• Food Science and Biotechnology
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• v.14 no.1
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• pp.1-5
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• 2005

Photostimulated luminescence (PSL), thermoluminescence (TL), electron spin resonance (ESR), and direct epiflourescent filter technique/aerobic plate count (DEFT/APC) were applied to detect dried green, black, and oolong teas irradiated between 0-10 kGy. Teas irradiated at 2.5 kGy and higher showed over 5000 photon counts/60 sec, while non-irradiated teas yielded 650-1000 photon counts/60 sec. TL glow curves for minerals separated from teas were detected at about $300^{\circ}C$ with low intensity in non-irradiated samples, whereas around $150^{\circ}C$ with high intensity in all irradiated samples. Ratio of $TL_1/TL_2$ based on re-irradiation step, showing lower than 0.1 and higher than 1.44 for non-irradiated and irradiated samples, respectively, enhanced reliability of TL results. ESR measurements for irradiated teas showed signals specific to irradiation. Log DEFT/APC ratio increased with irradiation dose; this result could be applied to identify irradiated tea samples.

• Macromolecular Research
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• v.12 no.1
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• pp.112-118
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• 2004

With the goal of enhancing the creep resistance of ultra-high molecular weight polyethylene (UHMWPE), we performed gamma irradiation and post-irradiation annealing at a low temperature, and investigated the crystalline structures and mechanical properties of the samples. Electron spin resonance spectra reveal that most of the residual radicals are stabilized by annealing at 100$^{\circ}C$ for 72 h under vacuum. Both the melting temperature and crystallinity increase after increasing the dose and by post-irradiation annealing. When irradiated with the same dose, the quenched sample having a higher amorphous fraction exhibits a lower swell ratio than does the slow-cooled sample. The measured tensile properties correlate well to the crystalline structure of the irradiated and annealed samples. For enhancing creep resistance, high crystallinity appears to be more critical than a high degree of crosslinking.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.91-91
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• 2000

a-C:H 혹은 a-SiC:H 박막은 광전소자 및 태양전지 등의 개발에 있어서 중요한 물질이다. 우리는 a-C:H 및 a-SiC:H 박막을 PECVD (plasma-enhanced chemical vapor deposition) 방법으로 증착시키고, 박막의 가열에 따른 스핀밀도의 변화를 ESR (electron spin resonance) 측정을 통하여 조사하였다. PECVD 증착가스는 Ch4, SiH4 가스를 사용하였고, 기판은 Corning 1737glass를 사용하였으며, 기판 온도는 300-40$0^{\circ}C$, 증착 압력은 0.1-0.3 Torr, r.f. 전력은 3-36W 사이에서 변화되었다. ESR 측정은 상온 X-band 영역에서 수행되었고, modulation amplitude는 2.5G, modulation frequency는 100kHz 이었다. a-C:H 혹은 a-SiC:H 박막은 진공상태의 reactor, 혹은 공기중의 furnace 안에서 300-50$0^{\circ}C$ 영역에서 3-8시간 정도 가열되거나, 혹은 상온에서 약 50$0^{\circ}C$ 정도까지 단계적으로 가열되었다. 증착된 a-C:H 박막의 초기 구조는 Raman 측정으로부터 polymer-like Carbon으로 추정되었으며, 300-35$0^{\circ}C$ 가열시 초기 1시간 정도 사이에는 스핀밀도가 증가되었으나, 그 후 8시간 정도까지의 가열의 경우에도 대체로 동일하게 나타났다. 또한 상온으로부터 약 50$0^{\circ}C$까지 단계적으로 온도를 높여주며, 각 단계마다 1시간씩 가열했을 때도 30$0^{\circ}C$ 정도까지는 스핀밀도가 증가하다가 더 높은 온도로 가면서 다시 스핀밀도가 감소함을 볼 수 있었다. 이러한 스핀밀도의 초기 증가 및 감소를 일으키는 메카니즘에 대해서 논의해 볼 것이다.

