• Bulletin of the Korean Chemical Society
• /
• 제20권10호
• /
• pp.1145-1148
• /
• 1999

1H NMR spectra of methyl-, ethyl-, propyl-, isopropyl-, butyl-, N-methylethyl-, N-methylpropyl-, and N-methylisopropylamine coordinated to the paramagnetic 11-tungstocobalto(II)silicate anion (SiW11Co) in dimethylsulfoxide-d6 or dimethylformamide-d7 are reported. For these complexes the ligand exchange is slow on the NMR time scale and pure 1H NMR signals have been observed at room temperature. No complex is detected in D2O. From the pseudocontact shifts of the CH2 and CH3 groups in ethylamine the energy of the gauche conformers with respect to the anti conformer is estimated. Two diastereotopic protons in the CH2 group of N-methylethylamine have quite different chemical shifts especially at low temperatures (e.g. 48.5 vs. 19.4 ppm at -10℃). This may be attributed mainly to the different positions of the two protons in the most stable (gauche) conformer.

• Bulletin of the Korean Chemical Society
• /
• 제22권11호
• /
• pp.1197-1201
• /
• 2001

In the spectrum of uniformly 15N labeled cytochrome c3, the relative linewidths of the doublet peaks of the 15N-coupled imido proton of the coordinated imidazole group were reversed on oxidation. This inversion was explained by the interference relaxation process between the electron-proton dipolar and 15N-1H dipolear interactions. The inversion can be used to assign the imido protons of the coordinated imidazole groups in heme proteins.

• Nuclear Engineering and Technology
• /
• 제53권10호
• /
• pp.3158-3163
• /
• 2021

Chromium material is commonly used for fusion plasma facing applications because of the low neutron activation property. The Monte Carlo method is one of the useful ways to investigate the ion-target interactions. In this study, Chromium target irradiated by protons was investigated using Monte Carlo based simulation tools. In this context, the calculations of radiation damage on Chromium material irradiated with protons at 17.9 and 22.3 MeV energies were carried out using GEANT4 and SRIM codes. Besides, the cross sections for proton interaction with Chromium target were calculated by the TALYS 1.9 code using CTM + FGM, BSFGM, and GSFM level densities. As a result, GEANT4, SRIM and TALYS 1.9 codes provide a suitable tool for the predictions of radiation damage and cross cross section with proton irradiation.

• Nuclear Engineering and Technology
• /
• 제49권7호
• /
• pp.1495-1504
• /
• 2017

In a previous study, a set of polygon-mesh (PM)-based skin models including a $50-{\mu}m-thick$ radiosensitive target layer were constructed and used to calculate skin dose coefficients (DCs) for idealized external beams of electrons. The results showed that the calculated skin DCs were significantly different from the International Commission on Radiological Protection (ICRP) Publication 116 skin DCs calculated using voxel-type ICRP reference phantoms that do not include the thin target layer. The difference was as large as 7,700 times for electron energies less than 1 MeV, which raises a significant issue that should be addressed subsequently. In the present study, therefore, as an extension of the initial, previous study, skin DCs for three other particles (photons, protons, and helium ions) were calculated by using the PM-based skin models and the calculated values were compared with the ICRP-116 skin DCs. The analysis of our results showed that for the photon exposures, the calculated values were generally in good agreement with the ICRP-116 values. For the charged particles, by contrast, there was a significant difference between the PM-model-calculated skin DCs and the ICRP-116 values. Specifically, the ICRP-116 skin DCs were smaller than those calculated by the PM models-which is to say that they were under-estimated-by up to ~16 times for both protons and helium ions. These differences in skin dose also significantly affected the calculation of the effective dose (E) values, which is reasonable, considering that the skin dose is the major factor determining effective dose calculation for charged particles. The results of the current study generally show that the ICRP-116 DCs for skin dose and effective dose are not reliable for charged particles.

• Journal of the Optical Society of Korea
• /
• 제13권1호
• /
• pp.28-32
• /
• 2009

In order to obtain high quality images of thin objects, we performed an experiment of proton radiography by using low energy protons generated from the interaction of an ultrashort ultraintense laser with solid targets. The protons were produced from a thin polyimide target irradiated by the laser pulse, and their maximum energy was estimated at up to 1.8 MeV. A CR-39 nuclear track detector was used as a proton radiography screen. The proton images were obtained by using an optical microscope and the spatial resolution was evaluated by a Modulation Transfer Function (MTF). We have achieved about $10\;{\mu}m$ spatial resolution of images. The obtained spatial resolution shows about $4{\sim}5$ times better value than the conventional X-ray radiography for inspection or non-destructive test (NDT) purpose.

