ◽  
A Melatos
Keyword(s):  
Waiting Time ◽  
Waiting Times ◽  
P Value ◽  
Spearman Correlation ◽  
Stress Release ◽  
Release Process ◽  
Meta Model ◽  
State Dependent ◽  
Cross Correlations ◽  
Stress Release Process

ABSTRACT Among the five pulsars with the most recorded rotational glitches, only PSR J0534+2200 is found to have an autocorrelation between consecutive glitch sizes that differs significantly from zero (Spearman correlation coefficient ρ = −0.46, p-value = 0.046). No statistically compelling autocorrelations between consecutive waiting times are found. The autocorrelation observations are interpreted within the framework of a predictive meta-model describing stress release in terms of a state-dependent Poisson process. Specific combinations of size and waiting time autocorrelations are identified, alongside combinations of cross-correlations and size and waiting time distributions, that are allowed or excluded within the meta-model. For example, future observations of any ‘quasi-periodic’ glitching pulsar, such as PSR J0537–6910, should not reveal a positive waiting time autocorrelation. The implications for microphysical models of the stress-release process driving pulsar glitches are discussed briefly.

scholarly journals Statistical Estimates of the Pulsar Glitch Activity

Universe ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 8
Author(s):  
Alessandro Montoli ◽  
Marco Antonelli ◽  
Brynmor Haskell ◽  
Pierre Pizzochero
Keyword(s):  
Linear Regression ◽  
Upper Bound ◽  
Bootstrap Method ◽  
Waiting Times ◽  
Statistical Estimates ◽  
Equal Variance ◽  
Linear Fit ◽  
The Moment ◽  
The Bootstrap Method

A common way to calculate the glitch activity of a pulsar is an ordinary linear regression of the observed cumulative glitch history. This method however is likely to underestimate the errors on the activity, as it implicitly assumes a (long-term) linear dependence between glitch sizes and waiting times, as well as equal variance, i.e., homoscedasticity, in the fit residuals, both assumptions that are not well justified from pulsar data. In this paper, we review the extrapolation of the glitch activity parameter and explore two alternatives: the relaxation of the homoscedasticity hypothesis in the linear fit and the use of the bootstrap technique. We find a larger uncertainty in the activity with respect to that obtained by ordinary linear regression, especially for those objects in which it can be significantly affected by a single glitch. We discuss how this affects the theoretical upper bound on the moment of inertia associated with the region of a neutron star containing the superfluid reservoir of angular momentum released in a stationary sequence of glitches. We find that this upper bound is less tight if one considers the uncertainty on the activity estimated with the bootstrap method and allows for models in which the superfluid reservoir is entirely in the crust.

MULTIFRACTAL DETRENDED CROSS-CORRELATION ANALYSIS FOR LARGE-SCALE WAREHOUSE-OUT BEHAVIORS

Fractals ◽  
2015 ◽  
Vol 23 (04) ◽  
pp. 1550044 ◽  
Author(s):  
CAN-ZHONG YAO ◽  
JI-NAN LIN ◽  
XU-ZHOU ZHENG
Keyword(s):  
Correlation Analysis ◽  
Large Scale ◽  
Cross Correlation ◽  
Correlation Property ◽  
Long Term Memory ◽  
Correlation Relationship ◽  
Term Memory ◽  
Wire Rod ◽  
Cross Correlation Analysis

Based on cross-correlation algorithm, we analyze the correlation property of warehouse-out quantity of different warehouses, respectively, and different products of each warehouse. Our study identifies that significant cross-correlation relationship for warehouse-out quantity exists among different warehouses and different products of a warehouse. Further, we take multifractal detrended cross-correlation analysis for warehouse-out quantity among different warehouses and different products of a warehouse. The results show that for the warehouse-out behaviors of total amount, different warehouses and different products of a warehouse significantly follow multifractal property. Specifically for each warehouse, the coupling relationships of rebar and wire rod reveal long-term memory characteristics, no matter for large fluctuation or small one. The cross-correlation effect on long-range memory property among warehouses probably has less to do with product types,and the long-term memory of YZ warehouse is greater than others especially in total amount and wire rod product. Finally, we shuffle and surrogate data to explore the source of multifractal cross-correlation property in logistics system. Taking the total amount of warehouse-out quantity as example, we confirm that the fat-tail distribution of warehouse-out quantity sequences is the main factor for multifractal cross-correlation. Through comparing the performance of the multifractal detrended cross-correlation analysis (MF-DCCA), centered multifractal detrending moving average cross-correlation analysis (MF-X-DMA) algorithms, the forward and backward MF-X-DMA algorithms, we find that the forward and backward MF-X-DMA algorithms exhibit a better performance than the other ones.

