Fe₂O₃가 dope된 Na-K Borosilicate 유리의 Mossbauer 효과와 전기적 특성

동철,박문제,백승도 동국대학교 자연과학연구소 1986 자연과학연구 논문집 Vol.6 No.-

FeO(3~9 mole%)가 dope된 15% Na₂O : 14%K₂O 19%B₂O₃: 52%SiO₂유리구조를 Mossbauer spectroscopy로 조사하였으며 Fe₂O₃함량에 따른 d.c 전기전도와 유전율을 조사하였다. 상온에서 측정한 Mossbauer spectra를 Lorentzian line shape식에 fitting하여 얻은 isomer shipt값으로소 유리내에서 Fe가 Fe? 이온으로 존재하며 tetrahedral 구조를 가짐을 알 수 있었다. 또한isomer shift와 quadrupole splitting값을 변화가 없는 것으로 보아 Fe₂O₃양에 따른 구조 변화가 거의 없음을 알 수 있었다. 또한 d.c 전기전도도는 25~250℃ 영역에서 Fe₂O₃가 증가함에 따라 감소하였으며 유전율 역시 감소하였는데 이는 Fe₂O₃가 유리내에서 glass former로 작용하여 alkali 이온의 구속에 기인한다. Mossbauer parameters fo 15Na₂O-14K₂O-19B₂O₃-52SiO₂ glasses containning x Fe₂O₃ (3?x?9) have been studied at roon temperature. The d.c. conductivities and permities fo the glasses were measured over a temperature range from 25℃ to 250℃. From the isomer shift values of mossbauer spectra, it is concluded that the Fe ion is trivalent and the cordination number of Fe ion is four. The d.c. conductivities and permitivities of the glasses decreased as the Fe₂O₃concertration increased. These rewults mean that the Fe₂O₃behaves like a glass-forming oxide.

A Study on the Reduction Mechanism of Wustite in CO/CO₂and H₂/H₂O Systems

Cho,Tong-Rae,Hayes,P.C. 忠南大學校 産業技術硏究所 1986 산업기술연구논문집 Vol.1 No.2

본 연구는 Wustite가 CO/CO₂, H₂/H₂O 가스에 의해 환원될 때의 환원기구를 연구하였다. Wustite 가 CO/CO₂, H₂/H₂O가스에 의해 환원될 때 먼저 표면에 환원철의 딱딱한 피막이 형성된다. 이 피막속으로 H₂중의 H나 CO중의 C가 확산해 들어가서 가스핵 (adsorbed speices)을 만들고 이 가스핵이 모여서 기포(gas bubble)을 만든다. 이 기포가 팽창해서 피막을 터지게 하고, 이터진 부분으로 가스가 들어가서 환원이 진행된다. 이 현상이 반복되어 환원이 진행된다. 이때 가스핵의 양은 기포의 크기를 결정하는데 가스핵의 양이 많으면 큰 기포를 만들고, 작으면 작은 기포를 만드는데 이것은 환원철의 기공(pore of porour Iron)의 크기를 결정한다. 즉, 피막의 터짐을 좌우하는 인자는 ①반응가스농도, ②반응가스온도, ③반응시간, ④Wusitie의 결정구조, ⑤철피막의 구조등이다. Examination of wustite single crystals reduced in CO/CO₂and H₂2/H₂O gas mixtures has shown that in all cases a dense iron layer is formed initially on the oxide surface and that the porous growth of iron which is obtained under certain experimental conditions occurs as a direct result of the breakdown of this initial dense iron layer. Possible mechanisms of the iron layer breakdown are examined and compared with the experimental observations. A model of the breakdown process involving the nucleation of gas bubbles and the expansion of these bubbles in the iron layer is presented. The breakdown of preformed dense iron layers on wustite during reduction in CO/CO₂gas mixtures which has been observed in previous is confirmed. The present investigation has also shown that the breakdown of preformed dense iron layers can occur in H₂/H₂O systems. In addition it has been show that in single stage reductions under all conditions that lead to a final porous iron morphology, a dense iron layer initially covers the wustite surface. Therefore porous iron morphologies occur as a direct result of the breakdown of dense iron layers and hence the breakdown is an essential prerequisite for porous growth. During the reduction of wustite covered with a dense iron layer in CO/CO₂or H₂/H₂O systems, carbon or hydrogen diffuse to the iron/wustite interface where they may form adsorbed species. The bursting phenomena must involve the nucleation of gas bubbles and the expansion of these bubbles to an extent where fracturing of the covering iron layer occurs allowing direct gas access to the underlying wustite. In the refinement of the bursting model presented in the present paper it is argued that the nucleation of gas bubbles depends both upon the concentration of adsorbed species and the defect concentrations at the iron/wustite interface, and that the expansion of the bubbles is determined by the gas pressures generated in the bubbles and the strength of the iron layer. Experimental evidence indicates that the gas pressures generated in the bubbles are much greater than those predicted from equilibrium considerations. It therefore appears that the gas pressures are determined by the rates of desorption of the adsorbed species from the solid/solid interfaces. At the present time it is not possible to show categorically which of these mechanisms, void nucleation or fracture of the layer, controls the bursting. However, the evidence obtained from experiments in H₂/N₂and CO/CO₂systems and the effect of iron upon the limiting conditions for porous growth in H₂/H₂O gas mixtures suggests that in most cases void nucleation is limiting.

