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Approximate entropy

Zhi-Gang Shao
The complexity of the climate of the past 122;000 years and recent 2000 years was investigated by analyzing the δ (18) O records of ice cores based on the sample entropy (SampEn) method and Lempel-Ziv (LZ) complexity. In using SampEn method, the climate complexity is measured by the sample entropy, which is a modified approximate entropy defined in terms of the occurring probability of new modes in a record. A larger sample entropy reflects a higher probability to spot a new mode in the data, and in this sense signals a larger complexity of the sample...
June 23, 2017: Scientific Reports
H Sotirakis, A Kyvelidou, N Stergiou, V Hatzitaki
Previously we have demonstrated that the effect of aging on posture and gaze active tracking of a visual target moving in the horizontal direction is dependent on target's complexity. In this study, we asked whether a similar phenomenon is present when tracking a visual target moving with varying complexity in the vertical direction. Ten young (22.98±2.9years) and 10 older adults (72.45±4.72years) tracked for 120s, a visual target moving vertically by shifting their bodyweight in the anterior-posterior direction...
June 16, 2017: Neuroscience Letters
Bridget Salna, Abdelkrim Benabbas, Douglas Russo, Paul M Champion
A proper description of proton donor-acceptor (D-A) distance fluctuations is crucial for understanding tunneling in proton-coupled electron transport (PCET). The typical harmonic approximation for the D-A potential results in a Gaussian probability distribution, which does not appropriately reflect the electronic repulsion forces that increase the energetic cost of sampling shorter D-A distances. Because these shorter distances are the primary channel for thermally activated tunneling, the analysis of tunneling kinetics depends sensitively on the inherently anharmonic nature of the D-A interaction...
June 19, 2017: Journal of Physical Chemistry. B
Y Adiguzel
Based on the Shannon's information communication theory, information amount of the entire length of a polymeric macromolecule can be calculated in bits through adding the entropies of each building block. Proteins, DNA and RNA are such macromolecules. When only the building blocks' variation is considered as the source of entropy, there is seemingly lower information in case of the protein if this approach is applied directly on a protein of specific size and the coding sequence size of the mRNA corresponding to the particular length of the protein...
June 15, 2017: Bio Systems
Yuriy Shevchenko, Konstantin Nefedev, Yutaka Okabe
We use a Monte Carlo simulation to study the diluted antiferromagnetic Ising model on frustrated lattices including the pyrochlore lattice to show the dilution effects. Using the Wang-Landau algorithm, which directly calculates the energy density of states, we accurately calculate the entropy of the system. We discuss the nonmonotonic dilution concentration dependence of residual entropy for the antiferromagnetic Ising model on the pyrochlore lattice, and compare it to the generalized Pauling approximation proposed by Ke et al...
May 2017: Physical Review. E
Robert A Evarestov, Andrei V Bandura, Vitaly V Porsev, Alexey V Kovalenko
Hybrid density functional theory calculations were performed for the first time on structure, stability, phonon frequencies, and thermodynamic functions of hafnia-based single-wall nanotubes. The nanotubes were rolled up from the thin free layers of cubic and tetragonal phases of HfO2 . It was shown that the most stable HfO2 single-wall nanotubes can be obtained from hexagonal (111) layer of the cubic phase. Phonon frequencies have been calculated for different HfO2 nanolayers and nanotubes to prove the local stability and to find the thermal contributions to their thermodynamic functions...
June 15, 2017: Journal of Computational Chemistry
Chuyao Jian, Miaoluan Wei, Jie Luo, Jiayin Lin, Wen Zeng, Weitian Huang, Rong Song
The performance of the masticatory muscle is frequently affected and presents high heterogeneity poststroke. Surface electromyography (EMG) is widely used to quantify muscle movement patterns. However, only a few studies applied EMG analysis on the research of masticatory muscle activities poststroke, and most of which used single parameter-root mean squares (RMS). The aim of this study was to fully investigate the performance of masticatory muscle at different head positions in healthy subjects and brainstem stroke patients with multiparameter EMG analysis...
