Stoichiometric Layered Potassium Transition Metal Oxide for Rechargeable Potassium Batteries

Kim, Haegyeom,Seo, Dong-Hwa,Urban, Alexander,Lee, Jinhyuk,Kwon, Deok-Hwang,Bo, Shou-Hang,Shi, Tan,Papp, Joseph K.,McCloskey, Bryan D.,Ceder, Gerbrand American Chemical Society 2018 Chemistry of materials Vol.30 No.18

<P>K-ion batteries are promising alternative energy storage systems for large-scale applications because of the globally abundant K reserves. K-ion batteries benefit from the lower standard redox potential of K/K<SUP>+</SUP> than that of Na/Na<SUP>+</SUP> and even Li/Li<SUP>+</SUP>, which can translate into a higher working voltage. Stable KC<SUB>8</SUB> can also be formed via K intercalation into a graphite anode, which contrasts with the thermodynamically unfavorable Na intercalation into graphite, making graphite a readily available anode for K-ion battery technology. However, to construct practical rocking-chair K-ion batteries, an appropriate cathode material that can accommodate reversible K release and storage is still needed. We show that stoichiometric KCrO<SUB>2</SUB> with a layered O3-type structure can function as a cathode for K-ion batteries and demonstrate a practical rocking-chair K-ion battery. In situ X-ray diffraction and electrochemical titration demonstrate that K<SUB><I>x</I></SUB>CrO<SUB>2</SUB> is stable for a wide K content, allowing for topotactic K extraction and reinsertion. We further explain why stoichiometric KCrO<SUB>2</SUB> is unique in forming the layered structure unlike other stoichiometric K-transition metal oxide compounds, which form nonlayered structures; this fundamental understanding provides insight for the future design of other layered cathodes for K-ion batteries.</P> [FIG OMISSION]</BR>

Relationship Between K_trans and K₁ with Simultaneous Versus Separate MR/PET in Rabbits with VX2 Tumors

Lee, K. H.,Kang, S. K.,Goo, J. M.,Lee, J. S.,Cheon, G. J.,Seo, S.,Hwang, E. J. INTERNATIONAL INSTITUTE OF ANTICANCER RESEARCH 2017 Anticancer research Vol.37 No.3

<P>Background/Aim: To compare the relationship between Ktrans from DCE-MRI and K1 from dynamic (NNH3)-N-13- PET, with simultaneous and separate MR/PET in the VX-2 rabbit carcinoma model. Materials and Methods: MR/PET was performed simultaneously and separately, 14 and 15 days after VX-2 tumor implantation at the paravertebral muscle. The Ktrans and K-1 values were estimated using an in-house software program. The relationships between Ktrans and K-1 were analyzed using Pearson's correlation coefficients and linear/non-linear regression function. Results: Assuming a linear relationship, Ktrans and K-1 exhibited a moderate positive correlations with both simultaneous ( r=0.54-0.57) and separate ( r=0.53-0.69) imaging. However, while the Ktrans and K-1 from separate imaging were linearly correlated, those from simultaneous imaging exhibited a non-linear relationship. The amount of change in K-1 associated with a unit increase in Ktrans varied depending on Ktrans values. Conclusion: The relationship between K-trans and K-1 may be mis-interpreted with separate MR and PET acquisition.</P>

고온기 초지의 예취관리에 관한 연구 6 . 고온기간중 예취높이와 질소 및 칼리추비가 혼파초지의 식생과 수량 및 목초품질에 미치는 영향

서성(S . Seo),조무환(M . H . Jo),박문수(M . S . Park),이종경(J . K . Lee),한영춘(Y . C . Han) 한국축산학회 1988 한국축산학회지 Vol.30 No.8

