Finite difference calculations of permeability in large domains in a wide porosity range.

Determining effective hydraulic, thermal, mechanical and electrical properties of porous materials by means of classical physical experiments is often time-consuming and expensive. Thus, accurate numerical calculations of material properties are of increasing interest in geophysical, manufacturing, bio-mechanical and environmental applications, among other fields. Characteristic material properties (e.g. intrinsic permeability, thermal conductivity and elastic moduli) depend on morphological details on the porescale such as shape and size of pores and pore throats or cracks. To obtain reliable predictions of these properties it is necessary to perform numerical analyses of sufficiently large unit cells. Such representative volume elements require optimized numerical simulation techniques. Current state-of-the-art simulation tools to calculate effective permeabilities of porous materials are based on various methods, e.g. lattice Boltzmann, finite volumes or explicit jump Stokes methods. All approaches still have limitations in the maximum size of the simulation domain. In response to these deficits of the well-established methods we propose an efficient and reliable numerical method which allows to calculate intrinsic permeabilities directly from voxel-based data obtained from 3D imaging techniques like X-ray microtomography. We present a modelling framework based on a parallel finite differences solver, allowing the calculation of large domains with relative low computing requirements (i.e. desktop computers). The presented method is validated in a diverse selection of materials, obtaining accurate results for a large range of porosities, wider than the ranges previously reported. Ongoing work includes the estimation of other effective properties of porous media.

Effect of bleaching agents containing fluoride or calcium on enamel microhardness, roughness and permeability

Aim: To evaluate the effect of different in-office bleaching agents on the permeability, roughness and surface microhardness of human enamel. Methods: For evaluation of roughness and microhardness, 40 hemi-faces of 20 premolars were subjected to initial roughness (Ra parameter) and microhardness (VHN) measurements. Thirty-two premolar’s crowns were used for permeability test. Then, all specimens were randomly divided into four groups: C - without bleaching (control), HP35 - bleaching with 35% hydrogen peroxide (HP), HPF38 - 38% HP+fluoride, HPC35 - 35% HP+calcium. Final roughness (FR) and microhardness (FM) measurements were evaluated. For permeability, the 32 crowns were immersed in 1% sodium hypochlorite (20 min) and silver nitrate solutions (2 h) and subjected to developing solution under fluorescent light (16 h). Three sections from the crowns were analyzed in light microscope (100x) to evaluate the scores of permeability: Score 0 - no tracer agent penetration; Score 1 - less than half the thickness of enamel penetration; Score 2 - tracer agent reaching half the enamel thickness; Score 3 - entire enamel depth penetration, without reaching dentin and Score 4 - tracer agent reaching dentin. For roughness and microhardness evaluation were used one-way ANOVA and Dunnet post-test for independent samples, and t test for paired samples. For permeability, the data were analyzed by Kruskal Wallis and Dunn tests. Results: A significantly higher permeability and surface roughness were observed in groups HP35, HPF38 and HPC35 compared to the C group, as well as decreased microhardness (p<0.05). Conclusions: All bleaching agents increased permeability and surface roughness, and decreased microhardness of human enamel; thus, the addition of fluoride or calcium was not beneficial.

Predicting water permeability in sedimentary rocks from capillary imbibition and pore structure

In this paper, absolute water permeability is estimated from capillary imbibition and pore structure for 15 sedimentary rock types. They present a wide range of petrographic characteristics that provide degrees of connectivity, porosities, pore size distributions, water absorption coefficients by capillarity and water permeabilities. A statistical analysis shows strong correlations among the petrophysical parameters of the studied rocks. Several fundamental properties are fitted into different linear and multiple expressions where water permeability is expressed as a generalized function of the properties. Some practical aspects of these correlations are highlighted in order to use capillary imbibition tests to estimate permeability. The permeability–porosity relation is discussed in the context of the influence of pore connectivity and wettability. As a consequence, we propose a generalized model for permeability that includes information about water fluid rate (water absorption coefficient by capillarity), water properties (density and viscosity), wetting (interfacial tension and contact angle) and pore structure (pore radius and porosity). Its application is examined in terms of the type of pores that contribute to water transport and wettability. The results indicate that the threshold pore radius, in which water percolates through rock, achieves the best description of the pore system. The proposed equation is compared against Carman–Kozeny's and Katz–Thompson's equations. The proposed equation achieves very accurate predictions of the water permeability in the range of 0.01 to 1000 mD.

