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Dynamic systems theory

Sophie Pask, Cathryn Pinto, Katherine Bristowe, Liesbeth van Vliet, Caroline Nicholson, Catherine J Evans, Rob George, Katharine Bailey, Joanna M Davies, Ping Guo, Barbara A Daveson, Irene J Higginson, Fliss Em Murtagh
BACKGROUND: Palliative care patients are often described as complex but evidence on complexity is limited. We need to understand complexity, including at individual patient-level, to define specialist palliative care, characterise palliative care populations and meaningfully compare interventions/outcomes. AIM: To explore palliative care stakeholders' views on what makes a patient more or less complex and insights on capturing complexity at patient-level. DESIGN: In-depth qualitative interviews, analysed using Framework analysis...
February 1, 2018: Palliative Medicine
Kentaro Yamamoto, Kazuo Takatsuka
We theoretically studied the chemical principles behind the photodynamics of water splitting: 2H2 O + 4hν + M → 4H+ + 4e- + O2 + M. To comprehend this simple looking but very complicated reaction, the mechanisms of at least three crucial phenomena, among others, need to be clarified, each of which is supposed to constitute the foundation of chemistry: (i) charge separation (4H+ + 4e- ), (ii) the catalytic cycle for essentially the same reactions to be repeated by each of four photon absorptions with a catalyst M, and (iii) the generation of oxygen molecules of spin triplet...
February 19, 2018: Physical Chemistry Chemical Physics: PCCP
Florent Calvo, Ersin Yurtsever, Adem Tekin
The interaction between hydrogen and carbonaceous nanostructures is of fundamental interest in various areas of physical chemistry. In this contribution we have revisited the physisorption of hydrogen molecules and H2 clusters on fullerenes, following a first-principles approach in which the interaction is quantitatively evaluated for the C20 system using high-level electronic structure methods. Relative to coupled cluster data at the level of single, double, and perturbative triple excitations [CCSD(T)] taken as benchmark, the results for rotationally averaged physisorbed H2 show a good performance of MP2 variants and symmetry-adapted perturbation theory (SAPT), but significant deviations and basis set convergence issues are found for dispersion-corrected density functional theory (DFT)...
February 16, 2018: Journal of Physical Chemistry. A
Tapomoy Bhattacharjee, Christopher P Kabb, Christopher S O'Bryan, Juan M Urueña, Brent S Sumerlin, W Gregory Sawyer, Thomas E Angelini
Micro-scale hydrogel particles, known as microgels, are used in industry to control the rheology of numerous different products, and are also used in experimental research to study the origins of jamming and glassy behavior in soft-sphere model systems. At the macro-scale, the rheological behaviour of densely packed microgels has been thoroughly characterized; at the particle-scale, careful investigations of jamming, yielding, and glassy-dynamics have been performed through experiment, theory, and simulation...
February 16, 2018: Soft Matter
Diego Camargo, J A de la Torre, D Duque-Zumajo, Pep Español, Rafael Delgado-Buscalioni, Farid Chejne
Density Functional Theory (DFT) is a successful and well-established theory for the study of the structure of simple and complex fluids at equilibrium. The theory has been generalized to dynamical situations when the underlying dynamics is diffusive as in, for example, colloidal systems. However, there is no such a clear foundation for Dynamic DFT (DDFT) for the case of simple fluids in contact with solid walls. In this work, we derive DDFT for simple fluids by including not only the mass density field but also the momentum density field of the fluid...
February 14, 2018: Journal of Chemical Physics
Mallory Carlu, Francesco Ginelli, Antonio Politi
We discuss the behavior of the largest Lyapunov exponent λ in the incoherent phase of large ensembles of heterogeneous, globally coupled, phase oscillators. We show that the scaling with the system size N depends on the details of the spacing distribution of the oscillator frequencies. For sufficiently regular distributions λ∼1/N, while for strong fluctuations of the frequency spacing λ∼lnN/N (the standard setup of independent identically distributed variables belongs to the latter class). In spite of the coupling being small for large N, the development of a rigorous perturbative theory is not obvious...
