| 1. |
- Månsson, Erik, et al.
(författare)
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Double ionization probed on the attosecond timescale
- 2014
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 10:3, s. 207-211
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Tidskriftsartikel (refereegranskat)abstract
- Double ionization following the absorption of a single photon is one of the most fundamental processes requiring interaction between electrons(1-3). Information about this interaction is usually obtained by detecting emitted particles without access to real-time dynamics. Here, attosecond light pulses(4,5), electron wave packet interferometry(6) and coincidence techniques(7) are combined to measure electron emission times in double ionization of xenon using single ionization as a clock, providing unique insight into the two-electron ejection mechanism. Access to many-particle dynamics in real time is of fundamental importance for understanding processes induced by electron correlation in atomic, molecular and more complex systems.
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| 2. |
- Anrup, Roland, et al.
(författare)
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Centrala universitetsvärden hotas av bolagiseringsidén
- 2013
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Ingår i: Dagens nyheter. - 1101-2447.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Högskolestiftelser. Förslaget att driva svenska universitet i stiftelseform öppnar för bolagisering. Men det är ingen riktig utredning, utan en politisk pamflett utan eftertanke. Privatisering av universitet hotar både oberoendet, forskningskvaliteten och samhällsnyttan, skriver 36 forskare vid svenska högskolor och universitet.
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| 3. |
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| 4. |
- Campos, Paula F, et al.
(författare)
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Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics
- 2010
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 107:12, s. 5675-5680
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Tidskriftsartikel (refereegranskat)abstract
- The causes of the late Pleistocene megafaunal extinctions are poorly understood. Different lines of evidence point to climate change, the arrival of humans, or a combination of these events as the trigger. Although many species went extinct, others, such as caribou and bison, survived to the present. The musk ox has an intermediate story: relatively abundant during the Pleistocene, it is now restricted to Greenland and the Arctic Archipelago. In this study, we use ancient DNA sequences, temporally unbiased summary statistics, and Bayesian analytical techniques to infer musk ox population dynamics throughout the late Pleistocene and Holocene. Our results reveal that musk ox genetic diversity was much higher during the Pleistocene than at present, and has undergone several expansions and contractions over the past 60,000 years. Northeast Siberia was of key importance, as it was the geographic origin of all samples studied and held a large diverse population until local extinction at approximately 45,000 radiocarbon years before present ((14)C YBP). Subsequently, musk ox genetic diversity reincreased at ca. 30,000 (14)C YBP, recontracted at ca. 18,000 (14)C YBP, and finally recovered in the middle Holocene. The arrival of humans into relevant areas of the musk ox range did not affect their mitochondrial diversity, and both musk ox and humans expanded into Greenland concomitantly. Thus, their population dynamics are better explained by a nonanthropogenic cause (for example, environmental change), a hypothesis supported by historic observations on the sensitivity of the species to both climatic warming and fluctuations.
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| 5. |
- Gisselbrecht, Mathieu, et al.
(författare)
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Charge migration and decay of doubly charged ammonia clusters
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:2, s. 022112-
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Tidskriftsartikel (refereegranskat)abstract
- The photo-fragmentation of ammonia molecular clusters ionized with soft x-rays is studied for photon energies near the N-1s threshold. The fragmentation is studied with a 3D momentum mass spectrometer to access the energy and angular correlations between fragments. By choosing the cluster sizes below or above the critical size of stable dication, we investigate the coulomb explosion dynamics and the interplay between charge delocalization and mobility of molecules in the clusters.
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| 6. |
- Goon, Anthony, et al.
(författare)
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Correlation between Stated and Measured Concentrations of Acrylate and Methacrylate Allergens in Patch-Test Preparations
- 2011
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Ingår i: Dermatitis. - : Mary Ann Liebert Inc. - 1710-3568. ; 22:1, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- Background: Contact allergy to acrylates and methacrylates is not uncommon. The allergy is confirmed by patch-testing patients with commercial patch-test preparations. Objective: To investigate acrylate and methacrylate allergens used for patch testing in nine different dermatology departments from Europe, America, Asia, and Australia. Methods: The acrylate and methacrylate (methyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, and triethylene glycol diacrylate) allergen samples were analyzed with high-performance liquid chromatography to measure the allergen content. Results: Variation in measured versus stated concentrations was seen in these samples. The ratio of measured to stated concentrations ranged from 0.11 to 1.1. Only 22 (63%) of 35 samples were within the arbitrary acceptable limits of 80 to 120% of the stated concentrations. Conclusion: The results may have implications for individual diagnosis and prevention and when test results from various centers are compared.
