A New Phase Boundary in (Bi1/2Na1/2)TiO3BaTiO3 Revealed via a Novel Method of Electron Diffraction Analysis

A new phase boundary is revealed in (1-x)(Bi1/2Na1/2)TiO3xBaTiO3, the most extensively studied lead-free piezoelectric solid solution. This discovery results from a novel method of electron diffraction analysis, which allows for the precise determination of oxygen octahedra tilting in multi-domain perovskite ferroelectrics. The study using this method supports the recently proposed Cc symmetry for pure (Bi1/2Na1/2)TiO3, and, more importantly, indicates the crystal structure evolves into the R3c symmetry with the addition of BaTiO3, forming a Cc/R3c phase boundary at x = 3~4%. In the poling field Epol vs. composition x phase diagram for polycrystalline ceramics, this phase boundary exists with Epol below 5.5 kV/mm; the Cc phase is transformed to the R3c phase during poling at higher fields. The results reported here provide the microstructural origin for the previously unexplained strain behavior and clarify the low-BaTiO3-content phase relationship in this popular lead-free piezoelectric system

Electrical poling below coercive field for large piezoelectricity

Isotropic polycrystalline ferroelectric ceramics have to be electrically poled to develop a net macroscopic polarization and hence piezoelectricity. It is well accepted that a sufficient poling can only be realized under an electric field that is much higher than the coercive field. In this study, we observed in (Bi1/2 Na 1/2)TiO3-BaTiO3 ceramics that large piezoelectricity can develop at poling fields far below the measured coercive field. Using in situ transmission electron microscopy, such an unusual behavior, is interpreted with the polarization alignment of polar nanodomains in the non-ergodic relaxor phase

Creation and Destruction of Morphotropic Phase Boundaries through Electrical Poling: A Case Study of Lead-Free (Bi1/2Na1/2)TiO3-BaTiO3 Piezoelectrics

We report the first direct evidence that the morphotropic phase boundary in ferroelectric materials, along with the associated strong piezoelectricity, can be created, destroyed, or even replaced by another morphotropic phase boundary through phase transitions during electrical poling. The real-time evolution of crystal structure and domain morphology during the poling-induced phase transitions in (Bi1/2Na1/2)TiO3-BaTiO3 is observed with in situ transmission electron microscopy. These observations elucidate the microstructural origin of the macroscopic piezoelectricity’s dependence on the poling field and previously unexplained strain behaviors. This study demonstrates that the ferroelectric-to-ferroelectric transitions during the poling process can completely alter the morphotropic phase boundaries and, hence, must be comprehensively investigated when interpreting the microscopic mechanism of macroscopic piezoelectric behaviors

The Antiferroelectric ↔ Ferroelectric Phase Transition in Lead-Containing and Lead-Free Perovskite Ceramics

A comprehensive review on the latest development of the antiferroelectric ferroelectric phase transition is presented. The abrupt volume expansion and sudden development of polarization at the phase transition has been extensively investigated in PbZrO3-based perovskite ceramics. New research developments in these compositions, including the incommensurate domain structure, the auxetic behavior under electric fields in the induced ferroelectric phase, the ferroelastic behavior of the multicell cubic phase, the impact of radial compression, the unexpected electric field-induced ferroelectric-to-antiferroelectric transition, and the phase transition mechanical toughening effect have been summarized. Due to their significance to lead-free piezoelectric ceramics, compounds with antiferroelectric phases, including NaNbO3, AgNbO3, and (Bi1/2Na1/2)TiO3, are also critically reviewed. Focus has been placed on the (Bi1/2Na1/2)TiO3–BaTiO3 solid solution where the electric field-induced ferroelectric phase remains even after the applied field is removed at room temperature. Therefore, the electric field-induced antiferroelectric-to-ferroelectric phase transition is a key to the poling process to develop piezoelectricity in morphotropic phase boundary (MPB) compositions. The competing phase transition and domain switching processes in 0.93(Bi1/2Na1/2)TiO3–0.07BaTiO3 are directly imaged with nanometer resolution using the unique in situ transmission electron microscopy (TEM) technique

