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21.
Fumio Kawamura Masaki TanpoNaoya Miyoshi Mamoru ImadeMasashi Yoshimura Yusuke MoriYasuo Kitaoka Takatomo Sasaki 《Journal of Crystal Growth》2009,311(10):3019-3024
We have discovered a mechanism which can significantly reduce the dislocation density during the growth of GaN single crystals in the Na flux method. The significant reduction of the dislocation density occurs in the later stage of LPE growth, rather than solely at the seed-LPE interface for which we have already reported evidence indicating the presence of bundling dislocations. The two-step dislocation reduction is the key in achieving extremely low dislocation density using this method. 相似文献
22.
The 7-endo Friedel-Crafts cyclization of arylpropyl vinyloxiranes was found to proceed regio- and stereoselectively to afford polyfunctional seven-membered carbocycles in excellent yields. 相似文献
23.
24.
Geometry optimization was performed for the ground states of FeCO, Fe(CO)2, and Fe(CO)3 at various levels of ab initio calculations, and the bond lengths and dissociation energies obtained were in reasonable agreement
with experimental results. The nature of bonding was studied for these molecules using a complete-active-space self-consistent-field
method. From the Mulliken population analysis, it was found that the traditional donation and back donation mechanism is valid
for these molecules, including Fe(CO)3, which has a pyramidal structure.
Received: 27 September 1999 / Accepted: 13 January 2000 / Published online: 19 April 2000 相似文献
25.
Daisuke Nagae Koichiro Asahi Hisanori Miyoshi Kenzi Shimada Akihiro Yoshimi Hideki Ueno Jiro Murata Makoto Uchida Daisuke Kameda Go Kato Shoken Emori Go Kijima Sachiko Oshima Makoto Takemura Takemasa Arai Yoshio Kobayashi Tomohito Haseyama W.D. Schmidt-Ott 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):580
A device that produces a low-energy and largely spin polarized RI beam based on the atomic beam resonance method (RIABR) has been developed. We have performed measurements of stopping and drifting an incoming RI ion beam in a gas chamber, extraction of the ions into a vacuum region, and neutralization of the extracted low-energy ion beam. The drift efficiency of RI ions in a gas and the extraction efficiency at a Laval-type glass nozzle were found to be 0.72±0.04 and 0.033, respectively. The result of the experiment for the neutralization is also discussed. 相似文献
26.
An electronic gas-flow controller system called Advanced Flow Control (AFC), which controls not only carrier gas pressure at the column inlet but also the total gas flow including the split flow, was designed and evaluated. BASIC programming of repetitive analyses of standard mixtures under varied split ratios and pressure programs allowed automated optimization of those conditions for the desired column loading and resolution between adjacent peaks. 相似文献
27.
Usuki H Yamamoto Y Arima J Iwabuchi M Miyoshi S Nitoda T Hatanaka T 《Organic & biomolecular chemistry》2011,9(7):2327-2335
A new S9 family aminopeptidase derived from the actinobacterial thermophile Acidothermus cellulolyticus was cloned and engineered into a transaminopeptidase by site-directed mutagenesis of catalytic Ser(491) into Cys. The engineered biocatalyst, designated aminolysin-A, can catalyze the formation of peptide bonds to give linear homo-oligopeptides, hetero-dipeptides, and cyclic dipeptides using cost-effective substrates in a one-pot reaction. Aminolysin-A can recognize several C-terminal-modified amino acids, including the l- and d-forms, as acyl donors as well as free amines, including amino acids and puromycin aminonucleoside, as acyl acceptors. The absence of amino acid esters prevents the formation of peptides; therefore, the reaction mechanism involves aminolysis and not a reverse reaction of hydrolysis. The aminolysin system will be a beneficial tool for the preparation of structurally diverse peptide mimetics by a simple approach. 相似文献
28.
Novel stable core/shell Fe(3)O(4)@SiO(2)/PAH nanoparticles are synthesized using 15 nm Fe(3)O(4) as the template that is modified with PAH. The resulting nanoparticles can absorb plasmid DNA to mediate gene transfer in cultured HeLa cells. An electrophoretic assay suggests that the Fe(3)O(4)@SiO(2)/PAH nanoparticles protect the plasmid DNA from serum and DNase I degradation. A cell viability assay shows that the Fe(3)O(4)@SiO(2)/PAH nanoparticles exhibit a low cytotoxicity toward endothelial cells. Qualitative analysis of transfection in HeLa cells by nanoparticles carrying a plasmid DNA encoding EGFP demonstrates a fairly high expression level, even in the presence of serum. Thus, Fe(3)O(4)@SiO(2)/PAH nanoparticles are biocompatible and suitable for nonviral delivery, and may find applications in cancer therapy. 相似文献
29.
Ueda M Sugita S Aoi N Sato A Ikeda Y Ito Y Miyoshi T Naito T Miyata O 《Chemical & pharmaceutical bulletin》2011,59(9):1206-1208
The synthetic utility of N-alkoxyimidoyl halides is demonstrated using the palladium-catalyzed cross-coupling reaction. The Sonogashira and Suzuki-Miyaura coupling reactions of N-alkoxyimidoyl bromides produced versatile ketoxime ethers in good to excellent yields. A one-pot reaction of the imidoyl bromides with arylboronic acid and allylmagnesium bromide to produce N-arylamines via Suzuki-Miyaura coupling followed by domino reaction involving sequential addition-eliminative rearrangement-addition reactions was developed. 相似文献
30.
The kinetics and mechanisms of the self-reaction of allyl radicals and the cross-reaction between allyl and propargyl radicals were studied both experimentally and theoretically. The experiments were carried out over the temperature range 295-800 K and the pressure range 20-200 Torr (maintained by He or N(2)). The allyl and propargyl radicals were generated by the pulsed laser photolysis of respective precursors, 1,5-hexadiene and propargyl chloride, and were probed by using a cavity ring-down spectroscopy technique. The temperature-dependent absorption cross sections of the radicals were measured relative to that of the HCO radical. The rate constants have been determined to be k(C(3)H(5) + C(3)H(5)) = 1.40 × 10(-8)T(-0.933) exp(-225/T) cm(3) molecule(-1) s(-1) (Δ log(10)k = ± 0.088) and k(C(3)H(5) + C(3)H(3)) = 1.71 × 10(-7)T(-1.182) exp(-255/T) cm(3) molecule(-1) s(-1) (Δ log(10)k = ± 0.069) with 2σ uncertainty limits. The potential energy surfaces for both reactions were calculated with the CBS-QB3 and CASPT2 quantum chemical methods, and the product channels have been investigated by the steady-state master equation analyses based on the Rice-Ramsperger-Kassel-Marcus theory. The results indicated that the reaction between allyl and propargyl radicals produces five-membered ring compounds in combustion conditions, while the formations of the cyclic species are unlikely in the self-reaction of allyl radicals. The temperature- and pressure-dependent rate constant expressions for the important reaction pathways are presented for kinetic modeling. 相似文献