Complexity Digest 2001.35

27-Aug-2001

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Content

  1. Achilles' Heel In Missile Plan: Crude Weapons, NYTimes
  2. Scientists Track Down Human Longevity Genes, Yahoo! News/Reuters
    1. A Genome-Wide Scan For Linkage To Human Exceptional Longevity Identifies A Locus On Chromosome 4, PNAS
  3. What Only The Embryo Knows, NYTimes
  4. Chip Lithography Harnessed To Grow Living Brain Cells, EE Times
  5. Artificial Neurons with Arbitrarily Complex Internal Structures, arXiv
  6. 'Spin' Could Be Quantum Boost For Computers, NYTimes
    1. MIT, HP To Build Quantum Computer, CNN, 01/08/20
  7. Theory Grounding in Embodied Artificially Intelligent Systems, CogPrints
  8. Nonadiabatic Dynamics In Semiquantal Physics, Reports on Progress in Physics
  9. What's On Tap? Why, Haptics, Wired News
  10. Taming the Web, Technology Review
  11. Highly Clustered Scale-Free Networks, arXiv
  12. All Data On The Weather Map Are Not Equal, Physics Update
  13. Two-Path Quantum Interference In A Liquid, Physics Today
  14. Modeling Vocal Fold Motion With A Continuum Fluid Dynamic Model, arXiv
  15. Atoms Hop between Islands of Regular Motion in a Sea of Chaos, Physics Today
  16. Turbulent Heat Flow: Structures and Scaling, Physics Today
  17. Making Traffic Jams Less Sticky, Fortune
  18. The Many Faces Of Adaptation, Nature
    1. Efficiency And Ambiguity In An Adaptive Neural Code, Nature
  19. Evidence For Chaos In The Neocortex, Physics News Update
  20. Links & Snippets
    1. Other Articles
      1. Impairments of Attention and Effort Among Patients With Major Affective Disorders, J. Neuropsychiatry Clin. Neurosci.
      2. Study Finds West Nile Virus Infections Are Underreported, The Associated Press
      3. The Neurology of Impaired Consciousness: Global Disorders and Implied Models, Netforum
      4. Effects Of Autonomic Blockers On Linear And Nonlinear Indexes Of Blood Pressure And Heart Rate, AJP: Heart
    2. Announcements
      1. Tjurunga Launches New Complexity Site For Business And Government, Canberra, 01/08/16
    3. Conferences

  1. Achilles' Heel In Missile Plan: Crude Weapons, NYTimes Next Article Bookmark and Share

    Excerpts: The missile defense planned by the Bush administration may be least able to destroy warheads from countries that are thought to pose the biggest threat (...).

    The trouble is that so-called rogue nations, like North Korea, Iran and Iraq, would fire wobbling, rudimentary warheads during an attack, and those turn out to be among the hardest to hit. (...)

    Creating any antimissile system would be enormously complex, but stopping a rudimentary missile would be far harder even than hitting advanced warheads (...)


  2. Scientists Track Down Human Longevity Genes, Yahoo! News/Reuters Next Article Bookmark and Share

    Excerpts: An exhaustive analysis of the DNA of exceptionally long-lived siblings has enabled scientists to find the location of genes that appear to give certain people the ability to live to age 100 and beyond. (...)

    But the researchers said it certainly will help explain why some people can live decades longer than the average life expectancy, and could pave the way for the development of drugs that mimic what centenarians possess genetically to escape the ravages of aging. (...)


    1. A Genome-Wide Scan For Linkage To Human Exceptional Longevity Identifies A Locus On Chromosome 4, PNAS Next Article Bookmark and Share

      Excerpts: Substantial evidence supports the familial aggregation of exceptional longevity. The existence of rare families demonstrating clustering for this phenotype suggests that a genetic etiology may be an important component. (...) In this study, a genome-wide scan for such predisposing loci was conducted by using 308 individuals belonging to 137 sibships demonstrating exceptional longevity. (...)Identification of the genes in humans that allow certain individuals to live to extreme old age should lead to insights on cellular pathways that are important to the aging process.

