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Approximate entropy

Eric Detmar, Simin Yazdi Nezhad, Ulrich K Deiters
Extensive Monte Carlo simulations were performed for (neon + krypton) mixtures for temperatures between 200 and 600 K and pressures up to 1 GPa, using Lennard-Jones potentials to describe the intermolecular interactions. The residual entropies were obtained via Widom's insertion method as well as by an integration technique. At high pressures, the residual entropy is, to a very good approximation, a linear function of 1/λ_a, the reciprocal value of the average Monte Carlo displacement parameter that gives the acceptance ratio "a" for translational moves...
July 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hui Li, Janamejaya Chowdhary, Lei Huang, Xibing He, Alexander D MacKerell, Benoît Roux
Additive force fields are designed to account for induced electronic polarization in a mean-field average way using effective empirical fixed charges. The limitation of this approximation is cause for serious concerns, particularly in the case of lipid membranes, where the molecular environment undergoes dramatic variations over microscopic length scales. A polarizable force field based on the classical Drude oscillator offers a practical and computationally efficient framework for an improved representation of electrostatic interactions in molecular simulations...
July 21, 2017: Journal of Chemical Theory and Computation
Angeliki Papana, Catherine Kyrtsou, Dimitris Kugiumtzis, Cees Diks
Different resampling methods for the null hypothesis of no Granger causality are assessed in the setting of multivariate time series, taking into account that the driving-response coupling is conditioned on the other observed variables. As appropriate test statistic for this setting, the partial transfer entropy (PTE), an information and model-free measure, is used. Two resampling techniques, time-shifted surrogates and the stationary bootstrap, are combined with three independence settings (giving a total of six resampling methods), all approximating the null hypothesis of no Granger causality...
2017: PloS One
Juan Bolea, Jesús Lázaro, Eduardo Gil, Eva Rovira, José M Remartínez, Pablo Laguna, Esther Pueyo, Augusto Navarro, Raquel Bailón
Prophylactic treatment has been proved to reduce hypotension incidence after spinal anesthesia during cesarean labor. However, the use of pharmacological prophylaxis could carry out undesirable side-effects on mother and fetus. Thus, the prediction of hypotension becomes an important challenge. Hypotension events are hypothesized to be related to a malfunctioning of autonomic nervous system (ANS) regulation of blood pressure. In this work, ANS responses to positional changes of 51 pregnant women programmed for a cesarean labor were explored for hypotension prediction...
July 11, 2017: Annals of Biomedical Engineering
Yue Li, Devesh K Jha, Asok Ray, Thomas A Wettergren
This paper presents information-theoretic performance analysis of passive sensor networks for detection of moving targets. The proposed method falls largely under the category of data-level information fusion in sensor networks. To this end, a measure of information contribution for sensors is formulated in a symbolic dynamics framework. The network information state is approximately represented as the largest principal component of the time series collected across the network. To quantify each sensor's contribution for generation of the information content, Markov machine models as well as x-Markov (pronounced as cross-Markov) machine models, conditioned on the network information state, are constructed; the difference between the conditional entropies of these machines is then treated as an approximate measure of information contribution by the respective sensors...
July 6, 2017: IEEE Transactions on Cybernetics
Massimo Mischi, Chuan Chen, Tanya Ignatenko, Hinke de Lau, Beijing Ding, Guid S Oei, Chiara Rabotti
OBJECTIVE: Preterm birth is a large-scale clinical problem involving over 10% infants. Diagnostic means for timely risk assessment are lacking and the underlying physiological mechanisms unclear. To improve the evaluation of pregnancy before term, we introduce dedicated entropy measures derived from a single-channel electrohysterogram (EHG). METHODS: The estimation of Approximate Entropy (ApEn) and Sample Entropy (SampEn) is adjusted to monitor variations in the regularity of single-channel EHG recordings, reflecting myoelectrical changes due to pregnancy progression...
July 10, 2017: IEEE Transactions on Bio-medical Engineering
Xuemei Zhang, Yanxian Lin, Neil A Eschmann, Hongjun Zhou, Jennifer N Rauch, Israel Hernandez, Elmer Guzman, Kenneth S Kosik, Songi Han
Nonmembrane-bound organelles that behave like liquid droplets are widespread among eukaryotic cells. Their dysregulation appears to be a critical step in several neurodegenerative conditions. Here, we report that tau protein, the primary constituent of Alzheimer neurofibrillary tangles, can form liquid droplets and therefore has the necessary biophysical properties to undergo liquid-liquid phase separation (LLPS) in cells. Consonant with the factors that induce LLPS, tau is an intrinsically disordered protein that complexes with RNA to form droplets...
July 2017: PLoS Biology
Jianbing Shen, Jianteng Peng, Xingping Dong, Ling Shao, Fatih Porikli
A novel energy minimization method for general higher-order binary energy functions is proposed in this paper. We first relax a discrete higher-order function to a continuous one, and use the Taylor expansion to obtain an approximate lower-order function, which is optimized by the quadratic pseudo-boolean optimization (QPBO) or other discrete optimizers. The minimum solution of this lower-order function is then used as a new local point, where we expand the original higher-order energy function again. Our algorithm does not restrict to any specific form of the higher-order binary function or bring in extra auxiliary variables...
July 3, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
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...
July 27, 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...
July 11, 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...
September 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
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