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Sökning: WFRF:(Svensson Olle) > Naturvetenskap

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1.
  • Svensson, Glenn, et al. (författare)
  • Assessment of genetic and pheromonal diversity of the Cydia strobilella species complex (Lepidoptera: Tortricidae)
  • 2013
  • Ingår i: Systematic Entomology. - : Wiley. - 1365-3113 .- 0307-6970. ; 38:2, s. 305-315
  • Tidskriftsartikel (refereegranskat)abstract
    • Combining pheromone trapping and genetic analyses can be useful whentrying to resolve complexes of closely related insect taxa that are difficult to distinguishbased on morphological characters. Nearctic and Palearctic populations of the spruceseed moth, Cydia strobilella L., have been considered taxonomically synonymoussince 1983, but more recent work revealing distinct sex pheromones for Canadianand Swedish moths suggest that populations in the two regions belong to differentspecies. In order to test this hypothesis, we performed field trapping using differentpheromone lures at ten sites in North America, Europe and Asia, and reconstructedphylogenetic relationships among trapped moths using mitochondrial (cytochromeoxidase subunit I ) and nuclear (elongation factor 1 alpha) DNA sequence data.Trapping data and tree topologies for both genes revealed distinct pherotypes in NorthAmerica and Eurasia. A genetically distinct population from China was investigatedfurther with respect to its sex pheromone. Electrophysiological data indicated thatChinese females produce a deviant ratio of the sex pheromone components (dienicacetates) compared to Swedish females. However, trapping experiments in both areasrevealed a similar broad response profile in males to a wide range of acetate ratios,and these populations should be considered taxonomically synonymous. A previoussuggestion of an agonistic effect on the attraction of C. strobilella males in Swedenwhen adding the corresponding alcohols to the binary acetate blend was also testedin Sweden as well as in China, with no observed effect on attraction of males. In conclusion, our study demonstrates the great potential of using pheromone trappingas a tool for identification and delimitation of taxa within cryptic species complexes.Based on our data, Nearctic and Palearctic populations of C. strobilella should beconsidered different species, and C. youngana Kearfott stat. rev. is resurrected hereas valid name for North American populations, which was the case before the revisionin 1983.
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2.
  • Tchaplyguine, Maxim, et al. (författare)
  • Absolute core-level binding energy shifts between atom and solid: The Born-Haber cycle revisited for free nanoscale metal clusters
  • 2008
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 166, s. 38-44
  • Tidskriftsartikel (refereegranskat)abstract
    • Core-level binding energy shifts between the free atom and corresponding large clusters, the latter closely approximating the infinite solid, have been experimentally derived for several elemental metals. The cluster core-level binding energies in question have been determined relative to the vacuum level using synchrotron-based photoelectron spectroscopy. As expected, the experimental shift values show reasonable agreement with those calculated using the thermochemical Born–Haber cycle approach. The largest uncertainty factors defining the discrepancies between the experiment and the model, such as the difference in the multiplet structure of free atoms and the solid, the in some cases indirectly established cluster work functions, and the metal solvation energy, are discussed.
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3.
  • Jakobsson, Johan, et al. (författare)
  • Visual cues of oviposition sites and spectral sensitivity of Cydia strobilella L.
  • 2017
  • Ingår i: Journal of Insect Physiology. - : Elsevier BV. - 0022-1910. ; 101, s. 161-168
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated whether the spruce seed moth (Cydia strobilella L., Tortricidae: Grapholitini), an important pest in seed orchards of Norway spruce (Picea abies (L.) Karst.), can make use of the spectral properties of its host when searching for flowers to oviposit on. Spectral measurements showed that the flowers, and the cones they develop into, differ from a background of P. abies needles by a higher reflectance of long wavelengths. These differences increase as the flowers develop into mature cones. Electroretinograms (ERGs) in combination with spectral adaptation suggest that C. strobilella has at least three spectral types of photoreceptor; an abundant green-sensitive receptor with maximal sensitivity at wavelength λmax = 526 nm, a blue-sensitive receptor with λmax = 436 nm, and an ultraviolet-sensitive receptor with λmax = 352 nm. Based on our spectral measurements and the receptor properties inferred from the ERGs, we calculated that open flowers, which are suitable oviposition sites, provide detectable achromatic, but almost no chromatic contrasts to the background of needles. In field trials using traps of different spectral properties with or without a female sex pheromone lure, only pheromone-baited traps caught moths. Catches in baited traps were not correlated with the visual contrast of the traps against the background. Thus, visual contrast is probably not the primary cue for finding open host flowers, but it could potentially complement olfaction as a secondary cue, since traps with certain spectral properties caught significantly more moths than others.