THE PERFORMANCE AND MODIFICATION OF RECYCLED ELECTRONIC WASTE PLASTICS FOR THE IMPROVEMENT OF ASPHALT PAVEMENT MATERIALS

Bulk electric waste plastics were recycled and reduced in size into plastic chips before pulverization or cryogenic grinding into powders. Two major types of electronic waste plastics were used in this investigation: acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS). This research investigation utilized two approaches for incorporating electronic waste plastics into asphalt pavement materials. The first approach was blending and integrating recycled and processed electronic waste powders directly into asphalt mixtures and binders; and the second approach was to chemically treat recycled and processed electronic waste powders with hydro-peroxide before blending into asphalt mixtures and binders. The chemical treatment of electronic waste (e-waste) powders was intended to strengthen molecular bonding between e-waste plastics and asphalt binders for improved low and high temperature performance. Superpave asphalt binder and mixture testing techniques were conducted to determine the rheological and mechanical performance of the e-waste modified asphalt binders and mixtures. This investigation included a limited emissions-performance assessment to compare electronic waste modified asphalt pavement mixture emissions using SimaPro and performance using MEPDG software. Carbon dioxide emissions for e-waste modified pavement mixtures were compared with conventional asphalt pavement mixtures using SimaPro. MEPDG analysis was used to determine rutting potential between the various e-waste modified pavement mixtures and the control asphalt mixture. The results from this investigation showed the following: treating the electronic waste plastics delayed the onset of tertiary flow for electronic waste mixtures, electronic waste mixtures showed some improvement in dynamic modulus results at low temperatures versus the control mixture, and tensile strength ratio values for treated e-waste asphalt mixtures were improved versus the control mixture.

Lattice Boltzmann Modeling and Specialized Laboratory Techniques to Determine the Permeability of Megaporous Karst Rock

The Pleistocene carbonate rock Biscayne Aquifer of south Florida contains laterally-extensive bioturbated ooltic zones characterized by interconnected touching-vug megapores that channelize most flow and make the aquifer extremely permeable. Standard petrophysical laboratory techniques may not be capable of accurately measuring such high permeabilities. Instead, innovative procedures that can measure high permeabilities were applied. These fragile rocks cannot easily be cored or cut to shapes convenient for conducting permeability measurements. For the laboratory measurement, a 3D epoxy-resin printed rock core was produced from computed tomography data obtained from an outcrop sample. Permeability measurements were conducted using a viscous fluid to permit easily observable head gradients (~2 cm over 1 m) simultaneously with low Reynolds number flow. For a second permeability measurement, Lattice Boltzmann Method flow simulations were computed on the 3D core renderings. Agreement between the two estimates indicates an accurate permeability was obtained that can be applied to future studies.

INVESTIGATIVE COMPARISON OF TANK AND RECOVERED ASPHALT SAMPLES THROUGH PHYSICAL PERFORMANCE TESTING AND CHEMICAL ANALYSIS

Despite the development of improved performance test protocols by renowned researchers, there are still road networks which experience premature cracking and failure. One area of major concern in asphalt science and technology, especially in cold regions in Canada is thermal (low temperature) cracking. Usually right after winter periods, severe cracks are seen on poorly designed road networks. Quality assurance tests based on improved asphalt performance protocols have been implemented by government agencies to ensure that roads being constructed are at the required standard but asphalt binders that pass these quality assurance tests still crack prematurely. While it would be easy to question the competence of the quality assurance test protocols, it should be noted that performance tests which are being used and were repeated in this study, namely the extended bending beam rheometer (EBBR) test, double edge-notched tension test (DENT), dynamic shear rheometer (DSR) test and X-ray fluorescence (XRF) analysis have all been verified and proven to successfully predict asphalt pavement behaviour in the field. Hence this study looked to probe and test the quality and authenticity of the asphalt binders being used for road paving. This study covered thermal cracking and physical hardening phenomenon by comparing results from testing asphalt binder samples obtained from the storage ‘tank’ prior to paving (tank samples) and recovered samples for the same contracts with aim of explaining why asphalt binders that have passed quality assurance tests are still prone to fail prematurely. The study also attempted to find out if the short testing time and automated procedure of torsion bar experiments can replace the established but tedious procedure of the EBBR. In the end, it was discovered that significant differences in performance and composition exist between tank and recovered samples for the same contracts. Torsion bar experimental data also indicated some promise in predicting physical hardening.

