Low Water Permeability Research Articles

Molecular mechanisms underlying active desalination and low water permeability in the esophagus of eels acclimated to seawater.

Marine teleosts can absorb imbibed seawater (SW) to maintain water balance, with esophageal desalination playing an essential role. NaCl absorption from luminal SW was enhanced 10-fold in the esophagus of SW-acclimated eels, and removal of Na+ or Cl- from luminal SW abolished the facilitated absorption, indicating coupled transport. Mucosal/serosal application of various blockers for Na+/Cl- transporters profoundly decreased the absorption. Among the transporter genes expressed in eel esophagus detected by RNA-seq, dimethyl amiloride-sensitive Na+/H+ exchanger (NHE3) and 4,4'-diisothiocyano-2,2'-disulfonic acid-sensitive Cl-/[Formula: see text] exchanger (AE) coupled by the scaffolding protein on the apical membrane of epithelial cells, and ouabain-sensitive Na+-K+-ATPases (NKA1α1c and NKA3α) and diphenylamine-2-carboxylic acid-sensitive Cl- channel (CLCN2) on the basolateral membrane, may be responsible for enhanced transcellular NaCl transport because of their profound upregulation after SW acclimation. Upregulated carbonic anhydrase 2a (CA2a) supplies H+ and [Formula: see text] for activation of the coupled NHE and AE. Apical hydrochlorothiazide-sensitive Na+-Cl- cotransporters and basolateral Na+-[Formula: see text] cotransporter (NBCe1) and AE1 are other possible candidates. Concerning the low water permeability that is typically seen in marine teleost esophagus, downregulated aquaporin genes (aqp1a and aqp3) and upregulated claudin gene (cldn15a) are candidates for transcellular/paracellular route. In situ hybridization showed that these upregulated transporters and tight-junction protein genes were expressed in the absorptive columnar epithelial cells of eel esophagus. These results allow us to provide a full picture of the molecular mechanism of active desalination and low water permeability that are characteristic to marine teleost esophagus and gain deeper insights into the role of gastrointestinal tracts in SW acclimation.

Polymersome Popping by Light-Induced Osmotic Shock under Temporal, Spatial, and Spectral Control.

The light-triggered, programmable rupture of cell-sized vesicles is described, with particular emphasis on self-assembled polymersome capsules. The mechanism involves a hypotonic osmotic imbalance created by the accumulation of photogenerated species inside the lumen, which cannot be compensated owing to the low water permeability of the membrane. This simple and versatile mechanism can be adapted to a wealth of hydrosoluble molecules, which are either able to generate reactive oxygen species or undergo photocleavage. Ultimately, in a multi-compartmentalized and cell-like system, the possibility to selectively burst polymersomes with high specificity and temporal precision and to consequently deliver small encapsulated vesicles (both polymersomes and liposomes) is demonstrated.

Polymersome Popping by Light‐Induced Osmotic Shock under Temporal, Spatial, and Spectral Control

AbstractThe light‐triggered, programmable rupture of cell‐sized vesicles is described, with particular emphasis on self‐assembled polymersome capsules. The mechanism involves a hypotonic osmotic imbalance created by the accumulation of photogenerated species inside the lumen, which cannot be compensated owing to the low water permeability of the membrane. This simple and versatile mechanism can be adapted to a wealth of hydrosoluble molecules, which are either able to generate reactive oxygen species or undergo photocleavage. Ultimately, in a multi‐compartmentalized and cell‐like system, the possibility to selectively burst polymersomes with high specificity and temporal precision and to consequently deliver small encapsulated vesicles (both polymersomes and liposomes) is demonstrated.