  3. What Only The Embryo Knows, NYTimes Next Article Bookmark and Share

    Excerpt: One can first tell that an embryo will become a vertebrate and not some sort of invertebrate, then a mammal and not another kind of vertebrate, then a carnivore and not a rodent or ruminant, then a dog and not a cat, and finally Buster the Beagle and not another breed.

    Von Baer summarized his principle in an epigram: "The development of the organism is the history of growing individuality in every respect." In other words, successive narrowing and determination of parts as complexity coagulates.


  4. Chip Lithography Harnessed To Grow Living Brain Cells, EE Times Next Article Bookmark and Share

    Excerpt: In an attempt to decipher the communications codes used by mammalian brain cells, University of Illinois researchers are using chip lithography to "microprint" furrows that growing brain cells will follow when budding inputs (dendrites) and outputs (axons). Theoretically, the method would use off-the-shelf electrode arrays and allow engineers to characterize living nerve cells by precisely "wiring" together test circuits and measuring their performance.

    Manipulating the attachment and growth patterns of individual nerve cells has the potential of creating "designer" biosensors, implants and prosthetics, the researchers said.


  5. Artificial Neurons with Arbitrarily Complex Internal Structures, arXiv Next Article Bookmark and Share

    Abstract: Artificial neurons with arbitrarily complex internal structure are introduced. The neurons can be described in terms of a set of internal variables, a set activation functions which describe the time evolution of these variables and a set of characteristic functions which control how the neurons interact with one another. The information capacity of attractor networks composed of these generalized neurons is shown to reach the maximum allowed bound. A simple example taken from the domain of pattern recognition demonstrates the increased computational power of these neurons. Furthermore, a specific class of generalized neurons gives rise to a simple transformation relating attractor networks of generalized neurons to standard three layer feed-forward networks. Given this correspondence, we conjecture that the maximum information capacity of a three layer feed-forward network is 2 bits per weight.

  6. 'Spin' Could Be Quantum Boost For Computers, NYTimes Next Article Bookmark and Share

    Excerpt: Electronic devices like radios and computers work by shuttling around the electric charge of electrons. Hence, the "electron" in "electronics."

    But besides their electric charge, electrons also have a less exploited property: "spin," an angular momentum that makes electrons act like tiny bar magnets. Researchers are beginning to tap into electrons' magnetic side as part of an emerging field known as spintronics.

    Already, spintronics has yielded a couple of uses and may eventually provide the underpinning for computers that employ quantum mechanical efforts to perform calculations.


    1. MIT, HP To Build Quantum Computer, CNN, 01/08/20 Next Article Bookmark and Share

      Excerpt: Hewlett-Packard Co. (HP) and the Massachusetts Institute of Technology (MIT) have announced a joint $2.5 million quantum computing project to advance computing development beyond its current physical limits.

      Quantum computing development is necessary because the current classical computing model is reaching its limit, said an HP spokesman Friday.

      "Moore's Law is going to reach its natural conclusion because of the physical limitations of present technology. When you get to the atomic scale you can't take it much further," the spokesman said.


  7. Theory Grounding in Embodied Artificially Intelligent Systems, CogPrints Next Article Bookmark and Share

    Excerpts: (...) Enabling computer systems to have skills with theories would be useful from a practical standpoint. Just as humans find theories practically useful, theories can be useful to artificially intelligent (AI) systems. Theories constrain the possible set of hypotheses an AI system considers in its search space (i.e., they act as biases) and also improve the quality and increase the acquisition rate of hypotheses. In short, theories help both AI systems and humans make generalizations. Theories used in combination with data enable principled generalizations to be formed.

    This paper introduces theory grounding as a new conceptual approach to imbuing computers with theory skills and knowledge.

    Contributing Editor's Note: Taking humans as models for building intelligent systems might seem simplistic to some. But after all, we judge the "intelligence" of a system comparing it with human intelligence. If we want a system to simulate human intelligence, why not to base our models in humans?