Axotomy-induced dopaminergic neurodegeneration is accompanied with c-Jun phosphorylation and activation transcription factor 3 expression

Song, Dae Y.,Yang, Young C.,Shin, Dong H.,Sugama, Shuei,Kim, Yoon S.,Lee, Bong H.,Joh, Tong H.,Cho, Byung P. Elsevier 2008 Experimental neurology Vol.209 No.1

<P><B>Abstract</B></P><P>Accumulating evidence has shown that both phosphorylated c-Jun (pc-Jun) and activating transcription factor 3 (ATF3) were upregulated in a variety of tissue injuries and proposed to play an important role in cell death/survival. To elucidate the significance and functional role of these immediate-early genes during neuronal damage in the central nervous system, we examined temporal and spatial profiles of pc-Jun and ATF3 in dopaminergic neurons of the substantia nigra (SN) following transection of the medial forebrain bundle (MFB) in adult rats. Morphological characteristics of pc-Jun-positive dopaminergic neurons as well as microglial reaction in response to the axotomy-induced neurodegeneration were also investigated. Following MFB transection, both c-Jun phosphorylation and ATF3 were found in the nuclei of tyrosine hydroxylase-immunoreactive (TH-ir) neurons of the ipsilateral SN, but not in those of the contralateral SN. In the ipsilateral SN, the number of pc-Jun- and ATF3-positive nuclei was increased by 5–7?days post-lesion, and then progressively decreased probably due to the loss of neurons. Retrograde tracing with FluoroGold (FG) in hemi-axotomized rat brain demonstrated that none of the intact, unaxotomized (FG-ir) neurons was pc-Jun-positive, indicating phosphorylation of c-Jun occurs only in axotomized neurons. Concomitant co-localization of pc-Jun and ATF3 in the same TH-ir neuron was also demonstrated by triple immunofluorescence labeling. Many TH-ir neurons that underwent various steps of consecutive neurodegenerative changes retained pc-Jun in the condensed or fragmented nuclei. Moreover, numerous activated microglia, identified by both phagocytic (ED1) and MHC II (OX6) markers, closely apposed to these neurons throughout the entire neurodegenerative process, suggesting that they are actively phagocytosing dying neurons. Taken together, these results support the idea that pc-Jun and its putative dimeric partner ATF3 may be closely participating in axotomy-induced neurodegeneration.</P>

한국산 철광석에 관한 기초연구 (제3보) : 환원방정식 및 피환원성지수에 대하여 Reduction Equation and Reduciblity Index

조정완,윤동석 대한금속재료학회(대한금속학회) 1965 대한금속·재료학회지 Vol.3 No.2

In a stationary reducing atmosphere, H₂or CO, fifteen Korean iron ores were reduced at the temperatures ranging from 500℃ to 1050℃ to find out the effect of temperature on the reduction degree of iron ores. Generally an initial reduction rate is accelerated at the higher temperature. Most of the Korean magnetite, however, reach to the critical reduction degree at the range between 650℃ and 900℃. Temperature, on the other hand, has a minor effect on the critical reduction degree of hematite and siderite. It is found that reduction rate of H₂gas is 3∼4 times higher than that of CO at the magnetite reduction, and that initial reduction rate is reciprocal to the size of ore. Two types of reduction equation are available in accordance with the degree of reduction rate. At higher reduction rate, namely at an initial stage of reduction, for example. and at lower reduction rate, As a result of this investigation, the following formula is presented for the representation of reducibility in terms of "reducibility index."

