| 1. |
- Aronsson, Henrik, 1971, et al.
(författare)
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Toc64/OEP64 is not essential for the efficient import of proteins into chloroplasts in Arabidopsis thaliana
- 2007
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Ingår i: Plant Journal. - 0960-7412. ; 52:1, s. 53-68
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Tidskriftsartikel (refereegranskat)abstract
- Toc64/OEP64 was identified biochemically in pea as a putative component of the chloroplast protein import apparatus. In Arabidopsis, three paralogous genes (atTOC64-III, atTOC64-V and atTOC64-I) encode Toc64-related proteins, and these have been reported to localize in chloroplasts, mitochondria and the cytosol, respectively. To assess the role of the atToc64-III protein in chloroplast protein import in an in vivo context, we identified and characterized Arabidopsis knockout mutants. The absence of detectable defects in toc64-III single mutants raised the possibility of redundancy, and prompted us to also identify toc64-V and toc64-I mutants, cross them to toc64-III, and generate double- and triple-mutant combinations. The toc64 mutants were analysed carefully with respect to a variety of criteria, including chlorophyll accumulation, photosynthetic performance, organellar ultrastructure and chloroplast protein accumulation. In each case, the mutant plants were indistinguishable from wild type. Furthermore, the efficiency of chloroplast protein import was not affected by the toc64 mutations, even when a putative substrate of the atToc64-III protein (wheatgerm-translated precursor of the 33 kDa subunit of the oxygen-evolving complex, OE33) was examined. Moreover, under various stress conditions (high light, osmotic stress and cold), the toc64 triple-mutant plants were not significantly different from wild type. These results demonstrate that Toc64/OEP64 is not essential for the efficient import of proteins into chloroplasts in Arabidopsis, and draw into question the functional significance of this component.
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| 2. |
- Boij, Mats, et al.
(författare)
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On the Weak Lefschetz Property for artinian Gorenstein algebras of codimension three
- 2014
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Ingår i: Journal of Algebra. - : Elsevier BV. - 0021-8693 .- 1090-266X. ; 403, s. 48-68
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Tidskriftsartikel (refereegranskat)abstract
- We study the problem of whether an arbitrary codimension three graded artinian Gorenstein algebra has the Weak Lefschetz Property. We reduce this problem to checking whether it holds for all compressed Gorenstein algebras of odd socle degree. In the first open case, namely Hilbert function (1, 3, 6, 6, 3, 1), we give a complete answer in every characteristic by translating the problem to one of studying geometric aspects of certain morphisms from P2 to P3, and Hesse configurations in P2.
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| 3. |
- Boij, Mats, et al.
(författare)
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The minimal resolution conjecture on a general quartic surface in P-3
- 2019
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Ingår i: Journal of Pure and Applied Algebra. - : Elsevier. - 0022-4049 .- 1873-1376. ; 223:4, s. 1456-1471
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Tidskriftsartikel (refereegranskat)abstract
- Mustata has given a conjecture for the graded Betti numbers in the minimal free resolution of the ideal of a general set of points on an irreducible projective algebraic variety. For surfaces in P-3 this conjecture has been proven for points on quadric surfaces and on general cubic surfaces. In the latter case, Gorenstein liaison was the main tool. Here we prove the conjecture for general quartic surfaces. Gorenstein liaison continues to be a central tool, but to prove the existence of our links we make use of certain dimension computations. We also discuss the higher degree case, but now the dimension count does not force the existence of our links.
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| 4. |
- Boij, Mats, et al.
(författare)
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The non-Lefschetz locus
- 2018
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Ingår i: Journal of Algebra. - : Academic Press. - 0021-8693 .- 1090-266X. ; 505, s. 288-320
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Tidskriftsartikel (refereegranskat)abstract
- We study the weak Lefschetz property of artinian Gorenstein algebras and in particular of artinian complete intersections. In codimension four and higher, it is an open problem whether all complete intersections have the weak Lefschetz property. For a given artinian Gorenstein algebra A we ask what linear forms are Lefschetz elements for this particular algebra, i.e., which linear forms ℓ give maximal rank for all the multiplication maps ×ℓ:[A]i⟶[A]i+1. This is a Zariski open set and its complement is the non-Lefschetz locus. For monomial complete intersections, we completely describe the non-Lefschetz locus. For general complete intersections of codimension three and four we prove that the non-Lefschetz locus has the expected codimension, which in particular means that it is empty in a large family of examples. For general Gorenstein algebras of codimension three with a given Hilbert function, we prove that the non-Lefschetz locus has the expected codimension if the first difference of the Hilbert function is of decreasing type. For completeness we also give a full description of the non-Lefschetz locus for artinian algebras of codimension two.
