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Highlights • A novel method for identifying pore-body to pore-throat aspect ratio is defined. • This 'Morphological Aspect Ratio' scales linearly with non-wetting phase trapping. • Critical pore sizes are derived from connectivity and morphology of pore spaces. • Pore size relevant for capillary-dominated flow is defined by morphological opening. • The Morphological Aspect Ratio is applicable to a wide range of porous media. Abstract We introduce a new method for defining a pore-body to pore-throat aspect ratio from segmented 3D image data, based on a connectivity metric applicable to porous media with widely varying pore-space connectivity and pore-space morphology. The 'Morphological Aspect Ratio' (MAR) is identified from the pore-space connectivity, using the Euler number (χ) as a function of a pore-space size defined by a morphological opening (erosion and dilation) of the pore space. We show that residual non-wetting phase trapping in porous media resulting from secondary imbibition scales with the MAR. Trapping was investigated in a Bentheimer sandstone core and five columns of partially sintered glass-particle packs with different combinations of glass beads and crushed glass ranging in size from 0.3 to 1.2 mm, resulting in porosity levels of 22–36%. Residual non-wetting phase trapping scales with the MAR, in contrast to the aspect ratio calculated with the traditional Maximum Inscribed Sphere (MIS) algorithm applied after partitioning the pore space into pore bodies and pore throats with a watershed transform followed by a region merging algorithm. This novel aspect ratio is a robust method that is less affected by segmentation errors compared to other methods for calculating aspect ratio and is applicable to residual non-wetting phase trapping resulting from capillary-driven flow of a wetting fluid through water-wet porous media. [ABSTRACT FROM AUTHOR]

We investigate trapping of a nonwetting (NW) phase, air, within Bentheimer sandstone cores during drainage–imbibition flow experiments, as quantified on a three dimensional (3D) pore-scale basis via x-ray computed microtomography (X-ray CMT). The wetting (W) fluid in these experiments was deionized water doped with potassium iodide (1:6 by weight). We interpret these experiments based on the capillary–viscosity–gravity force dominance exhibited by the Bentheimer–air–brine system and compare to a wide range of previous drainage–imbibition experiments in different media and with different fluids. From this analysis, we conclude that viscous and capillary forces dominate in the Bentheimer–air–brine system as well as in the Bentheimer–supercritical CO 2 –brine system. In addition, we further develop the relationship between initial (post-drainage) NW phase connectivity and residual (post-imbibition) trapped NW phase saturation, while also taking into account initial NW phase saturation and imbibition capillary number. We quantify NW phase connectivity via a topological measure as well as by a statistical percolation metric. These metrics are evaluated for their utility and appropriateness in quantifying NW phase connectivity within porous media. Here, we find that there is a linear relationship between initial NW phase connectivity (as quantified by the normalized Euler number, χ ˆ ) and capillary trapping efficiency; for a given imbibition capillary number, capillary trapping efficiency (residual NW phase saturation normalized by initial NW phase saturation) can decrease by up to 60% as initial NW phase connectivity increases from low connectivity ( χ ˆ ≈ 0) to very high connectivity ( χ ˆ ≈ 1). We propose that multiphase fluid-porous medium systems can be efficiently engineered to achieve a desired residual state (optimal NW phase saturation) by considering the dominant forces at play in the system along with the impacts of NW phase topology within the porous media, and we illustrate these concepts by considering supercritical CO 2 sequestration scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Microporous materials such as zeolites, metal organic frameworks, activated carbons and aluminum phosphates are suitable for catalysis and separation applications. These high surface area materials are invariably produced in particulate forms and need to be transformed into hierarchically porous structures for high performance adsorbents or catalysts. Structuring of porous powders enables an optimized structure with high mass transfer, low pressure drop, good heat management, and high mechanical and chemical stability. The requirements and important properties of hierarchically porous structures are reviewed with a focus on applications in gas separation and catalysis. Versatile powder processing routes to process porous powders into hierarchically porous structures like extrusion, coatings of scaffolds and honeycombs, colloidal processing and direct casting, and sacrificial approaches are presented and discussed. The use and limitations of the use of inorganic binders for increasing the mechanical strength is reviewed, and the most important binder systems, e.g. clays and silica, are described in detail. Recent advances to produce binder-free and complex shaped hierarchically porous monoliths are described and their performance is compared with traditional binder-containing structured adsorbents. Needs related to better thermal management and improved kinetics and volume efficiency are discussed and an outlook on future research is also given. [Copyright &y& Elsevier]

