Simulating Dynamical Features Of Escape Panic, Nature 
There is an old joke about a theoretical physicist who
worked as agricultural consultant and who started his analysis
with the phrase: "Let's assume a spherical cow ...". The work by
Helbing et al. on the dynamics of crowds of people in panic did
not assume spherical people but instead circular people of radius
ri~30cm moving in a two-dimensional "flatland". They assumed
further that the "psychological" repulsive force between people in
a crowd is exponentially increasing with distance reaching the
force of an Olympic weight lifter upon contact. When people touch
each other an additional, elastically repulsive "body force" sets
in. The authors must assume very "firm" bodies since squeezing
them just a few millimeters would require a pretty strong pinch.
At least this is a parameter that can be tested experimentally
(preferably with somebody whose psychological repulsive force is
negative).
The authors admit that it is quite difficult to obtain
quantitative data to calibrate their model and therefore they
adjusted their parameters so that the simulation would produce
"reasonable" dynamical behaviors such as average distances between
people in a closed space. But being able to tweak a complex
model's parameters such that it reproduces some features of the
modeled system is not very convincing as many computer games can
do the same thing. But the authors also claim that their model has
heuristic value in that it provided them with novel insights:
"Our simulations suggest practical ways to prevent dangerous
crowd pressures. Moreover, we find an optimal strategy for escape
from a smoke-filled room, involving a mixture of individualistic
behavior and collective `herding' instinct."
Actually, the " smoke-filled room" simulation only assumes that
one cannot see the exits and emphasizes the importance of clearly
marked exit routes, a concept that is apparently alien to
overcrowded night markets in Taipei.
"Our continuous pedestrian model is based on plausible
interactions, and, owing to its simplicity, is robust with respect
to parameter variations. Therefore, it is suitable for drawing
conclusions about the possible mechanisms underlying the effects
of escape panic (regarding an increase of the desired velocity,
strong friction effects during physical interactions, and
herding)."
In the paper only simple one-dimensional parameter scans are
presented presenting only weak evidence for robustness in
nonlinear models. Thus it remains to be seen if the model
describes universal properties that hold up against realistic data
and indeed lead to useful improvements in building safety and
panic control.
Labeling Genetically Altered Food Is A Thorny Issue, NYTimes
Taco Bell, a popular US fast food chain recalled some of
their tacos because they were made of genetically altered corn
"StarLink" that contained proteins which make the plant more pest
resistant but which also might cause allergies. Therefore
"StarLink" had only been approved for use as animal feed but not
for human consumption.
This example demonstrates how small changes in food composition
could potentially have severe effects on our health: it could
determine if we develop and suffer from allergies. Other minor
changes for instance in the type of fatty acids a food contains
("omega-3" vs. "omega-6") could determine if we will develop
arteriosclerosis or not.
Today probably nobody will seriously question the more or less
subtle correlations between nutrition and health, many of which
probably have not been discovered yet. The subtlety of those
correlations also make it clear that even the most elaborate
"safety tests" applied by the food and drug administration will
not be able to guarantee that there will not be new adverse health
effects discovered one day.
We also understand that those problems are not confined to
genetically altered food but could depend on the type of animal
feed, e.g. meat from animals that feed on grass apparently produce
more "omega-3" fatty acids. This second order correlation also
demonstrates the complexity of the information that contain even
marginally feasible parameters that affect public health.
Technical difficulties in implementing more comprehensive food
labeling practices should be met easily with upcoming (wireless)
technologies in the information industry. (See the experimental
wml site at UIUC's
AIM lab)
But there are also other economical reason why food labeling
meets considerable resistance from the agricultural
industries:
"Biotechnology and food industry executives say the critics
want labeling because it will scare people away. "It is not
designed to inform people; it is designed to alarm people," said
Gene Grabowski, a spokesman for the Grocery Manufacturers of
America, which represents food companies. 'In Britain, where they
have mandatory labeling, you cannot find biotech foods.' "
This statement seems to imply that consumers only buy biotech
foods if they are denied this information about the food that they
eat. This also seems to indicate that there is a big market for
food that consumers can trust is not genetically altered. With
modern information technology it will be possible to proactively
add value to food by creating an electronic "paper trail" for
individual food items, thereby making testing much more
reliable:
"Unless you know the history of the sample, you don't know
what you are testing for," said Eluned Jones, associate professor
of agriculture and agribusiness at Virginia Tech. "It has to start
at the farm level. You can't just test it at the final level and
put a label on."
