Complexity Digest 2001.29 Archive: http://comdig.unam.mx "I think the next century will be the century of complexity." Stephen Hawking, 2000 _________________________________________________________________ 01. Immune Control, Memory, And Vaccines, Science 01.01. 'Breeding' Antigens For New Vaccines, Science 01.02. The Art Of The Probable: System Control In The Adaptive Immune System, Science 01.03. Tampering With The Immune System, Science 02. Selection Pressure And Organizational Cognition: Implications For The Social Determinants Of Health, Cogprints 03. Major Challenges For Bush's Climate Initiative, Science 03.01. Sizzling Sun Makes Cloudy Days, CNN 04. Surprise Variation Found In Human Genes, New Scientist 04.01. Huge Genetic Variation Found In Human Beings, abcNEWS 05. Borna Disease Virus Linked With Severe Mood Disorders, Medscape 05.01. Odorants May Arouse Instinctive Behaviours, Nature 05.02. A Model Of The Interaction Between Mood And Memory, Network: Comput. Neural Syst. 06. Babies Recognize Music From The Womb, abcNEWS 06.01. Music In Broca's Area, Trends In Neurosciences 06.02. Song From Neighbor Star Has Familiar Ring, CNN 07. A Hebbian Form Of Long-Term Potentiation, PNAS 08. Creativity And Problem Solving: Elements For A Model Of Creativity, CogPrints 09. Biological Model Generates Prime Numbers, Science 09.01. Prime Number Selection Of Cycles In A Predator-Prey Model, Complexity 10. Intentional Walks On Scale Free Small Worlds, arXiv 11. Another Emissary From The Dawn Of Humanity, Science 11.01. Late Miocene Hominids From the Middle Awash, Ethiopia, Nature 12. A Trick Shot In Quantum Billiards, Science 12.01. No Mere Anarchy, Science 12.02. Atoms Island-Hop, Science Now 12.03. Observation of Chaos-Assisted Tunneling Between Islands of Stability, Science 13. Entangling Atomic Collisions, Science/PRL 14. Dynamic Cerebrovascular Response Between Stepwise Up Tilt And Down Tilt In Humans, AJP: Heart 15. Complex AV Nodal Dynamics During Ventricular-Triggered Atrial Pacing In Humans, AJP: Heart 16. Predictability Of Catastrophic Events, arXiv 17. Paediatric Head Injury, Brain 18. Danish Study Finds No Link Between Cell Phone Use And Cancer, J. Radiol. Prot. 18.01. Mobile Phones: Developments In The UK, J. Radiol. Prot. News And Information 19. Chameleon Code Gives Hackers Advantage, New Scientist 20. Links & Snippets 20.01. Announcements _________________________________________________________________ 01. Immune Control, Memory, And Vaccines , Science Excerpt: A sweeping offensive to prevent infectious disease through vaccination remains a compelling goal in the movement toward improved public health in industrialized and developing societies. Expectations are high that vaccines will also soon be deployed in less conventional ways: to destroy tumors and prevent autoimmune diseases, for example. Yet the current range of vaccine targets remains remarkably narrow. How, then, will the scope and power of vaccination be improved? The brisk pace of genome-related discoveries brings hope of revolutionary change (...) Immune Control, Memory, and Vaccines, Stephen Simpson and Eliot Marshall, Science 2001 July 13; 293(5528): p. 233 _________________________________________________________________ 01.01. 'Breeding' Antigens For New Vaccines , Science Excerpt: Rather than carefully manipulating genes to develop a product with specific characteristics, a handful of biotechs are using a technique known as directed molecular evolution to hunt for chance offspring that have the desired features. This approach mimics natural selection, but on a minuscule scale and with a focused purpose. One company is now using this strategy to hunt for vaccines. Its work is still in the early stages of test tube and animal testing, but if it succeeds, it could add a novel tool to the vaccinemaker's workbench. 'Breeding' Antigens For New Vaccines, Jon Cohen, Science 2001 July 13; 293(5528): P. 236) _________________________________________________________________ 01.02. The Art Of The Probable: System Control In The Adaptive Immune System , Science Excerpt: The immune system provides very effective host defense against infectious agents. Although many details are known about the cells and molecules involved, a broader "systems engineering" view of this complex system is just beginning to emerge. Here the argument is put forward that stochastic events, potent amplification mechanisms, feedback controls, and heterogeneity arising from spatially dispersed cell interactions give rise to many of the gross properties of the immune system. The Art Of The Probable: System Control In The Adaptive Immune System, Ronald N. Germain, Science 2001 July 13; 293(5528): P. 240-245 _________________________________________________________________ 01.03. Tampering With The Immune System , Science Excerpts: The immune system must maintain a delicate balance between the positive signals that activate lymphocytes and the negative signals that dampen inappropriate immune responses. If this balance is upset, the immune system either does not respond to pathogens or responds inappropriately, resulting in autoimmune disease. Antigens, cytokines, and death-inducing members of the tumor necrosis factor (TNF) family (1, 2) all contribute to homeostatic regulation of the immune system. (…)the Tyro-3 family of receptor tyrosine kinases [has been identified] as important players in immune regulation. Tampering with the Immune System, Pamela L. Schwartzberg, Science 2001 July 13; 293(5528): P. 228 _________________________________________________________________ 02. Selection Pressure And Organizational Cognition: Implications For The Social Determinants Of Health , Cogprints Abstract: We model the effects of Schumperterian 'selection pressures' -- in particular Apartheid and the neoliberal 'market economy' -- on organizational cognition in minority communities, given the special role of culture in human biology. Our focus is on the dual-function social networks by which culture is imposed and maintained on individuals and by which immediate patterns of opportunity and threat are recognized and given response. A mathematical model based on recent advances in complexity theory displays a joint cross-scale linkage of social, individual central nervous system, and immune cognition with external selection pressure through mixed and synergistic punctuated 'learning plateaus.' This provides a natural mechanism for addressing the social determinants of health at the individual level. The implications of the model, particularly the predictions of synergistic punctuation, appear to be empirically testable. Selection pressure And Organizational Cognition: Implications For The Social Determinants Of Health, Rodrick Wallace, CogPrints, 2001. Contributed by Carlos Gershenson _________________________________________________________________ 03. Major Challenges For Bush's Climate Initiative , Science Editor's Note: Climate modeling requires significant computer resources (comparable with those of nuclear weapons and protein-folding simulations) and today the US has lost the leadership in that area to simulation centers in Europe using fast vector super-computers built in Japan. Another handicap for US climat simulation research is described by climate modeler Jeffrey Kiehl of NCAR: Excerpt: "But at each center, climate change modeling must vie for available computer time with other research on atmospheric science. "It's a matter of dedicating computer hardware to climate modeling," says Kiehl. "We don't do that here. There's also a cultural issue. The competition [among many centers] is viewed as a healthy way to stimulate research. I agree, but the climate modeling field has reached such a level of complexity that we have to change the way we've been working." Major Challenges For Bush's Climate Initiative, Richard A. Kerr, Science 2001 July 13; 293(5528): P. 199-201 _________________________________________________________________ 03.01. Sizzling Sun Makes Cloudy Days , CNN Excerpts: The United States becomes cloudier during cyclical periods of heightened solar activity, possibly because the increased radiation heats the upper atmosphere and nudges the jet stream northward enough to change regional weather, researchers said this week. Their study, which investigates a link between weather and the composition of the stratosphere, could help scientists identify large-scale mechanisms that influence climate. (…) The work supports previous observations finding a connection between more clouds and the peak of an 11-year cycle during which the sun unleashes more potent bursts of energy. Sizzling Sun Makes Cloudy Days, Richard Stenger, CNN, 010713 _________________________________________________________________ 04. Surprise Variation Found In Human Genes , New Scientist Excerpts: The new study suggests that while humans have only 30,000 genes, there are between 400,000 and 500,000 gene versions. Vovis said these differences might partly explain why people respond so differently to the same medications. (...) They found no variation between gene versions that could define any one of the ethnic groups, Volvis said. But they did find that different versions of a gene are more common in a group of people from one geographical region, compared with people from another. Surprise Variation Found In Human Genes, Emma Young, New Scientist, 01/07/13 _________________________________________________________________ 