Learning Neural Implicit through Volume Rendering with Attentive Depth Fusion Priors

Learning neural implicit representations has achieved remarkable performance in 3D reconstruction from multi-view images. Current methods use volume rendering to render implicit representations into either RGB or depth images that are supervised by multi-view ground truth. However, rendering a view each time suffers from incomplete depth at holes and unawareness of occluded structures from the depth supervision, which severely affects the accuracy of geometry inference via volume rendering. To resolve this issue, we propose to learn neural implicit representations from multi-view RGBD images through volume rendering with an attentive depth fusion prior. Our prior allows neural networks to perceive coarse 3D structures from the Truncated Signed Distance Function (TSDF) fused from all depth images available for rendering. The TSDF enables accessing the missing depth at holes on one depth image and the occluded parts that are invisible from the current view. By introducing a novel attention mechanism, we allow neural networks to directly use the depth fusion prior with the inferred occupancy as the learned implicit function. Our attention mechanism works with either a one-time fused TSDF that represents a whole scene or an incrementally fused TSDF that represents a partial scene in the context of Simultaneous Localization and Mapping (SLAM). Our evaluations on widely used benchmarks including synthetic and real-world scans show our superiority over the latest neural implicit methods. Project page: https://machineperceptionlab.github.io/Attentive_DF_Prior/Comment: NeurIPS 202

Neutron Activation Background in the NvDEx Experiment

An extremely low-background environment is a crucial requirement for any neutrinoless double beta decay experiment. Neutrons are very difficult to stop, because they can pass through the shields and activate nuclei in the detector, even inside the fiducial volume itself. Using Geant4 simulations we have studied the neutron background for N$\nu$DEx-100 and the most efficient way to reduce it. Using a 60 cm thick external HDPE shield the neutron background can be reduced down to $0.24\pm 0.06$ events/year, lower than the background rate due to natural radioactivity (0.42 events/year), which was used as a benchmark for these calculations. The amount of shielding material needed can be significantly reduced by placing HDPE in the empty space between the lead shield and the steel vessel; in this way, it is sufficient to add 20 cm external HDPE shield to reduce the neutron background down to $0.15\pm0.05$ events/year.Comment: 13 pages, 11 figure

High-Resolution Tip-Enhanced Raman Scattering Probes Sub-Molecular Density Changes

Tip-enhanced Raman spectroscopy (TERS) exhibits new selection rule and sub- nanometer spatial resolution, which is attributed to the plasmonic near-field confinement. Despite recent advances in simulations of TERS spectra under highly confined fields, a simply physical mechanism has remained elusive. In this work we show that single-molecule TERS images can be explained by local sub-molecular density changes induced by the confined near-field during the Raman process. The local sub-molecular density changes determine the spatial resolution in TERS and the gradient-based selection rule. Using this approach we find that the four-fold symmetry of meso-tetrakis(3,5- di-tert-butylphenyl)porphyrin (H2TBPP) TERS images observed in experiments arises from the combination of degenerate normal modes localized in the functional side groups rather than the porphyrin ring as previously considered. As an illustration of the potential of the method, we demonstrate how this new theory can be applied to microscopic structure characterization.</div

A Structure Load Performance Integrated Model Method for the Bridge-Type Displacement Amplification Mechanism

The modeling of compliant bridge-type displacement amplification mechanisms has challenges due to the intrinsic coupling of kinematic and mechanical behaviors. A structure load performance integrated model method for the bridge-type displacement amplification mechanism is presented. The established modeling based on Castigliano’s second theorem considers the deformations of all members, the effect of external load and the nonlinear shear effect. Compared to the finite element model (FEM) and existing models, the established modeling precisely predicts significant nonlinearity of the displacement amplification ratio (DAR) with the driving force, strong sensitivity of DAR to the external load and corresponding relationships of structural parameters with DAR, which is the closest to the FEM result over existing models. The variance-based sensitivities of structural parameters to DAR are thoroughly analyzed, indicating that sensitive structure parameters need to be focused on. Modeling applications further prove the reliability and expandability of the proposed model method. The proposed model method can provide support for the design, optimization and control of compliant systems with bridge-type displacement amplification mechanisms

A Structure Load Performance Integrated Model Method for the Bridge-Type Displacement Amplification Mechanism

