Ki Jung Paeng

Antibacterial Effects of the Urushiol Component in the Sap of the Lacquer Tree (Rhus verniciflua Stokes) on Helicobacter pylori

Background:  Urushiol is a major component of the lacquer tree which has been used as a folk remedy for the relief of abdominal discomfort in Korea. The aim of this study was to evaluate the antibacterial effects of the urushiol on Helicobacter pylori.

Removal of iopromide and degradation characteristics in electron beam irradiation process

The aim of this study is to evaluate the removal efficiency of iopromide using electron beam (E-beam) irradiation technology, and its degradation characteristics with hydroxyl radical (OH) and hydrated electron (e(aq)(-)). Studies are conducted with different initial concentrations of iopromide in pure water and in the presence of hydrogen peroxide, bicarbonate ion, or sulfite ion. E-beam absorbed dose of 19.6 kGy was required to achieve 90% degradation of 100 μM iopromide and the E-beam/H(2)O(2) system increased the removal efficiency by an amount of OH· generation. In the presence of OH scavengers (10 mM sulfite ion), the required dose for 90% removal of 100 μM iopromide was only 0.9 kGy. This greatly enhanced removal was achieved in the presence of OH· scavengers, which was rather unexpected and unlike the results obtained from most advanced oxidation process (AOP) experiments. The reasons for this enhancement can be explained by a kinetic study using the bimolecular rate constants of each reaction species. To explore the reaction scheme of iopromide with OH· or e(aq)(-) and the percent of mineralization for the two reaction paths, the total organic carbon (TOC), released iodide, and intermediates were analyzed.

Compositional analysis of electrodeposited bismuth telluride thermoelectric thin films using combined electrochemical quartz crystal microgravimetry--stripping voltammetry.

Bismuth telluride (Bi 2Te 3 ) is a benchmark material for thermoelectric power generation and cooling applications. Electrodeposition is a versatile technique for preparing thin films of this material; however, it affords films of variable composition depending on the preparation history. A simple and rapid assay of electrodeposited films, therefore, has both fundamental and practical importance. In this study, a new protocol for the electroanalysis of Bi 2Te 3 thin films is presented by combining the two powerful and complementary techniques of electrochemical quartz crystal microgravimetry (EQCM) and stripping voltammetry. First, any free (and excess) tellurium in the electrodeposited film was reduced to soluble Te ( 2- ) species by scanning to negative potentials in a 0.1 M Na 2SO 4 electrolyte, and the accompanying frequency increase (mass loss) was used to determine the content of free tellurium. The film was again subjected to cathodic stripping in the same medium (to generate Bi (0) and soluble Te (2-) from the Bi 2 Te 3 film component of interest), and the EQCM frequency change was used to determine the content of chemically bound Te in the Bi 2Te 3 thin film and thereby the compound stoichiometry. Finally, the EQCM frequency change during Bi oxidation to Bi (3+) and the difference between total Bi and Bi in Bi 2Te 3 resulted in the assay of free (excess) Bi in the electrodeposited film. Problems associated with the chemical/electrochemical stability of the free Bi species were circumvented by a flow electroanalysis approach. Data are also presented on the sensitivity of electrodeposited Bi 2Te 3 film composition to the electrodeposition potential. This newly developed method can be used for the compositional analysis of other thermoelectric thin-film material candidates in general.

Adsorption Studies for the Removal of Methyl tert-Butyl Ether on Various Commercially Available GACs from an Aqueous Medium

This study highlights the potential of four commercially available granular-activated carbons (GACs) to remove Methyl tert-butyl ether (MTBE) from an aqueous medium. Thermodynamics and kinetics parameters were elucidated. The FT-IR spectra showed decrease in peak intensity after the adsorption. The decline in the peak intensity revealed that the adsorption occurred on available active sites over the surface of the GACs. The adsorption on GACs was maximum in the pH range 7–8, with maximum adsorption capacity (47.82 mg/g, pH 8) observed with CGAC. The contact time studies showed optimum adsorption of MTBE on CGAC (67.05 mg/g) at 300 mg/L initial MTBE concentration. The applicability of the Freundlich model illustrates a multilayer adsorption process. The adsorption process is endothermic in nature. The kinetics studies showed that the adsorption follows the pseudo-second-order model on GACs and the intraparticle diffusion is the rate-controlling mechanism on CGAC.

Resonance Raman Studies of Compounds I and II of Arthromyces ramosus Peroxidase: Close Similarities in Their Raman Spectra But Distinct Oxygen Exchangeability of the Fe=O Heme

Simultaneous measurements of resonance Raman and absorption spectra were performed for intermediates generated upon addition of hydrogen peroxide to ferric Arthromyces ramosus peroxidase (ARP) using the microcirculating system constructed in this laboratory, which enables generation of desirable intermediates under steady-state conditions. Compound I of ARP generated at neutral pH was stable over tens of minutes in the absence of laser illumination with this circulation system, but was gradually degraded under laser illumination, giving rise to a new irreversible species with an iron-oxo heme. Such photosensitivity was not observed for compound II in the steady state at alkaline pH. Surprisingly, the Raman spectrum of compound I of ARP in the high-frequency region, where characteristic frequency shifts are expected upon oxidation of the macrocycle, was quite close to that of compound II, despite the fact that the reduced Soret absorption indicated the formation of a π-cation radical. The Fe=O stretching (νFe=O) frequency of compound I was observed at 781 cm−1 for the 16O derivative but appeared as a doublet at 744 and 731 cm−1 for the 18O derivative. The isotope sensitivity of the νFe=O mode of compound I was seen upon H216O/H218O solvent substitution but not upon H216O2/H218O2 peroxide substitution in H216O at neutral pH. This directly indicates the occurrence of an oxygen atom exchange between the oxo-heme and bulk water, providing the first example of such exchange in compound I of peroxidases. The oxygen exchange was abolished for compound II at alkaline pH, for which the νFe=o mode was seen at 787/749 cm−1 only upon H216O2/H218O2 peroxide substitution. The oxygen exchangeability seems to depend on protonation of a nearby residue with pKα ∼ 9 and to correlate with stability of compound I.