Low Membrane Resistance Research Articles

A low-impedance cation exchange membrane for extending the voltage window of a BiFeO3-based hybrid supercapacitor through the pH-decoupling strategy

Aqueous hybrid supercapacitors usually suffer from narrow voltage window and poor energy density limited by the thermodynamic decomposition of water. Based on necessary ion exchange membranes, the pH-decoupling strategy can be employed to extend the voltage windows of hybrid supercapacitors. We propose a novel low-impedance cation exchange membrane (CEM) with the interpenetrating network structure for the pH-decoupling strategy, which can be served as the separator for a AC//BiFeO3 supercapacitor to enhance its electrochemical performances. Two CEMs (CEM-1 and CEM-2) with different contents of the sulfonic acid (-SO3H) groups, are fabricated through the copolymerization of various monomers according to the predetermined stoichiometric ratios. FTIR, Raman and XPS spectra reflect that the CEM-2 has the higher content of the -SO3H groups than the CEM-1. The membrane parameter measurements confirm that the CEM-2 has the higher water content, lower membrane resistance and smaller membrane thickness than the CEM-1. The AC//BiFeO3 supercapacitor with the CEM-2 separator provides the higher gravimetric specific capacitance of 61 F g−1 at 1 A g−1, better coulombic efficiencies (97 % ∼ 103 %) and lower Rs value (39.74 Ω) than the AC//BiFeO3 supercapacitors with the CEM-1 separator. Moreover, the AC//BiFeO3 supercapacitor with the CEM-2 separator delivers the maximum energy density of 41.0 Wh kg−1 at the power density of 1.1 kW kg−1. The pH-decoupling strategy with this low-impedance CEM, opens up a new avenue for developing high-performance aqueous electrochemical energy storage devices.

Novel CNT/MXene composite membranes with superior electrocatalytic efficiency and durability for sustainable wastewater treatment

Self-assembled composite membranes are increasingly acknowledged for their potential in wastewater treatment due to their superior selectivity, high operational efficiency, and environmental sustainability. Nonetheless, challenges such as inadequate removal efficiencies for low molecular weight dyes and significant membrane fouling restrict their broader industrial application. To address these challenges, a structurally stable composite membrane of sodium lignosulfonate carbon nanotubes/alkalized MXene (SLS-CNT/alk-MXene) has been engineered. This membrane employs a polyethersulfone substrate pretreated with dopamine for uniform nanoparticle assembly through a layer-by-layer self-assembly technique. The manufacturing process includes hydrophilic modification of carbon nanotubes with lignosulfonate, followed by alkalization of MXene using sodium hydroxide. Performance evaluation of the M2 composite membrane, with a content ratio of SLS-CNT to alk-MXene of 4:2 by weight, revealed outstanding membrane properties. It achieved high selective permeability, with over 99 % retention efficiency for Methyl Blue and Congo Red, and a permeation flux of 51.6 L m-2h−1 bar−1. This membrane efficiently degraded various organic dyes within 1h, including Methyl Orange, Methylene Blue, Malachite Green, and Rhodamine B, and thanks to the integration of electrocatalysis with membrane separation, while maintaining a low membrane resistance of only 813 Ω. After environmentally sustainable testing, the membrane displayed excellent stability and 80 % recovery capacity, presenting a novel approach and design blueprint for enhancing clean water resources and environmental protection.

Two contrasting mediodorsal thalamic circuits target the mouse medial prefrontal cortex.

