THE INTERACTION BETWEEN UNBURNT HYDROCARBONS AND SOOT IN DIESEL EXHAUSTS

The potential health risk of diesel particulate (DP) has stimulated research into its physical and chemical composition. Its interaction with unburnt hydrocarbons (UHC) at exhaust temperatures was studied (i.e. composition and microstructure), at varying engine conditions. A hot whole exhaust filtration system was developed to collect DP on Pallflex TX-40 PTFE coated filters (for minimal artefact formation) down the exhaust of a Ricardo E6/T IDI diesel engine. Electron microscopy (SEM and TEM) and a gravimetric BET method determined particle size, specific surface area (SSA) and pore character. An in vacuo gravimetric thermal degassing (TD) apparatus was constructed to extract adsorbed volatiles (filter extractable sample - FES). The volatile FES was trapped and analysed by gas chromatography and identified as fuel and oil derived UHC's. Ultrasonic and soxhlet extraction techniques were employed for comparison studies. DP are graphitic carbonaceous aggregates of 30-40nm mean particle diameter. Structural analysis indicated that slit-shaped pores (Type II isotherm) were formed between crystallite layers. Highly adsorbed pore-bound FES fractions were identified (fuel i n ultramicropores, 0.355-lnm; fuel/oil in supermicropores, 1-2nm), trapped by overlapping crystallite van der Waal's fields. Engine load influenced micropore adsorption and DP SSA. High loads with high combustion temperatures, efficiently pyrolysed fuel, producing DP with little adsorbed FES and SSA's of 100m² /g. Low loads with lower in-cylinder temperatures, formed less DP and more fuel survived, producing soots of low SSA(<20m² /g). Between aggregated particles, 'ink-bottle' mesopores (2-50nm) were evident (Type IV isotherm) where fuel FES was weakly adsorbed by temperature dependent chemical scavenging as exhaust temperature declined , reducing SSA and increasing particle size. Thermal degassing was more efficient than soxhlet or ultrasonic extraction methods, because the solvent methods failed to penetrate the smallest pores. TD increased soot SSA, greatest for low load samples (by 200m²/g) compared to high load samples (by 50m² /g). TD was highly advantageous for DP extraction and allowed progressive removal of volatiles. A modern DI engine showed structurally similar soots, but the lower DP emissions produced high relative %FES for all engine conditions giving low SSA's. The research findings are related to cylinder and environmental processes for engineers and environmental scientists to improve control strategies.PERKINS TECHNOLOGY BUSINESS PETERBOROUGH CAMBRIDGESHIR

The literature of low g propellant behavior

Annotated bibliography on low-g liquid propellant behavio

Patronin-mediated minus end growth is required for dendritic microtubule polarity.

Microtubule minus ends are thought to be stable in cells. Surprisingly, in Drosophila and zebrafish neurons, we observed persistent minus end growth, with runs lasting over 10 min. In Drosophila, extended minus end growth depended on Patronin, and Patronin reduction disrupted dendritic minus-end-out polarity. In fly dendrites, microtubule nucleation sites localize at dendrite branch points. Therefore, we hypothesized minus end growth might be particularly important beyond branch points. Distal dendrites have mixed polarity, and reduction of Patronin lowered the number of minus-end-out microtubules. More strikingly, extra Patronin made terminal dendrites almost completely minus-end-out, indicating low Patronin normally limits minus-end-out microtubules. To determine whether minus end growth populated new dendrites with microtubules, we analyzed dendrite development and regeneration. Minus ends extended into growing dendrites in the presence of Patronin. In sum, our data suggest that Patronin facilitates sustained microtubule minus end growth, which is critical for populating dendrites with minus-end-out microtubules

Caracterización y origen de las dolomías del sector sudeste de Picos de Europa (Norte de España)

In this work we focus on the dolomitization processes which affected the southeastern sector of Picos de Europa Unit. The dolostones formed consequently with this process are rocks with a varied and irregular geometry, wich reminds that observed in intrusive rocks. Their chemical composition show a slight excess of calcium in relation to stoichiometric dolomite. Their iron and strontium contents are low in relation to other comparable dolomites. The abundance of dolostones is much bigger at the Frontal Unit than in upper structural Units. The dolomitization processes respond to an epigenetic dolomitization model and they are previous to the formation of Pb-Zn orebodies. We suggest a per ascensum dolomitization model tiggered by formation waters of the Pisuerga-Carrion Unit. With regard to age, the dolomitization was later than Lower Estephanian B and possibly earlier than some undetermined time during the Permian.En el presente trabajo se pone de manifiesto la existencia de un proceso de dolomitización que afectó al sector sudeste de la región de Picos de Europa. Las dolomías formadas como consecuencia de este proceso son rocas de geometría muy variada e irregular, que recuerda a la de las masas intrusivas. Su composición química muestra un ligero exceso en calcio respecto a la fórmula estequiométrica de la dolomita. Sus contenidos en hierro y estroncio son bajos respecto a los de otras dolomías comparables. El volumen de dolomías formado es mucho mayor en la Unidad Frontal de Picos de Europa que en Unidades estructurales superiores. Los procesos dolomitizadores obedecen a un modelo de dolomitización epigenético y son previos a la deposición de mineralizaciones de Pb-Zn. Se propone un modelo de dolomitización per ascensum a partir de aguas de formación de los sedimentos de la región de Pisuerga-Carrión. En cuanto a la edad, la dolomitización es posterior al Estefaniense B inferior y posiblemente anterior a un momento del Pérmico no determinado