• Investigative Magnetic Resonance Imaging
• /
• v.10 no.2
• /
• pp.98-107
• /
• 2006

Magnetization Transfer (MT) imaging generates contrast dependent on the phenomenon of magnetization exchange between free water proton and restricted proton in macromolecules. In biological materials in knee, MT or cross-relaxation is commonly modeled using two spin pools identified by their different T2 relaxation times. Two models for cross-relaxation emphasize the role of proton chemical exchange between protons of water and exchangeable protons on macromolecules, as well as through dipole-dipole interaction between the water and macromolecule protons. The most essential tool in medical image manipulation is the ability to adjust the contrast and intensity. Thus, it is desirable to adjust the contrast and intensity of an image interactively in the real time. The proton density (PD) and T2-weighted SE MR images allow the depiction of knee structures and can demonstrate defects and gross morphologic changes. The PD- and T2-weighted images also show the cartilage internal pathology due to the more intermediate signal of the knee joint in these sequences. Suppression of fat extends the dynamic range of tissue contrast, removes chemical shift artifacts, and decreases motion-related ghost artifacts. Like fat saturation, phase sensitive methods are also based on the difference in precession frequencies of water and fat. In this study, phase sensitive methods look at the phase difference that is accumulated in time as a result of Larmor frequency differences rather than using this difference directly. Although how MT work was given with clinical evidence that leads to quantitative model for MT in tissues, the mathematical formalism used to describe the MT effect applies to explaining to evaluate knee disorder, such as anterior cruciate ligament (ACL) tear and meniscal tear. Calculation of the effect of the effect of the MT saturation is given in the magnetization transfer ratio (MTR) which is a quantitative measure of the relative decrease in signal intensity due to the MT pulse.

• Journal of the Korean Vacuum Society
• /
• v.19 no.4
• /
• pp.293-299
• /
• 2010

Vertically aligned ZnO nanorods on Si (111) substrate were prepared by hydrothermal method. The ZnO nanorods on spin-coated seed layer were synthesized at $140^{\circ}C$ for 6 hours in autoclave and were thermally annealed in argon atmosphere for 20 minutes at temperature of 300, 500, $700^{\circ}C$. The effects of the thermal annealing on the structural and optical properties of the grown on ZnO nanorods were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL). All the ZnO nanorods show a strong ZnO (002) and weak (004) diffraction peak, indicating c-axis preferred orientation. The residual stress of the ZnO nanorods is changed from compressive to tensile by increasing annealing temperature. The hexagonal shaped ZnO nanorods are observed. The PL spectra of the ZnO nanorods show a sharp near-band-edge emission (NBE) at 3.2 eV, which is generated by the free-exciton recombination and a broad deep-level emission (DLE) at about 2.12~1.96 eV, which is caused by the defects in the ZnO nanorods. The intensity of the NBE peak is decreased and the DLE peak is red-shifted due to oxygen-related defects by thermal annealing.

• Journal of the Korean Magnetics Society
• /
• v.16 no.1
• /
• pp.23-27
• /
• 2006

By substituting Mn or Cr for Co in inverse spinel $CoFe_2O_4,\;Mn_xCo_{1-x}Fe_2O_4\;and\;Cr_xCo_{1-x}Fe_2O_4$ and thin films were prepared by sol-gel method and their structural and magnetic properties were investigated. X-ray diffraction indicates that the cubic lattice constant increase for the Mn substitution while it hardly changes for the Cr substitution. Substitution of $Mn^{2+}$ for octahedral $Co^{2+}$ sites can explain the increase of lattice constant in $Mn_xCo_{1-x}Fe_2O_4$. On the other hand, Substitution of $Cr^{3+}$ for octahedral $Co^{2+}$ and subsequent reduction of $Fe^{3+}$ ion into $Fe^{2+}$ are expected to happen. Mossbauer spectroscopy measurements on $Cr_xCo_{1-x}Fe_2P_4$ indicate the existence of tetrahedral $Fe^{2+}$ ions that are created through reduction of tetrahedral $Fe^{3+}$ ions in order to compensate charge imbalance happened by $Cr^{3+}$ substitution for octahedral $Co^{2+}$ sites. On the other hand, no $Fe^{2+}$ ions were detected by Mossbauer spectroscopy for $Mn_xCo_{1-x}Fe_2O_4$. A migration of $Fe^{3+}$ ions from octahedral to tetrahedral sites In $Mn_xCo_{1-x}Fe_2O_4$ was detected by Mossbauer spectroscopy for x>0.47. Vibrating sample magnetometry measurements on the samples at room temperature revealed that the saturation magnetization increases by Mn and Cr substitution for certain range of x, qualitatively explainable in terms of the comparison of spin magnetic moment among the related transition-metal ions.