At the heart of the prefrontal network is the mediodorsal (MD) thalamus. Despite the importance of MD in a broad range of behaviors and neuropsychiatric disorders, little is known about the physiology of neurons in MD. We injected the retrograde tracer cholera toxin subunit B (CTB) into the medial prefrontal cortex (mPFC) of adult wild-type mice. We prepared acute brain slices and used current clamp electrophysiology to measure and compare the intrinsic properties of the neurons in MD that project to mPFC (MD→mPFC neurons). We show that MD→mPFC neurons are located predominantly in the medial (MD-M) and lateral (MD-L) subnuclei of MD. MD-L→mPFC neurons had shorter membrane time constants and lower membrane resistance than MD-M→mPFC neurons. Relatively increased hyperpolarization-activated cyclic nucleotide-gated (HCN) channel activity in MD-L neurons accounted for the difference in membrane resistance. MD-L neurons had a higher rheobase that resulted in less readily generated action potentials compared with MD-M→mPFC neurons. In both cell types, HCN channels supported generation of burst spiking. Increased HCN channel activity in MD-L neurons results in larger after-hyperpolarization potentials compared with MD-M neurons. These data demonstrate that the two populations of MD→mPFC neurons have divergent physiologies and support a differential role in thalamocortical information processing and potentially behavior.NEW & NOTEWORTHY To realize the potential of circuit-based therapies for psychiatric disorders that localize to the prefrontal network, we need to understand the properties of the populations of neurons that make up this network. The mediodorsal (MD) thalamus has garnered attention for its roles in executive functioning and social/emotional behaviors mediated, at least in part, by its projections to the medial prefrontal cortex (mPFC). Here, we identify and compare the physiology of the projection neurons in the two MD subnuclei that provide ascending inputs to mPFC in mice. Differences in intrinsic excitability between the two populations of neurons suggest that neuromodulation strategies targeting the prefrontal thalamocortical network will have differential effects on these two streams of thalamic input to mPFC.

Casting Electrodes on PEEK Reinforced Sulfonated Polyphenylsulfone Membrane

Researchers are exploring the potential of proton exchange membranes made from hydrocarbon polymers that do not contain fluorine. These polymers possess desirable properties that could make them more environmentally friendly and cost-effective compared to current perfluorinated sulfonic acids (PFSA). Hydrocarbon polymers have a unique structure that maintains high proton conductivity while reducing gas crossover, thus presenting a promising alternative to PFSA membranes [1]. Previous studies have demonstrated the potential of hydrocarbon membranes in electrolyzers using sulfonated polyphenylene sulfone (sPPS) [2]. However, sPPS has a high ion exchange capacity (2.17 – 3.57 meq/g), leading to excessive water uptake that causes the membrane to swelling and impedes upscaling, such as casting anodes directly onto the membrane. To overcome this issue, a woven, open-mesh PEEK substrate was incorporated into the membrane. The reinforced membrane exhibited a significant reduction in water uptake of up to 53% at room temperature and 43% at 60°C compared to the initial membrane. This improvement made it possible to cast the anode directly onto the membrane, resulting in a homogeneous surface (Fig. 1 left). In addition, preliminary electrolysis tests showed promising performance with low membrane resistance of 69 mΩcm² for a 74 µm thick membrane (Fig. 1 right). Literature: [1] Miyake, J.; Taki, R.; Mochizuki, T.; Shimizu, R.; Akiyama, R.; Uchida, M.; Miyatake, K. Design of flexible polyphenylene proton-conducting membrane for next-generation fuel cells. Sci. Adv. 2017, 3(10), eaao0476. DOI: 10.1126/sciadv.aao0476[2] Klose, C.; Saatkamp, T.; Münchinger, A.; Bohn, L.; Titvinidze, G.; Breitwieser, M.; Kreuer, K.; Vierrath, S. All‐Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency. Adv. Energy Mater. 2020, 10 (14), 1903995. DOI: 10.1002/aenm.201903995 Figure 1

Novel sulfonated rGOHfO2/PVDF hybrid nanocomposite ultrafiltration membrane towards direct potable reuse water production

