• Applied Microscopy
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• v.24 no.4
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• pp.13-31
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• 1994

The fine structure of palisade chloroplasts has been studied in the mature leaves of 3 Dubautia species (D. scabra var. leiophylla, D. knudsenii and D. scabra var. leiophylla${\times}$D. knudsenii) to explore variation at the ultrastructural level, since the parental species exhibit quite different morphological and anatomical features. Types of thylakoidal membrane systems, occurrence and distribution of phytoferritin-like structures, lipid droplets, starch grains, mitochondria and microbodies were examined. Four different types of thylakoidal membranes were found in D. scabra var. leiophylla, 2 rather uniform types in D. knudsenii and 3 intermediate types in their hybrid. D. scabra var. leiophylla and the hybrid were marked by statistically significant differences in mean numbers of thylakoids per granum, while no significant difference was found between D. knudsenii and the hybrid. Phytoferritin-like structures which were about $100-120{\AA}$ in diameter as a whole particle each were found in all 3 species. The amount and distribution of particles varied by species. Lipid droplets, plastoglobuli, and starch grains occurred in all 3 species, but the frequency of starch grains also varied with the species. More frequent and larger starch grains were observed in D. knudsenii than in the other two species. Microbodies, or peroxisome, were observed throughout all species. They occurred, either with or without crystalline inclusions, around the chloroplasts.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.11a
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• pp.193-194
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• 2004

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.176-179
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• 2004

Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Current technologies for the treatment of VOC contaminated off-gasses are expensive to operate and more cost effective technologies are needed.(omitted)

• Membrane Journal
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• v.18 no.1
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• pp.44-52
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• 2008

Pervaporation separation for water-ethanol mixtures has been carried out using crosslinked poly(vinyl alcohol) (PVA) membranes with poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA) and at which tetraethylorthosilicate (TEOS) was introduced. The concentration of PSSA_MA was fixed 7 wt% over PVA and the TEOS contents, 3, 5, and 7 wt%, were varied against PVA. The composition of the feed mixtures were 10, 20, 30 and 50 wt% of water in it. PVA/PSSA_MA/5 wt% TEOS membrane showed the separation factor, 1730 and the permeability, $16.3g/m^2{\cdot}hr$ for water : ethanol = 10 : 90 at $50^{\circ}C$.

• Polymer(Korea)
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• v.30 no.2
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• pp.175-181
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• 2006

Hybrid process of thermally-induced phase separation and stretching was developed for the preparation of microporous polypropylene hollow fiber membranes. Precursor for stretching was prepared by using soybean oil as a diluent and benzoic acid as a nucleating agent far the sphenlite control and it was stretched far the micrporous hollow fiber membrane. The effects of stretching ratio and deformation rate for stretching process were investigated. Increase of stretching ratio resulted in the greater pore size with nonuniform size distribution. Higher deformation rate also increaser the pore size with uniform size distribution. Stretching ratio was closely related with the orientation of polymer chain and increased the mechanical strength of the fiber. Increase of deformation rate had little effects on the orientation of crystalline phase, and decreased the orientation of amorphous phase which caused the decrease of tensile strength of the fiber and broke the micro-fibrils connecting spherulites to form a circular pore shape.

• Membrane Journal
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• v.22 no.3
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• pp.155-170
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• 2012

Fuel cells have been considered as alternative power generation system in the twenty-first century because of eco-friendly system, high power density and efficiency compare with petroleum engine system. Proton exchange membranes (PEMs) are the key components in fuel cell system. Currently, Nafion has been used in fuel cell system. However, Nafion has disadvantages such as low conductivity at high temperature and high cost. The researchers have focused to reach the high properties such as high proton conductivity, low permeability to fuel, good chemical/thermal stability, good mechanical properties and low manufacturing cost. Various methods have been developed for preparation of proton exchange membrane with high performance and commercialization of fuel cell system. The hybrid organic/inorganic membrane has the potentials to provide a unique combination of organic and inorganic properties with improved proton conductivity and mechanical property at high temperatures. So, this paper presents an overview of research trend for the composite membranes prepared by organic/inorganic system using various inorganic materials.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.85-93
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• 2023

