Neutron Energy Spectrum Measurements with a Compact Liquid Scintillation Detector on EAST

A neutron detector based on EJ301 liquid scintillator has been employed at EAST to measure the neutron energy spectrum for D-D fusion plasma. The detector was carefully characterized in different quasi-monoenergetic neutron fields generated by a 4.5 MV Van de Graaff accelerator. In recent experimental campaigns, due to the low neutron yield at EAST, a new shielding device was designed and located as close as possible to the tokamak to enhance the count rate of the spectrometer. The fluence of neutrons and gamma-rays was measured with the liquid neutron spectrometer and was consistent with 3He proportional counter and NaI (Tl) gamma-ray spectrometer measurements. Plasma ion temperature values were deduced from the neutron spectrum in discharges with lower hybrid wave injection and ion cyclotron resonance heating. Scattered neutron spectra were simulated by the Monte Carlo transport Code, and they were well verified by the pulse height measurements at low energies.Comment: 19 pages,10 figures, 1 tabl

Simulation-assisted investigation on the formation of layer bands and the microstructural evolution in directed energy deposition of Ti6Al4V blocks

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Virtual and Physical Prototyping on 2021, available online at: http://www.tandfonline.com/10.1080/17452759.2021.1942077Additive manufacturing (AM) of titanium alloy entails severe microstructural heterogeneity and layer bands due to diverse thermal histories. While the thermal-microstructure relationship in AM has been reported, the details on how complex thermal histories influence the microstructural evolution have not been so addressed, and the formation of layer bands in multi-layer multi-pass builds is still unclear. To undertake such investigation, a thermal model is firstly calibrated using two part-scale blocks fabricated on differently sized substrates, and then used to study the relationship between key microstructural characteristics and the thermal cycling involved. Results show that the different evolutions of the temperature ranges just underneath the ß-transus temperature (Tß) controlled by the printing path are responsible for the different band distributions at the centre and corner of the blocks. Also, the a sizes in the normal region are closely linked to the integral area obtained from the thermal curve as temperature fluctuates between Tß and a dissolution temperature, which helps linking AM variables to metallurgy. This further demonstrates that the a coarsening during thermal cycles is primarily driven by multi dissolution and precipation transformations instead of Ostwald ripening. Finally, the quantitative thermal-microstructure-microhardness relationship is established, helpful for the microstructural design.This work was funded by the National Key Technologies R & D Program (No. 2016YFB1100100), the National Natural Science Foundation of China (Grants No. 51874245), the European KYKLOS 4.0 project (No. 872570), the Severo Ochoa Programme for Centres of Excellence in R&D (CEX2018-000797-S) and the China Scholarship Council (No. 201906290011).Peer ReviewedPostprint (author's final draft

DDA simulation study on fracturing failure reproducibility of heterogenous rock

The mesoscale heterogeneity of rock determines its macroscale mechanical performance to a large extent. In this paper, a sub-block element discontinuous deformation analysis (DDA) method coupled with a statistic heterogeneity model was used to simulate the fracturing failure of pre-notched rock specimens. The simulation recreated the macroscale whole-process nonlinear deformation and fracturing failure of pre-notched disc and rectangular specimens with some important features explored in experiments or other numerical simulations. Combing intact heterogeneous rock specimen simulations in previous work, the effect of the heterogeneity on the reproducibility of macroscale strength and failure patterns of the specimens were investigated. Results indicate that the influence degree of the heterogeneity on the macroscale equivalent strength and fracturing failure pattern reproducibility varies with the specimen particularities (disc or rectangular, pre-notched or intact, and inclination of the pre-existing flaw), and the reason behind was discussed from the point view of stress concentration. This work is meaningful for the understanding of the result discreteness of rock specimen experiments, and assures the importance to consider the rock heterogeneity in practical rock engineering

Apoptosis of Endothelial Cells Contributes to Brain Vessel Pruning of Zebrafish During Development