Using wastewater to produce safe and reliable reclamation water is a sustainable means of reducing water scarcity. Membrane technology can be a viable path for producing advanced treated water from wastewater. Numerous three-dimensional metal oxide nanoparticles with graphene oxide (GO) have been evaluated in membrane fabrication. On the other hand, there are no reports on the use of GO combined with hafnium oxide (HfO2) for the fabrication of ultrafiltration (UF) membranes to produce direct potable reuse (DPR) water. In this study, rGOHfO2 (reduced GOHfO2) was synthesized using a microwave method. A novel sulfonated rGOHfO2 (SrGOHfO2) nanocomposite was fabricated and added to the polyvinylidene fluoride (PVDF) to develop advanced nanohybrid UF membranes toward the production of DPR water and improve dispersibility and hydrophilicity. The incorporation of SrGOHfO2 into PVDF membranes had very positive effects on hydrophilicity, MWCO, and morphology. The P-SGOHf-2 membrane (0.2 wt % SrGOHfO2) exhibited excellent pure water flux of approximately 301 ± 3% and 133.3 ± 2% than PVDF and P-GOHf membrane, respectively. The P-SGOHf-2 membrane showed high separation efficiency up to 94 ± 1% and 98 ± 04% towards humic acid (HA) and bovine serum albumin (BSA), respectively. The superior antifouling properties were observed in the SrGOHfO2 incorporated membranes compared to the P-GOHf and PVDF membranes, with a 2.9% irreversible fouling ratio (Rir) and a 97.1% flux recovery ratio (FRR) for the P-SGOHf-2 membrane. The excellent performance of the P-SGOHf-2 membrane was attributed to the larger number of sulfonic acid groups (-SO3H) in the SrGOHfO2 nanocomposite. In the tertiary UF membrane filtration mode operation using the secondary effluent of the field-scale wastewater treatment plant, the P-SGOHf-2 membrane performed high flux with reliable effluent quality (154 ± 5L m−2 h−1, 0.26 ± 0.03 NTU, no pathogens), while it exhibited lower membrane resistances during filtration. These advanced nanohybrid membranes can be a sustainable, viable alternative technology compared to the traditional tertiary treatment processes that utilize expensive and complex multi-step processes to produce DPR water.

Effectiveness of biophotovoltaics system modified with fuller-clay composite separators for chromium removal

The performance of biophotovoltaics (BPVs) having clay separators modified with 10, 15, and 20% of Fuller's earth-material (FEM) to improve the cation exchange capacity was assessed on the basis of wastewater treatment and electrochemical analyses. Among the three variants of clay separators other than the commercial proton exchange membrane (PEM), clay separator modified with 15% of FEM resulted in peak power density (7.87 W/m3) with high organic matter removal (82 ± 3.78%) and Cr (VI) reduction (94 ± 0.85%). FEM provides cationic sites enhancing the proton transfer rate as confirmed from the electrochemical analysis. Membrane characterization also showed high proton transfer coefficient with low membrane resistance in FEM-15%. This first ever study on the utilization of the low-cost 15% FEM clay separator BPV achieved high power outputs and proved its suitability for field-scale applications due to its long-term stability, and thus can be an alternate to the costly polymeric membrane.

Mussel-inspired polyphenol/polyethyleneimine assembled membranes with highly positive charged surface for unprecedented high cation perm-selectivity

Mono/multivalent cation separation techniques have shown increasing importance in diverse environmental and energy applications. The separation performance of emerging monovalent cation exchange membranes (MCEMs) is greatly determined by the architecture and charge property of MCEMs, which should be finely tuned for the energy efficiency applications. Herein, a series of mussel-inspired polyphenol/polyethyleneimine assembled membranes (PPAMs) with highly positively-charged surfaces were elegantly constructed through a facile layer-by-layer assembly method. Based on the synergetic reactions between polyphenols with multiple reactive groups and PEI with abundant amino groups, the denser membrane surfaces with a higher crosslinking degree and more positive charges were readily formed. As a result, the Na+/Mg2+ and Li+/Mg2+ perm-selectivities of PPAMs with such surface architecture and charge property followed the same order as gallic acid/polyethyleneimine membrane (M-GA/PEI) > pyrogallic/polyethyleneimine membrane (M-Pyrogallic/PEI) > protocatechuic acid/polyethyleneimine membrane (M-PA/PEI) > caffeic acid/polyethyleneimine membrane (M-CA/PEI). Most interestingly, the M-GA/PEI fabricated exhibited the unprecedented perm-selectivity (Na+/Mg2+) up to 180.4 with Na+ flux of 6.01 × 10−8 mol cm−2 s−1, which exceeded the current “Upper Bound” plot of MCEMs. The low membrane resistance and excellent separation performance of PPAMs brought great potential for resource recovery and environmental remediation.

