Increase In Membrane Thickness Research Articles

Enhancing ammonia selectivity in membrane distillation: The role of membrane structural characteristics

Ammonia is emerging as a promising carbon-free fuel in the pursuit of carbon neutrality due to its combustion process, which produces no carbon dioxide emissions. Membrane distillation (MD) for recovering ammonia from wastewater is an alternative to conventional energy-intensive production methods. However, the efficiency of MD processes is hindered by the low purity of the recovered ammonia stream, primarily due to excessive water permeation. In this study, we investigated the influence of membrane properties on water and ammonia permeation using poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) nanofibrous membranes fabricated in-house via electrospinning. Additionally, we compared the impact of manipulating membrane characteristics with adjusting operating conditions, employing a commercial PVDF membrane as the conventional approach for controlling ammonia purity. Our findings revealed that increasing membrane thickness (from 82 to 283 μm) under isothermal conditions substantially enhanced the ammonia separation factor (from 4.07 to 7.28) by approximately 80 %, whereas reducing the feed temperature from 50 °C to 43 °C yielded only a 20 % improvement. Mechanistic modeling of MD for the water-ammonia system illustrated the critical role of membrane thickness in improving ammonia selectivity by markedly reducing water flux while maintaining relatively consistent ammonia flux. The combination of experimental and simulation outcomes suggests that modifying membrane properties or selecting membranes with specific characteristics can enhance ammonia selectivity without significant alterations to operating conditions or configuration.

Numerical study of gas crossover effect on hydrogen-oxygen proton exchange membrane fuel cell

Hydrogen-oxygen proton exchange membrane fuel cell (H2/O2 PEMFC) is a typical fuel cell for the applications of air-free environments, such as aerospace and underwater. Gas crossover has an adverse effect on the cell performance especially on open-circuit voltage (OCV), and this phenomenon would be severe for H2/O2 PEMFC. In this study, we develop a H2/O2 PEMFC model considering hydrogen and oxygen crossover, and investigate the gas crossover effect on H2/O2 PEMFC, and effects of temperature, relative humidity, inlet pressure and membrane thickness. The numerical results show that the gas crossover effect on the cell performance is obvious in the low current density region, and this effect becomes weak with current density. Although the crossover flux rate of hydrogen is generally greater than that of oxygen, the crossover current density of oxygen could be greater than that of hydrogen. Increasing temperature and relative humidity will decrease the OCV, and increase hydrogen and oxygen crossover current density. The temperature effect on OCV is more obvious at high relative humidity conditions. Increasing inlet pressure only slightly increases the OCV with considering the gas crossover effect. The OCV increases with increasing membrane thickness, and this positive effect becomes weak when the membrane thickness is greater than 75 μm in the investigated range. The work illustrates the basic influence rules and some quantified results of the critical parameters on the gas crossover effect and OCV of H2/O2 PEMFC.

PH and potential-controlled multi-modal mass transport in block copolymer nanochannel membranes

Inspired by the hydrophobic gating for achieving fast and selective ion/molecular transport in cell membranes, wetting/dewetting transition in solid-state nanopores controlled by external stimuli such as voltage, pH, electrostatics, and light have attracted increasing attention. For an accurate and better understanding, a single nanopore or low-density array of nanopores was preferred to investigate the wetting and dewetting transitions owing to their well-defined chemical functions and physical structures. However, high-density nanochannel membranes capable of processing high-throughput and multi-modal mass transport are more beneficial with the aim of practical use. In this regard, pH- and potential-responsive nanochannel membranes consisting of a polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) are prepared to demonstrate a multi-modal transport system with high-throughput capability. At pH < pKa(P4VP) (pKa ∼ 4.8), the cylindrical P4VP nanodomains are hydrophilic and positively charged, acting as an anion-exchange membrane. In contrast, at pH > pKa(P4VP), the P4VP domains switch to be charge-neutral and hydrophobic, naturally blocking the mass transport through the nanochannels. Applying a sufficiently positive potential to a BCP membrane-coated electrode may induce oxidative wetting in the hydrophobic nanochannels to facilitate mass transport across the membrane with no charge-selectivity. Releasing the bias makes the hydrophobic nanochannel membranes retrieve the original dewetted state, blocking the transport again. In addition, direct observation of the wetting-dewetting transition dynamics in the hydrophobic nanochannels is investigated by monitoring potential-correlated electrochemiluminescence (ECL) signals arising from Ru(bpy)32+ and co-reactant tripropylamine (TPA) under potential modulations. ECL signals tend to decrease with increasing membrane thickness ranging from 0 nm to 820 nm because it requires higher potentials to induce wetting in the nanochannels due to elongated hydrophobic nanochannels. The multi-modal transport system developed in the present work will be useful for applications such as water treatment, biosensors, and smart valve systems like controlled drug release/delivery.

