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961.
A novel siderophore analog (4) has been designed to facilitate iron transport-mediated drug delivery and drug release. This mixed ligand siderophore analog includes three bidentate ligands intended to octahedrally coordinate iron (III). The ligands include a 2,3-dihydroxy benzoic acid moiety, N5-acetyl-N5-hydroxy-l-ornithine, and a β-N-hydroxy-α,β-diaminopropionic acid derivative. The total synthesis of 15, a form of 4 that is suitably protected, yet contains a free carboxylic acid for subsequent drug conjugation, is described. 相似文献
962.
不对称加氢催化剂[Ru(BINAP)(OAc)2]的合成及其固载化研究 总被引:1,自引:0,他引:1
对文献报道的实验反应条件进行优化改进后,合成了不对称加氢催化剂[Ru((S)-BINAP)(OAc)2]和[Ru((R)-BINAP)(OAc)2]。将合成的催化剂应用于惕各酸的不对称催化氢化,(S)-2-甲基丁酸得率为88%,立体选择性可达85%e.e.。为了提高催化剂的利用率,将催化剂[Ru(BINAP)(OAc)2]负载在新型介孔分子筛SBA-15上,用于惕各酸的不对称催化氢化,循环应用3次后,(S)-2-甲基丁酸得率仍可达到59%,立体选择性达57%e.e.。 相似文献
963.
A method has been developed for the simultaneous quantification of metformin (I) and glipizide (II) in human plasma. It is based on high-performance liquid chromatography with electrospray ionization tandem mass (LC-ESI-MS/MS) spectrometric detection in positive ionization mode. Phenformin (III) and gliclazide (IV) were used as internal standards for I and II, respectively. The MS/MS detection was performed in multiple reaction monitoring (MRM) mode. The precursor-product ion combinations of m/z 130 --> 71, 446 --> 321, 206 --> 60 and 324 --> 127 were used to quantify I, II, III and IV, respectively. This method was validated in the concentration ranges of 0.02-4 microg/mL for I and 0.004-0.8 microg/mL for II. It was utilized to support a clinical pharmacokinetic study after single dose oral administration of a combination of I and II. 相似文献
964.
Qiding Mi Lianxun Gao Leiming Li Yu Ma Xing Zhang Mengxian Ding 《Journal of polymer science. Part A, Polymer chemistry》1997,35(15):3287-3297
A series of new optically active aromatic polyimides containing axially dissymmetric 1,1′-binaphthalene-2,2-diyl units were prepared from optically pure (R)-(+)- or(S)-(−)-2,2′-bis(3,4-dicarboxyphenoxy)-1,1′-binaphthalene dianhydrides and various aromatic diamines via a conventional two-step procedure that included ring-opening polycondensation and chemical cyclodehydration. The optically pure isomer of dianhydride was prepared by a nucleophilic substitution of optically pure (R)-(+)- or(S)-(−)-1,1′-bi-2-naphthol with 4-nitrophthalonitrile in aprotic polar solvent and subsequent hydrolysis of the resultant tetranitrile derivatives, followed by the dehydration of the corresponding tetracarboxylic acids to obtain the dianhydrides. These polymers were readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc., and have glass transition temperatures of 251–296°C, and 5% weight loss occurs not lower than 480°C. The specific rotations of the optically active polyimides ranged from +196° to +263°, and the optical stability and chiroptical properties of them were also studied. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3287–3297, 1997 相似文献
965.
Convergence of the fractional step Lax-Friedrichs scheme and Godunov scheme for the isentropic system of gas dynamics 总被引:3,自引:0,他引:3
A convergence theorem of the fractional step Lax-Friedrichs scheme and Godunov scheme for an inhomogeneous system of isentropic gas dynamics (1<5/3) is established by using the framework of compensated compactness. Meanwhile, a corresponding existence theorem of global solutions with large data containing the vacuum is obtained.Partially supported by U.S. NSF Grant # DMS-850403 相似文献
966.
