Simultaneous uptake of ammonium and phosphate ions by compounds prepared from paper sludge ash

Al-containing CaO-SiO(2)-H(2)O phases were prepared by hydrothermal treatment of mixtures of paper sludge ash (PSA) with various silica and calcia sources and their properties were determined with particular reference to the simultaneous uptake of ammonium and phosphate ions, which are implicated in the eutrophication of lakes and ponds. After examination of various silica and calcia sources, Ca(OH)(2) and SiO(2) sol were selected as the most appropriate starting materials. Dry milling was found to be superior to wet milling in avoiding contamination from the milling media during mixing. Nine samples with three different Ca/Si ratios and Al(2)O(3) contents were prepared with various mass ratios of Ca(OH)(2), PSA and SiO(2). The chemical compositions of the hydrothermal products of these mixtures moved towards the tieline of CaSiO(3)-PSA, with respect to the starting compositions. The major phase formed in all samples was poorly crystalline C-S-H(I), with hydroxysodalite also formed in the Al-containing mixtures. All the products showed a capacity for the simultaneous uptake of ammonium and phosphate ions. The saturated sorption capacities calculated from the Langmuir equation ranged from 0.9 to 2.4mmol/g for the ammonium ion and from 3.3 to 5.2mmol/g for the phosphate ion. Since the sorption capacities for both ions increased with increasing Ca contents of the product, substitution of Ca(2+) for NH(4)(+) and the formation of calcium phosphate phases such as apatite and brushite by precipitation are thought to be the main sorption mechanisms.     

Parametric study of coiled carbon fibre synthesis on an in situ generated H2S-modified Ni/Al2O3 catalyst

Coiled carbon fibre (CCF) synthesis on an in situ generated H₂S-modified Ni/Al₂O₃ catalyst is investigated using a high-throughput reaction system that allows real time observation of weight changes. The influence of reduction and synthesis temperatures, reduction duration, H₂ addition during synthesis, synthesis duration, C₂H₂ concentration in the synthesis gas and catalyst loading are investigated and products are analysed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and thermogravimetric analysis. Thermodynamic equilibrium models of various experimental scenarios provide insight into the predominant species present at equilibrium. Reduction temperature and reduction duration affect H₂S concentration, a vital parameter for CCF synthesis, and CCFs form in only a narrow reduction and synthesis temperature range of 650 °C ± 50 °C with greatest coil yields observed at 650 °C and following reduction durations of between 1 and 20 min with greatest coil yields observed after a 10 min reduction. The presence of H₂ during synthesis was found to have a positive effect on CCF formation. The ratio of thick to thin carbon fibres increased with catalyst nickel loading and the greatest ratio of CCFs was produced with a 1:20 wt. Ni:Al₂O₃ catalyst.     

Chemical Synthesis and Gas Chromatographic Behaviour of γ‐Stearidonic (18:4n‐6) Acid

γ‐Stearidonic acid, 18:4n‐6, a potential product of β‐oxidation of arachidonic acid (20:4n‐6), was only recently positively identified in a living organism—a thermophilic cyanobacterium Tolypothrix sp., albeit at low levels, whilst some indirect evidence suggests its wider presence, e.g. in a unicellular marine alga. We have prepared 18:4n‐6 using an iodolactonisation chain‐shortening approach from 22:5n‐6 and obtained its ¹H‐, ¹³C‐, COSY‐ and HSQC NMR spectra, with 18:5n‐3 spectra also recorded for a comparison. The GC and GC‐MS behaviour of its methyl ester was also studied. Like another Δ3 polyunsaturated acid, octadecapentaenoic (18:5n‐3), 18:4n‐6 rapidly yields 2‐trans isomer upon formation of dimethyloxazoline derivative. On a polar ionic liquid phase (SLB‐IL100, 200 °C) the methyl ester could be mistaken for 18:3n‐3, while on methylsilicone phase (BP1, 210 °C) it eluted ahead of 18:3n‐6 and 18:4n‐3, suggesting that when present it may be easily misidentified during GC analysis of fatty acids.     

Change of Scene: The Geographic Dynamics of Resilience to Vehicular Accidents

Networks and Spatial Economics - Most have experienced the impact of vehicular accidents, whether it was in terms of increased commute time, delays in receiving goods, higher insurance premiums,...     

Synthesis of sodium and potassium aluminogermanate inorganic polymers

Synthesis of aluminogermanate inorganic polymers containing sodium as the charge-balancing ion was attempted by reacting NaAlO₂ solution with GeO₂ in an adaption of a sol-gel synthesis for aluminosilicate inorganic polymers. XRD and ²⁷Al MAS NMR suggested that only a small degree of reaction had occurred, based on the presence of unreacted GeO₂ and a trace of Na₃HGe₇O₁₆·4H₂O, with only a small amount of the tetrahedral aluminium characteristic of a true inorganic polymer. The addition of KOH markedly enhanced the reaction, producing a (Na,K) product with properties characteristic of a true inorganic polymer (an amorphous X-ray powder pattern and predominantly tetrahedral aluminium). An attempt to synthesise the potassium end-member aluminogermanate compound by replacement of the NaAlO₂ in the above synthesis with KAlO₂ produced only crystalline K(AlGeO₄)H₂O and K₃HGe₇O₁₆·4H₂O containing solely tetrahedral aluminium. Attempts to extend these syntheses to the gallium analogues of these aluminogermanate compounds were unsuccessful, producing only the crystalline products K(GaGeO₄)₆·7H₂O and K₃HGe₇O₁₆·4H₂O. Thus, the most successful sol-gel synthesis of a germanate compound with the properties of an inorganic polymer was of an aluminogermanate containing Na⁺ and K⁺ as the exchangeable cations.     

