Geo-Engineering: Sequestering CO2 By Iron Fertilization Of Oceans, Nature/G3-Online 
Attempts of controlling chaotic or complex systems
requires detailed knowledge about the system or else there might
be surprise outcomes that might be the complete opposite of the
desired goals or even worse. That is one reason why there always
was a strong opposition against experiments in controlling one of
the largest complex systems that we can lay our hands on, our
atmosphere. Early experiments in weather control had some dramatic
failures such as the potential change in the path of a hurricane
with tremendous damage and subsequent liability suits.
On the other hand one could argue that we are at a point of no
return in our uncontrolled modification of the global climate: The
amount of CO2 in the atmosphere is already outside the
bounds that are believed to have regulated the ice ages over the
past 420,000 years (1).
Geo-Engineering has therefore been proposed to actively influence
global parameters such as CO2 concentration in the
atmosphere. One of the most promising mechanisms was thought to be
fertilizing the oceans with Iron: "
"Almost half of the photosynthesis on Earth is carried out
by phytoplankton in the sea. So these tiny cells play a huge part
in the global carbon cycle, and in regulating climate by
controlling the amount of the greenhouse gas CO2 in the
atmosphere." (2)
Boyd et al. (35 co-authors) performed a first mesoscale
experiment in the Southern Ocean (SOIREE: Southern Ocean In Situ
Iron Enrichment Experiment) by depositing
More than eight tons of an iron compound into a patch of abut
ten kilometers diameter. Over the following weeks photosynthesis
of phytoplankton (mainly in the form of diatoms) sequestered about
the a hundred times as much CO2 from the atmosphere. This is more
than was expected. The patch of fertilizer and algae then spread
by the stirring forces of the ocean currents, providing valuable
information about their dynamics.
The experiment shows that the effect is real but has
side-effects that are quite poorly understood. In spite of that
there exist already a number of proposals for much larger
experiments with hopes that besides a positive effect on the
greenhouse effect a fertilized ocean might also be beneficial for
the fishing industry.
- A
Mesoscale Phytoplankton Bloom In The Polar Southern
Ocean Stimulated, Iron
Fertilization,
Philip W. Boyd, Andrew J. Watson, Cliff S. Law,
Edward R. Abraham, Thomas Trull, Rob Murdoch, Dorothee
C. E. Bakker, Andrew R. Bowie, K. O. Buesseler, Hoe
Chang, Matthew Charette, Peter Croot, Ken Downing,
Russell Frew, Mark Gall, Mark Hadfield, Julie Hall,
Mike Harvey, Greg Jameson, Julie Laroche, Malcolm
Liddicoat, Roger Ling, Maria T. Maldonado, R. Michael
Mckay, Scott Nodder, Stu Pickmere, Rick Pridmore,
Steve Rintoul, Karl Safi, Philip Sutton, Robert
Strzepek, Kim Tanneberger, Suzanne Turner, Anya Waite,
John Zeldis, Nature 407, 695 - 702 (2000)
- Oceanography:
Stirring Times In The Southern
Ocean, Sallie W.
Chisholm, Nature 407, 685 (2000)
- Importance
Of Stirring In The Development Of An Iron-Fertilized
Phytoplankton
Bloom, Edward R.
Abraham, Cliff S. Law, Philip W. Boyd, Samantha J.
Lavender, Maria T. Maldonado, Andrew R. Bowie, Nature
407, 727 (2000)
- Does
Iron Fertilization Lead To Rapid Carbon Export In The
Southern Ocean?
Charette, M. A., Buessler, K. O. Geochem. Geophys.
Geosyst. [online] 1, Paper number 2000GC000069
(2000).
- Iron-Fed
Plankton Absorbs Greenhouse
Gases, Andrew C.
Revkin, NY Times, 10/12/00
- Satellite Images at
Sea-viewing
Wide Field-of-view Sensor
(SeaWiFS)
The Global Carbon Cycle: A Test Of Our Knowledge Of Earth As A System, Science
Our planet is probably the largest and most complex
systems on which we humans now have a direct and significant
influence because of our population size and access to technology.
According to Falkowski et al. we are currently at the end of the
Holocene and enter a new era in Earth history, the
"Anthropocene" Era where the climate is dominated by human
activity. Since it is unlikely that we will be able to undo our
impacts on the Earth-system it would make sense to understand as
much as possible about the consequences of our activities. The
authors argue that this requires a significant integration of the
disciplines that study different Earth subsystems.
