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461.
We performed molecular dynamics (MD) simulations to study the characteristic sputtering process with large cluster ion impact. The statistical properties of incident Ar and sputtered Si atoms were examined using 100 different MD simulations with Ar1000 cluster impacting on a Si(0 0 1) target at a total acceleration energy of 50 keV. The results show that the kinetic energy distribution of Ar atoms after impact obeys the high-temperature Boltzmann distribution due to thermalization through high-density multiple collisions on the target. On the other hand, the kinetic energy distribution of sputtered target atoms demonstrates a hybrid model of thermalization and collision-cascade desorption processes. 相似文献
462.
463.
Zachary Powers Adam Scharf Andrea Cheng Feng Yang Martin Himmelbauer Takaaki Mitsuhashi Lena Barra Yoshimasa Taniguchi Takashi Kikuchi Makoto Fujita Ikuro Abe John A. Porco 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16287-16292
A biomimetic route to farnesyl pyrophosphate and dimethyl orsellinic acid (DMOA)‐derived meroterpenoid scaffolds has yet to be reported despite great interest from the chemistry and biomedical research communities. A concise synthetic route with the potential to access DMOA‐derived meroterpenoids is highly desirable to create a library of related compounds. Herein, we report novel dearomatization methodology followed by polyene cyclization to access DMOA‐derived meroterpenoid frameworks in six steps from commercially available starting materials. Furthermore, several farnesyl alkene substrates were used to generate structurally novel, DMOA‐derived meroterpenoid derivatives. DFT calculations combined with experimentation provided a rationale for the observed thermodynamic distribution of polycyclization products. 相似文献
464.
Shobu Hiraoka Tsutomu Matsumoto Koki Matsuzaka Takaaki Sato Noritaka Chida 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4425-4429
An approach to cyclic nitrones from N‐hydroxylactam derivatives is documented. The nucleophilic addition of an organolithium reagent to an N‐OSEM [SEM=2‐(trimethylsilyl)ethoxymethyl] lactam forms a five‐membered chelated intermediate, which undergoes both elimination and deprotection to give a fully substituted nitrone in a one‐pot process. When combined with the N‐oxidation of easily available chiral lactams, this method becomes especially useful for the quick synthesis of chiral nitrones in enantio‐pure form, enabling the concise total synthesis of cylindricine C. 相似文献
465.
Satoshi Ninomiya Takaaki Aoki Toshio Seki Jiro Matsuo 《Applied Surface Science》2006,252(19):6550-6553
Secondary ions emitted from Si targets were measured with a quadrupole mass spectrometer under large Ar cluster and monomer ion bombardment. Incident ion beams with energies from 7.5 to 25 keV were used and the mean size of the Ar cluster ion was about 1000 atoms/cluster. Sin+ ions with n values up to n = 8 were detected under Ar cluster ion bombardment, whereas Si cluster ions were scarcely detected under Ar monomer ion bombardment. These cluster ion yields showed the power law dependence on the cluster size. 相似文献
466.
Three water-soluble arsenic compounds were isolated from the green seaweed Codium fragile. These compounds were identified as 1-glycerophosphoryl-2-hydroxy-3-[5′-deoxy-5′-(dimethylarsinoyl)-β-ribofuranosyloxy]propane (1a), 1′ -(1,2-dihydroxypropyl)-5′ -deoxy-5′ -(dimethylarsinoyl)-β-ribofuranoside (1b), and dimethylarsinic acid ((CH3)2AsOOH). The structures of these compounds were ascertained by 1H NMR spectroscopy. Compounds 1a and 1b accounted for 60 % and dimethylarsinic acid for 5% of the water-soluble arsenic. 相似文献
467.
Takaaki Horaguchi Hiroto Kobayashi Kazuhiro Miyazawa Eietsu Hasegawa Takahachi Shimizu Tsuneo Suzuki Kiyoshi Tanemura 《Journal of heterocyclic chemistry》1990,27(4):935-940
Tetrahydrocyclohepta[cd]benzofurans 7a-e were synthesized by the treatment of ( 5 -oxo-tetrahydro-5H-benzocyclohepten-4-yloxy)acetic acids 5a-e with sodium acetate in acetic anhydride or by heating of their esters 6a-e with sodium hydroxide or sodium hydride in dioxane. The yield of furans 7 decreased as a substituent R of acids 5 or esters 6 was changed from hydrogen to a methyl, ethyl, or isopropyl group. When R was a phenyl group furan 7e was always prepared in good yield. Sodium hydride was a useful base for synthesis of tetrahydrocyclohepta[cd]benzofurans. 相似文献
468.
Mesopores created by platinum nanoparticles in zeolite crystals 总被引:1,自引:0,他引:1
Kato H Minami T Kanazawa T Sasaki Y 《Angewandte Chemie (International ed. in English)》2004,43(10):1251-1254
469.
470.
Motoyuki Matsuo Takaaki Kobayashi Tej Bahadur Singh Makoto Tsurumi Masami Ichikuni 《Hyperfine Interactions》1992,71(1-4):1255-1258
Chemical states of iron have been investigated by57Fe Mössbauer technique for the barks of Japanese cedar collected from urban and mountainous area of Japan. The Mössbauer spectra of all outer bark samples show two overlapping doublets and one sextet ascribable to paramagnetic ferrous, paramagnetic ferric and magnetic iron, respectively, whereas an inner bark sample consists only of the two doublets. The bark sample from urban area shows the higher relative amount of magnetic component and the smaller ferrous to ferric ratio. These features of iron species in the bark sample indicate that the bark sample can supply a more effective indicator of human activities than airborne particles collected directly by evacuation with an air sampler. 相似文献