Vol.24,

With the spatial coherence of X-rays and high flux and brightness of the 3^rd generation synchrotron radiation facility, X-ray phase contrast microscopy (XPCM) at Shanghai Synchrotron Radiation Facility (SSRF) can provide high resolution dynamic imaging of low electron density materials in principle. In this paper, we investigated the cavitation and water-refilling processes in rice and bamboo leaves utilizing XPCM at SSRF. The occurrence of xylem cavitation was recorded in vivo. The study also revealed that under different dehydration conditions, cavitation occurs in different degrees, and therefore, the refilling process is different. The results demonstrate that SSRF can provide high enough fluxes to study dynamic processes in plants in real-time, and XPCM is expected to be a promising method to reveal the mechanisms of cavitation and its repair in plants nondestructively.

512

Synchrotron radiation (SR) represents a unique and innovative anti-cancer treatment due to its unique physical features, including high flux density, and tunable and collimated radiation generation. The aim of this work is to assess the dosimetric properties of SR in Shanghai Synchrotron Radiation Facility (SSRF) for potential applications to clinical radiation oncology. The experiments were performed with 34 and 50 keV X-rays on the BL13W biomedical beamline of SSRF and the 6 MV X-rays from ARTISTE linac for the dosimetry study. The percentage depth dose (PDD) and the surface dose of the SR X-rays and the 6 MV photon beams were performed in solid water phantom with Gafchromic EBT3 ﬁlms. All curves are normalized to the maximum calculated dose. The depth of full dose buildup is about 10 µm deeper for the monoenergetic X-ray beams of 34 and 50 keV. The beam transmits through the phantom, with a linear attenuation coefficient. The profile in the horizontal plane shows that the dose distribution is uniform within the facula, while the vertical profile shows a Gaussian distribution of the dose. The penumbra is less than 0.2 mm in the horizontal profile. Gafchromic EBT film may be a useful and convenient tool for dose measurement and quality control for the high space and density resolution. It is therefore important to gain a thorough understanding about the physical features of SR before this novel technology can be applied to clinical practice.

465

In this paper, a genetic-algorithm-based artificial neural network (GAANN) model radioactivity prediction is proposed, which is verified by measuring results from Long Range Alpha Detector (LRAD). GAANN can integrate capabilities of approximation of Artificial Neural Networks (ANN) and of global optimization of Genetic Algorithms (GA) so that the hybrid model can enhance capability of generalization and prediction accuracy, theoretically. With this model, both the number of hidden nodes and connection weights matrix in ANN are optimized using genetic operation. The real data sets are applied to the introduced method and the results are discussed and compared with the traditional Back Propagation (BP) neural network, showing the feasibility and validity of the proposed approach.

370

Different channel lengths and layouts on 0.18 μm NMOS transistors are designed for investigating the dependence of short channel effects (SCEs) on the width of shallow trench isolation (STI) devices and designing in radiation hardness. Results show that, prior to irradiation, the devices exhibited near–ideal I–V characteristics, with no significant SCEs. Following irradiation, no noticeable shift of threshold voltage is observed, radiation–induced edge–leakage current, however, exhibits significant sensitivity on TID. Moreover, radiation–enhanced drain induced barrier lowering (DIBL) and channel length modulation (CLM) effects are observed on short–channel NMOS transistors. Comparing to stripe–gate layout, enclosed–gate layout has excellent radiation tolerance.

396

The properties of a Lanthanum bromide (LaBr₃) detector and its response functions were investigated via experiments and simulations in this paper. The LaBr₃ detector had good relative energy resolution and higher efficiency than a high-purity germanium detector. Monte Carlo and other numerical methods were used to calculate the efficiencies of a LaBr₃ detector with a square collimation window. A model of the numerical method was established based on a pure geometric model that was consistent with the experimental situation. The results showed that the detector response functions calculated by these methods were in great agreement with experimental results.

468

Copper nanoparticles were successfully synthesized by ⁶⁰Co-γ radiation with aqueous solution of cupric sulfate under inert nitrogen-purged conditions. Cu nanoparticles were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), laser particle size distribution analyzer (LSPSDA) and differential scanning calorimeter (DSC) techniques, respectively. The effects of solution system, pH, additive of surfactant and absorbed doses on the particle size and its distribution as well as stored stability of Cu naoparticles were investigated. High resolution TEM pictures showed the formation of homogeneous cubic-structured copper nanoparticles with different sizes depends on the synthetic conditions. This new kind of synthesis method shows the excellent stability, which may provide an efficient way to improve the fine tuning of the structure and size of copper nanoparticles.

