Complexity Digest 2001.34

20-Aug-2001

  1. Mobilized Bone Marrow Cells Repair The Infarcted Heart, PNAS
  2. Composite Index of Leading Economic Indicators: How to Make It More Timely, NBER
  3. Non-Linear EEGDynamics In Patients With Nocturnal Migraine Attacks, Neurosci Lett
  4. Spanwise Flow And The Attachment Of The Leading-Edge Vortex On Insect Wings, Nature
  5. Spatial-Temporal Imaging Of Bacterial Infection In Intact Animals, PNAS
  6. Researchers Target Deadly Tsunamis, Science
    1. Modeling a 3600-Year-Old Tsunami Sheds Light on Minoan Past, Science
  7. How Seedlings See the Light, Science
  8. Field Test Backs Model for Invader, Science
    1. Infiltration of a Hawaiian Community by Introduced Biological Control Agents, Science
    2. Parasitic Wasps Invade Hawaiian Ecosystem, Science
  9. Plants' Battle Against Disease Is 'Trench Warfare At Molecular Level', Cornell Press Rel
  10. Methods of Declarative Logic Programming for Intelligent Information Agents, arXiv
  11. Classes for Fast Maximum Entropy Training, arXiv
  12. Self-Adaptively Randomized Loop-Free Routing Algorithm, Chinese Patent App.
  13. Structural Mimicry In Bacterial Virulence, Nature
  14. Multitasking Is Overtaxing, Researchers Find, Medscape
  15. Crossmodal Binding Of Fear In Voice And Face, PNAS
  16. Packaging Proteins May Be Second Genetic Code, New Scientist
  17. Sub-Planck Structure And Its Relevance For Quantum Decoherence, Nature
  18. Laws of Nature May Change as Universe Ages, Yahoo! News
  19. Phase Transition Between Disordered And Ordered Foraging In Pharaoh's Ants, PNAS
  20. Links & Snippets
    1. Other Articles
      1. Preventative Mastectomies Save Lives, Study Finds, Linda A. Johnson, The Associated Press, 7/19/01

  1. Mobilized Bone Marrow Cells Repair The Infarcted Heart, PNAS Bookmark and Share

    Editor's Note: This might be one of the most important early applications of stem-cell research that does not require stem cells from embryos.

    Excerpts: Attempts to repair myocardial infarcts by transplanting cardiomyocytes or skeletal myoblasts have failed to reconstitute healthy myocardium and coronary vessels integrated structurally and functionally with the remaining viable portion of the ventricular wall. The recently discovered growth and transdifferentiation potential of primitive bone marrow cells (BMC) prompted us, in an earlier study, to inject in the border zone of acute infarcts Lin c-kitPOS BMC from syngeneic animals. These BMC differentiated into myocytes and vascular structures, ameliorating the function of the infarcted heart.



  2. Composite Index of Leading Economic Indicators: How to Make It More Timely, NBER Bookmark and Share

    Abstract: A major shortcoming of the U.S. leading index is that it does not use the most recent information for stock prices and yield spreads. The index methodology ignores these data in favor of a time-consistent set of components (i.e., all of the components must refer to the previous month). An alternative is to bring the series with publication lags up-to-date with forecasts and create an index with a complete set of most recent components. This study uses tests of ex-ante predictive ability of the U.S. leading index to evaluate the gains to this new 'hot box' procedure of statistical imputation. We find that, across a variety of simple forecasting models, the new approach offers substantial improvements.


  3. Non-Linear EEGDynamics In Patients With Nocturnal Migraine Attacks, Neurosci Lett Bookmark and Share

    Abstract: The present study was conducted to examine non-linear electroencephalogram (EEG) measures during the development of a spontaneous migraine attack. We investigated the sleep EEG of five patients with migraine without aura in the pain-free interval and at the onset of a nocturnal attack. Sleep EEG recordings were analysed using the method of global dimensional complexity compared to conventional sleep scoring techniques. We found no divergence between classical sleep architecture and the estimated dimensional course nor any relevant short-term changes related to the onset of headache. There was, however, a loss of dimensional complexity in the first two non-rapid eye movement sleep states in the migraine night, with statistical significance during the second sleep cycle. For the first time, these results provide evidence of a global dimension decrease that is related to cortical network changes during a migraine attack.


  4. Spanwise Flow And The Attachment Of The Leading-Edge Vortex On Insect Wings, Nature Bookmark and Share

    Excerpts: The flow structure that is largely responsible for the good performance of insect wings has recently been identified as a leading-edge vortex. But because such vortices become detached from a wing in two-dimensional flow, an unknown mechanism must keep them attached to (three-dimensional) flapping wings. (…) Here we report that, (…) flapping wings do not generate a spiral vortex akin to that produced by delta-wing aircraft. We also find that limiting spanwise flow with fences and edge baffles does not cause detachment of the leading-edge vortex.


