• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.3
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• pp.213-232
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• 2009

This document was prepared to review and summarize the analytical methods for airborne and bulk asbestos. Basic principles, shortcomings and advantages for asbestos analytical instruments using phase contrast microscopy(PCM), polarized light microscopy(PLM), X-ray diffractometer (XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM) were reviewed. Both PCM and PLM are principal instrument for airborne and bulk asbestos analysis, respectively. If needed, analytical electron microscopy is employed to confirm asbestos identification. PCM is used originally for workplace airborne asbestos fiber and its application has been expanded to measure airborne fiber. Shortcoming of PCM is that it cannot differentiate true asbestos from non asbestos fiber form and its low resolution limit ($0.2{\sim}0.25{\mu}m$). The measurement of airborne asbestos fiber can be performed by EPA's Asbestos Hazard Emergency Response Act (AHERA) method, World Health Organization (WHO) method, International Standard Organization (ISO) 10312 method, Japan's Environmental Asbestos Monitoring method, and Standard method of Indoor Air Quality of Korea. The measurement of airborne asbestos fiber in workplace can be performed by National Institute for Occupational Safety and Health (NIOSH) 7400 method, NIOSH 7402 method, Occupational Safety and Health Administration (OSHA) ID-160 method, UK's Health and Safety Executive(HSE) Methods for the determination of hazardous substances (MDHS) 39/4 method and Korea Occupational Safety and Health Agency (KOSHA) CODE-A-1-2004 method of Korea. To analyze the bulk asbestos, stereo microscope (SM) and PLM is required by EPA -600/R-93/116 method. Most bulk asbestos can be identified by SM and PLM but one limitation of PLM is that it can not see very thin fiber (i.e., < $0.25{\mu}m$). Bulk asbestos analytical methods, including EPA-600/M4-82-020, EPA-600/R-93/116, OSHA ID-191, Laboratory approval program of New York were reviewed. Also, analytical methods for asbestos in soil, dust, water were briefly discussed. Analytical electron microscope, a transmission electron microscope equipped with selected area electron diffraction (SAED) and energy dispersive X-ray analyser(EDXA), has been known to be better to identify asbestiform than scanning electron microscope(SEM). Though there is no standard SEM procedures, SEM is known to be more suitable to analyze long, thin fiber and more cost-effective. Field emission scanning electron microscope (FE-SEM) imaging protocol was developed to identify asbestos fiber. Although many asbestos analytical methods are available, there is no method that can be applied to all type of samples. In order to detect asbestos with confidence, all advantages and disadvantages of each instrument and method for given sample should be considered.

• Journal of the Korean Society of Radiology
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• v.11 no.2
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• pp.87-94
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• 2017

Monte Carlo simulations were used to assess dose enhancement effects for 60-, 90-, 120-, and 150-kV X-rays, and for 6- and 15-MV X-rays. The MCNPX code was used for a computer simulation of the ICRU slab phantom, and gold, gadolinium, and iron oxide (Fe2O3) were employed as dose enhancement agents. In consideration of the buildup region of the incident energy, agent concentrations of 5, 10, 15, and 20 mg/g were inserted on the surface of the phantom at a depth of 5 cm. Based on baseline values obtained in the absence of dose enhancement agents, a quantitative analysis was performed by evaluating depth-dependent changes in the absorbed energy and the dose enhancement factor (DEF). A higher concentration of dose enhancement agents led to a greater dose enhancement effect with iron oxide, gadolinium, and gold in descending order. For kilovoltage (kV) X-rays, as the incident energy was decreased and as the energy became closer to the ionization potential of the atoms in the enhancement agent, the dose enhancement effect increased. In the megavoltage (MV) X-ray range, dose enhancement was higher at 6 MV compared with 15 MV. However, the overall dose enhancements were significantly lower compared to the results obtained with kV X-rays.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.10
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• pp.1389-1393
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• 2001

