1,721,073 research outputs found
Hybrid adaptive control based on the characteristics of CNC end milling
No full textIn this paper, hybrid adaptive control algorithm that controls feedrate is proposed to regulate spindle current. For this purpose, variation of steady state spindle current, time constant and time delay were examined through experiments based on step end milling under various cutting condition. The developed hybrid adaptive control algorithm is composed of adjustable proportional feedback control (adjustable P control), fine control carries out detailed control, and entry feedrate control reduces the peak current produced when a tool makes contact with a workpiece. The adjustable P control was verified through comparisons between calculate P gains and experimentally obtained P gains. The hybrid adaptive control algorithm was applied to various cutting conditions and it showed global stability as well as excellent applicability behavior. (C) 2002 Published by Elsevier Science Ltd
Time to pay attention: attentional performance time-stamped prefrontal cholinergic activation, diurnality, and performance
No full textAlthough the impairments in cognitive performance that result from shifting or disrupting daily rhythms have been demonstrated, the neuronal mechanisms that optimize fixed-time daily performance are poorly understood. We previously demonstrated that daily practice of a sustained attention task (SAT) evokes a diurnal activity pattern in rats. Here, we report that SAT practice at a fixed time produced practice time-stamped increases in prefrontal cholinergic neurotransmission that persisted after SAT practice was terminated and in a different environment. SATtime-stamped cholinergic activation occurred regardless of whether the SAT was practiced during the light or dark phase or in constant-light conditions. In contrast, prior daily practice of an operant schedule of reinforcement, albeit generating more rewards and lever presses per session than the SAT, neither activated the cholinergic system nor affected the animals' nocturnal activity pattern. Likewise, food-restricted animals exhibited strong food anticipatory activity (FAA) and attenuated activity during the dark phase but FAA was not associated with increases in prefrontal cholinergic activity. Removal of cholinergic neurons impaired SAT performance and facilitated the reemergence of nocturnality. Shifting SAT practice away from a fixed time resulted in significantly lower performance. In conclusion, these experiments demonstrated that fixed-time, daily practice of a task assessing attention generates a precisely practice time-stamped activation of the cortical cholinergic input system. Time-stamped cholinergic activation benefits fixed time performance and, if practiced during the light phase, contributes to a diurnal activity patter
Prior daily practice of a sustained attention task during the light phase evokes a diurnal behavioral activity pattern and a task time-synchronized increase in prefrontal cholinergic neurotransmission
No full textWe recently observed that daily practice of a sustained attention task (SAT) during the light phase of the light/dark cycle causes a stable, entrained, diurnal behavioral activity pattern (Gritton et al. 2009). As SAT performance increases cortical acetylcholine (ACh) release, this experiment assessed the influence of the prefrontal ACh on SAT practice-induced diurnality. Circadian behavioral activity was recorded to verify the SAT effect on circadian activity, and prefrontal ACh release was measured, using microdialysis, 3 days following the last practice session. SAT practice occurred either during the light phase [ZT4] or during the dark phase, [ZT16]. A control group practiced a daily fixed interval 9 s [FI-9] schedule of reinforcement at ZT4. A second control group was handled at randomly selected times but was neither water-deprived nor performed a task [NP]. Dialysates were collected every 15 min for 180 min total, beginning 90 min before the prior onset of task practice and again during the equivalent time period twelve hours later. For all animals, ACh release was higher during the dark phase when compared with the light period. Furthermore, in previously SAT-performing animals, ACh levels increased for 45 min at ZT4 and ZT16. Collectively these results indicate that the diurnal activity pattern that results from SAT practice during the light phase is not mediated via global alterations in the circadian regulation of ACh release. However, prior practice of the SAT established a stable increase in ACh release that lasted as long as the prior SAT sessions, and this task time-synchronized increase in prefrontal cholinergic activity may contribute to the induction or maintenance of diurnality in ZT4 animals. Future research is testing whether removal of cholinergic neurons interferes with ZT4 SAT practice-induced diurnality. Furthermore, it will be important to determine the time point after cessation of SAT practice at which ZT4 animals reverse to a nocturnal pattern and whether this coincides with the loss of task time-synchronized cholinergic activity. This research provides new insights in understanding cognitive work-induced shifts in circadian rhythms, the cause and role of circadian abnormalities in neuropsychiatric disorders, and it eventually will inform the development of treatments of such disorders
Time to pay attention: Attentional performance time-stamped prefrontal cholinergic activation, diurnality, and performance
No full textAlthough the impairments in cognitive performance that result from shifting or disrupting daily rhythms have been demonstrated, the neuronal mechanisms that optimize fixed-time daily performance are poorly understood. We previously demonstrated that daily practice of a sustained attention task (SAT) evokes a diurnal activity pattern in rats. Here, we report that SAT practice at a fixed time produced practice time-stamped increases in prefrontal cholinergic neurotransmission that persisted after SAT practice was terminated and in a different environment. SATtime-stamped cholinergic activation occurred regardless of whether the SAT was practiced during the light or dark phase or in constant-light conditions. In contrast, prior daily practice of an operant schedule of reinforcement, albeit generating more rewards and lever presses per session than the SAT, neither activated the cholinergic system nor affected the animals' nocturnal activity pattern. Likewise, food-restricted animals exhibited strong food anticipatory activity (FAA) and attenuated activity during the dark phase but FAA was not associated with increases in prefrontal cholinergic activity. Removal of cholinergic neurons impaired SAT performance and facilitated the reemergence of nocturnality. Shifting SAT practice away from a fixed time resulted in significantly lower performance. In conclusion, these experiments demonstrated that fixed-time, daily practice of a task assessing attention generates a precisely practice time-stamped activation of the cortical cholinergic input system. Time-stamped cholinergic activation benefits fixed time performance and, if practiced during the light phase, contributes to a diurnal activity patter
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Characterization of halotolerant rhizobia isolated from root nodules of Canavalia rosea from seaside areas.
No full textEfficacy and Safety of Barnidipine Compared with Felodipine in the Treatment of Hypertension in Chinese Patients
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