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181.
基于高光谱的膜下滴灌小麦氮素营养评价研究 总被引:2,自引:0,他引:2
通过小麦氮素和品种对比试验,分析不同氮素和品种处理小麦生育期氮肥偏生产力与光谱参数的相关关系,建立小麦氮肥偏生产力的光谱参数估算模型,结果表明绿度植被指数(GREENNDVI)在拔节期与小麦氮肥偏生产力呈极显著相关,相关系数0.640 4。用GREENNDVI在拔节期建立小麦氮肥偏生产力的估算模型,均方根误差0.459 7。研究表明利用光谱参数可以有效地估算小麦氮肥偏生产力。 相似文献
182.
We present a componentwise perturbation analysis for the continuous‐time Sylvester equations. Componentwise, mixed condition numbers and new perturbation bounds are derived for the matrix equations. The small sample statistical method can also be applied for the condition estimation. These condition numbers and perturbation bounds are tested on numerical examples and compared with the normwise condition number. The numerical examples illustrate that the mixed condition number gives sharper bounds than the normwise one. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
183.
Fei Ding Li Zhang Ye Sun Jian-Xiong Diao Xin-Ling Yang Ying Sun Li Zhang 《Journal of luminescence》2012,132(3):629-635
Phenosafranine is a toxic and recalcitrant compound, whose capacity to intercalate with double stranded DNA has been shown. In this contribution, a biophysical discuss on the conjugation of phenosafranine with two model proteins human serum albumin (HSA) and lysozyme (Lys) has been identified utilizing a combination of molecular modeling, steady state and time-resolved fluorescence and circular dichroism (CD) approaches. The accurate binding domain of phenosafranine in protein has been characterized from molecular modeling, subdomain IIIA of HSA and Trp-62, Trp-63 and Trp-108 residues of Lys was designated to possess high-affinity for this compound, the dominant forces in the protein–phenosafranine adduct are hydrogen bonds and π–π interactions, but hydrophobic interactions between dye and Lys are also not exclude. The data of fluorescence displayed that the complex of phenosafranine with protein produces quenching through static property, this corroborates the time-resolved fluorescence results that the ground state complex formation with a moderate affinity of 104 M?1. Moreover, via synchronous fluorescence, CD and three-dimensional fluorescence we indicated some extent of polypeptide chain of protein partially unfolding upon conjugation with phenosafranine. Through this work, we anticipate it can supply salient clues on the toxicological action of phenosafranine and other azines, which have analogous configuration with phenosafranine. 相似文献
184.
本文介绍了一种新型低温热开关的工作原理.考虑到热开关充人的气体在连续介质区和自由分子状态的传热以及肋片沿轴向的导热对热开关的传热特性进行了详细的理论分析.建立了该种热开关传热的理论模型.给出了肋片的厚度、长度、气隙宽度、外壳壁厚与导通热导之间的关系曲线以及气体压强、外壳厚度与关断热导之间的关系曲线. 相似文献
185.
186.
A new isoflavone was obstained from the medicinal herb Amorpha fruticosa.It was elucidated asbenzopyran-12-one,1,4,10,11- tetrahydro-6′-[8′-(hydroxymethyl)ethenyl]-2,3-dimethoxy-8′-O-β-D-glucopyranosyl-O-α-D-arabinoside by spectroscopic methods including UV,IR,1D NMR and 2D NMR techniques.And the activity against acetaminophen-induced hepatotoxicity of this compound was also studied,and found this compound can protect liver obviously from hepatotoxicity induced by acetaminophen (AAP). 相似文献
187.
One new furofuran lignan 2-methoxy-9β-hydroxydiasesamin (1), and four analogues (2–5), together with eight alkaloids (6–13), were isolated from the ethanol extract of the aerial part of Clinacanthus nutans. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. All the compounds were isolated from the genus of Clinacanthus for the first time. In addition, lignans isolated from C. nutans was reported for the first time. Compound 1 exhibited modest activity against three human tumor cell lines Hela, MCF-7, and A549, with IC50 values of 68.55, 60.00, and 59.17 μM, respectively. 相似文献
188.
Shengbao Diao Mei Jin Chun Shi Jin Cheng-Xi Wei Jinfeng Sun 《Natural product research》2019,33(20):3021-3024
A new flavanone glycoside, (2S)-dihydrooroxylin A 7-O-[β-D-apiosyl(1→2)]-β-D-glucoside (1), and four known compounds (2–5) were isolated from Tournefortia sibirica L. The chemical structures of these compounds were determined by 1?D and 2?D NMR and HR-ESI-MS spectra, and results were compared with data from the literature. These five compounds (1–5) were isolated from the family Boraginaceae for the first time. Anti-inflammatory effects of compounds (1–5) were evaluated in terms of inhibition of production of NO, TNF-α, and IL-6 in LPS-induced RAW 264.7 cells. 相似文献
189.
A new asymmetric perfluordiarylethene (1O) was synthesized using 4, 5-[bis-(5-ethylacetate-yl)-2-thienyl]-1H-imidazole as a functional group. 1O exhibited favorable reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light. Both of its open- and closed-ring isomers were found to be highly selective towards Cu2+ with significant absorption and color changes, which could be used as a ‘naked-eye’ colorimetric sensor for Cu2+ detection. Upon exposure to acid, its fluorescence dramatically enhanced by 14-fold with a color change from dark to bright cyan due to the formation of the protonated compound. Moreover, 1O showed obvious fluorescence “turn-on” signal response towards Al3+, and the detection limit for Al3+ was determined to be 4.8 × 10?9 mol L?1. Based on the fluorescence signals of 1O, a combinational stimuli logic circuit were designed by using the fluorescence intensity as the output signal with the inputs of lights, Al3+ and EDTA. Finally, 1O could be used as a biological probe for detecting intracellular Al3+ in a physiological environmental. 相似文献
190.
A new diarylethene with ethylimidazo[2,1-b]thiazole-6-hydrazide unit was synthesized, and its photochromic and fluorescent behaviors have been systematically investigated by the stimulation of lights and metal ions in methanol. This new diarylethene exhibited high selectivity and sensitivity toward Al3+ and Zn2+. The addition of Al3+ and Zn2+ displayed excellent colorimetric response behaviour with the concomitant color change from colorless to yellow, which could be easily observed by the naked eye. Upon addition of Al3+, the fluorescence intensity was enhanced by 180–fold and the emission peak of 1O–Al3+ blue-shifted by 15?nm accompanied with a color change from colorless to bright blue. In contrast, when stimulated with Zn2+, its fluorescence intensity was enhanced by 35–fold and the emission peak of 1O–Zn2+ red-shifted by 16?nm with an evident color change from black to bright green. The LOD for Al3+ and Zn2+ were determined to be 2.97?×?10?9?mol?L?1 and 5.98?×?10?9?mol?L?1, respectively. Moreover, a logic circuit was constructed with the fluorescence intensity as the output signal responding to the light and chemical species as the inputs. 相似文献