Analysis of the microbial community structure and function of a laboratory scale enhanced biological phosphorus removal reactor

A laboratory scale sequencing batch reactor (SBR) operating for enhanced biological phosphorus removal (EBPR) and fed with a mixture of volatile fatty acids (VFAs) showed stable and efficient EBPR capacity over a four-year-period. Phosphorus (P), poly-beta-hydroxyalkanoate (PHA) and glycogen cycling consistent with classical anaerobic/aerobic EBPR were demonstrated with the order of anaerobic VFA uptake being propionate, acetate then butyrate. The SBR was operated without pH control and 63.67+/-13.86 mg P l(-1) was released anaerobically. The P% of the sludge fluctuated between 6% and 10% over the operating period (average of 8.04+/-1.31%). Four main morphological types of floc-forming bacteria were observed in the sludge during one year of in-tensive microscopic observation. Two of them were mainly responsible for anaerobic/aerobic P and PHA transformations. Fluorescence in situ hybridization (FISH) and post-FISH chemical staining for intracellular polyphosphate and PHA were used to determine that 'Candidatus Accumulibacter phosphatis' was the most abundant polyphosphate accumulating organism (PAO), forming large clusters of coccobacilli (1.0-1.5 mum) and comprising 53% of the sludge bacteria. Also by these methods, large coccobacillus-shaped gammaproteobacteria (2.5-3.5 mum) from a recently described novel cluster were glycogen-accumulating organisms (GAOs) comprising 13% of the bacteria. Tetrad-forming organisms (TFOs) consistent with the 'G bacterium' morphotype were alphaproteobacteria , but not Amaricoccus spp., and comprised 25% of all bacteria. According to chemical staining, TFOs were occasionally able to store PHA anaerobically and utilize it aerobically.

On the relation between ownership structure and capital structure

The agency relationship between managers and shareholders has the potential to influence decision-making in the firm which in turn potentially impacts on firm characteristics such as value and leverage. Prior evidence has demonstrated an association between ownership structure and firm value. This paper extends the literature by examining a further link between ownership structure and capital structure. Using an agency framework, it is argued that the distribution of equity ownership among corporate managers and external blockholders may have a significant relation with leverage. The empirical results provide support for a positive relation between external blockholders and leverage, and non-linear relation between the level of managerial share ownership and leverage. The results also suggest that the relation between external block ownership and leverage varies across the level of managerial share ownership. These results are consistent with active monitoring by blockholders, and the effects of convergence-of-interests and management entrenchment.

Quantum dynamics of spin polarized optoelectronic processes

We study the quantum dynamics of the emission of multimodal polarized light in light emitting devices (LED) due to spin polarized carriers injection. We present the equations for photon number and carrier numbers, and calculate the polarisation degree of the light generated by LED. (C) 2002 Elsevier Science B.V. All rights reserved.

Investigations into a power-combining structure using a reflect array of dual-feed aperture-coupled microstrip patch antennas

This paper details an investigation of a power combiner that uses a reflect array of dual-feed aperture-coupled microstrip patch antennas and a corporate-fed dual-polarized array as a signal distributing/combining device. In this configuration, elements of the reflect array receive a linearly polarized wave and retransmit it with an orthogonal polarization using variable-length sections of microstrip lines connecting receive and transmit ports. By applying appropriate lengths of these delay lines, the array focuses the transmitted wave onto the feed array. The operation of the combiner is investigated for a small-size circular reflect array for the cases of -3 dB, -6 dB and -10 dB edge illumination by the 2 x 2-element dual-polarized array.

The non-existence of a utility function and the structure of non-representable preference relations

In this paper we investigate the structure of non-representable preference relations. While there is a vast literature on different kinds of preference relations that can be represented by a real-valued utility function, very little is known or understood about preference relations that cannot be represented by a real-valued utility function. There has been no systematic analysis of the non-representation problem. In this paper we give a complete description of non-representable preference relations which are total preorders or chains. We introduce and study the properties of four classes of non-representable chains: long chains, planar chains, Aronszajn-like chains and Souslin chains. In the main theorem of the paper we prove that a chain is non-representable if and only it is a long chain, a planar chain, an Aronszajn-like chain or a Souslin chain. (C) 2002 Published by Elsevier Science B.V.

H-1 NMR study of the states of water in equilibrium Poly(HEMA-co-THFMA) hydrogels

The spin-spin relaxation times, T-2, of hydrated samples of poly(hydroxymethyl methacrylate), PHEMA, poly(tetrahydrofurfuryl methacrylate),PTHFMA, and the,corresponding HEMA-THFMA copolymers have been examined to probe the states of,the imbibed water in these polymers. The decay in the transverse magnetization of water. in fully hydrated samples of PHEMA, PTHFMA, and copolymers of HEMA and THFMA was described by a multiexponential function. The short component of T-2 was interpreted as water molecules that were strongly interacting with the polymer chains. The intermediate component of T-2 was assigned to water residing in the porous structure of the samples. The long component of T-2 was believed to arise from water residing in the remnants of cracks formed in the polymer network during water sorption.

Sub-structure syntheses and relative stereochemistry in the bistramide (bistratene) series of marine metabolites

The (6R*,9S*,11S*) and (22S*,23R*,27R*,31R*) stereochemistry, respectively, of the tetrahydropyranyl and spiroacetal moieties in bistramide A (1) have been established by stereoselective syntheses and high field NMR comparisons. Routes to the gamma-amino acid moiety are outlined. (C) 2002 Elsevier Science Ltd. All rights reserved.

