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Background Microbial interactions shape the structure and function of microbial communities; microbial co-occurrence networks in specific environments have been widely developed to explore these complex systems, but their interconnection pattern across microbiomes in various environments at the global scale remains unexplored. Here, we have inferred an Earth microbial co-occurrence network from a communal catalog with 23,595 samples and 12,646 exact sequence variants from 14 environments in the Earth Microbiome Project dataset. Results This non-random scale-free Earth microbial co-occurrence network consisted of 8 taxonomy distinct modules linked with different environments, which featured environment specific microbial co-occurrence relationships. Different topological features of subnetworks inferred from datasets trimmed into uniform size indicate distinct co-occurrence patterns in the microbiomes of various environments. The high number of specialist edges highlights that environmental specific co-occurrence relationships are essential features across microbiomes. The microbiomes of various environments were clustered into two groups, which were mainly bridged by the microbiomes of plant and animal surface. Acidobacteria Gp2 and Nisaea were identified as hubs in most of subnetworks. Negative edges proportions ranged from 1.9% in the soil subnetwork to 48.9% the non-saline surface subnetwork, suggesting various environments experience distinct intensities of competition or niche differentiation. 2NmSq7Q5noeLTtkrbKwa4L Video abstract Conclusion This investigation highlights the interconnection patterns across microbiomes in various environments and emphasizes the importance of understanding co-occurrence feature of microbiomes from a network perspective.

In this paper, a modeling framework is proposed for multi-period hub location. The problems to be studied are extensions of classical hub location problems to the situation in which the hub network can be progressively built and its capacity gradually expanded over time. Both the single allocation and the multiple allocation cases are considered. For each case, a mixed-integer linear programming formulation is proposed and a set of valid inequalities is derived for enhancing the corresponding model. The results of a set of computational tests performed using the formulations proposed and their enhancements are reported. The value of the multi-period solution is discussed as a measure for evaluating the relevance of considering a multi-period model instead of a static counterpart.

HIV/AIDS test laboratories in South Africa face growing demand for high quality, timely and efficient testing of blood samples in all regions of the country, however rural. The three main tests for HIV/AIDS, namely CD4, HIV Viral Load, and Infant PCR, are provided in a hierarchy of levels: CD4 is the most frequently needed test, with most laboratory coverage needed. HIV Viral Load is less frequently called for, and Infant PCR is the rarest test to be done, with correspondingly fewest laboratories needed. The National Health Laboratory Service (NHLS) of South Africa operates an inbound hub network for collection of blood samples and transfer to laboratories equipped to carry out the required tests: test results are transmitted electronically, so there is no outbound or return transport. This paper describes the development of modelling carried out over several years of collaboration with NHLS to advise decision-makers on an appropriate and efficient hub network. We present mixed integer programs to find efficient locations for both network hubs and locations for all levels of laboratory testing. Novel features include variable or range constraints on maximum travel times to test locations.

This article investigates the influence of psychic and geographic distance, as well as country and market-related variables, on the preference of high-technology small and medium-sized enterprises (SMEs) to connect with, and settle in major business hubs. Literature in the field of SME internationalization and international entrepreneurship increasingly emphasizes a network approach in which the characteristics and linkages of the internationalizing firm's network are studied. We aim to contribute to this network-based internationalization research by integrating a further element present in complex social and technical networks: network hubs. Hubs are highly connected nodes within a network. In global business, hubs can be defined as business sites that have a high interconnection with the world economy through tremendous flows of goods and capital. The empirical findings of our research suggest that internationalizing high technology SMEs tend to connect with, or settle in to foreign market business hubs, when focal markets are more distant from their home market. These findings are significant for both geographic and psychic distances between home and focal markets.

This article draws together specific results and facts relevant to a variety of networks (cyber and air) in the context of hubs and with a particular focus on their vulnerability and resilience. The paper highlights the features of networks that are exploitable to either detect or deter intrusions. This paper examines the vulnerability of hub interconnection points. The research points to parts of a network that require strengthened defenses to prevent loss or damage on a broader scale. A key aspect of the review is its emphasis on spatial organization.

Purpose: The overstocked goods flow in the hub of hub-and-spoke logistics network should be disposed of in time, to reduce delay loss and improve the utilization rate of logistics network resources. The problem we need to solve is to let logistics network cooperate by sharing network resources to shunt goods from one hub-and-spoke network to another hub-and-spoke network. Design/methodology/approach: This paper proposes the hub shunting cooperation between two hub-and-spoke networks. Firstly, a hybrid integer programming model was established to describe the problem, and then a multi-layer genetic algorithm was designed to solve it and two hub-and-spoke networks are expressed by different gene segments encoded by genes. The network data of two third-party logistics companies in southern and northern China are used for example analysis at the last step. Findings: The hub-and-spoke networks of the two companies were constructed simultaneously. The transfer cost coefficient between two networks and the volume of cargo flow in the network have an impact on the computation of hubs that needed to be shunt and the corresponding cooperation hubs in the other network. Originality/value: Previous researches on hub-and-spoke logistics network focus on one logistics network, while we study the cooperation and interaction between two hub-and-spoke networks. It shows that two hub-and-spoke network can cooperate across the network to shunt the goods in the hub and improve the operation efficiency of the logistics network.