  8. Nonadiabatic Dynamics In Semiquantal Physics, Reports on Progress in Physics Next Article Bookmark and Share

    Abstract: Every physical regime is some sort of approximation of reality. One lesser-known realm that is the semiquantal regime, which may be used to describe systems with both classical and quantum subcomponents. In the present review, we discuss nonadiabatic dynamics in the semiquantal regime. Our primary concern is electronic-nuclear coupling in polyatomic molecules, but we discuss several other situations as well. We begin our presentation by formulating the semiquantal approximation in quantum systems with degrees-of-freedom that evolve at different speeds. We discuss nonadiabatic phenomena, focusing on their relation to the Born-ppenheimer approximation. We present several examples - including Jahn-Teller distortion in molecules and crystals and the dynamics of solvated electrons, buckyballs, nanotubes, atoms in a resonant cavity, SQUIDs, quantum particle-spin systems, and micromasers. We also highlight vibrating quantum billiards as a useful abstraction of semiquantal dynamics.

    Author's note: One interesting aspect of modeling systems is how to properly consider more than one physical regime simultaneously. This can occur as multiple lengthscales and timescales enter into problems and can cause analytical, numerical, and conceptual difficulties. Turbulent systems, for example, exhibit plumes of an astounding array of sizes. See Leo Kadanoff's recent article in Physics Today for an excellent qualitative discussion of this phenomenon. A specific example of this occurs in semiquantum physics, which is one (of many) regimes that seek to interpolate between classical and quantum physics. It is relevant when some of a system's degrees-of-freedom are faster than another so that the slower degree-of-freedom is approximated as classical. One important class of systems in which this occurs is molecular systems, whose decomposition of speeds arises from the fact that nuclei and electrons have masses that differ by roughly four orders of magnitude. Moreover, this has become increasingly relevant in recent years, as nanomechanical devices seek to utilize the interaction between electronic and nuclear motion. Additionally, whenever one attempts to transit between multiple physical regimes, philosophical implications of model reduction become highly relevant.

    My paper is a survey article discussing the semiquantum phenomenon and its applications. It is intended primarily for non-experts and includes references to more technical work on the various systems and techniques discussed within. Feel free to contact me if you'd like to discuss this further.


  9. What's On Tap? Why, Haptics, Wired News Next Article Bookmark and Share

    Excerpts: Haptics is "based on the way the brain processes information," (...) "If the information is based on physical sensations, your reactions are much, much faster." (...)

    A sensing vest developed by the university is being tested by NASA in near-zero gravity environments in planes. Pilots in such situations often lose their sense of visual direction, and tactile cues can help orient them. "With JFK Jr., the consensus is that he probably got spatially disoriented," causing him to crash his plane, (...)


  10. Taming the Web, Technology Review Next Article Bookmark and Share

    Excerpts: "Information wants to be free." "The Internet can't be controlled." We've heard it so often that we sometimes take for granted that it's true. But THE INTERNET CAN BE CONTROLLED, and those who argue otherwise are hastening the day when it will be controlled too much, by the wrong people, and for the wrong reasons.

    First, the Net is said to be too international to oversee(...). Second, the Net is too interconnected to fence in (...). Third, the Net is too full of hackers (...)


  11. Highly Clustered Scale-Free Networks, arXiv Next Article Bookmark and Share

    Abstract: We propose a model for growing networks based on a finite memory of the nodes. The model shows stylized features of real-world networks: power law distribution of degree, linear preferential attachment of new links and a negative correlation between the age of a node and its link attachment rate. Notably, the degree distribution is conserved even though only the most recently grown part of the network is considered. This feature is relevant because real-world networks truncated in the same way exhibit a power-law distribution in the degree. As the network grows, the clustering reaches an asymptotic value larger than for regular lattices of the same average connectivity. These high-clustering scale-free networks indicate that memory effects could be crucial for a correct description of the dynamics of growing networks.

  12. All Data On The Weather Map Are Not Equal, Physics Update Next Article Bookmark and Share

    Excerpt: Researchers usually assume that all spots on a weather map are equally chaotic, meaning that small uncertainties in initial conditions lead to unpredictably different results. A realistic model of Earth's atmosphere must be high dimensional--there are a great many degrees of freedom--which further complicates the art of forecasting. Now, a multidisciplinary team of scientists at the University of Maryland has shown that, locally, the finite-time dynamics of the atmosphere is often low dimensional. (...)

