• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.24-30
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• 2013

The adsorption characteristics of cationic starches and starch-oligomers were investigated using the quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorbed amount of modified starches was higher than that of cationic surfactants such as $C_{12{\sim}16}$ trimethylammonium bromide. Cationic starches did not show the tendency depending on the degree of cationic substitution and molecular weight. On the other hand, the softness of the adsorption layer increased with the molecular weight of cationic starches in a viscoelasticity terms. During the adsorption/desorption steps, the amount of adsorbed cationic surfactants was 4~9 times. On the other hand, the difference in the amount of adsorption of all the $C_1$ grafted cationic starches was just 0~50%. In addition, the rigidity of the adsorption layer of cationic surfactant in the desorption step decreased, while, that of cationic starches increased at the same condition.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.273-278
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• 2018

Lithium-ion batteries have been considered the most important devices to power mobile or small-sized devices due to their high energy density. $LixCoO_2$ has been studied as a cathode material for the Li-ion battery. However, the limitation of its capacity impedes the development of high capacity cathode materials with Ni, Mn, etc. in them. The substitution of Mn and Ni for Co leads to the formation of solid solution phase $LiNi_xMn_yCo_{1-x-y}O_2$ (NMC, both x and y < 1), which shows better battery performance than unsubstituted $LiCoO_2$. However, despite a high discharge capacity in the Ni-rich compound (Ni > 0.8 in the metal site), poor cycle retention capability still remains to be overcome. In this study, aiming to improve the stability of the physical and chemical bonding, we investigate the stabilization effect of Ca in the Ni-rich layered compound $Li(Ni_{0.83}Co_{0.12}Mn_{0.05})O_2$, and then Ca is added to the modified secondary particles to lower the degree of cationic mixing of the final particles. For the optimization of the final grains added with Ca, the Ca content (x = 0, 2.5, 5.0, 10.0 at.%) versus Li is analyzed.

• Journal of the Korean Wood Science and Technology
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• v.27 no.3
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• pp.63-72
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• 1999

For the purpose of improving the wet strength properties of paper, cellulosic fibers were modified by the processes of carbarmoylethylation and N-chlorocarbamoylethylation. Carbamoylethylated cellulose was prepared by the reaction of acrylamide with cellulosic fibers under the alkali catalyst, and N-chlorocarbamoylethylated cellulose was prepared by the addition of sodium hypochlorite into the carbamoylethylated cellulose. In carbamoylethylation reaction, the conditions of NaOH concentration, temperature and acrylamide addition rate were considered to be important factors. An initial reactivity and degree of substitution(DS) in carbamoylethylation of cellulosic fibers were effective according to increasing the addition rates of alkali, acrylamide and the temperature condition of $40^{\circ}C$. The effective wet strength properties by N-chlorocarbamoylethylation of cellulosic fibers were indicated under the conditions of DS 0.06. The wet strength of sheet was improved to 85% at the 100% basis of dry strength. From the photograph of scanning electron microscopy, fiber cuttings on the edge of sheet sample used in tensile strength testing were found in the N-chlorocarbamoylethylated sheet, due to the improvement of fiber bonding strength. The hypochlorite treatment was effective in the recycling of N-chlorocarbamoylethylated sheet, and was reduced the wet strength of sheet to be able to reslush.

• Journal of Microbiology and Biotechnology
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• v.16 no.9
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• pp.1369-1376
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• 2006