Innovative Infrastructures for Sustainable Mobility in Urban Areas: Protective Asphalt to Prevent Vulnerable Road Users Injuries.

Nell’elaborato viene studiato il fenomeno dell’incidentalità singola delle utenze deboli sulla strada (perdita di controllo, scivolamento ecc..ecc..), con particolare enfasi nell’analizzare le conseguenze traumatiche dovute all’impatto con la superficie stradale. Una nuova tecnologia viene sviluppata per rendere le pavimentazioni di piste ciclabili, marciapiedi e zone pedonali con capacità di assorbimento degli impatti, prevenendo, o riducendo drasticamente, la probabilità e entità di eventi traumatici a seguito di una caduta. Attraverso una stesa di prova avvenuta ad Imola (BO), si sono analizzate e risolte le problematiche dovute alle discrepanze riscontrate fra “costruzione” in laboratorio e costruzione nella realtà urbana. La nuova tecnologia, infatti, è stata studiata come “construction-friendly”, permettendo alle società di costruzione e pavimentazione di stendere il nuovo manto protettivo con strumenti e macchinari tradizionali. Infine l’asfalto modificato è stato testato nei laboratori svedesi del KTH – Royal Institute of Technology per provarne l’efficacia in termini di assorbimento degli impatti. Nel “Drop Impact Test”, test specifico per l’approvazione dei caschi protettivi da bicicletta, l’asfalto modificato ha performato ben al di sotto della soglia di approvazione dei caschi da ciclista, e si colloca in un range di valore di accelerazione lineare perfino al di sotto della soglia di “Low Risk of Injuries”. La nuova tecnologia, inoltre, fa utilizzo di gomma granulata riciclata da pneumatici fuori uso. Tale dettaglio conferisce maggiore sostenibilità al progetto: oltre all’utilizzo di legante a freddo, che diminuisce le emissioni di CO2, e di incentivare l’utilizzo della mobilità dolce attraverso una più sicura rete infrastrutturale, l’utilizzo di gomma riciclata dà nuova vita al materiale che altrimenti andrebbe in discarica e prolunga, così, la vita utile del materiale.

Enhancing predictive capability of models for solubility and permeability in polymers and composites

The interpretation of phase equilibrium and mass transport phenomena in gas/solvent - polymer system at molten or glassy state is relevant in many industrial applications. Among tools available for the prediction of thermodynamics properties in these systems, at molten/rubbery state, is the group contribution lattice-fluid equation of state (GCLF-EoS), developed by Lee and Danner and ultimately based on Panayiotou and Vera LF theory. On the other side, a thermodynamic approach namely non-equilibrium lattice-fluid (NELF) was proposed by Doghieri and Sarti to consistently extend the description of thermodynamic properties of solute polymer systems obtained through a suitable equilibrium model to the case of non-equilibrium conditions below the glass transition temperature. The first objective of this work is to investigate the phase behaviour in solvent/polymer at glassy state by using NELF model and to develop a predictive tool for gas or vapor solubility that could be applied in several different applications: membrane gas separation, barrier materials for food packaging, polymer-based gas sensors and drug delivery devices. Within the efforts to develop a predictive tool of this kind, a revision of the group contribution method developed by High and Danner for the application of LF model by Panayiotou and Vera is considered, with reference to possible alternatives for the mixing rule for characteristic interaction energy between segments. The work also devotes efforts to the analysis of gas permeability in polymer composite materials as formed by a polymer matrix in which domains are dispersed of a second phase and attention is focused on relation for deviation from Maxwell law as function of arrangement, shape of dispersed domains and loading.

