Agglomeration effect on biomechanical performance of CNT-reinforced dental implant using micromechanics-based approach

Dental implants have long played an important role in restoring lost teeth, but there are still concerns about their durability and long-term success. Commercial dental implants have traditionally been made of metallic and ceramic materials like titanium and zirconia; however, each kind of material has restrictions regarding osseointegration and mechanical characteristics that differ between native bone and the implant material, limiting the implant's longevity and reliability. To address these concerns, this research explores the use of carbon nanotubes (CNTs) in restorative dentistry, their excellent properties make them an ideal candidate for promoting bone growth around implanted device and ensuring long-lasting success. The objective of this study was to understand how CNT properties when incorporated into the titanium matrix may be able to better adapt to the oral environment taking into consideration the CNT agglomeration effects when designing reinforced nanocomposite materials for dental implant. A mathematical formulation of the micromechanics model was developed and improved to extend its application for the case of CNT-based composite materials for dental implants. A three dimensional (3D) model of bone structure around the osseointegrated dental implant was established considering different compositions of implant material. Finite Element Analysis (FEA) were conducted to assess the aggregation effect of implant incorporating CNTs into the titanium matrix, considering CNTs with both spherical inclusions (CNT clusters), and randomly dispersive ones (CNTs) in the titanium matrix, on osseointegration and bone remodeling around the dental implant and supporting bone system over a period of 48 months. Firstly, the effects of CNT-Ti implantation on time-dependent performance are evaluated in a computational remodeling framework. Then, Von Mises equivalent stresses are investigated to evaluate the stress distributions and micromotions in jaw bones of loaded implant with different composition of prosthetic material. Three agglomeration patterns are considered, particularly without agglomeration (ζ = ξ), partial and complete agglomeration (ζ < ξ, ξ = 1). Further, the influence of CNTs volume fraction variation is taken into account to predict the mechanical response of the bony system after CNT-reinforced dental implantation. It can be inferred that the agglomeration of CNTs reduces the elastic stiffness of the matrix. This is due to the fact that when CNTs are agglomerated, the inter-tube contacts are reduced and the effective stiffness of the matrix is decreased.

National innovative city and green technology progress: empirical evidence from China

In this paper, a quasi-natural experiment of national innovative city pilot policy (NICPP) is carried out to investigate the impact of the NICPP on green technology innovation (GTI) and its intrinsic mechanism with the method of difference-in-differences. It is found that the NICPP significantly enhances GTI, and there is a certain lag and persistence in this effect. Heterogeneity analysis shows that the higher the administrative level and the more the geographical advantages of NICPP, the more obvious the driving effect of GTI. The mechanism test shows that the NICPP has an effect on the GTI through three channels: innovation factor input, agglomeration effect of science and technology talent, and entrepreneurial vitality empowerment. The findings of this study provide policy insights for further optimizing the construction of innovative cities and then promoting GTI development, ultimately realizing green dynamics transformation and high-quality development of China's economy.

Research on innovative mechanisms of financial agglomeration enabling green coordinated development in the Yangtze River Delta of China

Exploring innovative mechanisms for financial agglomeration affecting the green coordinated development of China's Yangtze River Delta is important for the city to take advantage of financial and innovative resources to promote high-quality green development. Using panel data from 41 cities in the Yangtze River Delta region from 2003 to 2019, the intermediate effects model and spatial Durbin model are conducted to deeply explore the impact of financial agglomeration on coordinated green development and the intermediary role of innovation. Results show that, first, financial agglomeration can drive green technology innovation to significantly improve the coordinated development of "production greening - social optimization - environmental protection deepening". Second, financial agglomeration significantly improves the green coordinated development in neighboring areas through inter-city innovative spatial connections, and the spatial spillover effect tends to decay with the critical point of the maximum impact range at 240 km. Third, the intermediate mechanism of green technology innovation performs well in the high-level financial agglomeration and financial capital agglomeration areas. The Banking and securities industries are the leading factors in financial capital agglomeration. Low-level financial agglomeration and financial personnel agglomeration cannot play the "driving green" role of the innovation mechanism.

