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71.
We have developed a positron microbeam using magnetic lenses based on the commercial scanning electron microscope (SEM). A slow positron beam was generated using a handmade source with 22Na and a solid neon moderator. The beam diameter was 3.9 μm on a target. Two-dimensional image of S parameter was successfully obtained. By introducing a beam pulsing section, positron lifetime measurement beam is also available. 相似文献
72.
Masayuki Yamane Hiroshi Kawazoe Atsuo Yasumori Toshikazu Takahashi 《Journal of Non》1988,100(1-3):506-510
A glass rod of the PbO---K2O---B2O3---SiO2 system having a radial gradient of refractive index has been prepared by the sol-gel process using aqueous solutions of lead acetate and potassium nitrate as the sources for index-modifying cations. A gel prepared by gelatinizing a sol from the mixture of tetramethoxysilane, tetraethoxysilane, and the aqueous solutions of boric acid and lead acetate was placed in an aqueous solution of potassium nitrate to form the concentration gradient of modifier cations by diffusion through the micropores of the gel. The glass rod of about 7 mm in diameter obtained by drying and sintering the gel had a refractive index of parabolic profile changing from the center toward the perimeter with a maximum difference of about 0.04. 相似文献
73.
74.
Regio-isomers, 6A6B, 6A6C, and 6A6D-ditosylates of β-cyclodextrin prepared by the reaction of β-cyclodextrin with tosyl chloride were easily and effectively separated through reversed phase column chromatography and assigned. 相似文献
75.
6A,6X-Dideoxy-6A-phenylthio-6X-[(β-naphthylsulfonyl)oxyl]-β-cyclodextrins (X=G and B) (5 and 6) were prepared together with the other isomers (X=C, D, E, and F) (1–4), isolated by reversed-phase column chromatography, and structurally assigned by use of Taka amylolysis. 相似文献
76.
Daisuke Mori Atsuo Yamada Masaki Azuma Katsumi Suda 《Journal of solid state chemistry》2006,179(3):935-940
Single crystals of the thallium ruthenium pyrochlore have been grown by flux method under high oxygen pressure. The growth conditions were determined by direct observations using in situ powder X-ray diffraction (XRD) method under high pressure and high temperature. The crystals were grown using NaCl-KCl flux at 1350 °C and B2O3 flux at 1150 °C. High growth temperature of 1350 °C for the NaCl-KCl flux caused Pt contamination from the crucible and oxygen deficiency for the crystals obtained. The crystal growth using B2O3 flux proceeded at lower temperature by grain growth with material transfer through B2O3. The crystal obtained was characterized by single-crystal XRD method, and was found to have a stoichiometric composition, Tl2Ru2O7−δ (δ=0), with a structural phase transition around 120 K. The grain growth technique with B2O3 is efficient for high-temperature single-crystal growth under high pressure. 相似文献
77.
78.
Kiyoshi Bannai Takeshi Toru Takeo
ba Toshio Tanaka Noriaki Okamura Kenzo Watanabe Atsuo Hazato Seizi Kurozumi 《Tetrahedron》1986,42(24):6735-6746
Syntheses of several stable PGI2 analogs substituted by halogen atoms(s) at C-5 or(and) C-7 are described. Reaction of protected PGI2 methyl ester (
) with
-chlorosuccinimide gave 5-chloro-Δ6-PGI1 derivative (
), which was transformed into 5-chloro- and 5,7-dichloro-PGI2 [(
) and (
)] by subsequent isomerization or chlorination. Similarly, reaction of
with
-bromosuccinimide gave 5-bromo-Δ6-PGI1 derivative (
), which was further transformed into 7-fluoro-PGI2 (
) by silver fluoride treatment. These halogenated PGI2 analogs were found to be much more stable than PGI2. 相似文献
79.
Atom-centered partial charges which exactly reproduce the lowest several multipoles of a molecule's charge distribution can be obtained in a straightforward and convenient manner from the output of existing electronic structure calculations. The multipole constraint method is demonstrated by a computation of partial charges for the twenty common amino acids. The electron density employed here, derived from a semiempirical MNDO calculation, incorporates Slater-type orbitals which imbue it with the exponential fall-off vital to electronic tunneling calculations. In addition, a procedure based on these charges is described which divides the original electron density into two components, a large component with a simple electrostatic potential, and a much smaller residual whose several lowest multipoles vanish. 相似文献
80.
A Divergent Approach to the Diastereoselective Synthesis of 3,3‐Disubstituted Oxindoles from Atropisomeric N‐Aryl Oxindole Derivatives
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Dr. Atsuo Nakazaki Ayako Mori Prof. Dr. Susumu Kobayashi Prof. Dr. Toshio Nishikawa 《化学:亚洲杂志》2016,11(22):3267-3274
3,3‐Disubstituted oxindoles were divergently synthesized by diastereoselective transformations including nucleophilic addition, alkylation, and cycloaddition using common, axially chiral N‐aryl oxindoles. Notably, high diastereoselectivities (up to >95:5) were observed with ortho‐monosubstituted N‐aryl oxindoles to give various oxindole scaffolds, and facile removal of the p‐(benzyloxy)aryl moiety in axially twisted amides was achieved by a mild, two‐step sequence. 相似文献