3D spray-coated gradient profile ceramic membranes enables improved filtration performance in aerobic submerged membrane bioreactor

Rational design of cross-sectional microstructure in ceramic membranes has shown to improve membrane filtration efficacy without affecting rejection performance. In this work, we adopted 3D spray-coating technique to generate multi-layered membrane layers on macro-porous flat-sheet ceramic supports. The thickness of each layer was controlled by spray-coating cycles, and a gradient membrane layer was rationalized by successively coating three ceramic slurries containing alumina powders of gradually refined particle sizes, followed by co-sintering. Gradient membrane layers on both sides of the various sized flat-sheet ceramic supports were fabricated. Compared to the non-gradient counterpart, the gradient membranes showed both higher pure water flux (at the same TMP) and lower membrane resistance, which clearly evidenced the benefits of gradient profile in the membrane layer. Further, their performance in aerobic membrane bioreactors (AeMBR) was comparably studied for the first time. The treatment performance was not significantly affected by the types of membranes used, while the gradient membrane showed better filtration performance (i.e., a slower rise in TMP). Although the fouling mechanisms were revealed to be similar, the fouling layer in the gradient membrane was composed of a higher percentage of smaller foulants compared to that of the non-gradient counterpart. The observed differences were closely correlated to the larger internal pore structure in the gradient membrane. The present work provides a feasible 3D spray-coating technique for the fabrication of gradient flat-sheet ceramic membranes, and clarifies the benefits in AeMBR for domestic wastewater treatment.

Simulation of the enhancement of Dean flow on the liquid–liquid extraction in membrane contactors

Dean vortices generated through the curved paths have been demonstrated to be beneficial to enhance gas–liquid mass transfer in membrane contactors. However, the effect of Dean vortices in liquid–liquid membrane extraction was seldom studied. This work implemented a numerical model describing the liquid–liquid extraction process in curved membrane contactors with the software of COMSOL. The liquid–liquid extraction experiments were first performed verifying the applicability of the simulation. Firstly, the discussion about the role of membrane resistance revealed the fact that enhancement provided by Dean flows would be more pronounced for systems with lower membrane resistance. A parametric study was then conducted including geometric parameters and physical properties of the fluid, which indicated smaller pitch, smaller curvature diameter, and less viscous fluid led to a better enhancement. The intensification factor was in the range of 1 ∼ 1.8, corresponding to the Dean number range of 5 ∼ 30. Considering the energy consumption, the values of modified intensification factors were lower than 1 only when the Dean numbers were smaller than 8. Finally, the performance of four curved geometries: helically-wound, 90-degree bend, meander-shaped, knotted were compared. The presented model yielded new insights into the liquid–liquid exaction enhancement in the curved membrane contactors.

In‐situ interfacial polymerization endows surface enrichment of COOH groups on anion exchange membranes for efficient Cl−/SO42− separation

AbstractIn‐situ interfacial polymerization technique is developed to prepare monovalent anion‐permselective membranes (MAPMs). The introduction of multi‐hydroxyl (OH) and cationic groups in the base membrane provide suitable routes towards the monovalent anion transport. Only trimesoyl chloride is employed to generate a crosslinked polyester layer on membrane surface. The ISIP transforms the surface of anion exchange membranes into a dense and negatively charged layer to promote the ion permselectivity. The modified membranes show a high limiting current density and low membrane resistance of 4.7 Ω cm2. The resultant membranes exhibit a high Cl− flux of 6.3 × 10−8 mol cm−2 s−1 and a high permselectivity of ~60 for Cl−/SO42−. The findings demonstrate the ISIP technique having great potentials for the fabrication of highly permselective MAPMs.

Imparting Ion Selectivity to Covalent Organic Framework Membranes Using de Novo Assembly for Blue Energy Harvesting.

It has long been a challenge to fabricate angstrom-sized functional pores for mimicking the function of biological channels to afford selective transmembrane transport. In this study, we describe a facile strategy to incorporate ionic elements into angstrom-sized channels using de novo encapsulation of charged dye molecules during the interface polymerization of a three-dimensional covalent organic framework (3D COF). We demonstrate that this approach is tailorable as it enables control over both the type and content of the guest and thus allows manipulation of the membrane function. The resulting membranes exhibit excellent permselectivity and low membrane resistance, thereby indicating the potential for harvesting salinity gradient (blue) energy. As a proof-of-concept study, the reverse electrodialysis device coupled with positive and negative dye encapsulated COF membranes afforded a power density of up to 51.4 W m-2 by mixing the simulated seawater and river water, which far exceeds the commercialization benchmark (5 W m-2). We envision that this strategy will pave the way for constructing new multifunctional biomimetic systems.