A field experiment was carried out to determine the effects of cutting height at the third cut and application of N and K₂O after cutting during mid-summer season on the soil temperature, plant height, grass coverage, percentages of grass and legume, yield and grass quality in orchardgrass dominated pasture. With three cutting heights (3, 6 and 9㎝) and 4 fertilizer levels (0, N 50㎏, K₂O 50㎏, and N 50㎏ + K₂O 50㎏ ㏊^(-1)), present experiment was conducted at Livestock Experiment Station, Suwon in 1987. 1. The soil temperature after the third cut was rapidly elevated, and lower value was observed with 9㎝ of cutting height through the regrowth period. Plant height after cutting was remarkably increased with higher stubble height regardless of fertilizer levels. 2. The grass coverage and percentage of grass were increased as stubble height was high, while the influence of fertilizer on those was very little. Application of N and K₂O with lower stubble height significantly increased the percentage of bareland. 3. The yield at the third cut was decreased with higher height. But the regrowth yield was significantly increased as the cutting height was increased regardless of fertilizer levels. Regrowth yield was great at N 50㎏ + K₂O 50㎏ $gt; 0 $gt; K₂O 50㎏, N 50㎏, in that order. However, there were not significantly different on regrowth yield among fertilizer treatment. 4. The contents of crude protein, crude fat, crude ash, P, K and Ca were decreased as stubble height was high, and that of crude fiber was increased at 9 ㎝ cutting height. Also the influence of N and K₂O fertilizer on grass quality was little.

TMEM175 Is an Organelle K⁺ Channel Regulating Lysosomal Function

Cang, C.,Aranda, K.,Seo, Y.j.,Gasnier, B.,Ren, D. Cell Press ; MIT Press 2015 Cell Vol.162 No.5

Potassium is the most abundant ion to face both plasma and organelle membranes. Extensive research over the past seven decades has characterized how K<SUP>+</SUP> permeates the plasma membrane to control fundamental processes such as secretion, neuronal communication, and heartbeat. However, how K<SUP>+</SUP> permeates organelles such as lysosomes and endosomes is unknown. Here, we directly recorded organelle K<SUP>+</SUP> conductance and discovered a major K<SUP>+</SUP>-selective channel K<SUB>EL</SUB> on endosomes and lysosomes. K<SUB>EL</SUB> is formed by TMEM175, a protein with unknown function. Unlike any of the ~80 plasma membrane K<SUP>+</SUP> channels, TMEM175 has two repeats of 6-transmembrane-spanning segments and has no GYG K<SUP>+</SUP> channel sequence signature-containing, pore-forming P loop. Lysosomes lacking TMEM175 exhibit no K<SUP>+</SUP> conductance, have a markedly depolarized ΔΨ and little sensitivity to changes in [K<SUP>+</SUP>], and have compromised luminal pH stability and abnormal fusion with autophagosomes during autophagy. Thus, TMEM175 comprises a K<SUP>+</SUP> channel that underlies the molecular mechanism of lysosomal K<SUP>+</SUP> permeability.

A Design of Transferable Sample Holder for Resistive Heating and Conductive Cooling

Seo, J.M.,Kim, K.J.,Ihm, S.,Koo, S.J.,Park, Ch.,Kim, Y.K. 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-

통전가열, 접촉냉각, 전기적 bias 및 시료 교환을 자유로이 할 수 있는 다기능의 새롭고 간단한 시료 고정장치를 저온 및 초고진공 상태에서 기체와 여러 방향의 시료표면 사이의 상호작용을 연구하기 위하여 고안하였다. 이 장치로써 2분 이내에 기판의 온도를 1600 K에서 20 K로 2분 이내에 냉각시킬 수 있었다. 그러므로 청결한 표면위에 수소나 He이나 Ne을 제외하고는 대부분의 기체를 흡착시킬 수 있게 되었다. 이러한 장치는 표면에서의 상변화, 기체와 표면의 화학반응의 연구에 중요하게 활용될 수 있다. A simple and novel sample-holder which has multi-functions of resistive heating, conductive cooling, electrical biasing and sample exchanging has been designed in order to inverstigate gas-surface interations for various surface direction under ultrahigh vacuum and low temperature. It has been proved that the wafer can be cooled from 1600 K to 20 K within two minutes. Therefore the controlled adsorption of most gases, except H, He and Ne, were possible on the clean surfaces. The design has substantial applocations in areas like surface phase transitions and gas-surface chemical reactions.