Analisys of gas permeability in perfluorosufonated polymeric membranes for CO2 separation

The present thesis focuses on the permebility analisys of Aquivion® 980 Perfluoro sulfonic acid (PFSA) polymer with particular reference to the influence of the equivalent weight (gram of polymer per molSO3H) on the permeation properties. Aquivion grade tested, indeed, were characterized by a lower equivalent weight ( 870 g/molSO3H against 980 of the present material) with respect to data present in the open literature. Permeability of different gases (CO2, N2, and CH4) was tested at different temperatures and different humidity, a parameter which greatly influences the gas transport in such hydrophilic material- Aquivion® swells consistently in humid conditions increasing its gas permeability of more than one order of magnitude with respect to values prevailing in dry conditions. Present data confirm such behavior being the permeability of all gases and vapors tested substantially increased in presence of water. Interestingly the increase in permeability results be similar for all the gases inspected, hence such enhanced permeation capability is not associated to a selectivity loss that happens in polymeric membranes. Although, the results, of CO2, are lower compared to those obtained with the different grades, with lower equivalent weight, of Aquivion, thus suggesting that an increase of this parameter is detrimental for both permeability and selectivity of the membranes with respect to CO2. This is likely related to the fact that a lower content of SO3H groups makes it difficult to have an interconnected water domain inside the membranes. A modeling approach was considered to describe the experimental data and to give a better insight into the observed behavior, unfortunately, it resulted not sensitive enough to catch the differences between the gas permeability in PSFAs with high and low equivalent weight. The latter were indeed usually contained within 10-20% which results to be the in the same range of model precision when used in a predictive way.

Silk Fibroin And Sodium Alginate Blend: Miscibility And Physical Characteristics.

Films of silk fibroin (SF) and sodium alginate (SA) blends were prepared by solution casting technique. The miscibility of SF and SA in those blends was evaluated and scanning electron microscopy (SEM) revealed that SF/SA 25/75 wt.% blends underwent microscopic phase separation, resulting in globular structures composed mainly of SF. X-ray diffraction indicated the amorphous nature of these blends, even after a treatment with ethanol that turned them insoluble in water. Thermal analyses of blends showed the peaks of degradation of pristine SF and SA shifted to intermediate temperatures. Water vapor permeability, swelling capacity and tensile strength of SF films could be enhanced by blending with SA. Cell viability remained between 90 and 100%, as indicated by in vitro cytotoxicity test. The SF/SA blend with self-assembled SF globules can be used to modulate structural and mechanical properties of the final material and may be used in designing high performance wound dressing.

Bleeding Complications In Dengue Are Not Associated With Significant Changes In The Modulators Of The Endothelial Barrier.

Bleeding complications in dengue may occur irrespective of the presence of plasma leakage. We compared plasma levels of modulators of the endothelial barrier among three dengue groups: bleedings without plasma leakage, dengue hemorrhagic fever, and non-complicated dengue. The aim was to evaluate whether the presence of subtle alterations in microvascular permeability could be detected in bleeding patients. Plasma levels of VEGF-A and its soluble receptors were not associated with the occurrence of bleeding in patients without plasma leakage. These results provide additional rationale for considering bleeding as a complication independent of endothelial barrier breakdown, as proposed by the 2009 WHO classification.

Design, Synthesis And Biological Evaluation Of Hybrid Bioisoster Derivatives Of N-acylhydrazone And Furoxan Groups With Potential And Selective Anti-trypanosoma Cruzi Activity.

