Complexity Digest 2001.10
  Archive: http://comdig.unam.mx
  "I think the next century will be the century of complexity." Stephen Hawking, 2000.
  1. Humans on the Move, Science
    1. In Search of the First Europeans, Science
    2. The Riddle of Coexistence, Science
    3. But Did They Mate?, Science
    4. Clovis First, Science
    5. Pre-Clovis Sites Fight for Acceptance, Science
    6. Tracking the Sexes by Their Genes, Science
    7. The Peopling of the Pacific, Science
    8. Genealogical and Evolutionary Inference with the Human Y Chromosome, Science
    9. Genetic Clues to Dispersal in Human Populations: Retracing the Past from the Present, Science
    10. Paleolithic Technology and Human Evolution, Science
  2. Isotopic Evidence For Microbial Sulphate Reduction In The Early Archaean Era, Nature
  3. The Origin Of Atmospheric Oxygen On Earth: The Innovation Of Oxygenic Photosynthesis, PNAS
  4. Crystals Prove Life on Mars, Discovery
    1. Chains Of Magnetite Crystals In The Meteorite ALH84001: Evidence Of Biological Origin, PNAS
  5. Power Laws of Wealth, Market Order Volumes and Market Returns, arXiv
  6. Quantifying Dynamics Of The Financial Correlations, arXiv
  7. Complex Structures In Generalized Small Worlds, arXiv
  8. Artificial Societies of Intelligent Agents, Thesis in Computing Engineering
  9. A Novel Microbial Habitat In The Mid-Ocean Ridge Subseafloor, PNAS
  10. The Evolution Of Social Behavior In Microorganisms, Trends in Ecology & Evolution
  11. Structural Colour: Now You See It --- Now You Don't, Nature
  12. Invariant Scaling Relationships For Interspecific Plant Biomass Production Rates And Body Size, PNAS
    1. Scaling Of Growth: Plants And Animals Are Not So Different, PNAS
  13. Circuit Training, Nature
  14. Nanohedra: Using Symmetry To Design Self Assembling Protein Cages, Layers, Crystals, And Filaments, PNAS
  15. Recent Improvements In Prediction Of Protein Structure By Global Optimization Of A Potential Energy Function, PNAS
  16. Solvent Effects On The Energy Landscapes And Folding Kinetics Of Polyalanine, PNAS
  17. Two Different Neurodegenerative Diseases Caused By Proteins With Similar Structures, PNAS
  18. Brain Cells Research Fuels Debate, Financial Times
    1. Of Mice And Men, Financial Times
  19. Synergistic Contributions Of Cyclin-Dependant Kinase 5/P35 And Reelin/Dab1 To The Positioning Of Cortical Neurons In The Developing Mouse Brain, PNAS
  20. Chaos On Centre Court, Nature
    1. Dynamics Of A Bouncing Ball In Human Performance, Rhys. Rev. E
  21. Getting The Joke, New Scientist
    1. Did You Hear The One About The Prefrontal Cortex?, Nature
  22. U.S. Scuttles Latest Chance to Avert Global Warming Catastrophe, Foreign Policy In Focus
  23. MIT Professor Claude Shannon Dies, MIT News Release
  24. Links & Snippets
    1. Other Articles
    2. Pub Alert
    3. Announcements

  1. Humans on the Move, Science Bookmark and Share

    A handful of ancient sites have convinced most anthropologists that early humans frequented southern Europe beginning perhaps 1.2 million years ago. But many researchers aren't sure just what species name to give to the first Europeans, or how many species they belonged to. There is even less agreement on where the first settlers came from and whether they gave rise to later Europeans. And yet recent discoveries here and at other sites in Spain and Italy indicate that Europe was more than just a neglected backwater during the early days of human evolution.
    • Humans On The Move, Elizabeth Culotta, Andrew Sugden, Brooks Hanson , Science 2001 291: 1721


    1. In Search of the First Europeans, Science Bookmark and Share

      A handful of ancient sites have convinced most anthropologists that early humans frequented southern Europe beginning perhaps 1.2 million years ago. But many researchers aren't sure just what species name to give to the first Europeans, or how many species they belonged to. There is even less agreement on where the first settlers came from and whether they gave rise to later Europeans. And yet recent discoveries here and at other sites in Spain and Italy indicate that Europe was more than just a neglected backwater during the early days of human evolution.


