Kinetic studies of the hydrolysis and condensation of tetraethylorthosilicate (TEOS) during the formation of uniform silica particles were performed through determining concentrations of TEOS and silicic acid by means of gas chromatography and a conductometer, respectively. It was shown that both hydrolysis of TEOS and condensation of Si(OH)4 are first order with TEOS and Si(OH)4, respectively, and the relationships of the hydrolysis and condensation rate constants with reaction condition variables, such as temperature, NH3 concentration, and H2O concentration, were determined. In addition, the particle growth rate was investigated with relation to the hydrolysis and condensation kinetics. Experiments showed that, during most of the reaction, the amount of formed particles is less than that of consumed TEOS, indicating that reaction intermediates exist during the process of silica formation. In the early stages of the Stöber process, the reaction intermediates include silicic acid and subparticles, while in the case of seed growth experiments without the formation of new particles or after the early stages of Stöber process, the reaction intermediates primarily consist of silicic acid and the growth rate of silica equals the rate of silicic acid condensation.

Abstract. The grass genetic model Brachypodium (Brachypodium distachyon (L.) Beauv., sequenced line Bd 21) was studied from germination to seed production to assess its potential as a phenotypic model for wheat (Triticum aestivum L.) and other cereal crops. Brachypodium and wheat shoot and root development and anatomy were highly similar. Main stem leaves and tillers (side shoots) emerged at the same time in both grasses in four temperature and light environments. Both developed primary and nodal axile roots at similar leaf stages with the same number and arrangement of vascular xylem tracheary elements (XTEs). Brachypodium, unlike wheat, had an elongated a mesocotyl above the seed and developed only one fine primary axile root from the base of the embryo, while wheat generally has three to five. Roots of both grasses could develop first, second and third order branches that emerged from phloem poles. Both developed up to two nodal axile roots from the coleoptile node at leaf 3, more than eight nodal axile roots from stem nodes after leaf 4, and most (97%) of the deepest roots at flowering were branches. In long days Brachypodium flowered 30 days after emergence, and root systems ceased descent 42 cm from the soil surface, such that mature roots can be studied readily in much smaller soil volumes than wheat. Brachypodium has the overwhelming advantage of a small size, fast life cycle and small genome, and is an excellent model to study cereal root system genetics and function, as well as genes for resource partitioning in whole plants.

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SiO2 opals of higher quality can be achieved by a procedure involving the stricter selection of SiO2 spheres. Monodispersity of the spheres is one of the major factors for obtaining opals with interesting optical properties and large size. In addition, the infiltration process of TiO2 into SiO2 opal in order to form inverse opal structures (see Figure) is discussed.

Titania coating on monodisperse silica spheres was carried out with a multistep method using titanium n-butoxide. Titania-coated silica spheres were characterized with transmission electron microscopy and energy-dispersive X-ray flourescence spectroscopy. Electrophoretic properties and size distributions of the particles were also measured. Starting from monodisperse silica spheres of 550 nm in mean diameter, the thickness of titania coatings achieved with five coating steps was up to 46 nm, or 125 monolayers of titania, equivalent to a titania weight loading of 54.7 wt %. The uniformity of the titania coating was confirmed by the precise agreement in the electrokinetic mobility of the resulting spheres with that of bulk titania particles. High monodispersity was maintained with a relative standard deviation in diameter of less than 5%. The aggregation extent of the coated spheres was only increased slightly from 11.8% for the silica spheres to 17.2% after three steps of titania coating.

We propose two schemes for the generation of the cluster states. One is based on cavity quantum electrodynamics (QED) techniques. The scheme only requires resonant interactions between two atoms and a singlemode cavity. The interaction time is very short, which is important in view of decoherence. Furthermore, we also discuss the cavity decay and atomic spontaneous emission case. The other is based on atomic ensembles. The scheme has inherent fault tolerance function and is robust to realistic noise and imperfections. All the facilities used in our schemes are well within the current technology.

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