Vol.28,

We conducted a retrospective analysis of 221 subjects with 256 suspected gastrointestinal lesions from 2007 to 2015 to explore the detecting efficiency of dual-time-point fluorine-18 fludeoxyglucose (¹⁸F-FDG) positron emission tomography / computed tomography (PET/CT) and pathology exam. The abdominal delayed PET/CT was performed within 45 min of the conventional scan. The change of maximum standardized uptake value (ΔSUV_max) and morphological features of the suspected lesions between the conventional and dual-time-point PET/CT were compared. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of conventional PET/CT were 81.6% (84/103), 56.2% (86/153), 55.6% (84/151), and 81.9% (86/105), respectively. Those of dual-time-point PET/CT were 94.1% (97/103), 78.4% (120/153), 74.6% (97/130), and 95.2% (120/126), respectively. There was a significant difference between the conventional and dual-time-point PET/CT (P<0.005). The SUV_early and the %ΔSUV_max could not present more information in differential diagnoses, but the rate of tumors with increased SUV_delay accounted for 79.6% (82/103) and more than that of nonneoplastic lesions (15.5%, 29/187) (x²=115.5, P<0.01). Therefore, the dual-time-point ¹⁸F-FDG PET/CT had a higher sensitivity and NPV than the conventional PET/CT to detect gastrointestinal tumors. The constant morphology and increased SUV_delay help to detect the tumors and adding delayed imaging on the locality will be an effective method when we accidentally find a suspected gastrointestinal tumor on the conventional PET/CT images.

380

Based on the geochemical prospecting data, we have calculated the gamma absorbed dose rates in air 1 m above the ground surface in the Chengdu Plain, analyzed the relationship between the geological conditions and the distribution of the natural radionuclides, and preliminarily studied the influence of the geological conditions on the terrestrial radiation level in the Chengdu Plain. The result shows that the terrestrial radiation level in the Chengdu Plain is slightly lower than the average values of China and varies greatly according to the complex geological conditions.

326

In order to satisfy the requirements of beam measurement in the Heavy Ion Medical Machine (HIMM) and other small nuclear physics experiments, we designed and built a Nuclear Instrumentation Module (NIM) based data acquisition (DAQ) system. This is composed of a set of functional modules and a purpose-built bus. One of the modules operates as a master, collecting data from the other slave modules. It then sends the data to the back-end computer via Ethernet. In addition to the hardware, dedicated software has been designed and implemented. In this paper, we provide a detailed description of the architecture of the system, the data frame and the software. The bus is the central part of the system. It can transmit data from the slave modules to the master at 33MB/s. The frame used to transmit the data also ensures its integrity and monitors the hardware architecture. The client software is designed to process data in real time and store data on a hard disk for later analysis.

376

A readout system for ground-based tests of the bismuth germanium oxide (BGO) calorimeter of the Dark Matter Particle Explorer (DAMPE) satellite is described in this paper. The system mainly consists of a data acquisition (DAQ) board with a field-programmable gate array (FPGA) to implement the control logic, and a graphical user interface software based on LabWindows/CVI. The system has been successfully applied in a series of ground-based environmental experiments and almost all the performance tests throughout the entire manufacturing processes. These contribute significantly to the development of the BGO calorimeter before being submitted for satellite-level integration.

354

The total dose effect of ⁶⁰Co γ-rays on 0.8 μm H-gate partially depleted silicon-on-insulator NMOS devices was investigated at different irradiation dose. The results show that the shift in saturation current at high dose rate is greater than that at low dose rate, due to increase in interface-state density with decreasing dose rate; the scattering effect of interface state on electrons in the channel causes degradation in carrier mobility; and the body current and transconductance of the back-gate enhances low dose rate sensitivity when the irradiation is under OFF-bias. A double transconductance peak is observed at 3 kGy(Si) under high dose rates.

482

A smoothing algorithm for energy spectrum based on differential nonlinearity (DNL) error elimination with total counts conservation (TCC-DEE) for high energy particle detector systems is presented. It is physics-based and is only determined by the DNL error of analog-to-digital converter (ADC) device itself. From the experimental results, this algorithm slightly improves both noise performance and energy resolution, while greatly reduces the testing errors by almost a half compared to their original values. In addition, the reduced-χ² statistic for evaluating the Gaussian fitting goodness is significantly reduced by almost two orders after smoothing. As a typical verification example, this algorithm is successfully applied in the ground calibration of the Low Energy X-ray Instrument (LE) onboard the Hard X-ray Modulation Telescope (HXMT) satellite, lending it a powerful, non-destructive and low-cost tool for both calibration and data processing for high-energy particle detector systems.