During development, immature blood vessel networks remodel to form a simplified and efficient vasculature to meet the demand for oxygen and nutrients, and this remodeling process is mainly achieved via the pruning of existing vessels. It has already known that the migration of vascular endothelial cells (ECs) is one of the mechanisms underlying vessel pruning. However, the role of EC apoptosis in vessel pruning remains under debate, especially in the brain. Here, we reported that EC apoptosis makes a significant contribution to vessel pruning in the brain of larval zebrafish. Using in vivo long-term time-lapse confocal imaging of the brain vasculature in zebrafish larvae, we found that EC apoptosis was always accompanied with brain vessel pruning and about 15% of vessel pruning events were resulted from EC apoptosis. In comparison with brain vessels undergoing EC migration-associated pruning, EC apoptosis-accompanied pruned vessels were longer and showed higher probability that the nuclei of neighboring vessels’ ECs occupied their both ends. Furthermore, we found that microglia were responsible for the clearance of apoptotic ECs accompanying vessel pruning, though microglia themselves were dispensable for the occurrence of vessel pruning. Thus, our study demonstrates that EC apoptosis contributes to vessel pruning in the brain during development in a microglial cell-independent manner

Cyclic di-GMP regulates bacterial colonization and further biocontrol efficacy of Bacillus velezensis against apple ring rot disease via its potential receptor YdaK

Bacillus species are among the most investigated beneficial bacteria and widely used in agricultural systems as biological control agents. Its biocontrol efficacy is controlled by diverse regulators. Cyclic diguanylate (c-di-GMP) is a nearly universal second messenger in bacteria and modulates various important physiological processes, including motility, biofilm formation, antifungal antibiotic production and host colonization. However, the impact of c-di-GMP on biocontrol efficacy of beneficial bacteria is unknown. Bacillus velezensis PG12 is an effective biocontrol strain against apple ring rot disease caused by Botryosphaeria dothidea. In this study, the contribution of c-di-GMP to biocontrol efficacy of B. velezensis PG12 was investigated. Deletion of single gene encoding diguanylate cyclase or phosphodiesterase did not affect its biocontrol efficacy against apple ring rot. However, artificial modulation of c-di-GMP level in the cells leads to a significant change of biocontrol efficacy, suggesting that c-di-GMP positively regulates biocontrol efficacy of B. velezensis PG12 against apple ring rot disease. More evidences indicate that c-di-GMP does not affect the antagonistic activity of B. velezensis PG12 against B. dothidea in vitro and in vivo, but positively regulates biofilm formation of B. velezensis PG12 and its colonization on apple fruits. Importantly, deletion of ydaK could rescue the inhibition of biofilm formation, bacterial colonization and biocontrol efficacy caused by low c-di-GMP level, indicating that YdaK is the potential c-di-GMP receptor to regulate biofilm formation, colonization and effective biological control. However, YdaK did not affect the antagonistic activity of B. velezensis PG12 against B. dothidea. Based on these findings, we propose that c-di-GMP regulates biofilm formation, subsequently the bacterial colonization on apple fruits and thus biocontrol efficacy of B. velezensis through its receptor YdaK. This is the first report showing that c-di-GMP plays a role in biocontrol efficacy of beneficial bacteria

The gut microbiome dysbiosis and regulation by fecal microbiota transplantation: umbrella review

BackgroundGut microbiome dysbiosis has been implicated in various gastrointestinal and extra-gastrointestinal diseases, but evidence on the efficacy and safety of fecal microbiota transplantation (FMT) for therapeutic indications remains unclear.MethodsThe gutMDisorder database was used to summarize the associations between gut microbiome dysbiosis and diseases. We performed an umbrella review of published meta-analyses to determine the evidence synthesis on the efficacy and safety of FMT in treating various diseases. Our study was registered in PROSPERO (CRD42022301226).ResultsGut microbiome dysbiosis was associated with 117 gastrointestinal and extra-gastrointestinal. Colorectal cancer was associated with 92 dysbiosis. Dysbiosis involving Firmicutes (phylum) was associated with 34 diseases. We identified 62 published meta-analyses of FMT. FMT was found to be effective for 13 diseases, with a 95.56% cure rate (95% CI: 93.88–97.05%) for recurrent Chloridoids difficile infection (rCDI). Evidence was high quality for rCDI and moderate to high quality for ulcerative colitis and Crohn’s disease but low to very low quality for other diseases.ConclusionGut microbiome dysbiosis may be implicated in numerous diseases. Substantial evidence suggests FMT improves clinical outcomes for certain indications, but evidence quality varies greatly depending on the specific indication, route of administration, frequency of instillation, fecal preparation, and donor type. This variability should inform clinical, policy, and implementation decisions regarding FMT