Ion Channels and Electrophysiological Properties of Astrocytes: Implications for Emergent Stimulation Technologies.

Astrocytes comprise a heterogeneous cell population characterized by distinct morphologies, protein expression and function. Unlike neurons, astrocytes do not generate action potentials, however, they are electrically dynamic cells with extensive electrophysiological heterogeneity and diversity. Astrocytes are hyperpolarized cells with low membrane resistance. They are heavily involved in the modulation of K+ and express an array of different voltage-dependent and voltage-independent channels to help with this ion regulation. In addition to these K+ channels, astrocytes also express several different types of Na+ channels; intracellular Na+ signaling in astrocytes has been linked to some of their functional properties. The physiological hallmark of astrocytes is their extensive intracellular Ca2+ signaling cascades, which vary at the regional, subregional, and cellular levels. In this review article, we highlight the physiological properties of astrocytes and the implications for their function and influence of network and synaptic activity. Furthermore, we discuss the implications of these differences in the context of optogenetic and DREADD experiments and consider whether these tools represent physiologically relevant techniques for the interrogation of astrocyte function.

Predicting Flux Rates against Pressure via Solution-Diffusion in Reverse Osmosis Membranes

This paper suggests a new method of predicting flux values at Reverse Osmosis (RO) desalination plants. The solution-diffusion model is utilized to determine the osmotic pressure drops for seawater sources. The same technique was applied to the groundwater source at the Abqaiq plant (500 RO plant) to calculate the osmotic pressure. The calculated osmotic pressures were utilized to determine the appropriate flux rates and membrane resistances of different BWRO Toray membranes and a performance comparison between various membranes has been established. The model results confirm an inverse relationship between membrane thickness and water flux rate. Also, a proportional linear relation between the overall water flux and the applied pressure is identified. Higher flux rates and lower salinity indicate lower membrane resistance yielding higher production. The modeled data predict that BWRO Toray TM720D-440 with an 8" membrane is the optimal choice for treating waters from the three water sources at the Abqaiq plant.

Intrinsic burst-firing in lamina I spinoparabrachial neurons during adolescence

A subset of glutamatergic interneurons in the neonatal spinal superficial dorsal horn (SDH) exhibits intrinsic burst-firing (i.e. ‘pacemaker’ activity), which is tightly regulated by persistent, voltage-gated Na+ channels and classic inward-rectifying K+ (Kir2) channels and downregulated over the course of postnatal development. Ascending lamina I projection neurons targeting the parabrachial nucleus (PB) or periaqueductal gray (PAG) can also display pacemaker activity during early life. However, the degree to which the ionic mechanisms driving pacemaker activity are conserved across different cell types in the spinal dorsal horn, as well as whether the intrinsic bursting is restricted to newborn projection neurons, remains to be elucidated. Using in vitro patch clamp recordings from identified lamina I spinoparabrachial neurons in rat spinal cord slices, here we demonstrate that adolescent projection neurons retain their ability to generate pacemaker activity. In contrast to previous findings in lamina I interneurons, pacemaker projection neurons possessed higher membrane capacitance, lower membrane resistance, and a greater Kir-mediated conductance compared to adjacent spinoparabrachial neurons that lacked intrinsic burst-firing. Nonetheless, as previously seen in interneurons, the bath application of riluzole to block persistent Na+ channels significantly dampened pacemaker activity in projection neurons. Collectively, these results suggest that intrinsic burst-firing in the developing dorsal horn can be generated by multiple combinations of ionic conductances, and highlight the need for further investigation into the mechanisms governing pacemaker activity within the major output neurons of the SDH network.

High-Performance and Durable Membrane Electrode Assemblies Fabricated By Reactive Spray Deposition Technology for Proton Exchange Membrane Electrolyzers

