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91.
为了研究α-四芳氧基取代酞菁在溴化反应中溴原子的取代位置问题,本文合成了1,8,15,22-四(4-甲基苯氧基)酞菁钯(Pc~1)、1,8,15,22-四(2,6-二溴-4-甲基苯氧基)酞菁钯(Pc~2)、1,8,15,22-四(2,4-二特丁基苯氧基)酞菁钯(Pc~3)和1,8,15,22-四(2,4-二特丁基苯氧基)酞菁铜(Pc~4),并对它们分别进行了相同条件下的溴化,得到相应的溴化产物Pc~5、Pc~6、Pc~7和Pc~8.综合对比研究酞菁Pc~1-4及其溴化产物Pc~5-8的最大吸收波长,推测酞菁溴化反应发生在酞菁大共轭体系的苯环上,而不是芳氧取代基的苯环上,并从电子结构的角度简要的说明了原因. 相似文献
92.
王海舟 《中国科学B辑(英文版)》2003,46(2)
The property of the material is closely related to its chemical compositions and microstruc-tures, which are the important parameters in the judgement of the quality of the material. The conventional chemical composition content of the material is an average value of the chemical composition of the whole material tested or the content of a fix position. Although it is still neces-sary to further improve these conventional methods, there are mature and systematic methods for analyzing the conve… 相似文献
93.
Summary The influence of the distance between the solvent entry and the starting zone positions, Z0, on the average plate height was studied. This factor was found to be of major importance and could be optimized. The Guiochon and Siouffi model greatly underestimates the plate height for low values of Z0. 相似文献
94.
95.
Yusuke Yoshimura Ryuichiro Hibi Akiho Nakata Moeka Togashi Shoujiro Ogawa Takayuki Ishige Mamoru Satoh Fumio Nomura Tatsuya Higashi 《Biomedical chromatography : BMC》2019,33(7)
A liquid chromatography/electrospray ionization–tandem mass spectrometry‐based method was developed for the identification of the conjugation positions of the monoglucuronides of 25‐hydroxyvitamin D3 [25(OH)D3] and 24,25‐dihydroxyvitamin D3 [24,25(OH)2D3] in human urine. The method employed derivatization with 4‐(4‐dimethylaminophenyl)‐1,2,4‐triazoline‐3,5‐dione to convert the glucuronides into fragmentable derivatives, which provided useful product ions for identifying the conjugation positions during the MS/MS. The derivatization also enhanced the assay sensitivity and specificity for urine sample analysis. The positional isomeric monoglucuronides, 25(OH)D3‐3‐ and ‐25‐glucuronides, or 24,25(OH)2D3‐3‐, ‐24‐ and ‐25‐glucuronides, were completely separated from each other under the optimized LC conditions. Using this method, the conjugation positions were successfully determined to be the C3 and C24 positions for the glucuronidated 25(OH)D3 and 24,25(OH)2D3, respectively. The 3‐glucuronide was not present for 24,25(OH)2D3, unlike 25(OH)D3, thus we found that selective glucuronidation occurs at the C24‐hydroxy group for 24,25(OH)2D3. 相似文献
96.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(1):31-36
In order to determine the impact of different substituents and their positions on intermolecular interactions and ultimately on the crystal packing, unsubstituted N‐phenyl‐2‐phthalimidoethanesulfonamide, C16H14N2O4S, (I), and the N‐(4‐nitrophenyl)‐, C16H13N3O6S, (II), N‐(4‐methoxyphenyl)‐, C16H16N3O6S, (III), and N‐(2‐ethylphenyl)‐, as the monohydrate, C18H18N2O4S·H2O, (IV), derivatives have been characterized by single‐crystal X‐ray crystallography. Sulfonamides (I) and (II) have triclinic crystal systems, while (III) and (IV) are monoclinic. Although the molecules differ from each other only with respect to small substituents and their positions, they crystallized in different space groups as a result of differing intra‐ and intermolecular hydrogen‐bond interactions. The structures of (I), (II) and (III) are stabilized by intermolecular N—H…O and C—H…O hydrogen bonds, while that of (IV) is stabilized by intermolecular O—H…O and C—H…O hydrogen bonds. All four structures are of interest with respect to their biological activities and have been studied as part of a program to develop anticonvulsant drugs for the treatment of epilepsy. 相似文献
97.
98.
Ming-Ling Lee 《Applied Mathematical Modelling》1989,13(12):693-701
A method for predicting the dynamic stability of a nonlinear barge-towing system is presented in which the equations of motion of the dynamic system are first transformed into a six-dimensional state-space equation. The governing equation is then linearized by using the Taylor series expanding with respect to the equilibrium configurations of the towed barge. It is found that the stability conditions of a towing system are determined by the signs of the real part of some associated eigenvalues: Positive and negative 1's will result in unstable and stable dynamic responses, respectively, and 0 corresponds to the marginally stable condition. The reliability of the foregoing criteria is confirmed by the time histories (simulations) of the nonlinear barge-towing system. The effects of the stabilizing skegs and significantly improve the course stability of the towed barge and that the length and material of the towrope are also key factors affecting the dynamic stability of the barge-towing system. 相似文献
99.
The class of metrizable spaces M with the following approximation property is introduced and investigated: M∈AP(n,0) if for every ε>0 and a map g:In→M there exists a 0-dimensional map g′:In→M which is ε-homotopic to g. It is shown that this class has very nice properties. For example, if Mi∈AP(ni,0), i=1,2, then M1×M2∈AP(n1+n2,0). Moreover, M∈AP(n,0) if and only if each point of M has a local base of neighborhoods U with U∈AP(n,0). Using the properties of AP(n,0)-spaces, we generalize some results of Levin and Kato-Matsuhashi concerning the existence of residual sets of n-dimensional Lelek maps. 相似文献
100.
在合作博弈的一般模型中总是假设所有联盟都能形成。不过,在实际中由于受到一些因素的制约,有些联盟是不能形成的。基于此,Myerson提出了具有图通讯结构的合作博弈。Myerson值和Position值是超图博弈上的两个重要分配规则。2005年,Slikker给出了在图博弈上Position值的公理化刻画。但超图博弈上Position值的公理化刻画一直悬而未决。本文通过引入“赋权平衡超边贡献公理”,并结合经典的“分支有效性”,提出了超图博弈上赋权Position值的公理化刻画。作为推论,解决了超图博弈上Position值的公理化刻画问题。 相似文献