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        검색결과 126

        61.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The effects of reaction temperature and flow rate of reactants on the methane conversion, product selectivity, product ratio, and carbon deposition were investigated with 13wt% Ni/MgO catalyst. Reaction temperatures were changed from 600 to 850℃, and reactants flow rates were changed from 100 to 200 mL/mim. There were no significant changes in the methane conversion observed in the range of temperatures used. It is possibly stemmed from the nearly total exhaustion of oxygen introduced. The selectiveties of hydrogen and carbon monoxide did not largely depend on the reaction temperature. The selectivities of hydrogen and carbon monoxide were 96 and 90%, respectively. Carbon deposition observed was the smallest at 750℃ and the largest at 850℃. It is found that the proper reaction temperature is 750℃. The best reactant flow rate was 150 ml/min.
        4,000원
        62.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Arrùno acid transpoπers play an important role in supplying nutrition to cells and for cell proliferation. System L is a major nutrient transport system responsible for the Na+-independent transport of large neutral amino acids including several essential amino acids. In malignant tumors, a system L transporter L-type amino acid transporter 1 (LATl) is upregulated to support tumor cell growth. In the present study, we have examined the expression and function of system L amino acid transporter in FaDu human pharyngeal squamous carcinoma cells. RT-PCR, real-time quantitative RT-PCR and westem blot analysis have revealed that the FaDu cells express LATl together with its associaω19 protem 4F2hc, whereas the FaDu cells do not express the other system L isoform L-type amino acid transporter 2 (LAT2). 까le uptake of L-(14Clleucine by FaDu cells is Na+-independent and almost completely inhibited by system L selective inhibitor 2-aminobicyclo-(2,2,1)-heptane-2- carboxylic acid (BCH). The profiles of the inhibition of L-[I4Cllellcine uptake by variolls amino acids in the FaDu cells are comparable with those for the LA T1 expressed in Xenopus 。()(찌es. π1e majority of L-[I4Clleucine uptake is, therefore, mediated by LAT1 in the FaDu cells. These results suggest that the transport of neutral amino acids including several essential amino acids in the FaDu human pharyngeal squamous carcinoma cells mediated by LAT1. In addition, specific inhibition of LAT1 by such agents as BCH in pharyngeal squamous cell carcinomas will be a new rationale for anti-cancer therapy.
        4,300원
        63.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Synthesis gas is commercially produced by a steam reforming process. However, the process is highly endothermic and energy-consuming. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to decrease the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H2 and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO2 solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.
        4,000원
        64.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Electrical properties of carbon filler/PVdF [poly(vinylidene fluoride)] composite were investigated as a funtion of carbon filler/PVdF ratio in the range of 0.2~0.5. Three kinds of comercialzied conductive carbon blacks such as Hiblack 41Y, KE300J, and KE600J, and carbon nanofibers prepared by the catalytic chemical vapor deposition of C2H4 over Ni-Cu catalysts were used as the carbon fillers. The electrical conductivity of carbon filler/PVdF composites were in the range of 0.65 to 13.5 S/cm depending the fillers' electrical conductivity ranging from 5.6 to 23.1 S/cm. Among the carbon fillers used, the KE600J carbon black showed the highest conductivity both in the composite and filler itself because of its high degree of graphitization due to the high-temperature thermal treatment and its high surface area due to the activation treatment.
        4,000원
        65.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.
        4,200원
        66.
        2003.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        It has been said that amino acid transporters play an important role in supplying nutrition to normal and cancer cells and for cell proliferation. System L is a major nutrient transport system responsible for the Na+-independent transport of large neutral amino acids including several essential amino acids. In malignant tumors, a system L transporter L-type amino acid transporter 1(LAT1) is up-regulated to support tumor cell growth. In the present study, we have examined the function of LAT1 and its expression in the KB human oral epidermoid carcinoma cells. RT-PCR, western blot analysis and immunohistochemical analysis have revealed that KB cells express LAT1 in the plasma membrane together with its associating protein 4F2hc, whereas KB cells do not express the other system L isoform LAT2. The uptake of L-[14C]leucine by KB cells is Na+-independent and almost completely inhibited by system L selective inhibitor BCH. The profiles of the inhibition of L-[14C]leucine uptake by amino acids in the KB cells are comparable with those for the LAT1 expressed in Xenopus oocytes. The majority of L-[14C]leucine uptake is, therefore, mediated by LAT1 in the KB cells. These results suggest that the uptakes of neutral amino acids including several essential amino acids in the KB oral epidermoid carcinoma cells mediated by LAT1. In addition, specific inhibition of LAT1 by such agents as BCH in human oral squamous cell carcinomas will be a new rationale for anti-cancer therapy.
