Effect of bubble morphology and behavior on power consumption in non-Newtonian fluids’aeration process

Due to a prolonged operation time and low mass transfer efficiency, the primary challenge in the aeration process of non-Newtonian fluids is the high energy consumption, which is closely related to the form and rate of impeller, ventilation, rheological properties and bubble morphology in the reactor. In this perspective, through optimal computational fluid dynamics models and experiments, the relationship between power consumption, volumetric mass transfer rate(kLa) and initial bubble size(d0) was constructed to establish an efficient operation mode for the aeration process of non-Newtonian fluids. It was found that reducing the d0could significantly increase the oxygen mass transfer rate, resulting in an obvious decrease in the ventilation volume and impeller speed. When d0was regulated within 2-5 mm,an optimal kLa could be achieved, and 21% of power consumption could be saved, compared to the case of bubbles with a diameter of 10 mm.

1.2 kW all-fiber narrow-linewidth picosecond MOPA system

Achieving an all-fiber ultra-fast system with above kW average power and mJ pulse energy is extremely challenging.This paper demonstrated a picosecond monolithic master oscillator power amplifier system at a 25 MHz repetition frequency with an average power of approximately 1.2 kW,a pulse energy of approximately 48μJ and a peak power of approximately 0.45 MW.The nonlinear effects were suppressed by adopting a dispersion stretched seed pulse(with a narrow linewidth of 0.052 nm)and a multi-mode master amplifier with an extra-large mode area;then an ultimate narrow bandwidth of 1.32 nm and a moderately broadened pulse of approximately 107 ps were achieved.Meanwhile,the great spatio-temporal stability was verified experimentally,and no sign of transverse mode instability appeared even at the maximum output power.The system has shown great power and energy capability with a sacrificed beam propagation product of 5.28 mm·mrad.In addition,further scaling of the peak power and pulse energy can be achieved by employing a lower repetition and a conventional compressor.

In situ investigation on densification mechanism of Ti-20Al-19Nb(at.%)alloy by TiH_(2)-assisted pressureless sintering

Dense Ti-20Al-19Nb(at.%)alloys can be cost-effectively fabricated by TiH_(2)-assisted pressureless sintering;nevertheless,the densification mechanism remains controversial without understanding the entire sintering process.By in situ observing the surface morphology of the Ti/Al/Nb and Ti/TiH_(2)/Al/Nb compacts upon heating,the densification mechanism of the Ti-20Al-19Nb alloys was elucidated in this study.In addition to the reported reason that the dehydrogenation of TiH_(2)provided reactive Ti,the densification of Ti-20Al-19Nb alloy was found to be strongly associated with the phase transformations upon sintering.The TiH_(2)participated in the reverse eutectoid transformation,α-Ti+δ-TiH_(2)→β-Ti,inducing theα/βand TiH_(2)/βgrain boundaries for the rapid diffusion of Al.The reaction of Ti(s)+Al(s)→TiAl_(3)(s)was then accelerated,and the majority of the Al phase was consumed in the solid state,which significantly reduced the pores from the transient liquid Al.The activation energy of the Ti-Al reaction decreased with the addition of TiH_(2),and the growth mode of the TiAl_(3)phase was changed.By removing the large pores at 700℃,the Ti-Al intermetallic phases were well connected,forming the continuous interdiffusion route for Ti,Al,and Nb.The diffusion of Nb,as well as the phase transformation ofα2→B2,was then promoted,and the ripening time for the B2 phase was increased.As a result,the density and mechanical properties were improved.The initial results of this study provided a foundation for the cost-effective fabrication of high-strength Ti-Al alloys containing refractory elements.

Experimental investigation of the stimulated Raman scattering effect in high-power nanosecond superfluorescent fiber source

In this work,we experimentally investigate the dependence of the stimulated Raman scattering(SRS)effect on the seed linewidth of a high-power nanosecond superfluorescent fiber source(ns-SFS).The results reveal that the SRS in the ns-SFS amplifier is significantly influenced by the full width at half maximum(FWHM)of the ns-SFS seed,and there is an optimal FWHM linewidth of 2 nm to achieve the lowest SRS in our case.The first-order SRS power ratio increases rapidly when the seed’s linewidth deviates from the optimal FWHM linewidth.By power scaling the ns-SFS seed with the optimal FWHM linewidth,a narrowband all-fiberized ns-SFS amplifier is achieved with a maximum average power of 602 W,pulse energy of 24.1 mJ and corresponding peak power of 422.5 kW.This is the highest average power and pulse energy achieved for all-fiberized ns-SFS amplifiers to the best of our knowledge.

Reoxidation of Transition-metal Catalysts with O2

Transition-metal catalyzed oxidation reactions are central components of organic chemistry. On behalf of green and sustainable chemistry, molecular oxygen （02） has been considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characters,

Continuous activation of polymorphonuclear myeloid-derived suppressor cells during pregnancy is critical for fetal development

The maternal immune system is vital in maintaining immunotolerance to the semiallogeneic fetus for a successful pregnancy.Although studies have shown that myeloid-derived suppressor cells(MDSCs)play an important role in maintaining feto-maternal tolerance,little is known about the role of MDSCs in pregnancies with intrauterine growth retardation(IUGR).Here,we reported that the activation of polymorphonuclear myeloid-derived suppressor cells(PMN-MDSCs)during pregnancy was closely associated with fetal growth.In humans,class E scavenger receptor 1(SR-E1),a distinct marker for human PMN-MDSCs,was used to investigate PMN-MDSC function during pregnancy.Continuous activation of SR-E1+PMN-MDSCs was observed in all stages of pregnancy,accompanied by high cellular levels of ROS and arginase-1 activity,mediated through STAT6 signaling.However,SR-E1+PMN-MDSCs in pregnancies with IUGR showed significantly lower suppressive activity,lower arginase-1 activity and ROS levels,and decreased STAT6 phosphorylation level,which were accompanied by an increase in inflammatory factors,compared with those in normal pregnancies.Moreover,the population of SR-E1+PMN-MDSCs was negatively correlated with the adverse outcomes of newborns from pregnancies with IUGR.In mice,decreases in cell population,suppressive activity,target expression levels,and STAT6 phosphorylation levels were also observed in the pregnancies with IUGR compared with the normal pregnancies,which were rescued by the adoptive transfer of PMN-MDSCs from pregnant mice.Interestingly,the growth-promoting factors(GPFs)secreted by placental PMN-MDSCs in both humans and mice play a vital role in fetal development.These findings collectively support that PMN-MDSCs have another new role in pregnancy,which can improve adverse neonatal outcomes.

HFIP-mediated three-component imidization of electron-rich arenes with in situ formed spiroindolenines for facile construction of 2-arylspiroindolenines

The three-component reaction of o-aminobenzaldehydes with 5-hydroxyindole and electron-rich areneshas been achieved through HFIP-mediated cascade hydride transfer/dearomative cyclization/CDC-typeimidization at room temperature under air,providing a variety of 2-arylspiroindolenines carrying diversefunctional groups with moderate to good yields.The derivatizations of the products also were conductedto enhance the synthetic practicality of this protocol.