• Journal of the Korean Electrochemical Society
• /
• v.16 no.2
• /
• pp.70-73
• /
• 2013

Iridium oxide is well known as an electrocatalyst for the water oxidation. Recently, Dr. Bard's group observed the electrocatalytic behavior of individual nanoparticle of Iridium oxide using the electrochemical amplification method by detecting the single nanoparticle collisions at the ultramicroelectrode (UME). However, the electrocatalytic current is decayed as a function of time. In this study, we investigated that the reason of electrocatalytic current decay of water oxidation at Iridium oxide nanoparticles. We identified it is due to the bubble overpotential because the cyclic current decay and recovery were synchronized to the oxygen bubble growth and coming away from an Iridium disk electrode.

• BMB Reports
• /
• v.32 no.2
• /
• pp.161-167
• /
• 1999

The role of oxidative stress in the initiation and the complication of diabetes was examined by monitoring blood glucose increase and oxidative DNA damage in rats treated with alloxan or streptozotocin (STZ). Oxidative DNA damage was assessed by quantitating 8-oxo-2'-deoxyguanosine ($oxo^8dG)$ excreted in urine and the $oxo^8dG$ accumulated in pancreas DNA. Both alloxan and STZ treatments resulted in an abrupt increase in blood glucose and significant increases in urinary and pancreatic $oxo^8dG$. Pretreatment of buthionine sulfoximine (BSO), a glutathione-depleting agent, slightly potentiated the increase of blood glucose and urinary $oxo^8dG$ in the alloxan- and STZ-treated rats. Furthermore, the BSO pretreatment caused significant amplification of pancreatic $oxo^8dG$ increase in the rats. On the other hand, pretreatment with 1,10- phenanthroline (o-phen), a chelator of divalent cations, showed different results between alloxan- and STZ-treated rats. The o-phen pretreatment completely blocked diabetes and the increase of $oxo^8dG$ by alloxan treatment, while it potentiated the increase of blood glucose and $oxo^8dG$ by STZ treatment. The results demonstrate that the causative effect of alloxan on diabetes may be the generation of reactive oxygen species through a Fenton type reaction, but that of STZ may not.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.8
• /
• pp.997-1009
• /
• 1999

Silica particle formation and growth process including chemical reaction, coagulation and sintering was studied in a counterflow diffusion flame burner. The counterflow geometry provides a one dimensional flow field, along the stagnation point streamline, which greatly simplifies interpretation of the particle growth characteristics. $SiCl_4$ has been used as the source of silicon in hydrogen/oxygen/argon flames. The temperature profiles obtained by calculation showed a good agreement with experiment data. Using one and two dimensional sectional method, aerosol dynamics equation in a flame was solved, and these two results were compared. The two dimensional section method can consider sintering effect and growth of primary particle during synthesis, thus it showed evolution of morphology of non-spherical particles (aggregates) using surface fractal dimension. The effects of flame temperature and chemical loading on particle dynamics were studied. Geometric mean diameter based on surface area and total number concentration followed the trend of experiment results, especially, the change of diameters showed the sintering effect in high temperature environment.

• Journal of Veterinary Clinics
• /
• v.16 no.1
• /
• pp.203-209
• /
• 1999

A 4-year-old female Shih-tzu with severe episcleral congestion and buphthalmos in left eye was referred to the Veterinary Teaching Hospital, Chonnam National University in October 1998. During two months in local veterinary clinics, the dog had been treated unsuccessfully with tarsorrhaphy and antibiotics. By history taking, cause of the glaucoma was ascertained as accidental nonpenetrated cornea trauma by owner, Ophthalmic examination revealed that the left eye was buphthalmic with severe episcleral congestion, pain and fever. The direct pupillary light response could not be evaluated in the left eye, but right eye had normal reaction. The intraocular pressure was 4.5 mmHg in the right eye and 33 mmHg in the left eye, as measured with a Schiotz tonometer, Ultrasonographic finding revealed hyperechoic vitrous body and central echofree material. The Schirmer tear test showed 20 mm in the left eye and 8 mm in the right eye. The hematologic examination revealed monocytosis. The initial medical treatment was admitted, but there was no response. Transpalpebral enucleation in the left eye under inhalation anesthesia with enflurane 1.2 vol% in oxygen was performed. The day after operation the left eye ravealed no exudate, and pain, and the systemic vital signs were normal. The prognosis is excellent.

• Membrane Journal
• /
• v.19 no.1
• /
• pp.1-6
• /
• 2009

Hydrogen energy id the 2nd clean energy able to be produced from the abundant resources, and the products of combustion or reaction do not spread an environmental pollution. Also, the hydrogen is the chemical media easily to transport and storage as energy source. The hydrogen production technology using by water splitting through electrolysis could be usable as a permanent renewable energy system without the environmental impact. The key technology of high temperature steam electrolysis is the development of an electrolyte rapidly to conduct an oxygen or proton ion decomposed from water. Subsequently, the important technology is to keep the joining technology of an electrolyte membrane and electrode materials to affect into the current efficiency.

