• Korea-Australia Rheology Journal
• /
• v.19 no.3
• /
• pp.125-131
• /
• 2007

Biodegradable polymeric blends are expected to be widely used by industry due to their environmental friendliness and comparable mechanical and thermal properties. Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) are such biodegradable polymers which aim to replace commodity polymers in future applications. Since cost and brittleness of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. In this study, blends of PLA and PBS with various compositions were prepared by using a laboratory-scale twin-screw extruder at $180^{\circ}C$. Morphological, thermal, rheological and mechanical properties were investigated on the samples obtained by compression molding to explore suitability of these compositions for packaging applications. Morphology of the blends was investigated by scanning electron microscopy (SEM). Morphology showed a clear phase difference trend depending on blend composition. Modulated differential scanning calorimetry (MDSC) thermograms of the blends indicated that the glass transition temperature ($T_g$) of PLA did not change much with the addition of PBS, but analysis showed that for PLA/PBS blend of up to 80/20 composition there is partial miscibility between the two polymers. The tensile strength and modulus were measured by the Instron Universal Testing Machine. Tensile strength, modulus and percentage (%) elongation at break of the blends decreased with PBS content. However, tensile strength and modulus values of PLA/PBS blend for up to 80/20 composition nearly follow the mixing rule. Rheological results also show miscibility between the two polymers for PBS composition less than 20% by weight. PBS reduced the brittleness of PLA, thus making it a contender to replace plastics for packaging applications. This work found a partial miscibility between PBS and PLA by investigating thermal, mechanical and morphological properties.

• Journal of the Korean Society of Tobacco Science
• /
• v.20 no.2
• /
• pp.166-171
• /
• 1998

In order to improve the efficiency of F$_1$ hybrid seeds production(KF 114), some experiments were carried out in a greenhouse this year. Mother plant(MSNC567) and pollen plant(NC) were grown in some pots (30 x 30cm, WxH). The gathered pollens were mixed with celite, pollen deluent dusts and stored in refrigerator at l$0^{\circ}C$ before pollination. To establish the critical range of the mixed rate and the storage period of pollens, the change in a percent of capsule set, number of seed and seed weight per capsule, weight of 1000 seeds and germination percent of seed resulted of pollination with pollen deluent dusts were investigated. The results are as follows; Percent of capsule set showed the mixed rate 1:5 resulted in no difference and those of 1:10 and 1:20 decreased about 5 ～15% when compared with trials using pollen alone. There was no difference among duration of storage in a same mixed rate. Numbers of seed per capsule showed a significant difference among the mixed rates and among durations of storage. Numbers of seed per capsule were decreased about 55 ～ 90 % as the mixed rate increase, about 2 ～ 28 % as the duration of storage increase. Weight of seed per capsule decreased about 16 ～ 23 % as the duration increase and decreased about 3 ～ 89 % as the mixed rate increase when compared with trials using pollen alone. Weight of 1000 seeds showed non significant difference among duration of storage but were higher than trials used pollen alone as the mixed rate increase.

• Transactions of Materials Processing
• /
• v.16 no.4 s.94
• /
• pp.293-298
• /
• 2007

Recently, there is a need to produce a large forged part for the flight, shipping, some energies, and military industries, etc. Therefore, an open die forging technique of cast ingots is required to obtain higher quality of large size forged parts. Cogging process is one of the primary stages in many open die forging processes. In the cogging process prior to some open die forging processes, internal cavities have to be eliminated for defect-free. The present work is concerned with the elimination of the internal cavities in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis is performed to investigate the overlap defect of cast ingots during cogging stage. The measured flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}-3D$. The calculated results of cavity closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

• Biomolecules & Therapeutics
• /
• v.20 no.6
• /
• pp.513-519
• /
• 2012

Although the immense efforts have been made for cancer prevention, early diagnosis, and treatment, cancer morbidity and mortality has not been decreased during last forty years. Especially, lung cancer is top-ranked in cancer-associated human death. Therefore, effective strategy is strongly required for the management of lung cancer. In the present study, we found that novel daphnane diterpenoids, yuanhualine (YL), yuanhuahine (YH) and yuanhuagine (YG) isolated from the flower of Daphne genkwa (Thymelaeaceae), exhibited potent anti-proliferative activities against human lung A549 cells with the $IC_{50}$ values of 7.0, 15.2 and 24.7 nM, respectively. Flow cytometric analysis revealed that the daphnane diterpenoids induced cell-cycle arrest in the G0/G1 as well as G2/M phase in A549 cells. The cell-cycle arrests were well correlated with the expression of checkpoint proteins including the up-regulation of cyclin-dependent kinase inhibitor p21 and p53 and down-regulation of cyclin A, cyclin B1, cyclin E, cyclin dependent kinase 4, cdc2, phosphorylation of Rb and cMyc expression. In the analysis of signal transduction molecules, the daphnane diterpenoids suppressed the activation of Akt, STAT3 and Src in human lung cancer cells. The daphnane diterpenoids also exerted the potent anti-proliferative activity against anticancer-drug resistant cancer cells including gemcitabine-resistant A549, gefitinib-, erlotinib-resistant H292 cells. Synergistic effects in the growth inhibition were also observed when yuanhualine was combined with gemcitabine, gefitinib or erlotinib in A549 cells. Taken together, these findings suggest that the novel daphnane diterpenoids might provide lead candidates for the development of therapeutic agents for human lung cancers.

