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101.
P. Romano F. Berrilli S. Criscuoli D. Del Moro I. Ermolli F. Giorgi B. Viticchié F. Zuccarello 《Solar physics》2012,280(2):407-416
We present a comparative study of photometric and dynamic properties of photospheric bright points (BPs) observed at the disk centre in the active region (AR) NOAA 10912 and in the quiet Sun. We found that the average concentration of BPs is 54% larger in the AR than in the quiet Sun. We also measure a decrease of the BP concentration and an increase of their size moving away from the AR centre. However, these variations can be ascribed to the variation of the spatial resolution and image quality in the field of view of the AR dataset. We also found that BPs in the quiet Sun are associated with larger downflow motions than those measured within the AR. Finally, from our measurements of contrast and velocity along the line of sight, we deduced that BPs are less bright in high magnetic flux density regions than in quiet regions, due to a lower efficiency of convection in the former regions. 相似文献
102.
In this paper we analyze the eruption of a prominence, characterized by a helical-like structure and by a non-linear rising motion. We approximated the prominence as a cylindrical curved flux tube and estimated the behaviour of several geometrical parameters during the activation and the eruption phases. We determined that, at the onset of the activation, the number N of turns of a magnetic field line over the whole length of the prominence was 5.0, while the value of the ratio P/r
0 between the pitch of the magnetic field lines and the prominence width was 0.45. These values are in good agreement with those predicted by the kink-mode instability. Moreover, we found a decrease of the total twist of one helical thread from 10 to 2 during the prominence eruption, indicating a relaxation of the magnetic field towards a less twisted configuration. We conclude that the prominence was initially destabilized by the kink-mode instability and, not succeeding in finding a new equilibrium configuration, it erupted. 相似文献
103.
Marine sediment contamination of an industrial site at Port of Bagnoli, Gulf of Naples, Southern Italy 总被引:1,自引:0,他引:1
Romano E Ausili A Zharova N Celia Magno M Pavoni B Gabellini M 《Marine pollution bulletin》2004,49(5-6):487-495
For almost one century an important steel plant has been active at the Bagnoli industrial area (Naples, Southern Italy). The environmental survey of near shore and offshore sediments has been carried out as fundamental part of a clean up project. The characteristics of the area, supposed type of pollution, national and international protocols in force were taken into consideration in designing sampling schemes and selecting analytical parameters. For this work, sediment grain size, PAHs, PCBs, trace elements, total hydrocarbons and organic matter were considered. Factor analysis evidenced two main types of pollution in the proximity of the industrial plant, both probably attributable to the activity of the industrial site. The first one, due to Cd, Pb, Zn and Mn seems determined by localised activities at the southern part of the plant. The second one, due to Fe and Mn, appears directly linked to the whole contaminated area. 相似文献
104.
The viscosities of hydrous haplogranitic melts synthesized by hydrothermal fusion at 2 kbar pressure and 800 to 1040° C have
been measured at temperatures just above the glass transition and at a pressure of 1 bar using micropenetration techniques.
The micropenetration viscometry has been performed in the viscosity range of 109 Pa s to 1012 Pa s. The samples ranged in water content from 0.4 to 3.5 wt%. For samples with up to 2.5 wt% H2O, the water contents have been determined using infrared spectroscopy obtained before and after each viscometry experiment
to be constant over the duration of the measurements. Above this water content a measurable loss of water occurs during the
viscometry.
The viscosity data illustrate an extremely nonlinear decrease in viscosity with added water. The viscosity drops drastically
with the addition of 0.5 wt% of water and then shallows out at water contents of 2 wt%. An additional viscosity datum point
obtained from the analysis of fluid inclusions in a water-saturated HPG8 confirms a near invariance of the viscosity with
the addition of water between 2 and 6 wt%. These measurements may be compared directly with the data of Hess et al. (1995,
in press) for the effects of excess alkali and alkaline earth oxides on the viscosity of HPG8 (also obtained at 1 bar). The
viscosity of the melts, compared on an equivalent molar basis, increases in the order H2O<(Li2O<Na2O< K2O<Rb2O,Cs2O<BaO<SrO<CaO<MgO< BeO). The extraordinary decrease in melt viscosity with added water is poorly reproduced by the calculation
scheme of Shaw (1972) for the range of water contents investigated here. The speciation of water in the quenched glasses can
be used to quantify the dependence of the viscosity on hydroxyl content. Considering only the hydroxyl groups as active fluidizers
in the hydrous melts the nonlinearity of the viscosity decrease and the difference with the effects of the alkali oxides becomes
larger. Consequences for degassing calcalkaline rhyolite are discussed.
