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Ryu, Zoon-Ha,Choi, Su-Han,Lim, Gui-Taek,Sung, Dea-Dong,Bentley, T. William Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.9
Pseudo-first order rate constants $(k_{obs})$ are reported for the following solvolyses in approximately isodielectric mixtures: 3- and 4-methoxybenzyl chloride, bromo- and chlorodiphenylmethane, and 4-chloro-, 4,4'-dichloro and 4-methyl-chlorodiphenylmethane in 0-80% v/v nitromethane-methanol mixtures; and bromo- and chlorodiphenylmethane and 4-methyl-chlorodiphenylmethane in various acetonitrile-methanol mixtures (in the range 0-50% v/v) at$25^{\circ}C.$ These data, and literature data for t-butyl halides (Cl, Br, and I), and for p-methoxybenzoyl chloride, show rate maxima in solvent compositions of ca. 30% aprotic cosolvent, explained by a stoichiometric solvent effect on electrophilic solvation. Linear relationships are observed between $(k_{obs})/[MeOH]^2$ and [AP]/[MeOH], where [AP] refers to the molar concentration of aprotic cosolvent. The results are consistent with competing third order contributions to $k_{obs}$, $k_{MM}[MeOH]^2$ with hydrogen-bonded methanol as electrophile, and $k_{MAP}[MeOH][AP]$ with hydrogen-bonding disrupted by the aprotic solvent.
박경원,이설아,오인환,남석우,하홍용,임태훈,홍성안,성영은 한국공업화학회 1999 응용화학 Vol.3 No.2
Direct methanol fuel cell (DMFC) needs better anode electrocatalysts than Pt, which suffers from self CO poisoning phenomena. The improved oxidation kinetics enabled by Pt promoters such as Ru, Sn, Mo, W or Os has been attributed to a bifunctional and/or an electronic effect. The alloy electrode materials were prepared by reduction and colloidal methods. It was generally proved that binary system such as those based on Pt, these components are much more active in promoting DMFC reactions than pure platinum catalysts. The oxidation onset on pure Pt was 0.45 V and the potentials decreased with alloying. Pt-Ru showed the lowest onset potential. However, chronoamperometry provided high stability at Pt-Mo on CO poisoning, which shows a promising candidate as DMFC anode material. The strategy of ternary or quaternary electrocatalysts, the effects of synthesis and particle sizes will be discussed.
Reduction of ultrafine particles emission from office laser printers
Sung, G.,Ha, S.,Kwon, S.B.,Kim, T. Pergamon Press 2017 Journal of aerosol science Vol.103 No.-
<P>Laser printers are widely used in modern society, and VOCs and ultrafine particles emitted from printers have been known to cause adverse effects on indoor environment. In this study we conducted experiments in order to evaluate the ultrafine particles emission characteristics of laser printers and to reduce its concentration. Ultrafine particles emission characteristics was assessed for 15 printers by measuring its number concentration inside the printers (before and after the fuser) while printing. In addition, chemical analysis was performed using transmission electron microscope (TEM), Matrix-assisted laser desorption ionization time of flight mass spectroscopy (MALDI-TOF MS) and gel permeation chromatography (GPC). In order to reduce the occurrence of ultrafine particles from laser printers, an experiment was conducted with lowered fusing temperature, which resulted in the sharp decrease of the ultrafine particles generation due to the decrease in particle nucleation rate. Additionally, based on the fact that ultrafine particles contains paramagnetic material, by applying electromagnetic field, ultrafine particles emitted from laser printer was reduced by similar to 40%.</P>
An Antioxidant System Required for Host Protection against Gut Infection in <i>Drosophila</i>
Ha, Eun-Mi,Oh, Chun-Taek,Ryu, Ji-Hwan,Bae, Yun-Soo,Kang, Sang-Won,Jang, In-hwan,Brey, Paul T.,Lee, Won-Jae Elsevier 2005 DEVELOPMENTAL CELL Vol.8 No.1
<P><B>Abstract</B></P><P>A fundamental question that applies to all organisms is how barrier epithelia efficiently manage continuous contact with microorganisms. Here, we show that in <I>Drosophila</I> an extracellular immune-regulated catalase (IRC) mediates a key host defense system that is needed during host-microbe interaction in the gastrointestinal tract. Strikingly, adult flies with severely reduced IRC expression show high mortality rates even after simple ingestion of microbe-contaminated foods. However, despite the central role that the NF-κB pathway plays in eliciting antimicrobial responses, NF-κB pathway mutant flies are totally resistant to such infections. These results imply that homeostasis of redox balance by IRC is one of the most critical factors affecting host survival during continuous host-microbe interaction in the gastrointestinal tract.</P>
STRATOSPHERIC IMAGES OF JUPITER DERIVED FROM HYDROCARBON EMISSIONS IN VOYAGER 1 AND 2 IRIS SPECTRA
Seo, Haing-Ja,Kim, Sang-Joon,Choi, W.K.,Kostiuk, T.,Bjoraker, G. The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.4
Spectroscopic data obtained by the Infrared Interferometer Spectrometer (IRIS) aboard Voyager 1 and 2 have been re-visited. Using the spectroscopic data and footprints of the IRIS aperture on the planet, we constructed images of the stratosphere of Jupiter at the emission bands of hydrocarbons including $CH_4,\;C_2H_6,\;C_2H_2,\;C_3H_4,\;C_6H_6$, and $C_2H_4$. Thermal emission from the hydrocarbons on Jupiter originates from a broad region of the stratosphere extending from 1 to 10 millibars. We averaged the data using a bin of 20 degrees of longitude and latitudes in order to increase signal-to-noise ratios. The resultant images show interesting wave structure in Jupiter's stratosphere. Fourier transform analyses of these images yield wavenumbers 5 - 7 at mid-Northern and mid-Southern latitudes, and these results are different from those resulted from previous ground-based observations and recent Cassini CIRS, suggesting temporal variations on the stratospheric infrared pattern. The comparisons of the Voyager 1 and 2 spectra also show evidence of temporal intensity variations not only on the infrared hydrocarbon polar brightenings of hydrocarbon emissions but also on the stratospheric infrared structure in the temperate regions of Jupiter over the 4 month period between the two Voyager encounters. Short running title: Stratospheric Images of Jupiter derived from Voyager IRIS Spectra.