Search

The homogenized Mg-13Gd-4Y-2Zn-0.6Zr alloy was subjected to different equal channel angular pressing (ECAP) passes to investigate the effect of long period-stacking order (LPSO) phase on microstructure evolution and mechanical properties. The heterogeneous bimodal microstructure can be obtained due to the inhibition effect of intragranular 14H-LPSO phase on dislocation slip and lattice rotation at early stage. The intragranular 14H-LPSO phase was kinked and broken, which facilitate the transformation from LAGBs to HAGBs and subdivision of the deformed grains. Furthermore, the interdendritic 14H-LPSO phase was crushed and broken with further ECAP passes, which contribute to the dynamic recrystallization (DRX) process at grain boundaries via particle-stimulated nucleation (PSN) mechanism. The microstructure after 3p-ECAP demonstrates finer randomly oriented dynamic recrystallization (DRX) grains, broken 14H-LPSO phase at grain boundaries and precipitated intragranular lamellar 14H-LPSO phase. In addition, the alloy after 3p-ECAP exhibits the ultimate tensile strength of 361 MPa, tensile yield strength of 197 MPa and fracture elongation of 9.3%. The elevated temperature ultimate tensile strength after 3p-ECAP exceeds 300 MPa at test temperature of 300 ℃ and strain rate of 0.001/0.003 s−1, which can be ascribed to the broken 14H-LPSO phase at grain boundaries and precipitated lamellar 14H-LPSO phase within DRX grains.

Additional file 1: Figure S1. miR-188-3p inhibits the replication of H7N9 and H5N6 influenza A virus in A549 cells. TCID50 values were used to assess the effects of miRNAs on replication of H7N9 (A) and H5N6 (B) influenza A virus in A549 cells. The strains used were A/quail/Hebei/CH06–07/2018(H7N9) and A/chicken/Hubei/XY918/2016(H5N6). Data were determined in triplicate at 0, 12, 24, 36, 48 and 60 h post infection. * (P

Background Influenza A virus (IAV) continues to pose serious threats to public health. The current prophylaxis and therapeutic interventions for IAV requires frequent changes due to the continuous antigenic drift and antigenic shift of IAV. Emerging evidence indicates that the host microRNAs (miRNAs) play critical roles in intricate host-pathogen interaction networks. Cellular miRNAs may directly target virus to inhibit its infection and be developed as potential anti-virus drugs. Methods In this study, we established a broad-spectrum anti-IAV miRNA screening method using miRanda software. The screened miRNAs were further verified by luciferase assay, viral protein expression assay and virus replication assay. Results Five cellular miRNAs (miR-188-3p, miR-345-5p, miR-3183, miR-15-3p and miR-769-3p), targeting 99.96, 95.31, 92.9, 94.58 and 97.24% of human IAV strains recorded in NCBI, respectively, were chosen for further experimental verification. Finally, we found that miR-188-3p downregulated PB2 expression at both mRNA and protein levels by directly targeted the predicted sites on PB2 and effectively inhibited the replication of IAV (H1N1, H5N6 and H7N9) in A549 cells. Conclusions This is the first report screening cellular miRNAs that broad-spectrum inhibiting IAV infection. These findings suggested that cellular miR-188-3p could be used for RNAi-mediated anti-IAV therapeutic strategies.