621

The processes and characteristics of secondary electron emission in insulators and semiconductors were studied, and the formulae for the maximum yield (δ_m) at W_p0m≤800eV and the secondary electron yield from insulators and semiconductors δ at the primary incident energy of 2 keV≤W_p0<10 keV (δ_2-10) and 10 keV≤W_p0≤100 keV (δ_10-100) were deduced. The calculation results were compared with their corresponding experimental data. It is concluded that the deduced formulae can be used to calculate δ_2-100 at W_p0m≤800eV.

376

Developing a molten salt reactor needs molten salt-impermeable nuclear graphite. Ultra-fine grain graphite is a good choice as it is better in permeability than fine grain graphite. In this paper, ultra-fine grain graphite (HPG-510) and fine grain graphite (IG-110) samples are irradiated at room temperature by 7 MeV Xe ions to doses of 1×10¹⁴–5×10¹⁵ ions/cm². Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and Nano-indentation are used to study the radiation induced changes. After irradiation of different doses, all the HPG-510 samples show less surface fragment than the IG-110 samples. The TEM and Raman spectra, and the hardness and modulus characterized by nano-indentation, also indicate that HPG-510 is more resistant to irradiation.

326

The central solenoid (CS) is an important component of China Fusion Engineering Test Reactor (CFETR), for producing, forming and stablizing plasma in the superconducting tokamak. It is a complicated work to design and manufacture the large superconducting CS magnet, so it is meaningful to design a central solenoid model coil (CSMC) and analyze its electromagnetic properties in advance. In this paper, the structure, design parameters and magnetic field distribution of the CS model coil are discussed. The peak power of radial and axial turn conductors and time bucket loss are analyzed by using piecewise-linear method. The CSMC AC loss with different Nb₃Sn CICCs and AC loss of ITER CS coil are compared. The special electrometric method to measure AC loss of the CS model coil for future reference is presented.

420

This paper presents the gas distribution analysis by injecting air-fountain into the containment and simulations with the HYDRAGON code. Turbulence models of standard k-ε (SKE), re-normalization group k-ε (RNG) and a realizable k-ε(RLZ) are used to assess the effects on the gas distribution analysis during a severe accident in a nuclear power plant (NPP). By comparing with experimental data, the simulation results of the RNG and SKE turbulence models agree well with the experimental data on the prediction of dimensionless density distributions. The results illustrate that the turbulence model choice had a small effect on the simulation results, particularly, the region near to the air-fountain source.

362

The present paper discusses entropy generation in fully-developed turbulent flows through a subchannel, arranged in square and triangle arrays. Entropy generation is due to contribution of both heat transfer and pressure drop. Our main objective is to study the effect of key parameters such as spacer grid, fuel rod power distribution, Reynolds number Re, dimensionless heat power ω, length-to-fuel-diameter ratio λ and pitch-to-diameter ratio ξ on subchannel entropy generation. The analysis explicitly shows the contribution of heat transfer and pressure drop to the total entropy generation. An analytical formulation is introduced to total entropy generation for situations with uniform and sinusoidal rod power distribution. It is concluded that power distribution affects entropy generation. A smoother power profile leads to less entropy generation. The entropy generation of square rod array bundles are more efficient than that of triangular rod arrays, and spacer grids generate more entropy.

342

The molten salt reactor (MSR), as one of the Generation IV advanced nuclear systems, has attracted a worldwide interest due to its excellent performances in safety, economics, sustainability, and proliferation resistance. The aim of this work is to provide and evaluate possible solutions to fissile ²³³U production and further the fuel transition to thorium fuel cycle in a thermal MSR by using plutonium partitioned from light water reactors spent fuel. By using an in-house developed tool, a breeding and burning (B&B) scenario is first introduced and analyzed from the aspects of the evolution of main nuclides, net ²³³U production, spectrum shift, and temperature feedback coefficient. It can be concluded that such a Th/Pu to Th/²³³U transition can be accomplished by employing a relatively fast fuel reprocessing with a cycle time less than 60 days. At the equilibrium state, the reactor can achieve a conversion ratio of about 0.996 for the 60-day reprocessing period (RP) case and about 1.047 for the 10-day RP case. The results also show that it is difficult to accomplish such a fuel transition with limited reprocessing (RP is 180 days), and the reactor operates as a converter and burns the plutonium with the help of thorium. Meanwhile, a pre-breeding and burning (PB&B) scenario is also analyzed briefly with respect to the net ²³³U production and evolution of main nuclides. One can find that it is more efficient to produce ²³³U under this scenario, resulting in a double time varying from about 1.96 years for the 10-day RP case to about 6.15 years for the 180-day RP case.

