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Inverse dynamic

Subhajit Paul, Subir K Das
Via event-driven molecular dynamics simulations we study kinetics of clustering in assemblies of inelastic particles in various space dimensions. We consider two models, viz., the ballistic aggregation model (BAM) and the freely cooling granular gas model (GGM), for each of which we quantify the time dependence of kinetic energy and average mass of clusters (that form due to inelastic collisions). These quantities, for both the models, exhibit power-law behavior, at least in the long time limit. For the BAM, corresponding exponents exhibit strong dimension dependence and follow a hyperscaling relation...
March 2018: Physical Review. E
M Xu, M R Paul
We explore the spatiotemporal dynamics of the spectrum of covariant Lyapunov vectors for chaotic Rayleigh-Bénard convection. We use the inverse participation ratio to quantify the amount of spatial localization of the covariant Lyapunov vectors. The covariant Lyapunov vectors are found to be spatially localized at times when the instantaneous covariant Lyapunov exponents are large. The spatial localization of the Lyapunov vectors often occurs near defect structures in the fluid flow field. There is an overall trend of decreasing spatial localization of the Lyapunov vectors with increasing index of the vector...
March 2018: Physical Review. E
Itai Pinkoviezky, Iain D Couzin, Nir S Gov
Collective decision-making regarding direction of travel is observed during natural motion of animal and cellular groups. This phenomenon is exemplified, in the simplest case, by a group that contains two informed subgroups that hold conflicting preferred directions of motion. Under such circumstances, simulations, subsequently supported by experimental data with birds and primates, have demonstrated that the resulting motion is either towards a compromise direction or towards one of the preferred targets (even when the two subgroups are equal in size)...
March 2018: Physical Review. E
M V Chushnyakova, I I Gontchar
We study the effect of backscattering of the Brownian particles as they escape out of a metastable state overcoming the potential barrier. For this aim, we model this process numerically using the Langevin equations. This modeling is performed for the wide range of the friction constant covering both the energy and spatial diffusion regimes. It is shown how the influence of the descent stage on the quasistationary decay rate gradually disappears as the friction constant decreases. It is found that, in the energy diffusion regime, the rescattering absents and the descent stage does not influence the decay rate...
March 2018: Physical Review. E
Mahdi Akbari, Mojtaba Shariaty-Niassar, Takeshi Matsuura, Ahmad Fauzi Ismail
Although polymeric membranes find important role in water and waste water treatment in recent years, their fouling is still an important problem. Application of hydrophilic nanoparticles (NPs) is one of the proposed methods for reducing fouling of membranes but their dispersion and stability in hydrophobic polymer matrix is challenging. In this study Janus functionalization of the NPs was introduced as a promising technique toward achieving this goal. Polysulfone (PSf) membranes containing various concentrations of graphene oxide (GO) nanosheets and Janus graphene oxide (Janus GO) nanosheets (as additives) were fabricated via phase inversion...
May 15, 2018: Journal of Colloid and Interface Science
Spencer T Brinker, Steven P Kearney, Thomas J Royston, Dieter Klatt
The mechanical properties of tissue are sensitive to pathological changes, which is the basis for using dynamic elastography as a diagnostic tool. The purpose of this study is a concurrent cross-modality comparison of two dynamic elastography methods, Magnetic Resonance Elastography (MRE) and Scanning Laser Doppler Vibrometry (SLDV) using a single vibration source method. Cylindrical soft tissue mimicking specimens of Plastisol and Ecoflex are stimulated with 60, 100, 150, and 250 Hz sinusoidal vibration during imaging...
May 8, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Frances M De Blasio, Robert J Barry
Ongoing EEG activity contributes to ERP outcomes of stimulus processing, and each of these measures is known to undergo (sometimes significant) age-related change. Variation in their relationship across the life-span may thus elucidate mechanisms of normal and pathological ageing. This study assessed the relationships between low-frequency EEG prestimulus brain states, the ERP, and behavioural outcomes in a simple equiprobable auditory Go/NoGo paradigm, comparing these for 20 young (Mage  = 20.4 years) and 20 healthy older (Mage  = 68...
