Complexity Digest 2000.22

29-May-2000

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Content

  1. A Novel Chaotic Secure Communication System, Int. J. Bifurcation & Chaos
  2. Communication Among Free Ranging Whales and Dolphins, Synopsis
  3. Macromolecular Ballet, Science
  4. Certain Genetic Mutations Affect Human Response To Environmental Contaminant, Science Daily News
  5. Market Ecology etc. in Microscopic Simulation of the LLS Stock Market Model, ArXiv
  6. Arctic Ozone Depletion And Polar Stratospheric Clouds, Science Daily News
  7. Why 2001 will be the Year of Streaming Media, ZDNet
  8. Internet and Society Conference 2000, Harvard University
  9. Four Choice Metaphors for Economic Systems Analysis, ICCS3 Conference
  10. The Scientist in the Crib, Minds, Brains, and How Children Learn, BioMedNet
  11. NIST Conference on Measuring Intelligence, Announcement
  12. Links & Snippets
    1. 1 How Ants Invade, Science
    2. 2 Brain Cells Reveal Surprising Versatility, Science
    3. 3 The Patterns Hidden in Market Swings, New York Times

  1. A Novel Chaotic Secure Communication System, Int. J. Bifurcation & Chaos Next Article Bookmark and Share

    Today's cell phones operate at Giga-Hertz frequencies basically producing microwaves which have been speculated to have adverse health effects on the user. The next generation of cell phones will not use a single high frequency but a "spread spectrum technology" originally invented during WW-II by actress Hedy Lamarr and composer George Antheil. The basic idea is not to use a fixed carrier frequency for the transmission but change the frequency rapidly in a manner that can only be predicted by the receiver. The connection to chaotic dynamics seems evident. Yang and Chua demonstrate a way how chaotic impulses can reliably implement this basic concept:

    Abstract: A chaotic impulse radio system is an ultrawide-band communication system that uses a train of very narrow baseband impulses as a carrier. In the transmitter of a chaotic impulse radio system, a message signal is modulated by two kinds of pulse carriers. Firstly, a frequency modulation is used to modulate the message signal into a subcarrier that functions as the clock pulses of a chaotic circuit. Driven by the modulated clock pulses, the chaotic circuit outputs a chaotic impulse positioning sequence which generates the positions of the carrier impulses. The specially designed chaotic circuit in the transmitter guarantees that the time intervals between the carrier impulses are chaotic. Thus the energy of the impulse carrier is distributed evenly over the entire bandwidth. In the receiver of a chaotic impulse radio system the message signal is demodulated in two stages. At the first stage, the time interval between two consecutive impulses is recovered. At the second stage, a simple algorithm based on the knowledge of the chaotic circuit in the transmitter is used to calculate partially the locations of the inner clock pulses which in turn are used to demodulate the message signal. No synchronization at any level is needed in this chaotic impulse radio system. The security of this chaotic impulse radio system depends on the hardware parameters of the chaotic circuit and the inner clock pulse train. Simulation results are presented to illustrate the design procedure of an example of this chaotic impulse radio system.


  2. Communication Among Free Ranging Whales and Dolphins, Synopsis Next Article Bookmark and Share

    Research with captive dolphins and whales has revealed that these animals are capable of highly complex and sophisticated syntactic communication with humans and among themselves. Although it has been known for a while that free-ranging dolphins and whales also show social vocalizations it is extremely difficult to analyze the communication patterns in more detail. One experimental difficulty is the fact that with several animals vocalizing simultaneously in a group it is a challenging task to associate a given vocalization with a specific animal and its behavior. In recent years there has been significant progress in analyzing signals from multiple hydrophone arrays that make it now feasible to "listen in to a conversation" in the open ocean.

    Vanik observed that dolphins (Tursiops truncatus) display a certain low frequency vocalization ("bray calls") predominantly when they are catching fish (e.g. salmon). The researcher also observed that other dolphins within hearing range will respond to those calls with rapid approach swimming. It still is not clear if this behavior is an epi-phenomenon to the hunting dolphin's vocalization e.g. towards the fish (one hypothesis is that the frequency is adjusted to the salmon's optimal hearing range and is intended to deafen and disorient the fish) or if the calls are intended to attract other dolphins (like a call for dinner).

    Other whales, especially sperm whales are known to use powerful blasts of sound energy as a tool to stun their prey. Now Andri et al. report that they found rhythmical sequences in echolocation click trains of sperm whales that they claim might be used for identification (acoustic "signature") and communication:

    Excerpt: (...) The Fourier spectrum, which yields the harmonic aspects of each isolated click sequence, shows a deterministic structure that appears as a strong modulating frequency. This shows that click production is not a random process and possibly characterises, in fact, a signature of the animal.