    2. The Riddle of Coexistence, Science Bookmark and Share

      A new look at archaeological sites throughout the Mediterranean region shows that Neandertals and modern humans coexisted in Europe for at least several thousand years and took turns occupying the same caves in the Middle East for much longer. Although modern humans had a clear technological and cultural advantage in Europe, they did not rout the Neandertals. There are no signs of war or rapid replacement. So far the evidence suggests that there was plenty of room for both groups for thousands of years, with competition for resources intensifying only as the climate worsened.


    3. But Did They Mate?, Science Bookmark and Share

      Successful reproduction would imply that Neandertals and humans were part of the same species and shared a recent evolutionary history. Studies of the maternally inherited mitochondrial DNA (mtDNA) from three Neandertals show it to be distinctly different from that of living humans, suggesting that Neandertal genes do not survive today and supporting a replacement view (…) variation between Neandertals and modern humans falls within the range of mtDNA variation between subspecies of chimpanzees.


    4. Clovis First, Science Bookmark and Share

      The timing of the Clovis people's journey is pinned down by the melting of the great glaciers of the last Ice Age. (…) might have trekked through a gap in the glaciers just east of the ice-covered Pacific coastal mountains and south of the arctic ice, to the Great Plains (see map). But they couldn't have gone very far south before the ice melted to open a path. (…) gap probably did not open earlier than 13,000 years before the present (BP) (…).


    5. Pre-Clovis Sites Fight for Acceptance, Science Bookmark and Share

      Leaders in the field remain skeptical, noting that the evidence from pre-Clovis sites is patchy and uneven, unlike the powerful stone record of the Clovis people. He and other skeptics have challenged pre-Clovis finds, questioning everything from dates to stratigraphy. A close look at a few of the most important and controversial sites illustrates why it is so difficult to prove very ancient occupation--and why the peopling of the Americas remains an open question.


    6. Tracking the Sexes by Their Genes, Science Bookmark and Share

      But molecular anthropologists tracking these ancient travelers by the trails left in their descendents' DNA are finding a surprise: striking differences in how the two sexes traveled about parts of this planet.

      (…) male explorers or warriors carried their genomes to distant places. But surprisingly, in general females seem to have stirred the genetic melting pot by dispersing their DNA more widely than their brothers dispersed theirs--perhaps as a result of thousands of years of moving to join their husbands' clans.



    7. The Peopling of the Pacific, Science Bookmark and Share

      Polynesia, with its dramatic volcanic islands rising out of the South Pacific, was the last area of the world to be settled by people. The fossil and archaeological trail shows that humans first set foot in Fiji only 3000 years ago, then sailed on within 500 years to Samoa and Tonga, and later reached Easter Island, Hawaii, and the fringes of remote Oceania, exploring a realm stretching 4500 kilometers. But just who was in those outrigger canoes has long been a mystery.



    8. Genealogical and Evolutionary Inference with the Human Y Chromosome, Science Bookmark and Share

      Population genetics has emerged as a powerful tool for unraveling human history. In addition to the study of mitochondrial and autosomal DNA, attention has recently focused on Y-chromosome variation. Ambiguities and inaccuracies in data analysis, however, pose an important obstacle to further development of the field. Here we review the methods available for genealogical inference using Y-chromosome data.

      Approaches can be divided into those that do and those that do not use an explicit population model in genealogical inference.



    9. Genetic Clues to Dispersal in Human Populations: Retracing the Past from the Present, Science Bookmark and Share

      Ongoing debate about proper interpretation of DNA sequence polymorphisms and their ability to reconstruct human population history illustrates a important change in perspective that we have achieved in the past 20 years of population genetics. To what extent does the history of a locus represent the history of a population? Tools originally developed for molecular systematics, where genetic lineages have been separated by speciation events, are routinely applied to the analysis of variation within our species, with conflicting results.



    10. Paleolithic Technology and Human Evolution, Science Bookmark and Share

      Human biological and cultural evolution are closely linked to technological innovations. Direct evidence for tool manufacture and use is absent before 2.5 million years ago (Ma), so reconstructions of australopithecine technology are based mainly on the behavior and anatomy of chimpanzees. Stone tool technology, robust australopithecines, and the genus Homo appeared almost simultaneously 2.5 Ma. Once this adaptive threshold was crossed, technological evolution was accompanied by increased brain size, population size, and geographical range.



