• Journal of Microbiology and Biotechnology
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• v.24 no.4
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• pp.483-488
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• 2014

In order to improve the expression of heat-resistant xylanase XYNB from Aspergillus niger SCTCC 400264, XynB has been cloned into Pichia pastoris secretary vector pPIC9K. The XynB production of recombinant P. pastoris was four times that of E. coli, and the $V_{max}$ and specific activity of XynB reached $2,547.7{\mu}mol/mg$ and 4,757 U/mg, respectively. XynB still had 74% residual enzyme activity after 30 min of heat treatment at $80^{\circ}C$. From the van der Waals force analysis of XYNB (ACN89393 and AAS67299), there is one more oxygen radical in AAS67299 in their catalytic site, indicating that the local cavity is much more free, and it is more optimal for substrate binding, affinity reaction, and proton transfer, etc, and eventually increasing enzyme activity. The H-bonds analysis of XYNB indicated that there are two more H-bonds in the 33rd Ser of XYNB (AAS67299) than in the 33rd Ala(ACN89393 ), and two H-bonds between Ser70 and Asp67.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.95-99
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• 2006

Electrochemical properties were studied for a single particle of active material of hydrogen storage alloy $(MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3})$ and nickel hydroxides $(NiOH)_2$ for the secondary Nickel Metal Hydride (Ni-MH) batteries using the microelectrode, which was manipulated to make electrical contact with an active material particle for cyclic voltammograms (CV) and potential-step experiments. As a result of CV test, it was found that three kinds of hydrogen oxidation peaks at -0.9, -0.75 and -0.65 V and hydrogen evolution peak at -0.98 V for hydrogen storage alloy were separately observed and two kinds of peaks of proton oxidation/reduction at 0.45 and 0.32 V and oxygen evolution reaction (OER) at 0.6 V for nickel hydroxides were also more clearly observed. Furthermore hydrogen diffusion coefficient within a single particle was also found to vary the order between $10^{-9}\;and\;10^{-10}cm^2/s$ over the course of hydrogenation and dehydrogenation process for potential-step experiments.

• Journal of the Korean Electrochemical Society
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• v.6 no.3
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• pp.212-216
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• 2003

The humidification measurement system designed in laboratory was used to measure relative humidity and temperature of reaction gases passing through internal or external humidifier which was used in proton exchange membrane fuel cell test station. The relative humidity of gases was stabilized after $10\~20$ minutes and thus credibility of data could be assured. The effect of relative humidity on fuel cell performance could be analyzed by humidity measurement system. Extreme caution was needed to avoid humidity sensor mal-function or failure which is probable in experiment of high humidity condition near $100\%$. The amount of water carried by gas through humidifier was increased along the flow rate of gas. However, the extent of increase was lowered at high gas flow rate. These phenomena could be analyzed as residence time effect of gas in humidifier.

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.131-135
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• 2011

It is, in general, believed that during the activation process, the proton conductivity increases due to wetting effect and the electrochemical resistance reduction, resulting in an increase in the fuel cell performance with time. However, until now, very scant information is available on the understanding of activation processes. In this study, dominant variables that effect on the performance increase of membrane electrode assemblies (MEAs) during the activation process were investigated. Wetting, pore restructuring and active metal utilization were analyzed systematically. Unexpectedly, the changes for both ohmic and reaction resistance characterized by the electrochemical impedance spectroscopy (EIS) after initial wetting process were much smaller when considering the degree of cell performance increases. However, the EIS spectra represents that the pore opening of electrode turns into gas transportable structure more easily. The increase in the performance with activation cycles was also investigated in a view of active metals. Though the particle size was grown, the number of effective active sites might be exposed more. The impurity removal and catalytic activity enhancement measured by cyclic voltammetry (CV) could be a strong evident. The results and analysis revealed that, not merely wetting of membrane but also restructuring of electrodeand catalytic activity increase are important factors for the fast and efficient activation of the polymer electrolyte fuel cells.

• Journal of Hydrogen and New Energy
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• v.25 no.1
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• pp.1-10
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• 2014

Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted phophomolybdic acid(Cs-MoPA) with cross-linking agent contents of 0.01mL. In conclusion, CL-SPEEK/$Cs_{(2.5)}$-MoPA/ceria(1%) membrane showed the optimum results such as 0.1095S/cm of proton conductivity at $80^{\circ}C$, 2.906meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 49.73MPa of tensile strength which were better than Nafion 117 membrane.

