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Jacobo-Villegas E, Obregón-Quintana B, Guzmán-Vargas L, Liebovitch LS. Conflict Dynamics in Scale-Free Networks with Degree Correlations and Hierarchical Structure. Entropy (Basel) 2022; 24:1571. [PMID: 36359665 PMCID: PMC9689849 DOI: 10.3390/e24111571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/28/2022] [Accepted: 10/28/2022] [Indexed: 06/16/2023]
Abstract
We present a study of the dynamic interactions between actors located on complex networks with scale-free and hierarchical scale-free topologies with assortative mixing, that is, correlations between the degree distributions of the actors. The actor's state evolves according to a model that considers its previous state, the inertia to change, and the influence of its neighborhood. We show that the time evolution of the system depends on the percentage of cooperative or competitive interactions. For scale-free networks, we find that the dispersion between actors is higher when all interactions are either cooperative or competitive, while a balanced presence of interactions leads to a lower separation. Moreover, positive assortative mixing leads to greater divergence between the states, while negative assortative mixing reduces this dispersion. We also find that hierarchical scale-free networks have both similarities and differences when compared with scale-free networks. Hierarchical scale-free networks, like scale-free networks, show the least divergence for an equal mix of cooperative and competitive interactions between actors. On the other hand, hierarchical scale-free networks, unlike scale-free networks, show much greater divergence when dominated by cooperative rather than competitive actors, and while the formation of a rich club (adding links between hubs) with cooperative interactions leads to greater divergence, the divergence is much less when they are fully competitive. Our findings highlight the importance of the topology where the interaction dynamics take place, and the fact that a balanced presence of cooperators and competitors makes the system more cohesive, compared to the case where one strategy dominates.
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Affiliation(s)
- Eduardo Jacobo-Villegas
- Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Ciudad de Mexico 04510, Mexico
| | | | - Lev Guzmán-Vargas
- Unidad Interdisciplinaria en Ingenieria y Tecnologias Avanzadas, Instituto Politecnico Nacional, Av. IPN No. 2580, L. Ticomán, Ciudad de Mexico 07340, Mexico
| | - Larry S. Liebovitch
- Department of Physics, Queens College, City University of New York, New York, NY 11367, USA
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2
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Huang Z, Luo YH, Geng WY, Wan Y, Li S, Lee CS. Marriage of 2D Covalent-Organic Framework and 3D Network as Stable Solar-Thermal Still for Efficient Solar Steam Generation. Small Methods 2021; 5:e2100036. [PMID: 34928098 DOI: 10.1002/smtd.202100036] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 02/26/2021] [Indexed: 06/14/2023]
Abstract
In this work, a diketopyrrolopyrrole-based 2D covalent-organic framework (COF) is realized and featured with broadband optical absorption and high solar-thermal conversion performance. Moreover, a 3D hierarchical structure, referred to as COF-based hierarchical structure (COFHS), is rationally designed to achieve an enhanced photothermal conversion efficiency. In this water evaporator, diketopyrrolopyrrole is immobilized into conjugated COF to achieve enhanced light absorption, whereas a porous PVA network scaffold is utilized to support COF sheets as well as to enhance the hydrophilicity of the evaporator. Due to this structural advantage, COFHS displays a high solar-to-vapor energy conversion efficiency of 93.2%. Under 1 sun AM1.5 G irradiation, a stable water evaporation rate of 2.5 kg m-2 h-1 can be achieved. As a proof-of-concept application, a water collection device prepared with the COFHS can achieve high solar-thermal water collection efficiency of 10.2 L m-2 d-1 under natural solar irradiation. The good solar-thermal conversion properties and high-water evaporation rate make the COFHS a promising platform for solar-thermal water production.
