Aspects of the in vitro bioactivity and antimicrobial properties of Ag+- and Zn2+-exchanged 11 Å tobermorites

11 Å tobermorite, Ca5Si6O16(OH)2 · 4H2O, is a layer lattice ion exchange mineral whose potential as a carrier for Ag+ and Zn2+ ions in antimicrobial, bioactive formulations has not yet been explored. In view of this, the in vitro bioactivity of Ag+- and Zn2+-exchanged 11 Å tobermorites and their bactericidal action against S. aureus and P.aeruginosa are reported. The in vitro bioactivity of the synthetic unsubstituted tobermorite phase was confirmed by the formation of bone-like hydroxycarbonate apatite (HCA) on its surface within 48 h of contact with simulated body fluid. The substitution of labile Ag+ ions into the tobermorite lattice delayed the onset of HCA-formation to 72 h; whereas, the Zn2+-substituted phase failed to elicit an HCA-layer within 14 days. Both Ag+- and Zn2+-exchanged tobermorite phases were found to exhibit marked antimicrobial action against S. aureus and P.aeruginosa, two common pathogens in biomaterial-centred infections.

US imperialism in action: An audit-based appraisal of the Coalition Provisional Authority in Iraq

This paper drawing from audit reports reflects upon the post-Iraq war administration the Coalition Provisional Authority (CPA). It argues that the CPA’s compliance with basic levels of decent public administration were akin to Guantanamo’s compliance with basic levels of natural justice. The audit reports demonstrate that the CPA was a chaotic administration which spent billions without proper controls or procedures and left precious Iraqi oil revenues open to fraudulent acts. The CPA failed to comply with its obligations under UN resolutions. It identifies the geopolitical/economic implications of the US government which was partly motivated by economic concerns but it was also motivated by political concerns—the imposition of US hegemony. It then turns to the broader economic imperatives of the falling rate of profit and the imposition of neoliberalism (market fundamentalism).

Twentieth Century Society Spring lecture series: second lives for Twentieth Century masterpieces

The Twentieth Century Society’s Spring lecture series (six in total) looks at the restoration and refurbishment of key C20 buildings in Britain and the US. Buildings covered: BBC Broadcasting House in London (G Val Meyer 1930-32, MacCormac Jamieson Prichard 2000-09). Speaker: Mark Hines (Mark Hines Architects), was the project architect and is the author of The Story of Broadcasting House: Home of the BBC. 5 February 2009. Crown Hall, Chicago (Mies van der Rohe 1952), the Art and Architecture Building, Yale University, New Haven (Paul Rudolf 1961-63) and the former Wills head office in Bristol (SOM with YRM 1970-75). Speaker: Patrick Bellew (Atelier 10 Engineers), 12 February 2009. Center for British Art, Yale University, New Haven (Louis Kahn 1969-77). Speaker: Peter Inskip (Inskip and Jenkins Architects), 17 February 2009. Brunswick Centre London (Patrick Hodgkinson 1967-72; Levitt Bernstein with Patrick Hodgkinson 2006). Speaker: Stuart Tappin (Stand Consulting Engineers Ltd), 26 February 2009. De La Warr Pavilion, Bexhill-on-Sea (Mendelsohn and Chermayeff 1934-5, John McAslan and Partners 2000-05). Speaker: Mark Cannata (HOK Architects), 5 March 2009. Finsbury Health Centre London (Lubetkin & Tecton 1938, first phase of conservation work Avanti Architects 1995.). Speaker: John Allan of Avanti Architects, 12 March 2009.

The interaction of zinc oxide-based dental cements with aqueous solutions of potassium fluoride

The ability of zinc oxide-based dental cements (zinc phosphate and zinc polycarboxylate) to take up fluoride from aqueous solution has been studied. Only zinc phosphate cement was found to take up any measurable fluoride after 5 h exposure to the solutions. The zinc oxide filler of the zinc phosphate also failed to take up fluoride from solution. The key interaction for this uptake was thus shown to involve the phosphate groups of the set cement. However, whether this took the form of phosphate/fluoride exchange, or the formation of oxyfluoro-phosphate groups was not clear. Fluoride uptake followed radicaltime kinetics for about 2 h in some cases, but was generally better modelled by the Elovich equation, dq(t)/dt = alpha exp(-beta q(t)). Values for alpha varied from 3.80 to 2.48 x 10(4), and for beta from 7.19 x 10(-3) to 0.1946, though only beta showed any sort of trend, becoming smaller with increasing fluoride concentration. Fluoride was released from the zinc phosphate cements in processes that were diffusion based up to M(t)/M(infinity) of about 0.4. No further release occurred when specimens were placed in fresh volumes of deionised water. Only a fraction of the fluoride taken up was re-released, demonstrating that most of the fluoride taken up becomes irreversibly bound within the cement.