Estimate of the Transition Value of Librational Invariant Curves     

Alessandra Celletti  Gabriella Della Penna  Claude Froeschlé 《Celestial Mechanics and Dynamical Astronomy》2002,83(1-4):257-274

We investigate the break-down threshold of librational invariant curves. As a model problem, we consider a variant of a mapping introduced by M. Hénon, which well describes the dynamics of librational motions surrounding a stable invariant point. We verify in concrete examples the applicability of Greene's method, by computing the instability transition values of a sequence of periodic orbits approaching an invariant curve with fixed noble frequency. However, this method requires the knowledge of the location of the periodic orbits within a very good approximation. This task appears to be difficult to realize for a libration regime, due to the different topology of the phase space. To compute the break-down threshold, we tried an alternative method very easy to implement, based on the computation of the fast Lyapunov indicators and frequency analysis. Such technique does not require the knowledge of the periodic orbits, but again, it appears very difficult to have a precision better than Greene's method for the computation of the critical parameter.  相似文献   

全球寒武-奥陶系界线划分对比的标志和纽带——中国北方小阳桥剖面的启示     

汪啸风  STOUGE Svend  王传尚  MALETZ J?rg  阎春波  BAGNOLI Gabriella  祁玉平  RAEVSKAYA Elena G 《华南地质与矿产》2022,38(1):1-26

根据对中国小阳桥剖面高精度生物、层序、化学和磁性地层学综合研究的新成果及其与绿岬全球界线层型剖面(GSSP)的详细对比,进一步厘定了加拿大绿岬"金钉子"剖面所定义的奥陶系底界划分与对比的标志,并指出:(1)与所定义的全球标准奥陶系底界相当的界线位于小阳桥剖面块状叠层石灰岩之上19.9 m处的薄层纹层灰岩中(BD-24层...  相似文献   

Exposure of the clam Tapes philippinarum to 4-nonylphenol: changes in anti-oxidant enzyme activities and re-burrowing capability     

Matozzo V  Ballarin L  Marin MG 《Marine pollution bulletin》2004,48(5-6):563-571

The effects of 4-nonylphenol on anti-oxidant enzyme (superoxide dismutase and catalase) activity in both gills and digestive gland and re-burrowing capability of the clam Tapes philippinarum were investigated after 7 days' exposure to various sublethal concentrations of nonylphenol (NP). NP caused a significant decrease in superoxide dismutase activity in both tissues from the lowest concentration tested, whereas no significant alteration with respect to controls was observed in catalase activity. NP effects on re-burrowing of clams were evaluated in two experiments. In the first, clams exposed to the highest NP concentrations showed a marked delay in re-burrowing 48 h after the end of exposure. Modifications in normal burrowing behaviour were also observed, suggesting that NP acts via narcosis and/or neurotoxic mechanisms. In the second experiment, the elapsed time for 50% of the exposed clams to re-burrow into the sediment (RT(50)) was also calculated in a 24-h re-burrowing response test. At the highest NP concentrations, it was not possible to estimate RT(50) values, as the percentage of clams showing complete burial was less than 50%. The present study demonstrates that NP causes oxidative stress by inhibiting superoxide dismutase activity and greatly affects the re-burrowing capability of T. philippinarum, even at environmentally realistic concentrations.  相似文献   

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances     

Gabriella Sátori  Earle Williams  Colin Price  Robert Boldi  Alexander Koloskov  Yuri Yampolski  Anirban Guha  Veronika Barta 《Surveys in Geophysics》2016,37(4):757-789

Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower ionosphere (Schumann in Z Naturforsch A 7:6627–6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth’s SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth–ionosphere cavity.  相似文献   

Large wood transport modelling by a coupled Eulerian–Lagrangian approach     

Persi  Elisabetta  Petaccia  Gabriella  Sibilla  Stefano 《Natural Hazards》2017,85(1):59-86

