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31.
Wi SG Chung BY Kim JS Kim JH Baek MH Lee JW Kim YS 《Micron (Oxford, England : 1993)》2007,38(6):553-564
This review discusses the morphological changes and biological responses of plants irradiated with gamma rays. Seedlings exposed to relatively low doses of gamma rays (1-5 Gy) developed normally, while the growth of plants irradiated with a high dose gamma ray (50 Gy) was significantly inhibited. Based on TEM observations, chloroplasts were extremely sensitive to gamma irradiation compared to other cell organelles, particularly thylakoids being heavily swollen. In addition, some portions of the mitochondria and endoplasmic reticulum were structurally altered, for example, distortion and swelling. The cerium perhydroxide deposition, as a maker for H(2)O(2) deposition, was typically manifest on the plasma membranes and cell walls of the tissues from both the control and irradiated plants. However, the intensities of cerium perhydroxide deposits (CPDs) were remarkably increased in the plasma membranes and cell walls of pumpkin tissues such as petiole, cotyledon, hypocotyl and especially leaf after gamma irradiation. These observations are in good agreement with the results of H(2)O(2) content in all tissues. The immuno-localization analysis for peroxidase (POD) on the tissues from pumpkin plant showed the same pattern between the control and irradiated plants, but the density of gold particles as indication of POD localization was significantly increased on the cell corner middle lamellae of parenchyma cells, especially in the petiole after gamma irradiation. However, accumulation and localization of H(2)O(2) and POD in vessels were not significantly different between both plants. The accumulation and localization of both H(2)O(2) and POD were differentially affected by gamma irradiation depending on the different tissue types. The deposition of both H(2)O(2) and POD in parenchyma cells appeared much higher than in vessels, suggesting that the former is more sensitive than the latter against gamma rays. 相似文献
32.
Highly Stable,Water‐Dispersible Metal‐Nanoparticle‐Decorated Polymer Nanocapsules and Their Catalytic Applications 下载免费PDF全文
Gyeongwon Yun Dr. Zahid Hassan Jiyeong Lee Jeehong Kim Dr. Nam‐Suk Lee Dr. Nam Hoon Kim Dr. Kangkyun Baek Dr. Ilha Hwang Prof. Dr. Chan Gyung Park Prof. Dr. Kimoon Kim 《Angewandte Chemie (International ed. in English)》2014,53(25):6414-6418
A facile synthesis of highly stable, water‐dispersible metal‐nanoparticle‐decorated polymer nanocapsules (M@CB‐PNs: M=Pd, Au, and Pt) was achieved by a simple two‐step process employing a polymer nanocapsule (CB‐PN) made of cucurbit[6]uril (CB[6]) and metal salts. The CB‐PN serves as a versatile platform where various metal nanoparticles with a controlled size can be introduced on the surface and stabilized to prepare new water‐dispersible nanostructures useful for many applications. The Pd nanoparticles on CB‐PN exhibit high stability and dispersibility in water as well as excellent catalytic activity and recyclability in carbon–carbon and carbon–nitrogen bond‐forming reactions in aqueous medium suggesting potential applications as a green catalyst. 相似文献
33.
Haidong Li Qichao Yao Feng Xu Yueqing Li Dayeh Kim Jeewon Chung Gain Baek Xiaofeng Wu Prima Fitria Hillman Eun Young Lee Haoying Ge Jiangli Fan Jingyun Wang Sang‐Jip Nam Xiaojun Peng Juyoung Yoon 《Angewandte Chemie (International ed. in English)》2020,59(25):10186-10195
Monitoring fluctuations in enzyme overexpression facilitates early tumor detection and excision. An AIEgen probe (DQM‐ALP) for the imaging of alkaline phosphatase (ALP) activity was synthesized. The probe consists of a quinoline‐malononitrile (QM) core decorated with hydrophilic phosphate groups as ALP‐recognition units. The rapid liberation of DQM‐OH aggregates in the presence of ALP resulted in aggregation‐induced fluorescence. The up‐regulation of ALP expression in tumor cells was imaged using DQM‐ALP. The probe permeated into 3D cervical and liver tumor spheroids for imaging spatially heterogeneous ALP activity with high spatial resolution on a two‐photon microscopy platform, providing the fluorescence‐guided recognition of sub‐millimeter tumorigenesis. DQM‐ALP enabled differentiation between tumor and normal tissue ex vivo and in vivo, suggesting that the probe may serve as a powerful tool to assist surgeons during tumor resection. 相似文献
34.
