-
One of the classic problems in the study of complex systems is the
spontaneous formation of patterns in physical, chemical and biological
systems. For biological morphogenesis the existence of chemical morphogens
have been postulated by Gierer and Meinhard who formulated a reaction
diffusion model in which many general phenomena could be predicted. The
identification of the morphogen and where it is produced has been a challenge
for developmental biology. In a recent series of elegant experiments with
chicken embryos Dahn and Fallon could show where the morphogen responsible for
the formation of the chicken's digits originates and how it determines the
identity of the different digits:
|
"Human feet and hands start out with webbing, much like that of a
duck or a frog. During embryonic development, this webbing dies and
fingers and toes emerge. John Fallon, a professor of anatomy at the
University of Wisconsin-Madison, was involved in discovering that more
than 30 years ago.
Now, research done on chickens in Fallon's lab has led to another
discovery: The webbing does more than sacrifice itself to make digits.
It also sends out chemical signals that tell the digits what to become,
such as a pinkie or a big toe. (...)
Fallon speculates that someday this type of information could find
application in artificial limb regeneration." |
Source: John F. Fallon, University of Wisconsin Medical
School |
- Webbing Between Digits Determines Shape,
Use, Charlotte Schubert, The Milwaukee
Journal Sentinel Online
- Interdigital Regulation of Digit Identity and Homeotic
Transformation by Modulated BMP Signaling, Randall D. Dahn and John F. Fallon
- Why Chicks Aren't All Thumbs,
Michael Hagmann, Science, Volume 289, Number 5478, Issue of 21 Jul
2000, pp.
372-373
>
Oscillatory Cluster Patterns In A Homogeneous Chemical System With Global Feedback, Nature 
The original discovery of the chemical reaction named after B. P.
Belousov, and A.M. Zhabotinsky (one of the authors of the current target
article) constituted a revolution in chemistry and became one of the
paradigmatic examples of spontaneous self organization. Instead of going
straight from a mixture of initial chemicals to the end product, the
BZ-reaction shows a more complex behavior either in the form of temporal
oscillations or of spatio-temporal pattern formation. Vanag et al. study how a
light sensitive version of this reaction is modified by global feedback
provided by uniform illumination of the chemicals. They observe oscillatory
clusters:
"(...) so-called 'localized clusters'-periodic antiphase oscillations in
one part of the medium, while the remainder appears uniform (...). We also
observe standing clusters with fixed spatial domains that oscillate
periodically in time and occupy the entire medium, and irregular clusters with
no periodicity in either space or time, with standing clusters transforming
into irregular clusters and then into localized clusters as the strength of
the global negative feedback is gradually increased. (...) we are able to
simulate successfully the experimental data."
These results are especially interesting in the light of new discoveries
that show that information processing in the brain takes place with the help
of neuronal cell assemblies whose activity is not only controlled by
electrical signal transduction but also by chemical waves and glia cells. (see
Complexity Digest 2000.28.3).
-
Abstract: Many complex systems display a surprising degree of
tolerance against errors. For example, relatively simple organisms grow,
persist and reproduce despite drastic pharmaceutical or environmental
interventions, an error tolerance attributed to the robustness of the
underlying metabolic network. Complex communication networks display a
surprising degree of robustness: while key components regularly malfunction,
local failures rarely lead to the loss of the global information-carrying
ability of the network. The stability of these and other complex systems is
often attributed to the redundant wiring of the functional web defined by the
systems' components. In this paper we demonstrate that error tolerance is not
shared by all redundant systems, but it is displayed only by a class of
inhomogeneously wired networks, called scale-free networks.
We find that scale-free networks, describing a number of systems, such
as the World Wide Web (www), Internet, social networks or a cell, display an
unexpected degree of robustness, the ability of their nodes to communicate
being unaffected by even unrealistically high failure rates. However, error
tolerance comes at a high price: these networks are extremely vulnerable to
attacks, i.e. to the selection and removal of a few nodes that play the most
important role in assuring the network's connectivity. Such error tolerance
and attack vulnerability are generic properties of communication networks,
such as the Internet or the www, with complex implications on assuring
information readiness.
