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- Kondo, Y., et al.
(author)
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First observation of 28 O
- 2023
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In: Nature. - 0028-0836 .- 1476-4687. ; 620:7976, s. 965-970
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Journal article (peer-reviewed)abstract
- Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton (N/Z) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N/Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist only as very short-lived resonances (about 10−21s), provide the most stringent tests of modern nuclear-structure theories. Here we report on the first observation of 28O and 27O through their decay into 24O and four and three neutrons, respectively. The 28O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers1,2, it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called ‘doubly magic’ nuclei. Both 27O and 28O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of 28O from a 29F beam is consistent with it not exhibiting a closed N = 20 shell structure.
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| 4. |
- Arnshav, Mirja, 1977-
(author)
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De små båtarna och den stora flykten : Arkeologi i spåren av andra världskrigets baltiska flyktbåtar
- 2020
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Doctoral thesis (other academic/artistic)abstract
- The Baltic states, Estonia, Latvia and Lithuania, were occupied no less than three times during the Second World War. Faced with a reign of terror, the threat of deportation, and compulsory conscription, over 30,000 people fled over the Baltic Sea to Sweden. On their arrival in Sweden, most escape boats were confiscated by the authorities and in 1945 were returned to the Soviet Union.This study, which began as an attempt to find out about the Baltic escape boats that ended up in Sweden, is inspired by a foreign boat in a small fishing harbour on the island of Gotland. My curiosity was piqued when I caught sight of the boat and heard that it had probably been an escape boat.The purpose of this thesis is to establish which, if any, Baltic escape boats survive in Sweden, in which contexts they remain, and to review their state of preservation, as well as to answer the question of their significance for the memory of the escape. It is an archaeology of the escape and its aftermath, based on the surviving escape boats – what the boats say about the escape, what happened to them afterwards, and how people relate to them and their historical legacy today.The study looks at 35 boats that have been described as Baltic escape boats in various contexts. It shows that they are found in a multitude of environments and in a range of different states of preservation. The boats illustrate experiences that few other source materials can convey, in a manner pertinent to the archaeological understanding of flight. In addition, the boats are rare traces of an earlier Estonian coastal culture eradicated by the second Soviet occupation.One of the most important outcomes of the study is the documentation from the survey and examinations carried out. Few of the boats were known outside their local context. A national compilation has been lacking, which has impeded research and ultimately our understanding of the breadth and complexity of the Swedish historical landscape when it comes to ship remains.
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- Bergwik, Jesper, et al.
(author)
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Binding of the human antioxidation protein α1-microglobulin (A1M) to heparin and heparan sulfate. Mapping of binding site, molecular and functional characterization, and co-localization in vivo and in vitro
- 2021
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In: Redox Biology. - : Elsevier BV. - 2213-2317. ; 41
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Journal article (peer-reviewed)abstract
- Heparin and heparan sulfate (HS) are linear sulfated disaccharide polymers. Heparin is found mainly in mast cells, while heparan sulfate is found in connective tissue, extracellular matrix and on cell membranes in most tissues. α1-microglobulin (A1M) is a ubiquitous protein with thiol-dependent antioxidant properties, protecting cells and matrix against oxidative damage due to its reductase activities and radical- and heme-binding properties. In this work, it was shown that A1M binds to heparin and HS and can be purified from human plasma by heparin affinity chromatography and size exclusion chromatography. The binding strength is inversely dependent of salt concentration and proportional to the degree of sulfation of heparin and HS. Potential heparin binding sites, located on the outside of the barrel-shaped A1M molecule, were determined using hydrogen deuterium exchange mass spectrometry (HDX-MS). Immunostaining of endothelial cells revealed pericellular co-localization of A1M and HS and the staining of A1M was almost completely abolished after treatment with heparinase. A1M and HS were also found to be co-localized in vivo in the lungs, aorta, kidneys and skin of mice. The redox-active thiol group of A1M was unaffected by the binding to HS, and the cell protection and heme-binding abilities of A1M were slightly affected. The discovery of the binding of A1M to heparin and HS provides new insights into the biological role of A1M and represents the basis for a novel method for purification of A1M from plasma.
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| 6. |
- Bimai, Ornella, et al.
