New Directions in Subband Coding

Two very different subband coders are described. The first is a modified dynamic bit-allocation-subband coder (D-SBC) designed for variable rate coding situations and easily adaptable to noisy channel environments. It can operate at rates as low as 12 kb/s and still give good quality speech. The second coder is a 16-kb/s waveform coder, based on a combination of subband coding and vector quantization (VQ-SBC). The key feature of this coder is its short coding delay, which makes it suitable for real-time communication networks. The speech quality of both coders has been enhanced by adaptive postfiltering. The coders have been implemented on a single AT&T DSP32 signal processo

Complexity and Expressivity of Branching- and Alternating-Time Temporal Logics with Finitely Many Variables

We show that Branching-time temporal logics CTL and CTL*, as well as Alternating-time temporal logics ATL and ATL*, are as semantically expressive in the language with a single propositional variable as they are in the full language, i.e., with an unlimited supply of propositional variables. It follows that satisfiability for CTL, as well as for ATL, with a single variable is EXPTIME-complete, while satisfiability for CTL*, as well as for ATL*, with a single variable is 2EXPTIME-complete,--i.e., for these logics, the satisfiability for formulas with only one variable is as hard as satisfiability for arbitrary formulas.Comment: Prefinal version of the published pape

Visual cortex maps are optimized for uniform coverage

articles Mammalian primary visual cortex contains a single continuous representation of retinotopic visual space, on which orderly, periodic maps of several different visual stimulus properties are superimposed. These properties include ocular dominance and preferred orientation [1][2] These maps are often structurally related. For example, in macaque monkey These findings are consistent with earlier suggestions 4 that visual cortex maps develop according to a combination of continuity and completeness constraints, which act in opposition. The continuity constraint specifies that neighboring cortical locations should have similar receptive field properties, whereas the completeness constraint ensures that all combinations of the parameters represented in individual maps are distributed uniformly over visual space. A quantitative measure of completeness, known as coverage uniformity, or c′, has been devised 16 . It is calculated in the following way: for a given combination of features (for example, some unique combination of orientation, spatial frequency, eye and retinal location), the total neural response, A, in the cortex is calculated, taking into account the spatial structure of the maps of these properties, and the receptive field tuning widths of individual cortical units. Uniform coverage means that A should be independent of the specific feature combination chosen. It is convenient to define c′ as the standard deviation of A divided by its mean, taken over some representative set of stimuli. This makes it a dimensionless measure of 'noise' in the cortical representation of a particular feature space. If c′ = 0, coverage is completely uniform; larger values correspond to an increasingly noisy representation: for example, if c′ = 1, the standard deviation of the signal across the feature space is equal to the mean. The hypothesis that cortical maps are organized so as to optimize (that is, minimize) c′ was tested here by systematically perturbing the spatial relationships between maps of orientation, ocular dominance and spatial frequency obtained simultaneously in area 17 of the cat 13 to see whether c′ is at a local minimum. Two different methods were used to do this, both of which left continuity in the individual maps unchanged. In the first, the spatial relationships were altered by various combinations of flips (mirror inversions) about either the horizontal or vertical axes and/or 180°rotation (equivalent to a mirror inversion about one axis followed by a mirror inversion about the other). For three rectangular maps, there are a total of 16 transformations that disturb the point-to-point relationships between the maps in a unique way. (Note that some combinations of flips are equivalent: for example, flipping two of the maps about the vertical axis is equivalent to flipping just the third one.) The second method examined the possibility that map structure is close to a local optimum for coverage uniformity. To test this, a single map was displaced sideways by a given number of pixels relative to the other two, which remained fixed relative to each other. Coverage was then calculated for the region common to all three maps. This was done separately for each of the ocular dominance, spatial frequency and orientation maps, for a range of Cat visual cortex contains a topographic map of visual space, plus superimposed, spatially periodic maps of ocular dominance, spatial frequency and orientation. It is hypothesized that the layout of these maps is determined by two constraints: continuity or smooth mapping of stimulus properties across the cortical surface, and coverage uniformity or uniform representation of combinations of map features over visual space. Here we use a quantitative measure of coverage uniformity (c') to test the hypothesis that cortical maps are optimized for coverage. When we perturbed the spatial relationships between ocular dominance, spatial frequency and orientation maps obtained in single regions of cortex, we found that cortical maps are at a local minimum for c'. This suggests that coverage optimization is an important organizing principle governing cortical map development

