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Dynamic systems theory

Amy Nimegeer, Hilary Thomson, Louise Foley, Shona Hilton, Fiona Crawford, David Ogilvie
The construction of new urban roads may cause severance, or the separation of residents from local amenities or social networks. Using qualitative data from a natural experimental study, we examined severance related to a new section of urban motorway constructed through largely deprived residential neighbourhoods in Glasgow, Scotland. Semi-structured and photo-elicitation interviews were used to better understand severance and connectivity related to the new motorway, and specifically implications for individual and community-level health and well-being through active travel and social connections...
November 29, 2017: Social Science & Medicine
Nir Gavish, Doron Elad, Arik Yochelis
The increasing number of experimental observations on highly concentrated electrolytes and ionic liquids show qualitative features that are distinct from dilute or moderately concentrated electrolytes, such as self-assembly, multiple-time relaxation, and under-screening, which all impact the emergence of fluid/solid interfaces, and transport in these systems. Since these phenomena are not captured by existing mean field models of electrolytes, there is a paramount need for a continuum framework for highly concentrated electrolytes and ionic liquids...
December 8, 2017: Journal of Physical Chemistry Letters
Bvudzai Priscilla Magadzire, Bruno Marchal, Tania Mathys, Richard O Laing, Kim Ward
BACKGROUND: Centralized dispensing of essential medicines is one of South Africa's strategies to address the shortage of pharmacists, reduce patients' waiting times and reduce over-crowding at public sector healthcare facilities. This article reports findings of an evaluation of the Chronic Dispensing Unit (CDU) in one province. The objectives of this process evaluation were to: (1) compare what was planned versus the actual implementation and (2) establish the causal elements and contextual factors influencing implementation...
December 4, 2017: BMC Health Services Research
Kerry L Gaskin
PURPOSE: The purpose of this study was to explore parents' experiences of one specific timepoint in their infant's journey: the transition from hospital to home, following the first stage of their infant's cardiac surgery for complex congenital heart disease. DESIGN AND METHODS: A prospective longitudinal mixed methods study, underpinned with Middle Range Transition Theory (Meleis, Sawyer, Im, Hilfinger Messias, & Schumacher, 2000). Face to face and telephone interviews were conducted and self-report forms completed by parents at four-time points: before discharge (T0), 2weeks after discharge (T1), 8weeks after discharge (T2) and after stage two surgery (T3)...
December 4, 2017: Journal of Pediatric Nursing
Vassiliy Lubchenko, Peter G Wolynes
Apart from not having crystallized, supercooled liquids can be considered as being properly equilibrated and thus can be described by a few thermodynamic control variables. In contrast, glasses and other amorphous solids can be arbitrarily far away from equilibrium and require a description of the history of the conditions under which they formed. In this paper we describe how the locality of interactions intrinsic to finite-dimensional systems affects the stability of amorphous solids far off equilibrium. Our analysis encompasses both structural glasses formed by cooling and colloidal assemblies formed by compression...
December 7, 2017: Journal of Physical Chemistry. B
Mehdi Zomorodian, Sai Hin Lai, Mehran Homayounfar, Shaliza Ibrahim, Gareth Pender
Conflicts over water resources can be highly dynamic and complex due to the various factors which can affect such systems, including economic, engineering, social, hydrologic, environmental and even political, as well as the inherent uncertainty involved in many of these factors. Furthermore, the conflicting behavior, preferences and goals of stakeholders can often make such conflicts even more challenging. While many game models, both cooperative and non-cooperative, have been suggested to deal with problems over utilizing and sharing water resources, most of these are based on a static viewpoint of demand points during optimization procedures...
2017: PloS One
Ellen van Velzen, Ursula Gaedke
The impact of rapid predator-prey coevolution on predator-prey dynamics remains poorly understood, as previous modelling studies have given rise to contradictory conclusions and predictions. Interpreting and reconciling these contradictions has been challenging due to the inherent complexity of model dynamics, defying mathematical analysis and mechanistic understanding. We develop a new approach here, based on the Geber method for deconstructing eco-evolutionary dynamics, for gaining such understanding. We apply this approach to a co-evolutionary predator-prey model to disentangle the processes leading to either antiphase or ¼-lag cycles...
