Interconnection Pattern Research Articles

Polymer-assisted self-assembly of silver nanoparticles into interconnected morphology and enhanced surface electric conductivity

Polymer films with an embedded silver surface and moderate electric conductivity were facilely fabricated. The silver/polymer nanocomposite films were prepared by homogenizing silver nitrate in aqueous poly(vinyl alcohol) (PVA), solution casting, evaporating water, and further annealing. During the process, the chemical transformations involved the initial generation of a unique fern-like morphology from the AgNO3–PVA complexes, reduction of silver nitrate into silver nanoparticles (AgNPs), and Ag particle migration and self-assembling into a 3D interconnected network on the film surface. Heating at 100 °C for 24 h resulted in the reduction of AgNO3 into AgNPs (50 to 200 nm in diameter) that consequently migrated and melted into an interconnected network in the film's surface upon annealing at 250 °C. The resulting film had a surface sheet resistance of 1.0 Ω sq−1, which is a significant drop from the value of 2.0 × 108 Ω sq−1 for the pristine PVA. The films were analyzed by using UV-Visible spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electric conductivity measurements by a four-point probe meter. The hierarchical self-assembly of the silver species was largely directed by the initial formation of the fern-like morphology from AgNO3–PVA complexes. The ultimate construction of an interconnected Ag pattern led to PVA films with enhanced surface electric conductivity that is capable of lighting LED bulbs.

Dynamics of spinodal decomposition coupled with chemical reaction in thermosetting phenol-formaldehyde resin-based solutions and its application in monolithic porous materials

A model comprised of a rate equation for polymerization and cross-linking reaction and the time-dependent Ginzburg–Landau equation for spinodal decomposition was utilized to describe reaction-induced spinodal decomposition (RISD). The effects of initial composition, curing temperature, and scaled diffusion coefficient and rate constant on the RISD dynamics were investigated numerically in thermosetting phenol-formaldehyde resin (PF)-based polymer solutions. As the initial composition increased, the final morphology varied from the regular droplet-like to interconnected pattern, and then transformed into another droplet-like one. The greater initial composition or higher curing temperature contributed to accelerate the RISD dynamics and caused the smaller dominant wavelength. When the curing point was determined, the increase of scaled diffusion coefficient gave rise to reduction of characteristic size and maximum structure factor, while the raise of scaled rate constant merely resulted in acceleration of the curing reaction. Based on the theoretical analyses, experiments were carried out to verify the influence of initial composition and curing temperature on the morphology of monolithic porous carbons. The results were in good agreement with the theoretical analyses and can provide guidance for synthesizing monolithic porous polymer and carbon materials with tunable pore morphology.

Cyst geometry in the egg chambers of Calliphora erythrocephala Mg. (Diptera: Calliphoridae) ovaries

In the germarium of polytrophic ovarioles of Calliphora erythrocephala (Mg.) fly, four mitotic divisions of cystoblasts give rise to 16-cell germ-line cysts. One cell differentiates into an oocyte, while the remaining 15 cells become nurse cells. Concomitantly actin-rich ring canals are formed at the intercellular junctions. The present study considers a mutual arrangement of the ring canals formed after the second to fourth mitoses relative to the ring canal formed after the first mitotic division in different regions of the germarium and egg chambers. During the cyst formation and its movement to the posterior end of the germarium, the ring canals are displaced relative to one another, thereby giving different branching variants of the cyst. The pattern of cell interconnections becomes stable in germarium region 2b and does not change during the cyst movement along the ovariole despite the cyst polarizes and increases in size.

Network sampling of social divisions in a rural Inuit community

This paper describes results from a network survey of Nain – a predominantly Inuit community of ~1200 people located on the northern coast of Labrador. As part of a larger social network research project, we used peer-referral sampling to recruit 330 residents for interviews about food sharing, housing, public health and community traditions. The peer-referral chains were analysed statistically to determine the presence and absence of social divisions in the community. The results of these analyses show that ethnic identification, relocation status and household income were the most significant social divisions in the community, while gender, education level and employment status show little or no effect on patterns of between-group interconnection. We argue that statistical patterns in the presence (and absence) of intergroup links offer novel ways to examine the interrelationship between recent economic development and the historical disruptions caused by Inuit community relocations in the 1950s.

