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排序方式: 共有69条查询结果,搜索用时 15 毫秒
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Accoroni S Romagnoli T Colombo F Pennesi C Di Camillo CG Marini M Battocchi C Ciminiello P Dell'Aversano C Dello Iacovo E Fattorusso E Tartaglione L Penna A Totti C 《Marine pollution bulletin》2011,62(11):2512-2519
Intense blooms of the benthic dinoflagellate Ostreopsis cf. ovata have occurred in the northern Adriatic Sea since 2006. These blooms are associated with noxious effects on human health and with the mortality of benthic organisms because of the production of palytoxin-like compounds. The O. cf. ovata bloom and its relationships with nutrient concentrations at two stations on the Conero Riviera (northern Adriatic Sea) were investigated in the summer of 2009. O. cf. ovata developed from August to November, with the highest abundances in September (1.3 × 106 cells g−1 fw corresponding to 63.8 × 103 cells cm−2). The presence of the single O. cf. ovata genotype was confirmed by a PCR assay. Bloom developed when the seawater temperature was decreasing. Nutrient concentrations did not seem to affect bloom dynamics. Toxin analysis performed by high resolution liquid chromatography-mass spectrometry revealed a high total toxin content (up to 75 pg cell−1), including putative palytoxin and all the ovatoxins known so far. 相似文献
3.
Armando Manzali Andrea De Luca Patrizia A. Caraveo 《Astrophysics and Space Science》2007,308(1-4):601-605
We report on our analysis of two XMM-Newton observations of the Vela pulsar performed in December 2000 (total exposure time:
96.5 ks). We succeeded in resolving the pulsar spectrum from the surrounding bright nebular emission taking advantage both
of the accurate calibration of the EPIC point spread function and of the Chandra/HRC surface brightness map of the nebula.
This made it possible to assess to pulsar spectral shape disentangling its thermal and non-thermal components. Exploiting
the photon harvest, we have also been able to perform a phase-resolved study of the pulsar emission.
相似文献
4.
Colucci?SimoneEmail authorView authors OrcID profile de’?Michieli?Vitturi?Mattia Landi?Patrizia 《Contributions to Mineralogy and Petrology》2017,172(11-12):100
Nucleation and growth of crystals, and the resulting crystal size distribution, play a fundamental role in controlling the physical properties of magmas and consequently the dynamics of the eruptions. In the past decades, laboratory experiments demonstrated that size and shape of crystals strongly control the physical properties of magma and lava. Additionally, natural and experimental samples are usually characterized in terms of their crystal size distribution to link it with physical processes that are not directly observable, such as cooling or decompression mechanisms. In this paper, we present CrystalMoM, a new predictive model, based on the quadrature-based method of moments, developed for studying the kinetic of crystallization in volcanic systems. The quadrature-based method of moments, well established in the field of chemical engineering, represents a mesoscale modelling approach that rigorously simulates the space–time evolution of a distribution of particles, by considering its moments. The method is applied here, for the first time, for studying the equilibrium/disequilibrium crystallization in magma, modelling the temporal evolution of the moments of a crystal size distribution. The model, verified against numerical and experimental data, represents a valuable tool to infer the cooling and decompression rates from the crystal size distribution observed in natural samples. 相似文献
5.
On 28 December 2002, new vents opened on the flanks of Stromboli, just below the summit craters, interrupting the persistent
activity of the volcano with a 7-month-long effusive eruption. We here report on the plagioclase size distribution (PlgSD)
in lava samples collected following the chronology of the 2002–2003 eruption. Data reveal a linear PlgSD similar to that found
in samples of normal Stromboli activity, indicating that the switch from Strombolian explosive to effusive activity is not
associated with changes in texture. Nevertheless, the crystal size distribution slopes and intercepts exhibit slight sinusoidal
temporal variations that are here ascribed to a magma supply mechanism able to induce “resonance” in the crystal size distribution,
with an amplitude that depends on the supply rate. 相似文献
6.
Rosolino Cirrincione Eugenio Fazio Patrizia Fiannacca Gaetano Ortolano Rosalda Punturo 《Pure and Applied Geophysics》2009,166(5-7):995-1010
In order to reveal any correlation between the preferred orientation of quartz and progressive intensity of strain, a suite of deformed leucogneiss collected within a ductile shear zone outcropping in Calabria (southern Italy) was investigated. Based on the microstructural approach and matrix-clast relationships, the method applied here may be useful for appraising the connection between deformation mechanisms of constituent minerals and bulk textural properties of naturally sheared rocks. Accordingly, quartz c-axis orientation patterns were determined by image-assisted analysis. Results revealed a correlation between finite strain and textural features: As strain increases, the matrix develops at the expense of the clast counterpart, which is instead progressively reduced in both size and amount. 相似文献
7.
Marina Manca Patrizia Comoli Teresa Spagnuolo 《Aquatic Sciences - Research Across Boundaries》1997,59(1):48-56
We compared three methods for calculating the standing stock biomass ofDaphnia hyalina galeata population in Lago Maggiore during a single year. We applied body length/carbon regression equations (LCR) obtained under
controlled laboratory conditions and directly from field data on carbon and body length to field data on length-specific abundance.
