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This study utilises computational fluid dynamics simulations with the OpenFOAM computational framework to investigate and compare the in-plane and through-plane permeability properties of four different gas diffusion layers (GDLs). Also the through-plane water and air relative permeability values and water saturations at different rates were simulated. Permeability analysis enhances our understanding of fluid flow, ways to decrease pressure loss in the GDL, and methods to enhance oxygen concentration at the catalyst layer interface through convection. The analysis reveals that the investigated GDL materials have spatial heterogeneity of porosity and permeability, especially in the Sigracet SGL 25 BA GDL. However, the porosity and permeability of the Toray TGP-H 060 and AvCarb 370 MGL GDLs exhibit less variations. The two-phase flow studies on GDL saturation show that at the same water injection flowrate, the AvCarb 370 MGL GDL has the largest remaining water saturation, with Sigracet SGL 25 BA GDL being the less saturated GDL among the four investigated GDLs. The compression from the ribs significantly affected the in-plane permeabilities of both Toray TGP-H 060 and especially impacted Sigracet SGL 25 BA GDL. This impact was expected as the pore size distribution varied significantly in the areas under the ribs versus the channel. [ABSTRACT FROM AUTHOR]

Mechanical properties of hydrate-bearing fine-grained sediments are crucial to effectively mitigate environmental risks caused by artificial and natural decomposition of natural gas hydrates, and the decomposition can induce laterally confined deformation. To explore the effect of natural gas hydrates on laterally confined compression properties, consolidation tests are conducted on remolded hydrate-free and hydrate-bearing samples by using natural fine-grained sediments collected from the northern South China Sea as the host sediments, and empirical equations are developed based on the analyses of consolidation characteristics. The results show that vertical loading induces a reduction in void ratio, and the reduction increases with decreasing hydrate saturation when samples are subjected to the same vertical stress change. The compression index of samples is about 0.53 whether there is hydrate or not, but the yield stress of samples increases sharply with increasing hydrate saturation once beyond the critical value. The coefficient of volume compression and the coefficient of consolidation of hydrate-bearing samples both increase firstly and then decrease to a relative stable level with increasing vertical stress, and the transition occurs at 200 kPa. The average consolidation degree with elapsed time increases rapidly under low vertical stresses, slowly under median vertical stresses, and under high vertical stresses, the consolidation increases a little faster but still slower than those under low vertical stresses. [ABSTRACT FROM AUTHOR]

Abstract This study utilises computational fluid dynamics simulations with the OpenFOAM computational framework to investigate and compare the in-plane and through-plane permeability properties of four different gas diffusion layers (GDLs). Also the through-plane water and air relative permeability values and water saturations at different rates were simulated. Permeability analysis enhances our understanding of fluid flow, ways to decrease pressure loss in the GDL, and methods to enhance oxygen concentration at the catalyst layer interface through convection. The analysis reveals that the investigated GDL materials have spatial heterogeneity of porosity and permeability, especially in the Sigracet SGL 25 BA GDL. However, the porosity and permeability of the Toray TGP-H 060 and AvCarb 370 MGL GDLs exhibit less variations. The two-phase flow studies on GDL saturation show that at the same water injection flowrate, the AvCarb 370 MGL GDL has the largest remaining water saturation, with Sigracet SGL 25 BA GDL being the less saturated GDL among the four investigated GDLs. The compression from the ribs significantly affected the in-plane permeabilities of both Toray TGP-H 060 and especially impacted Sigracet SGL 25 BA GDL. This impact was expected as the pore size distribution varied significantly in the areas under the ribs versus the channel.

In recent decades, with the growth of population and the development of metropolitans around the world, the issue of landfill and waste management has become more and more critical. Due to development of radioactive material applications, disposing these radioactive waste material became an important geo-environmental concern. Bentonite clay as an eco-friendly and natural shielding material is used as the main material for landfill barriers. The radiation shielding performance of bentonite clay modified by different percentages of basalt fiber and Polyvinyl alcohol (PVA) resin additives is investigated using experimental measurement, Monte Carlo N-Particle (MCNP) simulation, and XCOM database methods, in Gamma-ray energy levels of 60Co (1173.2 and 1332.5 keV). The employed sample mixtures include 0.25, 0.5, 1, and 2 percent of basalt fiber and PVA resin additive. The obtained results for Gamma-ray shielding measurement from these three methods have a good agreement, depicting an increasing trend in the linear attenuation coefficient for higher percentages of additives. The maximum increment is observed at 0.5 percent of additive, from 7.85 to 9.69 m-1, and 9.3 to 11.23 m-1, in energy levels of 1132.5 and 1173.2 keV, respectively. This improvement may decrease the bentonite clay Gamma-ray barrier thickness (half-value layers (HVL), tenth value layers (TVL)), up to 20 and 23 percent for 1173.2 and 1332.5 keV, correspondingly. Moreover, the hydraulic and gas permeability of the mixtures are controlled to find the standard and optimum mixture. In which the 0.5 to 1.0 percent of additives will keep the permeability requirement in an allowable and preferable range.

With brain white matter can be considered as a periodic fibrous porous medium mainly consisting of axons and interstitial fluid (ISF), the corresponding hydraulic permeability reflects the resistance of ISF flow in the extracellular space (ECS), thus playing a key role in molecular transport and drug delivery. As the ECS exhibits a typical width of 10–80 nm, the ISF flow poses a microscale flow problem with the wettability effect, which may induce a flow with a slip boundary and hence remains elusive. In this study, we idealized brain white matter as a periodic fibrous porous medium to quantify the effect of wettability on its hydraulic permeability, with fluid viscosity and slip boundary duly accounted for. We found that wettability led to enlarged hydraulic permeability by diminishing the effective viscosity and enlarging the slip length. We also found that, for the square arrangement of axons, wettability had a greater effect on perpendicular permeability relative to the parallel one, while for hexagonally arranged axons, the opposite held. Results presented in this study may provide theoretical guidance for cerebral edema treatment regimens and drug delivery. [ABSTRACT FROM AUTHOR]

