Experiments on Surface Waves Interacting with Flexible Aquatic Vegetation

Surface wave interaction with aquatic vegetation appears to play a key role in coastal hydro-morpho-dynamics. As an example, the presence of a dense meadow at intermediate water depth is usually associated with a stable and resilient shore. Wave-meadow interactions are investigated here by means of physical modelling, with a focus on wave height distribution and hydrodynamics. The central part of a wave flume is covered by flexible artificial seagrass, composed of polyethylene leaves. This vegetation is tested in both near emergent and submerged conditions. The wave height reduction is evaluated by means of a drag coefficient defined from linear wave theory, which contains all the unknowns of the adopted methodology. The behaviour of such a coefficient is investigated as a function of a wave related Reynolds number. The influence of the flexibility of the leaves is also considered, together with a wave frequency parameter. The results show a complex behaviour with three different trends for near rigid, intermediate or highly flexible leaves. Amplitudes of the orbital velocities are investigated and show a fairly good match with the linear wave theory. On the contrary, the mean velocity along the water column appears to be modified by the seagrass for submerged leaves.     

Characterizing impulsive wave-in-deck loads on coastal bridges by probabilistic models of impact maxima and rise times

When waves impact a seawall, a vertical breakwater, an exposed jetty, a pier or a coastal bridge, they abruptly transfer their momentum into the structure. This energy transfer can be very violent and its duration exceptionally short. In the case of coastal bridges, whose spans are designed to have very short vibration period, wave impacts might have duration comparable to the natural period of oscillation of the structure, which therefore becomes prone to damage and failure. Previous forensic studies have documented the relative importance of impulsive loads on deck suspended structure, demonstrating the need to assess the effect of wave impacts on both the stability and the integrity of structural members since the early stages of the design. This requires the estimation of the dynamic characteristics of the loading pattern, and in particular the wave impulse and corresponding impact maxima and rise times. Based on the conservation of momentum, functional relationships between these parameters have been identified since pioneering work dating back to the late '30s of the 20th century. The complexity of the loading process, however, results in a significantly large variability of wave impact maxima and rise times even under similar conditions, suggesting the need for a probabilistic approach to the definition of the relationship between these two variables, to be applied when estimating the dynamic properties of wave for use in structural analysis of coastal structures. In the recent past, some effort has been made to identify functional relationships between such quantities; these require the assessment of the conditional quantiles (or similarly the conditional distribution) of wave impact maxima given the rise times. In this paper, we compare three different statistical methods proposed in the literature to accomplish this task, in order to assess the reliability of the approach and suggest guidelines for practical applications. A copula-based method, Generalized Additive Models for Location, Scale and Shape (GAMLSS), and quantile regression are applied to measurements from large-scale 3-dimensional physical model tests. The investigation suggests that quantile regression gives the simplest results to be used in practice; copula approach and GAMLSS are possible alternative when semi-parametric or fully parametric modeling is needed.     

Biomarkers of Exposure and Effects for Assessing Toxicological Risk of Endocrine Disrupters in Top Predators of the Mediterranean Sea

Abstract. Endocrine Disrupting Chemicals (EDCs) have the potential to alter hormone pathways that regulate reproductive processes in wildlife and fisheries. In this research the unexplored hypothesis that Mediterranean top predator species (such as large pelagic fish and marine mammals) are potentially at risk due to EDCs is investigated. In the Mediterranean environment, top predators accumulate high concentrations of polyhalogenated aromatic hydrocarbons (PHAHs) and toxic metals, incurring high toxicological risk. Here we illustrate the need to develop sensitive biomarkers for evaluation of toxicological risk in top marine predators (Xiphias gladius, Thunnus thynnus thynnus) and non-lethal techniques, such as non-destructive biomarkers, for the hazard assessment of threatened species exposed to EDCs, such as marine mammals ( Stenella coeruleoalba, Tursiops truncatus, Delphinus delphis and Balaenoptera physalus ).     

Climate control on stacked paleosols in the Pleistocene of the Po Basin (northern Italy)

Paleosols are recurrent features in alluvial successions and provide information about past sedimentary dynamics and climate change. Through sedimentological analysis on six sediment cores, the mud-dominated succession beneath the medieval ‘Two Towers’ of Bologna was investigated down to 100 m depth. A succession of weakly developed paleosols (Inceptisols) was identified. Four paleosols (P1, P2, P3 and PH) were radiocarbon-dated to 40–10 cal ka bp . Organic matter and CaCO₃ determinations indicate low groundwater levels during soil development, which spanned periods < 5 ka. The development and burial of soils, which occurred synchronously in the Bologna region and in other sectors of the Po Plain, are interpreted to reflect climatic and eustatic variations. Climatic oscillations, at the scale of the Bond cycles, controlled soil development and burial during Marine Isotope Stage (MIS) 3 (P1 and P2). Rapid sea-level oscillations probably induced soil development at the MIS 3/2 transition (P3) and favored burial of PH after 10 ka bp . Weakly developed paleosols in alluvial successions can provide clues to millennial-scale climatic and environmental variations. In particular, the paleosol-bearing succession of the Po Plain represents an unprecedent record of environmental changes across the Late Pleistocene (MIS 3 and 2) in the Mediterranean region.     

