Dual layer SiC coating on matrix graphite sphere prepared by pack cementation and fluidized‐bed chemical vapor deposition

A dual layer silicon carbide (SiC) coating including inner porous SiC (p‐SiC) layer and outer dense SiC (d‐SiC) layer was fabricated on the matrix graphite (MG) spheres of high‐temperature gas‐cooled reactor fuel elements by pack cementation and fluidized‐bed chemical vapor deposition process to improve the oxidation‐resistant property. Microstructure of the coating demonstrates different density and structure of the two SiC layers with no obvious boundaries between them. Weight gain curves of oxidation tests at 1773 K for 200 hours show that the coating could effectively protected the MG sphere by isolating the air infiltration with p‐SiC layer as the main functional layer and d‐SiC layer as the transition layer to improve the bond strength. Due to the transition function of p‐SiC layer, the coated spheres could understand more than 50 times thermal shocking tests from 1773 K to room temperature with no stress cracking.     

Novel hydroperoxides as primary autoxidation products of a model ethoxylated surfactant

Ethoxylated alcohols, widely used as surfactants, are susceptible to oxidation when exposed to air. A complex mixture is formed, in which alkylated aldehydes, alkylated formates, hydroxyaldehydes, and formaldehyde have previously been identified by our group. The compounds identified so fat are all secondary oxidation products, some of which have been shown to be skin sensitizers and irritants. The primary oxidation products from ethoxylated surfactants have been described as peroxides and hydroperoxides, but their structures have not been elucidated more closely. Hydroperoxides are reactive species and can be suspected to be biologically active as skin sensitizers and irritants. In the present study we used a small model compound, diethylenglycol monoethylether (C₂E₂), to facilitate the identification of primary oxidation products formed at autoxidation of ethoxylated surfactants. By performing NMR and HPLC-MS analyses, we found that at least four different hydroperoxides were formed at autoxidation of C₂E₂, one of them dominating in concentration over the others. The hydroperoxide present in the highest concentration was identified as 2-[2-(1-hydroperoxyethoxy)ethoxy]ethanol.     

Hydrodynamics of a slurry airlift reactor at high solid concentrations

The hydrodynamics of a slurry airlift reactor at high solid concentrations were experimentally studied. The influences of the average solid concentration, superficial gas velocity and particle size on the radial and axial profiles of the solid holdup, average gas holdup and liquid circulation velocity were investigated. The local solid holdup was measured with an electrical conductivity probe. At low solid concentrations or high superficial gas velocities, the radial profile of the solid holdup was uniform. At high solid concentrations, the radial profile of the solid holdup was nonuniform, with higher values near the wall. This radial nonuniformity increased with decreased superficial gas velocity or increased average solid concentration. The axial profile of the cross-sectional average solid holdup was uniform at all conditions in this work, even at high solid concentrations. The average gas holdup and liquid circulation velocity increased with the superficial gas velocity but decreased with the average solid concentration. A mathematical model based on the balance of the transverse lift force and turbulent dispersion force was proposed to predict the radial profile of the solid holdup. Reasonable predictions were obtained from this model with an adjustable model parameter.     

Water and human livelihood resilience: a regional-to-global outlook

This article addresses the need to profoundly expand the way we think about freshwater. Stressing water’s role as the bloodstream of the biosphere, the article highlights water’s functions in sustaining life on the planet (control, state and moisture feedback functions), the role of water partitioning changes in inducing non-linear change at multiple scales, and humanity’s influence on a social-ecological system’s capacity to adapt and continue to function. It reviews water’s roles during its journey through the upper layers of the land mass, different types of water–ecosystem interactions, and water’s roles in landscape-scale resilience building.     

Stable linker peptides for a cellulose-binding domain-lipase fusion protein expressed in Pichia pastoris

Fusion proteins composed of a cellulose-binding domain fromNeocallimastix patriciarum cellulase A and Candida antarcticalipase B were constructed using different linker peptides. Theaim was to create proteolytically stable linkers that were ableto join the functional modules without disrupting their function.Six fusion variants containing linkers of 4–44 residueswere expressed in Pichia pastoris and analysed. Three variantswere found to be stable throughout 7-day cultivations. The cellulose-bindingcapacities of fusion proteins containing short linkers wereslightly lower compared with those containing long linkers.The lipase-specific activities of all variants, in solutionor immobilized on to cellulose, were equal to that of the wild-typelipase.     

Writers-in-residence: Goncourt and Huysmans at home without a plot

This article takes the plan drawing of Richard Meier's Westbeth Artists' Colony in Greenwich Village as a lens through which to examine a chain of events that formalised what today is referred to as loft architecture. Westbeth was the first legal loft building in the USA. Approved by the local planning administration in March, 1968, and completed in May, 1970, the building was the successful culmination of almost two decades of attempts to legalise joint live and work spaces in Lower Manhattan. Meier used an ingenious drawing process to usher Westbeth through the complex of codes and regulations that prohibited loft developments. His drawing process implies scholarship both on the spatial configuration of loft architecture, and on the jurisdictional and financial procedures that often combine to hamper architectural design. This article has been developed accordingly: it traces the distribution of loft units in Westbeth to extrapolate some principles of loft architecture; it analyses the two domestic features that, through code, inhibited legalisation of loft architecture in the late 1960s, which were windows and bedrooms; and it synthesises these two domestic features through an analytical evaluation of Meier's drawing.