Maze-Solving By An Amoeboid Organism, Nature
As long as people observed nature around them they were
struck by the complex and intricate patterns they found. In
ancient times this was a sign for a divine order. More recently
scientists are more tempted to evoke emergent properties,
universal computation, or intelligent systems to describe some of
the truly amazing phenomena. Ultimate computers have been
"designed" by estimating the computational complexity of photon
gases and black holes.
In a way one can view a cloud as an analog computer that solves
the hydrodynamic equations and phase transitions that describe
cloud dynamics in real time, millions and millions of times faster
than the fastest digital computer. But can on call clouds
intelligent because they solve the problem of transporting water
over large distances?
It has been claimed that chemical reactions like the
Belousov-Zhabotinsky reaction can solve partial differential
equations in a maze and there are many other examples of physical
systems whose "computational" capabilities solve real world
problems (e.g. a quartz-watch calculates sine waves at an amazing
speed with high accuracy).
It is not clear if the claims of Nakagaki et al that a slime
mold (one of the classic examples of complex biological systems)
shows any signs of intelligence by "solving" a maze problem does
not fall in this same category. Slime molds, like all biological
systems, are good in finding their food resources. They happen to
do that by sensing food concentration gradients and thereby
"solving" a partial differential equation. But electrolytic gels
can basically do the same trick but we probably wouldn't think of
gels as "intelligent".
Maybe this new slime mold story can remind us how we can tell
intelligence from spectacularly complex performances, like "idiot
savants" of nature. We can ask if it can do anything else, solve a
problem that it has never encountered before. Intelligent systems
should be able to do well in such a task.
Organizational Complexity in National Laboratories, Nature
The research communities at the US nuclear weapons
laboratories especially at Los Alamos National Laboratory (LANL)
evolved in a very special environment: Los Alamos, the town, was
built for the laboratory employees, in the middle of the high
desert; during the first years during and after world war II it
was a closed military area within which the scientists had a great
amount of freedom from administrative interference and quasi
unlimited resources.
In later years the laboratory overcame the relative academic
isolation by allocating considerable funds to support visiting
scientists, postdoctoral fellows, and even students who would work
on basic research interacting with weapons scientists who would do
their classified work "behind the fence". The special situation is
described by David Pines, co-director of the Institute for Complex
Adaptive Matter:
"What Los Alamos has given the United States and its allies
over its distinguished scientific and technological lifetime is a
special kind of science-based security founded on four
interlocking, essential ingredients: excellence, openness,
leadership and oversight. All four were put in place in its
earliest days; all four have been retained up to the present day;
and, sadly, all four are now at risk." (1)
The "lab" is operated by the University of California which
probably was the reason for an academic spirit that one would not
expect at a top nuclear weapons laboratory. In 1985 I was free to
publish (as LANL postdoc) a computer simulation of the impact on
Star Wars on the strategic arms race whose predictions were not
favorable to the program that contributed hundreds of millions of
dollars to the laboratory budget. Many lab scientists were not
happy about these results but the academic integrity was high
enough not to allow that unfavorable results would be
suppressed.
In the past year there have been a number of events that
question if the self-organized quality control and peer review
system within the National Laboratories and the UC system are
still working. Bodner and Paine claim that it failed in the
multi-billion $ project of the National Ignition Facility (NIF)
that was "sold" to the government by scientists as centerpiece of
the US nuclear "stockpile stewardship" program. It seems that
wishful thinking had replaced hard scientific evidence of the
facilities basic physical performance parameters:
- "The routine operating energy for avoiding optical
damage has been reduced to between a third and a half of the
project's promised 1.8 megajoules, considerably less than what
even the sponsoring laboratory believes is minimally required
to achieve thermonuclear ignition.
- The project's primary justification is now shifting from
fuel ignition to its residual capability for
"high-energy-density physics" experiments, but this has never
been seriously reviewed, and cheaper approaches are
available."(2)
It would be interesting to see if the public attention to the
emergent problems in this high powered scientific community will
lead to the emergence of creative solutions or if a more rigid
administration will take over control.
"Zip Codes" That Direct Cells In The Bloodstream, Science Daily
Excerpt: "Researchers at the University of
Pennsylvania and Cornell University have pinpointed a fundamental
mechanism that controls how cells coursing through our blood
"know" when to exit the bloodstream and go to work in the body's
tissues. The secret, they report in the Sept. 26 issue of the
Proceedings of the National Academy of Science, are so-called
"Goldilocks molecules" that bind blood cells to the walls of veins
and arteries neither too strongly nor too weakly, but with just
the right level of adhesion.
