Seagrass ecophysiology meets ecological genomics: are we ready?     

Gabriele Procaccini  Sven Beer  Mats Björk  Jeanine Olsen  Silvia Mazzuca  Rui Santos 《Marine Ecology》2012,33(4):522-527

In March 2011, the Ecophysiology and Genetics Working Groups of the European Science Foundation COST Action ES 0906, entitled Seagrass Productivity: From Genes to Ecosystem Management, organized an exploratory workshop entitled “Linking Ecophysiology and Ecogenomics in Seagrass Systems”. The goal of the workshop was to discuss how to integrate comparative gene expression studies with physiological processes such as photosynthetic performance, carbon and nitrogen utilization and environmental adaptation. The main questions discussed for integrative research related to mechanisms of carbon utilization, light requirements, temperature effects and natural variation in pH and ocean acidification. It was concluded that the seagrass research community is still in the nascent stages of linking ecophysiology with genomic responses, as carbon and nitrogen metabolism of seagrasses have not been sufficiently well studied. Likewise, genomic approaches have only been able to assign meaningful interpretations to a handful of differentially expressed genes. Nevertheless, the way forward has been established.  相似文献   

Investigating on the 1920 Garfagnana earthquake (M_w=6.5): Evidences of site effects in Villa Collemandina (Tuscany,Italy)     

Roberto De Ferrari  Gabriele Ferretti  Simone Barani  Daniele Spallarossa 《Soil Dynamics and Earthquake Engineering》2010

This paper presents a comprehensive ground response study for the municipality of Villa Collemandina in Northern Tuscany (Italy). This site was selected following a macroseismic analysis of the 1920 Garfagnana earthquake (M_w=6.5), which, at Villa Collemandina, produced damage and losses that were larger than at any other site near the earthquake epicentre, thus indicating the presence of possible site effects. Hence, both experimental and numerical methods are applied in order to investigate the ground response at different locations within the Villa Collemandina municipality. Results obtained from the spectral analysis of earthquake recordings using the reference site method and those from a 2-dimensional dynamic simulation reveal the presence of site effects due to the buried geomorphology (basin-like effects), allowing us to explain the severe damage and losses produced by the 1920 Garfagnana earthquake. As a further result, horizontal to vertical spectral ratio techniques and 1D soil modelling are proved to be inadequate for an effective characterization of the ground response at sites that, like Villa Collemandina, present a complex local geology.  相似文献   

Reliability of the automatic procedures for locating earthquakes in southwestern Alps and northern Apennines (Italy)     

Chiara Turino  Paola Morasca  Gabriele Ferretti  Davide Scafidi  Daniele Spallarossa 《Journal of Seismology》2010,14(2):393-411

Reliable automatic procedure for locating earthquake in quasi-real time is strongly needed for seismic warning system, earthquake preparedness, and producing shaking maps. The reliability of an automatic location algorithm is influenced by several factors such as errors in picking seismic phases, network geometry, and velocity model uncertainties. The main purpose of this work is to investigate the performances of different automatic procedures to choose the most suitable one to be applied for the quasi-real-time earthquake locations in northwestern Italy. The reliability of two automatic-picking algorithms (one based on the Characteristic Function (CF) analysis, CF picker, and the other one based on the Akaike’s information criterion (AIC), AIC picker) and two location methods (“Hypoellipse” and “NonLinLoc” codes) is analysed by comparing the automatically determined hypocentral coordinates with reference ones. Reference locations are computed by the “Hypoellipse” code considering manually revised data and tested using quarry blasts. The comparison is made on a dataset composed by 575 seismic events for the period 2000–2007 as recorded by the Regional Seismic network of Northwestern Italy. For P phases, similar results, in terms of both amount of detected picks and magnitude of travel time differences with respect to manual picks, are obtained applying the AIC and the CF picker; on the contrary, for S phases, the AIC picker seems to provide a significant greater number of readings than the CF picker. Furthermore, the “NonLinLoc” software (applied to a 3D velocity model) is proved to be more reliable than the “Hypoellipse” code (applied to layered 1D velocity models), leading to more reliable automatic locations also when outliers (wrong picks) are present.  相似文献   