Operando Characterization of Water Flux across Hydroxide-Exchange Membranes

The water balance in operating hydroxide-exchange-membrane fuel cells (HEMFCs) is a key challenge for improved performance and durability. For every 4 electrons produced in an HEMFC, 4 water molecules are generated in the anode, 2 water molecules are consumed in the cathode. Water is also transported from cathode to anode along with the hydroxide due to electroosmosis. Consequently, there is a concentration gradient of water that transport water from anode to cathode. Ineffective water management could lead to cathode dry-out, where insufficient water in the cathode limits the rate of reaction or causes ionomer degradation through alkaline instability, or to anode flooding, where excess liquid water in the anode limits gas diffusion. To address these issues, it is critical to measure the transport of water across the hydroxide-exchange membrane during cell operation. We built a water-flux station to measure the water in and out of the anode and cathode during cell operation with different inlet relative humidities and back pressures. Here, the effect of the membrane thickness and the effect of stacking hydroxide-exchange membranes on the water transport across the hydroxide exchange membrane is studied. The stacking of hydroxide-exchange membranes creates an interfacial ohmic resistance between membranes, measured from the high frequency resistance, but not an interfacial water transport resistance. This study shows that the water transport across the hydroxide-exchange membrane is sufficient for water consumption in the cathode and is not significantly affected by the membrane thickness or stacking. However, the added ohmic resistance from the increased membrane thickness or stacking membranes significantly affects the performance.

Cellular damage and response mechanisms of Candida tropicalis SHC-03 induced by toxic byproducts in corn stover hydrolysate

This study advances the understanding of cellular damage and response mechanisms in Candida tropicalis (SHC-03) when exposed to toxic byproducts in corn stover hydrolysate, which is used for optimizing the industrial production of bioethanol and bio-based products. We found that the hydrolysate's toxic byproducts led to 84.61% accumulation of reactive oxygen species and considerable mitochondrial damage, thus inhibiting SHC-03 cell growth by 40%. The yeast combated these effects by enhancing the glutathione and thioredoxin systems, and increased their activity by 60% and 70%, respectively, to maintain intracellular redox balance. The ubiquitin–proteasome pathway was involved and endoplasmic reticulum stress was alleviated, which increased membrane thickness through ergosterol biosynthesis and improved inhibitor tolerance via upregulated expression of transporters and aldehyde reductases. These adaptations, along with the overexpression of genes related to the biosynthesis of impaired proteins and fatty acid degradation, promote SHC-03's resilience to hydrolysate toxic byproducts. Our findings could be useful for genetic modifications to increase the tolerance of fermentation strains, which could accelerate the industrial production of bioethanol and bio-based products.

CFD modeling of braid-reinforced hollow fiber membranes for efficient water and bovine serum albumin (BSA) separation

This study presents a comprehensive investigation into the performance optimization of a braid-reinforced hollow fiber membrane (BHFM) system for protein separation from milk wastewater. Extensive CFD simulations were conducted to examine the effects of various effective parameters on system performance. The results reveal that at a feed protein concentration of 100 mg/l, the average water flux increases from 149.16 to 453.68 l/m2.h as the inlet feed pressure rises from 100 to 300 kPa. Similarly, for a feed protein concentration of 300 mg/l, the average flux rises from 98.69 to 299.84 l/m2.h. However, higher feed concentrations lead to increased fouling and lower water fluxes. Additionally, an increase in feed pressure results in a decrease in the protein rejection rate, particularly in the initial stages of separation. The study highlights that variations in membrane porosity and thickness significantly affect both protein rejection rate and water flux. Increasing membrane porosity from 0.2 to 0.8 leads to a decrease in protein rejection rate from 94.57 % to 78.47 % at an inlet pressure of 100 kPa, and from 93.33 % to 73.43 % at 300 kPa. Similarly, increasing membrane thickness from 0.1 to 1.0 mm decreases the time-averaged water flux from 105.76 to 8.64 l/m2.h at 100 kPa, and from 321.39 to 25.99 l/m2.h at 300 kPa. However, increasing membrane thickness also increases the protein rejection rate. The study's novelty lies in the quantitative results obtained through CFD simulations, providing valuable insights into BHFM system performance. Future research should focus on exploring innovative braid architectures and material selection to enhance the mechanical stability and durability of braid-reinforced structures under various operational conditions.

