• Journal of Sensor Science and Technology
• /
• v.7 no.1
• /
• pp.45-50
• /
• 1998

Platinum-Cobalt alloy thin films were deposited on $Al_{2}O_{3}$ substrate by magnetron cosputtering for RTD temperature sensors. We made Pt-Co alloy resistance patterns on the $Al_{2}O_{3}$ substrate by lift-off method and investigated the physical and electrical characteristics of these films under various conditions, the input power, working vacuum, annealing temperature and time, and also after annealing these films. The resistivity and sheet resistivity of these films were decreased with increasing the annealing temperature. At input power of Pt : $4.4\;W/cm^{2}$, Co : $6.91\;W/cm^{2}$, working vacuum of 10 mTorr and annealing conditions of $800^{\circ}C$ and 60 min, the resistivity and sheet resistivity of Pt-Co thin films was $15{\mu}{\Omega}{\cdot}cm$ and $0.5{\Omega}/{\square}$, respectively and the TCR value of Pt-Co alloy thin films with thickness of $3000{\AA}$ were $3740ppm/^{\circ}C$ in the temperature range of $25{\sim}600^{\circ}C$. These results indicate that Pt-Co alloy thin films have potentiality for the RTD temperature sensors.

• Resources Recycling
• /
• v.32 no.1
• /
• pp.21-32
• /
• 2023

Because the application of lithium has gradually increased for the production of lithium ion batteries (LIBs), more research studies about recycling using solvent extraction (SX) should focus on Li⁺ recovery from the waste solution obtained after the removal of the valuable metals nickel, cobalt and manganese (NCM). The raffinate obtained after the removal of NCM metal contains lithium ions and other impurities such as Na ions. In this study, we optimized a selective SX system using di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant and tri-n-butyl phosphate (TBP) as a modifier in kerosene for the recovery of lithium from a waste solution containing lithium and a high concentration of sodium (Li⁺ = 0.5 ~ 1 wt%, Na⁺ = 3 ~6.5 wt%). The extraction of lithium was tested in different solvent compositions and the most effective extraction occurred in the solution composed of 20% D2EHPA + 20% TBP + and 60% kerosene. In this SX system with added NaOH for saponification, more than 95% lithium was selectively extracted in four extraction steps using an organic to aqueous ratio of 5:1 and an equilibrium pH of 4 ~ 4.5. Additionally, most of the Na⁺ (92% by weight) remained in the raffinate. The extracted lithium is stripped using 8 wt% HCl to yield pure lithium chloride with negligible Na content. The lithium chloride is subsequently treated with high purity ammonium bicarbonate to afford lithium carbonate powder. Finally the lithium carbonate is washed with an adequate amount of water to remove trace amounts of sodium resulting in highly pure lithium carbonate powder (purity > 99.2%).

• Progress in Medical Physics
• /
• v.26 no.4
• /
• pp.193-200
• /
• 2015

The aim of this study is to present commissioning results of the ViewRay system. We verified safety functions of the ViewRay system. For imaging system, we acquired signal to noise ratio (SNR) and image uniformity. In addition, we checked spatial integrity of the image. Couch movement accuracy and coincidence of isocenters (radiation therapy system, imaging system and virtual isocneter) was verified. Accuracy of MLC positioing was checked. We performed reference dosimetry according to American Association of Physicists in Medicine (AAPM) Task Group 51 (TG-51) in water phantom for head 1 and 3. The deviations between measurements and calculation of percent depth dose (PDD) and output factor were evaluated. Finally, we performed gamma evaluations with a total of 8 IMRT plans as an end-to-end (E2E) test of the system. Every safety system of ViewRay operated properly. The values of SNR and Uniformity met the tolerance level. Every point within 10 cm and 17.5 cm radii about the isocenter showed deviations less than 1 mm and 2 mm, respectively. The average couch movement errors in transverse (x), longitudinal (y) and vertical (z) directions were 0.2 mm, 0.1 mm and 0.2 mm, respectively. The deviations between radiation isocenter and virtual isocenter in x, y and z directions were 0 mm, 0 mm and 0.3 mm, respectively. Those between virtual isocenter and imaging isocenter were 0.6 mm, 0.5 mm and 0.2 mm, respectively. The average MLC positioning errors were less than 0.6 mm. The deviations of output, PDDs between mesured vs. BJR supplement 25, PDDs between measured and calculated and output factors of each head were less than 0.5%, 1%, 1% and 2%, respectively. For E2E test, average gamma passing rate with 3%/3 mm criterion was $99.9%{\pm}0.1%$.

