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Spectra of Interacting Electrons in a Quantum Dot: Quasi-Exact Solution
Eser Olgar,Hayriye Tutunculer,Ramazan Koc 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1
We present a procedure to solve the Schrodinger equation of two interacting electrons in a quantum dot in the presence of an external magnetic field within the context of quasi-exactly-solvable spectral problems. We show that the symmetries of the Hamiltonian can be recovered for specific values of the magnetic field, which leads to an exact determination of the eigenvalues and eigenfunctions. We show that the problem possesses a hidden sl2ကalgebraic structure.
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Radiation Exposure to Premature Infants in a Neonatal Intensive Care Unit in Turkey
Turan Olgar,Esra Onal,Dogan Bor,Nurullah Okumus,Yildiz Atalay,Canan Turkyilmaz,Ebru Ergenekon,Esin Koc 대한영상의학회 2008 Korean Journal of Radiology Vol.9 No.5
Objective: The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room. Materials and Methods: We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESDTO) (n = 23) and from the use of thermoluminescent dosimetry (ESDTLD) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESDTO by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESDTO and ESDTLD were correlated using linear regression analysis. Results: The mean ESDTO for the chest and abdomen were 67 μGy and 65 μGy per procedure, respectively. The mean ESDTLD per radiograph was 70 μGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 μGy) per radiograph. Mean effective doses were 16 and 27 μSv per procedure for the chest and abdomen, respectively. ESDTLD was well correlated with ESDTO obtained from the total chest and abdomen radiographs for each infant (R2 = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 × 10-6 to 2 × 10-6 and 0.6 × 10-6 to 2.9 × 10-6 for chest and abdomen radiographs, respectively. Conclusion: The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other. Objective: The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room. Materials and Methods: We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESDTO) (n = 23) and from the use of thermoluminescent dosimetry (ESDTLD) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESDTO by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESDTO and ESDTLD were correlated using linear regression analysis. Results: The mean ESDTO for the chest and abdomen were 67 μGy and 65 μGy per procedure, respectively. The mean ESDTLD per radiograph was 70 μGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 μGy) per radiograph. Mean effective doses were 16 and 27 μSv per procedure for the chest and abdomen, respectively. ESDTLD was well correlated with ESDTO obtained from the total chest and abdomen radiographs for each infant (R2 = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 × 10-6 to 2 × 10-6 and 0.6 × 10-6 to 2.9 × 10-6 for chest and abdomen radiographs, respectively. Conclusion: The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other.
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