The impact of PAC-loaded polymer membrane thickness on chloroform removal and comparison of solvent and thermal membrane regeneration methods.

Powdered activated carbon (PAC) has better adsorption performance than granular activated carbon (GAC) and is widely used in water purification. In most cases, PAC is dosed into water directly, then precipitated as sludge, and landfilled. In this study, PAC was mixed with a polymer and dissolved in dimethylformamide (DMF) solvent to form a PAC-loaded membrane, which was then tested for chloroform removal. The chloroform adsorption capacity of the PAC membrane increased with increasing membrane thickness because of higher carbon loading. However, regardless of membrane thickness, the flux of the PAC membranes was similar since flux resistance predominantly occurred at the top dense polymer surface. This dense surface can be removed by sandpaper polishing, where the adsorption capacity of the polished PAC membranes was 20% higher than the unpolished membranes because of more even distribution of feed water on the polished surface. Removal of the dense surface via polishing increased the flux by 97% to 130%, exceeding the flux of typical household carbon block filters. Using DMF to regenerate the membrane recovered 48% to 66% of the initial adsorption capacity. Thermal regeneration of the exhausted PAC membrane at 250°C was more effective than DMF regeneration (both in terms of cost and performance), with 83% to 94% PAC membrane regeneration efficiency over four regeneration recycles. After four thermal regeneration cycles, flux increased by 300% and the membrane became brittle because of thermal aging of the polymer, indicating that a total of 6h of regeneration time (equivalent to three cycles in this study) was the limit for effective PAC membrane performance. PRACTITIONER POINTS: Powdered activated carbon was immobilized on a membrane to remove chloroform from water. Thicker membranes increased adsorption capacity but did not impact flux. Flux and capacity increased using polishing to remove the dense polymer surface and more evenly distribute flow across the membrane. Thermal regeneration of the membrane at 250°C was effective for up to three cycles and outperformed solvent-based regeneration. PAC-loaded filters are relevant for applications such as household carbon block filtration.

Effect of Operating Conditions on the Capacity of Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) present a viable solution to address the intermittent power output challenge associated with wind and solar energy generation. However, their development is impeded by their low energy density and high cost. To achieve the objective of cost reduction, it is crucial to optimize operating conditions, minimize capacity loss, and enhance battery performance. Through meticulous experimental analysis, this study thoroughly examines the impact of membrane thickness, current density, flow rate, and self-discharge on battery capacity. The experimental findings reveal that an increase in membrane thickness results in elevated resistance to proton transport, thereby weakening electrochemical reactions. Moreover, surpassing critical values for current density and flow rate also leads to a decrease in capacity. Prolonged shelving induces severe self-discharge reactions that accelerate deterioration of capacity fade. This research suggests that obtaining optimal operational parameters can effectively mitigate battery capacity fade.

Effect of leaflet asymmetry on the stretching elasticity of lipid bilayers with phosphatidic acid

