The Class 0 source Barnard 1c     

Brenda Matthews  Edwin Bergin  Antonio Crapsi  Michiel Hogerheijde  Jes Jørgensen  Dan Marrone  Ramprasand Rao 《Astrophysics and Space Science》2008,313(1-3):65-68

We present our most recent results from an ongoing study of the Class 0 source Barnard 1c in Perseus. This source is of particular interest because it exhibits evidence of strong alignment of grains all the way to the core’s centre, which is contrary to all other low-mass protostellar cores observed to date. Our goal is to clarify the source of poor alignment in other sources by identifying the source of strong alignment in B1c. A central cavity has been identified in N₂H⁺ emission; its anticorrelation with C¹⁸O emission suggests that heating in the centre has released CO from grain mantles, in turn destroying N₂H⁺. We present sensitivity-limited, high spatial resolution polarimetry data from the SubMillimeter Array and discuss the potential implications of these data.  相似文献   

Accurate hypocentre locations in the Middle-Durance Fault Zone, South-Eastern France     

Sebastiano Imposa  Jean-Pierre Fourno  Rosario Raffaele  Antonio Scaltrito  Luciano Scarfi 《Central European Journal of Geosciences》2009,1(4):416-423

A one-dimensional velocity model and station corrections for the Middle-Durance fault zone (south-eastern France) were computed by inverting P-wave arrival times recorded on a local seismic network of 8 stations. A total of 93 local events with a minimum of 6 P-phases, RMS 0.4 s and a maximum gap of 220° were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn from our findings. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of south-eastern France.  相似文献   

Salt Marsh and Fringing Oyster Reef Transgression in a Shallow Temperate Estuary: Implications for Restoration,Conservation and Blue Carbon     

Justin T. Ridge  Antonio B. Rodriguez  F. Joel Fodrie 《Estuaries and Coasts》2017,40(4):1013-1027

The importance of intertidal estuarine habitats, like salt marsh and oyster reef, has been well established, as has their ubiquitous loss along our coasts with resultant forfeiture of the ecosystem services they provide. Furthering our understanding of how these habitats are evolving in the face of anthropogenic and climate driven changes will help improve management strategies. Previous work has shown that the growth and productivity of both oyster reefs and salt marshes are strongly linked to elevation in the intertidal zone (duration of aerial exposure). We build on that research by examining the growth of marsh-fringing oyster reefs at yearly to decadal time scales and examine movement of the boundary between oyster reef and salt marsh at decadal to centennial time scales. We show that the growth of marsh-fringing reefs is strongly associated to the duration of aerial exposure, with little growth occurring below mean low water and above mean sea level. Marsh-shoreline movement, in the presence or absence of fringing oyster reefs, was reconstructed using transects of sediment cores. Carbonaceous marsh sediments sampled below the modern fringing oyster reefs indicate that marsh shorelines within Back Sound, North Carolina are predominantly in a state of transgression (landward retreat), and modern oyster-reef locations were previously occupied by salt marsh within the past two centuries. Cores fronting transgressive marsh shorelines absent fringing reefs sampled thinner and less extensive carbonaceous marsh sediment than at sites with fringing reefs. This indicates that fringing reefs are preserving carbonaceous marsh sediment from total erosion as they transgress and colonize the exposed marsh shoreline making marsh sediments more resistant to erosion. The amount of marsh sediment preservation underneath the reef scales with the reef’s relief, as reefs with the greatest relief were level with the marsh platform, preserving a maximum amount of carbonaceous sediments during transgression by buffering the marsh from erosional processes. Thus, fringing oyster reefs not only have the capacity to shelter shorelines but, if located at the ideal tidal elevation, they also keep up with accelerating sea-level rise and cap carbonaceous sediments, protecting them from erosion, as reefs develop along the marsh.  相似文献   

Uptake of hazardous elements by spring onion (<Emphasis Type="Italic">Allium fistulosum</Emphasis> L.) from soil irrigated with different types of water and possible health risk     

Kafeel Ahmad  Zafar Iqbal Khan  Asma Ashfaq  Muhammad Ashraf  Nudrat Aisha Akram  Muhammad Sher  Hazoor Ahmad Shad  Vincenzo Tufarelli  Antonio Lonigro  Mariano Fracchiolla  Eugenio Cazzato 《Environmental Earth Sciences》2017,76(8):322