• X-ray microtomography imaging of three-phase fluid distributions during quasi-static drainage-imbibition cycles of three-phase flow in water-wet porous media. • Initial water saturation (at the point of air injection) in three-phase flow does not affect the capillary pressure-saturation relationship or the interfacial area-saturation relationship under quasi-equilibrium conditions. • For the oil-water fluid pair in a three-phase flow system, hysteresis in the interfacial area-saturation relationship is minimal, and the capillary pressure-saturation-interfacial area relationship fully eliminates hysteresis. • For air-oil, the same conclusion can be drawn, as long as the system is in a quasi-equilibrated state. • Our results suggest that interface relaxation greatly affects formation of interfacial area, but it does not notably affect capillary pressure. We encounter three-phase flow in porous media within a range of settings, such as enhanced oil recovery, geologic CO 2 sequestration, and groundwater remediation. While an abundance of studies has been performed on the behavior of two fluid phases (e.g. oil/water or air/water) in porous media, relatively little information exists for three-phase flow systems (e.g. oil/water/air). This work explores the relationships between capillary pressure (P c), saturation (S) and fluid-fluid interfacial area (a) for water-wet three-phase flow systems where water is the wetting phase, oil is the intermediate-wet phase, and air (or gas) is the non-wetting phase. Specifically, we examine whether the P c - S - a relationships exhibit hysteresis during drainage and imbibition cycles. We present data collected via x-ray microtomography resulting in high-resolution three-dimensional images of the fluid configurations for varying degrees of saturation. Among the findings of the study (based on the available data), we highlight that (1) the P c - S - a relationship is non-hysteretic for both the oil-water fluid pair, and the air-oil fluid pair, and (2) that this same relationship is independent of the initial water saturation at the point of air injection. This finding suggests that both the oil-water and air-oil fluid pairs in a three-phase system can be adequately described by the thermodynamics-based theory originally proposed by Hassanizadeh and Gray (1993), as is the case for the equivalent two-phase system. [ABSTRACT FROM AUTHOR]

Background: Red blood cell (RBC) transfusions are associated with risks including immunological reactions and volume overload. Current guidelines suggest a restrictive transfusion strategy in most patients with sepsis but based on previous randomized controlled trials and observational studies, there are still uncertainties about the safety in giving low-grade RBC transfusions to patients with sepsis. Methods: Critically ill patients with severe sepsis or septic shock admitted to a university hospital intensive care unit between 2007 and 2018 that received less or equal to 2 units of RBCs during the first 5 days of admission were propensity score matched to controls. Outcomes were 90- and 180-day mortality, highest acute kidney injury network (AKIN) score the first 10 days, days alive and free of organ support the first 28 days after admission to the intensive care unit and highest sequential organ failure assessment score (SOFA-max). Results: Of 9490 admissions, 1347 were diagnosed with severe sepsis or septic shock. Propensity-score matching resulted in two well-matched groups with 237 patients in each. The annual inclusion rate in both groups was similar. The median hemoglobin level before RBC transfusion was 95 g/L (interquartile range 88–104) and the majority of the patients were transfused in first 2 days of admission. Low-grade RBC transfusion was associated with increased 90- and 180-day mortality with an absolute risk increase for death 9.3% (95% confidence interval: 0.6–18%, P = 0.032) and 11% (95% confidence interval: 1.7–19%, P = 0.018), respectively. Low-grade RBC transfusion also correlated with increased kidney, circulatory and respiratory failure and higher SOFA-max score. Conclusions: Low-grade RBC transfusion during the first 5 days of admission was associated with increased mortality and morbidity in a liberal transfusion setting. The results support the current practice of a restrictive transfusion strategy in septic critically ill patients. [ABSTRACT FROM AUTHOR]

We explore how X-ray computed microtomography can be used to generate highly-resolved 3D biofilm datasets on length scales that span multiple pore bodies. The data is integrated into a study of the effects of flow rate on three-dimensional growth of biofilm in porous media. Three flow rates were investigated in model packed-bed columns. Biofilm growth was monitored during an 11-day growth period using a combination of differential pressure and effluent dissolved oxygen measurements. At the end of the growth period, all columns were scanned using X-ray computed microtomography and a barium sulfate-based contrast agent. The resulting images were prepared for quantitative analysis using a novel image processing workflow that was tailored to this specific system. The reduction in permeability due to biofilm growth was studied using both transducer-based pressure drop measurements and image-based calculations using the Kozeny–Carman model. In addition, a set of structural measures related to the spatial distribution of biofilms were computed and analyzed for the different flow rates. We generally observed 1 to 2 orders of magnitude decrease in permeability as a result of bioclogging for all columns (i.e, across flow rates). The greatest average permeability and porosity reduction was observed for the intermediate flow rate (4.5 ml/h). A combination of results from different measurements all suggest that biofilm growth was oxygen limited at the lowest flow rate, and affected by shear stresses at the highest flow rate. We hypothesize that the interplay between these two factors drives the spatial distribution and quantity of biofilm growth in the class of porous media studied here. Our approach opens the way to more systematic studies of the structure-function relationships involved in biofilm growth in porous media and the impact that such growth may have on physical properties such as hydraulic conductivity. [ABSTRACT FROM AUTHOR]