Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain ...Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain networks.As a consequence,some non-random organizational features,such as"small world"(most of the nodes are not connected directly but can communicate with few intermediate relay steps)and"rich club"(nodes that are rich in connections tend to form strongly interconnected clubs),have been found in functional brain network.Recently,the"small world"organizational feature of neuronal functional networks in vitro was found to be influenced by external applications.However,little is known about the influence of chronic electrical stimulation on functional networks of dissociated cortical cultures during network development.In the present study,cortical cultures were electrically stimulated at a frequency of 0,0.02,and 0.2 Hz,between 7 and 26 days in vitro(DIV).The spontaneous activity of the cortical cultures was recorded using MEAs.Next,a cross-covariance method and graph theory were applied to investigate organizational feature of functional networks.Our results showed that over 3 weeks of stimulation,the network density significantly increased with maturation in the control and 0.02 Hz stimulation groups,but not in 0.2 Hz stimulation groups.Moreover,all the cultures had a small-world topology at 14,18,22,and 26 DIV,free from the effect of chronic electrical stimulation.Besides,we found an asymmetry effect that partial electrical stimulation inhibited the formation of node connections in stimulated areas.This effect was more pronounced at 0.2 Hz than at 0.02 Hz stimulation.Our results suggest that electrical stimulation does not affect the small-world properties of neural cultures.Instead,electrical stimulation modulates connectivity patterns,and neurons within the stimulated area are less connected than neurons outside the stimulated area.展开更多
Habitat loss and fragmentation of the wildlife species due to anthropogenic developments have been becoming serious issues in biological conservation. Alborz wild sheep, listed as threatened by IUCN, is distributed in...Habitat loss and fragmentation of the wildlife species due to anthropogenic developments have been becoming serious issues in biological conservation. Alborz wild sheep, listed as threatened by IUCN, is distributed in relatively small and isolated patches in an increasingly human dominated landscape in the north-central Iran and east of Tehran. We used maximum entropy modeling to identify habitat areas of the wild sheep, across Jajrud protected area and its neighbouring protected areas including varjin, lar, koohsefid and the surroundings. Regarding to seasonal variation of the species home range, winter, summer and multi seasonal (annual) habitats were predicted. To estimate habitat connectivity, we used models of connectivity based in electrical circuit theory. Applying core areas of multi season for connectivity analysis, movement pattern of the species was predicted and important connective areas for conservation were identified. Species distribution maps revealed that the summer and winter habitats were approximately occurred in similar areas. Distance to eco-guards’ post was the most important predictor for both habitat models of summer and winter. The annual model, which is a combination of summer and winter, shows that the largest suitable habitat patches are located in the north, south and west of the study area. Maximum current flow map demonstrates that the areas among patch pairs are covered in low current, reflecting low rates of the species dispersal. This map presented bottlenecks to the species movement across major roads and along extending human settlements. Cumulative current flow map displayed that current was highest in Jajrud north of Mamloo extending to the northern Jajrud. Overall, our study demonstrated a prediction of habitat suitability and connectivity for Alborz wild sheep in east of Tehran, which can be used to direct conservation endeavours dealing with maintenance of the wild sheep metapopulation dynamics.展开更多
Bibliographic reports on the electric conductivity of pure homoionic montmorillonite at low water content were analyzed in order to stress a general behavior of conductivity. At low water content, the conductivity is ...Bibliographic reports on the electric conductivity of pure homoionic montmorillonite at low water content were analyzed in order to stress a general behavior of conductivity. At low water content, the conductivity is attributed to a mechanism of charge transport involving protons due to the influence of the electric field of the exchangeable cations on water molecules at the solvation shell. Conductivity was analyzed in relation with the polarizing power （ionic potential） of the exchangeable cations and with the influence of the connectivity within samples. The general conclusion stressed is that the connectivity due to the association between 2：1 unit layers （clay fabric） is the main factor on the experimental or ＂macroscopic＂ electric conductivity of pure homoionic montmorillonite at low water content. Considerations on the experimental conditions of different bibliographic reports were also made. The conclusion and the considerations made on experimental conditions are a good starting point for future researches on electric conductivity ofhomoionic montmorillonite at low water content.展开更多
