Two cDNA clones for maize cytosolic glyceraldehyde-3-phosphate dehydrogenase are described. One is about 97% similar in coding capacity to a previously published clone [Brinkmann et al. (1987). J. Mol. Evol. 26, 320-328], while the other shows only 88% similarity. Evidence points toward the three cDNAs being the products of three genes, to be called Gpc1, Gpc2, and Gpc3. When the least similar clone, corresponding to Gpc3, was used to analyze RNA gel blots, anaerobic treatment for 6 hours induced RNA accumulation in the shoots 15.6-fold, while a 1-hour shift from 28 degrees C to 40 degrees C increased accumulation 5.1-fold. Roots had a higher basal level of expression, leading to a 6.0-fold anaerobic induction, and a 2.4-fold heat stress induction. RNA gel blot analysis using the clone corresponding to Gpc2 showed decreased RNA accumulation within 6 hours of anaerobiosis, while analysis with the previously published clone, corresponding to Gpc1, showed a decrease within 24 hours. Neither Gpc1 nor Gpc2 showed heat stress induction, while some other known anaerobic genes did. Through the use of hybrid selection, in vitro translation, and immune precipitation, the relative expression of the three genes is shown. The role of the observed changes in gene expression is discussed in relation to stress physiology.

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Positive Velocity and Position Feedback (PVPF) is a widely used control scheme in lightly damped resonant systems with collocated sensor actuator pairs. The popularity of PVPF is due to the ability to achieve a chosen damping ratio by repositioning the poles of the system. The addition of a necessary tracking controller causes the poles to deviate from the intended location and can be a detriment to the damping achieved. By designing the PVPF and tracking controllers simultaneously, the optimal damping and tracking can be achieved. Simulations show full damping of the first resonant mode whilst also achieving bandwidth greater than the natural frequency of the plant, allowing for high speed scanning with accurate tracking.

Abstract-Positive Velocity and Position Feedback (PVPF)is a widely used control scheme in lightly damped resonant systems with collocated sensor actuator pairs. The popularity of PVPF is due to the ability to achieve a chosen damping ratio by repositioning the poles of the system. The addition of a necessary tracking controller causes the poles to deviate from the intended location and can be a detriment to the damping achieved. By designing the PVPF and tracking controllers simultaneously, the optimal damping and tracking can be achieved. Simulations show full damping of the first resonant mode whilst also achieving bandwidth greater than the natural frequency of the plant, allowing for high speed scanning with accurate tracking.

Abstract.This paper presents a controller design to compensate the effects of time delay in a flexure-based piezoelectric stack driven nanopositioner. The effects of the time delay in flexure nanopositioners is illustrated and identified by means of experimentally obtaining the frequency response of the system. Moreover, a theoretical model which takes into account the dependence between the sampling time and the delay introduced is proposed. The proposed control design methodology not only accommodates for time delay but also ensures the robust stability and allows its application to systems with a larger delay than other schemes proposed previously. Limitations and future work are discussed.