• Journal of Astronomy and Space Sciences
• /
• 제39권4호
• /
• pp.145-158
• /
• 2022

The dynamics of the outer zone radiation belt has received a lot of attention mainly due to the correlation between the occurrence of enhancing relativistic electron flux and spacecraft operation anomalies or even failures (e.g., Baker et al. 1994). Relativistic electron events are often observed during great storms associated with ultra low frequency (ULF) waves. For example, a large buildup of relativistic electrons was observed during the great storm of March 24, 1991 (e.g., Li et al. 1993; Hudson et al. 1995; Mann et al. 2013). However, the dominant processes which accelerate magnetospheric radiation belt electrons to MeV energies are not well understood. In this paper, we present observations of Pc5 ULF waves in the recovery phase of the Bastille day storm of July 16, 2000 and electron and proton flux simultaneously oscillating with the same frequencies as the waves. The mechanism for the observed electron and proton flux modulations is examined using ground-based and satellite observations. During this storm time, multiple packets of discrete frequency Pc5 ULF waves appeared associated with energetic particle flux oscillations. We model the drift paths of electrons and protons to determine if the particles drift through the ULF wave to understand why some particle fluxes are modulated by the ULF waves and others are not. We also analyze the flux oscillations of electrons and protons as a function of energy to determine if the particle modulations are caused by a ULF wave drift resonance or advection of a particle density gradient. We suggest that the energetic electron and proton modulations by Pc5 ULF waves provide further evidence in support of the important role that ULF waves play in outer radiation belt dyanamics during storm times.

• Nuclear Engineering and Technology
• /
• 제55권9호
• /
• pp.3140-3149
• /
• 2023

In theory, the sharp dose falloff at the distal end of a proton beam allows for high conformal dose to the target. However, conformity has not been fully achieved in practice, primarily due to beam range uncertainty, which is approximately 4% and varies slightly across institutions. To address this issue, we developed a new range verification system prototype: a multi-slit prompt-gamma camera (MSPGC). This system features high prompt-gamma detection sensitivity, an advanced range estimation algorithm, and a precise camera positioning system. We evaluated the range measurement precision of the prototype for single spot beams with varying energies, proton quantities, and positions, as well as for spot-scanning proton beams in a simulated SSPT treatment using a phantom. Our results demonstrated high accuracy (<0.4 mm) in range measurement for the tested beam energies and positions. Measurement precision increased significantly with the number of protons, achieving 1% precision with 5 × 10⁸ protons. For spot-scanning proton beams, the prototype ensured more than 5 × 10⁸ protons per spot with a 7 mm or larger spot aggregation, achieving 1% range measurement precision. Based on these findings, we anticipate that the clinical application of the new prototype will reduce range uncertainty (currently approximately 4%) to 1% or less.

• 한국진공학회지
• /
• 제22권6호
• /
• pp.341-347
• /
• 2013

동시 계수 도플러 넓어짐 양전자 소멸 분광법으로 n형과 p형 실리콘 시료에 40.0, 3.98 MeV 에너지를 가진 $0.0{\sim}20.0{\times}10^{13}protons/cm^2$ 양성자 빔 조사에 의한 결함을 측정하여 시료 특성을 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 감마선 스펙트럼의 전자 밀도 에너지에 의한 수리적 해석 방법인 S-변수를 사용하여, 시료의 구조 변화를 측정하였다. 본 연구에서 측정된 S-변수는 시료에 조사된 양성자 조사량의 변화에 따라 결함이 증가하였으며, 그리고 40 MeV 양성자 빔의 세기는 n형 실리콘에서 빔의 조사량 $20.0{\times}10^{13}protons/cm^2$에서 3.98 MeV 보다 결함의 영향이 더 큰 것으로 나타났다. 그 결과 조사에 너지와 조사량의 상관관계를 비교 분석하였다. SRIM 시뮬레이션의 결과는, 양성자의 Bragg 피크 특성 때문에 시료 전체에 대한 결함으로 나타나기 보다는 양성자가 시료의 특정 깊이에 주로 결함을 형성하는 것을 보여 준다.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2003년도 somma/kms meeting
• /
• pp.345-345
• /
• 2003

• Bulletin of the Korean Chemical Society
• /
• 제25권4호
• /
• pp.539-544
• /
• 2004

The ability of protoberberine alkaloids, berberine and berberrubine, to act as topoisomerase II poisons is linked to the anti-cancer activity. Minor alterations in structure have a significant effect on their relative activity. Berberine, which has methoxy group at the 19-position, is significantly less potent than berberrubine. Several observations support non-specific binding to HP14 by the berberine: (i) nonspecific upfield changes in $^1H$ chemical shift for protons of the berberine; (ii) the broadening of imino protons of HP14 upon binding of the berberine; (iii) very small increases in duplex melting temperature in the presence of the berberine. Our results reveal that substitution of a hydroxyl group to a methoxy group on the 19-position, thereby converting the berberrubine to the berberine is associated with a non-specific DNA binding affinity and a reduced topoisomerase II poisoning. The presence of a bulky 19-methoxy substituent decreases intercalating properties of berberine and makes it inactive as topoisomerase II poison.