| 1. |
- Persson, Per, et al.
(författare)
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Determination of the detection limit of Ni-59 at the Lund AMS facility by using characteristic projectile X-rays
- 2000
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 160:4, s. 510-514
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Tidskriftsartikel (refereegranskat)abstract
- Accelerator mass spectrometry (AMS) is an ultra-sensitive method for counting atoms, both radionuclides and stable nuclides. When using small tandem accelerators to measure heavy isotopes, interfering isobars are often troublesome. One way to reduce this interference is to combine AMS with the detection of characteristic X-rays of the projectile. After analysis in the AMS system it is possible to identify ions of different atomic number by their characteristic X-rays, by slowing down the ions in a suitable target. In this paper, the detection limit of Ni-59 at the Land AMS facility is reported. A method for the chemical extraction of nickel from stainless steel, combined with a purification step to reduce the cobalt content in the sample by several orders of magnitude, is also described. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 2. |
- Axe, Kristina, et al.
(författare)
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Time-dependent surface speciation of oxalate at the water-boehmite (γ-AlOOH) interface: implications for dissolution
- 2001
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Ingår i: Geochimica et Cosmochimica Acta. ; 65:24, s. 4481-92
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Tidskriftsartikel (refereegranskat)abstract
- The surface speciation of oxalate at the water-boehmite (γ-AlOOH) interface during adsorption and dissolution reactions was studied by means of attenuated total reflectance infrared spectroscopy. The structural interpretations of infrared (IR) data were based on comparison with results from theoretical frequency calculations. Two different surface complexes were identified: an inner-sphere complex with a bidentate five-membered chelate structure involving both carboxylate groups; and a hydrogen-bonded surface complex with no direct bonding to Al atoms. A scheme was developed by which the surface concentrations of these complexes could be determined from IR spectroscopy data. The concentration of the hydrogen bonded complex was shown to be strongly dependent on the experimental conditions, and the concentration of the inner-sphere complex was comparatively insensitive to the conditions within the studied experimental range. The dissolution data indicated that an excess of oxalate with respect to a critical surface concentration of oxalate was necessary to induce significant boehmite dissolution. Under dissolving conditions, the concentration of the inner-sphere complex was shown to be almost identical to this critical concentration and thus a stable entity.
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| 3. |
- Björk, Glenn R, et al.
(författare)
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A primordial tRNA modification required for the evolution of life?
- 2001
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Ingår i: EMBO Journal. - : Wiley. - 0261-4189 .- 1460-2075. ; 20:1-2, s. 231-239
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of reading frame maintenance must have been an early event, and presumably preceded the emergence of the three domains Archaea, Bacteria and Eukarya. Features evolved early in reading frame maintenance may still exist in present-day organisms. We show that one such feature may be the modified nucleoside 1-methylguanosine (m(1)G37), which prevents frameshifting and is present adjacent to and 3' of the anticodon (position 37) in the same subset of tRNAs from all organisms, including that with the smallest sequenced genome (Mycoplasma genitalium), and organelles. We have identified the genes encoding the enzyme tRNA(m(1)G37)methyltransferase from all three domains. We also show that they are orthologues, and suggest that they originated from a primordial gene. Lack of m(1)G37 severely impairs the growth of a bacterium and a eukaryote to a similar degree. Yeast tRNA(m(1)G37)methyltransferase also synthesizes 1-methylinosine and participates in the formation of the Y-base (yW). Our results suggest that m(1)G37 existed in tRNA before the divergence of the three domains, and that a tRNA(m(1)G37)methyltrans ferase is part of the minimal set of gene products required for life.
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| 4. |
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| 5. |
- Clausén, Maria, et al.
(författare)
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Spectroscopic studies of aluminum and gallium complexes with oxalate and malonate in aqueous solution
- 2003
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Ingår i: Journal of Molecular Structure. ; 648:3, s. 225-35
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Tidskriftsartikel (refereegranskat)abstract
- The local structures of Ga(III) in aqueous oxalate and malonate complexes were studied by means of Ga K-edge EXAFS spectroscopy. Irrespective of the number and type of coordinated ligands, the EXAFS results showed very regular first coordination shells consisting of six oxygen atoms. Scattering paths from more distant atoms revealed that both oxalate and malonate form mononuclear chelate structures where one oxygen from each carboxylate group binds to Ga(III). Again, very little variation in bond distances and no changes in coordination modes were detected as the number of ligands coordinated to Ga(III) was varied. Based on the very close resemblance of IR spectra of oxalate and malonate complexes of Al(III), and the corresponding complexes of Ga(III), it is believed that the local structures of the Al(III) complexes are similar to those of the Ga(III) complexes in terms of ligand coordination modes and distortions. This conclusion was corroborated by results from theoretical frequency calculations.
