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991.
The t-Bu-P4 base was found to be an excellent catalyst for activating organozinc reagents and was used to promote the S(N)2' reaction of alpha,beta-unsaturated esters bearing a gamma-chloride using various organozinc reagents: these reactions proceeded in high yields with excellent chemo-and regioselectivity. 相似文献
992.
993.
Ge L Nagai K Gu Z Shimada Y Nishimura H Miyanaga N Izawa Y Mima K Norimatsu T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(18):10402-10406
Low-density tin dioxide (SnO2) is required for radiating monochromatic extreme ultraviolet (EUV) light with low debris and high conversion efficiency from a laser. In this paper, tin dioxide nanoparticle hollow microcapsules were successfully fabricated by a layer-by-layer template technique. The obtained capsules have a rougher surface (30 nm in rms) compared to the freshly prepared polyelectrolyte capsules. Based on the X-ray diffraction (XRD) results, the tin dioxide nanoparticles well maintained their size after they were assembled on the capsules' surfaces. In order to remove the polymer template, a heat treatment was introduced, and after the heat treatment the capsule sizes shrank about 71% (the average size was from 4.9 to 3.5 mum), and the obtained capsules maintained their round shape after water evaporation. The narrowest bandwidth at the 13.5 nm emission in the EUV region was observed when the capsules were irradiated by a CO2 laser with an intensity of 2.9 x 10(10) W/cm (2). 相似文献
994.
A liquid chromatographic tandem mass spectrometric (LC-MS/MS) assay was developed and validated to determine valproic acid in human plasma. The method involved a solid-phase extraction of valproic acid and betamethasone valerate, an internal standard, from plasma and detection using an LC-MS/MS system with electrospray ionization source in negative ion mode. Separation was achieved within 3 min on a non-porous silica column with mobile phase containing ammonium acetate and methanol. Multiple reaction monitoring was utilized for detection monitoring at 142.89-142.89 for valproic acid and 457.21-457.21 for the internal standard. The calibration curve for valproic acid was linear over the range of 0.5-150 microg/mL. The limit of detection was 0.17 microg/mL and the lower limit of quantification was 0.5 microg/mL, when 0.2 mL plasma was used for extraction. The percentage coefficient of validation for accuracy and precision (inter- and intra-day) for this method was less than 9.5% with recovery ranging from 82.3 to 86.9% for valproic acid. 相似文献
995.
Enantiomerically pure methyl Norphos (A), tolyl Norphos (B), CF(3) Norphos (C), methyl Renorphos (D), and tolyl Renorphos (E) were synthesized and used as chiral bisphosphine ligands for the catalyst system, Pd(2)(dba)(3) x CHCl(3)/PhCOOH, in an intramolecular hydroamination of aminoalkynes 15. Among the Norphos series, methyl Norphos (A) was the best ligand for the hydroamination, and the corresponding five- and six-membered nitrogen heterocycles 16 were obtained in high yields with high enantioselectivities. Among the Renorphos series, tolyl Renorphos (E) gave the best result; both methyl Norphos (A) and tolyl Renorphos (E) afforded high yields and high enantioselectivities. NMR investigation using Me-Norphos revealed that this ligand was oxidized gradually in the presence of Pd(2)(dba)(3).CHCl(3) in C(6)D(6) even under the conditions using Ar atmosphere to give Me-Norphos oxide, which prevented the intramolecular hydroamination. On the other hand, Me-Norphos was rather stable in C(6)D(6) in the absence of the palladium catalyst under Ar atmosphere and was not converted to its oxide even after 3 days. The gradual oxidation of ligands (A and E) in the presence of the Pd catalyst is perhaps a reason why 20 mol % of A or E was needed to obtain high yields and high ee's of 16. 相似文献
996.
The chloride effect on the photobleaching process of iodopsin, a chicken red-sensitive cone visual pigment, was studied in detail by time-resolved low-temperature spectroscopy at -40 degrees C to -10 degrees C. Decay-associated difference spectra obtained by kinetic analysis using the singular value decomposition method were composed of spectra of BL-iodopsin, lumiiodopsin, metaiodopsin I, metaiodopsin II and metaiodopsin III, essentially identical to those at room temperature. In each conversion step however, iodopsin was partially regenerated, which is not observed in the bleaching process for other visual pigments or iodopsin at room temperature. Moreover, iodopsin was slowly regenerated from the bleached species. The reverse reactions were completely suppressed by substitution of lyotropic NO(3)(-) for Cl(-), suggesting that Cl(-) binding to iodopsin interferes with light-induced cis-trans isomerization of the chromophore. It is likely that the water molecule hydrating Cl(-) forms the additional hydrogen bond(s), by which the protein conformational change necessary to release this steric hindrance becomes enthalpic. As progress of the bleaching process is a consequence of protein conformational change, it is suppressed at low temperatures, resulting in thermal back-isomerization. 相似文献
997.
998.
999.
1000.
Secondary ion species from plasma-enhanced chemical vapor deposited (PECVD) SiO2 films have been investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Comparative studies of PECVD SiO2 films prepared using a mixture of SiH4/N2O reaction gas at 400 °C with thermally oxidized SiO2 films grown at 900 °C were carried out in the mid-range mass spectra from 95 to 165 amu. Small amounts of ion species containing nitrogen atoms, including Si2O2N+, Si3O2N+and Si3O3N+, were detected in the SiO2 bulk from the PECVD SiO2 films. Furthermore, large amounts of Si3O2N+ and Si2O3N− were found at the interface between silicon and the SiO2 films. Depth analysis showed that the intensity peak shapes of these ion species containing nitrogen atoms at the interface were closely coincident with those of Si3O3+ corrected by subtracting the influence of the SiO2 matrix. The variation in the spectra of these ion species clearly indicates that two types of structures of oxynitride exist for the PECVD SiO2 films in the SiO2 bulk films and at the interface. These are likely produced by the reaction of reactive gas with SiO2 and silicon surfaces where dangling bonds of silicon may exist in the different form. 相似文献