The exciton relaxation process of CsPbI 3 perovskite nanocrystals (NCs) has been investigated by using transient absorption (TA) spectroscopy. The hot exciton relaxation process is confirmed to exist in the CsPbI 3 NCs, through comparing the TA data of CsPbI 3 NCs in low and high energy excitonic states. In addition, the Auger recombination and intrinsic decay paths also participate in the relaxation process of CsPbI 3 NCs, even the number of exciton per NC is estimated to be less than 1. Excitation intensity-dependent TA data further confirms the existence of Auger recombination. Meanwhile, the spectral data also confirms that the weight of hot exciton also increase together with that of Auger recombination at high excitation intensity when CsPbI 3 NCs in high energy excitonic states.The materials with nanoscale size exhibit many interesting characteristics, especially in the optoelectronic fields. Many optoelectronic devices based on nanocrystals have been prepared, such as light-harvesting and -emitting devices. With the development of synthesis techniques, many materials have been used to prepare nanocrystals, which opened a unique window for people to understand the world. Meanwhile the performance of optoelectronic devices based on nanocrystals have also improved continuously. Recently, a new family of nanocrystals has attracted tremendous world-wide attention. These all inorganic cesium lead halide perovskites (CsPbX 3 , X = Cl, Br, I or their mixed halide systems) nanocrystals exhibit excellent optical properties such as narrow emission line-width, tunable emission over entire visible spectrum, large optical absorption cross section, high quantum yields, and long carrier diffusion length and mobility. Apparently, the lead-halide perovskite nanocrystals exhibit a huge potential application in the light-emitting diodes 1 , electroluminescence devices 2 , low-threshold lasers 3,4 and sing-photon source 5 . Up to now, researchers have started focusing on the ultrafast dynamic processes occurring in perovskite materials, such as the charge carrier diffusion 6 , hot carriers relaxation, Auger recombination 7,8 process and interfacial charge transfer 9,10 which provides clear evidence that the free-carrier model is more suitable to interpret the optical properties of bulk perovskite materials 11 in comparison with the exciton model. The dynamic processes in perovskite materials are also sensitive to the structure 12 , chemical components 13 , detection positions 14,15 , and their surrounding environment 16 . If the perovskite materials are confined in a nano-scale space, such as two-dimensional quantum wells 17 and perovskite nanocrystals 18,19 , their relaxation processes become more dependent on the carrier recombination mechanism due to the limited scale. Although the understanding of ultrafast excitons and carriers dynamic processes have obtained noticeable improvement, the understanding about the nature of photo-excitation across the bandgap in perovskite nanocrystals remains limited. Moreover, dynamic beh...

No abstract

To explore the disassembly mechanism of tobacco mosaic virus (TMV), a model system for virus study, during infection, we have used single-molecule force spectroscopy to mimic and follow the process of RNA disassembly from the protein coat of TMV by the replisome (molecular motor) in vivo, under different pH and Ca(2+) concentrations. Dynamic force spectroscopy revealed the unbinding free-energy landscapes as that at pH 4.7 the disassembly process is dominated by one free-energy barrier, whereas at pH 7.0 the process is dominated by one barrier and that there exists a second barrier. The additional free-energy barrier at longer distance has been attributed to the hindrance of disordered loops within the inner channel of TMV, and the biological function of those protein loops was discussed. The combination of pH increase and Ca(2+) concentration drop could weaken RNA-protein interactions so much that the molecular motor replisome would be able to pull and disassemble the rest of the genetic RNA from the protein coat in vivo. All these facts provide supporting evidence at the single-molecule level, to our knowledge for the first time, for the cotranslational disassembly mechanism during TMV infection under physiological conditions.

This paper examines political favoritism of cites in national capital markets and the effect of that favoritism on city sizes. The paper estimates the city-by-city variation in the prices of capital across cities in China from 1998 to 2007. It relates how the prices facing the highest order political units and overall cross-city price dispersion change with changes in national policy and leadership. The effect of capital market favoritism on city growth after the national relaxation of migration restrictions in the early 2000's is investigated. The elasticity of the city growth rate with respect to the price of capital is estimated to be -0.07 in the OLS approach and -0.12 in the IV approach.

Private entrepreneurs, Political participation, Conformity, Corporate political activity (CPA), Transition economy,