Stoichiometric and kinetic characterisation of Nitrobacter in mixed culture by decoupling the growth and energy generation processes

The growth, maintenance and lysis processes of Nitrobacter were characterised. A Nitrobacter culture was enriched in a sequencing batch reactor (SBR). Fluorescent in situ hybridisation showed that Nitrobacter constituted 73% of the bacterial population. Batch tests were carried out to measure the oxygen uptake rate and/or nitrite consumption rate when both nitrite and CO2 were in excess, and in the absence of either of these two substrates. The results obtained, along with the SBR performance data, allowed the determination of the maintenance coefficient and in situ cell lysis rate of Nitrobacter. Nitrobacter spends a significant amount of energy for maintenance, which varies considerably with the specific growth rate. At maximum growth, Nitrobacter consume nitrite at a rate of 0.042 mgN/mgCOD(biomass)center dot h for maintenance purposes, which increases more than threefold to 0.143 mgN/mgCOD(biomass)center dot h in the absence of growth. In the SBR, where Nitrobacter grew at 40% of its maximum growth rate, a maintenance coefficient of 0.113 mgN/mgCOD center dot h was found, resulting in 42% of the total amount of nitrite being consumed for maintenance. The above three maintenance coefficient values obtained at different growth rates appear to support the maintenance model proposed in Pirt (1982). The in situ lysis rate of Nitrobacter was determined to be 0.07/day under aerobic conditions at 22 C and pH 7.3. Further, the maximum specific growth rate of Nitrobacter was estimated to be 0.02/h (0.48/day). The affinity constant of Nitrobacter with respect to nitrite was determined to be 1.50 mgNO(2)(-)-N/L, independent of the presence or absence of CO2. (c) 2006 Wiley Periodicals, Inc.

Synthesis and characterization of Pd(II) and Pt(II) complexes with triazolopyrimidine derivatives: The crystal structure of [Pd2L2Cl4] where L=5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L-1 (5,7-dimethyl-3-(2',3',5'-tri-O-benzoyl-beta-D-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L-2 (5,7-dimethyl-3-beta-D-ribofuranosyl-s-triazolo [4,3-a]pyrimidine) and L-3 (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L-1)](NO3)(2), (Pd(bpy)(L-1)](NO3)(2), cis-Pd(L-3)(2)Cl-2, [Pd-2(L-3)(2)Cl-4]center dot H2O, cis-Pd(L-2)(2)Cl-2 and [Pt-3(L-1)(2)Cl-6] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd-2(L-3)(2)Cl-4]center dot H2O complex was established by Xray crystallography. The two L-3 ligands are found in a head to tail orientation, with a (PdPd)-Pd-... distance of 3.1254(17) angstrom.L-1 coordinates to Pd(II) through N8 and N1 forming polymeric structures. L-2 coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L-2 does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond. (c) 2006 Elsevier B.V. All rights reserved.

Synthesis and spectroscopic observation of dendrimer-encapsulated gold nanoclusters

We report on the observation of the excitation/ emission spectrum of a dendrimer-encapsulated gold nanocluster; the synthesis of Au-PAMAM was based on reduction of HAuCl4 center dot 3H(2)O co-dissolved in methanol together with fourth-generation OH-terminated PAMAM.

The inhibitory effects of free nitrous acid on the energy generation and growth processes of an enriched Nitrobacter culture

The inhibitory effects of nitrite (NO2-)/free nitrous acid (HNO2-FNA) on the metabolism of Nitrobacter were investigated using a method allowing the decoupling of the growth and energy generation processes. A lab-scale sequencing batch reactor was operated for the enrichment of a Nitrobacter culture. Fluorescent in situ hybridization (FISH) analysis showed that 73% of the bacterial population was Nitrobacter. Batch tests were carried out to assess the oxygen and nitrite consumption rates of the enriched culture at low and high nitrite levels, in the presence or absence of inorganic carbon. It was observed that in the absence of CO2, the Nitrobacter culture was able to oxidize nitrite at a rate that is 76% of that in the presence of CO2, with an oxygen consumption rate that is 85% of that measured in the presence of CO2. This enabled the impacts of nitrite/FNA on the catabolic and anabolic processes of Nitrobacter to be assessed separately. FNA rather than nitrite was likely the actual inhibitor to the Nitrobacter metabolism. It was revealed that FNA of up to 0.05 mg HNO2-N center dot L-1 (3.4 mu M), which was the highest FNA concentration used in this study, did not have any inhibitory effect on the catabolic processes of Nitrobacter. However, FNA initiated its inhibition to the anabolic processes of Nitrobacter at approximately 0.011 mg HNO2-N center dot L-1 (0.8 mu M), and completely stopped biomass synthesis at a concentration of approximately 0.023 mg HNO2-N center dot L-1 (1.6 mu M). The inhibitory effect could be described by an empirical inhibitory model proposed in this paper, but the underlying mechanisms remain to be revealed.

