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101.
102.
The combination of vanadium-oxo compounds (3 or 4) with a lipase produced the regio- and enantioconvergent transformation of racemic allyl alcohols (1 or 2) into optically active allyl esters. In this system, the vanadium compounds catalyzed the continuous racemization of the alcohols along with the transposition of the hydroxyl group, while the lipase effected the chemo- and enantioselective esterification to achieve the dynamic kinetic resolution. 相似文献
103.
Yoshinao Kumagai Yuuki Enatsu Masanari Ishizuki Yuki Kubota Jumpei Tajima Toru Nagashima Hisashi Murakami Kazuya Takada Akinori Koukitu 《Journal of Crystal Growth》2010,312(18):2530-2536
Void formation at the interface between thick AlN layers and (0 0 0 1) sapphire substrates was investigated to form a predefined separation point of the thick AlN layers for the preparation of freestanding AlN substrates by hydride vapor phase epitaxy (HVPE). By heating 50–200 nm thick intermediate AlN layers above 1400 °C in a gas flow containing H2 and NH3, voids were formed beneath the AlN layers by the decomposition reaction of sapphire with hydrogen diffusing to the interface. The volume of the sapphire decomposed at the interface increased as the temperature and time of the heat treatment was increased and as the thickness of the AlN layer decreased. Thick AlN layers subsequently grown at 1450 °C after the formation of voids beneath the intermediate AlN layer with a thickness of 100 nm or above self-separated from the sapphire substrates during post-growth cooling with the aid of voids. The 79 μm thick freestanding AlN substrate obtained using a 200 nm thick intermediate AlN layer had a flat surface with no pits, high optical transparency at wavelengths above 208.1 nm, and a dislocation density of 1.5×108 cm−2. 相似文献
104.
105.
Yuuki Hirayama Kentaro Yamaguchi Shigeru Sakamoto Michiko Iwamura 《Tetrahedron letters》2005,46(6):1027-1030
A new AB2 type building block for synthesis of dendritic compounds is made starting from Michael addition of 2 equiv of 3-hydroxyacetophenone to acrylate, followed by decarboxylation and deprotection of either carboxyl or hydroxyl protecting groups. [G1]-[G4] dendrons and [G2] dendrimer were synthesized by the reiterative [hydrogenolysis then DCC/DPTS coupling] sequence using a combination of convergent and divergent growth methods. 相似文献
106.
Vinyl Grignard reagents reacted with cyclic ethers in the presence of a nickel catalyst giving rise to 2:1 coupling products 1 regioselectively. When chlorosilanes were used instead of cyclic ethers, 2:2 component coupling products 6 were obtained. A plausible reaction pathway via 1,3-butadiene-nickel complex and (2-butene-1,4-diyl)magnesium was proposed. 相似文献
107.
108.
Junya Kobayashi Motoo Kinoshita Jun-ichi Kita Katsumi Yoshino 《International Journal of Infrared and Millimeter Waves》1996,17(7):1149-1163
Experimental infrared modulator elements have been fabricated utilizing the transient light scattering effect of ferroelectric liquid crystal with asymmetric waveform voltage drive. The new elements perform 80% modulation degrees at the 632.8nm. We have also achieved 30% modulation degrees in the 4 to 5µ m region where the strongest CO2 absorption bands exist. A new type of analyzer which monitors ambient air quality has been developed. This analyzer uses non-dispersive infrared absorption method and composes of a double-beam, a single detector and a pair of liquid crystal light modulator as the IR chopper. The detection has achieved 10ppm noise equivalent concentration. 相似文献
109.
Rui UmedaTakashi Nishimura Kenta KaibaToshimasa Tanaka Yuuki TakahashiYutaka Nishiyama 《Tetrahedron》2011,67(38):7217-7221
It was found that rhenium complex was an efficient catalyst for the acylative cleavage of C-O bond of ethers with acyl chlorides. When acyclic ethers were allowed to react with acyl chlorides in the presence of a catalytic amount of ReBr(CO)5, acylative cleavage of C-O bond of acyclic ethers smoothly proceeded to give the corresponding esters in moderate to good yields. Similarly, cyclic ethers were acylative cleaved by acyl chlorides to give the corresponding chloro substituted esters in good yields by the use of Re2O7 catalyst. 相似文献
110.
Malicka E Sitko R Zawisza B Heimann J Kajewski D Kita A 《Analytical and bioanalytical chemistry》2011,399(9):3285-3292
The paper presents possibilities and difficulties in nondestructive analysis of small multielement single crystals performed
by means of X-ray spectrometry techniques: micro-X-ray fluorescence spectrometry (μ-XRF), energy-dispersive electron probe
microanalysis (ED-EPMA), and X-ray photoelectron spectroscopy (XPS). The capability of the X-ray spectroscopy techniques in
elemental analysis is demonstrated with the single crystals of selenide spinels of the general formula M
x
N
y
Cr
z
Se4 (M+2 and N+3 are, for example, Zn+2, V+3, Ga+3, Cd+2, In+3, and Sb+3). The results of the nondestructive analyses (μ-XRF, ED-EPMA, and XPS) are compared with those obtained by inductively coupled
plasma optical emission spectrometry (ICP-OES) and wavelength-dispersive X-ray spectrometry (WDXRF) following sample digestion.
The present study shows satisfactory agreement between the results of μ-XRF analysis performed using the standardless fundamental
parameter method and the results obtained with the WDXRF and ICP-OES analyses. If the measured single crystal is precisely
positioned, the difference between μ-XRF and wet analysis (WDXRF and ICP-OES) does not exceed 5% rel. The reliable results
of ED-EPMA can be obtained only if the measured area is sufficiently large, i.e., of 200 × 300 μm. Even if this condition
is fulfilled, the relative difference between the ED-EPMA and the wet analysis may reach 10% rel. In case of the XPS analysis,
the accuracy of results depends on the proper preparation of the sample surface. It should be free of contamination that can
be obtained by scraping in situ in ultrahigh vacuum. The ion etching, commonly used for cleaning the surface, leads to preferential
sputtering; therefore, the reliable results cannot be obtained. 相似文献