January 2018: Physical Review. E
James Dufty, Jeffrey Wrighton
The calculation of dynamical properties for matter under extreme conditions is a challenging task. The popular Kubo-Greenwood model exploits elements from equilibrium density-functional theory (DFT) that allow a detailed treatment of electron correlations, but its origin is largely phenomenological; traditional kinetic theories have a more secure foundation but are limited to weak ion-electron interactions. The objective here is to show how a combination of the two evolves naturally from the short-time limit for the generator of the effective single-electron dynamics governing time correlation functions without such limitations...
January 2018: Physical Review. E
Schuyler B Nicholson, Jonah S Greenberg, Jason R Green
According to the asymptotic equipartition property, sufficiently long sequences of random variables converge to a set that is typical. While the size and probability of this set are central to information theory and statistical mechanics, they can often only be estimated accurately in the asymptotic limit due to the exponential growth in possible sequences. Here we derive a time-inhomogeneous dynamics that constructs the properties of the typical set for all finite length sequences of independent and identically distributed random variables...
January 2018: Physical Review. E
Thomas Barthel, Caterina De Bacco, Silvio Franz
We introduce and apply an efficient method for the precise simulation of stochastic dynamical processes on locally treelike graphs. Networks with cycles are treated in the framework of the cavity method. Such models correspond, for example, to spin-glass systems, Boolean networks, neural networks, or other technological, biological, and social networks. Building upon ideas from quantum many-body theory, our approach is based on a matrix product approximation of the so-called edge messages-conditional probabilities of vertex variable trajectories...
January 2018: Physical Review. E
J Vorberger, D A Chapman
We present a quantum theory for the dynamic structure factors in nonequilibrium, correlated, two-component systems such as plasmas or warm dense matter. The polarization function, which is needed as the input for the calculation of the structure factors, is calculated in nonequilibrium based on a perturbation expansion in the interaction strength. To make our theory applicable for x-ray scattering, a generalized Chihara decomposition for the total electron structure factor in nonequilibrium is derived. Examples are given and the influence of correlations and exchange on the structure and the x-ray-scattering spectrum are discussed for a model nonequilibrium distribution, as often encountered during laser heating of materials, as well as for two-temperature systems...
January 2018: Physical Review. E
Bo-Bo Wei
In this work, we show that a universal quantum work relation for a quantum system driven arbitrarily far from equilibrium extends to a parity-time- (PT-) symmetric quantum system with unbroken PT symmetry, which is a consequence of microscopic reversibility. The quantum Jarzynski equality, linear response theory, and Onsager reciprocal relations for the PT-symmetric quantum system are recovered as special cases of the universal quantum work relation in a PT-symmetric quantum system. In the regime of broken PT symmetry, the universal quantum work relation does not hold because the norm is not preserved during the dynamics...
January 2018: Physical Review. E
Hiroaki S Yamada, Fumihiro Matsui, Kensuke S Ikeda
Dynamical localization phenomena of monochromatically perturbed standard map (SM) and Anderson map (AM), which are both identified with a two-dimensional disordered system under suitable conditions, are investigated by the numerical wave-packet propagation. Some phenomenological formula of the dynamical localization length valid for wide range of control parameters are proposed for both SM and AM. For SM the formula completely agree with the experimental formula, and for AM the presence of a new regime of localization is confirmed...
January 2018: Physical Review. E
Arunee Promsri, Thomas Haid, Peter Federolf
The main purposes of the current study were to examine bilateral asymmetry in postural control during single-leg standing between the dominant and non-dominant legs using a novel analysis approach based on principal component analysis (PCA). It was hypothesized that the asymmetry might manifest as differences in the coordinative structure (control strategies), or as differences in the frequency or regularity of corrective interventions of the motor control system. The static and dynamic leg dominance of 26 active young adults (14 males and 12 females) was determined from their preferred leg for dynamic and for static tasks...
