• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1061-1070
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• 2023

Over the last few years, lead-free inorganic metal perovskites have gained impressive ground in empowering satellites in space exploration owing to their material stability and performance evolution under extreme space environments. The present work has examined the versatility of eight such perovskites as space radiation shielding materials by computing their photon, charged particles and neutron interaction parameters. Photon interaction parameters were calculated for a wide energy range using PAGEX software. The ranges of heavy charged particles (H, He, C, N, O, Ne, Mg, Si and Fe ions) in these perovskites were estimated using SRIM software in the energy range 1 keV-10 GeV, and that of electrons was computed using ESTAR NIST software in the energy range 0.01 MeV-1 GeV. Further, the macroscopic fast neutron removal cross-sections were also calculated to estimate the neutron shielding efficiencies. The examined shielding parameters of the perovskites varied depending on the radiation type and energy. Among the selected perovskites, Cs₂TiI₆ and Ba₂AgIO₆ displayed superior photon attenuation properties. A 3.5 cm thick Ba₂AgIO₆-based shield could reduce the incident radiation intensity to half its initial value, a thickness even lesser than that of Pb-glass. Besides, CsSnBr₃ and La_0.8Ca_0.2Ni_0.5Ti_0.5O₃ displayed the highest and lowest range values, respectively, for all heavy charged particles. Ba₂AgIO₆ showed electron stopping power (on par with Kovar) better than that of other examined materials. Interestingly, La_0.8Ca_0.2Ni_0.5Ti_0.5O₃ demonstrated neutron removal cross-section values greater than that of standard neutron shielding materials - aluminium and polyethylene. On the whole, the present study not only demonstrates the employment prospects of eco-friendly perovskites for shielding space radiations but also suggests future prospects for research in this direction.

• Korean Journal of Environment and Ecology
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• v.38 no.2
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• pp.217-226
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• 2024

This study aimed to investigate the influence of anions in the air on the purification of fine dust (PM10 and PM2.5) and to evaluate the effects of plants on the generation of anions in the air and the purification of fine dust. Subsequently, the fine dust reduction models were compared according to each factor and plant volume. The characteristics of anion generation by each factor were observed to be in the order of Type N.I (negative ion generator; 204,133.33 ea/cm³) > Type P₃₀ (plant vol. 30%; 362.55 ea/cm³) > Type C (control; 46.22 ea/cm³), indicating that the amount of anion generation in the anion generator treatment group and the plant arrangement group were approximately 4,417 times and 7 times higher, respectively, than that in the untreated group. Consequently, the fine dust reduction characteristics by anion generation source showed that for PM10, Type NI had a purification efficiency 2.52 times higher than Type C, and Type P₃₀ was 1.46 times higher, while for PM2.5, Type NI had a purification efficiency 2.26 times higher than Type C, and Type P₃₀ was 1.31 times higher. The efficiency of fine dust purification by plant volume was in the order of Type P₂₀ (84.60 minutes) > Type P₃₀ (106.50 minutes) = Type P₂₅ (115.50 minutes) = Type P₁₅ (117.60 minutes) > Type P₅ (125.25 minutes) = Type P₁₀ (129.75 minutes), and for ultrafine dust, Type P₂₀ (104.00 minutes) > Type P₃₀ (133.20 minutes) = Type P₂₅ (144.00 minutes) = Type P₁₅ (147.60 minutes) > Type P₅ (161.25 minutes) = Type P₁₀ (168.00 minutes). Thus, a quantitative analysis of the anions and plants for purifying fine dust and suggested matters to be considered for future green space planning and plant planting considering fine dust purification.

• Journal of Microbiology
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• v.41 no.3
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• pp.207-211
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• 2003

Extracellular protease, from Aeromonas hydrophila Ni 39, was purified 16.7-fold to electrophoretic homogeneity with an overall yield of 19.9％, through a purification procedure of acetone precipitation, and Q Sepharose and Sephacryl S-200 chromatographies. The isoelectric point of the enzyme was 6.0 and the molecular mass, as determined by Sephacryl S-200 HR chromatography, was found to be about 102 kDa. SDS/PAGE revealed that the enzyme consisted of two subunits, with molecular masses of 65.9 kDa. Under standard assay conditions, the apparent $K_{m}$ value of the enzyme toward casein was 0.32 mg/ml. About 90％ of the proteolytic activity remained after heating at 60$^{\circ}C$ for 30 min. The highest rate of azocasein hydrolysis for the enzyme was reached at 60$^{\circ}C$, and the optimum pH of the enzyme was 9.0. The enzyme was inhibited by the serine protease inhibitor, phenylmethylsulfonyl fluoride (PMSF), by about 87.9％, but not by E64, EDTA, pepstatin or 1,10-phenanthroline. The enzyme activity was inhibited slightly by Ca$\^$2＋/, Mg$\^$2＋/ and Zn/supb 2＋/ ions.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1675-1680
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• 2012

