Temporal response of laminated graded-bandgap GaAs-based photocathode with distributed Bragg reflection structure:Model and simulation

To describe the dynamic response characteristics of the laminated graded-bandgap GaAs-based photocathode with distributed Bragg reflection structure,a general theoretical temporal response model is deduced by combining the unsteady continuity equation and numerical calculation method.Through the model,the contribution of the distribution Bragg reflec-tion structure and graded-bandgap emission layer to the temporal response are investigated.Meanwhile,the relationships between the temporal response characteristics of the laminated GaAs-based photocathode and different structural parame-ters are also analyzed,including average electron decay time,emission layer thickness,and incident light wavelength.It is found that the introduction of distribution Bragg reflection(DBR)layer solves the discrepancy between the absorption capability of the emission layer and the temporal response.Moreover,the distributed Bragg reflection layer can improve the time response by optimizing the initial photoelectron distribution.The improvement effect of the DBR layer on the temporal response is enhanced with the emission layer thickness decreasing or the incident light wavelength increasing.These results explain the effect of the DBR layer of the photocathode on the dynamic characteristics,which can offer a new insight into the dynamic research of GaAs-based photocathode.

Biological responses of small yellow croaker(Larimichthys polyactis) to multiple stressors: a case study in the Yellow Sea, China

Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k（growth coefficient） and t_0（zero-length age） gradually increased from 0.26 and –0.58 year in 1960 to 0.56 and –0.25 year in 2008, respectively. Although, L∞（body length）sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t_r（inflexion age） decreased from 3.78 year in1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as： fishing vessel power〉feeding grade〉sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.

Modelling envelope and temporal fine structure components of frequency-following responses in rat inferior colliculus

In studies of auditory perception, a dichotomy between envelope and temporal fine structure(TFS) has been emphasized. It has been shown that frequency-following responses(FFRs) in the rat inferior colliculus can be divided into the envelope component(FFREnv)and the temporal fine structure component(FFRTFS). However, the existing FFR models cannot successfully separate FFREnv and FFRTFS. This study was to develop a new FFR model to effectively distinguish FFREnv from FFRTFS by both combining the advantages of the two existing FFR models and simultaneously adding cellular properties of inferior colliculus neurons. To evaluate the validity of the present model, correlations between simulated FFRs and experimental data from the rat inferior colliculus were calculated. Different model parameters were tested, FFRs were calculated, and the parameters with highest prediction were chosen to establish an ideal FFR model. The results indicate that the new FFR model can provide reliable predictions for experimentally obtained FFREnv and FFRTFS.