• Journal of Magnetics
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• v.5 no.1
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• pp.23-25
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• 2000

We have investigated the effects of Ar and$O_2$-ion milling on the exchange coupling field ($H_{ex}$) and coercive field ($H_c$) at the interfaces between substrates and NiO/NiFe films, to understand the exchange biasing mechanism. The $O_2$-ion milling was successfully performed by means of the electron cyclotron resonance (ECR) process. We found that the local roughness gradient of the NiO surface increased by $O_2$-ion milling. The ratio of $H_{ex}/H_c$ increased from 0.87 to 1.77, whereas $H_c$ decreased by almost a half as a results of the ion milling. The decrease in $H_c$could be interpreted as due to the refinement of magnetic domain size, which arose from the increase of the local roughness gradient of the NiO surface. The decrease in low $H_c$, and increase in $H_{ex}$ in NiO spin valves by ECR-ion milling are in the right direction far use in magnetoresistance (MR) heads.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.303-306
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• 2003

Indonesia is a tropical country having a temperature range of 25-35$^{\circ}C$ which can affect the skin and causes damages like aging. This aging process is due, at least, to free radical reactions. For this reason, many attempts had been done to find out creams containing natural antioxidant compound which have a potential of free radical scavenger. Kluwek, a fermented form of foot ball fruit or picung (Pangium edule.Reinw), had been proved to contain antioxidant compound in its methanol fraction oil to which antiaging cream was formulated. Stability evaluation was conducted for cream with Kluwek oil compared to base cream, including organoleptic (colour and odour), pH, viscosity, particle size, centrifugation test and flow characteristics either in room temperature (27$^{\circ}C$) or stress condition (4$^{\circ}C$ and 5$0^{\circ}C$) for 8 weeks continuously, and six times cycling test at 4$^{\circ}C$ and 5$0^{\circ}C$ every 24 hours. The results showed that cream with Kluwek oil and base cream were stable at temperature 27 and 4$^{\circ}C$, cycling test and centrifugation test, but not stable at 5$0^{\circ}C$. Free radical evaluation was done by Electron Spin Resonance and the result showed that cream with Kluwek oil had less free radicals compared to base cream.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.502-508
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• 2011

Synthesis of $Nd_{2x}Cd_{2-3x}SiO_4$ ($0.01{\leq}x{\leq}0.21$) [S1-S3: x=0.01, 0.11 and 0.21] solid solutions were prepared by solgel method. Powder x-ray diffraction (XRD) results show monoclinic unit cell with space group P21/m. The average crystallite sizes are found to be 20 to 45 nm. The Scanning Electron Microcopy (SEM) images show morphology of the sample is in globular nature. The energy dispersive analysis of x-rays (EDX) and X-ray mapping results confirmed that all the constituent elements of the composites were present and that were distributed in uniformly. The optical absorption band at ~750 nm was due to $^4I_{9/2}{\rightarrow}^4F_{7/2}+^4S_{3/2}$ transition optically active $Nd^{3+}$ ions. Electron Paramagnetic Resonance (EPR) lineshapes of S1-S3 at 10, 40, 77 and 300 K show a broad unresolved isotropic lineshapes were observed due to rapid spin lattice relaxation of $Nd^{3+}$.

• Journal of Radiation Industry
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• v.4 no.3
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• pp.221-226
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• 2010

Physical detection methods, photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR) were applied to detect electron beam-irradiated agricultural products, such as red pepper, black pepper, raisin, walnut, beef seasoning and pistachio. The absorbed irradiation doses for representative samples were controled at 0, 1, 3, 5 and 10 kGy. PSL values for non-irradiated samples were <700 counts/60s (lower threshold, $T_1$) except beef seasoning, whereas those of irradiated samples were more than 5,000 photon counts, upper threshold ($T_2$) in black pepper, raisin, and beef seasoning and intermediates values of $T_1-T_2$ in red pepper, walnut, and pistachio. Minerals seperated from the samples for TL measurement showed that non-irradiated samples except pistachio (TL ratio, 0.12) were characterized by no glow curves situated at temperature range of $50{\sim}400^{\circ}C$ with TL ratio (0.01~0.08), while irradiated samples except pistachio at only 1 kGy (TL ratio, 0.08) indicated glow curve at about $150{\sim}250^{\circ}C$ with TL ratio (0.28~3.10). ESR measurements of irradiated samples showed any specific signals to irradiation. The samples of both red pepper and pistachio were produced specific signals derived from cellulose radicals as well as single line signals for black pepper and walnut, and multiple signals derived from crystalline sugar radicals for raisin and beef seasoning. In conclusion, The ESR methods can apply for detection of pistachio exposed to electron beam but PSL and TL are not suitable methods. Furthermore, TL and ESR suggeted that both techniques were more useful detection method than PSL to confirm whether red pepper, walnut and beef seasoning samples have been exposed to electron beam.