ESEEM of industrial quartz powders: insights into crystal chemistry of Al defects     

Maurizio?Romanelli  Francesco?Di BenedettoEmail author  Laura?Bartali  Massimo?Innocenti  Gabriele?Fornaciai  Giordano?Montegrossi  Luca?A.?Pardi  Alfonso?Zoleo  Fabio?Capacci 《Physics and Chemistry of Minerals》2012,39(6):479-490

A set of raw industrial materials, that is, pure quartz and quartz-rich mixtures, were investigated through electron paramagnetic resonance and electron spin echo-envelope modulation spectroscopies, with the aim of evaluating the effective role played by defect centres and of assessing whether they can be used to monitor changes in the physical properties of quartz powders with reference to their health effects. The obtained results point to two interactions of the Al defect centres with H⁺, hosted in sites within the channels parallel and perpendicular to the c axis of quartz, respectively. These two Al/H⁺ (h_Al) centres exhibit a weak chemical bond, and their relative amounts appear to be modified/controlled by the thermo-mechanical processes underwent by powders. Indeed, a mechanically promoted inter-conversion between the two kinds of site is suggested. As a consequence, the h_Al centres are effective in monitoring even modest activations of powders, through thermal or mechanical processes, and they are also supposed to play a specific, relevant role in quartz reactivity during the considered industrial processes.  相似文献   

Complementary techniques to assess physical properties of a fine soil irrigated with saline water   总被引：3，自引：2，他引：1  

Angelo Basile  Gabriele Buttafuoco  Giacomo Mele  Anna Tedeschi 《Environmental Earth Sciences》2012,66(7):1797-1807

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Magnetic properties and cation ordering of nanopowders of the synthetic analogue of kuramite, Cu3SnS4     

Francesco Di Benedetto  Daniele Borrini  Andrea Caneschi  Gabriele Fornaciai  Massimo Innocenti  Alessandro Lavacchi  Carlo Andrea Massa  Giordano Montegrossi  Werner Oberhauser  Luca A. Pardi  Maurizio Romanelli 《Physics and Chemistry of Minerals》2011,38(6):483-490

An extensive characterisation of the magnetic properties of synthetic powders of kuramite, with formal composition Cu₃SnS₄, was performed. Powders were investigated through superconducting quantum interference device (SQUID) magnetometry, electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRPD), scanning and transmission electron microscopies (SEM and TEM) and microanalysis. SEM and TEM reveal the presence of nanodimensioned particles. XRPD clearly shows that Cu₃SnS₄ crystallised in a cubic sphalerite-type structural model, in spite of the stannite-type tetragonal structure described for the natural phase. This difference arises from a full random distribution of cations. Synthetic kuramite nanopowders exhibit a marked paramagnetism, originated by the presence of Cu(II), definitely assessed by EPR measurements. Moreover, the overall magnetic behaviour of the sample cannot be simply ascribed to diluted paramagnetism, and this suggests the presence of strong superexchange interactions among Cu(II) ions even at room temperature. The main consequences of these results are the definitive assessment of the chemical formula Cu(I)₂Cu(II)SnS₄ and of a random distribution of Cu(II), Cu(I) and Sn(IV) ions within the available tetrahedral sites.  相似文献   

Empirically-based modeling of spatial sampling uncertainties associated with rainfall measurements by rain gauges     

Gabriele Villarini  Witold F. Krajewski 《Advances in water resources》2008

In the quantitative evaluation of radar-rainfall products (maps), rain gauge data are generally used as a good approximation of the true ground rainfall. However, rain gauges provide accurate measurements for a specific location, while radar estimates represent areal averages. Because these sampling discrepancies could introduce noise into the comparisons between these two sensors, they need to be accounted for. In this study, the spatial sampling error is defined as the ratio between the measurements by a single rain gauge and the true areal rainfall, defined as the value obtained by averaging the measurements by an adequate number of gauges within a pixel. Using a non-parametric scheme, the authors characterize its full statistical distribution for several spatial (4, 16 and 36 km²) and temporal (15 min and hourly) scales.  相似文献   

