Complexity Digest 2001.08

19-Feb-2001

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Content

  1. Draft Human Genome Sequence Published, Nature
    1. Initial Sequencing And Analysis Of The Human Genome, Nature
    2. The Sequence Of The Human Genome, Science
    3. The Humane Genome, Nature
    4. A Tale of Two Sequences, Science
    5. Brain Cell Connections Restored With Gene Therapy In Aged Monkeys, UCSD/Science Daily
    6. Dynamic Modeling Of Gene Expression Data, PNAS
    7. Implications for Congenital Heart Disease, Annu. Rev. Physiol.
  2. Searching For Life In The Stardust, BusinessWeek Online
    1. How Life Got The Upper Hand
  3. Some Economists Call Behavior A Key, NY Times
    1. Exuberance Is Rational, NY Times
  4. Web Frontier Is Alive And Thriving, Darwin Magazine
  5. Microbial Activity Key Component Of Global Environmental Change, Science Daily
  6. Storm Surges Increase With Warming Oceans, Science Daily
  7. Brain Responses Associated With Consciousness Of Breathlessness (Air Hunger), PNAS
    1. Neuroimaging Evidence Of Hypercapnia And Hunger For Air, PNAS
  8. Imaging The Sleeping Brain, Trends In Neurosciences
  9. The Neural Basis Of Task-Switching In Working Memory: Effects Of Performance And Aging, PNAS
  10. On A Common Circle: Natural Scenes And Gestalt Rules, PNAS
  11. Documenting Plant Domestication, PNAS
  12. Evolutionary Quantum Game, arXiv
  13. Chaos And The Exchange Rate, Working Papers In Economics
  14. Microeconomic Models For Long-Memory In The Volatility Of Financial Time Series, Working Papers in Economics
  15. Come On Feel The Noise, Nature
    1. Noise Suppression By Noise, Phys.Rev.Let.
  16. Dynamic Behavior During Noninvasive Ventilation: Chaotic Support?, Am. J. Respir. Crit. Care Med.
  17. Mimicking Biological Systems, Composite Material Heals Itself, Science Daily
    1. Plastic, Heal Thyself, Nature Science
    2. Autonomic Healing Of Polymer Composites
  18. Links & Snippets
    1. Other Complexity Related Articles
    2. Pub Alert
    3. Announcements

  1. Draft Human Genome Sequence Published, Nature Next Article Bookmark and Share

    Excerpts: Often called our genetic blueprint, the sequence is more an indistinct list of ingredients, and a pretty humbling one at that. What makes a human? Seemingly about 32,000 genes, 22,000 of which have been identified so far. Compare this with the 25,000 genes found in the genome of the weed thale cress Arabidopsis thaliana, and it is clear that there is more to life than the number of genes. (…) ours is by far the biggest genome to be sequenced in its entirety.


    1. Initial Sequencing And Analysis Of The Human Genome, Nature Next Article Bookmark and Share

      Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence. (…)

      Here we report the results of a collaboration involving 20 groups from the United States, the United Kingdom, Japan, France, Germany and China to produce a draft sequence of the human genome.


    2. The Sequence Of The Human Genome, Science Next Article Bookmark and Share

      A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies--a whole-genome assembly and a regional chromosome assembly--were used, each combining sequence data from Celera and the publicly funded genome effort.


    3. The Humane Genome, Nature Next Article Bookmark and Share

      It is with great pleasure that Nature presents this special section of the Genome Gateway to mark the publication of the initial sequencing and analysis of the human genome. We are delighted to uphold the principle at the heart of the Human Genome Project: free and unrestricted access to all our genome related material through these web pages.


    4. A Tale of Two Sequences, Science Next Article Bookmark and Share

      The publication of the sequence of the human genome is the result of years of intense effort and debate within the scientific community. A special news section (p. 1177) describes how we arrived at this momentous occasion, the debates that led to the publication of two separate sequences, some of the key players, and what lies in store for the sequencing centers. A pullout timeline (p. 1195) hits the high points of the genome story so far.

      With the completion of the human genome sequence, we have received a powerful tool for unlocking the secrets of our genetic heritage and for finding our place among the other participants in the adventure of life.

      This week's issue of Science contains the report of the sequencing of the human genome from a group of authors led by Craig Venter of Celera Genomics. The report of the sequencing of the human genome from the publicly funded consortium of laboratories led by Francis Collins appears in this week's Nature.