Laboratory-derived equations satisfactorily described our field estimates of length-specific carbon content in spring. As
the length-standardized carbon content decreased exponentially along the season, we included time of the year as an auxiliary
variable, and tested whether it affected slope, intercept or both. The decrease had no effect on slope but reduced the intercept
of the LCR. We also calculated biomass, using a single mean value from the literature. By comparing the results with those
obtained by simple conversion of individuals number into carbon we might discriminate between the effect of changes in the
size frequency distribution of the population and the decrease with time of the length-standardized carbon content. Although
we tested the different models for non-ovigerous females, the results did not change when we included also data on females
with eggs in the first three developmental stages, whereas they changed substantially when we included females with embryos.
We formulate two hypotheses to explain this result and discuss possible implications for the calculation of the standing stock
biomass ofDaphnia population. 相似文献
8.
We present a portable elevator-based facility for measuring \(\hbox {CO}_{2}\), water vapour, temperature and wind-speed profiles between the soil surface and the atmospheric surface layer above crop canopies. The end of a tube connected to a closed-path gas analyzer is continuously moved up and down over the profile range (in our case, approximately 2 m) while concentrations are logged at a frequency of \(20 \hbox { s}^{-1}\). Using campaign measurements in winter wheat, winter barley and a catch crop mixture (spring 2015 to autumn 2016) during different stages of crop development and different times of the day, we demonstrate a simple approach to correct for time lags, and the resulting profiles of 30-min mean mole fractions of \(\hbox {CO}_{2}\) and \(\hbox {H}_{2}\hbox {O}\) over height increments of 0.025 m. The profiles clearly show the effects of soil respiration and photosynthetic carbon assimilation, varying both during the diurnal cycle and during the growing season. Profiles of temperature and wind speed are based on a ventilated finewire thermocouple and a hot-wire anemometer, respectively. Measurements over bare soil and a short plant canopy were analyzed in the framework of Monin–Obukhov similarity theory to check the validity of the measurements and raw-data-processing approach. Derived fluxes of \(\hbox {CO}_{2}\), latent and sensible heat and momentum show good agreement with eddy-covariance measurements. 相似文献
9.
Patrizia Köpfli Lorenz M. Grämiger Jeffrey R. Moore Christof Vockenhuber Susan Ivy-Ochs 《Swiss Journal of Geoscience》2018,111(1-2):205-219
Landslide deposits dam Lake Oeschinen (Oeschinensee), located above Kandersteg, Switzerland. However, past confusion differentiating deposits of multiple landslide events has confounded efforts to quantify the volume, age, and failure dynamics of the Oeschinensee rock avalanche. Here we combine field and remote mapping, topographic reconstruction, cosmogenic surface exposure dating, and numerical runout modeling to quantify salient parameters of the event. Differences in boulder lithology and deposit morphology reveal that the landslide body damming Oeschinensee consists of debris from both an older rock avalanche, possibly Kandertal, as well as the Oeschinensee rock avalanche. We distinguish a source volume for the Oeschinensee event of 37 Mm3, resulting in an estimated deposit volume of 46 Mm3, smaller than previous estimates that included portions of the Kandertal mass. Runout modeling revealed peak and average rock avalanche velocities of 65 and 45 m/s, respectively, and support a single-event failure scenario. 36Cl surface exposure dating of deposited boulders indicates a mean age for the rock avalanche of 2.3 ± 0.2 kyr. This age coincides with the timing of a paleo-seismic event identified from lacustrine sediments in Swiss lakes, suggesting an earthquake trigger. Our results help clarify the hazard and geomorphic effects of rare, large rock avalanches in alpine settings. 相似文献
10.
Morgane Surdez Julien Beck Dimitris Sakellariou Hendrik Vogel Patrizia Birchler Emery Despina Koutsoumba Flavio S. Anselmetti 《Swiss Journal of Geoscience》2018,111(3):573-588
Franchthi Cave, bordering Kiladha Bay, in Greece, is a key archaeological site, due to its long occupation time, from?~?40,000 to?~?5000 year BP. To date, no clear evidence of Neolithic human dwellings in the cave was found, supporting the assumption that Neolithic people may have built a village where there is now Kiladha Bay. During the Neolithic period/Early Holocene, wide areas of the bay were indeed emerged above sea level. Bathymetric and seismic data identified a terrace incised by a valley in?~?1 to 2 m sediment depth. Eight sediment cores, up to 6.3-m-long, were retrieved and analysed using petrophysical, sedimentological, geochemical, and chronostratigraphic methods. The longest core extends into the exposure surface, consisting of a layer of carbonate rubble in a finer matrix, representing weathering processes. Dated organic remains place this unit at?~?8500 cal year BP. It is overlain by stiff silty mud representing an estuarine environment. This mud is capped by reduced sediments with roots marking an exposure surface. A shell-layer, dated to?~?6300 cal year BP, overlies this terrestrial sequence, reflecting the marine transgression. This layer occurs at 10.8 mbsl, 7.7 m deeper than the global sea level at that time, suggesting tectonic subsidence in the area. It is overlain by finer-grained marine carbonate-rich sediments. The top of the core shows traces of eutrophication, pebbles and marine shells, all likely a result of modern anthropogenic processes. These results are interpreted in the context of human occupation: the exposed surface contains pottery sherds, one dating to the Early to Middle Neolithic period, indicating that Neolithic people were present in this dynamic landscape interacting with a migrating coastline. Even if the artefacts are isolated, future investigations of the submerged landscape off Franchthi Cave might lead to the discovery of a Neolithic village, which eventually became buried under marine sediments. 相似文献