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251 results on '"Zhang, Aiyu"'

55. Effect of oligochitosan on development ofColletotrichum musae in vitroandin situand its role in protection of banana fruits

Author

Tang Yanxia, Zhang Zhaoqi, Huang Xuemei, Meng Xiangchun, and Zhang Aiyu

Subjects
Hypha, biology, Chemistry, food and beverages, Fungus, Horticulture, Colletotrichum musae, biology.organism_classification, Polyphenol oxidase, Fungicide, Botany, Chitinase, Postharvest, biology.protein, Agronomy and Crop Science, Mycelium, Food Science
Abstract

Introduction . Concerns about the potentially harmful effects of fungicides on human health and the environment encourage the search for alternative treatments for perishable fruit postharvest disease control. To this end, the potential use of oligochitosan as a natural antifungal compound to control postharvest anthracnose caused by Colletotrichum musae was investigated in banana fruits from the Cavendish group (genome AAA). Materials and methods . The influence of oligochitosan on the growth of C. musae was determined in vitro by micrographic analysis, while its in situ antifungal activity was monitored in banana fruits that were artificially injury-inoculated with C. musae ; the activities of several defense-related enzymes were measured. Results and discussion . Oligochitosan at (4 and 8) g·L–1 markedly inhibited radial mycelial growth of C. musae in vitro. The scanning electron micrograph of C. musae treated with oligochitosan at inhibitory concentrations showed distortion and thinning of the hyphal wall and reduction in fungus colony diameter. Dipping banana fruits in oligochitosan solution at (5 to 20) g·L–1 significantly reduced the diameter of the anthracnose lesion, and 20 g oligochitosan·L–1 almost reached the same inhibitory effect as 0.5 g·L–1 of Sportak® , a synthetic fungicide. Activities of defense-related enzymes such as phenylalanine ammonia-lyase (PAL), β-1, 3-glucanase (GLU) and chitinase (CHT), but not polyphenol oxidase (PPO), increased in banana fruits treated with 0.5 g oligochitosan·L–1 . Conclusion . The inhibitory effect of oligochitosan on anthracnose development is due to the combination of a direct antifungal effect on the pathogen and an indirect effect, whereby the activities of defense-related enzymes in the banana fruit were enhanced. To control anthracnose in harvested bananas, treatment with oligochitosan above 20 g·L–1 may substitute the use of synthetic fungicide.

Published
2012

57. Total internal reflection for precision small-angle measurement

Author

Zhang, Aiyu and Huang, Peisen S.

Subjects
Optics -- Research, Reflection (Optics) -- Analysis, Polarized beams (Nuclear physics) -- Measurement, Astronomy, Physics
Abstract

A method for precision small-angle measurement is proposed. This method is based on the total-internal-reflection effect of a light beam at a pair of glass prisms. Angular displacement of the light beam is measured when the intensity change of the reflected beam is detected as a result of the relative phase shift between the s- and the p-polarized beams. An initial phase shift between the s- and the p-polarized components is introduced to increase measurement sensitivity. For increased measurement linearity and reduced effect of laser power fluctuation on the output, a differential method is used in which the light beam is split equally into two beams, each reflected at a prism and detected by a photodiode. The output is obtained as the difference of the two detected intensities divided by their sum. A prototype device was built, which demonstrated a nonlinearity error of 1.3% in a measurement range of [+ or -] 0.6 [degrees] or 0.4% in [+ or -] 0.3 [degrees]. The peak-to-peak noise level was found to be at approximately 0.5 arc sec. This noise level can be reduced further and resolution increased by a reduction of the measurement range. [C] 2001 Optical Society of America OCIS codes: 120.0120, 120.3930, 120.3940, 120.5700, 260.3160, 260.5430, 260.6970.

Published
2001

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