449

Poly (methyl methacrylate) (PMMA) pellets are irradiated using ⁶⁰Co gamma-ray in air and successfully formed by hot pressing at constant conditions. The irradiated PMMA membranes are prepared by supercritical carbon dioxide (scCO₂) as a physical blowing agent using the pressure quench method. Effects of foaming conditions such as adsorbed dose, saturation temperature, pressure on the morphology and cell size of the microcellular PMMA membranes are investigated in detail. The results showed that the irradiated PMMA membranes possess spherically closed-cell structure with uniform cell size. They have a high cell density compared with virgin PMMA. The cell size uniformity becomes poor at dose lower than 10 kGy, but increases with the dose at dose higher than 10 kGy. The mean cell diameter is less than 10 μm and the cell density increases with increasing dose. The average cell size of irradiated PMMA membranes decreases and cell density increases with increased saturation temperature and pressure. The changes in morphology of membranes are attributed to the gamma-ray radiation and scCO₂ synergistic effect.

437

Asialoglycoprotein receptor (ASGP-R) is a hepatic membrane receptor that uniquely exists on the surface of mammalian hepatocytes, and has been used as target of liver functional imaging agents for many years. We labeled the Galactosyl-neoglycoalbumin (NGA) with ¹⁸F to get a PET molecular probe ¹⁸F-FB-NGA and evaluated its ability as a liver functional PET imaging agent. The ¹⁸F-FB-NGA was prepared with NGA by conjugation with N- succinimidyl-4-¹⁸F-fluorobenzoate (¹⁸F-SFB) and purified with PD-10 desalting column. The radiolabeling yield and radiochemical purity of ¹⁸F-FB-NGA were determined by radio-HPLC. Starting with ¹⁸F-F^–, the total time for ¹⁸F-FB -NGA was about 120±10 min. The decay-corrected radiochemical yield is about 25–30%. The radiochemical purity of purified ¹⁸F-FB-NGA was more than 98%. Labeled with 185–1850 MBq ¹⁸F-SFB, the specific activity of ¹⁸F -FB- NGA was estimated to be 7.83–78.3 TBq/mmol. Biodistribution of ¹⁸F-FB-NGA in normal mice was investigated after injection through the tail vein. The results showed that the liver accumulated 39.47±3.42 and 12.12±6.11%ID/g at 10 and 30 min after injection, respectively. Dynamic MicroPET images in mice were acquired with and without block after injection of the radiotracer, respectively. High liver activity accumulation was observed at 5 min after injection in normal group. On the contrary, the liver accumulation was significantly lower after block, indicating the specific binding to ASGP-R. ¹⁸F-FB-NGA is probably a potential PET liver imaging agent.

318

In this paper, the safety and efficacy of ¹³¹I-labeled mouse/human chimeric monoclonal antibody (¹³¹I-chTNT)-mediated radioimmunotherapy are evaluated because the patients have non-uptaking ¹³¹I pulmonary metastases from differentiated thyroid carcinoma (DTC). The 16 patients were injected intravenously by 29.6±3.7 MBq·kg^–1 using ¹³¹I-chTNT. The chest computer tomography was performed before treatment, as well as 28 and 70 days after treatment. Responses and safety were assessed during the treatment. The results show that the ¹³¹I-chTNT infusion was well tolerated with the 12.5% complete response, 18.8% partial response, 25.0% progressive disease, and the 43.8% stable disease, indicating that most treatment-related adverse effects are mild transient and reversible. The ¹³¹I-chTNT is promising for patients with non-uptaking the ¹³¹I pulmonary metastases from DTC.

