Resistance of supersulfated cement to strong sulfate solutions

One of the principal uses of supersulfated cement has been for structures exposed to sea water and sulfate bearing ground waters. The resistance to such environments has been related to the absence of calcium hydroxide and the combination of much of the free alumina into ettringite during hydration. This paper reports the resistance of SSC to sulfate solutions in which ettringite has been decomposed. Prism samples were subjected to initial water storage at 25°C for both 28 days and 6 months. Samples were also cured for 6 months at 95°C and at both 11% and 100% R.H. The control samples of 28 days were compared with the 6 months samples of a more mature undecomposed SSC paste. After curing the prisms were measured and all the samples were immersed in three sulfate solutions (0.7M Na₂SO₄ , 0.7M MgSO₄ and saturated CaSO₄), and water at the same time. Measurements of linear expansion over 6 months were carried out. Core and surface material following immersion was examined by DTG and XRD. The study indicated that SSC is resistant to sodium and calcium sulfate solutions. Strong magnesium sulfate solutions decomposed the samples under all conditions. A possible mechanism for this attack is suggested. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Dual‐Color Far‐Red to Near‐Infrared Firefly Luciferin Analogue Designed for Multiparametric Bioluminescence Imaging

Red‐shifted bioluminescent emitters allow improved in vivo tissue penetration and signal quantification, and have led to the development of beetle luciferin analogues that elicit red‐shifted bioluminescence with firefly luciferase (Fluc). However, unlike natural luciferin, none have been shown to emit different colors with different luciferases. We have synthesized and tested the first dual‐color, far‐red to near‐infrared (nIR) emitting analogue of beetle luciferin, which, akin to natural luciferin, exhibits pH dependent fluorescence spectra and emits bioluminescence of different colors with different engineered Fluc enzymes. Our analogue produces different far‐red to nIR emission maxima up to λ_max=706 nm with different Fluc mutants. This emission is the most red‐shifted bioluminescence reported without using a resonance energy transfer acceptor. This improvement should allow tissues to be more effectively probed using multiparametric deep‐tissue bioluminescence imaging.     

The influence of temperature and different storage conditions on the stability of supersulphated cement

The stability of Supersulphated Cement (SSC) is investigated at 95°C when subjected to relative humidities of 100, 53 and 11% of water vapour. Previously [1] investigations at 25, 50, 75°C under the same conditions of humidity reported the stability of ettringite, one of the initial hydration products. At 95°C, decomposition of ettringite, is found at all humidities and is rapid at 100% relative humidity. The hydration products of cement pastes at a water cement ratio of 0.27 were determined by thermogravimetry (TG) and X-ray diffraction (XRD). The formation of the hydragarnet, plazolite is recorded during the decomposition/dehydration process enhanced by possible carbonation. Rehydration studies on the products after storage for up to 9 months were carried out using distilled water and the samples tested for ettringite content. It is concluded that ettringite in SSC is inherently unstable at 95°C.     

Schwefelverbindungen

Ohne Zusammenfassung     

The influence of temperature and different storage conditions on the stability of supersulphated cement

The stability of supersulphated cement (SSC) is investigated. The hydration products of cement pastes prepared at a water cement ratio of 0.27 were determined by thermogravimetry (TG) and X-ray diffraction (XRD). Ettringite, one of the initial hydration products, is shown to be stable under conditions of storage at 25, 50 and 75°C and when subject to relative humidities of 100, 53 and 11% of water vapour in each case. The effect of drying on ettringite stability at the higher temperatures is discussed in relation to the relative humidity. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Synthesis of planar chiral ferrocenyl cyclopentadienyl chelate ligand precursors

Two families of planar chiral ferrocenyl cyclopentadienyl chelate ligands for use in ansa-half sandwich metallocene complexes of catalytically active transition metals are described. The first family was derived in 4–5 steps from an enzymatic resolution of 1-iodo-2-(methylalcohol)ferrocene and possesses a cyclopentadiene derivative [Cp(H) = 1-indenyl, 2-indenyl or Ph₄Cp(H)] directly attached to the ferrocene ring with an adjacent vicinal tether CH₂Z donor group (Z = OH, OMe, NHMe, NMe₂ or PPh₂). The second family was derived from a chiral auxiliary approach and has the donor group (Z = PPh₂ or NMe₂) attached directly to the ferrocene ring with an adjacent tether vicinal CH₂Cp(H) group [Cp(H) = Cp(H), fluorenyl, 1-indenyl, Me₄Cp(H) or Ph₄Cp(H)].