Reduction of the small gain condition for large‐scale interconnections

SummaryThe small gain condition is sufficient for input‐to‐state stability (ISS) of interconnected systems. However, verification of the small gain condition requires large amount of computations in the case of a large size of the system. To facilitate this procedure, we aggregate the subsystems and the gains between the subsystems that belong to certain interconnection patterns (motifs) by using three heuristic rules. These rules are based on three motifs: sequentially connected nodes, nodes connected in parallel, and almost disconnected subgraphs. Aggregation of these motifs keeps the structure of the mutual influences between the subsystems in the network. Furthermore, fulfillment of the reduced small gain condition implies ISS of the large network. Thus, such reduction allows to decrease the number of computations needed to verify the small gain condition. Finally, an ISS‐Lyapunov function for the large network can be constructed using the reduced small gain condition. Applications of these rules is illustrated on an example. Copyright © 2013 John Wiley & Sons, Ltd.

Efficient Cluster Labeling for Support Vector Clustering

We propose a new efficient algorithm for solving the cluster labeling problem in support vector clustering (SVC). The proposed algorithm analyzes the topology of the function describing the SVC cluster contours and explores interconnection paths between critical points separating distinct cluster contours. This process allows distinguishing disjoint clusters and associating each point to its respective one. The proposed algorithm implements a new fast method for detecting and classifying critical points while analyzing the interconnection patterns between them. Experiments indicate that the proposed algorithm significantly improves the accuracy of the SVC labeling process in the presence of clusters of complex shape, while reducing the processing time required by existing SVC labeling algorithms by orders of magnitude.

Effect of local stress on the heat-checking morphology in high temperature tool steels under thermal fatigue: Transition from multi-axiality to uniaxiality

Thermal fatigue experiments are performed on a high temperature tool steel X38CrMoV5 (AISI H11), under various maximum temperatures and heating rates. A microscopic interconnected crack pattern (named “heat-checking”) forms on the oxidised surface of the laboratory tubular specimen. A gradual transition is observed, from a “cell-type” cracking at the centre of the specimen to a “parallel cracking” at its extremities. This variation of the morphology is well demonstrated by geometrical and topological characteristics of the crack network (micro-crack orientations, cell shape and node density), which change along the longitudinal axis of the specimen. The thermo-elasto-plastic loading of the specimen is estimated by Finite Element Calculations using ABAQUS™. Whatever the thermal fatigue conditions, a linear correlation can be established between the longitudinal and hoop stress amplitude ratio Δσzz/Δσθθ and the hoop and longitudinal inter-crack spacing ratio dθθ/dzz. It is shown that a stress amplitude ratio close to 1 results in a multi-axial heat-checking, while a uni-axial cracking is generated when Δσzz/Δσθθ is close to or below 0.6. This means that the morphology of the heat-checking pattern (cell or parallel type) can be used as an indicator for the local stress ratio of the thermal fatigue specimen or industrial real tools.

Stochastic resonance in feedforward-loop neuronal network motifs in astrocyte field

Elucidating the underlying dynamical properties of neuronal network motifs, statistically significant patterns of interconnections, is essential to understand the dynamics of the whole networks. Besides, the brain is intrinsically noisy. Various noise-induced dynamical behaviors, in particular, the stochastic resonance (SR), have been found in both neuronal systems and neuronal network motifs. However, the effect of astrocytes, active partners in neuronal signal processing, has not yet received much attention. In this paper, we study the effect of astrocytes on the stochastic behaviors of the typical triple-neuron feedforward-loop (FFL) neuronal network motifs. The neurons are described by the Hodgkin–Huxley model, while the astrocytes are modeled by extending the Li–Rinzel model to a two-dimensional field with the effect of diffusion. The mutual neuron–astrocyte interactions are established correspondingly. Simulation results indicate that the stochastic behaviors of the FFL motifs show bell-shaped dependence on the intensities of both noise and astrocyte–neuron coupling. Moreover, in the presence of astrocytes, the performance of the FFL motifs on weak signal transmission in both noisy and noise-free environments can be significantly improved. From this point of view, the astrocytes can be regarded as a possible internal source of “noise”, which assist the neurons in signal processing.

Simple and effective graphene laser processing for neuron patterning application.