  2. Isotopic Evidence For Microbial Sulphate Reduction In The Early Archaean Era, Nature Bookmark and Share

    Our results provide the oldest evidence of microbial sulphate reduction in the geological record, pre-dating previous evidence by more than 0.75 Gyr. They also give the earliest indication of a specific microbial metabolism. Sulphate reduction is a complex metabolic process requiring advanced membrane-bound transport enzymes (…). Therefore, by 3.47 Gyr ago (…) microbes had already developed many of the critical cellular systems shared by their modern descendants. (…)

    This placement (…) represents the oldest evolutionary event thus far dated on the tree of life.



  3. The Origin Of Atmospheric Oxygen On Earth: The Innovation Of Oxygenic Photosynthesis, PNAS Bookmark and Share

    Abstract: The evolution of O2-producing cyanobacteria that use water as terminal reductant transformed Earth's atmosphere to one suitable for the evolution of aerobic metabolism and complex life. The innovation of water oxidation freed photosynthesis to invade new environments and visibly changed the face of the Earth. We offer a new hypothesis for how this process evolved, which identifies two critical roles for carbon dioxide in the Archean period. First, we present a thermodynamic analysis showing that bicarbonate (formed by dissolution of CO2) is a more efficient alternative substrate than water for O2 production by oxygenic phototrophs. This analysis clarifies the origin of the long debated "bicarbonate effect" on photosynthetic O2 production. We propose that bicarbonate was the thermodynamically preferred reductant before water in the evolution of oxygenic photosynthesis. Second, we have examined the speciation of manganese(II) and bicarbonate in water, and find that they form Mn-bicarbonate clusters as the major species under conditions that model the chemistry of the Archean sea. These clusters have been found to be highly efficient precursors for the assembly of the tetramanganese-oxide core of the water-oxidizing enzyme during biogenesis. We show that these clusters can be oxidized at electrochemical potentials that are accessible to anoxygenic phototrophs and thus the most likely building blocks for assembly of the first O2 evolving photoreaction center, most likely originating from green nonsulfur bacteria before the evolution of cyanobacteria.


  4. Crystals Prove Life on Mars, Discovery Bookmark and Share

    A crystal found in a meteorite from Mars could only have been formed by a microbe and may be evidence of the oldest life form ever found, researchers say.

    Scientists at the Johnson Space Center in Houston say that a crystallized magnetic mineral, called magnetite, found in a Martian meteorite is similar to crystals formed on Earth by bacteria.(…)

    Thomas-Keprta said there is no report of such magnetites being formed by any but biologic means.



    1. Chains Of Magnetite Crystals In The Meteorite ALH84001: Evidence Of Biological Origin, PNAS Bookmark and Share

      Abstract: The presence of magnetite crystal chains, considered missing evidence for the biological origin of magnetite in ALH84001 [Thomas-Keprta, K. L., Bazylinski, D. A., Kirschvink, J. L., Clemett, S. J., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., & Romanek, C. S. (2000) Geochim. Cosmochim. Acta 64, 4049-4081], is demonstrated by high-power stereo backscattered scanning electron microscopy. Five characteristics of such chains (uniform crystal size and shape within chains, gaps between crystals, orientation of elongated crystals along the chain axis, flexibility of chains, and a halo that is a possible remnant of a membrane around chains), observed or inferred to be present in magnetotactic bacteria but incompatible with a nonbiological origin, are shown to be present. Although it is unlikely that magnetotactic bacteria were ever alive in ALH84001, decomposed remains of such organisms could have been deposited in cracks in the rock while it was still on the surface on Mars.



  5. Power Laws of Wealth, Market Order Volumes and Market Returns, arXiv Bookmark and Share

    Abstract: Using the Generalised Lotka Volterra (GLV) model adapted to deal with muti agent systems we can investigate economic systems from a general viewpoint and obtain generic features common to most economies. Assuming only weak generic assumptions on capital dynamics, we are able to obtain very specific predictions for the distribution of social wealth. First, we show that in a 'fair' market, the wealth distribution among individual investors fulfills a power law. We then argue that 'fair play' for capital and minimal socio-biological needs of the humans traps the economy within a power law wealth distribution with a particular Pareto exponent $\alpha \sim 3/2$. In particular we relate it to the average number of individuals L depending on the average wealth: $\alpha \sim L/(L-1)$. Then we connect it to certain power exponents characterising the stock markets. We obtain that the distribution of volumes of the individual (buy and sell) orders follows a power law with similar exponent $\beta \sim \alpha \sim 3/2$. Consequently, in a market where trades take place by matching pairs of such sell and buy orders, the corresponding exponent for the market returns is expected to be of order $\gamma \sim 2 \alpha \sim 3$. These results are consistent with recent experimental measurements of these power law exponents ([Maslov 2001] for $\beta$ and [Gopikrishnan et al. 1999] for $\gamma$).



