Vol.20,

547

Conventional radiotherapy remains to be one of the most useful treatments for cancer, but it is not the best strategy to maximize the effects on the tumors and minimize the damage to the surrounding tissues because of its physical and radiobiological characteristics. Synchrotrons represent a unique method for an innovative anti-cancer treatment due to the physical features (i.e. high fluence, tunable and collimated) of X-ray induced by synchrotron, so photon activation therapy and microbeam radiation treatment have been developed, but it is very imperative to understand the radiobiological mechanism of synchrotron radiation before we could transfer the strategy into the clinic. This paper is to summary the results of in vitro and in vivo experiments with synchrotron radiation, and review the advances of molecular and cellular radiobiological mechanism involved in synchrotron radiation. Since Shanghai Synchrotron Radiation Facility (SSRF) has produced the first synchrotron, it will provide the unique opportunity for the study of radiobiological effects of synchrotron radiation.

517

DR1709 is a predicted Mn²⁺ transporter in Deinococcus radiodurans(D.radiodurans). The mensuration method to evaluate protein viability with two-dimensional electrophoresis in D.radiodurans and the mutants was established in this study. The results showed that after DR1709 was disrupted, the expressions of DR1120 (acetokinase), DR1691 (heat shock protein), DR1485 (putative lipase), DR2095 (putative c-type cytochrome) and other three hypothetical proteins (DR0124, DR0047 and DR2474) were repressed. However the expression of DR1794 (putative nosX) was induced. Phenomena above suggested that the increased radiation-sensitivity of the mutant cells may be attributed to not only the protection of gene DR1709, but also the proteins' different expressions between the wild type and the mutant might also play important roles in protecting D.radiodurans from irradiation. Although DR2095 was a homologue of c-type cytochrome, it has no realitic functions.

472

Radionuclides, such as ²³⁸U, ²³²Th and ⁴⁰K, can be found in urban soil. To evaluate the natural radioactivity in the environment, soil samples were collected form Shihezi city and radioisotope concentrations were determined by X-ray fluorescence. The dose rate of urban soil (mGy per year, mGy/a) was calculated. The results indicate that the U, Th and K concentrations of the urban soils were, respectively, 1.2–3.2 mg/kg, 6.4–12.3 mg/kg and 2.05%–2.24%, with the mean values of 2.47 mg/kg, 10.47 mg/kg and 2.16 %. Dose rates of urban soils were 10.04–19.55 mGy/a with the mean value of 16.31 mGy/a. This dose rate is the perfect and maximum value of natural radiation in soil and different with the air absorbed dose rate from terrestrial γ-rays. The mean value of air absorbed dose rate was about 57.42 nGy/h. The annual effective dose rate in air was about 0.07 mSv/a and the average value of Ra_eq in urban soil was 120.37 Bq/kg. The relative contribution of α particle to the dose rate is higher than that derived from β- and γ-rays in the urban soils.

453

This paper describes a rapid, accurate and precise method for determination of trace hafnium (Hf) in zirconium and zirconium alloys by inductively coupled plasma atomic emission spectrometry (ICP-AES). It was found that using a mixture of sulfuric acid (H₂SO₄) and ammonium sulfate (NH₄)₂SO₄, the total sample dissolution time was 15 min. Experimental works revealed that a high Zr concentration would result in a significant decrease in the peak height of the analyte lines, which was corrected by standard addition method. The performance of the developed method was evaluated by calculating the recovery percent and using standard reference material analysis. The recoveries were in the range of 97.6%–99.5% and the relative standard deviations were within 0.8%–3.0%. The detection limit (3σ) of Hf was found to be 0.01 µg·g⁻¹, respectively. The proposed technique, with high precision and accuracy, was applied to the analysis of trace Hf in zirconium-niobium ingots and tubes for the first time in Iran.

585

With the technology of coincidence method, transit time spreads (TTSs) of PMTs are measured with Cherenkov light on the photocathode window of photomultiplier tube (PMT) produced by cascade γ radiation source, ⁶⁰Co. TTSs with single and multi-photoelectron which are analyzed by convolution of Poisson and Gaussian are obtained. The study to XP2020 and XP2020Q PMTs shows that TTSs are consistent with data supplied by Philips. TTSs are inversely proportional to the square roots of number of photoelectrons. The method is feasible when single and multi-photoelectron can be distinguished.

507

The relationship between deoxyribonucleic acid (DNA) damage and the cell death induced by ¹²C ions irradiation was examined in four kinds of cells, Melanoma B16, cervical squamous carcinoma HeLa, Chinese hamster V79 and hepatoma SMMC-7721. Cell survival was determined by a colonogenic assay, and the sensitivity was described by D₅₀ (the dose of radiation necessary to reduce the survival to 50%). For all cell lines, D₅₀ ranged from 0.74 Gy to 3.85 Gy, among them B16 was the most radiosensitive to ¹²C ions, and V79 and HeLa cells had almost the same radio-sensitivity, SMMC-7721 was the last. The induction of deproteinized DNA double-strand breaks induced by ¹²C ions were measured by pulsed-field gel electrophoresis (PFGE), and the initial yield of the deproteinized DNA dsbs per unit dose was expressed as the DNA double break level (L). A linear dose-response curve was seen for initial DNA dsbs for all cell lines (slopes range from 0.40-0.98 (DSBs/100Mbp/Gy)). V79 was the steepest, B16 was the last. There was an inverse relationship between the initial DNA dsb and D₅₀ if the B16 cell line was not considered, but there was no relativity even excludes the B16 cell line. The present results indicate that there is no relationship between cellular sensitivity and initial DNA dsb, even exclude the effects of chromatin structure.

