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Network theory

Hye Jeong Choi, Michael Hecht, Rachel A Smith
Interpersonal communication among participants plays an important role in the impact and effectiveness of prevention programs (Southwell & Yzer, Communication Theory 19:1-8, 2009). This study focused on adolescents' informal conversations about a prevention program, referred to as social talk, from a social network perspective. We provide both a conceptualization of social talk in relation to prevention programs and an operationalization of it by examining adolescents' social networks. Participants (N = 185) were eighth-grade students attending a middle school substance-abuse prevention program called keepin' it REAL (kiR)...
February 18, 2017: Prevention Science: the Official Journal of the Society for Prevention Research
Yuan Xu, Aleks D Atrens, Jason R Stokes
HYPOTHESIS: Nanocrystalline cellulose (NCC) is a negatively charged rod-like colloid obtained from the hydrolysis of plant material. It is thus expected that NCC suspensions display a rich set of phase behaviour with salt and pH because of its anisotropic shape and electrical double layer that gives rise to liquid crystallinity and self-assembly respectively. It should thus be possible to tune the rheological properties of NCC suspensions for a wide variety of end-use applications. EXPERIMENTS: Rheology and structural analysis techniques are used to characterise surface-sulphated NCC suspensions as a function of pH, salinity (NaCl) and NCC concentration...
February 12, 2017: Journal of Colloid and Interface Science
Soo-Eun Chang, Michael Angstadt, Ho Ming Chow, Andrew C Etchell, Emily O Garnett, Ai Leen Choo, Daniel Kessler, Robert C Welsh, Chandra Sripada
PURPOSE: We combined a large longitudinal neuroimaging dataset that includes children who do and do not stutter and a whole-brain network analysis in order to examine the intra- and inter-network connectivity changes associated with stuttering. Additionally, we asked whether whole brain connectivity patterns observed at the initial year of scanning could predict persistent stuttering in later years. METHODS: A total of 224 high-quality resting state fMRI scans collected from 84 children (42 stuttering, 42 controls) were entered into an independent component analysis (ICA), yielding a number of distinct network connectivity maps ("components") as well as expression scores for each component that quantified the degree to which it is expressed for each child...
January 25, 2017: Journal of Fluency Disorders
Kyoko Ohashi, Carl M Anderson, Elizabeth A Bolger, Alaptagin Khan, Cynthia E McGreenery, Martin H Teicher
Childhood maltreatment is a major risk factor for psychopathology. It is also associated with alterations in the network architecture of the brain, which we hypothesized may play a significant role in the development of psychopathology. In this study, we analyzed the global network architecture of physically healthy unmedicated 18-25 year old subjects (n=262) using diffusion tensor imaging (DTI) MRI and tractography. Anatomical networks were constructed from fiber streams interconnecting 90 cortical or subcortical regions for subjects with no-to-low (n=122) versus moderate-to-high (n=140) exposure to maltreatment...
February 14, 2017: NeuroImage
Ali Mohseni, Shahriar Gharibzadeh, Fatemeh Bakouie
Synchronization is an important global phenomenon which could be found in a wide range of complex systems such as brain or electronic devices. However, in some circumstances the synchronized states are not desirable for the system and should be suppressed. For example, excessively synchronized activities in the brain network could be the root of neuronal disorders like epileptic seizures. According to the controllability theory of the complex networks, a minimum set of driver nodes has the ability to control the entire system...
February 15, 2017: Journal of Theoretical Biology
Ruoshi Yuan, Xiaomei Zhu, Gaowei Wang, Site Li, Ping Ao
Cancer is a complex disease: its pathology cannot be properly understood in terms of independent players-genes, proteins, molecular pathways, or their simple combinations. This is similar to many-body physics of a condensed phase that many important properties are not determined by a single atom or molecule. The rapidly accumulating large 'omics' data also require a new mechanistic and global underpinning to organize for rationalizing cancer complexity. A unifying and quantitative theory was proposed by some of the present authors that cancer is a robust state formed by the endogenous molecular-cellular network, which is evolutionarily built for the developmental processes and physiological functions...