The modeling of compliant bridge-type displacement amplification mechanisms has challenges due to the intrinsic coupling of kinematic and mechanical behaviors. A structure load performance integrated model method for the bridge-type displacement amplification mechanism is presented. The established modeling based on Castigliano&rsquo;s second theorem considers the deformations of all members, the effect of external load and the nonlinear shear effect. Compared to the finite element model (FEM) and existing models, the established modeling precisely predicts significant nonlinearity of the displacement amplification ratio (DAR) with the driving force, strong sensitivity of DAR to the external load and corresponding relationships of structural parameters with DAR, which is the closest to the FEM result over existing models. The variance-based sensitivities of structural parameters to DAR are thoroughly analyzed, indicating that sensitive structure parameters need to be focused on. Modeling applications further prove the reliability and expandability of the proposed model method. The proposed model method can provide support for the design, optimization and control of compliant systems with bridge-type displacement amplification mechanisms

Inversion and Effect Research on Dust Distribution of Urban Forests in Beijing

Urban forests affect the filtration and absorption of airborne particulate matter, which can minimize the harmful effects to human health caused by airborne particulate pollution. Evergreen plants in urban forests play a major role in absorbing dust and purifying the air, especially in winter. Studying the spatial distribution of leaf dust and exploring the dust retention effect of evergreen shrubs are important for scientifically guiding urban forest construction and improving the living environment of cities in winter. The purpose of this study was to establish a dust inversion model by correlation analysis of spectral reflectance and the amount of dust absorption (ADA) of vegetation, using Sentinel-2 satellite remote-sensing images to obtain the dust distribution of the evergreen vegetation (mainly Euonymus japonicus Thunb.) in the Beijing urban area, and to determine the effect of the spatial pattern of E. japonicus woodland on ADA intensity. The result showed that the red band and near-infrared band are most sensitive to dust. The normalized difference phenology index (NDPI) is more suitable for building an inversion model, where the determination coefficient (R2) of the inversion model constructed by the ratio of the NDPI (RNDPI) was 0.879. The inversion results show that the mean ADA in the enclosed area is smaller than that in semi-enclosed and open areas, and the regional distribution of high ADA in the urban area of Beijing was higher in the south with a tendency of the ADA to decrease from city center to the surrounding area. The size, shape, and percentage of landscape (PLAND) of E. japonicus woodland have a significant effect on ADA intensity. We found that, in the study area, when the PLAND of E. japonicus woodland is higher than 40%, its ADA intensity remains basically unchanged. When the vegetation coverage is fixed, the landscape shape index is negatively correlated with ADA intensity, and reduction of the overall shape complexity of forestland can enhance its dust retention effect and improve the air environment of the surrounding areas. The results of this study can be used as a reference for urban planners and landscape architects when building urban forests, providing a scientific basis for controlling and reducing air particulate pollution in Beijing&#8217;s winter and improving the living environment

Lung injuries induced by ozone exposure in female mice: Potential roles of the gut and lung microbes

Ozone (O3) is one of the most harmful pollutants affecting health. However, the potential effects of O3 exposure on microbes in the gut–lung axis related to lung injuries remain elusive. In this study, female mice were exposed to 0-, 0.5- and 1-ppm O3 for 28 days, followed by routine blood tests, lung function tests and histopathological examination of the colon, nasal cavity and lung. Mouse faeces and lungs were collected for 16s rRNA sequencing to assess the overall microbiological profile and screen for key differential enriched microbes (DEMs). The key DEMs in faecal samples were Butyricimonas, Rikenellaceae RC9 and Escherichia-Shigella, whereas those in lung samples were DNF00809, Fluviicola, Bryobacter, Family XII AD3011 group, Sharpea, MND1 and unclassified Phycisphaeraceae. After a search in microbe–disease databases, these key DEMs were found to be associated with lung diseases such as lung neoplasms, cystic fibrosis, pneumonia, chronic obstructive pulmonary disease, respiratory distress syndrome and bronchiectasis. Subsequently, we used transcriptomic data from Gene Expression Omnibus (GEO) with exposure conditions similar to those in this study to cross-reference with Comparative Toxicogenomic Database (CTD). Il-6 and Ccl2 were identified as the key causative genes and were validated. The findings of this study suggest that exposure to O3 leads to significant changes in the microbial composition of the gut and lungs. These changes are associated with increased levels of inflammatory factors in the lungs and impaired lung function, resulting in an increased risk of lung disease. Altogether, this study provides novel insights into the role of microbes present in the gut–lung axis in O3 exposure-induced lung injury

Spatiotemporal Characteristics of Intercellular Calcium Wave Communication in Micropatterned Assemblies of Single Cells

