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971.
Kyeong-Ho Yeon Heesu Park Seung-Hak Lee Yong-Min Park Sang-Hyup Lee Masakazu Iwamoto 《Korean Journal of Chemical Engineering》2008,25(5):1040-1046
Eutrophication caused by the excessive supply of phosphate to water bodies has been considered as one of the most important
environmental problems. In this study, the powder of zirconium mesostructure (ZM), which was prepared with the template of
surfactant, was immobilized in calcium alginate for practical application and the resulting material was tested to evaluate
the phosphate removal efficiency. Sorption isotherms and kinetic parameters were obtained by using the entrapped ZM beads
with 30 to 60% of ZM. The maximum sorption capacity increased with the higher ZM content. Q
max
in Langmuir isotherm was 51.74 mg/g for 60% of ZM with 7 mm of size. The smaller the particle size of the ZM beads, the faster
the rate of phosphate removal, because the phosphate ions had less distance to reach the internal pores of the immobilized
ZM beads. Chemical and electrochemical regeneration techniques were compared. Phosphates adsorbed on the ZM beads were effectively
desorbed with NaCl, NaOH, and Na2SO4 solutions. An electrochemical regeneration system consisting of an anion exchange membrane between two platinum-coated titanium
electrodes was successfully used to desorb and regenerate the phosphate-saturated ZM beads. Complete regeneration was reached
under optimal experimental conditions. Chemical and electrochemical regeneration proved the reusability of the bead form of
the entrapped ZM, and will enhance the economical performance of the phosphate treatment process. 相似文献
972.
Ramamourthy Gopal Jong Kook Lee Jun Ho Lee Young Gwon Kim Gwang Chae Oh Chang Ho Seo Yoonkyung Park 《International journal of molecular sciences》2013,14(1):2190-2202
In a previous study, we synthesized a series of peptides containing simple sequence repeats, (KW)n–NH2 (n = 2,3,4 and 5) and determined their antimicrobial and hemolytic activities, as well as their mechanism of antimicrobial action. However, (KW)5 showed undesirable cytotoxicity against RBC cells. In order to identify the mechanisms behind the hemolytic and cytotoxic activities of (KW)5, we measured the ability of these peptides to induce aggregation of liposomes. In addition, their binding and permeation activities were assessed by Trp fluorescence, calcein leakage and circular dichrorism using artificial phospholipids that mimic eukaryotic liposomes, including phosphatidylcholine (PC), PC/sphingomyelin (SM) (2:1, w/w) and PC/cholesterol (CH) (2:1, w/w). Experiments confirmed that only (KW)5 induced aggregation of all liposomes; it formed much larger aggregates with PC:CH (2:1, w/w) than with PC or PC:SM (2:1, w/w). Longer peptide (KW)5, but not (KW)3 or (KW)4, strongly bound and partially inserted into PC:CH compared to PC or PC:SM (2:1, w/w). Calcein release experiments showed that (KW)5 induced calcein leakage from the eukaryotic membrane. Greater calcein leakage was induced by (KW)5 from PC:CH than from PC:SM (2:1, w/w) or PC, whereas (KW)4 did not induce calcein leakage from any of the liposomes. Circular dichroism measurements indicated that (KW)5 showed higher conformational transition compared to (KW)4 due to peptide-liposome interactions. Taken together, our results suggest that (KW)5 reasonably mediates the aggregation and permeabilization of eukaryotic membranes, which could in turn explain why (KW)5 displays efficient hemolytic activity. 相似文献
973.