Fast, scalable, Bayesian spike identification for multi-electrode arrays

We present an algorithm to identify individual neural spikes observed on high-density multi-electrode arrays (MEAs). Our method can distinguish large numbers of distinct neural units, even when spikes overlap, and accounts for intrinsic variability of spikes from each unit. As MEAs grow larger, it is important to find spike-identification methods that are scalable, that is, the computational cost of spike fitting should scale well with the number of units observed. Our algorithm accomplishes this goal, and is fast, because it exploits the spatial locality of each unit and the basic biophysics of extracellular signal propagation. Human intervention is minimized and streamlined via a graphical interface. We illustrate our method on data from a mammalian retina preparation and document its performance on simulated data consisting of spikes added to experimentally measured background noise. The algorithm is highly accurate

Modal Logics of Topological Relations

Logical formalisms for reasoning about relations between spatial regions play a fundamental role in geographical information systems, spatial and constraint databases, and spatial reasoning in AI. In analogy with Halpern and Shoham's modal logic of time intervals based on the Allen relations, we introduce a family of modal logics equipped with eight modal operators that are interpreted by the Egenhofer-Franzosa (or RCC8) relations between regions in topological spaces such as the real plane. We investigate the expressive power and computational complexity of logics obtained in this way. It turns out that our modal logics have the same expressive power as the two-variable fragment of first-order logic, but are exponentially less succinct. The complexity ranges from (undecidable and) recursively enumerable to highly undecidable, where the recursively enumerable logics are obtained by considering substructures of structures induced by topological spaces. As our undecidability results also capture logics based on the real line, they improve upon undecidability results for interval temporal logics by Halpern and Shoham. We also analyze modal logics based on the five RCC5 relations, with similar results regarding the expressive power, but weaker results regarding the complexity

Distribution of metals exposure and associations with cardiometabolic risk factors in the “Modeling the Epidemiologic Transition Study”

Background: Metals are known endocrine disruptors and have been linked to cardiometabolic diseases via multiple potential mechanisms, yet few human studies have both the exposure variability and biologically-relevant phenotype data available. We sought to examine the distribution of metals exposure and potential associations with cardiometabolic risk factors in the “Modeling the Epidemiologic Transition Study” (METS), a prospective cohort study designed to assess energy balance and change in body weight, diabetes and cardiovascular disease risk in five countries at different stages of social and economic development. Methods: Young adults (25–45 years) of African descent were enrolled (N = 500 from each site) in: Ghana, South Africa, Seychelles, Jamaica and the U.S.A. We randomly selected 150 blood samples (N = 30 from each site) to determine concentrations of selected metals (arsenic, cadmium, lead, mercury) in a subset of participants at baseline and to examine associations with cardiometabolic risk factors. Results: Median (interquartile range) metal concentrations (μg/L) were: arsenic 8.5 (7.7); cadmium 0.01 (0.8); lead 16.6 (16.1); and mercury 1.5 (5.0). There were significant differences in metals concentrations by: site location, paid employment status, education, marital status, smoking, alcohol use, and fish intake. After adjusting for these covariates plus age and sex, arsenic (OR 4.1, 95% C.I. 1.2, 14.6) and lead (OR 4.0, 95% C.I. 1.6, 9.6) above the median values were significantly associated with elevated fasting glucose. These associations increased when models were further adjusted for percent body fat: arsenic (OR 5.6, 95% C.I. 1.5, 21.2) and lead (OR 5.0, 95% C.I. 2.0, 12.7). Cadmium and mercury were also related with increased odds of elevated fasting glucose, but the associations were not statistically significant. Arsenic was significantly associated with increased odds of low HDL cholesterol both with (OR 8.0, 95% C.I. 1.8, 35.0) and without (OR 5.9, 95% C.I. 1.5, 23.1) adjustment for percent body fat. Conclusions: While not consistent for all cardiometabolic disease markers, these results are suggestive of potentially important associations between metals exposure and cardiometabolic risk. Future studies will examine these associations in the larger cohort over time

Kidney disease and the cumulative burden of life course socioeconomic conditions: The Atherosclerosis Risk in Communities (ARIC) Study.

