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KIM, HOIKYUNG,KIM, HAEYOUNG,BANG, JIHYUN,BEUCHAT, LARRY R.,RYU, JEE-HOON International Association for Food Protection 2010 Journal of food protection Vol.73 No.7
<P>Studies were done to determine whether calcium hypochlorite (Ca(OCl)2) and chlorine dioxide (ClO2) treatment followed by drying had a synergistic killing effect on microorganisms on radish seeds intended for sprout production. Uninoculated radish seeds and seeds inoculated with Escherichia coli O157:H7 were treated with water, Ca(OCl)2 (free chlorine concentrations of 50 or 200 μg/ml), or ClO2 (50 or 200 μg/ml) for 5 min and subsequently dried at 25°C for up to 24 h. Populations of total aerobic bacteria (TAB), molds and yeasts (MY), and E. coli O157:H7 on the seeds treated with Ca(OCl)2 were not significantly different (P = 0.05) than populations on seeds treated with ClO2 at the same concentrations. However, populations of microorganisms on seeds treated with ClO2 decreased more rapidly during drying. Treatment with ClO2 (200 μg/ml) followed by drying caused reductions in TAB, MY, and E. coli O157:H7 of 3.1, 2.0, and 3.8 log CFU/g, respectively. When seeds were treated with water, Ca(OCl)2 (50 or 200 μg/ml), and ClO2 (50 μg/ml) and subsequently dried, reductions in TAB, MY, and E. coli O157:H7 were 0.2 to 2.0, 0.4 to 2.0, and 1.4 to 2.2 log CFU/g, respectively. Results indicate that inactivation of E. coli O157:H7 on radish seeds is greater after treatment with ClO2 followed by drying than after treatment with Ca(OCl)2 followed by drying, thus providing a synergistic treatment combination for reducing the safety risk associated with sprouts produced from these seeds.</P>
Metabolic Responses of Activated Sludge to Pentachlorophenol in SBR Systems
Kim, Sung Jae,Benefield, Larry D. 한국환경과학회 1994 한국환경과학회지 Vol.3 No.3
The primary objective of this study was to examine the toxic effects of PCP on activated sludge and to analyze its metabolic responses while treating wastewater containing pentachlorophenol (PCP) in a sequencing batch reactor (SBR) system operating under different control strategies. This study was conducted in two phases 1 and 2 (8-㏊ and 12-㏊ cycles) Each phase was operated with two control strategies I and II. Strategy I (reactor 1) involved rapid addition (5 minutes to complete) of substrate to the reactor with continuods mixing but no aeration for 2 hours. Strategy II (reactor 2) involved adding the feed continuodsly during the first 2 hours of the cycle when the system, was mixed but not aerated During both phases each reactor was operated at a sludge age of 15 days. The synthetic wastewater was used as a feed. The COD of the feed solution was about 380㎎/ℓ. After the reference response for both reactors was established, the steady state response of each system was established for PUP teed concentrations of 0.1 ㎎/ℓ, 1,0㎎/ℓ, and 5.0 ㎎/ℓin SBR systems operating on both 8-hr and 12-hr cycles. Soluble COD removal was not inhibited at any feed PCP concentrations used. At 5.0 ㎎/ℓfeed PCP concentration and in SBR systems operating on phase 2, the concentrations of MLVSS were dereased; selective pressure on the mixed biomass might be increased, narrowing the range of possible ecological responses; the settleability of activated sludge was poor; the SOURs were increased, showing that the systems were shocked. Nitrification was made to some extent at all concentrations of feed PCP in SBR systems operating on phase 2 whereas in SBR systems operating on phase I little nitrification was observed, Then, nitificaiion will be delayed as much as soluble COD removal is retarded due to PCP inbition effects. Enhanced biological phosphorus removal occurring in the sytem operating with control strategy I during phase I of this work and in the presence of low concentrations of PCP was unreliable and might cease at anytime, whereas enhanced biological phosphorus removal occurring in the system operating with either control strategy . I or II during phase 2 of this work and in the presence of feed PCP concentrations up to 1.0 ㎎/ℓ was reliable. When, however, such processes were exposed to 5.0 ㎎/ℓ PCP dose, enhanced phosphorus removal ceased and never returned.
