Local Structure Analysis of Lead Zinc Niobate-Barium Titanate Ceramic by X-Ray Absorption Spectroscopy and Density Functional Calculation

The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.

ABSORPTIVE FUNCTION OF SEGMENTAL ALLOTRANSPLANTED SMALL INTESTINES IN PIGS

Ten outbred pigs were each operated on for three times. First, a 130 cm length of terminal ileum of each pig was isolated on its vascular pedicle as a Thiry-Vella loop. One week later, the solitary ileal segments were transplanted heterotopically in two pigs. And after 28 days of heterotopic transplantation, the transplanted intestine was interposed into continuity of host intestine as orthotopic transplant. During the experiment, tests were made on 6th day after the first operation (period 1), the 14th (II), 28th (III) day after heterotopic transplantation, and 3 weeks after interposition (IV) respectively for the levels of glucose, palmitate and leucine. Additionally, at period I, III, and IV, a 3 cm length of intestinal mucosa was excised for morphologic observation and determination of DNA, RNA and protein contents. After heterotopic transplantation, the absorptive function of transplanted intestine was severely impaired for two weeks. The absorption of glucose! and palmitate was partially recovered by period III, at which time leucine level had return to normal. At period IV, the absorptive function of glucose and leucine had surpassed normal levels, while palmitate had risen to the level of pretransplantation. After transplantation, at period III, DNA, RNA and protein contents were well below normal. Three weeks after orthotopic transplantation, RNA and protein had risen to normal level, while DNA content remained below normal, The morphologic changes during the experiment were correlated with the changes of contents in RNA, protein and DNA. The area, height, width of villi and the area, depth, width:of crypt were below normal at III and recovered by 3 weeks after orthotopic transplantation (period IV), but were still lower than the levels at pretransplantation. Crypt depths were deeper than those of pretransplantation.

Effect of Conformation on UV-Vis Absorption Spectra of Disazo Reactive Red Dyes

In this study,twenty disazo reactive red dyes with J acid as coupling components were selected,and their ground state geometry were studied with BLYP functional and TZVP basis set. The UV-vis absorption spectra were calculated by time-dependent density functional theory（TDDFT） employing B3 LYP and PBE0 hybrid functionals and TZVP basis set,and the absolute mean errors are 0.094 e V and 0.133 e V for B3 LYP and PBE0,respectively. From the comparison of the calculated λ_（max） of the three conformations of disazo reactive red dye,cis-,trans-,and azo,with that of experimental one,we find out that conformation plays an important role on UV-Vis absorption. Dyes 6 and 8 exist in azo conformation rather than in cis-conformation. ＂Hole-electron＂ distribution analysis reveals that although these λ_（max） arises from different electron transitions,these electron excitations have the same character of local excitation（LE）.

Introducing Rich Heterojunction Surfaces to Enhance the High‑Frequency Electromagnetic Attenuation Response of Flexible Fiber‑Based Wearable Absorbers

With the rapid development of 5G communication and artificial intelligence(AI)technology,electromagnetic radiation pollution is emerging as a serious issue.Achieving both uniform dispersion and controllable loading of absorbers and obtaining functional wearable absorbers with high electromagnetic response are still considered great challenges.In this work,a flexible fiber-based absorber(VFT2h/MF/PPy)with a rich interfacial polarization relaxation was obtained by integrating heterostructures and performing nanostructure design and introducingπ-conjugated polymer components.Electrons migrated and redistributed between nanoparticles and nitrogen-carbon lattices with different electrostatic states.The formed heterogeneous interface promoted the electromagnetic attenuation response in the high-frequency region.More specifically,the effective absorption frequency bandwidth was up to 5.6 GHz(corresponds to the Ku-band with a matching thickness range up to 2.55–4.85 mm).Impressively,the abundant modification sites on the fiber surface adjusted the content and dispersion of the magnetic nanoparticles and enhanced the vector superposition effect generated by the structural distribution of the magnetic/electric fields.The introduction of dielectric components improved the interfacial polarization strength of the heterojunction surface and the synergistic effect of the dipolar polarization.The high-efficiency electromagnetic attenuation performance was attributed to multiple loss mechanisms.Our work provides a reference path for the microscopic regulation of the high-efficiency electromagnetic response mechanism of fiber-based flexible absorbing materials.