Conventional dialyzer membranes typically comprise of unevenly distributed polydisperse, tortuous, rough pores, embedded in relatively thick ≈20–50 µm polymer layers wherein separation occurs via size exclusion as well as differences in diffusivity of the permeating species. However, transport in such polymeric pores is increasingly hindered as the molecule size approaches the pore dimension, resulting in significant retention of undesirable middle molecules (≥15–60 kDa) and uremic toxins. Enhanced removal of middle molecules is usually accompanied by high albumin loss (≈66 kDa) causing hypoalbuminemia. Here, the scalable bottom‐up fabrication of wafer‐scale carbon nanotube (CNT) membranes with highly aligned, low‐friction, straight‐channels/capillaries and narrow pore‐diameter distributions (≈0.5–4.5 nm) is demonstrated, to overcome persistent challenges in hemofiltration/hemodialysis. Using fluorescein isothiocyanate (FITC)‐Ficoll 70 and albumin in phosphate buffered saline (PBS) as well as in bovine blood plasma, it is shown that CNT membranes can allow for significantly higher hydraulic permeability (more than an order of magnitude when normalized to pore area) than commercial high‐flux hemofiltration/hemodialysis membranes (HF 400), as well as greatly enhance removal of middle molecules while maintaining comparable albumin retention. These findings are rationalized via an N‐pore transport model that highlights the critical role of molecular flexing and deformation during size‐selective transport within nanoscale confinements of the CNTs. The unique transport characteristics of CNTs coupled with size‐exclusion and wafer‐scale fabrication offer transformative advances for hemofiltration, and the obtained insight into molecular transport can aid advancements in several other bio‐systems/applications beyond hemofiltration/hemodialysis. [ABSTRACT FROM AUTHOR]

In this paper, we show that the permeability of a porous material (Tartar (1980)) and that of a bubbly fluid (Lipton and Avellaneda. Proc. R. Soc. Edinburgh Sect. A: Math. 114 (1990), 71–79) are limiting cases of the complexified version of the two-fluid models posed in Lipton and Avellaneda (Proc. R. Soc. Edinburgh Sect. A: Math. 114 (1990), 71–79). We assume the viscosity of the inclusion fluid is $z\mu _1$ and the viscosity of the hosting fluid is $\mu _1\in \mathbb {R}^{+}$ , $z\in \mathbb {C}$. The proof is carried out by the construction of solutions for large $|z|$ and small $|z|$ with an iteration process similar to the one used in Bruno and Leo (Arch. Ration. Mech. Anal. 121 (1993), 303–338) and Golden and Papanicolaou (Commun. Math. Phys. 90 (1983), 473–491) and the analytic continuation. Moreover, we also show that for a fixed microstructure, the permeabilities of these three cases share the same integral representation formula (3.17) with different values of contrast parameter $s:=1/(z-1)$ , as long as $s$ is outside the interval $\left [-\frac {2E_2^{2}}{1+2E_2^{2}},-\frac {1}{1+2E_1^{2}}\right ]$ , where the positive constants $E_1$ and $E_2$ are the extension constants that depend only on the geometry of the periodic pore space of the material. [ABSTRACT FROM AUTHOR]

Vascular graft failure has persisted as a major clinical problem. Mechanical, structural, and transport properties of vascular grafts are critical factors that substantially affect their function and thus the outcome of implantation. The manufacturing method, post‐processing technique, and material of choice have a significant impact on these properties. The goal of this work is to use thermal treatment to modulate the transport properties of PCL‐based vascular engineered constructs. To this end, we electrospun PCL tubular constructs and thermally bonded the electrospun fibers in a convective oven at various temperatures (54, 57, and 60°C) and durations of treatment (15, 30, and 45 s). The effects of fiber thermal bonding (thermobonding) on the transport, mechanical, and structural properties of PCL tubular constructs were characterized. Increasing the temperature and treatment duration enhanced the degree of thermobonding by removing the interconnected void and fusing the fibers. Thermobonding at 57°C and 60°C for longer than 30 s increased the median tangential modulus (E = 126.1 MPa, [IQR = 20.7]), mean suture retention (F = 193.8 g, [SD = 18.5]), and degradation rate while it decreased the median permeability (kA = 0 m/s), and median thickness (t = 60 μm, [IQR = 2.5]). In particular, the thermobonding at 57°C allowed a finer modulation of permeability via treatment duration. We believe that the thermobonding method can be utilized to modulate the properties of vascular engineered constructs which can be useful in designing functional vascular grafts. [ABSTRACT FROM AUTHOR]

The radiation shielding performance of bentonite clay as the main component of the landfill liners is investigated using hematite powder as an additive. For this, theoretical and experimental methods have been used to examine different mixtures of hematite powder and bentonite clay, including pure bentonite, and bentonite with 15, 30, and 45% of hematite powder. Energy-dispersive X-ray (EDS) and scanning electron microscopy (SEM) experiments are undertaken to better understand and analyze bentonite and hematite from a chemical perspective. To evaluate the radiation shielding performance of the mixtures, the linear attenuation coefficient is calculated and simulated employing the XCOM database and MCNP code, respectively. The results are then compared with the experimental approach of radiation permeation by a NaI (Tl) detector which were in good agreement. The hydraulic permeability tests have been also conducted to ensure that the mixtures meet the requirement according to the EPA standard. The results revealed that with increasing the additive percentage the attenuation coefficient grows linearly; however, the hydraulic permeability increases simultaneously. The bentonite with 45% hematite powder outperformed other compounds in providing 30 and 50% improvement in gamma-ray radiation shielding and a 25% and 17% decrease in both TVL and HVL values, at the energy levels of 1173 and 1332 keV, respectively. [ABSTRACT FROM AUTHOR]

