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Network theory

Philip J Badawy, Markus H Schafer, Haosen Sun
Life-course transitions among older adults often produce a reshuffling of social network members. Moving is a common experience for U.S. seniors, but relatively little is known about how core networks change amid the relocation process. Drawing on longitudinal data from the National Social Life, Health, and Aging Project, the present study examines how late-life moving is associated with changes to network size and the loss and gain of particular network members. We find that when older adults undertake a long-distance move, they tend to add more family to their core network-yet this is moderated by their initial level of functional health...
January 1, 2018: Research on Aging
Tom Brughmans, Maaike S de Waal, Corinne L Hofman, Ulrik Brandes
This paper presents a study of the visual properties of natural and Amerindian cultural landscapes in late pre-colonial East-Guadeloupe and of how these visual properties affected social interactions. Through a review of descriptive and formal visibility studies in Caribbean archaeology, it reveals that the ability of visual properties to affect past human behaviour is frequently evoked but the more complex of these hypotheses are rarely studied formally. To explore such complex hypotheses, the current study applies a range of techniques: total viewsheds, cumulative viewsheds, visual neighbourhood configurations and visibility networks...
2018: Journal of archaeological method and theory
Edward Yelin, Laura Trupin, Jared Bunde, Jinoos Yazdany
OBJECTIVE: To obtain the perspective of individuals with SLE about the role of poverty, neighborhood, and chronic stress in SLE outcomes. METHODS: 723 persons with SLE were followed from 2003-2015 through annual structured interviews as part of the Lupus Outcomes Study to establish the effect of combinations of poverty, persistent poverty, living in an area of concentrated poverty, access to health care, and chronic stress on accumulated damage. We sampled 28 from the 723 on the basis of household income, geography, and outcomes in their last interview, and administered qualitative interviews to explore their perspectives on these factors on outcomes...
May 21, 2018: Arthritis Care & Research
German Alberto Parada, Xuanhe Zhao
In this article we introduce the concept of ideal reversible polymer networks, which have well-controlled polymer network structures similar to ideal covalent polymer networks but exhibit viscoelastic behaviors due to the presence of reversible crosslinks. We first present a theory to describe the mechanical properties of ideal reversible polymer networks. Because short polymer chains of equal length are used to construct the network, there are no chain entanglements and the chains' Rouse relaxation time is much shorter than the reversible crosslinks' characteristic time...
May 21, 2018: Soft Matter
René Weber, Bradly Alicea, Richard Huskey, Klaus Mathiak
This study investigates the dynamics of attention during continuous, naturalistic interactions in a video game. Specifically, the effect of repeated distraction on a continuous primary task is related to a functional model of network connectivity. We introduce the Non-linear Attentional Saturation Hypothesis (NASH), which predicts that effective connectivity within attentional networks increases non-linearly with decreasing distraction over time, and exhibits dampening at critical parameter values. Functional magnetic resonance imaging (fMRI) data collected using a naturalistic behavioral paradigm coupled with an interactive video game is used to test the hypothesis...
2018: Frontiers in Human Neuroscience
Arif Khan, Shahadat Uddin, Uma Srinivasan
BACKGROUND: Chronic diseases management outside expensive hospital settings has become a major target for governments, funders and healthcare service providers. It is well known that chronic diseases such as Type 2 Diabetes (T2D) do not occur in isolation, and has a shared aetiology common to many other diseases and disorders. Diabetes Australia reports that it is associated with a myriad of complications, which affect the feet, eyes, kidneys, and cardiovascular health. For instance, nerve damage in the lower limbs affects around 13% of Australians with diabetes, diabetic retinopathy occurs in over 15% of Australians with diabetes, and diabetes is now the leading cause of end-stage kidney disease...
July 2018: International Journal of Medical Informatics
Holly J Bowen, Cheryl L Grady, Julia Spaniol
Affective processing is one domain that remains relatively intact in healthy aging. Investigations into the neural responses associated with reward anticipation have revealed that older and younger adults recruit the same midbrain reward regions, but other evidence suggests this recruitment may differ depending on the valence (gain, loss) of the incentive cue. The goal of the current study was to examine functional covariance during gain and loss feedback in younger and healthy older adults. A group of 15 older adults (mean age = 68...
