Understanding the piezocatalytic properties of the BaTiO3(001) surface via density functional theory.

Piezoelectric materials have been reported to possess catalytic activity under mechanical excitation, such as by ultrasonic waves or collisions. Energy band theory (EBT) is often used to explain the piezocatalytic phenomenon caused by the strain-induced charge separation, but the correlation between the piezoelectric polarization and catalytic activity has still not been fully understood in early theoretical studies with the EBT model. To reveal the intrinsic connection between the piezoelectric feature and surface catalytic activity, in this work, we employ first-principles Density Functional Theory (DFT) to investigate the prototype piezocatalyst BaTiO3 (001) surface (BTO). Our simulation shows that the thickness of BTO has a significant impact on the band structure, polarization charge distribution and the surface work function of both positively and negatively polarized sides. As the driving force of piezocatalysis, the electrostatic potential difference (piezopotential) of the two sides shows strong a correlation with the band structure change under the applied strain, which determines the theoretical catalytic activity of BaTiO3 (001) for water splitting. Finally, we reveal the piezoelectric effects on the surface adsorption energy of H and OH species, which provide a new insight into the mechanism of piezocatalysis. Our work provides a new and in-depth physical insight into the fundamental mechanism of piezocatalysis, which may have important implications for the application of piezocatalysts in water treatment and renewable energy technologies.

Preparation and evaluation of novel bio-based Bis-GMA-free dental composites with low estrogenic activity.

OBJECTIVE: Although bisphenol Aglycidyl methacrylate (Bis-GMA) are widely used in the dental composite, its raw materials include the petroleum-based product bisphenol A (BPA) with high estrogenic activity (EA). In this study, two new BPA-free dimethacrylate monomers from bio-based material creosol were synthesized and evaluated. METHODS: The renewable bisphenol monomer 5, 5'-methylenedicreosol (BCF) was prepared from bio-based material creosol. By the human breast cancer cells (MCF-7 cells) proliferation assay, a risk assessment of BCF was performed to determine if BCF possessed reduced EA in comparison to BPA. Then, the novel monomers 5, 5'-methylenedicreosol diglycidyl ether diacrylate (BCF-EA) and 5, 5'-methylenedicreosol diglycidyl ether dimethacrylate (BCF-GMA) were synthesized from BCF with epichlorohydrin and (meth)acrylate. All products were investigated by 1H NMR and FT-IR spectra. The control resin was a mixture based on Bis-GMA and tri(ethyleneglycol) dimethacrylate (TEGDMA) with a weight ratio of 5:5 (5B5T). Similarly, experimental resin matrix was a mixture based on BCF-EA/TEGDMA (5E5T) and BCF-GMA/TEGDMA (5G5T). And their corresponding composites were then prepared with corresponding resin matrices and hybrid SiO2 (5E5TC, 5G5TC and 5B5TC). The properties of these composites were investigated according to the standard or referenced methods. Each sample was evaluated for double bond conversion (DC), shrinkage stress (SS) and volumetric polymerization shrinkage (VS). Water sorption (WS), water solubility (SL), mechanical properties and cytotoxicity were also measured. RESULTS: 1H NMR and FT-IR spectra confirmed the chemical structure of each monomer. EA test revealed that bio-based bisphenol monomer BCF as the precursor of BCF-EA and BCF-GMA showed lower EA than BPA. Cured resin matrix: Both 5E5T and 5G5T had nearly the same DC (p < 0.05), which was higher than 5B5T (p < 0.05); 5E5T and 5G5T had lower VS, SL and cytotoxicity than 5B5T (p < 0.05); mechanical properties of 5E5T and 5G5T were all better than those of 5B5T (p < 0.05). Cured composite: There was no significant difference in conversion (p < 0.05); 5E5TC and 5G5TC had significantly lower VS (p < 0.05); WS of 5E5TC and 5G5TC were similar (p < 0.05), but higher compared to 5B5TC (p < 0.05); 5E5TC and 5G5TC had the deeper depth of cure (p > 0.05); before water immersion, there was no significant difference in flexural strength between 5E5TC and 5G5TC (p > 0.05), and higher than 5B5TC (p < 0.05); 5E5TC and 5G5TC showed less cytotoxicity than 5B5TC (p < 0.05). SIGNIFICANCE: The new BPA-free di(meth)acrylates are promising photocurable dental monomers owning to bio-based raw material, high degree of conversion coupled with low curing shrinkage and good mechanical properties. Therefore, BCF-EA and BCF-GMA has a potential to be used as the substitution for Bis-GMA to prepare Bis-GMA-free dental composite.

[Pollution Characteristics and Risk Assessment of Tetracycline Antibiotics in Farmland Soil in Yinchuan].

