• Korean Journal of Veterinary Research
• /
• v.42 no.3
• /
• pp.327-333
• /
• 2002

The study was carried out to examine the distribution and survival rate of Listeria monocytogenes (L monocytogenes) from various source of waters using improved isolation method. In comparision of enrichment media for isolation of L monocytogenes from water, the isolation rate and 50% detection limit of the pathogen were higher in UVM modified Listeria enrichment broth (UVM) than Listeria enrichment broth (LEB). On the other hand, when compared the selective media for isolation of the pathogen from water, the isolation rate was highest in culture at Oxford agar followed by Fraser agar, and LEB agar. In order to improve enrichment method, 100 ml of water samples with 0.1 CFU/ml of L monocytogenes was inoculated into 10 ml of UVM concentrated at 10-fold, and incubated for 24 h at $36^{\circ}C$. Isolated frequency of the pathogens in improved enrichment method completely corresponded with common (filter) method. Of a total mumber of 147 water samples from river, lake and sea, the pathogen was isolated from 1 of 39 (2.6%) river water samples and 1 of 75 (1.3%) sea water samples, but no pathogen was isolated from 33 lake water samples. Serotypes of 2 isolates were identified as type 1. L monocytogenes decreased in number from 7.2-7.4 to 4.2-4.7 log CFU/ml for 1 week poststorage (5 and $20^{\circ}C$), but the pathogens were able to be detected in river and sea water until 8 weeks after storage. However, in tap water, L monocytogenes were decreased to undetectable level after 2 weeks of storage.

• Journal of Power Electronics
• /
• v.13 no.5
• /
• pp.746-756
• /
• 2013

The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC-DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC-DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations, and experiments confirm the theoretical analysis of the subunit of EPT.

• Fisheries and Aquatic Sciences
• /
• v.10 no.2
• /
• pp.53-59
• /
• 2007

In order to utilize skin of bullfrog (Rana catesbeiana Shaw) as an alternative source of collagen, we investigated and compared biochemical and physical properties of collagens isolated from bullfrog skin. Two kinds of collagen (BSASC; bullfrog skin acid-soluble collagen and BSPSC; bullfrog skin pepsin-solubilized collagen) were isolated by subsequent treatments with acetic acid and pepsin. The amounts of skin collagen isolated in the subsequent treatments were 7.3% BSASC and 18.2% BSPSC on the basis of lyophilized bullfrog skin weight, respectively. According to the electrophoretic pattern and CM-cellulose column chromatogram, the BSASC has the chain composition of ${\alpha}1{\alpha}2{\alpha}3$ heterotrimer, and the BSPSC consists of two ${\alpha}$ chains of ${\alpha}1{\alpha}2$. In addition, the denaturation temperatures of all collagens tested were ranged from $30^{\circ}C\;to\;38^{\circ}C$. This study suggests that there is a possibility to use bullfrog skin collagen as an alternative source of collagen for industrial purposes, and subsequently it may increase the economical value of the bullfrog.

• Korean Journal of Environmental Biology
• /
• v.19 no.1
• /
• pp.87-92
• /
• 2001

For the biological treatment of industrial wastewater containing high concentration of phenol, isolation and characterization of phenol - degrading bacterium were carried out. A bacterial strain P2 capable of degrading phenol was isolated from contaminated soils by enrichment culture technique and identified as the genus Rhodococcus by morphological, cultural, biochemical characteristics, and Biolog system. The optimal medium composition and cultural conditions for the growth and degradation of phenol by Rhodococcus sp. P2 were 0.1% of (NH$_4$)$_2$SO$_4$, 0.2% of KH$_2$PO$_4$, 0.25% of Na$_2$HPO$_4$ㆍ12$H_2O$, 0.2% of MgSO$_4$ㆍ7$H_2O$, and 0.008% of CaC1$_2$ㆍ2$H_2O$ along with initial pH 8.5 at 3$0^{\circ}C$. Rhodococcus sp. P2 could grow with phenol as the sole carbon source up to 1,800 ppm in batch cultures, but did not grow in medium containing above 2,000 ppm of phenol. When 800 ppm phenol was given in the optimal media, Rhodococcus sp. P2 completely degraded it within 24 h. Meanwhile, 1,800 ppm of phenol was degraded within 9 days. Rhodococcus sp. P2 could utilize toluene, n-hexane, xylene and benzene as sole carbon source .

• KSBB Journal
• /
• v.18 no.6
• /
• pp.479-484
• /
• 2003

34 strains were isolated from dyeing wastewater in order to improve treatment efficiency of dyeing wastewater containing PVA. Two strains of them were finally selected through the PVA degrading test, and identified as Microbacterium barkeri LCa and Paenibacillus amylolyticus LCb. As a result, optimal conditions for microbial growth and PVA degradation were 30$^{\circ}C$, neutral pH, starch as a carbon source, and peptone as a nitrogen source. And it was concluded that these two strains have good ability for PVA degradation. And 90% over PVA was degraded by single culture as well as a mixed culture of 2 different strains.