May 21, 2018: Neuropsychology, Development, and Cognition. Section B, Aging, Neuropsychology and Cognition
Peter Fransson, Björn C Schiffler, William Hedley Thompson
The characterization of brain subnetwork segregation and integration has previously focused on changes that are detectable at the level of entire sessions or epochs of imaging data. In this study, we applied time-varying functional connectivity analysis together with temporal network theory to calculate point-by-point estimates in subnetwork segregation and integration during an epoch-based (2-back, 0-back, baseline) working memory fMRI experiment as well as during resting-state. This approach allowed us to follow task-related changes in subnetwork segregation and integration at a high temporal resolution...
May 16, 2018: NeuroImage
Rachel Nicks, Lucie Chambon, Stephen Coombes
For coupled oscillator networks with Laplacian coupling, the master stability function (MSF) has proven a particularly powerful tool for assessing the stability of the synchronous state. Using tools from group theory, this approach has recently been extended to treat more general cluster states. However, the MSF and its generalizations require the determination of a set of Floquet multipliers from variational equations obtained by linearization around a periodic orbit. Since closed form solutions for periodic orbits are invariably hard to come by, the framework is often explored using numerical techniques...
March 2018: Physical Review. E
Giovanni M Cicuta, Johannes Krausser, Rico Milkus, Alessio Zaccone
A sparse random block matrix model suggested by the Hessian matrix used in the study of elastic vibrational modes of amorphous solids is presented and analyzed. By evaluating some moments, benchmarked against numerics, differences in the eigenvalue spectrum of this model in different limits of space dimension d, and for arbitrary values of the lattice coordination number Z, are shown and discussed. As a function of these two parameters (and their ratio Z/d), the most studied models in random matrix theory (Erdos-Renyi graphs, effective medium, and replicas) can be reproduced in the various limits of block dimensionality d...
March 2018: Physical Review. E
Hao Wang, Weitao Yang
We developed a novel neural network based force field for water based on training with high level ab initio theory. The force field was built based on electrostatically embedded many-body expansion method truncated at binary interactions. Many-body expansion method is a common strategy to partition the total Hamiltonian of large systems into a hierarchy of few-body terms. Neural networks were trained to represent electrostatically embedded one-body and two-body interactions, which require as input only one and two water molecule calculations at the level of ab initio electronic structure method CCSD/aug-cc-pVDZ embedded in the molecular mechanics water environment, making it efficient as a general force field construction approach...
May 18, 2018: Journal of Physical Chemistry Letters
Projesh Kumar Roy, Markus Heyde, Andreas Heuer
The recent experimental discovery of a semi two-dimensional silica glass has offered a realistic description of the random network theory of a silica glass structure, initially discussed by Zachariasen. To study the structure formation of silica in two dimensions, we introduce a two-body force field, based on a soft core Yukawa potential. The different configurations, sampled via Molecular dynamics simulations, can be directly compared with the experimental structures, which have been provided in the literature...
May 18, 2018: Physical Chemistry Chemical Physics: PCCP
Daryna Smyrnova, María Del Carmen Marín, Massimo Olivucci, Arnout Ceulemans
A set formed by five reversibly-switchable fluorescent proteins (RSFPs) display spread over 40~nm in absorption maxima and only 18~nm in emission. The five proteins -- Dronpa, rsFastLime, rsKame, Padron(anionic form) and bsDronpa -- carry exactly the same chromophore and differ just in a few mutations. Thus they form an ideal set for mechanistic investigation. Starting with the results of molecular dynamics simulations we use QM/MM calculations to investigate the effects controlling the spectral tuning . In this contribution we show that the models, which are based on CASPT2//CASSCF level of QM theory, reproduce the observed absorption trend with only a limited blue-shift of 4...
