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The buffer blocks used in deep geological repositories of high-level radioactive wastes (HLW) should be cured in an appropriate environment to prevent the deterioration of buffer blocks such as desiccation shrinkage and cracking. In this study, the bentonite-sand mixtures with different initial moisture contents (11.23-21.63%) were compressed in the laboratory to simulate the production of buffer blocks. The bentonite-sand mixtures were cured at different relative humidity (RH) of 33%, 75%, 85% and 100% in order to find the optimum curing humidity. During the curing process, the periodical mass change was weighed by a balance, the size change was measured by a vernier caliper, and the thermal conductivity was tested after the curing was balanced. The test results indicate that the moisture variation of bentonite-sand mixtures during curing was consistent with the soil-water characteristic curves (SWCCs) of the mixtures. When the compacted bentonite-sand mixtures were cured at the relative humidity of 33%, 75% and 85%, the samples were dehydrated and became dried, resulting in desiccation shrinkage and cracking. When the relative humidity was100%, the mixtures with a lower initial moisture content of 11.23-14.99% tended to absorb moisture from the environment and swelled. While the mixtures with a higher moisture content of 17.22-21.63% were desiccated to shrink, but no obvious cracks were observed on the surface of these cured specimens. Under the curing condition of RH =100%, the variation of water content and volume of the sample with an initial water content of 17.22% was the minimum, which was considered as the optimum curing humidity for buffer blocks. The optimal curing conditions (optimum RH) of industrial-scale buffer blocks used in the disposal repository can be estimated by the SWCCs of the small buffer blocks, and the development of drying shrinkage crack can be quantitatively evaluated by the thermal conductivity of buffer blocks.

The precise control of the regioselectivity in the transition metal‐catalyzed migratory hydrofunctionalization of alkenes remains a big challenge. With a transient ketimine directing group, the nickel‐catalyzed migratory β‐selective hydroarylation and hydroalkenylation of alkenyl ketones has been realized with aryl boronic acids using alkyl halide as the mild hydride source for the first time. The key to this success is the use of a diphosphine ligand, which is capable of the generation of a Ni(II)‐H species in the presence of alkyl bromide, and enabling the efficient migratory insertion of alkene into Ni(II)‐H species and the sequent rapid chain walking process. The present approach diminishes organosilanes reductant, tolerates a wide array of complex functionalities with excellent regioselective control. Moreover, this catalytic system could also be applied to the migratory hydroarylation of alkenyl azahetereoarenes, thus providing a general approach for the preparation of 1,2‐aryl heteroaryl motifs with wide potential applications in pharmaceutical discovery. [ABSTRACT FROM AUTHOR]

Abstract Background The architecture of biological networks has been reported to exhibit high level of modularity, and to some extent, topological modules of networks overlap with known functional modules. However, how the modular topology of the molecular network affects the evolution of its member proteins remains unclear. Results In this work, the functional and evolutionary modularity of Homo sapiens (H. sapiens) metabolic network were investigated from a topological point of view. Network decomposition shows that the metabolic network is organized in a highly modular core-periphery way, in which the core modules are tightly linked together and perform basic metabolism functions, whereas the periphery modules only interact with few modules and accomplish relatively independent and specialized functions. Moreover, over half of the modules exhibit co-evolutionary feature and belong to specific evolutionary ages. Peripheral modules tend to evolve more cohesively and faster than core modules do. Conclusion The correlation between functional, evolutionary and topological modularity suggests that the evolutionary history and functional requirements of metabolic systems have been imprinted in the architecture of metabolic networks. Such systems level analysis could demonstrate how the evolution of genes may be placed in a genome-scale network context, giving a novel perspective on molecular evolution.

Abstract Background The exploration of the structural topology and the organizing principles of genome-based large-scale metabolic networks is essential for studying possible relations between structure and functionality of metabolic networks. Topological analysis of graph models has often been applied to study the structural characteristics of complex metabolic networks. Results In this work, metabolic networks of 75 organisms were investigated from a topological point of view. Network decomposition of three microbes (Escherichia coli, Aeropyrum pernix and Saccharomyces cerevisiae) shows that almost all of the sub-networks exhibit a highly modularized bow-tie topological pattern similar to that of the global metabolic networks. Moreover, these small bow-ties are hierarchically nested into larger ones and collectively integrated into a large metabolic network, and important features of this modularity are not observed in the random shuffled network. In addition, such a bow-tie pattern appears to be present in certain chemically isolated functional modules and spatially separated modules including carbohydrate metabolism, cytosol and mitochondrion respectively. Conclusion The highly modularized bow-tie pattern is present at different levels and scales, and in different chemical and spatial modules of metabolic networks, which is likely the result of the evolutionary process rather than a random accident. Identification and analysis of such a pattern is helpful for understanding the design principles and facilitate the modelling of metabolic networks.