ROckfall risk MAnagement assessment: the RO.MA. approach   总被引：1，自引：1，他引：0  

Claudia Mignelli  Stefano Lo Russo  Daniele Peila 《Natural Hazards》2012,62(3):1109-1123

The analysis of risk for vehicles and drivers as a result of rockfall on a road is relevant to design management in geotechnical engineering. This process is very complex due to the large number of parameters involved. In this paper, we discuss risk analysis and management procedures for roads subject to rockfall phenomena. To this aims, we are proposing a quantitative method (the RO.MA. approach). We developed an abacus to define the threshold values of acceptable rockfall risk for a given road. Rockfall risk is calculated using an Event Tree approach and compared with the abacus thresholds to evaluate road safety and the need for additional protective measures to reduce the risk to an acceptable level. The approach was successfully applied at a test site located in Bard, Aosta Valley, north-western Italy.  相似文献   

Radiocarbon analysis of halophilic microbial lipids from an Australian salt lake     

P. Sargent Bray  Claudia M. Jones  Stewart J. Fallon  Jochen J. Brocks  Simon C. George 《Quaternary Research》2012,77(1):104-109

Assigning accurate dates to hypersaline sediments opens important terrestrial records of local and regional paleoecologies and paleoclimatology. However, as of yet no conventional method of dating hypersaline systems has been widely adopted. Biomarker, mineralogical, and radiocarbon analyses of sediments and organic extracts from a shallow (13 cm) core from a hypersaline playa, Lake Tyrrell, southeastern Australia, produce a coherent age-depth curve beginning with modern microbial mats and extending to ~ 7500 cal yr BP. These analyses are furthermore used to identify and constrain the timing of the most recent change in hydrological regime at Lake Tyrrell, a shift from a clay deposit to the precipitation of evaporitic sands occurring at some time between ~ 4500 and 7000 yr. These analyses show the potential for widespread dating of hypersaline systems integrating the biomarker approach, reinforce the value of the radiocarbon content of biomarkers in understanding the flow of carbon in modern ecologies, and validate the temporal dimension of data provided by biomarkers when dating late Quaternary sediments.  相似文献   

UV irradiation of natural organic matter (NOM): impact on organic carbon and bacteria     

Andrea Paul  Claudia Dziallas  Elke Zwirnmann  Egil T. Gjessing  Hans-Peter Grossart 《Aquatic Sciences - Research Across Boundaries》2012,74(3):443-454

UV-induced transformation of dissolved organic matter (DOC) is often accompanied by reduction of molecular weight and aromaticity and an increase of low-molecular weight (LMW) matter that can be utilized as a substrate by heterotrophic bacteria. Moreover, the generation of reactive transients and mineralization of DOC occurs. For a better understanding of the modification that starts after irradiation and to distinguish between possible chemical and biological modifications, we selected different natural organic matter (NOM) from Norway and Germany. The aqueous solutions were treated by UV irradiation and divided into two aliquot samples. NaN₃ anti-bacterial treatment was applied to one sample, and high-pressure size-exclusion chromatography (HPSEC) analysis was used for both. In all samples, we found typical modifications of NOM after UV irradiation. Incubation (>7?days) of UV-irradiated NOM samples resulted in lower levels of LMW matter and increased aromaticity. Parallel to these changes of carbon fractions, an increase in bacterial cell numbers was observed. Addition of NaN₃ to NOM, however, inhibited the reduction of LMW matter, indicating that microbial activity accounted for the observed changes in NOM. Analysis of the bacterial community composition by denaturing gradient gel electrophoresis (DGGE) of the amplified 16S rRNA genes revealed that bacterial communities of non-irradiated and UV-irradiated NOM were different and that UV selected for specific members of ??-proteobacteria, ??-proteobacteria, and Bacteriodetes. Our results imply that after UV-irradiation of NOM, specific bacterial members are well adapted to low pH, high LMW DOC concentrations, and oxidative stress, and therefore thrive well on UV-irradiated humic matter.  相似文献   

Effects of AGN feedback on ΛCDM galaxies     

Claudia del P. Lagos  Sofía A. Cora  Nelson D. Padilla 《Monthly notices of the Royal Astronomical Society》2008,388(2):587-602

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Past,present and potential uses of native flora and wildlife of the Monte Desert     

A. Vilela  M.L. Bolkovic  P. Carmanchahi  M. Cony  D. de Lamo  D. Wassner 《Journal of Arid Environments》2009,73(2):238-243

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Structure and position of the bottom salinity front in the Amazon Estuary     

Ernesto Molinas  Susana Beatriz Vinzon  Carla de Paula Xavier Vilela  Marcos Nicolas Gallo 《Ocean Dynamics》2014,64(11):1583-1599

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A User-Oriented Methodology for DInSAR Time Series Analysis and Interpretation: Landslides and Subsidence Case Studies     