Lead author Daniel A. Hammer, Ph.D., professor of
bioengineering and chemical engineering at Penn, likens this
process, known as cell trafficking, to the use of ZIP codes to
direct mail to communities nationwide. The presence of one of a
handful of key molecules on the surface of a cell, he says, guides
the cell just as surely as a five-digit number on an envelope
ensures that a piece of mail reaches a particular city.
"Trafficking of blood-borne cells into tissues is crucial to
the proper function of the immune response," says Dr. Hammer, a
member of Penn's Institute for Medicine and Engineering.
"Inflammation, lymphocyte function, and bone marrow replenishment
after transplantation all depend upon it."
While cell trafficking is ordinarily a beneficial and
necessary process, researchers also suspect that it's responsible
for the metastasis of cancerous cells that move with great
precision from the site of an initial tumor to colonize secondary
areas. Virtually all primary tumor locations are strongly
associated with secondary locations where cancer is most likely to
reassert itself later on, Dr. Hammer says. For instance, people
who develop skin cancer often subsequently develop lung cancer --
suggesting that melanoma cells may be programmed to direct
themselves to the lungs.
Cells exit the bloodstream millions of times per second,
binding fleetingly to vessel walls before slipping through them
into the surrounding tissues. The process begins with what's
called "rolling adhesion": blood cells skipping along the walls of
veins and arteries pause occasionally when molecules on their
surfaces form transient bonds with vessel-bound receptors. But
only if a bond forms between just the right molecules will the
cell be ushered out of the bloodstream. "(...)
First Evidence That Maximum Age At Death In Humans Is Rising, Science Daily
Excerpt: "The oldest age at death for humans has
been rising for more than a century and shows no signs of leveling
off, according to a demographer at the University of California,
Berkeley.
This new finding, based on Swedish national death records
for each year since 1861, calls into question the belief by many
scientists that the human life span has a set end-point of 120
years.
In research published today in Science, the nation's premier
science journal, UC Berkeley associate professor of demography
John Wilmoth and his colleagues in Sweden and the United States
show that, in the1860s in Sweden, the oldest ages at death for men
and women centered around 101. That average maximum age moved up
slowly throughout the century to about 105 in the 1960s and then
accelerated to 108 in the 1990s.
"We have shown that the maximum life span is changing. It is
not a biological constant. Whether or not this can go on
indefinitely is difficult to say. There is no hint yet that the
upward trend is slowing down," said Wilmoth.
Wilmoth said that Swedish demographic statistics -
considered the world's best records on birth and death - are a
good indication of patterns in other industrialized nations, where
it has become commonplace to survive to a very old age.
But until now, there has been no evidence that the maximum
age at death was being pushed back, leading to a lengthening of
the human life span, said Wilmoth. " (...)
-
The recent discussion on high oil prices demonstrated the
two basic different control strategies that the US and European
governments try to implement in order to reduce the negative
environmental impact of high oil consumption: The European
strategy is to increase the relative fitness of energy conserving
technologies by taxing the oil products heavily. The US approach
is to regulate technical requirements about maximal fuel
consumption of different types of cars:
"And Congress ought to do something about the most egregious
example of wasteful consumption around: the poor gas mileage of
many sport-utility vehicles. Considering that the corporate
average fuel economy (CAFE) standards have been stuck at 27.5
miles per gallon for passenger vehicles and 20.7 mpg for light
trucks and SUVs since 1995, Congress should allow the
Transportation Dept. to raise the standards for both categories.
And the exemption for the heaviest SUVs--which don't have to meet
any mileage standards at all--should be eliminated. "
(1)
Looking at the per capita efficiency of oil (the service
provided by one barrel of oil) one should be able to evaluate
which strategy works better. A second test could be to compare the
technological progress that car manufacturers in different
countries have made to make their models more fuel efficient.
Finally one can analyze the degree to which energy services are
provided without consumption of fossil fuels:
"Still, high fossil-fuel prices and growing environmental
concerns have given renewable power its first big boost since the
oil shocks of the '70s. What's more, over the last 25 years, the
technologies to harness wind, sun, and the bounty of
biomass--fuels such as ethanol and methane, derived from organic
waste--have improved by leaps and bounds.
