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F. Rubini C. Giovanardi S. Lorusso F. Leewin F. Bacciotti 《Astrophysics and Space Science》2004,293(1-2):181-187
Modelling the formation of the maximal emission regions in Herbig-Haro flows, the so-called ‘knots,’ remains a main challenge in the investigation of the YSO's outflows. Recent HST images of optical regions reveal their wide morphological variety. Knotty structures and arc-like regions coexist, suggesting that several mechanisms could be responsible for the global scenario. Arc-like emissions are probably due to other mini-working surfaces or non-axially symmetric interaction of the kinking jet matter with the external medium, while knots seen in [SII] are mostly axially symmetric objects and may have a different origin. In this paper we show that a pattern of regularly spaced, knotty emission regions forms in stationary jets, with emissivity and kinematic features consistent with observations. To this purpose, numerical simulations of non-equilibrium, radiative, hydrodynamical jets in axial symmetric geometry have been performed. 相似文献
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Pettine M Casentini B Fazi S Giovanardi F Pagnotta R 《Marine pollution bulletin》2007,54(9):1413-1426
The trophic status classification of coastal waters at the European scale requires the availability of harmonised indicators and procedures. The composite trophic status index (TRIX) provides useful metrics for the assessment of the trophic status of coastal waters. It was originally developed for Italian coastal waters and then applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black and Northern seas). The TRIX index does not fulfil the classification procedure suggested by the WFD for two reasons: (a) it is based on an absolute trophic scale without any normalization to type-specific reference conditions; (b) it makes an ex ante aggregation of biological (Chl-a) and physico-chemical (oxygen, nutrients) quality elements, instead of an ex post integration of separate evaluations of biological and subsequent chemical quality elements. A revisitation of the TRIX index in the light of the European Water Framework Directive (WFD, 2000/60/EC) and new TRIX derived tools are presented in this paper. A number of Italian coastal sites were grouped into different types based on a thorough analysis of their hydro-morphological conditions, and type-specific reference sites were selected. Unscaled TRIX values (UNTRIX) for reference and impacted sites have been calculated and two alternative UNTRIX-based classification procedures are discussed. The proposed procedures, to be validated on a broader scale, provide users with simple tools that give an integrated view of nutrient enrichment and its effects on algal biomass (Chl-a) and on oxygen levels. This trophic evaluation along with phytoplankton indicator species and algal blooms contribute to the comprehensive assessment of phytoplankton, one of the biological quality elements in coastal waters. 相似文献
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Rossella Boscolo Federica Cacciatore Otello Giovanardi 《Marine pollution bulletin》2007,55(10-12):485
Variation of polycyclic aromatic hydrocarbons (PAHs) levels was assessed in Tapes philippinarum from the Lagoon of Venice. Clams were transplanted from a polluted area next to Porto Marghera to two rearing areas of the Southern Lagoon. Analyses of PAHs were made in sediments and clams by GC/MS at first sampling and after 30, 60 and 180 days. Principal component analysis was performed to elucidate bioaccumulation and depuration pattern and input sources. Biota-Sediment-Accumulation-Factor (BSAF) was applied to evaluate the PAHs input sources from sediment. Condition index was calculated to compare the seasonal variation of clam tissue to PAHs levels. To propose results not affected by seasonal changes in flesh weight of clams, the approach based on the calculation of PAHs/SW index was applied. From the results, it was concluded that PAHs/SW index is more recommendable to asses temporal variation of PAHs levels in Manila clams. 相似文献
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This paper presents a detailed discussion of the properties of linear, periodic acoustic waves that propagate vertically in a non-isothermal atmosphere. In order to retain the basic feature of the solar atmosphere we have chosen a temperature profile presenting a minimum. An analytical solution of the problem is possible if T/, being the mean molecular weight, varies parabolically with height. The purpose of this study is to point out the qualitative differences existing between the case treated here and the customary analysis based on a locally isothermal treatment. The computed velocity amplitude and the temperature-perturbation as functions of the wave period exhibit a sharp peak in the region between 180 and 300 s, thus showing the possibility of interpreting the five-minute oscillations as a resonant phenomenon. The propagating or stationary nature of the waves is investigated by a study of the phase of the proposed analytical solution. 相似文献
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Tommaso Giovanardi Maurizio Mazzucchelli Alberto Zanetti Antonio Langone Massimo Tiepolo Anna Cipriani 《Central European Journal of Geosciences》2014,6(4):588-613
Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major- and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif. 相似文献
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The propagation and dissipation of acoustic waves in the lower solar atmosphere is studied. The level of shock formation is computed for various initial conditions. It is shown that shocks form rather low in the atmosphere and that this result does not depend critically on the assumed initial conditions. 相似文献
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The statistical study of the individual light curves of magnetic close binary system AM Herculis obtained in 1978–1988 led to the following conclusions: (a) there is a dependence of the amplitude of brightness variations on the luminosity; (b) the shape of the phased light curves is statistically dependent on the luminosity; (c) the photometric period underwent cyclic changes, the phase of minimum is correlated with luminosity. These results confirm the main observational predictions of the swinging dipole model (Astrophys. Space Sci., 1987,131, 557), but the details are to be investigated during the international programme Polar of coordinated observations of AM Her (27 July–8 August, 1989).Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献