        4,500원
        67.
        2003.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The impregnated activated carbons were prepared by the incipient wetness method with the contents of KIO3 varied from 1.0~10 wt% as the impregnation material. The specific surface area and micropore volume of the rice hulls activated carbon were 2,600~2,800 m2/g and 1.1~1.4 cc/g, respectively. With increasing the contents of impregnation materials, the surface area and micropore volume decreased by 3~21%. However, The amounts of hydrogen sulfide adsorbed increased by 2.1~2.8 times depending on the impregnation content. The optimum contents of KIO3 were 2.4 wt%. Although the breakthrough time and adsorption capacity of hydrogen sulfide decreased with increasing temperature in the case of the unimpregnated activated carbons, they increased by 1.2~ 3.2 times for the case of the impregnated activated carbons. The optimum aspect ratio(L/D) was 1.0 and the adsorption amount of hydrogen sulfide enhanced with increasing the gas flow rate. The regeneration temperature was determined as 400℃ from the TGA experiment. The adsorption capacity of hydrogen sulfide with the impregnated activated carbon decreased gradually as the regeneration continued. The hydrogen sulfide adsorption amount of the regenerated activated carbon up to 4 times was still higher than that of the unimpregnated activated carbon.
        4,000원
        68.
        2002.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Environmental friendly acrylic/urea high-solid paint(MUHC) were prepared through the curing reaction of acrylics resin(EBHC) containing 70wt% of solids content and butylated urea curing agent. The synthesis of EBHC Was done at 150℃ for 6 hours, and the results were obtained as follows : Mn=1830~2190, Mw 3290~4000, Mw/Mn=1.80~1.83 viscosity=110~352 cps, and conversion=82~92%. After the film was coated with MUHC, the various physical properties were measured. They showed that enhancement of the coating properties such as adhesion, flexibility, abrasion resistance, impact resistance, and water resistance could be expected through introdl1cing caprolactone acrylate component in acrylics resin for the high-solids content acrylics/urea coatings.
        4,000원
        69.
        2002.12 구독 인증기관 무료, 개인회원 유료
        A Study on the Youkjoron(逆調論) of the So Moon(素問) one of the classic book of oriental medicine, was carried out analytically for the right comments. The principal ideas abtained summerized as follows: The unbalance between Eum(陰) and Yang(陽) The unbalance between Su(水) and Wha(火) The Yuk Ga(肉苛) which is caused by the unbalance of the Young Wi(營衛) The Asthma(喘息) which is caused by the unbalance of the Viscera(臟腑)
        5,800원
        70.
