Vol.29,

In this study, a high-throughput screening method was established through the 24-square deep-well microliter plate (MTP) fermentation and micro-plate detection for large scale screening of the mutants. It was suitable for screening a large number of mutants and improving the breeding efficiency after heavy ion beam irradiation. Seventeen strains showed higher cellulase activity compared with the initial strain after the screening of plate and MTP fermentation. The filter paper activity (FPA) and β-Glucosidase (BGL) activity of Aspergillus niger H11201 had increased 38.74% and 63.23% separately compared with Aspergillus niger H11 by shaking flask fermentation and genetically stable after been passaged to nine generations. The results indicate that the high-throughput screening method can be used for the quick breeding of Aspergillus niger with high cellulase activity.

360

In this paper, radiation defects in bcc molybdenum with the PKA (Primary Knock-on Atom) energies of 2–40 keV are simulated by the molecular dynamics. The binding energy of single point defect-to-defect clusters increases with the cluster size. The stability and mobility of point defects and defect clusters are analyzed. The interstitial-type clusters are found to be easily migrating along the <111> direction with low barriers (0.01–0.10 eV). Then, the object kinetic Monte Carlo (OKMC) is used to gain insight into the long-term defect evolution in the cascade. The simulation results indicate that Stage I almost occurs at annealing temperature of 100K, which corresponds to the correlated recombination resulting from the motion of small interstitial clusters (n≤2). The formation of sub-stage partly as result of the small vacancy clusters motion. At about 460 K, the Stage II starts because of uncorrelated recombination due to an emitting mechanism of larger clusters. Size distribution of the clusters at the cascade quenching stage is positively correlated with the PKA energies, affecting notably the subsequent annealing process.

340

This work was to determine threshold values for accurate measurements of left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) from electrocardiography-gated myocardial perfusion imaging (MPI) in Chinese, these data was compared with those of echocardiography. Methods: A total of 110 patients with definite or suspected coronary artery disease (CAD) were referred for both gated MPI and echocardiography within one week. The EDV, ESV and EF automatically measured by MyoMetrix and echocardiography were analyzed using Bland-Altman plot correlation and paired-t test. The results showed that these parameters quantified by MyoMetrix software were correlated, moderately to highly, with those on echocardiography (ρ, r≥0.75, P<0.01). However, the EF was not significantly correlated, with post-exercise MPI ESV of <15 mL or resting MPI ESV of <20 mL. At or above this ESV value, EF was underestimated by MyoMetrix (t≥4.60, P<0.01). In a word, a small ESV was underestimated by MyoMetrix, which could lead to EF overestimation. On the contrary, a normal or large ESV was overestimated by MyoMetrix, which led to EF underestimation.

457

As a robust platform for genome editing, CRISPR/Cas9 is currently being explored for engineering biology or therapeutics, yet means for quantitative detection of Cas9 proteins remain to be fully realized. Here we expressed Cas9 proteins and developed a novel detection method that traced Cas9 based on radiolabeled iodine. Through optimizing the reaction conditions of reaction time, temperature and cycles, we obtained ¹²⁵I-Cas9 of high labeling yield. The prepared ¹²⁵I-Cas9 was stable in various media and preserved excellent genome editing efficiency. Thus, our strategy provides a convenient and efficient tool for further tracing biological behaviors of Cas9 proteins in living systems.

419

Based on the high energy resolution fluorescence spectrometer on the BL14W1 beamline at Shanghai Synchrotron Radiation Facility (SSRF), an in-situ high energy resolution X-ray absorption spectroscopy technique, with an in-situ heating cell, was developed. The high energy resolution fluorescence detection for X-ray absorption near-edge spectroscopy (HERFD-XANES) was tested in a UO₂ oxidation experiment to measure the U L₃-edge, with higher signal-to-noise ratio and higher energy resolution than conventional XANES. The technique has potential application for in-situ study of uranium-based materials.

429

Beam emittance reduction is an effective method to increase the brightness of a synchrotron light source. Robinson wiggler can play a role in the beam emittance reduction by increasing the horizontal damping partition number. A replacement of the quadrupoles in the arc section with short combined function dipoles will construct a single-periodic Robinson wiggler in the SSRF storage ring. This scheme provides a lower beam emittance, without occupying any straight section. Detailed analysis is presented in this paper.

374

Effect factors of the absorption of the source, air, entrance window, and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles, along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail. Therefore, the establishment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above. The detector response function is the convolution of an alpha particle pulse function, two exponential functions, and a Gaussian function, followed by calculation of the parameters of the detector response function using the weighted least squares (WLS) fitting method as proposed in this paper. In our experiment, ²³⁹Pu alpha spectra were measured by a high-resolution, passivated implanted planar silicon (PIPS) detector at 10 levels of vacuum and 10 source-detector distances. The spectrum fitting results were excellent as evaluated by reduced chi-square (χ²) and correlation coefficients. Finally, the variation of parameters with vacuum level and source-detector distance was studied. Results demonstrate that σ, τ₁, and τ₂ exhibit no obvious trend of variation with vacuum in the range 2000–20000 mTorr, and, at a confidence level of 95%, the values of τ₁ and τ₂ decline in a similar fashion with source-detector distance by the power exponential function, while the value of σdeclines linearly.