Capture into first-order resonances and long-term stability of pairs of equal-mass planets     

Gabriele Pichierri  Alessandro Morbidelli  Aurélien Crida 《Celestial Mechanics and Dynamical Astronomy》2018,130(8):54

Massive planets form within the lifetime of protoplanetary disks, and therefore, they are subject to orbital migration due to planet–disk interactions. When the first planet reaches the inner edge of the disk, its migration stops and consequently the second planet ends up locked in resonance with the first one. We detail how the resonant trapping works comparing semi-analytical formulae and numerical simulations. We restrict to the case of two equal-mass coplanar planets trapped in first-order resonances, but the method can be easily generalized. We first describe the family of resonant stable equilibrium points (zero-amplitude libration orbits) using series expansions up to different orders in eccentricity as well as a non-expanded Hamiltonian. Then we show that during convergent migration the planets evolve along these families of equilibrium points. Eccentricity damping from the disk leads to a final equilibrium configuration that we predict precisely analytically. The fact that observed multi-exoplanetary systems are rarely seen in resonances suggests that in most cases the resonant configurations achieved by migration become unstable after the removal of the protoplanetary disk. Here we probe the stability of the resonances as a function of planetary mass. For this purpose, we fictitiously increase the masses of resonant planets, adiabatically maintaining the low-amplitude libration regime until instability occurs. We discuss two hypotheses for the instability, that of a low-order secondary resonance of the libration frequency with a fast synodic frequency of the system, and that of minimal approach distance between planets. We show that secondary resonances do not seem to impact resonant systems at low amplitude of libration. Resonant systems are more stable than non-resonant ones for a given minimal distance at close encounters, but we show that the latter nevertheless play the decisive role in the destabilization of resonant pairs. We show evidence that as the planetary mass increases and the minimal distance between planets gets smaller in terms of mutual Hill radius, the region of stability around the resonance center shrinks, until the equilibrium point itself becomes unstable.  相似文献   

Checking vulnerability to pure loss of stability in long crested following waves: A probabilistic approach     

Gabriele Bulian 《Ocean Engineering》2010,37(11-12):1007-1026

This paper presents a probabilistic methodology for the analysis of the vulnerability of a ship to the risk of inception of pure loss of stability events. A pure loss of stability failure is modelled as the persistence of the metacentric height below a critical level for a too long time. The metacentric height is modelled as a stationary Gaussian process with a spectrum obtained from the sea elevation spectrum. The time dependent failure index is obtained under the assumption of filtered Poisson process for the occurrence of critical events. The analysis separates cases where the fluctuation of the metacentric height is narrow-band from those where the bandwidth of the spectrum is wide, with an intermediate blending. In case of narrow-band processes appropriate approximate solutions to the problem are provided, while in the wide-band cases an exponential distribution for the persistence time below the critical level is employed. A rational development for the critical persistence time is also provided considering an approximation of the roll dynamics during periods of time where the metacentric height is negative. Monte Carlo simulations are performed to check the developed approximate distributions for the persistence time, and examples of application are provided for a sample ship.  相似文献   

Microbial photosynthesis in coral reef sediments (Heron Reef, Australia)     

Ursula Werner  Anna Blazejak  Paul Bird  Gabriele Eickert  Raphaela Schoon  Raeid M.M. Abed  Andrew Bissett  Dirk de Beer   《Estuarine, Coastal and Shelf Science》2008,76(4):876-888

We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O₂ m⁻² h⁻¹ and was strongly correlated with Chl a content, which lay between 31 and 84 mg m⁻². An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2–1.0 mmol Ca²⁺ m⁻² h⁻¹). The sediments of at least three stations were net calcifying. Sedimentary N₂-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N₂ m⁻² h⁻¹ and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N₂-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling.  相似文献