Kim, Yong-Seog,Kim, Joong Kyun,Weber, Larry F. Institute of Electrical and Electronics Engineers 2017 IEEE transactions on electron devices Vol.64 No.8
<P>Exo-electron emission from MgO nanopowders sprayed on MgO thin film of alternating current plasma display panels was measured experimentally. Effects of several key parameters including panel temperature on the emission currents were measured and compared with a thermostimulated exo-electron emission model with three energy levels proposed in this paper. The results indicate that the exo-electronemission phenomenon is controlledby a thermal excitation of trapped electrons at shallow levels, similar to 0.2 similar to 0.3 eV below the conduction band edge. The MgO nanopowders increases the emission current significantly over the MgO thin film, possibly due to a higher concentration of recombination centers at deeper energy levels.</P>
Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska
Kim, Hye Min,Jung, Ji Young,Yergeau, Etienne,Hwang, Chung Yeon,Hinzman, Larry,Nam, Sungjin,Hong, Soon Gyu,Kim, Ok-Sun,Chun, Jongsik,Lee, Yoo Kyung Blackwell Publishing Ltd 2014 FEMS microbiology ecology Vol.89 No.2
<P>The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0–10 cm to 10–20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen ([FORMULA OMISSION] and [FORMULA OMISSION]). The community compositions of the two different depths showed that <I>Alphaproteobacteria</I> decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted <SMALL>UNIFRAC</SMALL> distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska.</P>
Park, Sunhyung,Choi, Seonyeong,Kim, Hoikyung,Kim, Yoonsook,Kim, Byeong-sam,Beuchat, Larry R.,Ryu, Jee-Hoon Elsevier 2015 FOOD MICROBIOLOGY Vol.48 No.-
<P><B>Abstract</B></P> <P>We compared the microbiological quality of chicken eggshells obtained from a traditional wholesale market and a modern supermarket. We also determined the survival and growth characteristics of naturally occurring mesophilic aerobic bacteria (MAB) and artificially inoculated <I>Salmonella enterica</I> on eggshells under various environmental conditions (presence of chicken feces, temperature [4, 12, or 25?°C], and relative humidity [RH; 43 or 85%]). The populations of MAB, coliforms, and molds and yeasts on eggshells purchased from a traditional wholesale market were significantly (<I>P</I>?≤?0.05) higher than those from a modern supermarket. In the second study, when we stored uninoculated eggs under various storage conditions, the population of MAB on eggshells (4.7–4.9 log CFU/egg) remained constant for 21 days, regardless of storage conditions. However, when eggshells were inoculated with <I>S.?enterica</I> and stored under the same conditions, populations of the pathogen decreased significantly (<I>P</I>?≤?0.05) under all tested conditions. Survival of <I>S.?enterica</I> increased significantly <I>(P</I>?≤?0.05) in the presence of feces, at low temperatures, and at low RH. These observations will be of value when predicting the behavior of microorganisms on eggshells and selecting storage conditions that reduce the populations of <I>S. enterica</I> on eggshells during distribution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microbial levels of eggshells from traditional market and supermarket were compared. </LI> <LI> Behaviors of microbes on eggshells as affected by storage conditions were studied. </LI> <LI> Eggshells from traditional market had more microbes than those from supermarket. </LI> <LI> Populations of <I>Salmonella</I> on eggshell surfaces decreased under all tested conditions. </LI> <LI> Survival of <I>Salmonella</I> increased when stored with feces at low temperature and RH. </LI> </UL> </P>
Kim, Hoikyung,Ryu, Jee-Hoon,Beuchat, Larry R. American Society for Microbiology 2007 Applied and environmental microbiology Vol.73 No.4
<B>ABSTRACT</B><P>The effectiveness of 13 disinfectants used in hospitals, day-care centers, and food service kitchens in killing <I>Enterobacter sakazakii</I> in suspension, dried on the surface of stainless steel, and in biofilm was determined. <I>E. sakazakii</I> exhibited various levels of resistance to the disinfectants, depending on the composition of the disinfectants, amount and type of organic matrix surrounding cells, and exposure time. Populations of planktonic cells suspended in water (7.22 to 7.40 log CFU/ml) decreased to undetectable levels (<0.30 log CFU/ml) within 1 to 5 min upon treatment with disinfectants, while numbers of cells in reconstituted infant formula were reduced by only 0.02 to 3.69 log CFU/ml after the treatment for 10 min. The presence of infant formula also enhanced the resistance to the disinfectants of cells dried on the surface of stainless steel. The resistance of cells to disinfectants in 6-day-old and 12-day-old biofilms on the surface of stainless steel was not significantly different. The overall order of efficacy of disinfectants in killing <I>E. sakazakii</I> was planktonic cells > cells inoculated and dried on stainless steel > cells in biofilms on stainless steel. Findings show that disinfectants routinely used in hospital, day-care, and food service kitchen settings are ineffective in killing some cells of <I>E. sakazakii</I> embedded in organic matrices.</P>
Imaging of the Lamina Cribrosa in Glaucoma: Perspectives of Pathogenesis and Clinical Applications*
Kim, Tae-Woo,Kagemann, Larry,Girard, Michaë,l J. A.,Strouthidis, Nicholas G.,Sung, Kyung Rim,Leung, Christopher K.,Schuman, Joel S.,Wollstein, Gadi Informa Healthcare USA, Inc. 2013 Current eye research Vol.38 No.9
<P>The lamina cribrosa (LC) is a sieve-like structure in the sclera where retinal ganglion cell axons exit from the eye. The LC has been known to play a critical role in the pathogenesis of glaucoma. With the advent of imaging technologies, such as enhanced depth imaging, spectral-domain optical coherence tomography (OCT) enables us to unveil the LC <I>in vivo</I> features. The application of adaptive optics technology and a compensatory image-processing algorithm has further improved the visualization of the beams and pores and neural pathways of the LC and the scleral insertion sites. Monitoring the changes of these structures in relation to acute and chronic elevation of intraocular pressure would be germane to decipher the relationship between the stress and strain response of the LC and optic nerve damage and improve our understanding of glaucoma pathophysiology. While the impact of investigating the integrity of LC is substantive, considerable challenges remain for imaging the LC. Nevertheless, with the rapid development of the OCT technology, it is expected that some of these limitations can be overcome and the potentials of LC imaging will be unraveled.</P>