| 1. |
- Aebi, Alexandre, et al.
(författare)
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The potential of native parasitoids for the control of Mexican bean beetles: A genetic and ecological approach
- 2008
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Ingår i: Biological Control. - : Elsevier BV. - 1090-2112 .- 1049-9644. ; 47:3, s. 289-297
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Tidskriftsartikel (refereegranskat)abstract
- Bruchid beetles in the genus Zabrotes are important pests of field and stored beans all around the world and cause enormous economical losses in Mexico and Central America. Native parasitoids have been successfully used to suppress infestations by bruchid beetles in Africa, but few studies have assessed their potential to reduce seed damage in the New World and no successful biological control programs have been implemented, mainly due to the poor knowledge on their biology, systematics and ecology in this region. In this study, we used molecular tools to describe a new complex of three parasitoid species of bruchid beetles in the genus Horismenus, and investigated the level of gene flow and presence of ecotypes in this complex. We also examined the specific association between species of Horismenus and two sibling species of Zabrotes beetles, in order to evaluate their potential as biological control agents. Microsatellite data support the previous morphological description of three species, H. butcheri, H. missouriensis and H. depressus, but suggest some gene flow between H. missouriensis and H. depressus. Host-plant is shown to be the most important factor determining the ecological distribution of the two Zabrotes species, whereas altitude explains most of the distribution of the three Horismenus species. These results complement our understanding of this tritrophic system, providing a solid base for a potential biological control program using native parasitoids. (C) 2008 Elsevier Inc. All rights reserved.
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| 4. |
- Andersson, Camilla, 1979-
(författare)
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Air Pollution Dependency on Climate Variability and Source Region : Past, Current and Future Air Pollution Scenarios over Europe
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objectives of this thesis were to investigate the dependency of European air pollution on climate variability and emission source region. Calculations with a chemistry transport model (CTM) were conducted to investigate the influence of climate variability. The CTM was forced by both simulated past (a re-analysis spanning 1958-2001) and future (a climate simulation spanning 1961-2100) meteorology keeping anthropogenic emissions constant. To investigate the influence of emission source region emissions were varied in western, eastern and northern Europe in seven-year (1997-2003) simulations. The main conclusions in this thesis are § There is variability in air pollution due to climate variability on time scales from year to year to decades and long-term trends. Hence, what is measured now will not be valid in a decade, or even next year. § Interannual variability in air pollution due to climate variability is greater than interannual variability in anthropogenic emissions. § The extreme conditions in 2003, resulting in elevated surface O3 concentrations, could be an indication on what we can expect in the future. § The trend in surface O3 over the past due to climate change is similar to the projected trend due to future climate change: increasing in south-western and central Europe and decreasing in north-eastern Europe. § Changes in isoprene emissions and dry deposition dependency on soil moisture are of importance for changes in surface O3 in central and southern Europe. It is vital to include these processes, especially the latter in climate change effect studies of surface O3. § This work indicates that it is of greater importance for health benefits of the European population to reduce primary PM emissions than precursors of secondary inorganic aerosol under the assumption of higher relative risk for primary PM. This is especially the case in western Europe.
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| 5. |
- Andersson, Michael, et al.
(författare)
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Fatigue crack propagation in Ti-6Al-4V subjected to high strain amplitudes
- 2005
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Ingår i: Fatigue & Fracture of Engineering Materials & Structures. - : Wiley. - 1460-2695. ; 28:3, s. 301-308
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue crack propagation in circular Ti-6Al-4V specimens subjected to high strain amplitudes has been investigated. Crack closure was measured with an electrical potential-drop technique. Closure was shown not to depend on strain ratio but to be a function of the applied strain range. At higher strain ranges, the crack was found to be closed for a smaller part of the load cycle than at lower strain ranges due to blunting of the crack tip. Furthermore, the use of a strain-intensity approach to predict crack-propagation rate was investigated, and it was found that for the upper parts of the da/dN curves the effective strain intensity yields good predictions. Also, the effective stress-intensity factor was found to collapse the da/dN curves for different load ratios.