The asymmetry of membranes has a significant impact on their biophysical characteristics and behavior. This study investigates the composition and mechanical properties of symmetric and asymmetric membranes in giant unilamellar vesicles (GUVs) made of palmitoyloleoyl phosphatidylcholine (POPC) and palmitoyloleoyl phosphatidic acid (POPA). A combination of fluorescence quantification, zeta potential measurements, micropipette aspiration, and bilayer molecular dynamics simulations are used to characterize these membranes. The outer leaflet composition in vesicles is found consistent across the two preparation methods we employed, namely electroformation and inverted emulsion transfer. However, characterizing the inner leaflet poses challenges. Micropipette aspiration of GUVs show that oil residues do not substantially alter membrane elasticity, but simulations reveal increased membrane thickness and decreased interleaflet coupling in the presence of oil. Asymmetric membranes with a POPC:POPA mixture in the outer leaflet and POPC in the inner leaflet display similar stretching elasticity values to symmetric POPC:POPA membranes, suggesting potential POPA insertion into the inner leaflet during vesicle formation and suppressed asymmetry. The inverse compositional asymmetry, with POPC in the outer leaflet and POPC:POPA in the inner one yield less stretchable membranes with higher compressibility modulus compared with their symmetric counterparts. Challenges in achieving and predicting compositional correspondence highlight the limitations of phase-transfer-based methods. In addition, caution is advised when using fluorescently labeled lipids (even at low fractions of 0.5 mol %), as unexpected gel-like domains in symmetric POPC:POPA membranes were observed only with a specific type of labeled DOPE (dioleoylphosphatidylethanolamine) and the same fraction of unlabeled DOPE. The latter suggest that such domain formation may result from interactions between lipids and membrane fluorescent probes. Overall, this study underscores the complexity of factors influencing GUV membrane asymmetry, emphasizing the need for further research and improvement of characterization techniques.

Analysis of the gas transport resistance of CO2 and CH4 through ultra-thin DD3R zeolite membrane

Ultra-thin DD3R zeolite membranes exhibit excellent separation properties for CO2 capture from natural gas, as well as the lower transmembrane resistance. However, the interfacial transport of permeation gas in such systems may dominate the whole separation process. In this work, we employed external force non-equilibrium molecular dynamic (EF-NEMD) simulation to predict the single-component permeabilities of CO2 and CH4 through a defect-free DD3R zeolite membrane at different pressured drops. By explicitly including the gas transport from bulk phase to zeolitic channels, the predicted results of EF-NEMD simulation showed good agreements with the reported experimental data. The contribution of interfacial resistance over the total transport resistance (Rinter/Rtotal) was further evaluated for the membranes with different thicknesses under temperatures between 273 K and 373 K. The results revealed a decrease in Rinter/Rtotal with increasing membrane thickness, leading to a reduction in CO2/CH4 selectivity, and the critical thickness (Rinter/Rtotal < 0.01) was determined to be approximately 300 nm at pressure of 1.0 MPa and temperature of 298 K. Similarly, the Rinter/Rtotal decreased with increasing temperature due to the augmentation in molecule kinetic energy. Furthermore, it was confirmed that the gas adsorption effect could expand the effective size of eight membered ring (8-MR) channels in DD3R zeolite membrane, thereby decreasing the CO2/CH4 selectivity, despite higher permeation fluxes. The above discoveries essentially benefit the design of the ultra-thin DD3R zeolite membrane through an understanding of CO2 and CH4 transport behaviors.

Efficient desalination in fluorinated multilayered covalent organic framework: Tunning the energy landscape inside the nanochannel

The design and construction of advanced nanochannels can significantly enhance the performance of reverse osmosis (RO) membranes in desalination, offering potential solutions to the severe freshwater shortage crisis. In this study, we investigated the desalination performance of nanochannels formed by multilayered covalent organic frameworks (COF) that had undergone various types of chemical functionalization, through nonequilibrium molecular dynamics simulations. Our data reveals that fluorination of the nanochannel results in the most impressive desalination performance, as evidenced by significant improvements in both water permeability (increasing from 39.1 to 100.1 L cm−2 day−1 MPa−1) and salt rejection (rising from 91.9 % to 97.1 %). Especially, in multilayered systems, fluorinated nanochannel mitigates the typical decline in water permeability with increasing membrane thickness. For the working mechanism, the free energy analysis indicates that fluorination contributes to a smooth energy landscape for water molecules inside the nanochannel, reducing their interaction with the nanochannel, which results in a more dispersed arrangement of water molecules with fewer hydrogen bonds and a significantly enhanced water velocity, thus facilitating their fast and unobstructed permeation. Therefore, this study offers a promising semipermeable membrane for high-efficiency desalination, achieved through fluorination. It also demonstrates an indicative approach for advanced channel design through fluorination engineering.