Diffuse gliomas, particularly glioblastomas, are incurable brain tumours 1 . They are characterized by networks of interconnected brain tumour cells that communicate via Ca 2+ transients 2 – 6 . However, the networks’ architecture and communication strategy and how these influence tumour biology remain unknown. Here we describe how glioblastoma cell networks include a small, plastic population of highly active glioblastoma cells that display rhythmic Ca 2+ oscillations and are particularly connected to others. Their autonomous periodic Ca 2+ transients preceded Ca 2+ transients of other network-connected cells, activating the frequency-dependent MAPK and NF-κB pathways. Mathematical network analysis revealed that glioblastoma network topology follows scale-free and small-world properties, with periodic tumour cells frequently located in network hubs. This network design enabled resistance against random damage but was vulnerable to losing its key hubs. Targeting of autonomous rhythmic activity by selective physical ablation of periodic tumour cells or by genetic or pharmacological interference with the potassium channel KCa3.1 (also known as IK1, SK4 or KCNN4) strongly compromised global network communication. This led to a marked reduction of tumour cell viability within the entire network, reduced tumour growth in mice and extended animal survival. The dependency of glioblastoma networks on periodic Ca 2+ activity generates a vulnerability 7 that can be exploited for the development of novel therapies, such as with KCa3.1-inhibiting drugs. A population of highly interconnected cells in glioblastoma makes these tumours resistant to general damage but vulnerable to targeted disruption of this small fraction of cells and their rhythmic Ca 2+ oscillations.

Brain network hubs are both highly connected and highly inter-connected, forming a critical communication backbone for coherent neural dynamics. The mechanisms driving this organization are poorly understood. Using diffusion-weighted magnetic resonance imaging in twins, we identify a major role for genes, showing that they preferentially influence connectivity strength between network hubs of the human connectome. Using transcriptomic atlas data, we show that connected hubs demonstrate tight coupling of transcriptional activity related to metabolic and cytoarchitectonic similarity. Finally, comparing over thirteen generative models of network growth, we show that purely stochastic processes cannot explain the precise wiring patterns of hubs, and that model performance can be improved by incorporating genetic constraints. Our findings indicate that genes play a strong and preferential role in shaping the functionally valuable, metabolically costly connections between connectome hubs. How genes sculpt the complex architecture of the human connectome remains unclear. Here, the authors show that genes preferentially influence the strength of connectivity between functionally valuable, metabolically costly connections between brain network hubs.

[...]digitalization is playing an increasingly important role in business and society, and all institutions are facing a fundamental need for radical changes in their strategy, structure, and corporate culture. Digitalization presents new opportunities in terms of skill sharing, open innovation, and partnership formation between companies. [...]internationalization and digitalization have become collective activities. Technology Innovation Management Review, 10(4): 3-4. rz http://doi.org/10.22215/timreview/1342 '- Keywords: Digital entrepreneurship, digitalization, international entrepreneurship, entrepreneurial orientation, MSMEs, SMEs, export practices, facilitators, impacts, SME internationalization, network view, business network hubs, liability of foreignness, scaling, business model, training, coaching, digital marketing, support institutions, internationalization

The brain's default mode network (DMN) has become closely associated with self-referential mental activity, particularly in the resting-state. While the DMN is important for such processes, it has functions other than self-reference, and self-referential processes are supported by regions outside of the DMN. In our study of 88 participants, we examined self-referential and resting-state processes to clarify the extent to which DMN activity was common and distinct between the conditions. Within areas commonly activated by self-reference and rest we sought to identify those that showed additional functional specialization for self-referential processes: these being not only activated by self-reference and rest but also showing increased activity in self-reference versus rest. We examined the neural network properties of the identified ‘core-self’ DMN regions—in medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC), and inferior parietal lobule—using dynamic causal modeling. The optimal model identified was one in which self-related processes were driven via PCC activity and moderated by the regulatory influences of MPFC. We thus confirm the significance of these regions for self-related processes and extend our understanding of their functionally specialized roles. [Display omitted] •Self-reference and rest-fixation evoked extensive common activation; though distinct differences were also evident.•Within commonly activated regions greater self-referential activation was shown in MPFC, PCC, and left IPL.•Dynamic causal modeling showed that self-related processes were driven via PCC activity, and moderated by MPFC.•We speculate that this brain model provides the basis for the conscious awareness of the self.