Mechanochemical Synthesis Of Alkaline Earth Carbides And Intercalation Compounds

High-energy ball milling has been successfully employed to produce alkaline earth carbides from the elements. In particular, CaC 2 yields of up to 98% can be realized in as little as 12 h. Similarly, the carbides of Mg (39% yield), Sr (87% yield), and Ba (82% yield) have been prepared. An intermediate in the synthesis of CaC 2 is the newly discovered gold-colored Ca-graphite intercalation compound CaC 6. Sr and Ba also go through initial intercalation phases (SrC 6 and BaC 6) before ultimately producing the carbides. The magnesium product consisted of Mg 2C 3 with no MgC 2 observed. The addition of sulfur to CaC 2 forming reactions did not adversely affect the overall synthesis; this suggests that this method may be utilized to sequester sulfur from high-sulfur coal. The preparation of these compounds by high-energy ball milling represents a novel method for producing pure carbides, as well as a convenient route to isotopically enriched ethyne. © 2009 American Chemical Society

Size Controlled Mechanochemical Synthesis Of Zrsi2

Mechanochemical metathesis reactions were utilized to synthesize nanocrystalline ZrSi2 ranging from 9–30 nm in size. Size was controlled through dilution with CaCl2. A linear relationship was found between diluent concentration and crystallite size. Unlike typical self-propagating metathesis reactions, this reaction did not self-propagate, requiring the input of mechanical energy. © The Royal Society of Chemistry

Mechanocatalysis For Biomass-Derived Chemicals And Fuels

Heterogeneous catalysis cannot be easily applied to solids such as cellulose. However, by mechanically grinding the correct catalyst and reactant, it is possible to induce solid–solid catalysis or mechanocatalysis. This process allows a wide range of solids to be effectively utilized as feedstock for commercially relevant compounds. Here we show a set of structural and physical parameters important for the implementation of catalysts in mechanocatalytic processes and their application in the catalytic depolymerization of cellulose. Using the best catalysts, which possess high surface acidities and layered structures, up to 84% of the available cellulose can be converted to water-soluble compounds in a single pass. This approach offers significant advantages over current methods - less waste, insensitivity to feedstock, multiple product pathways, and scalability. It can be easily integrated into existing biorefineries - converting them into multi-feedstock and multi-product facilities. This will expand the use of non-food polysaccharide sources such as switch grass. © 2010 The Royal Society of Chemistry

Synthesis and Crystal Structure of Cubic Ca₁₆Si₁₇N₃₄

Since the late 1960s, the exact structure of cubic calcium silicon nitride has been a source of debate. This paper offers evidence that the cubic phase CaSiN₂ described in the literature is actually Ca₁₆Si₁₇N₃₄. Presented here is a method for synthesizing single crystals of cubic-calcium silicon nitride from calcium nitride and elemental silicon under flowing nitrogen at 1500 °C. The colorless millimeter-sized crystals of Ca₁₆Si₁₇N₃₄ with a refractive index (<i>n</i>₂₅) = 1.590 were found to be cubic (<i>a</i> = 14.8882 Å) and belong to the space group <i>F</i>4̅3<i>m</i> (216). The synthesis of bulk, powdered cubic-Ca₁₆Si₁₇N₃₄ from calcium cyanamide and silicon is also discussed. Ca₁₆Si₁₇N₃₄ is a relatively air-stable refractory ceramic. In contrast to the orthorhombic phase of CaSiN₂, in which Ca²⁺ sits in octahedral sites, this cubic phase has Ca²⁺ in cubic sites that makes it an interesting host for new phosphors and gives rise to unique crystal field splitting

Relocation of the attTn7 Transgene Insertion Site in Bacmid DNA Enhances Baculovirus Genome Stability and Recombinant Protein Expression in Insect Cells

Baculovirus expression vectors are successfully used for the commercial production of complex (glyco)proteins in eukaryotic cells. The genome engineering of single-copy baculovirus infectious clones (bacmids) in E. coli has been valuable in the study of baculovirus biology, but bacmids are not yet widely applied as expression vectors. An important limitation of first-generation bacmids for large-scale protein production is the rapid loss of gene of interest (GOI) expression. The instability is caused by the mini-F replicon in the bacmid backbone, which is non-essential for baculovirus replication in insect cells, and carries the adjacent GOI in between attTn7 transposition sites. In this paper, we test the hypothesis that relocation of the attTn7 transgene insertion site away from the mini-F replicon prevents deletion of the GOI, thereby resulting in higher and prolonged recombinant protein expression levels. We applied lambda red genome engineering combined with SacB counterselection to generate a series of bacmids with relocated attTn7 sites and tested their performance by comparing the relative expression levels of different GOIs. We conclude that GOI expression from the odv-e56 (pif-5) locus results in higher overall expression levels and is more stable over serial passages compared to the original bacmid. Finally, we evaluated this improved next-generation bacmid during a bioreactor scale-up of Sf9 insect cells in suspension to produce enveloped chikungunya virus-like particles as a model vaccine.</p

Science fiction and human enhancement: radical life-extension in the movie ‘In Time’ (2011)

The ethics of human enhancement has been a hotly debated topic in the last 15 years. In this debate, some advocate examining science fiction stories to elucidate the ethical issues regarding the current phenomenon of human enhancement. Stories from science fiction seem well suited to analyze biomedical advances, providing some possible case studies. Of particular interest is the work of screenwriter Andrew Niccol (Gattaca, S1m0ne, In Time, and Good Kill), which often focuses on ethical questions raised by the use of new technologies. Examining the movie In Time (2011), the aim of this paper is to show how science fiction can contribute to the ethical debate of human enhancement. In Time provides an interesting case study to explore what could be some of the consequences of radical life-extension technologies. In this paper, we will show how arguments regarding radical life-extension portrayed in this particular movie differ from what is found in the scientific literature. We will see how In Time gives flesh to arguments defending or rejecting radical life-extension. It articulates feelings of unease, alienation and boredom associated with this possibility. Finally, this article will conclude that science fiction movies in general, and In Time in particular, are a valuable resource for a broad and comprehensive debate about our coming future