Enhancement of hydrogen-storage performance of MgH₂ by Mg₂Ni formation and hydride-forming Ti addition

Song, M.Y.,Kwak, Y.J.,Lee, S.H.,Song, J.,Mumm, D.R. Pergamon Press ; Elsevier Science Ltd 2012 International journal of hydrogen energy Vol.37 No.23

MgH<SUB>2</SUB>, rather than Mg, was used as a starting material in this work. A sample with a composition of MgH<SUB>2</SUB>-10Ni-4Ti was prepared by reactive mechanical grinding. Activation of the sample was completed after the first hydriding cycle. At n = 1, the sample desorbed 2.53 wt% H for 10 min, 3.99 wt% H for 20 min, 4.58 wt% H for 30 min, and 4.68 wt% H for 60 min at 593 K under 1.0 bar H<SUB>2</SUB>. At n = 2, the sample absorbed 3.59 wt% H for 5 min, 4.55 wt% H for 25 min, and 4.60 wt% H for 45 min at 593 K under 12 bar H<SUB>2</SUB>. The inverse dependence of the hydriding rate on the temperature in the initial stage and the normal dependence of the hydriding rate on the temperature in the later stage were discussed. The rate-controlling step for the dehydriding reaction of activated MgH<SUB>2</SUB>-10Ni-4Ti was analyzed as the chemical reaction at the hydride/α-solid solution interface.

Fermentation for Liquid-type Yogurt with Lactobacillus casei 911LC

Ko, I.H.,Wang, M.K.,Jeon, B.J.,Kwak, H.S. Asian Australasian Association of Animal Productio 2005 Animal Bioscience Vol.18 No.1

This study was carried out to find the attributes for liquid-type yogurt with Lactobacillus casei 911LC during 72 h fermentation at $37^{\circ}C$. The pH decreased up to 32 h and plauteaued thereafter, and the titratable acidity increased up to 40 h. The growth of lactic acid bacteria sharply increased with $3.5{\times}10^7$ cfu/ml up to 40 h of fermentation and slowly decreased thereafter. The free amino acids produced during fermentation reached the maximum value at 44 h and gradually decreased thereafter. Bitterness sensory scores were the highest at 44 h of fermentation. In the result of electrophoresis, the band mostly disappeared at 72 h fermentation. The present data showed that the range of optimum fermentation time for liquid-type yogurt using Lactobacillus casei 911LC was from 40 to 44 h.

Effect of acid-pretreatment on hydrogen fermentation of food waste: Microbial community analysis by next generation sequencing

Kim, D.H.,Jang, S.,Yun, Y.M.,Lee, M.K.,Moon, C.,Kang, W.S.,Kwak, S.S.,Kim, M.S. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.29

This work presents the effect of acid-pretreatment on H<SUB>2</SUB> fermentation of food waste with detailed microbial information by next generation sequencing. The pretreated food waste at pH 1.0-4.0 was cultivated under mesophilic conditions without external inoculum addition. From the food waste acid-pretreated at pH 1-3, H<SUB>2</SUB> yields in the range of 1.37-1.74 mol H<SUB>2</SUB>/mol hexose<SUB>added</SUB> were achieved, attaining the highest value at pH 2. Clostridium sp. such as Clostridium acetobutylicum ATCC 824 and Clostridium perfringens occupied more than 70% of total number of sequences at pH 1-3. On the other hand, in the control (no pretreatment) and at pH 4, lactic acid bacteria such as Lactobacillus and Streptococcus were found to be the dominant genus (>90% of total number of sequences), resulting in a low H<SUB>2</SUB> yield. In addition, the effect of substrate concentration on H<SUB>2</SUB> fermentation was investigated, and the maximum H<SUB>2</SUB> productivity was estimated to be 27.2 L H<SUB>2</SUB>/L/d by Andrew's model.