Efficiency Resource Allocation for Device-to-Device Underlay Communication Systems: A Reverse Iterative Combinatorial Auction Based Approach

Peer-to-peer communication has been recently considered as a popular issue for local area services. An innovative resource allocation scheme is proposed to improve the performance of mobile peer-to-peer, i.e., device-to-device (D2D), communications as an underlay in the downlink (DL) cellular networks. To optimize the system sum rate over the resource sharing of both D2D and cellular modes, we introduce a reverse iterative combinatorial auction as the allocation mechanism. In the auction, all the spectrum resources are considered as a set of resource units, which as bidders compete to obtain business while the packages of the D2D pairs are auctioned off as goods in each auction round. We first formulate the valuation of each resource unit, as a basis of the proposed auction. And then a detailed non-monotonic descending price auction algorithm is explained depending on the utility function that accounts for the channel gain from D2D and the costs for the system. Further, we prove that the proposed auction-based scheme is cheat-proof, and converges in a finite number of iteration rounds. We explain non-monotonicity in the price update process and show lower complexity compared to a traditional combinatorial allocation. The simulation results demonstrate that the algorithm efficiently leads to a good performance on the system sum rate.Comment: 26 pages, 6 fgures; IEEE Journals on Selected Areas in Communications, 201

A 3D Approach in Quantification of the Alveolar Bone Changes After Dental Implant Placement Based On CBCT Images

PhDThis retrospective clinical study aimed: (1) to establish and validate a reproducible geometrical measurement strategy in quantifying peri-implant alveolar bone changes based on CBCT images taken before and one year after implantation; (2) to quantify and compare the bone changes of Type 1 and Type 4 implant placement in the patient cohort that requested implant placement at premolar and molar sites; (3) to analyse the bone changes in relation to the two implant protocols in aspects of buccal and lingual, maxilla and mandible, within the cohort and combined cohorts. 3D imaging analysis in this study had used a software package - OnDemand3D. The evaluation of the measurement strategy was based on a simulation model which was made of human dry skull with and without a standard implant (Straumann Standard Plus, Ø3.3 mm diameter, L12 mm) to simulate before and after the implant placement. The recruited cases were 69 (44 Type 1 cases and 25 Type 4 cases); all data sets were provided by Shanghai 9th people’s hospital, China. Each case had two CBCT data sets at before and one year after implant placement. With 69 cases, bone grafting was applied to all Type 1 cases, and the flap surgery was applied to Type 1 cases when buccal bone recession greater than 3 mm. The measurements were made in bone height (HL) and bone thickness (L0O0, L1O1, L2O2, L3O) at lingual side, while the same at buccal side (HB, B0O0, B1O1, B2O2, B3O3). The four sections of bone thickness were at 0, 1 mm, 4 mm and 7 mm from the top of the implant. Additionally, six special cases were reported, as they provided extra information. They were two spilt-mouth control cases, three 2-year follow-up cases and one 3-year follow-up case. The evaluation of the measurement strategy showed the error of the measurement strategy was –0.06 mm and the measurement uncertainty was ±0.05 mm. The main measurement outcomes from the clinical cases were as follows: (1) at buccal side, the mean value of bone changes in height was a positive value of +0.18±1.64 mm for Type 1, which was significantly more than +0.01±0.86 mm for Type 4 (p<0.05). However the standard deviation over the 44 and 25 patient cohorts were as large as 1.64 mm and 0.86 mm; (2) at buccal side, the bone changes in thickness showed significantly more loss at B0O0 (p<0.01) and B1O1 (p<0.05) sections in Type 1 (-0.38±1.49 mm and -0.25±1.15 mm) compared with Type 4 (-0.19±0.34 mm and -0.16±0.76 mm); (3) in Type 1 cases, the bone thickness at buccal side showed significantly more absorption at L1O1B1 (p<0.05), L2O2B2 (p<0.01), L3O3B3 (p<0.01) section (-0.25±1.15 mm, -0.19±0.99 mm, -0.12±0.57 mm) compared to lingual side (-0.13±0.85 mm, -0.16±0.28 mm, -0.05±0.28 mm); and the bone height (+0.18±1.64 mm) increased significantly more at buccal side than lingual side (-0.25±0.79 mm) with bone augmentation procedure (p<0.01). However, within Type 4 cases, no significant difference in bone changes between buccal and lingual sides could be found. In conclusion, the measurement strategy established in this study was reproducible and provided valid quantifiable data of bone changes in relation to implant placement based on 3D CBCT images. The data analysis from these two patient cohorts suggested that Type 1 implant placement protocol could re-build the bone height at buccal side better than Type

