ALBERT

Description: In this study, a series of drained triaxial tests were performed in order to examine the effect of cementation on the shear behavior of granular soil. It was observed that the brittle nature and dilative tendency of granular soil is dominant under a low confining stress level, while high confining stress results in a contractive behavior despite the strong cementation bond. Based on experimental results, an idealized concept is suggested to define the shear strength of cemented sand in three distinctive zones: the cementation control zone with a constant cohesion intercept at a low confining stress level, the transition zone in which the cohesion intercept is gradually reduced after a breaking point, and the stress control zone with almost zero cohesion intercept due to breakage of cementation bonds at a high confining stress level. It was shown that the sitting pressures during cementation have little effect on the strength parameters of cemented sand, while the increase of gypsum content and relative density, and the decrease of particle size, result in an increase of the cohesion intercept and the breaking point. In addition, the prediction equations for the shear strength and cohesion intercept in the cementation control zone and the transition zone are suggested from the analytical and experimental interpretation.

Description: The distribution of five dominant calanoid copepods was related to different water masses in the Angola-Benguela Front system. Five water bodies were identified by principal component analysis, on the basis of abiotic parameter such as temperature, salinity, dissolved oxygen, phosphate, silicate, nitrate and nitrite. These parameters were reduced to single factors and arranged along two principal component axes. The copepod species incuded females and copepodites C5 of Calanoides carinatus and females of Metridia lucens, Centropages brachiatus, Nannocalanus minor and Aetideopsis carinata. The water bodies identified in the frontal system were related to currents, upwelling processes, an oxygen minimum layer and biological modification. The different copepod species, as well as the two ontogenetic stages of C. carinatus, showed clear preference for specific water bodies, and their behavioural and physiological adaptations to the environment are discussed.

Description: Force chain buckling, leading to unjamming and shear banding, is examined quantitatively via a discrete element analysis of a two-dimensional, densely-packed, cohesionless granular assembly subject to quasistatic, boundary-driven biaxial compression. A range of properties associated with the confined buckling of force chains has been established, including: degree of buckling, buckling modes, spatial and strain evolution distributions, and relative contributions to non-affine deformation, dilatation and decrease in macroscopic shear strength and potential energy. Consecutive cycles of unjamming–jamming events, akin to slip–stick events arising in other granular systems, characterize the strain-softening regime and the shear band evolution. Peaks in the dissipation rate, kinetic energy and local non-affine strain are strongly correlated: the largest peaks coincide with each unjamming event that is evident in the concurrent drops in the macroscopic shear stress and potential energy. Unjamming nucleates from the buckling of a few force chains within a small region inside the band. A specific mode of force chain buckling, prevalent in and confined to the shear band, leads to above-average levels of local non-affine strain and release of potential energy during unjamming. Ongoing studies of this and other buckling modes from a structural stability standpoint serve as the basis for the formulation of internal variables and associated evolution laws, central to the development of thermomicromechanical constitutive theory for granular materials.

Description: A new 30-arc second resolution global topography/bathymetry grid (SRTM30_PLUS) has been developed from a wide variety of data sources. Land and ice topography comes from the SRTM30 and ICESat topography, respectively. Ocean bathymetry is based on a new satellite-gravity model where the gravity-to-topography ratio is calibrated using 298 million edited soundings. The main contribution of this study is the compilation and editing of the raw soundings, which come from NOAA, individual scientists, SIO, NGA, JAMSTEC, IFREMER, GEBCO, and NAVOCEANO. The gridded bathymetry is available for ftp download in the same format as the 33 tiles of SRTM30 topography. There are 33 matching tiles of source identification number to convey the provenance of every grid cell. The raw sounding data, converted to a simple common format, are also available for ftp download.

Description: Cirripedes are one of the major groups of fouling organism in the marine environment. The cyprid can, before a permanent attachment, actively explore and walk on the substratum using its antennules in a bipedal fashion without leaving the surface. Studying the structure of the cyprid antennule is therefore important for understanding the events that culminate in biofouling by barnacles. There are at present no complete, standardised accounts of the structure of the cyprid antennules in thoracican barnacles, and moreover, the existing accounts vary in their use of terminology. This article describes the cyprid antennule of the barnacle Megabalanus rosa. This barnacle species is common in E Asia, and the cyprids have previously been used in several biofouling studies. All externally visible setae on the antennules have been mapped; these comprise both chemosensors with a terminal pore, a putative aesthetasc-like seta and mechano-sensory setae. More setae were found on the attachment disc than in previous scanning electron microscope-based studies, but not all structures that can be seen with transmission electron microscopy were visible. The disc itself seems to have a variable surface area, which could assist in exploring rough surfaces. The various lengths of the antennular setae, coupled with the disposition of the segments, enable the cyprid to cover a wide swath of substratum during exploratory walking. A new terminology is proposed for cyprid antennular setae, which will form a basis for future comparative and functional studies of cirripede settlement.

