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101.
An efficient and convenient transformation of α-haloketones to α-hydroxyketones using cesium formate
Fung Fuh Wong Po-Wei Chang Hui-Chang Lin Bang-Jau You Jiann-Jyh Huang Shao-Kai Lin 《Journal of organometallic chemistry》2009,694(21):3452-3455
A new safe and convenient transformation has been developed. In the presence of cesium formate in dry MeOH solution, α-haloketones underwent direct conversion reaction to afford α-hydroxyketone in excellent yields. Furthermore, this methodology can be extended and applied in 2-chloro-N-(1,3-diphenyl-1H-pyrazol-5-yl)acetamide, 2-chloro-N-(2,6-dimethylphen-yl)acetamide, 1-(bromomethylsulfonyl)benzene, and N-(bromomethyl)phthalimide to give the corresponding products in moderate to excellent yields. 相似文献
102.
The intriguing concept of “anti-cloaking” has been recently introduced within the framework of transformation optics (TO), first as a “countermeasure” to invisibility-cloaking (i.e., to restore the scattering response of a cloaked target), and more recently in connection with “sensor invisibility” (i.e., to strongly reduce the scattering response while maintaining the field-sensing capabilities). In this paper, we extend our previous studies, which were limited to a two-dimensional cylindrical scenario, to the three-dimensional spherical case. More specifically, via a generalized (coordinate-mapped) Mie-series approach, we derive a general analytical full-wave solution pertaining to plane-wave-excited configurations featuring a spherical object surrounded by a TO-based invisibility cloak coupled via a vacuum layer to an anti-cloak, and explore the various interactions of interest. With a number of selected examples, we illustrate the cloaking and field-restoring capabilities of various configurations, highlighting similarities and differences with respect to the cylindrical case, with special emphasis on sensor-cloaking scenarios and ideas for approximate implementations that require the use of double-positive media only. 相似文献
103.
104.
针对非均匀Winkler弹性地基上变厚度矩形板的自由振动问题,通过一种有效的数值求解方法——微分变换法(DTM),研究其无量纲固有频率特性。已知变厚度矩形板对边为简支边界条件,其他两边的边界条件为简支、固定或自由任意组合。采用DTM将非均匀Winkler弹性地基上变厚度矩形板无量纲化的自由振动控制微分方程及其边界条件变换为等价的代数方程,得到含有无量纲固有频率的特征方程。数值结果退化为均匀Winker弹性地基上矩形板以及变厚度矩形板的情形,并与已有文献采用的不同求解方法进行比较,结果表明,DTM具有非常高的精度和很强的适用性。最后,在不同边界条件下分析地基变化参数、厚度变化参数和长宽比对矩形板无量纲固有频率的影响,并给出了非均匀Winkler弹性地基上对边简支对边固定变厚度矩形板的前六阶振型。 相似文献
105.
Iulia Ghiu 《Physics letters. A》2010,374(45):4633-4634
The paper [Phys. Lett. A 373 (2009) 3610] by D.-C. Li analyzes the transformation between two-qubit mixed states by local operations and classical communication. We show that the proof of the main theorem, Theorem 2.6 in [Phys. Lett. A 373 (2009) 3610] is not complete. Therefore the generalization of Nielsen's theorem to mixed states still remains an open problem. 相似文献
106.
