A multi-scale approach to determine the REV in complex carbonate rocks

Complex porous carbonates display heterogeneity at different scales, influencing their reservoir properties (e.g. porosity) especially since different porosity types may exist on different spatial scales. This requires a quantitative geometric description of the complex (micro)structure of the rocks. Modern computer tomography techniques permit acquiring detailed information concerning the porosity network at different scales. These datasets allow evolvement to a more objective pore classification based on mathematical parameters. However computational limitations in complex reservoir models do not allow incorporating heterogeneities on small scales (e.g. sub-meter scale) in full-field reservoir simulations [Nordahl and Ringrose, 2008]. The suggested workflow allows characterizing different porosity networks in travertine rocks as well as establishing confidence intervals regarding the Representative Elementary Volume (REV) of these samples. The results of this study prove that one has to be very critical when determining the REV of heterogeneous complex carbonate rocks, since they are influenced by both resolution and size of the dataset

Computer Tomography as a data acquisition tool for quantifying and modeling in-pore gypsum crystallization in building materials

In the last few decades a new type of persistent efflorescence has started appearing on ceramic brick facades in the UK, the Netherlands and in Belgium. Since the problem undermines the aesthetic appearance of masonry buildings, it results in a growing number of complaints from building owners. In the laboratory, gypsum efflorescence is typically studied via wicking tests. However, these often yield gypsum subflorescence instead, leading to significant pore clogging just below the evaporation surface. To gain further insight in that subflorescence and pore clogging, a correct quantification of the amount and the distribution of the gypsum crystalised in the pore space is necessary. Micro-CT achieves this by allowing visual inspection as well as quantitative data gathering. Because of the non-destructiveness of micro-CT, samples can be scanned before and after subflorescence/pore clogging has occurred. The suggested methodology includes visualization and characterization of the pore space. Observing the changes in pore structure, with the assumption that these are induced only by the presence of the salt crystals, it is possible to accurately quantify the volume of gypsum present, as well as the location of the affected pores in 3D. Due to the partial volume effect, the CT dataset can be used to detect objects smaller than the voxel size because the density difference between gypsum and air is large enough. The obtained results confirm the presence of a thin gypsum layer just below the evaporation surface of the sample. Other techniques such as the wicking test and MIP also confirm the observations regarding pore size change and gypsum content

The application of Computed Tomography for characterising the pore structure of building materials

Flow and transport phenomena in porous media play a significant role in various fields of science and technology, comprising a spectrum from medical sciences over material sciences to soil and rock sciences. Also in building materials, the transfer of moisture and heat play a crucial role when assessing their properties and performances. Hence, three-dimensional analyses of the pore structure of building materials are becoming progressively more important in recent years, to obtain more accurate interpretations and simulations of their characteristics. Computed tomography has proven to be an excellent and versatile tool to perform these analyses non-destructively. The reconstruction of the pore structure is of high importance for establishing accurate models, as it plays a crucial role in determining important characteristics of building materials. These models allow to better understand the results of corresponding laboratory tests and in the near future might replace these time consuming experiments. In this paper the added value of Computed Tomography characterization will be demonstrated based on two case studies. The first will focus on the accurate simulation of moisture transfer while in the second one CT datasets are used to overcome a multiscale problem regarding the simulation of the effective thermal conductivity

Did Human Culture Emerge in a Cultural Evolutionary Transition in Individuality?

Evolutionary Transitions in Individuality (ETI) have been responsible for the major transitions in levels of selection and individuality in natural history, such as the origins of prokaryotic and eukaryotic cells, multicellular organisms, and eusocial insects.\ua0The integrated hierarchical organization of life thereby emerged as groups of individuals repeatedly evolved into new and more complex kinds of individuals. The Social Protocell Hypothesis (SPH) proposes that the integrated hierarchical organization of human culture can also be understood as the outcome of an ETI—one that produced a\ua0“cultural organism” (a “sociont”) from a substrate of socially learned traditions that were contained in growing and dividing social communities. The SPH predicts that a threshold\ua0degree of evolutionary individuality would have been achieved by 2.0–2.5 Mya, followed by an increasing degree of evolutionary individuality as the ETI unfolded. We here assess the SPH by applying a battery of criteria—developed to assess evolutionary individuality in biological units—to cultural units across the evolutionary history of Homo. We find an increasing agreement with these criteria, which buttresses the claim that an ETI occurred in the cultural realm

Nano- to millimeter scale morphology of connected and isolated porosity in the permo-triassic khuff formation of Oman

Carbonate reservoirs form important exploration targets for the oil and gas industry in many parts of the world. This study aims to differentiate and quantify pore types and their relation to petrophysical properties in the Permo-Triassic Khuff Formation, a major carbonate reservoir in Oman. For that purpose, we have employed a number of laboratory techniques to test their applicability for the characterization of respective rock types. Consequently, a workflow has been established utilizing a combined analysis of petrographic and petrophysical methods which provide the best results for pore-system characterization. Micro-computed tomography (μCT) analysis allows a representative 3D assessment of total porosity, pore connectivity, and effective porosity of the ooid-shoal facies but it cannot resolve the full pore-size spectrum of the highly microporous mud-/wackestone facies. In order to resolve the smallest pores, combined mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR), and BIB (broad ion beam)-SEM analyses allow covering a large pore size range from millimeter to nanometer scale. Combining these techniques, three different rock types with clearly discernible pore networks can be defined. Moldic porosity in combination with intercrystalline porosity results in the highest effective porosities and permeabilities in shoal facies. In back-shoal facies, dolomitization leads to low total porosity but well-connected and heterogeneously distributed vuggy and intercrystalline pores which improves permeability. Micro- and nanopores are present in all analyzed samples but their contribution to effective porosity depends on the textural context. Our results confirm that each individual rock type requires the application of appropriate laboratory techniques. Additionally, we observe a strong correlation between the inverse formation resistivity factor and permeability suggesting that pore connectivity is the dominating factor for permeability but not pore size. In the future, this relationship should be further investigated as it could potentially be used to predict permeability from wireline resistivity measured in the flushed zone close to the borehole wall. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Nano- to Millimeter Scale Morphology of Connected and Isolated Porosity in the Permo-Triassic Khuff Formation of Oman