    5. Brain Cell Connections Restored With Gene Therapy In Aged Monkeys, UCSD/Science Daily Next Article Bookmark and Share

      In new research that builds upon previous work with atrophied brain cells, UCSD School of Medicine researchers have found that essential brain fibers that shrivel up and disappear in aged monkeys can be restored to normal levels with infusion of tissue that has been genetically altered to produce nerve growth factor (NGF), a naturally occurring substance found in all vertebrate animals. Like telephone wires, these fibers, called axons, are vital for transmitting messages to and from neurons within the brain.

      According to the UCSD researchers, the new findings provide additional support for the potential use of gene therapy to treat loss of memory and cognitive function in Alzheimer’s patients. Two patients have been enrolled in a clinical trial now underway, and another six are being recruited to evaluate this procedure in humans.


    6. Dynamic Modeling Of Gene Expression Data, PNAS Next Article Bookmark and Share

      Abstract: We describe the time evolution of gene expression levels by using a time translational matrix to predict future expression levels of genes based on their expression levels at some initial time. We deduce the time translational matrix for previously published DNA microarray gene expression data sets by modeling them within a linear framework by using the characteristic modes obtained by singular value decomposition. The resulting time translation matrix provides a measure of the relationships among the modes and governs their time evolution. We show that a truncated matrix linking just a few modes is a good approximation of the full time translation matrix. This finding suggests that the number of essential connections among the genes is small.


    7. Implications for Congenital Heart Disease, Annu. Rev. Physiol. Next Article Bookmark and Share

      Abstract: More children die from congenital heart defects (CHD) each year than are diagnosed with childhood cancer, yet the causes remain unknown. The remarkable conservation of genetic pathways regulating cardiac development in species ranging from flies to humans provides an opportunity to experimentally dissect the role of critical cardiogenic factors. Utilization of model biological systems has resulted in a molecular framework in which to consider the etiology of CHD. As whole genome sequencing and single nucleotide polymorphism data become available, identification of genetic mutations predisposing to CHD may allow preventive measures by modulation of secondary genetic or environmental factors. In this review, genetic pathways regulating cardiogenesis revealed by cross-species studies are reviewed and correlated with human CHD.


  2. Searching For Life In The Stardust, BusinessWeek Online Next Article Bookmark and Share

    Excerpts: The concoction that the researchers made in a simulated deep-space environment isn't freeze-dried soup or Jell-O, nor will it get up and walk -- or even crawl, for that matter. But it demonstrates that the complex reactions essential to life can occur in the darkest and most inhospitable regions of the cosmos.(…)

    The result of the experiment was the spontaneous formation of hollow spheres made up of complex membranes -- akin to the cell walls that shelter the chemistry of life from the outside environment.


    1. How Life Got The Upper Hand Next Article Bookmark and Share

      Many biological molecules can exist in two forms that contain the same atoms, but are mirror images of each other - just like a pair of hands. But from bats to bacteria, all living things are made up of only 'left-handed' amino acids (the building blocks of proteins) and 'right-handed' DNA helices. (…)

      But on mixing the fragments, the researchers obtained predominantly homochiral products. Once formed, the homochiral molecules acted as templates, accelerating their own replication, the team says.


  3. Some Economists Call Behavior A Key, NY Times Next Article Bookmark and Share

    Excerpts: Behavioral economists help to explain how booms persist while busts, like the one that the United States may now be entering, are difficult to reverse. (…) If the behaviorists are correct, shares of companies on the New York Stock Exchange are overvalued and the Dow Jones industrial average has further to fall. And if the behaviorists prevail, the mainstream view of a rational, self-regulating economy may well be amended and policies adopted to control irrational, sometimes destructive behavior. Twenty-five years of deregulation might lose its appeal.

    1. Some Economists Call Behavior A Key, Louis Uchitelle, NY Times, 01/02/11

    1. Exuberance Is Rational, NY Times Next Article Bookmark and Share

      Thaler spearheaded a simple but devastating dissent. Rejecting the narrow, mechanical homo economicus that serves as a basis for neoclassical theory, Thaler proposed that most people actually behave like . . . people! They are prone to error, irrationality and emotion, and they act in ways not always consistent with maximizing their own financial well being. So serious was Thaler's challenge that Merton Miller, the late Nobelist and neoclassical deity, refused to talk to him;

      1. Exuberance Is Rational , Roger Lowenstein, NY Times, 01/02/11
      2. Social And Psychological Foundations Of Economic Life, European Science Days Steyr, Austria, July 2 - 5, 2001

  4. Web Frontier Is Alive And Thriving, Darwin Magazine Next Article Bookmark and Share

    Excerpt: Given that the Web isn't done evolving and you'll likely see even more aggressive dotcoms enter your territory, how do you balance the need for accountability with the imperative to keep thinking about what's next?