(author)
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Nucleotide binding to the ATP-cone in anaerobic ribonucleotide reductases allosterically regulates activity by modulating substrate binding
- 2024
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In: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 12
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Journal article (peer-reviewed)abstract
- A small, nucleotide-binding domain, the ATP-cone, is found at the N- terminus of most ribonucleotide reductase (RNR) catalytic subunits. By binding adenosine triphosphate (ATP) or deoxyadenosine triphosphate (dATP) it regulates the enzyme activity of all classes of RNR. Functional and structural work on aerobic RNRs has revealed a plethora of ways in which dATP inhibits activity by inducing oligomerisation and preventing a productive radical transfer from one subunit to the active site in the other. Anaerobic RNRs, on the other hand, store a stable glycyl radical next to the active site and the basis for their dATP-dependent inhibition is completely unknown. We present biochemical, biophysical, and structural information on the effects of ATP and dATP binding to the anaerobic RNR from Prevotella copri. The enzyme exists in a dimertetramer equilibrium biased towards dimers when two ATP molecules are bound to the ATP- cone and tetramers when two dATP molecules are bound. In the presence of ATP, P. copri NrdD is active and has a fully ordered glycyl radical domain ( GRD) in one monomer of the dimer. Binding of dATP to the ATP-cone results in loss of activity and increased dynamics of the GRD, such that it cannot be detected in the cryo-EM structures. The glycyl radical is formed even in the dATP-bound form, but the substrate does not bind. The structures implicate a complex network of interactions in activity regulation that involve the GRD more than 30 A away from the dATP molecules, the allosteric substrate specificity site and a conserved but previously unseen flap over the active site. Taken together, the results suggest that dATP inhibition in anaerobic RNRs acts by increasing the flexibility of the flap and GRD, thereby preventing both substrate binding and radical mobilisation.
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| 7. |
- Bimai, Ornella, et al.
(author)
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Nucleotide binding to the ATP-cone in anaerobic ribonucleotide reductases allosterically regulates activity by modulating substrate binding
- 2024
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In: eLife. - 2050-084X. ; 12
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Journal article (peer-reviewed)abstract
- A small, nucleotide-binding domain, the ATP-cone, is found at the N-terminus of most ribonucleotide reductase (RNR) catalytic subunits. By binding adenosine triphosphate (ATP) or deoxyadenosine triphosphate (dATP) it regulates the enzyme activity of all classes of RNR. Functional and structural work on aerobic RNRs has revealed a plethora of ways in which dATP inhibits activity by inducing oligomerisation and preventing a productive radical transfer from one subunit to the active site in the other. Anaerobic RNRs, on the other hand, store a stable glycyl radical next to the active site and the basis for their dATP-dependent inhibition is completely unknown. We present biochemical, biophysical, and structural information on the effects of ATP and dATP binding to the anaerobic RNR from Prevotella copri. The enzyme exists in a dimer– tetramer equilibrium biased towards dimers when two ATP molecules are bound to the ATP-cone and tetramers when two dATP molecules are bound. In the presence of ATP, P. copri NrdD is active and has a fully ordered glycyl radical domain (GRD) in one monomer of the dimer. Binding of dATP to the ATP-cone results in loss of activity and increased dynamics of the GRD, such that it cannot be detected in the cryo-EM structures. The glycyl radical is formed even in the dATP-bound form, but the substrate does not bind. The structures implicate a complex network of interactions in activity regulation that involve the GRD more than 30 Å away from the dATP molecules, the allosteric substrate specificity site and a conserved but previously unseen flap over the active site. Taken together, the results suggest that dATP inhibition in anaerobic RNRs acts by increasing the flexibility of the flap and GRD, thereby preventing both substrate binding and radical mobilisation.
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| 8. |
- Ekström, Erik, et al.
(author)
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Microstructure control and property switching in stress-free van der Waals epitaxial VO2 films on mica
- 2023
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In: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 229
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Journal article (peer-reviewed)abstract
- Realizing stress-free inorganic epitaxial films on weakly bonding substrates is of importance for applications that require film transfer onto surfaces that do not seed epitaxy. Film-substrate bonding is usually weakened by harnessing natural van der Waals layers (e.g., graphene) on substrate surfaces, but this is difficult to achieve in non-layered materials. Here, we demonstrate van der Waals epitaxy of stress-free films of a non-layered material VO2 on mica. The films exhibit out-of-plane 010 texture with three in-plane orientations inherited from the crystallographic domains of the substrate. The lattice parameters are invariant with film thickness, indicating weak film-substrate bonding and complete interfacial stress relaxation. The out-of-plane domain size scales monotonically with film thickness, but the in-plane domain size exhibits a minimum, indicating that the nucleation of large in-plane domains supports subsequent island growth. Complementary ab initio investigations suggest that VO2 nucleation and van der Waals epitaxy involves subtle polarization effects around, and the active participation of, surface potassium atoms on the mica surface. The VO2 films show a narrow domain-size-sensitive electrical-conductivity-temperature hysteresis. These results offer promise for tuning the properties of stress-free van der Waals epitaxial films of non-layered materials such as VO2 through microstructure control.
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| 9. |
- Ekström, Simon, 1966-
(author)
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Alfred Nobels känsla för hummer
- 2021
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In: Svenska dagbladet. - 1101-2412.
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Journal article (pop. science, debate, etc.)abstract
- Att läsa menyerna för de drygt hundra Nobelmiddagarna som hittills ordnats är att ta del av en veritabel kulinarisk teater. Inte minst belyser hummerns förändrade närvaro vid banketten en viktig förskjutning av idén om hur Sverige ska representeras vid dessa tillfällen.
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