Horizontal rotation signals detected by “G-Pisa” ring laser for the M w = 9.0, March 2011, Japan earthquake     

Jacopo Belfi  Nicolò Beverini  Giorgio Carelli  Angela Di Virgilio  Enrico Maccioni  Gilberto Saccorotti  Fabio Stefani  Alexander Velikoseltsev 《Journal of Seismology》2012,16(4):767-776

We report the observation of the ground rotation induced by the M _w = 9.0, 11th of March 2011, Japan earthquake. The rotation measurements have been conducted with a ring laser gyroscope operating in a vertical plane, thus detecting rotations around the horizontal axis. Comparison of ground rotations with vertical accelerations from a co-located force balance accelerometer shows excellent ring laser coupling at periods longer than 100?s. Under the plane wave assumption, we derive a theoretical relationship between horizontal rotation and vertical acceleration for Rayleigh waves. Due to the oblique mounting of the gyroscope with respect to the wave direction of arrival, apparent velocities derived from the acceleration/rotation rate ratio are expected to be always larger than or equal to the true wave propagation velocity. This hypothesis is confirmed through comparison with fundamental mode, Rayleigh-wave phase velocities predicted for a standard Earth model.  相似文献   

Asymptotic giant branch stars in the Phoenix dwarf galaxy     

John Menzies  Michael Feast  Patricia Whitelock  Enrico Olivier  Noriyuki Matsunaga  Gary Da Costa 《Monthly notices of the Royal Astronomical Society》2008,385(2):1045-1052

JHK _s near-infrared photometry of stars in the Phoenix dwarf galaxy is presented and discussed. Combining these data with the optical photometry of Massey et al. allows a rather clean separation of field stars from Phoenix members. The discovery of a Mira variable ( P = 425 d), which is almost certainly a carbon star, leads to an estimate of the distance modulus of 23.10 ± 0.18 that is consistent with other estimates and indicates the existence of a significant population of age ∼2 Gyr. The two carbon stars of Da Costa have   M _bol=−3.8  and are consistent with belonging to a population of similar age; some other possible members of such a population are identified. A Da Costa non-carbon star is  Δ K _s∼ 0.3  mag brighter than these two carbon stars. It may be an asymptotic giant branch star of the dominant old population. The nature of other stars lying close to it in the   K _s, ( J − K _s)  diagram needs studying.  相似文献   

Aliphatic hydrocarbons in metasomatized gabbroic xenoliths from Hyblean diatremes (Sicily): Genesis in a serpentinite hydrothermal system     

Enrico Ciliberto  Carmelo Crisafulli  Fabio Carmelo Manuella  Filippo Samperi  Salvatore Scirè  Vittorio Scribano  Marco Viccaro  Ezio Viscuso 《Chemical Geology》2009,258(3-4):258-268

Many tholeiite gabbro xenoliths from the Hyblean tuff-breccia deposits (Sicily, southern Italy) present mineralogical and geochemical evidence for hydrothermal alteration at different temperatures and water/rock ratios. In some cases, the primary mineral assemblage has been entirely replaced by Na-rich alkali feldspar, chlorite/smectite interlayers, zeolites, aegirine–augite, titanite, zircon etc. Hence the chemical composition of such metasomatic rocks displays larger amounts of volatiles, alkalis, Zr, Hf, U, Th and lower Ca, Mg, Fe with respect to the original gabbro. Five hydrothermally altered gabbroic xenoliths were selected for thermal decrepitation and bulk gas analyses by quadrupole mass spectrometry. All the samples analyzed display the same Electron Impact-Direct Pyrolysis Mass spectra (EI-DPMS). These show a series of peaks differing by 14 mass units due to loss of methylene groups (–CH₂), by a fragmentation process typical of saturated aliphatic and aliphatic–aromatic hydrocarbons. In addition, Fourier Transform Infrared (FT-IR) spectra of the samples present several bands typical of vibration frequencies of aliphatic hydrocarbons. The high-molecular-weight hydrocarbons observed probably originated from Fischer–Tropsch-type (FT-t) synthesis in the high temperature section of a serpentinite-hosted hydrothermal system. This suggestion may lend support to the recent hypothesis regarding the original oceanic nature of the Hyblean lithospheric basement.  相似文献   

Influence of FPS bearing properties on the seismic performance of base‐isolated structures          下载免费PDF全文

Paolo Castaldo  Enrico Tubaldi 《地震工程与结构动力学》2015,44(15):2817-2836

The paper analyzes the influence of friction pendulum system (FPS) isolator properties on the seismic performance of base‐isolated building frames. The behavior of these systems is analyzed by employing a two‐degree‐of‐freedom model accounting for the superstructure flexibility, whereas the FPS isolator behavior is described by adopting a widespread model that considers the variation of the friction coefficient with the velocity. The uncertainty in the seismic input is taken into account by considering a set of natural records with different characteristics scaled to increasing intensity levels. The variation of the statistics of the response parameters relevant to the seismic performance is investigated through the nondimensionalization of the motion equation and an extensive parametric study carried out for different isolator and system properties. The proposed approach allows to explore a wide range of situations while limiting the required nonlinear response history analyses. Two case studies consisting of base‐isolated building frames described as shear‐type systems are finally investigated in order to demonstrate the capabilities of the proposed simplified model in unveiling the essential characteristics of the performance of buildings isolated with FPS bearings. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

BeppoSAX observations of GRS 1915+105.     