• Korean Journal of Weed Science
• /
• v.15 no.4
• /
• pp.313-320
• /
• 1995

The major weeds observed in soybean(Glycine max(L.) Merr.) culture at the paddy field where transplanted rice was cultivated in previous year were Digitaria spp., Echinochloa spp., Chenopodium ficifolium, Rorippa islandica and Stellaria alsine. C. ficifolium and R. islandica increased as soybean was cultivated for two years in the same field. Weed biomass decreased by 84.8% as the seeding date was delayed from April 26 to May 20. Most of weeds started to emerge from 20 days after seeding(DAS) until 40 DAS, and higher seed yield was obtained by eliminating the weeds emerged until 40 DAS. The development of soybean branches, pods stem diameter was severely injured by weed interference, and thus soybean seed yield was reduced by 70% in comparison with a full season weed free plot. Herbicides such as pendimethalin, metolachlor, metolachlor+prometryn and alachlor controlled very effectively weeds present in soybean culture in rice-soybean rotated paddy field.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2001.04a
• /
• pp.26-26
• /
• 2001

사무용 고지의 상당량을 차지하는 복사고지는 열과 압력으로 융착된 합성고분자 물질인 토너를 함유하고 있으며 이들 토너는 펄핑 후 크고 판상 형태의 잉크 입자를 형성하 여 기존의 부유부상법으로 제거가 곤란한 문제점을 지니고 있었다. 이러한 문제점을 극복하 는 방안으로 응집제를 이용하는 방법을 검토하였다. 복사기용 인쇄 잉크로 널리 사용되는 토너 업자는 낮은 표면에너지를 가지는 소수 성 물질이므로 같은 표면 특성을 가지는 소수성 물질과 서로 잘 결합한다. 따라서 소수성의 응집제를 이용하면 분리된 토너 잉크업자를 응집시킬 수 있으며, 응집된 토너 응집체는 스 크린 또는 클리닝 같은 정선 공정을 이용하여 제거가 가능할 것이다. 따라서 복사고지를 효 과적으로 재활용할 수 있는 탈묵방법으로 응집제를 이용하여 토너 입자를 조대한 웅집체로 형성시키고 이를 기존 탈묵방법인 스크린처리로 제거하는 방법을 검토하였다. 본 연구에서는 고급알코올의 하나언 1 -octadecanol을 이용하여 기존의 탈묵 방법 인 부유부상법으로는 제거가 곤란한 토너 잉크의 업자를 웅집시켜 구형의 조대한 응집체로 형성시켜 이를 제거하는 기술에 대하여 연구하였다. 펄핑 시의 온도를 70C의 고온으로 설 정한 경우 토너 입자가 유리전이온도에 이르게 되며 이들 토너 입자는 응집제에 의하여 웅 집되어 구형으로 성장하는 특정이 뚜렷하였으며, 토너 응집체의 크기는 최대 800 µm에 이 르기까지 조대하게 성장하였다. 또한 슬롯 폭 $250\mu\textrm{m}$의 진동 스크린 처리에 의한 토너 제 거 효율 측정 결과 역시 이들 토너 업자 웅집체의 형태가 구형임을 보여주었다. 해리 및 응 집 처 리 시 의 pH를 3으로 조정 하였을 때 토너 입 자가 웅집 제인 1 -octadecanol에 의 해 가장 효과적으로 구형의 조대한 웅집체를 이루는 것으로 나타났으며, 스크련을 통한 토너 웅집체 제거효율이 향상되었다. 복사고지 내에 포함되어 있는 전분 또는 사이즈제는 웅집 효과를 떨어뜨리는 주요 인으로 나타났다.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.29 no.4
• /
• pp.7-17
• /
• 1997

