Hardening of Bi-Te based alloys by dispersing B₄C nanoparticles

Jung, S.J.,Park, S.Y.,Kim, B.K.,Kwon, B.,Kim, S.K.,Park, H.H.,Kim, D.I.,Kim, J.Y.,Hyun, D.B.,Kim, J.S.,Baek, S.H. Elsevier Science 2015 Acta materialia Vol.97 No.-

Thermoelectric devices have attracted a great attention for renewable energy harvesters and solid-state coolers. For practical applications, the mechanical properties of thermoelectric materials become critical for the device reliability, a persistent performance with a long time and high operation cycles. Bi-Te based single-crystals, mostly used in commercial thermoelectric devices, are intrinsically brittle with weak van der Waals bonding, often leading to device failures such as crack and debonding during fabrication and operation. Thus, it is highly desirable to enhance the mechanical property of Bi-Te based alloys as well as the thermoelectric property. Here, we investigate the effect of B<SUB>4</SUB>C nanoparticles (less than 0.5wt%) dispersed in p-type Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> matrix on the mechanical properties. X-ray diffraction (XRD) result confirms that B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> has a single phase. We observe that the grain size of Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> becomes decreased with the B<SUB>4</SUB>C nanoparticle concentration by electron backscatter diffraction (EBSD) technique. Hardness, Young's modulus, and flexural strength of B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> are enhanced, compared to the B<SUB>4</SUB>C-free Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> polycrystals. On the other hand, the thermoelectric figure-of-merit of B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> is almost identical to that of the pure Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB>. Such enhancements of the mechanical properties of the B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> are attributed to the grain boundary hardening and second-phase hardening. Beyond thermoelectric materials, our result implies that the grain refinement by nanoparticle dispersion is a simple and promising way to strengthen the mechanical properties of other brittle materials with layered structure.

Thermopower Enhancement of Bi2Te3 Films by Doping I Ions

Kim, K. C.,Baek, S. H.,Kim, H. J.,Hyun, D. B.,Kim, S. K.,Kim, J. S. Springer Science + Business Media 2014 Journal of electronic materials Vol.43 No.6

The thermoelectric properties of I-doped Bi2Te3 films grown by metal-organic chemical vapor deposition have been studied. I-doped epitaxial (00l) Bi2Te3 films were successfully grown on 4A degrees tilted GaAs (001) substrates at 360 A degrees C. I concentration in the Bi2Te3 films was easily controlled by the variation in a flow rate of H-2 carrier gas for the delivery of an isopropyliodide precursor. As I ions in the as-grown Bi2Te3 films were not fully activated, they did not influence the carrier concentration and thermoelectric properties. However, a post-annealing process at 400 A degrees C activated I ions as a donor, accompanied with an increase in the carrier concentration. Interestingly, the I-doped Bi2Te3 films after the post-annealing process also exhibited enhancement of the Seebeck coefficient at the same electron concentration compared to un-doped Bi2Te3 films. Through doping I ions into Bi2Te3, the thermopower was also enhanced in Bi2Te3, and a high power factor of 5 x 10(-3) W K-2 m(-1) was achieved.

High-Pressure Synthesis of $SmFeAsO_{1-x}F_x$(x=0.2) Single Crystals

이현숙,박재현,이재엽,김주영,조병기,정창욱,이후종,Lee, Hyun-Sook,Park, Jae-Hyun,Lee, Jae-Yeap,Kim, Ju-Young,Cho, B.K.,Jung, Chang-Uk,Lee, Hu-Jong The Korean Superconductivity Society 2009 Progress in superconductivity Vol.10 No.2

Fluorine-doped $SmFeAsO_{1-x}F_x$ single crystals with the nominal value of x=0.2 were grown at $1350-1450^{\circ}C$ under the pressure of 3.3 GPa by using the self-flux method. Plate-shaped single crystals in the range of a few-150 ${\mu}m$ in their lateral size were obtained. The detailed crystal structure was analyzed by using the x-ray diffractometry. Superconducting transition temperature, determined by the resistive transition, of a single crystal was about 49 K with a narrow resistive transition width of ${\sim}1$ K. A relatively sharp transition, a low residual resistivity, and a large residual resistivity ratio compared with those reported for $REFeAsO_{1-x}F_x$(RE=Sm, Nd) single crystals indicate the high quality of our single crystals.