04.01. Huge Genetic Variation Found In Human Beings , abcNEWS Excerpt: The researchers studied the genetic makeup of 21 whites, 20 blacks, 20 people of Asian descent, 18 Latinos and three American Indians. The groups proved to have a certain degree of genetic idiosyncrasies, likely because their ancestors had a common history in a geographical region over thousands of years, whether in Africa, Asia, Europe or the Americas. The two groups that shared the highest number of rare genetic variants with one another were the blacks and Latinos. The Asians shared comparatively little with the other groups. Huge Genetic Variation Found In Human Beings, abcNEWS, 01/07/12 _________________________________________________________________ 05. Borna Disease Virus Linked With Severe Mood Disorders , Medscape Excerpts: Borna disease virus targets limbic structure neurons and is known to cause behavioral abnormalities in animals (…). In group of 28 patients with major depressive disorder or depressive crisis in bipolar disorder and 28 patients with moderate depressive symptoms, the infection rate approached 100%, (…). Infection rates in a healthy control group of 65 subjects was only 32%. The investigators also noted that high immune complex levels paralleled severe depression. (…) conclude that "an etiopathogenic role of Borna disease virus in mood disorders seems considerably strengthened Borna Disease Virus Linked With Severe Mood Disorders, Medscape, 01/07/05 _________________________________________________________________ 05.01. Odorants May Arouse Instinctive Behaviours , Nature Excerpt: In contrast to the olfactory epithelium, there is no direct pathway from this organ to the higher cortical areas involved in odour perception and discrimination. Instead, inputs are targeted to the amygdala and hypothalamus, areas that control hormone levels, emotions, basic drives and instinctive behaviours. Like pheromones, some odorants may stimulate innate behavioural or physiological responses. As in insects, certain odorants may act in mammals as semiochemicals that influence behaviour. Volatile chemicals emitted by plants can elicit oviposition or pollination in insects, (...) Odorants May Arouse Instinctive Behaviours, Mehran Sam, Sadhna Vora, Bettina Malnic, Weidong Ma, Milos V. Novotny, Linda B. Buck, Nature 412, 142 (2001) _________________________________________________________________ 05.02. A Model Of The Interaction Between Mood And Memory , Network: Comput. Neural Syst. Abstract: This paper investigates a neural network model with two attractor networks that represent the inferior temporal cortex (IT), which stores representations of visual stimuli, and the amygdala, the activity of which reflects the mood state. The results are relevant to understand the interaction between structures important in mood and emotion and other brain areas involved in storing objects, faces and memories. A Model Of The Interaction Between Mood And Memory, Network, Institute Of Physics Publishing Network: Computation In Neural Systems 12 (2001) 89-109 Contributed by Atin Das _________________________________________________________________ 06. Babies Recognize Music From The Womb , abcNEWS Excerpts: Each speaker played a piece of music: One was the prenatal music and the other was a piece of music chosen for its similarity in key, pace, and loudness. (…) Researchers recorded the length of time the babies spent looking at each ball - implying they were listening to each piece of music. Each baby, none of whom could speak, showed a clear preference for the music they had been exposed to while in the womb. A control group of children showed no preference for either piece of music. Babies Recognize Music From The Womb, abcNEWS, 01/07/12/ _________________________________________________________________ 06.01. Music In Broca's Area , Trends In Neurosciences Excerpt: Using magnetoencephalography to measure brain activity in response to musical stimuli, researchers have found that anatomical regions that are important for verbal grammar might also be involved in musical syntax. Conventional, in-key chords primarily activate the auditory cortex, but incongruous chords activated Broca's speech area in the left temporal lobe, as well as the corresponding region on the right. Therefore, this brain area may process more broad collections of syntactic information than previously appreciated. Furthermore, as effects were observed in subjects with no musical training, the authors from the Max Planck Institute of Cognitive Neuroscience in Leipzig suggest the brain is innately able to apply harmonic principles in music. Music In Broca's Area, Lianna Orlando, Trends In Neurosciences, 