ALBERT

Description: The occurrence of heterogeneous perturbations of fluid mass density and solid elastic strain of a porous continuum, as a consequence of its undrained response is a very important topic in theoretical and applied poromechanics. The classical Mandel-Cryer effect provides an ex- planation of fluid overpressure in the central region of a porous sample, immediately after the application of the loading. However this effect fades away when the fluid leaks out of the porousnetwork.Herethisproblemisstudiedwithintheframeworkofasecondgradientthe- ory and a thorough description of the static and the dynamics of the phenomenon is given. We study how the presence of an impermeable wall affects the formation of the interface between two phases differing in the fluid content. Moreover, we show that the late time in- terface motion towards its stationary position is not affected by the impermeable wall and is characterizedby acommonseepagevelocity profile.

Description: Published

Description: 56-73

Description: JCR Journal

Description: arXiv admin note: text overlap with arXiv:1407.5309

Description: A phase transition model for porous media in consolidation is studied. The model is able to describe the phenomenon of fluid-segregation during the consolidation process, i.e., the coexistence of two phases differing from fluid content inside the porous medium under static load. Considering pure Darcy dissipation, the dynamics is described by a Cahn-Hilliard-like system of partial differential equations (PDE). The goal, here, is to study the dynamics of the formation of stationary fluid-rich bubbles. The evolution of the strain and fluid density profiles of the porous medium is analyzed in two physical situation: fluid free to flow through the boundaries of the medium and fluid flow prevented at one of the two boundaries. Morover, an analytic result on the position of the interface between the two phases is provided.

Description: Published

Description: 93-103

Description: N/A or not JCR

Description: In this work we study a Hebbian neural network, where neurons are arranged according to a hierarchical architecture such that their couplings scale with their reciprocal distance. As a full statistical mechanics solution is not yet available, after a streamlined introduction to the state of the art via that route, the problem is consistently approached through signal-to-noise technique and extensive numerical simulations. Focusing on the low-storage regime, where the amount of stored patterns grows at most logarithmical with the system size, we prove that these non-mean-field Hopfield-like networks display a richer phase diagram than their classical counterparts. In particular, these networks are able to perform serial processing (i.e. retrieve one pattern at a time through a complete rearrangement of the whole ensemble of neurons) as well as parallel processing (i.e. retrieve several patterns simultaneously, delegating the management of different patterns to diverse communities that build network). The tune between the two regimes is given by the rate of the coupling decay and by the level of noise affecting the system. The price to pay for those remarkable capabilities lies in a network's capacity smaller than the mean field counterpart, thus yielding a new budget principle: the wider the multitasking capabilities, the lower the network load and vice versa. This may have important implications in our understanding of biological complexity.

Description: Published

Description: 22-35

Description: JCR Journal

Description: Highlights • Accurate fault model can be built even when sparse drilling wells are available. • The multiresolution fault model provides information of faults with different sizes. • Fault model provides possibility of tectonic and fluid flow analysis simultaneously. • Modelling of faults in different scales, enable more accurate well path design. • The ANN provides optimized parameters for fault detection by ant tracking algorithm. Modelling faults plays a crucial step in the chain of studies through the first phase of the hydrocarbon exploration and its following studies in reservoir engineering, simulation and field development. This study introduces an innovative and automatic integrated approach that combines seismic multi-attributes and well data for faults modelling. The proposed strategy begins with extracting fault-related seismic attributes commonly used for seismic reservoir characterization. Chaos, variance and curvature attributes, typically highlight large-scale faults that shape the structural framework of the study field. In contrast, small-scale faults, influencing subsurface fluid flow in the fractured reservoir, are modeled using the ant-tracking algorithm applied to seismic data. Small-scale and large-scale fault models, then integrated with the conventional fault model to create an integrated discrete fracture network (DFN). This DFN model incorporates information on both large-scale and small-scale faults. The proposed strategy was applied on a geologically complex petroleum field in Iran. The results, validated using Formation Micro Imager (FMI) data, demonstrate accuracy of the integrated DFN model in comparison to conventional approaches on the studied filed, particularly in capturing small-scale faults. Consequently, it can be concluded that the proposed strategy provides a viable alternative for generating accurate DFN model.