594

This work is to evaluate correlated lesions in PET and CT images of patients suffering skeletal metastases so as to improve efficacy of ¹⁸F-FDG PET/CT in diagnosing bone metastases. PET and CT images of 25 patients with malignant tumor suspected bone metastases were reviewed independently by three experts. A region of interest was placed over each lesion, and the standardized uptake value (SUV) was calculated at the maximal single pixel value. The t and χ² tests were used for statistical analysis. Of the 203 lesions detected on the PET and CT images, 189 were malignant and 14 were benign lesions. PET alone identified 159 malignant lesions and 6 benign lesions, CT alone identified 152 malignant lesions and 11 benign lesions. For PET, the diagnostic sensitivity, specificity and accuracy were 84.1%, 71.4% and 83.3%, respectively, while 80.4%, 71.4% and 83.3% for CT. No significant difference was found between PET and CT in detecting bone metastases (χ²=0.89, 0.19, 0.59, P>0.05). Statistical difference of positive ratio of PET was found between osteoblastic and osteolytic or mixed lesions (χ²=47.33, 7.93, both P<0.05). Of the 122 positive lesions on both CT and PET scan, the mean SUV was 5.76±3.41, 8.52±5.37 and 7.78±4.96 in osteoblastic lesions, osteolytic lesions and mixed lesions, respectively. Significant difference was found between osteoblast lesions and osteolytic lesions (t=2.28, P<0.05). PET images alone may leave out half of osteoblastic letions, but combined analysis of PET and CT images gives better diagnosis.

420

A compensated neutron logger (CNL) is designed by using Monte-Carlo simulation for lead shield thickness, near-to-far detector spacing range, source-to-detector spacing range, and detector's effective length. The calculated results indicate that the optimum conditions for CNL are 80-mm thick lead plus 1-cm thick LiOH shield in front of the near detector, 250 mm for the near-to-far detector distance (Δr), and the source-to-detector distance (r) of 90mm. Simultaneously, some conclusion also obtained here, near/far detector counting response ratio (R) increases with the effective length of detector, R increases with the porosity for oil and water sandstones, and the oil sandstone is a bit greater than water sandstone.

411

⁵⁶Co and ⁶⁶Ga with γ-ray energies covering the range of 0.84–3.55 and 0.68–4.81MeV, respectively, are important radionuclides for Ge detector calibration. The newly evaluated relative γ-ray intensities were recommended using the measurements finished after 2000 year by Baglin and Browne in 2004. In 2005 China groups measured the relative γ-ray intensities. The China measurements were about 2% systematically lower than other measurements and these evaluations. In this paper the discrepancies among these measurements and the evaluations are analyzed carefully and the new evaluations are re-recommended.

442

This study obtains a suitable reaction to produce ⁸⁶Y. The ⁸⁶Y excitation functions via ⁸⁶Sr(p,n)⁸⁶Y, ⁸⁶Sr(d,2n)⁸⁶Y, ⁸⁵Rb(³He,2n) ⁸⁶Y and ⁸⁵Rb(α,3n)⁸⁶Y reactions were calculated by TALYS-1.0 code and compared with the reported measurement. Requisite thickness of targets was obtained by SRIM code for each reaction. The ⁸⁶Y production yield was evaluated with attention to excitation function and stopping power. The ⁸⁶Sr(p,n)⁸⁶Y reaction was determined as most interesting one due to its highest production yield and advantages to get high radionuclide and radiochemical purity.

481

It has been found that the pressure in the reactor coolant system (RCS) remains high in some severe accident sequences at the time of reactor vessel failure, with the risk of causing direct containment heating (DCH). Intentional depressurization is an effective accident management strategy to prevent DCH or to mitigate its consequences. Fission product behavior is affected by intentional depressurization, especially for inert gas and volatile fission product. Because the pressurizer power-operated relief valves (PORVs) are latched open, fission product will transport into the containment directly. This may cause larger radiological consequences in containment before reactor vessel failure. Four cases are selected, including the TMLB' base case and the opening one, two and three pressurizer PORVs. The results show that inert gas transports into containment more quickly when opening one and two PORVs, but more slowly when opening three PORVs; more volatile fission product deposit in containment and less in reactor coolant system (RCS) for intentional depressurization cases. When opening one PORV, the phenomenon of revaporization is strong in the RCS.

435

The thermal conductivity of uranium dioxide in the temperature range of 300–2400 K was estimated by non-equilibrium molecular dynamics calculation using Fourier law. The Kawamura function was adopted as the interatomic potential function. The calculated thermal conductivities are found to be strongly dependent on the temperature of the simulation cube. The thermal conductivity simulation results are compared with the experiment results and agreed well with the experimental results when the temperature is above 600 K. The thermal conductivities scale effects are found to be existed in uranium dioxide nanometer thin film. The approximate mean free paths of phonons in different temperatures can be examined.

437