Core Periphery Research Articles (Page 6)

Software development is incredibly complex. Specifically, open-source software (OSS) development requires developers to collaborate with each other to conduct their work. Because software systems are evolving with time, collaboration among software developers may affect the quality of evolved software. The OSS developer teams collaborate in various tasks, including communications, coordination, and making various social collaboration in the OSS projects (e.g., bug/issue report, discussion, code revisions, and so on) without access restriction, and all these activities are used to generate an implicit developer social network (DSN). The DSN that is based on a bug tracking system is one of the most important DSNs that reflect the real collaboration between developers. As the software system evolves, the DSN evolves. This paper describes an empirical study of the evolution of DSNs on OSS projects collected from GitHub. Four perspectives were used: social network analysis, DSN as an ecosystem, community evolution patterns, and the core-periphery structure. The results demonstrated the DSNs over time have followed the power law degree distribution with +1% or more as an increasing rate to be more fitting overtime. DSNs over time are considered a small-world community. DSNs over time exhibits about 55% diversity with 75% of evenness between the developers to contribute in different OSS projects in the same environment. Moreover, DSNs over time have a few developers as core members and large developers as peripheral members. Finally, about 10% of developers changed their positions frequently over time.

Structural correlation between communities and core-periphery structures in social networks: Evidence from Twitter data

In response to failures of central planning, the Chinese government has experimented not only with free-market trade zones, but with allowing non-profit foundations to operate in a decentralized fashion. A network study shows how these foundations have connected together by sharing board members, in a structural parallel to what is seen in corporations in the United States and Europe. This board interlocking leads to the emergence of an elite group with privileged network positions. While the presence of government officials on non-profit boards is widespread, government officials are much less common in a subgroup of foundations that control just over half of all revenue in the network. This subgroup, associated with business elites, not only enjoys higher levels of within-elite links, but even preferentially excludes government officials from the NGOs with higher degree. The emergence of this structurally autonomous sphere is associated with major political and social events in the state–society relationship. Cluster analysis reveals multiple internal components within this sphere that share similar levels of network influence. Rather than a core-periphery structure centered around government officials, the Chinese non-profit world appears to be a multipolar one of distinct elite groups, many of which achieve high levels of independence from direct government control.

How the ownership structures cause epidemics in financial markets: A network-based simulation model

Agent-based modeling of China’s rural–urban migration and social network structure

Zika virus (ZIKV) exhibits unique transmission dynamics in that it is concurrently spread by a mosquito vector and through sexual contact. Due to the highly asymmetric durations of infectiousness between males and females-it is estimated that males are infectious for periods up to 10 times longer than females-we show that this sexual component of ZIKV transmission behaves akin to an asymmetric percolation process on the network of sexual contacts. We exactly solve the properties of this asymmetric percolation on random sexual contact networks and show that this process exhibits two epidemic transitions corresponding to a core-periphery structure. This structure is not present in the underlying contact networks, which are not distinguishable from random networks, and emerges because of the asymmetric percolation. We provide an exact analytical description of this double transition and discuss the implications of our results in the context of ZIKV epidemics. Most importantly, our study suggests a bias in our current ZIKV surveillance, because the community most at risk is also one of the least likely to get tested.

ABSTRACTMore extensive attention has been paid to the heterogeneity of maritime transport network in topological rather than in spatial aspects. However, the importance of links and the roles of neighbors of a node has been ignored if not all. To fill this gap, this article introduced the approach of weighted ego network analysis (WENA) to visualize the spatial heterogeneity of the maritime network at global and local levels. The topological connectivity graph of the global marine network was derived, and its structural properties were analyzed. It is found out that the values of the degree of ports follow power-law distribution, which indicates that the global marine network is scale-free, that is, there are few well-connected ports and a majority of less connected ports. The spatial disparities of the network can be described by a core–periphery pattern. In global, most of the hubs or ports with extremely high values of degree locate in the big-three maritime regions including Far East, North America, and West Europe. Along the peripheral belts of the three regions, there are lots of less connected small ports. A different hierarchical structure of six continents was captured by WENA. It is found that Europe, Asia, North America, and Africa showcase a pyramid-shaped hierarchical structure with a scale-free feature similar to the entire network, while South America and Oceania exhibit the fusiform hierarchy like small-world networks. It is proposed that such spatial inequality and heterogeneity were caused by the geographical environments such as the hub-and-spoke organization, the embedded trade pattern, and the proximity of location. These findings help us to understand the characteristics of the international trade pattern and shed light on the strategies of development for the industry stakeholders.