A straightforward fabrication technique to obtain patterned substrates promoting ordered neuron growth is presented. Chemical vapor deposition (CVD) single layer graphene (SLG) was machined by means of single pulse UV laser ablation technique at the lowest effective laser fluence in order to minimize laser damage effects. Patterned substrates were then coated with poly-D-lysine by means of a simple immersion in solution. Primary embryonic hippocampal neurons were cultured on our substrate, demonstrating an ordered interconnected neuron pattern mimicking the pattern design. Surprisingly, the functionalization is more effective on the SLG, resulting in notably higher alignment for neuron adhesion and growth. Therefore the proposed technique should be considered a valuable candidate to realize a new generation of highly specialized biosensors.

Arching structures in granular sedimentary deposits

Experimental results on arching structures in sedimentary deposits are presented. Polydisperse mixtures of rough non-spherical natural calcite particles (ground limestone) settled collectively in a liquid, in a lab-scale experimental cylinder. At the bottom, layers of sediment were produced. The morphology of the deposit layers was studied with the help of visualization and image analysis. Families of inter-connected arching patterns in the form of voids or cavities were identified, of highly complex geometry. The effect of the mixture composition on the deposit structure was investigated. It was found that arches tend to form under specific conditions. Large and small grains promoted the arch formation, while the medium grains tended to inhibit arching. • experiments on complex sedimenting systems of real geological materials, • arching patterns within the deposit layer (cavities, voids, caverns), spatial distribution, • effect of polydispersity of the settling mixture on production of the arching structures.

Author Reply: Coregulation is a State of a Temporal Interpersonal Emotion System

People in an emotional exchange form a temporal interpersonal emotion system (TIES), in which their emotions are interconnected over time (Butler, 2011). These systems can be in various states, defined by the pattern of emotional interconnections. We have defined coregulation as one such state involving coupled dampened oscillations between partners’ emotions that converge on a stable level. Coregulation could be distinguished from other states, such as stress buffering, by comparing statistical models that represent the theoretical distinctions between states. Optimal data for such modeling includes assessments of both partners’ emotions over time and a contrast between securely attached partners, strangers, and being alone. Research of this sort is needed to uncover the mechanisms by which emotional interdependence promotes well-being.

Role of heat-flux density and mechanical loading on the microscopic heat-checking of high temperature tool steels under thermal fatigue experiments

Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected heat-checking pattern forms on the oxidized surface of the specimen. The evolution of the crack density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the heating period of the thermal cycle are reported. It is shown that the saturated heat-checking density is independent of the maximum temperature of the thermal cycle, but is dependent on the heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the heat-checking density and the maximum heat-flux density applied to the specimen. The saturated crack density is explained by the difference between the thermo-mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic heat-checking life.

Visually driven chaining of elementary swim patterns into a goal-directed motor sequence: a virtual reality study of zebrafish prey capture.

Prey capture behavior critically depends on rapid processing of sensory input in order to track, approach, and catch the target. When using vision, the nervous system faces the problem of extracting relevant information from a continuous stream of input in order to detect and categorize visible objects as potential prey and to select appropriate motor patterns for approach. For prey capture, many vertebrates exhibit intermittent locomotion, in which discrete motor patterns are chained into a sequence, interrupted by short periods of rest. Here, using high-speed recordings of full-length prey capture sequences performed by freely swimming zebrafish larvae in the presence of a single paramecium, we provide a detailed kinematic analysis of first and subsequent swim bouts during prey capture. Using Fourier analysis, we show that individual swim bouts represent an elementary motor pattern. Changes in orientation are directed toward the target on a graded scale and are implemented by an asymmetric tail bend component superimposed on this basic motor pattern. To further investigate the role of visual feedback on the efficiency and speed of this complex behavior, we developed a closed-loop virtual reality setup in which minimally restrained larvae recapitulated interconnected swim patterns closely resembling those observed during prey capture in freely moving fish. Systematic variation of stimulus properties showed that prey capture is initiated within a narrow range of stimulus size and velocity. Furthermore, variations in the delay and location of swim triggered visual feedback showed that the reaction time of secondary and later swims is shorter for stimuli that appear within a narrow spatio-temporal window following a swim. This suggests that the larva may generate an expectation of stimulus position, which enables accelerated motor sequencing if the expectation is met by appropriate visual feedback.