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Affiliation(s)
- Zhongming Huang
- Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, Hong Kong SAR, 999077, P. R. China
| | - Yu-Hui Luo
- School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang, Jiangsu Province, 222000, P. R. China
| | - Wu-Yue Geng
- School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang, Jiangsu Province, 222000, P. R. China
| | - Yingpeng Wan
- Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, Hong Kong SAR, 999077, P. R. China
| | - Shengliang Li
- Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, Hong Kong SAR, 999077, P. R. China
- College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, P. R. China
| | - Chun-Sing Lee
- Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, Hong Kong SAR, 999077, P. R. China
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Rasch F, Schütt F, Saure LM, Kaps S, Strobel J, Polonskyi O, Nia AS, Lohe MR, Mishra YK, Faupel F, Kienle L, Feng X, Adelung R. Wet-Chemical Assembly of 2D Nanomaterials into Lightweight, Microtube-Shaped, and Macroscopic 3D Networks. ACS Appl Mater Interfaces 2019; 11:44652-44663. [PMID: 31686498 PMCID: PMC7192525 DOI: 10.1021/acsami.9b16565] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Despite tremendous efforts toward fabrication of three-dimensional macrostructures of two-dimensional (2D) materials, the existing approaches still lack sufficient control over microscopic (morphology, porosity, pore size) and macroscopic (shape, size) properties of the resulting structures. In this work, a facile fabrication method for the wet-chemical assembly of carbon 2D nanomaterials into macroscopic networks of interconnected, hollow microtubes is introduced. As demonstrated for electrochemically exfoliated graphene, graphene oxide, and reduced graphene oxide, the approach allows for the preparation of highly porous (> 99.9%) and lightweight (<2 mg cm-3) aeromaterials with tailored porosity and pore size as well as tailorable shape and size. The unique tubelike morphology with high aspect ratio enables ultralow-percolation-threshold graphene composites (0.03 S m-1, 0.05 vol%) which even outperform most of the carbon nanotube-based composites, as well as highly conductive aeronetworks (8 S m-1, 4 mg cm-3). On top of that, long-term compression cycling of the aeronetworks demonstrates remarkable mechanical stability over 10 000 cycles, even though no chemical cross-linking is employed. The developed strategy could pave the way for fabrication of various macrostructures of 2D nanomaterials with defined shape, size, as well as micro- and nanostructure, crucial for numerous applications such as batteries, supercapacitors, and filters.
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Affiliation(s)
- Florian Rasch
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
| | - Fabian Schütt
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
- E-mail:
| | - Lena M. Saure
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
- Chair
of Engineering Mechanics, Brandenburg University
of Technology Cottbus-Senftenberg, Großenhainer Straße 57, 01968 Senftenberg, Germany
| | - Sören Kaps
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
| | - Julian Strobel
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
| | - Oleksandr Polonskyi
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
| | - Ali Shaygan Nia
- Department
of Chemistry and Food Chemistry, Center for Advancing Electronics
Dresden (cfaed), Technische Universität
Dresden, 01062 Dresden, Germany
| | - Martin R. Lohe
- Department
of Chemistry and Food Chemistry, Center for Advancing Electronics
Dresden (cfaed), Technische Universität
Dresden, 01062 Dresden, Germany
| | - Yogendra K. Mishra
- NanoSYD,
Mads Clausen Institute, University of Southern
Denmark, Alsion 2, DK-6400 Sønderborg, Denmark
| | - Franz Faupel
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
| | - Lorenz Kienle
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
| | - Xinliang Feng
- Department
of Chemistry and Food Chemistry, Center for Advancing Electronics
Dresden (cfaed), Technische Universität
Dresden, 01062 Dresden, Germany
| | - Rainer Adelung
- Chair for Functional Nanomaterials, Institute for
Materials Science, Chair for Synthesis
and Real Structure, Institute for Materials Science,
and Chair for Multicomponent
Materials, Institute for Materials Science, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany
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Gummadavelli A, Zaveri HP, Spencer DD, Gerrard JL. Expanding Brain-Computer Interfaces for Controlling Epilepsy Networks: Novel Thalamic Responsive Neurostimulation in Refractory Epilepsy. Front Neurosci 2018; 12:474. [PMID: 30108472 PMCID: PMC6079216 DOI: 10.3389/fnins.2018.00474] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 06/22/2018] [Indexed: 01/01/2023] Open
Abstract