  6. Quantifying Dynamics Of The Financial Correlations, arXiv Bookmark and Share

    Abstract: A novel application of the correlation matrix formalism to study dynamics of the financial evolution is presented. This formalism allows to quantify the memory effects as well as some potential repeatable intradaily structures in the financial time-series. The present study is based on the high-frequency Deutsche Aktienindex (DAX) data over the time-period between November 1997 and December 1999 and demonstrates a power of the method. In this way two significant new aspects of the DAX evolution are identified: (i) the memory effects turn out to be sizably shorter than what the standard autocorrelation function analysis seems to indicate and (ii) there exist short term repeatable structures in fluctuations that are governed by a distinct dynamics. The former of these results may provide an argument in favour of the market efficiency while the later one may indicate origin of the difficulty in reaching a Gaussian limit, expected from the central limit theorem, in the distribution of returns on longer time-horizons.
    • Quantifying Dynamics Of The Financial Correlations, S. Drozdz, J. Kwapien, F. Gruemmer, F. Ruf, J. Speth,,arxiv, Talk Presented By The First Author At The Nato Arw On Econophysics, Prague, February 8-10, 2001; To Be Published In Proceedings (Physica A), cond-mat/0102402 , 01/02/22



  7. Complex Structures In Generalized Small Worlds, arXiv Bookmark and Share

    Abstract: We propose a generalization of small world networks, in which the reconnection of links is governed by a function that depends on the distance between the elements to be linked. An adequate choice of this function lets us control the clusterization of the system. Control of the clusterization, in turn, allows the generation of a wide variety of topologies.


  8. Artificial Societies of Intelligent Agents, Thesis in Computing Engineering Bookmark and Share

    Summary: We developed artificial societies of adaptive autonomous agents, that we consider intelligent, in order to understand adaptive and social behaviour, creating a system that is able to simulate these behaviours. We developed a model for social action, where sociality emerges from the simple interactions of the members of a society. But first, we present a behaviours production system, capable of reproducing in an emergent way several properties of adaptive animal behaviour in artificial creatures. We test our models in a Behaviours Virtual Laboratory, available via Internet, where the user can perform several experiments to test our models and to understand adaptive and social behaviours.


  9. A Novel Microbial Habitat In The Mid-Ocean Ridge Subseafloor, PNAS Bookmark and Share

    Abstract: The subseafloor at the mid-ocean ridge is predicted to be an excellent microbial habitat, because there is abundant space, fluid flow, and geochemical energy in the porous, hydrothermally influenced oceanic crust. These characteristics also make it a good analog for potential subsurface extraterrestrial habitats. Subseafloor environments created by the mixing of hot hydrothermal fluids and seawater are predicted to be particularly energy-rich, and hyperthermophilic microorganisms that broadly reflect such predictions are ejected from these systems in low-temperature (15°C), basalt-hosted diffuse effluents. Seven hyperthermophilic heterotrophs isolated from low-temperature diffuse fluids exiting the basaltic crust in and near two hydrothermal vent fields on the Endeavour Segment, Juan de Fuca Ridge, were compared phylogenetically and physiologically to six similarly enriched hyperthermophiles from samples associated with seafloor metal sulfide structures. The 13 organisms fell into four distinct groups: one group of two organisms corresponding to the genus Pyrococcus and three groups corresponding to the genus Thermococcus. Of these three groups, one was composed solely of sulfide-derived organisms, and the other two related groups were composed of subseafloor organisms. There was no evidence of restricted exchange of organisms between sulfide and subseafloor habitats, and therefore this phylogenetic distinction indicates a selective force operating between the two habitats. Hypotheses regarding the habitat differences were generated through comparison of the physiology of the two groups of hyperthermophiles; some potential differences between these habitats include fluid flow stability, metal ion concentrations, and sources of complex organic matter.