Abstract: Motivated by the rapid increase in
atmospheric CO2 due to human activities since the
Industrial Revolution, several international scientific research
programs have analyzed the role of individual components of the
Earth system in the global carbon cycle. Our knowledge of the
carbon cycle within the oceans, terrestrial ecosystems, and the
atmosphere is sufficiently extensive to permit us to conclude that
although natural processes can potentially slow the rate of
increase in atmospheric CO2, there is no natural
"savior" waiting to assimilate all the anthropogenically produced
CO2 in the coming century. Our knowledge is
insufficient to describe the interactions between the components
of the Earth system and the relationship between the carbon cycle
and other biogeochemical and climatological processes. Overcoming
this limitation requires a systems approach.
- The
Global Carbon Cycle: A Test Of Our Knowledge Of Earth
As A System, P.
Falkowski, R. J. Scholes, E. Boyle, J. Canadell, D.
Canfield, J.Elser, N. Gruber, K. Hibbard, P. Hogberg,
S. Linder, F. T. Mackenzie, B. Moore Iii, T. Pedersen,
Y. Rosenthal, S. Seitzinger, V. Smetacek, W.
Steffen , Science, Vol. 290, No. 5490, 10/13/00,
pp. 291-296.
- About Epochs in Earth History
see: UCMP
Web Time Machine,
University of California Museum of Paleontology,
Berkeley
Assessing Climate Impacts, PNAS/Science
Abstract: Assessing climate impacts involves
identifying sources and characteristics of climate variability,
and mitigating potential negative impacts of that variability.
Associated research focuses on climate driving mechanisms,
biosphere-hydrosphere responses and mediation, and human
responses. Examples of climate impacts come from 1998 flooding in
the Yangtze River Basin and hurricanes in the Caribbean and
Central America. Although we have limited understanding of the
fundamental driving-response interactions associated with climate
variability, increasingly powerful measurement and modeling
techniques make assessing climate impacts a rapidly developing
frontier of science.
- Assessing
Climate Impacts, Ellen
E. Wohl, Roger S. Pulwarty , Jian Yun Zhang,
Chinese-American Frontiers Of Science Symposium, Proc.
Natl. Acad. Sci. Usa, Vol. 97, Issue 21, 11141-11142,
October 10, 2000
River Dolphins Are Different Animals, PNAS
"If it looks like a duck, and if it walks like a duck,
and if it quacks like a duck, then I'll sure call it a
'duck'". Not only chaos pioneer Joe Ford -a physicist by
training- seems to have used this rule to bring order into the zoo
of different phenomena. Phylogenetic analysis, however, shows that
this is not always true for all animals. What experts have lumped
together into one taxon "river dolphins" (they look like dolphins
and live in rivers) turns out to be quite different animals that
happened to evolve similar strategies to adapt to life in murky
rivers.
Today there are only four surviving species of river dolphins
and all of them are close to extinction; only about one hundred
Chinese Yangtze river dolphins, or ''baiji'' (Lipotes vexil-lifer)
are estimated today and there is a sad chance that they will
terminate their 35 Million year presence on this planet within our
generation.
Similarly threatened is an even more ancient species the blind
river dolphin, or ''susu'' (Platanista gangetica) living in the
Indus, Ganges, and Brahmaputra river systems on the Indian
subcontinent. The Amazon river dolphin, or ''boto'' (Inia
geoffrensis) and the La Plata dolphin, or ''franciscana''
(Pontoporia blainvillei) showed up in South America at the end of
the Oligocene ice age when Antarctica became isolated, the
circum-polar ocean circulation became established, and the
African-Arabian plate joined to Asia. (Note: Homo sapiens only
appeared about 100,000 years ago.)
Cassens et al. "demonstrate with statistical significance
that extant river dolphins are not monophyletic and suggest that
they are relict species whose adaptation to riverine habitats
incidentally insured their survival against major environmental
changes in the marine ecosystem or the emergence of
Delphinidae."
- Independent
Adaptation To Riverine Habitats Allowed Survival Of
Ancient Cetacean
Lineages, Insa Cassens,
Saverio Vicario, Victor G. Waddell, Heather
Balchowsky, Daniel Van Belle, Wang Ding, Chen Fan, R.
