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Nonlinear dynamics

Kara Pham, Emma Turian, Kai Liu, Shuwang Li, John Lowengrub
We consider the nonlinear dynamics of an avascular tumor at the tissue scale using a two-fluid flow Stokes model, where the viscosity of the tumor and host microenvironment may be different. The viscosities reflect the combined properties of cell and extracellular matrix mixtures. We perform a linear morphological stability analysis of the tumors, and we investigate the role of nonlinearity using boundary-integral simulations in two dimensions. The tumor is non-necrotic, although cell death may occur through apoptosis...
March 15, 2018: Journal of Mathematical Biology
Zhen Tian, Jingqi Yuan, Xiang Zhang, Lei Kong, Jingcheng Wang
The coordinated control system (CCS) serves as an important role in load regulation, efficiency optimization and pollutant reduction for coal-fired power plants. The CCS faces with tough challenges, such as the wide-range load variation, various uncertainties and constraints. This paper aims to improve the load tacking ability and robustness for boiler-turbine units under wide-range operation. To capture the key dynamics of the ultra-supercritical boiler-turbine system, a nonlinear control-oriented model is developed based on mechanism analysis and model reduction techniques, which is validated with the history operation data of a real 1000 MW unit...
March 12, 2018: ISA Transactions
Joseph R Cendagorta, Zlatko Bačić, Mark E Tuckerman
We introduce a scheme for approximating quantum time correlation functions numerically within the Feynman path integral formulation. Starting with the symmetrized version of the correlation function expressed as a discretized path integral, we introduce a change of integration variables often used in the derivation of trajectory-based semiclassical methods. In particular, we transform to sum and difference variables between forward and backward complex-time propagation paths. Once the transformation is performed, the potential energy is expanded in powers of the difference variables, which allows us to perform the integrals over these variables analytically...
March 14, 2018: Journal of Chemical Physics
Junhao Liang, Anwarud Din, Tianshou Zhou
While many physical or chemical systems can be modeled by nonlinear Langevin equations (LEs), dynamical analysis of these systems is challenging in the cases of moderate and strong noise. Here we develop a linear approximation scheme, which can transform an often intractable LE into a linear set of binomial moment equations (BMEs). This scheme provides a feasible way to capture nonlinear behaviors in the sense of probability distribution and is effective even when the noise is moderate or big. Based on BMEs, we further develop a noise reduction technique, which can effectively handle tough cases where traditional small-noise theories are inapplicable...
March 14, 2018: Journal of Chemical Physics
David Müller, Andreas Otto, Günter Radons
We show that the output of systems with time-varying delay can exhibit a new kind of chaotic behavior characterized by laminar phases, which are periodically interrupted by irregular bursts. Within each laminar phase the output intensity remains almost constant, but its level varies chaotically from phase to phase. In scalar systems, the periodic dynamics of the lengths and the chaotic dynamics of the intensity levels can be understood and also tuned via two one-dimensional maps, which can be deduced from the nonlinearity of the delay equation and from the delay variation, respectively...
February 23, 2018: Physical Review Letters
Y Wang, S Subhankar, P Bienias, M Łącki, T-C Tsui, M A Baranov, A V Gorshkov, P Zoller, J V Porto, S L Rolston
We report on the experimental realization of a conservative optical lattice for cold atoms with a subwavelength spatial structure. The potential is based on the nonlinear optical response of three-level atoms in laser-dressed dark states, which is not constrained by the diffraction limit of the light generating the potential. The lattice consists of a one-dimensional array of ultranarrow barriers with widths less than 10 nm, well below the wavelength of the lattice light, physically realizing a Kronig-Penney potential...
February 23, 2018: Physical Review Letters
Angus McMullen, Hendrick W de Haan, Jay X Tang, Derek Stein
Measurements and Langevin dynamics simulations of filamentous viruses driven through solid-state nanopores reveal a superlinear rise in the translocation velocity with driving force. The mobility also scales with the length of the virus in a nontrivial way that depends on the force. These dynamics are consequences of the buckling of the leading portion of a virus as it emerges from the nanopore and is put under compressive stress by the viscous forces it encounters. The leading tip of a buckled virus stalls and this reduces the total viscous drag force...
