X-ray-induced piezoresponse during X-ray photon correlation spectroscopy of PbMg1/3Nb2/3O3.

X-ray photon correlation spectroscopy (XPCS) holds strong promise for observing atomic-scale dynamics in materials, both at equilibrium and during non-equilibrium transitions. Here an in situ XPCS study of the relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) is reported. A weak applied AC electric field generates strong response in the speckle of the diffuse scattering from the polar nanodomains, which is captured using the two-time correlation function. Correlated motions of the Bragg peak are also observed, which indicate dynamic tilting of the illuminated volume. This tilting quantitatively accounts for the observed two-time speckle correlations. The magnitude of the tilting would not be expected solely from the modest applied field, since PMN is an electrostrictive material with no linear strain response to the field. A model is developed based on non-uniform static charging of the illuminated surface spot by the incident micrometre-scale X-ray beam and the electrostrictive material response to the combination of static and dynamic fields. The model qualitatively explains the direction and magnitude of the observed tilting, and predicts that X-ray-induced piezoresponse could be an important factor in correctly interpreting results from XPCS and nanodiffraction studies of other insulating materials under applied AC field or varying X-ray illumination.

Structure, Antiferroelectricity and Energy-Storage Performance of Lead Hafnate in a Wide Temperature Range.

Lead hafnate (PbHfO3) has attracted a lot of renewed interest due to its potential as antiferroelectric (AFE) material for energy storage. However, its room temperature (RT) energy-storage performance has not been well established and no reports on the energy-storage feature of its high-temperature intermediate phase (IM) are available. In this work, high-quality PbHfO3 ceramics were prepared via the solid-state synthesis route. Based on high-temperature X-ray diffraction data, the IM of PbHfO3 was found to be orthorhombic, Imma space group, with antiparallel alignment of Pb2+ ions along the [001]cubic directions. The polarization-electric field (P-E) relation of PbHfO3 is displayed at RT as well as in the temperature range of the IM. A typical AFE loop revealed an optimal recoverable energy-storage density (Wrec) of 2.7 J/cm3, which is 286% higher than the reported data with an efficiency (η) of 65% at 235 kV/cm at RT. A relatively high Wrec value of 0.7 J/cm3 was found at 190 °C with an η of 89% at 65 kV/cm. These results demonstrate that PbHfO3 is a prototypical AFE from RT up to 200 °C, making it a suitable material for energy-storage applications in a wide temperature range.

[Current status of oral health literacy and its influencing factors among adult orthodontic patients].

PURPOSE: To investigate the current status of oral health literacy among adult orthodontic patients and analyze its influencing factors. METHODS: Totally 163 adult orthodontic patients were recruited by convenience sampling method from November 2021 to February 2022 at the Department of Oral and Craniomaxillofacial Surgery, Center of Craniofacial Orthodontics in Shanghai Ninth People's Hospital. General information questionnaire, Chinese version of Health Literacy in Dentistry (HeLD-14), Chinese version of Self-Efficacy Scale for Self-care (SESS) and Social Support Rating Scale (SSRS) were applied. SPSS 21.0 software package was used for data analysis. RESULTS: The mean score of oral health literacy in adult orthodontic patients was (48.74±5.54), and the lowest score were obtained in concern (6.80±1.19) and support (6.40±1.59) dimensions. Multiple stepwise regression analysis showed that adult orthodontic patients' consultation self-efficacy, social support utilization, family or friends' orthodontic history and objective support were the influencing factors of oral health literacy. CONCLUSIONS: The oral health literacy in adult orthodontic patients is at a middle to high level, but concern and support literacy need to be improved. Strengthening consultation self-efficacy, objective support and utilization of social support can improve adult orthodontic patients' oral health literacy. Attention should be paid to patients who have no relatives or friends with history of orthodontic treatment.

Active and passive defects in tetragonal tungsten bronze relaxor ferroelectrics.

Tetragonal tungsten bronze (TTB) based oxides constitute a large family of dielectric materials which are known to exhibit complex distortions producing incommensurately modulated superstructures as well as significant local deviations from their average symmetry. The local deviations produce diffuse scattering in diffraction experiments. The structure as well as the charge dynamics of these materials are anticipated to be sensitive to defects, such as cation or oxygen vacancies. In this work, in an effort to understand how the structural and charge dynamical properties respond to these two types of vacancy defects, we have performed measurements of dielectric susceptibilities and single crystal diffraction experiments of two types of TTB materials with both 'filled' (Ba2NdFeNb4O15and Ba2PrFeNb4O15) and 'unfilled' (Sr0.5Ba0.5Nb2O6) cation sublattices. We also perform these measurements before and after oxygen annealing, which alters the oxygen vacancy concentrations. Surprisingly, we find that many of the diffuse scattering features that are present in the unfilled structure are also present in the filled structure, suggesting that the random fields and disorder that are characteristic of the unfilled structure are not responsible for many of the local structural features that are reflected in the diffuse scattering. Oxygen annealing clearly affected both color and dielectric properties, consistent with a diminishment of the oxygen vacancy concentration, but had little effect on observed diffuse patterns.

