• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.208-213
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• 1999

Space Physics Sensor (SPS) on-board the KOMPSAT-1 consists of the High Energy Particle Detector (HEPD) and the Ionospheric Measurement Sensor (IMS). The HEPD is to characterize the low altitude high energy particle environment and the effects on the microelectronics due to these high energy Particles. It is composed of four sensors: Proton and Electron Spectrometer(PES), Linear Energy Transfer Spectrometer (LET), Total Dose Monitor (TDM), and Single Event Monitor(SEM). 35MeV proton beam from the medical KCCH cyclotron, at Korea Cancer Center Hospital in Seoul, is used to calibrate the PES. Primary proton beam of 35MeV scattered by polypropylene target is converted to various energy Protons according to the elastic collision kinematics. In this calibration, the threshold level of the proton in the PES can be determined and the energy ranges of PES channels are also calibrated.

• Journal of radiological science and technology
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• v.41 no.2
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• pp.141-148
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• 2018

This study examined the properties of photons and the dose distribution in a human body via a simulation where the total body irradiation(TBI) is performed on a pediatric anthropomorphic phantom and a child size water phantom. Based on this, we tried to find the optimal photon beam energy and material for beam spoiler. In this study, MCNPX (Ver. 2.5.0), a simulation program based on the Monte Carlo method, was used for the photon beam analysis and TBI simulation. Several different beam spoiler materials (plexiglass, copper, lead, aluminium) were used, and three different electron beam energies were used in the simulated accelerator to produce photon beams (6, 10, and 15 MeV). Moreover, both a water phantom for calculating the depth-dependent dosage and a pediatric anthropomorphic phantom for calculating the organ dosage were used. The homogeneity of photon beam was examined in different depths for the water phantom, which shows the 20%-40% difference for each material. Next, the org an doses on pediatric anthropomorphic phantom were examined, and the results showed that the average dose for each part of the body was skin 17.7 Gy, sexual gland 15.2 Gy, digestion 13.8 Gy, liver 11.8 Gy, kidney 9.2 Gy, lungs 6.2 Gy, and brain 4.6 Gy. Moreover, as for the organ doses according to materials, the highest dose was observed in lead while the lowest was observed in plexiglass. Plexiglass in current use is considered the most suitable material, and a 6 or 10 MV photon energy plan tailored to the patient condition is considered more suitable than a higher energy plan.

• Korean Journal of Biological Psychiatry
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• v.7 no.2
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• pp.164-173
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• 2000

This study was carried out to investigate the direct neurotoxicity of alcohol on CNS and the effects of piracetam or vitamins on ultrastructural changes of the rat cerebellar and hippocampal neurons during long-term alcohol treatment. To evaluate the results, quantitative analysis were done for light and electronic microscopic findings. On the light microscopy, red degeneration of pyramidal cells and Purkinje cells was found more apparently in the alcohol only treated group than in the control group. On the electron microscopy, increased lipofuscin pigments were found in cerebellum and hippocampus. In quantitative analysis, vitamins significantly reduced red degeneration in both hippocampus and cerebellum. However, piracetam significantly reduced red degeneration in cerebellum but not in hippocampus. Lipofuscin pigments in Purkinje cells and pyramidal cells were significantly reduced in the alcohol with piracetam treated group than the alcohol only treated group. However, vitamins had no significant reducing effect of lipofuscin pigments in Purkinje cells and pyramidal cells. According to the results, it is concluded that vitamins deficiency might cause red degeneration of pyramidal cell after long-term alcohol treatment, but increment of lipofuscin pigments in pyramidal and Purkinje cell may be caused by alcohol itself or its metabolite rather than vitamins deficiency. Piracetam seems to improve cognitive function impairment caused by alcohol consumption.

