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s SiC nanowires (SiCnws) having different morphologies can be applied to reinforce ceramic materials. However, the in-situ synthesis of SiCnws in ceramic powders, which is critical to ensure satisfactory reinforcement effects, is challenging. To facilitate the reinforcement of ZrB2–ZrC composites, this study proposes a simple method for in-situ fabrication of SiCnws with various morphologies in nanosized ZrB2–ZrC powders by pyrolyzing ZrB2–ZrC–SiC gel precursors. The prepared ZrB2–ZrC ceramic powders had a mean diameter of approximately 100 nm, with uniformly distributed SiCnws having nanocylider, bead-like, bamboo-shape with tuneable nodes, chain-like, and hexagonal prism morphologies prepared by optimizing the preparation process. Moreover, the SiCnws had diameters ranging from 100 to 400 nm, and the length was controlled from tens to hundreds of microns. The generation of ZrB2/ZrC influences the formation of SiCnws with specific morphologies through the production of CO gas, which influences the local supersaturation of the SiO and CO vapours. The findings can provide a basis for fabricating SiCnw-reinforced ceramic materials with an enhanced strengthening effect while ensuring a reasonable fabrication process.

Constructing heterojunction is one promising strategy to improve the transfer and separation of photoinduced charge carriers of graphitic carbon nitride (CN). Herein, nonmetal N, S-doped graphene quantum dots (N, S-GQDs)/g-C3N4 nanocomposite photocatalysts were successfully synthesized by calcining N, S-GQDs (NSGs) and melamine at elevated temperature. The optimal 06NSG-CN composite effectively reduced the concentration of Escherichia coli flora under visible light irradiation by superoxide and super hydroxyl radicals. Meanwhile, the optimum photocatalytic hydrogen evolution reaches 50.9 [Formula: see text]mol/h, about 16.9 times that of pure phase CN under visible light. Graphitic carbon nitride ([Formula: see text]-C3N4) grafted with N, S-doped GQDs could increase the specific surface area, promote the absorption and utilization of visible light, and inhibited the recombination of photoinduced electron–hole pairs, resulting in excellent photocatalytic antibacterial activity.

Xi’an Institute of Optics and Precision Mechanics of CAS is developing a novel MCP-PMT with 2 × 2 matrix anode pixels with a time resolution of picosecond level. It is composed of a cermet shell, bi-alkali photocathode, and V-type cascade MCP layers. In order to study the method of measuring the characteristics of such MCP-PMT with picosecond time resolution, we develop a PMT test system to test its performance. A voltage divider resistor circuit for the MCP-PMT is designed to meet the requirements of both high gain and fast time response. The test system includes a picosecond laser source in the single-photon mode, a high-bandwidth oscilloscope, and another fast MCP-PMT as reference. Full waveforms of PMT signals are collected and analyzed offline. The overall system time error is 26 ps. The test result shows that the gain of the MCP-PMT achieves 1 × 107. The transit time spread (TTS) of all channels is better than 60 ps (σ). The uniformity and crosstalk among adjacent channels are also studied by scanning each channel’s response along the photocathode plane. The MCP-PMT shows excellent timing performance and the potential of achieving better spatial resolution by further pixelation.

The grouting materials are new fields where cement clinker (CC) can be replaced by high amounts of steel slag (SS). To develop steel slag composite grouts (SSCG) for constructions and repairs in underground engineering, it is necessary to determine and optimize the performance of SSCG. In this study, the SS and blast furnace slag (BFS) contents in ternary grouts were all 55–75%. The fly ash (FA) contents were 10% and 15% in quaternary grouts, and the SS and BFS contents were all 20–40%. The FA, SS and BFS contents in quinary grouts were 5–10%, 25–40% and 25–30%. The flue gas desulfurization gypsum (FGDG) content was 5%. The water-solid (W/S) range was selected as 0.65–1.2. The properties investigated were: fresh-state properties i.e., mini-slump, effective W/S, stone rate, flowability losing time, setting time; mechanical performance i.e., flexural strength (FS), unconfined compressive strength (UCS), FS/UCS and fracture characteristic; hydration products; microstructure and pore size distribution. The results show that the SS was suggested to combine with BFS to enhance the strengths, the 3-day and 28-day UCSs of the quinary SSCG (19#) increased by 105.3% and 167.7% with 2% B + 6% AA + 0.4% SP. With the approximate activation, the bigger pores (>100 nm) have been transformed into small pores under 30 or 100 nm effectively, and the compactness of gel structure has been improved. The workability, mechanical performance, and microstructures of optimized SSCG with high amount of SS (40%) and industrial residue (80%) are acceptable, it can meet the requirements of grouting practices for underground engineering.

