This study reports the synthesis of morphology-controlled BaTiO(3) nanostructures such as spherical, cube-shaped and rod-shaped BaTiO(3) using a molten-salt synthesis method. This method synthesized products from a reaction of BaO/BaCO(3) and TiO(2) with a eutectic mixture of NaCl-KCl flux at 700 degrees C for 1 h. The experiment used powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy to investigate the structure and morphology of the products. Moreover, the current work also provides a proposed synthetic mechanism of BaTiO(3) in the molten salt to illustrate the in situ transformation mechanism of BaTiO(3) nanostructures in the reaction. The results of the study revealed that the initial shape of the titania and the dissolution rate of the initial precursors critically determine the shapes of the final products.
Under a 980 nm laser pumping, quenching of green upconversion (UC) emission accompanied with enhancement of red UC emission observed was dominated by the energy back-transfer (EBT) process in Er(3+) and Yb(3+) co-doped PbTiO(3), BaTiO(3), and SrTiO(3) polycrystalline powders. The efficiency of the EBT process depends not only on Yb(3+) concentration but also on level match of the doped Er(3+) and Yb(3+) ions caused by the crystal fields with different symmetries. Our UC emission spectra and X-ray diffraction confirm that the centrosymmetric crystal field arising from reducing tetragonality causes level match of transition (4)S3/2-->I13/2 of Er(3+) and (2)F7/2-->(2)F5/2 of Yb(3+). This level match is responsible for enhancing red UC emission.
By applying a single-tetragonal-phase model to refine the crystal structure and the coupled-phonon model to analyze transverse optical (TO) modes of BaTiO 3 nanocrystals, we found, upon decreasing the particle size from 140 to 30 nm, that the tetragonality of BaTiO 3 nanocrystallites is reduced accompanied by expanding unit-cell volume, which is the dominant mechanism for reducing giant LO-TO splitting in the BaTiO 3 system. The weakening coupling of two low-frequency modes among three A 1 (TO) phonons leads to changing the lowest one from a spectral dip to a peak, whereas the increasing coupling strength between two high-frequency modes repels them farther so that there is less reduction in spectral separation.
Diaporthe species can infect forest trees, ornamentals, and crops, causing root and fruit rots, stem cankers, leaf spots, etc. (Yang et al. 2018). In February 2021, about 10-20% of jasmine plants showing stem canker, foot rot, and wilting were observed in Changhua (24°01'57.7"N 120°34'54.7"E), Taiwan. The diseased plants initially showed chlorosis, leaf drop, and dieback. Sunken lesions were observed on the infected stem and kept expanding gradually. Eventually, plants wilted and black spots formed on the lesions. The margin of healthy and infected tissues of six samples were cut into 4 pieces, disinfected with 10% NaOCl for 30 seconds, rinsed twice in sterilized distilled water for 1 minute, and cultured on water agar at 28℃ under 12 h light / 12 h dark cycle. Hyphae grown out from isolated tissues were sub-cultured on potato dextrose agar (PDA). All tissues grown out of fungi showed similar colony morphology. Two hyphal tips from different tissues were isolated as representatives and deposited in Bioresource Collection and Research Center, Hsinchu, Taiwan, under BCRC numbers FU31566 and FU31567. The colonies on PDA were white to pale gray and produced black pycnidial conidiomata. The two-week-old conidiomata scattered or aggregated in small groups, exuded cream to pale yellow conidial droplets, 0.3-1.1 mm (n=50). The α-conidia were one-celled, hyaline, ovoid to cylindrical with one or two droplets, 3.8-6.3 × 2.5-3.8 μm (n=50). β-conidia were absent. The internal transcribed spacer (ITS), translational elongation factor subunit 1-α (EF1α), and β-tubulin of the two isolates were amplified using primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), and Bt2a/Bt2b (Glass and Donaldson, 1995), respectively. The ITS (MZ389113, MZ389114), EF1α (MZ419338, MZ419339), and β-tubulin (MZ408893, MZ408894) sequences of two isolates showed 98.55-98.56% (KR936130), 98.82% (KR936133), and 99.11-99.33% (KR936132) match to those of Diaporthe tulliensis R.G. Shivas, Vawdery & Y.P. Tan ex-type isolate BRIP 62248a (Dissanayake et al. 2017), respectively. Based on the morphological and molecular characters, this fungus is identified as D. tulliensis. To confirm the pathogenicity, the needle-wounded stem bases of eight-month-old cutting jasmine seedlings were inoculated with BCRC FU31566 by two PDA disks with actively grown fungal edges or conidial suspension at the concentration of approximately 2 × 105 conidia/ml. Each method inoculated five seedlings, performed in the greenhouse at 25 ± 2°C. Non-inoculated plants served as control. Two weeks after inoculation, three plants inoculated with PDA disks of the fungal culture showed wilting, and conidiomata formed on the stem base. The same symptoms were observed in one plant inoculated with the conidial suspension 3 weeks after inoculation. By contrast, the controls remained symptomless. Koch’s postulates were completed by re-isolating the fungus from the inoculated plant. The re-isolated pathogen showed similar morphology and molecular characteristics to the original. D. tulliensis has been reported to cause cocoa rotted stem in Australia, kiwifruit stem canker in China, and Boston ivy leaf spot in Taiwan (Crous et al. 2015; Bai et al. 2017; Huang et al. 2021; Farr and Rossman 2021). To our knowledge, this is the first report of stem canker on jasmine associated with D. tulliensis in Taiwan. Furthermore, this is the first record of jasmine as a host of D. tulliensis worldwide.