S. Lal Mohan, Paulo C. Simoes-Lopes, Ricardo Bastida,
Axel Meyer, Michael J. Stanhope, Michel C.
Milinkovitch, PNAS 2000;97 11343-11347
Nyt Dyr Fundet I Kilde På Grønland (New Animal Found In Greenland), DPC/Reuters/Discovery.com
In times where one only hears about endangered
species that are at risk to go extinct it is a pleasant surprise
that even in the 21st century completely new kinds of animals are
discovered. This is the claim of Danish scientists who found a
small (0,1mm) creature in a well in Greenland. They had to create
a new phylum (family) for Limnognathia maerski, (see picture)
which is only the fourth such creatures discovered in the past
hundred years. Its outstanding feature is a set of very
complicated jaws.
"The researchers believe that the most significant highlight
of this study is that "the complexity of the jaw apparatus of
Limnognathia maerski is far beyond what is seen in other
invertebrates such as gnathostomulids, rotifers, and dorvilleid
polychaetes." They suggest that this study's findings have
significant implications, with regard to more clearly defining the
relationship between Rotifera, Gnathostomulida, and
Micrognathozoa. "
"Maerski uses its jaws to scrape the bacteria and algae it
feeds on from underwater moss growing in icy wells which freeze
over during the long Arctic winter.
The animal was found in samples taken in 1994 from a well in
Isunngua on Disco island in northwestern Greenland. A colony of
the tiny creatures, all females, is in a refrigerator at
Copenhagen University."
"Based on the findings of the research conducted, the
researchers specified the following classification for the newly
discovered microscopic animal: Phylum Gnathifera Ahlrichs, 1995;
Micrognathozoa, new class; Limnognathida, new order;
Limnognathiidae, new family; Limnognathia gen. nov.; Limnognathia
maerski sp. nov.
Only specimens with the female reproductive system have been
found. An intensive search for smaller males was conducted, but
none were found, indicating that all adult animals are
parthogenetic females. "
- Nyt
Dyr Fundet I Kilde På
Grønland,
Pressemeddelelse Fra Dansk Polarcenter,
10/11/00
- Endnu
En Kvist På Livets
Træ, Jens J.
Kjærgaard, Dansk Polarcenter, 10/10/00 ,
picture
- New
Animal Found In
Greenland,
Discovery.com/Reuters, Oct. 13, 2000
- Published in Journal of
Morphology, Volume 246, Number 1, October
2000
- Contributed by Prof.
Reinhardt Mobjerg Kristensen
Marijuana Use Rises And Falls With Price And Perceived Harm, UI Chicago/ Science Daily
Marijuana use rises and falls with price
and perceived harm, study shows Marijuana use among youth
decreases as marijuana prices and perceived harmfulness rise,
conclude researchers from the UIC ImpacTeen Project and
University of Michigan Youth Education and Society Project
(YES!). Their recent study also assesses the extent to which
trends in marijuana prices and perceptions of use risks predict
cycles in youth marijuana use.
Marijuana use among high school seniors declined to a
recorded low between 1981 and 1992, when price more than
tripled. The trend reversed itself after 1992, when price fell
by 16 percent.
The study shows that perceived risk of harm from
marijuana use had a substantial impact on the reduction in
marijuana use between 1981 and 1992 (as perceived risk rose)
and in the subsequent increase in use after 1992 (as perceived
risk declined). These conclusions, now taking price into
account, are consistent with ones reached earlier by the
University of Michigan investigators, who for years have argued
the importance of perceived risk in explaining trends in the
use of various drugs.
Complete findings are presented in the Bridging the Gap
paper titled "Marijuana and Youth," found under "Papers and
Presentations" at www.uic.edu/orgs/impacteen
"This is the first paper that uses nationally
representative data to look at the impact of prices on youth
marijuana use," said Frank Chaloupka, professor of economics at
UIC and director of the UIC ImpacTeen Project.
Traditionally, researchers have not considered price as a
determining factor in marijuana use among youth. The handful of
studies that have examined the relationship between youth
marijuana use and price relied on small, unrepresentative
samples, Chaloupka explained.
