In the News

[Thomas Fiddaman]

http://www.wired.com/thisdayintech/2010/05/0511magnetic-core-memory/

May 11, 1951: RAM Is Born

1951: Jay Forrester files a patent application for the matrix core memory.

Back when computers still weighed hundreds of pounds and were primarily used by the military, computer memory relied on cathode rays to retrieve information. But the Navy needed a faster computer that could run flight simulations in real time.

In stepped a team at the Massachusetts Institute of Technology. Led by professor Jay Forrester, the researchers developed a three-dimensional magnetic structure code-named Project Whirlwind.

The structure consisted of a plane made of wires and magnetic rings called cores. Each ring contained one bit of data. Every bit on the memory plane could be accessed with a single read-and-write cycle.

In short, magnetic core memory was the first random access memory that was practical, reliable and relatively high-speed. The time it took to request and retrieve information from memory was a microsecond — hundreds of thousands of times slower than memory today, but nonetheless a magnificent achievement in the 1950s.

“When we were working on this, in a million years we couldn’t imagine what would happen with memory,” said Bernard Widrow, who worked on Project Whirlwind with Forrester, in a 2009 interview with Edison Tech Center.

Forrester applied for a patent on his invention May 11, 1951. Project Whirlwind stayed active until 1959, though the technology was never used for a flight simulator.

[Roberta Spencer]

An article about the Whirlwind Computer, along with a photo including Jay Forrester is featured in the section "This Day in Tech" on the website http://www.wired.com/thisdayintech. The title of the article is "March 8, 1955: The Mother of All Operating Systems."

[Roberta Spencer]

The December issue of National Geographic Magazine features the work John Sterman has led at MIT and with Climate Interactive (http://climateinteractive.org) on mental models of climate change in their "Big Idea" feature (p. 26-29 of the print edition; online at:
http://ngm.nationalgeographic.com/big-idea/05/carbon-bath).

National Geographic Magazine did a nice job with the art and in conveying some complex ideas clearly. They also included a link to the online version of C-ROADS.

Please visit Climate Interactive – The Blog to see this and other posts. http://climateinteractive.wordpress.com/

Congratulations to everyone involved in this project.

[Bill Braun]

http://7thspace.com/headlines/308975/on ... stems.html

On the functional diversity of dynamical behaviour in genetic and metabolic feedback systems

Feedback regulation plays crucial roles in the robust control and maintenance of many cellular systems. Negative feedbacks are found to underline both stable and unstable, often oscillatory, behaviours.

We explore the dynamical characteristics of systems with single as well as coupled negative feedback loops using a combined approach of analytical and numerical techniques. Particularly, we emphasise how the loop's characterising factors (strength and cooperativity levels) affect system dynamics and how individual loops interact in the coupled-loop systems.

Results: We develop an analytical bifurcation analysis based on the stability and the Routh- Hurwitz theorem for a common negative feedback system and a variety of its variants. We demonstrate that different combinations of the feedback strengths of individual loops give rise to different dynamical behaviours.

Moreover, incorporating more negative feedback loops always tend to enhance system stability. We show that two mechanisms, in addition to the lengthening of pathway, can lower the Hill coefficient to a biologically plausible level required for sustained oscillations.

These include loops coupling and end-product utilisation. We find that the degradation rates solely affect the threshold Hill coefficient for sustained oscillation, while the synthesis rates have more significant roles in determining the threshold feedback strength.

Unbalancing the degradation rates between the system species is found as a way to improve stability.

Conclusion: The analytical methods and insights presented in this study demonstrate that reallocation of the feedback loop may or may not make the system more stable; the specific effect is determined by the degradation rates of the newly inhibited molecular species.

As the loop moves closer to the end of the pathway, the minimum Hill coefficient for oscillation is reduced. Furthermore, under general (unequal) values of the degradation rates, system extension becomes more stable only when the added species degrades slower than it is being produced; otherwise the system is more prone to oscillation.

The coupling of loops significantly increases the richness of dynamical bifurcation characteristics. The likelihood of having oscillatory behaviour is directly determined by the loops' strength: stronger loops always result in smaller oscillatory regions.

Author: Lan K Nguyen and Don Kulasiri
Credits/Source: BMC Systems Biology 2009, 3:51

Published on: 2009-05-12

Copyright by the authors listed above - made available via BioMedCentral (Open Access).

[Thomas Fiddaman]

http://climateinteractive.wordpress.com/2009/03/06/888/

"On March 5th Senator John Kerry of Massachusetts referred extensively to our work in remarks at a forum sponsored by Hitachi and featuring panels organized by the American Association for the Advancement of Science and the Brookings Institution. ..."

[Thomas Fiddaman]

http://dotearth.blogs.nytimes.com/2009/ ... /?emc=eta1

A new paper in the Proceedings of the National Academy of Sciences, concluding that the buildup of human-generated greenhouse gases could leave a profound millenniums-long imprint on climate and sea levels, focuses on a characteristic of global warming that the public, and many policymakers, have not absorbed — at least according to John Sterman at M.I.T.

That characteristic is the “bathtub effect” behind the human-amplified greenhouse effect. Dr. Sterman, a prominent analyst of risk perception and management at the Sloan School, has devised various tools akin to flight simulators to help corporate leaders understand the nature of a variety of problems and choose among various remedies. He recently turned this approach to climate, which he says bears much more resemblance to deficit spending and the national debt than it does to 20th-century-style pollution problems like acid rain.

[Jim Duggan]

A nice balancing loop example.

Thomas Friedman's reaction to the following CNN report sometime last december:

“After nearly a year of flagging sales, low gas prices and fat incentives are reigniting America’s taste for big vehicles. Trucks and S.U.V.’s will outsell cars in December ... something that hasn’t happened since February. Meanwhile, the forecast finds that sales of hybrid vehicles are expected to be way down.”

see: http://www.nytimes.com/2008/12/28/opini ... edman.html

Jim.

[Jim Duggan]

Hi,

Interesting article in the New York Times yesterday. Friedman talks of inflection points, stocks, flows and (unsustainable) growth, and the "Great Disruption Point."

See http://www.nytimes.com/2009/03/08/opini ... an.html?em

regards,
Jim.

[Ralf Lippold]

Hi all,

There is an interesting video of a Harvard Business School meeting on the financial crisis http://www.socialmediatoday.com/SMC/49728

On 1:16 Robert Merton talks specifically about feedback in the collapse of the sytem.

Practice meets SD - unintentially;-)

How can we put more such stories into a broader scope of visibility?

Best regards

Ralf

PS.: SD is all around us, modeling is clearly not yet for everybody (myself I am coping to learn more on that;-)).
It is like catching fish at a fish hatchery - really easy grab. We just have to move and take the opportunities.

[Robert Eberlein]

Use this thread for System Dynamics thinking and analysis showing up in the news.