Giorgio Matt  Enrico Costa  Marco Feroci  Tomaso Belloni  Marco Tavani 《New Astronomy Reviews》1998,42(9-10)

Results from a BeppoSAX observational campaign on GRS 1915+105, performed in October/November 1996, are presented. The source was observed 10 times (nine 10 ksec snapshots, one 100 ksec long observation). The broad band spectral analysis reveals a complex spectrum, including Compton reflection and an iron emission line, probably originating from a relativistic disc.  相似文献   

Gravothermal catastrophe in anisotropic spherical systems     

Manuela Magliocchetti  Giuseppe Pucacco  & Enrico Vesperini 《Monthly notices of the Royal Astronomical Society》1998,301(1):25-30

In this paper we investigate the gravothermal instability of spherical stellar systems endowed with a radially anisotropic velocity distribution. We focus our attention on the effects of anisotropy on the conditions for the onset of instability and in particular we study the dependence of the spatial structure of critical models on the amount of anisotropy present in a system. The investigation has been carried out by the method of linear series which has already been used in the past to study the gravothermal instability of isotropic systems._   We consider models described by King, Wilson and Woolley–Dickens distribution functions. In the case of King and Woolley–Dickens models, our results show that, for quite a wide range of the amount of anisotropy in the system, the critical value of the concentration of the system (defined as the ratio of the tidal to the King core radius of the system) is approximately constant and equal to the corresponding value for isotropic systems. Only for very anisotropic systems does the critical value of the concentration start to change and it decreases significantly as the anisotropy increases and penetrates the inner parts of the system. For Wilson models the decrease of the concentration of critical models is preceded by an intermediate regime in which critical concentration increases, reaches a maximum and then starts to decrease. The critical value of the central potential always decreases as the anisotropy increases.  相似文献   

Third-Order Moments for Shear Driven Boundary Layer     

Enrico?FerreroEmail author 《Boundary-Layer Meteorology》2005,116(3):461-466

A new third-order model for shear driven boundary layer is presented and tested against large-eddy simulation (LES) data. Numerical solutions are obtained using mean flow components and second-order moments as input. The calculated vertical profiles of the variances and turbulent kinetic energy fluxes and those provided by a LES experiment are compared and discussed  相似文献   

A Simple Parametrization for the Concentration Variance Dissipation in a Lagrangian Single-Particle Model     

Enrico Ferrero  Luca Mortarini  Federico Purghè 《Boundary-Layer Meteorology》2017,162(1):91-116

A new quasi-analytical mixed-layer model is formulated describing the evolution of the convective atmospheric boundary layer (ABL) during cold-air outbreaks (CAO) over polar oceans downstream of the marginal sea-ice zones. The new model is superior to previous ones since it predicts not only temperature and mixed-layer height but also the height-averaged horizontal wind components. Results of the mixed-layer model are compared with dropsonde and aircraft observations carried out during several CAOs over the Fram Strait and also with results of a 3D non-hydrostatic (NH3D) model. It is shown that the mixed-layer model reproduces well the observed ABL height, temperature, low-level baroclinicity and its influence on the ABL wind speed. The mixed-layer model underestimates the observed ABL temperature only by about 10 %, most likely due to the neglect of condensation and subsidence. The comparison of the mixed-layer and NH3D model results shows good agreement with respect to wind speed including the formation of wind-speed maxima close to the ice edge. It is concluded that baroclinicity within the ABL governs the structure of the wind field while the baroclinicity above the ABL is important in reproducing the wind speed. It is shown that the baroclinicity in the ABL is strongest close to the ice edge and slowly decays further downwind. Analytical solutions demonstrate that the \(\mathrm{e}\)-folding distance of this decay is the same as for the decay of the difference between the surface temperature of open water and of the mixed-layer temperature. This distance characterizing cold-air mass transformation ranges from 450 to 850 km for high-latitude CAOs.  相似文献   

Analyses of the Relationship Between Mucous Aggregates and Phytoplankton Communities in the Gulf of Trieste (Northern Adriatic Sea) by Multivariate Techniques     

Bruno  Cataletto  Enrico  Feoli  Serena Fonda  Umani  Marina  Monti Irene  Pecchiar 《Marine Ecology》1996,17(1-3):291-307

Abstract. Multivariate techniques (cluster analysis and Principal Component Analysis) applied on phytoplankton data collected in June, July, August, and September 1990, 1991, 1992, and 1993 in the Gulf of Trieste (Northern Adriatic Sea) highlighted a clear temporal pattern from 1990 to 1993. In the summer of 1991, phytoplankton communities showed a dramatic increase in the dinoflagellatddiatom ratio. In particular, during June and July 1991 only few specimens of diatoms ( Cylindrorhecu closreriurn. Probosciu alata, Nirzschio longissimu , and Nitzschiu spp.) were collected; this confirmed the diatom scarcity in the phytoplankton communities before and during the appearance of large mucous aggregates (mucilage) in July 1991 in the Gulf of Trieste. The differences observed between the structure of the phytoplankton communities inside the aggregates and in the ambient waters suggested two hypotheses: 1) the aggregates were not produced in the gulf, but were carried ints the gulf by the eastern bordering current; 2) the aggregates were produced by a few, scarce species with a high exudate production that are capable of quickly reaching a high reproductive rate within the aggregates.  相似文献   

Lake Cheko and the Tunguska Event: impact or non‐impact?     

Luca Gasperini  Enrico Bonatti  Giuseppe Longo 《地学学报》2008,20(2):169-172

Several lines of evidence were presented in Gasperini et al. [Terra Nova (2007), vol. 19 , pp. 245–251] suggesting that Lake Cheko, a small lake close to the alleged epicentre of the 1908 Tunguska Event, might be a secondary impact crater. Collins et al. [Terra Nova (2008), this volume] argue against this hypothesis. We reply here arguing in favour of an impact origin for Lake Cheko.  相似文献