February 16, 2018: Physical Review Letters
Maria Sole Morelli, Alberto Greco, Gaetano Valenza, Alberto Giannoni, Michele Emdin, Enzo Pasquale Scilingo, Nicola Vanello
Brain activations related to the control of breathing are not completely known. The respiratory system is a non-linear system. However, the relationship between neural and respiratory dynamics is usually estimated through linear correlation measures, completely neglecting possible underlying nonlinear interactions. This study evaluate the linear and nonlinear coupling between electroencephalographic (EEG) signal and variations in carbon dioxide (CO2 ) signal related to different breathing task. During a free breathing and a voluntary breath hold tasks, the coupling between EEG power in nine different brain regions in delta (1-3 Hz) and alpha (8-13 Hz) bands and end-tidal CO2 (PET CO2 ) was evaluated...
March 14, 2018: Scientific Reports
Motohisa Osaka
There are some reports that sympathetic nerve activity (SNA) shows a characteristic pattern a few hours before the onset of lethal ventricular arrhythmias. If so, it could be possible to predict sudden cardiac death a few hours in advance of its occurrence. Recently, we reported that a previously unidentified V-trough of SNA is a potential precursor of lethal cardiac events by examining 24-hour ambulatory electrocardiograms in which such an event was recorded by chance. In contrast, the chaotic nature of heart rate variability has been noted recently from the viewpoint of nonlinear dynamics...
2018: Journal of Nippon Medical School, Nippon Ika Daigaku Zasshi
Michelle Livne, Jens K Boldsen, Irene K Mikkelsen, Jochen B Fiebach, Jan Sobesky, Kim Mouridsen
BACKGROUND AND PURPOSE: Stroke imaging is pivotal for diagnosis and stratification of patients with acute ischemic stroke to treatment. The potential of combining multimodal information into reliable estimates of outcome learning calls for robust machine learning techniques with high flexibility and accuracy. We applied the novel extreme gradient boosting algorithm for multimodal magnetic resonance imaging-based infarct prediction. METHODS: In a retrospective analysis of 195 patients with acute ischemic stroke, fluid-attenuated inversion recovery, diffusion-weighted imaging, and 10 perfusion parameters were derived from acute magnetic resonance imaging scans...
March 14, 2018: Stroke; a Journal of Cerebral Circulation
Katherine Rouleau, Monique Bourget, Patrick Chege, Francois Couturier, Paula Godoy-Ruiz, Paul H Grand'Maison, Melanie Henry, Kerling Israel, Videsh Kapoor, Hendra Kurniawan, Louella Lobo, Mahamane Maiga, Samantha Pereira Franca, Lynda Redwood-Campbell, Jamie Rodas, Raman Sohal, Dawit Wondimagegn, Robert Woolard
BACKGROUND AND OBJECTIVES: There is a limited evidentiary base on the development of family medicine in different contexts and countries. The lack of evidence impedes our ability to compare and characterize family medicine models and identify areas of success that have led to the effective provision of care. This paper offers a comparative compilation and analysis of the development of family medicine training programs in seven countries: Brazil, Canada, Ethiopia, Haiti, Indonesia, Kenya, and Mali...
March 8, 2018: Family Medicine
Valessa F Carvalho, Priscilla Bf Soares, Crisnicaw Verissimo, Roberto S Pessoa, Antheunis Versluis, Carlos J Soares
PURPOSE: The purpose of this study was to evaluate mouthguard shock absorption ability, strain, and stress generation during impact on dental implants placed in the anterior maxilla. The mouthguard material was also characterized. MATERIALS AND METHODS: Sixty experimental models were created and divided into six groups (n = 10): implant type, external hexagon (EH) and Morse taper (MT); without and with two mouthguards (MTG), EVA custom-fitted (Ct-MTG) and standard self-adapted (St-MTG)...
March 2018: International Journal of Oral & Maxillofacial Implants
Andreas Venhorst, Dominic P Micklewright, Timothy D Noakes
INTRODUCTION: A three-dimensional framework of centrally regulated and goal-directed exercise behaviour emphasised the integration of distinct sensory-discriminatory, affective-motivational and cognitive-evaluative dimensions that underpin perceived fatigability. This study aimed to capture the complex interdependencies and temporal dynamics in these processes, their interrelations with observed pacing behaviour, performance and biochemical variables as well as their performance level- and competition outcome-dependent variances...