Comparison of two types of bioreactors for synthesis of bacterial nanocellulose tubes as potential medical prostheses including artificial blood vessels

AbstractBACKGROUNDBacterial nanocellulose (BNC) has prospects for use in applications of artificial blood vessels, esophagus and urethra. Several bioreactors have been utilized for synthesis of BNC tubes, however, little is known about differences in biosynthesis processes and tube properties. The current work for the first time compared two types of bioreactors, double‐silicone‐tube (D‐BNC) and single‐silicone‐tube (S‐BNC) bioreactors, to evaluate differences in preparation and properties of BNC tubes using fructose or glucose of 50 g L−1 and 100 g L−1, respectively.RESULTSThe two bioreactors showed different biosynthesis processes of BNC tube production. The D‐BNC bioreactor provided higher yields and better mechanical performance of tubes because of the greater oxygen supply. Higher fructose concentration resulted in increased production of D‐BNC, but sugar types and concentrations had little effect on S‐BNC yields. Fructose granted stronger mechanical properties, but lower water permeability. Both types of tubes prepared with 100 g L−1 fructose were composed of porous nano‐fibrillar networks but showed different cross‐sectional morphologies and fiber distributions.CONCLUSIONThis study revealed the biosynthesis processes of BNC tubes in two bioreactors and their correlation with properties. The results suggest how to regulate BNC tubes with particular structures and properties for biomedical prostheses including artificial blood vessels. © 2016 Society of Chemical Industry

Separation performance of poly(vinyl alcohol) based nanofiltration membranes crosslinked by malic acid for salt solutions

In this study, poly(vinyl alcohol) (PVA) based nanofiltration (NF) membranes were prepared by coating a thin PVA film on polysulfone ultrafiltration support substrates. The PVA film was cross-linked using malic acid in the presence of HCl as a catalyst. The impacts of crosslinker content and PVA molecular weight on physicochemical properties and separation performance of the prepared membranes were investigated. The obtained membranes were characterized using FTIR spectra, swelling degree, and sessile drop contact angles, respectively. Then, the separation performance of the NF membrane was systematically evaluated for pure water; magnesium sulfate (MgSO4) as well as sodium chloride (NaCl) solutions using a custom fabricated 4-cell crossflow desalination system. On increasing the malic acid content, the extent of crosslinking degree increased and disrupted the crystallinity of the PVA film. The salt rejection of the prepared membranes was found to increase and then decrease through the maximum point of malic acid content for 20 wt%, while the water permeability showed the opposite trend. Moreover, the results revealed that the prepared membrane with higher molecular weight exhibited lower water permeability but better salt rejection.

Free-standing graphene slit membrane for enhanced desalination

This study considers two novel ideas to further explore and enhance the graphene membrane for desalination. Firstly, while earlier molecular dynamics (MD) simulations studies have used frozen membranes, free-standing membrane is considered here. Since 2D membranes are usually embedded on porous support in the experimental reverse osmosis (RO) process, the free-standing membrane can more accurately model the behavior expected during operation. This study showed, using MD simulations, that a free-standing nanoporous graphene membrane can provide a higher salt rejection, but lower water permeability as compared to frozen membrane. Secondly, the performance of a slit membrane as compared to a membrane with circular pore is studied. At a pressure of 268 MPa, the critical diameter of circular pore that can maintain perfect salt rejection is found to be 5 Å and the critical size for a slit is determined to be 2.28 Å. It is shown that a slit membrane at its critical size can achieve water flux 3.5 times higher than a membrane with circular pore at its critical radius. This finding highlights the importance of slits over circular pores which can potentially widen the options for the design and fabrication of 2D graphene membranes for experimental verification of RO.

A Review on the Use of Engineered Cementitious Composite in Bridges

Engineered Cementitious Composite (ECC) is a material with high ductility, tensile strength and self-healing more than the standard concrete. Applications of ECC are beneficial due to its long life cycle, high strength, low cost in the long-term, low maintenance and environmentally friendly nature. Properties and hardened behavior of ECC highlights that ECC has a tight crack width development, which increases its ability to resist long-term effects of hot, frost and humid weather. Additionally, it results low water permeability coefficient and high steel corrosion resistance compared to other common alternative materials. One of the promising areas of application for ECC is in highway structures, especially highway bridges. Highway structures suffer constantly from adverse environmental loads and often require frequent repairing or replacing due to cracks; expansion; water and chlorides effects which cause steel corrosion or the slope between the pavement, slab and the support at the end of a bridge. Detailed review on different properties and characteristics of ECC and the current applications of ECC clearly highlights the motivation to enhance the use of ECC for bridge construction. In addition, ECC can be introduced in jointless bridges by putting an ECC link slab instead of the expandable mechanical joint.