967.
968.
Homogeneous interface-type resistance switching in Au/La0.67Ca0.33MnO3/SrTiO3/F:SnO2 heterojunction memories 下载免费PDF全文
La0.67Ca0.33MnO3 thin films are fabricated on fluorine-doped tin oxide conducting glass substrates by a pulsed laser deposition technique with SrTiO3 used as a buffer layer. The current-voltage characteristics of the heterojunetions exhibit an asymmetric and resistance switching behaviour. A homogeneous interface-type conduction mechanism is also reported using impedance spectroscopy. The spatial homogeneity of the charge carrier distribution leads to field- induced potential-barrier change at the Au-La0.67Ca0.33MnO3 interface and a concomitant resistance switching effect. The ratio of the high resistance state to the low resistance state is found to be as high as 1.3 x 10^4% by simulating the AC electric field. This colossal resistance switching effect will greatly improve the signal-to-noise ratio in nonvolatile memory applications. 相似文献
969.
李志超 赵航 龚韬 李欣 杨冬 蒋小华 郑坚 刘永刚 刘耀远 陈朝鑫 李三伟 李琦 潘凯强 郭亮 理玉龙 徐涛 彭晓世 吴畅书 张桦森 郝亮 蓝可 陈耀桦 郑春阳 古培俊 王峰 蔡洪波 郑无敌 邹士阳 杨家敏 江少恩 张保汉 朱少平 丁永坤 《强激光与粒子束》2020,32(9):092004-1-092004-14
当前,激光惯性约束聚变在越来越接近点火的极端能量密度条件下,实验与模拟的偏离逐渐增大,一个关键原因是缺乏对黑腔等离子体状态及其影响黑腔能量学和内爆对称性的细致研究和判断。光学汤姆逊散射主动式、诊断精确、参数完备的优点,使之成为激光惯性约束聚变黑腔等离子体状态参数精密诊断的标准方法。中国面向激光惯性约束聚变研究的光学汤姆逊散射实验技术的发展与神光系列激光装置的建设和在其上开展的物理实验紧密相关。近年来,四倍频汤姆逊散射实验技术在神光III原型和100 kJ激光装置上相继建立,部分实验结果不仅加深了对激光惯性约束聚变靶物理的认识,还反映了实验条件对汤姆逊散射诊断的影响,促进了实验技术的精密化发展。在未来,还需要进一步发展多支路汤姆逊散射、五倍频汤姆逊散射和超热相干汤姆逊散射等新技术,面向点火黑腔条件,大幅提升激光等离子体状态参数的诊断精度,开展新物理机制的探索和研究,在激光惯性约束聚变和其他高能量密度物理科学领域发挥更重要的作用。 相似文献
970.
Structure, room-temperature magnetic and optical properties of Mn-doped TiO2 nano powders prepared by the sol-gel process 下载免费PDF全文
TiO 2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol-gel process,and were annealed at 500 C and 800 C in air for 2 hrs.X-ray diffraction (XRD) measurements indicate that the Mn-TiO 2 nano powders with Mn concentration of 1 at% and 2 at% annealed at 500 and 800 C are of pure anatase and rutile,respectively.The scanning electron microscope (SEM) observations reveal that the crystal grain size increases with the annealing temperature,and the high resolution transmission electron microscopy (HRTEM) investigations further indicate that the samples are well crystallized,confirming that Mn has doped into the TiO 2 crystal lattice effectively.The room temperature ferromagnetism,which could be explained within the scope of the bound magnetic polaron (BMP) theory,is detected in the Mn-TiO 2 samples with Mn concentration of 2 at%,and the magnetization of the powders annealed at 500 C is stronger than that of the sample treated at 800 C.The UV-VIS diffuse reflectance spectra results demonstrate that the absorption of the TiO 2 powders could be enlarged by the enhanced trapped electron absorption caused by Mn doping. 相似文献