- To be presented at the Workshop Structure
and Dynamics of Complex Interactive Networks, Santa Fe 8/10-12/00, see Complexity
Digest 2000.28.2 by Albert-Laszlo
Barabasi
- The Internet's Achilles' Heel,
Reka Albert, Hawoong Jeong, Albert-Laszlo Barabasi, University of
Notre Dame Preprint
- Error And Attack Tolerance Of Complex
Networks, Reka Albert, Hawoong
Jeong, Albert-Laszlo Barabasi, Nature, 27 Jul 2000 Volume 406 No.
6794
Robustness, Complexity, And Web/Internet Traffic, SFI Workshop Abstract
Abstract: Recently, Carlson and Doyle introduced Highly
Optimized Tolerance (HOT) to describe essential and common properties of
complex systems in biology, ecology, technology, and socio-economic systems.
To function outside an idealized laboratory setting, such systems must be
robust to uncertainty in their environment and components, but occasional
catastrophic breakdowns remind us that this cannot be taken for granted.
HOT systems arise when deliberate robust design aims for a specific
level of tolerance to uncertainty, which is traded off against the cost of the
compensating resources. Optimization of this tradeoff may be associated with
some mixture of explicit planning as in engineering, or mutation and natural
selection, as in biology, but we use the word ``design' loosely to encompass
both. The resulting features of HOT systems are high performance and high
throughput, ubiquitous power law distributions of event sizes, and potentially
high sensitivities to design flaws and unanticipated or rare
uncertainties.
(...) For example, organisms and ecosystems exhibit remarkable
robustness to large variations in temperature, moisture, nutrients, and
predation, but can be catastrophically sensitive to tiny perturbations, such
as a genetic mutation, an exotic specie, or a novel virus. Engineers
deliberately design systems to be robust to common uncertainties. Cost and
performance tradeoffs force an acceptance of some hypersensitivity to
hopefully rare perturbations. In evolved or designed systems, this tradeoff
leads to the "robust, yet fragile" characteristic of complexity.
An example which has been studied in some detail is Web layout design
viewed as a coding problem (Doyle and Carlson; Zhu, Yie, and Doyle), and its
impact on self-similar internet traffic. The aim here is to minimize the
average size, and thus approximately the latency, of files downloaded during
Web browsing sessions, but with the novel object of design being Web site
layout rather than codeword selection. This modest introduction of meaning or
value into a coding context completely changes the results, producing
distributions for file transfers that are heavy tailed. It has also been shown
(e.g., in the work by Willinger, Paxson, Floyd, Crovella, and their
colleagues) that both LAN and WAN traffic have strongly self-similar
characteristics, quite unlike the traditionally assumed Poisson traffic
models. (...)
It is becoming widely recognized that important research challenges in
biology have many parallels with those in complex engineering systems.
Emphasis is shifting from components and molecules to the study of the vast
networks that biological molecules create that regulate and control life. And
the central role that robustness plays in complex systems has begun to move
from an exclusively engineering perspective to one of interest to biologists
as well. Biological systems are particularly extreme in their "robust, yet
fragile" characteristics. This is the most critical and universal
characteristic of complexity, not only in biology, but also in technological
and social systems, and is motivating new efforts to extend and integrate the
currently fragmented theoretical foundations for studying robustness and
complexity. This is in sharp contrast to the emphasis on self-organization,
emergence, phase transitions, criticality, fractals, self-similarity,
edge-of-chaos, and so on, that have been popularized as a "new science of
complexity." This talk will take a critical look at these and several other
issues relevant not only to internet traffic but also to biological
complexity, and particularly how "robust, yet fragile" features dominate a
systems view of everything from gene regulation to medical treatment to
ecosystem structure.
Complex Interactive Networks/Systems Initiative, SFI Workshop Abstract
(...) The Internet, computer networks, and our digital economy
have increased the demand for reliable and disturbance-free electricity;
banking and finance depends on the robustness of electric power, cable, and
wireless telecommunications. Transportation systems, including military and
commercial aircraft and land and sea vessels, depend on communication and
energy networks. Links between the power grid and telecommunications and
between electrical power and oil, water, and gas pipelines continue to be a
lynchpin of energy supply networks.
This strong interdependence means that an action in one part of one
infrastructure network can rapidly create global effects by cascading
throughout the same network and even into other networks. Moreover,
interdependence is only one of several characteristics that challenge the
control and reliable operation of these networks. (...)