The fractal characteristics of the ultra-low-frequency (ULF) magnetic field variations recorded prior to the Tohoku earthquake (EQ) with M _W = 9 which happened on 11 March 2011 are studied in this article with the use of detrended fluctuation analysis and Higuchi fractal dimension algorithm. In the specific study, we use for our calculations only nighttime (LT = 3 a.m. ± 2 h) data because of their lowest contamination by industrial noise. A key aspect of our analysis is the investigation about any possible correlation of the ULF magnetic field variations or their calculated fractal characteristics with geomagnetic indices. Different preprocessing approaches are examined aiming at the minimization of any possible influences from global phenomena in the fractal analysis results, while in the same time retaining the scale-invariant character of ULF magnetic field variations after preprocessing. The obtained fractal analysis results imply locally driven change in the fractal characteristics of the ULF data prior to the Tohoku EQ, which is compatible with the change that has been reported prior to other large EQs.  相似文献   

Genesis of garnets in some magmatic rocks from Hungary     

Dr. A. Embey-Isztin  Dr. Gabriella Noske-Fazekas  Doc. Dr. G. Kurat  Dr. F. Brandstätter 《Mineralogy and Petrology》1985,34(1):49-66

Summary Garnets from Miocene di-normative, medium-K andesites as well as from a Mesozoic fine-grained albite granite have been petrologically investigated. The chemical compositions of the garnets from the andesites as determined by electron microprobe (alm 57–65,pyr 14–22,gross 10–24,spess 2–5, -all in mol.-%) are compatible with the garnets being high pressure megacrysts. Garnets from the granite (alm 71–74,pyr 12–18,gross 3.5–5.5,spess 5.6–11) apparently crystallized in a low pressure environment. They are believed to have formed in an autometasomatic event.

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Die Genese von Granaten in einigen magmatischen Gesteinen Ungarns

Zusammenfassung Granate aus miozänen di-normativen, medium-K Andesiten und aus einem mesozoischen feinkörnigen Albit-Granit wurden petrologisch untersucht. Die chemische Zusammensetzung der Granate, (Alm 57–65,Pyr 14–22,Gross 10–24,Spess 2–5 Mol.-%), gemessen mittels Elektronenstrahl-Mikrosonde, macht es wahrscheinlich, daß diese Granate Hochdruck-Megakristalle sind. Die Granate im Granit (Alm 71–74,Pyr 12–18,Gross 3,5–5,5,Spess 5,6–11) kristallisierten bei niedrigen Drücken und sind wahrscheinlich das Produkt autometasomatischer Vorgänge.

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With 7 Figures  相似文献   

Charge distribution from least-energy structure in Ca - Mg orthosilicates     

Michele Catti  Gabriella Ivaldi 《Physics and Chemistry of Minerals》1983,9(3-4):160-166

Calcium-olivine, γ-Ca₂SiO₄, larnite, β-Ca₂SiO₄, merwinite, Ca₃Mg(SiO₄)₂, and monticellite, CaMgSiO₄, are considered. According to a rigid oxyanion scheme, eulerian orientation angles of the SiO₄ tetrahedra and translation coordinates of Ca and Si atoms are specified as structural variables τk. All derivatives of the static energy (Born model) contain atomic charges and repulsive parameters as unknowns; the minimum energy conditions ?E _L/?τ_k=0 yield 34 equations which are solved by a least-squares method. The set of energy parameters fitting structural properties of all four phases together is: z _Ca=1.50, z _o=?1.10 e, r _Ca=1.05, ρ=0.25 Å; the Mg charge was fixed at 1.38 e, from a previous study on forsterite. An average shift of 0.04 Å is observed between experimental and least-energy calculated atomic positions. Results are compared with those of Mg₂SiO₄, where the fit was based both on thermoelastic and on structural properties. If no charge values were fixed “a priori”, just ratios between charges could be determined by fitting them to structural data only.  相似文献   

New chronological and stratigraphical data on the Ivrea amphitheatre (Piedmont, NW Italy)     

Franco Gianotti  Maria Gabriella Forno  Susan Ivy-Ochs  Peter W. Kubik 《Quaternary International》2008,190(1):123