Topical interferon alfa-2b for the treatment of recalcitrant ocular surface squamous neoplasia

center dot PURPOSE: To evaluate topical interferon alfa-2b (IFN-alpha 2b) for the treatment of recalcitrant ocular surface squamous neoplasia (OSSN). center dot DESIGN: Prospective, noncomparative, interventional consecutive case series. center dot METHODS: Ten patients with recalcitrant OSSN were treated with topical IFN-alpha 2b (1 million IU/ml) four times a day until clinical resolution of the lesion or until the lesion appeared nonresponsive-that is, treatment failure. Progress was assessed by clinical examination and photographic records, with a minimum follow,up of six months. center dot RESULTS: Eight of 10 patients achieved clinical resolution from topical IFN-alpha 2b treatment. One patient developed invasive squamous cell carcinoma and underwent exenteration. The other patient required further mitomycin C therapy to achieve clinical resolution. The mean duration to clinical resolution for the eight patients treated with IFN-alpha 2b was 21.9 weeks (range six to 59 weeks). There have been no recurrences for any of the nine patients during follow-up (mean 55.0 weeks; range 26 to 84 weeks). center dot CONCLUSIONS: Topical IFN-alpha 2b is an important treatment modality for recalcitrant OSSN; it avoids the risks of further limbal stem cell destruction from other agents and surgical excision. If invasive disease is diagnosed at any stage, topical therapy is contraindicated, necessitating surgical excision. (Am J Ophthalmol 2006; 142:568-571. (c) 2006 by Elsevier Inc. All rights reserved.)

In-vitro study of the spontaneous calcification of PHEMA-based hydrogels in simulated body fluid

In-vitro calcification of poly(2-hydroxyethyl methacrylate) (PHEMA)-based hydrogels in simulated body fluid (SBF) under a steady/batch system without agitation or stirring the solutions has been investigated. It was noted that the formation of calcium phosphate (CaP) deposits primarily proceeded through spontaneous precipitation. The CaP deposits were found both on the surface and inside the hydrogels. It appears that the effect of chemical structure or reducing the relative number of oxygen atoms in the copolymers on the degree of calcification was only important at the early stage of calcification. The morphology of the CaP deposits was observed to be spherical aggregates with a thickness of the CaP layer less than 0.5 mu m. Additionally, the CaP deposits were found to be poorly crystalline or to have nano-size crystals, or to exist mostly as an amorphous phase. Characterization of the CaP phases in the deposits revealed that the deposits were comprised mainly of whitlockite [Ca9MgH(PO4)(7)] type apatite and DCPD (CaHPO4 center dot 2H(2)O) as the precursors of hydroxyapatite [Ca-10(PO4)(6)(OH)(2)]. The presence of carbonate in the deposits was also detected during the calcification of PHEMA based hydrogels in SBF solution.

Cobalt complexes of tripodal hexadentate ligands: Electrochemically driven rearrangements

The Co-III complexes of the hexadentate tripodal ligands HOsen (3-(2'-aminoethylamino)-2,2-bis((2 ''-aminoethylamino) methyl) propan-1-ol) and HOten (3-(2'-aminoethylthia)-2,2-bis((2 ''-aminoethylthia) methyl) propan-1-ol) have been synthesized and fully characterized. The crystal structures of [Co(HOsen)]Cl-3 center dot H2O and [Co(HOten)](ClO4)Cl-2 are reported and in both cases the ligands coordinate as tripodal hexadentate N-6 and N3S3 donors, respectively. Cyclic voltammetry of the N3S3 coordinated complex [Co(HOten)](3+) is complicated and electrode dependent. On a Pt working electrode an irreversible Co-III/II couple ( formal potential - 157 mV versus Ag-AgCl) is seen, which is indicative of dissociation of the divalent complex formed at the electrode. The free HOten released by the dissociation of [Co(HOten)](2+) can be recaptured by Hg as shown by cyclic voltammetry experiments on a static Hg drop electrode ( or in the presence of Hg2+ ions), which leads to the formation of an electroactive Hg-II complex of the N3S3 ligand (formal potential + 60 mV versus Ag-AgCl). This behaviour is in contrast to the facile and totally reversible voltammetry of the hexaamine complex [Co(HOsen)](3+) ( formal potential (Co-III/II) - 519 mV versus Ag-AgCl), which is uncomplicated by any coupled chemical reactions. Akinetic and thermodynamic analysis of the [Co(HOten)](2+)/[Hg(HOten)](2+) system is presented on the basis of digital simulation of the experimental voltammetric data.