Unraveling a Novel Mechanism of Altered Glomerular Hemodynamics in Pre-diabetic Obesity

Background: In pre-diabetic obesity, disrupted glomerular autoregulation leads to increased glomerular capillary pressure and renal blood flow, causing potential barotrauma-induced glomerular damage. A decrease in Afferent arteriole ( Af-Art) resistance causes higher glomerular capillary pressure but the underlying mechanism behind this, specifically in pre-diabetic obesity, remains unclear. Hyperinsulinemia is common in pre-diabetic obesity, but its role in reducing Af-Art resistance in the kidneys is unknown. Kidney blood flow is auto-regulated by vasoconstriction via tubuloglomerular feedback (TGF) and vasodilation through the Distal convoluted tubule-2/connecting tubule (DCT-2/CNT) mechanism. Our earlier studies indicate increased Af-Art dilation in pre-diabetic obese rats through the DCT-2/CNT mechanism without affecting TGF. This DCT-2/CNT induced Af-Art dilation requires initiation from epithelial sodium channels (ENaC) present at this tubular segment and interestingly insulin is a known ENaC activator. Hypothesis: We hypothesize that in the context of pre-diabetic obesity, hyperinsulinemia contributes to an increase in renal cortical blood flow (CBF) by increasing DCT-2/CNT-induced Af-Art dilation, subsequently leading to glomerular injury. Methods: We assessed the effects of insulin on Af-Art dilation by perfusing juxtaposed DCT-2/CNT segments with insulin in normal rabbits. Contribution of DCT-2/CNT induced Af-Art dilation was measured by co-administration of the ENaC blocker benzamil. To study hyperinsulinemia's role in an in-vivo setting without altering blood glucose levels, we used a hyperinsulinemic-euglycemic (HI-EUG) clamp in obese rats with intravenous (IV) glucose and insulin infusions. Renal CBF and blood pressure were monitored using a laser Doppler probe and femoral artery catheter, respectively, both with and without benzamil administration (400 μg/kg, IV). To evaluate insulin's potential role in causation of renal damage, we infused insulin directly into one kidney of lean rats for 6 weeks via a renal sub-capsular catheter, with the contralateral kidney serving as control. Glomerular basement membrane (GBM) thickness, a marker of renal damage, was measured via electron microscopy. Untargeted lipidomic analysis of the renal cortex was performed to identify potential renal damage pathways in insulin infused kidneys. Results: Insulin perfusion in rabbits' DCT-2/CNT potentiated the dilation of adherent Af-Art compared to control infusions with artificial tubular fluid. ENaC inhibition reversed the insulin-induced Af-Art dilation, confirming that insulin increases Af-Art dilation through the ENaC-initiated DCT-2/CNT mechanism. In obese rats, insulin delivery using a HI-EUG clamp resulted in a significant 20.8±4.9% increase in CBF, which was negated by the administration of the ENaC blocker benzamil, indicating the potential involvement of DCT-2/CNT-mediated vasodilation. Neither the HI-EUG clamp nor benzamil infusion affected blood pressure. Additionally, continuous direct insulin infusion into the kidneys of lean rats led to an increase in glomerular basement membrane (GBM) thickness and ceramide accumulation in the renal cortex, both indicative of renal damage. Conclusion: Our study demonstrates that insulin directly augments DCT-2/CNT-mediated Af-Art dilation and increases renal cortical blood flow in obese rats. Chronic renal insulin infusion led to structural changes and damage markers in the kidney, independent of blood glucose and blood pressure levels. Henry Ford Health System Internal Funding. Pilot and Feasibility grant from southeast center for integrated metabolomics. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Protective effect of dental pulp stem cells' conditioned medium against cisplatin-induced testicular damage in rats

Cisplatin is a highly effective chemotherapy drug used to treat most solid tumors. However, one of its side effects is testicular toxicity, which can lead to fertility abnormalities. This study investigated the effectiveness of dental pulp mesenchymal stem cells conditioned medium (DPSC-CM) on cisplatin-induced testicular toxicity. In this study, 36 eight-week-old male Wistar rats were randomly divided into three groups equally (n = 12). Group 1 control "CTR", which received normal saline (0.5 ml) intraperitoneally (i.p), group 2 "Cis" which received an intraperitoneal dose of cisplatin (7 mg/kg), and group 3 "Cis+CM" which received an i.p injection of DPSC-CM (0.5 mg/kg) after cisplatin injection. Biochemical, histomorphometric, and histopathological studies were performed on the testis. Our results exhibited that cis administration led to a decline in total body weight, testis weight, diameter, and volume. A decrease in testosterone and IL-6 serum levels, as well as a decrease in IL-6 and TNFα levels, the activity of catalase and SOD enzymes, and an increase in MDA in testicular tissue were detected. Testicular tissue damage was associated with a significant decrease in tube diameter, germinal epithelium height, number of spermatogonia and Sertoli cells, along with a noticeable increase in basement membrane thickness, and perivascular fibrosis. DMSC-CM improved all the mentioned parameters. Taken together, our results demonstrated that DMSC-CM due to its antioxidant and anti-inflammatory properties, could be effective in reversing cisplatin-induced testicular toxicity.

