• The Korean Journal of Physiology and Pharmacology
• /
• v.17 no.2
• /
• pp.149-156
• /
• 2013

Interstitial cells of Cajal (ICCs) are the pacemaker cells in the gastrointestinal tract, and histamine is known to regulate neuronal activity, control vascular tone, alter endothelial permeability, and modulate gastric acid secretion. However, the action mechanisms of histamine in mouse small intestinal ICCs have not been previously investigated, and thus, in the present study, we investigated the effects of histamine on mouse small intestinal ICCs, and sought to identify the receptors involved. Enzymatic digestions were used to dissociate ICCs from small intestines, and the whole-cell patch-clamp configuration was used to record potentials (in current clamp mode) from cultured ICCs. Histamine was found to depolarize resting membrane potentials concentration dependently, and whereas 2-PEA (a selective H1 receptor agonist) induced membrane depolarizations, Dimaprit (a selective H2-agonist), R-alpha-methylhistamine (R-alpha-MeHa; a selective H3-agonist), and 4-methylhistamine (4-MH; a selective H4-agonist) did not. Pretreatment with $Ca^{2+}$-free solution or thapsigargin (a $Ca^{2+}$-ATPase inhibitor in endoplasmic reticulum) abolished the generation of pacemaker potentials and suppressed histamine-induced membrane depolarization. Furthermore, treatments with U-73122 (a phospholipase C inhibitor) or 5-fluoro-2-indolyl des-chlorohalopemide (FIPI; a phospholipase D inhibitor) blocked histamine-induced membrane depolarizations in ICCs. On the other hand, KT5720 (a protein kinase A inhibitor) did not block histamine-induced membrane depolarization. These results suggest that histamine modulates pacemaker potentials through H1 receptor-mediated pathways via external $Ca^{2+}$ influx and $Ca^{2+}$ release from internal stores in a PLC and PLD dependent manner.

• Food Science and Preservation
• /
• v.5 no.3
• /
• pp.239-246
• /
• 1998

Polyimide membrane system was designed for manufacturing nitrogen-enriched gas, and basic technical data was suggested for appling this system to controlled atmosphere storage. The permeability characteristics of pure oxygen and nitrogen could be explained by dual-mode sorption model. There was substantial decrease in the permeation rates of oxygen, which is the more permeable gas, through the polyimide membrane due to the presence of nitrogen in comparison with pure oxygen. However, the permeation rates of nitrogen was increased by the presence of oxygen. The ideal separation factor was in the range of 5 to 6 in the range of temperature and pressure difference studied, and the separation factor of air was lower than the ideal separation factor. The increase of ideal separation factor with increasing temperature is due to the fact that the activation energy for oxygen is larger than that for nitrogen. Nitrogen concentration decreased rapidly with increasing product recovery, and it was found that this is a major operating factor to obtain nitrogen concentration required for controlled atmosphere storage. A relation equation, by which nitrogen concentration in storehouse can be predicted, was suggested under the establishment of a hypothetical model for controlled atmosphere storage process using polyimide membrane system.

• Journal of Korean Society of Water and Wastewater
• /
• v.29 no.2
• /
• pp.233-241
• /
• 2015

Polytetrafluoroethylene (PTFE) membrane has high resistance to chlorine, which is a great advantages in chemical cleaning to recover water flux during membrane processes in drinking water systems. A humic kaolin water with approximately 4 mg/L of DOC and 10 NTU of turbidity was prepared as a feed water. Coagulation pretreatment with or without settling was applied. The coagulation with settling showed the greatest water production. The reduced flux was effectively recovered by NaOCl cleaning, i.e., 21% recovery by 50 mg/L of NaOCl cleaning and 49% recovery by 500 mg/L NaOCl cleaning. The images of SEM and AFM analyses were corresponded to the water flux variation. However, when the floc was accumulated on the membrane surfaces, the efficiency of NaOCl cleaning was substantially limited. In addition, dynamic contact angle became greater after cleaning, which indicates changes in characteristics of fouling layer such as surface hydrophobicity. Proper cleaning technologies during enhanced backwash using NaOCl would expand application of PTFE membranes in drinking water systems.

• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.59-63
• /
• 2020

Radical scavenger is used to improve the durability of PEMFC polymer membrane. In this study, we investigated whether fucoidan extracted from seaweed as a radical scavenger prevents electrochemical degradation through Fenton and OCV Holding experiments. Fucoidan has an antioxidant effect, protecting the polymer membrane from hydrogen peroxide and oxygen radicals, reducing the degradation rate to 1/10. Fucoidan has been shown to be more effective than MnO₂, which is used as a radical scavenger. In the PEMFC cell, the accelerated durability evaluation method (OCV Holding) showed that fucoidan reduced the hydrogen permeability of the polymer membrane by 12% and enhanced the performance by 29.1% compared to without radical scavenger. And fucoidan was found to be more effective in the cathode side ionomer than the anode side.

• Journal of Korean Society of Water and Wastewater
• /
• v.31 no.4
• /
• pp.303-310
• /
• 2017

Pressure retarded osmosis(PRO) has attracted much attention as potential technology to reduce the overall energy consumption for reverse osmosis(RO) desalination. The RO/PRO hybrid process is considered as the most logical next step for future desalination. The PRO process aims to harness the osmotic energy difference of two aqueous solutions separated by a semipermeable membrane. By using the concentrated water(RO brine) discharged from existing RO plants, the PRO process can effectively exploit a greater salinity gradient to reduce the energy cost of processing concentrated water. However, in order to use RO brine as the draw solution, PRO membrane must have high water flux and enough mechanical strength to withstand the high operational pressure. This study investigates the development of a thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on the overall power density was studied using the characteristic factors of PRO membranes. Finally, the performance test of an 8-inch spiral wound module was carried out under various operating conditions(i.e. hydraulic pressure, flow rate, temperature). As the flow rate and temperature increased under the same hydraulic pressure, the PRO performance increased due to the growth of water permeability coefficient and osmotic pressure. For a high performance PRO system, in order to optimize the operating conditions, it is highly recommended that the flow pressure be minimized while the flow rate is maintained at a high level.

