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31.
Absorption of niacin from the rumen was tested in vivo using a buffer solution that contained either nicotinic acid or nicotinamide. The experimental design was a 3 X 3 Latin square with three midlactation, ruminally cannulated Holstein cows. Orthogonal comparisons were control versus niacin and nicotinic acid versus nicotinamide. Nicotinamide was more rapidly absorbed from the rumen than nicotinic acid; this may have been caused by differences in the dissociation constants of the compounds. The effects that differential absorption may have on ruminal fermentation and animal metabolism require further study. 相似文献
32.
Siddiqui O.F. Erickson S.J. Eleftheriades G.V. Mojahedi M. 《Microwave Theory and Techniques》2004,52(5):1449-1454
We have simulated and constructed a one-dimensional metamaterial composed of a periodically loaded transmission line that exhibits both negative and positive group velocities in a band of effective negative index of refraction. The negative group velocity or, equivalently, the negative group delay, is demonstrated theoretically and experimentally in the time domain using modulated Gaussian pulses. Due to this negative delay, we can show an output pulse peak emerging from the loaded transmission line prior to the input peak entering the line, i.e., the output pulse precedes the input pulse. The fact that this surprising behavior does not violate the requirements of relativistic causality is illustrated with time-domain simulations, which show that discontinuities in the pulse waveforms are traveling at exactly the speed of light in vacuum. The pulse-reshaping mechanism underlying this behavior is also illustrated using time-domain simulations. 相似文献
33.
David R. Vernon Paul A. Erickson Chang-Hsien Liao Jon Hsu Hong-Yue Tang 《International Journal of Hydrogen Energy》2009
Hydrogen can be produced via steam reformation of many feedstocks. External heat sources provide the thermal energy required by the endothermic steam reformation reactions. Temperature control of the steam reformation reactor is critical to reactor performance and catalyst life. Closed-loop control systems are typically used to modulate the heat input rate based on a comparison between a set point temperature and a temperature measurement. The location of the temperature sensor relative to the heat input location is a choice made during reactor design that can have significant impact on reactor temperature control. 相似文献
34.
Kurt Kornbluth Zach McCaffrey Paul A. Erickson 《International Journal of Hydrogen Energy》2009,34(22):9248-9257
A 0.745 L 2-cylinder spark-ignition engine was operated with compressed natural gas and with simulated landfill gas (60% CH4 and 40% CO2 by volume) containing hydrogen concentrations of 0, 30%, 40%, and 50% (by volume of the CH4 in the fuel) at constant rpm. This empirical data was compared with predictions from three existing semi-empirical engine models, using a first-law-based finite heat release model to correlate measured in-cylinder pressure data and burn rate for each fuel mixture. Of the three models only a two zone model incorporating thermal and prompt NOx came within 25% of predicting the measured NOx emissions. 相似文献
35.
Erickson BE 《Environmental science & technology》2002,36(21):408A-409A
36.
Erickson BE 《Analytical chemistry》2000,72(9):353A-357A
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