Part of the appeal is that green no longer necessarily means
pricey. " (2)
For instance the cost for electricity from wind energy is today
about eight times cheaper than it was in 1980.
Prions May Play Crucial Role In Evolution, Science Daily
Excerpt: "Prions, abnormally folded proteins
associated with several bizarre human diseases, may hold the key
to a major mystery in evolution: how survival skills that require
multiple genetic changes arise all at once when each genetic
change by itself would be unsuccessful and even harmful.
In a study in the September 28, 2000, issue of Nature
researchers at the Howard Hughes Institute at the University of
Chicago describe a prion-dependent mechanism that seems perfectly
suited to solving this dilemma, at least for yeast. It allows
yeast to stockpile an arsenal of genetic variation and then
release it to express a host of novel characteristics, including
the ability to grow well in altered environments.
"We found that a heritable genetic element based on protein
folding, not encoded in DNA or RNA, allows yeast to acquire many
silent changes in their genome and suddenly reveal them," said
Susan Lindquist, Ph.D., professor of molecular genetics and cell
biology at the University of Chicago, Howard Hughes Investigator
and principal author of the study.
There are thousands of proteins in every cell and each one
has to fold into just the right shape in order to function. In
prion diseases, which include mad cow disease and
Creutzfeldt-Jakob disease, a normal cell protein, PrP, assumes an
abnormal shape.
Mis-folded proteins are usually just degraded, but the prion
protein causes other PrP proteins to mis-fold, too, creating a
protein-folding chain reaction. Thus, they act as infectious
agents. As more and more of the proteins fold into the prion
shape, they form inactive aggregates which lead to dysfunction and
disease.
A few years ago geneticists made the startling discovery
that yeast, the organism found in bread and beer, has prions, too.
Yeast prions are unrelated to the mammalian prions, and don’t
harm humans or yeast. They do, however, have the unusual property
of mis-folding in the same peculiar way and spreading their change
in shape from one protein to another. Mother cells pass these
proteins to their daughters, so the change, once it occurs, is
inherited from generation to generation. "(...)
-
Excerpt: "Neural progenitor cells transplanted to
the diseased retina of rats have integrated into the eye, taken on
some of the characteristics of retinal cells and extended into the
optic nerve, a necessary prerequisite to re-establishing
connections to the brain, researchers reported today (Sept. 27,
2000).
The research shows promise for a new type of cellular
transplantation aimed at helping millions of people whose vision
has been impaired by retinal damage due to illnesses such as
macular degeneration, glaucoma, retinal detachment and diabetic
retinopathy, as well as brain disorders in which new neurons are
needed, such as stroke, Alzheimer's disease, Parkinson's disease,
and other forms of central nervous system injury such as spinal
paralysis.
In the first use of neural stem cells in a diseased retina -
in this case using cells derived from the hippocampus of adult
rats - the researchers found that the cells not only migrate to
the right place and appear to take on the right characteristics,
but also show early signs of trying to connect the retina to the
brain - a necessary step in restoring sight.
"This is very encouraging, since there are many blinding
diseases of the retina for which there are no cures," said Michael
Young, Assistant Scientist at The Schepens Eye Research Institute
who led the studies. "If we can transplant new cells into the
retina, we may be able to restore sight in instances where visual
loss is caused by damaged retinal cells." (...)
Nonlinear Dynamics Of Heart Rate Variability, AJP-Heart
Abstract: Indexes of heart rate variability (HRV)
based on linear stochastic models are independent risk factors for
arrhythmic death (AD). An index based on a nonlinear deterministic
model, a reduction in the point correlation dimension (PD2i), has
been shown in both animal and human studies to have a higher
sensitivity and specificity for predicting AD. Dimensional
reduction subsequent to transient ischemia was examined previously
in a simple model system, the intrinsic nervous system of the
isolated rabbit heart. The present study presents a new model
system in which the higher cerebral centers are blocked chemically
(ketamine inhibition of N-methyl-D-aspartate receptors) and the
system is perturbed over a longer 15-min interval by continuous
hemorrhage. The hypothesis tested was that dimensional reduction
would again be evoked, but in association with a more complex
relationship between the system variables. The hypothesis was
supported, and we interpret the greater response complexity to
result from the larger autonomic superstructure attached to the
heart. The complexities observed in the nonlinear heartbeat
dynamics constitute a new genre of autonomic response, one clearly
distinct from a hardwired reflex or a cerebrally determined
defensive reaction.
