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Variability + Entropy

Patrick P Potts, Peter Samuelsson
Fluctuation relations are powerful equalities that hold far from equilibrium. However, the standard approach to include measurement and feedback schemes may become inapplicable in certain situations, including continuous measurements, precise measurements of continuous variables, and feedback induced irreversibility. Here we overcome these shortcomings by providing a recipe for producing detailed fluctuation relations. Based on this recipe, we derive a fluctuation relation which holds for arbitrary measurement and feedback control...
November 23, 2018: Physical Review Letters
Norman Scheel, Eric Franke, Thomas F Münte, Amir Madany Mamlouk
Spontaneous fluctuations of resting-state functional connectivity have been studied in many ways, but grasping the complexity of brain activity has been difficult. Dimensional complexity measures, which are based on Eigenvalue (EV) spectrum analyses (e.g., Ω entropy) have been successfully applied to EEG data, but have not been fully evaluated on functional MRI recordings, because only through the recent introduction of fast multiband fMRI sequences, feasable temporal resolutions are reached. Combining the Eigenspectrum normalization of Ω entropy and the scalable architecture of the so called Multivariate Principal Subspace Entropy (MPSE) leads to a new complexity measure, namely normalized MPSE (nMPSE)...
2018: Frontiers in Human Neuroscience
L Hunakova, M Zvarik, K Majerova, M Mestanik, V Bella, I Tonhajzerova
Vagal activity of patients with metastatic or recurrent breast cancer can predict their survival and can be altered by behavioral, pharmacological, and surgical interventions. Tumor oxygenation is important in defining the cellular metabolic microenvironment of human malignancies, O2-depleted areas coincide with nutrient and energy deprivation and with a hostile metabolic microenvironment. In our work we simultaneously measured two oxygen-sensitive parameters in breast cancer patients, blood oxygen saturation (SpO2) and transcutaneous O2 partial pressure (tcpO2) in breast tissue...
October 13, 2018: Neoplasma
Anat V Lubetzky, Bryan D Hujsak, Jennifer L Kelly, Gene Fu, Ken Perlin
BACKGROUND: Deficits in sensory integration and fear of falling in complex environments contribute to decreased participation of adults with vestibular disorders. With recent advances in virtual reality technology, head-mounted displays are affordable and allow manipulation of the environment to test postural responses to visual changes. OBJECTIVES: To develop an assessment of static and dynamic balance with the Oculus Rift and (1) to assess test-retest reliability of each scene in adults with and without vestibular hypofunction; (2) to describe changes in directional path and sample entropy in response to changes in visuals and surface and compare between groups; and (3) to evaluate the relation between balance performance and self-reported disability and balance confidence...
November 2018: PM & R: the Journal of Injury, Function, and Rehabilitation
William Johnston, Martin O'Reilly, Ciara Duignan, Mairead Liston, Rod McLoughlin, Garrett F Coughlan, Brian Caulfield
BACKGROUND: Concussion is one of the most common sports-related injuries, with little understood about the modifiable and nonmodifiable risk factors. Researchers have yet to evaluate the association between modifiable sensorimotor function variables and concussive injury. PURPOSE: To investigate the association between dynamic balance performance, a discrete measure of sensorimotor function, and concussive injuries. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3...
December 3, 2018: American Journal of Sports Medicine
Vaclav Klika, Andrew L Krause
Phenomenological coefficients in linear non-equilibrium thermodynamics have been considered to be independent, apart from restrictions due to the Onsager-Casimir reciprocal relations and the requirement to have non-negative entropy production. Recently it has been shown that functional constraints between these coefficients may hold, restricting their dependence on state variables, especially in the case of coupled phenomena. Here we demonstrate that such restrictions require only mild assumptions on the system of interest, and are in fact much more constraining than previously reported...
December 1, 2018: Journal of Physical Chemistry Letters
Gregory R Hart, Andrew L Ferguson
Hepatitis C virus (HCV) afflicts 170 million people and kills 700 000 annually. Vaccination offers the most realistic and cost effective hope of controlling this epidemic, but despite 25 years of research, no vaccine is available. A major obstacle is HCV's extreme genetic variability and rapid mutational escape from immune pressure. Coupling maximum entropy inference with population dynamics simulations, we have employed a computational approach to translate HCV sequence databases into empirical landscapes of viral fitness and simulate the intrahost evolution of the viral quasispecies over these landscapes...