Fiber spectroscopic telescopes are important tools for astronomy research. In spectroscopic telescopes, the positioning of thousands of fibers on the focal plane is a big issue, which is usually solved by some compact structured devices with small-size motors installed. Stepper motors are normal choice for fiber positioner, however, stepper motors’ low efficiency leads to serious heating, so brushless DC motor becomes a more possible option when the fiber positioner is required to be less heating. Moreover, the size of brushless motor is much smaller than stepper motor in same situation. Brushless DC motor are synchronous motors powered by DC electricity via an inverter. Brushless DC motors complete commutating by switching power supply with an inverter, instead of with the help of carbon brush. Because of the absence of Mechanical Structures like carbon brush and slip ring, BLDC Motors can prevent problems like friction that caused by carbon brush. Both brushless DC motors and Steppers are DC synchronous motors, they generally share the same mechanical structures, but they have many different features. Brushless DC motors perform well in acceleration and they are less likely to generate remarkable amount of noise or heat. Steppers is made for position control, but they sometimes step out, what’s more, they generate a lot of heat and noise while running. Brushless DC motors are usually used when high speed and small size are required, while Steppers are used for positioner. If we can use brushless DC motors for position control, in one way, we can solve the stepping out problem of Steppers and managed to achieve higher accuracy and performance control of position, in the other way, circumstances that need small size and low heat and position control, which may have bothered us a lot, may have an convenient economic solution by using BLDC Motors. Although BLDC Motors are not made for position control, but the Mechanical Structure similarity with Steppers make it possible to realize some kind of position control theoretically. By now, there many ways (with sensor and without sensor) to detect the position of the brushless DC motors’ rotor’s position, which make the idea of using BLDC Motors for position control possible in practice. Generally, ways with sensors detect the rotor position by placing a sensor in the motor, and those without sensors usually calculate the rotor position by detect the voltage and current of the motor. This paper presents our efforts in applying sensorless rotor positioning technology in driving the brushless DC motors and in using the method of sensorless positioning to realize position control. During the process of rotor position detection, a three-terminal resistance network of star arrangement and a simple RC filter is used to get the zero-crossing point of the back EMF. The resistance network is used to extract the neutral voltage and the filter can filter high-frequency background and direct current component. The filtered signal’s zero-crossing point is a shift of the back EMF’s zero-crossing point and almost can be directly used as a reference of the rotor position. Pulse-width-modulation is used to make it possible for the driver to adapt to different brushless motors and different torque. For the purpose of inspecting the performance of the technique when used in position control, the brushless DC motor is mounted to an optical fiber positioner to avoid no-load running and to verify the possibility of applying it for small positioner. The detailed control scheme is introduced, the circuit is analyzed and experimental results obtained form position control experiment are shown to estimate the accuracy of the motor. The result of this paper may help to simplify the control of brushless DC motor and improve the performance of brushless DC motor.

Enol and keto tautomers of methyl 3-oxo pentanoate could be separated on a HP-5 capillary column. The chromatographic peaks were identified by examining characteristic mass ions arose from the corresponding enol and keto molecular ions. The study showed that the area percentage of enol tautomer is a function of temperature of the column. Treating the column as a reactor, the energy of activation for the on-column tautomerization could be extracted (35.1 kJ mol−1) by monitoring the loss of the enol tautomer, because the reaction is found to obey pseudo first-order kinetics. The enthalpy and the entropy changes (ΔH = −3.98 kJ mol−1, ΔS = −7.89 J K−1mol−1) for the enol-to-keto reaction in the stationary phase were also obtained.

Tautomerization of 2-benzylidene-4-methyl-3-oxo-pentanoic acid phenylamide has been studied by NMR and GC-MS. The two tautomers were separated on an HP-5 column, which enabled the kinetic and the thermodynamic behavior of on-column interconversion to be investigated. The enol-to-imide tautomerization was found to occur primarily in the stationary phase. By treating the column as a reactor, the interconversion was investigated as a function of retention time and oven temperature. This enabled determination of the rate constant (0.0605 s−1) by monitoring the increase of the less gas stable tautomer at a constant temperature of 260 °C and determination of the activation energy of the reaction for the net tautomerization (52.0 kJ mol−1), because it was found that the reaction obeyed pseudo first-order kinetics. The enthalpy and the entropy changes (▵H=1.68 kJ mol−1, ▵S=3.54 J K−1 mol−1) for the enol-to-imide reaction in the stationary phase were also obtained.

After being proposed by Sai-Halasz et al. in 1977, type-II superlattices (T2SLs) have demonstrated themselves as a very important material system in various fields such as lasers, photodetectors and transistors. In the field of infrared detection and imaging, InAs/GaSb T2SLs have become a viable candidate to compete with the state-of-the-art mercury-cadmium-telluride (MCT) compounds material system. By spatially separating electrons and holes into different quantum wells, the type-II band alignment enables the full control of the electronic bandstructure and thus, allows for great flexibility in hetero-structure device designs. Beside InAs/GaSb type-II superlattices, InAs/InAs1-xSbxT2SLs have been proved to have a longer carrier lifetime than InAs/GaSb T2SLs and have been proposed as an alternative for infrared photodetectors. We report demonstration of a high performance long-wavelength infrared nBn photodetectors based on InAs/InAs1-xSbx type-II superlattices on GaSb substrate. The photodetector’s 50% cut-off wavelength was ~10 mm at 77K. The photodetector with a 6 mm-thick absorption region exhibited a peak responsivity of 4.47 A/W at 7.9 mm, corresponding to a quantum efficiency of 54% at -90 mV bias voltage under front-side illumination and without any anti-reflection coating. With an R×A of 119 Ω·cm2 and a dark current density of 4.4×10-4 A/cm2 under -90 mV applied bias at 77 K, the photodetector exhibited a specific detectivity of 2.8×1011 cm./W.