Vol.15,

Two independent measurements of cross sections for the ¹⁹F+⁹³Nb dissipative heavy-ion collision (DHIC) have been performed at incident energies from 100 to 108 MeV in steps of 250 keV. Two independently prepared targets were used respectively with all other experimental conditions being identical in both experiments. The data indicate non-reproducibility of the non-self-averaging oscillation yields in the two measurements. The statistical analysis of this non-reproducibility supports recent theoretical predictions of spontaneous coherence, slow phase randomization and extreme sensitivity in highly excited quantum many-body systems.

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Nicotine [3-(1-methyl-2-pyrrolidinyl)-pyridine], a major alkaloid in tobacco products, has proven to be a potential genotoxic compound. Some polyphenolic compounds can suppress the DNA adduction, and hence act as the potential inhibitors of carcinogenesis. In this study, the inhibitory effects of three polyphenolic compounds, curcumin (diferuloylmethane), resveratrol (trans-3, 5, 4^´-trihydroxystilbene) and tea polyphenols, on the nicotine-DNA adduction have been investigated in vitro using radiolabelled nicotine and liquid scintillation counting (LSC) technique. Also, the inhibition mechanism of these chemopreventive agents in regard to the activity of the biotransformation enzymes, including cytochrome P450 (CYP450), cytochrome b₅ (CYb₅) and glutathione S-transferase (GST), has been studied. The results demonstrated that these three polyphenols induced marked dose-dependent decrease in nicotine-DNA adducts as compared with the controls. The elimination rate of adducts reached above 46% at the highest dose for all the three agents with 51.6% for resveratrol. Correspondingly, three polyphenols all suppressed CYP450 and CYb₅, whereas curcumin and resveratrol induced GST. We may arrive at a point that the three polyphenols are beneficial to prevent the nicotine adduct formation, and thus may be used to block the potential carcinogenesis induced by nicotine.

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To assess the clinical value of treatment with ¹³¹I for brain metastases from differentiated thyroid cancer (DTC), we have observed 8 cases of brain metastases from DTC who received follow-up after ¹³¹I therapy (2 male, 6 female, aged 12~65 years). The results of ¹³¹I therapy were evaluated with clinical presentation, imaging scan and survival analysis. The main results are as follows. (1) All cases had been survival for 2~35 years in follow-up. (2) A space-occupying lesion in right cerebellum was reduced after taking 20.65GBq and disappeared after 23.61GBq, demonstrated by computed tomography. (3) The sequences and doses of ¹³¹I therapy were clearly decreased for the cases with total thyroidectomy in comparison with those with semithyroidectomy (p<0.01). (4) The brain metastases with lung and/or bone metastasis from DTC were 75% (6/8) and it was difficult to cure these metastases at the same time. It is concluded that the postoperative treatment of ¹³¹I for brain metastases from DTC after undergoing thyroidectomy may improve clinical symptoms and life quality, reduce lesions, and prolong survival.

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In order to treat malignant tumors in human body, a stereotactic gamma-ray whole-body therapeutic system has been developed. This system is a typical large mechatronics treatment machine. in this paper, its main working principles and characteristics are introduced. This system comprises a special gallows frame with an open vertical structure, a changeable collimator device by which the size of convergence center can be chosen, and a 3D treatment couch. A computer brings the couch to target position automatically. Therefore precise and dynamic rotary converging therapy for tumors located anywhere in the body has been realized. The system's performance has been proved in practice, which includes good curative effect, reliable automation, and safe and secure operation.

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The HT-7 is a superconducting tokamak in China used to make researches on the controlled nuclear fusion as a national project for the fusion research. The plasma density feedback control subsystem is the one of the subsystems of the distributed control system in HT-7 tokamak (HT7DCS). The main function of the subsystem is to control the plasma density on real-time. For this reason, the real-time capability and good stability are the most significant factors, which will influence the control results. Since the former plasma density feedback control system (FPDFCS) based on Windows operation system could not fulfill such requirements well, a new subsystem has to be developed. The paper describes the upgrade of the plasma density feedback control system (UPDFCS), based on the dual operation system (Windows and Linux), in detail.

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Artificial neural networks (ANNs) are applied successfully to analyze the critical heat flux (CHF) experimental data from some round tubes in this paper. A set of software adopting artificial neural network method for predicting CHF in round tube and a set of CHF database are gotten. Comparing with common CHF correlations and CHF look-up table, ANN method has stronger ability of allow-wrong and nice robustness. The CHF predicting software adopting artificial neural network technology can improve the predicting accuracy in a wider parameter range, and is easier to update and to use. The artificial neural nefwork method used in this paper can be applied to some similar physical problems.

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To keep the void fraction of two-phase hydrogen in the moderator cell of the cold neutron source (CNS) of China Advanced Research Reactor (CARR) to a specified range, an annular vessel with the same size as the actual moderator cell was used as test section. Deionized water and alcohol, sucrose, and sodium chloride solutions with different concentrations were used as working fluid to find out influences of physical properties, such as density, viscosity and surface tension, of the two–phase mixture on void fraction. The tests proved that the ratio of surface tension to density of liquid phase has great influence on void fraction: the larger the ratio, the smaller the void fraction. Since the ratio of surface tension to density of Freon 113 is lower than that of liquid hydrogen, Freon 113 can be used as a working fluid to study the void fraction in the two-phase hydrogen thermosiphon loop in the CNS of CARR and the results will be conservative.

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Applying the extreme low-level γ-ray spectroscopic analysis the environmental neutron flux is measured using different moderator construction and environment through the reaction ¹⁹⁷Au (n, γ) ¹⁹⁸Au. The contribution of thermal and resonance neutrons is separated using the cadmium difference technique, while fast neutrons are measured by the paraffin moderator. The results of altitude dependence of the neutron flux are discussed. The thermal neutron flux near the surface of sea water is less than its value at 100 cm over ground near sea water, while the value over the surfaces of fresh water is higher than that near the surface of sea water. Also the thermal neutron flux at 5 cm soil depth increases, then decreases to its original value at 10 cm depth and still constant until 25 cm, then decreases rapidly to reach 27% of its original value at 60 cm depth. The soil compositions, corresponding neutron temperatures and effective absorption cross sections of earth are the most effective factors on the equilibrium region of thermal neutrons in the ground.

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