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Dynamic systems theory

M Lohöfer, S Wessel
By means of large-scale quantum Monte Carlo simulations, we examine the quantum critical scaling of the magnetic excitation gap (the triplon gap) in a three-dimensional dimerized quantum antiferromagnet, the bicubic lattice, and identify characteristic multiplicative logarithmic scaling corrections atop the leading mean-field behavior. These findings are in accord with field-theoretical predictions that are based on an effective description of the quantum critical system in terms of an asymptotically free field theory, which exhibits a logarithmic decay of the renormalized interaction strength upon approaching the quantum critical point...
April 7, 2017: Physical Review Letters
Aaron Sisto, Clem Stross, Marc W van der Kamp, Michael O'Connor, Simon McIntosh-Smith, Graham T Johnson, Edward G Hohenstein, Fred R Manby, David R Glowacki, Todd J Martinez
We recently outlined an efficient multi-tiered parallel ab initio excitonic framework that utilizes time dependent density functional theory (TDDFT) to calculate ground and excited state energies and gradients of large supramolecular complexes in atomistic detail - enabling us to undertake non-adiabatic simulations which explicitly account for the coupled anharmonic vibrational motion of all the constituent atoms in a supramolecular system. Here we apply that framework to the 27 coupled bacterio-chlorophyll-a chromophores which make up the LH2 complex, using it to compute an on-the-fly nonadiabatic surface-hopping (SH) trajectory of electronically excited LH2...
April 21, 2017: Physical Chemistry Chemical Physics: PCCP
Xiaobin Xu, Zhenghui Li, Guo Li, Zhe Zhou
Estimating the state of a dynamic system via noisy sensor measurement is a common problem in sensor methods and applications. Most state estimation methods assume that measurement noise and state perturbations can be modeled as random variables with known statistical properties. However in some practical applications, engineers can only get the range of noises, instead of the precise statistical distributions. Hence, in the framework of Dempster-Shafer (DS) evidence theory, a novel state estimatation method by fusing dependent evidence generated from state equation, observation equation and the actual observations of the system states considering bounded noises is presented...
April 21, 2017: Sensors
Uwe Manthe
Multi-configurational time-dependent Hartree (MCTDH) based approaches are efficient, accurate, and versatile methods for high-dimensional quantum dynamics simulations. Applications range from detailed investigations of polyatomic reaction processes in the gas phase to high-dimensional simulations studying the dynamics of condensed phase systems described by typical solid state physics model Hamiltonians. The present article presents an overview of the different areas of application and provides on a comprehensive review of the underlying theory...
April 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Christian Rohwer, Andrea Gambassi, Matthias Kruger
Second-order phase transitions are characterized by a divergence of the spatial correlation length of the order parameter fluctuations. For confined systems, this is known to lead to remarkable equilibrium physical phenomena, including finite-size effects and critical Casimir forces. We explore here some non-equilibrium aspects of these effects in the stationary state resulting from the action of external forces: by analyzing a model of a correlated fluid under shear, spatially confined by two parallel plates, we study the resulting viscosity within the setting of (Gaussian) Landau-Ginzburg theory...
April 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Shuang Liang, Yubo Zhao, Jian Zhang, Lianfa Song
Accurate description and modeling of fouling on hollow fibers imposes a serious challenge to more effective fouling mitigation and performance optimization of the membrane system. Although the governing equations for membrane fouling can be constructed based on the known theories from membrane filtration and fluid dynamics, they are unsolvable analytically due to the complex spatially and temporally varying nature of fouling on hollow fibers. The current available numerical solutions for the governing equations are either unreliable or inconvenient to use because of the uses of unfounded assumptions or cumbersome calculation methods...
April 20, 2017: Environmental Science and Pollution Research International
Alyssa Adams, Hector Zenil, Paul C W Davies, Sara Imari Walker
Open-ended evolution (OEE) is relevant to a variety of biological, artificial and technological systems, but has been challenging to reproduce in silico. Most theoretical efforts focus on key aspects of open-ended evolution as it appears in biology. We recast the problem as a more general one in dynamical systems theory, providing simple criteria for open-ended evolution based on two hallmark features: unbounded evolution and innovation. We define unbounded evolution as patterns that are non-repeating within the expected Poincare recurrence time of an isolated system, and innovation as trajectories not observed in isolated systems...
