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61.
62.
Schollmeier M Becker S Geissel M Flippo KA Blazević A Gaillard SA Gautier DC Grüner F Harres K Kimmel M Nürnberg F Rambo P Schramm U Schreiber J Schütrumpf J Schwarz J Tahir NA Atherton B Habs D Hegelich BM Roth M 《Physical review letters》2008,101(5):055004
This Letter demonstrates the transporting and focusing of laser-accelerated 14 MeV protons by permanent magnet miniature quadrupole lenses providing field gradients of up to 500 T/m. The approach is highly reproducible and predictable, leading to a focal spot of (286 x 173) microm full width at half maximum 50 cm behind the source. It decouples the relativistic laser-proton acceleration from the beam transport, paving the way to optimize both separately. The collimation and the subsequent energy selection obtained are perfectly applicable for upcoming high-energy, high-repetition rate laser systems. 相似文献
63.
An allylic alkylation/ring-closing metathesis domino catalytic process, wherein a palladium and a ruthenium catalyst are concomitantly present in the reaction mixture from the outset of the reaction, is developed. Evidence for Grubbs' catalysts activity in allylic alkylation is also reported. 相似文献
64.
5',8-Purine cyclonucleosides constitute an important class of oxidatively generated tandem lesions whose formation involves initial hydroxyl radical-mediated hydrogen atom abstraction from the 5-hydroxymethyl group of 2-deoxyribose followed by intramolecular cyclization. The present study deals with the synthesis of the 5'S diastereomer of 5',8-cyclo-2'-deoxyadenosine containing di- and tri-oligodeoxynucleotides as an attempt to delineate the conformational changes induced in the DNA fragments by the presence of a rigid modified nucleoside. For this purpose, extensive 1D and 2D NMR measurements that were completed by DFT theoretical calculations were performed. As a striking result, it was found that the covalent bond between C(5') and C(8) in the investigated purine cyclonucleoside induces an unusual West ((0)T(1)) conformation of the furanose ring. Thus it can be postulated that the rigid structure of the tandem lesion would strongly perturb the global geometry of oligonucleotides at the site of the modification and therefore affect the enzymatic activity of DNA polymerases and repair enzymes. 相似文献
65.
Gaillard de Sémainville P Hoffmann D George Ch Herrmann H 《Physical chemistry chemical physics : PCCP》2007,9(8):958-968
Using laser photolysis experiments, the reactivity of the nitrate radical towards four carbonyl compounds and three carboxylic acids was studied. All kinetics measurements were carried out as a function of the temperature in the range from 278 K to 318 K. Furthermore, the effect of the acid-base equilibrium on the reactivity of the three acids was studied by measuring the activation parameters of the dissociated and undissociated acids at pH = 6 and pH = 0.5, respectively. The following Arrhenius expressions were obtained: [Formulas: see text]. Errors stated throughout this study are statistical errors for a confidence interval of 95%. The importance of the obtained results for the understanding of the tropospheric oxidation processes is discussed. The kinetics resulting from this work are compared with results for other atmospheric radicals. 相似文献
66.
We used Monte Carlo method to generate the configurations of disassembly of hot nucleus Au* based on the Atomic Mass Table and the conservation of mass and charge number.The resulted charge distribution of fragments was then used to calculate the conditional moments.The logarithm correlation between second and third moments of experimental charge distribution is very well reproduced by theory.It seems that no connection to the critical phenomenon of concerned system exists. 相似文献
67.
In this paper a simplified method for the calculation of average Coulomb energy in statistical model of the disassembly processes of hot nuclei is proposed.The effect of freeze-out volume is studied based on the assumption of Gaussion-like distribution.It is indecated that the centre and dispersion of Gaussion-like distribution somewhat reflect the location and the renge of liquid-gas coexistence phase. 相似文献
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利用溶液聚合和成酰胺反应合成了多功能梳状两亲性共聚物,聚(甲基丙烯酸-co-甲基丙烯酸十八酯)-(乙醇胺-乙二胺叶酸)(PSM-EE-FA).用红外光谱(FTIR),核磁共振(1H-NMR)及凝胶渗透色谱(GPC)表征了该聚合物的结构及分子量分布.实验结果证明合成了该聚合物,其数均分子量(Mn)为28600,多分散性为1.375.用该两亲梳状聚合物包覆油溶性CdSe/ZnS量子点,通过相转移作用,得到水溶性靶向量子点(PSM-EE-FA-QDs).该水溶性量子点溶液具有较好的稳定性.通过紫外-可见(UV-Vis)及荧光发射光谱分析对该量子点的光学性质进行研究.结果表明,PSM-EE-FA-QDs的紫外-可见光谱及荧光发射光谱峰形与原量子点基本一致.由于量子点表面聚合物层的形成,峰位发生少量红移.该量子点水溶液的荧光强度是原量子点氯仿溶液的98%,荧光产率是原量子点氯仿溶液的95%.动态光散射(DLS)及透射电镜(TEM)测试结果表明水溶性量子点分布均匀.合成的水溶性量子点不但光学性能稳定,而且聚合物及水溶性量子点的合成方法较为简便. 相似文献