A Survey on Continuous Time Computations

We provide an overview of theories of continuous time computation. These theories allow us to understand both the hardness of questions related to continuous time dynamical systems and the computational power of continuous time analog models. We survey the existing models, summarizing results, and point to relevant references in the literature

The Simplest Non-Regular Deterministic Context-Free Language

We introduce a new notion of ?-simple problems for a class ? of decision problems (i.e. languages), w.r.t. a particular reduction. A problem is ?-simple if it can be reduced to each problem in ?. This can be viewed as a conceptual counterpart to ?-hard problems to which all problems in ? reduce. Our concrete example is the class of non-regular deterministic context-free languages (DCFL\u27), with a truth-table reduction by Mealy machines. The main technical result is a proof that the DCFL\u27 language L_# = {0^n1^n ? n ? 1} is DCFL\u27-simple, and can be thus viewed as one of the simplest languages in the class DCFL\u27, in a precise sense. The notion of DCFL\u27-simple languages is nontrivial: e.g., the language L_R = {wcw^R? w ? {a,b}^*} is not DCFL\u27-simple. By describing an application in the area of neural networks (elaborated in another paper), we demonstrate that ?-simple problems under suitable reductions can provide a tool for expanding the lower-bound results known for single problems to the whole classes of problems

Predicting Health Impacts of the World Trade Center Disaster: 1. Halogenated hydrocarbons, symptom syndromes, secondary victimization, and the burdens of history

The recent attack on the World Trade Center, in addition to direct injury and psychological trauma, has exposed a vast population to dioxins, dibenzofurans, related endocrine disruptors, and a multitude of other physiologically active chemicals arising from the decomposition of the massive quantities of halogenated hydrocarbons and other plastics within the affected buildings. The impacts of these chemical species have been compounded by exposure to asbestos, fiberglass, crushed glass, concrete, plastic, and other irritating dusts. To address the manifold complexities of this incident we combine recent theoretical perspectives on immune, CNS, and sociocultural cognition with empirical studies on survivors of past large toxic fires, other community-scale chemical exposure incidents, and the aftereffects of war. Our analysis suggests the appearance of complex, but distinct and characteristic, spectra of synergistically linked social, psychosocial, psychological and physical symptoms among the 100,000 or so persons most directly affected by the WTC attack. The different 'eigenpatterns' should become increasingly comorbid as a function of exposure. The expected outcome greatly transcends a simple 'Post Traumatic Stress Disorder' model, and may resemble a particularly acute form of Gulf War Syndrome. We explore the role of external social factors in subsequent exacerbation of the syndrome -- secondary victimization -- and study the path-dependent influence of individual and community-level historical patterns of stress. We suggest that workplace and other organizations can act as ameliorating intermediaries. Those without acess to such buffering structures appear to face a particularly bleak future

'Fat people and bombs':HPA axis cognition, structured stress, and the US obesity epidemic

We examine the accelerating 'obesity epidemic' in the US from the perspective of recently developed theory relating a cognitive hypothalamic-pituitary-adrenal axis to an embedding 'language' of structured psychosocial stress. Using a Rate Distortion argument, the obesity epidemic is found to represent the literal writing of an image of a ratcheting pathological social hierarchy onto the bodies of American adults and children. This process, while stratified by the usual divisions of class and ethnicity, is nonetheless relentlessly engulfing even affluent majority populations. Our perspective places the common explanation that 'obesity occurs when people eat too much and get too little exercise' in the same category as the remark by US President Calvin Coolidge on the eve of the Great Depression that 'unemployment occurs when large numbers of people are out of work'. Both statements ignore profound structural determinants of great population suffering which must be addressed by collective actions of equally great reform

The ecology of suffering: developmental disorders of structured stress, emotion, and chronic inflammation

'Punctuated equilibrium' models of cognitive process, adapted from the Large Deviations Program of probability theory, are applied to the interaction between immune function and emotion in the context of culturally structured psychosocial stress. The analysis suggests: (1) Chronic inflammatory diseases should be comorbid and synergistic with characteristic emotional dysfunction, and may form a collection of joint disorders most effectively treated at the individual level using multifactorial 'mind/body' strategies. (2) Culturally constructed psychosocial stress can literally write an image of itself onto the punctuated etiology and progression of such composite disorders, beginning a trajectory to disease in utero or early childhood, and continuing throughout the life course, suggesting that, when moderated by 'social exposures', these are developmental disorders. (3) At the community level of organization, strategies for prevention and control of the spectrum of emotional/inflammatory developmental disorders must include redress of cross-sectional and logitudinal (i.e. historical) patterns of inequality and injustice which generate structured psychosocial stress. Evidence further suggests that within 'Westernized' or 'market economy' societies, such stress will inevitably entrain high as well as lower stutus subopulations into a unified ecology of suffering

Structured Psychosocial Stress and Therapeutic Intervention: Toward a Realistic Biological Medicine

Using generalized 'language of thought' arguments appropriate to interacting cognitive modules, we explore how disease states can interact with medical treatment, including, but not limited to, drug therapy. The feedback between treatment and response creates a kind of idiotypic 'hall of mirrors' generating a pattern of 'efficacy', 'treatment failure', and 'adverse reactions' which will, from a Rate Distortion perspective, embody a distorted image of externally-imposed structured psychosocial stress. This analysis, unlike current pharmacogenetics, does not either reify 'race' or blame the victim by using genetic structure to place the locus-of-control within a group or individual. Rather, it suggests that a comparatively simple series of questions to identify longitudinal and cross-sectional stressors may provide more effective guidance for specification of individual therapy than complicated genotyping strategies of dubious meaning. These latter are likely to be both very expensive and utterly blind to the impact of structured psychosocial stress -- a euphemism for various forms of racism and ethnic cleansing -- which, we contend, is often a principal determinant of treatment outcome at both individual and community levels of organization. We propose, to effectively address 'health disparities' between populations, and in contrast to current biomedical ideology based on a simplistic genetic determinism, a richer program of biological medicine reflecting Lewontin's 'triple helix' of genes, environment, and development, a program more in concert with the realities of a basic human biology marked by hypersociality unusual in vertibrates. Aggressive social, economic, and other policies of affirmative action to redress the persisting burdens of history would be an integral component of any such project