Bacterial Nanotubes as Intercellular Linkages in Marine Assemblages

Several types of bacterial appendages, e.g., pili and fimbriae, are known for their role in promoting interactions and aggregation with particles and bacteria in the ocean. First discovered in Bacillus subtilis and Escherichia coli, but novel to marine bacteria, bacterial nanotubes are hollow tubular structures connecting cell pairs that allow for the internal transport of cytoplasmic metabolites across the connecting structure. While the significance of nanotubes in exchange of cytoplasmic content has been established in non-marine bacteria, their occurrence and potential ecological significance in marine bacteria has not been reported. Using multiple high-resolution microscopy methods (atomic force microscopy, scanning, and transmission electron microscopy), we have determined that marine bacteria isolates and natural assemblages from nearshore upper ocean waters can express bacterial nanotubes. In marine isolates Pseudoalteromonas sp. TW7 and Alteromonas sp. ALTSIO, individual bacterial nanotubes measured 50–160 nm in width and extended 100–600 nm between connected cells. The spatial coupling of different cells via nanotubes can last for at least 90 min, extending the duration of interaction events between marine bacteria within natural assemblages. The nanomechanical properties of bacterial nanotubes vary in adhesion and dissipation properties, which has implication for structural and functional variability of these structures in their ability to stick to surfaces and respond to mechanical forces. Nanotube frequency is low among cells in enriched natural assemblages, where nanotubes form short, intimate connections, <200 nm, between certain neighboring cells. Bacterial nanotubes can form the structural basis for a bacterial ensemble and function as a conduit for cytoplasmic exchange (not explicitly studied here) between members for multicellular coordination and expression. The structural measurements and nanomechanical analyses in this study also extends knowledge about the physical properties of bacterial nanotubes and their consequences for marine microenvironments. The discovery of nanotube expression in marine bacteria has significant potential implications regarding intimate bacterial interactions in spatially correlated marine microbial communities.

I3D: An Improved Three-Dimensional CNN Model on Hyperspectral Remote Sensing Image Classification

Hyperspectral image data are widely used in real life because it contains rich spectral and spatial information. Hyperspectral image classification is to distinguish different functions based on different features. The computer performs quantitative analysis through the captured image and classifies each pixel in the image. However, the traditional deep learning-based hyperspectral image classification technology, due to insufficient spatial-spectral feature extraction, too many network layers, and complex calculations, leads to large parameters and optimizes hyperspectral images. For this reason, I proposed the I3D-CNN model. The number of classification parameters is large, and the network is complex. This method uses hyperspectral image cubes to directly extract spectral-spatial coupling features, adds depth separable convolution to 3D convolution to reextract spatial features, and extracts the parameter amount and calculation time at the same time. In addition, the model removes the pooling layer to achieve fewer parameters, smaller model scale, and easier training effects. The performance of the I3D-CNN model on the test datasets is better than other deep learning-based methods after comparison. The results show that the model still exhibits strong classification performance, reduces a large number of learning parameters, and reduces complexity. The accuracy rate, average classification accuracy rate, and kappa coefficient are all stable above 95%.

Controllable Fano-like Resonance in Terahertz Planar Meta-Rotamers

Meta-molecules composed of meta-atoms exhibit various electromagnetic phenomena owing to the interaction among the resonance modes of the meta-atoms. In this study, we numerically investigated Fano-like-resonant planar metamaterials composed of meta-molecules at terahertz (THz) frequencies. We present meta-rotamers based only on the difference in the spatial position of their component meta-atoms (C- and Y-shapes) that can be interconverted by rotations and have tunable Fano-like resonance. This is because of the cooperative effects determined by the spatial coupling conditions of the nodes and antinodes of electric-dipole and inductive–capacitive (LC) resonances of the meta-atoms. The findings of this study provide potential options for exploring novel THz devices and for engineering high-level functionalities in metamaterial-based devices.

Tipping Cascades in a Multi-patch System with Noise and Spatial Coupling

Forecasting tipping points in spatially extended systems is a key area of interest to ecologists. A slowly declining spatially distributed population is an important example of an ecological system that could exhibit a cascade of tipping points. Here, we develop a spatial two-patch model with environmental stochasticity that is slowly forced through population collapse, in the presence of changing environmental conditions. We begin with a basic spatial model, then introduce a fast–slow version of the model using geometric singular perturbation theory, followed by the inclusion of stochasticity. Using the spectral density of the fluctuating subpopulation in each patch, we derive analytic expressions for candidate indicators of population extinction and evaluate their performance through a simulation study. We find that coupling and spatial heterogeneity decrease the magnitude of the proposed indicators in coupled populations relative to isolated populations. Moreover, the degree of coupling dictates the trends in summary statistics. We conclude that this theory may be applied to other contexts, including the control of invasive species.

