Search

Using the particle swarm optimization algorithm, we conducted an extensive search for the high-pressure stable structure of technetium diboride (TcB2) within the pressure range of 0–400 GPa. At zero pressure, the P63/mmc (hP6-TcB2) structure is considered the ground state configuration. As the pressure increases, a structural transition from hP6-TcB2 to P6/mmm (hP3-TcB2) occurs at approximately 174.9 GPa. We discuss the bonding between the two distinct phases and analyze the contribution of different atomic bonds to maintaining their structural stability. Meanwhile, the temperature–pressure phase diagram of TcB2 was successfully determined for the first time through the quasi-harmonic approximation method. It is predicted that the transition pressure from hP6-TcB2 to hP3-TcB2 can be reduced to about 164 GPa at a room temperature of 300 K. These results provide valuable insights into the behavior of TcB2 under different temperature and pressure conditions and open up new possibilities for exploring its potential applications in a variety of environments. [ABSTRACT FROM AUTHOR]

Bo Jian,1,2 Wei Wu,2 Yingliang Song,1 Naiwen Tan,3 Chao Ma1 1State Key Laboratory of Military Stomatology, Department of Implant Dentistry, School of Stomatology, The Fourth Military Medical University, Xi’an, Shaanxi, 710032, China; 2Department of Oral & Maxillofacial Surgery, School of Stomatology, The Fourth Military Medical University, Xi’an, Shaanxi, China; 3Department of Stomatology, Hospital 463 of PLA, Shenyang, Liaoning, People’s Republic of China Purpose: We aimed to fabricate guided bone regeneration (GBR) membrane using polyglycerol sebacate (PGS) and investigate the impact of scaffold pore size on osteogenesis.Materials and methods: PGS microporous membrane was fabricated by salt-leaching technique with various pore sizes. Twenty-eight male New Zealand rabbits were randomly divided into four groups: 25 µm PGS membrane, 53 µm PGS membrane, collagen membrane, and blank control group. Subsequently, standardized and critical-sized tibia defects were made in rabbits and the defective regions were covered with the specifically prepared membranes. After 4 and 12 weeks of in vivo incubation, bone samples were harvested from tibia. Micro-computed tomography scanning was performed on all bone samples. A three-dimensional visible representation of the constructs was obtained and used to compare the ratios of the ossifying volume to total construct volume (bone volume to tissue volume [BV/TV]) of each sample in different groups; then, bone samples were stained with H&E and Masson’s trichrome stain for general histology.Results: At 4 weeks, the BV/TV in the 25 µm PGS group was found higher than that in the 53 µm PGS and collagen groups. At 12 weeks, the bone defect site guided by the 25 µm PGS membrane was almost completely covered by the new bone. However, the site guided by the 53 µm PGS membrane or collagen membrane was covered only most of the defects and the left part of the defect was unoccupied. Histological observation further verified these findings.Conclusion: We thus concluded that the 25 µm PGS membrane played an advantageous role during 4–12 weeks as compared with those earlier degraded counterparts. Keywords: bone defect, biological membrane, degradation, salt-leaching technique, tibia