2001, 24:7373 _________________________________________________________________ 06.02. Song From Neighbor Star Has Familiar Ring , CNN Excerpts: Sound waves running through the sun have revealed some of its innermost properties. Now for the first time, astronomers have heard the faint song inside another point of light. And the tune sounds quite familiar. (…) But the oscillations of Alpha Centauri A can be translated into sounds waves. The most prominent note in the stellar symphony is an E flat, 15 or 16 octaves below audible levels, said Carrier. Shifted into the range of human hearing, the waves become what sounds like a simple, eerie organ fugue. Song From Neighbor Star Has Familiar Ring,CNN, 01/07/06 _________________________________________________________________ 07. A Hebbian Form Of Long-Term Potentiation , PNAS Abstract: Hippocampal inhibitory interneurons play important roles in controlling the excitability and synchronization of pyramidal cells, but whether they express long-term synaptic plasticity that contributes to hippocampal network function remains uncertain. We found that pairing postsynaptic depolarization with -burst stimulation induced long-term potentiation (LTP) of putative single-fiber excitatory postsynaptic currents in interneurons. Either postsynaptic depolarization or -burst stimulation alone failed to induce LTP. LTP was expressed as a decrease in failure rates and an increase in excitatory postsynaptic current amplitude, independent of N-methyl-D-aspartate receptors, and dependent on metabotropic glutamate receptors subtype 1a. LTP was induced specifically in interneurons in stratum oriens and not in interneurons of stratum radiatum/lacunosum-moleculare. Thus, excitatory synapses onto specific subtypes of inhibitory interneurons express a new form of hebbian LTP that will contribute to hippocampal network plasticity. A Hebbian Form Of Long-Term Potentiation, Yael Perez, France Morin, Jean-Claude Lacaille, PNAS, 10.1073/pnas.161493498 _________________________________________________________________ 08. Creativity And Problem Solving: Elements For A Model Of Creativity , CogPrints Abstract: The human creativity has already been theorized in practically all sciences. Some privilege the cognitive aspects, emphasizing the architecture of the thought, while others focus the empiric approach, describing the creativity as a productive technique. This paper tries to reconcile these two visions, offering glimpses of the creativity as technique and of the involved mental processes. Finally, it proposes an "architecture of the creativity" focused on an integration in artificial intelligence systems for the learning of the creativity. Creativity And Problem Solving: Elements For A Model Of Creativity, Bruno Carvalho Souza, CogPrints, 2001. Contributed by Carlos Gershenson _________________________________________________________________ 09. Biological Model Generates Prime Numbers , Science Summary: Cicadas spend 7, 13, or 17 years, depending on the species, underground before emerging as adults for the final weeks of their lives. Recently, Goles et al. investigated the selective forces that might have led to these prime-number life cycles. They produced spatiotemporal simulations of predator-prey cycles using cellular automata to yield periodicities of 13 and 17, indicating the selective optima for cicadas escaping predators. In this unexpected alliance of biology and number theory, the results suggest that these models have properties that favor the generation of prime numbers Biological Model Generates Prime Numbers, Andrew M. Sugden, Science 2001 July 13; 293(5528): P. 177b _________________________________________________________________ 09.01. Prime Number Selection Of Cycles In A Predator-Prey Model , Complexity Abstract: The fact that some species of cicadas appear every 7, 13, or 17 years and that these periods are prime numbers has been regarded as a coincidence. We found a simple evolutionary predator-prey model that yields prime-periodic preys having cycles predominantly around the observed values. An evolutionary game on a spatial array leads to travelling waves reminiscent of those observed in excitable systems. The model marks an encounter of two seemingly unrelated disciplines: biology and number theory. A restriction to the latter, provides an evolutionary generator of arbitrarily large prime numbers. Prime Number Selection Of Cycles In A Predator-Prey Model, Eric Goles, Oliver Schulz, Mario Markus, Published Online: 21 Jun 2001, DOI 10.1002/cplx.1040 _________________________________________________________________ 10. Intentional Walks On Scale Free Small Worlds , arXiv Excerpt: We present a novel algorithm that