Estimating flow resistance in steep slope rills

Recent research recognized that the slope of 18% can be used to distinguish between the ‘gentle slope’ case and that of ‘steep slope’ for the detected differences in hydraulic variables (flow depth, velocity, Reynolds number, Froude number) and those representatives of sediment transport (flow transport capacity, actual sediment load). In this paper, using previous measurements carried out in mobile bed rills and flume experiments characterized by steep slopes (i.e., slope greater than or equal to 18%), a theoretical rill flow resistance equation to estimate the Darcy-Weisbach friction factor is tested. The main aim is to deduce a relationship between the velocity profile parameter Γ, the channel slope, the Reynolds number, the Froude number and the textural classes using a data base characterized by a wide range of hydraulic conditions, plot or flume slope (18%–84%) and textural classes (clay ranging from 3% to 71%). The obtained relationship is also tested using 47 experimental runs carried out in the present investigation with mobile bed rills incised in a 18%—sloping plot with a clay loam soil and literature data. The analysis demonstrated that: (1) the soil texture affects the estimate of the Γ parameter and the theoretical flow resistance law (Equation 25), (2) the proposed Equation (25) fits well the independent measurements of the testing data base, (3) the estimate of the Darcy-Weisbach friction factor is affected by the soil particle detachability and transportability and (4) the Darcy-Weisbach friction factor is linearly related to the rill slope.     

Raw Materials for Archaeological Pottery from the Campania Region of Italy: A Petrophysical Characterization

We performed petrophysical analyses on 34 clayey samples of different geological origin within the Campania region of Italy in order to determine possible sources of raw materials used to produce ancient pottery. Possible raw material sources can be grouped into high‐CaO clays (HCC) and low‐CaO clays (LCC). HCC are mainly represented by more recent (Miocene‐Pleistocene) basinal sediments whereas LCC tend to be associated with basinal, alluvial, and pyroclastic deposits. A chemical comparison between clayey raw materials, modern ceramic replicas, and Campanian archaeological ceramics of several typologies (common ware, cooking ware, fine tableware, amphorae, and bricks) from 8th century B.C. to the Middle Ages (a total of 350 ceramic samples) indicates that HCC were extensively used for common wares and that these were either mixed with temper or levigated. In contrast, most of the LCC were used for the production of cookware. We also analyzed the technological potential of the sampled raw materials, taking into consideration their actual and possible uses. We observed that most HCC deposits were well suited for tableware and amphorae, whereas LCC were better for cookware and some fine tableware.     

The age of the Paludi Formation: a major constraint to the beginning of the Apulia-verging orogenic transport in the northern sector of the Calabria–Peloritani Arc

A stratigraphic revision of the Paludi Formation, cropping out in Northern Calabria on the north-eastern side of Sila Massif, has confirmed that it has been deposited between two main tectonic phases. Actually the formation is involved only by top to the north-east thrusts, different from those separating the crystalline and ophiolitic nappes of Northern Calabria, and rests unconformably on the Sila Unit, the uppermost nappe of the tectonic stack. In the frame of the interpretation of Northern Calabria as a fragment of the Alps, the Paludi Formation play the role of a deposit post-dating the eo-alpine tectonic phases and pre-dating the Apenninic orogenic transport. Therefore the Aquitanian age of the formation, obtained by nannofloras analyses, can be considered the minimum age to the Apulia-verging orogenic transport, witnessed by top to north-east thrusts. It fairly corresponds to the age referred to the Lucanian ocean closure.     

Seismology of the solar atmosphere

We describe a new instrument for seismically probing the properties of the Sun's lower atmosphere, and present some first results from an observational campaign carried out at the geographic South Pole during the austral summer of 2002/2003. A preliminary analysis of the data (simultaneous, high-cadence observations of the velocity signals from the photosphere and low chromosphere) shows that the well-known suppression of acoustic power in regions of strong magnetic field, and enhancement of high-frequency power around active regions (acoustic halos), are both consistent with a spreading out of the magnetic field lines with increasing height in the atmosphere. The data have also revealed some unexpected wave behavior. First, evanescent-like waves are found at frequencies substantially above the acoustic cut-off frequency in regions of intermediate magnetic field. Second, upward- and downward-propagating waves are detected in areas of strong magnetic field such as sunspots and plage: even at frequencies below the acoustic cut-off frequency. Third, the wave behavior in regions of strong magnetic field can change over periods of a few hours from propagating to evanescent. While we have no concrete explanation for the first two results, the latter result opens up the question of whether sound waves are involved in short-term events such as flares or CME's.     

Thermohaline circulation sensitivity to intermediate-level anomalies

Abstract A two-dimensional Boussinesq ocean model has been used to investigate the effect of intermediate-level thermal and saline anomalies on the known multiple equilibria structure of the thermohaline circulation. These anomalies are taken as a crude representation of the Mediterranean outflow in the Atlantic Ocean. The associated perturbation drives the system towards an overturning which resembles the present average Atlantic thermohaline circulation. The sensitivity to the depth at which the anomaly is placed is also investigated. We found that near-surface anomalies are more efficient in affecting the structure of the equilibria.     

Optical characterization of laser ablated silicates

We perform an optical characterization of UV laser ablated silicates (olivine, pyroxene), starting from their reflectance spectra in the 0.3-2.5 μm spectral range. The goal is to provide useful tools to model space weathering effects on surfaces of asteroids and TNOs (trans-neptunian objects). We determine that the reddening and darkening spectral trend is compatible with the Hapke's space weathering model, using the optical constants of metallic iron in a silicate matrix. This result is supported by new magnetic susceptibility measurements on laser ablated orthopyroxene. We also investigate the potential contribution of formation of amorphous silicates in the process. Applying our results to silicate-rich surfaces in the Solar System, we investigate the possibility of a weathered olivine component on the surface of Centaur 5145 Pholus. Inclusion of this component slightly decreases the amount of complex organics and water ice from those previously estimated. Thus, the current Pholus spectrum is consistent with the presence of either unweathered or weathered olivine, or potentially both materials.     

The green–blue swing: plasticity of plankton food‐webs in response to coastal oceanographic dynamics

The internal organization of plankton communities plays a key role in biogeochemical cycles and in the functioning of aquatic ecosystems. In this study, the structure of a marine plankton community (including both unicellular and multicellular organisms) was inferred by applying an ecological network approach to species abundances observed weekly at the long‐term ecological research station MareChiara (LTER‐MC) in the Gulf of Naples (Tyrrhenian Sea, Mediterranean Sea) in the summers of 2002–2009. Two distinct conditions, characterized by different combination of salinity and chlorophyll values, alternated at the site: one influenced by coastal waters, herein named ‘green’, and the other reflecting more offshore conditions, named ‘blue’. The green and blue ‘phases’ showed different keystone biological elements: namely, large diatoms and small‐sized flagellates, respectively. Several correlations amongst species belonging to different trophic groups were found in both phases (connectance ~0.30). In the green phase, several links between phytoplankton and mesozooplankton and within the latter were detected, suggesting matter flow from microbes up to carnivorous zooplankton. A microbial‐loop‐like sub‐web, including mixo‐ and heterotrophic dinoflagellates and ciliates, was present in the green phase, but it was relatively more important in the blue phase. The latter observation suggests a more intense cycling of matter at the microbial trophic level in the blue phase. These results show that different modes of ecological organization can emerge from relatively small changes in the composition of aquatic communities coping with environmental variability. This highlights a significant plasticity in the internal structure of plankton webs, which should be taken into account in predictions of the potential effects of climatic oscillations on aquatic ecosystems and biogeochemical cycles therein.