Membrane separation is widely used for several applications such as water treatment, membrane reactors and climate change. Cross-linked organic-inorganic hybrid polyvinylidene fluoride (PVDF) / Tetraethyl orthosilicate (TEOS) was adopted for the preparation of optimized hollow membrane (HFM) for membrane distillation or other low pressure separators for mechanical properties and permeability under varying pretreatment schemes. HFMs were prepared on semi-pilot membrane fabrication system. Novel adopted post-treatment schemes involved soaking in glycerol, magnesium sulphate (MgSO₄), sodium hypochlorite (NaOCl), and isopropanol for different durations. All fibers were characterized for morphology using a scanning electron microscope (SEM), surface roughness using atomic force microscope (AFM), elemental composition by examining Energy Dispersive Spectroscopy (EDS), water contact angle (CA°) and porosity. The performance of the fibers was evaluated for pure water permeation flux (PWF). Post-treatment with MgSO₄ gave the highest both tensile modulus and flux. Assessment of properties and performance revealed comparable results with other organic-inorganic separators, HF or flat. In spite of few reported data on post treatment using MgSO₄ in presence of TEOS, this proves the potential of low cost treatment without negative impact on other membrane properties. The flux is also comparable with hypochlorite which manifests substantial precaution requirements in actual industrial use.The relatively high values of flux/bar for sample treated with TEOS, post treated with MgSO₄ and hypochlorite are 88 and 82 LMH/bar respectively.

• Membrane Journal
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• v.27 no.6
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• pp.487-498
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• 2017

In this study, pervaporation performances of water/methanol and water/butanol mixture were evaluated using zeolite 4A membranes manufacutred by FINETECH by experimental works and numerical modeling. Permeation and separation characteristics, such as flux and separation factor, were analyzed by gas chromatography (TCD) and liquid nitrogen traps. Experiments have shown that water is selectively separated from a mixture of water and methanol (separation factor up to approximately 250) and water and butanol (separation factor up to approximately 1,500). Generalized Maxwell Stefan (GMS) theory was implemented to predict pervaporation behaviors of water/alcohol mixtures and diffusional coefficients of zeolite layer were obtained through parameter estimation using $MATLAB^{(R)}$ optimization toolbox. Since the pore size of zeolite 4A are much larger than kinetic diameter of water molecules and smaller than those of methanol and butanol, zeolite 4A membranes can be applied to in situ water removal process such as membrane reactors or hybrid reaction-dehydration process.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.561-569
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• 2014

Ceria ($CeO_2$) was used to increase the durability of the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance. The sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) to improve electrochemical characteristics. After sulfonation reaction, the organic-inorganic blended composite membranes were prepared by means of sol-gel casting method with loading the highly dispersed $CeO_2$ and Cs-substituted molybdophosphoric acid (Cs-MoPA) with cross-linking agent (tetrapropyl orthosilicate). Consequently, the composite membrane CL-SPEEK/Silane 4wt%/Cs-MoPA/Ceria(1%) showed the improved characteristics such as 82% of water content, 0.11136 S/cm of proton conductivity at $80^{\circ}C$, 55.50 MPa of tensile strength and 4.37% of breeding out of MoPA.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1078-1084
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• 1999

A synthetic cecropin A(1-13)-melittin(1-13) [CA-ME] hybrid peptide was known to be an antimicrobial peptide having strong antibacterial, antifungal and antitumor activity with minimal cytotoxic effect against human erythrocyte. Analogues were synthesized to investigate the influences of the flexible hinge region of CA-ME on the antibiotic activity. Antibiotic activity of the peptides was measured by the growth inhibition against bac-terial, fungal and tumor cells and vesicle-aggregating or disrupting activity. The deletion of Gln-Gly-Ile (P1) or Gly-Gln-Gly-Ile-Gly (P3) from CA-ME brought about a significant decrease on the antibiotic activities. In contrast, Gly-Ile-Gly deletion (P2) from CA-ME or Pro insertion (P5) instead of Gly-Gln-Gly-Ile-Gly of CA-ME retained antibiotic activity. This result indicated that the flexible hinge or β-bend structure provided by Gly-Gln-Gly-Ile-Gly, Gln-Gly, or Pro in the central region of the peptides is requisite for its effective antibiotic activity and may facilitate easily the hydrophobic C-terminal region of the peptide to penetrate the lipid bilayers of the target cell membrane. In contrast, P4 and P6 with Gly-Gln-Gly-Pro-Gly or Gly-Gln-Pro in the central region of the peptide caused a drastic reduction on the antibiotic activities. This result suggested that the con-secutive β-bend structure provided by Gly-Gln-Gly-Pro-Gly or Gly-Gln-Pro in the central hinge region of the peptide seems to interrupt the ion channel/pore formation on the target cell membranes.