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Approximate entropy

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
Jin Zhou, Long Chen, C L Philip Chen, Yingxu Wang, Han-Xiong Li
Uncertain data clustering has been recognized as an essential task in the research of data mining. Many centralized clustering algorithms are extended by defining new distance or similarity measurements to tackle this issue. With the fast development of network applications, these centralized methods show their limitations in conducting data clustering in a large dynamic distributed peer-to-peer network due to the privacy and security concerns or the technical constraints brought by distributive environments...
May 2, 2017: IEEE Transactions on Neural Networks and Learning Systems
Verena de Vassimon-Barroso, Aparecida Maria Catai, Marcele Stephanie De Souza Buto, Alberto Porta, Anielle Cristhine De Medeiros Takahashi
BACKGROUND: Adaptive postural control can be impaired in the presence of frailty syndrome, given that this condition causes homeostatic dysregulation in physiological systems. OBJECTIVES: To compare the center of pressure (CoP) displacements of non-frail, pre-frail, and frail elderly subjects in the standing position before and after postural transition of sitting and rising from a chair, using linear and nonlinear methods. METHODS: Forty-two elderly subjects were divided into 3 groups: non-frail (n=15), pre-frail (n=15), and frail (n=12)...
April 9, 2017: Brazilian Journal of Physical Therapy
Yukihiro Kimura, Shuwen Lyu, Akira Okoshi, Koudai Okazaki, Natsuki Nakamura, Akira Ohashi, Takashi Ohno, Manami Kobayashi, Michie Imanishi, Shinichi Takaichi, Michael T Madigan, Zheng-Yu Wang-Otomo
The light harvesting-reaction center (LH1-RC) complex from a new thermophilic purple sulfur bacterium Allochromatium (Alc.) tepidum was isolated and characterized by spectroscopic and thermodynamic analyses. The purified Alc. tepidum LH1-RC complex showed a high thermostability comparable to that of another thermophilic purple sulfur bacterium Thermochromatium tepidum, and spectroscopic characteristics similar to those of a mesophilic bacterium Alc. vinosum. Approximately 4-5 Ca(2+) per LH1-RC were detected by inductively coupled plasma atomic emission spectroscopy and isothermal titration calorimetry...
May 4, 2017: Journal of Physical Chemistry. B
Ferdinand Roelfsema, Rebecca J Yang, Thomas P Olson, Michael J Joyner, Paul Y Takahashi, Johannes D Veldhuis
Context: Exercise elicits incompletely defined adaptations of metabolic and endocrine milieu, including the gonadotropic and the corticotropic axes. Objective: To quantify the impact of acute exercise on coordinate LH and testosterone and ACTH and cortisol secretion in healthy men in relation to age. Participantsand design: Prospectively randomized, within-subject cross-over, study in 23 men, aged 19-77 yr. Subjects underwent rest and 30 min of mixed exercise at 65% of maximal aerobic capacity with 10-min blood sampling between 0700 and 1300 h 2 wks apart...
April 27, 2017: Journal of Clinical Endocrinology and Metabolism
Miha Lukšič, Barbara Hribar-Lee, Orest Pizio
The phase behavior of the continuous shouldered well model fluid proposed by Franzese [J. Mol. Liq. 136 (2007) 267] was examined using the Monte Carlo computer simulations in the grand canonical ensemble. The essential parts of the vapour-liquid and liquid-liquid coexistence envelopes were obtained. The Widom lines departing from coexistence envelopes were calculated using maxima of the fluctuations of the number of particles as a function of chemical potential along various isotherms. The region embracing anomalies in the properties of the model was located using the approximate criterion that involves the excess pair entropy...
February 2017: Journal of Molecular Liquids
G F R Saraiva, A S Ferreira, G M Souza
Research rationale: Studies on plant electrophysiology are mostly focused on specific traits of single cells. Inspired by the complexity of the signaling network in plants and by analogies with neurons in human brains, we have sought for evidences of high complexity in the electrical dynamics of plant signaling and a likely relation with environmental cues. Central methods: An EEG-like standard protocol was adopted for high-resolution measurements of the electrical signal in Glycine max seedlings. The signals were continuously recorded in the same plants before and after the osmotic stimuli with a -2 MPa mannitol solution...
April 27, 2017: Plant Biology
Alberto Porta, Vlasta Bari, Beatrice De Maria, Mathias Baumert
A network physiology approach to evaluate the strength of the directed interactions among cardiac controls at sinoatrial and ventricular levels and respiration (R) is proposed. The network is composed of three nodes (i.e. sinoatrial and ventricular cardiac controls and R) and their activity is exemplified by the variability of heart period (HP), the variability of the duration of the electrical activity of the heart approximated as the temporal distance between Q-wave onset and T-wave end or apex (i.e. QTe or QTa) and thoracic movements respectively...