generates scale free small world graphs such as those found in the World Wide Web, social and metabolic networks. We use the generated graphs to study the dynamics of a realistic search strategy on the graphs, and find that they can be navigated in a very short number of steps. ... Intentional Walks On Scale Free Small Worlds, Amit R Puniyani, Rajan M Lukose, Bernardo, A Huberman _________________________________________________________________ 11. Another Emissary From The Dawn Of Humanity , Science Excerpt: Fossils unearthed in Ethiopia and reported in this week's issue of Nature offer a glimpse of the time when humans and chimps were going their separate evolutionary ways--and may represent the earliest known human ancestor. The remains--a jawbone with teeth as well as arm, hand, and foot bones--have been dated at between 5.2 million and 5.8 million years old. From the shape of one nearly complete foot bone, the discoverers conclude that their specimen walked upright, a hallmark of all hominids. Another Emissary From The Dawn Of Humanity, Michael Balter, Ann Gibbons, Science 2001 293: 187-189 _________________________________________________________________ 11.01. Late Miocene Hominids From the Middle Awash, Ethiopia , Nature Excerpt: Molecular studies suggest that the lineages leading to humans and chimpanzees diverged approximately 6.5-5.5 million years (Myr) ago, in the Late Miocene. Hominid fossils from this interval, however, are fragmentary and of uncertain phylogenetic status, age, or both. Here I report new hominid specimens from the Middle Awash area of Ethiopia that date to 5.2-5.8 Myr and are associated with a wooded palaeoenvironment. These Late Miocene fossils are assigned to the hominid genus Ardipithecus and represent the earliest definitive evidence of the hominid clade. Late Miocene Hominids From the Middle Awash, Ethiopia, Yohannes Haile-Selassie, Nature 412, 178 - 181 (2001) _________________________________________________________________ 12. A Trick Shot In Quantum Billiards , Science Summary: When a cloud of atoms is cooled and held in an optical trap and then allowed to cool again, the trajectories of the atoms will depend on the geometry of the confining walls imposed by light beams. Most trajectories will be chaotic, but some geometries exist in which the scattering processes satisfy momentum-selection rules that give rise to stable trajectories. Steck et al. (p. 274; see the Perspective by Habib), using a system in which the atoms are confined in an optical standing wave and using a velocity-selection technique, show that for special regions of momentum space, termed "islands of stability," the atoms can tunnel between one stable momentum state and its symmetric opposite. Time-slice measurements show that the atoms oscillate between the two stable momentum states. _________________________________________________________________ 12.01. No Mere Anarchy , Science Excerpts: The study of quantum nonlinear systems is surprisingly young. Although Poincaré had understood key aspects of dynamical chaos at the turn of the 20th century, and Einstein had realized its consequences for early quantum theory, quantum dynamics of nonlinear systems remained an obscure topic until the recent explosion of interest in quantum chaos. (…) A good example is chaos-assisted tunneling, the first experimental observation of which is presented by Steck et al. (8) on page 274 of this issue. No Mere Anarchy, Salman Habib, Science 2001 293: 221-223 _________________________________________________________________ 12.02. Atoms Island-Hop , Science Now Excerpts: For the first time, physicists have seen cold atoms suddenly reverse their motion like a ball spontaneously changing direction mid-flight and returning to the thrower's hand. (…) Each "island" is a set of quantum states for particles at the same point in space but with opposite momentums, like pendulums swinging in different directions. Classical physics says that once a particle is marooned on an island of stability, it can never leave. But both teams saw particles flip from one island to another. Atoms Island-Hop, Mark Sincell, Science Now, 01/07/06 University of Queensland Laser Cooling site University of Texas Quantum Optics site _________________________________________________________________ 12.03. Observation of Chaos-Assisted Tunneling Between Islands of Stability , Science Abstract: We report the direct observation of quantum dynamical tunneling of atoms between separated momentum regions in phase space. We study how the tunneling oscillations are affected as a quantum symmetry is broken and as the initial atomic state is changed. We also provide evidence that the tunneling rate is greatly enhanced