The aim of the present study was to explore the risk factors and protective factors related to breast cancer onset in women, but there is still a big debate in this respect. Therefore, it is necessary to systematically review the risk factors induced by breast cancer by using meta methods to guide clinical prevention and treatment.Studies on factors related to breast cancer onset in Chinese women were retrieved from articles from Chinese, international databases published and organizations and websites, and registers from January 2014 to January 2021. Articles were independently screened, extracted, and evaluated for quality by 2 researchers. The Cochrane Collaboration Center provided Review Manger 5.2 software [Cochrane Information Management System (IMS)] for statistical analysis, and the risk ratio of dichotic variables was adopted.History of benign breast disease [odds ratio (OR) 1.03, 95% confidence interval (CI): 0.95-1.12, P=0.42], family history of breast cancer (OR: 2.02, 95% CI: 1.83-2.23, P0.00001), menopause onset50 years of age (OR: 1.78, 95% CI: 1.62-1.95, P0.00001), and use of oral contraceptives (OR: 1.16, 95% CI: 1.02-1.32, P=0.02) were found to be breast cancer risk factors. The number of term pregnancies (OR: 0.80, 95% CI: 0.66-0.97, P=0.03) and breastfeeding (OR: 0.84, 95% CI: 0.74-0.96, P=0.01) were found to be protective factors for breast cancer.In order to control the occurrence of breast cancer, effective measures should be taken to effectively avoid related risk factors, and breastfeeding and high-risk population screening should be advocated.

The application of high-throughput sequencing technologies has greatly enhanced our understanding to the human microbiome. The causal relations between human microbiome and diseases have become a critical issue to elucidate disease development and develop precision medicine. Recently, the study about vaginal microbiome (the microbial flora that inhabits the female vagina) has received wide interests. It has been shown that dysbiosis of vaginal microbiome was closely related to the development of genital tract diseases. This article summarizes the interaction between vaginal microbiome and disease and the treatment for the dysbiosis of vaginal microbiome. The culturomics of virginal microbiome, engineered probiotics and synthetic microbiome were also proposed.

SiC nanowires (SiCnws) with different morphologies have great potential for the reinforcement of ceramic materials. But it is a big challenge in the in-situ synthesis of SiCnws in the ceramic powders which is critical to ensure high reinforcing effects. For the reinforcement of ZrB2-ZrC composites, a simple method is developed to in-situ fabricate SiCnws with various morphologies in nano-sized ZrB2-ZrC powders through pyrolyzing ZrB2-ZrC-SiC gel precursors. The prepared ZrB2-ZrC ceramic powders have mean diameter of about 100 nm with uniformly distributed SiCnw in morphologies of nanocylider, bead-like, bamboo-shape with tunable nodes, chain-like and hexagonal prisms were prepared by optimizing the preparation process. Moreover, the SiCnws were in a diameter of ranging from 100 to 400 nm, while the length was controlled from tens to hundreds of microns. The generation of ZrB2/ZrC can determine the formation of SiCnws with specific morphologies by producing CO gas to affect the local supersaturation of the SiO and CO vapors. The study provides an opportunity for fabricating SiCnw reinforced ceramic materials with enhanced strengthening effect and also overcome its critical fabrication process.

This paper describes the design of the 8-inch and 20-inch photomultiplier tubes based on microchannel plates (MCP-PMT). In the large area MCP-PMT, the small MCPs replace the bulky dynode chain in the traditional large PMTs. Photoelectrons are electrostatically focused on MCPs. The MCP assembly, focusing electrodes as well as the supply voltages are carefully optimized to achieve a wide photosensitive area, high photon detection efficiency and good timing resolution.

