806 research outputs found

    Soil Geographical Database of Eurasia and the Mediterranean: Instructions Guide for Elaboration at Scale 1:1,000,000

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    Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

    Probing material nonlinearity at various depths by time reversal mirrors

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    International audienceIn this letter, the time reversal mirror is used to focus elastic energy at a prescribed location and to analyze the amplitude dependence of the focus signal, thus providing the nonlinearity of the medium. By varying the frequency content of the focused waveforms, the technique can be used to probe the surface, by penetrating to a depth defined by the wavelength of the focused waves. The validity of this concept is shown in the presence of gradual and distributed damage in concrete by comparing actual results with a reference nonlinear measurement and X ray tomography images

    Stratigraphy and chronology of a 15ka sequence of multi-sourced silicic tephras in a montane peat bog, eastern North Island, New Zealand.

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    We document the stratigraphy, composition, and chronology of a succession of 16 distal, silicic tephra layers interbedded with lateglacial and Holocene peats and muds up to c. 15 000 radiocarbon years (c. 18 000 calendar years) old at a montane site (Kaipo Bog) in eastern North Island, New Zealand. Aged from 665 +/- 15 to 14 700 +/- 95 14C yr BP, the tephras are derived from six volcanic centres in North Island, three of which are rhyolitic (Okataina, Taupo, Maroa), one peralkaline (Tuhua), and two andesitic (Tongariro, Egmont). Correlations are based on multiple criteria: field properties and stratigraphic interrelationships, ferromagnesian silicate mineral assemblages, glass-shard major element composition (from electron microprobe analysis), and radiocarbon dating. We extend the known distribution of tephras in eastern North Island and provide compositional data that add to their potential usefulness as isochronous markers. The chronostratigraphic framework established for the Kaipo sequence, based on both site-specific and independently derived tephra-based radiocarbon ages, provides the basis for fine-resolution paleoenvironmental studies at a climatically sensitive terrestrial site from the mid latitudes of the Southern Hemisphere. Tephras identified as especially useful paleoenvironmental markers include Rerewhakaaitu and Waiohau (lateglacial), Konini (lateglacial-early Holocene), Tuhua (middle Holocene), and Taupo and Kaharoa (late Holocene)

    Aquatic community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record

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    Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132′S–78°04.847′W) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328′S–78°09.175′W) is a glacially formed lake with an inflow and outflow in high Andean Páramo grasslands. In each lake we examined the dynamics of chironomids and other aquatic and semi-aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer-type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes

    Semiparametrically Efficient Inference Based on Signs and Ranks for Median Restricted Models

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    Since the pioneering work of Koenker and Bassett (1978), econometric models involving median and quantile rather than the classical mean or conditional mean concepts have attracted much interest.Contrary to the traditional models where the noise is assumed to have mean zero, median-restricted models enjoy a rich group-invariance structure.In this paper, we exploit this invariance structure in order to obtain semiparametrically efficient inference procedures for these models.These procedures are based on residual signs and ranks, and therefore insensitive to possible misspecification of the underlying innovation density, yet semiparametrically efficient at correctly specified densities.This latter combination is a definite advantage of these procedures over classical quasi-likelihood methods.The techniques we propose can be applied, without additional technical difficulties, to both cross-sectional and time-series models.They do not require any explicit tangent space calculation nor any projections on these.

    Optimal estimation of qubit states with continuous time measurements

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    We propose an adaptive, two steps strategy, for the estimation of mixed qubit states. We show that the strategy is optimal in a local minimax sense for the trace norm distance as well as other locally quadratic figures of merit. Local minimax optimality means that given nn identical qubits, there exists no estimator which can perform better than the proposed estimator on a neighborhood of size n1/2n^{-1/2} of an arbitrary state. In particular, it is asymptotically Bayesian optimal for a large class of prior distributions. We present a physical implementation of the optimal estimation strategy based on continuous time measurements in a field that couples with the qubits. The crucial ingredient of the result is the concept of local asymptotic normality (or LAN) for qubits. This means that, for large nn, the statistical model described by nn identically prepared qubits is locally equivalent to a model with only a classical Gaussian distribution and a Gaussian state of a quantum harmonic oscillator. The term `local' refers to a shrinking neighborhood around a fixed state ρ0\rho_{0}. An essential result is that the neighborhood radius can be chosen arbitrarily close to n1/4n^{-1/4}. This allows us to use a two steps procedure by which we first localize the state within a smaller neighborhood of radius n1/2+ϵn^{-1/2+\epsilon}, and then use LAN to perform optimal estimation.Comment: 32 pages, 3 figures, to appear in Commun. Math. Phy

    Monitoring mosaic biotopes in a marine conservation zone by autonomous underwater vehicle

