以锑化铯(Cs_(3)Sb)为代表的碱金属型半导体光阴极具有高量子效率、低电子发射度、光谱响应快等特点,可作为理想的新型电子发射源.然而Cs_(3)Sb中碱金属敏感于含氧气体,从而导致其结构不稳定,工作寿命低,影响电子发射效率.利用超薄层状...以锑化铯(Cs_(3)Sb)为代表的碱金属型半导体光阴极具有高量子效率、低电子发射度、光谱响应快等特点,可作为理想的新型电子发射源.然而Cs_(3)Sb中碱金属敏感于含氧气体,从而导致其结构不稳定,工作寿命低,影响电子发射效率.利用超薄层状的二维材料进行涂层保护Cs_(3)Sb基底,有望构建新型高性能光阴极材料,但目前仍然缺乏适合的二维材料,能够在保护基底同时维持低功函数(W)和高量子效率.近年来二维过渡金属碳/氮化物(MXene)材料逐渐成为研究热点,其灵活引入的悬挂键可以很好地调控MXene材料的结构和电子特性.本文系统构建了一系列M_(2)CT_(2)-Cs_(3)Sb异质结,基于第一性原理计算分析了过渡金属元素(M)、原子配比(M/C)、堆垛构型及悬挂键(T)等对其W的影响.研究表明,不同悬挂键类型对构建异质结的W影响显著,相对于其他悬挂键(—F/—O/—Cl/—S/—NH),带有—OH/—OCH_(3)悬挂键构成的M_(2)CT_(2)-Cs_(3)Sb异质结具有相对较低的W.利用差分电荷密度和能级矫正分析解释了异质结W的变化原因,即异质结界面电荷重新分布导致界面偶极方向不同,造成电子逸出的势垒不同.经过筛选后发现,M_(2)C(OH)_(2)(M=V,Ti,Cr)和M_(2)C(OCH_(3))_(2)(M=Ti,Cr,Nb)结构可以看作理想的涂层材料,尤其是V_(2)C(OH)_(2)-Cs_(3)Sb(W=1.602 e V)和Ti_(2)C(OCH_(3))_(2)-Cs_(3)Sb(W=1.877 e V).本研究不仅有助于深入理解MXene-Cs_(3)Sb异质结电子结构和光学性质,同时也为高性能光阴极材料的计算筛选提供参考依据.展开更多
The Paleogene Kalatar Formation is a main target for petroleum ex125 ploration in the southwestern region of the Tarim Basin （SWRTB） and a systematical summary of controls on reservoirs of high quality has important...The Paleogene Kalatar Formation is a main target for petroleum ex125 ploration in the southwestern region of the Tarim Basin （SWRTB） and a systematical summary of controls on reservoirs of high quality has important implications for this area. According to outcrop analysis, as well as core, and laboratory experiments based on theories of sedimentology, it can be inferred that the main pore types in the Kalatar Formation are moldic, vuggy, intercrystalline and interparticle pores, fractures, and mudstone microporosity, respectively. The foreshore in the shore-shelf depositional model is the most favorable target, wherein grainstone and dolomitized grainstone are characterized by high quality in a middle ramp subfacies of the carbonate ramp model. Diagenetic factors, such as micritization, cementation, compaction, neomorphism, silicification, and pyritization, are detrimental for reservoirs. At the same time, leaching and dolomitization can improve the quality of reservoirs. Permeability of reservoirs can be greatly improved by fractures, through which quality of reservoirs can be effectively enhanced. Concentration of CO2, temperature, and humidity are affected by changes in climate, which can have an influence on depositional setting, composition and diagenesis of sediments, and eventually the properties of reservoirs. The hot and arid climate of the Paleogene was harmful to development of reservoirs, which is demonstrated in the contemporaneous diagenetic and epigenetic stages. Shallow and deep-burial diagenesis are closely related to the formation and the connate water, however these are rarely affected by paleo-climatic variation. There is possible erosion that mainly resulted from organic acid in relative well intervals according to indications of hydrocarbons in the early diagenetic stage. Fracture systems can be established when acidic fluids are ernplaced during periods of uplift, by which pores can be effectively enlarged during the late diagenetic stages.展开更多
Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data...Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular （AI） and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.展开更多