Description: A simple unified critical state constitutive model for bonded geomaterials is presented in this paper. The model, which is called CASM-n, is an enhancement of an existing unified critical state model for reconstituted geomaterials (CASM). Characteristic behaviours of a bonded geomaterial such as the pre-yield higher strength and stiffness and the cohesive–frictional shearing mode in the post-yield region are taken into account and included in the reference model. The salient feature of the proposed model is the incorporation of cohesive component into the stress–dilatancy relationship. Consideration of the contribution of cohesion to plastic flow allows the modelling of delayed dilatancy and softening–contraction behaviour, which are two interesting phenomena observed in bonded geomaterials.

Description: Three new species of siphonophores (Rhodaliidae), a little known, uniquely benthic, family of Physonectae (Hydrozoa, Cnidaria), are described from specimens observed and collected at depths between 120 and 360 m off Indonesia and South Africa by the submersible JAGO. Special reference is made to in situ observations and video close‐ups that revealed detailed information on locomotory, fishing and feeding behaviour.

Description: The present study analyses the distribution of cephalopod paralarvae off the Portuguese coast. The effects of temporal and physical variables on Loligo vulgaris, Octopus vulgaris, sepiolid and ommastrephid abundances are analysed with generalized linear models. Their distribution patterns are discussed in relation to mesoscale features, including currents, thermal fronts and coastal upwelling cross-shelf transport, prevailing in the western Iberia upwelling system. Paralarvae of the neritic species occur during a considerably extended period of the year with two or three abundance peaks within the highly productive upwelling system of the western Portuguese coast and contrasting with the Gulf of Cadiz area. Temperature and upwelling were shown to be the most important variables in modulating seasonality and distribution of these paralarvae. The influence of the physical environment is particularly pronounced for the paralarvae of O. vulgaris, following distinct patterns according to the oceanography of the western Iberia and the Gulf of Cadiz systems. The paralarvae of oceanic species, which in many cases have their northern limit of distribution at these latitudes, were mainly found in the southern part of the sampling area. The distribution of these species indicates that the prevailing oceanographic features of the Gulf of Cadiz system, especially fronts, together with temperature act as boundaries to geographic dispersal, contributing to an area of high cephalopod biodiversity in the southern Portuguese waters.

Description: Post-collisional magmatism in the southern Iberian and northwestern African continental margins contains important clues for the understanding of a possible causal connection between movements in the Earth's upper mantle, the uplift of continental lithosphere and the origin of circum-Mediterranean igneous activity. Systematic geochemical and geochronological studies (major and trace element, Sr–Nd–Pb-isotope analysis and laser 40Ar/39Ar-age dating) on igneous rocks provide constraints for understanding the post-collisional history of the southern Iberian and northwestern African continental margins. Two groups of magmatic rocks can be distinguished: (1) an Upper Miocene to Lower Pliocene (8·2–4·8 Ma), Si–K-rich group including high-K (calc-alkaline) and shoshonitic series rocks; (2) an Upper Miocene to Pleistocene (6·3–0·65 Ma), Si-poor, Na-rich group including basanites and alkali basalts to hawaiites and tephrites. Mafic samples from the Si–K-rich group generally show geochemical affinities with volcanic rocks from active subduction zones (e.g. Izu–Bonin and Aeolian island arcs), whereas mafic samples from the Si-poor, Na-rich group are geochemically similar to lavas found in intraplate volcanic settings derived from sub-lithospheric mantle sources (e.g. Canary Islands). The transition from Si-rich (subduction-related) to Si-poor (intraplate-type) magmatism between 6·3 Ma (first alkali basalt) and 4·8 Ma (latest shoshonite) can be observed both on a regional scale and in individual volcanic systems. Si–K-rich and Si-poor igneous rocks from the continental margins of southern Iberia and northwestern Africa are, respectively, proposed to have been derived from metasomatized subcontinental lithosphere and sub-lithospheric mantle that was contaminated with plume material. A three-dimensional geodynamic model for the westernmost Mediterranean is presented in which subduction of oceanic lithosphere is inferred to have caused continental-edge delamination of subcontinental lithosphere associated with upwelling of plume-contaminated sub-lithospheric mantle and lithospheric uplift. This process may operate worldwide in areas where subduction-related and intraplate-type magmatism are spatially and temporally associated.

Description: Data from New Zealand and northern Victoria Land, Antarctica, indicate that the Cambrian Takaka Terrane intra-oceanic arc/backarc assemblage and the Bowers Terrane intra-oceanic arc/back-arc assemblage were accreted to the Gondwana margin by the Late Cambrian. Compelling similarities between the arc rocks and the immediate post-arc sediments firmly place the two regions in the same tectonic framework and imply close paleogeographic proximity. Currently, the Ross Orogen is thought to be the result of sinistral oblique convergence with west-directed subduction, and accretion of the arc assemblages is attributed to closure of backarc basins. Syntectonic fluvial conglomerates in both regions attest to the development of fluvial systems draining both the accreted arc and the contemporaneous continental margin arc. Trilobite faunas indicate that fluvial sedimentation commenced earlier in New Zealand than in northern Victoria Land. In the context of the widely accepted sinistral oblique convergence model, these data suggest an original position for New Zealand to the south of northern Victoria Land, probably in the region of the southern Ross Sea.