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排序方式: 共有92条查询结果,搜索用时 15 毫秒
31.
[reaction: see text] A new and efficient indium-mediated one-pot three-component reaction for the synthesis of N-aryl-substituted homoallylamines from aromatic amines, enol ethers, and allylic bromides in THF at room temperature is described. 相似文献
32.
The maximal Seshadri number μ(L) of an ample line bundle L on a smooth projective variety X measures the local positivity of the line bundle L at a general point of X. By refining the method of Ein-Küchle-Lazarsfeld, lower bounds on μ(L) are obtained in terms of L
n
, n=dim(X), for a class of varieties. The main idea is to show that if a certain lower bound is violated, there exists a non-trivial
foliation on the variety whose leaves are covered by special curves. In a number of examples, one can show that such foliations
must be trivial and obtain lower bounds for μ(L). The examples include the hyperplane line bundle on a smooth surface in ℙ3 and ample line bundles on smooth threefolds of Picard number 1.
Received: 29 June 2001 / Published online: 16 October 2002
RID="⋆"
ID="⋆" Supported by Grant No. 98-0701-01-5-L from the KOSEF.
RID="⋆⋆"
ID="⋆⋆" Supported by Grant No. KRF-2001-041-D00025 from the KRF. 相似文献
33.
Gi Heon Kim Chang Dae Keum Sung Jin Kim Lee Soon Park 《Journal of polymer science. Part A, Polymer chemistry》1999,37(19):3715-3722
Thermally stable poly(α-methyl styrene-co-maleimide) (MSMI) and poly(α-methyl styrene-co-4-carboxyphenyl maleimide) (MSCM) substrate polymers were obtained readily by free radical polymerization of comonomers. Introduction of a DR1 chromophore to the maleimide units of MSMI substrate polymer by the Mitsunobu reaction was dependent on the reaction solvent. The degree of substitution of DR1 into the MSMI polymer was bound to be 91.1 mol % and 0.4 mol % by UV spectrometers in the THF and DMF solvent, respectively. DR1 chromophore was, however, substituted in the MSCM polymer at 33.0 mol % by Mitsunobu reaction in the THF solvent. Both substrate and NLO polymer exhibited high thermal stability due to the incorporation of maleimide units in the polymer chain. The glass transition temperature (Tg) and initial decomposition temperature (Ti) of the NLO polymer were in the range of Tg = 185°C and Ti = 310–345°C. The electro-optic coefficient (r33) of NLO polymer was determined with an experimental setup capable of the real-time measurement while varying both the poling field and temperature. The NLO polymer MSMI-THF had a higher r33 value than MSCM-DR due to an increased degree of substitution of DR1 chromophore. MSMI-THF had a maximum r33 value of 16 pm/V at 135 MV/m poling field with a 632.8 nm light source. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3715–3722, 1999 相似文献
34.
Susan Swansburg Yoon-Ki Choi Sam-Rok Keum Erwin Buncel Robert P. Lemieux 《Liquid crystals》1998,24(3):341-346
Two series of mesogens derived from the non-activated spiropyran dyes 6-hydroxy-1 ,3 ,3- trimethylspiro\[2H -1-benzopyran-2,2-indoline] (series trimethylspiro\[2 H -1-benzopyran-2,2-indoline] (series 2 ) have been synthesized. Analysis by differential scanning calorimetry, polarizing microscopy and X-ray diffraction showed compounds in series 1 form monotropic nematic and SmA phases, while compounds in series 2 form only a monotropic nematic phase. 相似文献
35.
Novel stilbene‐based Fischer base analog of leuco‐TAM – (2E,2′Z)‐{2‐(4‐(E)‐styrylphenyl)propane‐1,3‐diylidene}bis(1,3,3‐trimethylindoline) – derivatives: synthesis and structural consideration by 1D NMR and 2D NMR spectroscopy 下载免费PDF全文
We report the synthesis of a series of novel stilbene‐based (St) Fischer base analogs of leuco‐triarylmethane (LTAM) dyes by treating Fischer base with (E)‐4‐styrylbenzaldehyde derivatives. All St‐LTAM molecules examined herein are characterized by 1D and 2D NMR. They were found to exhibit ZE configuration and isomerize to their diastereomers EE and ZZ in 2–3 h. They exhibit type I behavior of diastereomeric isomerization. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
36.
Byung Woo Yoo Heung Soo Baek Sam Rok Keum Cheol Min Yoon Ghil Soo Nam Sung Hoon Kim 《合成通讯》2013,43(23):4317-4322
The reductive cleavage of thiobenzoates promoted by samarium diiodide afforded various kinds of disulfides in good yields under mild and neutral conditions. 相似文献
37.
Amol Dighe Anirban Kundu K. Agashe B. Anantanarayan A. Chandra A. Datta P. K. Das S. P. Das A. Dighe R. Forty D. K. Ghosh Y. -Y. Keum A. Kundu N. Mahajan S. Majhi G. Mazumdar K. Mazumdar P. Mehta Y. Nir J. P. Saha R. Singh N. Sinha R. Sinha A. Soni S. Uma Sankar R. Vaidya 《Pramana》2004,63(6):1359-1365
This is a report of the low energy and flavour physics working group at WHEPP-8, held at the Indian Institute of Technology,
Mumbai, India, during 5–16 January 2004. 相似文献
38.
39.
In this paper, the residual vibration control problem of a nuclear power plant’s fuel-transport system is discussed. The purpose of the system is to transport fuel rods to the target position within the minimum time. But according to observations, the rods oscillate at the end of the maneuver, causing an undesirable delay in the operation and affecting the system’s performance in terms both of productivity and of safety. In the present study, a mathematical model of the system was developed to simulate the under-water sway response of the rod while keeping in view the effects of the hydrodynamic forces imposed by the surrounding water. Experiments were performed to validate the model’s correctness. Further, simulation results were used to design the input shaping control that generates shaped velocity commands for transport of the fuel rods to the target position with the minimum residual vibration. It was observed that due to the under-water maneuvering, the fuel-handling system behaves as a highly damped process and that the generated shaped velocity commands fail to effect the desired suppression of the residual vibration. Therefore, keeping in view the highly damped nature of the system, a modified shaped command was generated that transported the fuel rods to the target position with the minimum residual vibration. 相似文献
40.
We present methods to construct interesting surfaces of general type via ${\mathbb{Q}}$ -Gorenstein smoothing of a singular surface obtained from an elliptic surface. By applying our methods to special Enriques surfaces, we construct new examples of a minimal surface of general type with ${p_g=0, \pi_1=\mathbb{Z}/2\mathbb{Z}}$ , and K 2 ≤ 4. 相似文献