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71.
Giulio Bigazzi Zehra Yegingil Tuncay Ercan Massimo Oddone Mehmet Özdogan 《Bulletin of Volcanology》1993,55(8):588-595
Twenty obsidian samples from Central and North Anatolia were dated by the fission track method. Split samples analyzed in two different laboratories give consistent results. Data presented refer to three volcanic fields and are summarized as follows: Orta-Sakaeli (Northern Anatolia) obsidians with ages from 21–23 Ma; Göllü Dagi dome complex near Çiftlik (Central anatolia) has given ages between 1.33–0.98 Ma; Acigöl caldera (Central Anatolia) shows three age groups: (1) Eruptions of precaldera (Bogazköy) obsidians with ages 0.18–0.15 Ma; (2) Formation of the large intracaldera dome Kocadag-Taskesiktepe at about 0.08 Ma (uncorrected apparent age of 0.075 Ma); and (3) Acigöl peripheral obsidian domes with plateau ages of 0.020 and 0.019 Ma, and an additional uncorrected age of 0.018 Ma form a distinct age group. This fission track parameters discriminate between the various obsidian sources of prehistoric obsidian artifacts. 相似文献
72.
A Conjugated Toop-Samis-Flood-Grjotheim (CTSFG) model is developed by combining the framework of the Toop-Samis polymeric approach with the Flood-Grjotheim theoretical treatment of silicate melts and slags. Electrically equivalent ion fractions are computed over the appropriate matrixes (anionic and cationic) in a Temkin notation for fused salts, and are used to weigh the contribution of the various disproportionation reactions of type:
73.
Giulio Calamai 《Astrophysics and Space Science》1971,10(1):165-177
A static relativistic theory of the stability of the equilibrium of an isentropic spherically-symmetric star is deduced from the properties of a functionu which is solution of a second-order differential equation, and which is related to the model by means of the formulau = m(v, c)/c, wherem is the mass-energy inside the coordinate volumev and c is the central mass-energy density.Work done in the Laboratorio Astrofisico di Frascati, Roma. 相似文献
74.
The hepatopancreae of the ribbed mussel, Geukensia demissa, and the wedge clam, Rangia cuneata, were examined for their ability to catalyze the reduction/oxidation cycling of the bipyridyl herbicide paraquat. In vitro studies indicated a dose-dependent increase in the rate of superoxide anion (O2−) generation in microsomal fractions supplemented with NADPH; the highest concentration of paraquat employed (4 mm) elicited an 81 % increase in cytochrome c reduction in G. demissa and a 135% increase in R. cuneata. In both .species, cytochrome c reduction was inhibited by the addition of exogenous superoxide dismutase (SOD). For in vivo studies, a single application of paraquat (0·5, 1·0 or 2·0 mm) was added to aerated salt-water aquaria containing G. demissa. Biochemical analyses of antioxidant enzymes, reduced glutathione (GSH) and lipid peroxidation were performed in hepatopancreatic tissue after exposures of 6, 12, 24 and 36 h. Results support the hypotheses that these bivalves can activate redox cycling compounds and demonstrate in vivo responses typical of oxidative stress as observed in other organisms. 相似文献
75.
Lisa R. Bacanskas Julia Whitaker Richard T. Di Giulio 《Marine environmental research》2004,58(2-5):597
A population of killifish (Fundulus heteroclitus) inhabiting a creosote-polluted inlet of the Elizabeth River demonstrates tolerance to the acute toxic effects exerted by contaminated sediments on reference site killifish. Previous data have suggested that upregulated antioxidant defenses contribute to short-term tolerance in killifish exposed to Elizabeth River sediments. This study investigated population differences in antioxidant defenses from wild caught Elizabeth River and reference population killifish in different seasons, and after being held in the laboratory. Parameters measured in the killifish were total glutathione concentrations (GSHT), activities of glutathione reductase (GR), glutathione peroxidase (GPx), and lipid peroxidation (LPO), all in adult hepatic tissues. The Elizabeth River population exhibited greater GSHT, higher GPx activities, and increased LPO as compared to the reference population. Sex specific population differences were also observed in GSHT and GPx. Both populations displayed decreased GSHT and increased GR from early to late summer, as well as after being held in the laboratory. This study indicates that there are many factors that may contribute to differences in levels of antioxidant defenses in addition to exposure to contaminants, including reproductive status and environmental conditions. 相似文献
76.
YueFang Li Zhen Li Ju Huang Giulio Cozzi Clara Turett Carlo Barbante LongFei Xiong 《寒旱区科学》2017,9(6):568-579
Although previous investigations of the trace elements in snow and ice from the Qinghai-Tibetan Plateau obtained interesting information about pollution from human activities on the plateau, most were based on traditional acidification methods. To emphasize the influence of the different sample-preparation methods on the records of trace elements and rare earth elements, snow samples were collected from glaciers on the Qinghai-Tibetan Plateau in China and prepared using two methods: traditional acidification and total digestion. Concentrations of 18 trace elements (Al, Ti, Fe, Rb, Sr, Ba, V, Cr, Mn, Li, Cu, Co, Mo, Cs, Sb, Pb, Tl, and U), along with 14 rare earth elements (REEs: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), Y, and Th in the snow samples, were measured using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The results showed that the mass fraction of the trace elements (defined as ratio of concentration in the acid-leachable fraction to that in the digested sample) such as Mo, Ti, Al, Rb, and V, varied from 0.06 to 0.5. The mass fraction of other trace elements varied from about 0.6 to more than 0.9; those of the REEs, Y, and Th varied from 0.34 to 0.75. Lower mass fractions will lead to an overestimated contribution of other sources, especially human activities, and the underestimated fluxes of these trace elements (especially REEs, Y, and Th, as well as dust) if the REEs are used as the proxy for the crust dust. The two sample-preparation methods exhibited different REE normalized distribution patterns, REE ratios, and provenance-tracing results. The REE normalized distribution patterns and proxies in the digested samples are more reliable and integrated than those found in traditional acidification method for dust-provenance tracing. 相似文献
77.