Decomposition-Based Distributed Control for Continuous-Time Multi-Agent Systems

In this technical note, we consider the problem of designing distributed controller for a continuous-time system composed of a number of identical dynamically coupled subsystems. The underlying mathematical derivation is based on Kronecker product and a special similarity transformation constructed from interconnection pattern matrix that decomposes the system into modal subsystems. This along with the result of extended linear matrix inequality (LMI) formulation for continuous-time systems makes it possible to derive explicit expressions for computing the parameters of distributed controllers for both static state feedback and dynamic output feedback cases. The main contribution of the technical note is the solution of distributed control problem for continuous-time systems under <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> / α-stability and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> / α-stability performances by solving a set of LMIs with noncommon Lyapunov variables. The effectiveness of this method is demonstrated by means of a satellite formation example.

On the discovery of group-consistent graph substructure patterns from brain networks

Complex networks constitute a recurring issue in the analysis of neuroimaging data. Recently, network motifs have been identified as patterns of interconnections since they appear in a significantly higher number than in randomized networks, in a given ensemble of anatomical or functional connectivity graphs. The current approach for detecting and enumerating motifs in brain networks requires a predetermined motif repertoire and can operate only with motifs of small size (consisting of few nodes).There is a growing interest in methodologies for frequent graph-based pattern mining in large graph datasets that can facilitate adaptive design of motifs. The results presented in this paper are based on the graph-based Substructure pattern mining (gSpan) algorithm and introduce a manifold of ways to exploit it for data-driven motif extraction in connectomics research.Functional connectivity graphs from electroencephalographic (EEG) recordings during resting state and mental calculations are used to demonstrate our approach. Relying on either time-invariant or time-evolving graphs, characteristic motifs associated with various frequency bands were derived and compared. With a suitable manipulation, the gSpan discovers motifs which are specific to performing mental arithmetics. Finally, the subject-dependent temporal signatures of motifs’ appearance revealed the transient nature of the evolving functional connectivity (math-related motifs “come and go”).

Understanding Corporate Social Irresponsibility on Sports Organizations

For this study, we sought to understand the conceptualization of sports organizations in the CSR context from the customer perspective. Previous studies have mainly focused on the positive effect of CSR and neglected the negative effect of irresponsible behaviors. The associations on these entities are often treated discretely, whereas the interrelatedness of the associations are overlooked. This research employs the brand concept map (BCM) method to elucidate the complex and interconnected associations of how a sports organization is perceived, and presents these findings in a graphical network structure. The aggregated network of associations in people’s memory, consisting of performance, setting, and auxiliary elements, constitutes the core (brand) images and relevant patronage values of an organization. This research contributes to the understanding of sports brand on the association and network levels. This study identifies useful individual associations such as baseball, players, mascots, related products and corporations, CSR-related behaviors, and the interconnection patterns between elements. These identified factors are useful in detecting and developing patronage and in identifying incongruence in the conceptualization of brand and organization image. The interconnectivity and network structure of people’s associations are considered by the employed in this methodology in this study. This study identifies the framework of relevant associations, elements, values, and interconnection patterns, which not only provide comprehensive information in understanding complex conceptual perceptions, but might also be leveraged and focused on by marketers for an enhanced creative marketing and communication strategy.

Three-Dimensional Elastomeric Scaffolds Designed with Cardiac-Mimetic Structural and Mechanical Features

Tissue-engineered constructs, at the interface of material science, biology, engineering, and medicine, have the capacity to improve outcomes for cardiac patients by providing living cells and degradable biomaterials that can regenerate the native myocardium. With an ultimate goal of both delivering cells and providing mechanical support to the healing heart, we designed three-dimensional (3D) elastomeric scaffolds with (1) stiffnesses and anisotropy mimicking explanted myocardial specimens as predicted by finite-element (FE) modeling, (2) systematically varied combinations of rectangular pore pattern, pore aspect ratio, and strut width, and (3) structural features approaching tissue scale. Based on predicted mechanical properties, three scaffold designs were selected from eight candidates for fabrication from poly(glycerol sebacate) by micromolding from silicon wafers. Large 20×20 mm scaffolds with high aspect ratio features (5:1 strut height:strut width) were reproducibly cast, cured, and demolded at a relatively high throughput. Empirically measured mechanical properties demonstrated that scaffolds were cardiac mimetic and validated FE model predictions. Two-layered scaffolds providing fully interconnected pore networks were fabricated by layer-by-layer assembly. C2C12 myoblasts cultured on one-layered scaffolds exhibited specific patterns of cell elongation and interconnectivity that appeared to be guided by the scaffold pore pattern. Neonatal rat heart cells cultured on two-layered scaffolds for 1 week were contractile, both spontaneously and in response to electrical stimulation, and expressed sarcomeric α-actinin, a cardiac biomarker. This work not only demonstrated several scaffold designs that promoted functional assembly of rat heart cells, but also provided the foundation for further computational and empirical investigations of 3D elastomeric scaffolds for cardiac tissue engineering.

