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11.
M. Cortese E. Perozzi M. Micheli B. Borgia E. Dotto E. Mazzotta Epifani S. Ieva M. A. Barucci D. Perna 《Meteoritics & planetary science》2017,52(3):522-531
The present near‐Earth asteroids (NEA) discovery rate has surpassed 1500 objects per year, thus calling for extensive observation campaigns devoted to physical characterization in order to define successful mitigation strategies in case of possible impactors. A tool is presented which, through a prioritization algorithm, aims to optimize the planning and the execution of NEA physical observations. Two ranking criteria are introduced, Importance and Urgency, accounting for the need of satisfying the two basic observational modes for physical characterization, that is, rapid response and large observing programs, aimed at selecting targets for exploration and mitigation space missions. The resulting tool generates a daily table of observable targets and it can also be run as a stand‐alone tool in order to provide future observing opportunities at a specific date of interest. It has been developed and implemented within the framework of the NEOShield‐2 EU/HORIZON 2020 Project; the output of the prioritization algorithm is publicly available, in tabular format, on the NEOShield‐2 NEO Properties Portal ( http://www.neoshield.net/the-neoshield-project/project-activities/neo-properties-portal ), reachable from the main page of the Project website ( http://www.neoshield.eu ). 相似文献
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Water and Iron effect on the P-T-x coordinates of the 410-km discontinuity in the Earth upper mantle
Fiorenza Deon Monika Koch-Müller Dieter Rhede Richard Wirth 《Contributions to Mineralogy and Petrology》2011,161(4):653-666
We performed multi-anvil experiments in the system MgO-SiO2 ± H2O at 13.0–13.7 GPa and 1,025–1,300°C and in the system MgO-FeO-SiO2 ± H2O, under reducing conditions, at 11.0–12.7 GPa and 1,200°C, to depict the effect of H2O on the P-T-x coordinates of the 410-km discontinuity, i.e. the olivine–wadsleyite phase boundary. The charges were investigated
with Electron Microprobe (EMP), Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Secondary Ion Mass Spectrometry
(SIMS) and Electron Energy Loss Spectroscopy (EELS). We observe in the MgO-SiO2-H2O system at 1,200°C a 0.6 GPa shift of the phase boundary to lower pressure compared to dry conditions, due to the stronger
water fractionation into wadsleyite (wad) rather than in olivine (ol). In the MgO-FeO-SiO2-H2O system, we reproduced the triple point, i.e. observed coexisting hydrous ol, wad and ringwoodite (ring). SIMS H quantifications
provided partitioning coefficients for water:
D\textwad/ol\textwater D_{\text{wad/ol}}^{\text{water}} ~ 3.7(5) and
D\textring/ol\textwater D_{\text{ring/ol}}^{\text{water}} ~ 1.5(2) and
D\textwad/ring\textwater D_{\text{wad/ring}}^{\text{water}} ~ 2.5(5). For a bulk composition of x
Fe = 0.1, our data indicate only a slight difference in the width of the loop of the two phase field ol–wad under hydrous conditions
compared to dry conditions, i.e. no broadening with respect to composition but a shift to lower pressures. For bulk compositions
of x
Fe > 0.2, i.e. in regions where wad–ring and ol–ring coexist, we observe, however, an unexpected broadening of the loops with
a shift to higher iron contents. In total, the stability field of hydrous wad expands in both directions, to lower and higher
pressures. Fe3+ concentrations as determined by EELS are very low and are expected to play no role in the broadening of the loops. 相似文献
14.
Fabrizio Bernardi Marco Micheli David J. Tholen 《Meteoritics & planetary science》2009,44(12):1849-1852
Abstract— We present results from an observing campaign of 25143 Itokawa performed with the 2.2 m telescope of the University of Hawai'i between November 2000 and September 2001. The main goal of this paper is to determine the absolute magnitude H and the slope parameter G of the phase function with high accuracy for use in determining the geometric albedo of Itokawa. We found a value of H = 19.40 and a value of G = 0.21. 相似文献
15.
We measured the effect of wet meadow vegetation on the bank strength and failure mechanics of a meandering montane meadow stream, the South Fork of the Kern River at Monache Meadow, in California's Sierra Nevada. Streambanks colonized by ‘wet’ graminoid meadow vegetation were on average five times stronger than those colonized by ‘dry’ xeric meadow and scrub vegetation. Our measurements show that strength is correlated with vegetation density indicators, including stem counts, standing biomass per unit area, and the ratio of root mass to soil mass. Rushes appear better than sedges at stabilizing coarse bar surfaces, while sedges are far more effective at stabilizing actively eroding cut banks. Wet meadow floodplain vegetation creates a composite cut bank configuration (a cohesive layer overlying cohesionless materials) that erodes via cantilever failure. Field measurements and a geotechnical model of cantilever stability show that by increasing bank strength, wet meadow vegetation increases the thickness, width, and cohesiveness of a bank cantilever, which, in turn, increases the amount of time required to undermine, detach, and remove bank failure blocks. At Monache Meadow, it takes approximately four years to produce and remove a 1 m wide wet meadow bank block. Wet meadow vegetation limits bank migration rates by increasing bank strength, altering bank failure modes, and reducing bank failure frequency. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
16.
