The Australia Telescope 20-GHz (AT20G) Survey: the Bright Source Sample     

Marcella Massardi  Ronald D. Ekers  Tara Murphy  Roberto Ricci  Elaine M. Sadler  Sarah Burke  Gianfranco De Zotti  Philip G. Edwards  Paul J. Hancock  Carole A. Jackson  Michael J. Kesteven  Elizabeth Mahony  Christopher J. Phillips  Lister Staveley-Smith  Ravi Subrahmanyan  Mark A. Walker  Warwick E. Wilson 《Monthly notices of the Royal Astronomical Society》2008,384(2):775-802

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007.
The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic     ) radio sources south of  δ=−15°  with      Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz.
In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming   S ∝ν^α  , decreases from  α^8.6_4.8= 0.11  between 4.8 and 8.6 GHz to  α²⁰_8.6=−0.16  between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has  α²⁰_8.6 > −0.5)  . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies.  相似文献   

Observed and predicted earthquake damage scenarios: the case study of Pettino (L’Aquila) after the 6th April 2009 event     

Carlo Del Gaudio  Paolo Ricci  Gerardo M. Verderame  Gaetano Manfredi 《Bulletin of Earthquake Engineering》2016,14(10):2643-2678

A damage scenario based on observational data collected in L’Aquila Municipality after the 6th April 2009 earthquake is compared with a predicted damage scenario derived from the application of a simplified analytical method for seismic vulnerability assessment of Reinforced Concrete (RC) buildings at large scale. The observational damage scenario is derived from a database of 131 RC buildings located in the Municipality of L’Aquila, which after the 2009 earthquake were subjected to post-earthquake usability assessment procedure. The simplified analytical approach adopted is based on the Capacity Spectrum Method to evaluate seismic capacity at different Damage States (DSs) based on the displacement capacity of structural and non-structural elements. DSs and the corresponding displacement capacity are defined through the interpretation of the observational-based DSs provided by the European Macroseismic Scale EMS-98. Data predicted by the adopted methodology are in good agreement with the observed damage distribution. The observed damage scenario is also compared with predicted scenarios derived from other methodologies from literature.  相似文献   

Numerical investigation of small- and medium-diameter drain wells to stabilise deep landslides     

Aloi  Ferdinando  Pirone  Marianna  Urciuoli  Gianfranco 《Acta Geotechnica》2019,14(4):1065-1080

The stabilisation of deep landslides is still a challenge for geotechnical engineers, mainly due to the high cost of structural control works that generally lead engineers to opt for drain systems. Unfortunately there are operative difficulties affecting excavation of deep drain trenches in soils dislocated by landslides (especially as regards the provisional support of the excavation walls). Small- and medium-diameter wells are a valid alternative in deep landslides, being less expensive than large-diameter wells equipped with horizontal pipes and simpler to construct than deep trenches. However, no technical procedures for their proper design are reported in the literature: design criteria commonly used in practice are derived from pumping problems and are largely inadequate, being based on Dupuit’s hypothesis that presumes stream lines to be horizontal. This paper presents numerical solutions obtained from three-dimensional seepage and consolidation analyses of a slope drained by small- and medium-diameter wells, arranged according to various positions, showing that the efficiency of the well system decreases as the depth of the landslide slip surface increases. Comparison is also made between well systems and deep trenches occupying the same draining volume in the landslide body, showing that the former attains much greater efficiency than the latter. Non-dimensional abaci for the square grid of wells (which is the most effective arrangement) are reported herein to be used for practical purposes.

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New geological insights and structural control on fluid circulation in La Fossa cone (Vulcano,Aeolian Islands,Italy)     

S. Barde-Cabusson  A. Finizola  A. Revil  T. Ricci  S. Piscitelli  E. Rizzo  B. Angeletti  M. Balasco  L. Bennati  S. Byrdina  N. Carzaniga  A. Crespy  F. Di Gangi  J. Morin  A. Perrone  M. Rossi  E. Roulleau  B. Suski  N. Villeneuve 《Journal of Volcanology and Geothermal Research》2009