Received: 17 August 1995/Accepted: 8 January 1996 相似文献
105.
R. J. Stevenson N. S. Bagdassarov D. B. Dingwell C. Romano 《Bulletin of Volcanology》1998,60(2):89-97
As a major volatile in volcanic systems, water has a significant influence on the rheological properties of silicic magmas.
This is especially so at minor water contents relevant to the emplacement of silicic lavas. To investigate the influence of
water on the viscosity of natural rhyolitic obsidians, a novel strategy has been adopted employing parallel-plate and micropenetration
techniques. Viscosities have been determined on three types of material: (a) raw water-bearing obsidians; (b) remelted (1650 °C,
1 atm) degassed glasses of the obsidians; and (c) hydrothermally hydrated (1300 °C, 3 kbar) obsidians. Ten natural rhyolitic
obsidians (peraluminous, calc-alkaline and peralkaline) were employed: seven originated from lava flows and contained <0.2 wt.%
H2O, two samples were F-rich from pyroclastic successions, and one was an obsidian cobble with 1.5 wt.% water also associated
with pyroclastic units. Melt compositions and water contents were stable during viscometry. The measured decreases in activation
energies of viscous flow and viscosity with small amounts of water are much greater than the Shaw calculation scheme predicts.
In addition, a marked non-linear decrease in η exists with increasing water content. In contrast to the case for peralkaline
rhyolites, 0.1–0.2 wt.% water decreases activation energies significantly (up to 30%) for calc-alkaline compositions. These
results have important implications for the ease of near-surface degassing of silicic magmas during emplacement and permit
the testing of calculational models for viscosity, largely based on synthetic systems.
Received: 7 July 1997 / Accepted: 6 April 1998 相似文献
106.
P. Benon F. Blanc B. Bourgade P. David R. Kantin M. Leveau J.-C. Romano D. Sautriot 《Marine pollution bulletin》1978,9(3):71-75
Measurements of copper, lead, cadmium and zinc were determined using the differential pulse anodic stripping voltametry technique in a marine industrialized area, the Gulf of Fos, near Marseilles. Results show an important contamination of the whole area, with particularly high values near the coast. Comparing our results with those of the literature, we see that the Gulf of Fos is probably one of the most polluted areas in Europe. 相似文献
107.
Geochemistry of tholeiites from Lanai,Hawaii 总被引:3,自引:0,他引:3
H. B. West M. O. Garcia D. C. Gerlach J. Romano 《Contributions to Mineralogy and Petrology》1992,112(4):520-542
Lanai is the third smallest of the fifteen principal subaerial shield volcanoes of the Hawaiian hotspot. This volcano apparently became extinct during the shield-building stage of volcanism, as shown by the absence of both alkalic cap and post-erosional lavas. Major and trace element analyses of 22 new samples collected primarily from 3 stratigraphic sections show that Lanai tholeiites span a large range in composition. Some Lanai lavas are unique geochemically among Hawaiian tholeiites in having the lowest abundances of incompatible trace elements of any Hawaiian lavas and well-developed positive Eu anomalies. The geochemical characteristics of these low-abundance Lanai tholeiites are not the result of alteration, differences in mantle source modal mineralogy, the presence of residual accessory mantle phases or fractional crystallization of such phases, assimilation of depleted [MORB] wall-rock, or accumulation/resorption of phenocrysts or xenocrysts. Incompatible trace element ratios (e.g., Nb/La, Nb/Th, La/Th, La/Hf, Ce/Pb) in Lanai tholeiites span considerable ranges and form coherent trends with each other and with absolute abundances of these elements. Large variations in La/Sm, La/Yb, and absolute REE abundances at constant MgO suggest that Lanai tholeiites formed by variable amounts of partial melting. However, large ranges in incompatible element ratios cannot be explained solely by variations in partial melting of a geochemically homogeneous source, but must reflect geochemical heterogeneities in the Lanai source. Partial melting modeling indicates that the mixed Lanai source is probably LREE-enriched [i.e., (La/Yb)CN>1]. One component in the Lanai source, exemplified by the low-abundance tholeiites, has markedly lower REE/HFSE, Th/HFSE, alkali/HFSE, and Ce/Pb ratios than other Lanai or Hawaiian tholeiites and