-
Excerpt: "Recent accounts of young school
students shooting each other has sent a shiver through the nation;
journalists call the killings an "epidemic" and legislators have
begun debates on new gun control laws. As tragic as these
homicides are, however, they represent only the tip of an iceberg
of gun deaths in the United States. Every year, more than 30,000
people are shot to death in murders, suicides, and accidents.
Another 65,000 suffer from gun injuries.
"The total number of school shootings each year is typically
far less than one day's toll attributable to firearms in the
United States," notes David Hemenway, director of the Harvard
Injury Research and Control Center. "Defective Firestone tires may
have killed 103 people over a number of years, but firearms kill
about 85 people every day in this country."
Hemenway and his colleagues at the Harvard School of Public
Health have begun a pilot effort to develop the first national
reporting system for firearm deaths. It would be similar to that
used by the National Highway Traffic Safety Administration to
track motor vehicle deaths.
"When a motor vehicle fatality occurs in the United States,
more than 100 pieces of data are collected, everything from the
make of the vehicle to details of the road conditions," Hemenway
points out. Such statistics give lawmakers the information they
need to design new safety regulations. The Harvard pilot effort,
called the National Firearm Injury Statistics System (NFISS), is
expected to lead to the same kind of information for gun deaths.
The goal of the system is to let university researchers,
government agencies, and lawmakers know what they don't know now,
and to use that information to design laws aimed at reducing
firearm deaths. "The U.S. leads the industrial world in gun
suicides, murders, and accidents," says Hemenway. "No other
developed country comes close to our death rates, and that should
not be."
As an example, no one knows how effective the recent ban on
certain types of assault rifles has been because no record exists
of how many individuals were shot by such weapons before or after
the ban." (...)
Links & Snippets
1 Disruption, Subversion, Disorder, Yes!, Esquire
Excerpt: "Complexity offers insights for surviving
change. "The world changes faster than ever, and even the best
manager with a blueprint for a company's future will inevitably
find himself left behind," offers George Overholser of Capital
One. "If you're stuck in a company that's run on command and
control, you'll lose. Managers have to think of themselves as
venture capitalists; they shouldn't just manage their favorite
ideas, they should manage a portfolio of ideas and make sure
new ideas are coming in fast." Invite conflict; shun
equilibrium."
2 What Do You Get When You Cross An Ant With A Frog?, Financial Times
Excerpt: "MediaNet International-Asianet/Ants and
frogs interbreeding? That's at the core of a new software
system based on two companies' observations of how ants create
order from chaos, and how frogs identify and catch a juicy fly.
Colony Merlin, announced today, is a hybrid created by
two companies: Transcom Software Inc. (TransCom), whose
intelligent software is inspired by ants' sophisticated
problem-solving ability, and Excalibur Technologies (Nasdaq:
EXCA) whose market-leading RetrievalWare is based on the
biological behaviour of frogs. "
3 Creative Web Taxes In Europe, NYTimes
Excerpt: "Essentially, the legislation proposed in
June by the European Commission, the Brussels-based executive
arm of the 15-nation European Union, defines digital products
like software and video programming downloaded by computer as
services rather than goods.
The idea is to ensure that such transactions face the
value-added tax, an elaborate system begun in Europe in which
purchases are taxed at each stage from production to final
sale. (However lucrative, it is a system that politicians in
the United States have shied away from.)"
It will be interesting to watch how this decision will
affect the information economy in those countries.
-
A NAME="12.4">
The Workshop and Conference is designed to present major
advances and recent developments of econophysics and financial
complexity that highlight the modern trends being taking place.
The Workshop and Conference will invite some international
notable physicists and economicists as lecturers/speakers. Many
of them made important contributions to the new field and are
themselves participants in forming these modern trends. The
Workshop is mainly open to graduate students in all
universities in China. The Conference will bring together
economists, financial experts, physicists and mathematicians in
discussion of market models and applications of physics in
finance analysis.
Special Announcement: Artists Explore Complex Systems, Federal Reserve Board
COMPLEXITY,
the first major museum exhibition about complex systems, is on
display at the Federal
Reserve Board in Washington, DC, ongoing -
03/11/28. The Washington exhibition is being co-sponsored
by the Washington
Center for Complexity and Public Policy and the Fine
Arts Program of the Federal Reserve Board.