A study was carried out to investigate the nutritive value and utilization of three grass species, batiki grass (lschaemum aristatum var. indicum), guinea grass (Panicum maximum) and signal grass (Bracharia decumbens) by growing goats. Eighteen growing crossbred goats $(Anglo-Nubian{\times}Fiji\;local)$ of between 9-11 months of age and pre-trial average live weight of $9.50{\pm}1.60kg$ were divided on the basis of weight to three treatment groups in a completely randomized design. The grasses constituted the diets and they were harvested fresh and chopped into pieces before they were offered to the goats. Chemical composition of the grasses, DMI, body weight gain (BWG) and apparent nutrient digestibility coefficients were measured. The grasses had similar DM content. The CP content of the grasses was in the range of 8.3-11.2%. Crude fiber (CF) content was between 30.9-35.2%. Ether extract (EE) was low with a range of 1.2-1.8%. Nitrogen free extract (NFE) was similar (40.9%) for batiki and guinea grasses, while signal grass had more NFE content (51.1%). The grasses are good sources of minerals (ash). OM content was higher in signal grass while guinea and batiki grasses had similar OM content. The goats on signal grass had higher DMI than those on batiki and guinea grasses (p<0.05). The goats on batiki grass had lower average BWG (p<0.05) than those on guinea and signal grasses. Nutrients digestibility were significantly (p<0.05) higher in the goats on signal grass compared to those on guinea and batiki grasses. The goats on guinea grass were better (p<0.05) in the digestibility of CP, OM, NFE and ME than those on batiki grass. However, goats on batiki were significantly better (p<0.05) in digestibility of CF than those on guinea grass. Signal and guinea grasses had more DCP than batiki grass. DE was lower in batiki grass (p<0.05) than in guinea and signal grasses. There was no significant difference (p>0.05) between batiki and guinea grasses in TON. Data obtained in this experiment demonstrated that signal grass is better than guinea and signal in the nutrition of growing goats in the tropical environment of Samoa. It had the highest nutritive value, better apparent digestibility coefficients which have better growth rate and feed efficiency. In ranking, signal grass was better than guinea and batiki grasses, while guinea grass was better than batiki in nutritive value in the parameters measured. For future pasture establishment in Samoa, signal grass is recommended for consideration because of its higher nutritive value as a replacement for batiki, the most predominant grass.

• Ocean and Polar Research
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• v.24 no.2
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• pp.123-134
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• 2002

Seasonal variations of settling particles and metal fluxes were monitored at a nearshore site of Marian Cove, King Geroge Island, Antarctica from 28th February 1998 to 22nd January 2000. Near-bottom sediment traps were deployed at 30m water depth of the cove, and sampling bottles were recovered every month by SCUBA divers. Total particulate flux and metal concentrations were determined from the samples. Total particulate flux showed a distinct seasonality, high in austral summer and low in austral winter: the highest flux $(21.97g\;m^{-2}d^{-1})$ was found in February of 1999, and the lowest $(2.47g\;m^{-2}d^{-1})$ in September of 1998, when sea surface was frozen completely. Lithogenic particle flux accounted for 90% of the total flux, and showed a significantly negative correlation with the thickness of snow accumulation around the study site. It was suggested that the most of the lithogenic particles trapped in the bottles was transported by melt water stream from the surrounding land. Fluxes of Al, Fe, Ti, Mn, Zn, Cii, Co, Ni, Cr, Cd, and Pb showed similar seasonal variations with the total flux, and their averaged fluxes were 34000, 9000,960, 180, 13.8, 17.6, 3.0,2.1, 5.4, 0.02, and $1.5nmol\;m^{-2}d^{-1}$ respectively. Among the metals, Cu and Cd showed the most noticeable seasonal patterns. The Cd flux correlated positively with the fluxes of biogenic components while the Cu flux correlated with both the lithogenic and biogenic particle fluxes. The Cu flux peak in the late summer is likely related to a substantial amount of inflow of ice melt water laden with Cu-enriched lithogenic particles. On the other hands, the Cd flux peak in the early spring may be associated with the unusually early occurred phytoplankton bloom.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.4
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• pp.607-615
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• 2018

Objective: This study was conducted to isolate the cellulolytic microorganism from the rumen of Holstein steers and characterize endoglucanase gene (Cel5A) from the isolated microorganism. Methods: To isolate anaerobic microbes having endoglucanase, rumen fluid was obtained from Holstein steers fed roughage diet. The isolated anaerobic bacteria had 98% similarity with Eubacterium cellulosolvens (E. cellulosolvens) Ce2 (Accession number: AB163733). The Cel5A from isolated E. cellulolsovens sp. was cloned using the published genome sequence and expressed through the Escherichia coli BL21. Results: The maximum activity of recombinant Cel5A (rCel5A) was observed at $50^{\circ}C$ and pH 4.0. The enzyme was constant at the temperature range of $20^{\circ}C$ to $40^{\circ}C$ but also, at the pH range of 3 to 9. The metal ions including $Ca^{2+}$, $K^+$, $Ni^{2+}$,$Mg^{2+}$, and $Fe^{2+}$ increased the endoglucanase activity but the addition of $Mn^{2+}$, $Cu^{2+}$, and $Zn^{2+}$ decreased. The Km and Vmax value of rCel5A were 14.05 mg/mL and $45.66{\mu}mol/min/mg$. Turnover number, Kcat and catalytic efficiency, Kcat/Km values of rCel5A was $96.69(s^{-1})$ and 6.88 (mL/mg/s), respectively. Conclusion: Our results indicated that rCel5A of E. cellulosolvens isolated from Holstein steers had a broad pH range with high stability under various conditions, which might be one of the beneficial characteristics of this enzyme for possible industrial application.

