Water productivity in Zhanghe Irrigation System: issues of scale

Irrigation systemsWater productivityReservoirsWater useWater stressWater conservationRicePaddy fieldsCrop yield

The no-boundary measure in string theory: Applications to moduli stabilization, flux compactification, and cosmic landscape

We investigate the no-boundary measure in the context of moduli stabilization. To this end, we first show that for exponential potentials, there are no classical histories once the slope exceeds a critical value. We also investigate the probability distributions given by the no-boundary wave function near maxima of the potential. These results are then applied to a simple model that compactifies 6D to 4D (HBSV model) with fluxes. We find that the no-boundary wave function effectively stabilizes the moduli of the model. Moreover, we find the a priori probability for the cosmological constant in this model. We find that a negative value is preferred, and a vanishing cosmological constant is not distinguished by the probability measure. We also discuss the application to the cosmic landscape. Our preliminary arguments indicate that the probability of obtaining anti de Sitter space is vastly greater than for de Sitter.Comment: 27 pages, 8 figure

Low-Temperature-Induced Controllable Transversal Shell Growth of NaLnF4 Nanocrystals

Highly controllable anisotropic shell growth is essential for further engineering the function and properties of lanthanide-doped luminescence nanocrystals, especially in some of the advanced applications such as multi-mode bioimaging, security coding and three-dimensional (3D) display. However, the understanding of the transversal shell growth mechanism is still limited today, because the shell growth direction is impacted by multiple complex factors, such as the anisotropy of surface ligand-binding energy, anisotropic core–shell lattice mismatch, the size of cores and varied shell crystalline stability. Herein, we report a highly controlled transversal shell growth method for hexagonal sodium rare-earth tetrafluoride (β-NaLnF4) nanocrystals. Exploiting the relationship between reaction temperature and shell growth direction, we found that the shell growth direction could be tuned from longitudinal to transversal by decreasing the reaction temperature from 310 °C to 280 °C. In addition to the reaction temperature, we also discussed the roles of other factors in the transversal shell growth of nanocrystals. A suitable core size and a relative lower shell precursor concentration could promote transversal shell growth, although different shell hosts played a minor role in changing the shell growth direction