To explore the application of SiC nanowires (SiCnws) in ZrB2 based ceramic materials, a facile approach is reported to in situ synthesize homogeneously dispersed SiCnws in ZrB2-ZrC-SiC-ZrO2 nanopowders by pyrolyzing a B-Si-Zr containing sol precursor impregnated in polyurethane sponge. The sponge was used to provide porous skeletons for the growth of SiC nanowires and facilitate their uniform distribution in the powders. After heat-treatment of the precursor with a Si/Zr atomic ratio of 10 at 1500 °C for 2 h, ZrB2-ZrC-SiC-ZrO2 ceramic powders were obtained with an even and fine particle size of ~100 nm. The SiCnws were in a diameter of ~100 nm with a controllable length varying from tens to hundreds of microns by increasing the silicon content in the precursor. Moreover, the produced SiCnws were in high purity, and homogeneously dispersed in the hybrid nanopowders. The study can open up a feasible route to overcome the critical fabrication process in SiCnws reinforced ceramic matrix composites.

We demonstrate 2D reconstructions of the fast-ion velocity distribution from two-view fast-ion D-alpha (FIDA) measurements at the EAST tokamak. By expressing the distribution in a basis relying on the fast-ion slowing-down process in fusion plasmas, the smoothness and velocity-space resolution of reconstructions are improved. We reconstruct distributions of fast ions born from simultaneous co- and counter-current neutral beam injection and detect the expected distinct change in fast-ion birth pitch when comparing discharges utilizing different neutral beam injectors. For purely co-current injection, we find a good agreement between TRANSP-predicted and reconstructed fast-ion densities, pressures and current densities for energies above 20 keV. We furthermore illustrate the improvement of the reconstructed high-energy range (> 40 keV) of the distribution by combining FIDA with neutron emission spectroscopy measurements with the compact single-plate EJ301 scintillator.

Owing to the severe loss of photoelectrons striking at the input electrode of conventional microchannel plate (MCP), photoelectron collection efficiency (CE) of devices based on traditional MCP fluctuates around the MCP open area ratio and cannot make a breakthrough. Photoelectron backscattering from the MCP surface also causes late pulses smearing timing and spatial performance. In this work, a novel bowl-shaped MCP with an open area ratio higher than 90% whose input electrode is coated by a thin film with high secondary electron emission yield (SEY) is proposed as an effective approach to improve CE and suppress late pulses. A three-dimensional MCP-PMT model is developed in CST Studio Suite to evaluate CE and time performance of the bowl-shaped MCP, and compared with the traditional one. Results show that CE of the PMT based on the bowl-shaped MCP is nearly 100% and the delayed pulse is less than 2%. This indicates that good temporal and spatial resolution can be achieved with the bowl-shaped MCP.

The microchannel plate photomultiplier tube (MCP-PMT) used in high energy physics experiments usually needs to be able to operate in strong magnetic fields. In this paper, a 3D MCP-PMT model is developed in CST studio suite to study the magnetic field up to 5 T effect on the photoelectrons traveling from the photocathode to the MCP. Results predict that a growing number of photoelectrons strike back to the photocathode with enhancing magnetic field, which not only decreases electron collection efficiency and gain, but also impairs the photocathode lifetime.

The late pulse occurring in photomultiplier tubes (PMTs) is attributed to photoelectron backscattering. The small effective open area of microchannel plates (MCPs) increases the probability of photoelectrons bouncing on the front surface of MCPs and aggravates late pulses. In this work, a three-dimensional MCP-PMT model is developed in CST particle studio, a powerful electromagnetic field simulation program, to evaluate the effects of secondary emission yield (SEY) property of the MCP input facet and electric field on the photoelectron backscattering. Timing properties and the number of collected electrons are extracted without smearing due to electronic noise and finite pulse width. Results predict that the collection efficiency (CE) and the time performance can be improved by coating the MCP Nickel–Chromium input electrode with a high SEY material and operating in a proper photocathode-MCP bias voltage.