Rheology and phase inversion behavior of polyphenylenesulfone (PPSU) and sulfonated PPSU for membrane formation

Abstract Polyphenylenesulfone (PPSU) is widely used as a membrane material for water reuse applications because of its good chemical resistance, hydrolysis stability and outstanding mechanical strength. However, due to its hydrophobic nature, fouling and relatively low water permeability are potential drawbacks of PPSU membranes. Sulfonation of PPSU could significantly improve the hydrophilicity but compromise the mechanical strength. Moreover, the degree of sulfonation has great influences on the solution properties of the sulfonated PPSU (sPPSU) dopes. This study aims to investigate the rheological properties and phase separation behavior of PPSU and sPPSU polymers with various degrees of sulfonation, and disclose their molecular-level interactions. With relatively low degrees of sulfonation, sPPSU polymers exhibit much larger viscosity and dynamic moduli than PPSU, particularly at higher polymer concentrations. The sPPSU polymers also possess greater non-solvent (i.e., water) tolerance and display delayed demixing behavior for phase inversion. Molecular dynamics (MD) simulation shows that the π–π stacking of aromatic rings and hydrogen bonding among the sulfonic acid groups are the main interactions between the polymer molecules. The flat-sheet sPPSU membranes cast by the non-solvent induced phase separation (NIPS) method exhibit high water permeability with morphology closely correlated to the rheological properties and phase inversion characteristics of the polymer solutions. This fundamental study may provide pertinent insights of design strategies to prepare hydrophilic membranes from sulfonated polymers.

The influence of the molecular weight of the water-soluble polymer on phase-separated films for controlled release

Hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) can be used for extended release coatings, where the water-soluble HPC may act as a pore former. The aim was to investigate the effect of the molecular weight of HPC on the microstructure and mass transport in phase-separated freestanding EC/HPC films with 30% w/w HPC. Four different HPC grades were used, with weight averaged molecular weights (Mw) of 30.0 (SSL), 55.0 (SL), 83.5 (L) and 365 (M) kg/mol. Results showed that the phase-separated structure changed from HPC-discontinuous to bicontinuous with increasing Mw of HPC. The film with the lowest Mw HPC (SSL) had unconnected oval-shaped HPC-rich domains, leaked almost no HPC and had the lowest water permeability. The remaining higher Mw films had connected complex-shaped pores, which resulted in higher permeabilities. The highest Mw film (M) had the smallest pores and very slow HPC leakage, which led to a slow increase in permeability. Films with grade L and SL released most of their HPC, yet the permeability of the L film was three times higher due to greater pore connectivity. It was concluded that the phase-separated microstructure, the level of pore percolation and the leakage rate of HPC will be affected by the choice of HPC Mw grade used in the film and this will in turn have strong impact on the film permeability.

Comparative Characterization of Shiga Toxin Type 2 and Subtilase Cytotoxin Effects on Human Renal Epithelial and Endothelial Cells Grown in Monolayer and Bilayer Conditions.

Postdiarrheal hemolytic uremic syndrome (HUS) affects children under 5 years old and is responsible for the development of acute and chronic renal failure, particularly in Argentina. This pathology is a complication of Shiga toxin (Stx)-producing Escherichia coli infection and renal damage is attributed to Stx types 1 and 2 (Stx1, Stx2) produced by Escherichia coli O157:H7 and many other STEC serotypes. It has been reported the production of Subtilase cytotoxin (SubAB) by non-O157 STEC isolated from cases of childhood diarrhea. Therefore, it is proposed that SubAB may contribute to HUS pathogenesis. The human kidney is the most affected organ because very Stx-sensitive cells express high amounts of biologically active receptor. In this study, we investigated the effects of Stx2 and SubAB on primary cultures of human glomerular endothelial cells (HGEC) and on a human tubular epithelial cell line (HK-2) in monoculture and coculture conditions. We have established the coculture as a human renal proximal tubule model to study water absorption and cytotoxicity in the presence of Stx2 and SubAB. We obtained and characterized cocultures of HGEC and HK-2. Under basal conditions, HGEC monolayers exhibited the lowest electrical resistance (TEER) and the highest water permeability, while the HGEC/HK-2 bilayers showed the highest TEER and the lowest water permeability. In addition, at times as short as 20–30 minutes, Stx2 and SubAB caused the inhibition of water absorption across HK-2 and HGEC monolayers and this effect was not related to a decrease in cell viability. However, toxins did not have inhibitory effects on water movement across HGEC/HK-2 bilayers. After 72 h, Stx2 inhibited the cell viability of HGEC and HK-2 monolayers, but these effects were attenuated in HGEC/HK-2 bilayers. On the other hand, SubAB cytotoxicity shows a tendency to be attenuated by the bilayers. Our data provide evidence about the different effects of these toxins on the bilayers respect to the monolayers. This in vitro model of communication between human renal microvascular endothelial cells and human proximal tubular epithelial cells is a representative model of the human proximal tubule to study the effects of Stx2 and SubAB related to the development of HUS.