Three new cyanide-bridged $Cr^{III}Mn^{II}$ binuclear complexes, $[Mn(phen)_2Cl][Cr(bpmb)(CN)_2]{\cdot}H_2O$ ($\mathbf{1}$) (phen = 1,10-phenanthroline, $bpdmb^{2-}$ = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate), $[Mn(phen)_2Cl][Cr(bpmb)-(CN)_2]{\cdot}H_2O$ ($\mathbf{2}$) ($bpdmb^{2-}$ = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate), and $[Mn(phen)_2Cl]-[Cr(bpClb)(CN)_2]{\cdot}CH_3OH{\cdot}H_2O$ ($\mathbf{3}$) ($bpClb^{2-}$ = 1,2-bis(pyridine-2-carboxamido)-4-chloro-benzenate) were obtained based on $Mn(phen)_2Cl_2$ and a series of dicyanidechromate(III) building blocks. Single crystal X-ray diffraction analysis shows the structures of the three complexes are dimeric type with two different metal centers linked by a cyanide group from corresponding dicyanidechromate(III) building block. Magnetic investigations indicate the existence of relatively weak antiferromagnetic coupling between Cr(III) and Mn(II) ions with best-fit constants $J_{CrMn}=-2.78(5)cm^{-1}$ for $\mathbf{1}$, $J_{CrMn}=-3.02(2)cm^{-1}$ for $\mathbf{2}$ and $J_{CrMn}=-2.27(3)cm^{-1}$ for $\mathbf{3}$ based on the spin exchange Hamiltonian = $-2J_{CrMn}\hat{S}_{Cr}\hat{S}_{Mn}$. The magneto-structural correlation of cyanide-bridged $Cr^{III}Mn^{II}$ complexes has been discussed at last.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.270-276
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• 2010

Nickel-copper foam electrodes with pore gradient micro framework and nano-ramified wall have been prepared by using an electrochemical deposition process. Growth habit of nickel-copper co-deposits was quite different from that of pure nickel deposit. In particular, the ramified structure of the individual particles was getting clear with chloride ion content in the electrolyte. The ratio of nickel to copper in the deposits decreased with the distance away from the substrate and the more chloride ions in the electrolyte led to the more nickel content throughout the deposits. Compositional analysis for the cross section of a ramified branch, together with tactical selective copper etching, proved that the copper content increased with approaching central region of the cross section. Such a composition gradient actually disappeared after heat treatment. It is anticipated that the pore gradient nickel-copper nanostructured foams presented in this work might be a promising option for the high-performance electrode in functional electrochemical devices.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.511-516
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• 2004

A Li$[Co_{0.17}Li_{0.28}Mn_{0.55}]O_2$ cathode compound was prepared by a simple combustion method. The X-ray diffraction pattern showed that this compound could be classified as ${\alpha} -NaFeO_2$ structure type with the lattice constants of a = 2.8405(9) ${\AA}$ and c = 14.228(4) ${\AA}$. According to XANES analysis, the oxidation state of Mn and Co ions in the compound were 4+ and 3+, respectively. During the first charge process, the irreversible voltage plateau at around 4.65 V was observed. The similar voltage-plateau was observed in the initial charge profile of other solid solution series between $Li_2MnO_3\;and\;LiMnO_2$ (M=Ni, Cr...). The first discharge capacity was 187 mAh/g and the second discharge capacity increased to 204 mAh/g. As the increase of cycling number, one smooth discharge profile was converted to two distinct sub-plateaus and the discharge capacity was slowly decreased. From the Co and Mn K-edge XANES spectra measured at different cyclic process, it can be concluded that irreversible transformation of phase is occurred during continuous cycling process.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.4
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• pp.344-350
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• 2006

Thermoplasma acidophilum is a thermoacidophilic archaeon that grows optimally at $59^{\circ}C$ and pH 2. Along with another thermoacidophilic archaeon, Sulfolobus solfataricus, it is known to metabolize glucose by the non-phosphorylated Entner-Doudoroff (nED) pathway. In the course of these studies, the specific activities of glyceraldehyde dehydrogenase and glycerate kinase, two enzymes that are involved in the downstream part of the nED pathway, were found to be much higher in T. acidophilum than in S. solfataricus. To characterize glycerate kinase, the enzyme was purified to homogeneity from T. acidophilum cell extracts. The N-terminal sequence of the purified enzyme was in exact agreement with that of Ta0453m in the genome database, with the removal of the initiator methionine. Furthermore, the enzyme was a monomer with a molecular weight of 49kDa and followed Michaelis-Menten kinetics with $K_m$ values of 0.56 and 0.32mM for DL-glycerate and ATP, respectively. The enzyme also exhibited excellent thermal stability at $70^{\circ}C$. Of the seven sugars and four phosphate donors tested, only DL-glycerate and ATP were utilized by glycerate kinase as substrates. In addition, a coupled enzyme assay indicated that 2-phosphoglycerate was produced as a product. When divalent metal ions, such as $Mn^{2+},\;CO^{2+},\;Ni^{2+},\;Zn^{2+},\;Ca^{2+},\;and\;Sr^{2+}$, were substituted for $Mg^{2+}$ the enzyme activities were less than 10% of that obtained in the presence of $Mg^{2+}$. The amino acid sequence of T. acidophilum glycerate kinase showed no similarity with E. coli glycerate kinases, which belong to the first glycerate kinase family. This is the first report on the biochemical characterization of an enzyme which belongs to a member of the second glycerate kinase family.