Comprehensive in vitro and in vivo risk assessments of b-lactam antibiotic and b-lactamase inhibitor loaded chitosan nanoparticles

Arianna J. Partow,Miju Kim,Peixin Fan,Ting Liu,Zhaohui Tong,Kwangcheol C. Jeong 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.113 No.-

The safety of using nano-emulsion drug delivery systems is a growing concern. Here, we conducted riskassessments of an innovative combination therapy for multidrug resistant pathogens by encapsulatingcephalosporin antibiotics and b-lactamase inhibitors with chitosan nanoparticles (CNAIs) using in vitrohuman cell lines and an in vivo animal model, Caenorhabditis elegans. The four combinations of CNAIsincluding two cephalosporin antibiotics (cefotaxime and ceftiofur) with two b-lactamase inhibitors (tazobactamand clavulanate) were engineered as water–oil-water emulsions. CNAIs maintained stableantimicrobial activity in various thermal challenges. CNAIs exerted strong antimicrobial activity butdid not cause toxicity in human cell lines measured by cell membrane integrity, mitochondria activity,and reactive oxygen species generation. Reported damage was observed at 8 lg/mL and 16 lg/mL foronly two of the four combinations of CNAIs. More importantly, CNAIs at 4 lg/mL did not cause adverseeffects on the lifespan of C. elegans. In summary, CNAIs do not cause toxicity at working concentrationin vitro and in vivo risk assessments, suggesting that nano-emulsion drug delivery systems can be anew framework for developing treatments for multidrug pathogen infections.

Lespedeza sp. 뿌리혹에서 분리한 다양한 공생균의 식물생장촉진 특성

C.C.샤골 ( C. C. Shagol ),P.팔라니아판 ( P. Palaniappan ),P.S.차우한 ( P. S. Chauhan ),임우종 ( Woo Jong Yim ),이선미 ( Sun Mi Lee ),사동민 ( Tong Min Sa ) 한국토양비료학회 2010 한국토양비료학회 학술발표회 Vol.2010 No.1

Controlling field-emission patterns of isolated single-walled carbon nanotube rope (3 pages)

Tong, Y.,Lim, S. C.,Park, K. A.,Jeong, H. J.,Jeong, S. Y.,Lee, Y. H.,Liu, C.,Cheng, H.-M.,Choi, Y. AMERICAN INSTITUTE OF PHYSICS 2005 APPLIED PHYSICS LETTERS Vol.87 No.4

제련소 인근 중금속 오염토양에서 비소 내성 균주의 분리 및 동정

( C. C. Shagol ),주영규 ( Young Kyu Ju ),임우종 ( Woo Jong Yim ),( M. M Joe ),( P. S Chauhan ),정종배 ( Jong Bae Jung ),사동민 ( Tong Min Sa ) 한국토양비료학회 2011 한국토양비료학회 학술발표회 Vol.2011 No.-

Divergent reprogramming routes lead to alternative stem-cell states

Tonge, Peter D.,Corso, Andrew J.,Monetti, Claudio,Hussein, Samer M. I.,Puri, Mira C.,Michael, Iacovos P.,Li, Mira,Lee, Dong-Sung,Mar, Jessica C.,Cloonan, Nicole,Wood, David L.,Gauthier, Maely E.,Korn, Nature Publishing Group, a division of Macmillan P 2014 Nature Vol.516 No.7530

Pluripotency is defined by the ability of a cell to differentiate to the derivatives of all the three embryonic germ layers: ectoderm, mesoderm and endoderm. Pluripotent cells can be captured via the archetypal derivation of embryonic stem cells or via somatic cell reprogramming. Somatic cells are induced to acquire a pluripotent stem cell (iPSC) state through the forced expression of key transcription factors, and in the mouse these cells can fulfil the strictest of all developmental assays for pluripotent cells by generating completely iPSC-derived embryos and mice. However, it is not known whether there are additional classes of pluripotent cells, or what the spectrum of reprogrammed phenotypes encompasses. Here we explore alternative outcomes of somatic reprogramming by fully characterizing reprogrammed cells independent of preconceived definitions of iPSC states. We demonstrate that by maintaining elevated reprogramming factor expression levels, mouse embryonic fibroblasts go through unique epigenetic modifications to arrive at a stable, Nanog-positive, alternative pluripotent state. In doing so, we prove that the pluripotent spectrum can encompass multiple, unique cell states.

Statistical Study on the Fatigue Life of Tapered Roller Bearing with Roller Diameter Error

V. C. Tong(통반칸),S. W. Hong(홍성욱) 한국정밀공학회 2016 한국정밀공학회 학술발표대회 논문집 Vol.2016 No.10월