Waiting times for M/M systems under state-dependent processor sharing

2008 ◽  
Vol 59 (3-4) ◽  
pp. 297-319 ◽  
Author(s):  
Andreas Brandt ◽  
Manfred Brandt
Keyword(s):  
Waiting Times ◽  
Processor Sharing ◽  
State Dependent

Following the infection dynamics of the tropical trematode Oligogonotylus mayae in its intermediate and definitive hosts for 13 years

2020 ◽  
Vol 94 ◽  
Author(s):  
A.L. May-Tec ◽  
N.A. Herrera-Castillo ◽  
V.M. Vidal-Martínez ◽  
M.L. Aguirre-Macedo
Keyword(s):  
Time Series ◽  
Cross Correlation ◽  
Southern Oscillation ◽  
Fish Host ◽  
Snail Host ◽  
Monthly Data ◽  
Infection Dynamics ◽  
Infection Parameters ◽  
Over Time

Abstract We present a time series of 13 years (2003–2016) of continuous monthly data on the prevalence and mean abundance of the trematode Oligogonotylus mayae for all the hosts involved in its life cycle. We aimed to determine whether annual (or longer than annual) environmental fluctuations affect these infection parameters of O. mayae in its intermediate snail host Pyrgophorus coronatus, and its second and definitive fish host Mayaheros urophthalmus from the Celestun tropical coastal lagoon, Yucatan, Mexico. Fourier time series analysis was used to identify infection peaks over time, and cross-correlation among environmental forcings and infection parameters. Our results suggest that the transmission of O. mayae in all its hosts was influenced by the annual patterns of temperature, salinity and rainfall. However, there was a biannual accumulation of metacercarial stages of O. mayae in M. urophthalmus, apparently associated with the temporal range of the El Niño-Southern Oscillation (five years) and the recovery of the trematode population after a devasting hurricane. Taking O. mayae as an example of what could be happening to other trematodes, it is becoming clear that environmental forcings acting at long-term temporal scales affect the population dynamics of these parasites.

scholarly journals Cryopreservation: The secret of modern preservation of brewer’s yeasts – minireview

2021 ◽  
Vol 67 (1) ◽  
pp. 403-408
Author(s):  
Katarína Hanzalíková ◽  
Petra Kubizniakova ◽  
Lucie Kyselová ◽  
Dagmar Matoulková
Keyword(s):  
Cell Damage ◽  
Cellular Structures ◽  
Biological Functions ◽  
Freezing And Thawing ◽  
Thawing Processes ◽  
Thawing Rate ◽  
Brewer’S Yeasts ◽  
Long Term Preservation ◽  
Stress Accumulation

The aim of the long-term preservation of cells, tissues and organs is to maintain their cellular structures and biological functions for as long as possible. Cryopreservation is a process where biological material is stored and preserved at very low temperatures. However, freezing and thawing processes can cause irreversible cell damage, which is related to formation of ice crystals, osmotic stress, accumulation of reactive forms of oxygen, etc. Therefore the cell viability depends mainly on the freezing rate, the composition of the cryoprotective medium as well as on the thawing rate. Using a suitable cryoprotective medium can increase the viability rate of the yeasts after “revitalization“. Appropriate pre-cultivation before freezing also plays an important role. These facts show that cell freezing and thawing processes must be controlled to avoid cell damage.

scholarly journals Dollar’s Influence on Crude Oil and Gold Based on MF-DPCCA Method

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhonghui Ding ◽  
Kai Shi ◽  
Bin Wang
Keyword(s):  
Correlation Analysis ◽  
Crude Oil ◽  
Cross Correlation ◽  
Combined Effect ◽  
Analysis Method ◽  
Correlation Relationship ◽  
Cross Correlation Analysis ◽  
Correlation Analysis Method ◽  
Phase Randomization

This paper analyzed the influence of dollar on crude oil and gold based on the multifractal detrended partial cross-correlation analysis method. It showed that affected by the dollar, the crude oil and gold markets have a partial cross-correlation relationship which is stronger than their own cross-correlation. The partial cross-correlation is long-term and has multifractal characteristics. Through shuffled and Fourier-phase randomization, it is found that this multifractal feature is caused by the combined effect of the long-term cross-correlation between the returns and the fluctuation fat-tailed distribution, where the influence of the fat-tailed distribution is slightly greater than that of the long-term cross-correlation between the returns.

scholarly journals Sundew-Inspired Adhesive Hydrogel Threads through Reversible Complexation of Polyphenol and Boronic Acid

2021 ◽  
Vol 11 (18) ◽  
pp. 8591
Author(s):  
Jae Hyuk Choi ◽  
Donghee Son ◽  
Mikyung Shin
Keyword(s):  
Boronic Acid ◽  
Skin Wound ◽  
Body Fluids ◽  
The Body ◽  
Wound Dressings ◽  
Suture Materials ◽  
Wound Site ◽  
Long Term Stability ◽  
State Dependent

Adhesive hydrogels have been utilized as tissue sealants, hemostatic agents, and wound dressings, with the aim of replacing conventional sutures. To prevent immune response and serious inflammation from those hydrogels after sealing, natural biocompatible polysaccharides are widely used as a component of the hydrogels. However, the weak mechanical strength, insufficient adhesiveness, and rapid dissociation of the hydrogels necessitates additional suturing at the wound site. In this study, we report on a solid polysaccharide thread reversibly crosslinked with boronic acid-polyphenol complexation and its adhesive gelation for complete tissue sealing without additional suturing. The polysaccharide adhesive suture threads demonstrated long-term stability, which is useful when used for skin wound suturing. Specifically, their robust adhesion property occurred as soon as the threads were soaked, attaining a swollen hydrogel state, dependent on the presence of body fluids after suturing. Moreover, the pH of the body fluids affects the viscoelasticity and adhesiveness of the hydrogels in order to ensure a tight sealing. Therefore, we expect that these pH-responsive adhesive threads would be promising for the development of on-demand functional suture materials.

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