The researchers recommend that further research be
conducted to provide a more complete understanding of the
relative impact of price and attitudes on youth marijuana use.
"Changes in the price of marijuana and in the perceived
risk of harm from regular marijuana use contribute to an
understanding of the number of teens who use marijuana and
underscore the usefulness of considering price in addition to
more traditional determinants in future studies," said
Chaloupka.
ImpacTeen researchers have been leaders in investigating
the effects of price on the demand for tobacco, alcohol and
illicit drugs. In researching the effect of price on marijuana
use among youth, the paper's authors employed data on marijuana
prices and potency from the U.S. Drug Enforcement
Administration Office of Intelligence, and data on the demand
for marijuana among a nationally representative sample of
American high school seniors from the annual Monitoring the
Future Survey conducted by UM researchers. The National
Institute on Drug Abuse funds the survey.
Catalytic Tempering: A Method For Sampling Rough Energy Landscapes by Monte Carlo, PNAS
The dynamics of complex systems often is viewed as
movement on rugged or rough landscapes that evolve at the same
time. The elevation of a point in the landscape is interpreted as
the inverse fitness value of the (artificial) creature associated
with that point in the landscape. The goal is to follow the
landscape to the lowest point (corresponding to maximal fitness)
without being stuck in a local minimum. A number of methods such
as simulated annealing have been developed to allow an evolving
system to get unstuck in the false minimum. Stolovitzky et al
propose a new method with better results.
Abstract: "A new Monte Carlo algorithm is presented for the
efficient sampling of the Boltzmann distribution of configurations
of systems with rough energy landscapes. The method is based on
the introduction of a fictitious coordinate y so that the
dimensionality of the system is increased by one. This augmented
system has a potential surface and a temperature that is made to
depend on the new coordinate y in such a way that for a small
strip of the y space, called the "normal region," the temperature
is set equal to the temperature desired and the potential is the
original rough energy potential. To enhance barrier crossing
outside the "normal region," the energy barriers are reduced by
truncation (with preservation of the potential minima) and the
temperature is made to increase with |y|. The method, called
catalytic tempering or CAT, is found to greatly improve the rate
of convergence of Monte Carlo sampling in model systems and to
eliminate the quasi-ergodic behavior often found in the sampling
of rough energy landscapes."
Dynamic Organization Of Network Structures In Brain And Companies, Z. Betriebswirtschaft
Hierarchically arranged structures in private companies
(and the public sector) are becoming replaced more and more by
network-like structures in order to react faster and more
efficiently to changes in demand. A comparison with neuronal
networks of the brain, which also possess this feature, is
justifiable. Principles of dynamic organization of the brainstem
reticular formation are presented and compared with those of
companies.
The reticular formation is an important structure in the
central nervous system. Information from the whole body and the
environment is steadily received and processed. It controls and
coordinates many vital functional systems like circulation,
respiration, and muscle tone and their immediate reaction to
changes in internal and external conditions of the body and the
attention of the brain during wakefulness and sleep. In addition,
it exerts influences on perception and complex brain functions,
like learning and memory.
The principles of reticular formation organization have been
analyzed by experimental investigations. Three basic types of
organization were found and could be assigned to different
activity levels of the body. At the intermediate activity level,
nerve cells can be reorganized and assigned to different processes
of the body with high flexibility - depending on the incoming
information. According to the requirements of the body and the
state of the neuronal network, neuronal subunits ("working teams")
of neighboring nerve cells develop for a limited period. Due to
this dynamic organization - i.e. because no fixed "centers" exist
- the functional term "Common Brainstem System" (CBS) was chosen
instead of the more morphological name "reticular formation".
The paper describes essential features and conditions of
dynamic network organizations in the networks of both fields,
brain and companies: Multifunctional network elements (neurons or
employees of a company, respectively) can be organized dynamically
by the influence of information coming from inside the system or
its environment. Depending on their organizational state, they can
be integrated into several partial processes, belonging to several
operational subunits ("working teams") at the same time or,
temporarily, they can execute specific tasks. Essential for a
dynamic organization is the similarity in basic structure of the
network elements concerned and their basic information about the
processes into which they may be integrated, high availability of
information about the actual processes and network situation, as
well as the exchange of this information in the network. On
principle, networks have several pathways for ongoing processes
and are very suited to facilitating variable coordination of
partial processes under changing conditions. This is demonstrated
with the aid of a specific example, and how to create
prerequisites for the practical use of dynamic organization
principles in companies is discussed. It should be noted, however,
that any application needs adequate adaptation and should be open
to further development.
