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排序方式: 共有43条查询结果,搜索用时 796 毫秒
31.
Factors influencing enantiomeric fractions of hexabromocyclododecane measured using liquid chromatography/tandem mass spectrometry 总被引:1,自引:0,他引:1
Marvin CH MacInnis G Alaee M Arsenault G Tomy GT 《Rapid communications in mass spectrometry : RCM》2007,21(12):1925-1930
Hexabromocyclododecane (HBCD), the most heavily produced of the cycloaliphatic brominated flame retardants (BFRs), is a mixture of three predominant diastereomers (alpha-, beta-, and gamma-HBCD), each with a corresponding pair of enantiomers. We have investigated the liquid chromatography/mass spectrometry (LC/MS) behaviour of the HBCD enantiomers, and demonstrated that enantiomeric fractions (EFs) calculated using data uncorrected for instrument and/or matrix effects can result in potentially inaccurate EF values. However, use of labelled surrogates effectively corrects for these effects. Experiments with racemic HBCD standards indicate that chromatographic factors, including mobile phase composition and column bleed from chiral stationary phases, may be contributors to variations in the mass spectrometric response of the HBCD enantiomers. 相似文献
32.
Arsenault G Chittim B McAlees A McCrindle R Potter D Tashiro C Yeo B 《Rapid communications in mass spectrometry : RCM》2007,21(6):929-936
This work examines the mass spectra of several environmentally relevant amides, perfluorooctanesulfonamide (FOSA), NMeFOSA, NEtFOSA, and NMe(2)FOSA, under electron ionization conditions. A previous mass spectral study of FOSA and NEtFOSA led the authors to propose possible structures for some of the fragment ions and fragmentation pathways that might explain their formation. In the present communication, further fragment ions are identified for these two compounds and alternative fragmentation pathways proposed. Mass spectral analyses of NMeFOSA and NMe(2)FOSA and of mass-labeled NMeFOSA and NEtFOSA reinforce our conclusions about potential fragmentation pathways for these amides and the fragment ions expected. The mass spectral data presented here will help chemists to identify signals found in a gas chromatographic/mass spectrometric (GC/MS) analysis that stem from these perfluoroalkylsulfonamides. 相似文献
33.
Prashant K. Purohit Mark E. Arsenault Yale Goldman Haim H. Bau 《International Journal of Non》2008,43(10):1056-1063
The rapid development of single molecule experimental techniques in the last two decades has made it possible to accurately measure the force–extension response as well as the transverse fluctuations of individual rod-like macromolecules. This information is used in conjunction with a statistical mechanical model based on the treatment of the molecule as a fluctuating elastic rod to extract its bending and extension moduli. The models most commonly used to interpret the experimental data assume that the magnitude of the Brownian fluctuations are independent of the length of the macromolecule, an assumption that holds only in the asymptotic limit of infinitely long rods, and is violated in most experiments. As an alternative, we present a theoretical treatment of a finite length, fluctuating rod and determine its mechanical behavior by measuring the transverse Brownian fluctuations under the action of large stretching forces. To validate our theory, we have applied our methods to an experiment on short actin filaments whose force–extension relation is difficult to measure, but whose transverse deflections can be captured by current microscopy techniques. An important consequence of the short contour lengths is that the boundary conditions applied in the experiment affect the fluctuations and can no longer be neglected as is commonly done when interpreting data from force–extension measurements. Our theoretical methods account for boundary conditons and can therefore be deployed in conjunction with force–extension measurements to obtain detailed information about the mechanical response of rod-like macromolecules. 相似文献
34.
联苯胺分光光度法测定食盐中碘含量 总被引:2,自引:0,他引:2
基于在盐酸介质中,碘酸钾氧化联苯胺使其显色,提出了光度法测定食盐中微量碘的方法。在40℃的水浴中,当2 mol.L-1盐酸溶液用量为1.00 mL0、.42 g.L-1联苯胺溶液用量为0.80 mL时,方法的线性范围为100~1 400μg.L-1,最大吸收波长在425 nm处,表观摩尔吸光率为1.4×105L.mol-1.cm-1。用于测定加碘食盐中碘含量的测定,回收率在97.5%~101.2%之间,相对标准偏差(n=7)在0.9%~1.9%之间。 相似文献
35.
A formalism equivalent to the one previously introduced by the authors is used to determine the accuracy of a method to transform film-grain noise into signal-independent additive noise. Experimental results for film-grain noise that does not follow the classical square-root law are presented. 相似文献
36.
We further study the action of SL(n+1, C) on the space of finite action solutions of the bidimensional Euclidean CP
n
models. We decompose the space of k-instantons into strata. Each stratum in characterized by an integer m with 0mmin(k, n) which can be calculated from the instanton by purely algebraic means. The k-instantons with m=n are called generic. Their stratum is shown to be dense in the space of k-instantons when kn. The isotropy subgroups for each stratum are identified.
Supported in part by the Natural Sciences and Engineering Research Council of Canada and by the Fonds FCAR pour l'aide et le soutien à la recherche. 相似文献
Résumé Nous poursuivons l'étude de l'action de SL(n+1, C) sur l'espace des solutions à action finie du modèle CP n sur l'espace euclidien bi-dimensionnel. L'espace des k-instantons est décomposé en strates. Chaque strate est caractérisée par un entier m tel que 0 mmin(k, n) et qui peut être calculé à partir de l'instanton par des méthodes purement algébriques. Les k-instantons avec m=n sont dits génériques. Leur strate est dense dans l'espace des k-instantons (lorsque k n). Les sous-groupes d'isotropie de chacune des strates sont identifiés.
Supported in part by the Natural Sciences and Engineering Research Council of Canada and by the Fonds FCAR pour l'aide et le soutien à la recherche. 相似文献
37.
Wang XS Arsenault A Ozin GA Winnik MA Manners I 《Journal of the American Chemical Society》2003,125(42):12686-12687
Stable organometallic cylindrical nanostructures have been prepared by shell cross-linking of PI320-b-PFS53 wormlike micelles in hexane through metal-catalyzed hydrosilylation at 23 degrees C. The cross-linked structures permit the formation of cylindrical ceramic replicas containing size- and separation-tunable arrays of Fe nanoclusters. In addition, microfluidic alignment of the cross-linked cylinders was possible. 相似文献
38.
39.
A simple but effective rotation invariant pattern recognition method based on optical circular sampling of the input pattern is described. The object is decomposed by a set of concentric rings. The distribution of energy between those rings is independent of the orientation of the object and characterizes it sufficiently to allow its classification. A computer generated hologram formed of concentric diffraction grating rings of suitable spatial frequencies may perform the sampling in parallel. In combination with a lens, each ring is then focused to a given position on a CCD detector where the intensity distribution may be found. Translation invariance is added to the system by sampling the intensity of the Fourier transform of the input object in combination with a liquid crystal light valve. A phototypesetter is used to write the hologram whose quality is demonstrated by optical experiments. 相似文献
40.