328

This study investigated the impact of simulated microgravity on acute injury induced by low doses of carbon ions in male reproductive organs of mice, and determined alterations in spermatogenic function and expression levels of apoptotic factors in mice following exposure to acute irradiation after 7 days of simulated microgravity. The results demonstrated that significant reductions in spermatozoa, primary spermatocytes and spermatogonia, and increased globular cells in seminiferous tubule and pro-apoptotic proteins were observed in the group exposed to over 0.4 Gy irradiation. Collectively, the data suggest that lesions inflicted by simulated microgravity are not markedly modified by lower doses of irradiation (0.2 Gy) in mouse testis compared to the control group. However, testicular impairments were markedly evident in the group exposed to higher doses of carbon ions plus simulated microgravity, which may be due at least in part to elevated apoptosis initiated by the mitochondrial apoptosis pathway in germ cells.

358

Alterations of mitochondria DNA (mtDNA) 4977 bp common deletion (CD) and mtDNA copy number induced by ionizing radiation were observed in human different cell lines and total body irradiation patients. However, only few experiments have evaluated the levels of the CD and mtDNA copy number in human peripheral blood exposed to ionizing radiation till now. The aim of this study is to analyze the mtDNA alterations in irradiated human peripheral blood from healthy donors as well as to explore their feasibility as biomarkers for constructing new biodosimeter. Peripheral blood samples were collected from six healthy donors, and exposed to ⁶⁰Co gamma ray with the doses of 0 Gy, 1 Gy, 2 Gy, 3 Gy, 4 Gy and 5 Gy. Levels of the CD and mtDNA copy number in irradiated samples after 2h or 24h incubation were detected using TaqMan real-time PCR, and the CD ratio was calculated. The results showed that the mean of the CD ratio and the CD copy number exhibited a dose-dependent increase 2 h in the dose range from 0–5 Gy, and of the mtDNA copy number significantly increased 24 h in irradiated groups compared with 0 Gy group after irradiation. It indicates that the parameters in human peripheral blood may be considered as molecular biomarkers to applying construction of new biodosimeter.

417

On the basis of preliminary studies, a novel duo-parameter model consisting of amplitude filter factor and frequency filter factor for low-pass S-K filter is presented in this paper. The model is established by applying numerical differentiation method. Some simulation experiments and real data tests are carried out to verify the feasibility and superiority of the new algorithm. The results show that this duo-parameter model of low-pass S-K filter can be used to achieve high performance in signal processing and nuclear spectrum smoothing.

574

In this paper, a general method of data transmission system design on PXI platform is proposed. It can be used in readout system design for physical experiments. It aims at providing reusable and general interfaces for customized design of PXI while maintaining the transmission performance. It has three main features: (1)universal logic hardware interface, (2)ethernet based socket software interface, and (3)specific and simple data transmission protocol. Data transmission on PXI bus can be realized with the said two universal interfaces coordinated by this specific protocol. Test shows that this method is feasible and stable. This method can be easily reused in readout system designs for different experiments.

364

This article presents a prototype of beam position and phase measurement (BPPM) electronics designed for the LINAC in China Accelerator Driven Sub-critical system (ADS). The signals received from the Beam Position Monitor (BPM) detectors are narrow pulses with a repetition frequency of 162.5 MHz and a dynamic range more than 40 dB. Based on the high-speed high-resolution Analog-to-Digital conversion technique, the input RF signals are directly converted to In-phase and Quadrature-phase (IQ) streams through under-sampling, which simplifies both the analog and digital processing circuits. All signal processing is integrated in one single FPGA, in which real-time beam position, phase and current can be obtained. A series of simulations and tests have been conducted to evaluate the performance. Initial test results indicate that this prototype achieves a phase resolution better than 0.1 degree and a position resolution better than 20 μm over a 40 dB dynamic range with the bandwidth of 780 kHz, which is well beyond the application requirements.

386

This paper presents a novel approach to seek the bar width for ripple filter used in pencil beam scanning proton therapy. A weight decay quadratic programming method is employed for the new optimization strategy. Compared to the commonly used iterative-least-square technique, the ripple filter derived by the proposed method not only has better depth dose uniformity, i.e., the dose uniformity is within 0.5%, but also has triangle-like vertical cross-sectional shape which is suitable for manufacture. Moreover, the new method has such good robust characteristics that it is also applicable to the real application with unavoidable measurement errors and noises. The simulation results of this study may be helpful in improving the design of the ripple filter.

