An experimental and theoretical study on photoluminescence of Ce^(3+)-doped ZnS quantum dots and their application in Aspergillus oryzae

ZnS and ZnS:3.125%Ce^(3+)(ZSC)quantum dots(QDs)were synthesized by a low-temperature solid-phase method.The crystal structure,photoluminescence(PL)properties of ZSC QDs,and their effects on the growth and kojic acid production of Aspergillus oryzae(A.oryzae)were investigated.It is found that both QDs have a cubic blend structure with the average particle size ranging of 2.75-6.14 nm.Ce^(3+)doping not only increases the band gap of ZnS QDs from 3.43 to 3.48 eV,but also increases the PL intensity by about 2.23 times,which is due to the fact that the electron carrier concentration is improved,and then the rate of radiative recombination is increased.The integral emission intensity,biomass,extracellular proteins yield,and kojic acid production of A.oryzae cultured with ZSC(ZnS)QDs are about 4.31(3.23),1.61(1.20),1.12(1.09),and 2.99(1.68)times higher than that of medium without QDs,respectively.

Integrated modelling of vacuum flashover development:Above-surface processes and breakdown threshold analyses

The flashover in vacuum is a rapid interfacial discharge across the insulator surface when subjected to high applied voltage.Here a theoretical model covering above-surface processes is introduced.The model calculates the flashover threshold in vacuum,with revised secondary electron emission avalanche theory and improved desorbed neutral transport model.The model serves as the first part of an integrated flashover model,aiming for consistent treatment of both above-surface and subsurface processes during the entire flashover development.The flashover threshold is obtained by combining the desorbed neutral pressure at given applied voltage and the gas breakdown criterion dictated by the Paschen's law.An analytical formula for threshold estimation containing physical parameters,and a simplified formula consisting of empirical coefficients are introduced,catering for both conceptual understanding and practical application.The derived formulae are validated by experimental data for a variety of insulator materials.The theory generalisation for non-uniform electric field distribution is further discussed.

Stacked arrangement of substrate integrated waveguide cavity-backed semicircle patches for wideband circular polarization with filtering effect

We present a novel broadband circularly polarized(CP)antenna with filtering effect for X-and Kuband satellite wireless communication.The structure comprises a driven layer(also a filtering layer)and a stacked layer(also a CP layer).The bandpass filtering response consists of two radiation nulls,which is the combined effect of a substrate integrated waveguide(SIW)cavity-backed aperture and embedded driven patch.

Future biomass carbon sequestration capacity of Chinese forests

Chinese forests, characterized by relatively young stand age, represent a significant biomass carbon （C） sink over the past several decades. Nevertheless, it is unclear how forest biomass C sequestration capacity in China will evolve as forest age, climate and atmospheric CO2 concentration change continuously. Here, we present a semi-empirical model that incorporates forest age and climatic factors for each lbrest type to estimate the effects of forest age and climate change on total forest biomass, under three different sce-narios based on the fifth phase of the Coupled Model Intercomparison Project （CMIPS）. We estimate that age-related forest biomass C sequestration to be 6.69 Pg C （~0.17 Pg C a^-1） from the 2000s to the 2040s. Climate change induces a rather weak increase in total forest biomass C sequestration （0.52-0.60 Pg C by tile 2040s）. We show that rising CO2 concentrations could further increase tile total forest biomass C sequestration by 1.68-3.12 Pg C in the 2040s across all three scenarios. Overall, the total forest biomass in China would increase by 8.89-10.37 Pg C by the end of 2040s. Our findings highlight the benefits of Chinese afforestation programs, continued climate change and increasing CO2. concentration in sustaining the forest biomass C sink in the near future, and could therefore be useful for designing more realistic climate change mitigation policies such as continuous forestation programs and careful choice of tree species.

The polycaprolactone/silk fibroin/carbonate hydroxyapatite electrospun scaffold promotes bone reconstruction by regulating the polarization of macrophages

Macrophages are known to modulate the osteogenic environment of bone regeneration elicited by biological bone grafts.Alteration in certain chemical components tends to affect macrophages polarization.Comparatively to hydroxyapatite(HAp),carbonate hydroxyapatite(CHA)consists of 7.4(wt%)carbonate ions and more closely resembles the mineral content of bone.It remains unknown whether CHA scaffolds or HA scaffolds have better osteogenic properties.In this study,we fabricated PCL/SF scaffold,PCL/SF/HAp scaffold and PCL/SF/CHA scaffold using the electrospinning technique.Despite comparable mechanical properties,the PCL/SF/CHA scaffold exhibited better osteogenic properties than the PCL/SF/HAp scaffold.Although no significant differences were observed between the two scaffolds for promoting osteoblast differentiation in vitro,the PCL/SF/CHA group appeared to be more effective at promoting bone regeneration in cranial defects in vivo.The PCL/SF/CHA scaffold was found to promote macrophage polarization toward M2 via activating the JAK/STAT5 pathway which caused a pro-osteogenic microenvironment to facilitate osteoblast differentiation.The results of this study indicated a higher potential of CHA to substitute HAp in the production of bone scaffolds for better bone regeneration.