The performance of the bioretention system is significantly affected by the soil media characteristics. In order to standardize the gradation of packing soil media and then improve the construction level of bioretention facilities in Chongqing urban area, two types of traditional bioretention soil media (BSM1 and BSM2) are mixed with loamy sand and fine sand in a mass ratio of 1:9, and sandy soil and fine sand in a mass ratio of 2 : 8, respectively, combining the results of the soil background survey in Chongqing. And on this basis, vermiculite (Ver.), biochar (BC) and perlite (Per.) are added as modifiers into BSM1 and BSM2 in different mass ratios, which finally configurates 6 types of modified soil media. Furthermore, the hydraulic permeability and pollutants removal performance of bioretention system with different soil media are investigated. Results show that different soil media shows different initial hydraulic permeability coefficient and attenuation performance, among which, the hydraulic permeability of BSM2+8%Ver. soil medium changes in a stable range of 41~53 mm/h, while the permeability of BSM2+8%BC soil medium has the highest attenuated rate. All soil media show an effective removal performance in runoff pollutants, especially in suspended solids (SS), and the effluent turbidity can reach 10~16 NTU. The removal capacity of the bioretention columns packed with BSM1 and its modified groups in organic pollutants and nutrients are superior to the other columns. Finally, this paper considers the factors of soil medium decontamination capacity, hydraulic permeability and price, the comprehensive ranking of modified soil media using the projection pursuit method: BSM1+2%Ver. (0.60) >BSM1 (0.52) >BSM1+2%BC (0.41) >BSM1+2%Per. (0.40) >BSM2+ 8%Ver. (0.33)>BSM2+8%BC(0.23)>BSM2 (0.15)>BSM2+8%Per. (0.14). [ABSTRACT FROM AUTHOR]

In this paper, we propose an optimized protocol to synthesize reproducible, accurate, sustainable integrally skinned monophasic hybrid cellulose acetate/silica membranes for ultrafiltration. Eight different membrane compositions were studied, divided into two series, one and two, each composed of four membranes. The amount of silica increased from 0 wt.% up to 30 wt.% (with increments of 10 wt.%) in each series, while the solvent composition was kept constant within each series (formamide/acetone ratio equals 0.57 wt.% in series one and 0.73 wt.% in series two). The morphology of the membranes was analyzed by scanning electron microscopy and the chemical composition by Fourier transform infrared spectroscopy, in attenuated total reflection mode (FTIR-ATR). Mechanical tensile properties were determined using tensile tests, and a retest trial was performed to assess mechanical properties variability over different membrane batches. The hydraulic permeability of the membranes was evaluated by measuring pure water fluxes following membrane compaction. The membranes in series two produced with a higher formamide/acetone solvent ratio led to thicker membranes with higher hydraulic permeability values (47.2–26.39 kg·h−1·m−2·bar−1) than for the membranes in series one (40.01–19.4 kg·h−1·m−2·bar−1). Results obtained from the FTIR-ATR spectra suggest the presence of micro/nano-silica clusters in the hybrid membranes of series one, also exhibiting higher Young’s modulus values than the hybrid membranes in series two.

In haemodialysis (HD), unwanted substances (uraemic retention solutes or 'uraemic toxins') that accumulate in uraemia are removed from blood by transport across the semipermeable membrane. Like all membrane separation processes, the transport requires driving forces to facilitate the transfer of molecules across the membrane. The magnitude of the transport is quantified by the phenomenon of 'flux', a finite parameter defined as the volume of fluid (or permeate) transferred per unit area of membrane surface per unit time. In HD, as transmembrane pressure is applied to facilitate fluid flow or flux across the membrane to enhance solute removal, flux is defined by the ultrafiltration coefficient (KUF; mL/h/mmHg) reflecting the hydraulic permeability of the membrane. However, in HD, the designation of flux has come to be used in a much broader sense and the term is commonly used interchangeably and erroneously with other measures of membrane separation processes, resulting in considerable confusion. Increased flux is perceived to reflect more 'porous' membranes having 'larger' pores, even though other membrane and therapy attributes determine the magnitude of flux achieved during HD. Adjectival designations of flux (low-, mid-, high-, super-, ultra-) have found indiscriminate usage in the scientific literature to qualify a parameter that influences clinical decision making and prescription of therapy modalities (low-flux or high-flux HD). Over the years the concept and definition of flux has undergone arbitrary and periodic adjustment and redefinition by authors in publications, regulatory bodies (US Food and Drug Administration) and professional association guidelines (European Renal Association, Kidney Disease Outcomes Quality Initiative), with little consensus. Industry has stretched the boundaries of flux to derive marketing advantages, justify increased reimbursement or contrive new classes of therapy modalities when in fact flux is just one of several specifications that determine membrane or dialyser performance. Membranes considered as high-flux previously are today at the lower end of the flux spectrum. Further, additional parameters unrelated to the rate of diffusive or convective transport (flux) are used in conjunction with or in place of KUF to allude to flux: clearance (mL/min, e.g. of β2-microglobulin) or sieving coefficients (dimensionless). Considering that clinical trials in nephrology, designed to make therapy recommendations and guide policy with economic repercussions, are based on the parameter flux they merit clarification—by regulatory authorities and scientists alike—to avoid further misappropriation. [ABSTRACT FROM AUTHOR]

Type 1 diabetic patients with severe hypoglycemia unawareness have benefitted from cellular therapies, such as pancreas or islet transplantation; however, donor shortage and the need for immunosuppression limits widespread clinical application. We previously developed an intravascular bioartificial pancreas (iBAP) using silicon nanopore membranes (SNM) for immunoprotection. To ensure ample nutrient delivery, the iBAP will need a cell scaffold with high hydraulic permeability to provide mechanical support and maintain islet viability and function. Here, we examine the feasibility of superporous agarose (SPA) as a potential cell scaffold in the iBAP. SPA exhibits 66‐fold greater hydraulic permeability than the SNM along with a short (<10 μm) diffusion distance to the nearest islet. SPA also supports short‐term functionality of both encapsulated human islets and stem‐cell‐derived enriched β‐clusters in a convection‐based system, demonstrated by high viability (>95%) and biphasic insulin responses to dynamic glucose stimulus. These findings suggest that the SPA scaffold will not limit nutrient delivery in a convection‐based bioartificial pancreas and merits continued investigation. [ABSTRACT FROM AUTHOR]