• Journal of Radiation Industry
• /
• v.7 no.1
• /
• pp.69-74
• /
• 2013

This study examined radiation detection characteristics of spices (cumin, caper and turmeric), other small fruits (hut-gae berry and boxthorn), and pollen extract product. Each samples were irradiated at dose of 1, 5, and 10 kGy and analyzed by the thermoluminescence (TL) and electron spin resonance (ESR) methods. To compare between non-irradiated and irradiated food, all samples were irradiated with $^{60}Co$ gamma-ray source. In TL analysis, most of samples could be applied to detect irradiated foods because of showing TL ratio above 0.1. The glow curves examined by TL method were estimated in the range of $150{\sim}250^{\circ}C$ in irradiated samples. In ESR measurements, the intensity of ESR signal (single-line) increased as the increase of irradiation dose. In particular, the specific ESR signals of irradiation-induced radical were detected in hut-gae berry and pollen extract product. As a results, it is considered that TL and ESR methods can be used to detect both hut-gae berry and pollen extract product. But cumin, caper, turmeric and boxthorn irradiated with gamma ray could be detected only by TL method. It is concluded that TL and ESR methods are suitable for detection of irradiated samples and a combined method is recommendable for enhancing the reliability of detection results.

• Journal of Radiation Protection and Research
• /
• v.40 no.4
• /
• pp.194-201
• /
• 2015

We have investigated the EPR signal properties in 12 components of two mobile phones (LCD, OLED) using electron paramagnetic resonance (EPR) spectrometer in this study.EPR measurements were performed at normal atmospheric conditions using Bruker EXEXSYS-II E500 spectrometer with X-band bridge, and samples were irradiated by $^{137}Cs$ gamma-ray source. To identify the presence of radiation-induced signal (RIS), the EPR spectra of each sample were measured unirradiated and irradiated at 50 Gy. Then, dose-response curve and signal intensity variating by time after irradiation were measured. As a result, the signal intensity increased after irradiation in all samples except the USIM plastic and IC chip. Among the samples, cover glass(CG), lens, light guide plate(LGP) and diffusion sheet have shown fine linearity ($R^2$ > 0.99). Especially, the LGP had ideal characteristics for dosimetry because there were no signal in 0 Gy and high rate of increase in RIS. However, this sample showed weakness in fading. Signal intensity of LGP and Diffusion Sheet decreased by 50% within 72 hours after irradiation, while signals of Cover Glass and Lens were stably preserved during the short period of time. In order to apply rapidly EPR dosimetry using mobile phone components in large-scale radiation accidents, further studies on signal differences for same components of the different mobile phone, fading, pretreatment of samples and processing of background signal are needed. However, it will be possible to do dosimetry by dose-additive method or comparative method using unirradiated same product in small-scale accident.

• Journal of Food Hygiene and Safety
• /
• v.27 no.3
• /
• pp.233-246
• /
• 2012

In this study, we investigated the applicability of the photostimulated luminescence(PSL), thermoluminescence(TL) and electron spin resonance(ESR) methods for various foods which are not allowed to be irradiated in Korea. All 15 foods including sesame, almond, peanut, cocoa powder etc. were analyzed. Samples were irradiated at 1~10 kGy using a $^{60}Co$ gamma-ray irradiator. In PSL study, the photon counts of all the unirradiated samples showed negative(lower than 700). The photon counts irradiated(1 kGy) dried shrimp, roasted peanut and seasoned peanut showed positive(higher than 5,000) and the other samples were negative or intermediate(> 700 and < 5,000). In TL analysis, results showed that it is possible to apply TL method to all foods containing minerals. In ESR measurements, the ESR signal(single-line) intensity of irradiated foods was higher than non-irradiated foods. In particular, the specific ESR signals of irradiation-induced crystalline sugar, cellulose and bone radical were detected in dried plum, raisin, dried cherry, mango(dried, frozen), rambutan, cocoa(powder), cinnamon, parsley, carrot, broccoli, dried arrow squid, dried pollack and dried shrimp. According to the results, PSL, TL and ESR methods were successfully applied to detect the irradiated foods because TL method is not able to detect the irradiated foods rarely composed of minerals. ESR is also a difficult method to detect the changes of ESR signal patterns of food. It is concluded that TL analysis or ESR assay is suitable for detection of irradiated samples and a combined method is recommendable for enhancing the reliability of detection results.

