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21.
A. Gareth Brenton A. Ruth Godfrey 《Journal of the American Society for Mass Spectrometry》2010,21(11):1821-1835
High-resolution mass spectrometry has become ever more accessible with improvements in instrumentation, such as modern FT-ICR
and Orbitrap mass spectrometers. This has resulted in an increase in the number of articles submitted for publication quoting
accurate mass data. There is a plethora of terms related to accurate mass analysis that are in current usage, many employed
incorrectly or inconsistently. This article is based on a set of notes prepared by the authors for research students and staff
in our laboratories as a guide to the correct terminology and basic statistical procedures to apply in relation to mass measurement,
particularly for accurate mass measurement. It elaborates on the editorial by Gross in 1994 regarding the use of accurate
masses for structure confirmation [1]. We have presented and defined the main terms in use with reference to the International
Union of Pure and Applied Chemistry (IUPAC) recommendations for nomenclature and symbolism for mass spectrometry. The correct
use of statistics and treatment of data is illustrated as a guide to new and existing mass spectrometry users with a series
of examples as well as statistical methods to compare different experimental methods and datasets. 相似文献
22.
23.
Godfrey B.B. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(1):71-72
It is well known that a strongly magnetized electron beam propagating in an evacuated conducting pipe can exist in either of two equilibria, one with a shallow potential well and the other with a deep potential well. A Lorentz transformation connecting the two classes of equilibria is derived. Thus, since shallow-potential-well equilibria are known to be stable, the deep-potential-well equilibria must also be. The stability of space charge waves in the two equilibria should follow the same pattern 相似文献
24.
The influence of boundary layers on supersonic inlet flow unstart induced by mass injection 总被引:2,自引:0,他引:2
Hyungrok Do Seong-kyun Im M. Godfrey Mungal Mark A. Cappelli 《Experiments in fluids》2011,51(3):679-691
A transverse jet is injected into a supersonic model inlet flow to induce unstart. Planar laser Rayleigh scattering from condensed
CO2 particles is used to visualize flow dynamics during the unstart process, while in some cases, wall pressure traces are simultaneously
recorded. Studies conducted over a range of inlet configurations reveal that the presence of turbulent wall boundary layers
strongly affect the unstart dynamics. It is found that relatively thick turbulent boundary layers in asymmetric wall boundary
layer conditions prompt the formation of unstart shocks; in symmetric boundary conditions lead to the propagation of pseudo-shocks;
and in both cases facilitate fast inlet unstart, when compared with thin, laminar boundary layers. Incident shockwaves and
associated reflections are found to affect the speed of pressure disturbances. These disturbances, which induce boundary layer
separation, are found to precede the formation of unstart shocks. The results confirm the importance of and need to better
understand shock-boundary layer interactions in inlet unstart dynamics. 相似文献
25.
A transfer-matrix formalism is employed to study optical-phonon transport in a macroscopic continuum model for both periodic and Fibonacci polar-semiconductor superlattices. A phonon bandgap with subband structures is obtained for the periodic superlattices. However, in the Fibonacci superlattices, there is a spectrum trifurcation and self-similarity. The LO phonon localization length is calculated from which we confirm the existence of complete exponential localization of LO phonons. 相似文献
26.
Ronald D. Brown Peter D. Godfrey David A. Winkler 《Journal of Molecular Spectroscopy》1981,89(2):352-355
The microwave spectrum of the hydrogen-bonded HCN dimer was observed over the range 28–93 GHz. Improved values of the spectral parameters B = 1788.214(16) MHz, DJ = 2.582(16) kHz were obtained. The electric dipole moment was found to be 6.0(15) D (2.0(5) × 10?29 cm). 相似文献
27.
Ronald D Brown Peter D Godfrey Burkhard Kleibömer 《Journal of Molecular Spectroscopy》1985,114(2):257-273
An extensive study of the microwave spectrum of cyanamide has been undertaken, the analysis being based in part on semirigidbender calculations by the methods of Bunker and Szalay. Inversion lines of NH2CN, branches and a number of vibrational satellites of the J = 2?1 transition were observed. A two-vibrational-state Hamiltonian was used to fit simultaneously the 0+ and 0? microwave data and yielded rotational constants X, Y, Z, DJ, DJK, d1, HJK as well as the inversion splitting and the μyz-connecting matrix element. Vibrational satellite data of seven isotopic species and infrared frequencies of NH2CN were included in the semirigid bender calculations: The NCN spine is nonlinear by ca. 5° in the equilibrium structure of the molecule. Also, ; <HNH/2 = 60.39° ? 0.1134?2; (? is the inversion angle in rad); fixed. The inclusion of the NC bond flexing was necessary in order to reproduce the observed vibrational satellite patterns of NH2CN, NHDCN, and ND2CN. The barrier to inversion of the amino group is 510 ± 6 cm?1 with minima at ±45.0 ±0.2°. The inversion dipole moment is 0.91 ± 0.02 Debye. 相似文献
28.
Godfrey B. B. Newberger B. S. Taggart K. A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1975,3(4):185-193
The Landau problem in relativistic plasma is considered in detail. It is shown how all modes in the plasma arise through proper treatment of the inverse Laplace transforms without imposition of any external conditions. A correct derivation of the asymptotic behavior of the electric field is included and estimates of the contribution of more rapidly decaying Landau modes are made analytically and are compared with numerical computations. 相似文献
29.
Measurements have been made of the changes in the sensitivity of an outdoor microphone system when it is mounted with a B and K windscreen, type U A 0082. The measurements were made using both dry and wet windscreens in order to determine the magnitude of the change in system sensitivity for measurement conditions consistent with dry and wet weather, respectively.It is concluded that the standard practice of neglecting the effect of the windscreen on the system sensitivity will not appreciably affect the accuracy of traffic-noise measurement. 相似文献
30.
Godfrey Brendan B. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(4):380-383
We investigate the dispersion relation for long wavelength slow Langmuir waves in a relativistic particle beam propagating along a strong magnetic guide field in an evacuated metallic waveguide. For a large class of beam radial profiles, wave phase velocity drops to zero with infinite slope as beam current approaches the space-charge limit. This result is of importance to certain collective ion acceleration proposals. 相似文献