The main issue of the paper is the estimation of soil hydraulic permeability based on the DMT test. DMTA, DMTC and SASK methods performed in the Nielisz dam, Stegny and the SGGW Campus of the Warsaw University of Life Sciences sites are described. The article presents the implementation of the dilatometer Marchetti test (DMT) in the determination of soil fraction and effects of its occurrence in the subsoil, tested in the Nielisz dam located in the Wieprz river valley in the Lublin province, and in various sites in Warsaw (Stegny site and SGGW Campus of the Warsaw University of Life Sciences). In order to acquire the needed data, the flat dilatometer test (DMT) method was used. A direct and indirect pressure methodology of interpreting soil swelling was characterized in the article. The paper shows the possibilities of determining sand, silt and clay soil fractions based on po and p1 pressures from dilatometer tests (DMT) and the effective (σ’vo) and total (σvo) vertical in situ overburden stress. Additionally, the main advantage of this paper is the proposal of use of a new chart to determine hydraulic permeability and soil fraction, based on DMT tests.

The hydraulic permeability and normal stiffness of rock fractures are fundamentally related, which can serve as a probe for assessing hydro‐mechanical properties in a variety of geo‐engineering contexts. We present experimentally validated numerical simulations of fracture closure and fluid flow processes in realistic aperture structures with mean in the range of 0.01–2 mm. A relatively simple relationship between permeability and normal stiffness is derived in the effective medium regime, using the elastic modulus of the rock matrix, the mean mechanical aperture, and the relative standard deviation (RSD) of the local mechanical aperture. The established relationship between stiffness and permeability appears independent of scale or orientation. Plain Language Summary: A natural rock fracture is formed by two rough walls that create complex internal void space structures. Subject to an increasing normal stress, the bridging asperities jointing a fracture deform elastically at first, and then may fail when the local stress reaches critical strength. These elastic and elastic‐plastic mechanisms determine the closure behavior of a fracture and the evolution of void spaces that provide the paths for fluid flow. In such a manner, the deformability of a fracture (stiffness) is fundamentally related to the permeability that is controlled by the average aperture of void spaces and their spatial distributions. We prepared a series of natural and synthetic rock fractures with apertures falling in the typical engineering range. By conducting experimental and numerical investigations on the normal loading and fluid flow processes, we were able to obtain a relatively simple relationship between the permeability and normal stiffness in the effective flow regime. This relationship is composed of broadly accepted physical parameters and is independent of scale or direction. It can help the estimation of fracture stiffness from the permeability or fracture permeability from stiffness, depending on which quantity is observable in the field. Key Points: Laboratory tests and numerical simulations are combined to analyze the relationship between normal stiffness and permeability in rock fracturesEffects of surface roughness, matedness and fracture scale on normal stiffness and permeability are investigatedA physically based stiffness‐permeability relationship is established for rock fractures in the effective medium regime [ABSTRACT FROM AUTHOR]

Brain microstructure plays a key role in driving the transport of drug molecules directly administered to the brain tissue, as in Convection-Enhanced Delivery procedures. The proposed research analyzes the hydraulic permeability of two white matter (WM) areas (corpus callosum and fornix) whose three-dimensional microstructure was reconstructed starting from the acquisition of electron microscopy images. We cut the two volumes with 20 equally spaced planes distributed along two perpendicular directions, and, on each plane, we computed the corresponding permeability vector. Then, we considered that the WM structure is mainly composed of elongated and parallel axons, and, using a principal component analysis, we defined two principal directions, parallel and perpendicular, with respect to the axons' main direction. The latter were used to define a reference frame onto which the permeability vectors were projected to finally obtain the permeability along the parallel and perpendicular directions. The results show a statistically significant difference between parallel and perpendicular permeability, with a ratio of about two in both the WM structures analyzed, thus demonstrating their anisotropic behavior. Moreover, we find a significant difference between permeability in corpus callosum and fornix, which suggests that the WM heterogeneity should also be considered when modeling drug transport in the brain. Our findings, which demonstrate and quantify the anisotropic and heterogeneous character of the WM, represent a fundamental contribution not only for drug-delivery modeling, but also for shedding light on the interstitial transport mechanisms in the extracellular space. [ABSTRACT FROM AUTHOR]

Objective: Hydraulic permeability is a topic of deep interest in biological materials because of its important role in a range of drug delivery-based therapies. The strong dependence of permeability on the geometry and topology of pore structure and the lack of detailed knowledge of these parameters in the case of brain tissue makes the study more challenging. Although theoretical models have been developed for hydraulic permeability, there is limited consensus on the validity of existing experimental evidence to complement these models. In the present study, we measure the permeability of white matter (WM) of fresh ovine brain tissue considering the localised heterogeneities in the medium using an infusion-based experimental set up, iPerfusion. We measure the flow across different parts of the WM in response to applied pressures for a sample of specific dimensions and calculate the permeability from directly measured parameters. Furthermore, we directly probe the effect of anisotropy of the tissue on permeability by considering the directionality of tissue on the obtained values. Additionally, we investigate whether WM hydraulic permeability changes with post-mortem time. To our knowledge, this is the first report of experimental measurements of the localised WM permeability, also demonstrating the effect of axon directionality on permeability. This work provides a significant contribution to the successful development of intra-tumoural infusion-based technologies, such as convection-enhanced delivery (CED), which are based on the delivery of drugs directly by injection under positive pressure into the brain. [ABSTRACT FROM AUTHOR]