March 12, 2018: Sports Medicine
David J Páez, Olivier Restif, Peggy Eby, Raina K Plowright
Bats provide important ecosystem services such as pollination of native forests; they are also a source of zoonotic pathogens for humans and domestic animals. Human-induced changes to native habitats may have created more opportunities for bats to reside in urban settings, thus decreasing pollination services to native forests and increasing opportunities for zoonotic transmission. In Australia, fruit bats ( Pteropus spp. flying foxes) are increasingly inhabiting urban areas where they feed on anthropogenic food sources with nutritional characteristics and phenology that differ from native habitats...
May 5, 2018: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Nataliya Kraynyukova, Tatjana Tchumatchenko
A hallmark of cortical circuits is their versatility. They can perform multiple fundamental computations such as normalization, memory storage, and rhythm generation. Yet it is far from clear how such versatility can be achieved in a single circuit, given that specialized models are often needed to replicate each computation. Here, we show that the stabilized supralinear network (SSN) model, which was originally proposed for sensory integration phenomena such as contrast invariance, normalization, and surround suppression, can give rise to dynamic cortical features of working memory, persistent activity, and rhythm generation...
March 12, 2018: Proceedings of the National Academy of Sciences of the United States of America
Yueqing Du, Xuewen Shu
We found two kinds of soliton explosions based on the complex Ginzburg-Landau equation without nonlinearity saturation and high-order effects, demonstrating the soliton explosions as an intrinsic property of the dissipative systems. The two kinds of soliton explosions are caused by the dual-pulsing instability and soliton erupting, respectively. The transformation and relationship between the two kinds of soliton explosions are discussed. The parameter space for the soliton explosion in a mode-locked laser cavity is found numerically...
March 5, 2018: Optics Express
E C Welch, S Ya Tochitsky, J J Pigeon, C Joshi
A new method for a long-wave infrared (LWIR), picosecond difference frequency generation (DFG) source using one near-infrared laser and a Raman shifter is experimentally tested and characterized. The signal seed for DFG is a Stokes pulse generated via transient stimulated Raman scattering in a nonlinear medium with a Raman frequency in the 2-20 µm range. A study of the dynamics of the transient Raman regime in liquid C6 D6 has shown that the efficiency of Stokes production can be increased and the central wavelength can be controlled by chirping the pump pulse in order to compensate for chirping caused by self-phase modulation...
March 5, 2018: Optics Express
Jingbo Sun, Salih Z Silahli, Wiktor Walasik, Qi Li, Eric Johnson, Natalia M Litchinitser
Colloidal media with well-defined optical properties have been widely used as model systems in many fundamental and applied studies of light-matter interactions in complex media. Recent progress in the field of engineered nanoscale optical materials with fundamentally new physical properties opens new opportunities for tailoring the properties of colloids. In this work, we experimentally demonstrate the evolution of the optical vortex beams of different topological charges propagating in engineered nano-colloidal suspension of negative polarizability with saturable nonlinearities...
March 5, 2018: Optics Express
Ognjen Ilic, Nathan H Thomas, Thomas Christensen, Michelle C Sherrott, Marin Soljacic, Austin J Minnich, Owen D Miller, Harry A Atwater
We theoretically demonstrate a near-field radiative thermal switch based on thermally excited surface plasmons in graphene resonators. The high tunability of graphene enables substantial modulation of near-field radiative heat transfer, which, when combined with the use of resonant structures, overcomes the intrinsically broadband nature of thermal radiation. In canonical geometries, we use nonlinear optimization to show that stacked graphene sheets offer improved heat conductance contrast between "ON" and "OFF" switching states, but that a >10x higher modulation is achieved between isolated graphene resonators than for parallel graphene sheets...
March 12, 2018: ACS Nano
Mohammad Muneeb Sultan, Hannah K Wayment-Steele, Vijay S Pande
Variational auto-encoder frameworks have demonstrated success in reducing complex nonlinear dynamics in molecular simulation to a single non-linear embedding. In this work, we illustrate how this non-linear latent embedding can be used as a collective variable for enhanced sampling, and present a simple modification that allows us to rapidly perform sampling in multiple related systems. We first demonstrate our method is able to describe the effects of force field changes in capped alanine dipeptide after learning a model using AMBER99...
March 12, 2018: Journal of Chemical Theory and Computation
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