| 1. |
- Dunlap, Paul V, et al.
(författare)
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Genomic polymorphism in symbiotic populations of Photobacterium leiognathi.
- 2004
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Ingår i: Environmental Microbiology. - 1462-2912 .- 1462-2920. ; 6:2, s. 145-58
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Tidskriftsartikel (refereegranskat)abstract
- Photobacterium leiognathi forms a bioluminescent symbiosis with leiognathid fishes, colonizing the internal light organ of the fish and providing its host with light used in bioluminescence displays. Strains symbiotic with different species of the fish exhibit substantial phenotypic differences in symbiosis and in culture, including differences in 2-D PAGE protein patterns and profiles of indigenous plasmids. To determine if such differences might reflect a genetically based symbiont-strain/host-species specificity, we profiled the genomes of P. leiognathi strains from leiognathid fishes using PFGE. Individual strains from 10 species of leiognathid fishes exhibited substantial genomic polymorphism, with no obvious similarity among strains; these strains were nonetheless identified as P. leiognathi by 16S rDNA sequence analysis. Profiling of multiple strains from individual host specimens revealed an oligoclonal structure to the symbiont populations; typically one or two genomotypes dominated each population. However, analysis of multiple strains from multiple specimens of the same host species, to determine if the same strain types consistently colonize a host species, demonstrated substantial heterogeneity, with the same genomotype only rarely observed among the symbiont populations of different specimens of the same host species. Colonization of the leiognathid light organ to initiate the symbiosis therefore is likely to be oliogoclonal, and specificity of the P. leiognathi/leiognathid fish symbiosis apparently is maintained at the bacterial species level rather than at the level of individual, genomotypically defined strain types.
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| 2. |
- Antunes, Filipe, et al.
(författare)
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Network formation of catanionic vesicles and oppositely charged polyelectrolytes. Effect of polymer charge density and hydrophobic modification
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:11, s. 4647-4656
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Tidskriftsartikel (refereegranskat)abstract
- In nonequimolar solutions of a cationic and an anionic surfactant, vesicles bearing a net charge can be spontaneously formed and apparently exist as thermodynamically stable aggregates. These vesicles can associate strongly with polymers in solution by means of hydrophobic and/or electrostatic interactions. In the current work, we have investigated the rheological and microstructural properties of mixtures of cationic polyelectrolytes and net anionic sodium dodecyl sulfate/didodecyldimethylammonium bromide vesicles. The polyelectrolytes consist of two cationic cellulose derivatives with different charge densities; the lowest charge density polymer contains also hydrophobic grafts, with the number of charges equal to the number of grafts. For both systems, polymer-vesicle association leads to a major increase in viscosity and to gel-like behavior, but the viscosity effects are more pronounced for the less charged, hydrophobically modified polymer. Evaluation of the frequency dependence of the storage and loss moduli for the two systems shows further differences in behavior: while the more long-lived cross-links occur for the more highly charged hydrophilic polymer, the number of cross-links is higher for the hydrophobically modified polymer. Microstructure studies by cryogenic transmission electron microscopy indicate that the two polymers affect the vesicle stability in different ways. With the hydrophobically modified polymer, the aggregates remain largely in the form of globular vesicles and faceted vesicles (polygon-shaped vesicles with largely planar regions). For the hydrophilic polycation, on the other hand, the surfactant aggregate structure is more extensively modified: first, the vesicles change from a globular to a faceted shape; second, there is opening of the bilayers leading to holey vesicles and ultimately to considerable vesicle disruption leading to planar bilayer, disklike aggregates. The faceted shape is tentatively attributed to a crystallization of the surfactant film in the vesicles. It is inferred that a hydrophobically modified polyion with relatively low charge density can better stabilize vesicles due to formation of molecularly mixed aggregates, while a hydrophilic polyion with relatively high charge density associates so strongly to the surfactant films, due to strong electrostatic interactions, that the vesicles are more perturbed and even disrupted.
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| 3. |
- Blanco, A, et al.
(författare)
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Progress in timing Resistive Plate Chambers
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 535:1-2, s. 272-276
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Tidskriftsartikel (refereegranskat)abstract
- Timing RPCs are Resistive Plate Chambers made with glass and metal electrodes separated by precision spacers. Typical gas gaps are a few hundred micrometers wide. Such counters were introduced in 1999 and have since reached timing accuracies below 50 ps sigma with efficiencies above 99% for MIPs. Applications in high-energy physics have already taken place with several more under study. Some recent developments include the extension of the counting rate capability by over one order of magnitude, to 25 kHz/cm(2), with time resolutions below 100 ps sigma. A prototype RPC-based Positron Emission Tomograph yielded a reconstructed point-source resolution of 0.6 mm FWHM and a modified timing RPC design, featuring 50 mum pitch anode strips, allowed to reach extremely good position resolution for hard X-rays in digital readout mode. An analytically solvable model has allowed us to clarify the basic factors influencing the time resolution.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Lopes, L, et al.
(författare)
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Development of high-rate timing RPCs
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 533:1-2, s. 69-73
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Tidskriftsartikel (refereegranskat)abstract
- For many applications of RPCs to time-of-flight counters in heavy ion experiments the expansion to much higher values of the counting rate capability, so far limited to around 2 kHz/cm(2) is of fundamental importance. To address this issue we developed single-gap timing RPCs with resistive electrodes made from a commercially available plastic material. Tests performed in photon beams yielded a time resolution around 90 ps sigma, essentially unchanged from 2 kHz/ cm(2) to 27 kHZ/cm(2). This result establishes the basic feasibility of timing measurements with RPCs at rates of tens of kHZ/cm(2), keeping a time resolution below 100 ps a and using plastic electrode materials.