April 20, 2017: Scientific Reports
Chris Guiver, David Packman, Stuart Townley
We revisit the question of when can dispersal-induced coupling between discrete sink populations cause overall population growth? Such a phenomenon is called dispersal driven growth and provides a simple explanation of how dispersal can allow populations to persist across discrete, spatially heterogeneous, environments even when individual patches are adverse or unfavourable. For two classes of mathematical models, one linear and one non-linear, we provide necessary conditions for dispersal driven growth in terms of the existence of a common linear Lyapunov function, which we describe...
April 17, 2017: Journal of Theoretical Biology
Ouassim Zeriouh, José Vicente Reinoso-Moreno, Lorenzo López-Rosales, María Del Carmen Cerón-García, Asterio Sánchez-Mirón, Francisco García-Camacho, Emilio Molina-Grima
The economic and/or energetic feasibility of processes based on using microalgae biomass requires an efficient cultivation system. In photobioreactors (PBRs), the adhesion of microalgae to the transparent PBR surfaces leads to biofouling and reduces the solar radiation penetrating the PBR. Light reduction within the PBR decreases biomass productivity and, therefore, the photosynthetic efficiency of the cultivation system. Additionally, PBR biofouling leads to a series of further undesirable events including changes in cell pigmentation, culture degradation, and contamination by invasive microorganisms; all of which can result in the cultivation process having to be stopped...
April 20, 2017: Critical Reviews in Biotechnology
Mrinal Kanti Si, Anik Sen, Bishwajit Ganguly
G-quadruplexes are formed by the association of four guanine bases through Hoogsteen hydrogen bonding in guanine-rich sequences of DNA and exist in the telomere as well as in promoter regions of certain oncogenes. The sequences of G-quadruplex-DNA are targets for the design of molecules that can bind and can be developed as anti-cancer drugs. The linear and cyclic protonated diamines have been explored to bind to G-quadruplex-DNA through hydrogen bonding interactions. The quadruplex-DNA binders exploit π-stacking and hydrogen bonding interactions with the phosphate backbone of loops and grooves...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
Wenjun Wu, Huaide Xiang, Wei Fan, Jinglin Wang, Haifeng Wang, Xin Hua, Zhaohui Wang, Yi-Tao Long, He Tian, Wei-Hong Zhu
Up to date, development of organic sensitizers has been predominately focused on light harvesting, HOMO and LUMO energy levels, and electron transferring process. In contrast, their adsorption mode as well as dynamic loading behaviour onto nanoporous TiO2 is rarely considered. Herein we have employed the time of flight secondary ion mass spectrometry (TOF-SIMS) to take insight into the competitive dye adsorption mode and kinetics in cosensitized porphyrin system. Using the novel porphyrin dye FW-1 and D-A-π-A featured dye WS-5, the different bond-breaking mode in TOF-SIMS and dynamic dye-loading amount during the coadsorption process are well compared with two different anchoring groups such as benzoic acid and cyanoacrylic acid...
April 20, 2017: ACS Applied Materials & Interfaces
Francis Cheng-Hsuan Weng, Grace Tzun-Wen Shaw, Chieh-Yin Weng, Yi-Ju Yang, Daryi Wang
The concerted activity of intestinal microbes is crucial to the health and development of their host organisms. Investigation of microbial interactions in the gut should deepen our understanding of how these micro-ecosystems function. Due to advances in Next Generation Sequencing (NGS) technologies, various bioinformatic strategies have been proposed to investigate these microbial interactions. However, due to the complexity of the intestinal microbial community and difficulties in monitoring their interactions, at present there is a gap between the theory and biological application...
2017: Frontiers in Microbiology
Abhinav Parihar, Nikhil Shukla, Matthew Jerry, Suman Datta, Arijit Raychowdhury
While Boolean logic has been the backbone of digital information processing, there exist classes of computationally hard problems wherein this paradigm is fundamentally inefficient. Vertex coloring of graphs, belonging to the class of combinatorial optimization, represents one such problem. It is well studied for its applications in data sciences, life sciences, social sciences and technology, and hence, motivates alternate, more efficient non-Boolean pathways towards its solution. Here we demonstrate a coupled relaxation oscillator based dynamical system that exploits insulator-metal transition in Vanadium Dioxide (VO2) to efficiently solve vertex coloring of graphs...