There is not yet a significant and intimate interaction of an extensive
computer/communication network layer with the primary physical layer in the
operation and control of a power system. However, economic restructuring and
increasingly powerful sensing, computation and control possibilities are
changing the context in which power systems are operated and studied. A deeper
understanding of power systems as complex interacting networks is likely to
play an important role in the future.
The Complex Interactive Networks/Systems Initiative (CIN/SI), a joint
EPRI-US Department of Defense program, is addressing many of these
issues.
The goal of the 5-year, $30 million effort, which is part of the
Government-Industry Collaborative University Research program, is to develop
new tools and techniques that will enable large national infrastructures to
self-heal in response to threats, material failures, and other destabilizers.
Of particular interest is how to model enterprises at the appropriate level of
complexity in critical infrastructure systems.
Part of CIN/SI's work, which began in spring 1999 and involves 28
universities with participation from Tennessee Valley Authority and
Commonwealth Edison Co., draws from ideas in statistical physics, complex
adaptive systems (CAS), discrete-event dynamical systems, and hybrid, layered
networks. CAS researchers view the complex system as a collection of
individual intelligent agents that adapt to events and surroundings, acting
both competitively and cooperatively for the good of the entire system.
The objective of the CIN/SI is to significantly and strategically
advance the robustness, reliability, and efficiency of the interdependent
energy, communications, financial, and transportation infrastructures. CIN/SI
researchers are developing a mathematical basis and practical tools for
improving the security, performance, reliability and robustness of energy,
financial, telecommunications, and transportation networks. The first
challenges are to develop appropriate models for this degree of complexity and
create tools to enable components to adaptively reconfigure the network as
needed. Part of that work must determine if there is a unifying paradigm for
simulating, analyzing, and optimizing time-critical operations.
The science of complex adaptive systems (CAS) may provide a unifying
paradigm for bottom-up modeling, simulation, control, and optimization of
time-critical operations-both financial and physical-in these networks.
CAS-based methods, tools, and technologies may allow power grids and other
infrastructures to function in ways that are self-regulating, including
automatic reconfiguration in the event of material failures, threats, or
disturbances.
Computers Learn By Themselves To Play Checkers, Natural Selection, Inc.
(...) They (Dr. Fogel et al.) showed that a computer can learn
to play checkers at a level that is competitive with human experts, even when
starting with little more information than the positions of the pieces on the
board and the rules of the game.
The essential means for achieving this machine intelligence was a
computer simulation of evolution. An evolutionary program allowed the computer
to play games of checkers against itself. Over many generations of random
variation and selection to the strategies in its competing population, the
program evolved an expert strategy. Fogel and Chellapilla took the
best-evolved strategy and played it against people on the Internet at
www.zone.com without telling their opponents that they were using a computer
program. The evolved program rose to the top 1% of all registered players at
the Internet site.
"This research has been a great deal of fun," remarked Dr. Fogel, "and
more than a little humbling." Fogel and Chellapilla's evolutionary program was
able to defeat its creators by only its tenth generation. "Of course, neither
Kumar or I are very good at checkers. The game is actually quite difficult to
really master and the computer easily surpassed our own abilities. But we
never thought that we'd evolve a strategy that could compete with human
experts without preprogramming in the features that humans use."
In fact, such an achievement was thought to be impossible in the early
days of artificial intelligence research. National Medal of Science winner
Professor Alan Newell was quoted in 1961 as saying that it would simply be
hopeless to get machines to learn how to play games like checkers or chess
simply from the information contained in the final outcome: win, lose, or
draw. But much like the computer in the classic movie War Games, Fogel and
Chellapilla's computer has indeed taught itself to be a very tough opponent.
"Whatever the program knows, I can assure you that it didn't learn it from
us!" remarked Dr. Fogel.
The same technology that can be used to learn about tactics in a game
like checkers can be applied in other domains, such as military combat.
Natural Selection, Inc. is under contract to the United States Army on a Phase
II STTR effort, in collaboration with U.C. San Diego and Professor Kenneth
Kreutz-Delgado, to explore and develop evolutionary algorithms to assist tank
commanders in training exercises on the computer. Other applications include
developing strategies in business and financial markets.