Nir surface photometry of star-forming regions

We present a set of maps of the star-forming regions S140, Re 50, and Mon R2 in theJ, H, andK infrared bands (i.e., 1.2, 1.65, and 2.2 m), obtained with a resolution of 7 and 14 arc sec at the infrared 1.5 m TIRGO telescope, with the TIRGO InSb single channel photometer operating in a mapping mode.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.     

Galaxy formation and evolution – I. The Padua tree-sph code (pd-sph)

In this paper we report on pd-sph , the new tree-sph code developed in Padua. The main features of the code are described and the results of a new and independent series of 1D and 3D tests are shown. The paper is mainly dedicated to the presentation of the code and to the critical discussion of its performance. In particular, great attention is devoted to the convergency analysis. The code is highly adaptive in space and time by means of individual smoothing lengths and individual time-steps. At present it contains both dark and baryonic matter, this latter in the form of gas and stars, cooling, thermal conduction, star formation, feedback from Type I and II supernovae, stellar winds, and ultraviolet flux from massive stars, and finally chemical enrichment. New cooling rates that depend on the metal abundance of the interstellar medium are employed, and the differences with respect to the standard ones are outlined. Finally, we show the simulation of the dynamical and chemical evolution of a disc-like galaxy with and without feedback. The code is suitably designed to study in a global fashion the problem of formation and evolution of elliptical galaxies, and in particular to feed a spectrophotometric code from which the integrated spectra, magnitudes and colours (together with their spatial gradients) can be derived.     

Assessment of water vapor retrievals from a GPS receiver network

We present an assessment of a GPS receiver operational network to produce accurate integrated precipitable water vapour (IPWV) during a two-week field experiment carried out in Central Italy around the city of Rome, where different instruments were operative. This experimental activity provided an excellent opportunity to compare the GPS products with independent measurements provided by ground-based and space-based sensors and to evaluate their quality in terms of absolute accuracy of IPWV, analyzing also the spatial scale of GPS estimates. For instance, the assimilation into Numerical Weather Prediction models of IPWV provided by a GPS network or its exploitation in space geodesy applications to correct tropospheric effects requires an accuracy in the order of 0.1 cm to be ascribed to IPWV observations. In this work, we assessed that the accuracy for GPS IPWV estimates is 0.07 cm. Moreover, this experiment has pointed out strengths and limitations of an operational network for the water vapor estimation, such as a proper receiver distribution to achieve the desired spatial resolution and a coverage of GPS stations in both flat and mountains regions.     

An instrument for commissioning the active and adaptive optics of modern telescopes: the Infrared Test Camera for the Large Binocular Telescope

We describe the design, integration, and operation of the infrared test cameras for the commissioning of the Large Binocular Telescope. The design and construction phase lasted slightly more than one year from February 2007 to April 2008 and was the result of a joint collaboration among INAF Osservatorio Astronomico di Bologna, Università di Bologna Dipartimento di Astronomia (Italy) and the Max-Planck-Institut für Astronomie (Heidelberg, Germany). Thereafter, the camera was delivered to the LBT Observatory (USA) for commissioning of the telescope active optics and, more recently, for commissioning of the first light adaptive optics.     

Omeonga—A possible large impact structure on the Eastern Kasai Province (D.R. Congo)?

Abstract– The Omeonga ring structure (D.R. Congo) shows a remarkable drainage pattern encircling an area up to 45 km wide and encompassing a central smoothed relief 20 km wide. This inner circular ridge is elevated about 70 m above the ring depression corresponding to the bed of the Unia River, which flows between the inner ridge and an outer irregular ridge. Landsat 7 ETM and ASTER DEM show that the structural characteristics resemble those of several wide impact structures known on Earth. Other geological modes of origin that could produce ring structures, such as magmatic activity, salt diapirism, and karst dissolution have been considered. However, after evaluating the regional stratigraphy, the distribution of volcanism, and morphometry, these processes seem to be rather unlikely. If of impact origin, the age of the Omeonga structure can be constrained to the Late Cretaceous‐Cenozoic according to the youngest units in which the ring structure was formed.