• Journal of the Korean Chemical Society
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• v.29 no.2
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• pp.80-87
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• 1985

Radiation damage in a single crystal of ammonium sulfate caused by ${\gamma}$-irradiation at room temperature has given rise to several paramagnetic centers. Electron spin resonance (ESR) spectra of crystal are obtained with the X-band EPR spectrometer at room temperature. An intense and isotropic peak of Gaussian shape at g = 2.0036 is assigned to $SO_3^-$, which shows power saturation effects. Angular dependence of spectra is studied for the rotations about three mutually perpendicular axes a, b and c. The g-values are obtained from the relative distances between isotropic peak of $SO_3^-$ and anisotropic peak of the species. Principal $g^-$values and direction cosines were calculated by diagonalizing the 3${\times}$3 matrix whose elements are the $g^-$values for each species. From the analysis of characteristic principal $g^-$values and direction cosines for ammonium sulfate single crystal, anisotropic peaks corresponding to $SO_4^-,\;SO_2^-$ and defect structure corresponding to electron excess type are identified.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.124-130
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• 2013

Of all the brominated flame retardants (BFRs), TBBPA has the largest production volume (50% of the BFRs in current use). It is interest to investigate how they may degrade, because of it can pose an environmental hazard. By using UV-A (${\lambda}=352nm$ ), we have found that the UV-A irradiation increased the photodecomposition reaction rate of TBBPA in an intensity-dependent manner. We also observed 2,6-dibromo-p-benzosemiquinone radical ($a_{2H}=2.36G$, g = 2.0056) generated from TBBPA by reaction with singlet oxygen ($^1O_2$). On the other hand, when an aqueous preparation of HA was irradiated in the presence of TBBPA, the typical spectrum of semiquinone radical was detected by electron spin resonance (ESR). And then, we have found that the photodecomposition rate of TBBPA is decreased in depend on HA concentration. Radical formation and the reactive rate of TBBPA were inhibited by sodium azide used as a singlet oxygen quencher. Therefore we report that a similar $^1O_2$-induced oxidation can be initiate in aqueous solutions of TBBPA dissolved in humic acid (HA) by the UV-A irradiation (${\lambda}=352nm$). From these results, we suggest that the reaction rate of HA with $^1O_2$ is faster than that of TBBPA with $^1O_2$.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.237-243
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• 1995

The measurments of neutral semiquinone radicals, which were formed from the laser flash photolysis of anthraquinone (AQ) in the mixed solvents were carried out by the time resolved electron spin resonance (trESR) spectroscopy. The chemically induced dynamic electron polarization (CIDEP) spectra of the neutral semiquinone radical (AQH${\cdot}$) and semiquinone radical anion (AQ${\cdot}$-) were successively detected in the laser flash photolysis of AQ in the mixtures of 2-propanol (PrOH) and triethylamine (TEA). The neutral semiquinone radical was short-lived with the half-life of 0.8 ${\mu}sec$, whereas the semiquinone radical anion was relatively stable and then its cwESR could be observed. The rate constant of the spin-depolarization of semiquinone radical anion was $2.6{\times}10^5 sec^{-1}$ and the decay of the radical anion was the first order reaction with the rate constant of $3.0{\times}10^2\; sec^{-1}$. No CIDEP of semiquinone radical anion was observed in the mixture of PrOH and the lower concentration of TEA than 2 percent. The CIDEP spectrum of the neutral semiquinone radical was detected in the mixture of benzene and TEA with the half-life of 3.0 ${\mu}sec$. The neutral semiquinone radical could not be detected by cwESR. Neither CIDEP nor ESR absorption could be observed in PrOH, TEA or benzene only.