This paper aims to develop a comprehensive and subject-specific model to predict the drug reach in Convection-Enhanced Delivery (CED) interventions. To this end, we make use of an advance diffusion imaging technique, namely the Neurite Orientation Dispersion and Density Imaging (NODDI), to incorporate a more precise description of the brain microstructure into predictive computational models. The NODDI dataset is used to obtain a voxel-based quantification of the extracellular space volume fraction that we relate to the white matter (WM) permeability. Since the WM can be considered as a transversally isotropic porous medium, two equations, respectively for permeability parallel and perpendicular to the axons, are derived from a numerical analysis on a simplified geometrical model that reproduces flow through fibre bundles. This is followed by the simulation of the injection of a drug in a WM area of the brain and direct comparison of the outcomes of our results with a state-of-the-art model, which uses conventional diffusion tensor imaging. We demonstrate the relevance of the work by showing the impact of our newly derived permeability tensor on the predicted drug distribution, which differs significantly from the alternative model in terms of distribution shape, concentration profile and infusion linear penetration length. [ABSTRACT FROM AUTHOR]

ABSTRACT Mechanical properties and morphological features of the vertebral cancellous bone are related to resistance to fracture and capability of withstanding surgical treatments. In particular, vertebral strength is related to its elastic properties, whereas the ease of fluid motion, related to the success of incorporation orthopedic materials (eg, bone cement), is regulated by the hydraulic permeability (K). It has been shown that both elastic modulus and permeability of a material are affected by its morphology. The objective of this study was to establish relations between local values of K and the aggregate modulus (H), and parameters descriptive of the bone morphology. We hypothesized that multivariate statistical models, by including the contribution of several morphology parameters at once, would provide a strong correlation with K and H of the vertebral cancellous bone. Hence, μCT scans of human lumbar vertebra were used to determine a set of bone morphology descriptors. Subsequently, indentation tests on the bone samples were conducted to determine local values of K and H. Finally, a multivariate approach supported by principal component analysis was adopted to develop predictive statistical models of bone permeability and aggregate modulus as a function of bone morphology descriptors. It was found that linear combinations of bone volume fraction, trabecular thickness, trabecular spacing, structure model index, connectivity density, and degree of anisotropy provide a strong correlation (R2 ~ 76%) with K and a weaker correlation (R2 ~ 47%) with H. The results of this study can be exploited in computational mechanics frameworks for investigating the potential mechanical behavior of human vertebra and to develop strategies to treat or prevent pathological conditions such as osteoporosis, age‐related bone loss, and vertebral compression fractures. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Fibrous membranes with a nonwoven random structure and a quasi-parallel fibrous structure can be fabricated by the electrospinning technique. The membranes with different structures exhibited different behaviors to a hydraulic flow passing through the membranes. This work presents the effects of the fiber arrangement, fiber diameter, and deformations of the fibers on the hydraulic permeability. The results showed that the hydraulic flow can generate an extrusion pressure which affects the porosity and pore structure of the fibrous membranes. The quasi-parallel fibrous membranes and nonwoven membranes exhibited similar variation tendencies to the change of the experimental variables. However, the quasi-parallel fibrous membranes exhibited a higher sensibility to the change of the hydraulic flow rate. The hydraulic permeability of the quasi-parallel fibrous membranes was further analyzed with packing state models in this work.

BACKGROUND: Autotaxin (ATX-secretory lysophospholipase D) is the primary lysophosphatidic acid (LPA) producing enzyme. LPA promotes endothelial hyper-permeability and microvascular dysfunction following cellular stress. OBJECTIVE: We sought to assess whether ATX inhibition would attenuate endothelial monolayer permeability after anoxia-reoxygenation (A-R) in vitro and attenuate the increase in hydraulic permeability observed after ischemia-reperfusion injury (IRI) in vivo. METHODS: A permeability assay assessed bovine endothelial monolayer permeability during anoxia-reoxygenation with/without administration of pipedimic acid, a specific inhibitor of ATX, administered either pre-anoxia or post-anoxia. Hydraulic permeability (Lp) of rat mesenteric post-capillary venules was evaluated after IRI, with and without ATX inhibition. Lastly, Lp was evaluated after the administration of ATX alone. RESULTS: Anoxia-reoxygenation increased monolayer permeability 4-fold (p < 0.01). Monolayer permeability was reduced to baseline similarly in both the pre-anoxia and post-anoxia ATX inhibition groups (each p < 0.01, respectively). Lp was attenuated by 24% with ATX inhibition (p < 0.01). ATX increased Lp from baseline in a dose dependent manner (p < 0.05). CONCLUSIONS: Autotaxin inhibition attenuated increases in endothelial monolayer permeability during A-R in vitro and hydraulic permeability during IRI in vivo. Targeting ATX may be especially beneficial by limiting its downstream mediators that contribute to mechanisms associated with endothelial permeability. ATX inhibitors may therefore have potential for pharmacotherapy during IRI. [ABSTRACT FROM AUTHOR]

The hydraulic permeability of the lipid bilayer membrane of a single cell, a very important parameter in biological and medical fields, has been attracting increasing attention. To date, methods developed to determine this permeability are either operation-complicated or time-consuming. Therefore, we developed a chip for automatically and rapidly determining the permeability of cells that integrates microfluidics and cell impedance analysis. The chip is designed to automatically identify a single cell, capture the cell, and record the volume change in that cell. We confirmed the abilities of single-cell identification and capture with the upper and lower voltage thresholds determined, validated the performance of the differential electrode design for accurate cell volume measurements, deduced the extracellular osmotic pressure change in the presence of a hypertonic solution according to fluorescence intensity, and demonstrated the single-cell volume change recorded by the chip. Then, the accuracy of the permeability determined with the chip was verified using HeLa cells. Finally, the permeability of human-induced pluripotent stem cells (hiPSCs) was determined to be 0.47 ± 0.03 μm/atm/min. Using the chip, the permeability can be determined within 5 min. This study provides insights for the new design of an automatic single-cell identification and capture chip for single cell–related studies. [ABSTRACT FROM AUTHOR]