    Here we introduce a new concept: this rhythmic modulation represents the acoustic signature of each individual sperm whale, which we have called RIME (Rhythmic Identity Measurement). The RIME would allow a whale to distinguish its own echo time pattern from the background of other click trains during echolocation. The RIME appears to represent a new concept in communication strategies and might also be present in other-social-odontocete repertoires.


  3. Macromolecular Ballet, Science Next Article Bookmark and Share

    Living cells have been considered as one of the classic examples of mesoscopic systems with emergent universal properties that are independent of microscopic detailed mechanisms (see Complexity Digest 2000.1.1). That does not imply, however, that research into some of the fundamental processes that make a cell work cannot yield fascinating results and new insights. Vinson et al. review a number of recent discoveries of procedures that cells have developed to achieve their amazing tasks.

    One are of recent progress involves the central role of the cell nucleus of higher organisms. In a way the nucleus can be compared to a metropolitan city, a place where things happen. For instance in the nucleus chromosomes with their genetic material are accurately copied and then separated when cells divide and proteins are assembled under the direction of RNA molecules. Just as with big cities, the logistics of getting raw materials in and waste and finished products out of the nucleus is a major problem. The role of bridges and tunnels at a city boundary is played by nuclear pore complexes (NPCs), large protein complexes that are in charge of the transport across the nuclear membrane.

    Inside the nucleus with all that construction work going on it is a hard problem to determine what needs to be fixed and what is already a finished product like a chromosome. It is known that telomeres, repetitive DNA sequences that cap the ends of linear chromosomes, are indicators that these are the ends of finished products. For instance fusing two ends of chromosomes could have disastrous consequences for the cell. On the other hand things break like double-strands of chromosomes and they need to be repaired. It came as a surprise that quite similar proteins are involved both in marking the endpoints and in repairing the broken chromosomes. Researchers speculate that both processes might be linked via proper cell cycle progression.

    Other areas with recent progress are the timing of different phases in the cell cycle and the role of RNA in the formation of internal cell structures, control of gene expression (gene silencing) outside the nucleus, and how factors that control gene transcription recognize their targets.


  4. Certain Genetic Mutations Affect Human Response To Environmental Contaminant, Science Daily News Next Article Bookmark and Share

    University of Iowa researchers have found the first genetic evidence that mutations to a certain gene are associated with differences in the human response to inhaled endotoxin, a contaminant commonly found in agricultural dust, air pollution and household dust.

    The UI investigators determined that mutations in the toll-like receptor-4 (TLR4) gene can cause some people to be less responsive to inhaled endotoxin and less prone to develop an asthma-like response when exposed to this common environmental contaminant. The findings were published in the June issue of Nature Genetics.

    "In a fairly large study population of healthy individuals, we found that commonly occurring changes in the genetic sequence of TLR4 can make an individual more likely to be resistant to inhaled endotoxin than those who do not have the mutations," said David A. Schwartz, M.D., UI professor of internal medicine. "However, related studies with mice suggest that people with these mutations of TLR4 who are less responsive to inhaled endotoxin may prove to be more susceptible to systemic effects of endotoxin when they develop a blood-borne infection." (…)

    "Asthma-like reactions to endotoxin are determined in part by whether a person has the mutation, but it is not the only factor," he said. "This is a complex response that may involve other exposures and certainly involves other genes."

    Schwartz said the team also found that the mutation altered the ability of cells in culture to respond to endotoxin. In addition, cells obtained from individuals with the TLR4 mutations could be "rescued" or made to function normally through the addition of a normal copy of the TLR4 gene.

    "TLR4 is a cell membrane receptor of endotoxin," Schwartz explained. "The study shows that the mutation results in less expression of this important receptor on the cell surface. This lower receptor density then causes the cell to be less responsive to endotoxin. In effect, there are fewer sites on the cell that can trigger a response to endotoxin."

    In addition to treatment implications for asthma and sepsis, the findings could have implications for diseases such as acute lung injury, cystic fibrosis and pneumonia.

