Publications by authors named "Kum Chol Ri"

Sodium titanate NaTiO (NTO) has superior electrochemical properties as an anode material in sodium-ion batteries (SIBs), and Nb or V doping is suggested to enhance the electrode performance. In this work, we carry out systematic first-principles calculations of the structural, electronic and electrochemical properties of NTO and NaTiMO (M = Nb, V), using supercells to reveal the effect of Nb or V NTO-doping on its anode performance. It is found that Nb doping gives rise to the expansion of cell volume but V doping induces the shrinkage of cell volume due to the larger and smaller ionic radius of the Nb and V ions, respectively, compared to that of the Ti ion.

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Point defects can be formed readily in layered transition metal oxides used as electrode materials for alkali-ion batteries but their influence on the electrode performance is yet obscure. In this work, we report a systematic first-principles study of intrinsic point defects and defect complexes in sodium titanate NaTiO, a low-voltage anode material for sodium-ion batteries. Within the density functional theory framework, we calculate the defect formation energies with a set of atomic chemical potentials, which define the synthesis conditions for the stable NaTiO compound.

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Super-enhancer consists of a large cluster of transcription enhancers that regulates the expression of genes playing an important role in the growth and development of malignant tumors. Recently, several attempts for the identification of super-enhancers have been made, but their functional role in tumor cells remains unclear. This paper aims at elucidating the functional properties of KLF6 super-enhancer related to the growth regulation of HepG2 cells, in relation to transcription factors (TFs).

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A specific type II restriction endonuclease T.Smu451I has been purified to electrophoretic homogeneity from the frozen cells of soil bacterium Sphingobacterium multivorum 451 (formerly Flavobacterium multivorum 451), using ultrasonic grinding, nucleic acid removal by streptomycin sulfate, protein precipitation by ammonium sulfate and phosphocellulose P-11, DEAE-Cellulose DE-52, Hepharin-Sepharose CL-6B chromatography, and elucidated several characteristics of T.Smu451I.

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Due to their low cost and easy synthesis method, several kinds of sodium titanates have been explored as anode materials for sodium ion batteries (SIBs). However, some of them have not yet been considered as electrode materials for SIBs, and here we have carried out a first-principles study on NaTiO compounds with two different tunnel structures, denoted as single and double phases, to demonstrate their structural and electrochemical properties upon Na or Li insertion. Our calculation results reveal that these compounds exhibit structural stability during sodiation/desodiation and a moderate electrode voltage of ∼0.

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Photovoltaic solar cells based on organic-inorganic hybrid halide perovskites have achieved a substantial breakthrough via advanced interface engineering. Reports have emphasized that combining the hybrid perovskites with the Lewis base and/or graphene can definitely improve the performance through surface trap passivation and band alignment alteration; the underlying mechanisms are not yet fully understood. Here, using density functional theory calculations, we show that upon the formation of CHNHPbI interfaces with three different Lewis base molecules and graphene, the binding strength with S-donors thiocarbamide and thioacetamide is higher than with O-donor dimethyl sulfoxide, while the interface dipole and work function reduction tend to increase from S-donors to O-donor.

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Developing efficient anode materials with low electrode voltage, high specific capacity and superior rate capability is urgently required on the road to commercially viable sodium-ion batteries (SIBs). Aiming at finding a new SIB anode material, we investigate the electrochemical properties of NaxTiO2 compounds with unprecedented penta-oxygen-coordinated trigonal bipyramid (TB) structures by using first-principles calculations. Identifying the four different TB phases, we perform the optimization of their crystal structures and calculate their energetics such as sodium binding energy, formation energy, electrode potential and activation energy for Na ion migration.

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Bacillus circulans 528 produces a restriction endonuclease, Bci528I which is an isoschizomer of EcoRI. We purified the enzyme, using Sephadex G-150, Phospho-cellulose, DEAE-cellulose, Hepharin-Sepharose CL-6B chromatography. The specific activity of Bci528I was 29,400 U/mg·protein.

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Background: Recent studies have attempted to elucidate the function of super enhancers by means of microRNAs. Although the functional outcomes of miR-1301 have become clearer, the pathways that regulate the expressions of miR-1301 remain unclear.

Objective: The objective of this paper was to consider the pathway regulating expression of miR- 1301 and miR-1301 signaling pathways with the inhibition of cell proliferation.

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Among the recent achievements of sodium-ion battery (SIB) electrode materials, hybridization of two-dimensional (2D) materials is one of the most interesting appointments. In this work, we propose to use the 2D hybrid composites of SnS with graphene or graphene oxide (GO) layers as the SIB anode, based on the first-principles calculations of their atomic structures, sodium intercalation energetics, and electronic properties. The calculations reveal that a graphene or GO film can effectively support not only the stable formation of a heterointerface with the SnS layer but also the easy intercalation of a sodium atom with low migration energy and acceptable low volume change.

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