• Journal of Hydrogen and New Energy
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• v.22 no.5
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• pp.579-584
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• 2011

Sulfonated poly (ether sulfone)s containing BFBN were prepared from 2,3-bis(4-fluorophenyl)-2-butenedinitrile , 4,4-sulfonyldiphenol and sulfonated 4,4'-difluorodiphenylsulfone sodium salt using potassium carbonate, and followed acidification reaction with 1M $H_2SO_4$. BFBN was prepared from 4-fluorobenzylcyanide, $CCl_4$, NaOH using trimethylbenzylammoniumchloride . Sulfonated poly(ether sulfone)s containing BFBN were studied by FT-IR, $^1H$-NMR spectroscopy, and thermo gravimetric analysis (TGA). The water uptake of synthesized S-PBFBN membranes exhibit 31~62% compared with 28% of Nafion 211. The S-PBFBN membranes exhibit proton conductivities ($80^{\circ}C$, RH 100) of 53.8~117.4 mS/cm compared with 137.4 mS/cm of Nafion 211.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1462-1468
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• 2014

Xe gas is moved to target from GPM. It is used to feasible nuclear reaction from proton of 30MeV cyclotron being investigated by the Xe-124 gas target system. This system is divided into four parts. The hardware system was constructed by solidworks 3-D CAD and Helium supply is to cool the Havor foil. The Cooling water has the job of cooling down the temperature when Xe gas is being investigated in the target. Temperature and pressure gauges are attached to be checked easily. GPM has the part that prepares to transport Xe gas. There are storage vessel that stores Xe gas, the cold trap that filters humidity and impurity and lastly storage vessel that temporarily stores Xe gas. HCS using the helium is to clean and cool for each part. These parts are configured with SIEMENS PLC and PcVue monitoring program for more comfortable and easy maintenance.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.808-814
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• 2010

Activities of nanostructure HZSM-5 and Co-ZSM-5 catalysts (with different Co-loading) for catalytic conversion of ethyl acetate and toluene were studied. The catalysts were prepared by wet impregnation method and were characterized by XRD, BET, SEM, TEM and ICP-AES techniques. Catalytic studies were carried out inside a U-shaped fixed bed reactor under atmospheric pressure and different temperatures. Toluene showed lower reactivity than ethyl acetate for conversion on Co-ZSM-5 catalysts. The effect of Co loading on conversion was prominent at temperatures below $400^{\circ}C$ and $450^{\circ}C$ for ethyl acetate and toluene respectively. In a binary mixture of organic compounds, toluene and ethyl acetate showed an inhibition and promotional behaviors respectively, in which the conversion of toluene was decreased at temperatures above $350^{\circ}C$. Inhibition effect of water vapor was negligible at temperatures above $400^{\circ}C$. An artificial neural networks model was developed to predict the conversion efficiency of ethyl acetate on Co-ZSM-5 catalysts based on experimental data. Predicted results showed a good agreement with experimental results. ANN modeling predicted the order of studied variable effects on ethyl acetate conversion, which was as follows: reaction temperature (50%) > ethyl acetate inlet concentration (25.085%) > content of Co loading (24.915%).

• Molecules and Cells
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• v.37 no.4
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• pp.322-329
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• 2014

N-acetylglucosamine kinase (GlcNAc kinase or NAGK; EC 2.7.1.59) is highly expressed and plays a critical role in the development of dendrites in brain neurons. In this study, the authors conducted structure-function analysis to verify the previously proposed 3D model structure of GlcNAc/ATP-bound NAGK. Three point NAGK mutants with different substrate binding capacities and reaction velocities were produced. Wild-type (WT) NAGK showed strong substrate preference for GlcNAc. Conversion of Cys143, which does not make direct hydrogen bonds with GlcNAc, to Ser (i.e., C143S) had the least affect on the enzymatic activity of NAGK. Conversion of Asn36, which plays a role in domain closure by making a hydrogen bond with GlcNAc, to Ala (i.e., N36A) mildly reduced NAGK enzyme activity. Conversion of Asp107, which makes hydrogen bonds with GlcNAc and would act as a proton acceptor during nucleophilic attack on the ${\gamma}$-phosphate of ATP, to Ala (i.e., D107A), caused a total loss in enzyme activity. The overexpression of EGFP-tagged WT or any of the mutant NAGKs in rat hippocampal neurons (DIV 5-9) increased dendritic architectural complexity. Finally, the overexpression of the small, but not of the large, domain of NAGK resulted in dendrite degeneration. Our data show the effect of structure on the functional aspects of NAGK, and in particular, that the small domain of NAGK, and not its NAGK kinase activity, plays a critical role in the upregulation of dendritogenesis.

• Journal of Hydrogen and New Energy
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• v.23 no.5
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• pp.437-447
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• 2012

Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted tungstophosphoric acid (Cs-TPA) with cross-linking agent contents of 0.01 mL. In conclusion, CL-SPEEK/Cs-TPA/ceria (1%) membrane showed the optimum results such as 0.130 S/cm of proton conductivity at $80^{\circ}C$, 2.324 meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 65.03 MPa of tensile strength which were better than Nafion 117 membrane.