• Progress in Medical Physics
• /
• v.25 no.1
• /
• pp.46-52
• /
• 2014

Liquid ionization chamber is filled with liquid equivalent material unlike air filled ionization chamber. The high density material allow very small-volume chamber to be constructed that still have a sufficiently high sensitivity. However liquid ionization chamber should be considered for both initial recombination and general recombination. We, therefore, studied using the Co-60 beam as the continuous beam and the microLion chamber (PTW) for comparing the ion collection efficiency by Greening theory, two-dose rate method and our experiment method. The measurements were carried out using Theratron 780 as the cobalt machine and water phantom and 0.6 cc Farmer type ionization chamber was used with microLion chamber in same condition for measuring the charge of microLion chamber according to the dose rates. Dose rate was in 0.125~0.746 Gy/min and voltages applied to the microLion chamber were +400, +600 and +800 V. As the result, the collection efficiency by three method was generally less than 1%. In particular, our experimental collection efficiency was in good agreement within 0.3% with Greening theory except the lowest two dose rates. The collection efficiency by two-dose rate method also agreed with Greening theory generally less than 1%, but the difference was about 4% when the difference of two dose rates were lower. The ion recombination correction factors by Greening theory, two-dose rate method and our experiment were 1.0233, 1.0239 and 1.0316, respectively, in SSD 80 cm, depth 5 cm recommended by TRS-398 protocol. Therefore we confirmed that the loss by ion recombination was about 3% in this condition. We think that our experiment method for ion recombination correction will be useful tool for radiation dosimetry in continuous beam.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.22 no.2
• /
• pp.241-252
• /
• 1992

The purpose of this study was to investigate the changes of morphology and structure of bone tissue in the irradiated mandibular bone in rats which were fed a low calcium diet. In order to carry out this experimant, 64 seven-week old Sprague-Dawley strain rats weighing about 150gms were selected and equally divided into one experimental group of 32 rats and one control group with the remainder. The experimental group and the control group were then subdivided into two groups when the rats reached ten-week old, 16 were assigned rats for each subdivided group, exposed to irradiation. The two irradiation groups received a single dose of 20 Gy in the jaws area only and irradiated with a cobalt-60 teletherapy unit. The rats in the control and experimental groups were serially terminated by fours on the 3rd, the 7th, the 14th, and the 21st day after irradiation. Following termination, both sides of the dead rats mandibular bodies were removed and fixed with 10% neutral formalin. One side of the mandibular body was radiographed with a soft X-ray apparatus. Thereafter, the obtained microradiographs were observed by a light microscope. The remaining side of the mandibular bone was further decalcified and embedded in paraffin as using the general method. The specimen sectioned and stained with hematoxylin and eosin, and Rabit Anti-Human Tumor Necrosis Factor-a, observed by a light microscope. The obtained results were as follows: 1. Microradiogram revealed that thinning of the cortex and a decrease in the trabecula of the interradicular bone and mandibular body were observed and noted from the start to finish throughout the experiment in the non-irradiated rats on the low calcium diet rather than in the non-irradiated rats on the normal diet. In microscopic observations, there were marked osteolytic changes in the center of the bone marrow. 2. Microradiogram revealed that thinning of the cortex and a decrease in the trabecula of interradicular bone and mandibular body were more marked after 7 days in the irradiated rats on the low calcium diet rather than in the non-irradiated rats on the low clacium diet. In microscopic observations, osteoblasts were decreased markedly after 7 days, and a few osteoclasts were observed. 3. Microradiogram revealed that thinning of the cortex and a decrease in trabecula of interradicular bone and the mandibular body were more marked from the strart to finish troughout the experiment in the irradiated rats on the low calcium diet rather than in the irradiated rats on the normal diet. In microscopic observations, there were no osteolytic changes noted in the irradiated rats on the normal diet. 4. In immunocytochemical findings, a few bone marrow cells including Tumor Necrosis Factor were observed in the irradiated rats on the normal diet, but was not observed in the rats on the low calcium diet.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.22 no.2
• /
• pp.223-234
• /
• 1992