may indicate the presence of recycled residual subduction zone materials in the Hawaiian plume source. The positive Eu anomalies that characterize the low-abundance Lanai tholeiites are not the result of plagioclase accumulation or assimilation but are a feature of this source component. Progressive temporal geochemical variations in Lanai tholeiites from 2 stratigraphic sections indicate that the source composition of these lavas probably evolved over time. This change could have resulted from a progressive decrease in the extent of partial melting of the Lanai source. The compositional variability of Lanai tholeiites suggests that geochemical heterogeneities in their source are larger than the scale of partial melting. Lanai tholeiites could not have formed by smaller degrees of partial melting of plume material than did the larger-volume Hawaiian shields. Therefore, volume differences between Hawaiian shields must be controlled primarily by differences in the volume of supplied plume material rather than by differences in the degree of partial melting. The premature cessation of eruptive activity at Lanai may be attributed to relatively large degrees of partial melting of a small plume. 相似文献
108.
E. Paris D. B. Dingwell F. A. Seifert A. Mottana C. Romano 《Physics and Chemistry of Minerals》1994,21(8):510-515
The effect of pressure on titanium coordination in glasses, with composition K2TiSi4O11, quenched isobarically from liquids equilibrated at high pressure (5, 10, 15, 20, 25, 30 kbar respectively) and T=1600° C has been investigated by X-ray absorption spectroscopy (XAS). The XANES spectra collected at the Ti K-edge clearly show a variation with pressure that is related to changes in the geometrical environment around the Ti atoms. By comparison with spectra of standard materials, the XANES spectra of the glasses suggest a relatively low average coordination number (near 5) in samples quenched at low pressure and a higher coordination number (near 6) in samples quenched from the highest pressure. The combination of XANES data with density and compressibility measurements supports the idea that a mixture of 6- and lower coordinated (4- and/ or 5-coordinated) Ti geometries are present in the 1 bar glass, and an increasing proportion of 6-coordinated Ti occurs in the glasses synthesized at progressively higher pressures. 相似文献
109.
Nicola Masini Luigi Capozzoli Gerardo Romano Dominika Sieczkowska Maria Sileo Jose Bastante Fernando Astete Victoria Mariusz Ziolkowski Rosa Lasaponara 《Surveys in Geophysics》2018,39(6):1239-1262
Even if, in recent decades, the use of remote sensing technologies (from satellite, aerial and ground) for archaeology is stepping into its golden age, in Southern America geophysics for preventive archaeology is more recent and less used than in Europe, Central America and Middle East. In this paper, we provide a brief overview and show the preliminary results obtained from the investigations conducted in Chachabamba (Peru). The archaeological area is located on a strategic terrace overlooking three Inca roads, which served the most important ceremonial centres (including Machu Picchu) of the Urubamba Valley also known as the Sacred Valley. In particular, Chachabamba investigations were conducted with two principal aims: (1) to give new impetus to archaeological research with targeted investigations aimed at improving and completing the site’s knowledge framework; (2) to experiment and validate an archaeogeophysical approach to be reapplied in other sites of the Urubamba valley, including Machu Picchu, having similar characteristics as those found in Chachabamba. 相似文献
110.
Nathaniel Bensoussan Jean-Claude Romano Jean-Georges Harmelin Joaquim Garrabou 《Estuarine, Coastal and Shelf Science》2010
In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature (T) time series obtained during 1999–2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Réserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11–13 °C, and summer T mainly around 22–24 °C near surface to 18–20 °C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999, 2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1–2 °C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is extremely likely. In such context, the acquisition of dedicated high resolution T series proves to be crucial for increasing our detection, understanding and forecasting abilities. 相似文献