        2002.12 구독 인증기관 무료, 개인회원 유료
        A study on the Byungtae Ron(病能論) of the So Moon(素問), one of the classic book of oriental medicine, was carried out analytically for the right comments. The principal ideas obtained summarized as follows; Neng(能) is similar to tae(態) in the pronunciation and the meaning of a chinese character. Byungtae(病能) means the state of the symptoms and the pulse condition of the diseases, etc. It deals with ethological factor, mechanism of disease, the condition of an illness, method of diagnosis, rule of treatment, technique of treatment of seven diseases and taking this seven diseases as a example, mainly discuss the technique and significance of clinical observation and the pathogenesis and condition of an illness, so It named Byungtaeron(病能論) In this chapter it shows we can grasp condition of illness well only if we classify the pathogenesis and condition of an illness in details. this viewpoint provides the foundation of development in oriental diagnostics. It places emphasis on pulse feeling in this chapter, so it describes pulse condition of various kinds of diseases in details. It also presents how to compare pulse feeling like comparison between Inyoungmaek(人迎脈, arterial carotid communes, the pulsation of which is easily felt beside Adam's apple) and Ch'onkumaek(寸口脈, the radial artery on the wrist where the pulse is routinely taken for diagnosis), between right and left Ch'onkumaek(寸口脈), between Yangmyungsangdong (陽明常動) and Taeyangbudong(太陽不動), Soyangbudong(少陽不動), etc. In this chapter it explains pulse feeling occupies a high position in the diagnosis of diseases in Huangdi's internal Classic(黃帝內經) period and the technique of pulse feeling is already plentiful and minute. In this chapter it presents Tongbyungyichi(同病異治, to apply different methods of treatment to the same kind of disease) theory, taking tangible syndromes as examples. this is prominent viewpoint of determination of treatment based on the differentiation of symptoms and signs and much influence development of later ages' medicine. On the ground of oriental medical theory, it may bring about different symptoms in the same disease according to stage of disease, the seasons, the regions, the constitution of patient, therefore surely adopt different technique of treatment. this differentiation of symptoms and signs is an important character in oriental medicine.
        6,900원
        71.
        2002.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Activated carbons with high surface area of 2,600 m2/g and high pore volume of 1.2 cc/g could be prepared by KOH activation of rice hulls at a KOH:char ratio of 4:1 and 850℃. In order to increase the adsorption capacity of hydrogen sulfide, which is one of the major malodorous component in the waste water treatment process, various contents of Na2CO3 and KIO3 were impregnated to the rice-hull activated carbon. The impregnated activated carbon with 5 wt.% of Na2CO3 showed improved H2S adsorption capacity of 75 mg/g which is twice of that for the activated carbon without impregnation and the impregnated activated carbon with 2.4 wt.% of KIO3 showed even higher H2S adsorption capacity of 97 mg/g. The improvement of H2S adsorption capacity by the introduction of those chemicals could be due to the H2S oxidation and chemical reaction with impregnated materials in addition to the physical adsorption of activated carbon.
        4,000원
        72.
        2002.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The cutaneous tolerability of detergent formulations can be improved by means of suitable additives. They complex the surfactant molecules lowering the concentration of their free monomeric species. Proteins derivatives used as additives for detergency are usually prepared by partial hydrolysis of plant reserve proteins. The main purpose of the hydrolytic cleavage is to make them water soluble and suitable for liquid products. Water solubility and stability are obtained by means of complexation with surfactants which also increase their actual hydrophobicity, an important parameter affecting cosmetic properties of proteins. Transepidermal water loss (TEWL) and electric capacitance (EC) have been adopted as investigation technigues to evaluate the skin integrity/damage in vitro tests, The performance of native wheat protein / surfactant complexes has been compared with traditional protein hydrolysates as detergent additives. The results show a noticeable reduction of skin irritation in surfactant formulations with addition of native wheat protein.
        4,000원
        73.
        2001.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Due to its low density, good mechanical properties and chemical inertness, glassy carbon(GC) has been studied for appications in several fields. A raw thermosetting resin of furanic resin was polymerized with a curing agent of p-toluenesulfonic acid monohydrate. The maximum yield of GC was obtained at the curing agent content of 1.0 wt% in furanic resin. In order to make thick GC, the affect of graphite filler addition to the furanic resin was investigated. The density and electrical resitivity of GC after graphitization were 1.45 g/cm3 and 47 ×10-4 Ω · cm respectively and the amorphous structure of GC was confirmed by XRD profiles with very broad peaks comparable to those of graphite at 206˚ and 45˚.
        4,000원
        74.