Computational Neuroscience: Building Blocks Of Movement, Nature
Finding a convincing theory for the self-organization of
coordinated movement is one of the great challenges for complex
systems researchers. In traditional bio-mechanics mechanical
degrees of freedom were analyzed with the help of mechanistic mass
spring models. The more complex issue is how our muscles produce
time dependent forces that lead to precise coordinated movements.
Because voluntary movements are controlled by our spontaneous
decisions, the dimensional complexity of our movement is only
limited by practical factors such as limited maximal force
production and fatigue.
For simple, repeated movements such as reaching for an object
we can quickly adapt to external perturbations for instance those
one experiences in a moving subway. Thoroughman et al. constructed
a robot arm that will produce a programmable deflection force
perpendicular to the movement direction and with a magnitude that
is proportional to the movement velocity. After a few trials one
usually learns to compensate for the perturbation force and
reaches the target with a small error. As a consequence
interspersed "catch trials" lead to a large error in the direction
that the muscles would usually compensate for the anticipated
external force:
"The authors reason that if a reaching movement occurring
within a force field causes the brain to learn, and if this
learning is represented by changes to motor primitives, then
changes will be seen in subsequent reaching movements - not only
in the target direction but also in other directions. So, by
working out how learning 'spills over', or generalizes, between
movement directions, the mathematical shape of the motor
primitives can be uncovered."
This study also provides new evidence for the role of Purkinje
cells in the cerebellum for motor learning.
Intermittency In The Control Of Continuous Force Production, J. Neurophysiol
Abstract: The purpose of the current
investigation was to examine the influence of intermittency in
visual information processes on intermittency in the control
continuous force production. Adult human participants were
required to maintain force at, and minimize variability around, a
force target over an extended duration (15 s), while the
intermittency of on-line visual feedback presentation was varied
across conditions. This was accomplished by varying the frequency
of successive force-feedback deliveries presented on a video
display. As a function of a 128-fold increase in feedback
frequency (0.2 to 25.6 Hz), performance quality improved according
to hyperbolic functions (e.g., force variability decayed),
reaching asymptotic values near the 6.4-Hz feedback frequency
level. Thus, the briefest interval over which visual information
could be integrated and used to correct errors in motor output was
approximately 150 ms. The observed reductions in force variability
were correlated with parallel declines in spectral power at about
1 Hz in the frequency profile of force output. In contrast, power
at higher frequencies in the force output spectrum were
uncorrelated with increases in feedback frequency. Thus, there was
a considerable lag between the generation of motor output
corrections (1 Hz) and the processing of visual feedback
information (6.4 Hz). To reconcile these differences in visual and
motor processing times, we proposed a model where error
information is accumulated by visual information processes at a
maximum frequency of 6.4 per second, and the motor system
generates a correction on the basis of the accumulated information
at the end of each 1-s interval.
Learning To Forget: Continual Prediction With LSTM, Neural Comp
Abstract: Long short-term memory (LSTM;
Hochreiter & Schmidhuber, 1997) can solve numerous tasks not
solvable by previous learning algorithms for recurrent neural
networks (RNNs). We identify a weakness of LSTM networks
processing continual input streams that are not a priori segmented
into subsequences with explicitly marked ends at which the
network's internal state could be reset. Without resets, the state
may grow indefinitely and eventually cause the network to break
down. Our remedy is a novel, adaptive "forget gate" that enables
an LSTM cell to learn to reset itself at appropriate times, thus
releasing internal resources. We review illustrative benchmark
problems on which standard LSTM outperforms other RNN algorithms.
All algorithms (including LSTM) fail to solve continual versions
of these problems. LSTM with forget gates, however, easily solves
them, and in an elegant way.
Video Game Images Persist Despite Amnesia, Science
There seems to be increasing evidence that sleeping and
dreaming are important for learning because they are facilitating
"unlearning" of detailed information that is not relevant for the
learning goals and that is better forgotten in favor of task
relevant information.