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| 7. |
- Boij, Susann, et al.
(författare)
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Reflection properties of a flow pipe with a small angle diffuser outlet
- 2010
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Ingår i: 17th International Congress on Sound and Vibration 2010, ICSV 2010. - 9781617822551 ; , s. 706-712
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Konferensbidrag (refereegranskat)abstract
- The reflection of plane acoustic waves is studied for an open pipe termination where the outlet section about 10 cm long is a diffuser with a small angle. Diffuser angles up to 6o with a sharp outlet edge are considered both without and with a mean flow. The experiments are performed for Helmholtz numbers, He, based on the pipe diameter, up to 1.0 and mean flow Mach numbers, M, up to 0.25. A multi-microphone method is used for accurate measurements of the acoustic fields inside the pipe. With no mean flow, the reflection coefficient results are compared with the theories for thin walls by Levine and Schwinger [1] and for the end correction and thick walls by Ando [2], respectively. The data for the magnitude of the reflection coefficient for different pipe end geometries show that in the low frequency regime it is the outlet radius that determines the magnitude of the energy reflection coefficient. The same collapse in the data is not obtained for the end correction which is strongly affected by the pipe end geometry. Experimental results of the reflection coefficient in the presence of a mean flow show a similar behaviour as without flow. However, it is the Strouhal number of the outlet that governs the losses, i.e., radiation and flow losses. For a region of small Strouhal numbers, the reflection is larger than one, as predicted for straight pipes, [3, 4]. An increased diffuser angle and rounded edges both increase the reflection at the pipe termination in a critical range of Strouhal numbers, which indicates that the reflection coefficient is strongly dependent on the shape, half angle, and edge curvature of the pipe end in this region.
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| 10. |
- Mjösberg, Jenny, et al.
(författare)
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Systemic reduction of functionally suppressive CD4dimCD25highFoxp3+ T-regs in human second trimester pregnancy is induced by progesterone and 17 beta-estradiol
- 2009
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Ingår i: Journal of Reproductive Immunology(ISSN 0165-0378), vol 81, issue 2. - : Elsevier BV. ; , s. 160-161
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Konferensbidrag (refereegranskat)abstract
- CD4+CD25high regulatory T cells (Tregs) are implicated in maintenance of murine pregnancy. However, reports regarding circulating Treg frequencies in human pregnancy are inconsistent and the functionality and phenotype of these cells in pregnancy have not been clarified. The aim was to determine the frequency, phenotype and function of circulating Tregs in second trimester human pregnancy and the influence of progesterone and 17β-estradiol on Treg phenotype and frequency. Based on expression of Foxp3, CD127 and HLA-DR, as determined by multi-color flow cytometry, we defined a proper CD4dimCD25high Treg population and showed, in contrast to most previous reports, that this population was reduced in second trimester pregnancy. Unexpectedly, Foxp3 expression was decreased in the Treg, as well as in the CD4+ population. These changes could be replicated in an in vitro system resembling the pregnancy hormonal milieu, where 17β-estradiol, and in particular progesterone, induced, in line with the pregnancy situation, a reduction of CD4dimCD25highFoxp3+ cells in PBMC from non-pregnant women. By co-culturing FACS-sorted Tregs and autologous CD4+CD25- responder cells, we showed that Tregs from pregnant women still displayed the same suppressive capacity as non-pregnant women in terms of suppressing IL-2, TNF-α and IFN-γ secretion from responder cells while efficiently producing IL-4 and IL-10. Our findings support the view of hormones, particularly progesterone, as critical regulators of Tregs in pregnancy. Further, we suggest that in the light of the results of this study, early data on circulating Treg frequencies in pregnancy need re-evaluation.
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