Carbonate reservoirs form important exploration targets for the oil and gas industry in many parts of the world. This study aims to differentiate and quantify pore types and their relation to petrophysical properties in the Permo-Triassic Khuff Formation, a major carbonate reservoir in Oman. For that purpose, we have employed a number of laboratory techniques to test their applicability for the characterization of respective rock types. Consequently, a workflow has been established utilizing a combined analysis of petrographic and petrophysical methods which provide the best results for pore-system characterization. Micro-computed tomography (μCT) analysis allows a representative 3D assessment of total porosity, pore connectivity, and effective porosity of the ooid-shoal facies but it cannot resolve the full pore-size spectrum of the highly microporous mud-/wackestone facies. In order to resolve the smallest pores, combined mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR), and BIB (broad ion beam)-SEM analyses allow covering a large pore size range from millimeter to nanometer scale. Combining these techniques, three different rock types with clearly discernible pore networks can be defined. Moldic porosity in combination with intercrystalline porosity results in the highest effective porosities and permeabilities in shoal facies. In back-shoal facies, dolomitization leads to low total porosity but well-connected and heterogeneously distributed vuggy and intercrystalline pores which improves permeability. Micro- and nanopores are present in all analyzed samples but their contribution to effective porosity depends on the textural context. Our results confirm that each individual rock type requires the application of appropriate laboratory techniques. Additionally, we observe a strong correlation between the inverse formation resistivity factor and permeability suggesting that pore connectivity is the dominating factor for permeability but not pore size. In the future, this relationship should be further investigated as it could potentially be used to predict permeability from wireline resistivity measured in the flushed zone close to the borehole wall

Inhibition of major integrin αVβ3 reduces Staphylococcus aureus attachment to sheared human endothelial cells.

BACKGROUND: Vascular endothelial dysfunction with associated oedema and organ failure is one of the hallmarks of sepsis. While a large number of microorganisms can cause sepsis, Staphylococcus aureus is one of the primary etiological agents. Currently there are no approved specific treatments for sepsis and therefore the initial management bundle focuses on cardiorespiratory resuscitation and mitigation against the immediate threat of uncontrolled infection. The continuous emergence of antibiotic resistant strains of bacteria urges the development of new therapeutic approaches for this disease. OBJECTIVE: The objective of this study was to identify the molecular mechanisms leading to endothelial dysfunction as a result of Staphylococcus aureus binding. METHODS: Stahpylococcus aureus Newman and clumping factor A-deficient binding to endothelium were measured in vitro and in the mesenteric circulation of C57Bl/6 mice. The effect of the αVβ3 blocker, cilengitide, on bacterial binding, endothelial VE-cadherin expression, apoptosis, proliferation and permeability were assessed. RESULTS: Here we show that the major Staphylococcus aureus cell wall protein clumping factor A binds to endothelial cell integrin αVβ3 in the presence of fibrinogen. This interaction results in disturbances in barrier function mediated by VE-cadherin in endothelial cell monolayers and ultimately cell death by apoptosis. Using a low concentration of cilengitide, ClfA binding to αVβ3 was significantly inhibited both in vitro and in vivo. Moreover, preventing Staphylococcus aureus from attaching to αVβ3 resulted in a significant reduction in endothelial dysfunction following infection. CONCLUSION: Inhibition of Staphylococcus aureus ClfA binding to endothelial cell αVβ3 using cilengitide prevents endothelial dysfunction. This article is protected by copyright. All rights reserved

Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage

Compared to traditional pn-junction photovoltaics, hot carrier solar cells offer potentially higher efficiency by extracting work from the kinetic energy of photogenerated "hot carriers" before they cool to the lattice temperature. Hot carrier solar cells have been demonstrated in high-bandgap ferroelectric insulators and GaAs/AlGaAs heterostructures, but so far not in low-bandgap materials, where the potential efficiency gain is highest. Recently, a high open-circuit voltage was demonstrated in an illuminated wurtzite InAs nanowire with a low bandgap of 0.39 eV, and was interpreted in terms of a photothermoelectric effect. Here, we point out that this device is a hot carrier solar cell and discuss its performance in those terms. In the demonstrated devices, InP heterostructures are used as energy filters in order to thermoelectrically harvest the energy of hot electrons photogenerated in InAs absorber segments. The obtained photovoltage depends on the heterostructure design of the energy filter and is therefore tunable. By using a high-resistance, thermionic barrier an open-circuit voltage is obtained that is in excess of the Shockley-Queisser limit. These results provide generalizable insight into how to realize high voltage hot carrier solar cells in low-bandgap materials, and therefore are a step towards the demonstration of higher efficiency hot carrier solar cells