Radiocarbon dates from the Oxford AMS system: archaeometry datelist 35

This is the 35th list of AMS radiocarbon determinations measured at the Oxford Radiocarbon Accelerator Unit (ORAU). Amongst some of the sites included here are the latest series of determinations from the key sites of Abydos, El Mirón, Ban Chiang, Grotte de Pigeons (Taforalt), Alepotrypa and Oberkassel, as well as others dating to the Palaeolithic, Mesolithic and later periods. Comments on the significance of the results are provided by the submitters of the material

The importance of being beta: female succession in a cooperative breeder

In singular cooperative breeders few females breed successfully, but those that acquire dominant positions can achieve high levels of breeding success, leading to strong selection for traits that enable individuals to acquire and maintain dominance status. However, little is known about the process by which females acquire dominant breeding status or the traits that enable them to do so. Female meerkats, Suricata suricatta, can acquire dominance either by inheritance after the death of the previous dominant, by displacing the incumbent dominant or at the foundation of a new group. Here we investigated the possible fitness benefits associated with these different routes to dominance and the traits that affect an individual's probability of acquiring dominance via these routes. We found that all routes to dominance had similar fitness benefits and that when a dominance vacancy arose, weight was the main determinate of succession, with age still influencing within-group succession and the eldest subordinate female, the beta, often succeeding to dominance. Since the chance that subordinate females will acquire dominance is also positively correlated with the duration of their tenure in the beta position, we tested whether beta females adjusted their growth or cooperative behaviour to avoid eviction and increased their tenure length as the beta. However, there was no indication that betas employed either strategy to increase their tenure. Given that the differing routes to dominance have equivalent fitness pay-offs and are triggered stochastically, selection probably favours flexibility rather than strategies that commit individuals to a specific route.The Kalahari Meerkat Project was funded by the European Research Council (grant no. 294494), the Natural Environment Research Council (grant no. NE/G006822/1) and the Swiss National Science Foundation and supported by the Universities of Cambridge, Zurich and Pretoria

Don't bleach chaotic data

A common first step in time series signal analysis involves digitally filtering the data to remove linear correlations. The residual data is spectrally white (it is ``bleached''), but in principle retains the nonlinear structure of the original time series. It is well known that simple linear autocorrelation can give rise to spurious results in algorithms for estimating nonlinear invariants, such as fractal dimension and Lyapunov exponents. In theory, bleached data avoids these pitfalls. But in practice, bleaching obscures the underlying deterministic structure of a low-dimensional chaotic process. This appears to be a property of the chaos itself, since nonchaotic data are not similarly affected. The adverse effects of bleaching are demonstrated in a series of numerical experiments on known chaotic data. Some theoretical aspects are also discussed.Comment: 12 dense pages (82K) of ordinary LaTeX; uses macro psfig.tex for inclusion of figures in text; figures are uufile'd into a single file of size 306K; the final dvips'd postscript file is about 1.3mb Replaced 9/30/93 to incorporate final changes in the proofs and to make the LaTeX more portable; the paper will appear in CHAOS 4 (Dec, 1993

System data communication structures for active-control transport aircraft, volume 2

The application of communication structures to advanced transport aircraft are addressed. First, a set of avionic functional requirements is established, and a baseline set of avionics equipment is defined that will meet the requirements. Three alternative configurations for this equipment are then identified that represent the evolution toward more dispersed systems. Candidate communication structures are proposed for each system configuration, and these are compared using trade off analyses; these analyses emphasize reliability but also address complexity. Multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems

System data communication structures for active-control transport aircraft, volume 1

Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems

A biophysical model of prokaryotic diversity in geothermal hot springs

Recent field investigations of photosynthetic bacteria living in geothermal hot spring environments have revealed surprisingly complex ecosystems, with an unexpected level of genetic diversity. One case of particular interest involves the distribution along hot spring thermal gradients of genetically distinct bacterial strains that differ in their preferred temperatures for reproduction and photosynthesis. In such systems, a single variable, temperature, defines the relevant environmental variation. In spite of this, each region along the thermal gradient exhibits multiple strains of photosynthetic bacteria adapted to several distinct thermal optima, rather than the expected single thermal strain adapted to the local environmental temperature. Here we analyze microbiology data from several ecological studies to show that the thermal distribution field data exhibit several universal features independent of location and specific bacterial strain. These include the distribution of optimal temperatures of different thermal strains and the functional dependence of the net population density on temperature. Further, we present a simple population dynamics model of these systems that is highly constrained by biophysical data and by physical features of the environment. This model can explain in detail the observed diversity of different strains of the photosynthetic bacteria. It also reproduces the observed thermal population distributions, as well as certain features of population dynamics observed in laboratory studies of the same organisms

Including debris cover effects in a distributed model of glacier ablation

Distributed glacier melt models generally assume that the glacier surface consists of bare exposed ice and snow. In reality, many glaciers are wholly or partially covered in layers of debris that tend to suppress ablation rates. In this paper, an existing physically based point model for the ablation of debris-covered ice is incorporated in a distributed melt model and applied to Haut Glacier d’Arolla, Switzerland, which has three large patches of debris cover on its surface. The model is based on a 10 m resolution digital elevation model (DEM) of the area; each glacier pixel in the DEM is defined as either bare or debris-covered ice, and may be covered in snow that must be melted off before ice ablation is assumed to occur. Each debris-covered pixel is assigned a debris thickness value using probability distributions based on over 1000 manual thickness measurements. Locally observed meteorological data are used to run energy balance calculations in every pixel, using an approach suitable for snow, bare ice or debris-covered ice as appropriate. The use of the debris model significantly reduces the total ablation in the debris-covered areas, however the precise reduction is sensitive to the temperature extrapolation used in the model distribution because air near the debris surface tends to be slightly warmer than over bare ice. Overall results suggest that the debris patches, which cover 10% of the glacierized area, reduce total runoff from the glacierized part of the basin by up to 7%

Making Gestural Interaction Accessible to Visually Impaired People

International audienceAs touch screens become widely spread, making them more accessible to visually impaired people is an important task. Touch displays possess a poor accessibility for visually impaired people. One possibility to make them more accessible without sight is through gestural interaction. Yet, there are still few studies on using gestural interaction for visually impaired people. In this paper we present a comprehensive summary of existing projects investigating accessible gestural interaction. We also highlight the limits of current approaches and propose future working directions. Then, we present the design of an interactive map prototype that includes both a raised-line map overlay and gestural interaction for accessing different types of information (e.g., opening hours, distances). Preliminary results of our project show that basic gestural interaction techniques can be successfully used in interactive maps for visually impaired people