Description: Highlights • Alkaline magmas of the TLTF island chain result from a subduction-modified mantle source and two-stage partial melting. • The role of mantle source and parental melt composition for high Cu-Au mineral potentials is important but limited. • A shallow crustal magma reservoir is key for epithermal ore formation. Abstract The Tabar-Lihir-Tanga-Feni (TLTF) island chain in northeastern Papua New Guinea formed by tectonic and alkaline to shoshonitic magmatic activity since the Pliocene. Several volcanic centers are Cusingle bondAu mineralized including the world-class Ladolam Au deposit and Conical Seamount south of Lihir. The latter has been recognized as a juvenile analogue to the Ladolam deposit located on-shore. Whereas the mineralization at Conical Seamount is reasonably well studied, the specific magmatic processes that promote epithermal mineralization at this seamount but not at others are poorly understood. Here, we present new petrological and geochemical data from Conical Seamount, and compare them with those from the barren (unmineralized) Edison, Tubaf and New World seamounts nearby. We focus on whole rock compositions and major and trace element analysis of melt inclusions and minerals including clinopyroxene, sulfide and magnetite. We combine our observations with modelled constraints on mantle source composition and partial melting as well as magma evolution. A first-stage melting leaves a residual mantle source enriched in Au. Second-stage melting of a previously subduction-metasomatized mantle generally promotes the transfer and concentration of metals and volatiles in the ascending melts. These magmas are unlikely to control ore formation as all seamounts show evidence for similar mantle sources and parental melt composition. However, the presence of a shallow crustal magma chamber is unique to Conical Seamount. It is characterized by frequent melt replenishments and extensive magma fractionation leading to sulfide and magmatic volatile saturation. These specific magma chamber processes lead to the pre-enrichment of the magma in chalcophile elements including Au, while sulfide saturation coeval with magmatic volatile exsolution provide the way for an effective Au transfer from the magmatic to the epithermal system.

Description: Highlights • All investigated sites are in quiescent stage. Multi layers of clam shell debris were the ancient sediment surfaces during high methane flux. • Current fluxes contribute to less than 2 wt % of authigenic carbonates and 2 wt % iron sulfide minerals being precipitated in 600-800 cm sediment. • The sequestration of carbon could be 〉 50 mmol C cm-2 yr-1 under current in situ condition. Abstract Methane seepage records information of the local carbon cycle with respect to the generation, consumption and sequestration of carbon. Here presents the investigation of 7 gravity cores retrieved in 2004 during cruise SO-177 in the Haiyang 4 Area at the northern slope of the South China Sea. Porewater solutes, sulfate, methane, total alkalinity, sulfide and calcium demonstrate currently the weak seep activity. Local carbon cycling and sequestration is also revealed, that dominates by anaerobic oxidation of biogenic methane to dissolved bicarbonate inducing calcium carbonate and iron sulfide minerals (mainly pyrite) precipitation. A reactive transport model was employed to quantify the carbon cycle and budget. Model results show that current methane fluxes contribute to less than 2 wt % of authigenic carbonates and 2 wt % iron sulfide minerals being precipitated in 600–800 cm sediment depth. The sequestration of carbon could be 〉 50 mmol C cm−2 yr−1 under in situ condition. The observed increase of carbonate and iron sulfide minerals at ∼100 cm, however, require higher methane fluxes to shift the zone of anaerobic oxidation of methane upwards to around 1 m below the seafloor, which have occurred during sea level low stands in the geological past. The oscillation of seepage flux contributed to the formation of multiple layers of authigenic carbonates and pyrite, which indicates the high capability of carbon sink and is speculated to be induced by the dissociation of the underlying hydrates triggered by sea level drop and or temperature increase.