• Korean Journal of Materials Research
• /
• v.15 no.5
• /
• pp.323-333
• /
• 2005

Effects of gases to growth of $SiO_2$ nanowires were characterized. $N_2$, Ar, and $O_2$ gas's effect were determined. $SiO_2$ nanowires growth scheme was varied by kind and flow rates of gases because of amounts of $O_2$. Flow rates of gases and kind of substrates affected nanowires' diameters, lengths and morphologies of grown nano wires. With increasing flow rates of gases, nanowire's diameter increased because of additional VS and SLS reactions. By TEM characterization, We knows that, grown $SiO_2$ nanowires on Si substrate showed two shell structures. These shapes of nanowires were formed by reaction of additional SLS growth. Grown $SiO_2$ nanowires showed blue luminescence by PL characterization These Blue luminescence was due to quantum confinement effect and oxygen vacancies in the nanowires.

• Korean Journal of Materials Research
• /
• v.25 no.9
• /
• pp.455-461
• /
• 2015

SnS-$TiO_2$ nanocomposites are synthesized using simple, cheap, and less toxic $SnCl_2$ as the tin (II) precursor. The prepared nanoparticles are characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectra (DRS). The XRD and TEM results indicate that the prepared product has SnS nanoparticles and a grain diameter of 30 nm. The DRS demonstrate that SnS-$TiO_2$ possesses the absorption profile across the entire visible light region. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and photocatalytic effect increase with the modified SnS. Excellent catalytic degradation of Texbrite BA-L (TBA) solution is observed using the SnS-$TiO_2$ composites under visible light irradiation. It is proposed that both the strong visible light absorption and the multiple exciton excitations contribute to the high visible light photocatalytic activity.

• Journal of the Korean Magnetic Resonance Society
• /
• v.10 no.1
• /
• pp.115-125
• /
• 2006

Hippuryl-L-histidyl-L-leucine(HHL) is widely used as a substrate of angiotensin converting enzyme(ACE) cleaving the neurotransmitter angiotensin(I) to the octapeptide angiotensin(II). The structure of the substrate molecules should provide information regarding the geometric requirements of the ACE active site. For the purpose of determination of in vivo reaction, metallo(Cu, Zn)-HHL complexes were synthesized and the degree of complex formation were identified by MALDITOF, ESI mass spectrometric analysis. Tn addition, the pH-dependent species distribution curves were obtained by potentiometric titration. Nitrogen atoms of imidazole ring and oxygen atom of caboxylate groups in the peptide chain were observed to be participated in the metal complex formation. After purification of complexes further structural characterization were made by utilizing UV-Vis, electrochemical methods and NMR. Complete NMR signal assignments were carried out by using 2D-spectrum techniques COSY, TOCSY, NOESY, HETCOR. A complex that two imidazole and carboxylate groups are asymmetrically participating to coordination mode was predicted to the solution-state structure of $Cu(II)-HHL_2$ based on $^{13}C-NMR$ signal assignment and NOE information.

• Herbal Formula Science
• /
• v.6 no.1
• /
• pp.215-226
• /
• 1998

Geagibokrounghwan (桂技茯笭湯) has long been used to cure human diseases such as vascular and blood disorders. However, it is still unkown on its action mechanism, physiolosical and biochemical meaning. Thus, many attempts were tried to show the scientific background covering the above mentioned mechanism. The effect of Geagibokrounghwan, which was known to date, as follow; effective circulation of body blood system, proliferation of leucocytes and antioxidative action. In this study, we have applied the Geagibokrounghwan administration and feed to mouse, to see effects on the expression of superoxide dismutase(SOD) mRNA as antioxidative agent and oxygen radical scavenger. Total RNAs includingmRNA have been isolated from liver and white blood cells after mice were fed with cholesterol in high dose. Also, in a separate group, the cholesterol-administrated mice were fed with Geagibokrounghwan to see the effects on SOD transcription. and then reverse transcriptase-polymerase chain reaction (RT-PCR) usion each primer set (SOD-F;GATGAAAGCGGTGT-3'; SOD-R; 5'-CCTGTGGAGTGATT-3') were performed to trace theamounts of mRNA. SOD mRNA was specifically expressed in Geagibokrounghwan-fed mice at 2 weeks after treatment, however, gradually reduced after 4 weeks. These results indicate that Geagibokrounghwan is highly applicable in treatment of the above mentioned human diseases.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.6
• /
• pp.1087-1094
• /
• 2010

We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.