    Schwartz said the next research steps include studying how the TLR4 receptor works, especially as it relates to airway diseases caused by or exacerbated by endotoxin; using the naturally occurring mutations in TLR4 as a tool to study airway diseases; creating genetically-engineered mice with the human mutation to better understand the basic biology of endotoxin responsiveness; and investigating how the mutation affects other endotoxin-mediated diseases. (…)


  5. Market Ecology etc. in Microscopic Simulation of the LLS Stock Market Model, ArXiv Next Article Bookmark and Share

    Excerpts: Abstract: The LLS (Levy, Levy Solomon) stock market model is a model of heterogeneous quasi-rational investors operating in a complex environment about which they have incomplete information. We review the main features of this model and several of its extensions. We study the effects of investor heterogeneity and show that predation, competition, or symbiosis may occur between different investor populations. The dynamics of the LLS model lead to the empirically observed Pareto wealth distribution. Many properties observed in actual markets appear as natural consequences of the LLS dynamics: truncated Levy distribution of short-term returns, excess volatility, a return autocorrelation "U-shape" pattern, and a positive correlation between volume and absolute returns.

    1. The LLS Model

    LLS is a microscopic representation model of the stock market. (…) In the present account we introduce the basic LLS ideas and the model main results. We consider below a market with only two investment options: a bond and a stock. The model involves a large number of virtual investors characterized each by a current wealth, portfolio structure, probability expectations and risk taking preferences. (…)

    The bond is assumed to be a risk-less asset yielding a return at the end of each time period. The bond is exogenous and investors can buy from it as much as they wish at a given rate.

    The stock is a risky asset with overall returns rate H(t) composed of two elements:

    (i). Capital gain (loss): If an investor holds a stock, any rise (fall) in the market price of the stock contributes to an increase (decrease) in the investors' wealth.

    (ii). Dividends: The company earns income and distributes dividends.

    Each investor i is confronted with a decision where the outcome is uncertain: which is the optimal fraction X(i) of his/her wealth to invest in stock? (…)


  6. Arctic Ozone Depletion And Polar Stratospheric Clouds, Science Daily News Next Article Bookmark and Share

    Excerpts: A significant decline in ozone over the Arctic last winter was due to an increase in the size and longevity of polar stratospheric clouds, according to a group of researchers who participated in a massive, international atmospheric science campaign.

    The ozone-destroying clouds are made of ice and nitric acid, said University of Colorado at Boulder Professor Owen B. Toon, one of five project scientists heading up NASA's SAGE III Ozone Loss and Validation Experiment, or SOLVE. The SOLVE project involved satellites, aircraft, balloons and ground-based instruments operated from December 1999 through March 2000 by more than 200 scientists and support staff from the United States, Canada, Europe, Russia and Japan.

    Polar stratospheric clouds generally form about 13 miles above the poles when temperatures drop to minus 110 degrees Fahrenheit and below, said Toon, a professor in CU-Boulder's Laboratory for Atmospheric and Space Physics. The SOLVE campaign was staged out of Kiruna, Sweden.

    In some parts of the Arctic stratosphere -- which is located from about 10 miles to 30 miles above Earth -- ozone concentrations declined as much as 60 percent from November 1999 through March 2000. The fragile stratospheric ozone layer shields life on Earth from the harmful effects of ultraviolet radiation. (…)

    Although seasonal ozone loss is more severe in the Antarctic, the ozone loss in the Arctic presents more serious health threats to humans, said Toon. Ozone-depleted air from the Arctic drifts south toward North America, Europe and Russia each spring, increasing the amounts of UV light reaching Earth's surface in the highly populated mid-latitudes and causing potential increases in several types of cancer.

    Most chlorine compounds pumped into Earth's atmosphere in recent decades by humans initially were tied up as chlorine nitrate or hydrochloric acid, both of which are non-reactive. But if there is a surface area to attach to like the polar stratospheric cloud ice crystals, the chlorine compounds change into ozone-gobbling chlorine radicals in late winter and early spring after reacting with sunlight.

    The greenhouse effect, which warms Earth near its surface, may ironically be cooling the stratosphere enough to cause these clouds to form earlier and persist longer, said Toon. Greenhouse gases may be radiating energy and heat away from the upper stratosphere, creating prime conditions for polar stratospheric cloud formation.

    "With the clouds persisting longer, we are seeing greater ozone losses even though the amount of chlorine in the atmosphere has declined slightly," said Toon. The use of CFC's and other ozone-destroying chemicals were banned worldwide in 1996.

    Another troubling phenomenon observed for the first time during the SOLVE campaign last winter was a "denitrification" of some polar stratospheric clouds. Scientists observed nitrogen -- which can act to moderate the destructive activity of reactive chlorine compounds on ozone -- drizzling out of the clouds. "This was a real surprise," said Toon.

    The ozone loss over the Arctic has been generaly increasing since the winter of 1995-96, said Toon. If greenhouses gases warming Earth's atmosphere are shown to be the culprit in lengthening the amount of time the polar stratospheric clouds persist, the recovery of the Arctic ozone layer may be delayed by decades, scientists predict.


