Human health risks caused by PM
raise awareness to the role of trees as bio-filters of urban air pollution, but not all species are equally capable of filtering the air. The objectives of this ...current study were: (1) to determine the foliar traits for effective PM
-capture and (2) explore species-to-species differences in foliar PM
-recapture capacity following a rain event. The study concluded that overall, the acicular needle shape made conifers more efficient with PM
accumulation and post-rainfall recapture than broadleaved species. The foliar shape and venation of broadleaved species did not appear to influence the PM
accumulation. However, the number of the grooves and trichomes of broadleaved species were positively related to foliar PM
accumulation, suggesting that they could be used as indicators for the effectiveness of tree PM
capture. Furthermore, the amount of PM
removal by rainfall was determined by the total foliar PM
. Not all PM
remained on the foliage. In some species, PM
was resuspended during the growing season, and thus reduced the net particular accumulation for that species. These findings contribute to a better understanding of tree species potential for reducing PM
in urban environments.
Taking an injection station in polymer injection block (BLOCK A) as an example, this paper proposed a series of measures such as stratification polymer injection and regional overall profile control ...to improve the development effect and further enhance the final recovery factor of the block in view of the problems of low injection pressure in individual areas, profile in thrust and high comprehensive water cut of produced Wells in the block. It provides some basis and reference for production and development of other polymer injection blocks.
•We applied Morris sensitivity analysis in a complex 3-dimensional water quality model EFDC.•We compared different sample sizes, perturbation ranges, and output metrics.•We analyzed and compared the ...influential factors of four different water quality constituents.•We analyzed the spatiotemporal variability in sensitivities.
Sensitivity analysis is a primary approach used in mathematical modeling to identify important factors that control the response dynamics in a model. In this paper, we applied the Morris sensitivity analysis method to identify the important factors governing the dynamics in a complex 3-dimensional water quality model. The water quality model was developed using the Environmental fluid dynamics code (EFDC) to simulate the fate and transport of nutrients and algal dynamics in Lake Dianchi, one of the most polluted large lakes in China. The analysis focused on the response of four water quality constituents, including chlorophyll-a, dissolved oxygen, total nitrogen, and total phosphorus, to 47 parameters and 7 external driving forces. We used Morris sensitivity analysis with different sample sizes and factor perturbation ranges to study the sensitivity with regard to different output metrics of the water quality model, and we analyzed the consistency between different sensitivity scenarios. In addition to the analysis with aggregate outputs, a spatiotemporal variability analysis was performed to understand the spatial heterogeneity and temporal distribution of sensitivities. Our results indicated that it is important to consider multiple characteristics in a sensitivity analysis, and we have identified a robust set of sensitive factors in the water quality model that will be useful for systematic model parameter identification and uncertainty analysis.
To investigate the mechanical properties of fused deposition modeling (FDM) parts, a compatibilizer and nanoparticles were used as additions in Polycarbonate and Acrylonitrile‐Butadiene‐Styrene ...(PC/ABS) blends, and four PC/ABS composites were used to fabricate the FDM samples in this study. Two simplified deposition modes of the FDM process were proposed and used to investigate the bonding effect and deposition effect. The bonding effects of the four materials were first investigated using model I of the FDM process. Then, a linear relationship between the bonding strength and the porosity was found, and the optimal processing conditions that produced the best bonding strength were determined. These optimal processing conditions were then used in mode II of the FDM process to fabricate four samples. The mechanical properties and structural characterizations of these samples were studied using tensile tests, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). One interesting phenomenon observed from the tensile tests was that the necking of the PC/ABS FDM sample can spread throughout the total gauge length and measure more than 100% of the strain when the compatibilizer and the nanoparticles were added, which can be attributed to a balance between bonding properties and ductility. The results verify the applicability of PC/ABC composites to FDM technology and suggest that compatibilizers and nanoparticles are suitable candidates to improve the bonding strength and the deposition effect of PC/ABS FDM parts. In conclusion, the balance between bonding properties and ductility is key to improving the tensile behaviors of PC/ABS FDM parts by adjusting the compatibility and porosity of blended PC/ABS samples.