Hybrid bioisoster derivatives from N-acylhydrazones and furoxan groups were designed with the objective of obtaining at least a dual mechanism of action: cruzain inhibition and nitric oxide (NO) releasing activity. Fifteen designed compounds were synthesized varying the substitution in N-acylhydrazone and in furoxan group as well. They had its anti-Trypanosoma cruzi activity in amastigotes forms, NO releasing potential and inhibitory cruzain activity evaluated. The two most active compounds (6, 14) both in the parasite amastigotes and in the enzyme contain the nitro group in para position of the aromatic ring. The permeability screening in Caco-2 cell and cytotoxicity assay in human cells were performed for those most active compounds and both showed to be less cytotoxic than the reference drug, benznidazole. Compound 6 was the most promising, since besides activity it showed good permeability and selectivity index, higher than the reference drug. Thereby the compound 6 was considered as a possible candidate for additional studies.

Evidences Of Endocytosis Via Caveolae Following Blood-brain Barrier Breakdown By Phoneutria Nigriventer Spider Venom.

Spider venoms contain neurotoxic peptides aimed at paralyzing prey or for defense against predators; that is why they represent valuable tools for studies in neuroscience field. The present study aimed at identifying the process of internalization that occurs during the increased trafficking of vesicles caused by Phoneutria nigriventer spider venom (PNV)-induced blood-brain barrier (BBB) breakdown. Herein, we found that caveolin-1α is up-regulated in the cerebellar capillaries and Purkinje neurons of PNV-administered P14 (neonate) and 8- to 10-week-old (adult) rats. The white matter and granular layers were regions where caveolin-1α showed major upregulation. The variable age played a role in this effect. Caveolin-1 is the central protein that controls caveolae formation. Caveolar-specialized cholesterol- and sphingolipid-rich membrane sub-domains are involved in endocytosis, transcytosis, mechano-sensing, synapse formation and stabilization, signal transduction, intercellular communication, apoptosis, and various signaling events, including those related to calcium handling. PNV is extremely rich in neurotoxic peptides that affect glutamate handling and interferes with ion channels physiology. We suggest that the PNV-induced BBB opening is associated with a high expression of caveolae frame-forming caveolin-1α, and therefore in the process of internalization and enhanced transcytosis. Caveolin-1α up-regulation in Purkinje neurons could be related to a way of neurons to preserve, restore, and enhance function following PNV-induced excitotoxicity. The findings disclose interesting perspectives for further molecular studies of the interaction between PNV and caveolar specialized membrane domains. It proves PNV to be excellent tool for studies of transcytosis, the most common form of BBB-enhanced permeability.

Endocytosis Of Tight Junctions Caveolin Nitrosylation Dependent Is Improved By Cocoa Via Opioid Receptor On Rpe Cells In Diabetic Conditions.

Retinal pigment epithelium cells, along with tight junction (TJ) proteins, constitute the outer blood retinal barrier (BRB). Contradictory findings suggest a role for the outer BRB in the pathogenesis of diabetic retinopathy (DR). The aim of this study was to investigate whether the mechanisms involved in these alterations are sensitive to nitrosative stress, and if cocoa or epicatechin (EC) protects from this damage under diabetic (DM) milieu conditions. Cells of a human RPE line (ARPE-19) were exposed to high-glucose (HG) conditions for 24 hours in the presence or absence of cocoa powder containing 0.5% or 60.5% polyphenol (low-polyphenol cocoa [LPC] and high-polyphenol cocoa [HPC], respectively). Exposure to HG decreased claudin-1 and occludin TJ expressions and increased extracellular matrix accumulation (ECM), whereas levels of TNF-α and inducible nitric oxide synthase (iNOS) were upregulated, accompanied by increased nitric oxide levels. This nitrosative stress resulted in S-nitrosylation of caveolin-1 (CAV-1), which in turn increased CAV-1 traffic and its interactions with claudin-1 and occludin. This cascade was inhibited by treatment with HPC or EC through δ-opioid receptor (DOR) binding and stimulation, thereby decreasing TNF-α-induced iNOS upregulation and CAV-1 endocytosis. The TJ functions were restored, leading to prevention of paracellular permeability, restoration of resistance of the ARPE-19 monolayer, and decreased ECM accumulation. The detrimental effects on TJs in ARPE-19 cells exposed to DM milieu occur through a CAV-1 S-nitrosylation-dependent endocytosis mechanism. High-polyphenol cocoa or EC exerts protective effects through DOR stimulation.