Spectral shift of solid high-order harmonics from different channels in a combined laser field

We investigate theoretically the spectral shift of the high-order harmonic generation(HHG)in ZnO driven by a combined laser field by solving the two-band semiconductor Bloch equations(SBEs)in the velocity gauge.The combined laser field is synthesized by a fundamental laser pulse and its seventh-frequency laser pulse.When the seventh-frequency laser pulse is added to the rising or falling parts of the fundamental laser field,we find that the spectral blueshift or redshift appears,which is due to the unequal contribution of the rising and falling parts in the fundamental laser field to the harmonics.By analyzing the time-dependent conduction band population in k space,we found that,in addition to the tunneling ionization channel,there is also the resonant electron injection channels which is induced by the seventh-frequency laser pulse.The harmonics generated by the different channels show the spectral redshift or the spectral blueshift,respectively.Through analyzing the k-integrated transient conduction band population of the electrons from different channels,we found that if there is a certain delay in the process of the electron excitation,it will lead to the delay in the harmonic emission,which results in the spectral redshift of the harmonics.

Relationships between changes of kernel nutritive components and seed vigor during development stages of F_1 seeds of sh_2 sweet corn

The changes of kernel nutritive components and seed vigor in F1 seeds of sh2 sweet corn during seed development stage were investigated and the relationships between them were analyzed by time series regression (TSR) analysis. The results show that total soluble sugar and reducing sugar contents gradually declined, while starch and soluble protein contents increased throughout the seed development stages. Germination percentage, energy of germination, germination index and vigor index gradually increased along with seed development and reached the highest levels at 38 d after pollination (DAP). The TSR showed that, during 14 to 42 DAP, total soluble sugar content was independent of the vigor parameters determined in present experiment, while the reducing sugar content had a significant effect on seed vigor. TSR equations between seed reducing sugar and seed vigor were also developed. There were negative correlations between the seed reducing sugar content and the germination percentage, energy of germination, germination index and vigor index, respectively. It is suggested that the seed germination, energy of germination, germination index and vigor index could be predicted by the content of reducing sugar in sweet corn seeds during seed development stages.

Methane emissions from shale gas production sites in southern Sichuan,China:A field trial of methods

Shale gas is an important alternative natural gas source that can meet China's growing energy demand.However,methane emissions during shale gas production could largely determine whether it could be considered as a bridging clean energy source.In this study,we performed methane emission measurements using three methods(on-site optical gas imaging,on-site methane patrolling,and downwind measurement)at shale gas production sites in Sichuan province,China,covering 18 well sites with 81 wells.The results showed that flowback water tanks were the major methane sources,with valves,separators,chemical injection pumps,and pneumatic controllers as other sources.The methane concentrations inside the 18 sites ranged from 1.42 to 459μmol mol−1,with over 59%of the sites having the highest concentration less than 50μmol mol−1.The optical gas imaging method,with its low detection limit over 5000μmol mol−1,could not capture the emission effectively.The three successful downwind measurements resulted in site level emission rates between 0.02 and 0.17 kg h−1.When divided by the number of wells at each site,the emission intensity was 4%–28%of the wellhead emission factor for natural gas production in China.More measurements are required to better quantify methane emissions from shale gas sites in China.For sites in mountainous regions or long-term low-wind regions,detection methods other than downwind measurements should be suitable for quantifying site-level emissions.

Adsorption of methylene blue onto activated carbon produced from tea (Camellia sinensis L.) seed shells: kinetics, equilibrium, and thermodynamics studies

Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1 530.67 mg2/g and 0.7826 cm3/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudosecond-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue.

干燥温度通过赤霉素、脱落酸和抗氧化酶代谢影响水稻种子活力

目的:本研究旨在根据种子初始含水量确定水稻种子的最佳干燥温度,并阐明干燥温度和种子初始水分影响水稻种子干燥后种子活力的机制。创新点:根据不同初始水分的水稻种子,设置了不同梯度的干燥温度,系统地研究了干燥温度和种子初始水分对种子机械干燥过程与种子活力的影响,并得到了不同初始水分的适宜干燥温度。方法:在不同天气,分别收获初始含水量为20%、25%与30%的水稻种子样品,并分别设置4个温度梯度的干燥温度。采用三九远红外线干燥机(NP-120e)干燥水稻种子,对干燥后的水稻种子进行标准发芽试验,并测定相关生理生化指标,并进行相关性分析。结论:初始含水量为20%、25%与30%的水稻种子的适宜干燥温度分别为45、42与38°Co较高的干燥温度显著降低了水稻种子的活力。种子干燥过程与萌发初期水稻种子内部活性氧、抗氧化酶、赤霉素、脱落酸和a-淀粉酶的代谢可能与干燥温度调控水稻种子活力的机制密切相关。