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31.
A flow analysis system involving the on-line configuration of an anion-exchange column has been examined to enrich and determine trace concentrations of zirconium of several ppm to hundred ppm levels in silicate rocks and minerals. About 100 mg of sample is decomposed by fusion with a mixture of boric acid and lithium carbonate and taken up with 1M hydrochloric acid to a total of 100 ml. Depending upon the concentration of zirconium, either a 1- or 4-ml aliquot is introduced into an aqueous carrier stream, merged with sulphuric acid and passed through a small volume anion-exchange column. The enriched zirconium is then back eluted with hydrochloric acid, colour-developed with Arsenazo III, and detected spectrophotometrically at 665 nm. 相似文献
32.
Novel neutral glycosphingolipids isolated from the plerocercoids of a tapeworm, Spirometra erinacei, may be expected to be involved in host-parasite interactions. We have synthesized this glycosphingolipid analogue containing 2-branched fatty alkyl residue in place of ceramide. Glycosylation of nonreducing-end trisaccharide derivative 15 with the reducing-end disaccharide derivative 17 in the presence of trimethylsilyl triflate (TMSOTf) gave the desired oligosaccharide derivative in good yield. The fully per-O-acylated 2-(trimethylsilyl)ethyl glycoside 19 was converted to glycosylimidate 20, which was condensed with 2-(tetradecyl)hexadecanol and subsequently deacylated to give the target glycosphingolipid analogue 22. 相似文献
33.
A total of 13 samples of diamond separates studied so far, all contain excess 244Pu fission xenon. On the other hand, none of the SiC separates contains excess 244Pu fission xenon, while 5 out of 10 samples of graphite separates studied so far contain excess 244Pu fission xenon. 相似文献
34.
Re-calculation of the244Pu ages of lunar rocks 10057 and 12013 indicates that, while the former started to retain its xenon (4,189 ?74 +45 ) million years ago, the latter was formed at a much later time, after the extinct nuclide244Pu had essentially decayed away. 相似文献
35.
The intensities of the ΔM = ± 1 component of the 7fo→ 5D2 transition in D3 complexes containing the [ EuO9] cluster, and of other d-d or f-f transitions in D3 complexes with the yz- and xz-components of the electric quadrupole as the leading moment, are found to be dependent upon the polarizability anisotropy of the ligands. The expectation is supported by determinations of the single-crystal absorption intensities of Na3 [Eu(diglycollate)3]·2NaClO4·6H2O and [Eu(H2O)9] (C2H5SO4)3. 相似文献
36.
Takakazu Yamamoto Abla Mahmut Masahiro Abe Shin‐Ichi Kuroda Tatsuya Imase Shintaro Sasaki 《Journal of Polymer Science.Polymer Physics》2005,43(16):2219-2224
An alternating copolymer, Copoly‐1 , of thiophene and N‐(phenylethynyl)pyrrole was prepared by palladium‐catalyzed polycondensation. Powder X‐ray diffraction (XRD) analysis indicated that Copoly‐1 formed a stacked packing structure with doubly‐running polymer main chains. Optical data support the molecular and packing structures of Copoly‐1 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2219–2224, 2005 相似文献
37.
Dialkoxydichlorosilanes ((RO)2SiCl2, R = alkyl) react almost completely with interlayer silanol groups in a layered silicate octosilicate to create a new crystalline silicate structure consisting of new five-membered rings arranged regularly on both sides of the silicate layers. The introduction of dialkoxysilyl groups to the interlamellar region of layered silicates with regular reaction sites provides a new methodology for the design and construction of novel crystalline silicate frameworks by a soft chemical route. 相似文献
38.
We report the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the accurate measurement of mass of low molecular weight compounds (smaller than 1500 Da), a linear peptide, two types of cyclic depsipeptides, a polyhydroxy-macrocyclic lactone, and two prenylated flavonoids, with delayed extraction in the reflector mode. The performance of the MALDI-TOF instrument was less than those of fast atom bombardment and Fourier-transform ion cyclotron resonance mass spectrometry instruments and insufficient to give acceptable accuracy for literature reporting. Nevertheless, when combined with NMR spectrometry and/or amino acid analysis to give information on the numbers of carbon atoms and index of hydrogen deficiency, MALDI was useful for determination of the elemental composition of the low molecular weight compounds available in small quantities. 相似文献
39.
Summary The partial resolution of some drug enantiomers by counter-current extraction in an aqueous two-phase system using bovine serum albumin (BSA) or ovomucoid (OVM) as chiral discriminator is described. The phase system was prepared with dextran 40, polyethylene glycol and a protein. Ofloxacin (OFLX) enantiomer was well recognized by the BSA system, whereas the enantiomers of carvedilol (-blocker) and DG-5128 (a new oral hypoglycaemic drug) were hardly recognized by the OVM system. The distribution coefficients of (S)-, (R)- and rac-OFLX varied with pH. Good enantioselectivity for OFLX was obtained at relatively high pH ( pH 9). The crude optically enriched OFLX enantiomers were extracted from the aqueous fractions and finally purified by thin-layer chromatography. 相似文献
40.
Y. Ohsumi T. Higashimura S. Okamura R. Chujo T. Kuroda 《Journal of polymer science. Part A, Polymer chemistry》1967,5(12):3009-3016
The di-isotacticity of poly(methylpropenyl ether) obtained by the cationic polymerization has been studied by NMR spectra. The NMR spectra of β-methyl protons of the polymer are decoupled from the β-methine proton spectra to determine the di-isotactic fraction in a polymer. The signals of β-methyl protons at 8.78 and 8.89 τ are estimated as spectra based on threo- and erythro-di-isotactic diads, respectively. With BF3·O(C2H5)2 as a catalyst, the trans monomer yields a crystalline polymer and its structure is threo-di-isotactic. Otherwise, cis monomer produces an amorphous polymer, and it is a mixture of threo- and erythro-di-isotactic structure. From these results, it is concluded that the double bond in trans monomer is opened exclusively in the cis type, and in cis monomer cis- and trans-openings take place at almost the same rate. 相似文献