  10. The Evolution Of Social Behavior In Microorganisms, Trends in Ecology & Evolution Bookmark and Share

    Abstract: Recent studies of microorganisms have revealed diverse complex social behaviors, including cooperation in foraging, building, reproducing, dispersing and communicating. These microorganisms should provide novel, tractable systems for the analysis of social evolution. The application of evolutionary and ecological theory to understanding their behavior will aid in developing better means to control the many pathogenic bacteria that use social interactions to affect humans.



  11. Structural Colour: Now You See It --- Now You Don't, Nature Bookmark and Share

    Excerpt: The second, more striking effect arising from the tilted multilayering accounts for the strongly bistable nature of the wing reflectivity in diffuse white light: it is either 'on', when an observer sees one of a broad range of colours, or it is 'off' and produces no reflected iridescence. (…)

    This structural arrangement is important in signalling by the butterfly. On or near the edge of the A. meliboeus dark zone, wing movements of no more than a few degrees generate ultra-high-contrast colour flicker in reflectivity.



  12. Invariant Scaling Relationships For Interspecific Plant Biomass Production Rates And Body Size, PNAS Bookmark and Share

    Abstract: The allometric relationships for plant annualized biomass production ("growth") rates, different measures of body size (dry weight and length), and photosynthetic biomass (or pigment concentration) per plant (or cell) are reported for multicellular and unicellular plants representing three algal phyla; aquatic ferns; aquatic and terrestrial herbaceous dicots; and arborescent monocots, dicots, and conifers. Annualized rates of growth G scale as the 3/4-power of body mass M over 20 orders of magnitude of M (i.e., G M3/4); plant body length L (i.e., cell length or plant height) scales, on average, as the 1/4-power of M over 22 orders of magnitude of M (i.e., L M1/4); and photosynthetic biomass Mp scales as the 3/4-power of nonphotosynthetic biomass Mn (i.e., Mp Mn3/4). Because these scaling relationships are indifferent to phylogenetic affiliation and habitat, they have far-reaching ecological and evolutionary implications (e.g., net primary productivity is predicted to be largely insensitive to community species composition or geological age).


    1. Scaling Of Growth: Plants And Animals Are Not So Different, PNAS Bookmark and Share

      Excerpt: The relationship of body size to the anatomical, physiological, behavioral, and ecological characteristics of animals has long been a focus of interest in zoology. As one considers animal species of different sizes, regular, predictable changes are seen in the relative proportions of the body's organs and the relative rates of physiological processes such as metabolism and growth. Students of zoology are familiar with these scaling relationships (also called allometries) and many of their ecological and adaptive implications (1-3). For example, the relative scaling of metabolism versus that of the volume of the digestive tract affects the potential diets of herbivorous mammals, which in turn influences their social behavior (4, 5).



  13. Circuit Training, Nature Bookmark and Share

    Abstract: Robots that can assemble themselves from components smaller than bacteria are beginning to seem less like science fiction. A team at Pennsylvania State University has used DNA to encourage gold wires millionths of a millimetre across to take up specific positions on a gold surface, bringing self-wiring nano-circuitry within the bounds of possibility.(…)

    The wires whose DNA strands matched those on the surface were up to four times more likely to become attached than those with non-complementary DNA tags, Mallouk's group found.



  14. Nanohedra: Using Symmetry To Design Self Assembling Protein Cages, Layers, Crystals, And Filaments, PNAS Bookmark and Share

    Abstract: A general strategy is described for designing proteins that self assemble into large symmetrical nanomaterials, including molecular cages, filaments, layers, and porous materials. In this strategy, one molecule of protein A, which naturally forms a self-assembling oligomer, An, is fused rigidly to one molecule of protein B, which forms another self-assembling oligomer, Bm. The result is a fusion protein, A-B, which self assembles with other identical copies of itself into a designed nanohedral particle or material, (A-B)p. The strategy is demonstrated through the design, production, and characterization of two fusion proteins: a 49-kDa protein designed to assemble into a cage approximately 15 nm across, and a 44-kDa protein designed to assemble into long filaments approximately 4 nm wide. The strategy opens a way to create a wide variety of potentially useful protein-based materials, some of which share similar features with natural biological assemblies.