Selection of Currently Relevant Memories by the Human Posterior Medial Orbitofrontal Cortex, The Journal of Neuroscience
Abstract: We have demonstrated previously that patients
producing spontaneous confabulations fail to suppress currently irrelevant
memory traces, so that they act and think on the basis of a false, temporally
displaced (past) reality. All spontaneous confabulators had anterior limbic
damage, in particular of the orbitofrontal cortex and basal forebrain. These
findings indicated that these structures are essential for distinguishing
between mental representations of ongoing reality and currently irrelevant
memories. In the present study, we used a similar experimental paradigm as in
our clinical studies and H215O positron emission tomography to explore the
selection of currently relevant memories by the healthy human brain.
Subjects were repeatedly presented with the same set of pictures,
arranged in different order each time, and were requested to indicate picture
recurrences within the runs. Thus, performance in the first run depended on
new learning, whereas subsequent runs required the distinction between picture
repetitions within the current run ("now") and previous picture presentations
in earlier runs. Whereas initial learning activated medial temporal
structures, subsequent runs provoked circumscribed posterior medial
orbitofrontal activation. We suggest that this area is essential for sorting
out mental associations that pertain to ongoing reality.
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Chaos Theory has taken over the world of modern science,
according to Dr. Allan Combs, the keynote speaker at the Chaos Theory in
Psychology and the Life Sciences meeting held at the University of
Pennsylvania last weekend. It is now part of the everyday work of scientists
in every discipline. Combs said that at first many physicists were visibly
upset with the idea that the universe was not a machine, and that many things
could never be predicted perfectly, no matter how hard they worked. Combs
reassured them that the universe would not fall apart because "instead of
mechanism, we will have algorithm." An algorithm is a step-by-step
mathematical procedure, so precise that it can be carried out by a computer,
yet often yielding chaotic results because a number of procedures are
interacting with each other.
An exciting application of chaos theory revealed at the conference is
Webmind, a computer program modeled on the human brain. According to Dr. Ben
Goertzel, founder of The Webmind Corporation in New York, Webmind consists of
a large number of nodes containing algorithms that interact with each other to
produce an intelligence greater than any achieved by previous computer
programs. There is a psycore that models the fundamental logic of the brain,
as well as specialized nodes for applications such as predicting financial
markets and reading email letters. The Webmind software is about two-thirds
finished, according to Dr. Goertzel, but it is already being tested by leading
investment firms.
Also at the conference was Dr. Ted Goertzel, Ben's father, who discussed
how chaos theory can explain why George W. Bush is doing so well in the
current election campaign.
-
Global problems of different dimensions can lead to the emergence
of self-organized global structures such as the United Nations or numerous
non-governmental organizations (NGOs). A structure that has a significant
potential for global change due to the combined economic power is the "G8"
group of eight major industrialized democracies. Through economic incentives
they are able to change global systems control parameters more informally and
quickly than rigid organizations like the United Nations. In the summit
meeting in Odinawa they identified a number of urgent global issues and some
approaches to their solution. Among them are:
- The world economy and the goal of a 21st century
of greater prosperity, where prosperity is defined in economic terms and not
in general well being. A specal role plays Information and
Communications Technology (IT): "IT empowers, benefits and links
people the world over, allows global citizens to express themselves and know
and respect one another. It also has immense potential for enabling economies
to expand further, countries to enhance public welfare and promote stronger
social cohesion and thus democracy to flourish. Access to the digital
opportunities must, therefore, be open to all."
- Development: "The 21st century must be a century of
prosperity for all, and we commit ourselves to the agreed international
development goals, including the overarching objective of reducing the share
of the world's population living in extreme poverty to half its 1990 level by
2015", " We also agree to give special attention to three issues:
debt, health, and education, as a spur to growth."
- Trade: "The multilateral trading system embodied by the
WTO, which represents the achievements of half a century of untiring efforts
on the part of the international community to realise rule-based free trade,
has provided its Members, developed and developing countries alike, with
enormous trade opportunities, spurring economic growth and promoting social
progress." (...)
- Cultural Diversity "is a source of social and economic
dynamism which has the potential to enrich human life in the 21st century, as
it inspires creativity and stimulates innovation. "
- Crime and Drugs "We reaffirm our support for the adoption
by the end of 2000 of the United Nations Transnational Organised Crime
Convention and three related Protocols on firearms, smuggling of migrants and
trafficking in persons."