    At Northwest Airlines, Al Lenza, the vice president of distribution planning, explains that it's crucial for the e-commerce group to work closely with the rest of the organization. "We recently started letting customers print out their own boarding passes at home," Lenza says. "That required the cooperation of all of our airport personnel." And there are clear metrics by which the e-commerce team's progress is tracked—for example, how much incremental revenue is the team bringing in with its online-only travel promotions.

    • Final Frontier, The Web Frontier Is Alive And Thriving, Scott Kirsner, Darwin Magazine, 01/02/01

  5. Microbial Activity Key Component Of Global Environmental Change, Science Daily Next Article Bookmark and Share

    Excerpt: Managing microbial activity can play a significant role in slowing adverse effects of greenhouse gases and other global environmental changes, according to a new report from the American Society for Microbiology (ASM).

    The report, "Global Environmental Change: Microbial Contributions, Microbial Solutions," points out that the basic chemistry of Earth's surface is determined by biological activity, especially that of the many trillions of microbes in soil and water. Microbes make up the majority of the living biomass on Earth and, as such, have major roles in the recycling of elements vital to life.

    Since the microbial world can contribute to as well as mitigate global change, its activities are important to understand as a sound basis for policy decisions and regulations.

    "We must better understand the human-microbe partnership so that environmental decisions that impact microbial processes will achieve appropriate balances in the atmosphere and biosphere. Otherwise, we will be increasingly challenged by unprecedented environmental problems," predicts Dr. James M. Tiedje, Michigan State University, an author of the report who chairs ASM's Committee on Environmental Microbiology.

    Microbial roles in global change include producing and consuming atmospheric gases that affect climate; mobilizing toxic elements such as mercury, arsenic and selenium; and producing toxic algal blooms and creating oxygen depletion zones in lakes, rivers and coastal environments (eutrophication). Furthermore, the incidence of microbial diseases such as plague, cholera, Lyme disease, and West Nile Virus are linked to global change.

    The report makes four recommendations to enhance microbiological solutions to global change.

    • Integrate understanding of microbiological processes from organism to ecosystem level. This will lead, in part, to an improved understanding of the global carbon budget, eutrophication and the changes in greenhouse gases that affect climate.
    • Discover, characterize and harness the abilities of microbes that transform the active greenhouse trace gases and toxic elements.
    • Establish multi-year research programs that draw on microbiology and partner disciplines such as earth and atmospheric sciences to gain an integrated understanding of complex global change problems.
    • Begin training scientists and policy makers for the future's complex environmental problems.

  6. Storm Surges Increase With Warming Oceans, Science Daily Next Article Bookmark and Share

    Excerpt: Ocean warming and thermal expansion will be the largest contributor to sea-level rise during the 21st century, says an Australian scientist.

    Coastal storm surges will become an increasing threat to life and property, says Dr John Church, a scientist at Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Antarctic Cooperative Research Centre.

    Dr Church was a lead author on sea-level rise for the Intergovernmental Panel on Climate Change's assessment approved in Shanghai, China last month.

    The Third Assessment Report - Climate Change 2001:The Scientific Basis - was prepared over the past three years by several hundred experts reviewing the published science, and more than 100 scientific authors drawing this together into the final report.

    Global average sea level is projected to rise between 9 and 88 cm between 1990 and 2100 for a global average surface temperature rise projected to be between 1.4 and 5.8 degrees Celsius.

    Addressing a national conference in Hobart of climate scientists and meteorologists today, Dr Church said computer calculations indicate increasing atmospheric concentrations of greenhouse gases will result in warmer atmospheric and ocean temperatures.