In this work, CO2 hydrogenation over In2O3-supported rhenium (Re) catalysts was found to be highly size-dependent. When the Re loading was less than 1 wt %, the strong interaction between Re and ...In2O3 caused atomically dispersed Re species with a positive charge, resulting in high activity for CO2 hydrogenation to methanol with enhanced stability at elevated temperatures. The space–time yield of methanol over the 1 wt % Re/In2O3 catalyst reached 0.54 gMeOH gcat –1 h–1 with a methanol selectivity of 72.1% at 5 MPa and 573 K. With increasing Re loading, the In2O3 supported Re catalysts become more favored for CO2 methanation. Under the same experimental conditions, the methane selectivity is close to 100.0% over the 10 wt % Re/In2O3 catalyst. Catalyst characterizations and density functional theoretical (DFT) calculations further confirm that the size of the Re/In2O3 catalyst has a significant effect on hydrogen activation and the selectivity of the CO2 hydrogenation reaction. Due to the strong Re–In2O3 interaction, the atomically dispersed Re in the In2O3 surface lattice not only stabilizes oxygen vacancies but also results in Hδ+ formation upon hydrogen adsorption. This significantly promotes methanol synthesis from CO2 hydrogenation. Meanwhile, the 10 wt % Re/In2O3 catalyst with supported Re nanoclusters induces H δ‑ formation, which eventually leads to more methane production. The present study demonstrates the atomically dispersed Re/In2O3 catalyst is promising for CO2 hydrogenation to methanol.
Flexible ultrasensitive piezoresistive strain sensors were fabricated by CO2 Laser ablating of the surface of the multiwall carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) composite film prepared ...by a coating process. The effects of the MWCNT content and the applied laser power on the electrical and sensing performances of the MWCNT/PDMS composite strain sensor were systematically investigated. It is found that, after laser ablating, the electrical conductivity and the sensing gauge factor of the MWCNT/PDMS film were greatly improved only by the addition of 1.0 wt% of MWCNT, which is below the percolation threshold of the MWCNT in the PDMS matrix. A novel boscage-like structure at the surface of the film formed by the ablation of the PDMS and the rearrangement of the MWCNT during the laser ablating process was found responsible for the ultrahigh gauge factor of the composite strain sensor, which is about 513 at the strain of 5.0%. The facile and cost-effective fabrication process of the flexible ultrasensitive strain sensor could be simply extended to other polymer composites for the development of new multifunctional and wearable electronic devices.
Selective expansion of high-affinity antigen-specific B cells in germinal centers (GCs) is a key event in antibody affinity maturation. GC B cells with improved affinity can either continue ...affinity-driven selection or exit the GC to differentiate into plasma cells (PCs) or memory B cells. Here we found that deleting E3 ubiquitin ligases Cbl and Cbl-b (Cbls) in GC B cells resulted in the early exit of high-affinity antigen-specific B cells from the GC reaction and thus impaired clonal expansion. Cbls were highly expressed in GC light zone (LZ) B cells, where they promoted the ubiquitination and degradation of Irf4, a transcription factor facilitating PC fate choice. Strong CD40 and BCR stimulation triggered the Cbl degradation, resulting in increased Irf4 expression and exit from GC affinity selection. Thus, a regulatory cascade that is centered on the Cbl ubiquitin ligases ensures affinity-driven clonal expansion by connecting BCR affinity signals with differentiation programs.
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•Deletion of Cbl ubiquitin ligases in GC B cells abolishes antibody affinity maturation•Cbls control the clonal expansion of high- but not low-affinity B cells in GCs•Cbls prevent early exit of B cells from GC by promoting Irf4 ubiquitination•Strong CD40 and BCR signals trigger degradation of Cbls in LZ B cells, promoting GC exit
Li et al. find that clonal expansion of high affinity B cells in GCs depends on the Cbl ubiquitin ligases, which prevent premature GC exit by promoting the degradation of Irf4 in light zone B cells. Strong CD40 and BCR signals trigger Cbl degradation, thus enabling GC exit.
The quiescence of hematopoietic stem cells (HSCs) is critical for preserving a lifelong steady pool of HSCs to sustain the highly regenerative hematopoietic system. It is thought that specialized ...niches in which HSCs reside control the balance between HSC quiescence and self-renewal, yet little is known about the extrinsic signals provided by the niche and how these niche signals regulate such a balance. We report that CXCL12 produced by bone marrow (BM) stromal cells is not only the major chemoattractant for HSCs but also a regulatory factor that controls the quiescence of primitive hematopoietic cells. Addition of CXCL12 into the culture inhibits entry of primitive hematopoietic cells into the cell cycle, and inactivation of its receptor CXCR4 in HSCs causes excessive HSC proliferation. Notably, the hyperproliferative Cxcr4(-/-) HSCs are able to maintain a stable stem cell compartment and sustain hematopoiesis. Thus, we propose that CXCR4/CXCL12 signaling is essential to confine HSCs in the proper niche and controls their proliferation.
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