Pervaporation Separation of Tetrahydrofuran/Water Azeotropic Mixtures using Phosphorylated Blend Membranes

In this study, we developed novel phosphoric acid crosslinked blend membranes for the pervaporation separation of tetrahydrofu-ran/water mixtures. Sodium alginate and chitosan blend membranes were prepared by solution casting and solvent evaporation technique. These blend membranes were crosslinked with phosphoric acid in isopropanol/water baths and used for pervaporation separation of feed mixtures ranging from 6 to 43 wt.% water in tetrahydrofuran (THF)/water mixtures at 30 °C. Crosslinking was confirmed by Fourier transform infrared (FTIR) and Ion Exchange Capacity (IEC) study. Thermal stability and crystallinity of the membranes were determined from thermogravimetric analysis (TGA) and X-ray diffraction (XRD) studies respectively. The surface morphology of the membranes was observed using Scanning electron microscopy (SEM). Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the membranes in THF, water and binary mixtures. The effect of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance of the phosphorylated membranes were determined. These membranes were found to have good potential for breaking the azeotrope of 94 wt.% THF with a selectivity of 459 and normalized flux of 0.25 kg m−2 h−1 10 µm. The membrane performance exhibited a reduction in selectivity and an improvement in flux with increasing feed water compositions. Selectivity improved and flux decreased with increasing membrane thickness. Both flux and selectivity decreased with increasing permeate pressure.

Control of gas selectivity and permeability through COF-GO composite membranes for sustainable decarbonization and hydrogen production

A promising way to address modern environmental and energy supply challenges is via rapid implementation of decarbonization and hydrogen production technologies. Development of gas separation membranes with high selectivity and permeability is essential for these processes but is still a bottleneck. Our research focuses on achieving precise control of gas diffusion pathways through on-demand regulation of material interactions in thin composite membranes. We combine 2D covalent organic frameworks (COFs) and graphene oxide (GO) to create COF-GO composite membranes with desirable nanosheet stacking, controllable thicknesses and pathways for gases. By pH-assisted self-assembly, we fine-tune material interactions and achieve simultaneous enhancement of permeability and selectivity by increasing membrane thickness and regulating the interactions between COF and GO nanosheets by pH. At a thickness of 1.3 μm, the COF-GO membrane, assembled under pH 4, demonstrates good working characteristics for H2/CO2 equimolar mixture (at room temperature and 1 bar), with a H2 permeability of 366 Barrer, selectivity of 15.6, and long-term stability exceeding 200 h. This work paves the way for tailored, performing gas separation with long-term stability. It guides the unique 2D transport mechanism to be utilized under practical conditions. Our research offers a novel strategy for the design of composite membranes from two-dimensional (2D) materials for gas separation technologies. It contributes to sustainable decarbonization and hydrogen production solutions, bringing us closer to a greener, more environmentally friendly future.

Decellularisation and Characterisation of Porcine Pleura as Bioscaffolds in Tissue Engineering