Effects of Fly Ash and Silica Fume on Permeability of Concrete Made With Porous Limestone and Non-Porous Aggregates

The research objective was to assess the permeability of concrete made with porous limestone and non-porous aggregates. Fifty-eight concrete mixes were made and tested to study the effects of fly ash, silica fume, and aggregate type on the permeability of concretes. Class F fly ash and silica fume were used at the levels of 10 to 50 %, and 5 to 20 % as cement replacement on weight basis, respectively. Nine different aggregates, seven in-states and two out-of-states, were collected to study the effects of aggregate type. The test results indicated that silica fume may cause considerable effects on both water and rapid chloride permeability of concrete, while the initial and prolonged moist curing was found essential for the fly ash concrete. In addition, the permeability of aggregate was positively affecting the permeability of concrete. The concretes mixed with aggregates of low permeability showed lower water permeability than those made with porous aggregates. The effect of the permeability of aggregate was also noticeable when the water cementitious material ratio (w/cm) of concrete was high. At lower w/cm ratio, the bond at the cement paste-aggregate interface reduced the effect of the permeability of aggregate.

Innovative Oxygen Selective Membrane for Li-Air Battery Operating in Ambient Air

The demand for high-energy storage systems is constantly increasing, as is the interest to explore alternatives to commercially available batteries. The rechargeable Li-air battery represents an exciting opportunity to design batteries that may satisfy some of the requirements of our future by coupling the light Li metal with the inexhaustible source of O2 of the surrounding air, resulting in high theoretical specific energy density. Currently, most of the researches on the Li-air battery comprise a cell fed with pure O2 allowing that way to maintain long-term operation, owing to the high O2 concentration free of contaminants. However, for many practical applications such as EV, air is the only viable option to supply the battery. In this context, moisture and gases other than O2 may cause side reactions and corrosion. Herein, we report a facile strategy to fabricate an effective oxygen selective membrane with poly(vinylidene fluoride co-hexafluoropropylene) (PVDF-HFP) via non-solvent induced phase separation, casted as a 240 micron thin sheets for cell protection in ambient air condition. The use of different additives helps enhancing the barrier properties as well as the membrane specificity toward O2. For instance, sacrificial silica nanoparticles (SiO2 NPs) were incorporated into the precursor solution to create a controlled alveolar-like structure inside the membrane. The membrane was loaded with polydimethylsiloxane (PDMS) under vacuum. Another kind of additive considered is the cyclodextrine. Indeed, thanks to their unique structure, cyclodextrines are able to form host-guest complexes with hydrophobic molecules such as our polymer matrix. Nanosponges based on cyclodextrines were prepared and added to the polymer precursor solution before membrane casting. The as prepared membranes showed higher oxygen permeability and lower water permeability. Galvanostatic charge-discharge cycling tests of a Li-air pouch cell in a potential/time controlled mode showed an outstanding cycling life superior to 1500h with more than 150 cycles.

