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Dynamic systems theory

M A Torlopov, I S Martakov, V I Mikhaylov, N V Tsvetkov, P V Krivoshapkin
The hydrosols of chitin nanocrystals (ChN) are promising as modifiers of properties, drug delivery systems, and media. The purpose of this work is to clarify the mechanisms for regulating processes of stability and structure formation occurring in the ChN hydrosols under the influence of varying ionic strength. ChN were isolated from the crab shell; ChN hydrosols are obtained with different concentrations of the dispersed phase. The structure and morphology of the particles was studied by atomic force microscopy and X-ray diffraction...
October 15, 2017: Carbohydrate Polymers
Timothy E Hoffman, Katherine J Barnett, Lyle Wallis, William H Hanneman
Research in biogerontology has largely focused on the complex relationship between mitochondrial dysfunction and biological aging. In particular, the mitochondrial free radical theory of aging (MFRTA) has been well accepted. However, this theory has been challenged by recent studies showing minimal increases in reactive oxygen species (ROS) as not entirely deleterious in nature, and even beneficial under the appropriate cellular circumstances. To assess these significant and nonintuitive observations in the context of a functional system, we have taken an in silico approach to expand the focus of the MFRTA by including other key mitochondrial stress response pathways, as they have been observed in the nematode Caenorhabditis elegans...
August 16, 2017: Aging Cell
Judith A Feeney, Gery C Karantzas
The experience of conflict is often cited as a highly stressful relational phenomenon by romantic couples, and can have negative implications for relationship satisfaction and for the longevity of romantic relationships. In this paper, we review extant research on couple conflict in romantic relationships from an attachment theory perspective. The research we review is underpinned by two central tenets: firstly, severe or persistent conflict activates the attachment system; secondly, responses to couple conflict involve complex attachment dynamics, shaped by partners' attachment anxiety and avoidance...
February 2017: Current Opinion in Psychology
Michael Lässig, Ville Mustonen, Aleksandra M Walczak
The face of evolutionary biology is changing: from reconstructing and analysing the past to predicting future evolutionary processes. Recent developments include prediction of reproducible patterns in parallel evolution experiments, forecasting the future of individual populations using data from their past, and controlled manipulation of evolutionary dynamics. Here we undertake a synthesis of central concepts for evolutionary predictions, based on examples of microbial and viral systems, cancer cell populations, and immune receptor repertoires...
February 21, 2017: Nature ecology & evolution
William R Shoemaker, Kenneth J Locey, Jay T Lennon
Microorganisms are the most abundant, diverse and functionally important organisms on Earth. Over the past decade, microbial ecologists have produced the largest ever community datasets. However, these data are rarely used to uncover law-like patterns of commonness and rarity, test theories of biodiversity, or explore unifying explanations for the structure of microbial communities. Using a global scale compilation of >20,000 samples from environmental, engineered and host-related ecosystems, we test the power of competing theories to predict distributions of microbial abundance and diversity-abundance scaling laws...
April 3, 2017: Nature ecology & evolution
Shai Pilosof, Mason A Porter, Mercedes Pascual, Sonia Kéfi
Although networks provide a powerful approach to study a large variety of ecological systems, their formulation does not typically account for multiple interaction types, interactions that vary in space and time, and interconnected systems such as networks of networks. The emergent field of 'multilayer networks' provides a natural framework for extending analyses of ecological systems to include such multiple layers of complexity, as it specifically allows one to differentiate and model 'intralayer' and 'interlayer' connectivity...
March 23, 2017: Nature ecology & evolution
Jameal F Samhouri, Adrian C Stier, Shannon M Hennessey, Mark Novak, Benjamin S Halpern, Phillip S Levin
One of the twenty-first century's greatest environmental challenges is to recover and restore species, habitats and ecosystems. The decision about how to initiate restoration is best-informed by an understanding of the linkages between ecosystem components and, given these linkages, an appreciation of the consequences of choosing to recover one ecosystem component before another. However, it remains difficult to predict how the sequence of species' recoveries within food webs influences the speed and trajectory of restoration, and what that means for human well-being...