Crystal structure of yeast acetohydroxyacid synthase: A target for herbicidal inhibitors

Acetohydroxyacid synthase (AHAS; EC 4.1.3.18) catalyzes the first step in branched-chain amino acid biosynthesis. The enzyme requires thiamin diphosphate and FAD for activity, but the latter is unexpected, because the reaction involves no oxidation or reduction. Due to its presence in plants, AHAS is a target for sulfonylurea and imidazolinone herbicides. Here, the crystal structure to 2.6 A resolution of the catalytic subunit of yeast AHAS is reported. The active site is located at the dimer interface and is near the proposed herbicide-binding site. The conformation of FAD and its position in the active site are defined. The structure of AHAS provides a starting point for the rational design of new herbicides. (C) 2002 Elsevier Science Ltd.

Interaction of temperature and vegetative flush maturity influences shoot structure and development of lychee (Litchi chinensis Sonn.)

Potted lychee trees (cv. Tai so) of varying vegetative flush maturity were grown under a range of temperature regimes and monitored for subsequent shoot structure and development. A combination of low temperature (15/17 or 18/13 degreesC day/night) and high vegetative flush maturity was necessary for floral initiation to occur, Exposure to high temperatures (28/23 degreesC) invariably resulted in the production of vegetative shoots, irrespective of flush maturity. Strong floral initiation was marked by the emergence of terminal particles and accompanying axillary particles. A decrea,;e in vegetative flush maturity or increase in temperature (e.g. 23/18 degreesC) resulted in a decrease in axillary shoot formation and the production of several intermediate shoot structures. These included leafy particles, stunted particles, partially emerged buds and non-emergent swollen buds, often produced on the same tree. At 23/18 degreesC, closer synchronisation of initial flush maturity was required for the production of a consistent shoot-type. Trees with synchronised mature flushes (I-2) at 23/18 degreesC resulted in the production of swollen terminal buds. Healthy trees were maintained in this state for at least 11 months. These results indicate that both temperature and flush maturity can influence subsequent shoot structure of lychee. In the absence of either a strong floral temperature (18/13 degreesC) or strong vegetative temperature (28/23 degreesC), slight differences in initial flush maturity have gteater impact on the type of emerging shoot formed. (C) 2002 Elsevier Science B.V. All rights reserved.

Reversible luminescence thermochromism in dipotassiumsodium tris[dicyanoargentate(I)] and the role of structural phase transitions

As a function of temperature, the layered compound K2Na[Ag(CN)213 displays dramatic variations in luminescence thermochromism with major trend changes occurring around 80 K. In order to understand these interesting optical properties, high-resolution neutron diffraction investigations were performed on a polycrystalline sample of this material in the temperature range from 1.5 to 300 K, and previous synchrotron X-ray data of Larochelle et al. (Solid State Commun. 114, 155 (2000)) were reinterpreted. The corresponding significant structural changes were found to be continuous with an anomalous increase of the monoclinic c-lattice parameter with decreasing temperature, associated with slight reorientations of two inequivalent, approximately linear N-C-Ag-C-N units. In the whole temperature range, the crystal structure is monoclinic with the space group C2/m. Based on the structural results, the major luminescence thermochromism changes around 80 K are attributed to the dominance of a back energy transfer process from low- to high-energy excitons at high temperatures. (E) 2002 Elsevier Science (USA).

Influence of nano-structure on electrolytic properties in CeO2 based system

Doped ceria (CeO2) compounds are fluorite type oxides that show oxygen ionic conductivity higher than yttria stabilized zirconia, in oxidizing atmosphere. In order to improve the conductivity, the effective index was suggested to maximize the oxygen ionic conductivity in doped CeO2 based oxides. In addition, the true microstructure of doped CeO2 was observed at atomic scale for conclusion of conduction mechanism. Doped CeO2 had small domains (10-50 nm) with ordered structure in a grain. It is found that the electrolytic properties strongly depended on the nano-structural feature at atomic scale in doped CeO2 electrolyte.

Dynamic Behavior of the Jahn-Teller distorted Cu(H2O)(6)(2+) ion in Cu2+ doped Cs-2[Zn(H2O)(6)](ZrF6)(2) and the crystal structure of the host lattice

The temperature dependence of the X- and Q-band EPR spectra of Cs-2[Zn(H2O)(6)](ZrF6)(2) containing similar to1% Cu2+ is reported. All three molecular g-values vary with temperature, and their behavior is interpreted using a model in which the potential surface of the Jahn-Teller distorted Cu(H2O)(6)(2+) ion is perturbed by an orthorhombic strain induced by interactions with the surrounding lattice. The strain parameters are significantly smaller than those reported previously for the Cu(H2O)(6)(2+) ion in similar lattices. The temperature dependence of the two higher g-values suggests that in the present compound the lattice interactions change slightly with temperature. The crystal structure of the Cs-2[Zn(H2O)(6)](ZrF6)(2) host is reported, and the geometry of the Zn(H2O)(6)(2+) ion is correlated with lattice strain parameters derived from the EPR spectrum of the guest Cu2+ complex.