Vol.21,

Five of the seven Phase I beamlines of Shanghai Synchrotron Radiation Facility (SSRF) are based on insertion devices (IDs), which include two wigglers, one elliptically polarized undulator (EPU), and two in-vacuum undulators. There were some inevitable field integral errors in manufacturing the IDs, and these would affect performance of the storage ring. The integrated multipoles were corrected by using the magic fingers technique. In this paper, we report the correction method based on the simulated-annealing algorithm. The results show that the integrated multipole components were corrected to meet the design specifications.

316

In this paper, automobile exhaust particles of Gol and Santana 3000 were studied by spectromicroscopy. The STXM results show that the single particulate is sized at 500 nm, with the mass distribution reducing towards the center. The N 1s NEXAFS spectra of automobile exhaust particles have similar structure with those of nitrates, which can be deduced as the main chemical species of nitrogen in automobile exhaust particles. There are minor amounts of ammoniums and organic nitrogen compounds in automobile exhaust particles. A single Gol automobile exhaust particle was stack scanned in the energy range of 396–416 eV. By principal component analysis and cluster analysis, it can be deduced that there are main three chemical species of nitrogen. The particle surface consists of mainly nitrates, the inside consists of mainly ammonium and organic nitrogen compounds, and the middle layer is an intergradation consisting of mainly nitrates and organic nitrogen compounds.

313

In recent years, people are looking for a new compact THz source with high emission power, one potential choice is to build small accelerator with Smith-Purcell radiation. The main difficulty is how to obtain high quality electron beam. In this paper, the beam dynamics design of a compact THz source is presented. The electron beam is produced by an electron gun and compressed by permanent magnets. The electron gun is similar to the Shanghai EBIT, but permanent magnets are used, instead of the superconducting magnets in Shanghai EBIT. With this design, we can reduce the size and cost of the whole device. Poisson/Pandira was employed to simulate and optimize the magnetic field. Egun was used to simulate the beam trajectories from the electron gun to the collector. Within 2 centimeters around the center of longitudinal magnetic field, the calculation showed that the beam satisfies to our design aim.

302

Behaviors and properties of helium in titanium were explored by molecular dynamics (MD) simulation in this study. The influence of He number, vacancy number and He density (ratio of helium to vacancy) on the thermal stability of He_nV_m clusters (where n and m denote the number of He atoms and vacancies) were investigated. Meanwhile, interactions among He atoms, SIA atoms and vacancies were discussed. The results demonstrate that the binding energies of an interstitial helium atom primarily depend on He and vacancy numbers rather than the helium-to-vacancy ratio (n/m). It is different from the previous report of other researchers. The binding energies of an isolated vacancy and a self-interstitial titanium atom depend on both the number of helium atoms and the helium-to-vacancy ratio (n/m) of clusters. The thermal stability of clusters is decided by the competitive processes among thermal emissions of vacancy, SIA and helium atom.

330

In comparison with conventional radiotherapy techniques, ¹²C beam therapy has its significant advantage in cancer treatment because the radiation dose are mostly concentrated near the Bragg peak region and damage to normal tissues along the beam path is thus greatly reduced. In-beam PET provides a way to monitor dose distribution inside human body since several kinds of positron-emitting nuclei are produced through the interaction between ¹²C beam and body matters. In this work, we study the quantitative relationship between the spatial location of the Bragg peak and the spatial distribution of positrons produced by positron-emitting nuclei. Monte Carlo package GATE is used to simulate the interactions between the incident ¹²C beam of different energies (337.5, 270.0 and 195.0 MeV/u) and various target matters (water, muscle and spine bone). Several data post-processing operations are performed on the simulated positron-emitting nuclei distribution data to mimic the impacts of positron generation and finite spatial resolution of a typical PET imaging system. Simulation results are compared to published experimental data for verification. In all the simulation cases, we find that ¹⁰C and ¹¹C are two dominant positron-emitting nuclei, and there exists a significant correlation between the spatial distributions of deposited energy and positrons. Therefore, we conclude that it is possible to determine the location of Bragg peak with 1 mm accuracy using current PET imaging systems by detecting the falling edge of the positron distribution map in depth direction.

352

For the measurement of X-ray energy spectrum with filter-fluorescer method, the high energy tail at the rearward of response function is the main source of background. There are, traditionally, two techniques for measuring the background contributions: the same element Z for the fluorescer and filter, or the same element Z−1 for them. Using the formula of fluorescence intensity, and the elemental combinations of cobalt and iron, the backgrounds which the two techniques provide and the real one for measuring black-body radiation at equilibrium temperature of 7×10⁶ K, were calculated. The results show that the Co-Co combination for the filter-fluorescer spectrometer can achieve better effect. A semi-quantitative analysis for the calculation results is discussed.

315

Surface contamination by conducting materials, metals in particular, is one of the important causes for electric breakdown of insulators under high voltage. In order to explore the feasibility of nuclear track modification for anti-metallic contamination, polyester membranes with different thickness were bombarded by ³²S ions from the HI-13 tandem accelerator of CIAE. The tracks formed on the surface of the membranes were etched under different conditions. The insulating capability of the treated membranes was evaluated by using silver coatings to simulate the surface metallic contamination. The results indicated insulators with the surface modified by nuclear pore technique have an improved capability of anti-contamination of metals. The sample with 144 nm Ag coating is not breakdown under 1000 V.