March 1, 2017: Nature ecology & evolution
Luis Valente, Rampal S Etienne, Liliana M Dávalos
Islands are ideal systems to model temporal changes in biodiversity and reveal the influence of humans on natural communities. Although theory predicts biodiversity on islands tends towards an equilibrium value, the recent extinction of large proportions of island biotas complicates testing this model. The well-preserved subfossil record of Caribbean bats-involving multiple insular radiations-provides a rare opportunity to model diversity dynamics in an insular community. Here, we reconstruct the diversity trajectory in noctilionoid bats of the Greater Antilles by applying a dynamic model of colonization, extinction and speciation to phylogenetic and palaeontological data including all known extinct and extant species...
January 9, 2017: Nature ecology & evolution
Lisette H J C Kikkert, Nicolas Vuillerme, Jos P van Campen, Bregje A Appels, Tibor Hortobágyi, Claudine J Lamoth
BACKGROUND: A detailed gait analysis (e.g., measures related to speed, self-affinity, stability, and variability) can help to unravel the underlying causes of gait dysfunction, and identify cognitive impairment. However, because geriatric patients present with multiple conditions that also affect gait, results from healthy old adults cannot easily be extrapolated to geriatric patients. Hence, we (1) quantified gait outcomes based on dynamical systems theory, and (2) determined their discriminative power in three groups: healthy old adults, geriatric patients with- and geriatric patients without cognitive impairment...
August 15, 2017: Journal of Neuroengineering and Rehabilitation
Kyle S Gustafson, Guoxi Xu, Karl F Freed, Jian Qin
The multiple-scattering theory for the electrostatics of many-body systems of monopolar spherical particles, embedded in a dielectric medium, is generalized to describe the electrostatics of these particles with embedded dipoles and multipoles. The Neumann image line construction for the electrostatic polarization produced by one particle is generalized to compute the energy, forces, and torques for the many-body system as functions of the positions of the particles. The approach is validated by comparison with direct numerical calculation, and the convergence rate is analyzed and expressed in terms of the discontinuity in dielectric contrast and particle density...
August 14, 2017: Journal of Chemical Physics
Andrej Junginger, Lennart Duvenbeck, Matthias Feldmaier, Jörg Main, Günter Wunner, Rigoberto Hernandez
In chemical or physical reaction dynamics, it is essential to distinguish precisely between reactants and products for all times. This task is especially demanding in time-dependent or driven systems because therein the dividing surface (DS) between these states often exhibits a nontrivial time-dependence. The so-called transition state (TS) trajectory has been seen to define a DS which is free of recrossings in a large number of one-dimensional reactions across time-dependent barriers and thus, allows one to determine exact reaction rates...
August 14, 2017: Journal of Chemical Physics
Pablo de Castro, Peter Sollich
New insights into phase separation in colloidal suspensions are provided via a dynamical theory based on the polydisperse lattice-gas model. The model gives a simplified description of polydisperse colloids, incorporating a hard-core repulsion combined with polydispersity in the strength of the attraction between neighbouring particles. Our mean-field equations describe the local concentration evolution for each of an arbitrary number of species, and for an arbitrary overall composition of the system. We focus on the predictions for the dynamics of colloidal gas-liquid phase separation after a quench into the coexistence region...
August 15, 2017: Physical Chemistry Chemical Physics: PCCP
Matthias Wohlgemuth, Mitsuhiko Miyazaki, Kohei Tsukada, Martin Weiler, Otto Dopfer, Masaaki Fujii, Roland Mitrić
Most proteins work in aqueous solution and the interaction with water strongly affects their structure and function. However, experimentally the motion of a specific single water molecule is difficult to trace by conventional methods, because they average over the heterogeneous solvation structure of bulk water surrounding the protein. Here, we provide a detailed atomistic picture of the water rearrangement dynamics around the -CONH- peptide linkage in the two model systems formanilide and acetanilide, which simply differ by the presence of a methyl group at the peptide linkage...
August 15, 2017: Physical Chemistry Chemical Physics: PCCP
Mohammad S Jalali, Hazhir Rahmandad, Sally Lawrence Bullock, Alice Ammerman
In this study, we present case studies to explore the dynamics of implementation and maintenance of health interventions. We analyze how specific interventions are built and eroded, how the building and erosion mechanisms are interconnected, and why we can see significantly different erosion rates across otherwise similar organizations. We use multiple comparative obesity prevention case studies to provide empirical information on the mechanisms of interest, and use qualitative systems modeling to integrate our evolving understanding into an internally consistent and transparent theory of the phenomenon...