Electric resistivity tomography (ERT), self-potential (SP), soil CO₂ flux, and temperature are used to study the inner structure of La Fossa cone (Vulcano, Aeolian Islands). Nine profiles were performed across the cone with a measurement spacing of 20 m. The crater rims of La Fossa cone are underlined by sharp horizontal resistivity contrasts. SP, CO₂ flux, and temperature anomalies underline these boundaries which we interpret as structural limits associated to preferential circulation of fluids. The Pietre Cotte crater and Gran Cratere crater enclose the main hydrothermal system, identified at the centre of the edifice on the base of low electrical resistivity values (<20 Ω m) and strong CO₂ degassing, SP, and temperature anomalies. In the periphery, the hydrothermal activity is also visible along structural boundaries such as the Punte Nere, Forgia Vecchia, and Palizzi crater rims and at the base of the cone, on the southern side of the edifice, along a fault attributed to the NW main tectonic trend of the island. Inside the Punte Nere crater, the ERT sections show an electrical resistive body that we interpret as an intrusion or a dome. This magmatic body is reconstructed in 3D using the available ERT profiles. Its shape and position, with respect to the Pietre Cotte crater fault, allows replacing this structure in the chronology of the development of the volcano. It corresponds to a late phase of activity of the Punte Nere edifice. Considering the position of the SP, soil CO₂ flux, and temperature maxima and the repartition of conductive zones related to hydrothermal circulation with respect to the main structural features, La Fossa cone could be considered as a relevant example of the strong influence of pre-existing structures on hydrothermal fluid circulation at the scale of a volcanic edifice.  相似文献   

Preliminary geochemical characterization of groundwater drained by the Roman emissary of Lake Albano (Italy)     

Paolo Madonia  Marianna Cangemi  Carla Galeazzi  Carlo Germani  Mario Parise  Rocco Favara 《Environmental Earth Sciences》2017,76(7):289

Many lakes have been the object of hydraulic works in historical times, and the drainage tunnel carved by Romans for regulating the level of Lake Albano (Central Italy) can be considered as one of the most important historical hydraulic tunnels in the world. We sampled and analysed lake water, as well as groundwater samples from the Lake Albano emissary and another hydraulic work in the area (Ninfeo), which were analysed for their geochemical and isotopic composition in order to extract useful information for a possible reuse of the tunnel for anthropogenic purposes. The collected water samples exhibit common chemical features, typical of water–rock interaction processes in volcanic areas. Analyses of minor and trace elements confirmed the abovementioned results, indicating the presence of an atmospheric pollution source for heavy metals, although their concentrations are mostly below the Maximum Admitted Concentrations for drinking water issued by the World Health Organization. The chemical composition of dissolved gases indicated that both lake and groundwater are mainly enriched in CO₂. Isotopic analyses suggested a clear volcanic origin for CO₂ dissolved in lake water, while carbon dioxide in groundwater from the Roman emissary is produced by soil respiration. As further confirmed by Oxygen and Deuterium isotopic composition, the Roman emissary drains local suspended aquifers neither in contact with the lake water body nor influenced by volcanic activity, suggesting the opportunity to use the tunnel as a “zero-condition” monitoring site for individuating a possible future renewal of volcanic activity.  相似文献   

Analysis of Extreme Events in Geoelectrical Time Series Measured in a Seismic Area of Southern Appenine Chain (Italy)     

Luciano?TelescaEmail author  Marianna?Balasco  Gerardo?Colangelo  Vincenzo?Lapenna 《Natural Hazards》2005,34(2):177-198

In the present paper we analyse the series of extreme events in geoelectrical signals recorded at the monitoring station Tito located in a seismic area of southern Italy. Applying an objective criterion to estimate the probability of occurrence of extreme events in the time series (Cuomo et al., 1996; Cuomo et al., 1997), we found a correlation between the geoelectrical anomalies and earthquakes in the area monitored during the period of recording.  相似文献   

Nutrient dynamics in the Pomeranian Bay (southern Baltic): Impact of the Oder River outflow     

Marianna?PastuszakEmail author  Klaus?Nagel  Alfred?Grelowski  Volker?Mohrholz  Mariusz?Zalewski 《Estuaries and Coasts》2003,26(5):1238-1254