Seizures have traditionally been considered hypersynchronous excitatory events and epilepsy has been separated into focal and generalized epilepsy based largely on the spatial distribution of brain regions involved at seizure onset. Epilepsy, however, is increasingly recognized as a complex network disorder that may be distributed and dynamic. Responsive neurostimulation (RNS) is a recent technology that utilizes intracranial electroencephalography (EEG) to detect seizures and delivers stimulation to cortical and subcortical brain structures for seizure control. RNS has particular significance in the clinical treatment of medically refractory epilepsy and brain–computer interfaces in epilepsy. Closed loop RNS represents an important step forward to understand and target nodes in the seizure network. The thalamus is a central network node within several functional networks and regulates input to the cortex; clinically, several thalamic nuclei are safe and feasible targets. We highlight the network theory of epilepsy, potential targets for neuromodulation in epilepsy and the first reported use of RNS as a first generation brain–computer interface to detect and stimulate the centromedian intralaminar thalamic nucleus in a patient with bilateral cortical onset of seizures. We propose that advances in network analysis and neuromodulatory techniques using brain–computer interfaces will significantly improve outcomes in patients with epilepsy. There are numerous avenues of future direction in brain–computer interface devices including multi-modal sensors, flexible electrode arrays, multi-site targeting, and wireless communication.
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Affiliation(s)
- Abhijeet Gummadavelli
- Department of Neurosurgery, Yale University School of Medicine, Yale University, New Haven, CT, United States
| | - Hitten P Zaveri
- Department of Neurology, Yale University School of Medicine, Yale University, New Haven, CT, United States
| | - Dennis D Spencer
- Department of Neurosurgery, Yale University School of Medicine, Yale University, New Haven, CT, United States
| | - Jason L Gerrard
- Department of Neurosurgery, Yale University School of Medicine, Yale University, New Haven, CT, United States.,Department of Neuroscience, Yale University School of Medicine, Yale University, New Haven, CT, United States
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Weiner KS, Jonas J, Gomez J, Maillard L, Brissart H, Hossu G, Jacques C, Loftus D, Colnat-Coulbois S, Stigliani A, Barnett MA, Grill-Spector K, Rossion B. The Face-Processing Network Is Resilient to Focal Resection of Human Visual Cortex. J Neurosci 2016; 36:8425-40. [PMID: 27511014 DOI: 10.1523/JNEUROSCI.4509-15.2016] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 06/22/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Human face perception requires a network of brain regions distributed throughout the occipital and temporal lobes with a right hemisphere advantage. Present theories consider this network as either a processing hierarchy beginning with the inferior occipital gyrus (occipital face area; IOG-faces/OFA) or a multiple-route network with nonhierarchical components. The former predicts that removing IOG-faces/OFA will detrimentally affect downstream stages, whereas the latter does not. We tested this prediction in a human patient (Patient S.P.) requiring removal of the right inferior occipital cortex, including IOG-faces/OFA. We acquired multiple fMRI measurements in Patient S.P. before and after a preplanned surgery and multiple measurements in typical controls, enabling both within-subject/across-session comparisons (Patient S.P. before resection vs Patient S.P. after resection) and between-subject/across-session comparisons (Patient S.P. vs controls). We found that the spatial topology and selectivity of downstream ipsilateral face-selective regions were stable 1 and 8 month(s) after surgery. Additionally, the reliability of distributed patterns of face selectivity in Patient S.P. before versus after resection was not different from across-session reliability in controls. Nevertheless, postoperatively, representations of visual space were typical in dorsal face-selective regions but atypical in ventral face-selective regions and V1 of the resected hemisphere. Diffusion weighted imaging in Patient S.P. and controls identifies white matter tracts connecting retinotopic areas to downstream face-selective regions, which may contribute to the stable and plastic features of the face network in Patient S.P. after surgery. Together, our results support a multiple-route network of face processing with nonhierarchical components and shed light on stable and plastic features of high-level visual cortex following focal brain damage. SIGNIFICANCE STATEMENT Brain networks consist of interconnected functional regions commonly organized in processing hierarchies. Prevailing theories predict that damage to the input of the hierarchy will detrimentally affect later stages. We tested this prediction with multiple brain measurements in a rare human patient requiring surgical removal of the putative input to a network processing faces. Surprisingly, the spatial topology and selectivity of downstream face-selective regions are stable after surgery. Nevertheless, representations of visual space were typical in dorsal face-selective regions but atypical in ventral face-selective regions and V1. White matter connections from outside the face network may support these stable and plastic features. As processing hierarchies are ubiquitous in biological and nonbiological systems, our results have pervasive implications for understanding the construction of resilient networks.