  15. Recent Improvements In Prediction Of Protein Structure By Global Optimization Of A Potential Energy Function, PNAS Bookmark and Share

    Abstract: Recent improvements of a hierarchical ab initio or de novo approach for predicting both a and b structures of proteins are described. The united-residue energy function used in this procedure includes multibody interactions from a cumulant expansion of the free energy of polypeptide chains, with their relative weights determined by Z-score optimization. The critical initial stage of the hierarchical procedure involves a search of conformational space by the conformational space annealing (CSA) method, followed by optimization of an all-atom model. The procedure was assessed in a recent blind test of protein structure prediction (CASP4). The resulting lowest-energy structures of the target proteins (ranging in size from 70 to 244 residues) agreed with the experimental structures in many respects. The entire experimental structure of a cyclic a -helical protein of 70 residues was predicted to within 4.3 Å a -carbon (Ca) rms deviation (rmsd) whereas, for other a -helical proteins, fragments of roughly 60 residues were predicted to within 6.0 Å Ca rmsd. Whereas b structures can now be predicted with the new procedure, the success rate for a /b- and -proteins is lower than that for a -proteins at present. For the b portions of a /b structures, the Ca rmsd's are less than 6.0 Å for contiguous fragments of 30-40 residues; for one target, three fragments (of length 10, 23, and 28 residues, respectively) formed a compact part of the tertiary structure with a Ca rmsd less than 6.0 Å. Overall, these results constitute an important step toward the ab initio prediction of protein structure solely from the amino acid sequence.


  16. Solvent Effects On The Energy Landscapes And Folding Kinetics Of Polyalanine, PNAS Bookmark and Share

    Abstract: The effect of a solvation on the thermodynamics and kinetics of polyalanine (Ala12) is explored on the basis of its energy landscapes in vacuum and in an aqueous solution. Both energy landscapes are characterized by two basins, one associated with a -helical structures and the other with coil and b-structures of the peptide. In both environments, the basin that corresponds to the a -helical structure is considerably narrower than the basin corresponding to the b -state, reflecting their different contributions to the entropy of the peptide. In vacuum, the a -helical state of Ala12 constitutes the native state, in agreement with common helical propensity scales, whereas in the aqueous medium, the a -helical state is destabilized, and the b -state becomes the native state. Thus solvation has a dramatic effect on the energy landscape of this peptide, resulting in an inverted stability of the two states. Different folding and unfolding time scales for Ala12 in hydrophilic and hydrophobic chemical environments are caused by the higher entropy of the native state in water relative to vacuum. The concept of a helical propensity has to be extended to incorporate environmental solvent effects.


  17. Two Different Neurodegenerative Diseases Caused By Proteins With Similar Structures, PNAS Bookmark and Share

    Abstract: The downstream prion-like protein (doppel, or Dpl) is a paralog of the cellular prion protein, PrPC. The two proteins have ~25% sequence identity, but seem to have distinct physiologic roles. Unlike PrPC, Dpl does not support prion replication; instead, overexpression of Dpl in the brain seems to cause a completely different neurodegenerative disease. We report the solution structure of a fragment of recombinant mouse Dpl (residues 26-157) containing a globular domain with three helices and a small amount of b-structure. Overall, the topology of Dpl is very similar to that of PrPC. Significant differences include a marked kink in one of the helices in Dpl, and a different orientation of the two short b-strands. Although the two proteins most likely arose through duplication of a single ancestral gene, the relationship is now so distant that only the structures retain similarity; the functions have diversified along with the sequence.


  18. Brain Cells Research Fuels Debate, Financial Times Bookmark and Share

    US scientists have produced laboratory mice in which as much as a quarter of the brain cells are human, in a development that could carry great promise for treating disease but poses questions about the boundaries between people and animals.

    The scientists are now considering a research project to grow a mouse whose brain is populated almost entirely with human cells, but are worried by the ethics.

    The research could lead to treatments for diseases such as Parkinson's, Alzheimer's and stroke by regenerating patients' brains with healthy cells.



    1. Of Mice And Men, Financial Times Bookmark and Share

      A mouse with a brain that is biochemically human would be a scientific goldmine. It would help basic research in neurobiology, while giving pharmacologists the best possible system for testing drugs on the brain before starting clinical trials.

      In the short term, the risks of going ahead are small. (…) Scientists would just be taking advantage of the fact that the biological and genetic gap between us and other living creatures turns out to be much smaller than anyone had suspected.