Self-organized nanogels were prepared from pullulan/biotin conjugates (PU/Bio) for the development of an effective anticancer drug delivery system. The degree of biotin substitution was 11, 19, and 24 biotin groups per 100 anhydroglucose units of pullulan. The physicochemical properties of the nanogels (PU/Bio1, 2 and 3) in aqueous media were characterized by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The mean diameter of all the samples was less than 300 nm with a unimodal size distribution. The critical aggregation concentrations (CACs) of the nanoparticles in distilled water were $2.8{\times}10^{-2},\;1.6{\times}10^{-2}$, and $0.7{\times}10^{-2}mg/ml$ for the PU/Bio1, 2, and 3, respectively. The aggregation behavior of the nanogels indicated that biotin can perform as a hydrophobic moiety. To observe the specific interaction with a hepatic carcinoma cell line (HepG2), the conjugates were labeled with rhodamine B isothiocyanate (RITC) and their intensities measured using a fluorescence microplate reader. The HepG2 cells treated with the fluorescence-labeled PU/Bio nanoparticles were strongly luminated compared with the control (pullulan). Confocal laser microscopy also confirmed internalization of the PU/Bio nanogels into the cancer cells. Such results demonstrated that the biotin in the conjugate acted as both a hydrophobic moiety for self-assembly and a tumor-targeting moiety for specific interaction with tumor cells. Consequently, PU/Bio nanogels would appear to be a useful drug carrier for the treatment of liver cancer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.198-198
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• 2016

An ideal orthopedic implant should provide an excellent bone-implant connection, less implant loosening and minimum adverse reactions. Commercial pure titanium (CP-Ti) and Ti alloys have been widely utilized for biomedical applications such as orthopedic and dental implants. However, being bioinert, the integration of such implant in bone was not in good condition to achieve improved osseointegraiton, there have been many efforts to modify the composition and topography of implant surface. These processes are generally classified as physical, chemical, and electrochemical methods. Plasma electrolytic oxidation (PEO) as an electrochemical route has been recently utilized to produce this kind of composite coatings. Mg ion plays a key role in bone metabolism, since it influences osteoblast and osteoclast activity. From previous studies, it has been found that Mg ions improve the bone formation on Ti alloys. PEO is a promising technology to produce porous and firmly adherent inorganic Mg containing $TiO_2$($Mg-TiO_2$ ) coatings on Ti surface, and the amount of Mg introduced into the coatings can be optimized by altering the electrolyte composition. In this study, a series of $Mg-TiO_2$ coatings are produced on Ti-6Al-4V ELI dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. Based on the preliminary analysis of the coating structure, composition and morphology, a bone like apatite formation model is used to evaluate the in vitro biological responses at the bone-implant interface. The enhancement of the bone like apatite forming ability arises from $Mg-TiO_2$ surface, which has formed the reduction of the Mg ions. The promising results successfully demonstrate the immense potential of $Mg-TiO_2$ coatings in dental and biomaterials applications.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.120-120
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• 2016

Ti-6Al-4V alloy have been used for dental implant because of its excellent biocompatibility, corrosion resistance, and mechanical properties. However, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton. For solving this problem, calcium phosphate (CaP) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue. Various metallic elements, such as strontium (Sr), magnesium (Mg), zinc (Zn), sodium (Na), silicon (Si), silver (Ag), and yttrium (Y) are known to play an important role in the bone formation and also affect bone mineral characteristics, such as crystallinity, degradation behavior, and mechanical properties. Especially, Zn is essential for the growth of the human and Zn coating has a major impact on the improvement of corrosion resistance. Plasma electrolytic oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Zn containing $TiO_2(Zn-TiO_2)$coatings on Ti surface, and the a mount of Zn introduced in to the coatings can be optimized by altering the electrolyte composition. In this study, corrosion behavior of Ti-6Al-4V alloy after plasma electrolytic oxidation in solutions containing Ca, P and Zn were studied by scanning electron microscopy (SEM), AC impedance, and potentiodynamic polarization test. A series of $Zn-TiO_2$ coatings are produced on Ti dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to +2000mV. Also, AC impedance was performed at frequencies ranging from 10MHz to 100kHz for corrosion resistance.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2535-2541
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• 2009