망간계 산화물 La₁??Ce??MnO₃(x=0.2, 0.3, 0.4)의 전기,자기 및 열적 특성 연구

서금영,이보화 한국외국어대학교 외국학종합연구센터 부설 기초과학연구소 1999 기초과학연구 Vol.9 No.-

망간계 산화물 La₁???Ce??MnO₃(x=0.2, 0.3, 0.4)의 전기, 자기 및 열적 특성에 관한 연구를 X-선 회절, 전기저항, 자화율, 비열 및 광음향 신호 측정을 통하여 수행하였다. LaMnO₃의La대신 Ce 이온의 치환은 강자성 정렬의 발생과 더불어서 금속-절연체의 전이를 일으킨다. 강자성 전이는 x=0.2, 0.3, 0.4에 대햐여 각각 249K, 259K, 249K에서 일어난다. x=0.3의 경우, 온도에 따른 비저항 곡선에서 열적 이력현상은 관찰할 수 없었으며, 광음향 신호의 크기의 변화 또한 온도를 올리거나 내리는 경우 같은 온도에서 일어났다. 이것은 상전이가 전이온도에서 잠열이 존재하지 않는 2차 상전이임을 의미한다. Resencwaig와 Gersho의 이론을 사용하여 열전도도의 상대적인 값을 광음향 신호에서 얻을 수 있었다. Electric, magnetic, and therma] properties for La₁???Ce??MnO₃ (x=0.2, 0.3, 0.4) were investigated by means of X-ray diffraction, electrical resistivity, magnetization, specific heat, and photoacoustic signal measurements. The substitution of La by Ce in LaMnO₃ induces a metal-insulator transition accompanied by the occurrence of ferromagnetic ordering. The ferromagnetic transition temperatures are 249K, 259K, 249K for x=0.2, 0.3, 0.4, respectively. For x=0.3, there is no observable thermal hysteresis in resistivity measurement, and the change of photoacoustic signal amplitude arises at the same temperature in both cases with decreasing and increasing temperatures. This implies that the phase transition can be regarded as a second-order phase transition with no latent heat at transition temperature. Using Rosencwaig and Gersho's theory, the relative value of thermal conductivity can be obtained from the photoacoustic signal.

Enhancement of methane-water volumetric mass transfer coefficient by inhibiting bubble coalescence with electrolyte

Kim, K.,Lee, J.,Seo, K.,Kim, M.G.,Ha, K.S.,Kim, C. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.33 No.-

<P>The effect of electrolyte on methane-water volumetric mass transfer coefficient (k(L)a) was investigated in this study. Various electrolytes including MgSO4, K2SO4, Na2SO4, MgCl2, KCl, NaCl, MgBr2, NaBr, KBr, Mg(NO3)(2), KNO3, and NaNO3 were employed and enhancement of k(L)a from 103 h(-1) (in pure water) to 711 h(-1) was observed, depending on electrolyte type and concentration. This is the highest methanewater kLa value measured at ambient condition. For all electrolytes, ions with large charge density (charge valency per ionic volume) exhibited larger enhancement in methane-water kLa values. Furthermore, anions exhibited larger influence than cations on the enhancement of k(L)a. Enhancement of methane-water kLa by electrolytes was due to the inhibition of methane bubble coalescence. (C) 2015 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>

Characterization of glycosyl hydrolase family 3 β-N-acetylglucosaminidases from Thermotoga maritima and Thermotoga neapolitana

Choi, K.H.,Seo, J.Y.,Park, K.M.,Park, C.S.,Cha, J. Society for Bioscience and Bioengineering, Japan ; 2009 Journal of bioscience and bioengineering Vol.108 No.6