• Korean Journal of Microbiology
• /
• v.25 no.4
• /
• pp.339-345
• /
• 1987

A bacterium K-4-3, producing $\beta$-glucan hydrolyzing enzyme, was isolated from soil and identified to be Bacillus subtilis by its morpholohical and physiological characteristics. $\beta$-glucan was coloured using cibacron blue 3G-A and cross linded by the addition of 1, 4-butanedioldiglycidyl ether. This substrate was used for the isolation of $\beta$-glucanase producing microorganism. The $\beta$-glucan hydrolyzing enzyme actibity from isolated K-4-3 strain was also measured using the modified substrate. Bacillus subtilis K-4-3 produced the highest extracellular $\beta$-glucan hydrolyzing activity in the basal medium containing $\beta$-glucan as a carbon source, peptone and tryptone as a nitrogen source, and magnesium sulfate as an inorganic salt. The optimum temperature and initial pH for $\beta$-glucanase production by Bacillus subtilis K-4-3 were $37^{\circ}C$ and pH6. The highest enzyme activity was obtained at the culture age of 54 hrs with rotary shaking at $37^{\circ}C$. The crude enzyme showed the highest activity at pH 7.5-8.0 and $65^{\circ}C$.

• Journal of Animal Reproduction and Biotechnology
• /
• v.38 no.1
• /
• pp.10-16
• /
• 2023

Intermuscular fat is essential for enhancing the flavor and texture of cultured meat. Mesenchymal stem cells derived from intermuscular adipose tissues are a source of intermuscular fat. Therefore, as a step towards developing a platform to derive intermuscular fat from mesenchymal stem cells (MSCs) for insertion between myofibrils in cultured beef, an advanced protocol of intermuscular adipose tissue dissociation effective to the isolation of MSCs from intermuscular adipose tissues was developed in cattle. To accomplish this, physical steps were added to the enzymatic dissociation of intermuscular adipose tissues, and the MSCs were established from primary cells dissociated with physical step-free and step-added enzymatic dissociation protocols. The application of a physical step (intensive shaking up) at 5 minutes intervals during enzymatic dissociation resulted in the greatest number of primary cells derived from intermuscular adipose tissues, showed effective formation of colony forming units-fibroblasts (CFU-Fs) from the retrieved primary cells, and generated MSCs with no increase in doubling time. Thus, this protocol will contribute to the stable supply of good quality adipose-derived mesenchymal stem cells (ADMSCs) as a fat source for the production of marbled cultured beef.

• Korean Journal of Optics and Photonics
• /
• v.8 no.6
• /
• pp.476-481
• /
• 1997

Optimum operating conditions of the 0.98 $\mu\textrm{m}$-pumped broadband erbium-doped fiber sources, where the mean wavelength variation is minimized, have been experimentally investigated. The optimum conditions for the mean wavelength stabilization were found to be different between the case of the isolated source and the case of the presence of feedback. In case of feedback, the proper pump power that yields zero slope of mean wavelength variation was found to be lower than that of the isolated case, and the mean wavelength was found nearly unchanged over the wide range of pump power. Howerer, the feedback resulted in lower output power and the mean wavelength was found to be sensitive to the variation of feedback level. In the respect of mean wavelength stability, the better performance could be obtained with some feedback, provided that the feedback level is kept constant. Thus we could also enhance the mean wavelength stability by allowing appropriate constant feedback into the source.

• Journal of Power Electronics
• /
• v.15 no.5
• /
• pp.1217-1226
• /
• 2015

In a grid-connected photovoltaic (PV) system, the traditional Z-source inverter uses a low frequency transformer to ensure galvanic isolation between the grid and the PV system. In order to combine the advantages of both Z-source inverters and transformerless PV inverters, this paper presents a modified single-phase transformerless Z-source PV grid-connected inverter and a corresponding PWM strategy to eliminate the ground leakage current. By utilizing two reversed-biased diodes, the path for the leakage current is blocked during the shoot-through state. Meanwhile, by turning off an additional switch, the PV array is decoupled from the grid during the freewheeling state. In this paper, the operation principle, PWM strategy and common-mode (CM) characteristic of the modified transformerless Z-source inverter are illustrated. Furthermore, the influence of the junction capacitances of the power switches is analyzed in detail. The total losses of the main electrical components are evaluated and compared. Finally, a theoretical analysis is presented and corroborated by experimental results from a 1-kW laboratory prototype.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.366-370
• /
• 2006

In this study, characteristics of impact force and impact sound of impact source such as bang machine, impact ball, and children's jumping were review. Results of review showed that impact ball has most similar characteristic to real impact sources in terms of objective properties such as impact force and impact sound. The effects of various isolator on floor impact sound were also investigated in apartment building and test facilities building using bang machine an impact ball. From the field measurement, it was found that the difference in reduction sound level between bang machine and impact ball was relatively large and the reduction sound level by impact ball was much larger than bang machine.