This article examines the global distribution of wealth within the capitalist world-economy over the longue durée. In stark contrast to the convergence of wealth predicted by modernization theory, the relatively stable bimodal (core-periphery) structure predicted by dependency theory, and the relatively stable trimodal (core-semiperiphery-periphery) structure, this article finds that the structure of the distribution of wealth in the world economy has transformed with each successive world hegemonic cycle. By adopting a longue durée perspective and a new statistical approach, I develop Arrighi and Drangel's (1986) method of conceptualizing, operationalizing, and measuring the global distribution of wealth within the capitalist world-economy. Through an examination of the period from 1500 to 2008, this article shows that the global distribution of wealth within the capitalist world-economy has transformed from a unimodal distribution during the period of Dutch hegemony to a bimodal distribution during the period of British hegemony, then to a trimodal distribution during the period of US hegemony, and now to a quadrimodal distribution in the early twenty-first century. While the global wealth hierarchy remained stable during periods of world hegemonies, it was transformed during periods of systemic crisis and hegemonic transition, thereby creating new forms of hierarchies.

Determining how cells generate and transduce mechanical forces at the nanoscale is a major technical challenge for the understanding of numerous physiological and pathological processes. Podosomes are submicrometer cell structures with a columnar F-actin core surrounded by a ring of adhesion proteins, which possess the singular ability to protrude into and probe the extracellular matrix. Using protrusion force microscopy, we have previously shown that single podosomes produce local nanoscale protrusions on the extracellular environment. However, how cellular forces are distributed to allow this protruding mechanism is still unknown. To investigate the molecular machinery of protrusion force generation, we performed mechanical simulations and developed quantitative image analyses of nanoscale architectural and mechanical measurements. First, in silico modeling showed that the deformations of the substrate made by podosomes require protrusion forces to be balanced by local traction forces at the immediate core periphery where the adhesion ring is located. Second, we showed that three-ring proteins are required for actin polymerization and protrusion force generation. Third, using DONALD, a 3D nanoscopy technique that provides 20 nm isotropic localization precision, we related force generation to the molecular extension of talin within the podosome ring, which requires vinculin and paxillin, indicating that the ring sustains mechanical tension. Our work demonstrates that the ring is a site of tension, balancing protrusion at the core. This local coupling of opposing forces forms the basis of protrusion and reveals the podosome as a nanoscale autonomous force generator.

Predicting the stone composition of children preoperatively by Hounsfield unit detection on non-contrast computed tomography

Two cationic dendrons bearing terminal groups of triethylene glycol monomethyl ether in different generations were used to encapsulate a paramagnetic polyoxometalate cluster K13[Gd(β2-SiW11O39)2], in which the Gd3+ ion was sandwiched by the coordination of two lacunary [β2-SiW11O39]8- sub-clusters, through electrostatic interaction. Benefiting from the surface covering of cationic dendrons and ionic complexation, both inorganic polyanionic core and the complexes formed maintained chemical stability in a physiological environment. In addition, the formed charge-neutralized supramolecular complex dendrimers with biocompatible periphery had low cytotoxicity but high relaxivity for in vitro and in vivo magnetic resonance imaging (MRI) in the self-assembled state. Because of the branched structure of organic components on the cluster surface and the disordered packing of complexes in aggregations, a reasonable communication of cluster core with the bulk environment was concluded. Importantly, due to the assembled particle size and molecular weight, the complex dendrimers were a suitable model for liver-specific MRI contrast agents. The results obtained showed that the dendritic supramolecular hybrid complexes represent potential MRI contrast agents in the development of new biomedical materials.