Spatial Coupling and Causal Effects between the Recreational Use of Ecological Land and Restoration: A Case Study of the Pearl River Delta Urban Agglomeration

As the urbanization and industrialization of China’s urban agglomerations reach increasingly high levels, residents are voicing a growing demand for improved green public sport and recreational space. The coordination of ecological land restoration (ELR) and recreational use at the regional level is therefore urgent. This study demonstrates the spatiotemporal evolution of coupled ELR and the recreational use of ecological land (RUoEL) in the Pearl River Delta urban agglomeration based on spatial interpretation, remote sensing mapping, and spatial statistical analysis. A geographical and temporally weighted regression is used to test the spatial effects of the RUoEL on the evolution of the ELR patterns. The results show that the RUoEL (mainly greenways and ecological recreational spaces) and ELR exert a certain degree of coupled spatial characteristics, and that the former significantly impacts the latter. These spatial differences are more notable in areas with high-level ecological recreational spaces, or which are located near densely populated built-up areas. Recreation-oriented ELR is therefore relatively easy to develop in these areas. The results provide important guidelines for the development of ecosystem service patterns in urban agglomerations that include the coexistence of ELR and recreational use, which will strengthen the academic support for regional ELR planning and improve public health.

Hippocampus maintains a flexible and coherent map under reward flavor-landmark cue conflict.

Animals predominantly use salient visual cues (landmarks) for efficient navigation over other sensory modalities. When the relative position of the visual cues is altered, the hippocampal population exhibits heterogeneous responses and constructs context-specific spatial maps. Another critical factor that can strongly modulate spatial representation is the presence of reward. Reward features can drive behavior and are known to bias spatial attention. However, it is unclear whether reward flavors are used for spatial reference in the presence of distal cues and how the hippocampus population dynamics changes when the association between reward flavors and distal cues is altered. We investigated these questions by recording place cells from the CA1 while the rats ran in an environment with the conflicting association between reward flavors and distal cues. We report that the hippocampal place cells coherently and dynamically bind to reward flavors or distal cues across sessions, but not simultaneously suggesting the use of a single spatial map. We found that place cells maintained their spatial offset in the cue conflict conditions, thus showing a robust spatial coupling featuring an attractor-like property in the CA1. When the textures were added on the track, the coherency of the CA1 is degraded, as the hippocampus showed a heterogeneous response and weak spatial coupling of co-recorded cells suggesting a break away from the attractor network. These results indicate that reward flavors alone may be used for spatial reference but may not cause sufficient input difference to create context-specific spatial maps in the CA1.

Extraction of urban built-up area based on the fusion of night-time light data and point of interest data

The accurate extraction of urban built-up areas is an important prerequisite for urban planning and construction. As a kind of data that can represent urban spatial form, night-time light data has been widely used in the extraction of urban built-up areas. As one of the geographic open-source big data, point of interest (POI) data has a high spatial coupling with night-time light data, so researchers are beginning to explore the fusion of the two data in order to achieve more accurate extraction of urban built-up areas. However, the current research methods and theoretical applications of the fusion of POI data and night-time light data are still insufficient compared with the dramatically changing urban built-up areas, which needed to be further supplemented and deepened. This study proposes a new method to fuse POI data and night-time light data. The results before and after data fusion are compared, and the accuracy of urban built-up area extracted by different data and methods is analysed. The results show that the data fusion can avoid the shortage of single data and effectively improve the extraction accuracy of urban built-up areas, which is greatly helpful to supplement the study of data fusion in urban built-up areas, and also can provide decision-making guidance for urban planning and construction.

The Coupling between Urban Expansion and Population Growth: An Analysis of Urban Agglomerations in China (2005–2020)

Exploring the coordinated development process of people–land allocation in the urbanization process of urban agglomerations is of great significance to promote improvement of the urbanization development level and quality and realize the healthy development of urbanization. We took nine urban agglomerations in China as the research object and the coupling between urban expansion and population growth as the entry point. The overall coupling and the spatial coupling were used to reveal the people–land coupling relationship of nine urban agglomerations at different time periods. We found that both construction land and population within each urban agglomeration were in the stage of continuous growth, and the increase of both was similar and synchronous. The overall and spatial coupling between urban expansion and population growth is increasing. The expansion rate of construction land is a factor that influences the overall and spatial coupling between urban expansion and population growth, i.e., the greater the expansion rate of construction land, the higher the overall and spatial coupling between urban expansion and population growth. This study provides a new perspective for exploring the coupling between urban expansion and population growth and offers a new approach for studying the relationship between the two.