Charles
Minard's map of Napoleon's disastrous Russian campaign of 1812. The graphic is
notable for its representation in two dimensions of six types of data: the
number of Napoleon's troops; distance; temperature; the latitude and longitude;
direction of travel; and location relative to specific dates.[1]
[1] Corbett, John. "Charles Joseph Minard:
Mapping Napoleon's March, 1861". Center for Spatially Integrated Social
Science. Retrieved 21 September 2014.
A feedback loop where all outputs of a process are available as causal inputs to that process - https://en.wikipedia.org/wiki/Feedback
There are two types of feedback: positive feedback and negative feedback.
As an example of negative feedback, the diagram might represent a cruise control system in a car, for example, that matches a target speed such as the speed limit. The controlled system is the car; its input includes the combined torque from the engine and from the changing slope of the road (the disturbance). The car's speed (status) is measured by a speedometer. The error signal is the departure of the speed as measured by the speedometer from the target speed (set point). This measured error is interpreted by the controller to adjust the accelerator, commanding the fuel flow to the engine (the effector). The resulting change in engine torque, the feedback, combines with the torque exerted by the changing road grade to reduce the error in speed, minimizing the road disturbance.
The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the regenerative circuit.[10] Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where the "feed-back" action is positive in contrast to negative feed-back action, which they mention only in passing.[11]Harold Stephen Black's classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:
- "Positive feed-back increases the gain of the amplifier, negative feed-back reduces it."[12]
According to Mindell (2002) confusion in the terms arose shortly after this:
- "...Friis and Jensen had made the same distinction Black used between 'positive feed-back' and 'negative feed-back', based not on the sign of the feedback itself but rather on its effect on the amplifier’s gain. In contrast, Nyquist and Bode, when they built on Black’s work, referred to negative feedback as that with the sign reversed. Black had trouble convincing others of the utility of his invention in part because confusion existed over basic matters of definition."[10](p121)
Even prior to the terms being applied, James Clerk Maxwell had described several kinds of "component motions" associated with the centrifugal governors used in steam engines, distinguishing between those that lead to a continual increase in a disturbance or the amplitude of an oscillation, and those that lead to a decrease of the same.[13]
https://en.wikipedia.org/wiki/Feedback
Product Ecosystem Networked Feedback loop diagram
Tackling obesities: future choices - full systems map (high resolution)
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/296290/obesity-map-full-hi-res.pdf
Product Ecosystem Networked Feedback loop diagram
FIGURE 2 | A positive feedback loop linking metabolism, glycosylation and growth factor signalling.
Most growth factor receptors (GFRs) are N-glycosylated, and their cell-surface expression depends on proper folding and the degree of N-glycan branching61. Glucose is necessary for glycosylation, in part through its utilization in the hexosamine biosynthetic pathway, which produces UDP-N-acetylglucosamine (UDP-GlcNAc), and for the generation of UDP-glucose (UDP-Glc). The hexosamine pathway branches off from glycolysis at fructose-6-phosphate (F6P) and requires contributions from glucose, glutamine and acetyl-CoA62. UDP-GlcNAc is used in the endoplasmic reticulum (ER) for the initiation of N-glycosylation (not shown) and in the Golgi for branching reactions61, 64. The phosphoinositide 3-kinase (PI3K)–AKT pathway regulates these processes by promoting increased glucose metabolism, thus supplying more UDP-GlcNAc and UDP-Glc and by promoting the expression of the ER UDPase ectonucleoside triphosphate diphosphohydrolase 5 (ENTPD5), a component of the protein folding pathway72. UDP-Glc has an important role in protein folding in the ER; glucose is added to an unfolded glycoprotein to target it for folding and then removed before the protein enters the Golgi for further modification. ENTPD5 activity increases ATP consumption, thus relieving the feedback inhibition of phosphofructokinase 1 (PFK1) by ATP and further promoting glycolysis. Hence, by stimulating ENTPD5 expression and increasing glucose uptake and hexosamine pathway flux, PI3K–AKT signalling can promote glycosylation-dependent GFR surface expression, perpetuating signalling through the PI3K–AKT pathway. F1,6BP, fructose-1,6-bisphosphate; GLUT, glucose transporter.
Tackling obesities: future choices - full systems map (high resolution)
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/296290/obesity-map-full-hi-res.pdf