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4.
  • Svensson, Glenn P., et al. (författare)
  • Challenges of pheromone-based mating disruption of Cydia strobilella and Dioryctria abietella in spruce seed orchards
  • 2018
  • Ingår i: Journal of Pest Science. - : Springer Science and Business Media LLC. - 1612-4758 .- 1612-4766. ; 91, s. 639-650
  • Tidskriftsartikel (refereegranskat)abstract
    • Seed orchards function as the primary source of high-quality seeds for reforestation in many European countries, but their seed yields can be severely reduced due to seed- and cone-feeding insects. We evaluated various parameters of pheromone-based mating disruption for control of the moths Cydia strobilella and Dioryctria abietella, which are major pests in European Picea abies seed orchards. We applied different types of pheromone dispensers (rubber septa or wax droplets) at different densities and heights, and with different amounts of active components, covering whole orchards or part of an orchard. The efficacy of the treatment was evaluated by analysing male captures in pheromone-baited assessment traps, and presence of larvae in cones. A dramatic decrease (94–100%) in capture of males in traps occurred in all pheromone-treated plots compared to control plots for both moth species. In contrast, a subsequent reduction in larval numbers in cones was only achieved when wax droplets were used as the dispensing formulation at high density and at the highest pheromone dose tested, and only in half of the trials for each pest species. Electrophysiological recordings using antennae of male C. strobilella indicated elevated pheromone concentrations in a treated plot versus a control plot. Our results show that mating disruption has potential to reduce cone damage in spruce seed orchards caused by C. strobilella and D. abietella, but optimisation of the technique is required to achieve consistent and efficient population suppression of these pests.
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5.
  • Wang, Hong-Lei, et al. (författare)
  • Sex pheromone of the cloaked pug moth, Eupithecia abietaria (Lepidoptera: Geometridae), a pest of spruce cones
  • 2015
  • Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 139:5, s. 352-360
  • Tidskriftsartikel (refereegranskat)abstract
    • The sex pheromone of the cloaked pug moth, Eupithecia abietaria Götze, an important cone-feeding pest in spruce seed orchards in Europe, was investigated. Chemical and electrophysiological analyses of pheromone gland extracts of female moths and analogous analyses of synthetic hydrocarbons and epoxides of chain length C19 and C21 revealed (3Z,6Z,9Z)-3,6,9-nonadecatriene (3Z,6Z,9Z-19:H) and 3Z,6Z-cis-9,10-epoxynonadecadiene (3Z,6Z-cis-9,10-epoxy-19:H) as candidate pheromone components, which were found in a gland extract in a ratio of 95 : 5. In field trapping experiments, conspecific males were only attracted to a combination of 3Z,6Z,9Z-19:H and the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-19:H. The (9R,10S)-enantiomer was not attractive, which is in agreement with studies on other Eupithecia species, for which males have only been attracted by the (9S,10R)-enantiomer of epoxides. Subsequent experiments showed that E. abietaria males were attracted to a wide range of ratios of the two active compounds and that trap catches increased with increasing dose of the binary blend. A two-component bait containing 300 μg 3Z,6Z,9Z-19:H and 33 μg of the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-19:H was efficient for monitoring E. abietaria in spruce seed orchards in southern Sweden, where this species has probably been overlooked as an important pest in the past. With sex pheromones recently identified for two other moths that are major pests on spruce cones, the spruce seed moth, Cydia strobilella L., and the spruce coneworm, Dioryctria abietella Denis & Schiffermüller, pheromone-based monitoring can now be achieved for the whole guild of cone-feeding moths in European spruce seed orchards.
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6.
  • Björklund Svensson, Jonas, et al. (författare)
  • Low-divergence femtosecond X-ray pulses from a passive plasma lens
  • 2021
  • Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 17:5, s. 639-645
  • Tidskriftsartikel (refereegranskat)abstract
    • Electron and X-ray beams originating from compact laser-wakefield accelerators have very small source sizes that are typically on the micrometre scale. Therefore, the beam divergences are relatively high, which makes it difficult to preserve their high quality during transport to applications. To improve on this, tremendous efforts have been invested in controlling the divergence of the electron beams, but no mechanism for generating collimated X-ray beams has yet been demonstrated experimentally. Here we propose and realize a scheme where electron bunches undergoing focusing in a dense, passive plasma lens can emit X-ray pulses with divergences approaching the incoherent limit. Compared with conventional betatron emission, the divergence of this so-called plasma lens radiation is reduced by more than an order of magnitude in solid angle, while maintaining a similar number of emitted photons per electron. This X-ray source offers the possibility of producing brilliant and collimated few-femtosecond X-ray pulses for ultra-fast science, in particular for studies based on X-ray diffraction and absorption spectroscopy. X-ray pulses with low divergences are produced in a laser-wakefield accelerator by focusing electron bunches in a dense passive plasma lens.
