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991.
Detailed analyses were carried out on 3 specimens of serum to compare the precision and accuracy of 4 typical chemical methods for magnesium, and to determine whether wet-ashing or deprotemisation with trichloroacetic or acetic acid affected the results. Two ammonium phosphate precipitation methods involving spectrophotometry of phosphate in the precipitate, a spectrophotometric method with Titan Yellow and a visual EDTA titration method were studied. The analyses were designed to reveal systematic errors and the results were analysed statistically.One ammonium phosphate method on untreated and wet-ashed samples and the EDTA method gave concordant and relatively precise results, which were used to estimate the true values. On this basis, another ammonium phosphate method involving overnight precipitation, gave consistently high results. The Titan Yellow method gave large random errors, particularly when proteins were not removed. The preliminary treatment of the samples did not appear to have any consistent effect. 相似文献
992.
Duncan S. Holmes John A. Sherringham Ulrich C. Dyer Simon T. Russell John A. Robinson 《Helvetica chimica acta》1990,73(2):239-259
As a direct test of the Cane-Westley hypothesis concerning the mode of assembly of ether rings in the polyether class of ionophore antibiotics, we describe experiments culminating in the synthesis of three putative intermediates on the monensin biosynthetic pathway and incorporation experiments with these materials and the monensin-producing organism Streptomyces cinnamonensis. The putative intermediates synthesised include the trienes [21-3H]- 7 and [13-3H]- 10 , and the diene [9-3H]- 11 . The results of the incorporation experiments conducted with whole cell cultures suggest that [13-3H]- 10 and [21-3H]- 7 are unable to cross the intact cell membrane of S. cinnamonensis, whereas diene [9-3H]- 11 can gain entry to the cellular interior, but is then degraded efficiently, most likely by a pathway closely related to β-oxidation, without being specifically incorporated into the antibiotic. 相似文献
993.
Xianfeng Li Anna Katrin Szardenings Christopher P. Holmes Liang Wang Ashok Bhandari Lihong Shi Marc Navre Larry Jang J. Russell Grove 《Tetrahedron letters》2006,47(1):19-22
A new method for the synthesis of functionalized biaryl α-ketophosphonic acids has been developed. The key step involves the use of sodium bromobenzoyl phosphonates to react with polymer-bound boronic acids via microwave-assisted aqueous Suzuki coupling. This approach provides rapid access to a wide range of diverse biaryl analogues containing an α-ketophosphonic acid moiety. 相似文献
994.
A new experimental apparatus for porous track etched membrane production has been designed, tested and installed near the core of the IEA-R1 nuclear reactor at IPEN-Sao Paulo. The thermal neutron flux close to the centre of the reactor core has been used to produce fission fragments from uranium sample which was deposited on a rod located at the centre of an evacuated aluminium chamber. 相似文献
995.
The synthesis of a new generation of high-capacity oxidation-resistant ion-exchange resins and membranes is described which are sulfonic acid polyelectrolytes prepared from high molecular weight poly-α,β,β-trifluorostyrene. The difficult sulfonation of poly-α,β,β-trifluorostyrene is discussed in terms of the finding that this sulfonation must be effected upon an aromatic ring possessing a meta-directing substituent group. The oxidative stability of these new types of perfluoroalkyl aromatic sulfonic acid polyelectrolytes is both demonstrated and described with comparisons to their polystyrenesulfonic acid homologs. The difference in their oxidation–depolymerization stabilities is described in terms of benzylic carbon substituents. 相似文献
996.
We used a continuum model to investigate the isochoric radial expansion of a right circular cylindrical specimen composed of a nematic elastomer that is crosslinked in a uniaxial state and then annealed. Numerical solutions show that, above a certain radial expansion, the material has a definitive energetic preference for a state involving a disclination of strength +1 along the cylinder axis. Surrounding such a disclination is a core with radial dimension on the order of 10?2 μm, which coincides with observations in conventional liquid‐crystal melts. Examination of the normal‐stress differences indicates that the first of these differences depends nonmonotically on the extent of radial expansion and possesses a local minimum at the point where a disclination becomes energetically preferred. This suggests a practical experimental method for testing the predictions of our model. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2098–2106, 2002 相似文献
997.
A new ROMP-derived scavenging reagent, oligomeric phosphonyl dichloride (OPC), with high-load and selectivity is reported. This reagent can be readily generated via the ROM polymerization of bicyclo[2.2.1]hept-5-en-2-ylphosphonic dichloride, which is conveniently assembled from the Diels-Alder reaction of cyclopentadiene and vinyl phosphonic dichloride. The OPC has been exploited in the rapid, efficient scavenging of primary and secondary amines that are present in excess following a common benzoylation event at room temperature (30-60 min) or under microwave conditions in shorter duration (<5 min). 相似文献
998.
The vapor phase absorption spectra of PF3, PF2Cl, PFCl2, and PCl3 are reported in the vacuum ultraviolet spectral region 2400—1200 A. These results are compared with information obtained from photoelectron spectra. A brief discussion of the spectra in terms of analogous absorption regions and results from CNDO/2 calculations are given. 相似文献
999.
D.K. Russell 《Chemical physics letters》1984,108(6):562-564
A method is proposed for the detection of low-frequency spectroscopic transition in gaseous molecular ions by monitoring the motion induced by inhomogeneous fields at the sum frequency of harmonic motion in an ion trap and the transition frequency. Numerical examples are given. 相似文献
1000.
Molecular integral formulas and corresponding computational algorithms are developed for the relativistic spin-orbit and core potential operators that are obtained from atomic relativistic calculations by means of the effective core potential procedure. Much use is made of earlier work on core potential integrals by McMurchie and Davidson. The resulting computer code has been made part of the ARGOS (Argonne, Ohio State) program from the C?OLUMBUS suite of programs, which computes the needed integrals over symmetry-adapted combinations of generally contacted Gaussian atomic orbitals. 相似文献