Stickgold et al. tested this hypothesis with subject who were
asked to learn the computer game tetris:
"People in both groups reported that, as they fell asleep,
they dreamed about images of blocks falling and rotating, as they
do on the computer screen when the game is in progress. They did
not actually dream about the game itself.
The amnesia patients did not remember playing the game and
they did not ever improve, unlike the volunteers with normal
memory. Three of them did report the strange dreams, however.
"
"The researchers found that people who have just learned to
play Tetris have vivid images of the game pieces floating before
their eyes as they fall asleep, a phenomenon the researchers say
is critical for building memories. Much more surprisingly, the
team also found that the images appear to people with amnesia who
have played the game--even though they have no recollection of
having done so."
- Video
Game Images Persist Despite
Amnesia,
Science, Vol. 290, No.5490,
p.247a
- Replaying
The Game: Hypnagogic Images In Normals And
Amnesics, Robert
Stickgold, April Malia, Denise Maguire, David
Roddenberry, Margaret O'connor,
Science, Vol. 290, No.5490, p.
350
- Dreaming
Of Tetris, Aries
Keck,
Discovery.Com News, Oct. 12, 2000
- Study
Shows Why Your Dreams Are So
Weird, CNN.com
health, October 13, 2000
Learning Chaotic Attractors By Neural Networks, Neural Comp.
Abstract: An algorithm is introduced that trains
a neural network to identify chaotic dynamics from a single
measured time series. During training, the algorithm learns to
short-term predict the time series. At the same time a criterion,
developed by Diks, van Zwet, Takens, and de Goede (1996) is
monitored that tests the hypothesis that the reconstructed
attractors of model-generated and measured data are the same.
Training is stopped when the prediction error is low and the model
passes this test. Two other features of the algorithm are (1) the
way the state of the system, consisting of delays from the time
series, has its dimension reduced by weighted principal component
analysis data reduction, and (2) the user-adjustable prediction
horizon obtained by "error propagation"—partially propagating
prediction errors to the next time step.
The algorithm is first applied to data from an
experimental-driven chaotic pendulum, of which two of the three
state variables are known. This is a comprehensive example that
shows how well the Diks test can distinguish between slightly
different attractors. Second, the algorithm is applied to the same
problem, but now one of the two known state variables is ignored.
Finally, we present a model for the laser data from the Santa Fe
time-series competition (set A). It is the first model for these
data that is not only useful for short-term predictions but also
generates time series with similar chaotic characteristics as the
measured data.
Econophysics And Financial Complexity, Conference Report
The Workshop attracted over 80 participants from
different institutions in Mainland China, and from other places
including Germany, Hong Kong, Singapore, Switzerland, Taiwan, UK,
and USA. While the Workshop was hosted by the Centre of Nonlinear
Science at USTC, participants, however, are not restricted to
physicists and nonlinear scientists. In fact, they represent a
board spectrum including economists, faculty members from business
schools, and analysts from research institutes and companies.
A total of 21 invited talks and 12 contributed talks were
delivered. The opening talk was given by Lei-Han Tang (Hong Kong
Baptist University) on time series analysis of high frequency data
in financial physics. Pak-Ming Hui (Chinese University of Hong
Kong) reviewed the exciting developments in several agent-based
models of a competing population that formed the basic models for
markets. Joe McCauley (U. Houston, USA), in his three hours of
lectures, argued that the Adam Smith's hand does not exist and
discussed in detail the wrong definitions of "equilibrium" in
economics and finance. Yongmiao Hong, an economist and
statistician at Cornell University, gave detailed accounts on
novel techniques in econometrics including the generalized
spectral analysis, entropy as a measure of serial dependence in
financial data, and wavelet-based testing for special correlation
and ARCH effects. Kan Chen (NSU, Singapore) reviewed works on
learning algorithm for optimization problems and on new findings
in forest fire models. Geoff Rodgers (Brunel University, UK) gave
lectures on herding in financial markets and on a model giving the
size distribution of shops in a price driven market. Chin-Kun Hu
(Institute of Physics, Academia Sinica, Taipei) reviewed the ideas
of scaling and universality in critical systems and his recent
work on synchronization in complex systems.
The highlight of the conference was the five hours of talks by
Yi-Cheng Zhang (Fribough University, Switzerland), who is one of
the leaders in the field of econophysics. Zhang challenged the
economists by giving various examples pointing at an "wonderfully
inefficient market", which is also the title of a book that Zhang
is working on. It was argued that economists might have made too
crude an approximation in taking the market to be efficient.