The purpose of this study was to investigate the changes of periodontal tissues in the irradiated mandibular bone in rats which were fed normal diet and low calcium diet In order to carry out this experiment, 64 seven-week old Sprague-Dawley strain rats weighing about 150gms were selected and equally divided into one experimental group of 32 rats and one control group with the remainder. The experimental group and the control group were then subdivided into two groups when the rats reached the age of 10 weeks, 16 rats were allotted for each subdivided group was composed of 16 rats and exposed to irradiation. The two groups were irradiated a single dose of 20Gy on the only jaw area and irradiated with a cobalt-60 teletherapy unit The rats in the control and experimental groups were serially dissected by fours on the 3rd, the 7th, the 14th, and the 21st day after irradiation. After each dissection, both sides of the dead rat mandibular bodies were removed and fixed with 10% neutral formalin. The specimens sectioned and observed in histopathological. histochemical. and immunocellular chemical methods. The obtained results were as follows: 1. In the mandibles of rats with low calcium diet the increased number of fibroblasts of periodontal ligaments. many small capillaries and irregular arrangement of loose collagen fibers were detected and the partial resorption of dentin and cementum could be found by the microscopic studies. 2. In the group of irradiated rats, degenerated periodontal tissues led to the condition of irregular arrangement of collagen fibers and the decreased number of fibroblasts. But this condition was somewhat restored after 21 days of experiment. 3. Periodontal tissues of the irradiated rat group with low calcium diet were destroyed earlier than those of the irradiated rat group with normal diet. Soon this condition was restored and then high cellularity and dense collagen fibers were observed. 4. Many periodontal cells bearing tumor necrosis factor could be clearly observed in the nonirradiated group of rats with normal diet, whereas could not be observed on the 7th day and reappeared on 14th day in the irradiated group of rats with normal diet. A few of them could be observed in the group of rats with low calcium diet, but they could be clearly observed in the both groups after 21 days of experiment.

• Radiation Oncology Journal
• /
• v.19 no.2
• /
• pp.146-152
• /
• 2001

Purpose : To investigate the regulation of apoptosis and cell cycle in mouse brain irradiation. Materials and Methods : 8-week old male mice, C57B1/6J were given whole body $\gamma-radiation$ with a single dose of 25 Gy using Cobalt 60 irradiator. At different times 1, 2, 4, 8 and 24hr after irradiation, mice were killed and brain tissues were collected. Apoptotic cells were scored by TUNEL assay. Expression of p53, Bcl-2, and Bax and cell cycle regulating molecules; cyclins Bl, Dl, E and cdk2, cdk4, $p34^{cdc2}$ were analysed by Western blotting. Cell cycle was analysed by Flow cytometry. Results : The peak of radiation induced apoptosis is shown at 8 hour after radiation. With a single 25 Gy irradiation, the peak of apoptotic index in C57B1/6J is $24.0{\pm}0.25$ (p<0.05) at 8 hour after radiation. Radiation upregulated the expression of p53/tubulin, Bax/tubulin, and Bcl-2/tubulin with 1.3, 1.1 and 1.45 fold increase, respectively were shown at the peak level at 8 hour after radiation. The levels of cell cycle regulating molecules after radiation are not changed significantly except cyclin D1 with 1.3 fold increase. Fractions of Go-Gl, G2-M and S phase in the cell cycle does not specific changes by time. Conclusion : In mouse brain tissue, radiation induced apoptosis is particularly shown in a specific area, subependyma. These results and lack of radiation induced changes in cell cycle ofter better understanding of radiation response of noraml brain tissue.

