Quantum limits of cold damping with optomechanical coupling

Thermal noise of a mirror can be reduced by cold damping. The displacement is measured with a high-finesse cavity and controlled with the radiation pressure of a modulated light beam. We establish the general quantum limits of noise in cold damping mechanisms and we show that the optomechanical system allows to reach these limits. Displacement noise can be arbitrarily reduced in a narrow frequency band. In a wide-band analysis we show that thermal fluctuations are reduced as with classical damping whereas quantum zero-point fluctuations are left unchanged. The only limit of cold damping is then due to zero-point energy of the mirrorComment: 10 pages, 3 figures, RevTe

Nematic elastomers with aligned carbon nanotubes: new electromechanical actuators

We demonstrate, for the first time, the large electromechanical response in nematic liquid crystalline elastomers filled with a very low (~0.01%) concentration of carbon nanotubes, aligned along the nematic director at preparation. The nanotubes create a very large effective dielectric anisotropy of the composite. Their local field-induced torque is transmitted to the rubber-elastic network and is registered as the exerted uniaxial stress of order ~1kPa in response to a constant field of order ~1MV/m. We investigate the dependence of the effect on field strength, nanotube concentration and reproducibility under multiple field-on and -off cycles. The results indicate the potential of the nanotube-nematic elastomer composites as electrically driven actuators

Comparison between buried uncultivated and cultivated Iron Age soils on the west coast of Jutland, Denmark

Wind blown sands have buried and preserved the soil profiles of some lron Age soils near an Iron Age settlement in the present day Parish of Lodbjerg on the west coast of Jutland, Denmark. Some of these buried soils show signs of Iron Age agriculture, while others were not disturbed. The present study attempts to clarify this difference and to see how lron Age cultivation affected soil-forming processes. We have found that the cultivated soils contain an abundance of fine charcoal and silt, which is integrated with the top horizon of the soil. In fact, this can be used as a diagnostic criterion for the cultivated soils. Our physical and chemical data show that the ancient cultivation affected particle size distribution, distribution of organic matter, C/N ratio, and organic phosphorous content, as well as some other parameters

Standard geological methods used on archaeological problems

This paper presents some examples of geological methods applied to archaeological problems. The site is an Iron Age village at Heltborg, Thy, Northern Denmark. The very thick layer of occupation material found in this and other Iran Age villages in the area seems to come from the accumulation of grass turf walls of the houses. This explanation can be confirmed by the geological methods. The boundary between a brownish and a more gray horizon in the occupation material can be explained as a redox boundary. As such it is not related to any archaeological event and in fact crosses the archaeological horizons in the material. Micramorphological methods were used, especially on samples from a burnt house. Here it was possible to identify the floor material as till and to identify wattle and daub material. lt proved possible even to give a likely estimation of the appearance of the wall and the technique used in preparing the inside of the house

Soil micromorphological evidence of early agriculture in north-west Europe

International audienceThe study of early agricultural soils using micromorphology is outlined. The effects of tillage due to modern agriculture are reviewed and the results from four experiments in ‘prehistoric cultivation’ are presented. These are used in the interpretation of prehistoric agricultural practices, based on a study of soils from various archaeological sites in north‐west Europe. It is suggested that microfabric features, varying according to soil texture, can be diagnostic of tillage. Microfabric type, textural features (e.g. coatings) and structure are, taken together, better indicators of ancient tillage than single features

Interpretation and significance of urban deposits

In many United Kingdom cities, the late Roman to Medieval periods are an archaeological blank. The study of contemporary anthropogenic deposits is therefore crucial to any understanding of urban activity. Using pedological and micromorphological techniques, urban anthropogenic deposits of this age from London and Exeter were therefore investigated. lt can be suggested from the results that previous interpretations of such deposits, once thought of as »flood loams» and often termed »Dark Earth », as i progressively thickening within-urban area »market garden» soils, orii simple accumulations of urban dump material through time, are inadequate. Analysis of undisturbed soil samples through optical microscopy, complemented by archaeological information from individual sites, allow us to be more specific. Our observations may indicate phases of dumping of mainly local soil material from, for example, military ditch digging at Exeter; whereas, at the London sites the deposits are tentatively interpreted as accumulations of partially or fully reworked materials derived from the destruction and collapse of insubstantial buildings. This finding may infer a gross under-estimation of urban activity at this time. Micromorphology has proven tobe the best analytical technique. In contrast, analyses of bulk samples may only provide very general information in these often extremely heterogeneous deposits

Phase chirality and stereo-selective swelling of cholesteric elastomers

Cholesteric elastomers possess a macroscopic ``phase chirality'' as the director n rotates in a helical fashion along an optical axis $z$ and can be described by a chiral order parameter. This parameter can be tuned by changing the helix pitch p and/or the elastic properties of the network. The cholesterics also possess a local nematic order, changing with temperature or during solvent swelling. In this paper, by measuring the power of optical rotation, we discover how these two parameters vary as functions of temperature or solvent adsorbed by the network. The main result is a finding of pronounced stereo-selectivity of cholesteric elastomers, demonstrating itself in the retention of the ``correct'' chirality component of a racemic solvent. It has been possible to quantify the amount of such stereo-separation, as the basic dynamics of the effect