  7. Brain Responses Associated With Consciousness Of Breathlessness (Air Hunger), PNAS Next Article Bookmark and Share

    Abstract: Little is known about the physiological mechanisms subserving the experience of air hunger and the affective control of breathing in humans. Acute hunger for air after inhalation of CO2 was studied in nine healthy volunteers with positron emission tomography. Subjective breathlessness was manipulated while end-tidal CO2- was held constant. Subjects experienced a significantly greater sense of air hunger breathing through a face mask than through a mouthpiece. The statistical contrast between the two conditions delineated a distributed network of primarily limbic/paralimbic brain regions, including multiple foci in dorsal anterior and middle cingulate gyrus, insula/claustrum, amygdala/periamygdala, lingual and middle temporal gyrus, hypothalamus, pulvinar, and midbrain. This pattern of activations was confirmed by a correlational analysis with breathlessness ratings. The commonality of regions of mesencephalon, diencephalon and limbic/paralimbic areas involved in primal emotions engendered by the basic vegetative systems including hunger for air, thirst, hunger, pain, micturition, and sleep, is discussed with particular reference to the cingulate gyrus. A theory that the phylogenetic origin of consciousness came from primal emotions engendered by immediate threat to the existence of the organism is discussed along with an alternative hypothesis by Edelman that primary awareness emerged with processes of ongoing perceptual categorization giving rise to a scene [Edelman, G. M. (1992) Bright Air, Brilliant Fire (Penguin, London)].


    1. Neuroimaging Evidence Of Hypercapnia And Hunger For Air, PNAS Next Article Bookmark and Share

      Abstract: Recent neuroimaging and neurological data implicate cerebellum in nonmotor sensory, cognitive, vegetative, and affective functions. The present study assessed cerebellar responses when the urge to breathe is stimulated by inhaled CO2. Ventilation changes follow arterial blood partial pressure CO2 changes sensed by the medullary ventral respiratory group (VRG) and hypothalamus, entraining changes in midbrain, pons, thalamus, limbic, paralimbic, and insular regions. Nearly all these areas are known to connect anatomically with the cerebellum. Using positron emission tomography, we measured regional brain blood flow during acute CO2-induced breathlessness in humans. Separable physiological and subjective effects (air hunger) were assessed by comparisons with various respiratory control conditions. The conjoint physiological effects of hypercapnia and the consequent air hunger produced strong bilateral, near-midline activations of the cerebellum in anterior quadrangular, central, and lingula lobules, and in many areas of posterior quadrangular, tonsil, biventer, declive, and inferior semilunar lobules. The primal emotion of air hunger, dissociated from hypercapnia, activated midline regions of the central lobule. The distributed activity across the cerebellum is similar to that for thirst, hunger, and their satiation. Four possible interpretations of cerebellar function(s) here are that: it subserves implicit intentions to access air; it provides predictive internal models about the consequences of CO2 inhalation; it modulates emotional responses; and that while some cerebellar regions monitor sensory acquisition in the VRG (CO2 concentration), others influence VRG to adjust respiratory rate to optimize partial pressure CO2, and others still monitor and optimize the acquisition of other sensory data in service of air hunger aroused vigilance.

      1. Neuroimaging Evidence Implicating Cerebellum In The Experience Of Hypercapnia And Hunger For Air, Parsons, L. M., Egan, G., Liotti, M., Brannan, S., Denton, D., Shade, R., Robillard, R., Madden, L., Abplanalp, B., Fox, P. T. (2001). Proc. Natl. Acad. Sci. U. S. A. 98: 2041-2046

  8. Imaging The Sleeping Brain, Trends In Neurosciences Next Article Bookmark and Share

    Excerpt: In the December issue of Neuron, a research group at the Institute of Neurology, UK, has reported that a human sleeping brain can be influenced by external auditory stimuli in a stimulus-specific manner. Using fMRI images, researchers found that saying the participant's name evoked a greater activation compared with a generic beep in orbitofrontal regions and the amygdaloid complex in both awake and sleep states. Amazingly, the activation in response to the name stimulus was greatest during non-REM sleep, when these regions are normally deactivated. This suggests that during sleep, important external information can reactivate neural circuits to a higher level compared with that achieved when awake. The implications of this study extend beyond sleep research and auditory processing to touch upon issues of consciousness in normal and altered states.


  9. The Neural Basis Of Task-Switching In Working Memory: Effects Of Performance And Aging, PNAS Next Article Bookmark and Share

    Abstract: We studied the performance of young and senior subjects on a well known working memory task, the Operation Span. This is a dual-task in which subjects perform a memory task while simultaneously verifying simple equations. Positron-emission tomography scans were taken during performance. Both young and senior subjects demonstrated a cost in accuracy and latency in the Operation Span compared with performing each component task alone (math verification or memory only). Senior subjects were disproportionately impaired relative to young subjects on the dual-task. When brain activation was examined for senior subjects, we found regions in prefrontal cortex that were active in the dual-task, but not in the component tasks. Similar results were obtained for young subjects who performed relatively poorly on the dual-task; however, for young subjects who performed relatively well in the dual-task, we found no prefrontal regions that were active only in the dual-task. Results are discussed as they relate to the executive component of task switching.


