Transforming submerged-arc welding slags into magnetic glass-ceramics

Submerged-arc welding slag (SAWS) and rice husk (RH) wastes represent two particularly abundant metallurgical and agricultural wastes. This work focusses on the feasibility of SAWS, together with glass cullet and RHs, to develop lightweight porous glass–ceramics that could be useful for technical purposes. Effects of temperatures and amounts of RHs on the porosity and water absorption of porous glass–ceramics were discussed at various dosages of husks up to 20 wt%. Depending on the sintering temperature, XRD measurements confirmed the presence of more than two crystalline phases: diopside, jacobsite, MgAl₂O₄, Ca_1.82Al_3.64Si_0.36O₈ and pyrope. These samples exhibited magnetic properties which were related to the presence of jacobsite phase. Magnetization curve is a characteristic of soft ferromagnetic materials with magnetization saturating at ~0.82 emu/g. The present results show a promising way to treat submerged-arc welding slags, transforming it into useful porous and functional glass–ceramic products via a simple powder technology and sintering approach.     

Darwin's special difficulty: the evolution of “neuter insects” and current theory

In the Origin of Species, Darwin discussed several challenges that worker insects presented to his theory of natural selection. Complex instincts such as building of combs of hexagonal cells were one problem and were explained by showing plausible intermediate stages. A more serious challenge was posed by the multiple worker castes seen in many ants. How could sterile individuals continue to evolve? A careful reading of the Origin suggests that Darwin was not primarily concerned by the evolution of worker sterility itself, which he considered a minor difficulty. Some modern commentaries on Darwin and insect workers seem to be cases of present interests interfering with the interpretation of the past. From a modern perspective, the evolution of a worker caste, and its corollary altruism, are evolutionary puzzles inasmuch as natural selection normally favors greater, not lesser, individual reproduction. These puzzles were resolved by Hamilton's theory of inclusive fitness. We now have a good functional understanding of how natural selection can cause both the origin of workers and their elaboration into greater levels of sterility and multiple morphological castes. Mechanistic understanding of morphological castes is also increasing via research into alternative developmental pathways. When the Origin was written, genetics did not exist and it would have been virtually impossible for Darwin to elaborate such ideas. However, the Origin probably addressed the main questions in the minds of Victorian readers in relation to insect workers. Darwin was prescient in having insights with close relationships to modern-day interests and the key principles involved, including kinship and benefits to the colony, even if these are not exact precursors to modern thinking.     

Disinfection byproduct regulatory compliance surrogates and bromide-associated risk

Natural and anthropogenic factors can alter bromide concentrations in drinking water sources. Increasing source water bromide concentrations increases the formation and alters the speciation of disinfection byproducts (DBPs) formed during drinking water treatment. Brominated DBPs are more toxic than their chlorinated analogs, and thus have a greater impact on human health. However, DBPs are regulated based on the mass sum of DBPs within a given class (e.g., trihalomethanes and haloacetic acids), not based on species-specific risk or extent of bromine incorporation. The regulated surrogate measures are intended to protect against not only the species they directly represent, but also against unregulated DBPs that are not routinely measured. Surrogates that do not incorporate effects of increasing bromide may not adequately capture human health risk associated with drinking water when source water bromide is elevated. The present study analyzes trihalomethanes (THMs), measured as TTHM, with varying source water bromide concentrations, and assesses its correlation with brominated THM, TTHM risk and species-specific THM concentrations and associated risk. Alternative potential surrogates are evaluated to assess their ability to capture THM risk under different source water bromide concentration conditions. The results of the present study indicate that TTHM does not adequately capture risk of the regulated species when source water bromide concentrations are elevated, and thus would also likely be an inadequate surrogate for many unregulated brominated species. Alternative surrogate measures, including THM3 and the bromodichloromethane concentration, are more robust surrogates for species-specific THM risk at varying source water bromide concentrations.     

A Tracer Study of Dispersion Over a City

The planning and conduct of series of tracer experiments carried out in St. Louis in the period between 1963 and 1965 is described. Tentative results indicate that horizontal dispersion over an urban area does not differ greatly from that observed over open country, except for a much greater initial spreading of the tracer plume. Vertical dispersion during the daytime does not appear to differ greatly from that observed over open country, and can be best expressed in terms of travel time rather than travel distance. Vertical dispersion during the evening over an urban area is much greater than that observed over open country; the limited results obtained suggest the formation of a slightly unstable layer as the air flows over the city.     

Application of an Improved Micro-amount of Virion Enrichment Technique (MiVET) for the Detection of Avian Influenza A Virus in Spiked Chicken Meat Samples

Food and Environmental Virology - Highly sensitive detection of pathogens is effective for screening meat during quarantine inspection and export. The “micro-amount of virion enrichment...