- Ageing: "As the vitality of our societies increasingly
depends on active participation by older people, we must foster economic and
social conditions, including IT-related developments, that allow people of all
ages to remain fully integrated into society, to enjoy freedom in deciding how
to relate and contribute to society, and to find fulfilment in doing so. The
concept of "active ageing", as articulated at the Denver Summit, remains our
guiding principle in this endeavour."
- Biotechnology/Food Safety: "Maintenance of effective
national food safety systems and public confidence in them assumes critical
importance in public policy."
- Human Genome: Opening new medical frontiers points to
unprecedented opportunities for the benefit of humankind and will have to be
achieved taking account of principles of bioethics.
- Environment: We must all work to preserve a clean and
sound environment for our children and grandchildren.
- Nuclear Safety: "We renew the commitment we made at the
1996 Moscow Summit to safety first in the use of nuclear power and achievement
of high safety standards world wide."
- Conflict Prevention: "The international community should
act urgently and effectively to prevent and resolve armed conflict."
- Disarmament, Non-proliferation and Arms Control: "We
welcome the successful outcome of the 2000 Nuclear Non-Proliferation Treaty
(NPT) Review Conference."
- Terrorism: "We renew our condemnation of all forms of
terrorism regardless of their motivation."
Okinawa Charter on Global Information Society, Government of Japan
1. Information and Communications Technology (IT) is one of the
most potent forces in shaping the twenty-first century. Its revolutionary
impact affects the way people live, learn and work and the way government
interacts with civil society.(...)
2. The essence of the IT-driven economic and social transformation is
its power to help individuals and societies to use knowledge and ideas. Our
vision of an information society is one that better enables people to fulfill
their potential and realize their aspirations. To this end we must ensure that
IT serves the mutually supportive goals of creating sustainable economic
growth, enhancing the public welfare, and fostering social cohesion, and work
to fully realize its potential to strengthen democracy, increase transparency
and accountability in governance, promote human rights, enhance cultural
diversity, and to foster international peace and stability. Meeting these
goals and addressing emerging challenges will require effective national and
international strategies. (...)
- Protection of intellectual property rights for IT-related
technology is vital to promoting IT-related innovations, competition and
diffusion of new technology; we welcome the joint work already underway
among intellectual property authorities and further encourage our experts to
discuss future direction in this area;(...)
8.International efforts to develop a global information society must be
accompanied by coordinated action to foster a crime-free and secure
cyberspace. We must ensure that effective measures, as set out in the OECD
Guidelines for Security of Information Systems, are put in place to fight
cyber-crime. G8 co-operation within the framework of the Lyon Group on
Transnational Organized Crime will be enhanced. We will further promote
dialogue with industry, building on the success of the recent G8 Paris
Conference "A Government/Industry Dialogue on Safety and Confidence in
Cyberspace". Urgent security issues such as hacking and viruses also require
effective policy responses. We will continue to engage industry and other
stakeholders to protect critical information infrastructures.
9.Bridging the digital divide in and among countries has assumed a
critical importance on our respective national agendas. Everyone should be
able to enjoy access to information and communications networks. We reaffirm
our commitment to the efforts underway to formulate and implement a coherent
strategy to address this issue. We also welcome the increasing recognition on
the part of industry and civil society of the need to bridge the divide.
Mobilizing their expertise and resources is an indispensable element of our
response to this challenge. We will continue to pursue an effective
partnership between government and civil societies responsive to the rapid
pace of technological and market developments.
10.A key component of our strategy must be the continued drive toward
universal and affordable access. We will continue to:
- Foster market conditions conducive to the provision of affordable
communications services;
- Explore other complementary means, including access through publicly
available facilities;
- Give priority to improving network access, especially in underserved
urban, rural and remote areas;
- Pay particular attention to the needs and constraints of the socially
under-privileged, people with disabilities, and older persons and actively
pursue measures to facilitate their access and use;
- Encourage further development of "user-friendly", "barrier-free"
technologies, including mobile access to the Internet, as well as greater
utilization of free and publicly available contents in a way which respects
intellectual property rights.