2017: Frontiers in Neurology
David Cuesta-Frau, Pau Miró-Martínez, Jorge Jordán Núñez, Sandra Oltra-Crespo, Antonio Molina Picó
This paper evaluates the performance of first generation entropy metrics, featured by the well known and widely used Approximate Entropy (ApEn) and Sample Entropy (SampEn) metrics, and what can be considered an evolution from these, Fuzzy Entropy (FuzzyEn), in the Electroencephalogram (EEG) signal classification context. The study uses the commonest artifacts found in real EEGs, such as white noise, and muscular, cardiac, and ocular artifacts. Using two different sets of publicly available EEG records, and a realistic range of amplitudes for interfering artifacts, this work optimises and assesses the robustness of these metrics against artifacts in class segmentation terms probability...
May 31, 2017: Computers in Biology and Medicine
Chan-Hee Lee, Jung-Hee Lee, Jang-Won Son, Ung Kim, Jong-Seon Park, Jeon Lee, Dong-Gu Shin
BACKGROUND: Heart rate variability (HRV) analysis is an important clinical tool for characterising cardiac autonomic status. We sought to determine the normative values and characteristics of the HRV parameters derived from a short-term study in Koreans and to determine their clinical role in predicting mortality. METHODS: A total of 1828 consecutive patients (range 20-84 years, men 64.8%) with no serious comorbid conditions were recruited. The RR intervals from 10-minute electrocardiograms were used for computation of the following HRV parameters: conventional time- and frequency-domain measures and nonlinear measures...
May 17, 2017: Heart, Lung & Circulation
Zuojin Li, Liukui Chen, Jun Peng, Ying Wu
Fatigued driving is a major cause of road accidents. For this reason, the method in this paper is based on the steering wheel angles (SWA) and yaw angles (YA) information under real driving conditions to detect drivers' fatigue levels. It analyzes the operation features of SWA and YA under different fatigue statuses, then calculates the approximate entropy (ApEn) features of a short sliding window on time series. Using the nonlinear feature construction theory of dynamic time series, with the fatigue features as input, designs a "2-6-6-3" multi-level back propagation (BP) Neural Networks classifier to realize the fatigue detection...
May 25, 2017: Sensors
Meagan A Cauble, Matthew J Muckley, Ming Fang, Jeffrey A Fessler, Kathleen Welch, Edward D Rothman, Bradford G Orr, Le T Duong, Mark M Banaszak Holl
The impact of estrogen depletion and drug treatment on type I collagen fibril nanomorphology and collagen fibril packing (microstructure) was evaluated by atomic force microscopy (AFM) using an ovariectomized (OVX) rabbit model of estrogen deficiency induced bone loss. Nine month-old New Zealand white female rabbits were treated as follows: sham-operated (Sham; n = 11), OVX + vehicle (OVX + Veh; n = 12), OVX + alendronate (ALN, 600 μg/kg/wk., s.c.; n = 12), and OVX + cathepsin-K inhibitor L-235 (CatKI, 10 mg/kg, daily, p...
December 2016: Bone Reports
Iker Malaina, Luis Martinez, Roberto Matorras, Carlos Bringas, Larraitz Aranburu, Luis Fernández-Llebrez, Leire Gonzalez, Itziar Arana, Martín-Blas Pérez, Ildefonso Martínez de la Fuente
Preterm delivery affects about one tenth of human births and is associated with an increased perinatal morbimortality as well as with remarkable costs. Even if there are a number of predictors and markers of preterm delivery, none of them has a high accuracy. In order to find quantitative indicators of the immediacy of labor, 142 cardiotocographies (CTG) recorded from women consulting because of suspected threatened premature delivery with gestational ages comprehended between 24 and 35 weeks were collected and analyzed...
2017: PloS One
Andrew E Teschendorff, Tariq Enver
The ability to quantify differentiation potential of single cells is a task of critical importance. Here we demonstrate, using over 7,000 single-cell RNA-Seq profiles, that differentiation potency of a single cell can be approximated by computing the signalling promiscuity, or entropy, of a cell's transcriptome in the context of an interaction network, without the need for feature selection. We show that signalling entropy provides a more accurate and robust potency estimate than other entropy-based measures, driven in part by a subtle positive correlation between the transcriptome and connectome...