    See also: ComDig 2001.14:


  13. Two-Path Quantum Interference In A Liquid, Physics Today Next Article Bookmark and Share

    Excerpt: Interference experiments have unequivocally shown the quantum wave nature of photons, electrons, neutrons, atoms, molecules, and even Bose-Einstein condensates. Now, a team of physicists at the University of California, Berkeley, has demonstrated quantum interference for superfluid helium-3. (...) Theory predicts--again similar to SQUIDS--that the total mass current depends on the superfluid phase winding. To adjust the quantum phase in the uncharged superfluid 3He, the team varied the loop's orientation with respect to Earth's rotation vector. (...)

  14. Modeling Vocal Fold Motion With A Continuum Fluid Dynamic Model, arXiv Next Article Bookmark and Share

    Abstract: Vocal fold (VF) motion is fundamental to voice production and diagnosis in speech and health sciences. The motion is a consequence of air flow interacting with elastic vocal fold structures. Motivated by existing lumped mass models and known flow properties, we propose to model the continuous shape of vocal fold in motion by the two dimensional compressible Navier-Stokes equations coupled with an elastic damped driven wave equation on the fold cover. In this paper, instead of pursuing a direct two dimensional numerical simulation, we derive reduced quasi-one-dimensional model equations by averaging two dimensional solutions along the flow cross sections. We then analyze the oscillation modes of the linearized system about a flat fold, and found that the fold motion goes through a Hopf bifurcation into temporal oscillation if the flow energy is sufficient to overcome the damping in the fold consistent with the early models. We also analyze the further reduced system under the quasi-steady approximation and compare the resulting vocal fold equation in the small vibration regime with that of the Titze model. Our model shares several qualitative features with the Titze model yet differs in the specific form of energy input from the air flow to the fold. Numerical issues and results of the quasi-one-dimensional model system will be presented in part II (view resulting web VF animation )


  15. Atoms Hop between Islands of Regular Motion in a Sea of Chaos, Physics Today Next Article Bookmark and Share

    Excerpt: We've long since grown used to the idea that atoms in a double potential well can go back and forth between wells, even though classically an atom with insufficient energy is precluded from urmounting the energy barrier between the two compartments. We should not be too surprised then to learn that an atom executing one type of regular motion can suddenly be found to be moving 180 out of phase with its initial motion: At a point in the motion when the atom should be moving to the right, it's seen to be moving to the left. That's the idea behind dynamical tunneling, or the hopping between separate, stable regions in phase space. Although there's been some evidence for dynamical tunneling in molecular systems, it has now been seen very directly in two new experiments on ultracold atoms. (...)

  16. Turbulent Heat Flow: Structures and Scaling, Physics Today Next Article Bookmark and Share

    Excerpt: For very many years, scientists have studied the motion of enclosed fluids heated from below and cooled from above. The containers for these Rayleigh-Benard systems have ranged in size from soda cans to swimming pools. Usually, as a fluid is heated it will become less dense. A heated blob will feel a force pushing it upward, the blob will tend to rise, and cooler fluid will fall into its place. At the lowest heating rates, there is no motion. Then, as the heating rate is increased, one sees successively a steady motion, a periodic oscillation, and a chaotic domain. At yet higher heating rates, one finds turbulent motion in which the fluid swirls in highly structured but never-repeating patterns (...)

  17. Making Traffic Jams Less Sticky, Fortune Next Article Bookmark and Share

    Excerpt: In congested traffic, these jamlets can merge to form massive, persistent jams--like icebergs floating together and freezing into a vast sheet that won't melt until spring.

    This phenomenon may be one reason for phantom jams. These peculiar slowdowns may also be the result of obstacles that have long since been cleared.

    So what's the best way to minimize tie-ups? In theory, says Knospe, computerized speed-limit signs that change to reflect the level of congestion would help; they would encourage anticipatory slowing when traffic gets dense.


