| 1. |
- Andersson, Marie-Louise, et al.
(författare)
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Differential expression of human endogenous retroviral sequences similar to mouse mammary tumor virus in normal peripheral blood mononuclear cells
- 1996
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Ingår i: AIDS Research and Human Retroviruses. - 0889-2229 .- 1931-8405. ; 12:9, s. 833-40
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Tidskriftsartikel (refereegranskat)abstract
- Mouse mammary tumor virus (MMTV) is a retrovirus that causes breast cancer in certain strains of mice. In a previous study we identified, by sequencing clones from human lymphocytes, six groups with similarities to MMTV. Using a primer pair derived from pol sequences conserved within types A, B, and D retroviruses and probes from the six human MMTV-like (HML-1 to HML-6) groups in an internally controlled hybridization assay we investigated the normal variation of expression in PBMCs. Variations occurred within all groups but was most significant within group HML-1, where hybridization signals differed by more than 500-fold between individuals. Groups HML-2 and HML-3 showed consistently stronger hybridization signals than groups HML-1 and HML-5, while group HML-6 resulted in weak signals for all individuals. Stringent hybridization of the amplified cDNA to 20 individual HML clones also demonstrated a marked heterogeneity of expression. Hybridization signals from some groups and sequences were found to be correlated, either in a positive or negative fashion. RNA isolated from PBMCs collected from two donors at four different time points (in the morning and in the afternoon on the same day, repeated 1 week later) was also analyzed using the six hml probes. A small variation in hybridization signals was seen in samples collected on the same day, but a larger difference was observed in samples taken 1 week later. The correlations and the differences in the expression of HMLs between individuals implicate a complex transcriptional regulation system of these sequences.
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| 2. |
- Andersson, Patrik, et al.
(författare)
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Readability of vertically vibrating aircraft displays
- 1999
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Ingår i: Displays (Guildford). - 0141-9382 .- 1872-7387. ; 20:1, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- Vibrations pose a problem to the visual system. The vibrations in aircraft are mainly vertical and cause reading errors when the pilots read the instruments. In three experiments, reading capability was tested during vertical vibration of modern military aircraft, using symbols presented on a computer monitor. The results showed that complexity of symbols have a significant effect on the performance. The orientations of symbols were also of importance for their readability. Indexes made up of horizontally oriented lines were found to be especially difficult to read during vertical vibration. Orienting them 45° up or down improved readability in a significant way. The size of the symbols was found to be of importance especially when they were horizontally oriented.
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| 3. |
- Andersson, Patrik, et al.
(författare)
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The internal barriers of rotation for the 209 polychlorinated biphenyls
- 1997
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Ingår i: Environmental Science and Pollution Research. - 0944-1344 .- 1614-7499. ; 4:2, s. 75-81
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Tidskriftsartikel (refereegranskat)abstract
- The internal barrier of rotation (Erot) was calculated for all 209 polychlorinated biphenyls (PCBs) by using a semi-empirical method, viz. the Austin Model 1 (AM1) Hamiltonian. The difference in total energy between a forced planar state and an optimised twisted structure was defined as Erot. The Erot values were in the range of 8.33 to 483 kJ/mol, and were significantly influenced by the number of chlorine atoms in ortho position. An additional structural characteristic of the PCBs influencing Erot of ortho substituted congeners was substitution by chlorine atoms in vicinal meta positions, which is assumed to prevent outward bending of ortho substituents. This so-called buttressing effect contributed with 4 to 31 kJ/mol per added chlorine atom. In conclusion, the internal barrier of rotation, calculated for all 209 PCBs, provides an important structure dependent physico-chemical parameter for multivariate modelling of future quantitative structure-activity and structure-property relationships (QSARs/QSPRs).
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| 4. |
- Andersson, Patrik, et al.
(författare)
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Ultraviolet absorption characteristics and calculated semi-empirical parameters as chemical descriptors in multivariate modelling of polychlorinated biphenyls
- 1996
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Ingår i: Journal of Chemometrics. - 0886-9383 .- 1099-128X. ; 10:2, s. 171-185
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Tidskriftsartikel (refereegranskat)abstract
- The structural variation within the polychlorinated biphenyls (PCBs) was characterized by using principal component analysis (PCA). A multivariate model was evolved from 52 physicochemical descriptors including measured ultraviolet (UV) absorption spectra, calculated semiempirical parameters (AM1) and properties captured from the literature. Parameters calculated by using the AM1-Hamiltonian were e.g. heat of formation, dipole moments, ionization potential and the barrier of internal rotation. The UV spectra were measured and digitized in the range 200-300 nm. The multivariate model revealed that most of the information within the set of physicochemical parameters was related to molecular size. Descriptors depending on size were e.g. GC retention times, partition coefficients and a subset of semiempirically derived energy terms. Important also were parameters reflecting differences in substitution patterns and related to electronic and steric properties, such as UV absorption in the wavelength region 245-300 nm, the barrier of internal rotation and the ionization potential. The developed model describes the large variation in physicochemical characteristics within the PCBs. The importance of a broad chemical characterization is illustrated by a quantitative structure-activity relationship (QSAR) for the potency of inhibition of intercellular communication for 27 structurally diverse tetra- to heptachlorinated PCBs.
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| 5. |
- Andersson, Patrik, et al.