  5. Spatial-Temporal Imaging Of Bacterial Infection In Intact Animals, PNAS Bookmark and Share

    Excerpts: We describe imaging the luminance of green fluorescent protein (GFP)-expressing bacteria from outside intact infected animals. This simple, nonintrusive technique can show in great detail the spatial-temporal behavior of the infectious process. The bacteria, expressing the GFP, are sufficiently bright as to be clearly visible from outside the infected animal and recorded with simple equipment. (…).This imaging technology affords a powerful approach to visualizing the infection process, determining the tissue specificity of infection, and the spatial migration of the infectious agents.


  6. Researchers Target Deadly Tsunamis, Science Bookmark and Share

    Istanbul --Computer models, improved maps of the ocean floor, and new sensory equipment are giving scientists a handle on the causes of giant waves. By spotting a tsunami early and taking its measure, scientists can help head off disaster before it strikes. Such data are now being provided by the Deep-ocean Assessment and Reporting of Tsunamis (DART) warning system, scheduled to deploy its sixth instrument this month to help predict and analyze the giant waves on the open ocean.


    1. Modeling a 3600-Year-Old Tsunami Sheds Light on Minoan Past, Science Bookmark and Share

      Excerpts: The collapse of the Stronghyle volcano on the Greek island of Thera (now Santorini) in about 1600 B.C. generated a tsunami that smashed into the strongholds of the ancient Minoan civilization, Crete, and other islands in the Aegean Sea. Some archaeologists have speculated that the tsunami might be the cause of the mysterious disappearance of the seafaring Minoans. But recent research by tsunami modeling experts--based on data collected by geologists on coasts around the Aegean Sea--now indicates that the tsunami probably didn't do in the Minoans on its own.



  7. How Seedlings See the Light, Science Bookmark and Share

    Excerpts: Exactly how light touches off the chain of events that converts a ghostly pale seedling into a green, photosynthesizing plant has long been a mystery. Now, a team of scientists has uncovered a surprisingly simple three-step pathway involving blue light that solves part of the mystery. In a report published online this week by Science (www.sciencexpress.org), they show that in the plant Arabidopsis thaliana, the photoreceptors that detect blue light interact directly with a protein known to regulate light responses in plants. This suggests that the light signal may be transmitted to that protein without the intercession of other proteins.


  8. Field Test Backs Model for Invader, Science Bookmark and Share

    Excerpts: Researchers trying to forecast the degree of damage that will be caused by an invasive species have devised computer models for target species. Here at the annual meeting of the Ecological Society of America last week, a researcher presented results that meld such modeling with field tests of a weed currently plaguing the southeastern United States. And although the results are grim, they demonstrate the importance of attacking weeds early in their invasion, before they take hold.


    1. Infiltration of a Hawaiian Community by Introduced Biological Control Agents, Science Bookmark and Share

      Excerpts: Insects have frequently been drafted to fight invasive weeds and pests, but these so-called biological control agents can also attack innocent native species. Now comes the most detailed example yet of how deeply a control agent can infiltrate an ecosystem. On page 1314, ecologists report that parasitic wasps from Texas and China that were introduced into Hawaii more than 50 years ago to prey on sugarcane pests are now dominant players in the food web of a remote native forest.



    2. Parasitic Wasps Invade Hawaiian Ecosystem, Science Bookmark and Share

      Excerpt: (...) By observing the battle between bacterial speck disease and tomatoes, biologists have discovered how plant cells resist some ailments. Researchers from the Boyce Thompson Institute (BTI) for Plant Research Inc. and Cornell University can now demonstrate how disease-causing organisms deliver destructive agents to plants, and how the plants fight back. "It's like radar detecting an incoming missile" says Gregory B. Martin, senior scientist at BTI and a Cornell plant pathologist. "Consider it trench warfare at the molecular level." (...)

      One combatant is Pseudomonas syringae, the bacterium responsible for causing bacterial speck disease. (...) P. syringae attacks healthy tomato plants by attaching itself to the plant cell, inserting a microscopic tube and sending a pathogenic protein (...) into the cell. Despite the attack, the plant cell is prepared for the invading onslaught. Using a molecular surveillance system behind the cell wall, the plant cell detects alien proteins and mounts a defense. Although bacterial speck disease has been known since the early 1930s, it did not result in serious losses until the winter tomato crop of 1977-78 in southern Florida. Cool, moist environmental conditions contributed to the development of the disease, and it has now established itself as a major production problem (...)