How To Prevent 4.3 Million Unintended Pregnancies Each Year, The Alan Guttmacher Institute
As part of his FY 2001 budget request, the President urged
Congress last February to appropriate an additional $169 million above current
levels for international population and family planning programs, which would
restore funding for the program to the FY 1995 level. Approval of the funding
increase proposed by the President would have a measurable impact on the
health and well-being of women and their families in the countries receiving
financial and technical assistance from the U.S. Agency for International
Development (USAID) as summarized below.
ESTIMATED IMPACT OF THE PROPOSED FUNDING INCREASE
Leading researchers estimate that if the $169 million increase for USAID
population assistance were allocated among the countries receiving USAID
funding in the same manner that past expenditures have been distributed, and
if the cost per public sector family planning user in each country remains
constant, the following would occur:
11.7 million more couples in developing countries receiving USAID
population assistance will have access to and use a modern method of
contraception.
As a result, 4.3 million women will be able to avoid an unintended
pregnancy each year, leading to:
- · 1.5 million fewer unintended births;
- · 2.2 million fewer abortions; and
- · 0.5 million fewer miscarriages each year.
By preventing these unintended pregnancies, 15,000 fewer women will die
each year:
- · 7,000 fewer from pregnancy-related causes other than induced
abortion; and
- · 8,000 fewer from unsafe abortions.
In addition, there will be 92,000 fewer infant deaths.
Editor's note: Population control was not emphasized at the G8
summit. Education in women in developing countries is estimated to be the
single factor that is most strongly correlated with reduction in population
growth and improved living conditions.
Links & Snippets
Visualization Tool For Business Networks, Link
This web-site shows some interesting visualization about how different
companies are connected: The stronger the connection (measured by some metric
that is not released by the author yet) two companies attract each other with
a certain force. The combination of all forces leads to a arrangement of
companies reflecting their stable position according to this metric. Try the
right-click options [ctrl-click on Macintosh] and experience how perturbing
one company will affect the position of the ones linked to it.
The Internet Architecture: Principles, Reality, and Trends, SFI Workshop Abstract
Abstract: In this talk, I will describe the basic architectural
principles of the Internet, focusing on the aspects that influence its
robustness and scalability. Armed with this ideal view of the Internet, we
will proceed to look at the reality of its deployment today in terms of how
competing network providers provide a global utility, and how some of its
architectural elegance is compromised in practice.
I will describe the trends in three important areas that profoundly
affect the behavior and performance of the Internet: stable routing,
congestion management, and security in the face of attacks; and speculate on
the impact of two rapidly emerging trends: wireless access and content
distribution overlay networks.
To be presented at: Structure
and Dynamics of Complex Interactive Networks, SFI, 8/10-12/00,by Hari
Balakrishnan
Characterizing The Nonlinear Growth Of Large-Scale Structure In The Universe, Nature
Excerpt: The local Universe displays a rich hierarchical pattern of
galaxy clusters and superclusters. The early Universe, however, was almost
smooth, with only slight 'ripples' (...). During the early stages of this
expansion, the ripples evolve independently, like linear waves on the surface
of deep water. As the structures grow in mass, they interact with each other
in nonlinear ways, more like waves breaking in shallow water. (...)We develop
a statistical method based on information entropy to separate linear from
nonlinear effects, and thereby are able to disentangle those aspects of galaxy
clustering that arise from initial conditions (the ripples) from the
subsequent dynamical evolution.
Complexity Digest's Information Dimension?, Letter to the Editor
Sir,
I would like to be able to predict the time series
0 1 2 3 4 5 8 9 10 11 13 17 18 19 20 23 24 26 27
28
but I couldn't find out the information dimension of that (presumably)
deterministic chaotic time series.
Can you help me?
Hans-Paul
Schwefel
- P.S.1 The numbers above are those of Complexity Digest issues I got
this year;
- P.S.2 The issues are highly welcome!
Response:
Dear Hans-Paul Schwefel,
Thank you for your response and implicit assumption of a positive
information dimension. That would imply an infinite sequence and that is
certainly a nice wish for the future of ComDig. As for the next
elements in the sequence I can tell you the answer. It is 29,30,31,etc
You can prove that statement by using e.g. Fred Worth's algorithm described
on " Sequences of
Numbers" but we will also do our best to deliver an empirical proof as
well. In the meantime I would ask you to download the missing issues from our
archive www.comdig.org.
Thanks again for your valuable feedback and patience with our chaotic time
series.
