منابع مشابه
Positive feedback
Positive feedback is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation.[1] That is, A produces more of B which in turn produces more of A.[2] In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback.[1][3] Mathematically, positive feedback is...
متن کاملFeedback and positive feedback stabilizability and holdability
Consider the following problem. Given a discrete-time linear system, find, if possible, linear state-feedback control laws such that under these laws all trajectories originating in the non-negative orthant of the state space remain non-negative while asymptotically deteriorating to the origin. This problem is called feedback stabilizability-holdability problem (FSH). If, in addition, the requi...
متن کاملPhysiological Positive Feedback Mechanisms
In positive feedback mechanisms, the response to a stimulus does not stop or reverse it but instead keeps the sequence of events going up. At first glance, this would appear to be a counter to the principle of homeostasis, since a positive feedback loop has no obvious means of stopping. Not surprisingly, therefore, the positive feedback is less common in nature than the negative one. A positive...
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Acute allergic angioedema is an abrupt-onset, unpredictable inflammatory reaction of the skin and mucous membranes. Without treatment, the condition may resolve within hours; however, when swallowing or breathing is affected, emergent medical attention is required. We report an atypical presentation of this condition, with a unique dietary cause. A 50-year-old man with no relevant medical histo...
متن کاملPositive feedback in the transition from sexual reproduction to parthenogenesis.
Understanding how new phenotypes evolve is challenging because intermediate stages in transitions from ancestral to derived phenotypes often remain elusive. Here we describe and evaluate a new mechanism facilitating the transition from sexual reproduction to parthenogenesis. In many sexually reproducing species, a small proportion of unfertilized eggs can hatch spontaneously ('tychoparthenogene...
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ژورنال
عنوان ژورنال: Nature
سال: 2002
ISSN: 0028-0836,1476-4687
DOI: 10.1038/418734a