Key Features in the Operation of KSTAR

Jong-Gu Kwak,Oh, Y. K.,Kim, K. P.,Kim, S. W.,Hong, S. H.,Chu, Y.,Lee, H. J.,Kim, Y. O.,Kim, J.,Park, S. L.,Hahn, S. H.,Park, M. K.,Kim, H. K.,Bak, J. G.,Bae, Y. S.,Ko, W. H.,Lee, S. G.,Lee, J. H.,Jung IEEE 2012 IEEE transactions on plasma science Vol.40 No.3

<P>The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb<SUB>3</SUB>Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb<SUB>3</SUB>Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350°C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ~1.8, δ>;0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at B<SUB>T</SUB> = 2 T with I<SUB>p</SUB> = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.</P>

Preparation and characterization of NbF₅-added Mg hydrogen storage alloy

Lee, S.H.,Kwak, Y.J.,Park, H.R.,Song, M.Y. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.29

A sample with a composition of 95 wt% Mg-5 wt% NbF<SUB>5</SUB> (named Mg-5NbF<SUB>5</SUB>) was prepared by reactive mechanical grinding using Mg instead of MgH<SUB>2</SUB> as a starting material. Its hydriding and dehydriding rates were then measured under nearly constant hydrogen pressures. The activation of Mg-5NbF<SUB>5</SUB> was not required, and Mg-5NbF<SUB>5</SUB> had an effective hydrogen storage capacity, which was defined as the quantity of hydrogen absorbed for 60 min, of 5.50 wt%. At the first cycle (n = 1) at 593 K, the sample absorbed 4.37 wt% H for 5 min and 5.50 wt% H for 30 min under 12 bar H<SUB>2</SUB>, and desorbed 1.03 wt% H for 5 min, 4.66 wt% H for 30 min, and 5.43 wt% H for 60 min under 1.0 bar H<SUB>2</SUB>. Reactive mechanical grinding of Mg with NbF<SUB>5</SUB>, which formed MgH<SUB>2</SUB>, MgF<SUB>2</SUB>, NbH<SUB>2</SUB>, and NbF<SUB>3</SUB> by the reaction of 11 Mg + 7NbF<SUB>5</SUB> + 3H<SUB>2</SUB> → MgH<SUB>2</SUB> + 10MgF<SUB>2</SUB> + 2NbH<SUB>2</SUB> + 5NbF<SUB>3</SUB>, is considered to create defects, to produce reactive clean surfaces, and to reduce the particle size of Mg. The XRD pattern of Mg-5NbF<SUB>5</SUB> dehydrided at n = 3 revealed Mg, small amounts of β-MgH<SUB>2</SUB> and MgO, and very small amounts of MgF<SUB>2</SUB> and NbH<SUB>2</SUB>. An increase in the dehydriding rate of Mg-5NbF<SUB>5</SUB> was attempted by adding Ni to Mg-5NbF<SUB>5</SUB>. Mg-5NbF<SUB>5</SUB> had higher initial hydriding and dehydriding (after the incubation period) rates and a larger effective hydrogen storage capacity than Mg-10NbF<SUB>5</SUB>, Mg-10MnO, and Mg-10Fe<SUB>2</SUB>O<SUB>3</SUB>, which were reported to have quite high hydriding rate and/or dehydriding rate.

Immobilization of hemoglobin on functionalized multi-walled carbon nanotubes-poly-l-histidine-zinc oxide nanocomposites toward the detection of bromate and H₂O₂

Vilian, A.,Chen, S.M.,Kwak, C.H.,Hwang, S.K.,Huh, Y.S.,Han, Y.K. Elsevier Sequoia 2016 Sensors and actuators. B Chemical Vol.224 No.-