  9. Plants' Battle Against Disease Is 'Trench Warfare At Molecular Level', Cornell Press Rel Bookmark and Share

    Abstract: The search for information on the web is faced with several problems, which arise on the one hand from the vast number of available sources, and on the other hand from their heterogeneity. A promising approach is the use of multi-agent systems of information agents, which cooperatively solve advanced information-retrireview problems. This requires capabilities to address complex tasks, such as search and assessment of sources, query planning, information merging and fusion, dealing with incomplete information, and handling of inconsistency. In this paper, our interest is in the role which some methods from the field of declarative logic programming can play in the realization of reasoning capabilities for information agents. In particular, we are interested in how they can be used and further developed for the specific needs of this application domain. We review some existing systems and current projects, which address information-integration problems. We then focus on declarative knowledge-representation methods, and review and evaluate approaches from logic programming and nonmonotonic reasoning for information agents. We discuss advantages and drawbacks, and point out possible extensions and open issues.



  10. Methods of Declarative Logic Programming for Intelligent Information Agents, arXiv Bookmark and Share

    Excerpt: Here I formalize and quantitatively validate two conjectures drawing connections from link information to lexical and semantic Web content. The clink-content conjecture states that a page is similar to the pages that link to it, i.e., one can infer the lexical content of a page by looking at the pages that link to it. I also show that lexical inferences based on link cues are quite heterogeneous across Web communities. The link-cluster conjecture states that pages about the same topic are clustered together, i.e., one can infer the meaning of a page by looking at its neighbours. These results explain the success of the newest search technologies and open the way for more dynamic and scalable methods to locate information in a topic or user driven way.



  11. Classes for Fast Maximum Entropy Training, arXiv Bookmark and Share

    Abstract: Maximum entropy models are considered by many to be one of the most promising avenues of language modeling research. Unfortunately, long training times make maximum entropy research difficult. We present a novel speedup technique: we change the form of the model to use classes. Our speedup works by creating two maximum entropy models, the first of which predicts the class of each word, and the second of which predicts the word itself. This factoring of the model leads to fewer non-zero indicator functions, and faster normalization, achieving speedups of up to a factor of 35 over one of the best previous techniques. It also results in typically slightly lower perplexities. The same trick can be used to speed training of other machine learning techniques, e.g. neural networks, applied to any problem with a large number of outputs, such as language modeling.

    Contributing Editor's Note: The improvement of learning algorithms and the increase of processing speed seem to converge in the near future into machines capable of simulating human intelligence in a seamless way. If this is achieved, even in a restricted context (well, it has been achieved long ago for quite restricted contexts, but the idea is to enlarge the contexts where machines are able to simulate intelligence), will we call these machines "cognitive" even if they "think" (function) in a different way we do? Or, they will be so similar to us that we will learn by them how do we "think"?



  12. Self-Adaptively Randomized Loop-Free Routing Algorithm, Chinese Patent App. Bookmark and Share

    Abstract: Current IP routing algorithms, Distance Vector (DV) and Link State (LS) are based on the thought of local optimization, which every router try their best to transfer packages bypass the shortest path. Because of scale-free bursts of network load, bandwidth is often critical resources. In this case, routing algorithms based on local optimization might lead a severe disadvantage: routing oscillation, which will remarkably depress global performances. The paper proposes a novel self-Adaptively Randomized loop-free Link State (ARLS) algorithm that utilizes local information to achieve self-adaptive randomization and harmonize each router's local performance requests. ARLS can effectively eliminates routing oscillation phenomena and improve global performance of communication networks. Computer simulation demonstrates that ARLS can gain a prominent superiority in average queueing delay and package loss rate over basic LS. The work, as a real example, implies that dynamical components of complex system could not be exactly modeled by math models may result in a stable status of inferior performance with a considerable prob. and proper randomization can help system get rid of the inferior status rapidly.


  13. Structural Mimicry In Bacterial Virulence, Nature Bookmark and Share

    Excerpts: An important mechanism underlying the strategies used by microbial pathogens to manipulate cellular functions is that of functional mimicry of host activities. (…) convergent evolution has produced new effectors that, although having no obvious amino-acid sequence similarity to host factors, are revealed by structural studies to display mimicry at the molecular level.

    Such a protein would usually have a distinct three-dimensional architecture from that of the molecule it mimics, but would typically have evolved to imitate the chemical groups on the surface of its functional homologue.