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6
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Krishnagopal S, Lehnert J, Poel W, Zakharova A, Schöll E. Synchronization patterns: from network motifs to hierarchical networks. Philos Trans A Math Phys Eng Sci 2017; 375:20160216. [PMID: 28115613 PMCID: PMC5311436 DOI: 10.1098/rsta.2016.0216] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/04/2016] [Indexed: 05/12/2023]
Abstract
We investigate complex synchronization patterns such as cluster synchronization and partial amplitude death in networks of coupled Stuart-Landau oscillators with fractal connectivities. The study of fractal or self-similar topology is motivated by the network of neurons in the brain. This fractal property is well represented in hierarchical networks, for which we present three different models. In addition, we introduce an analytical eigensolution method and provide a comprehensive picture of the interplay of network topology and the corresponding network dynamics, thus allowing us to predict the dynamics of arbitrarily large hierarchical networks simply by analysing small network motifs. We also show that oscillation death can be induced in these networks, even if the coupling is symmetric, contrary to previous understanding of oscillation death. Our results show that there is a direct correlation between topology and dynamics: hierarchical networks exhibit the corresponding hierarchical dynamics. This helps bridge the gap between mesoscale motifs and macroscopic networks.This article is part of the themed issue 'Horizons of cybernetical physics'.
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Affiliation(s)
- Sanjukta Krishnagopal
- Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
- Department of Physics, Birla Institute for Technology and Science Pilani, Pilani, Goa 403726, India
| | - Judith Lehnert
- Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Winnie Poel
- Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Anna Zakharova
- Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Eckehard Schöll
- Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
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7
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Eguchi A, Mender BMW, Evans BD, Humphreys GW, Stringer SM. Computational modeling of the neural representation of object shape in the primate ventral visual system. Front Comput Neurosci 2015; 9:100. [PMID: 26300766 PMCID: PMC4523947 DOI: 10.3389/fncom.2015.00100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 07/17/2015] [Indexed: 11/13/2022] Open
Abstract
Neurons in successive stages of the primate ventral visual pathway encode the spatial structure of visual objects. In this paper, we investigate through computer simulation how these cell firing properties may develop through unsupervised visually-guided learning. Individual neurons in the model are shown to exploit statistical regularity and temporal continuity of the visual inputs during training to learn firing properties that are similar to neurons in V4 and TEO. Neurons in V4 encode the conformation of boundary contour elements at a particular position within an object regardless of the location of the object on the retina, while neurons in TEO integrate information from multiple boundary contour elements. This representation goes beyond mere object recognition, in which neurons simply respond to the presence of a whole object, but provides an essential foundation from which the brain is subsequently able to recognize the whole object.