[Analysis of information needs of patients with dentofacial deformities at different stages of treatment].

PURPOSE: To investigate the treatment experience and information needs of patients with dentofacial deformities in the process of surgical program design, surgical treatment and postoperative rehabilitation. METHODS: Thirty-six patients with dentofacial deformities at different treatment stages from March to July 2019 were selected for semi-structured interview. Colaizzi content analysis method and QSR NVivo 12.0 software were used to analyze and code the data, as well as extract the theme and genus. RESULTS: Three themes and eight categories were extracted, including① information needs in different treatment stages, mainly specific content of information needs at pre-operative preparation stage, orthognathic perioperative stage and post-operative rehabilitation stage; ② information support methods, i.e., diversified information support methods and patients' recognition of internet information;③ patients' cognition difference,namely the difference between patients' psychological expectation and the results of operation. CONCLUSIONS: Due to the treatment characteristics of orthognathic surgery and individual cognitive differences of patients, there is a large demand for information support at different stages of treatment. However, the current information support mode is limited, so it is necessary to further improve and provide scientific, professional and targeted information support for patients with dentofacial deformities.

Ferroelectric phase-transition frustration near a tricritical composition point.

Phase transition describes a mutational behavior of matter states at a critical transition temperature or external field. Despite the phase-transition orders are well sorted by classic thermodynamic theory, ambiguous situations interposed between the first- and second-order transitions were exposed one after another. Here, we report discovery of phase-transition frustration near a tricritical composition point in ferroelectric Pb(Zr1-xTix)O3. Our multi-scale transmission electron microscopy characterization reveals a number of geometrically frustrated microstructure features such as self-assembled hierarchical domain structure, degeneracy of mesoscale domain tetragonality and decoupled polarization-strain relationship. Associated with deviation from the classic mean-field theory, dielectric critical exponent anomalies and temperature dependent birefringence data unveil that the frustrated transition order stems from intricate competition of short-range polar orders and their decoupling to long-range lattice deformation. With supports from effective Hamiltonian Monte Carlo simulations, our findings point out a potentially universal mechanism to comprehend the abnormal critical phenomena occurring in phase-transition materials.

Synthesis and characterization of bulk Nd1-x Sr x NiO2 and Nd1-x Sr x NiO3.

The recent reports of superconductivity in Nd1-x Sr x NiO2/SrTiO3 heterostructures have reinvigorated interest in potential superconductivity of low-oxidation state nickelates. Synthesis of Ni1+-containing compounds is notoriously difficult. In the current work, a combined sol-gel combustion and high-pressure annealing technique was employed to prepare polycrystalline perovskite Nd1-x Sr x NiO3 (x = 0, 0.1, and 0.2). Metal nitrates and metal acetates were used as starting materials, and the latter were found to be superior to the former in terms of safety and reactivity. The Nd1-x Sr x NiO3 compounds were subsequently reduced to Nd1-x Sr x NiO2 using calcium hydride in a sealed, evacuated quartz tube. To understand the synthesis pathway, the evolution from NdNiO3 to NdNiO2 was monitored using in situ synchrotron x-ray diffraction during the reduction process. Electrical transport properties were consistent with an insulator-metal transition occurring between x = 0 and 0.1 for Nd1-x Sr x NiO3. Superconductivity was not observed in our bulk samples of Nd1-x Sr x NiO2. Neutron diffraction experiments at 3 and 300 K were performed on Nd0.9Sr0.1NiO2, in which no magnetic Bragg reflections were observed, and the results of structural Rietveld refinement are provided.

[Qualitative study on the decision-making of orthognathic surgery in adult patients with malocclusion].