The Pomeranian Bay is a coastal region fed by the Oder River, one of the seven largest Baltic rivers, whose waters flow through a large and complex estuarine system before entering the bay. Nutrients (NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, Ntot, PO₄ ³⁻, P_tot, DSi), chlorophylla concentrations, oxygen content, salinity, and temperature were measured in the Pomeranian Bay in nine seasonally distributed cruises during 1993–1997. Strong spatial and temporal patterns were observed and they were governed by: the seasonally variable riverine water-nutrient discharges, the seasonally variable uptake of nutrients and their cycling in the river estuary and the Bay, the character of water exchange between the Pomeranian Bay and the Szczecin Lagoon, and the water flow patterns in the Bay that are dominated by wind-driven circulation. Easterly winds resulted in water and nutrient transport along the German coastline, while westerly winds confined the nutrient rich riverine waters to the Polish coast and transported them eastward beyond the study area. Two water masses, coastal and open, characterized by different chemical and physical parameters and chla content were found in the Bay independently of the season. The role of the Oder estuary in nutrient transformation, as well as the role of temperature in transformation processes is stressed in the paper. The DIN:DIP:DSi ratio indicated that phosphorus most probably played a limiting role in phytoplankton production in the Bay in spring, while nitrogen did the same in summer. During the spring bloom, predominated by diatoms, the DSi:DIN ratio dropped to 0.1 in the coastal waters and to 0.6 in the open bay waters, pointing to silicon limitation of diatom growth, similar to what is being observed in other Baltic regions.  相似文献   

Solar opacity, neutrino signals and helioseismology     

B. Ricci 《Astroparticle Physics》1997,6(3-4):257-261

In connection with the recent suggestion by Tsytovich et al. that opacity in the solar core could be overestimated, we consider the following questions: (i) What would a 10% opacity reduction imply for the solar neutrino puzzle? (ii) Is there any hope of solving the solar neutrino puzzle by changing opacity? (iii) Is a 10% opacity reduction testable with helioseismological data?  相似文献   

Flow-type landslides in pyroclastic soils on flysch bedrock in southern Italy: the Bosco de’ Preti case study     

Antonio Santo  Giuseppe Di Crescenzo  Giovanni Forte  Raffaele Papa  Marianna Pirone  Gianfranco Urciuoli 《Landslides》2018,15(1):63-82

In the last 20 years, major efforts have been made to investigate shallow flow-type landslides. Such phenomena are usually rainfall-induced and in the geological context of Campania (Southern Italy) occur in pyroclastic soils resting on steep slopes mainly constituted by carbonate or volcanic bedrock and by flysch deposits. They are generally complex landslides with an early soil slide and a subsequent flow evolution. In this paper, a database of flowslides occurring in recent years within the flysch deposits of Avellino (Campanian Apennines) is first discussed and then the case study of Bosco de’ Preti landslide on March 4, 2005, is described. The geological and geotechnical characteristics of the soils involved are described and the monitoring of the groundwater heads collected over 1 year from June 2005 to June 2006 is also shown. The last part of the paper illustrates the results of numerical modelling of the landslide triggering to gain insights into such phenomena. Slope stability analyses are preceded by hydrological modelling of the slope based on the monitoring data. Numerical analysis demonstrated that the rainfall during the 2 months preceding the event was able to fully saturate the pyroclastic cover and to establish positive pore water pressure at the depth of the surface of rupture, a soil condition never witnessed in carbonatic contexts. Hence, a combination of antecedent (predisposing factors) and single rainfall events (triggering factors) led to slope failure, as usually happens in pyroclastic soils in carbonatic and volcanic contexts. Finally, analysis of the historical landslides together with detailed investigation of the Bosco de’ Preti case study permitted comparison between flow-type landslides in pyroclastic soils on carbonatic/volcanic bedrock and those on flysch.  相似文献   

Influence of the properties of tropical soils in the toxicity and bioavailability of heavy metals in sewage sludge-amended lands     

Ricardo Cesar  Marianna Silva  Juan Colonese  Edison Bidone  Silvia Egler  Zuleica Castilhos  Helena Polivanov 《Environmental Earth Sciences》2012,66(8):2281-2292

The toxicity and potential bioavailability of heavy metals were studied in sewage sludge-amended ferralsols and chernosols, using bioassays with earthworms (Eisenia andrei). Acute toxicity tests and avoidance assays were performed according to standard protocols. Potentially bioavailable concentrations of heavy metals were estimated by quantifying their concentrations in tissues of survival earthworms. The results revealed that soil properties played an important role in the toxicity and bioavailability of heavy metals. In this respect, higher levels of toxicity were detected for the ferralsol. The abundance of 2:1 clay minerals, high fertility and more basic values of pH seem to be very important in the reduction of toxicity levels for earthworms. Organisms exposed to the chernosols were able to uptake higher amount of metals. In that case, higher contents of nutrients in chernosols may have influenced such bioavailability processes. Avoidance responses were the most sensible indicator of toxicity. In the near future, such data can subsidize the establishment of toxic reference concentrations able to reflect the characteristics of important tropical pedological occurrences, supporting the definition of sustainable indicators for using sewage sludge in the tropical agriculture.  相似文献