Jin-Young Kim Ramamourthy Gopal Sang Young Kim Chang Ho Seo Hyang Burm Lee Hyeonsook Cheong Yoonkyung Park 《International journal of molecular sciences》2013,14(2):4349-4360
In an earlier study, we isolated potamin-1 (PT-1), a 5.6-kDa trypsin-chymotrypsin protease inhibitor, from the tubers of a potato strain (Solanum tuberosum L cv. Gogu Valley). We established that PT-1 strongly inhibits pathogenic microbial strains, but not human bacterial strains, and that its sequence shows 62% homology with a serine protease inhibitor. In the present study, we isolated an antifungal and antibacterial peptide with no cytotoxicity from tubers of the same potato strain. The peptide (peptide-G2, PG-2) was isolated using salt-extraction, ultrafiltration and reverse-phase high performance liquid chromatography (RP-HPLC). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) showed the protein to have a molecular mass of 3228.5 Da, while automated Edman degradation showed the N-terminal sequence of PG-2 to be LVKDNPLDISPKQVQALCTDLVIRCMCCC-. PG-2 exhibited antimicrobial activity against Candida albicans, a human pathogenic yeast strain, and Clavibacter michiganensis subsp. michiganensis, a plant late blight strain. PG-2 also showed antibacterial activity against Staphylococcus aureus, but did not lyse human red blood cells and was thermostable. Overall, these results suggest PG-2 may be a good candidate to serve as a natural antimicrobial agent, agricultural pesticide and/or food additive. 相似文献
974.
The size of the primary particles in aerosol agglomerates is determined in part by the interplay of surface growth, coagulation, and sintering. These processes are modelled by a one-dimensional (1-D) discrete-sectional model, DISGLOM2, which predicts the evolution of agglomerate and primary particle size distributions. DISGLOM2 is an extended version of DISGLOM (Rogak 1997), in which particles smaller than the "melting diameter" were assumed to sinter instantly while bigger particles did not sinter at all. Gradual sintering, "condensational obliteration" (whereby primary particles are lost during heavy surface growth), and diffusional wall deposition have been incorporated into DISGLOM2. Results from DISGLOM2 were comparable with those from 2-D sectional models, but DISGLOM2 was much faster. In addition, DISGLOM2 includes the effects of "condensation" of small spherical particles on large agglomerates, which were not modelled previously. The effect of condensation was shown to be significant at low temperature. DISGLOM2 was used to predict the primary particle diameter of titania particles generated by precursor reaction. By adding gradual sintering, the growth rate of agglomerate particles by coagulation was slightly decreased and the primary particle size considerably increased compared with the results given by DISGLOM. Although DISGLOM2 is an efficient model of the relevant physical processes, the predictions are sensitive to the kinetics of precursor reactions and particle sintering, which can be difficult to characterize in real experimental systems. 相似文献
975.
Catalytic iron nanoparticles generated by spark discharge were used to site-selectively grow carbon nanotubes (CNTs) and control their density. The generated aerosol nanoparticles were deposited on a cooled substrate by thermophoresis. The shadow mask on top of the cooled substrate enabled patterning of the catalytic nanoparticles and, thereby, patterning of CNTs synthesized by chemical vapor deposition. The density of CNTs could be controlled by varying the catalytic nanoparticle deposition time. It was also demonstrated that the density could be adjusted by changing the gap between the shadow mask and the substrate, taking advantage of the blurring effect of the deposited nanoparticles, for an identical deposition time. As all the processing steps for the patterned growth and density control of CNTs can be performed under dry conditions, we also demonstrated the integration of CNTs on fully processed, movable silicon microelectromechanical system (MEMS) structures. 相似文献
976.
Ping Xu Kuan Chang Young Il Park Bin Zhang Leilei Kang Yunchen Du Rashi S. Iyer Hsing-Lin Wang 《Polymer》2013,54(2):485-489
Two water soluble conjugated polymers, poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and ammonium ion stabilized poly(phenylene vinylene) (P2), are found to be able to reduce noble metal ions to zero-valent metals via a direct chemical deposition technique. Au nanoparticle clusters can be obtained through reduction of Au3+ ions by PEDOT:PSS and the electronic coupling between them can be controlled by HAuCl4 concentration. Core/shell Ag/polymer nanostructures are prepared from reduction of Ag+ ions by P2, which have a ppb detection limit for 4-MBA using surface-enhanced Raman spectroscopy (SERS). This conjugated polymer mediated synthesis of metal nanoparticles may open a new avenue for fabricating nanomaterials and nanocomposites with tunable optical properties that are dominated by their structure and electronic coupling between nanoparticles. 相似文献
977.