  10. On A Common Circle: Natural Scenes And Gestalt Rules, PNAS Next Article Bookmark and Share

    Abstract:To understand how the human visual system analyzes images, it is essential to know the structure of the visual environment. In particular, natural images display consistent statistical properties that distinguish them from random luminance distributions. We have studied the geometric regularities of oriented elements (edges or line segments) present in an ensemble of visual scenes, asking how much information the presence of a segment in a particular location of the visual scene carries about the presence of a second segment at different relative positions and orientations. We observed strong long-range correlations in the distribution of oriented segments that extend over the whole visual field. We further show that a very simple geometric rule, cocircularity, predicts the arrangement of segments in natural scenes, and that different geometrical arrangements show relevant differences in their scaling properties. Our results show similarities to geometric features of previous physiological and psychophysical studies. We discuss the implications of these findings for theories of early vision.


  11. Documenting Plant Domestication, PNAS Next Article Bookmark and Share

    Excerpt: For more than a million years our distant ancestors were hunter-gatherers, relying exclusively on the gathering of wild plants and the hunting of wild animals for their food. Then, between 10,000 and 5,000 years ago, dramatic changes took place in this longstanding way of life, as human societies in more than a half dozen regions of the world, including Mexico, independently domesticated a variety of different plants and animals (1, 2). These early domesticates, and the agricultural economies subsequently based on them, marked a major turning point in the history of the earth and our species, in that they formed the lever with which humans have relentlessly transformed the earth and its terrestrial ecosystems.


  12. Evolutionary Quantum Game, arXiv Next Article Bookmark and Share

    Abstract: We present the first study of a dynamical quantum game. Each agent has a `memory' of her performance over the previous m timesteps, and her strategy can evolve in time. The game exhibits distinct regimes of optimality. For small m the classical game performs better, while for intermediate m the relative performance depends on whether the source of qubits is `corrupt'. For large m, the quantum players dramatically outperform the classical players by `freezing' the game into high-performing attractors in which evolution ceases.


  13. Chaos And The Exchange Rate, Working Papers In Economics Next Article Bookmark and Share

    Abstract: The interest of economists in chaos theory started in the 1980s. The first to draw the attention of economists to chaos theory was, in fact, Brock (1986), who examined the quarterly US real GNP data 1947-1985 using the Grassberger-Procaccia correlation dimension and Lyapunov exponents. Subsequent studies generally found absence of evidence for chaos in macroeconomic variables (GNP, monetary aggregates) while the study of financial variables such as stock-market returns and exchange rates gave mixed evidence. Studies aimed at detecting chaos in economic variables can be roughly classified into two categories. On the one hand, there are studies that simply examine the data and apply various tests, such as the studies mentioned. These tests have been originally developed in the physics literature and typically require several thousand observations. Apart from this data problem, such an approach is not very satisfactory from our point of view, which aims at finding the dynamic model underlying the data. On the other hand, structural models are built and analysed. This analysis can in principle be carried out in several ways: a) theoretically, namely showing that plausible economic assumptions give rise to dynamic structures having one of the mathematical forms known to give rise to chaotic motion; b) empirically, namely building a theoretical model and then b1) giving plausible values to the parameters, simulating the model, and testing the resulting data series for chaos; or b2) estimating the parameters econometrically, and then proceeding as in b1. Existing chaotic exchange rate models (De Grauwe and Versanten, 1990; Reszat, 1992; De Grauwe and Embrechts, 1992, 1993a,b; De Grauwe, Dewachter, Embrechts, 1993; Ellis, 1994; Szpiro, 1994; Da Silva, 1997) follow the structural approach: they are structural models built in discrete time (difference equations). From the theoretical point of view, these models show that with orthodox assumptions (PPP, interest parity, etc.) and introducing economically plausible nonlinearities in the dynamic equations, it is possible to obtain a dynamic system capable of giving rise to chaotic motion. However, none of these models is estimated, and the conclusions are based on simulations: the empirical validity of these models is not tested. Hence they can all be classified in category b1. In this paper, a continuous time exchange rate model is built as a nonlinear set of three differential equations and its theoretical properties (steady state, stability. etc.) are analysed. The model is then econometrically estimated in continuous time with Italian data and examined for the possible presence of chaotic motion. So far as we know, this is the first (tentative) study in category b2. However, this is not the main motivation of this paper. From our point of view it is important to show that the continuous time estimation of systems of nonlinear differential equations is a very powerful tool in the hands of the profession to tackle dynamic nonlinear problems.