The technology of atomic layer deposition has been used to improve the lifetime of the microchannel plate-photomultiplier tube (MCP-PMT) effectively and makes MCP possible to choose to coat different potential emissive materials on the internal surface of the MCP channels in the future. However, it is still an open question to what extent the secondary electron emission (SEE) yield properties of the emissive materials influence the behavior of the ALD-coated MCP. In this work, the dependences of the gain and timing performance on the SEE yield properties were assessed by using the Monte Carlo and particle-in-cell methods. We established the three-dimensional MCP single channel model in Computer Simulation Technology (CST) Particle Studio. Three important secondary electron emissions, the backscattered, rediffused and true SEEs, were discussed numerically based on the probabilistic model. The secondary electron cascade processes in the MCP single channel were simulated. The simulation results indicate that the opportunities for improving the gain of the ALD-coated MCP by improving the SEE yields corresponding to the incident energies of 0 eV–100 eV. The backscattered and rediffused electrons are found to have strong effects on the gain and timing performance of the MCP. Although the higher the SEE yield the higher the MCP gain, the drawback is the extremely high SEE yield will make the MCP saturated prematurely and degrade the time resolution. The simulation results will be used to guide the design and selection of emissive material for ALD-coated MCP development.

Microchannel plates (MCPs) are widely used as electron, ion, and X-ray detectors. The gain factor and time resolution of the MCP are strongly dependent on its operating and geometry parameters (applied voltage, length-to-diameter ratio, bias angle, and electrode penetration depth). Measurements about this dependence are sparse and do not cover the full range of the parameters. In this paper, 3-D single channel models are developed in computer simulation technology studio suit to systematically and comprehensively calculate the MCP gain and time resolution for various operating and geometry parameters. Furman secondaries electron emission model is employed in our simulation. Simulated result of the gain versus bias voltage is validated by the available experimental data. Finally, geometry parameters of $L = 373.6~\mu \text{m}$ , $D =10~\mu \text{m}$ , $h_{{{\text {in}}}}=h_{{{\text {out}}}}= 5~\mu \text{m}$ , and $\theta =12^{\circ }$ are proposed to optimize the MCP performances. Simulation results show that the gain, mean transit time, and transit time spread of the optimized MCP are expected to reach 128 012, 128 ps and 19 ps at the applied voltage of 1000 V.

This paper discusses the electron optical system of an 8-in. spherical MCP-PMT. The MCP assembly, the supporting pole and the supply voltages are carefully designed to optimize the photoelectron collection efficiency and the transit time spread. Coating the MCP nickel-chromium electrode with an additional high secondary emission material is employed to make a breakthrough on the collection efficiency. With the simulation software CST, the Finite Integration method and the Monte Carlo method are combined to evaluate the collection efficiency, the time properties and the Earth's magnetic field effects. Simulation results show that the photocathode active solid angle is over 3.5 πsr, the average collection efficiency can exceed 95% with the coated MCP and the mean transit time spread is 2.2 ns for a typical electric potential of 500 V applied between the photocathode and the MCP input facet. The prototype and the measured single photoelectron spectrum are also presented.

This paper describes the simulation work for optimizing the newly developed 20-in. elliptical MCP-PMT by enlarging the outside diameters of the two focusing electrodes and the open area of the glass bulb. Effects of biasing voltages applied to the two focusing electrodes and the MCP input facet are studied. With the new design of the 20 in. MCP-PMT, the transit time spread of the prototype can be less than 3 ns and the collection efficiency is as much as the present prototype.

To obtain a high spatial resolution of a image intensifier based on microchannel plate (MCP), the long tail in the exit energy distribution of the output electrons (EDOE) is undesirable. The existing solution is increasing the penetration depth of the MCP output electrode, which will result in a serious gain reduction. Coating the MCP output electrode with efficient secondary electron yield (SEY) materials is supposed to be an effective approach to suppress the unfavorable tail component in the EDOE without negative effects on the gain. In our work, a three-dimensional MCP single channel model is developed in CST STUDIO SUITE to systematically investigate the dependences of the EDOE and the gain on the SEY property of the coated material, based on the Finite Integral Technique and Monte Carlo method. The results show that besides the high SEY of the coated material, the low incident energy corresponding to the peak SEY is another essential element affecting the electron yield in the final stage of multiplication and suppressing the output energy spread.