Mengyan Li Patrick Conlon Stephanie Fiorenza Rock J. Vitale Pedro J.J. Alvarez 《Ground Water Monitoring & Remediation》2011,31(4):70-76
An innovative micro‐extraction of aqueous samples coupled with gas chromatography/mass spectrometry in selected ion‐monitoring mode (GC/MS‐SIM) was developed to selectively analyze for 1,4‐dioxane with low part‐per‐billion detection sensitivity. Recoveries of 1,4‐dioxane ranged from 93% to 117% for both spiked laboratory reagent water and natural groundwater matrices, the later having elevated organic carbon content (8.34 ± 0.31 mg/L as total organic carbon). We observed that freezing the aqueous sample along with the extraction solvent enhanced the extraction efficiency, minimized physical interferences, and improved sensitivity resulting in a limit of detection for 1,4‐dioxane to approximately 1.6 μg/L. This method substantially reduces the labor, time, reagents and cost, and uses instruments that are commonly found in analytical laboratories. This method requires a relatively small sample volume (200 μL), and can be considered a green analytical method as it minimizes the use of toxic solvents and the associated laboratory wastes. 相似文献
17.
Stress-induced proton disorder in hydrous ringwoodite 总被引：1，自引：1，他引：0
Monika Koch-Müller Sergio Speziale Fiorenza Deon Maria Mrosko Ulrich Schade 《Physics and Chemistry of Minerals》2011,38(1):65-73
We have measured in situ high-pressure IR absorption of synthetic hydrous (MgxFe1−x)2SiO4 ringwoodites (x = 0.00 to 0.61) up to a maximum pressure of 30 GPa. In our study, we combined the megabar-type diamond-anvil cell (DAC) with
conventional and synchrotron FTIR spectroscopy. The high-pressure measurements were performed in three different pressure-transmitting
environments: (1) CsI powder, (2) cryogenically loaded liquid argon, and (3) cryogenically loaded liquid argon annealed at
8.6 GPa at temperature of 120°C before further pressure increase. Between 10 and 12 GPa, all the samples loaded with methods
(1) and (2), independent on composition, showed a sudden disappearance of the prominent OH-stretching feature and simultaneous
discontinuities and/or changes in the pressure dependence of lattice vibrations compared with spectra of samples loaded with
method (3). In experiments performed with method (3) the OH-stretching vibrations as well as lattice vibrations could be observed
up to 30 GPa and their pressure behavior (dν/dP) can well be described by linear fits. Molecular vibrations, such as the OH stretching, are sensitive to non-hydrostatic
conditions, especially in minerals with highly symmetric structures. We interpret the disappearance of the OH bands using
methods (1) and (2) as a stress-induced proton disordering in hydrous ringwoodite. Our results confirm that argon pressure
medium produces strongly non-hydrostatic conditions comparable to CsI or KBr, if it is not thermally annealed at pressures
above 8 GPa. Our results suggest that the transition observed in hydrous Mg-ringwoodite end member is not present in compositions
containing Fe. By comparing the behavior of samples compressed in different environments, we suggest that sudden disappearance
of the OH-stretching band in hydrous ringwoodite could be driven by deterioration of the quasi-hydrostatic stress condition
instead of a pressure-induced effect. 相似文献
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Daniel Silva Leite Leonardo Sandrini-Neto Manuela Zeglin Camargo Micheli Cristina Thomas Paulo C. Lana 《Marine pollution bulletin》2014
This study assesses through a multiple before-after-control-impact (MBACI) design the effects of diesel oil on the structure of nematode assemblages in unvegetated tidal flats of a subtropical estuary. Oil-exposed treatments were contrasted with controls for a duration of four successive days before and after an experimental spill in three distinct areas of the Paranaguá Estuarine Complex (Southern Brazil). No significant differences were observed in nematode total density, number of taxa and the overall assemblage structure between the control and impact treatments from before to after the experimental spill. This reinforces the idea that, despite being good indicators of environmental stress, free-living marine nematodes are able to tolerate low concentrations of hydrocarbons and to survive in moderately contaminated areas. We also show that robust experimental designs are useful to avoid confounding expected natural variability with the effects of a mild impact. 相似文献
20.
Marine Protected Areas in the Mediterranean Sea: Objectives, Effectiveness and Monitoring 总被引：1，自引：0，他引：1
Simonetta Fraschetti Antonio Terlizzi Fiorenza Micheli Lisandro Benedetti-Cecchi Ferdinando Boero 《Marine Ecology》2002,23(S1):190-200
Abstract. The number of Marine Protected Areas (MPAs) is continuously increasing worldwide because of the increasing recognition of the profound effects that humans can have on marine systems. A large body of literature deals with marine reserves and their potential as conservation and management tools. In several cases, empirical evidence demonstrated that reserves can harbour greater diversity, higher abundance, and larger organisms than unprotected areas. In most cases, however, reserve design and site selection involved little scientific justification, with no direct test of most of the mechanisms assumed to work in a marine reserve. Field investigations of subtidal marine reserves are generally confounded by intrinsic ecological differences between sites investigated inside and outside reserves, by a lack of site and reserve replication, or by the absence of information about the biota before reserve establishment. This is particularly true in the Mediterranean Sea. The aim of this paper is to show that, at least in the Mediterranean basin, the effectiveness of MPAs has been rarely demonstrated because of lack of appropriate sampling designs. An MPA can be considered as a zone subjected to human impact, presumably a positive one. As a consequence, we propose the use of experimental procedures generally utilised for detecting environmental impacts. 相似文献