  18. The Many Faces Of Adaptation, Nature Next Article Bookmark and Share

    Excerpts: Sensory neurons constantly adapt to the changing environment. (…) do this surprisingly quickly, and without losing their absolute frame of reference.

    [They] can produce only a small number of distinct outputs, so they cannot generate a unique response to every relevant stimulus. To solve this problem, neurons adapt to the prevailing conditions, so the same limited set of outputs can be reassigned to different stimuli in different contexts. (…), after a sudden change in the strength of a stimulus, neurons abruptly change their average responses.


    1. Efficiency And Ambiguity In An Adaptive Neural Code, Nature Next Article Bookmark and Share

      Excerpts: We examine the dynamics of a neural code in the context of stimuli whose statistical properties are themselves evolving dynamically. Adaptation to these statistics occurs over a wide range of timescales-from tens of milliseconds to minutes. Rapid components of adaptation serve to optimize the information that action potentials carry about rapid stimulus variations within the local statistical ensemble (…). The speed with which information is optimized and ambiguities are resolved approaches the physical limit imposed by statistical sampling and noise.


  19. Evidence For Chaos In The Neocortex, Physics News Update Next Article Bookmark and Share

    Excerpt: Evidence for chaos in the neocortex, the most complex brain structure specific to humans and other mammals, has been obtained in a model (...) Chaos in the brain would manifest itself as unpredictable and seemingly random electrical activity in a population of nerve cells, or neurons.Chaos may have an important neurological function: it could provide, as researchers have speculated, a flexible and rapid means for the brain to discriminate between different sounds, odors, and other perceptual stimuli. (...)

  20. Links & Snippets Next Article Bookmark and Share

    1. Other Articles Next Article Bookmark and Share

      1. Impairments of Attention and Effort Among Patients With Major Affective Disorders, J. Neuropsychiatry Clin. Neurosci. Next Article Bookmark and Share

        Impairments of Attention and Effort Among Patients With Major Affective Disorders, Ronald Cohen, Ilan Lohr, Robert Paul, Robert Boland, J. Neuropsychiatry Clin. Neurosci. 2001 August 1; 13(3): p. 385-395

      2. Study Finds West Nile Virus Infections Are Underreported, The Associated Press Next Article Bookmark and Share

        Study Finds West Nile Virus Infections Are Underreported, The Associated Press, 7/27/01

      3. The Neurology of Impaired Consciousness: Global Disorders and Implied Models, Netforum Next Article Bookmark and Share

        The Neurology of Impaired Consciousness: Global Disorders and Implied Models, Nicholas D. Schiff, Fred Plum, Netforum (Aug 18, 2001)

      4. Effects Of Autonomic Blockers On Linear And Nonlinear Indexes Of Blood Pressure And Heart Rate, AJP: Heart Next Article Bookmark and Share

        Effects Of Autonomic Blockers On Linear And Nonlinear Indexes Of Blood Pressure And Heart Rate In SHR, Denis Mestivier, Hubert Dabire, and Nguyen Phong Chau, AJP: Heart 2001 September 1; 281(3): p. H1113-H1121

    2. Announcements Next Article Bookmark and Share

      1. Tjurunga Launches New Complexity Site For Business And Government, Canberra, 01/08/16 Next Article Bookmark and Share

        Tjurunga Launches New Complexity Site For Business And Government, Canberra, 16 August 2001

        Tjurunga Pty Ltd, a complexity science consultancy, launched its new website for business and government today (www.tjurunga.com). The site allows business and government to explore the ways in which the science of complexity may be applied to the strategic problems of enterprises in both the private and public sectors.

        ComDig Contributing Editors Wanted: Due to the overwhelming success of Complexity Digest in both the academic and practioner communities we are in the fortunate situation to offer one or several positions of contributing editors especially in the areas of economic and business applications. Requirements are a solid background in complexity, reliable access to the Internet, and good editorial skills. Financial support could be available. Please send applications to editor@comdig.org

    3. Conferences Bookmark and Share


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