June 1, 2017: Nature Communications
Christopher J Moore, Tom Marchant
Reconstructive volumetric imaging permeates medical practice because of its apparently clear depiction of anatomy. However, the tell tale signs of abnormality and its delineation for treatment demand experts work at the threshold of visibility for hints of structure. Hitherto, a suitable assistive metric that chimes with clinical experience has been absent. This paper develops the complexity measure approximate entropy (ApEn) from its one-dimensional physiological origin into a three-dimensional (3D) algorithm to fill this gap...
May 30, 2017: Physics in Medicine and Biology
Ahmed Almazroa, Sami Alodhayb, Kaamran Raahemifar, Vasudevan Lakshminarayanan
We introduce here a new technique for segmenting optic cup using two-dimensional fundus images. Cup segmentation is the most challenging part of image processing of the optic nerve head due to the complexity of its structure. Using the blood vessels to segment the cup is important. Here, we report on blood vessel extraction using first a top-hat transform and Otsu's segmentation function to detect the curves in the blood vessels (kinks) which indicate the cup boundary. This was followed by an interval type-II fuzzy entropy procedure...
2017: Clinical Ophthalmology
Heinz-Jürgen Schmidt, Andreas Hauser, Andre Lohmann, Johannes Richter
The high temperature expansion (HTE) of the specific heat of a spin system fails at low temperatures, even if it is combined with a Padé approximation. On the other hand, we often have information about the low-temperature asymptotics (LTA) of the system. Interpolation methods combine both kind of information, HTE and LTA, in order to obtain an approximation of the specific heat that holds for the whole temperature range. Here we revisit the entropy method that has been previously published and propose two variants that better cope with problems of the entropy method for gapped systems...
April 2017: Physical Review. E
G P Beretta, Omar Al-Abbasi, M R von Spakovsky
The steepest entropy ascent (SEA) dynamical principle provides a general framework for modeling the dynamics of nonequilibrium (NE) phenomena at any level of description, including the atomistic one. It has recently been shown to provide a precise implementation and meaning to the maximum entropy production principle and to encompass many well-established theories of nonequilibrium thermodynamics into a single unifying geometrical framework. Its original formulation in the framework of quantum thermodynamics (QT) assumes the simplest and most natural Fisher-Rao metric to geometrize from a dynamical standpoint the manifold of density operators, which represent the thermodynamic NE states of the system...
April 2017: Physical Review. E
Ulisse Ferrari, Tomoyuki Obuchi, Thierry Mora
The principle of maximum entropy provides a useful method for inferring statistical mechanics models from observations in correlated systems, and is widely used in a variety of fields where accurate data are available. While the assumptions underlying maximum entropy are intuitive and appealing, its adequacy for describing complex empirical data has been little studied in comparison to alternative approaches. Here, data from the collective spiking activity of retinal neurons is reanalyzed. The accuracy of the maximum entropy distribution constrained by mean firing rates and pairwise correlations is compared to a random ensemble of distributions constrained by the same observables...
April 2017: Physical Review. E
Ridha Djemal, Khalil AlSharabi, Sutrisno Ibrahim, Abdullah Alsuwailem
Autism spectrum disorder (ASD) is a type of neurodevelopmental disorder with core impairments in the social relationships, communication, imagination, or flexibility of thought and restricted repertoire of activity and interest. In this work, a new computer aided diagnosis (CAD) of autism ‎based on electroencephalography (EEG) signal analysis is investigated. The proposed method is based on discrete wavelet transform (DWT), entropy (En), and artificial neural network (ANN). DWT is used to decompose EEG signals into approximation and details coefficients to obtain EEG subbands...
2017: BioMed Research International
Ying Yuan, Jie Wang, Dongyu Wu, Xiaobo Huang, Weiqun Song
BACKGROUND: Swallowing apraxia is characterized by impaired volitional swallowing but relatively preserved reflexive swallowing. Few studies are available on the effectiveness of behavioral therapy and management of the condition. OBJECTIVE: This study aimed to investigate the effect of transcranial direct current stimulation (tDCS) on swallowing apraxia and cortical activation in stroke patients. METHODS: The study included three inpatients (age 48-70 years; 1 male, 2 females; duration of stroke, 35-55 d) with post-stroke swallowing apraxia and six age-matched healthy subjects (age 45-65 years; 3 males, 3 females)...
May 5, 2017: Topics in Stroke Rehabilitation
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