Persistent air leaks caused by thoracic surgery, physical trauma, or spontaneous pneumothoraces are a cause of patient morbidity with need for extended chest tube durations and surgical interventions. Current treatment measures involve mechanical closure of air leaks in the compromised pleura. Organ and membrane decellularisation offers a broad range of biomimetic scaffolds of allogeneic and xenogeneic origins, exhibiting innate tissue‐specific characteristics. We explored a physicochemical method for decellularising porcine pleural membranes (PPM) as potential tissue‐engineered surrogates for lung tissue repair. Decellularised PPM (dPPM) was characterised with histology, quantitative assays, mechanical testing, and sterility evaluation. Cytotoxicity and recellularisation assays assessed biocompatibility of decellularised PPM (dPPM). Haematoxylin and Eosin (H&amp;E) staining showed an evident reduction in stained nuclei in the dPPM, confirmed with nuclear staining and analysis ( ∗∗∗∗p &lt; 0.0001). Sulphated glycosaminoglycans (sGAG) and collagen histology demonstrated minimal disruption to the gross structural assembly of core extracellular matrix (ECM) in dPPM. Confocal imaging demonstrated realignment of ECM fibres in dPPM against native control. Quantitative analysis defined a significant change in the angular distribution ( ∗∗∗∗p &lt; 0.0001) and coherence ( ∗∗∗p &lt; 0.001) of fibre orientations in dPPM versus native ECM. DNA quantification indicated ≥85% reduction in native nuclear dsDNA in dPPM ( ∗∗p &lt; 0.01). Collagen and sGAG quantification indicated reductions of both ( ∗∗p &lt; 0.01). dPPM displayed increased membrane thickness ( ∗∗∗p &lt; 0.001). However, Young’s modulus (459.67 ± 10.36 kPa) and ultimate tensile strength (4036.22 ± 155.1 kPa) of dPPM were comparable with those of native controls at (465.82 ± 10.51 kPa) and (3912.9 ± 247.42 kPa), respectively. In vitro cytotoxicity and scaffold biocompatibility assays demonstrated robust human mesothelial cell line (MeT‐5A) attachment and viability. DNA quantification in reseeded dPPM with MeT‐5A cells exhibited significant increase in DNA content at day 7 ( ∗∗p &lt; 0.01) and day 15 ( ∗∗∗∗p &lt; 0.0001) against unseeded dPPM. Here, we define a decellularisation protocol for porcine pleura that represents a step forward in their potential tissue engineering applications as bioscaffolds.

The Effect of Ferritin Level on Respiratory Functions in Patients with β-Thalassemia Major

Introduction-Purpose β-thalassemia major (β-TM) is an autosomal recessive disorder caused by mutations in the β-globin gene of hemoglobin. The disease is characterized by splenomegaly due to ineffective erythropoiesis, iron accumulation signs in tissues as a result of increased iron absorption, bone expansion due to increased erythropoietic activity, and decreased tissue oxygenation. One of the effected organ can be the lungs due to excessive iron deposition in these patients. The current study aimed to investigate the effect of serum ferritin level, which is known as a marker of iron accumulation in tissues, on pulmonary function tests (PFT) in patients with β-TM. Methods and Materials Patients aged ≥6 years who were regularly followed in the pediatric hematology section of Mersin City Research and Training Hospital with a diagnosis of β-TM were included. All patients received regular blood transfusion and iron chelation therapy. Study participants underwent PFT prior to blood transfusion in the pediatric pulmonology section Results A total of 43 patients with β-TM were studied. Included patients were divided into two groups according to the mean annual ferritin level; low ferritin group if below 2000 ml/ng and high ferritin group if above 2000 ml/ng. The low ferritin group was consisted of 19 patients and the high ferritin group was consisted of 24 patients. The characteristics of these two groups are shown in Table 1. There were no statistical significance in age, gender, body mass index, age at diagnosis, mean annual hemoglobin, splenectomy, cardiac involvement and oxygen saturation among both groups, but the number of annual transfusion was significantly higher in the high ferritin group than lower ferritin group. When PFT parameters of both groups were compared, FVC (forced vital capacity) was statistically lower in the high ferritin group compared to the low ferritin group. Other parameters included FEV 1 (forced expiratory volume in 1 second), FEV 1/FVC ratio, PEF (peak expiratory flow) and FEF 25-75 (forced expiratory flow between 25% and 75% of vital capacity) were similar among groups. (Table 2) Discussion Patients with β-TM may accumulate iron in the interstitial area of the lungs which can lead fibrosis and impaired lung function over time. There are several studies investigated lung dysfunction and its etiology in these patients. Although the results of the studies are varied, the majority of them reported a restrictive pattern of respiratory dysfunction in thalassemia patients. Additionally, some studies showed the presence of mild or moderate obstruction in small airways and decrease in diffusion capacity with the increase of alveolar-capillary membrane thickness at advanced ages. In the present study, we found that patients with β-TM who had high ferritin level showed restrictive type lung function compared to those with low ferritin level. There were no difference among the groups in obstructive parameters (i.e. FEV 1, FEV 1/FVC, FEF 25-75) of PFT. In the literature, studies investigating PFT in patients with high ferritin levels had variable results, impaired or no change, in pulmonary status. In conclusion, loss of respiratory function and impaired tissue oxygenation in patients with β-TM may develop over time due to iron deposition in the interstitial area. PFT assessment of these patients is essential and recommended for the detection of early lung disease. Routine PFT follow in patients with β-TM of high ferritin values is highly important.