• KSBB Journal
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• v.27 no.6
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• pp.352-360
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• 2012

Bacillus clausii I-52 which produced SDS- and $H_2O_2$-tolerant extracellular alkaline protease (BCAP) was isolated from heavily polluted tidal mud flat of West Sea in Incheon, Korea and stable strain (transformant C5) of B. clausii I-52 harboring another copy of BCAP gene in the chromosome was developed using the chromosome integration vector, pHPS9-fuBCAP. When investigated the production of BCAP using B. clausii transformant C5 through pilot-scale submerged fermentation (500 L) at $37^{\circ}C$ for 30 h with an aeration rate of 1 vvm and agitation rate of 250 rpm, protease yield of approximately 105,700 U/mL was achieved using an optimized medium (soybean meal 2%, wheat flour 1%, sodium citrate 0.5%, $K_2HPO_4$ 0.4%, $Na_2HPO_4$ 0.1%, NaCl 0.4%, $MgSO_4{\cdot}7H_2O$ 0.01%, $FeSO_4{\cdot}7H_2O$ 0.05%, liquid maltose 2.5%, $Na_2CO_3$ 0.6%). The enzyme stability of BCAP was increased by addition of polyols (10%, v/v) and also, the stabilities of BCAP towards not only the thermal-induced inactivation at $50^{\circ}C$ but also the SDS and $H_2O_2$-induced inactivation at $50^{\circ}C$ were enhanced. Among the polyols examined, the best result was obtained with propylene glycol (10%, v/v). The BCAP supplemented with propylene glycol exhibited extreme stability against not only the detergent components such as ${\alpha}$-orephin sulfonate (AOS) and zeolite but also the commercial detergent preparations. The granulized enzyme of BCAP was prepared with approximately 1,310,000 U/g of granule. Wash performance analysis using EMPA test fabrics revealed that BCAP granule exhibited high efficiency for removal of protein stains in the presence of anionic surfactants as well as bleaching agents. When compared to Savinase 6T$^{(R)}$ and Everlase 6T$^{(R)}$ manufactured by Novozymes, BCAP under this study probably showed similar or higher efficiency for the removal of protein stains. These results suggest that the alkaline protease produced from B. clausii transformant C5 showing high stability against detergents and high wash performance has significant potential and a promising candidate for use as a detergent additive.

• Resources Recycling
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• v.25 no.2
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• pp.33-41
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• 2016

A scale up tests (380 kg/day) using a continuous solvent extraction and electro-winning system was carried out to separate and recover cobalt from a solution containing 1.91 g/L Co and 14.65 g/L Ni. The solution was obtained during a process including solvent extraction and precipitation stages for removal of Cu and Fe from a synthetic sulfuric acid solution of manganese nodule matte. The optimal condition for solvent extraction was : solvent concentration of 0.22M Na-Cyanex 272 (45% saponified with NaOH) and O:A phase ratios of 1:1.5, 10:1 and 1.5:1 used in extraction, scrubbing and stripping stages, respectively. The extraction and stripping efficiencies were found to be 99.8% and 99.88%, respectively. The stripped solution contained 40.27 g/L Co with 4 ppm Ni. Cobalt metal of 99.963% purity was yielded with current efficiency of 67% and current density of $0.563A/dm^2$ during the electro-winning process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.143-143
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• 2017