Micropatterned substrates offer a unique possibility to define and control spatial organization of biological cells at the microscale, which greatly facilitates investigations of the cell-to-cell communication in vitro. Here, we developed a simple micropatterning strategy to resolve various spatiotemporal characteristics of intercellular calcium wave (ICW) communication among isolated BV-2 microglial cells. By using a single-ring assembly, we found that the direction of the initial transmitter secretion was strongly correlated with the site of the cell at which the mechanical stimulus triggering the ICWs was imposed. By using multiring assemblies, we observed that the response ratio of the same outmost cells 160 μm away from the center increased from 0% in the single-ring assembly to 9.6% in the four-ring assembly. This revealed that cells located in the interring acted as regenerative amplifiers for the ICWs generated by the central cell. By using a special oval-type micropattern, we found that calcium mobilization in lamellipodia of a fusiform BV-2 microglia cell occurred 2.9 times faster than that in the middle part of the cell, demonstrating a higher region-specific sensitivity of lamellipodia to the transmitter. Taken together, our micropatterning strategy opened up new experimental prospects to study ICWs and revealed novel spatiotemporal characteristics of ICW communication including stimulation site-dependent secretion, regenerative propagation, and region-specific cell sensitivity

Nucleotide transmitters ATP and ADP mediate intercellular calcium wave communication via P2Y_12/13 receptors among BV-2 microglia

<div><p>Nerve injury is accompanied by a liberation of diverse nucleotides, some of which act as ‘find/eat-me’ signals in mediating neuron-glial interplay. Intercellular Ca²⁺ wave (ICW) communication is the main approach by which glial cells interact and coordinate with each other to execute immune defense. However, the detailed mechanisms on how these nucleotides participate in ICW communication remain largely unclear. In the present work, we employed a mechanical stimulus to an individual BV-2 microglia to simulate localized injury. Remarkable ICW propagation was observed no matter whether calcium was in the environment or not. Apyrase (ATP/ADP-hydrolyzing enzyme), suramin (broad-spectrum P2 receptor antagonist), 2-APB (IP₃ receptor blocker) and thapsigargin (endoplasmic reticulum calcium pump inhibitor) potently inhibited these ICWs, respectively, indicating the dependence of nucleotide signals and P2Y receptors. Then, we detected the involvement of five naturally occurring nucleotides (ATP, ADP, UTP, UDP and UDP-glucose) by desensitizing receptors. Results showed that desensitization with ATP and ADP could block ICW propagation in a dose-dependent manner, whereas other nucleotides had little effect. Meanwhile, the expression of P2Y receptors in BV-2 microglia was identified and their contributions were analyzed, from which we suggested P2Y_12/13 receptors activation mostly contributed to ICWs. Besides, we estimated that extracellular ATP and ADP concentration sensed by BV-2 microglia was about 0.3 μM during ICWs by analyzing calcium dynamic characteristics. Taken together, these results demonstrated that the nucleotides ATP and ADP were predominant signal transmitters in mechanical stimulation-induced ICW communication through acting on P2Y_12/13 receptors in BV-2 microglia.</p></div

Spatiotemporal Characteristics of Intercellular Calcium Wave Communication in Micropatterned Assemblies of Single Cells

Micropatterned substrates offer a unique possibility to define and control spatial organization of biological cells at the microscale, which greatly facilitates investigations of the cell-to-cell communication in vitro. Here, we developed a simple micropatterning strategy to resolve various spatiotemporal characteristics of intercellular calcium wave (ICW) communication among isolated BV-2 microglial cells. By using a single-ring assembly, we found that the direction of the initial transmitter secretion was strongly correlated with the site of the cell at which the mechanical stimulus triggering the ICWs was imposed. By using multiring assemblies, we observed that the response ratio of the same outmost cells 160 μm away from the center increased from 0% in the single-ring assembly to 9.6% in the four-ring assembly. This revealed that cells located in the interring acted as regenerative amplifiers for the ICWs generated by the central cell. By using a special oval-type micropattern, we found that calcium mobilization in lamellipodia of a fusiform BV-2 microglia cell occurred 2.9 times faster than that in the middle part of the cell, demonstrating a higher region-specific sensitivity of lamellipodia to the transmitter. Taken together, our micropatterning strategy opened up new experimental prospects to study ICWs and revealed novel spatiotemporal characteristics of ICW communication including stimulation site-dependent secretion, regenerative propagation, and region-specific cell sensitivity