Owning to the serious loss of photoelectrons striking at the input electrode of traditional microchannel plate (MCP), photoelectron collection efficiency (CE) of photomultiplier tubes based on MCP (MCP-PMTs) fluctuates around the MCP open area fraction and cannot make a breakthrough. Depositing a thin film of high secondary electron yield material on the MCP is proposed as an effective approach to improve the CE. The available simulation and experimental data to validate it, however, is sparse. In our work, a three-dimensional small area MCP model is developed in CST Studio Suite to evaluate the collection efficiencies of PMTs based on the traditional MCP and the coated one, respectively. Results predict that CE of the PMT based on the coated MCP has a significant increase and a better uniformity, which is expected to reach 100%.

A novel large-area (20-inch) photomultiplier tube based on microchannel plate (MCP-PMTs) is proposed for the Jiangmen Underground Neutrino Observatory (JUNO) experiment. Its photoelectron collection efficiency C-e is limited by the MCP open area fraction (A(open)). This efficiency is studied as a function of the angular (theta), energy (E) distributions of electrons in the input charge cloud and the potential difference (U) between the PMT photocathode and the MCP input surface, considering secondary electron emission from the MCP input electrode. In CST Studio Suite, Finite Integral Technique and Monte Carlo method are combined to investigate the dependence of C-e on theta, E and U. Results predict that C-e can exceed A(open), and are applied to optimize the structure and operational parameters of the 20-inch MCP-PMT prototype. C-e of the optimized MCP-PMT is expected to reach 81.2%. Finally, the reduction of the penetration depth of the MCP input electrode layer and the deposition of a high secondary electron yield material on the MCP are proposed to further optimize C-e. (C) 2016 Elsevier B.V. All rights reserved.

A quinary Cr–12Nb–5Ti–5Mo–5Si (at.%) alloy was prepared by arc melting in this study to improve the strength and toughness of Laves phase Cr2Nb alloy. The quinary alloy was solidified with full eutectic Cr2Nb/Cr, in which the Cr2Nb phase exceeded 55 vol % and existed as matrix. The eutectic was developed with an orientation relationship of {001}Cr2Nb//{001}Cr, leading to a low lattice mismatch of 15.57% at the eutectic interface. The yield strength and fracture toughness of the quinary alloy reached 1950–1980 MPa and 14.0–14.8 MPa⋅m1/2, respectively, much higher than most reported Cr2Nb alloys. The reason for the superior properties is the synergistic effects of solid solution strengthening, alloying toughening, and eutectic strengthening-toughening.

Three Cr–8Ta-xSi (x = 0, 6, 10) (at.%) alloys were fabricated by vacuum non-consumable arc melting in this study to investigate the microstructure evolutions and mechanical properties of the Si-modified Cr2Ta/Cr in-situ composites. The element Si was incorporated preferentially into Cr2Ta rather than phase Cr, thus the microstructure transited from the dendrite Cr plus the eutectic Cr2Ta/Cr in the Cr–8Ta alloy, to the full eutectic Cr2Ta/Cr in the Cr–8Ta–6Si alloy, and finally to the dendrite Cr2Ta plus the eutectic Cr2Ta/Cr in the Cr–8Ta–10Si alloy. The Cr–8Ta–6Si alloy was developed with a good combination of strength and toughness, and the yield strength and fracture toughness of this alloy reached up to 960 ± 20 MPa and 15 ± 0.3 MPa m1/2, respectively. The good combination of strength and toughness in the Cr–8Ta–6Si alloy resulted from the synergistic effects of solid solution strengthening, alloying toughening, interface strengthening and second phase toughening.