• Childhood Kidney Diseases
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• v.10 no.2
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• pp.174-181
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• 2006

Purpose : To analyse the results of the renal biopsies and the clinical diagnoses of patients who had undergone percutaneous kidney biopsies in the department of pediatrics at Kyunghee University Hospital for 22 years from 1984 to 2005. Methods : We retrospectively reviewed the medical records of 1559 patients and analyzed the chief complaints that led to a renal biopsy, age, sex, histopathologic findings and diagnosis. Routine kidney biopsies were performed by automated gun biopsy guided by real time ultrasonography. The diagnoses were made based on the specimen's light microscopy, immunofluorescence microscopy and electron microscopy findings and clinical symptoms and signs. Results : The mean age of the patients was 10 years with the male to female ratio being 1.3:1. The chief complaints that led to a renal biopsy included hematuria only(753 cases, 48.3%), proteinuria only(125 cases, 8.0%) and hematuria combined with proteinuria(537 cases, 34.4%). The most frequent histopathological finding was primary glomerular disease(75.4%) which included IgA nephropathy(30.1%) and mesangial proliferative glomerulonephritis(27.6 %). Systemic disease comprised 11.4% which included Henoch-$Sch\ddot{o}nlein$ nephritis(10.5%) and lupus nephritis(0.8%). Alport syndrome was found in 1.1% of cases which was attributed to hereditary causes. 628 children(40.3%) visited the clinic due to abnormal school urine screening abnormalities and among these, 237 children had mesangial proliferative glomerulonephritis and 234 children who had IgA nephropathy were managed thereafter. Conclusion : IgA nephropathy and mesangial proliferative glomerulonephritis were the two major forms of primary glomerulonephritis found in Korean children who had kidney biopsies from 1984 to 2005.

• Toxicological Research
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• v.27 no.3
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• pp.153-160
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• 2011

To evaluate the whitening effect of black tea water extract (BT), BT was topically applied to artificially hyperpigmented spots on the back skins of brown guinea-pigs (weight: 450~500 g) induced by 1,500 mJ/$cm^2$ of ultraviolet B (UVB) irradiation. The test compounds of 30 ${\mu}l$ were applied twice a day, six days a week, for four weeks. The artificially hyperpigmented spots were divided into 5 groups: control (UVB + saline, C), vehicle control [UVB + propylene glycol: ethanol: water (5 : 3 : 2), VC], positive control (UVB + 2% hydroquinone, PC), experimental 1 (UVB + 1% BT), experimental 2 (UVB + 2% BT). After 4-week application, the spots were removed by biopsy punch under anesthetic condition and used as specimens for the histological examination. The total polyphenol and flavonoid contents of BT were 104 and 91 mg/g, respectively. The electron-donating ability of BT revealed a dose-dependent response, showing the excellent capacities of 86% at 800 ${\mu}g$/ml. The artificially hyperpigmented spots treated with the PC and BT were obviously lightened compared to the C and VC groups. At the fourth week, the melanin indices for the PC and BT groups were significantly lower (p < 0.001) than those of the C and VC groups. In histological examination, PC and BT groups were significantly reduced in the melanin pigmentation, the proliferation of melanocytes and the synthesis of melanosomes compared to the C and VC groups. It is found that BT inhibits the proliferation of melanocytes and synthesis of melanosomes in vivo using brown guinea pigs, thereby showing a definite skin whitening effect.

• Analytical Science and Technology
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• v.5 no.1
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• pp.83-90
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• 1992

The $^{14}C$-warfarin used as rodenticids was identified from various organs of sprague dawley with scintillation counter. And the cytochrome p-450 which was induced by coumarin derivatives was identified with electrophoresis. The distributions of $^{14}C$-warfarin after $14.8{\mu}Ci/kg$ oral application at each organ was as follows; urine-7.5%, blood-0.44%, feces-0.9%, liver-0.66%, lung-0.86%, kidney-0.8%, heart-0.43% and spreen-0.33% after 24hrs. The cytochrome p-450 was purified by Octyl Sepharose CL-4B hydrophobic chromatography and isozymes were 50.8 Kd in control group, 53.3 Kd and 55.2 Kd in coumarin pretreated group and 50.8 Kd, 54.6 Kd and 57.7 Kd in warfarin pretreated group.