Characterization and in Vitro Inhibition Studies of Bacillus anthracis FtsZ: A Potential Antibacterial Target

Park, H. C.,Gedi, V.,Cho, J. H.,Hyun, J. W.,Lee, K. J.,Kang, J.,So, B.,Yoon, M. Y. HUMANA PRESS INC 2014 Applied biochemistry and biotechnology Vol.172 No.6

FtsZ is an essential bacterial cell division protein that is an attractive target for the development of antibacterial agents. FtsZ is a homologue of eukaryotic tubulin, has GTPase activity, and forms a ring-type structure to initiate cell division. In this study, the FtsZ of Bacillus anthracis was cloned into a bacterial expression vector and overexpressed into Escherichia coli BL21 (DE3) cells. The overexpressed B. anthracis FtsZ was soluble and purified to homogeneity using Ni-His-tag affinity chromatography. Like other known FtsZs, the recombinant B. anthracis FtsZ also showed GTP-dependent polymerization, which was analyzed using both spectrophotometric and Transmission Electronic Microscopic (TEM) analysis. Using the purified FtsZ, we screened a naturally extracted chemical library to identify potent and novel inhibitors. The screening yielded three chemicals, SA-011, SA-059, and SA-069, that inhibited the in vitro polymerization activity of FtsZ in the micromolar range (IC50 of 55-168 mu M). The inhibition potency was significantly comparable with that of berberine, a known potential inhibitor of FtsZ. Understanding the biochemical basis of the effect of these inhibitors on B. anthracis growth would provide a promising path for the development of new antianthracis drugs.

Down-regulation of tyrosinase, TRP-1, TRP-2 and MITF expressions by citrus press-cakes in murine B16 F10 melanoma

Kim, S.S.,Kim, M.J.,Choi, Y.H.,Kim, B.K.,Kim, K.S.,Park, K.J.,Park, S.M.,Lee, N.H.,Hyun, C.G. China Humanity Technology Publishing House 2013 Asian Pacific journal of tropical biomedicine Vol.3 No.8

Objective: To investigate the suitability of citrus-press cakes, by-products of the juice industry as a source for the whitening agents for cosmetic industry. Methods: Ethylacetate extracts of citrus-press cakes (CCE) were examined for their anti-melanogenic potentials in terms of the inhibition of melanin production and mechanisim of melanogenesis by using Western Blot analysis with tyrosinese, tyrosinase-related protein-1 (TRP-1), TRP2, and microphthalmia-associated transcription factor (MITF) proteins. To apply the topical agents, citrus-press cakes was investigated the safety in human skin cell line. Finally flavonoid analysis of CCE was also determined by HPLC analysis. Results: Results indicated that CCE were shown to down-regulate melanin content in a dose-dependent pattern. The CCE inhibited tyrosinase, TRP-2, and MITF expressions in a dose-dependent manner. To test the applicability of CCE to human skin, we used MTT assay to assess the cytotoxic effects of CCE on human keratinocyte HaCaT cells. The CCE exhibited low cytotoxicity at 50 μg/mL. Characterization of the citrus-press cakes for flavonoid contents using HPLC showed varied quantity of rutin, narirutin, and hesperidin. Conclusions: Considering the anti-melanogenic activity and human safety, CCE is considered as a potential anti-melanogenic agent and may be effective for topical application for treating hyperpigmentation disorders.

PINUS RIGDA X P. TAEDA. PINUS RIGIDA X P. RADIATA 및 PINUS RIGIDA X P. ELLIOTT의 授精過程

玄信圭,任慶彬 서울대학교 1963 서울대학교 論文集 Vol.13 No.-

1) Pinus rigida x P. taeda,P rigida x P. radiata, 및 P. rigida x P. elliottii에 있어서 그 授精過程을 組織學的으로 究明코저 1961年 5月 上旬에 授粉된 球果를 1962年 4月 5日 에서 8月 1日에 이르기까지 5回에 걸쳐 採取하여 Formaldehyde-Ethyl alcohol acetic acid 液에 固定하고 胚珠만을 抽出하여 Paraffin embedding, Sectioning 및 Safranin 과 Hematoxylin에 依한 二重染色에 依하여 檢鏡하였다. 2) 授粉後 260日頃인 5月 4日 採取材料에 있어서도 胚珠의 生長을 볼 수 있었으나 授粉後 390日이 經過된 6月 6日 採取材料에서부터 胚珠의 顯著한 發達을 볼 수 있었다. 3) 胚珠의 發達度는 Pinus rigida x Pinus. taeda 에서는 Pinus rigida x wind에 比하여 큰 差異가 없었으나 Pinus rigida x P. radiata 및 P. rigida x P. elliottii에 있어서는 顯著하게 不良함을 보았다. 4) 花粉管의 侵入狀態도 Pinus rigida x P. taeda 및 Pinus rigida x P. elliottii에서는 觀察할 수 있었으나 Pinus rigida x P. radiata에 있어서는 이를 觀察치 못하였다. 5) 授精의 結果 形成되는 胚의 發達도 Pinus rigida x P. radiata에서는 볼 수 없었으므로 Pinus rigida x P. radiata 는 交配親和力이 없는 것같이 보였으나 實地交配結果 相當한 量의 稔性種子의 生産을 보았으므로 이 組合의 交雜의 眞相을 알기 爲하여는 7月 上旬頃에 일어나리라고 推測되는 授精現象을 追窮할 必要가 있다. 6) 以上에 依하여 上記組合間의 交雜親和力은 分類學의 類綠과 密接한 關係가 있음을 알 수 있다. 1.The sequences of fertilization which have taken place during the period from 330 days to 450 days after pollination in the following three interspecies hybridization of pines were observed. Pinus rigida x P. taeda Pinus rigida x P. radiata Pinus rigida x P. elliottii 2. The growth of nucellus of ovulate cones already noticiable in all crossings from the first 12 months after the pollination, and the remarkable growth of the nucellus were taken place from 13 months after pollination. 3. The growth rate nucellus, however, was differ among the crosses, being the highest in the cross of Pinus rigida x P. taeda and the lowest in the cross of Pinus rigida x P. radiata, thus indicating the poor crossability between Pinus rigida x P. radiata. As a matter of fact, the megasporangia tissues have become gradually shriveled even though the size of nucellus has shown an increase in the cross of Pinut rigida x P. radiata. 4. In the light of the fact that a considerable amount of fertile hybrid seeds of Pinus rigida x P. radiata were obtained despite of no evidence of successful development of the nucellus of the sample cones, further investigation on the mechanism of the success and the failure in the fertilization of the crossing of Pinus rigida x P. radiata is needed. 5. The actual fertilization seemed to take pace in some time of middle of July in those crossings. 6. It may be said, however, that the crossability between species nould be an indices of the affinities between based on an evolutional view point.