Bio-concentration of elements such as Mo, As, Se, Fe, Cu, Zn, Ni and Pb was analyzed in spring onion (Allium fistulosum L.) in three different locations of central Punjab, Pakistan. At location GW, relatively low level of hazardous elements was found in spring onion, suggesting that groundwater is a safe source of water for irrigating food crops. The pH of soil at wastewater irrigation was found less acidic (pH 7.4) than the other sites. The range of concentration in the different samples of spring onion was as follows: 6.15–8.16 mg kg^?1 for Mo, 2.77–4.28 mg kg^?1 for As, 0.395–0.705 mg kg^?1 for Se, 36.73–48.17 mg kg^?1 for Fe, 10.58–16.26 mg kg^?1 for Cu, 28.87–39.79 mg kg^?1 for Zn, 6.66–8.75 mg kg^?1 for Ni and 4.33–6.09 mg kg^?1 for Pb, respectively. High bio-concentration of Zn (15.37) from soil to spring onion was found at canal water irrigated location. The estimated daily intake of metal for spring onion was less, but the health risk index was higher than 1 for Mo, As, Cu, Pb and Ni, respectively. This was due to higher proportion of spring onion in diet, which consequently increased the health risk index for metals. Therefore, it is recommended to avoid growing vegetables in untreated urban and rural wastewater containing elevated amounts of metals.  相似文献   

Local- and global-scale seismic analyses of historical masonry compounds in San Pio delle Camere (L’Aquila,Italy)     

Antonio Formisano 《Natural Hazards》2017,86(2):465-487

Masonry building aggregates are large parts of the Italian building heritage often designed without respecting seismic criteria. The current seismic Italian code does not foresee a clear calculation method to predict their static nonlinear behaviour. For this reason, in this paper firstly, a simple methodology to forecast the seismic response of masonry aggregates in San Pio delle Camere (L’Aquila, Italy) has been set up starting from the provisions of the Italian Guidelines on Cultural Heritage. The implemented procedure has been calibrated on the results of two FEM structural analysis programs used to investigate three masonry building compounds. As a result, a design chart used to correctly predict the base shear of aggregate masonry units starting from code provisions has been set up. Later on, the large-scale seismic vulnerability and damage appraisal of the inspected historical centre has been done on the basis of a quick methodology, already implemented and experienced by the author in some historical centres of the Campania region. The analysis result was a numerical correlation between vulnerability index and mean damage grade of examined building compounds. In particular, a damage forecast under numerical way has been firstly estimated and then compared with the real one. The post-earthquake scenario has represented an ideal term of comparison for effectively testing the reliability of the employed technique, which should be further extended to other Italian historical centres.  相似文献   

A novel nuclear forensic tool involving deposit type normalized rare earth element signatures   总被引：1，自引：0，他引：1       下载免费PDF全文

Tyler L. Spano  Antonio Simonetti  Thomas Wheeler  Grace Carpenter  Devonee Freet  Enrica Balboni  Corinne Dorais  Peter C. Burns 《地学学报》2017,29(5):294-305

Identifying the provenance of uranium‐rich materials is a critical objective of nuclear forensic analysis. Rare earth element (REE) distributions within uranium ores are well‐established forensic indicators, but quantifying and correlating trace element signatures for U ores to known deposits has thus far involved intricate statistical analyses. This study reports average chondrite normalized (CN)‐REE signatures for important U deposit types worldwide, which are then employed to evaluate U ore paragenesis using a simple linear regression analysis. This technique provides a straightforward method that can aid in determining the deposit type of U ores based on their REE abundances, and combined with other forensic indicators (e.g. radiogenic isotope signatures) can provide essential provenance information for nuclear materials.  相似文献   

Constraints on the genesis of gold mineralization at the Homestake Gold Deposit, Black Hills, South Dakota from rhenium–osmium sulfide geochronology     

Ryan M. Morelli  Chris C. Bell  Robert A. Creaser  Antonio Simonetti 《Mineralium Deposita》2010,45(5):461-480

The Homestake gold deposit, located in the Black Hills, South Dakota, USA, is one of the largest known hydrothermal gold deposits globally, with total mining production exceeding 40 Moz Au. Rhenium–osmium geochronology of ore-associated arsenopyrite and pyrrhotite was performed in an effort to delineate the timing of gold mineralization in relation to known tectonothermal events in the northern Black Hills. Arsenopyrite yields a rhenium–osmium (Re–Os) age of 1,736 ± 8 Ma (mean squared weighted deviation = 1.6), consistent with existing age constraints for gold mineralization, whereas Re–Os pyrrhotite data are highly scattered and do not yield a meaningful mineralization age. This is taken to indicate that the Re–Os arsenopyrite chronometer is robust to at least 400°C, whereas the Re–Os pyrrhotite chronometer is likely disturbed by temperatures of 300–350°C. The Re–Os arsenopyrite age and initial Os ratio (0.28 ± 0.15) are interpreted to indicate that gold was introduced at ca. 1,730 Ma, coincident with the onset of exhumation of crustal blocks and, possibly, the earliest intrusive phases of Harney Peak granite magmatism. New in situ U–Pb monazite analyses from an aplite dike in the east-central Black Hills indicate that granite magmatism was a protracted event, persisting until at least ca. 1,690 Ma.  相似文献   