基金supported by the National Natural Science Fund for Outstanding Young Scholar(Grant No.81622027)the Key Program of the National Key Research and Development Program of China(Grant No.2017YFA0106100)the research fund of PLA of China(Grant Nos.AWS17J011,BWS17J024)。
文摘Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain networks.As a consequence,some non-random organizational features,such as"small world"(most of the nodes are not connected directly but can communicate with few intermediate relay steps)and"rich club"(nodes that are rich in connections tend to form strongly interconnected clubs),have been found in functional brain network.Recently,the"small world"organizational feature of neuronal functional networks in vitro was found to be influenced by external applications.However,little is known about the influence of chronic electrical stimulation on functional networks of dissociated cortical cultures during network development.In the present study,cortical cultures were electrically stimulated at a frequency of 0,0.02,and 0.2 Hz,between 7 and 26 days in vitro(DIV).The spontaneous activity of the cortical cultures was recorded using MEAs.Next,a cross-covariance method and graph theory were applied to investigate organizational feature of functional networks.Our results showed that over 3 weeks of stimulation,the network density significantly increased with maturation in the control and 0.02 Hz stimulation groups,but not in 0.2 Hz stimulation groups.Moreover,all the cultures had a small-world topology at 14,18,22,and 26 DIV,free from the effect of chronic electrical stimulation.Besides,we found an asymmetry effect that partial electrical stimulation inhibited the formation of node connections in stimulated areas.This effect was more pronounced at 0.2 Hz than at 0.02 Hz stimulation.Our results suggest that electrical stimulation does not affect the small-world properties of neural cultures.Instead,electrical stimulation modulates connectivity patterns,and neurons within the stimulated area are less connected than neurons outside the stimulated area.
文摘Habitat loss and fragmentation of the wildlife species due to anthropogenic developments have been becoming serious issues in biological conservation. Alborz wild sheep, listed as threatened by IUCN, is distributed in relatively small and isolated patches in an increasingly human dominated landscape in the north-central Iran and east of Tehran. We used maximum entropy modeling to identify habitat areas of the wild sheep, across Jajrud protected area and its neighbouring protected areas including varjin, lar, koohsefid and the surroundings. Regarding to seasonal variation of the species home range, winter, summer and multi seasonal (annual) habitats were predicted. To estimate habitat connectivity, we used models of connectivity based in electrical circuit theory. Applying core areas of multi season for connectivity analysis, movement pattern of the species was predicted and important connective areas for conservation were identified. Species distribution maps revealed that the summer and winter habitats were approximately occurred in similar areas. Distance to eco-guards’ post was the most important predictor for both habitat models of summer and winter. The annual model, which is a combination of summer and winter, shows that the largest suitable habitat patches are located in the north, south and west of the study area. Maximum current flow map demonstrates that the areas among patch pairs are covered in low current, reflecting low rates of the species dispersal. This map presented bottlenecks to the species movement across major roads and along extending human settlements. Cumulative current flow map displayed that current was highest in Jajrud north of Mamloo extending to the northern Jajrud. Overall, our study demonstrated a prediction of habitat suitability and connectivity for Alborz wild sheep in east of Tehran, which can be used to direct conservation endeavours dealing with maintenance of the wild sheep metapopulation dynamics.
文摘Bibliographic reports on the electric conductivity of pure homoionic montmorillonite at low water content were analyzed in order to stress a general behavior of conductivity. At low water content, the conductivity is attributed to a mechanism of charge transport involving protons due to the influence of the electric field of the exchangeable cations on water molecules at the solvation shell. Conductivity was analyzed in relation with the polarizing power （ionic potential） of the exchangeable cations and with the influence of the connectivity within samples. The general conclusion stressed is that the connectivity due to the association between 2：1 unit layers （clay fabric） is the main factor on the experimental or ＂macroscopic＂ electric conductivity of pure homoionic montmorillonite at low water content. Considerations on the experimental conditions of different bibliographic reports were also made. The conclusion and the considerations made on experimental conditions are a good starting point for future researches on electric conductivity ofhomoionic montmorillonite at low water content.