Description: In addition to endangering sea traffic, cable routes, and wind farms, sunken warship wrecks with dangerous cargo, fuel, or munitions on board may emerge as point sources for environmental damage. Energetic compounds such as TNT (which could leak from these munitions) are known for their toxicity, mutagenicity, and carcinogenicity. These compounds may cause potential adverse effects on marine life via contamination of the marine ecosystem, and their entry into the marine and human food chain could directly affect human health. To ascertain the impending danger of an environmental catastrophe posed by sunken warships, the North Sea Wrecks (NSW) project (funded by the Interreg North Sea Region Program) was launched in 2018. Based on historical data (derived from military archives) including the calculated amount of munitions still on board, its known location and accessibility, the German World War II ship “Vorpostenboot 1302” (former civilian name - “JOHN MAHN”) was selected as a case study to investigate the leakage and distribution of toxic explosives in the marine environment. The wreck site and surrounding areas were mapped in great detail by scientific divers and a multibeam echosounder. Water and sediment samples were taken in a cross-shaped pattern around the wreck. To assess a possible entry into the marine food chain, aged mussels were exposed at the wreck, and wild fish (pouting), a sedentary species that stays locally at the wreck, were caught. All samples were analyzed for the presence of TNT and derivatives thereof by GC–MS/MS analysis. As a result, we could provide evidence that sunken warship wrecks emerge as a point source of contamination with nitroaromatic energetic compounds leaking from corroding munitions cargo still on board. Not only did we find these explosive substances in bottom water and sediment samples around the wreck, but also in the caged mussels as well as in wild fish living at the wreck. Fortunately so far, the concentrations found in mussel meat and fish filet were only in the one-digit ng per gram range thus indicating no current concern for the human seafood consumer. However, in the future the situation mayworsen as the corrosion continues. Fromour study, it is proposed that wrecks should not only be ranked according to critical infrastructure and human activities at sea, but also to the threats they pose to the environment and the human seafood consumer.

Description: The present work intended to investigate the fate of contaminant-loaded microplastics if ingested by benthic filter feeder Mytilus edulis under laboratory conditions. In the course of a 7-day experiment the mussels were exposed to PVC microplastics in a size range 〉40 mm, in doses of 2000 particles L_1 (11.56 mg L_1). Particles were either virgin or loaded with one of four different nominal concentrations of the polycyclic aromatic hydrocarbon (PAH) fluoranthene (500, 125, 31.25 and 7.8125 mg g_1). Verification of fluoranthene concentrations on the particles provided evidence of the high absorptive capacity of PVC for this PAH, indicating that comparable particles may serve as considerable accumulation sites for high concentrations of hydrophobic contaminants in the aquatic environment. Analysis of digestive gland tissues via polarised light microscopy revealed the occurrence of particles and particle aggregates within stomach and intestines of all mussels treated with microplastics, thus making the xenobiotic bioavailable. Results of contaminant analysis in mussel tissues via equilibrium sampling point to a considerable capability of microplastics for the accumulation of hydrophobic contaminants from the environment and their potential to act as vehicles for the transport of theses contaminants into organismal tissues. of fluoranthene concentrations on the particles provided evidence of the high absorptive capacity of PVC for this PAH, indicating that comparable particles may serve as considerable accumulation sites for high concentrations of hydrophobic contaminants in the aquatic environment. Analysis of digestive gland tissues via polarised light microscopy revealed the occurrence of particles and particle aggregates within stomach and intestines of all mussels treated with microplastics, thus making the xenobiotic bioavailable. Results of contaminant analysis in mussel tissues via equilibrium sampling point to a considerable capability of microplastics for the accumulation of hydrophobic contaminants from the environment and their potential to act as vehicles for the transport of theses contaminants into organismal tissues. © 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license