DEM investigation on strain localization in a dense periodic granular assembly with high coordination number

Strain localization is one of key phenomena which have been studied extensively in geomaterials and for different kinds of materials including metals and polymers. This well-known phenomenon appears when structure/material is closed to failure. Theoretical, experimental, and numerical research have been dedicated to this subject for a long while. In the numerical aspects, strain localization inside the periodic granular assembly has not been well studied in the literature. In this paper, we investigate the occurrence and development of strain localization within a dense cohesive-frictional granular assembly with high coordination number under bi-periodic boundary conditions by Discrete Element Modeling (DEM). The granular assembly is composed of 2D circular disks and subjected to biaxial loading with constant lateral pressure. The results show that the formation of shear bands is of periodic type, consistent with the boundary conditions. This formation has the origins of the irreversible losing of cohesive contacts, viewed as micro-crackings which strongly concentrated in the periodic shear zones. This micromechanical feature is therefore strongly related to the strain localization observed at the sample scale. Finally, we also show that the strain localization is in perfect agreement with the sample’s displacement fluctuation fields.

Synthesis and Coordination Properties of a Water-Soluble Material by Cross-Linking Low Molecular Weight Polyethyleneimine with Armed Cyclotriveratrilene

In this study, a full organic and water-soluble material was synthesized by coupling low molecular weight polyethylenimine (PEI-800) with cyclotriveratrilene (CTV). The water-soluble cross-linked polymer contains hydrophobic holes with a high coordination capability towards different organic drug molecules. The coordinating capability towards hydrophilic drugs (doxorubicin, gatifloxacin and sinomenine) and hydrophobic drugs (camptothecin and celastrol) was analyzed in an aqueous medium by using NMR, UV-Vis and emission spectroscopies. The coordination of drug molecules with the armed CTV unit through hydrophobic interactions was observed. In particular, celastrol exhibited more ionic interactions with the PEI moiety of the hosting system. In the case of doxorubicin, the host–guest detachment was induced by the addition of ammonium chloride, suggesting that the intracellular environment can facilitate the release of the drug molecules.

Designing narcissistic self-sorting terpyridine moieties with high coordination selectivity for complex metallo-supramolecules

Coordination-driven self-assembly is a powerful approach for the construction of metallosupramolecules, but designing coordination moieties that can drive the self-assembly with high selectivity and specificity remains a challenge. Here we report two ortho-modified terpyridine ligands that form head-to-tail coordination complexes with Zn(II). Both complexes show narcissistic self-sorting behaviour. In addition, starting from these ligands, we obtain two sterically congested multitopic ligands and use them to construct more complex metallo-supramolecules hexagons. Because of the non-coaxial structural restrictions in the rotation of terpyridine moieties, these hexagonal macrocycles can hierarchically self-assemble into giant cyclic nanostructures via edge-to-edge stacking, rather than face-to-face stacking. Our design of dissymmetrical coordination moieties from congested coordination pairs show remarkable self-assembly selectivity and specificity.

The Spatial–Temporal Changes of the Coupling Relationship among Agricultural Labor Force, Agricultural Economy, and Farmland in Chongqing

Agricultural labor force, agricultural economy, and farmland use are momentous components of sustainable development in rural areas, as well as essential causes of drastic changes in the urban–rural transformation. This paper studies the spatial–temporal characteristics of the labor–farmland–economy coupling structure from 2000 to 2018 in rural areas of Chongqing using spatial analysis technology. The study has four main results. First and foremost, not only has the average annual rate of the agricultural labor force in Chongqing reduced by 3.73%, but the reduction rates in Jiangbei District, Dadukou District, Nan’an District, Shapingba District, and Yubei District have exceeded 15%. Then, the average annual rate of the agricultural economy has increased by 9.32%, but it has been in a downward trend in Dadukou District, Jiangbei District, and Shapingba Districts. Furthermore, the average annual decline rate of farmland area is 0.34% with larger reduction occurring in the nine of the central urban districts, Chengkou County and Wushan County. Ultimately, there have been 33 districts and counties with the temporal–spatial characteristics of labor–farmland–economy coupling above primary coordination, which includes 16 districts and counties reaching a high coordination. This provides theoretical and methodical supports for the coordinated development of human and land industries in different regions.

