A new method of measuring alcohol clusters in polyimide membrane: combination of inverse gas chromatography with equilibrium swelling

A new method of measuring the mean size of solvent clusters in swollen polymer membrane is presented in this paper. This method is based on a combination of inverse gas chromatography (IGC) and equilibrium swelling. The mechanism is that weight fraction activity coefficient of solvent in swollen polymer is influenced by its clusters size. The mean clusters size of solvent in swollen polymer can be calculated as the quotient of the weight fraction activity coefficient of clustering system dividing the weigh fraction activity coefficient of non-clustering system. In this experiment, the weigh fraction activity coefficient of non-clustering system was measured with IGC. Methanol, ethanol and polyimide systems were tested with the new method at three temperatures, 20, 40, and 60degreesC. The mean clusters size of methanol in polyimide was five, four, and three at each temperature condition, respectively. Ethanol did not form clusters (the mean clusters size was one). In contrast to the inherent narrow temperature range in DSC, XRD, and FTIR methods, the temperature range in IGC and equilibrium swelling is broad. Compared with DSC. XRD. and FTIR, this new method can detect the clusters of solvent-polymer system at higher temperature.

Ceramic carbon/polypyrrole materials for the construction of bienzymatic amperometric biosensor for glucose

A novel amperometric glucose biosensor was constructed by electrochemical formation of a polypyrrole (PPy) membrane in the presence of glucose oxidase (GOD) on the surface of a horseradish peroxidase (HRP) modified ferrocenecarboxylic acid (FCA) mediated sol-gel derived ceramic carbon electrode. The amperometric detection of glucose was carried out at +0.16 V (vs. SCE) in 0.1 mol/L phosphate buffer solution (pH 6.9) with a linear response range between 8.0x10(-5) and 1.3x10(-3) mol/L of glucose. The biosensor showed a good suppression of interference and a negligible deviation in the amperometric detection.

SURFACE-MODIFIED HYDROPHILIC MEMBRANES IN MEMBRANE DISTILLATION

The porosity and the hydrophobicity of membranes are two essential requirements for membrane distillation (MD) of aqueous solutions. So far, the hydrophobic porous membranes used in MD studies have been prepared from hydrophobic materials. In this work, hydrophilic cellulose acetate and cellulose nitrate membranes were modified into hydrophobic membranes by radiation grafting polymerization and plasma polymerization, and used in MD studies successfully. The results indicated that modified membranes with good performance in MD can be obtained if the modifying conditions are controlled appropriately. Especially plasma polymerization, in which many particular kinds of monomer could be polymerized onto the surface of porous materials, has become an efficient method to prepare hydrophobic porous membrane with high performance from hydrophilic membranes. It will stimulate the development and practical application of MD.

PLASMA POLYMERIZATION OF OCTAFLUOROCYCLOBUTANE AND HYDROPHOBIC MICROPOROUS COMPOSITE MEMBRANES FOR MEMBRANE DISTILLATION

In this paper, hydrophilic microporous cellulose nitrate membranes have been surface-modified by plasma polymerization of octafluorocyclobutane (OFCB). The microporous composite membranes with a hydrophilic layer sandwiched between two hydrophobic layers have been obtained. The obtained composite membranes have been used in a membrane distillation (MD) process and have exhibited good performance. The effects of polymerization conditions, such as glow-discharge power and deposition time, on the structures and MD performances of the obtained composite membranes have been investigated by SEM, X-ray microscopical analysis, and XPS. The polymerization conditions should be as mild as possible in order to prepare the hydrophobic composite membrane with good MD performance. The typical MD behaviors of the obtained hydrophobic composite membranes are in agreement with that of hydrophobic membranes directly prepared from hydrophobic polymeric materials, like PVDF, PTFE, or PP.

Modification of nylon membrane used for affinity adsorption

Nylon membrane was modified by binding with polyhydroxyl-containing materials to increase its hydrophilicity and reduce its nonspecific interaction with proteins. The effect of binding hydrophilic materials on amount of ligand bound-Cibacron Blue F3GA (CBF) was investigated. Experimental data showed that the amount of CBF bound can be increased significantly after binding of hydrophilic materials.

Synthesis of a high-permeance NaA zeolite membrane by microwave heating

Zeolite membranes with high permeance and separation factors are highly desirable for practical applications. Although, in the past, very good separation factors have been obtained, it has proved difficult to achieve a high permeance. Ken a comparative study of microwave versus conventional heating in the hydrothermal synthesis of NaA zeolite membranes is made. It is demonstrated that membranes prepared by microwave heating have not only a higher permeance but also a considerably shorter synthesis time. These observations are rationalized by examining the mechanism of membrane formation.

