Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

Upon photolysis at 355 nm, dioxygen is released from a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)cobalt-(III)] complex in aqueous solutions and at physiological pH with a quantum yield of 0.04. The [Co(bpy)2(H2O)2]2+ (bpy = bipyridyl) photoproduct was generated on a nanosecond or faster time scale as determined by time-resolved optical absorption spectroscopy. A linear correspondence between the spectral changes and the oxygen production indicates that O2 is released on the same time scale. Oxyhemoglobin was formed from deoxyhemoglobin upon photodissociation of the (mu-peroxo) (mu-hydroxo)bis[bis(bipyridyl)cobalt(III)] complex, verifying that dioxygen is a primary photoproduct. This complex and other related compounds provide a method to study fast biological reactions involving O2, such as the reduction of dioxygen to water by cytochrome oxidase.

Hypoxia-inducible factor 1 is a basic-helix-loop-helix-PAS heterodimer regulated by cellular O2 tension.

Hypoxia-inducible factor 1 (HIF-1) is found in mammalian cells cultured under reduced O2 tension and is necessary for transcriptional activation mediated by the erythropoietin gene enhancer in hypoxic cells. We show that both HIF-1 subunits are basic-helix-loop-helix proteins containing a PAS domain, defined by its presence in the Drosophila Per and Sim proteins and in the mammalian ARNT and AHR proteins. HIF-1 alpha is most closely related to Sim. HIF-1 beta is a series of ARNT gene products, which can thus heterodimerize with either HIF-1 alpha or AHR. HIF-1 alpha and HIF-1 beta (ARNT) RNA and protein levels were induced in cells exposed to 1% O2 and decayed rapidly upon return of the cells to 20% O2, consistent with the role of HIF-1 as a mediator of transcriptional responses to hypoxia.

Evaluation of hectorites, synthesized in different conditions, as soot combustion catalysts after impregnation with copper

Two microporous hectorites were prepared by conventional and microwave heating, and a delaminated mesoporous hectorite by an ultrasound-assisted synthesis. These three hectorites were impregnated with copper. The characterization techniques used were XRD, N2 adsorption, TEM and H2 reduction after selective surface copper oxidation by N2O (to determine copper dispersion). The catalytic activity for soot combustion of the copper-free and the copper-containing hectorites was tested under a gas mixture of 500 ppm NOx/5% O2/N2 (and 5% O2/N2 in some cases), evaluating their stability through three consecutive soot combustion experiments. The delaminated hectorite showed the highest surface area (353 m2/g) allowing the highest dispersion of copper. This copper-containing catalyst was the most active for soot combustion among those prepared and tested in this study. We have also concluded that the Cu/hectorite-catalyzed soot combustion mechanism is based on the activation of the O2 molecule and not on the NO2-assisted soot combustion.

NOx storage and reduction over copper-based catalysts. Part 2: Ce0.8M0.2O�� supports (M = Zr, La, Ce, Pr or Nd)

5% copper catalysts with Ce0.8M0.2O�� supports (M = Zr, La, Ce, Pr or Nd) have been studied by rapid-scan operando DRIFTS for NOx Storage and Reduction (NSR) with high frequency (30 s) CO, H2 and 50%CO + 50%H2 micropulses. In the absence of reductant pulses, below 200���250 ��C NOx was stored on the catalysts as nitrite and nitro groups, and above this temperature nitrates were the main species identified. The thermal stability of the NOx species stored on the catalysts depended on the acid/basic character of the dopant (M more acidic = NOx stored less stable ��� Zr4+ < none < Nd3+ < Pr3+ < La3+ ��� M more basic = NOx stored more stable). Catalysts regeneration was more efficient with H2 than with CO, and the CO + H2 mixture presented an intermediate behavior, but with smaller differences among the series of catalyst than observed using CO alone. N2 is the main NOx reduction product upon H2 regeneration. The highest NOx removal in NSR experiments performed at 400 ��C with CO + H2 pulses was achieved with the catalyst with the most basic dopant (CuO/Ce0.8La0.2O��) while the poorest performing catalyst was that with the most acidic dopant (CuO/Ce0.8Zr0.2O��). The poor performance of CuO/Ce0.8Zr0.2O�� in NSR experiments with CO pulses was attributed to its lower oxidation capacity compared to the other catalysts.

Valutazione sperimentale degli effetti della pressione d'iniezione dell'AdBlue sull'efficienza di abbattimento degli NOx nei sistemi SCR

In questo lavoro vengono indagati i benefici dell���aumento della pressione d���iniezione dell���AdBlue nei sistemi SCR. Dopo aver esposto le ipotesi teoriche a supporto della tesi, si passa all���allestimento del veicolo dimostrativo impiegato per l���attivit�� sperimentale. In questa fase viene illustrato tutto il processo di preparazione, che comprende: la messa a punto del circuito idraulico, la caratterizzazione degli iniettori impiegati, la strumentazione della linea di scarico, e il software INCA impiegato per il comando delle centraline. Dopodich�� vengono descritti nel dettaglio i test, condotti con il veicolo sperimentale, sul banco a rulli. Attraverso le prove, eseguite su due differenti punti motore, si �� potuto dimostrare l���effettivo aumento di efficienza di abbattimento degli NOx, da parte del sistema SCR, all���aumentare della pressione d���iniezione dell���AdBlue. Inoltre si hanno effetti positivi anche in merito al fenomeno dell���ammonia slip, che viene sensibilmente ridotto ai livelli di pressione pi�� alti.

Sourcebook, NOx control technology data /

Mode of access: Internet.

Effects of coal-bound chlorine on furnace-wall corrosion under low-NOx conditions /

"5/02"--Colophon.

Application of nox-restriction fragment length polymorphism for the differentiation of Brachyspira intestinal spirochetes isolated from pigs and poultry in Australia

Sixty-nine intestinal spirochetes isolated from pigs and poultry in eastern Australia were selected to evaluate the effectiveness of a species-specific PCR-based restriction fragment length polymorphism (RFLP) analysis of the Brachyspira nox gene. For comparative purposes, all isolates were subjected to species-specific PCRs for the pathogenic species Brachyspira hyodysenteriae and Brachyspira pilosicoli, and selected isolates were examined further by sequence analysis of the nox and 16S ribosomal RNA genes. Modifications to the original nox-RFLP method included direct inoculation of bacterial cells into the amplification mixture and purification of the PCR product, which further optimized the nox-RFLP for use in a veterinary diagnostic laboratory, producing sufficient product for both species identification and future comparisons. Although some novel profiles that prevented definitive identification were observed, the nox-RFLP method successfully classified 45 of 51 (88%) porcine and 15 of 18 (83%) avian isolates into 5 of the 6 recognized species of Brachyspira. This protocol represents a significant improvement over conventional methods currently used in veterinary diagnostic laboratories for rapid specific identification of Brachyspira spp. isolated from both pigs and poultry.