        2001.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Density, viscosity, conductance, dye solubility and carbon-13 nmr studies were performed in aqueous solution of three disodium 4-n-alkyl-3-sulfonatosuccinate anionic surfactant at 20℃. The cmc values were 0.14 mol/l for the disodium-4-n-octyl-3-sulfonatosuccinate(R8)S), 0.041mol/l for the disodium-4-n-decyl-3-sulfonatosuccinate(R10S), and 0.018mol/l for the disodium-n-dodecyl-3-sulfonatosuccinate 〈R12S). The aggregation numbers determined viscometrically and conductimetrically were 28 for R8S, 48 for R10S, and 67 for R12S. The volume changes upon micellization were 8.9cm3/mol for R8S, 9.5cm3/mol for R10S, and 10.1cm3/mol for R12S. Binding constants for the dye pada to the micelles and the fractions of unbound counter-ion were also obtained. The two polar heads with their carbon linkage were likely in an aqueous environment in the R8S micelles with the micelles themselves being spherical.
        4,000원
        75.
        2001.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Recently, there has been considerably interested in the development to new functional gemini type anionic surfactant, sodium bis-n-alkyl sulfonatosuccinate, had been synthesized through the addition reaction of sodium bisulfite to bis-n-alkyl maleate, in which water was azeotropically distilled by adding benzene to the reaction system, gave a good yield. All the surface activities including krafft point, surface tension, emulsion power and foaming were measure and cmc was evaluated in dilute solution. This results showed a lower ability in 27~30dyne/cm than single-chain surfactant with 32~35dyne/cm to surface tension. Also its cmc value much smaller in (6.5~10)×10-4mcal/l than single-chain surfactant with (40~45)×10-4mcal/l concentration. In foaming ability and foam stability of gemini surfactant had especially a good ability in approximately 100~150ml, and in emulsing power they exhibited a good emulsing phase and stability, and Krafft points were 0~10℃.
        4,000원
        76.
        2001.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Acrylic quarternary polymers were synthesized to prepare high-solid coatings. Acrylic resins were synthesized by the radical polymerization of n-butyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate and acetoacetoxyethyl methacrylate. From the results of experiment on reaction condition to get high-solid acrylic resins with 70% solid content and viscosity of 1200cps, it was found that di-tert-amyl peroxide among the four types of initiators have lower viscosity and higher degree of conversion. The optinum initiator amount, chain transfer agent, reaction temperature and the dropping time were 5wt%, 4wt%, 150℃ and 5hrs, respectively.
        4,000원
        79.
        2000.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A conductimetric study of foam formed from mixture of the protein, β-lactoglobulin, and the nonioinc surfactant, SML, revealed that their stability was reduced at concentrations of SML in the range 3~10mM. The interaction of SML with β-lactoglobulin was investigated by fluorimetry and a dissociation constant of 0.2μM was calculated for the complex. Surface tension studies confirmed the presence of interaction between the two components and provided evidence for the progressive displacement of β-lactogloblin from the air/water interface with increasing SML concentration. Experiments using air-suspended microscopic thin liquid films revealed transitions in the chainage characteristics and thickness of the film at SML concentrations below that which resulted in destabilization of the foam. However, measurements of surface mobility of fluorescent-labeled β-lactoglobulin by a photobleaching method identified that a transition to a mobile system occurred at a SML concentration which correlated with the onset of instability in the disperse phase. The results would indicate that maintenance of the viscoelastic properties of the surface is paramount importance in determining the stability of interfaces comprising mixtures of protein and surfactant.
        4,000원
        80.
        2000.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The synthesis of N-methyl glucamine was performed in two step reaction. The first step involves the amination between methylamine and glucose in methane. The N-methyl glucamine was obtained by the reduction of using Ni catalyst under the high pressure. The second step was glucamide anionic derivatives synthesis from N-methyl glucamine, maleic anhydride, lauryl alcohol and laurylamine by Schotten Banmann reaction respectively. Their molecular structures of N-methyl glucamine and glucamide (EG-MAS and AC-MAS) were investigated by IR and 1H-NMR. Basic physical properties and biodegradability of there glucamide anionic surfactant was investigated. The range of cmc values determined by measurements of surface tention was 10-5~10-4mol/l and the surface tension of the aqueous solution revealed in the range 28~30 dyne/cm and their biodegradability was very good in the pH 5~10.
        4,000원
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