Effect of thermal treatment on the growth,structure and luminescence of nitride-passivated silicon nanoclusters

Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L_3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra.     

Experimental validation of polyhedral discrete element model

The flow of polyhedral granular particles in a small 3D slice hopper is studied experimentally and computationally by applying the discrete element method (DEM). A high speed camera was used to obtain the experimental results. The experimental packing structure, flow behaviour, arching and discharging in the hopper are analysed and compared with the DEM results for three hopper half angles. Reasonable agreement is shown on the static packing, flow behaviour and hopper discharge rates. The critical orifice length at which flow ceases to be smooth is investigated and arching of the material around the orifice is demonstrated experimentally and computationally. Spherical particles of nearly identical volume and density to the average of the polyhedral particles are also tested and compared to the polyhedra. The DEM is shown to be reasonably adept at modelling the interactions between polyhedral particles in a system in which there are very many possible particle geometrical interactions. Further work should consider the cohesion between the particles and the particle and the wall. Simulations of a greater number of particles in different hopper geometries should also be explored.     

Syntheses of Ring C Oxysterols: Inhibitors of Sterol Biosynthesis

Oxygenated derivates of cholesterol and lanosterol, known as oxysterols, have consistently displayed significant activity as inhibitors of 3-hydroxy-3-methylglutaryl (HMG) CoA reductase, a key regulatory enzyme in sterol biosynthesis. We have developed the chemical syntheses of ring C oxysterols for evaluation as inhibitors of sterol biosynthesis. A key intermediate in the chemical synthesis was 3beta-benzoyloxy-9alpha, 1alpha-epoxy-5alpha-cholest-7-ene (1), whose structure was confirmed by X-ray crystallographic analysis and is presented herein.     

Evaluation of the Interaction between Phosphohistidine Analogues and Phosphotyrosine Binding Domains

We have investigated the interaction of peptides containing phosphohistidine analogues and their homologues with the prototypical phosphotyrosine binding SH2 domain from the eukaryotic cell signalling protein Grb2 by using a combination of isothermal titration calorimetry and a fluorescence anisotropy competition assay. These investigations demonstrated that the triazole class of phosphohistidine analogues are capable of binding too, suggesting that phosphohistidine could potentially be detected by this class of proteins in vivo.     

Homology modelling of two subtilisin-like proteases from the hyperthermophilic archaea Pyrococcus furiosus and Thermococcus stetteri

The hyperthermophilic archaeon Pyrococcus furiosus produces an extracellular, glycosylated hyperthermostable subtilisin-like serine protease, termed pyrolysin (Voorhorst,W.G.B., Eggen,R.I.L., Geerling,A.C.M., Platteeuw,C., Siezen,R.J. and de Vos,W.M. (1996) J. Biol. Chem., 271, 20426-20431). Based on the pyrolysin coding sequence, a pyrolysin-like gene fragment was cloned and characterized from the extreme thermophilic archaeon Thermococcus stetteri. Like pyrolysin, the deduced sequence of this serine protease, designated stetterlysin, contains a catalytic domain with high homology with other subtilases, allowing homology modelling starting from known crystal structures. Comparison of the predicted three-dimensional models of the catalytic domain of stetterlysin and pyrolysin with the crystal structure of subtilases from mesophilic and thermophilic origin, i.e. subtilisin BPN' and thermitase, and the homology model of subtilisin S41 from psychrophilic origin, led to the identification of features that could be related to protein stabilization. Higher thermostability was found to be correlated with an increased number of residues involved in pairs and networks of charge-charge and aromatic-aromatic interactions. These highly thermostable proteases have several extra surface loops and inserts with a relatively high frequency of aromatic residues and Asn residues. The latter are often present in putative N-glycosylation sites. Results from modelling of known substrates in the substrate- binding region support the broad substrate range and the autocatalytic activation previously suggested for pyrolysin.      

Calculated and measured outdoor UV doses

The ultraviolet (UV) radiation dose received by a sample is often the determining factor in its outdoor weathering lifetime. However, little relevant data exist for UV doses except for certain standard locations and orientations such as for the commercial test sites in Florida and Arizona. We have modified a computer program by Jokela based on other atmospheric radiation models in the literature to calculate UV doses for any latitude and orientation relative to standard exposure in Florida and have used the fraction of sunshine data for various sites that are readily available from meteorlogical compendia to correct for cloudiness. The usefulness of the calculations have been substantiated by examining the amount of yellowing in unstabilized polycarbonate films exposed at several orientations at six sites in the northern hemisphere. The calculations and doses inferred from the yellowing data are in generally good agreement, although there is increased error in highly cloudy regions and for the northerly exposures.     

Composition of Chemical Attractants Affects Trap Catches of the Australian Sheep Blowfly, Lucilia cuprina, and Other Blowflies

Numbers of Lucilia cuprina (Australian sheep blowfly), Chrysomya spp., and Calliphora spp. blowflies caught on sticky traps baited with various synthetic attractants or a standard liver/sodium sulfide attractant in western Queensland were recorded. Numbers of each genus collected were influenced by the composition of the chemical attractants. Attractant mixtures based on 2-mercaptoethanol, indole, butanoic/pentanoic acid, and a sodium sulfide solution gave 5- to 20-fold higher L. cuprina catches than the liver standard. These blends attracted similar numbers of Chrysomya spp. (0.85-2.7x) and fewer Calliphora spp. (0.02-0.2x) compared to the liver standard. These synthetic attractants were more effective and selective for L. cuprina than the standard liver/sodium sulfide attractant, and they can be packaged in controlled-release dispensers to generate constant, prolonged release of the attractant.     

Comparative Analysis of Synthetic Natural Gas versus Hydrogen Production from Bagasse

A rigorous and comparative evaluation of two biomass‐to‐gases (BtG) conversion routes was performed and, according to this outcome, it is suggested which of the options evaluated is most desirable. These options, the hydrogen and synthetic natural gas (SNG) production, were designed in Aspen Plus process simulation software. Sugar cane bagasse was considered as feedstock. Mass and energy balance data were extracted from the simulations, and consequently thermodynamic (exergy analysis), economic (financial and uncertainty analysis), and environmental (CO₂ emissions) evaluations were carried out. Exergy and environmental analysis favor the SNG production while the hydrogen route provides higher profits.     

Stepwise optimisation of enzyme production in solid state fermentation of waste bread pieces

When it is not consumed, bread presents a major source of food waste, both in terms of the amount and its economic value. However, bread also possesses the characteristics of an ideal substrate for solid state fermentation. Yet nearly all wasted bread ends up in landfill sites, where it is converted into methane by anaerobic digestion. Governments are finally taking action and, according to the EU Landfill Directive, for example, biodegradable municipal waste disposed into landfills must be decreased to 35% of 1995 levels, by 2020. Solid state fermentation of waste bread for the production of value added products is a novel idea, which could help with the achievement of this target. In this study, glucoamylase and protease production from waste bread pieces, via solid state fermentation, was investigated in detail. The optimum fermentation conditions for enzyme production were evaluated as, 20 mm particle size, 1.8 (w/w, db) initial moisture ratio, and duration of 144 h. Under these conditions, glucoamylase and protease activities reached up to 114.0 and 83.2 U/g bread (db), respectively. This study confirms that waste bread could be successfully utilised as a primary raw material in cereal based biorefineries.