MiR-138 ameliorates myocardial ischemia/reperfusion injury by targeting intercellular cell adhesion molecule 1

Purpose: To explore the effect of miR-138 on regulating intercellular cell adhesion molecule 1 (ICAM-1) expression in endothelial cells to alleviate cardiac ischemia/reperfusion (I/R) injury and its related mechanisms. Methods: The left anterior descending artery of the heart was occluded for 30 min and then perfused for 2 h to induce a rat model of cardiac I/R injury. H9C2 cells were cultured in an anoxic medium without serum to establish the model of hypoxia/reoxygenation (H/R). Triphenyl tetrazolium chloride (TTC) staining was applied to measure myocardial infarction sizes in rat hearts. The mRNA expression levels of miR-138 and ICAM-1 were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Dual luciferase reporter assay was used to identify the target of miR-138. The agomiR-138 and miR-138 mimics were transfected into H9C2 cells; exogenous ICAM-1 was also administered, and ROS accumulation, cell viability, and apoptosis were measured. Furthermore, the underlying mechanism was investigated. Results: MiR-138 was downregulated both in vitro and in vivo. AgomiR-138 reduced myocardial infarction area, decreased ROS production and suppressed cell apoptosis in a rat model of cardiac I/R injury. On the other hand, miR-138 mimics increased cell viability, enhanced ROS production and induced cell apoptosis in H/R-induced H9C2 cells. Further analysis verified ICAM-1 as a target of miR- 138. Besides, exogenous ICAM-1 inhibited the protective effect of miR-138 on H/R-induced apoptosis in vitro. Conclusion: MiR-138 may protect against injury of myocardial I/R by targeting ICAM-1. The results also provide insight into miR-138/ICAM-1 axis as new therapeutic targets for myocardial I/R injury. Keywords: Intercellular cell adhesion molecule 1, MicroRNA-138, Myocardial/ischemia reperfusion injury, Reactive oxygen specie

The IAS2024 coastal sea level dataset and first evaluations

A new dedicated coastal sea level dataset called the International Altimetry Service 2024 (IAS2024, https://doi.org/10.5281/zenodo.13208305, Peng et al., 2024c) has been presented to monitor sea level changes along the world&rsquo;s coastlines. One of the reasons for generating this dataset is the quality of coastal altimeter data has been greatly improved with advanced coastal reprocessing strategies. In this study, the Seamless Combination of Multiple Retrackers (SCMR) strategy is adopted to obtain the reprocessed Jason data for January 2002 and April 2022. The evaluation results show that the data availability of the IAS2024 dataset over global coastal oceans is much higher than that of the European Space Agency Climate Change Initiative version 2.3 (ESA CCI v2.3) dataset. The closure of trend differences (0.16 &plusmn; 3.98 mm yr&minus;1) between IAS2024 and Permanent Service for Mean Sea Level (PSMSL) tide gauge data is observed at the global scale, which further demonstrates the good performance of the IAS2024 dataset in monitoring the coastal sea level changes. The altimeter-based virtual stations have been built with the IAS2024 dataset over 0&minus;10 km, 5&minus;15 km and 10&minus;20 km coastal strips, which will contribute to the analysis of coastal sea levels for the ocean community and the risk management for the policy makers. Our study also points out that no obvious variations exist in linear sea level trends from offshore to the coast in most coastal zones. In addition, the vertical land motion (VLM) estimates from the combination of coastal altimeter data with tide gauge records agree well with the University of La Rochelle 7a (ULR7a) Global Navigation Satellite System (GNSS) solution (0.09 &plusmn; 2.22 mm yr&minus;1), suggesting that altimeter-derived VLM estimates can be an independent data source to validate the GNSS solutions