To analyze the anti-seepage performance of geosynthetic clay liner (GCL) after long-term freeze-thaw cycles， the 6-hour freezing and 6-hour thawing cycle tests on GCL material were carried out. The permeability coefficient and free swelling ratio of GCL after different freeze-thaw cycles were studied. The results show that the frost heave of GCL can reach a stable state within 4h， and when frozen again， differential frost heave can occur in the GCL sample after freeze-thaw cycles. When the number of freeze-thaw cycles is low (≤30times)， the permeability coefficient of GCL decreases with increase of the number of freeze-thaw cycles， and the permeability coefficient is between 10-11m/s and 10-10m/s. As the number of freeze-thaw cycles increases， the free swelling ratio of bentonite in GCL increases first， then decreases and finally reaches a steady value. [ABSTRACT FROM AUTHOR]

Mechanical properties and morphological features of the vertebral cancellous bone are related to resistance to fracture and capability of withstanding surgical treatments. In particular, vertebral strength is related to its elastic properties, whereas the ease of fluid motion, related to the success of incorporation orthopedic materials (eg, bone cement), is regulated by the hydraulic permeability (K). It has been shown that both elastic modulus and permeability of a material are affected by its morphology. The objective of this study was to establish relations between local values of K and the aggregate modulus (H), and parameters descriptive of the bone morphology. We hypothesized that multivariate statistical models, by including the contribution of several morphology parameters at once, would provide a strong correlation with K and H of the vertebral cancellous bone. Hence, μCT scans of human lumbar vertebra were used to determine a set of bone morphology descriptors. Subsequently, indentation tests on the bone samples were conducted to determine local values of K and H. Finally, a multivariate approach supported by principal component analysis was adopted to develop predictive statistical models of bone permeability and aggregate modulus as a function of bone morphology descriptors. It was found that linear combinations of bone volume fraction, trabecular thickness, trabecular spacing, structure model index, connectivity density, and degree of anisotropy provide a strong correlation (R2 ~ 76%) with K and a weaker correlation (R2 ~ 47%) with H. The results of this study can be exploited in computational mechanics frameworks for investigating the potential mechanical behavior of human vertebra and to develop strategies to treat or prevent pathological conditions such as osteoporosis, age‐related bone loss, and vertebral compression fractures. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research. [ABSTRACT FROM AUTHOR]

The features of tritium adsorption by clay rocks, which mainly consist of clay minerals with high adsorption abilities for tritium oxide (НTO) and super heavy water (T2O), were studied after their thermal treatment at a temperature of 105 and 500 °C. The observation was carried out in a closed system “tritiated water - clay rock”. Indicators of the dynamics of growth of tritium adsorption by heat-treated clay rocks over 380 days are obtained. It was found that the adsorption of tritium in this observation system actively grows for the first 30 - 40 days for all the studied minerals, and then slows down. White clays retain an increase in adsorption over the entire observation period of 380 days. [ABSTRACT FROM AUTHOR]

Stabilization of swelling soils with high volume change potential is an important topic in geotechnical engineering because irreversible and catastrophic damages will occur if they are not appropriately managed. This study aimed to determine the effect of travertine powder on the swelling, strength, and permeability properties of weak and swellable soils. Within the scope of the study, soil improvement performance of travertine powder, which can be used as a soil improvement tool, was analyzed in detail, and the effect of travertine powder on the hydraulic and strength properties of the soil was discussed comparatively. Waste powder from travertine quarries taken from Eskipazar (Turkey) and Bentonite clay with high swelling potential taken from Tokat (Turkey) was used in the study. Samples were prepared by adding 10%, 20%, 30%, and 40% by weight of travertine powder to the Bentonite, and these mixtures were cured for 0-7-14-21-28-35 and 42-day periods. Unconfined compressive strength test, direct shear test, swelling pressure, and permeability tests were then conducted on each of the cured-stabilized samples. While the permeability coefficient, unconfined compressive strength, cohesion, and internal friction angle of bentonite samples with the additive increased over the curing time, the swelling pressure value decreased. The addition of travertine led to a substantial enhancement in the unconfined compressive strength (by 35%), internal friction angle (by 350), and cohesion (by 26%), while simultaneously reducing the swelling pressure by 58%. These findings emphasize that travertine powder enhances weak and swellable soils, offering an eco-friendly and cost-effective solution for improving engineering properties. • Travertine powder was used as a soil improvement tool for weak and swellable soils. • Bentonite clay was mixed with 10–40% by weight of travertine powder and cured for different periods. • The addition of travertine powder improved engineering properties, reduced swelling potential, and increased permeability. • Permeability coefficient increased while unconfined compressive strength, cohesion, and internal friction angle also increased. • The study provides insights into the potential use of travertine powder for soil improvement. [ABSTRACT FROM AUTHOR]

Glioblastomas represent a challenging problem with an extremely poor survival rate. Since these tumour cells have a highly invasive character, an effective surgical resection as well as chemotherapy and radiotherapy is very difficult. Convection-enhanced delivery (CED), a technique that consists in the injection of a therapeutic agent directly into the parenchyma, has shown encouraging results. Its efficacy depends on the ability to predict, in the pre-operative phase, the distribution of the drug inside the tumour. This paper proposes a method to compute a fundamental parameter for CED modelling outcomes, the hydraulic permeability, in three brain structures. Therefore, a bidimensional brain-like structure was built out of the main geometrical features of the white matter: axon diameter distribution extrapolated from electron microscopy images, extracellular space (ECS) volume fraction and ECS width. The axons were randomly allocated inside a defined border, and the ECS volume fraction as well as the ECS width maintained in a physiological range. To achieve this result, an outward packing method coupled with a disc shrinking technique was implemented. The fluid flow through the axons was computed by solving Navier–Stokes equations within the computational fluid dynamics solver ANSYS. From the fluid and pressure fields, an homogenisation technique allowed establishing the optimal representative volume element (RVE) size. The hydraulic permeability computed on the RVE was found in good agreement with experimental data from the literature. [ABSTRACT FROM AUTHOR]