Optimisation of microwave-assisted acid digestion for the purification of supported carbon nanotubes

Experimental optimisation of microwave-assisted acid digestion for supported carbon nanotube (CNT) purification is reported. Process variables including ramp rate, temperature, duration, scalability, acid type, volume and concentration were investigated using thermogravimetric, Fourier transform infra-red and Raman spectroscopy performance metrics. Key factors in purification were temperature, duration and acid. HNO₃ damaged CNTs and introduced carboxyl and C–O functional groups. HCl and H₂SO₄ achieved similar impurity removal but, despite the incorporation of sulphur-based functional groups, H₂SO₄ was preferred due to a more homogeneous product. Concentration and volume variables could be condensed into a single factor – the stoichiometric excess of acid to impurities – for process simplification and to permit direct literature comparison. The scalable optimised process increased CNT purity from ∼22 wt% to > 95 wt% with negligible damage in a single 15 min isothermal treatment at 230 °C with a H₂SO₄ excess of 4.5 times the required stoichiometry (1 M).     

UK construction skills shortage response strategies and an analysis of industry perceptions

The construction industry is heavily dependent on the adequate supply of a skilled labour force, and as a result the skilled labour shortage in the UK has received considerable attention in recent years. With the current economic recovery the industry is expected to experience considerable skills shortages in both traditional and new skills areas. This paper analyses the views of construction employers in relation to the response strategies promoted by industry and government and identified in previous research which tackle elements of the skills shortage problem within the UK construction industry. The paper describes seven existing industry and government schemes, and a further nine alternative response strategies to the construction skills shortage. The survey analysis demonstrates that construction employers support: (i) the Construction Skills Certification Scheme, (ii) the Investors in People standard, (iii) economic stability within the industry; (iv) long term industry-wide training plans, (v) a return to direct employment; and (vi) the development of new technologies and construction techniques. It is concluded that the effectiveness of alternative response strategies is linked to the traditional approach of most contractors.     

Advancements in THM-Grown CdZnTe for Use as Substrates for HgCdTe

The focus of this work is to evaluate the suitability and substrate potential of Cd_0.9Zn_0.1Te and Cd_0.96Zn_0.04Te crystals grown by the traveling heater method (THM). THM-grown Cd_0.9Zn_0.1Te crystals used for gamma spectroscopy have shown very good spectral performance owing partly to the very low concentration of Te inclusions and precipitates. Inspection in the infrared (IR) of annealed THM-grown CdZnTe wafers reveals no inclusions >3 μm, and Fourier-transform infrared measurements show IR transmission values in excess of 60%. Wafer etch pit density values are typically less than 4 × 10^?4 pits/cm², and double-crystal x-ray rocking-curve measurements show full-width at half-maximum values approaching 40 arcsec. 〈211〉 wafers have been produced with off orientation within 0.3°. (111)-Oriented, seeded THM growth runs have the ability to provide 10 60 mm × 60 mm × 2 mm wafers from a 75-mm-diameter boule or 20 90 mm × 90 mm × 2 mm wafers from a 100-mm-diameter boule.     

Synthesis,characterisation and thermal behaviour of lithium aluminosilicate inorganic polymers

Lithium aluminosilicate inorganic polymers were synthesised from dehydroxylated kaolin-type clay (halloysite) by the conventional method under highly alkaline conditions with lithium hydroxide or lithium silicate solutions of two different Li₂O/SiO₂ molar ratios. Variants were also developed of a solid-state synthesis method involving the thermal reaction of dehydroxylated halloysite with LiOH followed by hydration of the product. The molar compositions of the materials prepared by all three methods (SiO₂/Al₂O₃ = 2.41–3.27, Li₂O/SiO₂ = 0.30–0.61, and H₂O/Li₂O = 9.33–10.40) fall within the range of compositions previously reported to produce viable geopolymers. Curing at 40 °C produces solid samples of varying viability depending on the amount of synthesis water. The cured materials are not characteristically X-ray amorphous, but contain the lithium zeolites Li-ABW and fibrous Li-EDI, the latter in the materials synthesised by solid-state reaction. The ²⁷Al and ²⁹Si MAS NMR spectra of the cured materials contain narrow resonances more characteristic of zeolites than of inorganic polymers. Heating the synthesised products at <800 °C produces β-eucryptite, LiAlSiO₄. In a further series of thermal reactions, β-spodumene, LiAlSi₂O₆ is formed at 900 °C, decomposing at 1100 °C to form additional β-eucryptite. At 1275 °C, β-spodumene reappears in the samples of higher silica content. Judicious manipulation of the composition and thermal treatment of the Li-zeolites formed in these lithium aluminosilicate syntheses could make them useful precursors to β-eucryptite and β-spodumene ceramics.     

Structure-based prediction of the stability of transmembrane helix-helix interactions: the sequence dependence of glycophorin A dimerization

The ability to predict the effects of point mutations on the interaction of alpha-helices within membranes would represent a significant step toward understanding the folding and stability of membrane proteins. We use structure-based empirical parameters representing steric clashes, favorable van der Waals interactions, and restrictions of side-chain rotamer freedom to explain the relative dimerization propensities of 105 hydrophobic single-point mutants of the glycophorin A (GpA) transmembrane domain. Although the structure at the dimer interface is critical to our model, changes in side-chain hydrophobicity are uncorrelated with dimer stability, indicating that the hydrophobic effect does not influence transmembrane helix-helix association. Our model provides insights into the compensatory effects of multiple mutations and shows that helix-helix interactions dominate the formation of specific structures.