428

Due to insufficiency of a platform based on experimental results for numerical simulation validation using computational fluid dynamic method (CFD) for different geometries and conditions, in this paper we propose a modeling approach based on the artificial neural network (ANN) to describe spatial distribution of the particles concentration in an indoor environment. This study was performed for a stationary flow regime. The database used to build the ANN model was deducted from bibliography literature and composed by 261 points of experimental measurement. Multilayer perceptron type neural network (MLP-ANN) model was developed to map the relation between the input variables and the outputs. Several training algorithms were tested to give a choice of the Fletcher Conjugate Gradient algorithm (Traincgf). The predictive ability of the results determined by simulation of the ANN model was compared with the results simulated by the CFD approach. The developed neural network was beneficial and easy to predict the particle dispersion curves compared to CFD model. The average absolute error given by the ANN model doesn't reach 5% against 18% by the Lagrangian model and 28% by the Euler Drift-Flux model of the CFD approach.

393

Knowledge of actinides (n,f) fission process induced by neutron is of importance in the field of nuclear power and nuclear engineering, especially for reactor applications. In this work, fission characteristics of ²³⁸U(n,f) reaction induced by D-T neutron source were simulated with Geant4 code from multiple perspectives, including the fission production yields, total nubar, kinetic energy distribution, fission neutron spectrum and cumulative γ-ray spectrum of the fission products. The simulation results agree well with the experimental nuclear reaction data (EXFOR) and evaluated nuclear data (ENDF). Mainly, this work was to examine the rationality of the parametric nuclear fission model in Geant4, and to direct our future experimental measurements for the cumulative fission yields of ²³⁸U(n,f) reaction.

395

The broad-energy germanium (BEGe) detector, with the ability of background discrimination using pulse shape discrimination (PSD), is a competitive candidate for neutrinoless double beta decay (0νββ) experiments. In this paper, we report our measurements of key parameters for detector modeling in a commercial p-type BEGe detector. Point-like sources are used to investigate energy resolution and linearity of the detector. A cylindrical volume source is used for efficiency calibration. With an assembled device for source positioning and a collimated ¹³³Ba source, the detector is scanned to check its active volume. Using an ²⁴¹Am point-like source, the dead layer thicknesses is measured at about 0.17 mm on the front and 1.18 mm on the side. The detector characterization is of importance for BEGe detectors to be used in the 0νββ experiments at China JinPing underground Laboratory (CJPL).

453

Identification of nuclear pulse signal is of importance in radioactive measurements, especially in recognizing adjacent overlapping nuclear pulses. In this article we propose an estimation method for parameters of typical overlapping nuclear pulse signals. First, the nuclear pulses are regarded as individual genes and the norm is set as the fitness function. Second, the global optimal solution is found by searching the population of genetic algorithm, so as to estimate the parameters of nuclear pulse. With high precision, this method can identify parameters of overlapping nuclear pulses in the Sallen-Key(S-K) Gaussian signal decomposition experiments. This pulse recognition method is of great significance to improve precision of radioactive measurement, and is suitable for serious overlap of nuclear pluses.

351

We predict proton single event effect (SEE) error rates for the VATA160 ASIC chip on the DArk Matter Particle Explorer (DAMPE) to evaluate its radiation tolerance. Lacking proton test facilities, we built a Monte Carlo simulation tool named PRESTAGE to calculate the proton SEE cross-sections. PRESTAGE is based on the particle transport toolkit Geant4. It adopts a location-dependent strategy to derive the SEE sensitivity of the device from heavy-ion test data, which have been measured at the HI-13 tandem accelerator of the China Institute of Atomic Energy (CIAE) and the Heavy Ion Research Facility in Lanzhou (HIRFL). The AP-8, SOLPRO, and August 1972 worst-case models are used to predict the average and peak proton fluxes on the DAMPE orbit. Calculation results show that the averaged proton SEE error rate for the VATA160 chip is approximately 2.17×10^-5/device/day. Worst-case error rates for the Van Allen belts and solar energetic particle events are 1-3 orders of magnitude higher than the averaged error rate.

566

The readout electronics for a prototype soft X-ray spectrometer based on Silicon Drift Detector (SDD), for precisely measuring the energy and arrival time of X-ray photons, is presented in this paper. The system mainly consists of two parts, i.e., an analog electronics section (including a pre-amplifier, a signal shaper and filter, a constant fraction timing circuit, and a peak-hold circuit) and a digital electronics section (including an ADC and a TDC). Test results with X-ray sources show that an energy dynamic range of 1–10 keV with an integral non-linearity of less than 0.1% can be achieved, and the energy resolution is better than 160 eV @ 5.9 keV FWHM. Using a waveform generator, test results also indicate that time resolution of the electronics system is about 3.7 ns, which is much less than the transit time spread of SDD (< 100 ns) and satisfies the requirements of future applications.

614

Since the Fukushima accident in 2011, more and more attention has been paid to nuclear reactor safety. A number of evolutionary passive systems have been developed to enhance the inherent safety of reactors. This paper presents a passive safety system applied on CPR1000, which is a traditional generation II+ reactor. The passive components selected are as follows: (1) the RMT (reactor makeup tank); (2) the A-ACC (advanced accumulators); (3) the PEFS (passive emergency feed water system); (4) the PDS (passive depressurization system); (5) the IRWST (in-containment refueling water storage tank). The model of the coolant system and the passive systems were established by utilizing a system code (RELAP5/MOD3.3). The SBLOCA (small-break loss of coolant) was analyzed to test the passive safety systems. When the SBLOCA occurred, the RMTs were initiated. The water in the RMTs was then injected into the pressure vessel. The RMTs’ low water level triggered the PDS, which depressurized the coolant system drastically. As the pressure of the coolant system decreased, the A-ACCs and the IRWST were put to work to prevent the uncovering of the core. The results show that, after the small-break loss-of-coolant accident, the passive systems can prevent uncovering of the core and guarantee the safety of the plant.

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