Abstract Current literature has not considered or provided any data on the permeability of the iris stroma. In this study, we aimed to determine the hydraulic permeability of porcine irides from the isolated stroma. Fifteen enucleated porcine eyes were acquired from the local abattoir. The iris pigment epithelium was scraped off using a pair of forceps and the dilator muscles were pinched off using a pair of colibri toothed forceps. We designed an experimental setup, based on Darcy's law, and consisting of a custom 3D-printed pressure column using acrylonitrile butadiene styrene (ABS) plastic. PBS solution was passed through the iris stroma in a 180° arc shape, with a column height of approximately 204 mm (2000 Pa). Measurements of iris stromal thickness were conducted using optical coherence tomography (OCT). To measure flow rate, we measured the mass (volume) of PBS solution using a mass balance in approximately 1 min. Histology was performed using hematoxylin and eosin (H&E) and anti-smooth muscle antibody (anti-α-SMA) for validation. The permeability experiments demonstrated that the iris stroma is a biphasic tissue that allows fluid flow. Our image processing results determined the area of flow to be 7.55 mm2 and the tissue thickness to be between 180 and 430 μm. The hydraulic permeability of the porcine stroma, calculated using Darcy's law, was 5.13 ± 2.39 × 10−5 mm2/Pa•s. Histological and immunochemical studies confirmed that the tissues used for this permeability study were solely iris stroma. Additionally, anti-α-SMA staining revealed staining specific for stromal blood vessels, with the notable absence of dilator and sphincter muscle staining. Our study combined experimental microscopic data with the theory of biphasic materials to investigate the hydraulic permeability of the iris stroma. This work will serve as a basis on which to validate future biomechanical studies of human irides with which may ultimately aid disease diagnosis and inform the design of novel treatments. Highlights • We were able to isolate the porcine iris stroma to determine the permeability of the biphasic tissue. • A highly permeable iris stroma allows for effective ocular physiology. • Permeability of the iris stroma could be directly related to pathologies such as angle closure glaucoma. • More accurate finite element (FE) models can be utilized by incorporating the poroelasticity of the iris stroma. [ABSTRACT FROM AUTHOR]

Highlights • A bi-porous graphite felt electrode is prepared for high-performance VRFB. • The bi-porous structure boosts the specific surface area of the electrode. • The bi-porous graphite felt shows excellent electrochemical performances. • The assembled battery achieves an energy efficiency of 82.47% at 300 mA cm−2. • The assembled battery exhibits high electrolyte utilization. Abstract In this work, a bi-porous graphite felt electrode is prepared by a simple yet effective catalytic etching method for vanadium redox reflow batteries (VRFBs). The primary pores, ∼100 μm in size and formed by voids between interconnected carbon fibers, act as the macroscopic pathways for electrolyte flow, while the secondary pores, ∼200 nm in size and formed onto carbon fibers, increase the active surfaces for electrochemical reactions. The Brunauer-Emmett-Teller results show that the specific surface area of bi-porous graphite felt is 17.73 m2 g−1, which is 7 times larger than that of the original graphite felt. The cyclic voltammetry and electrochemical impedance spectroscopy tests demonstrate the higher peak currents, smaller peak potential separations and lower charge transfer resistances of the bi-porous graphite felt than the original graphite felt. Battery tests show that the VRFB with the bi-porous graphite felt electrode achieves an energy efficiency of 87.02% and an electrolyte utilization of 84.07% at the current density of 200 mA cm−2, which are 17.90% and 38.91% higher than that with the original graphite felt electrodes. More importantly, the battery can be operated at the high current densities of 300 and 400 mA cm−2 with the energy efficiencies of 82.47% and 77.69%, among the highest performance in the open literature. All these superior results demonstrate that the bi-porous graphite felt prepared in this work offers a promise to replace conventional mono-scale porous graphite felt electrodes for VRFBs. [ABSTRACT FROM AUTHOR]

The hydrodynamics of electrodialysis and reverse electrodialysis is commonly studied by neglecting membrane deformation caused by transmembrane pressure (TMP). However, large frictional pressure drops and differences in fluid velocity or physical properties in adjacent channels may lead to significant TMP values. In previous works, we conducted one-way coupled structural-CFD simulations at the scale of one periodic unit of a profiled membrane/channel assembly and computed its deformation and frictional characteristics as functions of TMP. In this work, a novel fluid−structure interaction model is presented, which predicts, at the channel pair scale, the changes in flow distribution associated with membrane deformations. The continuity and Darcy equations are solved in two adjacent channels by treating them as porous media and using the previous CFD results to express their hydraulic permeability as a function of the local TMP. Results are presented for square stacks of 0.6-m sides in cross and counter flow at superficial velocities of 1 to 10 cm/s. At low velocities, the corresponding low TMP does not significantly affect the flow distribution. As the velocity increases, the larger membrane deformation causes significant fluid redistribution. In the cross flow, the departure of the local superficial velocity from a mean value of 10 cm/s ranges between −27% and +39%.

Good drainage is the most important design consideration for a road, both to miniaturize road maintenance costs and maximize the time the road is operational. The lack of good drainage lead to the structural damages and costly repairs. Many of roads are built in intensively drained agricultural land. The effective way to drain subgrades is reconstruction of existing agricultural drainage. The impact of cross-subsurface drainage system on water level fluctuation was measured using Plane geofiltration mathematical model, one of 3D geofiltration modelling programs. The hydraulic permeability characteristics were determined in field of Pikeliai, close to local road in Kėdainiai district, Lithuania. This object is composed of clay and loamy soils. Subsurface cross drains trenches spacing of 20 m, 30 m and 40 m were simulated. The hydraulic permeability of cross drain trenches and lateral trenches modelled was from 0.006 m/a day to 6 m/a day. The simulation of cross drains trenches showed that the most effective distance between them are 20 m. The highest water depression occurs when the permeability of cross drain trenches and lateral trenches is ~ 6 m/day, at the distance of 20 m. The water recession is 20 cm lower compared to the drainage systems without cross drains trenches. By installing cross drains trenches every 30 m, water recession is 10 cm lower when the trench permeability is about 6 m/day. When increasing the distance between the cross drains up to 40 m their influence disappears.