A first step towards understanding Saudi political activities on Twitter

PurposeThis study aims to understand the underlying social structure of Saudi citizens' interaction and discussion of political topics over the Twitter sphere.Design/methodology/approachThe study employs social network analysis (SNA) measurements such as centrality, eigenvector and graph density on tweets produced in June 2012 by the Saudi community.FindingsThe result of SNA reveals relevant differences in the patterns of interconnection among different political topics. It also provides insights into sociological characteristics of modern political issues in Saudi Arabia.Research limitations/implicationsThe limitation of this study resides in the lack of large data set for robust analysis.Originality/valueThis is the first study aiming to understand social network dynamics of Twitter targeting the Saudi community.

“More than the house”: a Canadian perspective on housing stability

PurposeThe challenges of achieving housing stability are examinable from a variety of locations and perspectives, resulting in a range of solutions and recommendations for practice. Attending to the experiences and understandings of both service users and service providers within a broad environmental scan, one can obtain a more complete picture of how housing stability can be supported and sustained. The purpose of this research is to better understand the practical landscape, human relationships, interdisciplinary understandings and everyday activities of housing stability.Design/methodology/approachThe paper draws on thematic analysis from expert informant interviews conducted during an environmental scan of housing options and facilities for those who have been labelled “hard to house” in a large, ethnically‐diverse urban city in western Canada. Interviews of selected service users yielded information on their perspectives of the barriers and facilitators of housing stability. Parallel interviews of service providers and/or policy makers were also conducted, and responses compared and contrasted with those of service users.FindingsThree interconnected patterns on the path to housing stability were experienced by the expert informants, and are explored herein. The overlapping and developmental themes “more than a house,” “finding support,” and “connecting multiple supports” are discussed. Conditions and realities of coordinated support need, particularly for those deemed “hard to house” because of addictions or mental health problems were revealed by the expert informants in this study.Research limitations/implicationsThematic analysis of the parallel interviews brought the landscape of housing stability into clearer focus and contributed to practice recommendations. This qualitative research approach was not intended to provide generalizable findings, but rather sheds light on particular experiences and understandings in ways that may contribute to further research. The themes identified may resonate in differing circumstances having arisen from the more generalized practical realities and social conditions which warrant an ongoing analysis.Practical implicationsThe analysis revealed an ongoing gap of support for the management and coordination of the often complex requirements of support for housing stability for service users. Various service agencies, providing houses, providing financial aid, providing health and social support need to “connect multiple levels of support” something identified as an all too often missing link in achieving housing stability. Recommendations include recognizing the necessity of multiple sectors working together with multiple sites and layers of support, in particular for those who experience addictions or mental health problems. More tailored support, follow up and recognition of the potential for instability is a particular practical implication of the study. Invigorating a coordinative, case management role, with a view to bridging and bringing together seemingly disparate sectors and service providers are relevant practical implications of this study.Originality/valueThe research is novel in approach, drawing on a parallel expert informant interview process, and findings are of relevance to practical activities in housing, social and health services and policy as well as for scholarly dialogue and discussion.

A three-dimensional highly stable cobalt(II) metal–organic framework based on terephthalic acid: synthesis, crystal structure, thermal and physical properties

A metal–organic framework complex, [Co(μ3–tp)(μ2−pyz)]n, where H2tp = 1,4-benzenedicarboxylic acid (terephthalic acid) and pyz = pyrazine, has been synthesized under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods, thermogravimetric analysis and single-crystal X-ray diffraction. Each Co(II) center is surrounded by four carboxylate oxygen atoms from three tp ligands and two nitrogen atoms from two pyrazine ligands, giving a distorted octahedral geometry. The entire framework is made up of two-dimensional sheets of dicobalt ions linked via terephthalate ligands to form rectangles. The sheets are then linked into each other via the axial pyrazine ligands, forming an interlocked 3-D network, which is finally arranged as an ABAB interconnected pattern. Photoluminescence measurements for the polymer in the solid state show an emission at 414 nm, which suggests this complex as a potential blue-light material. The electrochemical behavior of a modified carbon paste electrode prepared from the complex has been studied by cyclic voltammetry, indicating quasi-reversible redox behavior.