April 21, 2017: Physiological Measurement
Umberto Marini Bettolo Marconi, Andrea Puglisi, Claudio Maggi
Methods of stochastic thermodynamics and hydrodynamics are applied to a recently introduced model of active particles. The model consists of an overdamped particle subject to Gaussian coloured noise. Inspired by stochastic thermodynamics, we derive from the system's Fokker-Planck equation the average exchanges of heat and work with the active bath and the associated entropy production. We show that a Clausius inequality holds, with the local (non-uniform) temperature of the active bath replacing the uniform temperature usually encountered in equilibrium systems...
April 21, 2017: Scientific Reports
Yunlong Zan, Yong Long, Kewei Chen, Biao Li, Qiu Huang, Grant T Gullberg
PURPOSE: Our previous works have found that quantitative analysis of (123) I-MIBG kinetics in the heart with dynamic single-photon emission computed tomography (SPECT) offers the potential to quantify the innervation integrity at an early stage of left ventricular hypertrophy. However, conventional protocols involving a long acquisition time for dynamic imaging reduce the animal survival rate and thus make longitudinal analysis difficult. The goal of this work was to develop a procedure to reduce the total acquisition time by selecting non-uniform acquisition times for projection views while maintaining the accuracy and precision of estimated physiologic parameters...
April 21, 2017: Medical Physics
Harini Pattabhiraman, Marjolein Dijkstra
Using Monte Carlo simulations and free-energy calculations, we investigate the phase behaviour of a two-dimensional core-corona system. We model this system as particles consisting of an impenetrable hard core of diameter σHD surrounded by a purely repulsive soft corona of diameter δ = 1.95σHD. At low densities, we observe the spontaneous formation of a phase with a stripe texture as well as a honeycomb-like phase driven by both energy and entropy considerations. At high densities, we find that a two-dimensional analogue of the periodic sigma phase, considered as an approximant of dodecagonal quasicrystals, is energetically stabilised with respect to two distinct dodecagonal quasicrystals, namely, a square-triangle tiling and a square-triangle-shield tiling...
April 18, 2017: Soft Matter
Kathryn L Gatford, Beverly Muhlhausler, Lili Huang, Pamela S-L Sim, Claire T Roberts, Johannes D Veldhuis, Chen Chen
Placenta-derived hormones including growth hormone (GH) in humans contribute to maternal adaptation to pregnancy, and intermittent maternal GH administration increases fetal growth in several species. Both patterns and abundance of circulating GH are important for its activity, but their changes during pregnancy have only been reported in humans and rats. The aim of the present study was to characterise circulating profiles and secretory characteristics of GH in non-pregnant female mice and throughout murine pregnancy...
April 12, 2017: Endocrine Connections
Henning Meyerhenke, Martin Nollenburg, Christian Schulz
Drawing large graphs appropriately is an important step for the visual analysis of data from real-world networks. Here we present a novel multilevel algorithm to compute a graph layout with respect to the maxent-stress metric proposed by Gansner et al. (2013) that combines layout stress and entropy. As opposed to previous work, we do not solve the resulting linear systems of the maxent-stress metric with a typical numerical solver. Instead we use a simple local iterative scheme within a multilevel approach...
March 29, 2017: IEEE Transactions on Visualization and Computer Graphics
Julius Koettgen, Tobias Zacherle, Steffen Grieshammer, Manfred Martin
The rate of oxygen ion jumps in a solid oxide depends not only on the activation energy but also on the pre-exponential factor of diffusion. In order to allow a fully ab initio prediction of the oxygen ion conductivity in pure and samarium doped ceria, we calculated the attempt frequency for an oxygen ion jump from first principles combining DFT+U, the NEB method, phonon calculations and the transition state theory. Different definitions of the jump attempt frequency are presented. The equivalence of the Eyring and the Vineyard method is shown without restriction to the Gamma point...
April 12, 2017: Physical Chemistry Chemical Physics: PCCP
Hongqin Yang, Jiuyang Liu, Yanmei Huang, Rui Gao, Bin Tang, Shanshan Li, Jiawei He, Hui Li
Alisertib (MLN8237) is an orally administered inhibitor of Aurora A kinase. This small-molecule inhibitor is under clinical or pre-clinical phase for the treatment of advanced malignancies. The present study provides a detailed characterization of the interaction of MLN8237 with a drug transport protein called human serum albumin (HSA). STD and WaterLOGSY nuclear magnetic resonance (NMR)-binding studies were conducted first to confirm the binding of MLN8237 to HSA. In the ligand orientation assay, the binding sites of MLN8237 were validated through two site-specific spy molecules (warfarin sodium and ibuprofen, which are two known site-selective probes) by using STD and WaterLOGSY NMR competition techniques...
March 30, 2017: Scientific Reports
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