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7.
  • Jönsson, Anna Maria, et al. (författare)
  • Enhanced science-stakeholder communication to improve ecosystem model performances for climate change impact assessments.
  • 2015
  • Ingår i: Ambio: a Journal of Human Environment. - : Springer Science and Business Media LLC. - 0044-7447. ; 44:3, s. 249-255
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years, climate impact assessments of relevance to the agricultural and forestry sectors have received considerable attention. Current ecosystem models commonly capture the effect of a warmer climate on biomass production, but they rarely sufficiently capture potential losses caused by pests, pathogens and extreme weather events. In addition, alternative management regimes may not be integrated in the models. A way to improve the quality of climate impact assessments is to increase the science-stakeholder collaboration, and in a two-way dialog link empirical experience and impact modelling with policy and strategies for sustainable management. In this paper we give a brief overview of different ecosystem modelling methods, discuss how to include ecological and management aspects, and highlight the importance of science-stakeholder communication. By this, we hope to stimulate a discussion among the science-stakeholder communities on how to quantify the potential for climate change adaptation by improving the realism in the models.
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8.
  • De Facci, Monica, et al. (författare)
  • Chemical composition of anal droplets of the eusocial gall-inducing thrips Kladothrips intermedius
  • 2014
  • Ingår i: Chemoecology. - : Springer Science and Business Media LLC. - 1423-0445 .- 0937-7409. ; 24:3, s. 85-94
  • Tidskriftsartikel (refereegranskat)abstract
    • The eusocial Acacia gall-inducing thrips Kladothrips intermedius (Thysanoptera: Phlaeothripinae) secretes defensive anal droplets when threatened. In addition to harmful substances, droplets of other thysanopteran species are known to contain semiochemicals such as alarm pheromones and/or repellents against enemies. Both Kl. intermedius larval stages and adult castes (soldiers and dispersers) produce anal droplets. In addition, a recent study has shown that soldier droplets may contain an alarm pheromone. Using multiple sampling methods (extraction in solvent, solid phase microextraction and direct injection), we analyzed the content of adults and second instar larvae anal droplets by gas chromatography coupled to mass spectrometry. Anal droplets comprised of a set of saturated and monounsaturated short-chain fatty acids, including three compounds with a terminal double bond (7-octenoic acid, 8-nonenoic acid and 9-decenoic acid). The latter are here reported for the first time in an insect species. In addition, putative unsaturated wax esters similar to those found in the secretion of other social insects were also detected in droplets. In order to investigate the physiological activity of the acids, single sensillum recordings were performed on adult Kl. intermedius as well as on adults of its kleptoparasite, Koptothrips dyskritus, targeting olfactory receptor neurons in the antennal sensilla basiconica. While olfactory perception of the acids in these species cannot be completely excluded, our analyses indicate that sensilla basiconica are not strongly sensitive to these droplet compounds.
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9.
  • Gadisa, Abay, et al. (författare)
  • Improvements of fill factor in solar cells based on blends of polyfluorene copolymers as electron donors
  • 2007
  • Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:5, s. 3126-3131
  • Tidskriftsartikel (refereegranskat)abstract
    • The photovoltaic characteristics of solar cells based on alternating polyfluorene copolymers, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)) (APFO-3), and poly(2,7-(9,9-didodecyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)) (APFO-4), blended with an electron acceptor fullerene molecule [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), have been investigated and compared. The two copolymers have the same aromatic backbone structure but differ by the length of their alkyl side chain. The overall photovoltaic performance of the solar cells is comparable irrespective of the copolymer used in the active layer. However, the fill factor (FF) values of the devices are strongly affected by the copolymer type. Higher FF values were realized in solar cells with APFO-4 (with longer alkyl side chain)/PCBM bulk heterojunction active layer. On the other hand, devices with blends of APFO-3/APFO-4/PCBM were found to render fill factor values that are intermediate between the values obtained in solar cells with APFO-3/PCBM and APFO-4/PCBM active film. Upon using APFO-3/APFO-4 blends as electron donors, the cell efficiency can be enhanced by about 16% as compared to cells with either APFO-3 or APFO-4. The transport of holes in each polymer obeys the model of hopping transport in disordered media. However, the degree of energetic barrier against hopping was found to be larger in APFO-3. The tuning of the photovoltaic parameters will be discussed based on studies of hole transport in the pure polymer films, and morphology of blend layers. The effect of bipolar transport in PCBM will also be discussed.
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10.
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