Synthesis and characterization of gallium-based perovskite-type dense membrane with oxygen semipermeability

La0.15Sr0.85Ga0.3Fe0.7O3-delta (LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-delta (LSCFO) mixed oxygen-ion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding dense membranes were fabricated. The properties of the oxide powders and membranes were characterized with combined SEM, XRD, H-2-TPR, O-2-TPD techniques, mechanical strength and oxygen permeation measurement. The results showed that LSGFO had much higher thermochemical stability than LSCFO due to the higher valence stability of Ga3+. After the temperature-programmed reduction by 5% H-2 in Ar from 20 degreesC to 1020 degreesC, the basic perovskite structure of LSGFO was successfully preserved. LSGFO also favors the oxygen vacancy formation better than LSCFO. Oxygen permeation measurement demonstrated that LSGFO had higher oxygen permeation flux than LSCFO, but they had similar activation energy for oxygen transportation, with a value of 110 and 117 kJ . mol(-1), respectively The difference in oxygen permeation fluxes was correlated with the difference in oxygen vacancy concentrations for the two materials.

Stainless-steel-net-supported zeolite NaA membrane with high permeance and high permselectivity for oxygen over nitrogen

A stainless-steel net is used to support a zeolite NaA membrane synthesized using a 'seeded-growth' method. The zeolite and stainless-steel net are tightly integrated (see Figure), showing large-scale order and high mechanical stability. High oxygen permeance and high permselectivity for O-2 over N-2 (about 7) is demonstrated.

Preparation of a novel polysulfone/polyethylene oxide/silicone rubber multilayer composite membrane for hydrogen-nitrogen separation

A novel poly sulfone/polyethylene oxide/silicone rubber (PSOPEO/SR) multilayer composite membrane was fabricated by double coating polysulfone substrate membrane with polyethylene oxide and silicone rubber. Gas permeation experiments were performed at 30 degrees C for hydrogen and nitrogen. PSf(PEO/SR membrane displayed high and steady performance for H-2/N-2: permeances of H-2 and N-2 of 49.51 and 0.601 GPU, respectively, and H-2/N-2 ideal separation factor of 82.3. It was explained that layer interfaces due to the introduction of PEO layer act as the permselective media and are responsible for the higher H-2/N-2 ideal separation factor which has exceeded the intrinsic permselectivities of the three polymers used in this study. (c) 2005 Elsevier B.V. All rights reserved.

Molecular dynamics-based approach to study the anisotropic self-diffusion of molecules in porous materials with multiple cage types: Application to H-2 in losod

Van den Berg, A. W. C., Flikkema, E., Lems, S., Bromley, S. T., Jansen, J. C. (2006). Molecular dynamics-based approach to study the anisotropic self-diffusion of molecules in porous materials with multiple cage types: Application to H-2 in losod. Journal of physical chemistry b, 110 (1), 501-506. RAE2008

Depolarization of sperm membrane potential is a common feature of men with subfertility and is associated with low fertilization rate at IVF

STUDY QUESTION. Are significant abnormalities in outward (K+) conductance and resting membrane potential (Vm) present in the spermatozoa of patients undertaking IVF and ICSI and if so, what is their functional effect on fertilization success? SUMMARY ANSWER. Negligible outward conductance (≈5% of patients) or an enhanced inward conductance (≈4% of patients), both of which caused depolarization of Vm, were associated with a low rate of fertilization following IVF. WHAT IS KNOWN ALREADY. Sperm-specific potassium channel knockout mice are infertile with defects in sperm function, suggesting that these channels are essential for fertility. These observations suggest that malfunction of K+ channels in human spermatozoa might contribute significantly to the occurrence of subfertility in men. However, remarkably little is known of the nature of K+ channels in human spermatozoa or the incidence and functional consequences of K+ channel defects. STUDY DESIGN, SIZE AND DURATION. Spermatozoa were obtained from healthy volunteer research donors and subfertile IVF and ICSI patients attending a hospital assisted reproductive techniques clinic between May 2013 and December 2015. In total, 40 IVF patients, 41 ICSI patients and 26 normozoospermic donors took part in the study. PARTICIPANTS/MATERIALS, SETTING, METHODS. Samples were examined using electrophysiology (whole-cell patch clamping). Where abnormal electrophysiological characteristics were identified, spermatozoa were further examined for Ca2+ influx induced by progesterone and penetration into viscous media if sufficient sample was available. Full exome sequencing was performed to specifically evaluate potassium calcium-activated channel subfamily M α 1 (KCNMA1), potassium calcium-activated channel subfamily U member 1 (KCNU1) and leucine-rich repeat containing 52 (LRRC52) genes and others associated with K+ signalling. In IVF patients, comparison with fertilization rates was done to assess the functional significance of the electrophysiological abnormalities. MAIN RESULTS AND THE ROLE OF CHANCE. Patch clamp electrophysiology was used to assess outward (K+) conductance and resting membrane potential (Vm) and signalling/motility assays were used to assess functional characteristics of sperm from IVF and ICSI patient samples. The mean Vm and outward membrane conductance in sperm from IVF and ICSI patients were not significantly different from those of control (donor) sperm prepared under the same conditions, but variation between individuals was significantly greater (P< 0.02) with a large number of outliers (>25%). In particular, in ≈10% of patients (7/81), we observed either a negligible outward conductance (4 patients) or an enhanced inward current (3 patients), both of which caused depolarization of Vm. Analysis of clinical data from the IVF patients showed significant association of depolarized Vm (≥0 mV) with low fertilization rate (P= 0.012). Spermatozoa with electrophysiological abnormities (conductance and Vm) responded normally to progesterone with elevation of [Ca2+]i and penetration of viscous medium, indicating retention of cation channel of sperm (CatSper) channel function. LIMITATIONS, REASONS FOR CAUTION. For practical, technical, ethical and logistical reasons, we could not obtain sufficient additional semen samples from men with conductance abnormalities to establish the cause of the conductance defects. Full exome sequencing was only available in two men with conductance defects. WIDER IMPLICATIONS OF THE FINDINGS. These data add significantly to the understanding of the role of ion channels in human sperm function and its impact on male fertility. Impaired potassium channel conductance (Gm) and/or Vm regulation is both common and complex in human spermatozoa and importantly is associated with impaired fertilization capacity when the Vm of cells is completely depolarized.