Davide Notti  Fabiana Calò  Francesca Cigna  Michele Manunta  Gerardo Herrera  Matteo Berti  Claudia Meisina  Deodato Tapete  Francesco Zucca 《Pure and Applied Geophysics》2015,172(11):3081-3105

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High-resolution mm interferometry and the search for massive protostellar disks: the case of Cep-A HW2     

Claudia Comito  Peter Schilke  Ulrike Endesfelder  Izaskun Jiménez-Serra  Jesus Martín-Pintado 《Astrophysics and Space Science》2008,313(1-3):59-63

The direct detection of accretion onto massive protostars through rotating disks constitutes an important tile in the massive-star-formation-theory mosaic. This task is however observationally very challenging. A very interesting example is Cepheus A HW2. The properties of the molecular emission around this YSO seems to suggest the presence of a massive rotating disk (cf. Patel et al. in Nature 437:109, 2005). We have carried out sub-arcsec-resolution PdBI observations of high-density and shock tracers such as SO₂, SiO, CH₃CN, and CH₃OH towards the center of the outflow. A detailed analysis of the spatial distribution and of the velocity field traced by all observed species leads us to conclude that, on a ∼700 AU scale, the Cep-A “disk” is actually the result of the superposition of multiple hot-core-type objects, at least one of them ejecting an outflow at a small angle with respect to the line of sight. Together with the well-known large-scale outflow ejected by HW2, this setup makes for a very complex spatial and kinematic picture. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).  相似文献   

Methane gas Seeps Along the Oxic/Anoxic Gradient in the Black Sea: Manifestations, Biogenic Sediment Compounds and Preliminary Results on Benthic Ecology   总被引：2，自引：0，他引：2  

Claudia Luth  Ulf Luth  Audrey V. Gebruk  &Hjalmar Thiel 《Marine Ecology》1999,20(3-4):221-249

Abstract. Sediment parameters (grain size, organic content, chloroplastic pigments, Adenylates, Potential hydrolytic activity and electron transport system activity) and benthic biota were studied in methane seep area south-west of the Crimean Peninsula in the Black Sea over a depth range from 60 to 260m. A control transect with similar depths was performed in an adjacent nonseep area. Methane seepage in this region occurs from 35 to ˜ 85m depth, passing the oxic anoxic interface zone at 130 to 180m. The methane seep areas were characterized by abundant carbonate precipitates which occurred in various shapes from small, flat structures to tall chimneys with increasing anoxia. The carbonates were associated with distinct bacterial mats. Most of the measured biochemical parameters in the sediment were quite similar in the seep and nonseep areas. The content of organic matter was higher and grain size was more uniform in the nonseep areas. However, the seep areas were charaterized by highter proportions of the larger fauna (size classes 0.5–1 mm and ≥ 1mm) as well as increased total numbers of benthic fauna in the suboxic and upper anoxic zone. The animals did not show any seep-specific adaptations. In addition to methane seepage, highly variable hydrochemical and sedimentary conditions on the lower shelf and upper slope may also play an important role in structuring the composition and distribution of the benthic fauna.  相似文献   

Black hole spin and radio loudness in a Λ cold dark matter universe     

Claudia del P. Lagos  Nelson D. Padilla  Sofía A. Cora 《Monthly notices of the Royal Astronomical Society》2009,395(2):625-636

We use a combination of a cosmological N -body simulation of the concordance Λ cold dark matter paradigm and a semi-analytic model of galaxy formation to investigate the spin development of central supermassive black holes (BHs) and its relation to the BH host galaxy properties. In order to compute BH spins, we use the α model of Shakura & Sunyaev and consider the King et al. warped disc alignment criterion. The orientation of the accretion disc is inferred from the angular momentum of the source of accreted material, which bears a close relationship to the large-scale structure in the simulation. We find that the final BH spin depends almost exclusively on the accretion history and only weakly on the warped disc alignment. The main mechanisms of BH spin-up are found to be gas cooling processes and disc instabilities, a result that is only partially compatible with Monte Carlo models where the main spin-up mechanisms are major mergers and disc instabilities; the latter results are reproduced when implementing randomly oriented accretion discs in our model. Regarding the BH population, we find that more massive BHs, which are hosted by massive ellipticals, have higher spin values than less massive BHs, hosted by spiral galaxies. We analyse whether gas accretion rates and BH spins can be used as tracers of the radio loudness of active galactic nuclei (AGN). We find that the current observational indications of an increasing trend of radio-loud AGN fractions with stellar and BH mass can be easily obtained when placing lower limits on the BH spin, with a minimum influence from limits on the accretion rates; a model with random accretion disc orientations is unable to reproduce this trend. Our results favour a scenario where the BH spin is a key parameter to separate the radio-loud and radio-quiet galaxy populations.  相似文献