松類의 揷木에 關한 硏究 (第一報) : 季節과 生長素가 Pinus Rigida 揷木의 發根에 미치는 影響 The Effects of Season of Collection and Growth Substances on the Rooting of Cuttings of Pinus Rigida

玄信圭,任慶彬 서울대학교 1956 서울대학교 論文集 Vol.3 No.-

In order to find out the basic factors governing the rooting ability of pine cuttings, the rooting of cuttings of Pinus rigida were examined under various conditions. A total of 17 different solutions of growth hormones made up of 3- indole butyric acid, 3- indole acetic acid and naphthalene acetic acid were employed at three different times of year the middle of April, early June and the middle of July. Cuttings were prepared from the terminal shoots os 1-1 transplant of Pinus rigida growing in the nursery beds of the School of Forestry in Suwon. The terminal shoots used in April were one year old, whereas those used in June and July were newly formed shoots in the current year. Fifty cuttings of 10 to 15cm in length were prepared for each item of treatment, and the needles on the lower one-third part of the shoots were taken off before these cutting were sbjected to treatment. In treatting the cuttings, the ends of cuttings were kept in desingnated growth-substances solution for 24 hours. The cuttings, after treatment, were planted in the nursery bed, and were covered with double layer of lath screen, and were watered once every day. The assessment on the rooted cuttings was made on September 6th and the result has shown a wide variation in the number of rooted cutting ranging from zero to a maximum of 20 percent of the total number of treated cuttings planted in accordance with the time of planting and the kind of growth-substances employed. A general trend noted was that earlier in the growing season treated cuttings were planted, the larger was the proportion which rooted. And it was also shown that cuttings of Pinus figida do not root irrespective of the time of planting unless treated with growth-substances.

Slag/Metal 향유유통 (向流流通) 에 의한 용선의 연속정련법 연구

현도빈,김경식,심재동,오영주,정형효 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.6

The continuous refining process which enables to refine the molten iron in stream lined flow was studied the slag metal counter current operating method in runner type reactor. The simultaneous desiliconization and dephosphorization proceeded over 60% in spite of high Si content, while the decarburization was supressed. The simulation model based on the mass transfer in reaction zones with and without O₂ blowing expressed fairly the actual reaction in the reactor. The contributions of the slag/metal reaction zone with out O₂blowing were estimated to be 26-32% for desiliconization and 47-53% for dephosphorization. From the results obtained here, the continuous process for pre-treatment of molten pig iron was conformed to be possible technically.

전도성 Al-ZnO (AZO) 나노입자의 광경화 투명 코전도성 Al-ZnO(AZO) 나노입자의 광경화 투명 코팅

김현종 ( Hyun Jong Kim ),신치호 ( Chi Ho Shin ),문정호 ( Jung Ho Moon ),한명근 ( M. K. Han ),임병태 ( B. T. Lim ),신태욱 ( T. W. Shin ) 한국공업화학회 2010 응용화학 Vol.14 No.2

Al-doped ZnO (AZO) nanoparticle was synthesized with the size of 100 nm and the sheet resistance of 445 kΩ/□ by polyol precess. The synthesized AZO nanoparticle was directly dispersed in iso-propyl alcohol to form a homogeneous solution. Then, it was mixed with photocurable acrylate monomer which was act as the both of binder and stabilizer, when the AZO was coated on the slide glass, it showed better transparency and conductivity than commercial one.

난소과자극 증후군 1예

이병석,박기현,박찬규,허갑범,이현철,임승길,조용욱,김유곤 대한내분비학회 1988 Endocrinology and metabolism Vol.3 No.2

Ovarian hyperstimulation syndrome (OHS) is a rare complication in the use of human menopausal gonadotropin (HMG) and human chorionic gonadotropin (HCG) for ovulation induction. The pathophysiology is unclear and treatments are mainly conservative. We presented a case of ovulation induction with HMG and HCG in secondary amenorrhea due to hypogonadotropic hypogonadism after brain surgery for craniopharyngeoma with abscess formation. A brief review on the literatures was made in comment.