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91.
A recently developed rf echo planar imaging method has been modified to rapidly generate spectroscopic information along one in-plane axis and spatial information along the other. The method allows the production of one-dimensional chemical shift images (1D CSIs) in acquisition times of 18 sec or less. A specific phase-encode-reordering algorithm provides convenient manipulation of T2 weighting, yielding partial suppression of short T2 species like muscle water. The method is demonstrated in phantoms and in vivo with 1D CSIs of human brain and limbs. Abnormal fat distribution is demonstrated in the calf of a patient with aggressive fibromatosis. The advantages of short acquisition times obtainable with SIRFEN are offset by limited spectral resolution, suggesting that primary applications will be confined to rapid spatial mapping of major spectral components. 相似文献
92.
A new ultrasonic method — thermoacoustic analysis — is reported for the detection of the added chemical preservatives in branded
milk. The nature of variation and shift in the thermal response of the acoustic parameters specific acoustic impedance, adiabatic
compressibility and Rao’s specific sound velocity for different samples of branded milk as compared to the chemical added
pure milk are explained as due to the presence of chemicals in these branded samples. 相似文献
93.
van Der Lee AM van Druten NJ van Exter MP Woerdman JP Poizat JP Grangier P 《Physical review letters》2000,85(22):4711-4714
We investigate the impact of the Petermann-excess-noise factor K>/=1 on the possibility of intensity noise squeezing of laser light below the standard quantum limit. Using an N-mode model, we show that squeezing is limited to a floor level of 2(K-1) times the shot noise limit. Thus, even a modest Petermann factor significantly impedes squeezing, which becomes impossible when K>/=1.5. This appears as a serious limitation for obtaining sub-shot-noise light from practical semiconductor lasers. We present experimental evidence for our theory. 相似文献
94.
T. C. Lilly 《Applied physics. B, Lasers and optics》2011,104(4):961-968
The continuing advance of laser technology enables a range of broadly applicable, laser-based flow manipulation techniques
relevant to a number of aerospace, basic physics, and microtechnology applications. Theories for laser-molecule interactions
have been under development since the advent of laser technology. Yet, the theories have not been adequately integrated into
kinetic flow solvers. Realizing this integration would greatly enhance the scaling of laser-species interactions beyond the
realm of ultra-cold atomic physics. This goal was realized in the present study. A representative numerical investigation
of laser-based neutral nonpolar molecular flow manipulations was conducted using non-resonant pulsed laser fields. The numerical
tool employed for this study was a specifically modified version of the Direct Simulation Monte Carlo statistical kinetic
solver known as SMILE. Flow steering and collimation was simulated for a nitrogen effluence with a stagnation condition of
1 Pa and 300 K emptying into vacuum. The laser pulses were 250 mJ, 5 ns pulses at a wavelength of 532 nm. Flow modification
mapped out contours which followed the intensity gradient of the laser field, consistent with the use of the induced dipole
gradient force along the field’s radial direction and previously published experiments. 相似文献