393

The effect of gamma ray energies and volume ratio of micro steel fiber (1% and 1.5%) on attenuation properties of reactive powder concrete (70 MPa compressive strength) was investigated. Different characteristics have been considered such as linear attenuation coefficient, mass attenuation coefficient, and half value thickness. Sodium iodide crystal with a gamma ray spectrometer and collimated beam of gamma ray has been implemented to perform the experimental test. Three sources (Cs-137, Co-60, and Bi-207) with energies of (0.662, 1.17 1.33, 0.569, and 1.063) MeV were adopted in the test. The results obtained indicated that mass attenuation coefficient is proportioned inversely with gamma ray energies and directly with volume ratio of micro steel fiber. The linear attenuation coefficient and half value thickness of the tested samples have been calculated and discussed. The obtained results showed that increasing the volume ratio of steel fiber has modified the adequacy of the reactive powder concrete as a shielding element since it increases the density and reduces the half value thickness.

437

Hamamatsu R1924A is one of the most widely used photomultiplier tubes (PMTs) in nuclear physics. Since the active base suitable for R1924A is still not available in market, an active base is designed for Hamamatsu R1924A PMT and the test results at high counting rates are presented. The active bases with two different sets of resistor chains were tested and compared by a frequency controlled green straw hat LED light. A stable signal output up to 100 kHz is achieved using frequency controlled LED pulsed light. The temperature of bases, which reflects the power consumption and is crucial for applications in vacuum, is also monitored with the same LED pulsed light. The temperature of the active base with smaller resistances reaches about twice of that of the active base with larger resistances in the resistor chain. For the applications in vacuum, the active base with resistance between the two sets of resistor chains may be preferable.

426

In furtherance to improving agreement between calculated and experimental nuclear data, the nuclear reaction code GAMME was used to calculate the multi-step compound (MSC) nucleus double-differential cross-sections (DDCs) for proton-induced neutron emission reactions using the Feshbach-Kerman-Koonin (FKK) formalism. The cross-sections were obtained for reactor structural materials involving ⁵²Cr(p, n)⁵²Mn, ⁵⁶Fe(p, n)⁵⁶Co and ⁶⁰Ni(p, n)⁶⁰Cu reactions at 22.2 MeV incident energy using the zero-range reaction mechanism. Effective residual interaction strength was 28 MeV and different optical potential parameters were used for the entrance and exit channels of the proton-neutron interactions. The calculated DDCs were fitted to experimental data at the same backward angle of 150°, where the MSC processes dominate. The calculated and experimental data agree well in the region of pre-equilibrium (MSC) reaction dominance against a weaker fit at the lower emission energies. We attribute underestimations to contributions from the other reaction channels; and disagreement at higher outgoing energies to reactions to collectively excited states. Contrary to the FKK multi-step direct (MSD) calculations, contributions from the higher stages to the DDCs are significant. Different sets of parameters resulted in varying levels of agreement of calculated and experimental data for the considered nuclei.

512

Heat shock protein 90 (Hsp90) can promote growth and proliferation of cancer cells by helping in folding, conformational maturation and activation of various client proteins. Therefore, Hsp90 has been paid more attention to as an anti-cancer drug target. Reported Hsp90 inhibitors have several limitations such as poor solubility, limited bioavailability, hepatotoxicity. Here, a novel small inhibitor RJ19has been designed using fragment-based drug discovery and synthesized. Additionally, a crystal structure of Hsp90^N-RJ19was determined by X-ray diffraction (resolution limit, 2.0 Å, PDB code 4L90). The crystal structure of Hsp90^N-RJ19 was analyzed in detail and compared with that of native Hsp90^N, Hsp90^N-ATP and Hsp90^N- GDM, respectively. It was indicated that RJ19 interacted with Hsp90^N at the ATP-binding pocket, which suggests that RJ19 may replace nucleotides to bind with Hsp90^N to result inchaperone function failure of Hsp90. RJ19, therefore, has emerged as a promising anti-cancer lead compound. Rearrangement and displacement of L2 Loop in Hsp90^N-RJ19 plays key role in the function failure, which also makes the pocket wider and longer facilitating structure modification of RJ19 later. The complex crystal structure and interaction between RJ19 and Hsp90^N provide a rational basis for the design and optimization of novel anti-cancer drugs.

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