Modelling the rainfall-induced mobilization of a large slope movement in northern Calabria 总被引:2,自引:1,他引:1
Giovanna Capparelli Pasquale Iaquinta Giulio G. R. Iovine Oreste G. Terranova Pasquale Versace 《Natural Hazards》2012,61(1):247-256
Two recent phases of mobilization of a large, rainfall-induced debris slide are analysed in terms of relationships between
rains and phases of displacement. The first activation at San Rocco (San Benedetto Ullano, Calabria) occurred on 28 January
2009, after extraordinary rains had stricken the region for a couple of months. Detailed geomorphologic field surveys, combined
with measurements of superficial displacements at datum points, were performed to properly recognize the evolution of the
phenomenon. In addition, a real-time control system of rains and superficial displacements measured at extensometers was implemented,
to better analyse the evolution of the phenomenon. In early May 2009, the activity reduced to very slow displacements, persisting
in the same condition for the following 8 months. On 1 February 2010, premonitory signs of a new phase of activation were
noticed, again following 2 months of extraordinary rainfalls. After few days of further precipitations, the middle sector
of the landslide activated since 11 February, disrupting the road network and threatening the major lifelines and some buildings.
A hydrological analysis aimed at simulating the dates of activation and the main phases of acceleration of the phenomenon
was carried out, by calibrating the empirical model FLaIR against the daily rainfalls and the history of known phases of mobilization since 1970. Calibration allowed to successfully
simulate both the cited phases of activity of the San Rocco landslide, by predicting the beginning of the movements as well
as the following paroxysmal stages, as testified by the measurements at datum points and extensometers. The set of parameters
obtained through calibration reflects the influence of both prolonged antecedent rains, and of high-intensity rainfalls of
shorter duration, which slightly preceded the major displacements. Once calibrated the model, a suitable threshold could be
defined, by analysing the trend of the mobility function against the history of activations of the considered slope movement,
and by excluding false alarms. Accordingly, a reliable tool for predicting the phases of activity of a large slope movement
could therefore be obtained. 相似文献
78.
Asymptotic solution for the two-body problem with constant tangential thrust acceleration 总被引:1,自引:0,他引:1
Claudio Bombardelli Giulio Baù Jesus Peláez 《Celestial Mechanics and Dynamical Astronomy》2011,110(3):239-256
An analytical solution of the two body problem perturbed by a constant tangential acceleration is derived with the aid of
perturbation theory. The solution, which is valid for circular and elliptic orbits with generic eccentricity, describes the
instantaneous time variation of all orbital elements. A comparison with high-accuracy numerical results shows that the analytical
method can be effectively applied to multiple-revolution low-thrust orbit transfer around planets and in interplanetary space
with negligible error. 相似文献
79.
Massimo Cerdonio Fabrizio De Marchi Roberto De Pietri Philippe Jetzer Francesco Marzari Giulio Mazzolo Antonello Ortolan Mauro Sereno 《Celestial Mechanics and Dynamical Astronomy》2010,107(1-2):255-264
The analysis of non-radiative sources of static or time-dependent gravitational fields in the Solar System is crucial to accurately estimate the free-fall orbits of the LISA space mission. In particular, we take into account the gravitational effects of Interplanetary Dust (ID) on the spacecraft trajectories. The perturbing gravitational field has been calculated for some ID density distributions that fit the observed zodiacal light. Then we integrated the Gauss planetary equations to get the deviations from the LISA Keplerian orbits around the Sun. This analysis can be eventually extended to Local Dark Matter (LDM), as gravitational fields are expected to be similar for ID and LDM distributions. Under some strong assumptions on the displacement noise at very low frequency, the Doppler data collected during the whole LISA mission could provide upper limits on ID and LDM densities. 相似文献
80.
Marsh soil properties vary drastically across estuarine salinity gradients, which can affect soil strength and, consequently, marsh edge erodibility. Here, we quantify how marsh erosion differs between saline and brackish marshes of the Mississippi Delta. We analyzed long-term (1932–2015) maps of marsh loss and developed an algorithm to distinguish edge erosion from interior loss. We found that the edge erosion rate remains nearly constant at decadal timescales, whereas interior loss varies by more than 100%. On average, roughly half of marsh loss can be attributed to edge erosion, the other half to interior loss. Based on data from 42 cores, brackish marsh soils had a lower bulk density (0.17 vs. 0.27 g/cm3), a higher organic content (43% vs. 26%), a lower shear strength (2.0 vs. 2.5 kPa), and a lower shear strength in the root layer (13.8 vs. 20.7 kPa) than saline marsh soils. We then modified an existing marsh edge erosion model by including a salinity-dependent erodibility. By calibrating the erodibility with the observed retreat rates, we found that the brackish marsh is two to three times more erodible than the saline marshes. Overall, this model advances the ability to simulate estuarine systems as a whole, thus transcending the salinity boundaries often used in compartmentalized marsh models. 相似文献