The endothelial dysfunction and the unbalanced secretion of vasoactive substances are the main causes of the macro and micro vascular complications for patients with diabetic mellitus (DM). This paper investigates the blood flow and the nitric oxide (NO) transport in a permeable capillary by using a finite element method. The computational domain consists of a permeable straight or bifurcated capillary and the surrounding tissue with different endothelial hydraulic permeability. The blood flow in the lumen of a capillary is assumed to be governed by the Stokes equation. The fluid flow in the surrounding tissue is simplified as the Darcy flow. The advection-diffusion reaction equation is employed to investigate the NO distribution in a lumen-tissue model, which is originated from the endothelial cells inside the capillary wall. The characteristic Galerkin method is employed for the discretization of the advection-diffusion reaction equation. The simulated results show that the NO transport is effectively affected by different hydraulic permeabilities due to the changes of the blood velocity. When the hydraulic permeability increases considerably, the NO concentration ([NO]) in the whole domain decreases accordingly. Moreover, the NO concentration increases in the area after the bifurcation of the capillary owing to the convective effect. It is also shown that even if the NO production by the endothelial cells is enhanced, the increase of the convection inside the vessel may reduce the endothelial NO concentration. As a signal transduction molecule, the spatial location with discriminating NO distribution may be useful for determining the position of the microangiopathy in the DM. [ABSTRACT FROM AUTHOR]

In Fontainebleau sandstone, the evolution of transport properties with porosity is related to changes in both the size and connectivity of the pore space. Microcomputed tomography can be used to characterize the relevant geometric attributes, with the resolution that is sufficiently refined for realistic simulation of transport properties based on the 3D image. In this study, we adopted a hybrid computation scheme that is based on a hierarchical multi-scale approach. The specimen was partitioned into cubic sub-volumes for pore-scale simulation of hydraulic permeability and formation factor using the lattice Boltzmann method. The pore-scale results were then linked with finite element simulation in a homogenized scheme to compute and upscale the transport properties to specimen scale. The simulated permeability and formation factor have magnitude and anisotropy that are in good agreement with experimental rock physics data. Together with simulated and measured values of connected porosity and specific surface area, they provide useful insights into how pore geometry controls the evolution of the transport properties. [ABSTRACT FROM AUTHOR]

Hybrid cellulose acetate (CA) silica (SiO 2 ) (CA/SiO 2 ) membranes were synthesized by promoting the in situ condensation between silanols from the SiO 2 precursor and the C OH or acetate groups from the CA polymer. For all the CA/SiO 2 membranes, the ATR-FTIR peak assigned to (Si O C) proves the hybrid condensation reaction and confirms the synthesis of monophasic hybrid membranes. ATR-FTIR shows the presence of uncondensed highly reactive Si OH species, in membranes with silica contents higher than 20 mol%. Together with RMN studies, results show molecular water strongly hydrogen-bonded with Si OH groups, yielding a drastic decrease in the membrane hydraulic permeability, from 57 to 10 kg/h/m 2 /bar. The incorporation of 5 and 10 mol% of silica increased the hydraulic permeability from 32 to 82 kg/h/m 2 /bar when compared to the CA membrane. [ABSTRACT FROM AUTHOR]

Collagen gels are considered a promising biomaterial for the manufacturing of tissue engineering scaffolds, however, their mechanical properties often need to be improved to enable them to provide enough mechanical support during the course of tissue regeneration process. In this paper, we present a simple self-compression technique for the improvement of the mechanical properties of collagen gels, identified by the fitting of bespoke biphasic finite element models. Radially-confined highly hydrated gels were allowed to self-compress for 18 h, expelling fluid, and which were subsequently subjected to unconfined ramp-hold compression. Gels, initially of 0.2%, 0.3% and 0.4% (w/v) collagen and 13 mm thickness, transformed to 2.9 ± 0.2%, 3.2 ± 0.3% and 3.6 ± 0.1% (w/w) collagen and 0.45 ± 0.06 mm, 0.69 ± 0.04 mm and 0.99 ± 0.07 mm thickness. Young's moduli of the compressed gels did not increase with increasing collagen fibril density, whilst zero-strain hydraulic permeability significantly decreased from 51 to 21 mm 4 /Ns. The work demonstrates that biphasic theory, applied to unconfined compression, is a highly appropriate paradigm to mechanically characterise concentrated collagen gels and that confined compression of highly hydrated gels should be further investigated to enhance gel mechanical performance. [ABSTRACT FROM AUTHOR]

Purpose: About 70% of eye drops contain benzalkonium chloride (BAK) to maintain sterility. BAK is an effective preservative but it can cause irritation and toxicity. We propose to mitigate ocular toxicity without compromising sterility by incorporating a filter into an eye drop bottle to selectively remove BAK during the process of drop instillation. Methods: The filter is a packed bed of particles made from poly(2-hydroxyethyl methacrylate) (pHEMA), which is a common ophthalmic material. We showed that pHEMA particle prepared by using ethoxylated trimethylolpropane triacrylate as crosslinker can be incorporated into a modified eyedrop bottle tip to selectively remove the preservative as the formulation is squeezed out of the bottle. Hydraulic permeability of the plug is measured to determine the resistance to eye drop squeezing, and % removal of BAK and drugs are determined. Results: The modified tip has a hydraulic permeability of about 2 Darcy, which allows eyedrops formulations to flow through without excessive resistance. The tip is designed such that the patients can create an eyedrop of solution of 1-10 cP viscosity in 4 s with a nominal pressure. During this short contact time, the packed particles removed nearly 100% of benzalkonium chloride (BAK) from a 15 mL, 0.012% BAK solution but have only minimal impact on the concentration of contained active components. Conclusion: Our novel design can eliminate the preservative induced toxicity from eye drops thereby impacting hundreds of millions of patients with chronic ophthalmic diseases like glaucoma and dry eyes. [ABSTRACT FROM AUTHOR]