• Journal of Life Science
• /
• v.25 no.9
• /
• pp.1051-1058
• /
• 2015

Citrus mutant fruits were induced by irradiation of citrus budsticks with 120 Gy of cobalt (⁶⁰CO) gamma irradiation. The citrus mutant inhibited the growth and induced apoptosis in various human cancer cells, including A549, HepG2, HCT116, MCF-7, and Hela. The results of a trypan blue exclusion assay showed that citrus mutant fruits exhibited excellent antiproliferation activity in various human cancer cells and low cytotoxicity in normal 16HBE140- and CHANG cells. In addition, the cell death induced by the citrus mutant fruits was associated with an increased population of cells in sub-G1 phase, and it caused DNA fragmentation in human lung adenocarcinoma A549 and hepatocellular carcinoma HepG2 cells. It also up-regulated the amount of cellular nitric oxide (NO^•) produced as a result of nitric oxide synthase (NOS) activation and suppressed the inhibitor of apoptosis protein (IAP) family in A549 and HepG2 cells. These findings indicate that the citrus mutant fruits activates the NO^•-mediated apoptotic pathway in A549 and HepG2 cells. It may merit further investigation as a potential chemotherapeutic and chemopreventive agent for the treatment of various types of cancer cells. The results provide important major new insights into the mechanisms of the anticancer activity of citrus mutant fruits.

• Radiation Oncology Journal
• /
• v.24 no.4
• /
• pp.211-216
• /
• 2006

$\underline{Purpose}$: An analysis of the infrastructure for radiotherapy in Korea was performed to establish a baseline plan in 2006 for future development. $\underline{Materials\;and\;Methods}$: The data were obtained from 61 radiotherapy centers. The survey covered the number of radiotherapy centers, major equipment and personnel. Centers were classified into technical level groups according to the IAEA criteria. $\underline{Results}$: 28,789 new patients were treated with radiation therapy in 2004. There were 104 megavoltage devices in 61 institutions, which included 96 linear accelerators, two Cobalt 60 units, three Tomotherapy units, two Cyberknife units and one proton accelerator in 2006. Thirty-five high dose rate remote after-loading systems and 20 CT-simulators were surveyed. Personnel included 132 radiation oncologists, 50 radiation oncology residents, 64 medical physicists, 130 nurses and 369 radiation therapy technologists. All of the facilities employed treatment-planning computers and simulators, among these thirty-two percent (20 facilities) used a CT-simulator. Sixty-six percent (40 facilities) used a PET/CT scanner, and 35% (22 facilities) had the capacity to implement intensity modulated radiation therapy. Twenty-five facilities (41%) were included in technical level 3 group (having one of intensity modulated radiotherapy, stereotactic radiotherapy or intra-operative radiotherapy system). $\underline{Conclusion}$: Radiation oncology in Korea evolved greatly in both quality and quantity recently and demand for radiotherapy in Korea is increasing steadily. The information in this analysis represents important data to develop the future planning of equipment and human resources.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.4
• /
• pp.606-612
• /
• 2018

The enzyme xylose isomerase (E.C. 5.3.1.5, XI) is responsible for the conversion of an aldose to ketose, especially xylose to xylulose. Owing to the ability of XI to isomerize glucose to fructose, this enzyme is used in the food industry to prepare high-fructose corn syrup. Therefore, we studied the characteristics of XI from Anoxybacillus kamchatkensis G10, a thermophilic bacterium. First, the gene coding for XI (xylA) was inserted into the pET-21a(+) expression vector and the construct was transformed into the Escherichia coli competent cell BL21 (DE3). The expression of recombinant XI was induced in the absence of isopropyl-thio-${\beta}$-galactopyranoside and purified using Ni-NTA affinity chromatography. The optimum temperature of recombinant XI was $80^{\circ}C$ and measurement of the heat stability indicated that 55% of residual activity was maintained after 2 h incubation at $60^{\circ}C$. The optimum pH was found to be 7.5 in sodium phosphate buffer. Magnesium, manganese, and cobalt ions were found to increase the enzyme activity; manganese was the most effective. Additionally, recombinant XI was resistant to the presence of $Ca^{2+}$ and $Zn^{2+}$ ions. The kinetic properties, $K_m$ and $V_{max}$, were calculated as 81.44 mM and $2.237{\mu}mol/min/mg$, respectively. Through redundancy analysis, XI of A. kamchatkensis G10 was classified into a family containing type II XIs produced by the genera Geobacillus, Bacillus, and Thermotoga. These results suggested that the thermostable nature of XI of A. kamchatkensis G10 may be advantageous in industrial applications and food processing.