by the presence of chaos in the classical dynamics. This tunneling phenomenon represents a dramatic manifestation of underlying classical chaos in a quantum system. Observation of Chaos-Assisted Tunneling Between Islands of Stability, Daniel A. Steck, Windell H. Oskay, and Mark G. Raizen, Science 2001 293: 274-278 See quicktime movies of the experimental results. _________________________________________________________________ 13. Entangling Atomic Collisions , Science/PRL Excerpt: We usually think of collisions as destructive processes, but in the quantum world, collisions can be constructive and even desirable events. When quantum systems are brought into close contact and allowed to interact under the right conditions, the wave functions of the systems can become entangled so that the once separate systems effectively become one. Such entanglement could be used for logical operations in quantum computers. However, the entanglement process is rather inefficient for bare atom collisions, and methods are being explored that make the process more efficient. Entangling Atomic Collisions, Ian S. Osborne, Science, 2001 293: 177 Abstract: Following a recent proposal by S. B. Zheng and G. C. Guo [Phys. Rev. Lett. 85, 2392 (2000)], we report an experiment in which two Rydberg atoms crossing a nonresonant cavity are entangled by coherent energy exchange. The process, mediated by the virtual emission and absorption of a microwave photon, is characterized by a collision mixing angle 4 orders of magnitude larger than for atoms colliding in free space with the same impact parameter. The final entangled state is controlled by adjusting the atom-cavity detuning. This procedure, essentially insensitive to thermal fields and to photon decay, opens promising perspectives for complex entanglement manipulations. Coherent Control of an Atomic Collision in a Cavity, S. Osnaghi, P. Bertet, A. Auffeves, P. Maioli, M. Brune, J. M. Raimond, S. Haroche, Published 27 June 2001, Phys. Rev. Lett. 87, 037902 (2001). _________________________________________________________________ 14. Dynamic Cerebrovascular Response Between Stepwise Up Tilt And Down Tilt In Humans , AJP: Heart Abstract: We studied dynamic cerebrovascular responses in eight healthy humans during repetitive stepwise upward tilt (SUT) and stepwise downward tilt (SDT) maneuvers between supine and 70¢X standing at intervals of 60 s. Mean cerebral blood flow velocity (FVMCA) was measured at the middle cerebral artery (MCA) with transcranial Doppler ultrasonography. Mean arterial blood pressure (ABP) was measured via the radial artery and adjusted at the level of the MCA (ABPMCA). Cerebral critical closing pressure (PCC) was estimated from the systolic-diastolic relationship between FVMCA and ABPMCA. ABPMCA minus PCC was considered the cerebral perfusion pressure (CPP). The tilt maneuvers produced stepwise changes in both CPP and FVMCA. The FVMCA response to SUT was well characterized by a linear second-order model. However, that to SDT presented a biphasic behavior that was described significantly better (P < 0.05) by the addition of a slowly responding component to the second-order model. This difference may reflect both different cardiovascular responses to SUT or SDT and different cerebrovascular autoregulatory behaviors in response to decreases or increases in CPP. Dynamic Cerebrovascular Response Between Stepwise Up Tilt And Down Tilt In Humans, AJP: Heart, Jiro Sato, Masatoshi Tachibana, Tsutomu Numata, Takashi Nishino, Akiyoshi Konno, AJP: Heart, 01/08/01; 281(2): P. H774-H783 _________________________________________________________________ 15. Complex AV Nodal Dynamics During Ventricular-Triggered Atrial Pacing In Humans , AJP: Heart Abstract: In vitro experiments have shown that the complexity of atrioventricular nodal (AVN) conduction dynamics increases with heart rate. Although complex AVN dynamics (e.g., alternans) have been observed clinically, human AVN dynamics during rapid pacing have not been systematically investigated. We studied such dynamics during ventricular-triggered atrial pacing in 37 patients with normal AVN function (18 patients with dual AVN pathway physiology and 19 patients without). Alternans, which always resulted from single pathway conduction, occurred in 18 patients. In 16 patients (3 of whom also had alternans), quasisinusoidal AVN conduction oscillations occurred (mean frequency 0.02 Hz); such oscillations have not been previously reported. There were no significant differences in the dynamics for patients with or without dual AVN pathways. To illuminate the governing dynamic mechanism, a second atrial pacing trial was performed on 12 patients after autonomic blockade. Blockade