A particle model of rolling grain ripples under waves

A simple model is presented for the formation of rolling grain ripples on a flat sand bed by the oscillatory flow generated by a surface wave. An equation of motion is derived for the individual ripples, seen as "particles", on the otherwise flat bed. The model account for the initial apperance of the ripples, the subsequent coarsening of the ripples and the final equilibrium state. The model is related to physical parameters of the problem, and an analytical approximation for the equilibrium spacing of the ripples is developed. It is found that the spacing between the ripples scale with the square-root of the non-dimensional shear stress (the Shields parameter) on a flat bed. The results of the model are compared with measurements, and reasonable agreement between the model and the measurements is demonstrated.Comment: 9 pages incl. figures. Revised versio

Correction to: Quality traits of raw and cooked cupped oysters

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Exploring the canal environment in terms of water, bed sediments and vegetation in a reclaimed floodplain of Northern Italy

The Po plain (Italy) is one of the largest floodplains in Europe that needs environmental restoration. To achieve this goal, the knowledge of the 'environment' (water, bed sediments and vegetation) of the canals crossing such floodplain is necessary. The water flow of the canals was kept low for hydraulic safety purposes from October to March (NIR), and high for irrigation purposes from April to September (IR). Within this framework, this study aimed to assess in 9 sites of the east part of Po plain 1) the canals' environment quality in terms of vegetation diversity, and water and bed sediment physicochemical properties; and 2) how these features are influenced by canal managements and landscape properties. Water was monthly sampled both in NIR and IR periods, the bed sediments were sampled in summer and winter pe-riods, while the vegetation was recorded in spring and autumn. The low water flow during NIR worsened the water quality by increasing the concentrations of nutrients and salts. A higher salt and nutrient concentrations were observed both in water and bed sediments of canals crossing areas with fne texture alluvial deposits than in those flowing through medium texture alluvial deposits. Further, higher nutrient and salt concentrations were observed for the ca-nals used as collectors of the water coming from other canals. Despite the differences observed for the bed sediments and water quality, the vegetation type and biodiversity did not show differences among the study sites probably be-cause affected by the land use of the surrounding landscape. Indeed, the canals cross agricultural land which limit the developments of natural vegetation and do not promote plant biodiversity. Overall, the present study found out the key role of landscape properties and canal managements on 'canal environment' quality which need to be consid-ered to perform an appropriate reclamation of such environments

Spatial microbial community structure and biodiversity analysis in "extreme" hypersaline soils of a semiarid Mediterranean area

In recent years specific attention has been paid on the biotechnological potential of microorganisms in extreme soils, in particular in saline soils. Salinity is one of the most widespread soil degradation processes on the Earth, and saline soils can be defined as extreme soils or border line habitats in which several factors, as high salt content, may limit the growth of organisms. In this study, the physical, chemical and microbiological soil properties were investigated in the shallower horizon of natural salt-affected soils in Sicily (Italy). The main aim of the research was to evaluate the structure and diversity of bacterial and archaeal communities by terminal-restriction fragment length polymorphism (T-RFLP) according to arbitrary different classes of vegetation and salt crust cover in soils. Furthermore, the structure of microbial communities was assessed considering the heterogeneity of physical-chemical properties of the habitat under investigation, as a function of vegetation, crust cover, and salinity classes. The results provided information on the type of distribution of different microbial community composition and diversity as a function of both vegetation and crust cover as well as salinity classes. In particular, the archaeal community showed a richness and diversity significantly affected by the spatial gradients of soil salinity, conversely, the bacterial one showed a decreasing trend with increasing gradient of soil salinity. The T-RFLP cluster analysis showed the formation of two groups for both bacterial and archaeal community, significantly (. p<. 0.05) influenced by sand and silt content, electrical conductivity (EC. e), vegetation cover percentage, salt crust and for by texture composition. In particular, the discriminant analysis obtained for the different salt crust classes for archaeal community stressed the membership of one of the two clusters to the class with the lower salt crust percentage (0-40%)

Pedodiversity and Organic Matter Stock of Soils Developed on Sandstone Formations in the Northern Apennines (Italy)

Pedodiversity is considered the cornerstone of biodiversity. This work aimed to (1) assess pedodiversity according to vegetation, topographic factors, and lithology and to (2) identify the major soil-forming factors on soil organic matter (SOM) stock at a 0-30 cm depth. These goals were reached using data from 147 georeferenced soil profiles distributed along 400-1000 m (<= 1000) and 1000-2134 m (>1000) altitudinal gradients in the northern part of the Apennine chain in Italy. Soils showed mainly weak or incipient development (i.e., Entisols and Inceptisols), which could be attributed to sand-based lithology, high slope gradients, and low SOM accumulation rates, which promote soil erosion processes. However, higher pedodiversity was observed at >1000 m than at <= 1000 m, likely due to the higher vegetation cover diversity and climate variability; Spodosols and Mollisols were also found. A greater SOM stock was found at >1000 than <= 1000 m, and vegetation seemed to not affect SOM amounts, suggesting a greater influence of climate on SOM content compared to vegetation. Considering ecosystem conservation, the observed spatial pedodiversity could be considered a critical basis for the protection of soil resources and pedodiversity itself in mountain regions

Fatigue life under non-Gaussian random loading from various models

Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for fatigue life calculation in the frequency domain. The best and very similar results of fatigue life assessment have been obtained using the models proposed by Socie and by Łagoda–Macha, both in time and frequency domains for the last one.With the support of the Commission of the European Communities under the FP5, GROWTH Programme, contract No. G1MA-CT-2002-04058 (CESTI)