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81.
Thillaye du Boullay O Marchal E Martin-Vaca B Cossío FP Bourissou D 《Journal of the American Chemical Society》2006,128(51):16442-16443
The alpha-lactone equivalent lacOCA exhibits remarkable reactivity compared with lactide in nucleophile-catalyzed ROP. PLAs of controlled molecular weights and narrow polydispersities are typically obtained under mild conditions using DMAP and various protic initiators. 相似文献
82.
Studying the signaling role of 2-oxoglutaric acid using analogs that mimic the ketone and ketal forms of 2-oxoglutaric acid 总被引:1,自引:0,他引:1
Chen H Laurent S Bédu S Ziarelli F Chen HL Cheng Y Zhang CC Peng L 《Chemistry & biology》2006,13(8):849-856
2-Oxoglutaric acid (2-OG), a Krebs cycle intermediate, is a signaling molecule in many organisms. To determine which form of 2-OG, the ketone or the ketal form, is responsible for its signaling function, we have synthesized and characterized various 2-OG analogs. Only 2-methylenepentanedioic acid (2-MPA), which resembles closely the ketone form of 2-OG, is able to elicit cell responses in the cyanobacterium Anabaena by inducing nitrogen-fixing cells called heterocysts. None of the analogs mimicking the ketal form of 2-OG are able to induce heterocysts because none of them are able to interact with NtcA, a 2-OG sensor. NtcA interacts with 2-MPA and 2-OG in a similar manner, and it is necessary for heterocyst differentiation induced by 2-MPA. Therefore, it is primarily the ketone form that is responsible for the signaling role of 2-OG in Anabaena. 相似文献
83.
Construction of Hexahydropyrido[3,2‐c]carbazole and Hexahydropyrrolo[3,2‐c]carbazole Skeletons for the Synthesis of Related Indole Alkaloids 下载免费PDF全文
Synthesis of tetracyclic hexahydropyrido[3,2‐c]carbazoles ( 9a and 9b ) and hexahydropyrrolo[3,2‐c]carbazoles ( 13a and 13b ) structures was achieved via a new synthetic approach for the synthesis of related indole alkaloids such as deethylaspidospermidine and deethylibophyllidine. Hexahydropyrrolo[3,2‐c]carbazole structure was constructed for the first time starting from ethyl 4‐oxo‐cyclohexanecarboxylate in seven steps. Some tetrahydrocarbazole derivatives ( 4 , 5 , 6 , 7 , 11 , and 12 ) were also synthesized. 相似文献
84.
Three different crystal forms were obtained from the crystallisation of a flexible imidazole based ligand and CdBr(2) under different conditions. Structural analysis reveals that the correlation between the three metallocyclic compounds can be described in terms of isostructurality, solvatomorphism and supramolecular isomerism. 相似文献
85.
Laser beam shaping by phase-only transformations, often referred to as field mapping, has for a long time been considered wavelength dependent. In this Letter we outline a simple mathematical argument that shows how the problem may be formulated in a wavelength tunable manner, requiring only a minor adjustment in the observation plane. We verify the theoretical prediction by experiment using the example of a Gaussian-to-flattop-beam transformation, and we show that the shaping is valid across a wide range of wavelengths for a single diffractive optical element. 相似文献
86.
High power resonant tracking amplifier using admittance locking. 总被引:2,自引:0,他引:2
A high power resonance tracking ultrasonic amplifier is described. The amplifier is a class D type inverter, configured as a half-bridge in which the output MOSFETs are driven into saturation when on. The resonance tracking system makes use of a new method of frequency locking; admittance locking is used to track the optimum power conversion frequency for the transducer. This new arrangement offers some advantages over phase locking and motional feedback methods. The system is capable of delivering up to 3 kW at up to 25 kHz in resonance tracking operation. 相似文献
87.
88.
比较了Snyder经验公式中的K0w 与S和溶质计量置换保留模型 (SDM R)中溶质保留参数Z(1mol溶剂化溶质被溶剂化固定相吸附时 ,在其接触表面处释放出溶剂或置换剂的总摩尔数 )与lgI(与 1mol溶质对固定相的亲和势有关的常数 )之间的定量关系。SDM R中的两个参数间不仅对同系物溶质可以有很好的线性关系 ,而且对非同系物溶质也有很好的线性关系。其线性关系的好坏主要取决于这两个参数数值范围的大小 ,与文献中报告的线性关系取决于是否单因素影响溶质的保留和完全由统计学规律决定的结论不同。 相似文献
89.
90.