December 7, 2017: Scientific Reports
Pritam Ganguly, Pablo Boserman, Nico F A van der Vegt, Joan-Emma Shea
Osmolytes are small organic molecules that can modulate the stability and function of cellular proteins by altering the chemical environment of the cell. Some of these osmolytes work in conjunction, via mechanisms that are poorly understood. An example is the naturally-occurring protein-protective osmolyte trimethylamine N-oxide (TMAO) that stabilizes cellular proteins in marine organisms against the detrimental denaturing effects of another naturally occurring osmolyte, urea. From a computational standpoint, our understanding of this counteraction mechanism is hampered by the fact that existing force fields fail to capture the correct balance of TMAO and urea interactions in ternary solutions...
December 7, 2017: Journal of the American Chemical Society
Ismail Belgacem, Stefano Casagranda, Edith Grac, Delphine Ropers, Jean-Luc Gouzé
The aim of this paper is to analyze the dynamical behavior of biological models of gene transcription and translation. We focus on a particular positive feedback loop governing the synthesis of RNA polymerase, needed for transcribing its own gene. We write a high-dimension model based on mass action laws and reduce it to a two-variable model (RNA polymerase and its mRNA) by means of monotone system theory and timescale arguments. We show that the reduced model has either a single globally stable trivial equilibrium in (0, 0), or an unstable zero equilibrium and a globally stable positive one...
December 6, 2017: Bulletin of Mathematical Biology
Ciyuan Qiu, Yuxing Yang, Chao Li, Yifang Wang, Kan Wu, Jianping Chen
All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms (e.g., silicon and III-V semiconductors). However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions...
December 6, 2017: Scientific Reports
Michael Roemelt, Vera Krewald, Dimitrios A Pantazis
The accurate description of magnetic level energetics in oligonuclear exchange-coupled transition metal complexes remains a formidable challenge for quantum chemistry. The density matrix renormalization group (DMRG) brings such systems for the first time easily within reach of multireference wave function methods by enabling the use of unprecedentedly large active spaces. But does this guarantee systematic improvement in predictive ability, and if so, under which conditions? We identify operational parameters in the use of DMRG using as a test system an experimentally characterized mixed valence bis-μ-oxo/μ-acetato Mn(III,IV) dimer, a model for the oxygen-evolving complex of photosystem II...
December 6, 2017: Journal of Chemical Theory and Computation
Majid Moosavi, Fatemeh Khashei, Elaheh Sedghamiz
In this work, the structural and dynamical properties of two imidazolium-based geminal dicationic ionic liquids (GDILs), i.e. [Cn(mim)2][NTf2]2 with n = 3 and 5, have been studied to obtain a fundamental understanding of the molecular basis of the macroscopic and microscopic properties of the bulk liquid phase. To achieve this purpose, molecular dynamics (MD) simulation, density functional theory (DFT) and atoms in molecule (AIM) methods were used. Interaction energies, charge transfers and hydrogen bonds between the cation and anions of each studied GDIL were investigated by DFT calculations and also AIM...
December 6, 2017: Physical Chemistry Chemical Physics: PCCP
Natalia B Janson, Christopher J Marsden
It is well known that architecturally the brain is a neural network, i.e. a collection of many relatively simple units coupled flexibly. However, it has been unclear how the possession of this architecture enables higher-level cognitive functions, which are unique to the brain. Here, we consider the brain from the viewpoint of dynamical systems theory and hypothesize that the unique feature of the brain, the self-organized plasticity of its architecture, could represent the means of enabling the self-organized plasticity of its velocity vector field...
December 5, 2017: Scientific Reports
Laurence C Smith, Kang Yang, Lincoln H Pitcher, Brandon T Overstreet, Vena W Chu, Åsa K Rennermalm, Jonathan C Ryan, Matthew G Cooper, Colin J Gleason, Marco Tedesco, Jeyavinoth Jeyaratnam, Dirk van As, Michiel R van den Broeke, Willem Jan van de Berg, Brice Noël, Peter L Langen, Richard I Cullather, Bin Zhao, Michael J Willis, Alun Hubbard, Jason E Box, Brittany A Jenner, Alberto E Behar
Meltwater runoff from the Greenland ice sheet surface influences surface mass balance (SMB), ice dynamics, and global sea level rise, but is estimated with climate models and thus difficult to validate. We present a way to measure ice surface runoff directly, from hourly in situ supraglacial river discharge measurements and simultaneous high-resolution satellite/drone remote sensing of upstream fluvial catchment area. A first 72-h trial for a 63.1-km2 moulin-terminating internally drained catchment (IDC) on Greenland's midelevation (1,207-1,381 m above sea level) ablation zone is compared with melt and runoff simulations from HIRHAM5, MAR3...