  19. Synergistic Contributions Of Cyclin-Dependant Kinase 5/P35 And Reelin/Dab1 To The Positioning Of Cortical Neurons In The Developing Mouse Brain, PNAS Bookmark and Share

    Abstract: Cyclin-dependent kinase (Cdk) 5 is a unique member of the Cdk family, because Cdk5 kinase activity is detected only in the nervous tissue. Two neuron-specific activating subunits of Cdk5, p35 and p39, have been identified. Overlapping expression pattern of these isoforms in the embryonic mouse brain and the significant residual Cdk5 kinase activity in brain homogenate of the p35/ mice indicate the redundant functions of the Cdk5 activators in vivo. Severe neuronal migration defects in p35/Cdk5 +/ mice further support the idea that the redundant expression of the Cdk5 activators may cause a milder phenotype in p35/ mice compared with Cdk5/ mice. Mutant mice lacking either Cdk5 or p35 exhibit certain similarities with Reelin/Dab1-mutant mice in the disorganization of cortical laminar structure in the brain. To elucidate the relationship between Cdk5/p35 and Reelin/Dab1 signaling, we generated mouse lines that have combined defects of these genes. The addition of heterozygosity of either Dab1 or Reelin mutation to p35/ causes the extensive migration defects of cortical neurons in the cerebellum. In the double-null mice of p35 and either Dab1 or Reelin, additional migration defects occur in the Purkinje cells in the cerebellum and in the pyramidal neurons in the hippocampus. These additional defects in neuronal migration in mice lacking both Cdk5/p35 and Reelin/Dab1 indicate that Cdk5/p35 may contribute synergistically to the positioning of the cortical neurons in the developing mouse brain.


  20. Chaos On Centre Court, Nature Bookmark and Share

    When bouncing a tennis ball, we instinctively navigate our way around the complex world of mathematical chaos, new research reveals.

    On the face of it, the maths governing how a ball bounces on a tennis racket are straightforward. But lurking inside the equations is something called dynamical chaos.

    Under certain conditions, the ball bounces regularly. But change things just slightly and it all unravels: small disturbances grow until the ball could end up anywhere.



    1. Dynamics Of A Bouncing Ball In Human Performance, Rhys. Rev. E Bookmark and Share

      Abstract: On the basis of a modified bouncing-ball model, we investigated whether human movements utilize principles of dynamic stability in their performance of a similar movement task. Stability analyses of the model provided predictions about conditions indicative of a dynamically stable period-one regime. In a series of experiments, human subjects bounced a ball rhythmically on a racket and displayed these conditions supporting that they attuned to and exploited the dynamic stability properties of the task.



  21. Getting The Joke, New Scientist Bookmark and Share

    Exerpts: Jokes are funny partly because they lead you along one line of thought, only to take you in an unexpected direction. (…).

    The researchers used functional MRI to scan 14 healthy people while they listened to two types of jokes. Half the jokes were "semantic", for instance, "Why don't sharks bite lawyers? Professional courtesy". The other half were puns, such as "Why did the golfer wear two pairs of pants? He had a hole in one." Control jokes were set-ups with punchless punchlines.(…)

    Semantic jokes used a bilateral network in the temporal lobes, whereas the puns used areas near those for speech production, on the left side.



    1. Did You Hear The One About The Prefrontal Cortex?, Nature Bookmark and Share

      Excerpt: So although getting jokes might be specific to different regions, responding to them happens in the same place. "Irrespective of the kind of joke," says Dolan, "it's the same system that's being accessed."

      What's more, because this region is activated when humans and primates receive rewards, it seems that the brain itself feels rewarded by finding something funny. This, says Dolan, lends credence to the idea that laughter might be therapeutic: "For some people it's almost like a drug."



  22. U.S. Scuttles Latest Chance to Avert Global Warming Catastrophe, Foreign Policy In Focus Bookmark and Share

    Excerpt: Nonetheless, the U.S. insisted that it meet its paltry obligation under the Kyoto Protocol (emissions reductions of seven percent below 1990 levels) simply by planting trees (known as carbon sinks), and by "emissions trading" with countries too poor even to pollute. Refusing to cave to U.S. pressure, the Europeans insisted that the U.S. get no more than 50% of its commitment from sinks and trading. The result was a flameout of the talks.

    In contrast, Europeans are deadly serious about the climate crisis. Holland will cut emissions by 80% in the next 40 years. Britain is committed to 60% cuts by 2050. Germany is considering 50% reductions over a similar period. They will achieve those cuts not by planting trees but by drawing increasing proportions of their energy from fuel cells, windfarms, and solar systems.