February 17, 2017: Reports on Progress in Physics
Nicholas T Longford
Necrotising enterocolitis is an oft-fatal disease of the intestinal tract in neonates born prematurely and with low birthweight. We study the variation of its rates across the neonatal networks (groups of hospital-based neonatal care units) in England. We illustrate the problematic nature of hypothesis testing for a key decision, which an analysis is meant to inform, and apply an approach based on decision theory. We emphasise the role of sensitivity analysis in dealing with the ambiguity encountered in the process of eliciting information about the perspective of the client or sponsor for whom the analysis is conducted...
February 17, 2017: Statistics in Medicine
José M Alcalá, Jesús Ureña, Álvaro Hernández, David Gualda
The ageing of the population, and their increasing wish of living independently, are motivating the development of welfare and healthcare models. Existing approaches based on the direct heath-monitoring using body sensor networks (BSN) are precise and accurate. Nonetheless, their intrusiveness causes non-acceptance. New approaches seek the indirect monitoring through monitoring activities of daily living (ADLs), which proves to be a suitable solution. ADL monitoring systems use many heterogeneous sensors, are less intrusive, and are less expensive than BSN, however, the deployment and maintenance of wireless sensor networks (WSN) prevent them from a widespread acceptance...
February 11, 2017: Sensors
Taşkın Deniz, Stefan Rotter
Pairs of neurons in brain networks often share much of the input they receive from other neurons. Due to essential nonlinearities of the neuronal dynamics, the consequences for the correlation of the output spike trains are generally not well understood. Here we analyze the case of two leaky integrate-and-fire neurons using an approach which is nonperturbative with respect to the degree of input correlation. Our treatment covers both weakly and strongly correlated dynamics, generalizing previous results based on linear response theory...
January 2017: Physical Review. E
Uttam Bhat, Munik Shrestha, Laurent Hébert-Dufresne
The giant k-core-maximal connected subgraph of a network where each node has at least k neighbors-is important in the study of phase transitions and in applications of network theory. Unlike Erdős-Rényi graphs and other random networks where k-cores emerge discontinuously for k≥3, we show that transitive linking (or triadic closure) leads to 3-cores emerging through single or double phase transitions of both discontinuous and continuous nature. We also develop a k-core calculation that includes clustering and provides insights into how high-level connectivity emerges...
January 2017: Physical Review. E
Forrest C Sheldon, Massimiliano Di Ventra
The development of neuromorphic systems based on memristive elements-resistors with memory-requires a fundamental understanding of their collective dynamics when organized in networks. Here, we study an experimentally inspired model of two-dimensional disordered memristive networks subject to a slowly ramped voltage and show that they undergo a discontinuous transition in the conductivity for sufficiently high values of memory, as quantified by the memristive ON-OFF ratio. We investigate the consequences of this transition for the memristive current-voltage characteristics both through simulation and theory, and demonstrate the role of current-voltage duality in relating forward and reverse switching processes...
January 2017: Physical Review. E
Hongrun Wu, Alex Arenas, Sergio Gómez
The understanding and prediction of information diffusion processes on networks is a major challenge in network theory with many implications in social sciences. Many theoretical advances occurred due to stochastic spreading models. Nevertheless, these stochastic models overlooked the influence of rational decisions on the outcome of the process. For instance, different levels of trust in acquaintances do play a role in information spreading, and actors may change their spreading decisions during the information diffusion process accordingly...
January 2017: Physical Review. E
Flavio Iannelli, Andreas Koher, Dirk Brockmann, Philipp Hövel, Igor M Sokolov
We show that the recently introduced logarithmic metrics used to predict disease arrival times on complex networks are approximations of more general network-based measures derived from random walks theory. Using the daily air-traffic transportation data we perform numerical experiments to compare the infection arrival time with this alternative metric that is obtained by accounting for multiple walks instead of only the most probable path. The comparison with direct simulations reveals a higher correlation compared to the shortest-path approach used previously...