Preparation and electrochemical properties of the layered material of LixVyO2 (x=0.86 and y=0.8)

Layered lithium-vanadium oxide with a composition of LixVyO2 (x = 0.86 and y = 0.8) was prepared by the hydrothermal reaction of V2O3 with LiOH center dot H2O at 180 degrees C. This material corresponds to a layered rhombohedral structure related to alpha-NaFeO2 in which the vanadium ions are disordered in alternate layers of octahedral 3a (0, 0, 0) and 3b (0, 0, 1/2) sites. The electrochemical properties of this Li0.86V0.8O2 material were investigated and compared with those of the layered Li0.96VO2 made by the conventional solid-state reaction. It was found that the electrochemical capacity and reversibility of the Li0.86V0.8O2 material are significantly improved compared to those of the Li0.96VO2 material; the reversible specific capacities of the Li/Li0.86V0.8O2 and Li/Li0.96VO2 systems are similar to 100 and similar to 50 mAh g(-1), respectively, under the current densities of 7.14 mA g(-1) over 20 charge-discharge cycles with a potential window of 1.50-4.50 V. Such a reversibility results from the structural stability of Li0.86V0.8O2, whereas the increase in the reversible specific capacity can be qualitatively interpreted in terms of the presence of vanadium vacancies in the structure. (c) 2005 The Electrochemical Society.

Formation and growth mechanism of tungsten oxide microtubules

Tungsten oxide microtubules, arrayed in a radial flower-like structure, were synthesized by simply using W powders reacting with Ni(NO3)(2) center dot 6H(2)O at a elevated temperature. The formed microtubules, with lengths more than 100 pin and outer diameters of 1-5 mu m, have irregular open ends, showing clear grooves along the growth direction on the tubule surface. A novel aggregation mechanism based on chemical-vapor-deposit process was proposed to describe the growth process of the synthesized tubules, and the possible mechanism for the arrangement of the radial flower-like morphology was discussed.

Interference pattern with a dark center from two atoms driven by a coherent laser field

In a recent paper Meyer and Yeoman [Phys. Rev. Lett. 79, 2650 (1997)] have shown that the resonance fluorescence from two atoms placed in a cavity and driven by an incoherent field can produce an interference pattern with a dark center. We study the fluorescence from two coherently driven atoms in free space and show that this system can also produce an interference pattern with a dark center. This happens when the atoms are in nonequivalent positions in the driving: field, i.e., the atoms experience different intensities and phases of the driving field. We discuss the role of the interatomic interactions in this process and find that the interference pattern with a dark center results from the participation of the antisymmetric state in the dynamics of the driven two-atom system.

Interference pattern with a dark center in resonance fluorescence from two atoms driven by a squeezed vacuum field

We study the resonance fluorescence from two interacting atoms driven by a squeezed vacuum field and show that this system produces an interference pattern with a dark center. We discuss the role of the interatomic interactions in this process and find that the interference pattern results from an unequal population of the symmetric and antisymmetric states of the two-atom system. We also identify intrinsically nonclassical effects versus classical squeezed field effects, (C) 1998 Elsevier Science B.V. All rights reserved.

A new approach to current and noise in double quantum dot systems

We use a quantum master equation to describe transport in double-dot devices. The coherent dot-to-dot coupling affects the noise spectra strongly. For phonon-assisted tunneling, the calculated current spectra are consistent with those of experiments. The model shows that quantum stochastic theory may he applied to some advantage in mesoscopic electronic systems. (C) 2000 Elsevier Science B.V. All rights reserved.

Content and context of monocular regions determine perceived depth in random dot, unpaired background and phantom stereograms

Perceived depth was measured for three-types of stereograms with the colour/texture of half-occluded (monocular) regions either similar to or dissimilar to that of binocular regions or background. In a two-panel random dot stereogram the monocular region was filled with texture either similar or different to the far panel or left blank. In unpaired background stereograms the monocular region either matched the background or was different in colour or texture and in phantom stereograms the monocular region matched the partially occluded object or was a different colour or texture. In all three cases depth was considerably impaired when the monocular texture did not match either the background or the more distant surface. The content and context of monocular regions as well as their position are important in determining their role as occlusion cues and thus in three-dimensional layout. We compare coincidence and accidental view accounts of these effects. (C) 2002 Elsevier Science Ltd. All rights reserved.