Thin-film composite membrane on a compacted woven backing fabric for pressure assisted osmosis

The water flux in forward osmosis (FO) process declines substantially when the draw solution (DS) concentration reaches closer to the point of osmotic equilibrium with the feed solution (FS). Using external hydraulic pressure alongside the osmotic driving force in the pressure assisted osmosis (PAO) has been found effective in terms of enhancing water flux and even potentially diluting the DS beyond osmotic equilibrium. The net gain in water flux due to the applied pressure in the PAO process closely depends on the permeability of the FO membrane. The commercial flat sheet cellulose triacetate (CTA) FO membrane has low water permeability and hence the effective gain in water flux in the PAO process is low. In this study, a high performance thin film composite membrane was developed especially for the PAO process through casting polyethersulfone (PES) polymer solution on a compacted woven fabric mesh support followed by interfacial polymerisation for polyamide active layer. This PAO membrane possesses a water flux of 37Lm2h−1 using 0.5M NaCl as DS and deionised water as the feed at an applied hydraulic pressure of 10bar. Besides, the membrane was able to endure the external hydraulic pressure required for the PAO process owing to the embedded backing fabric support. While the membranes with low structural parameters are essential for higher water flux, this study shows that for PAO process, polymeric membranes with larger structural parameters may not be suitable for PAO. They generally resulted in compaction and poor mechanical strength to withstand hydraulic pressure.

Influence of micro-cracking on the permeability of engineered cementitious composites

Engineered Cementitious Composites (ECC) forms multiple micro-cracks under tension when loaded to beyond the elastic stage. Unlike normal concrete, such tight cracks help to maintain low water permeability even in the cracked stage. Therefore ECC shows great potential for application in hydraulic structures, such as dams and levees for which water seepage control is critical for their performance. In this paper, the permeability of ECC under constant tensile load was experimentally studied using a specially designed displacement-control loading device, providing permeability data for ECC under realistic loading conditions. In addition, an analytical model capable of predicting permeability property of ECC composite based on tensile strain and crack patterns has been proposed and experimentally verified on two different ECC mixtures. The findings of this research are expected to support future design and application of ECC for hydraulic structures.

Auto-Adhesion Potential of Extraocular Aqp0 during Teleost Development.

AQP0 water channels are the most abundant proteins expressed in the mammalian lens fiber membranes where they are essential for lens development and transparency. Unlike other aquaporin paralogs, mammalian AQP0 has a low intrinsic water permeability, but can form cell-to-cell junctions between the lens fibers. It is not known whether the adhesive properties of AQP0 is a derived feature found only in mammals, or exists as a conserved ancestral trait in non-mammalian vertebrates. Here we show that a tetraploid teleost, the Atlantic salmon, expresses four Aqp0 paralogs in the developing lens, but also expresses significant levels of aqp0 mRNAs and proteins in the epithelia of the pronephros, presumptive enterocytes, gill filament and epidermis. Quantitative PCR reveals that aqp0 mRNA titres increase by three orders of magnitude between the onset of somitogenesis and pigmentation of the eye. Using in situ hybridization and specific antisera, we show that at least two of the channels (Aqp0a1, -0b1 and/or -0b2) are localized in the extraocular basolateral and apical membranes, while Aqp0a2 is lens-specific. Heterologous expression of the Aqp0 paralogs in adhesion-deficient mouse fibolast L-cells reveals that, as for human AQP0, each intact salmon channel retains cell-to-cell adhesive properties. The strongest Aqp0 interactions are auto-adhesion, suggesting that homo-octamers likely form the intercellular junctions of the developing lens and epithelial tissues. The present data are thus the first to show the adhesion potential of Aqp0 channels in a non-mammalian vertebrate, and further uncover a novel extraocular role of the channels during vertebrate development.

Aggregate Impact of the Country in Concrete Durability, that Works in Normal Environmental Conditions

Production and use of durable concrete in reinforced concrete structures is a necessity in our country. In this article it was treated as affecting the characteristics of aggregates in durable concrete production, when they work in normal environmental conditions . To achieve this goal have produced concrete of class C35 / 45 with aggregate taken in careers mountain and river. The other components are the same in mix design concrete. Water-cement ratio is 0.5 and 0:35 realized. Comparisons are made of the resistance to compression and water penetration. Cubes of concrete had been produced and treated in terms shipyard. There have been comparisons of results and following. Today in Durres, even wider, buildings constructed with durable concrete are very few in now days. Geological studies show that the soil in foundation has low retaining capacity for this city due to high friction angle. This is also one of the other factors that Seismicity of the area is very high, up to level 9 ball of Rihter. The purpose of this article is the production of durable concrete with low permeability of water. The project is constructed in our country and in particular in Durres where groundwater level is higher and the use of space efficiently needs to build parking with underground floor.

