A Sublattice Phase-Field Model for Direct CALPHAD Database Coupling

The phase-field method has been established as a de facto standard for simulating the microstructural evolution of materials. In quantitative modeling the assessment and compilation of thermodynamic/kinetic data is largely dominated by the CALPHAD approach, which has produced a large set of experimentally and computationally generated Gibbs free energy and atomic mobility data in a standardized format: the thermodynamic database (TDB) file format. Harnessing this data for the purpose of phase-field modeling is an ongoing effort encompassing a wide variety of approaches. In this paper, we aim to directly link CALPHAD data to the phase-field method, without intermediate fitting or interpolation steps. We introduce a model based on the Kim-Kim-Suzuki (KKS) approach. This model includes sublattice site fractions and can directly utilize data from TDB files. Using this approach, we demonstrate the model on the U-Zr and Mo-Ni-Re systems.Comment: 8 pages, 8 figure

Radiation re-solution of fission gas in non-oxide nuclear fuel

Renewed interest in fast nuclear reactors is creating a need for better understanding of fission gas bubble behavior in non-oxide fuels. Collisions between fission fragments and their subsequent cascades can knock fission gas atoms out of bubbles and back into the fuel lattice, resulting in a loss term for the bubble. By assuming these collisions can be treated as binary collisions, we calculated a re-solution parameter as a function of bubble radius. The calculations showed that there is a sharp decrease as bubble size increases until about 100 nm when the re-solution parameter stays nearly constant. The bubble size dependence may explain the large bubble size distribution found in some uranium carbide and nitride fuels. Furthermore, our model shows ion cascades created in the fuel result in many more implanted fission gas atoms than collisions directly with fission fragments. Utilization of our calculated re-solution parameter can be used to find a re-solution rate for future bubble behavior simulations

Ultrafast carrier dynamics in tetrahedral amorphous carbon: carrier trapping versus electron–hole recombination

We report the investigation of the ultrafast carrier dynamics in thin tetrahedral amorphous carbon films by means of femtosecond time-resolved reflectivity. We estimated the electronphonon relaxation time of a few hundred femtoseconds and we observed that under low optical excitation photo-generated carriers decay according to two distinct mechanisms attributed to trapping by defect states and direct electronhole recombination. With high excitation, when photo-carrier and trap densities are comparable, a unique temporal evolution develops, as the time dependence of the trapping process becomes degenerate with the electronhole recombination. This experimental evidence highlights the role of defects in the ultrafast electronic dynamics and is not specific to this particular form of carbon, but has general validity for amorphous and disordered semiconductors. peerReviewe

In vivo imaging of systemic transport and elimination of xenobiotics and endogenous molecules in mice

We describe a two-photon microscopy-based method to evaluate the in vivo systemic transport of compounds. This method comprises imaging of the intact liver, kidney and intestine, the main organs responsible for uptake and elimination of xenobiotics and endogenous molecules. The image quality of the acquired movies was sufficient to distinguish subcellular structures like organelles and vesicles. Quantification of the movement of fluorescent dextran and fluorescent cholic acid derivatives in different organs and their sub-compartments over time revealed significant dynamic differences. Calculated half-lives were similar in the capillaries of all investigated organs but differed in the specific sub-compartments, such as parenchymal cells and bile canaliculi of the liver, glomeruli, proximal and distal tubules of the kidney and lymph vessels (lacteals) of the small intestine. Moreover, tools to image immune cells, which can influence transport processes in inflamed tissues, are described. This powerful approach provides new possibilities for the analysis of compound transport in multiple organs and can support physiologically based pharmacokinetic modeling, in order to obtain more precise predictions at the whole body scale

Land use change impacts on floods at the catchment scale: Challenges and opportunities for future research

Research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage and terracing are identified. Potential strategies in addressing these gaps are proposed, such as complex systems approaches to link processes across time scales, long-term experiments on physical-chemical-biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology and geomorphology

Soy isoflavones and their relationship with microflora: beneficial effects on human health in equol producers

The bioavailability of soy isoflavones depends on the composition of the microflora for each subject. Bacteria act on different isoflavones with increased or reduced absorption and cause biotransformation of these compounds into metabolites with higher biological activity. S-equol is the most important metabolite and only 25–65 % of the population have the microflora that produces this compound. The presence of equol-producing bacteria in soy product consumers means that the consumption of such products for prolonged periods leads to lower cardiovascular risk, reduced incidence of prostate and breast cancer, and greater relief from symptoms related to the menopause such as hot flushes and osteoporosis

Manganese-doped ZnO nanobelts for spintronics

©2004 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/84/783/1DOI:10.1063/1.1645319Zinc oxide (ZnO) nanobelts synthesized by thermal evaporation have been ion implanted with 30 keV Mn+ ions. Both transmission electron microscopy and photoluminescence investigations show highly defective material directly after the implantation process. Upon annealing to 800 °C, the implanted Mn remains in the ZnO nanobelts and the matrix recovers both in structure and luminescence. The produced high-quality ZnO:Mn nanobelts are potentially useful for spintronics