Water electrolysis is a very old and promising technology for hydrogen production that started about two centuries ago. Hydrogen, considered the best source for fuel and energy storage, can be produced by the electrochemical conversion of water into hydrogen and oxygen through the water electrolysis process. Since the 1950s, proton exchange membrane water electrolyzers (PEMWEs) have been commercially developed as a green source of high-purity hydrogen for many chemical applications as well as energy storage. However, high cost, high maintenance, low durability, poor safety, poor reliability, and low efficiency of PEMWEs compared to other available technologies have hampered their widespread commercialization. To address the economic and technical issues of the PEMWEs, research should consider improved electrocatalysts, low cost electrodes, corrosive resistant electrodes, reduction of electrode surface tension, and lower membrane resistance and hydrogen crossover [1, 2].This work presents high-performance, cost-effective and durable membrane electrode assemblies (MEAs; 86 cm2 active area) developed by the unique reactive spray deposition technology (RSDT) [3-6]. The RSDT-fabricated MEAs possess total platinum group metal (PGM) loading of 0.2-0.3 mgPt cm-2 for the Pt/C cathode catalyst layer, and 0.2-0.3 mgIr cm-2 for the Ir/IrOx anode catalyst layer, respectively. This is an order of magnitude reduction of the PGM loadings in the catalyst layers in comparison to the state-of-the-art commercial MEAs, resulting in substantial reduction of the cost of PEMWEs. An ultra-thin Pt recombination layer (Pt RL), positioned between two PEM membranes, was fabricated by RSDT to lower hydrogen cross-over and eliminate the PEMWE’s safety concerns. Furthermore, the RSDT-fabricated MEAs showed stable performance for 3000 hours operation at 1.8 A cm-2, 50°C, 400 psi hydrogen pressure and ambient oxygen pressure without significant loss in the polarization performance.

Pilot‐scale microalgae harvesting with ceramic microfiltration modules: evaluating the effect of operational parameters and membrane configuration on filtration performance and membrane fouling

AbstractBACKGROUNDMembrane fouling is one of the major drawbacks in microalgae harvesting that prevents the widespread application of membrane filtration. This study investigates the effects of operating parameters on the filtration performance and the fouling phenomenon of a pilot‐scale microfiltration (MF) system equipped with different ceramic membranes for Chlorella vulgaris culture harvesting.RESULTSA higher permeate flux was obtained with increasing the transmembrane pressure, resulting in lower irreversible and reversible filtration resistances. On the other hand, at a higher crossflow velocity above 4 m s−1, a high amount of extracellular organic matter (EOM) released by microalgal cells led to a higher irreversible resistance which, in turn, caused severe membrane fouling and a lower filtration flux. Furthermore, the membrane configuration and pore size have also significantly affected the permeate flux. Compared to the tubular membranes, and regardless of pore sizes, the multichannel MF membrane (pore size: 0.2 μm) exhibited a higher permeate flux that resulted in lower membrane resistances due to the lower release of EOM by microalgae cells. Moreover, the tubular membrane (pore size: 0.8 μm) showed a higher flux reduction with higher pore size because of the increase in the irreversible resistance with a high amount of EOM release.CONCLUSIONThe results revealed that the amount of EOM significantly associated with filtration conditions plays an important role in membrane fouling control. Considering the membrane configurations, the multichannel ceramic MF membrane (pore size: 0.2 μm) demonstrated a higher permeate flux due to its lower fouling property. © 2020 Society of Chemical Industry (SCI)

Backwash sequence optimization of a pilot-scale ultrafiltration membrane system using data-driven modeling for parameter forecasting

Optimizing the backwashing procedure of ultrafiltration membranes poses novel challenges in regards to the modeling and simulation of the fouling process. Traditional modeling approaches the problem through a physical and chemical understanding of the complicated fouling phenomena. In this study, a large amount of data has been collected from a pilot-scale ultrafiltration membrane system treating spent filter backwash water at a water treatment plant. Environmental variables and operational parameters including temperature, hydraulic pressure, water turbidity, etc. are monitored continuously. This work focuses on revealing the hidden nonlinear relationships of these variables via data driven methodologies without building a first principles process model. Machine learning tools are used to establish a connection between environmental variables, dynamic parameters, the efficiency of foulant removal through backwashing, and the increase rate of foulants. The prediction performance is compared to regression models including linear regression, artificial neural networks, and random forests. Our data driven model of the fouling dynamics is then used for optimization purposes, in particular, to optimize the backwashing sequence timing by applying tools from stochastic dynamic programming. Optimized backwash performance is compared with experimental data acquired via a fixed interval sequence and shows a more efficient schedule at less cost and with lower membrane resistance. This work establishes a full pipeline of data processing, model building, and operational optimization. The only requirement for employing our methodology is the collection of operational data, in order to identify the membrane dynamics. The reported methodology offers a great potential for implementation on large-scale ultrafiltration applications, which can improve energy consumption and elongate membrane life.