A novel biocompatible sensing strategy has been developed based on functionalized multi-walled carbon nanotube (f-MWCNT), poly-l-histine (P-l-His), and ZnO nanocomposite film for the immobilization of hemoglobin (Hb). The direct electron transfer properties and bioelectrocatalytic activity of the Hb in f-MWCNT-P-l-His-ZnO composite film is further investigated. The apparent heterogeneous electron transfer rate constant (k<SUB>s</SUB>) of Hb confined to f-MWCNT-P-l-His-ZnO nanocomposite is found to be 5.16s<SUP>-1</SUP> using Laviron's equation. Moreover, the surface coverage concentration (Γ) of the electroactive Hb in the f-MWCNT-P-l-His-ZnO film is estimated to be 1.88x10<SUP>-9</SUP>molcm<SUP>-2</SUP>. The fabricated electrochemical biosensor based on the immobilized Hb revealed a fast response time (<3s) with a wide linear range (4-18,000μM and 2-15,000μM) and detection limit (as low as 0.01μM and 0.30μM) for the electrocatalytic determination of a mediator-free H<SUB>2</SUB>O<SUB>2</SUB> and bromate under optimal experimental conditions. The ca. apparent Michaelis-Menten constant is 0.14mM, which indicates that the Hb has a high affinity to H<SUB>2</SUB>O<SUB>2</SUB>. The high sensitivity, good reproducibility, and long-term stability of the proposed nanocomposite film indicates that it can serve as an electrode for the development of an amperometric H<SUB>2</SUB>O<SUB>2</SUB> and bromate-based biosensor. The proposed third-generation biosensor was successfully applied to milk and urine samples for the detection of H<SUB>2</SUB>O<SUB>2</SUB> and bromate.

In vivo imaging of tumor apoptosis using histone H1-targeting peptide

Wang, K.,Purushotham, S.,Lee, J.Y.,Na, M.H.,Park, H.,Oh, S.J.,Park, R.W.,Park, J.Y.,Lee, E.,Cho, B.C.,Song, M.N.,Baek, M.C.,Kwak, W.,Yoo, J.,Hoffman, A.S.,Oh, Y.K.,Kim, I.S.,Lee, B.H. Elsevier Science Publishers 2010 Journal of controlled release Vol.148 No.3

In vivo imaging of apoptosis could allow monitoring of tumor response to cancer treatments such as chemotherapy. Using phage display, we identified the CQRPPR peptide, named ApoPep-1(Apoptosis-targeting Peptide-1), that was able to home to apoptotic and necrotic cells in tumor tissue. ApoPep-1 also bound to apoptotic and necrotic cells in culture, while only little binding to live cells was observed. Its binding to apoptotic cells was not dependent on calcium ion and not competed by annexin V. The receptor for ApoPep-1 was identified to be histone H1 that was exposed on the surface of apoptotic cells. In necrotic cells, ApoPep-1 entered the cells and bound to histone H1 in the nucleus. The imaging signals produced during monitoring of tumor apoptosis in response to chemotherapy was enhanced by the homing of a fluorescent dye- or radioisotope-labeled ApoPep-1 to tumor treated with anti-cancer drugs, whereas its uptake of the liver and lung was minimal. These results suggest that ApoPep-1 holds great promise as a probe for in vivo imaging of apoptosis, while histone H1 is a unique molecular signature for this purpose.

Improved reversible redox cycles on MTiOx (M=Fe, Co, Ni, and Cu) particles afforded by rapid and stable oxygen carrier capacity for use in chemical looping combustion of methane

Kwak, B.S.,Park, N.K.,Ryu, S.O.,Baek, J.I.,Ryu, H.J.,Kang, M. Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.309 No.-