May 15, 2018: International Journal of Psychophysiology
Rebecca Hager, Anastasios A Tsiatis, Marie Davidian
Clinicians often make multiple treatment decisions at key points over the course of a patient's disease. A dynamic treatment regime is a sequence of decision rules, each mapping a patient's observed history to the set of available, feasible treatment options at each decision point, and thus formalizes this process. An optimal regime is one leading to the most beneficial outcome on average if used to select treatment for the patient population. We propose a method for estimation of an optimal regime involving two decision points when the outcome of interest is a censored survival time, which is based on maximizing a locally efficient, doubly robust, augmented inverse probability weighted estimator for average outcome over a class of regimes...
May 18, 2018: Biometrics
Chia-Yu Yang, Yuan-Ming Yeh, Hai-Ying Yu, Chia-Yin Chin, Chia-Wei Hsu, Hsuan Liu, Po-Jung Huang, Song-Nian Hu, Chun-Ta Liao, Kai-Ping Chang, Yu-Liang Chang
Oral squamous cell carcinoma (OSCC) is a highly aggressive cancer and the fourth leading malignancy among males in Taiwan. Some pathogenic bacteria are associated with periodontitis and oral cancer. However, the comprehensive profile of the oral microbiome during the cancer's progression from the early stage to the late stage is still unclear. We profiled the oral microbiota and identified bacteria biomarkers associated with OSCC. The microbiota of an oral rinse from 51 healthy individuals and 197 OSCC patients at different stages were investigated using 16S rRNA V3V4 amplicon sequencing, followed by bioinformatics and statistical analyses...
2018: Frontiers in Microbiology
Jan Dvorak, Le Wang, Tingting Zhu, Chad M Jorgensen, Karin R Deal, Xiongtao Dai, Matthew W Dawson, Hans-Georg Müller, Ming-Cheng Luo, Ramesh K Ramasamy, Hamid Dehghani, Yong Q Gu, Bikram S Gill, Assaf Distelfeld, Katrien M Devos, Peng Qi, Frank M You, Patrick J Gulick, Patrick E McGuire
Homology was searched with genes annotated in the Aegilops tauschii pseudomolecules against genes annotated in the pseudomolecules of tetraploid wild emmer wheat, Brachypodium distachyon, sorghum, and rice. Similar searches were initiated with genes annotated in the rice pseudomolecules. Matrices of colinear genes and rearrangements in their order were constructed. Optical Bionano genome maps were constructed and used to validate rearrangements unique to the wild emmer and Ae. tauschii genomes. Most common rearrangements were short paracentric inversions and short intrachromosomal translocations...
May 16, 2018: Plant Journal: for Cell and Molecular Biology
David Hallac, Sagar Vare, Stephen Boyd, Jure Leskovec
Subsequence clustering of multivariate time series is a useful tool for discovering repeated patterns in temporal data. Once these patterns have been discovered, seemingly complicated datasets can be interpreted as a temporal sequence of only a small number of states, or clusters . For example, raw sensor data from a fitness-tracking application can be expressed as a timeline of a select few actions ( i.e. , walking, sitting, running). However, discovering these patterns is challenging because it requires simultaneous segmentation and clustering of the time series...
August 2017: KDD: Proceedings
David Hallac, Youngsuk Park, Stephen Boyd, Jure Leskovec
Many important problems can be modeled as a system of interconnected entities, where each entity is recording time-dependent observations or measurements. In order to spot trends, detect anomalies, and interpret the temporal dynamics of such data, it is essential to understand the relationships between the different entities and how these relationships evolve over time. In this paper, we introduce the time-varying graphical lasso (TVGL) , a method of inferring time-varying networks from raw time series data...
August 2017: KDD: Proceedings
Benjamin T Martin, Stephan B Munch, Andrew M Hein
Ecologists have long sought to understand the dynamics of populations and communities by deriving mathematical theory from first principles. Theoretical models often take the form of dynamical equations that comprise the ecological processes (e.g. competition, predation) believed to govern system dynamics. The inverse of this approach-inferring which processes and ecological interactions drive observed dynamics-remains an open problem in ecology. Here, we propose a way to attack this problem using a machine learning method known as symbolic regression, which seeks to discover relationships in time-series data and to express those relationships using dynamical equations...