文摘以锑化铯(Cs_(3)Sb)为代表的碱金属型半导体光阴极具有高量子效率、低电子发射度、光谱响应快等特点,可作为理想的新型电子发射源.然而Cs_(3)Sb中碱金属敏感于含氧气体,从而导致其结构不稳定,工作寿命低,影响电子发射效率.利用超薄层状的二维材料进行涂层保护Cs_(3)Sb基底,有望构建新型高性能光阴极材料,但目前仍然缺乏适合的二维材料,能够在保护基底同时维持低功函数(W)和高量子效率.近年来二维过渡金属碳/氮化物(MXene)材料逐渐成为研究热点,其灵活引入的悬挂键可以很好地调控MXene材料的结构和电子特性.本文系统构建了一系列M_(2)CT_(2)-Cs_(3)Sb异质结,基于第一性原理计算分析了过渡金属元素(M)、原子配比(M/C)、堆垛构型及悬挂键(T)等对其W的影响.研究表明,不同悬挂键类型对构建异质结的W影响显著,相对于其他悬挂键(—F/—O/—Cl/—S/—NH),带有—OH/—OCH_(3)悬挂键构成的M_(2)CT_(2)-Cs_(3)Sb异质结具有相对较低的W.利用差分电荷密度和能级矫正分析解释了异质结W的变化原因,即异质结界面电荷重新分布导致界面偶极方向不同,造成电子逸出的势垒不同.经过筛选后发现,M_(2)C(OH)_(2)(M=V,Ti,Cr)和M_(2)C(OCH_(3))_(2)(M=Ti,Cr,Nb)结构可以看作理想的涂层材料,尤其是V_(2)C(OH)_(2)-Cs_(3)Sb(W=1.602 e V)和Ti_(2)C(OCH_(3))_(2)-Cs_(3)Sb(W=1.877 e V).本研究不仅有助于深入理解MXene-Cs_(3)Sb异质结电子结构和光学性质,同时也为高性能光阴极材料的计算筛选提供参考依据.
基金supported by the National Natural Sciences Foundation of China(Grant No.40872078)the Knowledge Innovation Program of South China Sea Institute of Oceanology(GrantNo.LYQY200806)the Research Project of Tarim Oilfield Company(Grant No.41009080051)
文摘The Paleogene Kalatar Formation is a main target for petroleum ex125 ploration in the southwestern region of the Tarim Basin （SWRTB） and a systematical summary of controls on reservoirs of high quality has important implications for this area. According to outcrop analysis, as well as core, and laboratory experiments based on theories of sedimentology, it can be inferred that the main pore types in the Kalatar Formation are moldic, vuggy, intercrystalline and interparticle pores, fractures, and mudstone microporosity, respectively. The foreshore in the shore-shelf depositional model is the most favorable target, wherein grainstone and dolomitized grainstone are characterized by high quality in a middle ramp subfacies of the carbonate ramp model. Diagenetic factors, such as micritization, cementation, compaction, neomorphism, silicification, and pyritization, are detrimental for reservoirs. At the same time, leaching and dolomitization can improve the quality of reservoirs. Permeability of reservoirs can be greatly improved by fractures, through which quality of reservoirs can be effectively enhanced. Concentration of CO2, temperature, and humidity are affected by changes in climate, which can have an influence on depositional setting, composition and diagenesis of sediments, and eventually the properties of reservoirs. The hot and arid climate of the Paleogene was harmful to development of reservoirs, which is demonstrated in the contemporaneous diagenetic and epigenetic stages. Shallow and deep-burial diagenesis are closely related to the formation and the connate water, however these are rarely affected by paleo-climatic variation. There is possible erosion that mainly resulted from organic acid in relative well intervals according to indications of hydrocarbons in the early diagenetic stage. Fracture systems can be established when acidic fluids are ernplaced during periods of uplift, by which pores can be effectively enlarged during the late diagenetic stages.
基金Supported by National Natural Science Foundation of China under Grant Nos. 10802043 and 10832006, Program for Science ＆ Technology Innovation Talents in Universities of Henan under Grant No. 2009HASTIT033 and Key Disciplines of Shanghai municipality （$30104）
文摘Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular （AI） and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.
