The Experts below are selected from a list of 108348 Experts worldwide ranked by ideXlab platform
Nagendra Krishnapura - One of the best experts on this subject based on the ideXlab platform.
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VLSI Design - Tutorial T6A: Pedagogy of Negative Feedback Circuits
2014 27th International Conference on VLSI Design and 2014 13th International Conference on Embedded Systems, 2014Co-Authors: Nagendra KrishnapuraAbstract:Summary form only given, as follws. This tutorial presents an introduction to Negative Feedback circuits using an integrator as the central element instead of a high gain amplifier as is normally done. It is shown that it is easier to make a connections to our intuitive notion of Negative Feedback in the time domain than in the frequency domain. It is also shown that certain aspects of Negative Feedback systems that they have a nonzero time constant(finite bandwidth), that delay can lead to instability, and that Negative Feedback systems can be stabilized by slowing them down become immediately clear with this approach. It is also shown that the opamp and the phase locked loop can be synthesized from the prototype Negative Feedback system using an integrator to continuously drive the output until the error between the desired and actual outputs becomes zero. Realizing such a Negative Feedback amplifier using real components and striving to improve its performance leads to different opamp topologies. Attempting to realize a frequency multiplier and improving its performance leads to typeI and typeII Feedback loops. The synthesis based approach from a common foundation helps one to easily make connections between different Negative Feedback circuits.
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introducing Negative Feedback with an integrator as the central element
International Symposium on Circuits and Systems, 2012Co-Authors: Nagendra KrishnapuraAbstract:Negative Feedback is introduced using an integrator as the central element by making intuitive connections with the way we sense the difference between desired and actual values and continuously adjust the latter so that it reaches the desired value. In contrast to the traditional use of a memoryless high gain amplifier as the central element, this approach makes it clear right from the beginning that Negative Feedback circuits take time to respond (have a finite bandwidth), that some excess delay can be tolerated, while larger excess delays lead to ringing and eventually instability, and that Negative Feedback circuits can be stabilized by slowing them down. Time domain intuition and analysis lead to key conclusions regarding the stability margin of Negative Feedback circuits. This approach complements the conventional frequency domain approach by serving as an introduction that anticipates the results that are derived by the latter. The presented approach also lends itself better to synthesis of key Negative Feedback blocks such as opamps and the phase locked loop.
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ISCAS - Introducing Negative Feedback with an integrator as the central element
2012 IEEE International Symposium on Circuits and Systems, 2012Co-Authors: Nagendra KrishnapuraAbstract:Negative Feedback is introduced using an integrator as the central element by making intuitive connections with the way we sense the difference between desired and actual values and continuously adjust the latter so that it reaches the desired value. In contrast to the traditional use of a memoryless high gain amplifier as the central element, this approach makes it clear right from the beginning that Negative Feedback circuits take time to respond (have a finite bandwidth), that some excess delay can be tolerated, while larger excess delays lead to ringing and eventually instability, and that Negative Feedback circuits can be stabilized by slowing them down. Time domain intuition and analysis lead to key conclusions regarding the stability margin of Negative Feedback circuits. This approach complements the conventional frequency domain approach by serving as an introduction that anticipates the results that are derived by the latter. The presented approach also lends itself better to synthesis of key Negative Feedback blocks such as opamps and the phase locked loop.
Mitchell J. Prinstein - One of the best experts on this subject based on the ideXlab platform.
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Reciprocal, Longitudinal Associations Among Adolescents' Negative Feedback-Seeking, Depressive Symptoms, and Peer Relations
Journal of Abnormal Child Psychology, 2006Co-Authors: Jessica L. Borelli, Mitchell J. PrinsteinAbstract:This study examined reciprocal associations among adolescents' Negative Feedback-seeking, depressive symptoms, perceptions of friendship quality, and peer-reported social preference over an 11-month period. A total of 478 adolescents in grades 6–8 completed measures of Negative Feedback-seeking, depressive symptoms, friendship quality, global-self-esteem, and social anxiety at two time points. Peer-reported measures of peer status were collected using a sociometric procedure. Consistent with hypotheses, path analyses results suggested that Negative Feedback-seeking was associated longitudinally with depressive symptoms and perceptions of friendship criticism in girls and with lower social preference scores in boys; however, depressive symptoms were not associated longitudinally with Negative Feedback-seeking. Implications for interpersonal models of adolescent depression are discussed.