May 16, 2018: Proceedings. Biological Sciences
Alex P Gaiduk, Jeffrey A Gustafson, Francois Gygi, Giulia Galli
We carried out first-principles simulations of liquid water at ambient conditions using a dielectric-dependent hybrid functional, where the fraction of exact exchange is set equal to the inverse of the high-frequency dielectric constant of the liquid. We found excellent agreement with experiment for the oxygen-oxygen partial correlation function at the experimental equilibrium density and 311±3 K. Other structural and dynamical properties such as the diffusion coefficient, molecular dipole moments, and vibrational spectra, are also in good agreement with experiment...
May 16, 2018: Journal of Physical Chemistry Letters
Xie Zhang, Jimmy-Xuan Shen, Chris G Van de Walle
Hybrid perovskites such as MAPbI3 (MA=CH3 NH3 ) exhibit a unique spin texture. The spin texture (as calculated within the Rashba effective model) has been suggested to be responsible for a suppression of radiative recombination due to a mismatch of spins at the band edges. Here we compute the spin texture from first principles and demonstrate that it does not suppress recombination. The exact spin texture is dominated by the inversion asymmetry of the local electrostatic potential, which is determined by the structural distortion induced by the MA molecule...
May 15, 2018: Journal of Physical Chemistry Letters
Elaheh Sedghamiz, Majid Moosavi
The surface properties of three symmetric linear tricationic ionic liquids (LTILs) with the common anion, bis(trifluoromethylsulfonyl)imide ([NTf2]-), were studied using atomistic molecular dynamics simulation and identification of the truly interfacial molecules (ITIM) analysis. A refined version of the CL&P force field with the partial charges based on quantum calculations for isolated ion quartets was used to calculate the number densities, orientation of the cations, charge densities and surface tensions...
May 15, 2018: Physical Chemistry Chemical Physics: PCCP
Nelmary Roas-Escalona, Yhan Williams, Eliandreina Cruz-Barrios, Jhoan Toro-Mendoza
The combined effect of viscosity ratio, interfacial tension, and disperse phase density on the process of droplet formation during emulsification was evaluated. For that aim, emulsification by ultrasonication of oil/water systems with viscosity ratios between 1 and 600, with and without surfactant were performed. The time evolution of the average droplet size was estimated by dynamic light scattering measurements. For viscosity ratios between 1 and 200 in presence of surfactant, our results partly reproduce those of the intriguing U-type reported in the literature...
May 14, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Yuri Kwon, Ji-Won Kim, Jae-Hoon Heo, Hyeong-Min Jeon, Eui-Bum Choi, Gwang-Moon Eom
BACKGROUND: The sitting in an awkward posture for a prolonged time may lead to spinal or musculoskeletal disease. It is important to investigate the joint loads at spine while sitting. OBJECTIVE: The purpose of this study was to investigate the joint moment and antero-posterior (AP) reaction force at cervico-thoracic and lumbosacral joint for various sitting postures. METHODS: Twenty healthy males participated in this study. Six sitting postures were defined from three spinal curvatures (slump, flat, and lordosis) and two arm postures (arms-on-chest and arms-forward)...
April 24, 2018: Technology and Health Care: Official Journal of the European Society for Engineering and Medicine
Mohammadali Rahmati Seyed, Rostami Mostafa, Beigzadeh Borhan
The parametric optimization techniques have been widely employed to predict human gait trajectories; however, their applications to reveal the other aspects of gait are questionable. The aim of this study is to investigate whether or not the gait prediction model is able to justify the movement trajectories for the higher average velocities. A planar, seven-segment model with sixteen muscle groups was used to represent human neuro-musculoskeletal dynamics. At first, the joint angles, ground reaction forces (GRFs) and muscle activations were predicted and validated for normal average velocity (1...
April 27, 2018: Technology and Health Care: Official Journal of the European Society for Engineering and Medicine
Naftali R Smith, Alex Kamenev, Baruch Meerson
We study the short-time distribution P(H,L,t) of the two-point two-time height difference H=h(L,t)-h(0,0) of a stationary Kardar-Parisi-Zhang interface in 1+1 dimension. Employing the optimal-fluctuation method, we develop an effective Landau theory for the second-order dynamical phase transition found previously for L=0 at a critical value H=H_{c}. We show that |H| and L play the roles of inverse temperature and external magnetic field, respectively. In particular, we find a first-order dynamical phase transition when L changes sign, at supercritical H...
April 2018: Physical Review. E
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