Critical-edge based tabu search algorithm for solving large-scale multi-vehicle Chinese postman problem.

The min-max multi-vehicle Chinese postman problem is an NP-hard problem, which is widely used in path planning problems based on road network graphs, such as urban road structure probing planning, urban road underground cavity detection planning, high-voltage line inspection planning, and so on. With the rapid increase in the number of nodes and connections of road network graph, the solution time and path equilibrium constraints pose new challenges to the problem solving. In this paper, we propose a critical-edge tabu search algorithm, CTA-kroutes, for solving the min-max multi-vehicle postman problem for large-scale road networks. First, the initial solution with balanced path lengths is obtained by segmenting the Eulerian paths; second, the critical edges are moved in the initial solution to construct the neighborhood solution, and the tabu search algorithm is used to find the optimal solution iteratively; and lastly, the solution optimization algorithm is used at the end of each iteration to de-duplicate and optimally reconstruct the current search result. Experiments show that the CTA-kroutes algorithm can effectively improve the equalization of multi-vehicle paths and its applicability to large-scale road networks.

Anomalous crystalline ordering of particles in a viscoelastic fluid under high shear.

Addition of particles to a viscoelastic suspension dramatically alters the properties of the mixture, particularly when it is sheared or otherwise processed. Shear-induced stretching of the polymers results in elastic stress that causes a substantial increase in measured viscosity with increasing shear, and an attractive interaction between particles, leading to their chaining. At even higher shear rates, the flow becomes unstable, even in the absence of particles. This instability makes it very difficult to determine the properties of a particle suspension. Here, we use a fully immersed parallel plate geometry to measure the high-shear-rate behavior of a suspension of particles in a viscoelastic fluid. We find an unexpected separation of the particles within the suspension resulting in the formation of a layer of particles in the center of the cell. Remarkably, monodisperse particles form a crystalline layer which dramatically alters the shear instability. By combining measurements of the velocity field and torque fluctuations, we show that this solid layer disrupts the flow instability and introduces a single-frequency component to the torque fluctuations that reflects a dominant velocity pattern in the flow. These results highlight the interplay between particles and a suspending viscoelastic fluid at very high shear rates.

Core-Shell Nanohydrogels with Programmable Swelling for Conformance Control in Porous Media.

Conformance control during waterflooding in an oil reservoir is utilized to redistribute water and increase the sweep efficiency and hence oil production. Using preformed gel particles can effectively redirect the flow by blocking the high-permeability zones and forcing water into low-permeability zones where the oil is trapped. However, the size of such gel particles can limit their applications deeper within the reservoir and can result in shear-induced degradation near the well bore. Here, we fabricate core-shell nanohydrogels with delayed swelling behavior; their volume increases by a factor of 200 after about 30 days in brine under reservoir conditions. We study their effect on the flow behavior in a three-dimensional porous medium micromodel consisting of randomly packed glass beads. Using confocal microscopy, we directly visualize the spatial variations of flow in the micromodel before and after nanohydrogel injection and swelling. The swollen nanohydrogels block some pores reducing the permeability of the micromodel and diverting the water into low-permeability regions. A core flood experiment further confirms that the nanohydrogels can significantly reduce the permeability of a reservoir sample and divert the fluid flow. Our results demonstrate that these core-shell nanohydrogels might be useful for flow control in porous media and can be used as a conformance control agent.

Plant-Based Nanoparticles Prepared from Proteins and Phospholipids Consisting of a Core-Multilayer-Shell Structure: Fabrication, Stability, and Foamability.

Gliadin-phospholipid hybrid nanoparticles with a core-multilayered-shell internal structure were fabricated using a coassembly approach based on antisolvent coprecipitation. The mean particle diameters of the nanoparticles depended on their composition, increasing from 78 to 145 nm as the mass ratio of gliadin to phospholipid (G/P) increased from 7:3 to 3:7. The hybrid nanoparticles had better pH, salt, and thermal stabilities than simple gliadin nanoparticles. Hybrid nanoparticles with the highest phospholipid fraction (G/P 3:7) had the best pH, salt, and thermal stabilities, remaining stable from pH 3 to 8, from 0 to 300 mmol/L NaCl, and when boiled at pH 4 or 5 for 90 min. Hybrid nanoparticles also had better foam-formation and stability characteristics than gliadin nanoparticles, particularly at the highest phospholipid level. The structured nanoparticles developed in this study may therefore be useful for application in commercial products, for example, as delivery systems, emulsifiers, or foaming agents.

Transcriptome sequencing and ITRAQ reveal the detoxification mechanism of Bacillus GJ1, a potential biocontrol agent for Huanglongbing.

Huanglongbing (HLB) is the most serious disease affecting citrus production worldwide. No HLB-resistant citrus varieties exist. The HLB pathogen Candidatus Liberibacter asiaticus is nonculturable, increasing the difficulty of preventing and curing the disease. We successfully screened the biocontrol agent Bacillus GJ1 for the control of HLB in nursery-grown citrus plants. RNA sequencing (RNA-seq) of the transcriptome and isobaric tags for relative and absolute quantification of the proteome revealed differences in the detoxification responses of Bacillus GJ1-treated and -untreated Ca. L. asiaticus-infected citrus. Phylogenetic tree alignment showed that GJ1 was classified as B. amyloliquefaciens. The effect of eliminating the HLB pathogen was measured using real-time quantitative polymerase chain reaction (qPCR) and PCR. The results indicate that the rate of detoxification reached 50% after seven irrigations, of plants with an OD600nm≈1 Bacillus GJ1 suspension. Most importantly, photosynthesis-antenna proteins, photosynthesis, plant-pathogen interactions, and protein processing in the endoplasmic reticulum were significantly upregulated (padj < 0.05), as shown by the KEGG enrichment analysis of the transcriptomes; nine of the upregulated genes were validated by qPCR. Transcription factor analysis of the transcriptomes was performed, and 10 TFs were validated by qPCR. Cyanoamino acid metabolism, regulation of autophagy, isoflavonoid biosynthesis, starch and sucrose metabolism, protein export, porphyrin and chlorophyll metabolism, and carotenoid biosynthesis were investigated by KEGG enrichment analysis of the proteome, and significant differences were found in the expression of the genes involved in those pathways. Correlation analysis of the proteome and transcriptome showed common entries for the significantly different expression of proteins and the significantly different expression of genes in the GO and KEGG pathways, respectively. The above results reveal important information about the detoxification pathways.

A fluorescent ratiometric chemodosimeter for Cu2+ based on TBET and its application in living cells.

Based on a through bond energy transfer (TBET) between Rhodamine and a naphthalimide fluorophore, a fluorescent ratiometric chemodosimeter RN1 was designed and prepared for single selective detection of Cu(2+) in aqueous solution and in living cells, as Cu(2+) acts as not only a selective recognizing guest but also a hydrolytic promoter.