PURPOSE: The main purpose of this study was to explore the experience associated with patient's decision to have or not have orthognathic treatment. METHODS: Phenomenological methodology was used in this study. Ten patients were collected from January 2018 to March 2018, who were consulted in the Department of Oral and Craniomaxillofacial Surgery, Center of Craniofacial Orthodontics in Shanghai Ninth People's Hospital. They were interviewed by semi-structured, face to face in-depth interviews. Data were organized and analyzed by Colaizzi methods. RESULTS: By reading, analysis and extraction, two topics, i.e, motivation and interference factor were obtained. CONCLUSIONS: The treatment information service was limited. Further research is needed to improve the information services that support the treatment decision of malocclusion patients and help them to make the best choice.

[Gene cloning and prokaryotic expression of glycosyltransferase from Ligustrum quihoui].

According to the previous results from transcriptome analysis of Ligustrum quihoui, a glycosyltransferase gene(xynzUGT) was cloned by rapid amplification of cDNA ends(RACE). The full length cDNA of xynzUGT was 1 598 bp, consisting of 66 bp 5'-UTR, 1 440 bp ORF and 92 bp 3'-UTR. The ORF encoded a 480 amino-acid protein(xynzUGT) with a molecular weight of 54 826.67 Da and isoelectric point of 5.82. The structure of enzyme was analyzed by using bioinformatics method, the results showed that the primary structure contained a highly conserved PSPG box of glycosyltransferase, the secondary structure included α helix(38%), ß sheet(12.1%) and random coil(49.9%), and tertiary structure was constructed by peptide chain folding to form two face-to-face α/ß/α domains(often referred to as a Rossmann domains), between which a substrate binding pocket is sandwiched. The phylogenetic tree analysis indicated that xynzUGT might catalyze glycosylation of phenylpropanoids, such as tyrosol. Further simulation experiment of molecular docking between enzyme and tyrosol showed that Gly138 and Ser285 located in the binding pocket interacted with tyrosol by hydrogen bonding. SDS-PAGE analysis exhibited that the prokaryotic expression system successfully expressed recombinant xynzUGT with molecular weight of 58 370.57 Da, but it exists in the form of non-soluble inclusion bodies. Using the molecular chaperone and enzyme co-expression method, the soluble expression was promoted to some extent. The above works laid the foundation for further studying on enzymatic reaction in vitro and clarifying the functional mechanism of enzyme.

Néel-like domain walls in ferroelectric Pb(Zr,Ti)O3 single crystals.

In contrast to the flexible rotation of magnetization direction in ferromagnets, the spontaneous polarization in ferroelectric materials is highly confined along the symmetry-allowed directions. Accordingly, chirality at ferroelectric domain walls was treated only at the theoretical level and its real appearance is still a mystery. Here we report a Néel-like domain wall imaged by atom-resolved transmission electron microscopy in Ti-rich ferroelectric Pb(Zr1-xTix)O3 crystals, where nanometre-scale monoclinic order coexists with the tetragonal order. The formation of such domain walls is interpreted in the light of polarization discontinuity and clamping effects at phase boundaries between the nesting domains. Phase-field simulation confirms that the coexistence of both phases as encountered near the morphotropic phase boundary promotes the polarization to rotate in a continuous manner. Our results provide a further insight into the complex domain configuration in ferroelectrics, and establish a foundation towards exploring chiral domain walls in ferroelectrics.

[Effects of aluminum stress on ecophysiological characteristics of male and female Populus cathayana seedlings].

This paper studied the sex-specific differences of male and female Populus cathayana seedlings in their ecophysiological characteristics and photosynthesis under the stress of aluminum (216 mg Al(3+) x kg(-1)). Under the effects of aluminum, the malonaldehyde (MDA) and soluble protein (Pr) contents of the male and female seedlings increased significantly (P < 0.001), and the males had a significantly lower MDA content and a significantly higher Pr content than the females. The peroxidase (POD) activity of the males increased but the superoxide dismutase (SOD) activity decreased significantly, while the POD and SOD activities of the females had no significant variation. The net photosynthetic rate (Pn) of both male and female seedlings decreased significantly (P = 0.001), and the transpiration rate (Tr) of the female seedlings decreased (P = 0.007) and the instant water use efficiency (WUEi) increased significantly, while no significant variations were observed in the Tr and WUEi of the male seedlings. The total chlorophyll and chlorophyll a contents and chlorophyll a/b ratio of the females decreased significantly, resulting in a significantly higher chlorophyll a/b ratio of the males. The specific leaf area (SLA) of the females decreased but that of the males increased significantly. No significant variation was observed on the leaf- and stem dry mass. Comparing with the females, the males had higher Pr and chlorophyll contents and higher active antioxidant enzymes activity to maintain higher Pn, and thus, had greater resistance against aluminum stress.