• Journal of Radiation Industry
• /
• v.7 no.1
• /
• pp.7-14
• /
• 2013

In this study, we investigated the applicability of the photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR) methods for various foods. The analysed samples consist of 11 items including dried fruits (6 items) and mushrooms (5 items). To compare between non-irradiated and irradiated food, all samples were irradiated with $^{60}Co$ gamma-ray source. In PSL study, the photon counts of all the unirradiated sample were identified negative (lower than 700). The photon counts irradiated (1, 5, 10 kGy) dried date-palm, dried jujube and mushrooms (Auricularia auricula, Phellinus linteus and Sarcodon aspratus) showed positive (higher than 5,000) and the results for the other samples were negative or intermediate (>700 and >5,000). In TL analysis most of items can be applicable to detect irradiated foods because of showing TL ratio above 0.1. The glow curves by TL method were estimated in the range of $150{\sim}250^{\circ}C$ in irradiated samples. In ESR measurements, the intensity of ESR signal (single-line) increased as the dose of irradiation increased. In particular, the specific ESR signals of irradiation-induced radical were detected in dried papaya, dried date-palm, dried banana, dried pineapple and S. aspratus. According to the results, PSL, TL and ESR methods were successfully applied to detect the irradiated foods. It is concluded that PSL, TL and ESR methods are suitable for detection of irradiated samples and a combined method is recommendable for enhancing the reliability of detection results.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.46 no.1
• /
• pp.46-55
• /
• 2017

In this study, extracts of gamma-irradiated Aralia continentalis for health and beauty food resources were examined on antioxidant activities and increasing extraction yield. In photostimulated luminescence analysis, non-irradiated (0 kGy) sample showed an intermediate result of 891.00 photon counts (PCs), whereas irradiated (5 and 10 kGy) samples showed positive results of 79,956.67 and 282,498.67 PCs, respectively. The thermoluminescence ratio of non-irradiated samples was 0.018, whereas the values of irradiated samples (5 and 10 kGy) were 0.395 and 0.464, respectively. Electron spin resonance (ESR) analysis as a physical technique for irradiation identification of Aralia continentalis showed a pair of peaks on a space of 6.0 mT in the symmetric ESR spectrums. For phenolics of gamma-irradiated Aralia continentalis, water extracts had the highest amounts of 7.61 mg/g at non-irradiated condition (0 kGy) while 50% ethanol extracts had the highest amounts of 6.86 mg/g at 10 kGy irradiation. 2,2-Diphenyl-1-picrylhydrazyl scavenging activity of water and 50% ethanol extracts from non-irradiated and irradiated Aralia continentalis were very high (94.99~100.00%). 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation inhibitory activity was over 95.00% at $200{\mu}g/mL$ phenolics. Antioxidant protection factor (PF) showed a very high level of activity (1.38~2.51 PF). Thiobarbituric acid reactive substance inhibitory activity was high (70% and 95%, respectively). Thus, treatment of gamma irradiation can be used as a method of storage for long-term preservation of Oriental medicine.

• The Journal of Korean Society for Radiation Therapy
• /
• v.16 no.2
• /
• pp.63-67
• /
• 2004

Purpose : New therapy technique appeared in 3D-CRT or IMRT according to a radiation treatment developing and worked. Such treatment technique requires the radiation irradiation of many direction. It has many restriction at radiation irradiation of many direction to the linear acceleration deception of now actually. Consequently We make new fix device and measure consequently the improvement of the activate range. Method and Material : We upload the fix device on a linear accelerator Couch. We fixed Gantry at 45, 90, 135 and Couch is spin and measure the clearance of the equipment. Couch is fixed at 0 45 90 and measures the clearance of Gantry. We upload the Extended head holder(EHH) on a linear accelerator Couch. and We measure with the experiment of the front. Result : The action range did not have big difference to increase Gantry45. but The activate range of Couch increases the angle in Gantry 90 and Gantry 135 when it uses EHH. The activate range of Gantry increases the angle in Couch 45 when it uses EHH. We showed good activate situation all in Couch 0 and Couch 90. The utility of EHH could keep a behind radiation diminution. Conclusion : The radiation irradiation of many direction comes to be possible the utility of the fix instrument(EHH). The safety space between the patient and equipment or between equipment and equipment increased the utility of the fix device. Also, The manufacture is possible imports to rather cheap price. and We could bring the frugality of the treatment expendable supplies.