균체가 생산하는 laccase 효소가 다방면으로 이용되면서, 이 효소를 균체로부터 대량으로 생산하고 분리.정제하여야 할 필요성이 대두되고 있다. 아울러 이 효소의 활성을 유도하기 위한 inducer 로서 2,5-xylidine 이 주로 사용되고 있는바, 이 xylidine 의 유독성이 인정되면서 사람에게 독성을 주지 않는 환경친화적 inducer의 검색이 필요하게 되었다. 본 연구에서는 백색부후균 Cerrena unicolor가 분비하는 laccase 효소의 유도를 위한 inducer로서 ferulic acid를 사용하였으며, 균체로부터 생산 및 분리된 laccase 효소의 정제특성을 구명코자 하였다. 본효소(constitutive enzyme)로서 I 및 II를, ferulic acid를 inducer로 사용한 경우 inducing 효소 III을 분리.정제하였다. 본 효소 I 및 II의 Michaelis 정수는 각각 737 M, 716 M 이었고, inducing효소 III은 167 M 로서, 기질에 대한 높은 친화성을 보여주고 있다. 분자량도 각각 65 kD, 63 kD 였으며, inducing효소 III은 59 kD 였다. 두효소 모두 15-19%의 당 및 단백질분자당 4M의 동(Cu)을 함유하고 있었다. 정제효율은 효소 I 및 II가 10.1%, 9.4% 였으며, III은 3.2% 였다. 모든 효소의 최적 pH 는 5.5였으며, 최적온도는 비교적 높은 $40^{\circ}C$였다.

• Korean Journal of Materials Research
• /
• v.25 no.4
• /
• pp.165-170
• /
• 2015

Ceramics biomaterials are useful as implant materials in orthopedic surgery. In this study, porous HA(hydroxyapatite)/${\beta}$-TCP(tricalcium phosphate) composite biomaterials were successfully fabricated using HA/${\beta}$-TCP powders with 10-30 wt% $NH_4HCO_3$ as a space holder(SH) and $TiH_2$ as a foaming agent, and MgO powder as a binder. The HA/${\beta}$-TCP powders were consolidated by spark plasma sintering(SPS) process at $1000^{\circ}C$ under 20 MPa conditions. The effect of SH content on the pore size and distribution of the HA/${\beta}$-TCP composite was observed by scanning electron microscopy(SEM) and a microfocus X-ray computer tomography system(SMX-225CT). These microstructure observations revealed that the volume fraction of the pores increased with increasing SH content. The pore size of the HA/${\beta}$-TCP composites is about $400-500{\mu}m$. The relative density of the porous HA/${\beta}$-TCP composite increased with decreasing SH content. The porous HA/${\beta}$-TCP composite fabricated with 30%SH exhibited an elastic modulus similar to that of cortical bone; however, the compression strength of this composite is higher than that of cortical bone.

• Korean Journal of Animal Reproduction
• /
• v.21 no.1
• /
• pp.19-23
• /
• 1997

This present study was carried out to examine the effect of maturation media and liquid boar semen on in vitro maturation and feritilization of pig oocytes. The results obtained were as follows : When the oocytes were cultured for 36∼42 hours in mTCM-199, Waymouth MB 725/1 and mTLP-PVA medium, the maturation rates were 90%, 92% and 88%, respectively. The sperm penetration rates of pig oocyte matured in vitro were 87%(mTCM-199), 90%(Waymouth MB 725/1) and 86%(mTLP-PVA), respectively. The rates of nuclear maturation and fertilization of pig oocytes among three different media did not differ. However, the rate of male pronucleus formation of pig oocytes was significantly higher in pig oocytes matured in Waymouth MB 725/1(91%) than oocytes matured in mTCM-199(66%) and mTLP-PVA(62%) medium (P<0.05). When the collected sperm-rich fraction without diluent was used fro in vitro fertilization in mTCM-199 fertilization medium, the fertilization rate was 87.9%. However, when the liquid boar semen diluted with B tschwiler diluent was used at day 3 and 5 after dilution, the fertilization rate was 40.8% and 0.0%, respectively.

• Journal of Pharmaceutical Investigation
• /
• v.26 no.3
• /
• pp.169-174
• /
• 1996

Inclusion complexes of diclofenac sodium with ${\beta}-cyclodextrin$ were prepared in aqueous solution, alkaline solution and solid phase. The interaction of diclofenac sodium with ${\beta}-cyclodextrin$ in pH 9.0 alkaline solution was evaluated by the solubility method and the instrumental analysis such as thermal analysis, infrared spectroscopy, X-ray diffractometry. The solubility of diclofenac sodium was increased linearly with the increase in the concentration of ${\beta}-cyclodextrin$up to 0.15 mol and showed that the aqueous solubility rate of diclofenac sodium was significantly increased by complex with ${\beta}-cyclodextrin$. The optimum composition of this complex was one molecule of ${\beta}-cyclodextrin$ included 1.59 molecular weight of diclofenac sodium as a guest molecule. The pharmacokinetic parameters of the diclofenac sodium and the complex with ${\beta}-cyclodextrin$ were studied in rats by oral route. $T_{max}$ between drug alone and inclusion complex showed significant difference to be 120 minute and 20 minute respectively. Both of $C_{max}$ and AUC of inclusion complex was about 40% higher than drug alone. It is estimated from the data in this study that complexation of diclofenac sodium with ${\beta}-cyclodextrin$ increased the absorption rate and improved the bioavalability of the diclofenac sodium by the formation of a water-soluble complexes.