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排序方式: 共有121条查询结果,搜索用时 15 毫秒
91.
Measurement of multilamellar onion dimensions under shear using frequency domain pulsed gradient NMR
We present a simple method by which the dimensions of shear-induced multilamellar vesicles (MLVs), also known as onions, can be measured during the shearing process itself. This approach is based on the use of a closely spaced train of magnetic field gradient pulses applied during a CPMG echo sequence. The CPMG train compensates flow effects while the frequency-dependence of apparent diffusion can reveal the onion size. We present here a simple phenomenological model for restricted diffusion in multilamellar vesicles, which may be used to interpret the resulting diffusion spectrum. We demonstrate this approach with MLVs formed from the lamellar phase of sodium dodecyl sulfate (SDS) in water and octanol. 相似文献
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Robinson JN Coy A Dykstra R Eccles CD Hunter MW Callaghan PT 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2006,182(2):343-347
We demonstrate the first two-dimensional correlation NMR (COSY) spectra obtained at ultra low frequencies (ULF) using the Earth's magnetic field. Using a specially developed spectrometer with multiple audio-frequency pulses under controlled pulse phase, we observe magnetisation transfer arising from heteronuclear J-couplings in trifluoroethanol and para-difluorobenzene. The 2D COSY spectra exhibit all diagonal and off-diagonal multiplets consistent with known J-couplings in these molecules. 相似文献
96.
Lesson study (LS) is a form of professional development, with a strong foundation in mathematics education, based on teachers collaborating to design lesso 相似文献
97.
The relationship between measured vibrato characteristics and perception in Western operatic singing
Patricia Howes Jean Callaghan Pamela Davis Dianna Kenny William Thorpe 《Journal of voice》2004,18(2):216-230
This study examined the association between acoustic and perceptual data related to vibrato in Western operatic singing using recordings of performances by internationally famous opera singers. Three related studies were conducted. Study 1 used commercial recordings of the same five singers and the same cadenza examined by Siegwart and Scherer(1), measured vibrato rate and extent in each singer's performance of the cadenza and tested possible associations between these vibrato attributes and judges' preference for singers. Studies 2 and 3, using recordings of different internationally famous singers and a different cadenza, measured vibrato onset, rate, and extent in each singer's performance of the cadenza, required judges to rank the singers in order of personal preference, to identify the emotion expressed, and to assess the degree of success in communicating emotion achieved by the singer. The findings showed that the perception of the singers' vibrato did not always agree with acoustic measurements. However, a comparison of the acoustic measurements with the preference and emotion judgments suggest that some elements of vibrato may affect listeners' perception of the voice, their preference for a particular singer, and assist the communication of emotion between singer and audience. 相似文献
98.
P. T. Callaghan A. Coy R. Dykstra C. D. Eccles M. E. Halse M. W. Hunter O. R. Mercier J. N. Robinson 《Applied magnetic resonance》2007,32(1-2):63-74
We review here two decades of development of Earth's field nuclear magnetic resonance (NMR), starting with the first demonstration
of resonant refocusing and the generation of spin echoes, the first measurement of diffusion using Earth's field NMR, and
its application to Antarctic research, the adaptation of the apparatus to allow its use indoors, in a conventional laboratory
setting, and finally, the construction of a flexible laboratory-based Earth's field NMR system capable of not only a range
of relaxation and spectroscopy applications but also the straightforward demonstration of NMR Imaging.
Authors' address: Paul T. Callaghan, MacDiarmid Institute, Victoria University of Wellington, PO Box 600, Wellington, New
Zealand 相似文献
99.
P. T. Callaghan P. J. Back D. H. Chaplin H. R. Foster G. V. H. Wilson 《Hyperfine Interactions》1985,22(1-4):39-45
A novel extension of the Single or Adiabatic Fast Passage NMR/ON technique is described. Its principal advantages in extracting the mode magnitudes and distribution widths of weak nuclear electric quadrupole splittings much less than the magnetic inhomogeneous broadening are its simplicity and generality requiring no assumptions on the degree of adiabaticity of the nuclear spin motion during sweep through the quadrupolar split subresonances. The technique is applied to a concentrated single crystal sample of60CoFe which failed to yield a well resolved mid passage signal to conventional single passage NMR/ON. The result is an asymmetric frequency distribution of quadrupole frequencies with a mode value of P=3e2qQ/4I (2I-1)=+4.5 ±1.0 kHz and half maxima of +2.5 kHz and +7.0 kHz. 相似文献
100.