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    The number of marine protected areas (MPAs) has increased dramatically in the last decade and poses a major logistic challenge for conservation practitioners in terms of spatial extent and the multiplicity of habitats and biotopes that now require assessment. Photographic assessment by autonomous underwater vehicle (AUV) enables the consistent description of multiple habitats, in our case including mosaics of rock and sediment. As a case study, we used this method to survey the Greater Haig Fras marine conservation zone (Celtic Sea, northeast Atlantic). We distinguished 7 biotopes, detected statistically significant variations in standing stocks, species density, species diversity, and faunal composition, and identified significant indicator species for each habitat. Our results demonstrate that AUV‐based photography can produce robust data for ecological research and practical marine conservation. Standardizing to a minimum number of individuals per sampling unit, rather than to a fixed seafloor area, may be a valuable means of defining an ecologically appropriate sampling unit. Although composite sampling represents a change in standard practice, other users should consider the potential benefits of this approach in conservation studies. It is broadly applicable in the marine environment and has been successfully implemented in deep‐sea conservation and environmental impact studies. Without a cost‐effective method, applicable across habitats, it will be difficult to further a coherent classification of biotopes or to routinely assess their conservation status in the rapidly expanding global extent of MPAs

    Dwarf Copper-Gold Porphyry Deposits of the Buchim-Damjan-Borov Dol Ore District, Republic of Macedonia (FYROM)

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    The metallogenic aspects, tectonic setting, magmatism, structure, and composition of Au-and Ag-bearing porphyry copper deposits in the Buchim-Damjan-Borov Dol ore district and their genetic features are considered and compared with earlier published data. Special attention is paid to supergene gold in heavy concentrate halos of the Borov Dol deposit. The total Cu reserves of the deposits discussed in this paper do not exceed 150 kt. The Buchim deposit likely is the world's smallest deposit of this type currently involved in mining. A comprehensive study of these dwarf porphyry copper deposits is undertaken to answer questions on the conditions of their formation. How do they differ from formation conditions of giant deposits

    Drivers for international innovation activities in developed and emerging countries

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    This paper aims to shed light on firm specific drivers that lead firms to internationalise their innovation activities. The paper draws a comprehensive picture of driving forces by including firm capabilities, characteristics of the firm’s competitive environment and the influence of innovation obstacles in the home country. In particular, the role of the potential driving forces is tested on the probability to carry out different innovative activities abroad (R&D, design/conception of new products, manufacturing of innovative products and implementation of new processes). In a second step these driving forces are used to observe their impact on the decision to locate innovation activities in various countries and regions (China, Eastern Europe, Western Europe and North America) as well as in groups of countries with similar levels of knowledge (country clubs). The analysis is based on the Mannheim Innovation Panel survey which represents the German CIS (Community Innovation Survey) contribution. Two survey waves are combined and result in a sample of about 1400 firms. The results show that the decision to perform innovation activities abroad is mainly driven by organisational capabilities such as absorptive capacities, international experience and existing technological competences of the respective firm. Innovation barriers at the German home base such as lack of labour and high innovation costs foster the set up of later-stage innovation activities abroad while the lack of demand demonstrates a barrier to the internationalisation decision for the development and manufacturing of new products. Location decisions receive the strongest influencing effects from the international experience of the firm. Firms which innovate in developing countries seem to require a more extensive level of international experience by international R&D cooperation

    The relationship between eruptive activity, flank collapse, and sea level at volcanic islands: A long-term (>1 Ma) record offshore Montserrat, Lesser Antilles

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    Hole U1395B, drilled southeast of Montserrat during Integrated Ocean Drilling Program Expedition 340, provides a long (>1 Ma) and detailed record of eruptive and mass-wasting events (>130 discrete events). This record can be used to explore the temporal evolution in volcanic activity and landslides at an arc volcano. Analysis of tephra fall and volcaniclastic turbidite deposits in the drill cores reveals three heightened periods of volcanic activity on the island of Montserrat (?930 ka to ?900 ka, ?810 ka to ?760 ka, and ?190 ka to ?120 ka) that coincide with periods of increased volcano instability and mass-wasting. The youngest of these periods marks the peak in activity at the Soufrière Hills volcano. The largest flank collapse of this volcano (?130 ka) occurred towards the end of this period, and two younger landslides also occurred during a period of relatively elevated volcanism. These three landslides represent the only large (>0.3 km3) flank collapses of the Soufrière Hills edifice, and their timing also coincides with periods of rapid sea-level rise (>5 m/ka). Available age data from other island arc volcanoes suggests a general correlation between the timing of large landslides and periods of rapid sea-level rise, but this is not observed for volcanoes in intra-plate ocean settings. We thus infer that rapid sea-level rise may modulate the timing of collapse at island arc volcanoes, but not in larger ocean-island settings
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