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Affiliation(s)
- Akihiro Eguchi
- Department of Experimental Psychology, Oxford Centre for Theoretical Neuroscience and Artificial Intelligence, Oxford UniversityOxford, UK
| | - Bedeho M. W. Mender
- Department of Experimental Psychology, Oxford Centre for Theoretical Neuroscience and Artificial Intelligence, Oxford UniversityOxford, UK
| | - Benjamin D. Evans
- Department of Experimental Psychology, Oxford Centre for Theoretical Neuroscience and Artificial Intelligence, Oxford UniversityOxford, UK
| | - Glyn W. Humphreys
- Department of Experimental Psychology, Oxford Cognitive Neuropsychology Centre, Oxford UniversityOxford, UK
| | - Simon M. Stringer
- Department of Experimental Psychology, Oxford Centre for Theoretical Neuroscience and Artificial Intelligence, Oxford UniversityOxford, UK
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8
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Shams SM, Afshin-Pour B, Soltanian-Zadeh H, Hossein-Zadeh GA, Strother SC. Automated iterative reclustering framework for determining hierarchical functional networks in resting state fMRI. Hum Brain Mapp 2015; 36:3303-22. [PMID: 26032457 DOI: 10.1002/hbm.22839] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Revised: 04/25/2015] [Accepted: 05/03/2015] [Indexed: 11/06/2022] Open
Abstract
To spatially cluster resting state-functional magnetic resonance imaging (rs-fMRI) data into potential networks, there are only a few general approaches that determine the number of networks/clusters, despite a wide variety of techniques proposed for clustering. For individual subjects, extraction of a large number of spatially disjoint clusters results in multiple small networks that are spatio-temporally homogeneous but irreproducible across subjects. Alternatively, extraction of a small number of clusters creates spatially large networks that are temporally heterogeneous but spatially reproducible across subjects. We propose a fully automatic, iterative reclustering framework in which a small number of spatially large, heterogeneous networks are initially extracted to maximize spatial reproducibility. Subsequently, the large networks are iteratively subdivided to create spatially reproducible subnetworks until the overall within-network homogeneity does not increase substantially. The proposed approach discovers a rich network hierarchy in the brain while simultaneously optimizing spatial reproducibility of networks across subjects and individual network homogeneity. We also propose a novel metric to measure the connectivity of brain regions, and in a simulation study show that our connectivity metric and framework perform well in the face of low signal to noise and initial segmentation errors. Experimental results generated using real fMRI data show that the proposed metric improves stability of network clusters across subjects, and generates a meaningful pattern for spatially hierarchical structure of the brain.
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Affiliation(s)
- Seyed-Mohammad Shams
- Control and Intelligent Processing Center of Excellence (CIPCE), School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.,Rotman Research Institute, Baycrest, Toronto, Ontario, Canada
| | | | - Hamid Soltanian-Zadeh
- Control and Intelligent Processing Center of Excellence (CIPCE), School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.,School of Cognitive Sciences, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran.,Department of Radiology, Image Analysis Laboratory, Henry Ford Hospital, Detroit, Michigan
| | - Gholam-Ali Hossein-Zadeh
- Control and Intelligent Processing Center of Excellence (CIPCE), School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.,School of Cognitive Sciences, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
| | - Stephen C Strother
- Rotman Research Institute, Baycrest, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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Heris HK, Rahmat M, Mongeau L. Characterization of a hierarchical network of hyaluronic acid/gelatin composite for use as a smart injectable biomaterial. Macromol Biosci 2012; 12:202-10. [PMID: 22147507 PMCID: PMC4490586 DOI: 10.1002/mabi.201100335] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Indexed: 11/09/2022]
Abstract
Hybrid HA/Ge hydrogel particles are embedded in a secondary HA network to improve their structural integrity. The internal microstructure of the particles is imaged through TEM. CSLM is used to identify the location of the Ge molecules in the microgels. Through indentation tests, the Young's modulus of the individual particles is found to be 22 ± 2.5 kPa. The overall shear modulus of the composite is 75 ± 15 Pa at 1 Hz. The mechanical properties of the substrate are found to be viable for cell adhesion. The particles' diameter at pH = 8 is twice that at pH = 5. The pH sensitivity is found to be appropriate for smart drug delivery. Based on their mechanical and structural properties, HA-Ge hierarchical materials may be well suited for use as injectable biomaterials for tissue reconstruction.