Understandably, the talks have led to lively discussions and
debates, especially from the economists in the audience.
As summarized by Bing-Hong Wang (USTC), the conference chairman
who reviewed techniques for handling time series in financial
data, "It was the first international conference on the topic in
China. I am glad to see that researchers from different
disciplines came all over China to participant in the conference.
The general feeling at the conclusion of the conference was that
physicists, economists, and financial analysts can all be
benefited from strengthening their collaborations and talking to
each other more effectively. It is a good start and the conference
served its purpose. I am sure that the physics community in China
will keep up with the pace of the world in this arena."
The conference ended with a relaxing trip to the beautiful
Yellow Mountain.
Links & Snippets
-
The Center
for Business Innovation invited about three dozen
complexity notables to its Cambridge, Massachusetts, USA,
center for a day and a half discussion on application of
complexity to future developments. Most where academics and
research projects were discussed in general terms. Most of the
discussion was on artificial life, biological metaphors and
corporate applications of adaptive systems. Dean
LeBaron, publisher of ComDig,
was a participant and provides a brief video introduction and
videoed some clips from the meeting.
- Note: To view these videos, you'll need RealPlayer.
Click here
to download the latest version
-
2 Spatial Distribution Of Contextual Interactions In Primary Visual Cortex And In Visual Perception, J. Neurophysiol
Abstract: To examine the role of primary visual
cortex in visuospatial integration, we studied the spatial
arrangement of contextual interactions in the response
properties of neurons in primary visual cortex of alert monkeys
and in human perception. We found a spatial segregation of
opposing contextual interactions. At the level of cortical
neurons, excitatory interactions were located along the ends of
receptive fields, while inhibitory interactions were strongest
along the orthogonal axis. Parallel psychophysical studies in
human observers showed opposing contextual interactions
surrounding a target line with a similar spatial distribution.
The results suggest that V1 neurons can participate in multiple
perceptual processes via spatially segregated and functionally
distinct components of their receptive fields. "
3 Kinematic And Dynamic Control Of Multijoint Movement, J. Neurophysiol.
Abstract: We previously showed that inactivating the
anterior interpositus nucleus in cats disrupts prehension; paw
paths, normally straight and accurate, become curved,
hypometric, and more variable. In the present study, we
determined the joint kinematic and dynamic origins of this
impairment. Animals were restrained in a hammock and trained to
reach and grasp a cube of meat from a narrow food well at
varied heights; movements were monitored using the MacReflex
analysis system. The anterior interpositus nucleus was
inactivated by microinjection of the GABA agonist muscimol
(0.25-0.5 µg in 0.5 µL saline). For each joint, we
computed the torque due to gravity, inertial resistance (termed
self torque), interjoint interactions (termed interaction
torque), and the combined effects of active muscle contraction
and passive soft tissue stretch (termed generalized muscle
torque). Inactivation produced significant reductions in the
amplitude, velocity, and acceleration of elbow flexion.
However, these movements continued to scale normally with
target height. Shoulder extension was reduced by inactivation
but wrist angular displacement and velocity were not.
Inactivation also produced changes in the temporal coordination
between elbow, shoulder, and wrist kinematics. Dynamic analysis
showed that elbow flexion both before and during inactivation
was produced by the combined action of muscle and interaction
torque, but that the timing depended on muscle torque.
(...)
4 Neural Systems As Nonlinear Filters, Neural Comp
Abstract: Experimental data show that biological
synapses behave quite differently from the symbolic synapses in
all common artificial neural network models. Biological
synapses are dynamic; their "weight" changes on a short
timescale by several hundred percent in dependence of the past
input to the synapse. In this article we address the question
how this inherent synaptic dynamics (which should not be
confused with long term learning) affects the computational
power of a neural network. In particular, we analyze
computations on temporal and spatiotemporal patterns, and we
give a complete mathematical characterization of all filters
that can be approximated by feedforward neural networks with
dynamic synapses. It turns out that even with just a single
hidden layer, such networks can approximate a very rich class
of nonlinear filters: all filters that can be characterized by
Volterra series. This result is robust with regard to various
changes in the model for synaptic dynamics. Our
characterization result provides for all nonlinear filters that
are approximable by Volterra series a new complexity hierarchy
related to the cost of implementing such filters in neural
systems.