facilitated alternans but inhibited oscillations. This study suggests that rapid AVN excitation in vivo can lead to autonomically mediated AVN conduction oscillations or single pathway alternans that are a function of inherent nonlinear dynamic AVN tissue properties. Complex AV Nodal Dynamics During Ventricular-Triggered Atrial Pacing In Humans, David J. Christini, Kenneth M. Stein, Steven M. Markowitz, Suneet, Mittal, David J. Slotwiner, Sei Iwai, Bruce B. Lerman, AJP: Heart 01/08/01; 281(2): P. H865-H872 _________________________________________________________________ 16. Predictability Of Catastrophic Events , arXiv Excerpt: We propose that catastrophic events are "outliers" with statistically different properties than the rest of the population and result from mechanisms involving amplifying critical cascades. Applications and the potential for prediction arediscussed in relation to the rupture of composite materials, great earthquakes, turbulence and abrupt changes of weather regimes, ... Editor's Note: The relatively frequent occurence of (up to 30m) "rogue waves" have been described as a result of non-linear phenomena in New Scientist, 01/06/30; unfortunately the article is not available on-line. Predictability Of Catastrophic Events: Material Rupture, Earthquakes, Turbulence, Financial Crashes, Human Birth, D. Sornette, arXiv, cond-mat/0107173 _________________________________________________________________ 17. Paediatric Head Injury , Brain Contributing Editor's Note: The immature brain, at a time when it is rapidly acquiring new information, responds differently from the adult brain when subjected to an equivalent amount of mechanical force. Head injury in infants younger than 2 years of age is second only to road traffic accidents as a cause of death in childhood. Measurable deficits occur even after mild to moderate head injury. Head injury in infancy and childhood causes impaired cognition, motor impairments, disruption of attention and information processing, and psychiatric disturbances, even death. Still there is relatively little information about the structural basis of the clinical deficits. Excerpt: The current belief is that head-injured infants are likely to have undergone shaking followed by sudden inertial injury from impact. "Why is it that there are continuing uncertainties about the nature, the distribution and the pathologies in accidental and non-accidental injury in infants and children?" To answer this, the authors have undertaken a meticulous clinicopathological correlation in 53 cases and data were analyzed by median age at head injury, statistically significant patterns of age-related damage emerged. The most important finding was "the predominant neurohistological abnormality in the cases of non-accidental injury in infants was due to hypoxia and not diffuse axonal injury". Paediatric Head Injury, David I. Graham, Brain, Vol. 124, No. 7, 1261-1262, July 2001 Contributed by Atin Das _________________________________________________________________ 18. Danish Study Finds No Link Between Cell Phone Use And Cancer , J. Radiol. Prot. Abstract: No relationship between cellular telephone use and the incidence of cancer was found in a study of all Danish users of cell phones. The study, which covered more than 400000 Danish users of cell phones from 1982 through 1995, compares the numbers of cancers observed in the group with the expected numbers of cancers calculated for cancer incidence rates in the entire Danish population. No excesses of brain or nervous system cancers, of cancer of the salivary gland, of leukaemia, or of cancer generally, were observed in cell phone users. Danish Study Finds No Link Between Cell Phone Use And Cancer, J. Radiol. Prot. J. Radiol. Prot 21 No 2 (June 2001) 192-193, News And Information Contributed by Atin Das _________________________________________________________________ 18.01. Mobile Phones: Developments In The UK , J. Radiol. Prot. News And Information Abstract: The Independent Expert Group on Mobile Phones (IEGMP) recommended precautionary approach. One of this was the adoption of International Commission for Non-Ionising Radiation Protection (ICNIRP). Another recommendation was that children should be encouraged to use mobile phones for essential purposes only, and to keep all calls short. Industry should refrain from promoting the use of phones by children which is under review. There is controversy again of using hands-free kits which is believed to greatly reduce exposures to the brain has been challenged by those who favour a different way of measuring such exposures. Work continues in order to develop a standard for such measurements. Contributing Editor's Note: A typical cell phone operates at a power output of 0.25 W, which is associated with a maximum rise in brain temperature of only 0.1deg C. Some limited laboratory tests point to a potential link between cell phone use and cancer. Editor's Comment: Non-thermal effects of microwave radiation (such as what is emitted by cell phones) and biological systems has been observed for more than 20 years. Whereas the earlier discussions stressed that microwave photons have not enough energy for ionization effects it might be interesting to estimate the effects on dynamic processes like protein-folding. Mobile Phones: Developments In The UK, J. Radiol. Prot. News And Information. 