  14. Microeconomic Models For Long-Memory In The Volatility Of Financial Time Series, Working Papers in Economics Next Article Bookmark and Share

    Abstract: We show that a class of microeconomic behavioral models with interacting agents, introduced by Kirman (1991, 1993), can replicate the empirical long-memory properties of the two first conditional moments of financial time series. The essence of these models is that the forecasts and thus the desired trades of the individuals in the markets are influenced, directly, or indirectly by those of the other participants. These 'field effects' generate 'herding' behaviour which affects the structure of the asset price dynamics. The series of squared returns and absolute returns generated by these models display long-memory, while the returns are uncorrelated. Furthermore, this class of models is able to replicate the common long-memory properties in the volatility and co-volatility of financial time series, uncovered by Teyssière (1997, 1998). These properties are investigated by using various model independent tests and estimators, i.e., semiparametric and nonparametric, introduced by Lo (1991), Kwiatkowski, Phillips, Schmidt and Shin (1992), Robinson (1995), Lobato adn Robinson (1998), Giraitis, Kokoszka and Leipus (1999), Giraitis, Kokoszka, Leipus and Teyssière (1999). The relative performance of these tests and estimators for long-memory in an non-standard data generating process is then assessed.


  15. Come On Feel The Noise, Nature Next Article Bookmark and Share

    Excerpt: Vilar and Rubi have developed a mathematical model, based on how nerve impulses pass between cells, which suggests that adding more random variation to an incoming signal can even out the emergent signal. (…)

    Take, for example, the phenomenon 'stochastic resonance', in which the transmission of a signal, such as an information-laden radio broadcast, is enhanced by the addition of some static. You add some noise to an input signal, and the signal-to-noise ratio of the output improves.


    1. Noise Suppression By Noise, Phys.Rev.Let. Next Article Bookmark and Share

      Abstract: We have analyzed the interplay between an externally added noise and the intrinsic noise of systems that relax fast towards a stationary state, and found that increasing the intensity of the external noise can reduce the total noise of the system. We have established a general criterion for the appearance of this phenomenon and discussed two examples in detail.


  16. Dynamic Behavior During Noninvasive Ventilation: Chaotic Support?, Am. J. Respir. Crit. Care Med. Next Article Bookmark and Share

    Abstract: Acute noninvasive ventilation is generally applied via face mask, with modified pressure support used as the initial mode to assist ventilation. Although an adequate seal can usually be obtained, leaks frequently develop between the mask and the patient's face. This leakage presents a theoretical problem, since the inspiratory phase of pressure support terminates when flow falls to a predetermined fraction of peak inspiratory flow. To explore the issue of mask leakage and machine performance, we used a mathematical model to investigate the dynamic behavior of pressure-supported noninvasive ventilation, and confirmed the predicted behavior through use of a test lung. Our mathematical and laboratory analyses indicate that even when subject effort is unvarying, pressure-support ventilation applied in the presence of an inspiratory leak proximal to the airway opening can be accompanied by marked variations in duration of the inspiratory phase and in autoPEEP. The unstable behavior was observed in the simplest plausible mathematical models, and occurred at impedance values and ventilator settings that are clinically realistic.


  17. Mimicking Biological Systems, Composite Material Heals Itself, Science Daily Next Article Bookmark and Share

    Excerpt: Inspired by biological systems in which damage triggers an autonomic healing response, researchers at the University of Illinois have developed a synthetic material that can heal itself when cracked or broken.

    The material – consisting of a microencapsulated healing agent and a special catalyst embedded in a structural composite matrix – could increase the reliability and service life of thermosetting polymers used in a wide variety of applications ranging from microelectronics to aerospace.

    “Once cracks have formed within typical polymeric materials, the integrity of the structure is significantly compromised,” said Scott White, a UI professor of aeronautical and astronautical engineering and lead author of a paper published in the Feb. 15 issue of the journal Nature that described the new self-healing material. “Often these cracks occur deep within the structure where detection is difficult and repair is virtually impossible.”

    In the new material, however, the repair process begins as soon as a crack forms.

    “When the material cracks, the microcapsules rupture and release the healing agent into the damaged region through capillary action,” White said. “As the healing agent contacts the embedded catalyst, polymerization is initiated which then bonds the crack face closed.”