A multi-anode microchannel plate photomultiplier (Ma MCP-PMT) is an appropriate photo sensor for particle identification in high energy physics experiments such as PANDA, Belle II, etc. Since these detectors usually work in a strong magnetic field, the sensors must be immune to the field. In this article, the effects of the magnetic field on the conventional MCP and the atomic layer deposited MCP (ALD-MCP) are studied by simulating the electron multiplication in the microchannel of the MCP . Simulation results show that the gain of conventional MCP-PMTs increases a little before it starts decreasing while the magnetic field is further increasing. We found that the shortening of electronic trajectories and the reduction of secondary electrons mainly contribute to gain variations of a conventional MCP . For the ALD-MCP that usually has higher secondary emission yields, it is found that high re-diffusion secondary electron yields could make it more vulnerable to magnetic fields.

For the next generation neutrino experiment, number of experienced researchers and engineers in research institutes and companies related to PMT fabrication in China jointly worked on the large area MCP-PMT collaboration group. In the past 5 years by collaborative work, the 8-inch and 20-inch prototypes were produced. And also get the high detection efficiency 20-inch MCP-PMT for JUNO in 2015, and get the 75% order of the JUNO-PMT. This manuscript will introduce the progress of the R&D of this new design of the MCP-PMT, also the performance tested result in the PMT Lab in IHEP.

This manuscript discusses a new design of large area MCP-PMT for the next generation neutrino experiments. The main motivation of the design is to improve the quantum efficiency (photo detection efficiency) of the PMT. Two sets of small MCP units, the transmission photocathode coated on the front hemisphere and the reflection photocathode coated on the rear hemisphere are assembled in the same glass envelope to form nearly 4π viewing angle to enhance the efficiency of the photoelectron detection. The photoelectrons from the 4π photocathode are collected and amplified by two sets of MCP units. Our goal is eventually to produce 20 in. diameter PMT following such an approach. We will report preliminary results of our ptoelectronic simulation and the results of a 5 in. diameter prototype PMT. Future plans and prospects are discussed at the end.

The Institute of High Energy Physics, Chinese Academy of Sciences have designed a new type of photomultiplier tube (PMT) based on microchannel plates (MCPs) with large area photocathode, known as large area microchannel plate photomultiplier tube (MCP–PMT). The aging characteristics of the large area MCP–PMTs are different from dynode PMTs and small proximity-focus MCP–PMT. In this work, a prototype large area MCP–PMT was aged by operating with nearly 1000 photoelectrons per pulse for 3 months, and aging process of the MCP–PMT was discussed based on the aging curve.

The effect of 6H-SiC crystal growth shapes on the thermo-elastic stress distribution in the growing crystal was systematically investigated by using a finite element method. The thermo-elastic stress distribution in the crystal with a flat growth shape was more homogeneous than that in the crystals with concave and convex growth shapes, and the value of thermo-elasticity in the crystal with a flat growth shape was also smaller than that in the two other types of crystals. The maximum values of thermo-elastic stress appeared at interfaces between the crystal and the graphite lid. If the lid was of the same properties as 6H-SiC, the thermo-elastic stress would decrease in two orders of magnitude. Thus, to grow 6H-SiC single crystals of high quality, a transition layer of SiC formed by deposition or reaction is suggested; meanwhile the thermal field in the growth chamber should be adjusted to maintain the crystals with flat growth shapes.

In this paper, silicon carbide whiskers (SiC w ) were fabricated by the physical vapor transport (PVT) technique at 2293 K with Fe as the catalyst. X-ray diffraction, scanning electronic microscope, energy-dispersive X-ray spectroscopy and transmission electron microscopy were used to identify the phase formation and morphology of the SiC w . The results showed that 6H-SiC w with growth direction of [0001] were obtained with the diameters ranging from 0.2 μm to 4 μm, and the length up to 700 μm. The whiskers appeared as a cluster characteristic on the activated carbon fiber. Meanwhile, the catalyst ball at the tip of each whisker indicated the vapor–liquid–solid growth mechanism for 6H-SiC w .The growth mechanism was investigated on the basis of the physical and chemical phenomena during the PVT growth process of SiC w . It was found that high temperature guaranteed the evaporation of raw materials to form the catalyst, Si- and C-containing vapor specials and promoted the nucleation and growth of 6H-SiC w . Finally, a growth model was proposed.