5 Clustering Irregular Shapes Using High-Order Neurons, Neural Comp.
Abstract: This article introduces a method for
clustering irregularly shaped data arrangements using
high-order neurons. Complex analytical shapes are modeled by
replacing the classic synaptic weight of the neuron by
high-order tensors in homogeneous coordinates. In the first-
and second-order cases, this neuron corresponds to a classic
neuron and to an ellipsoidal-metric neuron. We show how
high-order shapes can be formulated to follow the
maximum-correlation activation principle and permit simple
local Hebbian learning. We also demonstrate decomposition of
spatial arrangements of data clusters, including very close and
partially overlapping clusters, which are difficult to
distinguish using classic neurons. Superior results are
obtained for the Iris data.
6 Induction Of Photosensitivity In Neonatal Rat Pineal Gland, PNAS
Abstract: Pineal glands removed from neonatal rats
at 5, 7, and 9 days of age and explanted into short-term
culture, synthesized melatonin when stimulated with
norepinephrine (NE); their melatonin synthesis could not be
suppressed with bright white light. Dispersed pineal cell
cultures or pineal explants prepared from 1-day-old neonates
and held in culture for 7 or 9 days also synthesized melatonin
when stimulated with NE, but in these cases melatonin synthesis
was significantly suppressed by light, demonstrating that the
pineals had become photosensitive while in culture. The
development of photosensitivity in culture could be partially
or completely abolished by the continuous presence of 1 or 10
µm of NE in the culture medium. The pineals of all
nonmammalian vertebrates are photoreceptive, whereas those of
mammals do not normally respond to light. We hypothesize that a
mechanism to suppress pineal photosensitivity by using NE
released from sympathetic nerve endings evolved early in the
history of mammals.
7 Self-Assembled Ceramics Produced ,Complex-Fluid Templation, Annu. Rev. Phys. Chem
- Abstract: This review examines the use of
self-assembly in the fabrication of ceramic mesostructures,
emphasizing the use of amphiphilic surfactants and block
copolymers. The association between this area of research
and biomimetics is discussed, linking developments in
synthetic self-assembly with biomineralization. The
fabrication of hierarchical structures through the use of
simultaneous processing is shown to be a necessary condition
for applications of this new technology.
8 A Bacterial Toxin That Controls Cell Cycle Progression As A Deoxyribonuclease I-Like Protein, Science
- Abstract: Many bacterial pathogens encode a
multisubunit toxin, termed cytolethal distending toxin
(CDT), that induces cell cycle arrest, cytoplasm distention,
and, eventually, chromatin fragmentation and cell death. In
one such pathogen, Campylobacter jejuni, one of the subunits
of this toxin, CdtB, was shown to exhibit features of type I
deoxyribonucleases. Transient expression of this subunit in
cultured cells caused marked chromatin disruption.
Microinjection of low amounts of CdtB induced cytoplasmic
distention and cell cycle arrest. CdtB mutants with
substitutions in residues equivalent to those required for
catalysis or magnesium binding in type I deoxyribonucleases
did not cause chromatin disruption. CDT holotoxin containing
these mutant forms of CdtB did not induce morphological
changes or cell cycle arrest.
9 Second Thoughts On Skill Of El Nino Predictions, Science
- "The use of more complex, physically realistic
dynamical models does not automatically provide more
reliable forecasts," the NOAA researchers write. They don't
investigate the reason, but it probably involves the
unrealistic way the models simulate the distribution of rain
in the tropics."(...)
"…so-called empirical models are, in essence,
automated rules of thumb that compare sea surface
temperature and atmospheric pressure in the tropical Pacific
with conditions preceding El Niños of the past 40
years"
10 Birth Control Policies In Wasp Societies, Nature
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- Excerpt: Kin-selection theory predicts that in
social-insect colonies where the queen has mated multiple
times, the workers will enforce cooperation by policing each
other's reproduction. We have discovered a species, the wasp
Dolichovespula saxonica, in which some queens mate once and
others mate many times, and in which workers frequently
attempt reproduction, allowing this prediction to be tested
directly. We find that multiple mating by the queen leads to
mutual policing by workers, whereas single mating does
not.