Advanced polymer membrane development in pervaporation dehydration and lateral flow diagnostics

The work in this thesis concerns the advanced development of polymeric membranes of two types; pervaporation and lateral-flow. The former produced from a solution casting method and the latter from a phase separation. All membranes were produced from casting lacquers. Early research centred on the development of viable membranes. This led to a supported polymer blend pervaporation membrane. Selective layer: plasticized 4:1 mass ratio sodium-alginate: poly(vinyl-alcohol) polymer blend. Using this membrane, pervaporation separation of ethanol/water mixtures was carefully monitored as a function of film thickness and time. Contrary to literature expectations, these films showed increased selectivity and decreased flux as film thickness was reduced. It is argued that morphology and structure of the polymer blend changes with thickness and that these changes define membrane efficiency. Mixed matrix membrane development was done using spherical, discreet, size-monodisperse mesoporous silica particles of 1.8 - 2μm diameter, with pore diameters of ~1.8 nm were incorporated into a poly(vinyl alcohol) [PVA] matrix. Inclusion of silica benefitted pervaporation performance for the dehydration of ethanol, improving flux and selectivity throughout in all but the highest silica content samples. Early lateral-flow membrane research produced a membrane from a basic lacquer composition required for phase inversion; polymer, solvent and non-solvent. Results showed that bringing lacquers to cloud point benefits both the pore structure and skin layers of the membranes. Advancement of this work showed that incorporation of ethanol as a mesosolvent into the lacquer effectively enhances membrane pore structure resulting in an improvement in lateral flow rates of the final membranes. This project details the formation mechanics of pervaporation and lateral-flow membranes and how these can be controlled. The principle methods of control can be applied to the formation of any other flat sheet polymer membranes, opening many avenues of future membrane research and industrial application.

Templated electrodeposition of silver nanowires in a nanoporous polycarbonate membrane from a nonaqueous ionic liquid electrolyte

Template electrodeposition has been used to prepare a wide range of nanostructures but has generally been restricted to aqueous electrolytes. We report the deposition of silver nanowires in a commercial nuclear track-etched polycarbonate template from the nonaqueous ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) using silver electrochemically dissolved from the anode. Transmission electron microscopy (TEM) shows that the nanowires have a very high aspect ratio with an average diameter of 80 nm and length of 5 mu m. Ionic liquid electrolytes should greatly extend the range of metals that can be electrodeposited as nanowires using templates.

KCNQ Currents and Their Contribution to Resting Membrane Potential and the Excitability of Interstitial Cells of Cajal From the Guinea Pig Bladder

PURPOSE: The presence of novel KCNQ currents was investigated in guinea pig bladder interstitial cells of Cajal and their contribution to the maintenance of the resting membrane potential was assessed. MATERIALS AND METHODS: Enzymatically dispersed interstitial cells of Cajal were patch clamped with K(+) filled pipettes in voltage clamp and current clamp modes. Pharmacological modulators of KCNQ channels were tested on membrane currents and the resting membrane potential. RESULTS: Cells were stepped from -60 to 40 mV to evoke voltage dependent currents using a modified K(+) pipette solution containing ethylene glycol tetraacetic acid (5 mM) and adenosine triphosphate (3 mM) to eliminate large conductance Ca activated K channel and K(adenosine triphosphate) currents. Application of the KCNQ blockers XE991, linopirdine (Tocris Bioscience, Ellisville, Missouri) and chromanol 293B (Sigma) decreased the outward current in concentration dependent fashion. The current-voltage relationship of XE991 sensitive current revealed a voltage dependent, outwardly rectifying current that activated positive to -60 mV and showed little inactivation. The KCNQ openers flupirtine and meclofenamic acid (Sigma) increased outward currents across the voltage range. In current clamp mode XE991 or chromanol 293B decreased interstitial cell of Cajal resting membrane potential and elicited the firing of spontaneous transient depolarizations in otherwise quiescent cells. Flupirtine or meclofenamic acid hyperpolarized interstitial cells of Cajal and inhibited any spontaneous electrical activity. CONCLUSIONS: This study provides electrophysiological evidence that bladder interstitial cells of Cajal have KCNQ currents with a role in the regulation of interstitial cell of Cajal resting membrane potential and excitability. These novel findings provide key information on the ion channels present in bladder interstitial cells of Cajal and they may indicate relevant targets for the development of new therapies for bladder instability.