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| 8. |
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| 9. |
- Marques, Marcia, et al.
(författare)
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Water environments : Anthropogenic pressures and ecosystem changes in the Atlantic drainage basins of Brazil
- 2004
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 33:1-2, s. 68-77
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Tidskriftsartikel (refereegranskat)abstract
- Densely occupied drainage basins and coastal zones in developing countries that are facing economic growth are likely to suffer from moderate to severe environmental impacts regarding different issues. The catchment basins draining towards the Atlantic coast from northeastern to southern Brazil include a wide range of climatic zones and diverse ecosystems. Within its borders lies the Atlantic rain forest, significant extensions of semiarid thorn forests (caatinga), vast tree and scrub woodlands (cerrado) and most of the 6670 km of the Brazilian coast and its marine ecosystems. In recent decades, human activities have increasingly advanced over these natural resources. Littoralization has imposed a burden on coastal habitats and communities. Most of the native vegetation of the cerrado and caatinga was removed and only 7% of the original Atlantic rainforest still exists. Estuaries, bays and coastal lagoons have been irreversibly damaged. Land uses, damming and water diversion have become the major driving forces for habitat loss and aquatic ecosystem modification. Regardless of the contrast between the drought-affected northeastern Brazil and the much more prosperous and industrialized southeastern/southern Brazil, the impacts on habitat and communities were found equally severe in both cases. Attempts to halt environmental degradation have not been effective. Instead of focusing on natural resources separately, it is suggested that more integrated environmental policies that focus on aquatic ecosystems integrity are introduced.
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| 10. |
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| 11. |
- Nammari, Diauddin R., et al.
(författare)
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Emissions from a controlled fire in municipal solid waste bales
- 2004
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 24:1, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- Environmental and safety aspects of seasonal storage of baled municipal solid waste to be used as fuel for energy production (waste fuel), was investigated and experiments were carried out on burning of bales. The flammability, combustion processes and emissions were studied by simulating, in small-scale, potential effects of a possible fire in full-scale bale storage area. Despite the high water content and the high density of the bales, after setting fire, the bales burned well, even though no risk for self-ignition exists. The following parameters of the combustion product were measured continuously: O2, CO2, CO, SO2, NO, NO2, NOx,THC, smoke gas rate and the temperature of the smoke. Soot particles in the smoke were collected and analysed for Hg, Pb, Cd, As,Ni, Cr, Mn, Cu, Co, Sb and V concentrations. The analysis of the moisture content, concentrations of Hg, Cd, HCl, HF, HBr, NH3, polyaromatic hydrocarbons (PAH), chlorinated and brominated dioxins (PCDD/F and PBrDD/F, respectively) were carried out. It was found that the PCDD/F levels (TEQs) varied according to the system used: 12.53 ng (I-TEF-88)/Nm3; 14.09 ng (I-TEF-99)/Nm3;13.86 ng (Eadons)/Nm3. The PAH concentration was 3.04 mg/Nm3. The contents of the metals in the smoke (with the exceptions of Pb and Cd with mean values of 1.74 and 0.36 mg/m3, respectively) were below the limit values established by the Swedish Ministry ofEnvironment for emissions from incineration plants [Swedish Ministry of Environment, (2002:1060), Förordning 2002:1060 omavfallsförbränning. Available from http://www.notisum.se/rnp/SLS/LAG/20021060.HTM]/EU-directive [(2000/76/EC), Directive 2000/76/EC, of the European Parliament and of the Council of 4 December 2000 on the Incineration of Waste. http://www.Scotland.gov.uk/library5/environment/iecda.pdf]. The HCl concentration was 10 times higher than the limit value (mean value of 99 mg/m3).
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| 12. |
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| 13. |
- Nammari, Diauddin R., et al.
(författare)
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Physical and chemical processes in baled waste fuel, with emphasis on gaseous emissions
- 2003
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Ingår i: Waste Management & Research. - : Sage Publications. - 0734-242X .- 1096-3669. ; 21:4, s. 309-317
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Tidskriftsartikel (refereegranskat)abstract
- Over a period of seven months, the temperature and the emissions from six cylindrical and two rectangular stored bales containing waste for later use as fuel were measured. The bales were kept at two different ranges of temperatures: 30-35˚C and 20-25˚C respectively. It was foundthat only the rectangular bales showed significant productionof CO2. The increase of emission for one of the rectangular bales kept at 30-35˚C, was 0.246% vol. CO2 per day for a 2-week period, after which there was a decrease of CO2 concentrations at a rate of 0.0224% vol. during a 32-week period. The other rectangular bale kept at 20-25˚C, exhibited a similar trend. However, the increase of CO2 concentrations was less at a rate of 0.0259% vol. per day during a 8-week period, after which the CO2 emission decreased at a rate of 0.0224% vol. per day during a 25-week period. All the bales exhibited aerobic decomposition in the sampling point. However, on measuring the leachate concentrations, it was evident that the bales were actually in the equivalent acid-generating phase of a young landfill. The temperature inside the bales did not increase higher than the ambient air temperature.
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| 14. |
- Nammari, Diauddin R, et al.
(författare)
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Treatment Methods for Stormwater Runoff Originated in Various Areas in a Waste Management Park
- 2001
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Ingår i: Proceedings of Kalmar Eco-Tech’01 - Leachate and Waste Water Treatment with High-Tech and Natural Systems, the 3rd Conference on the Establishment of Cooperation Between Companies/Institutions in the Nordic Countries and the Countries in the Baltic Sea Region. - Kalmar, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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