• Elastomers and Composites
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• 제33권2호
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• pp.110-116
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• 1998

A new technology was introduced to the emulsion polymerization. It is the ultrasonic activation method which replaced a chemical initiator and the environmentally benign process. In this study, free radicals were produced by a pulse type ultrasound energy irradiation, then polystyrene latex was polymerized without chemical initiator. With ultrasonic energy density, the degree of polymerization, average molecular weight, and particle size were increased, but the polydispersity index for the molecular weight and the particle size were decreased. The optimum condition of emulsifier concentration and temperature was found to be 1.0 wt.% SDS and $40^{\circ}C$, respectively. As a result, the emulsion polymerization process without chemical initiator was proved to be comparable to common latex properties such as average molecular weight, molecular weight distribution, particle size, etc.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
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• pp.480-507
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• 2003

A rapid and efficient method for analyzing the nonionic surfactants and silicone polymers, which control the shape and characteristics of cosmetic products and give influence on product quality, has been developed using Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI- TOF IMS). The MALDI-TOF/MS could easily and effectively determine the molecular weight distribution and monomer units of nonionic surfactants. As a result, creating a library of mass spectrum data of surfactants used in cosmetic products using MALDI-TOF/MS and analyzing surfactants extracted from the products may become a useful method for detailed structural characterization of the surfactants. Furthermore, the MALDI-TOF/MS analysis was effective in obtaining the spectrum of silicone polymers from which the molecular weight distribution could be determined. The repetition units and structural data could also be obtained through molecular mass peaks. Additionally, the monomer ratio and terminal groups as properties of silicone copolymers could be determined

• Elastomers and Composites
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• 제37권4호
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• pp.234-243
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• 2002

A general scheme of a rubber structure is proposed. Using the thermomechanical method(TMA), some changes in the molecular and topological structures for uncured and cured, and unfilled and filled rubbers during processing are shown. In our investigations as region it is understood a complex structure, which is expressed at the thermomechanical curve(TMC) as a zone differed from others in thermal expansion properties. This zone is between the noticed temperatures of relaxation transitions, usually on the level like those determined by DMTA at 1Hz. These regions, which shares, are not stable, and differ in molecular-weight distribution(MWD) of chain fragments between the junctions. Differences in dynamics of the formation of the molecular and topological structures of a vulcanizate are dependent on the rubber formulation, mixing technology and curing time. Some of characteristics of these regions correlate with mechanical properties of vulcanizates what is shown for NR rubbers containing ENR or CPE as a polymeric additive. It is well known that the state of order influences diffusivity of low-molecular substances into the polymer matrix. Because of this, the two topological amorphous regions should influence the distribution of the ingredients and resulting in rubber compounds' heterogeneity, and related properties of cured rubber. Investigation of this problem is expected to be, in the future, one of the essential factors in determining further improvement of polymeric materials properties by compounding with additives and in reprocessing of rubber scrap.

• Journal of Microbiology
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• 제34권2호
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• pp.131-136
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• 1996

In order to known the extend of contribution to the degradation of organic materials and nutrient recycling by sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB) in sediment, the distribution and activity of these two groups of microorganisms were studied montly in 1994 at two sites, one littoral (Sanggulri) and the other profunndal (DAM), in Lake Soyang. In the seasonal distribution of two microorganisms, SRB were 1.07 $\times$ 10$^{3}$-2.42 $\times$ 10$^{5}$ cells/g-dry weight at Sanggulri, 2.40 $\times$ 10$^{5}$ -1.29 $\times$ 10$^{6}$ at Dam and MPB were 0.52 $\times$ 10$^{3}$ cells/g-dry weight at Sangguri and 1.44 $\times$ 10$^{3}$-6.89 $\times$ 10$^{3}$ at Dam. In these results, the density of SRB in Lake Soyang is much higher than other lakes. These high values might be due to higher sulfate concentration, 0.69-4.05 mM, than normal freshwater, 0.01-1.2 mM. And a good correlation of SRB and chlorophyll a concentration implied that the important environmental factor on distribution of SRB might be the concentration of available organic matter. In a comparison of sulfate-reducing rate and methane producing rate in 1995, the activity of SRB for the degradation of organic matter was higher than MPB by factor of 359. Conclusively SRB superior to MPB in the distribution and activity are more important annearobic bacteria in Lake Soyang sediments.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2002년도 생물공학의 동향 (X)
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• pp.41-42
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• 2002

• 한국기계가공학회지
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• 제18권5호
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• pp.60-65
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• 2019

Since nanofluids (NFs), which are a mixture of a small amount of nanoparticles and a bulk liquid solvent, were first proposed by Stephen Choi at the Argonne National Lab in 1995, they have been considered for use in many technical studies of power cooling systems and their practical application due to their high thermal conductivity and heat transfer coefficients compared to conventional coolants. Although nanofluids are a well-known form of engineering fluid that show great promise for use in future cooling systems, their underlying physics as demonstrated in experiments remain unclear. One proven method of determining the heat transfer performance of nanofluids is measuring the concentration of nanoparticles in a mixture. However, it is experimentally inefficient to build testbeds to systematically observe particle distributions on a nanoscale. In this paper, we demonstrate the distribution of nanoparticles under a temperature gradient in a solution using molecular dynamics simulations. First, temperature profiles based on substrate temperature are introduced. Following this, the radial pair distribution functions of pairs of nanoparticles, solvents, and substrates are calculated. Finally, the distribution of nanoparticles in different heating regions is determined.