Naiwen Tan,1–3,* Xiangwei Liu,1,2,* Yanhui Cai,4 Sijia Zhang,1,2 Bo Jian,1,2 Yuchao Zhou,1,2 Xiaoru Xu,1,2 Shuai Ren,1,2 Hongbo Wei,1,2 Yingliang Song1,2 1State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Shaanxi Engineering Research Center for Dental Materials and Advanced Manufacture, Xi’an, Shaanxi, China; 2Department of Implant Dentistry, School of Stomatology, The Fourth Military Medical University, Xi’an, Shaanxi, China; 3Department of Stomatology, Hospital 463 of PLA, Xi’an, Shaanxi, China; 4Department of Anesthesiology, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi, China *These authors contributed equally to this work Background: High failure rates of oral implants have been reported in diabetic patients due to the disruption of osseointegration. The aim of this study was to investigate whether direct laser metal sintering (DLMS) could improve osseointegration in diabetic animal models. Methods: Surface characterizations were carried out on two types of implants. Cell morphology and the osteogenic-related gene expression of MG63 cells were observed under conditions of DLMS and microarc oxidation (MAO). A diabetes model in mini-pigs was established by intravenous injection of streptozotocin (150 mg/kg), and a total of 36 implants were inserted into the mandibular region. Micro-computed tomography (micro-CT) and histologic evaluations were performed 3 and 6 months after implantation. Results: The Ra (the average of the absolute height of all points) of MAO surface was 2.3±0.3 µm while the DLMS surface showed the Ra of 27.4±1.1 µm. The cells on DLMS implants spread out more podia than those on MAO implants through cell morphology analysis. Osteogenic-related gene expression was also dramatically increased in the DLMS group. Obvious improvement was observed in the micro-CT and Van Gieson staining analyses of DLMS implants compared with MAO at 3 months, although this difference disappeared by 6 months. DLMS implants showed a higher bone–implant contact percentage (33.2%±11.2%) at 3 months compared with MAO group (18.9%±7.3%) while similar results were showed at 6 months between DLMS group (42.8%±10.1%) and MAO group (38.3%±10.8%). Conclusion: The three-dimensional environment of implant surfaces with highly porous and fully interconnected channel and pore architectures can improve cell spreading and accelerate the progress of osseointegration in diabetic mini-pigs. Keywords: laser manufacturing, dental implants, diabetes mellitus, osseointegration

The structure stability, mechanical properties, thermal conductivity, and optical properties of a novel layered tetragonal compound Bi3O2S2Cl have been investigated at pressure up to 25 GPa by using first-principles calculations based on density functional theory in this work. The lattice parameters of Bi3O2S2Cl calculated by Perdew–Burke–Ernzerhof functional in the ground state agree well with the experimental results. Moreover, the calculated phonon dispersion curves and elastic constants Cij suggest that Bi3O2S2Cl is mechanically and dynamically stable from 0 to 25 GPa. The bulk modulus B and the shear modulus G calculated from Cij at different pressures demonstrate that the ductility of Bi3O2S2Cl is increased by external pressure. Furthermore, the influence of pressure on longitudinal sound velocity vl, transverse sound velocity vt, aggregate acoustic velocities vm, Debye temperature ΘD, Poisson's ratio σ, and Grüneisen parameter γ are systematically studied. Meanwhile, the elastic anisotropy index AU and the shear anisotropy factors A1, A2, and A3 are also investigated, together with the directional linear compressibility and Young's modulus under pressure from 0 to 25 GPa. The results show that the anisotropy of Bi3O2S2Cl increases under external pressure. Afterward, we further evaluated the minimum thermal conductivity of Bi3O2S2Cl under pressure by using both Clark's model and Cahill's model. At ambient pressure, it exhibits a relatively low thermal conductivity of 0.365 Wm−1 K−1. Although the minimum thermal conductivity increases with the increase of pressure, it remains a potential thermal barrier coating material in extreme environments. Finally, the calculations of the optical properties of Bi3O2S2Cl under different pressures show that this new layered tetragonal compound is a promising energy harvesting and optoelectrical material in extreme environments. [ABSTRACT FROM AUTHOR]

Recently, a new layered-ternary compound V2SnC was successfully synthesised by reacting V, Sn, and C powder mixture at 1000°C. Its space group was identified as P63/mmc. In this work, the structural, mechanical properties, and thermal conductivity of this new layered-ternary compound have been studied under pressure up to 100 GPa by density functional theory. The calculated lattice parameters and cell volume of V2SnC at the ground state are in good coincidence with the experimental values. With the increase of pressure, the a-axis of V2SnC crystal structure has greater compressibility than the c-axis. In addition, the calculated results of elastic constants and phonon dispersion curves indicated that V2SnC is mechanically and dynamically stable from 0 to 100 GPa. Furthermore, the influence of pressure on bulk modulus B, shear modulus G, aggregate acoustic velocities vm, Debye temperature ΘD, Poisson's ratio σ, and Grüneisen parameter γ are systematically investigated. Meanwhile, the elastic anisotropy of V2SnC under external pressure is also studied for the first time. Finally, the minimum thermal conductivity of V2SnC under external pressure is further studied. The results show that this material has good thermal insulation performance. [ABSTRACT FROM AUTHOR]