(författare)
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Ultraviolet absorption spectra of all 209 polychlorinated biphenyls evaluated by principal component analysis
- 1997
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Ingår i: Fresenius' Journal of Analytical Chemistry. - : Springer Science and Business Media LLC. - 0937-0633 .- 1432-1130. ; 357:8, s. 1088-1092
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Tidskriftsartikel (refereegranskat)abstract
- The ultraviolet absorption spectra of all 209 polychlorinated biphenyls (PCBs) were recorded in the range 200-300 nm and displayed two important absorption maxima, viz., the main-band, lambda(max) 200-225 nm, and the kappa-band, lambda(max) 245-265 nm. By utilising principal component analysis, substitution related spectral characteristics of the PCBs, underlying the main patterns of the spectra, were examined. Captured in the multivariate evaluation were e.g., the importance of chlorine atoms in ortho positions, determining the intensity and existence of the kappa-band, chlorine substitution in para-para position, and the total number of chlorine atoms. The measured UV-spectra of all 209 polychlorinated biphenyls provide important physico-chemical descriptors for use in future quantitative structure-activity and structure-property relationship (QSAR/QSPR) studies.
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| 6. |
- Andersson, Patrik, 1969
(författare)
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Wavelets and Local Regularity
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We treat a number of topics related to wavelets and the description of local regularity properties of functions. First we prove several different exact characterizations of pointwise Hölder spaces, and use these characterizations to improve a theorem by Jaffard on Hölder exponents. Next we generalize the two-microlocal spaces of Bony to a Triebel-Lizorkin setting, and show that these new spaces can be characterized by wavelet coefficients. We also prove two alternative characterizations, formulated in terms of local norms and weighted spaces. Then we construct a new type of basis that combines the active segmentation properties of local trigonometric bases with the ability of wavelets to analyze a multitude of function spaces. Finally, we study the set of functions such that all the wavelet coefficients with respect to a compactly supported wavelet basis vanish, and show how this relates to characterization of homogeneous smoothness spaces and large-scale renormalization of homogeneous wavelet expansions.
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| 7. |
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| 8. |
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| 9. |
- Björkman, Johanna, et al.
(författare)
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Novel ribosomal mutations affecting translational accuracy, antibiotic resistance and virulence of Salmonella typhimurium
- 1999
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Ingår i: Molecular Microbiology. - : BLACKWELL SCIENCE LTD. - 0950-382X .- 1365-2958. ; 31:1, s. 53-58
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Many mutations in rpsL cause resistance to, or dependence on, streptomycin and are restrictive (hyperaccurate) in translation. Dependence on streptomycin and hyperaccuracy can each be reversed phenotypically by mutations in either rpsD or rpsE. Such compensatory mutations have been shown to have a ram phenotype (ribosomal ambiguity), increasing the level of translational errors. We have shown recently that restrictive rpsL alleles are also associated with a loss of virulence in Salmonella typhimurium. To test whether ram mutants could reverse this loss of virulence, we have isolated a set of rpsD alleles in Salmonella typhimurium. We found that the rpsD alleles restore the virulence of strains carrying restrictive rpsL alleles to a level close to that of the wild type. Unexpectedly, three out of seven mutant rpsD alleles tested have phenotypes typical of restrictive alleles of rpsL, being resistant to streptomycin and restrictive (hyperaccurate) in translation. These phenotypes have not been previously associated with the ribosomal protein S4. Furthermore, all seven rpsD alleles (four ram and three restrictive) can phenotypically reverse the hyperaccuracy associated with restrictive alleles of rpsL. This is the first demonstration that such compensations do not require that the compensating rpsD allele has a ribosomal ambiguity (ram) phenotype.
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| 10. |
- Nyberg, Lars, et al.
(författare)
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Skogsmarkens kemi i Värmland : En jämförelse av ståndortskarteringen och Värmlandsundersökningen
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten redovisar en jämförelse av två markkemiska undersökningar i Värmland, Värmlandsundersökningen på 180 platser 1994, och den nationella ståndortskarte-ringen på upp till 89 platser 1983-87. I jämförelsen har data för mark-pH, utbytbart förråd av katjoner och mineraljordens totalinnehåll av element tagits med. Jämförelsen påverkades av ett antal faktorer som skiljde sig åt i de båda undersökningarna, t ex att antalet provpunkter var olika, att provtagningen i ståndortskarteringen omfattade olika typer av jordmåner medan Värmlandsundersökningen endast omfattade podsolerade jordar och att de kemiska analyserna utfördes med delvis olika metoder.För mark-pH och de olika katjonerna i det utbytbara förrådet var såväl medelnivåerna som de regionala variationsmönstren olika för ståndortskarteringen och Värmlands-undersökningen. Skill-naden i nivå kan förklaras av att rikare jordar ingick i ståndorts-karteringen. Dessutom kan surt ned-fall under de ca tio år som skiljde undersökning-arna i tiden ha sänkt mark-pH och minskat det utbytbara förrådet av baskatjoner, även om det sura nedfallet minskat under perioden. Jämförelser av huvudelementen i mine-raljorden visade på relativt god överensstämmelse mellan ståndortskarteringen och Värmlandsundersökningen, såväl vad gäller medelnivå i länet och vad gäller den geo-grafiska variationen. För spårelementen i mineraljorden skilde medelnivåerna stort mellan ståndortskarteringen och Värmlandsundersökningen, troligen beroende på att provtagningsdjupen var olika
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