Astrocytes of the early postnatal brain.

In the rodent forebrain, the majority of astrocytes are generated during the early postnatal phase. Following differentiation, astrocytes undergo maturation which accompanies the development of the neuronal network. Neonate astrocytes exhibit a distinct morphology and domain size which differs to their mature counterparts. Moreover, many of the plasma membrane proteins prototypical for fully developed astrocytes are only expressed at low levels at neonatal stages. These include connexins and Kir4.1, which define the low membrane resistance and highly negative membrane potential of mature astrocytes. Newborn astrocytes moreover express only low amounts of GLT-1, a glutamate transporter critical later in development. Furthermore, they show specific differences in the properties and spatio-temporal pattern of intracellular calcium signals, resulting from differences in their repertoire of receptors and signalling pathways. Therefore, roles fulfilled by mature astrocytes, including ion and transmitter homeostasis, are underdeveloped in the young brain. Similarly, astrocytic ion signalling in response to neuronal activity, a process central to neuron-glia interaction, differs between the neonate and mature brain. This review describes the unique functional properties of astrocytes in the first weeks after birth and compares them to later stages of development. We conclude that with an immature neuronal network and wider extracellular space, astrocytic support might not be as demanding and critical compared to the mature brain. The delayed differentiation and maturation of astrocytes in the first postnatal weeks might thus reflect a reduced need for active, energy-consuming regulation of the extracellular space and a less tight control of glial feedback onto synaptic transmission.

Nanofiber membranes by multi-jet electrospinning arranged as arc-array with sheath gas for electrodialysis applications

Multi-jet electrospinning arranged in an arc array with sheath gas has been developed for the high-efficiency production of nanofiber membranes. The arc array constrains the electric field interferences among multiple nozzles and the sheath gas in laminar flow overcomes the electric repulsive force among the jets. The stretching and focusing effect from the sheath gas reduces both the nanofiber diameter and the diameter range, which helps to realize the continuous stable multi-jet electrospinning to fabricate uniform nanofiber membranes. After the treatment of 98% concentrated sulfuric acid for the reactive exchange groups and a hot-pressing process, the membrane is then applicable to electrodialysis applications. Thanks to the net structure, there are many ion transmission passageways within the membrane, leading to the low membrane resistance and high ion transmission efficiency. Experimentally, the increase of membrane thickness results in the decrease of porosity, ion exchange capacity (IEC) and selective permeability and the increase in membrane resistance. The electrodialysis tests show good ion selection performance with a high desalinization ratio of NaCl solution.

Possible use of organic compounds on shelf life and quality properties of peeled pomegranate.

Pomegranate cultivar (“Ardestani”) peeled and packed in polyethylene containers and treated with different natural products. Two concentrations of Aloe vera gel (10 and 15%), two different levels of saffron petal extracts (10 and 20% V/V) and two concentrations of saffron style extract (0.1 and 1% V/V) and control in one storage condition (7°C and 85% RH) were the treatments that applied by a full factorial randomized method. We examined natural substances for their possible application in extending the shelf life of fresh‐cut horticultural products to find a new approach for packaging and exporting pomegranates. About 13.8% mass loss in the 12th day of storage occurred because of higher enzymatic activity and lower membrane resistance. Our results show that all treatments significantly reduced mass loss, and Aloe vera gel treatments combined with saffron petal extract were the best. Although all treatments decreased ion leakage, Aloe vera gel and saffron petal extract reduced it significantly. Ion leakage incidence of arils at day 12 was lower in Aloe vera gel and saffron petal extract treatment compare to control. Application of both saffron extracts on arils reduced decay incidence and chilling injury from 86.67% to 6.67% and 60% to 26.67%, respectively. Total acidity, soluble solids content, total phenol content, anthocyanin content, and antioxidant capacity of arils changed differently in different treatments, and saffron petal extract significantly was the best one and increased anthocyanin content, total phenol content, and antioxidant capacity in arils. The microbial contamination increased in more extended storage, although both saffron extracts were successfully suppressed mold and bacteria growth below acceptable limits in 14 days at 7°C.