In this study, rutile TiO<SUB>2</SUB> particles (MTiOx) incorporating 3d-metals, with their electrons more than half-filled, are synthesized for use in the chemical looping combustion of methane. The specific structures are obtained by doping the M-sites with Fe, Co, Ni, and Cu (FeTiOx, CoTiOx, NiTiOx, and CuTiOx), and they have the same M/Ti molar ratio of 1.0. XRD, SEM, CH<SUB>4</SUB>-TPD, TGA, and BET techniques were used to characterize the prepared materials. The XRD results confirmed that all of the prepared materials possessed pure hexagonal phases in the case of Co1Ti1Ox and Ni1Ti1Ox and mixed formations composed of metal oxides and rutile TiO<SUB>2</SUB> in the case of Fe1Ti1Ox and Cu1Ti1Ox. The CH<SUB>4</SUB>-TPD and H<SUB>2</SUB>-TPR analyses showed that the highest adsorption is obtained on CuTiOx, in particular on Cu1.5Ti1Ox. The oxygen carrier capacities of the samples were measured in H<SUB>2</SUB> (FR)/air (AR) and CH<SUB>4</SUB>-CO<SUB>2</SUB> (FR)/air (AR) redox systems at 850<SUP>o</SUP>C using TGA analysis. Their variability was shown to be associated with the different doping elements and doping concentrations. In particular, the Cu1.5Ti1Ox material in the CH<SUB>4</SUB>-CO<SUB>2</SUB> (FR)/air (AR) redox system exhibits oxygen uncoupling behaviour, leading to improved capture and release of oxygen compared to the other materials.

대학생의 암 예방 수칙에 대한 인식 및 실천행태 연구

곽지연,김서연,김자영,이혜연,정문정,진수현,천선우,하소현,한희진,양숙자,김지연 이화여자대학교 간호과학대학 2016 이화간호학회지 Vol.- No.50

Purpose: The purpose of this study was to identify college student's perception and practice of 'National Cancer Prevention Actions' and the factors that influence the perception and practice. Method: The participants were 310 undergraduates selected by convenience sampling at colleges in Seoul. Instrument was 2014 Survey of Perception and Practice of National Cancer Prevention Actions by National Cancer Center(2014), and has been modified for the purpose of the study. The data were analyzed by t-test, ANOVA and Scheffe test with SPSS 23.0 Windows software. Results: The most recognized action for cancer prevention in college students was "Do not smoke, also avoid smoking smoke"(96.8%) while the most unrecognized was "Get a type B hepatitis vaccination"(58.7%). The most practiced action for cancer prevention in college students was "Sexually as to safe sex"(94.8%) while the most unpracticed was "Exercise five times a week or more, for at least 30 minutes a day"(33.9%). Among general characteristics, participants' age (t=-2.015, p<.05), major (F=3.109, p<.001), and residential type (F=4.959, p<.01) were statistically significant in the recognition of Cancer Prevention Actions and major(F=3.341 p<.05) and residential type(F=3.827, p<.05) were also significant in the practice of Cancer Prevention Actions. Among health characteristics, health concern(F=3.154, p<.05) and education in cancer(t=-3.112, p<.01) showed statistically significant differences in the recognition of Cancer Prevention Actions while health concern(F=7.896 p<.001) and subjective health status(F=9.913, p<.001) showed differences in the practice of Cancer Prevention Actions. Conclusion: These findings showed the gap between the perception and practice of cancer prevention actions. Considering the importance of individual characteristics, it is essential to develop a differentiated cancer prevention education program for college students. Also, nursing intervention program should be developed to raise the alertness of cancer in order to enhance cancer preventive practice.

Optimization of β-Cyclodextrin Recycling Process for Cholesterol Removal in Cream

Kwak, H.S.,Suh, H.M.,Ahn, J.,Kwon, H.J. Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.4

This study was designed to find optimum conditions of four different factors (ratio of solvent to cholesterol-$\beta$-cyclodextrin complex, mixing speed, mixing temperature, and mixing time) for cholesterol dissociation in cream. Using the ratio of 6 to 1 (solvent to the complex) showed the highest cholesterol dissociation rate (82.50%) when mixed at 100 rpm at $50^{\circ}C$ for 1 h. Mixing speed did not significantly affect the cholesterol dissociation. Also, mixing time appeared to be insignificant. The optimum mixing temperature was $50^{\circ}C$ and mixing at $40^{\circ}C$ resulted in a significantly lower rate, compared with that at $50^{\circ}C$. In a subsequent experiment, using recycled $\beta$-cyclodextrin only showed 75.07% of cholesterol removal in cream, while the mixture of recycled to unused $\beta$-CD with the ratio of 6 to 4 increased cholesterol removal to 95.59%, which is highly close to that of 100% unused $\beta$-CD.