Designing Narcissistic Self-Sorting Terpyridine Moieties with High Coordination Selectivity for Complex Metallo-Supramolecules

Coordination-driven self-assembly serves as a powerful approach for the construction of metallo-supramolecules, however, it still remains its infancy in design of coordination moieties with high selectivity and specificity. Herein, two unique ortho-modified terpyridine ligands (MA and MB) were designed and synthesized to form head-to-tail coordination complexes with Zn(II) respectively. Both of them showed excellent narcissistic self-sorting process due to the exquisite design. Further, two multitopic ligands (LA and LB) with narcissistic self-sorting moieties were obtained and used to construct more complex metallo-supramolecules hexagons. More interestingly, because of the non-coaxial structural restrictions in the rotation of terpyridine moieties, the obtained hexagonal macrocycles were able to hierarchically self-assemble into giant cyclic nanostructures via side-to-side stacking rather than face-to-face stacking. Our design of dissymmetrical coordination moieties could pave a new avenue for the development of congested coordination pairs with high selectivity and specificity.

Understanding uptake of community groundwater monitoring in rural Brazil

Resource monitoring is often cited as important for effective common pool resources management. In practice, not all monitoring interventions are successful, particularly when the resource, such as groundwater, is challenging to monitor and measure. We conducted a field experiment on groundwater monitoring in Ceará, Brazil, where communities are increasingly reliant on groundwater yet do not engage in monitoring. Despite careful implementation, uptake of monitoring within the 80 treatment communities was low. To unpack this low uptake, we conduct multimethods exploratory research. We find that uptake is less likely in communities facing high coordination costs, either within the community leadership or across the broader community. Uptake is also less likely when there are physical barriers to monitoring, when there are more substitutes for groundwater, and when there is lower variability in water availability. Our findings can inform future monitoring interventions in similar contexts worldwide.

Matching and Coordination among Elderly Services, Aging, and Economy in China

Under the background of China getting old before getting rich, the elderly service, as a public project, should be coordinated with the degree of aging and economic level to avoid the improper allocation of public resources. This article aims to investigate whether an insufficient or overthreshold phenomenon exists in China. Firstly, based on the “active aging theory,” the elderly service index is constructed, and then matching and coordination models are proposed to obtain coordination degrees among aging, the elderly service, and the economy. In terms of coordination, elderly service-aging is at a low level and elderly service-economic level shows an agglomeration of high in the east and low in the west, while the elderly service-aging-economic level is quite different among provinces. In provinces with high coordination (e.g., Beijing and Guangdong), the elderly services are appropriate. In comparison, in provinces with low coordination, the elderly services may either lag behind the aging degree (e.g., Sichuan) or exceed the local economic level (e.g., Shannxi). Therefore, the development of aging services should focus on coordination rather than quantification and scale. Considering the regional heterogeneity, we can formulate soft constraints allowing a lower minimum limit and greater flexibility range.

Structure and New Substructure of α-Ti2O3: X-ray Diffraction and Theoretical Study

The Crystal structure of both α-Ti2O3 and its new substructure with a halved c-axis has been investigated by single-crystal X-ray diffraction and density functional theory (DFT) calculations. The α-Ti2O3 substructure described in the R-3m space group, reveals an unusual 12-fold high coordination of Ti atoms forming edge and face-sharing distorted hexagonal prisms TiO12 stacking along the c-axis. The Hubbard-corrections predict a close bandgap for both α-Ti2O3 and its substructure; whereas a comparative study of their relative stability indicates that the substructure is thermodynamically less stable.

Reproductive behavior of the european roller (Coracias garrulus Linnaeus, 1758)

In the European part of Russia, there is a decrease in the area and number of the European Roller. We performed a preliminary study of the role of behavioral ecology in the survival of the species. The material was collected in the Stavropol krai in 2004, 2006-2019. Females and males were distinguished by color intensity (females' plumage is paler) and behavior. Birds exhibit complex biocommunication with features of a foraging economy, distribution of parental roles, and high coordination of partner actions. Additional research is needed to elucidate the behavior of birds whose partners died in the flyover or wintering areas.