21 No 2 (June 2001) 191-192 Contributed by Atin Das _________________________________________________________________ 19. Chameleon Code Gives Hackers Advantage , New Scientist Excerpts: The arms race between malicious hackers and the guardians of computer networks looks set to intensify with the development of "chameleon code". The new weapon could leave networks defenceless as malicious hackers gain access undetected. Hackers routinely break into networks using "scripts", instructions they send to the network to allow them to issue commands remotely. The hackers' new tool, known as polymorphic code, camouflages scripts so they can evade detection. (...) K2's camouflaging software can take the same script and make it look different every time it is used. Chameleon Code Gives Hackers Advantage, Duncan Graham-Rowe, New Scientist, 01/07/12 _________________________________________________________________ 20. Links & Snippets _________________________________________________________________ 20.01. Announcements EPSRC Research Fellow post, Birmingham UK, to work on Fractals & Cancer. Design and Complexity MScA (design et complexité) , Université de Montréal International Master Economics & Complexity, Università degli Studi di Salerno SFI Graduate Workshop in Computational Economics, Santa Fe, NM, 01/07/15-28 (Limited Participation) The 3nd Symp. on Systems Res. in the Arts Music, Environmental Design, and the Choreography of Space, Baden-Baden, Germany, 01/07/30-08/04 SFI Complex Systems Summer School, Budapest, Santa Fe, NM, 01/07/16-08/10 (Limited Participation) SFI Workshop on Poverty Traps," Santa Fe, NM, 01/07/20-22 (Limited Participation) 6th Experimental Chaos Conference Potsdam, Germany 01/07/22-26 Fractal Structures and Self-Organization, L'Habana, Cuba, 01/07/23-28 Intl. Conf. DYNAMICAL NETWORKS IN COMPLEX SYSTEMS, Kiel, Germany, 01/07/25-27 SFI Summer Workshop: Mathematical Models in Molecular and Cellular Biology, Santa Fe, New Mexico, 01/07/29-08/10 (Limited Participation) 11th Annual International Conference The Society For Chaos Theory in Psychology & Life Sciences, Madison, WI, USA, 01/08/3-6 5th Intl Conf on COMPUTING ANTICIPATORY SYSTEMS, Liege, Belgium, 01/08/13-18 Artificial Life Models for Musical Applications, Workshop of the 6th European Conference on Artificial Life, Prague, Czech Republic, 01/09/09-14 Complex Systems And Sports, Barcelona, Spain, 01/09/14-15 SFI Workshop on Economic Inequality and Economic Sustainability, Santa Fe, NM, 01/09/21-23 (Limited Participation) Frontiers in Social Sciences Simulations, Kazimierz Dolny, Poland, 01/09/21-23 Adaptive Agents, Intelligence and Emergent Human Organization: Capturing Complexity through Agent-Based Modeling, Arthur M. Sackler Colloquium of the National Academy of Sciences, Irving CA, 01/10/5-6 International Symposium on Technology, Economic and Social Applications of Distributed Intelligence (TESADI'01) at the 2001 IEEE International Conference on Systems, Man, and Cybernetics (SMC'01), Tucson, Arizona, USA, 01/10/7-10 Workshop On Interdisciplinary Studies And Complexity, National University of Mexico, 01/10/22-26 1st Asia-Pacific Conf On Web Intelligence, Maebashi TERRSA, Maebashi City, Japan, 01/10/23-26 International Conference on Systems Thinking Globally Concerned, University of Vienna and Vienna University of Technology, 01/11/01-04 Digitizing Decisions and Markets, Decision Sciences Institute Annual Meeting, San Francisco, 01/11/17-20 From Worker to Colony: Understanding the Organisation of Insect Societies, Isaac Newton Institute, Cambridge, UK. , 01/12/7-8 Complex Systems , Modeling Nonlinear Natural and Human Systems, Hawaii International Conference On System Sciences, HICSS-35, Hawaii, 02/01/7-10 ComDig Contributing Editors Wanted: Due to the overwhelming success of Complexity Digest in both the academic and practioner communities we are in the fortunate situation to offer one or several positions of contributing editors especially in the areas of economic and business applications. 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