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| 6. |
- Andersson, Martin, et al.
(författare)
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Single microgel particle studies demonstrate the influence of hydrophobic interactions between charged micelles and oppositely charged polyions.
- 2005
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:9, s. 3773-3781
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Tidskriftsartikel (refereegranskat)abstract
- The binding of two cationic surfactants, dodecyltrimethylammonium bromide (DoTAB) and N-(1,1,2,2-tetrahydroperfluorodecanyl)pyridinium bromide (HFDePB), to covalently cross-linked sodium poly(styrenesulfonate) (PSS) microgels has been investigated by means of micromanipulator-assisted time-resolved light microscopy on single gels. It is demonstrated that repeated measurements on the same microgel under conditions of controlled liquid flow give highly reproducible results. The two surfactants are found to behave very differently with respect to degree of swelling, surfactant distribution in the gels, both during shrinking and at equilibrium, and kinetics of volume changes induced by them. The main difference is attributed to the presence of a hydrophobic interaction between PSS and the DoTAB micelles, absent in the case of HFDePB. Kinetic shrinking curves are recorded and analyzed using a model for steady-state transport of surfactant between the solution and the gels. Aggregation numbers for DoTAB in PSS solutions obtained from fluorescence quenching measurements are presented. A strong dependence on the surfactant-to-polyion concentration ratio is observed. Relations between surfactant binding isotherms, phase diagrams for linear polyelectrolyte/surfactant/water systems, and the binding to gels are discussed.
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| 8. |
- Bergendorff, Ola, et al.
(författare)
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Chemical changes in rubber allergens during vulcanization
- 2007
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Ingår i: Contact Dermatitis. - : Wiley. - 0105-1873 .- 1600-0536. ; 57:3, s. 152-157
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Tidskriftsartikel (refereegranskat)abstract
- Allergic contact dermatitis to rubber is caused by residues of chemicals used in manufacturing a rubber product. Several different additives are used to achieve a final product of the desired characteristics. Accelerators such as thiurams, dithiocarbamates, and mercaptobenzothiazoles are often among the additives responsible for allergic reactions recognized by dermatologists. The chemistry of the vulcanization process is complicated; as it occurs at an elevated temperature with a mixture of reactive chemicals, the compositions of the initial and final products differ. This paper investigates the changes in composition of common allergens during vulcanization, doing so by chemically analysing various rubber formulations at different stages of the process. Major changes were found in which added chemicals were consumed and new ones produced. An important observation is that thiuram disulfides rarely appear in the final rubber although they may have been used as additives. Instead, thiurams are often converted to dithiocarbamates or to products formed by addition to mercaptobenzothiazole structures, if these have been used together with thiurams as accelerators.
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| 9. |
- Bergendorff, Ola, et al.
(författare)
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Contact dermatitis to a rubber allergen with both dithiocarbamate and benzothiazole structure.
- 2007
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Ingår i: Contact Dermatitis. - : Wiley. - 0105-1873 .- 1600-0536. ; 56:5, s. 278-280
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Tidskriftsartikel (refereegranskat)abstract
- Contact dermatitis to rubber products are often caused by additives used during manufacture, and diagnosed from patch test with established rubber allergen series. In these series the compounds are divided into separate groups such as thiurams, dithiocarbamates and mercaptobenzothiazoles. The objectives were to investigate the substances with allergenic structures present in a diving mask giving rise to facial dermatitis, also those substances including structures from different groups of rubber chemicals. The rubber material was analysed by high-performance liquid chromatography and diode-array detector. The patient was tested by epicutaneous tests using pure substances, extracts and authentic rubber material. 2-Benzothiazolyl-N,N-diethylthiocarbamylsulfide, was found in the diving mask and the patient showed positive reaction to the pure compound and to extracts of the diving mask. This compound has structures of both mercaptobenzothiazole and thiuram/dithiocarbamate in its formulae. Besides the established groups of rubber accelerators, uncommon allergens with structures from more than one group can be formed or added at vulcanization. Chemical analysis of the product is needed to find these allergens.
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