November 28, 2018: Physical Biology
Ali Azareh, Omid Rahmati, Elham Rafiei-Sardooi, Joel B Sankey, Saro Lee, Himan Shahabi, Baharin Bin Ahmad
Gully erosion susceptibility mapping is a fundamental tool for land-use planning aimed at mitigating land degradation. However, the capabilities of some state-of-the-art data-mining models for developing accurate maps of gully erosion susceptibility have not yet been fully investigated. This study assessed and compared the performance of two different types of data-mining models for accurately mapping gully erosion susceptibility at a regional scale in Chavar, Ilam, Iran. The two methods evaluated were: Certainty Factor (CF), a bivariate statistical model; and Maximum Entropy (ME), an advanced machine learning model...
November 17, 2018: Science of the Total Environment
Zhimin Zhang, Shoushui Wei, Guohun Zhu, Feifei Liu, Yuwen Li, Xiaotong Dong, Chengyu Liu, Feng Liu
OBJECTIVE: Sleep quality helps to reflect on the physical and mental condition, and efficient sleep stage scoring promises considerable advantages to health care. The aim of this study is to propose a simple and efficient sleep classification method based on entropy features and a support vector machine classifier, named SC-En&SVM. APPROACH: Entropy features, including fuzzy measure entropy (FuzzMEn), fuzzy entropy, and sample entropy are applied for the analysis and classification of sleep stages...
November 26, 2018: Physiological Measurement
Tuhin Paul, Kevin G Stanley, Nathaniel D Osgood
Accurate prediction of the motion of objects is a central scientific goal. For deterministic or stochastic processes, models exist which characterize motion with a high degree of reliability. For complex systems, or those where objects have a degree of agency, characterizing motion is far more challenging. The information entropy rate of motion through a discrete space can place a limit on the predictability of even the most complex or history-dependent actor, but the variability in measured encountered locations is inexorably tied to the spatial and temporal resolutions of those measurements...
October 2018: Royal Society Open Science
Sara Lorio, Tim M Tierney, Amy McDowell, Owen J Arthurs, Antoine Lutti, Nikolaus Weiskopf, David W Carmichael
Quantitative proton density (PD) maps measure the amount of free water, which is important for non-invasive tissue characterization in pathology and across lifespan. PD mapping requires the estimation and subsequent removal of factors influencing the signal intensity other than PD. These factors include the T1, T2* relaxation effects, transmit field inhomogeneities, receiver coil sensitivity profile (RP) and the spatially invariant factor that is required to scale the data. While the transmit field can be reliably measured, the RP estimation is usually based on image post-processing techniques due to limitations of its measurement at magnetic fields higher than 1...
November 19, 2018: NeuroImage
Arjun Thapa, Ruidong Wu, Yibo Hu, Yonggang Nie, Paras B Singh, Janak R Khatiwada, Li Yan, Xiaodong Gu, Fuwen Wei
An upsurge in anthropogenic impacts has hastened the decline of the red panda ( Ailurus fulgens ). The red panda is a global conservation icon, but holistic conservation management has been hampered by research being restricted to certain locations and population clusters. Building a comprehensive potential habitat map for the red panda is imperative to advance the conservation effort and ensure coordinated management across international boundaries. Here, we use occurrence records of both subspecies of red pandas from across their entire range to build a habitat model using the maximum entropy algorithm (MaxEnt 3...
November 2018: Ecology and Evolution
Montserrat R Delgado, Carlos O Arean
The thermodynamics of dinitrogen adsorption in faujasite-type zeolites, Na-Y, Ca-Y and Sr-Y, were investigated by means of variable-temperature infrared spectroscopy, a technique that affords determination of the standard adsorption enthalpy (Δ H ⁰) and entropy (Δ S ⁰) from an analysis of the IR spectra recorded over a range of temperatures. The results obtained, taken together with previously reported values for N₂ adsorption on protonic zeolites, revealed a non-linear correlation between Δ H ⁰ and Δ S ⁰...