Cutting characteristics of viscoelastic membranes under hypodermic needle insertion

Cutting characteristics of thin membranes and the mechanics of their interactions with sharp aggressors like needles are critical in many industrial and medical applications. In this study, we performed needle insertion experiments to study the cutting behaviour of membranes made with polyethylene (PE) and nitrile butadiene rubber (NBR) and investigated different stages of the procedure by analyzing the needle reaction force. Moreover, using a detailed parametric study, we investigated the effect of different insertion and membrane parameters on the most important features of the insertion process. The results showed that, in most cases, the crack size, maximum insertion force, puncture displacement, kinetic frictional force, and static frictional force increase with the increase of needle diameter, increase of membrane thickness, or inclining of the needle. On the other hand, the effect of the velocity on features of the insertion process is negligible except for the kinetic frictional force which increases with the insertion velocity. We also showed although lubrication cannot considerably change the maximum needle insertion force into thin membranes, it can substantially decrease the puncture displacement and frictional forces. Furthermore, we observed that the maximum insertion force, puncture displacement, and frictional forces for PE are greater than the values obtained for NBR, while the crack sizes obtained for PE are smaller than those for NBR. Additionally, we proposed a combined experimental-numerical approach using finite-element (FE) modelling to calculate fracture toughness. The fracture toughness values obtained for PE and NBR are 6.66 ± 1.16 kJ/m2 and 3.98 ± 0.56 kJ/m2, respectively. We also exploited the developed finite-element model to predict the whole-field membrane deformation and its mechanical stress.

Analysis of dead-end anode operation phenomena based on a novel transient 3D model of high-temperature proton exchange membrane fuel cell

The dead-end anode (DEA) mode effectively improves hydrogen utilization rate of high-temperature proton exchange membrane fuel cell (HT-PEMFC). However, being in DEA mode for a long time can lead to hydrogen starvation in HT-PEMFC and reduce its performance. This study aims to reduce the adverse effects of DEA on HT-PEMFC by setting up appropriate operating conditions. A novel transient model of HT-PEMFC was successfully developed by considering gas crossover phenomena. The paper evaluates the effects of key operating parameters, geometric parameters, and gas crossover phenomena on the transient performance of HT-PEMFC in DEA mode. The results show that the performance deterioration over time during the DEA process varies under different operating conditions. The amount of hydrogen and oxygen crossover decrease significantly with the increase of membrane thickness. In DEA mode, the performance of HT-PEMFC decreases with increasing of water vapor transport coefficient; when the anode is open, the comprehensive performance of medium water vapor transport coefficient is the best. This work can provide a suitable working condition scheme to reduce the adverse effects of DEA on HT-PEMFC.

Seawater pervaporation through carbon honeycomb membrane: A molecular dynamics study

In this work, the seawater desalination performance of carbon honeycomb (CHC) membrane via the pervaporation (PV) process is investigated by molecular dynamics simulations. The simulation results show that the CHC membrane can lead to superior evaporation water flux with complete salt rejection. Unintuitively, the evaporation water flux first increases and then decreases with the increase of membrane thickness, showing a nonmonotonic dependence. Detailed analysis of the density distribution and diffusion dynamics of the water molecules indicates that this nonmonotonic dependence is closely related to the density gradient in the vapor phase, backward diffusion of evaporated water molecules, and flow resistance of the liquid phase. Increasing the pore size of the CHC membrane can lead to a significant increase in the evaporation water flow. However, an excessively large pore size permits the permeation of Na+ and Cl− ions into the CHC membrane, which impedes the diffusion of water molecules and slows down the increasing trend. With the increase in temperature, the evaporation water flux increases as expected because the change in Gibbs free energy becomes increasingly negative. Overall, this work provides insights into the PV performance of CHC membranes and promotes their application in next-generation PV membranes.