Intergovernmental competition, industrial spatial distribution, and air quality in China

As clean air is a public good, local governments play an irreplaceable role in environmental protection. This study examines how intergovernmental competition affects air quality in China. The results reveal that intergovernmental tax competition increases regional sulfur dioxide and haze emissions and worsens regional air quality, while competition in infrastructure investment does not have such effects. Furthermore, tax competition will affect air quality through industrial spatial distribution. Intergovernmental competition attracts low-technical content capital flowing into where it is more aggressive, triggering a "race to the bottom" effect on industrial structure and attracting similar industries through an agglomeration economy. On this basis, this study uses the Spatial Durbin model to test the spatial impact of intergovernmental competition on air quality. The effects are manifested in two forms: pollution spillover and pollution transfer. Pollution spillover has a major effect on the air quality of neighboring regions at close geographical distances, while pollution transfer is mainly responsible for the air quality of regions with similar levels of economic development. The relocation of capital and industries between regions due to intergovernmental competition causes the spillover and transfer effects on air quality. In addition, this study analyzes the regulatory effect of fiscal decentralization and environmental regulation on the impact of intergovernmental competition on air quality.

Sorption behavior of 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) on four kinds of nano-materials

6:2 chlorinated polyfluorinated ether sulfonate (with the trade name F-53B, a substitute for PFOS) is one type of Per- and polyfluoroalkyl substances (PFASs), which is widely used as a chromium mist inhibitor in China. It has been found in environment commonly. In this study, the sorption behavior of F-53B on four kinds of nano-materials: alumina nanopowder (ANP), alumina nanowires (ANW), hydrophilic bentonite nanoclay (HBNC) and surface modified nanoclay (SMNC) were investigated. The kinetics results indicated that the sorption of F-53B on four nano-materials reached equilibrium within 2 h and the sorption process were fitted better by the pseudo-second-order kinetic model than the pseudo-first-order kinetic model. The thermodynamic study showed that the sorption of F-53B on nano-materials were exothermic and spontaneous. As the increase of temperature, the maximum sorption capacity of ANP, ANW, HBNC, SMNC increased, and reached 868.75, 91.35, 5.15, 2465.09 μg/g at 25 °C, respectively. The surface modified nanoclay (SMNC) was better than the others for removing F-53B from aquatic environment. To investigate the effects of pH and ion strength, the particle size and zeta potential of sorbents at different pH and ion strength were measured by Dynamic Light Scattering (DLS), and concluded that the sorption mechanism of F-53B on two kinds of nanoalumina mainly included electrostatic attraction and agglomeration effects, while hydrophobic interaction played an important role on the sorption of F-53B on nanoclay. This study revealed the sorption behavior and mechanism of F-53B on four kinds of nano-materials, and the results provided theoretical support for removing F-53B from electroplating wastewater with nano-materials.

Understanding land use volatility and agglomeration in northern Southeast Asia

Land use change has generally been considered a cause and consequence of environmental change. Here, we interpreted the land cover in northern Southeast Asia (including parts of Myanmar, Thailand, Laos, Vietnam and China) year by year from 2000 to 2018 with the Google Earth Engine (GEE) platform. The results show that the areas of old growth forest, young growth forest and annual crops have changed dramatically in the study area. The average frequency of land use change was determined to be 5.4 times (that is, the land use changed every 3.4 years) by comparing the land use types in each year throughout the entire study period, and the frequency of land use change showed a significant agglomeration effect. In addition, there was a substantial difference between the land use change determined with an annual approach and that determined with the commonly used time-stage approach; time-stage land use change studies may overlook gradual change processes in land use change, which highlights the necessary of determining a suitable time period for studying land use change at the local scale. The results show that understanding land use volatility and agglomeration has become important to deepen the understanding of land use change and to help formulate land use policy.