  7. Why 2001 will be the Year of Streaming Media, ZDNet Next Article Bookmark and Share

    Excerpts: (…) For the unfamiliar, streaming media is the technology that lets you get live audio and video delivered to you over the Internet. Streaming media's failings to date have been many: jerky video motion, tiny screens and robotic sounding voices. That's changing. I'll tell you why below, but first, let's check out the landscape now. (…)

    FOUR INGREDIENTS FOR STREAMING MEDIA

    Four converging trends will move streaming media into its growth phase beginning next year:

    More bandwidth. Faster Internet connections are on the way. Some 4 million households will have DSL next year, and nearly 49 million U.S. households will have broadband by 2004, according to a study by Cahners In-Stat Group. Click for more.

    Better infrastructure. Companies now offer serving and caching services that improve streaming performance. Think of Akamai, Edgix, cidera, E-Media and others. Click for more.

    Better streaming technology. RealNetworks' Real Player 8, just released in beta, does a fantastic job of fitting a lot of information through narrow pipes. Click for more.

    Appropriate content. Content suppliers are creating products designed for the limitations of today's products. Look at AtomFilms, which won an Oscar for one of its short films, and others adapting the big screen to the little monitor. Click for more. Even better is the use of animation and comics, which use less bandwidth. Likewise, training companies are learning intelligent ways to stream audio and video to help students without bogging them down. (…)


  8. Internet and Society Conference 2000, Harvard University Next Article Bookmark and Share

    Many conferences with the Internet as a topic don't do what they preach: The papers are given in a form that is tailored to the on-site audience typically ignoring the fact that a much larger audience could participate if access via Internet to the conference was provided. The conference Internet and Society Conference 2000 that just ended at Harvard University shows what can be done with the current state of technology: Live webcasts and archived videos of earlier presentations are of a quality that is smooth and has hardly any of the patchiness of early Internet video broadcasts. And this quality is available for current dial-up connections without the performance of coming broadband connections. It seems we are at a point already where video-tele-presence at conferences is a reasonable alternative to on-site participation.

    Conference participant Dean LeBaron sent the following notes: "Internet technologies are rapid change agents in the most rigidly institutionalized industries. These structures are less likely to adapt in the normal course of events. However, when they receive a shock like the internet which challenges their traditional hierarchies and roles, the improvements offered can be huge but the resistance to change firm.

    Less than one percent of doctors use email, one of the lowest percentages of any professional group. The legendary poor handwriting of physicians may be the cause of deaths and certainly inefficiency. Compare the record keeping and communication of FedEx with doctors...would you send you packages through your doctor or hospital?

    And universities are local, lecture centric. Meanwhile there are now over one thousand corporations granting degrees, most in distance learning modes. And lifetime learning will not be campus based. Education is growing but increasingly it is determined by self programs rather than institutionalized."


  9. Four Choice Metaphors for Economic Systems Analysis, ICCS3 Conference Next Article Bookmark and Share

    This paper presents a four-step argument for a paradigm shift from 'neoclassical' to a 'horizonal' economics, using the notion of 'planning horizons' as a means to understand boundedly-rational choice in irreversibly-interdependent dynamic Complex Systems environments. The VARIATION and INTERPERSONAL LINKAGES of planning horizons -- respectively called 'horizon effects' and 'interhorizonal complementarity' -- offer a useful generalization of neoclassical theory by acting like cases of increasing returns in costs and complementary interdependencies. As such, they indicate that the economic case for COMPETITION (based on substitution and diminishing returns) is special, incomplete, and is keeping our planning horizons short: that THE GENERAL SOLUTION for efficient and equitable social organization through learning and growth is COOPERATION, not competition.

    The first two of the four metaphors supporting this sequence of arguments are of INDIVIDUAL CHOICE; the last two place the individual into A SOCIAL SETTING. Within each pair, the second extends the static conception of the first into its 'horizonal' dynamic complex-systems equivalent:

    (1) THE NEIGHBORHOOD STORE is where (almost) all neoclassical choices are made.

    (2) THE CHESSBOARD: The 'move horizon' in chess is analogous to the 'planning horizon' of choice in a rivalrous strategic game environment.

    (3) THE TRANSPORTATION NETWORK gives us a means of 'grouping' firms with respect to any member in terms of their 'net' substitution (negative feedbacks) or complementarity (positive feedbacks).