February 12, 2018: Human Movement Science
Corinna Klingler, Fatiha Ismail, Georg Marckmann, Katja Kuehlmeyer
Hospitals in Germany employ increasing numbers of foreign-born and foreign-trained (FB&FT) physicians. Studies have investigated how FB&FT physicians experience their professional integration into the German healthcare system, however, the perspectives of stakeholders working with and shaping the work experiences of FB&FT physicians in German hospitals have so far been neglected. This study explores relevant stakeholders' opinions and attitudes towards FB&FT physicians-which likely influence how these physicians settle in-and how these opinions were formed...
2018: PloS One
Markus Heyl
Quantum theory provides an extensive framework for the description of the equilibrium properties of quantum matter. Yet experiments in quantum simulators have now opened up a route towards generating quantum states beyond this equilibrium paradigm. While these states promise to show properties not constrained by equilibrium principles such as the equal a priori probability of the microcanonical ensemble, identifying general properties of nonequilibrium quantum dynamics remains a major challenge especially in view of the lack of conventional concepts such as free energies...
February 15, 2018: Reports on Progress in Physics
Richard A Cangelosi, Elissa J Schwartz, David J Wollkind
Analysis of previously published target-cell limited viral dynamic models for pathogens such as HIV, hepatitis, and influenza generally rely on standard techniques from dynamical systems theory or numerical simulation. We use a quasi-steady-state approximation to derive an analytic solution for the model with a non-cytopathic effect, that is, when the death rates of uninfected and infected cells are equal. The analytic solution provides time evolution values of all three compartments of uninfected cells, infected cells, and virus...
2018: Frontiers in Microbiology
Yang Ni
In this paper, we present a new logarithmic pixel design currently under development at New Imaging Technologies SA (NIT). This new logarithmic pixel design uses charge domain logarithmic signal compression and charge-transfer-based signal readout. This structure gives a linear response in low light conditions and logarithmic response in high light conditions. The charge transfer readout efficiently suppresses the reset (KTC) noise by using true correlated double sampling (CDS) in low light conditions. In high light conditions, thanks to charge domain logarithmic compression, it has been demonstrated that 3000 electrons should be enough to cover a 120 dB dynamic range with a mobile phone camera-like signal-to-noise ratio (SNR) over the whole dynamic range...
February 14, 2018: Sensors
Darren E Irwin
Theory and empirical patterns suggest a disproportionate role for sex chromosomes in evolution and speciation. Focusing on ZW sex determination (females ZW, males ZZ; the system in birds, many snakes, and lepidopterans), I review how evolutionary dynamics are expected to differ between the Z, W, and the autosomes, discuss how these differences may lead to a greater role of the sex chromosomes in speciation, and use data from birds to compare relative evolutionary rates of sex chromosomes and autosomes. Neutral mutations, partially or completely recessive beneficial mutations, and deleterious mutations under many conditions are expected to accumulate faster on the Z than on autosomes...
February 14, 2018: Molecular Ecology
Alberto Scacchi, Joseph M Brader
For a system of Brownian particles interacting via a soft exponential potential we investigate the interaction between equilibrium crystallisation and spatially varying shear flow. For thermodynamic state points within the liquid part of the phase diagram, but close to the crystallisation phase boundary, we observe that imposing a Poiseuille flow can induce nonequilibrium crystalline ordering in regions of low shear gradient. The physical mechanism responsible for this phenomenon is shear-induced particle migration, which causes particles to drift preferentially towards the center of the flow channel, thus increasing the local density in the channel center...
March 7, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Lee Harten, Yasmin Matalon, Naama Galli, Hagit Navon, Roi Dor, Yossi Yovel
Social foraging theory suggests that group-living animals gain from persistent social bonds, which lead to increased tolerance in competitive foraging and information sharing. Bats are among the most social mammals, often living in colonies of tens to thousands of individuals for dozens of years, yet little is known about their social foraging dynamics. We observed three captive bat colonies for over a year, quantifying >13,000 social foraging interactions. We found that individuals consistently used one of two foraging strategies, either producing (collecting) food themselves or scrounging it directly from the mouth of other individuals...
February 2018: Science Advances
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