This study compared the antimicrobial efficacy of shampoos against meticillin-sensitive Staphylococcus pseudintermedius (MSSP), meticillin-resistant S. pseudintermedius (MRSP), antibiotic-sensitive Pseudomonas aeruginosa (PA), multidrug-resistant P. aeruginosa (MDR-PA) and Malassezia pachydermatis. Three isolates were incubated for 10, 30 and 60 min with each shampoo diluted in phosphate-buffered saline. Aliquots were then incubated for 16-18 h on sheep blood agar (bacteria) or for 3 days on Sabouraud's dextrose agar (Malassezia). The minimal bactericidal concentrations (MBCs) for chlorhexidine products (Malaseb(®), Pyoderm(®)/Microbex(®) and Hibiscrub(®)) were 1:1,024-1:2,048 for MSSP and MRSP, 1:512-1:1,024 for PA and MDR-PA, and 1:2,048-1:5,096 for Malassezia at all time points. The MBCs for benzoyl peroxide (Paxcutol(®)) for MSSP and MRSP were 1:2-1:8 at 10 min, and 1:256 after 30 and 60 min. A 1:2 dilution was effective against Pseudomonas, and 1:512-1:1,024 dilutions were effective against Malassezia at all time points. The MBCs for ethyl lactate (Etiderm(®)) for MSSP and MRSP were 1:2 at 10 min, and 1:2-1:16 after 30 and 60 min. A 1:2 dilution was effective against Pseudomonas, and a 1:512 dilution was effective against Malassezia at all time points. Chloroxylenol (Coatex(®)) and acetic acid-boric acid (Malacetic(®)) were not effective against MSSP, MRSP or Pseudomonas. Both were effective against Malassezia at 1:8-1:16 dilution at 10 min, and at 1:8-1:32 dilution after 30 and 60 min. In conclusion, chlorhexidine appeared to be the most effective topical biocide, and MRSP and MDR-PA were no less susceptible than antibiotic-sensitive organisms. These results should, however, be confirmed with larger numbers of isolates.
Microseismic events or acoustic emissions induced by petroleum extraction in the Ekofisk field operated by the Phillips Petroleum Licence 018 group in the Norwegian sector of the North Sea' were monitored for 18 days in April 1997. The monitoring consisted of a 6 level, triaxial VSP wireline tool deployed within the reservoir in the 2/4-C 11 a observation well located near the crest of the field. 2100 microseismic events were recorded, corresponding to roughly 5 per hour. The rnajority of the events were located in the upper part of the reservoir, predominantly in low porosity layers overlying relatively porous layers which are undergoing water flooding and compaction. Events were most accurately located near the monitoring borehole, with the position of events further away being more uncertain. A cluster of activity surrounded the nearby well C 16, confirming the event positioning accuracy. Within 300 m of the well, most events were precisely located to an accuracy of better than 30 m, and found to cluster along discrete lineations. These lineations, which are parallel to major structures in the region, are attributed to induced definition of preexisting fractures. Comparisons with simulations of the water flood front indicated that the saturated zones around the injection wells were aseismic. The position of the water flood front was not accurately enough known to test if any of the clusters of microseismicity were associated with it. However, compaction of the chalk may be strongest at the water front. If a significant proportion of the total acoustic activity is caused in association with the water front, then time-lapse microseismic monitoring could represent a useful tool for tracking the position of the water flood. P. 387
Two methods were used to examine the effects of stress changes and microfracture activity during Brazilian disk tests performed on Lac du Bonnet Granite. Acoustic emission analyses examining source locations and source mechanisms led to two main findings. Firstly, the sources were clustered in the regions with the greatest difference between the minimum and maximum principal stresses. Secondly many sources involved some degree of shear motion. This indicates that dilatancy in these rocks may be largely controlled by hybrid shear-tensile microfractures. Ultrasonic tomographic imaging of p-wave speed was the second technique used to study stress induced effects on the samples. The images created have successfully delineated areas of the rock with high stress concentrations.
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