• Korean Chemical Engineering Research
• /
• v.56 no.1
• /
• pp.29-41
• /
• 2018

Separating a mixture having an azeotrope or low relative volatility with single distillation column is difficult. Separating water-acetic acid mixture and water-ethanol mixture with a distillation column consumes a lot of energy. Pervaporation membrane can be used to separate the mixture in the concentration region where separation is difficult with distillation. We simulated a distillation-membrane hybrid process where membrane is located on the head of the distillation column for efficient separation of water-acetic acid and water-ethanol mixture. Permeability data were obtained from experiments and literature. We formulated an optimization problem for the process with total annual cost (TAC) as an objective function and major design variables as optimization variables. Major optimization variable affecting TAC of the hybrid process was shown to be distillate concentration. We also suggested a simplified optimization procedure to get a close-to-optimal solution.

• Journal of the Korean Ceramic Society
• /
• v.39 no.10
• /
• pp.994-1000
• /
• 2002

Oxygen permeability and the mechanical properties of mixed ionic-electronic conductive $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ perovskite-type membrane, fabricated by solid state reaction, were investigated with regard to microstructure. The microstructure of the membrane was controlled by changing the sintering temperature and holding time. The average grain size and relative density were evaluated as a function of sintering conditions. As the fraction of grain boundary decreased, oxygen permeability showed a tendency to increase. Especially the maximum oxygen flux of 0.37 ml/$cm^2$${\cdot}$min was measured for the specimen sintered at 1300${\circ}C$ for 10 h, which has high density and relatively large grain size. Fracture strength was dependent on the relative density of sintered body, while fracture toughness increased with average grain size.

• Journal of the Korean Ceramic Society
• /
• v.40 no.6
• /
• pp.594-600
• /
• 2003

L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ perovskite-type mixed conducting membranes, which could permeate oxygen selectively, have been fabricated and the microstructural features developed by varying the sintering conditions have been analyzed. The effects of surface modification and the membrane thickness on oxygen permeability have been evaluated under He/air environment. With increasing a grain boundary fraction, the overall oxygen permeability decreased. The syngas (CO+ $H_2$) has been produced by partial oxidation reaction of methane with the oxygen permeated through the membrane. Methane conversion and syngas yield have been evaluated as functions of the compositional ratio of feed gas and reaction temperature. In long-term duration test for 600 h, under C $H_4$+He/air environment, L $a_{0.7}$S $r_{0.3}$G $a_{0.6}$F $e_{0.4}$ $O_{3-}$$\delta$/ membrane showed a highly stable performance.

• Membrane Journal
• /
• v.12 no.2
• /
• pp.107-119
• /
• 2002

Carbon-silica ($C-SiO_2$) membranes can be easily prepared by the pyrolysis of two-phase copolymers containing an aromatic imide block and a siloxane block and remarkably high permselectivities of $He/N_2, O_2/N_2,$ and $CO_2/N_2$. The pyrolysis of the imide-siloxane block copolymers was carried out at different final temperatures, $600^{\circ}C, 800^{\circ}C,$ and $1000^{\circ}C$ under an inert atmosphere, and is the first reported case of the precursors being used for the preparation of carbon membrane. The polymeric precursors were synthesized in a wide range of siloxane content and different final morphology, and the pyrolozed membranes were tested with a high vacuum time-lag method at $25^{\circ}C$ and 76cmHg of feed pressure. In experiments with He, $CO_2, O_2 \;and \;N_2$, the membranes were found to have good $O_2/N_2$ selectivity up to 32.2 and $O_2$ permeability on the order of $10-8/cm^2(STP)cm/cm^2seccmHg.$.

• Membrane Journal
• /
• v.25 no.2
• /
• pp.123-131
• /
• 2015

The PTMSP/PDMS graft copolymer were synthesized from the PTMSP[poly(1-trimethylsilyl-1-propyne)] and the PDMS[poly(dimethylsiloxane)] and then the PTMSP/PDMS-borosilicate composite membranes were prepared by adding the porous borosilicates to the PTMSP/PDMS graft copolymer. The number-average molecular weight (${\bar{M}}_n$) and the weight-average molecular weight (${\bar{M}}_w$) of PTMSP/PDMS graft copolymer were 460,000 and 570,000 respectively, and glass transition temperature ($T_g$) of PTMSP/PDMS graft copolymer appeared at $33.53^{\circ}C$ according to DSC analysis. According to the TGA measurements, the addition of borosilicate to the PTMSP/PDMS graft copolymer leaded the decreased weight loss and the completed weight loss temperature went down. SEM observation showed that borosilicate was dispersed in the PTMSP/PDMS-borosilicate composite membranes with the size of $1{\sim}5{\mu}m$. Gas permeation experiment indicated that the addition of borosilicate to PTMSP/PDMS graft copolymer resulted in the increase in free volume, cavity and porosity resulting in the gradual shift of the mechanism of the gas permeation from solution diffusion to molecular sieving surface diffusion, and Knudsen diffusion. Consequently, the permeability of $H_2$ and $N_2$ increased and selectivity ($H_2/N_2$) decreased as the contents of borosilicate increased.