Wooseup Hwang Jejoong Yoo In‐Chul Hwang Jiyeon Lee Young Ho Ko Hyun Woo Kim Younghoon Kim Yeonsang Lee Moon Young Hur Kyeng Min Park Jongcheol Seo Kangkyun Baek Kimoon Kim 《Angewandte Chemie (International ed. in English)》2020,59(9):3460-3464
Hierarchical self‐assembly of building blocks over multiple length scales is ubiquitous in living organisms. Microtubules are one of the principal cellular components formed by hierarchical self‐assembly of nanometer‐sized tubulin heterodimers into protofilaments, which then associate to form micron‐length‐scale, multi‐stranded tubes. This peculiar biological process is now mimicked with a fully synthetic molecule, which forms a 1:1 host‐guest complex with cucurbit[7]uril as a globular building block, and then polymerizes into linear poly‐pseudorotaxanes that associate laterally with each other in a self‐shape‐complementary manner to form a tubular structure with a length over tens of micrometers. Molecular dynamic simulations suggest that the tubular assembly consists of eight poly‐pseudorotaxanes that wind together to form a 4.5 nm wide multi‐stranded tubule. 相似文献
35.
Jinny Claire Lee Hye Yun Kim Sejin Lee Jisu Shin Hyunjin Vincent Kim Kyeonghwan Kim Seungyeop Baek Donghee Lee Hanna Jeon DaWon Kim Seung‐Hoon Yang Gyoonhee Han Keunwan Park Jaeho Choi Jinwoo Park Jason A. Moss Kim D. Janda YoungSoo Kim 《Angewandte Chemie (International ed. in English)》2020,59(28):11491-11500
Amyloid‐β (Aβ) oligomers are implicated in Alzheimer disease (AD). However, their unstable nature and heterogeneous state disrupts elucidation of their explicit role in AD progression, impeding the development of tools targeting soluble Aβ oligomers. Herein parallel and anti‐parallel variants of Aβ(1–40) dimers were designed and synthesized, and their pathogenic properties in AD models characterized. Anti‐parallel dimers induced cognitive impairments with increased amyloidogenesis and cytotoxicity, and this dimer was then used in a screening platform. Through screening, two FDA‐approved drugs, Oxytetracycline and Sunitinib, were identified to dissociate Aβ oligomers and plaques to monomers in 5XFAD transgenic mice. In addition, fluorescent Astrophloxine was shown to detect aggregated Aβ in brain tissue and cerebrospinal fluid samples of AD mice. This screening platform provides a stable and homogeneous environment for observing Aβ interactions with dimer‐specific molecules. 相似文献
36.
37.
We consider a MAP-modulated fluid flow queueing model with multiple vacations. As soon as the fluid level reaches zero, the server leaves for repeated vacations of random length V until the server finds any fluid in the system. During the vacation period, fluid arrives from outside according to the MAP (Markovian Arrival Process) and the fluid level increases vertically at the arrival instance. We first derive the vector Laplace–Stieltjes transform (LST) of the fluid level at an arbitrary point of time in steady-state and show that the vector LST is decomposed into two parts, one of which the vector LST of the fluid level at an arbitrary point of time during the idle period. Then we present a recursive moments formula and numerical examples. 相似文献
38.
39.
S. H. Lee J. J. Choi W. K. Han S. W. Baek 《International Journal of Infrared and Millimeter Waves》1999,20(12):2011-2022
A design study of a double-anode magnetron-injection-gun is performed to incorporate the electron gun into a high power 28GHz gyroklystron amplifier operating at 70kV and 8.2A. The electron gun is designed to be used in a tapered magnetic field in the cathode region produced from an iron-free superconducting magnet. An electron trajectory code predicts a beam axial velocity spread of 5.9% at = 1.5, 70kV, 8.2A and 10.4kG, which is a high quality electron beam suitable for the high gain, high efficiency, five-cavity gyroklystron amplifier. The successful design of the high quality electron gun is attributed to a longer gap between the modulating anode and the grounded anode compared with the case of the first 28GHz electron gun built with an iron enclosed electromagnet. 相似文献
40.
Single-mode plane-polarized ytterbium-doped large-core fiber laser with 633-W continuous-wave output power 总被引:3,自引:0,他引:3
Jeong Y Nilsson J Sahu JK Soh DB Dupriez P Codemard CA Baek S Payne DN Horley R Alvarez-Chavez JA Turner PW 《Optics letters》2005,30(9):955-957
We demonstrate a cladding-pumped single-mode plane-polarized ytterbium-doped fiber laser generating 633 W of continuous-wave output power at 1.1 microm with 67% slope efficiency and a polarization extinction ratio better than 16 dB. The laser is end pumped through both fiber ends and shows no evidence of roll-over, even at the highest output power, which is limited only by the available pump power. 相似文献