We show the destruction of a displacement of Ti in the short-range structure by observing the disappearance of emission and Raman signals when the Er 3+ concentration exceeds 7 mol% in sol-gel-derived Pb 0.8 La 0.2 TiO 3 polycrystalline films. It is believed that there always exists disorder due to displacement of B ions in the skeleton of BO 6 in perovskite ABO 3 materials. This disorder due to the displacement of Ti ions breaks the center of symmetry to activate emission of rare-earth ions such as Er 3+ and Raman modes of perovskites. We found that the breaking of symmetry can be diminished by introducing more Er 3+ ions.
Zinnia elegans L., known as common zinnia, is an annual flowering plant belonging to the Asteraceae family and native to North America. The plant has colorful flowers and is one of the popular ornamental bedding plants for gardening. In March 2020, powdery mildew symptoms were observed in a zinnia floral field with an incidence of >70% in Dacun Township, Changhua County, Taiwan. The symptoms were spotted on the stems, flower petals and leaves which appeared as irregular colonies and white patches on the surfaces. When disease progressed, most of the plant surfaces were covered by the white fungal colonies and became yellowish. Under microscopic examination, hyphal appressoria of the fungus were indistinct or slightly nipple-shaped. The conidiophores were unbranched, erect, straight, smooth to slightly rough, 75.0 to 200.0 × 10.0 to 15.0 µm (n=10), composed of a cylindrical, flexuous foot cell, 40.0 to 100.0 × 8.8 to 15.0 µm (n=10), and following 1 to 5 shorter cells. The conidia were ellipsoid to ovoid, 25.0 to 37.5 × 15.0 to 23.8 µm (n=60), with an average length-to-width ratio of 1.8 and contained fibrosin bodies. No chasmothecia were found. Three voucher specimens (TNM Nos. F0033680, F0033681, and F0033682) were deposited in the National Museum of Natural Science, Taichung City, Taiwan. To confirm the identification, the internal transcribed spacer (ITS) regions of the three specimens were amplified using primer pairs ITS1/PM6 and PM5/ITS4 (Shen et al. 2015) and sequenced from both ends. The resulting sequences were deposited in GenBank under Accession Nos. MT568609, MT568610, and MT568611. The sequences were identical to each other and shared a 100% identity with that of Podosphaera xanthii MUMH 338 on Z. elegans from Japan (Accession No. AB040355) (Ito and Takamatsu 2010) over a 475 bp alignment. Accordingly, the fungus was identified as P. xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012) based on its morphological and molecular characters. Pathogenicity was demonstrated through inoculation by gently pressing naturally infected leaves onto leaves of three healthy potted common zinnia that had been sprayed with 0.02% Tween 20. Additional three non-inoculated plants treated in the same way without inoculating the powdery mildew served as the controls. Powdery mildew colonies were observed on inoculated leaves after 10 days at room temperature, later the diseased leaves became yellowish and deteriorated. The morphological traits of the fungus on the inoculated leaves were similar to those of the first observed. In addition, the ITS sequence from a colony on the inoculated leaves was 100% identical to MT568609-MT568611, fulfilling the Koch’s postulates. All the controls remained symptomless. Z. elegans is known to be a host for different species of powdery mildew in the genus Erysiphe, Golovinomyces, and Podosphaera (Farr and Rossman 2020). In Taiwan, powdery mildew has been briefly reported on zinnia without detailed descriptions (Hsieh 1983). This study confirmed P. xanthii as a causal agent of powdery mildew in Taiwan and the awareness of the disease may benefit the floral industry. To our knowledge, this is the first confirmed report of P. xanthii on Z. elegans in Taiwan.
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