    In recent fracture tests, the self-healed composites recovered as much as 75 percent of their original strength. And because microcracks are the precursors to structural failure, the ability to heal them will enable structures that last longer and require less maintenance.


    1. Plastic, Heal Thyself, Nature Science Next Article Bookmark and Share

      Excerpt: Structural composite materials consist of fibres of glass, carbon or some other component embedded in a polymer matrix. When subjected to vibrations, loads and stresses, these materials develop tiny cracks, which get bigger until they render the material useless.

      White's team tackled the problem by embedding tiny capsules within the polymer matrix. As the crack propagates, it ruptures the capsules, releasing a liquid healing agent. The liquid molecules come into contact with a catalyst that is also embedded within the polymer matrix, causing the healing agent to polymerize.


    2. Autonomic Healing Of Polymer Composites Next Article Bookmark and Share

      Excerpt: Cracking leads to mechanical degradation of fibre-reinforced polymer composites; in microelectronic polymeric components it can also lead to electrical failure. (…) Experiments exploring the concept of self-repair have been previously reported, but the only successful crack-healing methods that have been reported so far require some form of manual intervention. Here we report a structural polymeric material with the ability to autonomically heal cracks. The material incorporates a microencapsulated healing agent that is released upon crack intrusion.


  18. Links & Snippets Next Article Bookmark and Share

    1. Other Complexity Related Articles Next Article Bookmark and Share


    2. Pub Alert Next Article Bookmark and Share

      These references can be found in http://www.thescientificworld.com/. To retrieve the articles connect to the site and search for the title.