Nanocrystalline Ca2.76Cu0.24Co4O9 powders (25 nm in crystallite size) are synthesized by the solution combustion method, using aspartic acid as the combustion fuel. In this study, we discuss the effect of sintering temperature on the microstructure and thermoelectric properties of Ca2.76Cu0.24Co4O9. The density and grain size increase with an increase in sintering temperature. The Ca2.76Cu0.24Co4O9 sintered at 900 °C shows the largest value of electrical conductivity and Seebeck coefficient, resulting in the largest power factor (3.8×10?4 W m?1 K?2 at 800 °C). This value is more than 22 times larger than that of the Ca2.76Cu0.24Co4O9 sintered at 940 °C (1.7×10?5 W m?1 K?2 at 800 °C). 相似文献
978.
Hem Raj Pant Bishweshwar Pant Han Joo Kim Altangerel Amarjargal Chan Hee Park Leonard D. Tijing Eun Kyo Kim Cheol Sang Kim 《Ceramics International》2013,39(5):5083-5091
In this study, Ag–ZnO/reduced graphene oxide (Ag–ZnO/RGO) composite was synthesized by a green and facile one-step hydrothermal process. Aqueous suspension containing Ag and ZnO precursors with graphene oxide (GO) sheets was heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and Photoluminescence (PL) spectroscopy which revealed the formation of composite of metal, metal oxide and RGO. It was observed that the presence of Ag precursor and GO sheets in the hydrothermal solution could sufficiently decrease the size of ZnO flowers. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to have good photocatalytic and antibacterial activity. The perfect recovery of catalyst after reaction and its unchanged efficiency for cyclic use showed that it will be an economically and environmentally friendly photocatalyst. 相似文献
979.
Blends of linear‐low‐density polyethylene (LLDPE), low‐density polyethylene (LDPE), and high‐ density polyethylene (HDPE) were foamed and characterized in this research. The goal was to generate clear dual peaks from the expanded polyethylene (EPE) foam beads made from these blends in autoclave processing. Three blends were prepared in a twin‐screw mixing extruder at two rotational speeds of 5 and 50 rpm: Blend1 (LLDPE with 20 wt% HDPE), Blend 2 (LLDPE with 20 wt% LDPE), and Blend 3 (LLDPE with 10 wt% HDPE and 10 wt% LDPE). The differential scanning calorimetric (DSC) measurement was taken at two cooling rates: 5 and 50°C/min. Although no dual peaks were present, the results showed that blending with HDPE has a more noticeable effect on the DSC curve of LLDPE than blending with LDPE. Also, the rotational speed and cooling rate affected the shape of the DSC curves and the percentage area below the onset point. The DSC characterization of the batch foamed blends revealed multiple peaks at certain temperatures, which may be mainly due to the annealing effect during the gas saturation process. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers 相似文献
980.
Se Ho Park Dong Chin Lee Jong Heo Hyoun Soo Kim 《Journal of the American Ceramic Society》2000,83(5):1284-1286
Fluorescence emissions at both 1.31 and 1.55 μm communication windows were observed from Pr3+ /Er3+ codoped Ge-As-Ga-S glasses with a single wavelength pumping at 986 nm. The lifetime of the Er3+ :4 I 11/2 level decreased as the Pr3+ concentration increased, and that of the Pr3+ :1 G 4 level increased as the Er3+ concentration increased. Energy transfer from the Er3+ :4 I 11/2 level to the Pr3+ :1 G 4 level was responsible for emission of the 1.31 μm fluorescence from the Pr3+ :1 G 4 level. Ge-As-Ga-S glasses that have been doped with Pr3+ and Er3+ cations are promising amplifier materials for both 1.31 and 1.55 μm communication windows. 相似文献