337

Based on the statistical characteristics of energy spectrum and the features of spectrum-shifting in spectrometry, the parameter adjustment method of Gaussian function space was applied in the simulation of spectrum-shifting. The transient characteristics of energy spectrum were described by the Gaussian function space, and then the Gaussian function space was transferred by parameter adjustment method. Furthermore, the spectrum-shifting in measurement of energy spectrum was simulated. The applied example shows that the parameters can be adjusted flexibly by this method to meet the various requirements in simulation of energy spectrum-shifting. This method was one parameterized simulation method with good performance for the practical application.

423

In order to realize the on-line real-time measurement of neutron spectrum of ITER fusion, this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors, namely SP9 ³He proportional counter, embedded in eight different diameter polyethylene spheres. The response function of eight polyethylene spheres of multi-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4. The peak of the response function is in the low energy region for smaller diameter polyethylene sphere. As the polyethylene sphere diameter increased, the peak of the response function moves to the high energy region. The experimental calibration adopts ²⁴¹Am-Be neutron source. The relative error between normalized data of experiment 4π solid angle counts and normalized data of simulated detection efficiency of 4in to 8in polyethylene sphere is from 1.152% to 12.222%.The experimental results verify the response function of the simulation. All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion.

369

Trapezoidal shaping method is widely applied to pulse amplitude extraction in digital nuclear spectrometer system, the optimal selection of the shaping parameters can improve the energy resolution and pulse counting rate. From the view of noise characteristics, ballistic deficit compensation characteristics and pulse pile-up characteristics, in this paper the optimal selection of the trapezoidal shaping parameters is studied on. According to the theoretical analysis and experimental verification, the optimal choice of trapezoidal shaping parameters is similar to the triangle, the rise time is longer and the flat-top width is shorter.

502

A principle and method of constructing the digital acquisition system is presented in this work, which is convenient for the study on the theories and algorithms of digital nuclear signal processing. The hardware system of the digital acquisition system consists of front-end controller, waveform digitizer and PC workstation, on which the software system has been developed based on Visual C++ under Windows environment. The alterable-frequency sampling (AFS) algorithm and the alterable-frequency trapezoidal filter (AFTF) algorithm have also been studied in the real-time environment, along with a digital nuclear spectrum acquisition system being set up based on the new algorithms and the γ-ray spectra of ²⁴¹Am being shown. A useful experimental platform could be provided by this work for the successive work such as the development of global digitized nuclear measurement system and the study of digital nuclear signal processing.

399

Based on the experiment of onset of nucleate boiling (ONB) in natural circulation and the nonequilibrium thermodynamics dissipative theory, the mechanism of ONB in narrow rectangle channels of natural circulation is proposed. It points out that the onset of nucleate boiling is influenced by the degree of superheat and the special conditions of narrow channels. Under the conditions of both density difference in natural circulation and narrow rectangle channels, the prediction model of ONB in natural circulation of narrow channels based on fluctuating is established. The experimental results show that the present model can be used to predict the heat flux of ONB in narrow rectangle channels. Features of ONB in natural circulation narrow rectangle channels are as follows: heating power is the incentive of the happen of ONB; the higher the heating power is, the higher the degree of superheat is, and the earlier the ONB will appear. With the pressurizing, the appearance of ONB will be delayed. The higher the degree of supercooling is, the later the ONB appears. The ONB will happen easier when there are noncondensable gases and roughness in the channels.

373

Most materials can be easily corroded or ineffective in carbonaceous atmospheres at high temperatures in the reactor core of the high temperature gas-cooled reactor (HTGR). To solve the problem, a material performance test apparatus was built to provide reliable materials and technical support for relevant experiments of the HTGR. The apparatus uses a center high-purity graphite heater and surrounding thermal insulating layers made of carbon fiber felt to form a strong carbon reducing atmosphere inside the apparatus. Specially designed tungsten rhenium thermocouples which can endure high temperatures in carbonaceous atmospheres are used to control the temperature field. A typical experimental process was analyzed in the paper, which lasted 76 hours including seven stages. Experimental results showed the test apparatus could completely simulate the carbon reduction atmosphere and high temperature environment the same as that confronted in the real reactor and the performance of screened materials had been successfully tested and verified. Test temperature in the apparatus could be elevated up to 1600ºC, which covered the whole temperature range of the normal operation and accident condition of HTGR and could fully meet the test requirements of materials used in the reactor.

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