CrAlN 코팅은 높은 경도, 낮은 표면 조도 등의 상온에서의 우수한 기계적 특성 이외에 고온에서 안정한 합금상의 형성으로 인하여 우수한 내산화성 및 내열성을 보유하여 공구 코팅으로의 적용 가능성이 크다. 그러나 최근 공구사용 환경의 가혹화로 인하여 코팅의 내마모성 및 내열성 등의 물성 향상을 통한 공구의 수명 향상이 필요시 되고 있으며, 다양한 코팅 물질을 활용하여 다층 코팅을 합성함으로써 난삭재용 공구 코팅의 물성을 높이는 연구들이 진행되고 있다. 본 연구에서는 CrAlN 코팅과 WC-Co 6wt.% 모재 사이에 CrZrN, CrN, CrN/CrZrSiN 등의 중간층을 합성하여 CrAlN 코팅의 상온 및 고온 특성을 향상시키는 연구가 진행되었다. 합성된 코팅의 구조 및 물성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, atomic force microscopy(AFM) 및 ball-on-disk wear tester를 사용하였다. 코팅의 고온 특성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였고, $500^{\circ}C$ annealing 코팅의 표면 조도 분석 및 $500^{\circ}C$에서 마찰마모시험을 실시하였다. CrAlN 코팅의 상온 특성을 분석한 결과, 모든 코팅의 경도(35.5-36.2 GPa)와 탄성계수(424.3-429.2 GPa)는 중간층의 종류에 상관없이 비슷한 값을 보인 것으로 확인됐다. 그러나, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 마찰계수는 0.33로 CrZrN 중간층을 증착한 CrAlN 코팅의 마찰계수(0.41)에 비해 향상된 값 보였으며, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아 코팅의 내마모성이 향상된 것으로 판단된다. 이것은 중간층의 H/E ratio가 코팅의 내마모성에 미치는 영향에 의한 결과로 사료된다. H/E ratio는 파단시의 최대 탄성 변형율로써, 모재/중간층/코팅의 H/E ratio 구배에 따라 코팅 내의 응력의 완화 정도가 변하게 된다. WC 모재 (H/E=0.040)와 CrAlN 코팅(H/E=0.089) 사이에서 CrN, CrZrSiN 중간층의 H/E ratio는 각각 0.076, 0.083 으로 모재/중간층/코팅의 H/E ratio 구배가 점차 증가함을 확인 할 수 있었고, 일정 응력이 지속적으로 가해지면서 진행되는 마모시험중에 CrN과 CrZrSiN 중간층이 WC와 CrAlN 코팅 사이에서 코팅 내부의 응력구배를 완화시키는 역할을 함으로써 CrAlN 코팅의 내마모성이 향상된 것으로 판단된다. 내열성 시험 결과, CrN/CrZrSiN 중간층을 증착한 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었다. $500^{\circ}C$ annealing 후 진행된 표면 조도와 마모시험 결과, 모든 코팅의 조도 값 및 마찰계수는 상온 값에 비해 증가하였으며 CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 변화량이 가장 낮은 값을 보였다. 이는 CrZrSiN 중간층 내에 존재하는 $SiN_x$ 비정질상이 고온 annealing시에 산소 차폐막 역할을 하여, 코팅내의 잔류 산소에 의한 산화작용을 효과적으로 방지함으로써 코팅의 고온 특성이 향상된 것으로 판단된다.

• Economic and Environmental Geology
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• v.29 no.1
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• pp.45-55
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• 1996

Although the Dongjin Au-Ag-Cu mine had been abandoned since about forty years ago, the results of this study on the dispersion patterns and contamination level of heavy metals in the hydrologic system flowing via the waste rump show that the environmental impacts from the mine wastes are still significant. The stream water in the vicinity of the waste rump is severely acidified (pH 3.8 to 4.4) and highly enriched in various dissolved heavy metals. The heavy metal contents of the stream water and stream sediments are systematically attenuated with increasing distance from the mine area. However, it is worth to note that continuous attenuation of heavy metal contents in both media were reenriched in downstream area more than 800 m apart from the mine because it can be acted as a secondary source of heavy metal pollution. The heavy metals, especially Cd, Cu and Zn of polluted downstream sediments mainly occur in Fe-Mn oxides and organic materials, which indicates that these elements are the main pollutants from the waste rump of the Dongjin mine. The heavy metal contents of crops, such as sesame, perilla, red Pepper and brown rice, collected from the polluted farm land in the downstream area are lower than those of land plants from stream sides, but significantly higher in Cd, Cr, Cu and Zn than those from the unpolluted farm land. Especially, almost all of the crops in polluted farm land have been severly contaminated by Cd (>0.4 ppm). On the other hand, the heavy metal contents of the crops collected from refreshed farm land by means of a soil addition method shows significantly lowered level comparing with those of polluted area, which indicates that a soil addition method was effective for the refreshment of polluted farm land by toxic metallic pollutants. Wormwoods from this area showed very high contents in a11 the heavy metals even in unpolluted area (Cd > 1 ppm, Cr > 1 ppm, Cu > 11 ppm, Pb> 4 ppm, Zn > 55 ppm), indicating that a special caution must be payed when one takes ingest them.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.93-99
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• 2017

Dose enhancement effects at megavoltage (MV) X and ${\gamma}-ray$ energies, and the effects of different energy levels on incident energy, dose enhancement agents, and concentrations were analyzed using Monte Carlo simulations. Gold, gadolinium, Iodine, and iron oxide ($Fe_2O_3$) were compared as dose enhancement agents. For incident energy, 4, 6, 10 and 15 MV X-ray spectra produced by a linear accelerator and a Co-60 ${\gamma}-ray$ were used. The dose enhancement factor (DEF) was calculated using an ICRU Slab phantom for concentrations of 7, 18, and 30 mg/g. The DEF was higher at higher concentrations of dose enhancement agents and at lower incident energies. The calculated DEF ranged from 1.035 to 1.079, and dose enhancement effects were highest for iron oxide, followed by iodine, gadolinium, and gold. Thus, this study contributes to improving the therapeutic ratio by delivering larger doses of radiation to tumor volume, and provides data to support further in vivo and in vitro studies.