A total of 43 surface soil samples were collected from Yinchuan farmland and high performance liquid chromatography(HPLC) was used to measure the concentrations of oxytetracycline(OTC), tetracycline(TC), chlortetracycline(CTC), and doxycycline(DOC). The pollution characteristics and spatial distribution of TC were further analyzed using spatial Kriging interpolation, and the ecological risks of OTC, TC, CTC, and DOC in farmland soils were also assessed. Tetracycline antibiotics were detected in all the soil samples at concentrations ranging from 40.68 to 1074.42 µg·kg-1 and an average of 462.24 µg·kg-1. The average proportions were ranked ΣTCs: CTC(69.26%) > OTC(16.34%) > TC(12.86%) > DOC(1.54%), and CTC pollution was the most serious among. The space tended to be high in the middle and low in the periphery, but the concentrations of TC were highest in the northwest. The average contents of ΣTCs in different soils was ranked as follows:vegetable field(596.01 µg·kg-1) > pasture(487.04 µg·kg-1) > cultivated land(437.52µg·kg-1) > garden plot(404.99 µg·kg-1). The average risk values of OTC, TC, CTC, and DOC in farmland soils were 0.14, 0.69, 0.14, and 1.02, respectively. TC and DOC represented a high level of risk in 23.26% and 6.98% of the samples, respectively, which requires particular attention.

Construction and application of meteorological index for Apis cearna cearna activity in nor-thern mountainous area of Sichuan Basin, China.

We analyzed the climate ecological suitability of Apis cerana cerana in the northern mountain area of Sichuan Basin, based on the meteorological data of two meteorological stations, the production and the ecological characteristics and activity of A. cerana cerana. Taking temperature, moisture, light, wind and weather conditions as impact indices and referring to life meteorological index, we constructed a hierarchical calculation method for activity meteorological index and annual evaluation of A. cerana cerana in northern mountainous area of Sichuan Basin. Results showed that the main meteorological factors affecting A. cerana cearna activity in the study were temperature, relative humidity, sunshine hour, wind power and daytime cumulative duration of precipitation. Among those factors, temperature and daytime cumulative duration of precipitation were the main ones. The meteorological index of A. cerana cerana activity was constructed through the combination of different values of these five index factors, with which the grading evaluation being carried out. When the index was greater than 12, the weather condition was good and suitable for A. cerana cearna activity. When the index was 7-12, the weather condition was general, which was sub-suitable for A. cerana cearna activity. When the index was 1-7, the weather condition was poor, the activity of A. cerana cearna would significantly decrease. When the index was less than or equal to 1, the weather condition was bad and would not be suitable for A. cerana cearna to be active or in the overwintering period. We used this index to evaluate the climate of Zhongshan bee farm. Results showed that the average comprehensive meteorological index was 129.3 (score 60.4) for many years (April to October), the overall meteorological condition was good. The yield of "local honey" was significantly correlated with the annual comprehensive meteorological index. The accuracy rate of annual meteorological evaluation was 90%.

The incorporation of phosphorylated chitosan/amorphous calcium phosphate nanocomplex into an experimental composite resin.

This study evaluated the effect of incorporating phosphorylated chitosan/amorphous calcium phosphate nanocomplex (Pchi/ACP) into an experimental light-cure composite resin on mechanical-chemical properties and human dentin remineralization. The results showed that the mechanical strength and contact angles of the resins decreased with the increase incorporation of Pchi/ACP. Release concentrations of calcium in saline solution were measured at different time points, showing the incorporation of Pchi/ACP significantly increased calcium release within 14 days, and kept steady thereafter. Finally, the demineralized dentin slabs treated with our resins for four weeks were characterized by SEM-EDS. Various amounts of apatite were formed on the dentin slabs which were treated with the resins containing Pchi/ACP, whereas no apatite was formed without Pchi/ACP. In conclusion, the Pchi/ACP-incorporating composite resin can be a promising dental material due to its favorable mechanical and remineralization properties.

Research progress on the antibacterial properties of dental resin materials / 口腔疾病防治

@#Dental resin materials have been widely used in the treatment of dental defects. However, the polymerization shrinkage of the resin materials tends to cause microleakage and accumulation of bacterial plaque, which leads to secondary dental caries. Endowing dental resin with antibacterial properties is an important way to solve this problem. Adding antibacterial agents to dental resin is the main method to give it antibacterial properties. Antimicrobial agents are mainly divided into three types: release type, non-release type and mixed type. In terms of antibacterial effects, the selection and addition of antibacterial agents will affect the antibacterial and mechanical properties of dental resin materials; and the long-term antibacterial effect of antimicrobial agents in the oral cavity remains to be verified; as antimicrobial agents or other environmental factors can lead to drug resistance and even dormant persistent bacteria. In recent years, researchers have been committed to improving the antibacterial effect by modifying antibacterial agents. The sustained release of antimicrobial agents via carriers is also the main research direction. This paper reviews the research progress on the antibacterial properties of dental resin materials.

[Recent progress of robots in stomatology].

With the development of industrial robot technology, robotics has entered the medical field, and the research and development of new robots for many medical applications have become a significant research direction in global robotics. Robots are widely used in various aspects of dentistry, such as prosthodontics, orthodontics, implants, endodontics, and oral surgery. This article mainly introduces the application of robots in stomatology from the above five aspects.