| 1. |
- Baquero, María-Rosario, et al.
(författare)
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Polymorphic mutation frequencies in Escherichia coli : emergence of weak mutators in clinical isolates
- 2004
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 186:16, s. 5538-5542
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Tidskriftsartikel (refereegranskat)abstract
- Polymorphisms in the rifampin resistance mutation frequency (f) were studied in 696 Escherichia coli strains from Spain, Sweden, and Denmark. Of the 696 strains, 23% were weakly hypermutable (4 x 10(-8) < or = f < 4 x 10(-7)), and 0.7% were strongly hypermutable (f > or = 4 x 10(-7)). Weak mutators were apparently more frequent in southern Europe and in blood isolates (38%) than in urinary tract isolates (25%) and feces of healthy volunteers (11%).
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| 2. |
- Costa, José-Luis, et al.
(författare)
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Sequence based data supports a single Nostoc strain in individual coralloid roots of cycads
- 2004
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Ingår i: FEMS Microbiology: Ecology. ; 49, s. 481-487
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Tidskriftsartikel (refereegranskat)abstract
- The genertic diversity of cyanobacteria associated with cycads was examined using the tRNA Leu (UAA) intron as a genetic marker. Coralloid roots of both natural populations of the cycad Macrozamia riedlei (Fischer ex Gaudichaud-Beaupré) C.A. Gardner growing in Perth, Australia and cycads growing in greenhouses, also in Perth, were used and their respective cyanobionts analyzed. Several Nostoc strains were found to be involved in this symbiosis, both in natural populations and greenhouse-orginated cycads. However, only one strain was present in individual coralloid roots and in individual plants, even when analyzing different coralloid roots from the same plant. Moreover, when examining plants growing close to each other (female plants and their respective offspring) the same cyanobacterium was consistently present in the different coralloid roots. Whether this reflects a selective mechanism or merely the availability of Nostoc strains remains to be ascertained. The high cyanobacterial diversity in coralloid roots of cycads revealed by PCR fingerprinting is, therefore, contested. In this study, the potential probems of using different methods (e.g. PCR fingerprinting) to study the genetic diversity of symbiotic cyanobacteria, is also addressed.
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| 3. |
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| 4. |
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| 5. |
- Sidborn, Magnus, et al.
(författare)
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Two-dimensional Dynamic Model of a Copper Sulphide Ore Bed
- 2003
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Ingår i: Hydrometallurgy. - 0304-386X .- 1879-1158. ; 71, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional dynamic model for bioleaching of secondary copper minerals from a pile has been developed. In the model. aeration of the pile is considered to be due to natural convection caused by the density gradient in the air within the bed. The rate of sulphide mineral dissolution is modelled according to the unreacted core model. The transport of ferric ions from the particle surface to the reaction zone is calculated considering film diffusion, diffusion within the particle and reaction kinetics. The rate of oxidation of the ferrous ion by bacteria attached to the ore surface is modelled using the Michaelis-Menten relationship. The influences of temperature, dissolved ferric iron and dissolved oxygen in the leaching solution are considered in the kinetic formulation. The set of partial differential equations is solved using the FEMLAB(R) software. The model was used to study the influence of process variables on copper recovery in the bed with time. This model is a useful tool to aid the design and optimisation of industrial operations.
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