The Ivrea amphitheatre (IA) in NW Italy has been studied since 1850, on pedostratigraphic and morphological bases. Three stratigraphic groups of glacial sediments were distinguished. Newly recognized stratigraphic boundaries are based on interstadial/interglacial units, palaeosols and lacustrine organic layers interbedded with glacigenic deposits, and on pedostratigraphy. Mapping of morphological features and associated marginal and sub-glacial deposit facies was used to characterize and reconstruct glacial margin fluctuations. Based on the field evidence, the stratigraphical limits recognized at single sites can be interpolated over the whole amphitheatre. Ten stratigraphic units (referred to as alloformations: Afs) were distinguished and mapped. They are related to at least as many glacial episodes ranging in age from the end of the Early Pleistocene to the Late Pleistocene. The youngest three glacial units (Serra Af, Piverone Af and Ivrea Af) and one interstadial level (Alice Superiore Unit between Serra and Piverone Afs) are discussed in detail. Based on biostratigraphical and pedological, as well as sedimentological and morphological data, the Serra Af can be attributed to MIS 6 and Piverone Af to MIS 4. The ¹⁰Be surface exposure ages from two boulders (27.9±3.1, 32.4±4.0 kyr) on the Serra d’Ivrea moraine provide only a minimum age for moraine construction. The alignment of typical ice marginal landforms (moraines and kame terraces) for the more recent unit (Ivrea Af) has allowed recognition of 12 principal stadials during the LGM and Lateglacial; 6 stadials in the amphitheatre and 6 stadials in Dora Baltea Valley, and reconstruction of the nature of the last glacial retreat from the amphitheatre to the cirques. ¹⁰Be exposure ages from three boulders related to Ivrea Af are 13.1±1.0, 17.4±2.6 and 20.8±1.5 ka. The latter two ages indicate that the Dora Baltea Glacier deposited the Ivrea Af in the IA during MIS 2. The ¹⁰Be exposure ages of 14.6±1.2 and 14.0±0.9 ka from a polished bedrock surface some 15 km upstream from the amphitheatre provide a minimum age for ice decay.  相似文献   

Proposed GSSP for the base of Cambrian Stage 9, coinciding with the first appearance of <Emphasis Type="Italic">Agnostotes orientalis</Emphasis>, at Duibian,Zhejiang, China     

ShanChi Peng  Loren E. Babcock  JingXun Zuo  HuanLing Lin  XueJian Zhu  XianFeng Yang  YuPing Qi  Gabriella Bagnoli  LongWu Wang 《中国科学D辑(英文版)》2009,52(4):434-451

Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata. The section fulfills all the requirements for a GSSP, and the horizon can be constrained not only by the primary stratigraphic marker (A. orientalis) but also with secondary biostratigraphic, chemostratigraphic, and sequence-stratigraphic correlation tools. The first appearance of A. orientalis is one of the most readily recognizable levels in Cambrian, and can be correlated with precision to all paleocontinents. Supported by Chinese Academy of Sciences (Grant No. KZCX2-YW-122), the Ministry of Science and Technology of China (Grant Nos. 2006FY120300, 2006CB806400), National Natural Science Foundation of China (Grant Nos. 40072003, 40023002, 40332018, 40672023, 40602002), and the U.S. National Science Foundation (Grant No. EAR-0106883)  相似文献   

Development of a fluorescent antibody method for the detection of Enterococcus faecium and its potential for coastal aquatic environment monitoring     

Caruso G  Monticelli LS  Caruso R  Bergamasco A 《Marine pollution bulletin》2008,56(2):318-324

A direct, microscopic fluorescent antibody method was developed to detect the occurrence of Enterococcus faecium in coastal aquatic environments and was compared with the conventional membrane filtering method. The "in situ" application of the antibody-based protocol in the analysis of water samples collected from coastal polyhaline habitats demonstrated good sensitivity and ease of implementation. Data obtained with the microscopic technique were in agreement with those obtained from culture counts. The fluorescent antibody method proved to be a rapid and reliable technique for the detection of E. faecium. The advantages and limitations intrinsic to the method are discussed, highlighting the potential of this new technique for monitoring coastal aquatic environments.  相似文献