November 15, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Luis Eduardo Juarez-Orozco, Andrea G Monroy-Gonzalez, Friso M van der Zant, Nick Hoogvorst, Riemer H J A Slart, Remco J J Knol
BACKGROUND: It is thought that heart failure (HF) patients may benefit from the evaluation of mechanical (dys)synchrony, and an independent inverse relationship between myocardial perfusion and ventricular synchrony has been suggested. We explore the relationship between quantitative myocardial perfusion and synchrony parameters when accounting for the presence and extent of fixed perfusion defects in patients with chronic HF. METHODS: We studied 98 patients with chronic HF who underwent rest and stress Nitrogen-13 ammonia PET...
November 15, 2018: Journal of Nuclear Cardiology: Official Publication of the American Society of Nuclear Cardiology
Nathan Harding, Ramil Nigmatullin, Mikhail Prokopenko
We present a novel approach to the study of epidemics on networks as thermodynamic phenomena, quantifying the thermodynamic efficiency of contagions, considered as distributed computational processes. Modelling SIS dynamics on a contact network statistical-mechanically, we follow the maximum entropy (MaxEnt) principle to obtain steady-state distributions and derive, under certain assumptions, relevant thermodynamic quantities both analytically and numerically. In particular, we obtain closed-form solutions for some cases, while interpreting key epidemic variables, such as the reproductive ratio of a SIS model, in a statistical mechanical setting...
December 6, 2018: Interface Focus
Riccardo Pernice, Michal Javorka, Jana Krohova, Barbora Czippelova, Zuzana Turianikova, Alessandro Busacca, Luca Faes
The gold standard method to monitor heart rate variability (HRV) comprises measuring the time series of interbeat interval durations from electrocardiographic (ECG) recordings. However, due to the widespread use, simplicity and usability of photoplethysmographic (PPG) techniques, monitoring pulse rate variability (PRV) from pulse wave recordings has become a viable alternative to standard HRV analysis. The present study investigates the accuracy of PRV, measured as a surrogate of HRV, for the quantification of descriptive indexes computed in the time domain (mean, variance), frequency domain (low-to-high frequency power ratio LF/HF, HF band central frequency) and information domain (entropy, conditional entropy)...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Celine Franco, Anthony Fleury, Bruno Diot, Nicolas Vuillerme
Assessing the amount of attention invested in the control of balance is crucial when evaluating balance abilities. The purpose of the present study was to examine the relevance of applying entropy to human center of foot pressure data to assess attention investment in balance control. To achieve this goal, young healthy adults were tested in a static postural task consisting in standing as immobile as possible with their eyes closed under normal, altered (foam) and improved (ankle-foot orthosis). The center of foot pressure displacements were recorded using a force platform...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Mouad S Azz, Ahsan H Khandoker, Herbert F Jelinek
This study explored the autonomic nervous system (ANS) adaptation in relation to exercise and how this correlates with the ratings of perceived exertion (Borg-RPE) over four ranges 6-8; 9-12; 13-16; 17-20, by using the time domain parameters and the multi-lag Tone-Entropy (T-E) of heart rate variability (HRV). ECG signals were collected from ten subjects who were recruited to participate in a graded exercise protocol on a treadmill. Results showed that SDNN and RMSSD decreased from lower to higher Borg-RPE, indicating a decrease in HRV...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Alberto Porta, Beatrice De Maria, Beatrice Cairo, Emanuele Vaini, Vlasta Bari
The study compares a recently proposed shortterm model-based linear multiscale complexity approach to a single-scale application of the same method and to a model-free nonlinear one based on the computation of conditional entropy with the aim at assessing the complementary information. Comparison was carried out over 24 hours Holter recordings of heart period variability during daytime and nighttime in 12 healthy men (age: 34-55 years). Single-scale methods were able to detect the increased complexity of the cardiac control during nighttime...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
An Nguyen, Sardar Ansari, Mohsen Hooshmand, Kaiwen Lin, Hamid Ghanbari, Jonathan Gryak, Kayvan Najarian
Detection of atrial fibrillation (AFib) using wearable ECG monitors has recently gained popularity. The signal quality of such recordings is often much lower than that of traditional monitoring systems such as Holter monitors. Larger noise contamination can lead to reduced accuracy of the QRS detection which is the basis of the heart rate variability (HRV) analysis. Hence, it is crucial to accurately classify short ECG recording segments for AFib monitoring. A comparative study was conducted to investigate the applicability and performance of a variety of HRV feature extraction methods applied to short single lead ECG recordings to detect AFib...
July 2018: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
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