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| 7. |
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| 8. |
- Goon, Anthony, et al.
(författare)
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Variation in allergen content over time of acrylates/methacrylates in patch test preparations
- 2011
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 1365-2133 .- 0007-0963. ; 164:1, s. 116-124
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Tidskriftsartikel (refereegranskat)abstract
- P>Background Acrylates/methacrylates are volatile substances. There might be a gradual decrease in acrylate/methacrylate allergen content over time in patch test preparations but this has not yet been documented. Objectives To determine the allergen content of acrylates/methacrylates in patch test preparations over time under different storage conditions. Methods Five acrylate/methacrylate allergens [2-hydroxyethyl methacrylate (2-HEMA), methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA), triethylene glycol diacrylate (TREGDA) and 2-hydroxypropyl acrylate (2-HPA)] in syringes and IQ (TM) chambers (Chemotechnique Diagnostics, Vellinge, Sweden) were analysed using gel permeation chromatography and high-performance liquid chromatography to measure the allergen content over time in samples stored in the freezer, refrigerator and under room temperature. Results The concentration of allergens in syringes decreased with time. Those stored at room temperature had the fastest rate of decrease, followed by those in the refrigerator and freezer. In most cases, in syringes or IQ (TM) chambers under all storage conditions, the MMA decreased most rapidly, followed by 2-HPA, 2-HEMA, EGDMA and TREGDA. The allergens in the IQ (TM) chambers rapidly disappeared, with almost all samples reaching nondetectable levels by day 8. MMA was the first to reach a nondetectable level - at day 2. Conclusions Acrylate/methacrylate allergens are lost rapidly from IQ (TM) chambers especially if stored at room temperature. Allergens in syringes remain above 80% of their initial concentrations for longer periods compared with IQ (TM) chambers. In syringes and IQ (TM) chambers there is a slower rate of decrease in concentration when the storage temperature is lower. Allergens should be stored refrigerated, replaced regularly, and freshly applied on to test patches on the day of use.
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| 9. |
- Laksman, Joakim, et al.
(författare)
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Development and characterization of a multiple-coincidence ion-momentum imaging spectrometer.
- 2013
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 84:12
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Tidskriftsartikel (refereegranskat)abstract
- The design and performance of a high-resolution momentum-imaging spectrometer for ions which is optimized for experiments using synchrotron radiation is presented. High collection efficiency is achieved by a focusing electrostatic lens; a long drift tube improves mass resolution and a position-sensitive detector enables measurement of the transverse momentum of ions. The optimisation of the lens for particle momentum measurement at the highest resolution is described. We discuss the overall performance of the spectrometer and present examples demonstrating the momentum resolution for both kinetics and for angular measurements in molecular fragmentation for carbon monoxide and fullerenes. Examples are presented that confirm that complete space-time focussing is possible for a two-field three-dimensional imaging spectrometer.
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| 10. |
- Laksman, Joakim, et al.
(författare)
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Rapid bond rearrangement in core-excited molecular water.
- 2013
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 15:44, s. 19322-19329
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Tidskriftsartikel (refereegranskat)abstract
- The angular anisotropy of fragments created in the dissociation of core-electron excited water molecules is studied to probe the correlation between fragmentation channels, kinematics and molecular geometry. We present fragment kinetic measurements for water molecules where the inner-shell oxygen electron is excited to the unoccupied 4a1 and 2b2 valence molecular orbitals. The kinematics of individual fragmentation channels are measured using fully three-dimensional momentum imaging of fragments. The results show that the geometry of the molecule and the kinetic energy of fragments are strongly coupled in the atomisation process. In addition we identify a fragmentation process arising from bond rearrangement evidenced by the H2(+)-O(+) ion pair which is accessible for resonant excitation of the 1s electron. In all of the two-body fragmentation processes the dissociation takes place along the potential-energy surface, while atomisation reveals both dissociation along the potential surface and Coulomb explosion. The angular distribution of fragments suggests that the bond rearrangement is very rapid; likely on a sub 10 fs time scale.
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