• 한국식품조리과학회지
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• 제18권2호
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• pp.200-205
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• 2002

본 연구는 옥수수 전분의 기능 특성을 개선시키고자, 다양한 sodium hypochlorite(NaOCl)농도에서 산화시킨 산화 전분의 분자 구조적 변화에 대하여 시험하였다. 전분의 분자량 분포에서 산화 전분은 고분자량의 피크가 점차 작아지고 저분자량 부분의 피크가 높아져 전체적 분자량 분포가 낮은 쪽으로 이동하였고, 요오드 최대 흡수 파장이 감소되면서 색깔이 변화하였다. 무처리 전분은 온도가 증가함에 따라 분자량이 큰 부분의 용출이 증가하였다. 산화전분의 경우 아밀로펙틴이 산화에 의해 분해되어 전분 입자내에 큰 분자량을 가진 분자가 감소되면서 작은 분자량을 가지는 분자가 증가되기 때문에 가용성 탄수화물의 양이 증가하였다. DSC 특성에서는 상전이 온도 범위와 엔탈피의 차이는 없었으나 산화 전분이 무처리 전분보다 노화경향이 더 크게 나타났다. 산화전분용액의 광투과도는 증가하였다.

• BMB Reports
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• 제41권6호
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• pp.415-434
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• 2008

Phosphoinositide-specific phospholipase C is an effector molecule in the signal transduction process. It generates two second messengers, inositol-1,4,5-trisphosphate and diacylglycerol from phosphatidylinositol 4,5-bisphosphate. Currently, thirteen mammal PLC isozymes have been identified, and they are divided into six groups: PLC-$\beta$, -$\gamma$, -$\delta$, -$\varepsilon$, -$\zeta$ and -$\eta$. Sequence analysis studies demonstrated that each isozyme has more than one alternative splicing variant. PLC isozymes contain the X and Y domains that are responsible for catalytic activity. Several other domains including the PH domain, the C2 domain and EF hand motifs are involved in various biological functions of PLC isozymes as signaling proteins. The distribution of PLC isozymes is tissue and organ specific. Recent studies on isolated cells and knockout mice depleted of PLC isozymes have revealed their distinct phenotypes. Given the specificity in distribution and cellular localization, it is clear that each PLC isozyme bears a unique function in the modulation of physiological responses. In this review, we discuss the structural organization, enzymatic properties and molecular diversity of PLC splicing variants and study functional and physiological roles of each isozyme.

• 전자공학회논문지D
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• 제35D권3호
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• pp.18-27
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• 1998

Molecular dynamicsinvestigations of ion implantation considering point defect generation were performed with ion energies in the range of ~1keV, Simulation starts perfect diamond cubic lattice site. Stillinger-Weber potential and ZBL potential were used to calculate forces between atoms. We have simulated slowing-down of ion velocity, ion trajectory and coupled-coing between ion and silicon. We also discussed distribution of point defect using rdial distribution function. We found that interstitial produced by ion bombardment mainly formed interstitial cluster.

• 대한미생물학회지
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• 제35권2호
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• pp.171-180
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• 2000

Ninety two strains of Streptococcus pyogenes were isolated from patients with pharyngitis, scarlet fever, skin infection, and invasive streptococcal infections in Seoul, Korea from January to December, 1998. All isolates were epidemiologically characterized by T protein serotype, and serum opacity factor (OF) detection to phenotypes. To analyze the genetic relationship, fifty two isolates including 32 erythromycin-clindamycin (Em-Cm) resistant strains, 20 antimicrobial susceptible strains were attempted to the pulsed-field gel electrophoresis (PFGE). T protein serotype showed 16 kinds in distribution including T12 and T4. Among the total isolates, 40 strains (43.5%) belonged to the T12 serotype and twenty strains (21.7%) to T4 serotype. On the other hand, when infection aspect of S. pyogenes isolates were analysed by T serotype distribution, T12 type was predominant for pharyngitidis which contributed to 21 strains (53%) and for skin infection isolates which contributed to 11 strains (28%), respectively. In case of T4 type, it was the most predominant pharyngitidis isolates which contributed to 8 strains (40%). In T serotype distribution of Em-Cm resistant strains, 27 strains (84%) of the thirty two showed T12 serotype. In minimum inhibitory concentration (MIC) values of Em-Cm resistance isolates, thirty two isolates showed resistant to erythromycin 27 strains (84%), had high MIC of >$128\;{\mu}g/ml$. And also to clindamycin, twenty two strains (69%) had high MIC of >$128\;{\mu}g/ml$. When OF detection of Em-Cm resistance of S. pyogenes isolates were analyzed by T serotype distribution, T12 serotype isolates revealed that all of the isolates except one strain were OF negative. In PFGE profile analysis to Em-Cm resistance isolates, of the twenty seven, Em-Cm resistance of T12 serotype isolates, 26 strains showed identical PFGE profile and all of these isolates revealed that OF negative. Eighty four percent of Em-Cm resistance S. pyogenes isolates had identical phenotype and PFGE profile. These results strongly suggested that the Em-Cm resistant S. pyogenes isolates from Seoul area showed close genetic correlation and PFGE could be available tool for molecular epidemiology.