Influence of biodegradable polymer coatings on corrosion, cytocompatibility and cell functionality of Mg-2.0Zn-0.98Mn magnesium alloy

Four kinds of biodegradable polymers were employed to prepare bioresorbable coatings on Mg-2.0Zn-0.98Mn (ZM21) alloy to understand the relationship between polymer characteristics, protective effects on substrate corrosion, cytocompatibility and cell functionality. Poly-l-lactide (PLLA), poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or poly(lactic-co-glycolic) acid (PLGA) was spin-coated on ZM21, obtaining a smooth, non-porous coating less than 0.5μm in thickness. Polymer coating characterization, a degradation study, and biocompatibility evaluations were performed. After 4 w of immersion into cell culture medium, degradation of PLGA and PLLA coatings were confirmed by ATR-FTIR observation. The coatings of PLLA, PHB and PHBV, which have lower water permeability and slower degradation than PLGA, provide better suppression of initial ZM21 degradation and faster promotion of human osteosarcoma cell growth and differentiation.

Preparation and Characterization of Boron Controlled-Release Film as a Potential Coating Material

The blend film is a favorable coating material for controlled-release fertilizer.The biodegradable PVA-boric acid controlled-release film and PVA-borax controlled-release film were prepared by the solution casting method.The water permeability and water absorbency were systematically investigated. The mechanical properties of these materials were determined with a strength-testing machine.The composite structure was determined by Fourier transform infrared (FTIR) spectroscopy and the scanning electron microscopy (SEM).The good controlled-release properties,lower water permeability and better tensile strength implied that the boron controlled-release film may be a potential coating material for the application in the controlled-release fertilizer.

Fabrication and characterization of TiO2/ZrO2 ceramic membranes for nanofiltration

TiO2/ZrO2 ceramic nanofiltration membranes are successfully fabricated through the polymeric sol–gel route followed by the dip-coating technique. Disk type α-alumina supported mesoporous γ-alumina (pore size: 5–6 nm) is employed as the support in dip-coating. The unsupported and supported composite ceramic membranes are systematically characterized and evaluated in terms of phase composition, chemical stability, gas adsorption, molecular weight cut-off (MWCO), membrane pore size, water flux and salt rejection. It is found that the TiO2/ZrO2 ceramic membranes have amorphous phase at 400 and 500 °C, suggesting the high thermal stability. The fabricated membranes have the MWCO of 620–860 Da, corresponding to the membrane pore size of 1.2–1.5 nm. Relatively low water permeability can be attributed to the low microporosity of the membrane. Donnan exclusion is the dominant transport mechanism of the NF membrane in the single-component system, and salt rejection is closely related to the hydration properties of the ions (e.g., the hydration radius).

Preparation and characterization of antibacterial films based on polyvinyl alcohol/quaternized cellulose

Quaternized cellulose (YM) was homogeneously synthesized by grafting 3-chloro-2-hydroxypropyldodecyldimethylammonium groups onto cellulose molecules in a NaOH/urea aqueous solution. YM was blended with a poly(vinyl alcohol) (PVA) matrix to prepare composite films via co-regeneration from the alkaline solution. The PVA film and the blend films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction measurements, thermogravimetric analysis, and scanning electron microscopy. Mechanical properties, water vapor barrier properties, light transmission, and antibacterial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria were also evaluated. The results reveal that PVA and YM in the composite films interacted by hydrogen bonding. Compared with pure PVA film, the PVA/YM blend films had higher tensile strength, higher thermostability, lower water permeability, and especially, higher antibacterial activity. The blend films exhibited good UV-shielding performance. Our study demonstrates a simple and efficient method for preparing a functional, environment-friendly composite film.