Prebiotic isomaltooligosaccharide preparations contain $\alpha$-D-glucooligosaccharides comprising isomaltooligosaccharides (IMOs) and non-prebiotic maltooligosaccharides (MOs). They are both glucose oligosaccharides characterized by their degree of polymerization (DP) value (from 2 to $\sim$10), linkages types and positions (IMOs: $\alpha$-(1$\rightarrow$2, 3, 6 and in a lower proportion internal 1$\rightarrow$4) linkages, MOs: α-(1$\rightarrow$4) linkages). Their structure is the key factor for their prebiotic potential. In order to determine and elucidate the exact structure of unknown IMOs and MOs, unambiguous assignments of $^{13}C$ and $^1H$ chemical shifts of commercial standards, representative of IMOs and MOs diversity, have been determined using optimized standard one and two-dimensional experiments such as $^1H$ NMR, $^{13}C$ NMR, APT and ${^1}H-{^1}H$ COSY, TOCSY, NOESY and <$^1H-{^{13}}C$ heteronuclear HSQC, HSQC-TOCSY, and HMBC. Here we point out the differential effect of substitution by a glucose residue at different positions on chemical shifts of anomeric as well as ring carbons together with the effect of the reducing end configuration for low DP oligosaccharides and diasteroisotopic effect for H-6 protons. From this study, structural $^{13}C$ specific spectral features can be identified as tools for structural analysis of isomaltooligosaccharides.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.970-972
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• 2003

Due to rapid increase in the demand of Natural Rubber (NR) few years ago, NR price sore very higher. The rubber plantation in Thailand expanded very fast to non traditional areas with the result Thai become the biggest NR exporting country in the world. However, the average yield is still lower compared to experimental yield of RRIT (Rubber Research Institute of Thailand) or just 60 % (RRIT, 1998). This is due to many of new rubber planting areas, which are not suitable. The Thai Ministry of Agriculture and Cooperatives thus has set 'The complete cycle development strategies for natural rubber' in the medium-term measures by reducing the rubber planting areas by 300,000 rai (1 rai = 0.16ha) through replanting with oil palm. The aim of this study is to find out land having lowest potential for rubber production (R3) but highest for oil palm production (P1). Find areas which are unsuitable for rubber and can be replaced by oil palm in order to get a better agricultural production. The study was applied upon Krabi province, Thailand. Crops requirement, degree of limitation to crops growth, climatic data, crops yield, soil map, topographic map etc., were used to evaluate land potential for both rubber and oil palm production according to FAO framework (Sys, 1992). An Agro-ecological suitability map for rubber and oil palm were produced. This was done by mean of GIS. The database was generated and guide map for the decision makers in view of suitable crop substitution was prepared.

• Korean Journal of Microbiology
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• v.42 no.2
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• pp.156-159
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• 2006

A base substitution was introduced at the position 789 in Escherichia coli 16S rRNA, which was previously identified as an invariant residue for ribosome function and the ability of the mutant ribosomes to translate chloramphenicol acetyltransfernse mRNA was measured by determining the degree of resistance to chloramphenicol of cells expressing these mutant ribosomes. As expected, mutant ribosomes containing a base sub-stitution at the position 789 showed significantly reduced protein-synthesis ability and to identify a functional role played by this residue in protein synthesis, we developed an efficient genetic method to select second-site revertants in 16S rRNA that restore protein-synthesis function to these mutant ribosomes.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.226-230
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• 2005

Chitosan derivatives, 6-amino-6-deoxychitosan (6A6DC) was successively prepared as a reactive carbohydrate for the stabilization of epidermal growth factor (EGF) by the reactions of chitosan with tosyl chloride, sodium azide, and lithium aluminum tetrahydride. The structure of 6A6DC was confirmed by EA, FT-IR, $^1H-NMR$ and $^{13}C\{^1H\}-NMR$. The degree of substitution (ds) of amino groups in 6A6DC was determined to be 0.7. 6A6DC did not show any cytotoxicity on the normal human dermal fibroblast (NHDF) proliferation at least in the range tested (0.3 g/mL 600 g/mL) and was considered as a suitable material for the stabilization of EGF against proteolytic degradation due to its non-cytotoxicity and high reactivity.