• Journal of Biomedical Engineering Research
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• v.37 no.5
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• pp.168-177
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• 2016

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.433-441
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• 1998

This study was performed to evaluate the effects of surface flaw on the fracture of all-ceramic materials. A feldspathic porce lain of VMK68, a cashable ceramic of IPS-Empress, and an alumina-glass composite of In-Ceram were used. Specimens were prepared as 12$\times$3$\times$1mm in dimensions, and a Vickers-produced indentation crack was made at the center of the tensile surface. Test specimens were immersed in dlstilled water and In oil, which were broken under a crosshead speed of 0.05 mm/min by 3-point bend test at 37$^{\circ}C$. The characteristic patterns of Vickers indentation and fracture surfaces were examined by an optical microscope and a scanning electron microscope. The fracture surfaces of the VMK68 and the IPS-Empress showed a median crack pattern at the fracture origin and indicated a tendency to cleavage hackle. The fracture surface of the alumina-glass composite, In-Ceram, showed a Palmqvist crack pattern at the fracture origin and indicated a tendency of toughening by the frictional Interlocking between the microstructurally rough fracture surfaces.

• Journal of Microbiology and Biotechnology
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• v.27 no.8
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• pp.1483-1490
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• 2017

In this study, silver nanoparticles (AgNPs) were synthesized by the citrate reduction process and, with the assistance of n-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, were successfully loaded with the macromolecular drug vancomycin (VAM) to form AgNP-VAM bioconjugates. The synthesized AgNPs, VAM, and AgNP-VAM conjugate were characterized by UV-visible spectroscopy, zeta potential analysis, confocal microscopy, and transmission electron microscopy. The effect of loading VAM onto AgNPs was investigated by testing the internalization of the bioconjugate into Mycobacterium smegmatis. After treatment with the AgNP-VAM conjugate, the bacterial cells showed a significant decrease in UV absorption, indicating that loading of the VAM on AgNPs had vastly improved the drug's internalization compared with that of AgNPs. All the experimental assessments showed that, compared with free AgNPs and VAM, enhanced internalization had been successfully achieved with the AgNP-VAM conjugate, thus leading to significantly better delivery of the macromolecular drug into the M. smegmatis cell. The current research provides a new potential drug delivery system for the treatment of mycobacterial infections.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.1
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• pp.39-47
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• 2009

Gaegurin 4(GGN 4), an antimicrobial peptide isolated from a Korean frog, is five times more potent against Gram-positive than Gram-negative bacteria, but has little hemolytic activity. To understand the mechanism of such cell selectivity, we examined GGN4-induced $K^+$ efflux from target cells, and membrane conductances in planar lipid bilayers. The $K^+$ efflux from Gram-positive M. luteus(2.5 ${\mu}g/ml$) was faster and larger than that from Gram-negative E. coli(75 ${\mu}g/ml$), while that from RBC was negligible even at higher concentration(100 ${\mu}g/ml$). GGN4 induced larger conductances in the planar bilayers which were formed with lipids extracted from Gram-positive B. subtilis than in those from E. coli(p<0.01), however, the effects of GGN4 were not selective in the bilayers formed with lipids from E. coli and red blood cells. Addition of an acidic phospholipid, phosphatidylserine to planar bilayers increased the GGN4-induced membrane conductance(p<0.05), but addition of phosphatidylcholine or cholesterol reduced it(p<0.05). Transmission electron microscopy revealed that GGN4 induced pore-like damages in M. luteus and dis-layering damages on the outer wall of E. coli. Taken together, the present results indicate that the selectivity of GGN4 toward Gram-positive over Gram-negative bacteria is due to negative surface charges, and interaction of GGN4 with outer walls. The selectivity toward bacteria over RBC is due to the presence of phosphatidylcholine and cholesterol, and the trans-bilayer lipid asymmetry in RBC. The results suggest that design of selective antimicrobial peptides should be based on the composition and topology of membrane lipids in the target cells.