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.722-727
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• 2005

Cytosolic sialidase (Neu2), a member of the sialidase family that is responsible for hydrolysis of sialic acid from the terminal position of sialoglycoconjugates, is poorly expressed in skeletal muscle and not detected in any other adult tissues. Thus, we isolated Neu2 cDNA using splicing by overlap extension (SOEing). In order to further characterize this enzyme, a His-tagged derivative was expressed in the bacterial expression system and purified by $Ni^{2+}$-affinity chromatography. A recombinant product of approximately 42 kDa had sialidase activity toward 4-methyl-umbelliferyl-$\alpha$-D-N-acetylneuraminic acid (4MU-NeuAc). The optimal pH and temperature of the recombinant Neu2 for 4MU-NeuAc was 6.0 and $37.5^{\circ}C$, respectively. The metal ions, such as $Cu^{2+}\;and\;Cd^{2+}$, showed strong inhibitory effect on the activity of the enzyme. The enzyme efficiently hydrolyzed the gangliosides GM3 and GD3 and had relatively low activities on ganglioside GD1a and GD1b, $\alpha$2-3 sialyllactose, and sialylated glycoproteins such as fetuin, transferrin, and orsomucoid, but had hardly any activities on $\alpha$2-6 sialyllactose and ganglioside GM1 and GM2. We concluded that the recombinant Neu2 has a sialidase activity toward glycoproteins as well as gangliosides.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.2
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• pp.165-170
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• 2005

Al-Zn alloy/$MnO_2$, seawater cell was considered as a primary aqueous cell with an average voltage range from 1.0 to 1.1V, and the electrolyte of seawater was uptaken into the cell. Eventually, the capacity of its usage will be used for long-term. However, the more use of this cell, the higher corrosion phenomenon of the electrode occurred. Due to its corrosion phenomenon, one main default has been observed with gradual decrease during a discharge process. In this research, a common-used active material for anode was $LiNiO_2$. An active material for cathode, $Zn_{X}FeS_2$ was synthesized in high temperature by uptaken a small amount of 1.3 wt% of ZnS into $FeS_2$, one of the transition-metal dichalcogenides in high temperature. Consequently, based on their usages shown above, this secondary aqueous lithium cell could be more developed. This cell was shown as remarkable charge/discharge performance during the charge/discharge processes. This cathode with active material was given a considerable efficiency of inserting $Li^+$ ions. Moreever, in accordance with the characteristic of the crystal structure for $Zn_{x}FeS_2$, a small amount of ZnS was added which made it possible to reduce prominently velocity of corrosion during the charge/discharge cycle. By applying those merits, Al-Zn alloy/$MnO_2$ seawater cell will be used as a fundamental data in order to transform into a secondary aqueous cell.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.1
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• pp.11-23
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• 1998

The purpose of this study was to survey chemical distribution of inorganic elements and ions in the submicron particles, to characterize qualitatively emitting sources by factor analysis, and finally to reveal existing patterns in terms of chemical compounds by a stepwise multiple regression analysis. Total of 141 samples were collected by a cascade impactor from 1989 to1996. Fifteen chemical species (Al, Ba, Cd, K, Pb, Cu, Fe, Ni, $Cl^-, NO_3^-, SO_4^{2-}, K^+, Mg^{2+}, Ca^{2+}, and Na^+$) were characterized by AAS and IC. The study showed that average seasonal levels of submicron particulate matters $(d_p<0.43 \mum)$ were 18.7 $\mug/m^3$ in spring, 15.5 $\mug/m^3$ in summer, 15.7 $\mug/m^3$ in fall, and 24.5 $\mug/m^3$ in winter, respectively. All of the anion concentrations in the particle were highest in the winter season. By applying a factor analysis, 5 source patterns were qualitatively obtained, such as sulfate related source, nitrate related source, oil burning source, calcium related source, and coal combustion source. Finally, when applying a stepwise multiple regression analysis, the results clearly showed that $Na^+ and Ca^{2+}, K^+ and Ca^{2+}, NO_3^-$ and relative humidity, $Cl^-$ and ambient temperature, $Ca^{2+} and Cl^-, Mg^{2+} and SO_4^{2-}, Na^+ and NO_3^-, and Ca^{2+} and NO_3^-$, respectively, are negatively contributed to each other. As a result of those statistical analysis, we could suggest that some chemical compounds in the submicron particles such as$NaNO_3, MgSO_4, Ca(NO_3)_2, and CaCl_2$ may not exist on the filter as final composing products; however, other compounds may possibly exist in the form of $Mg(NO_3)_2, CaSO_4, Na_2SO_4, K_2SO_4, MgCl_2, NaCl, and KCl$. Thus, it must be necessary to identify differences between the results of above statistical analysis and of the real world by laboratory experiments.