An ion-pairing reversed-phase liquid chromatography–mass spectrometry (IP-RP-LC–MS) was developed for the determination of nucleotides, nucleosides and their transformation products in Cordyceps. Perfluorinated carboxylic acid, namely pentadecafluorooctanoic acid (PDFOA, 0.25 mM), was used as volatile ion-paring agent and a reversed-phase column (Agilent ZORBAX SB-Aq column) was used for the separation of three nucleotides namely uridine-5′-monophosphate (UMP, 0.638–10.200 μg/mL), adenosine-5′-monophosphate (AMP, 0.24–7.80 μg/mL) and guanosine-5′-monophosphate (GMP, 0.42–13.50 μg/mL), seven nucleosides including adenosine (0.55–8.85 μg/mL), guanosine (0.42–6.75 μg/mL), uridine (0.33–10.50 μg/mL), inosine (0.21–6.60 μg/mL), cytidine (0.48–15.30 μg/mL), thymidine (0.20–6.30 μg/mL) and cordycepin (0.09–1.50 μg/mL), as well as six nucleobases, adenine (0.22–6.90 μg/mL), guanine (0.26–4.20 μg/mL), uracil (0.38–12.15 μg/mL), hypoxanthine (0.13–4.20 μg/mL), cytosine (0.39–12.45 μg/mL) and thymine (0.26–8.25 μg/mL) with 5-chlorocytosine arabinoside as the internal standard. The overall LODs and LOQs were between 0.01–0.16 μg/mL and 0.04–0.41 μg/mL for the 16 analytes, respectively. The contents of 16 investigated compounds in natural and cultured Cordyceps were also determined and compared after validation of the developed IP-RP-LC-MS method. The transformations of nucleotides and nucleosides in Cordyceps were evaluated based on the quantification of the investigated compounds in three extracts, including boiling water extraction (BWE), 24 h ambient temperature water immersion (ATWE) and 56 h ATWE extracts. Two transformation pathways including UMP → uridine → uracil and GMP → guanosine → guanine were proposed in both natural Cordyceps sinensis and cultured Cordyceps militaris. The pathway of AMP → adenosine → inosine → hypoxanthine was proposed in natural C. sinensis, while AMP → adenosine → adenine in cultured C. militaris. However, the transformation of nucleotides and nucleosides was not found in commercial cultured C. sinensis. 相似文献
107.
Yu-Mei Wang Xiao-Chun Lin Kai-Ming Mo Prof. Dr. Mo Xie Dr. Yong-Liang Huang Prof. Dr. Guo-Hong Ning Prof. Dr. Dan Li 《Angewandte Chemie (International ed. in English)》2023,62(9):e202218369
The synthesis of atomically precise copper nanoclusters (Cu-NCs) with high chemical stability is a prerequisite for practical applications, yet still remains a long-standing challenge. Herein, we have prepared a pyrazolate-protected Cu-NC ( Cu8 ), which exhibited exceptional chemical stability either in solid-state or in solution. The crystals of Cu8 are still suitable for single crystal X-ray diffraction analysis even after being treated with boiling water, 8 wt % H2O2, high concentrated acid (1 M HCl) or saturated base (≈20 M KOH), respectively. More importantly, the structure of Cu8 in solution also remained intact toward oxygen, organic acid (100 eq. HOAc) or base (400 eq. dibutylamine) confirmed by 1H NMR and UV/Vis analysis. Taking advantage of high alkali-resistant, Cu8 illustrates excellent catalytic activity for the synthesis of indolizines, and it can be reused for at least 10 cycles without losing catalytic performance. 相似文献
108.
The paper describes an implicit finite difference approach to the pricing of American options on assets with a stochastic volatility. A multigrid procedure is described for the fast iterative solution of the discrete linear complementarity problems that result. The accuracy and performance of this approach is improved considerably by a strike-price related analytic transformation of asset prices and adaptive time-stepping. 相似文献
109.
110.
通过FTIR光学信息研究液态和固态磷脂酶D的二级结构,结果表明FTIR光学信息是一种有效的蛋白质分子二级结构研究方法。FTIR的光学信息分析表明冻干胁迫下,磷脂酶D的FTIR光学信息及二级结构发生较大变化。在磷脂酶D活性构象时的pH冻干使磷脂酶Dα螺旋大大下降,无规卷曲大大上升,β折叠几乎没有变化,说明PLD蛋白质分子空间有序构象解体严重。功能性试验表明,磷脂酶D二级结构的变化直接导致了其活性发生很大变化。 相似文献