  14. Multitasking Is Overtaxing, Researchers Find, Medscape Bookmark and Share

    Excerpts: To gauge the amount of brain being activated, subjects underwent magnetic resonance imaging (MRI). (…)

    Done alone, the language and visual tasks each activated 37 voxels of tissue. However, when subjects were asked to do both tasks at once, the brain areas registered a total of only 42 voxels.

    "The brain can only be activated a limited amount and you have to decide where to use that activation," says Marcel A. Just, PhD, from the Center for Cognitive Imaging at Carnegie Mellon.



  15. Crossmodal Binding Of Fear In Voice And Face, PNAS Bookmark and Share

    Abstract: In social environments, multiple sensory channels are simultaneously engaged in the service of communication. In this experiment, we were concerned with defining the neuronal mechanisms for a perceptual bias in processing simultaneously presented emotional voices and faces. Specifically, we were interested in how bimodal presentation of a fearful voice facilitates recognition of fearful facial expression. By using event-related functional MRI, that crossed sensory modality (visual or auditory) with emotional expression (fearful or happy), we show that perceptual facilitation during face fear processing is expressed through modulation of neuronal responses in the amygdala and the fusiform cortex. These data suggest that the amygdala is important for emotional crossmodal sensory convergence with the associated perceptual bias during fear processing, being mediated by task-related modulation of face-processing regions of fusiform cortex.


  16. Packaging Proteins May Be Second Genetic Code, New Scientist Bookmark and Share

    Excerpt: Breakthrough research on proteins once thought to be simply "packaging" for DNA may have revealed a master on/off gene switch, say US researchers.

    If the switch is as important as the scientists believe, its discovery should lead to new treatments for disease and provide vital information for researchers who hope to one day grow whole replacement organs from embryonic stem cells, says David Allis of the University of Virginia.

    Allis co-authored one of a series of new journal papers revealing details of the "histone methylation switch". Histones are proteins that DNA coils around to form "chromatin" in a cell nucleus.



  17. Sub-Planck Structure And Its Relevance For Quantum Decoherence, Nature Bookmark and Share

    Editor's Note: This work shows that basic limitations to quantum computation might be much weaker than expected originally. The special role of chaotic dynamics could indicate that problems of decoherence of entangled quantum states (especially at room temperature) might have been solved e.g. by (biological) evolution.

    Excerpts: Heisenberg's principle states that the product of uncertainties of position and momentum should be no less than the limit set by Planck's constant, /2. This is usually taken to imply that phase space structures associated with sub-Planck scales ( ) do not exist, or at least that they do not matter. Here I show that this common assumption is false: non-local quantum superpositions (or 'Schrödinger's cat' states) (…) develop spotty structure on the sub-Planck scale (…). Structure saturates on this scale particularly quickly in quantum versions of classically chaotic systems (…)



  18. Laws of Nature May Change as Universe Ages, Yahoo! News Bookmark and Share

    Editor's Note: It complex systems we often encounter the situation that (fixed) control parameters change on time-scales that are long compared to the timescales of the state variables. Now it seems that even a parameter considered fundamental in physics - the fine structure constant- is changing slowly, supporting the notion that the universe itself might follow evolutionary selection processes.

    Excerpts: Scientists based their findings on observation of light from a quasar (…) passing through a cosmic gas cloud.

    They first took a spectrum pattern as elements such as magnesium, zinc and hydrogen, which were present in the cloud, absorbed the quasar's light. This was then compared with a spectrum pattern created down on Earth -- and they found small unexplained differences.

    Those differences suggested that something, possibly the speed of light, had changed by the time it reached the Earth, trillions upon trillions of miles from the cloud.



  19. Phase Transition Between Disordered And Ordered Foraging In Pharaoh's Ants, PNAS Bookmark and Share

    Abstract: The complex collective behavior seen in many insect societies strongly suggests that a minimum number of workers are required for these societies to function effectively. Here we investigated the transition between disordered and ordered foraging in the Pharaoh's ant. We show that small colonies forage in a disorganized manner, with a transition to organized pheromone-based foraging in larger colonies. We also show that when food sources are difficult to locate through independent searching, this transition is first-order and exhibits hysteresis, comparable to a first-order phase transition found in many physical systems. To our knowledge, this is the first experimental evidence of a behavioral phase transition between a maladaptive (disorganized) and an adaptive (organized) state.


  20. Links & Snippets Bookmark and Share


    1. Other Articles Bookmark and Share



      1. Preventative Mastectomies Save Lives, Study Finds, Linda A. Johnson, The Associated Press, 7/19/01 Bookmark and Share