August 15, 2017: International Journal of Environmental Research and Public Health
Naresh Khatri, Vishal Gupta, Arup Varma
Based on theoretical frameworks of resource-based theory, dynamic capabilities, and behavioral perspective on human resource management, we developed a multidimensional construct of human resource (HR) capabilities and tested its relationship with quality of patient care using a national sample of U.S. hospitals. The data on HR capabilities were collected from senior managers (421 individuals nested in 279 hospitals) representing both the administrative and clinical sides of the hospitals. The data on quality of patient care were gathered from two unique sources - patients of 207 hospitals who reported the data via the Hospital Consumer Assessment of Healthcare Providers and Systems Survey and 421 senior managers of 279 hospitals...
July 2017: Human Resource Management
Fan Zuo, Priyadarshini Panda, Michele Kotiuga, Jiarui Li, Mingu Kang, Claudio Mazzoli, Hua Zhou, Andi Barbour, Stuart Wilkins, Badri Narayanan, Mathew Cherukara, Zhen Zhang, Subramanian K R S Sankaranarayanan, Riccardo Comin, Karin M Rabe, Kaushik Roy, Shriram Ramanathan
A central characteristic of living beings is the ability to learn from and respond to their environment leading to habit formation and decision making. This behavior, known as habituation, is universal among all forms of life with a central nervous system, and is also observed in single-cell organisms that do not possess a brain. Here, we report the discovery of habituation-based plasticity utilizing a perovskite quantum system by dynamical modulation of electron localization. Microscopic mechanisms and pathways that enable this organismic collective charge-lattice interaction are elucidated by first-principles theory, synchrotron investigations, ab initio molecular dynamics simulations, and in situ environmental breathing studies...
August 14, 2017: Nature Communications
Thomas E White, Darrell J Kemp
BACKGROUND: Theory predicts that colour polymorphism may be favored by variation in the visual context under which signals are perceived. The context encompasses all environmental determinants of light availability and propagation, but also the dynamics of perception in receivers. Color vision involves the neural separation of information into spectral versus luminance channels, which often differentially guide specific tasks. Here we explicitly tested whether this discrete perceptual basis contributes to the maintenance of polymorphism in a prey-luring system...
August 14, 2017: BMC Evolutionary Biology
Di Su, Xiaocai Hu, Chaoqing Dong, Jicun Ren
Caspase-3 is a key enzyme executing apoptosis during ontogenesis and homeostasis of multicellular organisms, and is a very important and potential drug target in treatment of apoptosis disturbance. So far, no commercial drugs for caspase-3 are available, and it is urgently necessitated to develop an effective method for caspase-3 activity assay and its inhibitor screening. In this paper, we propose a new method for determination of caspase-3 activity and its inhibition constant by combining single molecule fluorescence correlation spectroscopy (FCS) with a microwell chip...
August 14, 2017: Analytical Chemistry
Daoling Peng, Shaopeng Li, Liang Peng, Feng Long Gu, Weitao Yang
Time-dependent coupled perturbed Hartree-Fock/Density-Functional-Theory (TDHF/TDDFT) approach has been reformulated based on non-orthogonal localized molecular orbitals (NOLMOs). Based on the NOLMO Fock equation, we have derived the corresponding NOLMO-TDHF/TDDFT equations up to the third order, and the formula for the frequency dependent (hyper)polarizabilities have been given. Our approach has been applied to calculate both static and dynamic (hyper)polarizabilities of molecules varying from small molecules to large molecules...
August 14, 2017: Journal of Chemical Theory and Computation
Stefanie Winkelmann, Christof Schütte
Accurate modeling and numerical simulation of reaction kinetics is a topic of steady interest. We consider the spatiotemporal chemical master equation (ST-CME) as a model for stochastic reaction-diffusion systems that exhibit properties of metastability. The space of motion is decomposed into metastable compartments, and diffusive motion is approximated by jumps between these compartments. Treating these jumps as first-order reactions, simulation of the resulting stochastic system is possible by the Gillespie method...
December 7, 2016: Journal of Chemical Physics
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