      • The Complexity of Planetary Quarantine, Morowitz, H., COMPLEXITY -NEW YORK-
      • What Organizational Leaders Should Know About the New Science of Complexity, Kupers, R., COMPLEXITY -NEW YORK-
      • Evolutionary Transitions: How Do Levels of Complexity Emerge?, Heylighen, F., COMPLEXITY -NEW YORK-
      • Some Regularities in Human Group Formation and the Evolution of Societal Complexity, Kosse, K., COMPLEXITY -NEW YORK-
      • The Complex Link Between Neuroanatomy and Consciousness, Ascoli, G. F., COMPLEXITY -NEW YORK-
      • On the Challenge of Developing a Formal Mathematical Theory for Establishing Emergence in Complex Systems, Solow, D., COMPLEXITY -NEW YORK-
      • Mental Workload Beyond Computational Complexity, Tsang, P. S., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Complex responses of Chaoborus to changes in fish populations, Ramcharan, C. W.; Yan, N. D.; McQueen, D. J.; Perez-Fuentetaja, A.; Demers, E.; Rusak, J. A., ERGEBNISSE DER LIMNOLOGIE
      • Complex Treatment And Prophylaxis Of Post-Burn Cicatrization In Childhood, Dyakov, R., ANNALS OF BURNS AND FIRE DISASTERS
      • Transfer of Production Planning and Scheduling from Staff to Production Personnel in a Complex Maintenance Company, Berglund, M., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Eye-Movements during Unit-Task Execution in a Complex Problem-Solving Situation, Sohn, M.-H.; Douglass, S. A.; Chen, M.-C.; Anderson, J. R., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Psychophysiological Aspects of Macroergonomic Approach to Design of Complex Technological Systems (An Example of Power Industry), Burov, A., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Individual Differences in Complex Task Learning via Interactive Systems, Cuevas, H. M.; Fiore, S. M.; Oser, R. L., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Creation of Interface System for Nuclear Reactor Operation - Practical Implication of Implementing EID Concept on Large Complex System, Yamaguchi, Y.; Tanabe, F., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Understanding Excellence in Complex, Dynamic Medical Systems, Carthey, J.; de Leval, M. R.; Reason, J. T., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Fermenting change: capitalizing on the inherent change found in dynamic non-linear (or complex) systems, Black, J. A., JOURNAL OF ORGANIZATIONAL CHANGE MANAGEMENT
      • Phenomenal complexity theory as informed by Bergson, Letiche, H., JOURNAL OF ORGANIZATIONAL CHANGE MANAGEMENT
      • Phenomenal complexity theory and change at Disney: response to Letiche, Boje, D. M., JOURNAL OF ORGANIZATIONAL CHANGE MANAGEMENT
      • Organizational responses to complexity: the effect on organizational performance, Ashmos, D. P.; Duchon, D.; McDaniel, R. R., JOURNAL OF ORGANIZATIONAL CHANGE MANAGEMENT
      • Team Decision-Making Strategies: Implications for Designing the Interface in Complex Tasks, Miller, S. L.; Adelman, L.; Henderson, E. D.; Schoelles, M. J.; Yeo, C., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Human Factors Issues in Implementation of AA to Complex Systems, Tan, K.-W.; Kaber, D. B.; Riley, J. M.; Endsley, M. R., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • The Application of Human Performance Models in the Design and Operation of Complex Systems, Campbell, G. E.; Cannon-Bowers, J. A., PROCEEDINGS OF THE HUMAN FACTORS AND ERGONOMICS SOCIETY ANNUAL MEETING
      • Complex social structure, alliance stability and mating access in a bottlenose dolphin `super-alliance', Connor, R. C.; Heithaus, M. R.; Barre, L. M., PROCEEDINGS- ROYAL SOCIETY OF LONDON B
      • Classification of Complex Signal Patterns With Artificial Neuronal Nets in Hearing and Voice Diagnostics, Schonweiler, R., LARYNGORHINOOTOLOGIE
      • Cathy Young: Venus at the Ballot Box Women may lean toward the "Mommy State," but their politics are more complex than pundits recognize, Unknown Author, REASON -SANTA BARBARA THEN LOS ANGELES-
      • The Locus of Age x Health-Related Physical Fitness Interactions in Serial Choice Responding as a Function of Task Complexity: Central Processing or Motor Function?, Bunce, D., EXPERIMENTAL AGING RESEARCH
      • Air Traffic Control Switches Much more complex than a typical finger-pushing switch, even more so than a telephone exchange, ATC switches perform tasks of heroic proportions, Marsh, G., AVIONICS MAGAZINE
      • Complex Management Of Neurocardiogenic (Vaso-Vagal) Syncope, Lorincz, I.; Varga, E.; Szabo, Z.; Karanyi, Z. S.; Varga, Z. S., Europace -London
      • Monitoring Of Haemodynamic Performance In Complex Pacing System With A Microchip Pacer Patient Card, Lorincz, I.; Varga, E.; Szabo, Z.; Karanyi, Z. S.; Varga, Z. S., EUROPACE -LONDON-
      • Consultants, Keep Out. Vite's Sim-Vision lets companies model complex projects in-house, Unknown Author, INFORMATION WEEK -MANHASSET-
      • Simple (Wrong) Models for Complex Trees: A Case from Retroviridae, Posada, D.; Crandall, K. A., MOLECULAR BIOLOGY AND EVOLUTION
      • The Complexity of Evolution, Cohen, J., NATO ASI SERIES A LIFE SCIENCES
      • The genetics of type 2 diabetes: the consequences of complexity, McCarthy, M., GENESCREEN -OXFORD-
      • Pluralism and the Complexity of Knowledge, De Marchi, B., POLITICS AND THE LIFE SCIENCES
      • Investigation of Variability of Indexes of Myocardial Contractility by Complexity Measures in Patients with Hypertension, Matcharashvili, T.; Janiashvili, M., NATO ASI SERIES A LIFE SCIENCES
      • Problems and advances in analysis for gene discovery of complex traits, Spector, T. D.; MacGregor, A. J.; Sneider, H., GENESCREEN -OXFORD-
      • Uses of twins in studying the genetics of complex traits, Spector, T. D.; MacGregor, A. J.; Snieder, H., GENESCREEN -OXFORD-
      • Challenges for genetic analysis in the 21st century: localizing and characterizing genes for common complex diseases and their quantitative risk factors, Almasy, L.; Blangero, J., GENESCREEN -OXFORD-
      • Setting the Stage for a Structured Finance Transaction An introduction to a complex corporate practice, Helewitz, J. A., LEGAL ASSISTANT TODAY
      • Quantitative Languages for Complex Systems Applied to Biological Structure, Smith, M. A.; Bar-Yam, Y.; Gelbart, W., NATO ASI SERIES A LIFE SCIENCES
      • Managing the Complexity of Best Practice Health Care, Brown, S. J., JOURNAL OF NURSING CARE QUALITY
      • Calculation of Stress Intensity Factors for Cracks of Complex Geometry and Subjected to Arbitrary Nonlinear Stress Fields, Glinka, G.; Reinhardt, W., ASTM SPECIAL TECHNICAL PUBLICATION
      • PIV measurements and data accuracy analysis of flow in complex terrain (Invited Paper) [4221-41], Yao, R.; Hao, H.; Qiao, Q., PROCEEDINGS- SPIE THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING

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