355

CrN coatings were deposited on Si(100) and piston rings by ion source assisted 40 kHz magnetron sputtering. Structure and composition of the coatings were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Mechanical and tribological properties were assessed by microhardness and pin-on-disc testing. The ion source-assisted system has a deposition rate of 3.88 μm/h, against 2.2 μm/h without ion-source assistance. The CrN coatings prepared with ion source assistance exhibited an increase in microhardness (up to 16.3 GPa) and decrease in friction coefficient (down to 0.48) at the optimized cathode source-to-substrate distance. Under optimized conditions, CrN coatings were deposited on piston rings, with a thickness of 25 μm and hardness of 17.85 GPa.

339

Tumor cells often develop resistance to radiotherapy by fractionated radiation possibly due to the heterogeneity and hypoxia in tumor tissue. However, the mechanism of refractory effect remains unclear. In the present study, a radioresistant variant HepG2/R60 cell line was isolated from human HepG2 cells by repeated exposure to radiation. The results showed that, after irradiation, the higher survival rate was in HepG2/R60 cells compared to parental cells. Hypoxia treatment could further increase the radioresistance of HepG2/R60 cells concomitant with high level of intracellular GSH and overexpression of HIF-1α. When hypoxic HepG2/R60 cells were pretreated with BSO, a GSH depleter, the refractory response was significantly reduced showing a decrease in intracellular GSH level, followed by the suppression of HIF-1α in hypoxic cells. Subsequent study found that the level of BCL-2 was down-regulated, targeted by HIF-1 prompting transcription in hypoxic cells. The effect of HIF-1α on the radiosensitivity of hypoxic cells was confirmed using YC-1, a specific inhibitor of HIF-1α. Consequently, our results suggest that the radiosensitivity of tumor cells might be regulated by fractionated radiation, and the radioresistance of cells induced by repeated exposure, under hypoxic condition, could be correlated with overexpression of HIF-1α dependent on the alteration of intracellular GSH contents.

454

The cyclic peptide YG5 and the t-butyloxycarbonyl (Boc)-modified analog (Boc-YG5) were labeled with radioiodine. The radiochemical purity of ¹³¹I-YG5 or ¹³¹I-Boc-YG5 was almost 100% after purification by RP-HPLC. Biodistribution in BALB/C nude mice bearing MCF-7 tumor was measured. After t-butyloxycarbonyl (Boc)-modification, the ¹³¹I-Boc-YG5 was quite resistant to deiodination in vivo, resulting in negligible radioactivity accumulation in thyroid. The radiotracer clearance in tumor became faster, the absolute tumor uptake decreased for ¹³¹I-Boc-YG5, but the tumor-to-tissue uptake ratios increased. The uptake ratios of tumor to muscle, blood, heart, and lung at 1 h post injection reached 4.73, 1.70, 4.09 and 1.70, respectively. It is demonstrated that Boc-group is an effective prosthetic one to prevent deiodination in vivo and improve tumor imaging for radioiodinated NGR.

288

A standardized uptake value(SUV) of 2.5 is frequently used as criteria to evaluate pulmonary lesions. However, false results may occur. Some studies have shown the usefulness of delayed PET for improving accuracy, while others recently have shown fewer promising results. This study was designed to investigate the accuracy of dual time point (DTP) FDG PET imaging in the evaluation of pulmonary lesions with an initial SUV less than 2.5. DTP FDG PET studies were conducted about 1 and 2 hours after FDG injection, and pulmonary lesions with an initial SUV less than 2.5 were identified. Nodules with pathologic results or imaging follow up were included. The differences in SUV and retention index (RI) between benign and malignant pulmonary lesions were analyzed. Receiver operating characteristics (ROC) analysis was performed to evaluate the discriminating validity of SUV and RI. 51 lesions were finally included. A RI greater than 0% was observed in 64% of the benign lesions; 56% had a RI greater than 10%. Among the malignancies, 80.8% had a RI greater than 0%, and 61.5% had a RI greater than 10%. We found no significant differences in SUV and RI between benign and malignant lesions. The area under the ROC curve did not differ from 0.5 whether using SUV or the retention index. Utilizing a SUV increase of 10%, the sensitivity was 61.5%, specificity 44% and accuracy was 52.9%. Dual time point FDG PET may not be of benefit in the evaluation of pulmonary nodules with low FDG avidity.

490

The objective of this paper is to design and simulate a shaping amplifier circuit for silicon strip, Si(Li), CdZnTe and CsI detectors, etc., which can be further integrated the whole system and adopted to develop CMOS - based application, specific integrated circuit for Front End Electronics(FEE) of read-out system of nuclear physics, particle physics and astrophysics research, etc. It's why we used only CMOS transistor to develop the entire system. A Pseudo-Gaussian shaping amplifier made by fourth-order integration stage and a differentiation stage give a result same as a true CR-RC⁴ filter, we perform shaping time in the range, 465 ns to 2.76μs with a low output resistance and the linearity almost good.

320

In this paper, we propose a novel probe to identify phases in any two-phase flows where one phase is conductive and the other nonconductive. We can further obtain many parameters such as void fraction, bubble velocity, and interfacial area concentration. Compared with the traditional probe, the novel probe has unique advantages that it is less dependent on water conductance or distance between the electrodes, and that the amplitude is bigger between high and low levels. Theoretical analyses showed that the measurement error became higher when water conductance decreases or distance increases, which is consistent with the theoretical analyses. Experimental results showed that the output signal kept constant with salt content of 0−5% and electrode distance of 0−30 mm in tap water. The level difference was up to 6.4 V, resulting in identifying two phases easily. Time traces of phase identification were completely consistent with the flow structures.

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