January 2017: Physical Review. E
John S Hyatt, Alison M Douglas, Chris Stanley, Changwoo Do, Thomas H Barker, Alberto Fernández-Nieves
We investigate microgels synthesized from N-isopropylacrylamide (NIPAM) copolymerized with a large mol% of acrylic acid, finding that when the acid groups are partially ionized at high temperatures, competition between ion-induced swelling and hydrophobic deswelling of poly(NIPAM) chains results in microphase separation. In cross-linked microgels, this manifests as a dramatic decrease in the ratio between the radius of gyration and the hydrodynamic radius to ∼0.2, indicating that almost all the mass of the microgel is concentrated near the particle center...
January 2017: Physical Review. E
Jonathan Touboul, Alain Destexhe
Critical states are sometimes identified experimentally through power-law statistics or universal scaling functions. We show here that such features naturally emerge from networks in self-sustained irregular regimes away from criticality. In these regimes, statistical physics theory of large interacting systems predict a regime where the nodes have independent and identically distributed dynamics. We thus investigated the statistics of a system in which units are replaced by independent stochastic surrogates and found the same power-law statistics, indicating that these are not sufficient to establish criticality...
January 2017: Physical Review. E
B Bravi, M Opper, P Sollich
We present average performance results for dynamical inference problems in large networks, where a set of nodes is hidden while the time trajectories of the others are observed. Examples of this scenario can occur in signal transduction and gene regulation networks. We focus on the linear stochastic dynamics of continuous variables interacting via random Gaussian couplings of generic symmetry. We analyze the inference error, given by the variance of the posterior distribution over hidden paths, in the thermodynamic limit and as a function of the system parameters and the ratio α between the number of hidden and observed nodes...
January 2017: Physical Review. E
Debsankha Manik, Martin Rohden, Henrik Ronellenfitsch, Xiaozhu Zhang, Sarah Hallerberg, Dirk Witthaut, Marc Timme
We introduce the concept of network susceptibilities quantifying the response of the collective dynamics of a network to small parameter changes. We distinguish two types of susceptibilities: vertex susceptibilities and edge susceptibilities, measuring the responses due to changes in the properties of units and their interactions, respectively. We derive explicit forms of network susceptibilities for oscillator networks close to steady states and offer example applications for Kuramoto-type phase-oscillator models, power grid models, and generic flow models...
January 2017: Physical Review. E
Paul C Bressloff
We analyze the stochastic dynamics of a large population of noninteracting particles driven by a global environmental input in the form of a dichotomous Markov noise process (DMNP). The population density of particle states evolves according to a stochastic Liouville equation with respect to different realizations of the DMNP. We then exploit the connection with previous work on diffusion in randomly switching environments, in order to derive moment equations for the distribution of solutions to the stochastic Liouville equation...
January 2017: Physical Review. E
Tianyu Yuan, Kazuyuki Aihara, Gouhei Tanaka
The dynamical tolerance of coupled oscillator networks against local failures is studied. As the fraction of failed oscillator nodes gradually increases, the mean oscillation amplitude in the entire network decreases and then suddenly vanishes at a critical fraction as a phase transition. This critical fraction, widely used as a measure of the network robustness, was analytically derived for random failures but not for targeted attacks so far. Here we derive the general formula for the critical fraction, which can be applied to both random failures and targeted attacks...
January 2017: Physical Review. E
Gili Greenbaum, Nina H Fefferman
In populations occupying discrete habitat patches, gene flow between habitat patches may form an intricate population structure. In such structures, the evolutionary dynamics resulting from interaction of gene flow patterns with other evolutionary forces may be exceedingly complex. Several models describing gene flow between discrete habitat patches have been presented in the population genetics literature; however, these models have usually addressed relatively simple settings of habitable patches, and have stopped short of providing general methodologies for addressing non-trivial gene flow patterns...
February 16, 2017: Molecular Ecology
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