December 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
Akash V Maharaj, Elliott W Rosenberg, Alexander T Hristov, Erez Berg, Rafael M Fernandes, Ian R Fisher, Steven A Kivelson
The paradigmatic example of a continuous quantum phase transition is the transverse field Ising ferromagnet. In contrast to classical critical systems, whose properties depend only on symmetry and the dimension of space, the nature of a quantum phase transition also depends on the dynamics. In the transverse field Ising model, the order parameter is not conserved, and increasing the transverse field enhances quantum fluctuations until they become strong enough to restore the symmetry of the ground state. Ising pseudospins can represent the order parameter of any system with a twofold degenerate broken-symmetry phase, including electronic nematic order associated with spontaneous point-group symmetry breaking...
December 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
Qihua Huang, Gunog Seo, Chunhua Shan
The study of effects of environmental toxins on ecosystems is of great interest from both environmental and conservation points of view. In this paper, we present a global stability and bifurcation analysis of a toxin-dependent aquatic population model. Our analytical and numerical results show that both the environmental toxin level and the depuration capability of the population significantly affect the population persistence. The model exhibits a multifarious array of dynamics. While low levels of external toxin allow population persistence and high levels of toxin lead to an extirpation, intermediate toxin concentrations can produce very rich dynamics, such as transient oscillations, hysteresis, heteroclinic orbits, and a codimension-two bifurcation...
December 2, 2017: Mathematical Biosciences
Kathleen P Conte, Sisse Groen, Victoria Loblay, Amanda Green, Andrew Milat, Lina Persson, Christine Innes-Hughes, Jo Mitchell, Sarah Thackway, Mandy Williams, Penelope Hawe
BACKGROUND: The effectiveness of many interventions to promote health and prevent disease has been well established. The imperative has therefore shifted from amassing evidence about efficacy to scale-up to maximise population-level health gains. Electronic implementation monitoring, or 'e-monitoring', systems have been designed to assist and track the delivery of preventive policies and programs. However, there is little evidence on whether e-monitoring systems improve the dissemination, adoption, and ongoing delivery of evidence-based preventive programs...
December 6, 2017: Implementation Science: IS
Vladimir A Andryushchenko, Sergei F Chekmarev
Recently, when studying folding of a SH3 domain, we discovered that the flows of transitions between protein states can be surprisingly similar to turbulent fluid flows. This similarity was not restricted by a vortex pattern of the flow fields but extended to a spatial correlation of flow fluctuations, resulting, in particular, in the structure functions such as in the Kolmogorov theory of homogeneous and isotropic turbulence. Here, we undertake a detailed analysis of spatial distribution of folding flows and their similarity to turbulent fluid flows...
2017: PloS One
Geng Dong, Ulf Ryde, Hans Jørgen Aa Jensen, Erik D Hedegård
The combination of density functional theory (DFT) with a multiconfigurational wave function is an efficient way to include dynamical correlation in calculations with multiconfiguration self-consistent field wave functions. These methods can potentially be employed to elucidate reaction mechanisms in bio-inorganic chemistry, where many other methods become either too computationally expensive or too inaccurate. In this paper, a complete active space (CAS) short-range DFT (CAS-srDFT) hybrid was employed to investigate a bio-inorganic system, namely H2 binding to the active site of [NiFe] hydrogenase...
December 5, 2017: Physical Chemistry Chemical Physics: PCCP
Sangita Dutta, Tilak Das, Soumendu Datta
The structural, electronic and optical properties of bulk bismuth oxyhalides, BiOX (X = F, Cl, Br, and I), were studied using state-of-the-art density functional theory (DFT)-based calculations. The effects of compressive and tensile strains on the in-plane lattice parameters were analyzed to better understand their good performance in photo-catalytic applications. Our present first-principles calculations show that at least 4% in-plane bi-axial compressive strain over the experimental lattice parameters of BiOF is needed for phonon stability of this material, whereas other BiOX systems can accept up to 2% in-plane bi-axial compressive strain and retain their dynamical stability...
December 5, 2017: Physical Chemistry Chemical Physics: PCCP
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