The end of the Messinian Salinity Crisis in the western Mediterranean: Insights from the carbonate platforms of south-eastern Spain   总被引：1，自引：0，他引：1  

Raphaël Bourillot  Emmanuelle Vennin  Jean-Marie Rouchy  Marie-Madeleine Blanc-Valleron  Antonio Caruso 《Sedimentary Geology》2010,229(4):224-485

How the Messinian Salinity Crisis (MSC) ended is still a matter of intense debate. The Terminal Carbonate Complex (TCC) is a late Messinian carbonate platform system that recorded western Mediterranean hydrological changes from the final stages of evaporite deposition till the advent of Lago-Mare fresh- to brackish water conditions at the very end of Messinian times. A multidisciplinary study has been carried out in three localities in south-eastern Spain to reconstruct the history of TCC platforms and elucidate their significance in the MSC. Overall, this study provides evidence that the TCC formed following a regional 4th order water level rise and fall concomitant with an opening-restriction trend. It can be subdivided into four 5th order depositional sequences (DS1 to DS4) recording two phases: (1) from DS1 to DS3, a tide-dominated ooidic to oobioclastic system with stenohaline faunas developed as a result of a 70 m water level rise. During this period, the TCC developed in a shallow sea with close to normal marine salinity; (2) in depositional sequence 4, a microbialite-dominated platform system developed. This is indicative of a significant environmental change and is attributed to a 30 to 40 m water level fall in the basins under study. These restricted conditions were coeval with intense evaporite deformation and brine recycling. The syn-sedimentary deformation of evaporites had a major impact on platform architecture and carbonate production, affecting the Messinian series throughout south-eastern Spain at the end of the TCC history. At that time, the TCC developed in a lake with fluctuating, brackish- to hypersaline water. These findings suggest a temporary restoration of marine conditions in the western Mediterranean marginal basins due to Atlantic water influxes prompted by a global sea level rise around 5.6 Ma. Whether marine conditions extended to the entire western Mediterranean still needs to be investigated.  相似文献   

Source of parental melts to carbonatites–critical isotopic constraints     

Keith Bell  Antonio Simonetti 《Mineralogy and Petrology》2010,98(1-4):77-89

The restriction of most carbonatites to continental areas raises questions as to whether the parental liquids to carbonatites are generated within the continental lithosphere, or whether they are derived from deeper parts of the mantle with the lithosphere playing a subsidiary, but important, role in trapping volatile-rich melts/fluids. The constraints imposed by both radiogenic and stable isotopic data from carbonatites world-wide are consistent with a sub-lithospheric source for the parental melts, associated with either asthenospheric ‘upwellings’ or more deep-seated, plume-related activity. Crucial evidences that support the generation of carbonated melts from sub-lithospheric mantle are: the petrogenetic and temporal association of carbonatites with large igneous provinces (LIPs; e.g., Deccan, Parana), carbonatites with primitive noble gas isotopic signatures, radiogenic isotope ratios similar to OIBs (i.e. involving HIMU, EM1 and FOZO mantle components), and the uniform, time-integrated Rb/Sr and Sm/Nd development lines for Sr and Nd isotopic data for carbonatites from the Superior Province, Canada, and the Kola Peninsula, Russia. Such findings are difficult to reconcile with a lithospheric origin. Even if a metasomatized lithospheric mantle is considered to be the sole source of carbonated melts, an unknown mantle process is required, large enough to generate widespread, synchronous metasomatism spanning regions in excess of 1?×?10⁶?km².  相似文献   

Portland Cement Stabilization of Soil–Bentonite for Vertical Cutoff Walls Against Diesel Oil Contaminant     

Nilo Cesar Consoli  Karla Salvagni Heineck  J. Antonio H. Carraro 《Geotechnical and Geological Engineering》2010,28(4):361-371

The objective of this study was to evaluate the effect of water-cement ratio and cement content on the hydraulic behavior of soil–cement–bentonite (SCB) and soil–bentonite (SB) mixtures permeated with water and diesel oil, to assist with the design of vertical cutoff walls constructed with those mixtures. The experimental program included unconfined compression tests, hydraulic conductivity tests and X-ray diffraction analysis. The test results indicated changes in hydraulic conductivity take place due to the variation of the water-cement ratio and permeant fluid. The hydraulic conductivity of the SB mixtures permeated with diesel oil was higher than the hydraulic conductivity of the same samples permeated with water. X-ray diffraction analyses suggest that this might be due to the decrease in double layer thickness and increase of seepage pore space imparted by diesel oil permeation. Conversely, Portland cement addition increased the hydraulic conductivity of the SCB specimens permeated with water, whereas subsequent diesel oil permeation reduced the hydraulic conductivity of the SCB specimens; this might be due to the relatively lower impact imparted by diesel permeation on the double layer characteristics of the bentonite stabilized with Portland cement.  相似文献