May 17, 2018: Journal of Chemical Theory and Computation
Zhanshan Wang, Lei Liu, Yanming Wu, Huaguang Zhang
This paper investigates the problem of optimal fault-tolerant control (FTC) for a class of unknown nonlinear discrete-time systems with actuator fault in the framework of adaptive critic design (ACD). A pivotal highlight is the adaptive auxiliary signal of the actuator fault, which is designed to offset the effect of the fault. The considered systems are in strict-feedback forms and involve unknown nonlinear functions, which will result in the causal problem. To solve this problem, the original nonlinear systems are transformed into a novel system by employing the diffeomorphism theory...
June 2018: IEEE Transactions on Neural Networks and Learning Systems
Huaguang Zhang, Qiuxia Qu, Geyang Xiao, Yang Cui
Based on integral sliding mode and approximate dynamic programming (ADP) theory, a novel optimal guaranteed cost sliding mode control is designed for constrained-input nonlinear systems with matched and unmatched disturbances. When the system moves on the sliding surface, the optimal guaranteed cost control problem of sliding mode dynamics is transformed into the optimal control problem of a reformulated auxiliary system with a modified cost function. The ADP algorithm based on single critic neural network (NN) is applied to obtain the approximate optimal control law for the auxiliary system...
June 2018: IEEE Transactions on Neural Networks and Learning Systems
Mohammad Tehrani, Zahra Ghalamzan, Alireza Sarvestani
The classical theory of polymer elasticity is built upon the assumption of network monodispersity, the premise that polymer networks are comprised from sub-chains of equal length. The crosslinking of biopolymers, however, is a random process and the resultant networks are likely to be polydisperse. The effect of structural polydispersity on mechanical behavior of biopolymer networks is not well understood. The purpose of this contribution is to show how network polydispersity controls the mechanical behavior and ultimate properties of crosslinked semi-flexible filaments at finite deformations...
May 17, 2018: Physical Biology
Tobias Mütze, Ekkehard Glimm, Heinz Schmidli, Tim Friede
Count data and recurrent events in clinical trials, such as the number of lesions in magnetic resonance imaging in multiple sclerosis, the number of relapses in multiple sclerosis, the number of hospitalizations in heart failure, and the number of exacerbations in asthma or in chronic obstructive pulmonary disease (COPD) are often modeled by negative binomial distributions. In this manuscript, we study planning and analyzing clinical trials with group sequential designs for negative binomial outcomes. We propose a group sequential testing procedure for negative binomial outcomes based on Wald statistics using maximum likelihood estimators...
January 1, 2018: Statistical Methods in Medical Research
Hao Yin, Austin R Benson, Jure Leskovec, David F Gleich
Local graph clustering methods aim to find a cluster of nodes by exploring a small region of the graph. These methods are attractive because they enable targeted clustering around a given seed node and are faster than traditional global graph clustering methods because their runtime does not depend on the size of the input graph. However, current local graph partitioning methods are not designed to account for the higher-order structures crucial to the network, nor can they effectively handle directed networks...
August 2017: KDD: Proceedings
Miguel Aguilera, Manuel G Bedia
Many biological and cognitive systems do not operate deep within one or other regime of activity. Instead, they are poised at critical points located at phase transitions in their parameter space. The pervasiveness of criticality suggests that there may be general principles inducing this behaviour, yet there is no well-founded theory for understanding how criticality is generated at a wide span of levels and contexts. In order to explore how criticality might emerge from general adaptive mechanisms, we propose a simple learning rule that maintains an internal organizational structure from a specific family of systems at criticality...
May 16, 2018: Scientific Reports
Laura Ribeiro Ferreira, Elizabeth Artmann
This paper presents the pronouncements on humanization of professionals and users of a health care and research institution. Interviews were conducted with 16 professionals and 44 users. The analytical method employed was the Discourse of the Collective Subject, the results of which were discussed based on the theoretical framework presented, which includes the Theory of communicative action of Habermas and recognized authors in the public health area. The findings point to the importance of the set of hard, light-hard and light technologies for humanized practice...
May 2018: Ciência & Saúde Coletiva
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