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Affiliation(s)
- Hossein K. Heris
- Department of Mechanical Engineering, McGill University, 817 Sherbrooke St. West, Montreal, QC H3A 2K6, Canada
| | - Meysam Rahmat
- Department of Mechanical Engineering, McGill University, 817 Sherbrooke St. West, Montreal, QC H3A 2K6, Canada
| | - Luc Mongeau
- Department of Mechanical Engineering, McGill University, 817 Sherbrooke St. West, Montreal, QC H3A 2K6, Canada
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Shein-Idelson M, Ben-Jacob E, Hanein Y. Engineered neuronal circuits: a new platform for studying the role of modular topology. Front Neuroeng 2011; 4:10. [PMID: 21991254 PMCID: PMC3180629 DOI: 10.3389/fneng.2011.00010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Accepted: 08/23/2011] [Indexed: 12/05/2022]
Abstract
Neuron–glia cultures serve as a valuable model system for exploring the bio-molecular activity of single cells. Since neurons in culture can be conveniently recorded with great fidelity from many sites simultaneously, it has long been suggested that uniform cultured neurons may also be used to investigate network-level mechanisms pertinent to information processing, activity propagation, memory, and learning. But how much of the functionality of neural circuits can be retained in vitro remains an open question. Recent studies utilizing patterned networks suggest that they provide a most useful platform to address fundamental questions in neuroscience. Here we review recent efforts in the realm of patterned networks’ activity investigations. We give a brief overview of the patterning methods and experimental approaches commonly employed in the field, and summarize the main results reported in the literature. The general picture that emerges from these reports indicates that patterned networks with uniform connectivity do not exhibit unique activity patterns. Rather, their activity is very similar to that of unpatterned uniform networks. However, by breaking the connectivity homogeneity, using a modular architecture, it is possible to introduce pronounced topology-related gating and delay effects. These findings suggest that patterned cultured networks may serve as a new platform for studying the role of modularity in neuronal circuits.
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Abstract
The intrinsic relationship between the architecture of the brain and the range of sensory and behavioral phenomena it produces is a relevant question in neuroscience. Here, we review recent knowledge gained on the architecture of the anatomical connectivity by means of complex network analysis. It has been found that cortico-cortical networks display a few prominent characteristics: (i) modular organization, (ii) abundant alternative processing paths, and (iii) the presence of highly connected hubs. Additionally, we present a novel classification of cortical areas of the cat according to the role they play in multisensory connectivity. All these properties represent an ideal anatomical substrate supporting rich dynamical behaviors, facilitating the capacity of the brain to process sensory information of different modalities segregated and to integrate them toward a comprehensive perception of the real world. The results here exposed are mainly based on anatomical data of cats’ brain, but further observations suggest that, from worms to humans, the nervous system of all animals might share these fundamental principles of organization.
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12
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Abstract
In a recent publication (Müller-Linow et al., 2008) two types of correlations between network topology and dynamics have been observed: waves propagating from central nodes and module-based synchronization. Remarkably, the dynamic behavior of hierarchical modular networks can switch from one of these modes to the other as the level of spontaneous network activation changes. Here we attempt to capture the origin of this switching behavior in a mean-field model as well in a formalism, where excitation waves are regarded as avalanches on the graph.
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Affiliation(s)
- Marc-Thorsten Hütt
- School of Engineering and Science, Jacobs University BremenBremen, Germany
| | - Annick Lesne
- Institut des Hautes Études ScientifiquesBures-sur-Yvette, France
- Université Pierre et Marie CurieParis, France
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