Seismic attenuation due to wave-induced fluid flow at microscopic and macroscopic scales

Wave-induced fluid flow at microscopic and mesoscopic scales arguably constitutes the major cause of intrinsic seismic attenuation throughout the exploration seismic and sonic frequency ranges. The quantitative analysis of these phenomena is, however, complicated by the fact that the governing physical processes may be dependent. The reason for this is that the presence of microscopic heterogeneities, such as micro-cracks or broken grain contacts, causes the stiffness of the so-called modified dry frame to be complex-valued and frequency-dependent, which in turn may affect the viscoelastic behaviour in response to fluid flow at mesoscopic scales. In this work, we propose a simple but effective procedure to estimate the seismic attenuation and velocity dispersion behaviour associated with wave-induced fluid flow due to both microscopic and mesoscopic heterogeneities and discuss the results obtained for a range of pertinent scenarios.

Roles of multiple acyl-CoA oxidases in the routing of carbon flow towards β-oxidation and polyhydroxyalkanoate biosynthesis in Yarrowia lipolytica.

The oleaginous yeast Yarrowia lipolytica possesses six acyl-CoA oxidase (Aox) isoenzymes encoded by genes POX1-POX6. The respective roles of these multiple Aox isoenzymes were studied in recombinant Y. lipolytica strains that express heterologous polyhydroxyalkanoate (PHA) synthase (phaC) of Pseudomonas aeruginosa in varying POX genetic backgrounds, thus allowing assessment of the impact of specific Aox enzymes on the routing of carbon flow to β-oxidation or to PHA biosynthesis. Analysis of PHA production yields during growth on fatty acids with different chain lengths has revealed that the POX genotype significantly affects the PHA levels, but not the monomer composition of PHA. Aox3p function was found to be responsible for 90% and 75% of the total PHA produced from either C9:0 or C13:0 fatty acid, respectively, whereas Aox5p encodes the main Aox involved in the biosynthesis of 70% of PHA from C9:0 fatty acid. Other Aoxs, such as Aox1p, Aox2p, Aox4p and Aox6p, were not found to play a significant role in PHA biosynthesis, independent of the chain length of the fatty acid used. Finally, three known models of β-oxidation are discussed and it is shown that a 'leaky-hose pipe model' of the cycle can be applied to Y. lipolytica.

Properties of debris flow deposits and source materials compared: implications for debris flow characterization

In the Alps, debris flow deposits generally contain < 5% clay-size particles, and the role of the surface-charged < 2 mu m particles is often neglected, although these particles may have a significant impact on the rheological properties of the interstitial fluid. The objective of this study was to compare debris flow deposits and parent materials from two neighbouring catchments of the Swiss Alps, with special emphasis on the colloidal constituents. The catchments are small in area (4 km(2)), 2.5 km long, similar in morphology, but different in geology. The average slopes are 35-40%. The catchments were monitored for debris flow events and mapped for surface aspect and erosion activity. Debris flow deposits and parent materials were sampled, the clay and silt fractions extracted and the bulk density, < 2 mm fraction bulk density, particle size distribution, chemical composition, cation exchange capacity (CEC) and mineralogy analysed. The results show that the deposits are similar to the parent screes in terms of chemical composition, but differ in terms of: (i) particle size distribution; and (ii) mineralogy, reactivity and density of the < 2 mm fraction. In this fraction, compared with the parent materials the deposits show dense materials enriched in coarse monocrystalline particles, of which the smallest and more reactive particles were leached. The results suggest that deposit samples should not be considered as representative of source or flow materials, particularly with respect to their physical properties.

Vehicular Traffic Flow Map, 1988

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 1990

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 1992

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 1994

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 1996

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 1998

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 2000

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 2002

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 2004

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 2006

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Vehicular Traffic Flow Map, 2008

Traffic volumes represented on this map are annual average daily traffic volumes between major traffic generators: highway junctions and cities.

Interstate Route Flow Map, 1992

Interstate Route Flow represented on this map are annual average daily traffic volumes between major traffic.