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| 6. |
- Faarinen, Mikko, et al.
(författare)
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Al-26 at the AMS facility in Lund
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 223-24, s. 130-134
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Tidskriftsartikel (refereegranskat)abstract
- To broaden the AMS programme in Lund by including Al studies, a new injector has been installed and tested at the 3 MV Pelletron accelerator. Detailed optical calculations have been performed to obtain maximum mass and energy resolution. The design of the injector, the improvement in the resolution compared to the old injector, as well as preliminary tests with a Al-26-beam, are presented. By using accelerator mass spectrometry (AMS) to measure the long-lived aluminium isotope Al-26 it has become possible to study the uptake, distribution and retention of aluminium in biological system under physiologically realistic conditions. Results from a pilot project on Al-26 in wheat plants are presented.
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| 7. |
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| 8. |
- Faldt, J., et al.
(författare)
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Correlations between selected monoterpene hydrocarbons in the xylem of six Pinus (pinaceae) species
- 2001
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Ingår i: Chemoecology. - 0937-7409 .- 1423-0445. ; 11:2, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- The compositions of 23 monoterpene hydrocarbons of six pine species (Pinus sylvestris, P. yunnanensis ll,ris, P. armandii, P. tropicalis, P. cubensis and P. caribaca) were compared, using multivariate data analysis. Four of the six species were clearly different from the other species in a Principal Components Analysis (PCA) model, based on the relative amounts (selective normalization) of the monoterpenes. The correlation coefficients between constituents were determined separately for each species and the strongest correlations were found between (+)-alpha -pinene and (+)-camphene and between the corresponding (-)-enantiomers, in all species. This pattern, i.e. a good correlation in all species, was neither shown by the correlation of the structurally more similar (+)-alpha/beta -pinenes, nor by the (-)-alpha/beta -pinenes or within the enantiomeric pairs of alpha -pinene and beta -pinene. For these pairs of monoterpenes, good correlations were found in some species. None of the species showed good correlations in all the investigated monoterpene pairs presented here. Correlations between monoterpenes in insect-attacked trees (P. cubensis and P. caribaea, attacked by Dioryctria horneana, and P. yunnanensis, attacked by Tomicus piniperda) were also determined. The results are discussed from chemotaxonomic and biosynthetic points of view.
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| 9. |
- Finnbogadottir, Hafrún, et al.
(författare)
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Expectant first-time fathers’ experiences of pregnancy
- 2003
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Ingår i: Midwifery. - : Elsevier. - 0266-6138 .- 1532-3099. ; 19:2, s. 96-105
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Tidskriftsartikel (refereegranskat)abstract
- Objective: to describe first-time-expectant fathers’ experiences of pregnancy.Design: an inductive method using narrative interview formand qualitative content textanalysis.The text of the transcriptswas coded and categorised.Settings and participants: seven first-time-expectant fathers living in a multicultural industrial town in southern Sweden were interviewed individually when their partner was in the 38th to 39thweek of pregnancy.Measurements and findings: all the fathers-to-be experienced some psychological, socialand/or physical change during the pregnancy. The main category, was ‘time of transition’. Eight categories were found under this. They were: ‘feelings of unreality, ‘insufficiency and inadequacy’, ‘exclusion’, ‘reality’, ‘social changes’, ‘physical changes’, ‘responsibility, and development’.Key conclusion: the fathers’-to-be special needs for support and encouragement durin gpregnancymay be as important as those of the mothers’-to-be. The caregiver needs to be as aware of and sensitive to these needs. However, before any interventions can be recommendedmore research is needed.
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| 10. |
- Hellborg, Ragnar, et al.
(författare)
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A high resolution AMS-injector for the Pelletron in Lund
- 2002
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Ingår i: Pramana. - 0973-7111. ; 59:6, s. 1061-1073
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Tidskriftsartikel (refereegranskat)abstract
- A high resolution injector system has recently been installed at the Lund 3 MV tandem Pelletron accelerator. The new injector, designed mainly for Al-26 ions, will increase the experimental potential of the Lund AMS facility considerably. High quality energy- and mass-resolution is obtained by using a 90degrees spherical electrostatic analyzer followed by a 90degrees magnetic analyzer. The injector is equipped with a high intensity sputtering source with a spherical ionizer. A new analytical technique for acceptance calculations as well as PC-based computational methods have been used in the design of the ion optical system of the new injector. Compared to our old injector system which has a magnetic analyzer with a bending angle of only 15degrees, the new system has a more than ten times better resolution. The beam optics of the new system is also better designed to match the accelerator acceptance. In this way the ion transmission from the ion source to the detector, for different ions of interest in our AMS programme, has been increased.
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