Luis Serrano - One of the best experts on this subject based on the ideXlab platform.
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noise in transcription Negative Feedback loops simulation and experimental analysis
Molecular Systems Biology, 2006Co-Authors: Yann Dublanche, Konstantinos Michalodimitrakis, Nico Kummerer, Mathilde Foglierini, Luis SerranoAbstract:Negative Feedback loops have been invoked as a way to control and decrease transcriptional noise. Here, we have built three circuits to test the effect of Negative Feedback loops on transcriptional noise of an autoregulated gene encoding a transcription factor (TF) and a downstream gene (DG), regulated by this TF. Experimental analysis shows that self-repression decreases noise compared to expression from a non-regulated promoter. Interestingly enough, we find that noise minimization by Negative Feedback loop is optimal within a range of repression strength. Repression values outside this range result in noise increase producing a U-shaped behaviour. This behaviour is the result of external noise probably arising from plasmid fluctuations as shown by simulation of the network. Regarding the target gene of a self-repressed TF (sTF), we find a strong decrease of noise when repression by the sTF is strong and a higher degree of noise anti-correlation between sTF and its target. Simulations of the circuits indicate that the main source of noise in these circuits could come from plasmid variation and therefore that Negative Feedback loops play an important role in suppressing both external and internal noise. An important observation is that DG expression without Negative Feedback exhibits bimodality at intermediate TF repression values. This bimodal behaviour seems to be the result of external noise as it can only be found in those simulations that include plasmid variation.
Ivan Aprahamian - One of the best experts on this subject based on the ideXlab platform.
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Hydrazone Switch-Based Negative Feedback Loop.
Journal of the American Chemical Society, 2016Co-Authors: Susnata Pramanik, Ivan AprahamianAbstract:A Negative Feedback loop that relies on the coordination-coupled deprotonation (CCD) of a hydrazone switch has been developed. Above a particular threshold of zinc(II), CCD releases enough protons to the environment to trigger a cascade of reactions that yield an imine. This imine sequesters the excess of zinc(II) from the hydrazone switch, hence lowering the effective amount of protons, and switching the cascade reactions “OFF”, thus establishing the Negative Feedback loop.
Mogens H. Jensen - One of the best experts on this subject based on the ideXlab platform.
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Oscillation patterns in Negative Feedback loops
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Simone Pigolotti, Sandeep Krishna, Mogens H. JensenAbstract:Organisms are equipped with regulatory systems that display a variety of dynamical behavior ranging from simple stable steady states, to switching and multistability, to oscillations. Earlier work has shown that oscillations in protein concentrations or gene expression levels are related to the presence of at least one Negative Feedback loop in the regulatory network. Here, we study the dynamics of a very general class of Negative Feedback loops. Our main result is that, when a single Negative Feedback loop dominates the dynamical behavior, the sequence of maxima and minima of the concentrations exhibit a pattern that uniquely identifies the interactions of the loop. This allows us to devise an algorithm to (i) test whether observed oscillating time series are consistent with a single underlying Negative Feedback loop, and if so, (ii) reconstruct the precise structure of the loop, i.e., the activating/repressing nature of each interaction. This method applies even when some variables are missing from the data set, or if the time series shows transients, like damped oscillations. We illustrate the relevance and the limits of validity of our method with three examples: p53-Mdm2 oscillations, circadian gene expression in cyanobacteria, and cyclic binding of cofactors at the estrogen-sensitive pS2 promoter.