The authors investigated the cumulative effects of life course social class and neighborhood socioeconomic conditions on the prevalence of chronic kidney disease (CKD) in adulthood. Subjects were members of the Atherosclerosis Risk in Communities (ARIC) Study, a longitudinal cohort study of four US communities. CKD was defined by glomerular filtration rate <45ml/min/1.73m(2) or hospital discharge diagnosis. Working class was defined by workplace roles for subjects and their fathers; area socioeconomic status (SES) was based on census information. Being working class for all life course periods or for some life course periods was associated with increased odds of CKD, compared to being non-working class for all periods (adjusted odds ratio, OR, for all periods (95% confidence interval) 1.4 (0.9, 2.0) in Whites and 1.9 (1.3, 2.9) in African-Americans; OR for some periods 1.3 (1.0, 1.9) in Whites and 1.4 (0.9, 2.2) in African-Americans). Low area SES over the life course was not significantly related to CKD compared to living in a higher SES areas at all life course periods. Adjustment for age, gender, community of residence, cumulative social class (for neighborhood measures), cumulative low-neighborhood SES (for cumulative individual social class), hypertension and diabetes does not account for these associations. Our conclusion is that chronic kidney disease is associated with life course socioeconomic conditions. As such, life course social class and neighborhood conditions deserve further attention in accounting for socioeconomic disparities in kidney disease.http://deepblue.lib.umich.edu/bitstream/2027.42/60950/1/Kidney disease and the cumalive burden of life course socioeconomic conditions - The ARIC study.pd

Protocol for the modeling the epidemiologic transition study: a longitudinal observational study of energy balance and change in body weight, diabetes and cardiovascular disease risk.

BACKGROUND: The prevalence of obesity has increased in societies of all socio-cultural backgrounds. To date, guidelines set forward to prevent obesity have universally emphasized optimal levels of physical activity. However there are few empirical data to support the assertion that low levels of energy expenditure in activity is a causal factor in the current obesity epidemic are very limited. METHODS/DESIGN: The Modeling the Epidemiologic Transition Study (METS) is a cohort study designed to assess the association between physical activity levels and relative weight, weight gain and diabetes and cardiovascular disease risk in five population-based samples at different stages of economic development. Twenty-five hundred young adults, ages 25-45, were enrolled in the study; 500 from sites in Ghana, South Africa, Seychelles, Jamaica and the United States. At baseline, physical activity levels were assessed using accelerometry and a questionnaire in all participants and by doubly labeled water in a subsample of 75 per site. We assessed dietary intake using two separate 24-hour recalls, body composition using bioelectrical impedance analysis, and health history, social and economic indicators by questionnaire. Blood pressure was measured and blood samples collected for measurement of lipids, glucose, insulin and adipokines. Full examination including physical activity using accelerometry, anthropometric data and fasting glucose will take place at 12 and 24 months. The distribution of the main variables and the associations between physical activity, independent of energy intake, glucose metabolism and anthropometric measures will be assessed using cross-section and longitudinal analysis within and between sites. DISCUSSION: METS will provide insight on the relative contribution of physical activity and diet to excess weight, age-related weight gain and incident glucose impairment in five populations' samples of young adults at different stages of economic development. These data should be useful for the development of empirically-based public health policy aimed at the prevention of obesity and associated chronic diseases.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

A genetic approach for long term virtual organization distribution

Electronic versíon of an article published as International Journal on Artificial Intelligent Tools, Volume 20, issue 2, 2011. 10.1142/S0218213011000152. © World Scientific Publishing Company[EN] An agent-based Virtual Organization is a complex entity where dynamic collections of agents agree to share resources in order to accomplish a global goal or offer a complex service. An important problem for the performance of the Virtual Organization is the distribution of the agents across the computational resources. The final distribution should provide a good load balancing for the organization. In this article, a genetic algorithm is applied to calculate a proper distribution across hosts in an agent-based Virtual Organization. Additionally, an abstract multi-agent system architecture which provides infrastructure for Virtual Organization distribution is introduced. The developed genetic solution employs an elitist crossover operator where one of the children inherits the most promising genetic material from the parents with higher probability. In order to validate the genetic proposal, the designed genetic algorithm has been successfully compared to several heuristics in different scenarios. © 2011 World Scientific Publishing Company.This work is supported by TIN2008-04446, TIN2009-13839-C03-01, CSD2007-00022 and FPU grant AP2008-00600 of the Spanish government, and PROMETEO 2008/051 of the Generalitat Valenciana.Sánchez Anguix, V.; Valero Cubas, S.; García Fornes, AM. (2011). A genetic approach for long term virtual organization distribution. International Journal on Artificial Intelligence Tools. 20(2):271-295. https://doi.org/10.1142/S0218213011000152S27129520