BACKGROUNDMathematical modeling of biothermal processes is widely used to enhance the quantitative understanding of thermoregulation system of human body organs. This quantitative knowledge of thermal information of various human body organs can be used for developing clinical applications. In the past, investigators have studied thermal distribution in hemisphere-shaped human breast in the presence of sphere-shaped tumor. The shape and size of the breast as well as tumor may also affect thermal distribution which can have serious implications in thermography. In this article, a model of thermal disturbances in peripheral regions of ellipsoid-shaped human breast involving ellipse-shaped nonuniformly perfused tumor has been developed for a 2-dimensional steady-state case. The modeling study will provide biomedical scientists vital insights of thermal changes occurring due to the shape and size of breast and tumor which can influence the development of protocols of thermography for diagnosis of tumors in women’s breast.METHODWe have incorporated the significant parameters such as blood flow, metabolic activity, and thermal conductivity in the thermal model for normal and malignant tissues. The controlled metabolic activity has been incorporated for normal tissues, and uncontrolled metabolic activity has been incorporated for tumor regions. The peripheral regions of breast are divided into 3 major layers, namely, epidermis, dermis, and subdermal tissues. An ellipse-shaped nonuniformly perfused tumor is assumed to be present in dermal layers. The nonuniformly perfused tumor is divided into 2 natural components, namely, the necrotic core and tumor periphery. The outer surface of the breast is assumed to be exposed to the environment, and the heat loss takes place by conduction, convection, radiation, and evaporation. The finite element approach is used to obtain the solution. The numerical results have been used to study the effect of shape and size of tumor on temperature distribution in matured breast of different shapes.RESULTSBy selecting appropriate model parameters, we have shown the spatial thermal variation in matured breast of different shapes which could be replicated by the proposed model. We have also shown the thermal disturbances caused by different shapes and sizes of tumors by selecting appropriate values of parameters. In addition, the thermal information from our model provides us the basis for prediction of shape and size of tumors in terms of change of the slope of temperature profiles at the junction of tumor and normal tissues and tumor periphery and tumor core.CONCLUSIONSThe proposed model was successfully used to study the impact of different sizes and shapes of nonuniformly perfused tumor on thermograms in peripheral regions of ellipse-shaped woman’s breast. The proposed model is more realistic in terms of shape and size of tumors and woman’s breast in comparison with earlier models reported in the literature. The finite element discretization of breast into large number of triangular ring elements effectively models the heterogeneity of region. The changes in slope of the thermal curves at the junctions of various peripheral and tumor layers are due to the nonhomogeneous nature of the region. The location of major thermal disturbances in the tissues indicates the presence of tumor. The change in the slope of the thermal curves gives us idea about the position, type, and size of the tumors in the peripheral tissues. This thermal information can be exploited for detection of tumors by thermographic techniques.

ABSTRACTSince the mid-twentieth century, small islands have emerged as important tourist destinations, whether as island-states (Barbados, Fiji), island dependencies (Guadeloupe, Jersey) or state-islands (Okinawa, Cozumel). A longstanding core–periphery narrative holds that small islands are geographically and economically marginal entities fated to spawn homogeneous tourism monocultures within contexts of persistent external dependency. However, further investigation reveals several attendant and pervasive paradoxes which challenge this conventional thinking. This paper outlines these as the juxtaposition of (a) geographic peripherality and experiential core, (b) economic marginality and tourism centrality, (c) tourism monocultures and opportunistic innovation, (d) geopolitical dependency and optimal autonomy and (e) tourism homogeneity and cultural/ecological distinctiveness. A resultant ‘virtuous periphery syndrome’, the product of both necessity and endowment, positions small islands as sites of impressive resilience and innovation capable of providing peak experiences that support robust tourism sectors within contexts of balanced autonomy and cultural distinctiveness. Resolution-based dialectics allow the positive elements of both core and periphery to be identified and combined towards achieving the ideal of enlightened mass tourism.

Abstract Financial institutions’ interconnectedness is a key component of systemic risk. However there is still no consensus on its measurement. Using a unique database of network of exposures of French financial institutions, we compare three strategies to measure interconnectedness: closeness of exposure distributions, identification of core-periphery structure and contagion models. The closeness of exposure distributions is adequate to identify outlier institutions. The “core-periphery” structure, usually applied to banking network, is still valid with insurance companies. However this approach is not immune to size effect. This result contrasts with previous analyses where size was not accounted for. Contagion-based stress-tests are the best suited to capture institutions’ systemic fragility, emphasizing their importance as a supervisory tool.

This study relates the local property of node dominance to local and global properties of a network. Iterative removal of dominated nodes yields a distributed algorithm for computing a core-periphery decomposition of a social network, where nodes in the network core are seen to be essential in terms of network flow and global structure. Additionally, the connected components in the periphery give information about the community structure of the network, aiding in community detection. A number of explicit results are derived, relating the core and periphery to network flow, community structure, and global network structure, which are corroborated by observational results. The method is illustrated using a real world network (DBLP co-authorship network), with ground-truth communities.

Financial networks, bank efficiency and risk-taking

Core-Periphery Trading Networks

Bargaining in endogenous trading networks

Dilatometric study of a co-converted (U,Am)O2 powder

Broadly speaking, the structural approach to creativity and innovation looks at how network positions influence the ability of social actors to generate novel and useful ideas and to implement them...