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RISS 인기검색어
- 검색키워드
- 저자 : Pengelly, R. S. (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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Short-Term Study on the Effects of Rosemary on Cognitive Function in an Elderly Population
Andrew Pengelly,James Snow,Simon Y. Mills,Andrew Scholey,Keith Wesnes,Leah Reeves Butler 한국식품영양과학회 2012 Journal of medicinal food Vol.15 No.1
Rosemary (Rosmarinus officinalis L.) has traditional reputations that justify investigation for a potential role in reducing widespread cognitive decline in the elderly. A randomized, placebo-controlled, double-blinded, repeated-measures crossover study was conducted to investigate possible acute effects of dried rosemary leaf powder on cognitive performance. Twenty-eight older adults (mean age, 75 years) were tested using the Cognitive Drug Research computerized assessment system 1, 2.5, 4, and 6hours following a placebo and four different doses of rosemary. Doses were counterbalanced, and there was a 7-day washout between visits. There was a biphasic dose-dependent effect in measures of speed of memory: the lowest dose (750mg) of rosemary had a statistically significant beneficial effect compared with placebo (P= .01), whereas the highest dose (6,000mg) had a significant impairing effect (P< .01). There were significant deleterious effects on other measures of cognitive performance, although these were less consistent. Speed of memory is a potentially useful predictor of cognitive function during aging. The positive effect of the dose nearest normal culinary consumption points to the value of further work on effects of low doses over the longer term.
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Highly Efficient Saturated Power Amplifier
Junghwan Moon,Juyeon Lee,Pengelly, R. S.,Baker, R.,Bumman Kim IEEE 2012 IEEE microwave magazine Vol.13 No.1
<P>In this article, a high-efficiency saturated amplifier has been presented. This amplifier takes advantage of the nonlinear output capacitor to shape the voltage waveform. The nonlinear capacitor generates substantial second harmonic voltage with small higher order harmonics. Thus, using √2 times larger fundamental load and the proper second harmonic termination, the resultant voltage waveform can be half-sinusoidal. For high efficiency, the PA should be driven by the large input power. Therefore, the current of the PA is bifurcated, resulting in the quasirectangular current shape. The resultant output waveforms are similar to those of class-F<SUP>1</SUP> amplifiers, whose waveforms are optimal for high efficiencies. Based on harmonic source/ load-pull simulation, the saturated amplifier has been designed using Cree's GaN HEMT CGH40006P packaged model. The matching networks for the input and output were optimized using the Momentum simulator. The implemented amplifier delivered a PAE of 80.1% at 3.475 GHz. The simulation and measurement results verify that the saturated amplifier is suitable for a high-efficiency PA over a relatively high frequency band.</P>
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