    (4) THE EDUCATIONAL SYSTEM provides a theory of organizational learning, where 'horizon effects' -- an interpersonal lengthening (collapse) of planning horizons -- shift the balance of interpersonal interdependence in favor of (away from) complementarity and against (toward) substitution.

    Many economic phenomena are explained by 'horizon effects' (the extension and collapse of horizons), which serve as an ordinal measure of: knowledge, perspective, impatience and conscience. Formally, horizonal theory extends the neoclassical framework of static price-quantity models by opening them out orthogonally onto a third 'horizonal' axis along which all of the orthodox curves and relations shift in predictable ways to generate quite different results.

  10. The Scientist in the Crib, Minds, Brains, and How Children Learn, BioMedNet Next Article Bookmark and Share

    Excerpt: (...) We think there are very strong similarities between some particular types of early learning - learning about objects and about the mind, in particular - and scientific theory change. In fact, we think they are not just similar but identical. We don't just think that the baby computers have the same general structure as the adult-scientist computers. . . . We think that children and scientists actually use some of the same machinery. Scientists are big children. Scientists are such successful learners because they use cognitive abilities that evolution designed for the use of children. (...)


  11. NIST Conference on Measuring Intelligence, Announcement Next Article Bookmark and Share

    Excerpts: "Many researchers have suggested measures of performance for intelligent machine systems. Perhaps the most famous is the Turing test. Turing proposed that if a human using a keyboard cannot tell whether it is a human or a machine on the other end of an electronic conversation, then the machine is intelligent. There are two important features to this test. The first is that human performance is the metric against which machine performance is compared. The second is that the test is limited to language text. Turing's test does not measure of the ability of a machine to perceive images, to perform tasks, to plan and execute action, or even to understand spoken language. Newell expanded the list of abilities that a system must have to qualify as intelligent2. He proposed the following list:
    • recognize and make sense of a scene
    • understand a sentence
    • construct a correct response from the perceived situation
    • form a sentence that is both comprehensible and carrying a meaning of the selected response
    • represent a situation internally
    • be able to do tasks that require discovering relevant knowledge

    This definition requires sensing, modeling, and output. However, it does not specify what "tasks" the machine must be capable of performing. This suggests that intelligence may be domain specific. Certainly, knowledge of situations and actions and the ability to perform tasks may vary with changes in the environment. (…)

    In the proposed workshop, we want to focus on measurement of engineering parameters that enable behavior comparable to that demonstrated by living creatures. For example, we will address methods for measuring the ability of intelligent systems to:

    • sense the environment and the internal state of the machine
    • perceive and recognize objects, events, and situations
    • remember, understand, and reason about what is perceived
    • attend to what is important and ignore what is irrelevant
    • predict what will probably happen in the future under a variety of assumptions
    • evaluate what is perceived and predicted
    • make decisions, plan, and act so as to achieve goals
    • learn from experience and from instructions


  12. Links & Snippets Next Article Bookmark and Share


    1. 1 How Ants Invade, Science Next Article Bookmark and Share

      (…) The Argentine ant was introduced to the United States from South America a century ago and has displaced many other species of ant.

      Tsutsui et al. have pinpointed a key difference between introduced and native populations of the Argentine ant. The former apparently have passed through a genetic bottleneck and have lower genetic variability (half as many alleles at the seven microsatellite loci sampled) than the ancestral Argentinian populations. The reduction in genetic variation reduces, in turn, the amount of intraspecific aggression among the ants, permitting the existence of much larger supercolonies and thus conferring more invasive potential. (…)


    2. 2 Brain Cells Reveal Surprising Versatility, Science Next Article Bookmark and Share

      Excerpt: When a team of scientists reported last year that stem cells from the brains of adult mice could become functional blood cells, many scientists were intrigued, if a bit skeptical. Now, these versatile cells have shown even more surprising abilities: When injected into embryos, it seems, they can develop into nearly every type of tissue in the body. The work, described on page 1660, leaves a number of questions open. Even so, scientists are amazed at the cells' apparent flexibility.


    3. 3 The Patterns Hidden in Market Swings, New York Times Bookmark and Share

      Excerpt: (…) Technical analysts examine charts, draw geometric shapes, connect points and mark off familiar patterns. Each pattern has a meaning in the analyst's lexicon, providing a glimpse of what might happen next.

      Some technical analysts, having seen a promise of pictorial order, go further, arguing that there are even more basic rules governing these shapes, rules that grow out of what they consider basic laws of nature and geometry; some get even more fantastical, invoking the principles of astrology. (…)

      The Patterns Hidden in Market Swings, Edward Rothstein, New York Times, June 3, 2000

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