April 19, 2017: Scientific Reports
Rebecka Janols, Helena Lindgren
A methodology was defined and developed for designing theory-based behaviour change systems for health promotion that can be tailored to the individual. Theories from two research fields were combined with a participatory action research methodology. Two case studies applying the methodology were conducted. During and between group sessions the participants created material and designs following the behaviour change strategy themes, which were discussed, analysed and transformed into a design of a behaviour change system...
2017: Studies in Health Technology and Informatics
Nathan Szanto, Vignesh Narayanan, Sarangapani Jagannathan
In this paper, a novel event-triggered implementation of a tracking controller for an uncertain strict-feedback system is presented. Neural networks (NNs) are utilized in the backstepping approach to design a control input by approximating unknown dynamics of the strict-feedback nonlinear system with event-sampled inputs. The system state vector is assumed to be unknown and an NN observer is used to estimate the state vector. By using the estimated state vector and backstepping design approach, an event-sampled controller is introduced...
April 12, 2017: IEEE Transactions on Neural Networks and Learning Systems
Michael J Servis, David T Wu, Jenifer C Braley
Extraction of polar molecules by amphiphilic species results in a complex variety of clusters whose topologies and energetics control phase behavior and efficiency of liquid-liquid separations. A computational approach including quantum mechanical vibrational frequency calculations and molecular dynamics simulation with intermolecular network theory is used to provide a robust assessment of extractant and polar solute association through hydrogen bonding in the tributyl phosphate (TBP)/HNO3/H2O/dodecane system for the first time...
April 18, 2017: Physical Chemistry Chemical Physics: PCCP
Najeh Rekik
Theoretical IR spectral density of the high-frequency stretching mode of hydrogen bond (H-bond) systems is reported using a three-dimensional approach. The model, studied within the framework of linear response theory, involves the mechanical anharmonicity of the high-frequency stretching mode by contemplating its potential as an asymmetric double well potential, the mechanical anharmonicity of the H-bond Bridge by contemplating its potential as a Morse potential, Fermi resonances which occur between the high frequency stretching mode and the overtones of the bending modes, the electrical anharmonicity translated by the non-linearity to second order in the electric dipole moment function of the fast mode, the second order modulation of the angular frequency and the equilibrium position of the fast mode on the slow mode coordinate, and direct and indirect relaxation mechanism...
April 18, 2017: Journal of Physical Chemistry. A
Luis Craco, Stefano Leoni
Transport properties of tetragonal iron monosulfide, mackinawite, show a range of complex features. Semiconductive behavior and proximity to metallic states with nodal superconductivity mark this d-band system as unconventional quantum material. Here, we use the density functional dynamical mean-field theory (DFDMFT) scheme to comprehensively explain why tetragonal FeS shows both semiconducting and metallic responses in contrast to tetragonal FeSe which is a pseudogaped metal above the superconducting transition temperature...
April 18, 2017: Scientific Reports
Gregor Mönke, Elena Cristiano, Ana Finzel, Dhana Friedrich, Hanspeter Herzel, Martin Falcke, Alexander Loewer
Cellular signaling systems precisely transmit information in the presence of molecular noise while retaining flexibility to accommodate the needs of individual cells. To understand design principles underlying such versatile signaling, we analyzed the response of the tumor suppressor p53 to varying levels of DNA damage in hundreds of individual cells and observed a switch between distinct signaling modes characterized by isolated pulses and sustained oscillations of p53 accumulation. Guided by dynamic systems theory we show that this requires an excitable network structure comprising positive feedback and provide experimental evidence for its molecular identity...
April 18, 2017: Scientific Reports
Julian Barreiro-Gomez, Carlos Ocampo-Martinez, Nicanor Quijano
Model predictive control (MPC) is a suitable strategy for the control of large-scale systems that have multiple design requirements, e.g., multiple physical and operational constraints. Besides, an MPC controller is able to deal with multiple control objectives considering them within the cost function, which implies to determine a proper prioritization for each of the objectives. Furthermore, when the system has time-varying parameters and/or disturbances, the appropriate prioritization might vary along the time as well...
April 15, 2017: ISA Transactions
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