The genes encoding β-N-acetylglucosaminidase (nagA and cbsA) from Thermotoga maritima and Thermotoga neapolitana were cloned and expressed in Escherichia coli in order to investigate whether Thermotoga sp. is capable of utilizing chitin as a carbon source. NagA and CbsA were purified to homogeneity by HiTrap Q HP and Sephacryl S-200 HR column chromatography. Both enzymes were homodimers containing a family 3 glycoside hydrolase (GH3) catalytic domain, with a monomer molecular mass of 54 kDa. The optimal temperatures and pHs for the activities of the β-N-acetylglucosaminidases were found to be 65-75 <SUP>o</SUP>C and 7.0-8.0, respectively. Both enzymes hydrolyzed chitooligomers such as di-N-acetylchitobiose and tri-N-acetylchitotriose, and synthetic substrates such as p-nitrophenyl-β-d-glucose (pNPGlc), p-nitrophenyl N-acetyl β-d-glucosamine (pNPGlcNAc), p-nitrophenyl di-N-acetyl β-d-chitobiose (pNPGlcNAc<SUB>2</SUB>) and p-nitrophenyl tri-N-acetyl β-d-chitotriose (pNPGlcNAc<SUB>3</SUB>). However, the enzymes had no activity against p-nitrophenyl-β-d-galactose (pNPGal) and p-nitrophenyl N-acetyl β-d-galactosamine (pNPGalNAc) or highly polymerized chitin. The k<SUB>cat</SUB> and K<SUB>m</SUB> values were determined for pNPGlcNAc, pNPGlcNAc<SUB>2</SUB> and pNPGlcNAc<SUB>3</SUB>. The k<SUB>cat</SUB>/K<SUB>m</SUB> value for pNPGlcNAc was the highest among three synthetic substrates. NagA and CbsA initially hydrolyzed p-nitrophenyl substrates to give GlcNAc, suggesting that the enzymes have exo-activity with chitin oligosaccharides from the non-reducing ends, like other β-N-acetylglucosaminidases. However, NagA and CbsA can be distinguished from other GH3-type β-N-acetylglucosaminidases in that they are highly active against di-N-acetylchitobiose. Thus, the present results suggest that the physiological role of both enzymes is to degrade the chitooligosaccharides transported through membrane following hydrolysis of chitin into β-N-acetylglucosamine to be further metabolized in Thermotoga sp.

Synthesis and Thermoelectric Properties of Ce1−z Pr z Fe4−x Co x Sb12 Skutterudites

Song, K. M.,Shin, D. K.,Jang, K. W.,Choi, S. M.,Lee, S.,Seo, W. S.,Kim, I. H. Springer Science + Business Media 2017 Journal of electronic materials Vol.46 No.5

<P>p-Type Ce1-z Pr (z) Fe4-x Co (x) Sb-12 skutterudites were prepared by encapsulated melting, quenching, annealing, and hot pressing. While the skutterudite phase was successfully synthesized, a small amount of the secondary phase (FeSb2) was observed. According to the scanning electron microscope analysis, (Ce,Pr)Sb-2 phases were also observed for Co-substituted specimens (x = 0.5). The electrical conductivity decreased with increasing temperature, implying a degenerate semiconductor behavior, and also decreased with increasing Co contents. All specimens showed p-type characteristics having positive signs of the Hall coefficient and the Seebeck coefficient. The Seebeck coefficient increased with increasing temperature and reached a maximum value at 823 K. The power factor (PF) increased with decreasing Co content and Ce0.75Pr0.25 Fe4Sb12 showed a peak value of PF = 3.2 mW m(-1) K-2 at 823 K. The electronic thermal conductivity decreased with increasing Co contents and the lattice thermal conductivity decreased with decreasing Ce and Co contents at high temperature. The thermal conductivity increased at temperatures above 623 K due to bipolar conduction. The dimensionless figurea of pound merit (ZT) showed a maximum value of ZT = 0.84 at 823 K for Ce0.25Pr0.75Fe4Sb12.</P>

Existence of metastable molecular precursors to dissociative oxygen chemisorption on Si(111) and Si(100) at 40 K

Seo, J. M.,Kim, K. J.,Yeom, H. W.,Park, Ch. 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-

The presence of metastable molecular precursor to dissociative oxygen chemisorption has been identified, for the first time, on Si(100) and Si(111) surfaces using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy at 40 K. Density of valence states for such species shows three distinct peaks at 1.8, 3.4, and 4.9 eV below the Fermi energy of substrates. The precursor stabilized on Si(100) at 40 K induces a large work- function increase of 1.5 eV at saturation coverage. It also gives rise to a shoulder to O 1s photoemission spectrum that it located at 1.2 eV lower binding energy than the O 1s peak of stable and dissociated oxygen species. It has been concluded that the major reason of a larger work-function increment at 40 K is the existence of a molecular precursor, or peroxy radical type, on Si(100) and Si(111). These results strongly suggest that exists a general mechanism of oxygen adsorption onto silicon surfaces.