    Not only is the foot-dragging by the U.S. courting real ecological catastrophe, it is also withholding from the U.S. and the rest of the world a huge surge in jobs. In order to cut emissions by 70% to allow the climate to stabilize, the planet must be rewired with low-carbon and renewable technologies, dramatically expanding the amount of wealth in the global economy.



  23. MIT Professor Claude Shannon Dies, MIT News Release Bookmark and Share

    MIT Professor Emeritus Claude E. Shannon, known as the father of modern digital communications and information theory, died Saturday, February 24 at the Courtyard Nursing Care Center in Medford, Mass., after a long battle with Alzheimer’s disease. He was 84 years old.

    Professor Shannon, a distant relative of Thomas Edison, was affiliated with Bell Laboratories from 1941 to 1972, during which time he wrote the landmark A Mathematical Theory of Communication (1948). This pioneering paper on information theory begins by observing that "the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point."

    The information content of a message, he theorized, consists simply of the number of 1s and 0s it takes to transmit it. "Nobody had come close to this idea before," said MIT Professor emeritus Robert G. Gallager, who worked with Professor Shannon. "This was not something somebody else would have done for a very long time."



  24. Links & Snippets Bookmark and Share


    1. Other Articles Bookmark and Share

      1. The Emergent Ego: Complexity And Coevolution In The Psychoanalytic Process, Harold I. Eist, Am. J. Psychiatry 2001 March 1; 158(3): p. 505
      2. Spatiotemporal Connectionist Networks: A Taxonomy and Review, Stefan C. Kremer, Neural Comp. 2001 February 1; 13(2): p. 249-306
      3. A Competitive-Layer Model for Feature Binding and Sensory Segmentation, Heiko Wersing, Jochen J. Steil, Helge Ritter, Neural Comp. 2001 February 1; 13(2): p. 357-387


    2. Pub Alert 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.

      1. Joyce, Chaos, and Complexity, by Thomas Jackson Rice, Dasenbrock, R. W.; Mines, R., JAMES JOYCE QUARTERLY
      2. p53 from complexity to simplicity: mutant p53 stabilization, gain-of-function, and dominant-negative effect, Blagosklonny, M. V., FASEB JOURNAL
      3. A Relative Complexity Metric for Decision-theoretic Applications in Complex Systems, Bendett, R. M.; Neelakanta, P. S., COMPLEX SYSTEMS -CHAMPAIGN-
      4. Environmental risk assessment of a complex solid waste product from a pesticide factory, Winther-Nielsen, M.; Rasmussen, D.; Samsoe-Petersen, L., EUROPEAN WATER MANAGEMENT
      5. Fats in the new millennium: more complexity but a better understanding? editorial comment, Calder, P. C.; Deckelbaum, R. J., CURRENT OPINION IN CLINICAL NUTRITION AND METABOLIC CARE
      6. Evaluation in Complex Policy Systems, Sanderson, I., EVALUATION -LONDON-
      7. Development of Complex Scheme of Ferruginous Waste Utilization, Smirnov, L. A., STAL'
      8. The complex decisions on the transportation, dosing/dispensing and storage of powder-like and granulated products, Unknown Author, PISHCHEVAIA PROMYSHLENNOST' -MOSKVA- AGROPROMIZDAT-
      9. The search for complex disease genes: fault by linkage or fault by association?, Baron, M., MOLECULAR PSYCHIATRY
      10. Minimum Wage and Overtime Rules are Complex Issues for RNs, Unknown Author, KANSAS NURSE
      11. Characterization of Complex Chromosomal Abnormalities in Uveal Melanoma by Fluorescence In Situ Hybridization, Spectral Karyotyping, and Comparative Genomic Hybridization, Naus, N. C.; van Drunen, E.; de Klein, A.; Luyten, G. P. M.; Paridaens, D. A.; Alers, J. C.; Ksander, B. R.; Beverloo, H. B.; Slater, R. M., GENES CHROMOSOMES AND CANCER
      12. The complexity of phenotypic plasticity in the intertidal snail Nodilittorina australis, Yeap, K. L.; Black, R.; Johnson, M. S., BIOLOGICAL JOURNAL- LINNEAN SOCIETY
      13. The Salience of Visuospatial and Organizational Skills in Reproducing the Rey-Osterreith Complex Figure in Subjects with High and Low IQs, Fujii, D. E.; Lloyd, H. A.; Miyamoto, K., CLINICAL NEUROPSYCHOLOGIST


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