| 1. |
- Cossarizza, A., et al.
(författare)
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Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)
- 2019
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Ingår i: European Journal of Immunology. - : Wiley. - 0014-2980 .- 1521-4141. ; 49:10, s. 1457-1973
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Tidskriftsartikel (refereegranskat)abstract
- These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.
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| 2. |
- Lestinsky, M., et al.
(författare)
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Physics book: CRYRING@ESR
- 2016
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Ingår i: European Physical Journal: Special Topics. - : Springer Science and Business Media LLC. - 1951-6401 .- 1951-6355. ; 225:5, s. 797-882
-
Forskningsöversikt (refereegranskat)abstract
- The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).
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| 3. |
- Abila, R., et al.
(författare)
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Oil extraction imperils Africa’s Great Lakes
- 2016
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 354:6312, s. 561-562
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- As the world's demands for hydrocarbons increase (1), remote areas previously made inaccessible by technological limitations are now being prospected for oil and gas deposits. Virtually unnoticed by the public, such activities are ongoing in the East African Great Lakes region, threatening these ecosystems famed for their hyper-diverse biota, including the unique adaptive radiations of cichlid fishes (2). Countries in the region see exploitation of hydrocarbon reserves as a vital economic opportunity. In the Lake Albert region of Uganda, for example, the government foresees a $3.6 billion oil profit per year starting in 2018—a sum almost as high as the country's current annual budget (3). However, oil extraction in the East African Great Lakes region poses grave risks to the environment and local communities.
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| 4. |
- Cocolios, T. E., et al.
(författare)
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Early Onset of Ground State Deformation in Neutron Deficient Polonium Isotopes
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:5, s. 052503-
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Tidskriftsartikel (refereegranskat)abstract
- In-source resonant ionization laser spectroscopy of the even-A polonium isotopes Po-192-210,Po-216,Po-218 has been performed using the 6p(3)7s S-5(2) to (6)p(3)7p P-5(2) (lambda = 843.38 nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in Po200-210 with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by beyond mean field calculations.
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| 5. |
- Mondal, S., et al.
(författare)
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Photoelectron angular distributions for the two-photon sequential double ionization of xenon by ultrashort extreme ultraviolet free electron laser pulses
- 2013
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16
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Tidskriftsartikel (refereegranskat)abstract
- Xenon atoms are double-ionized by sequential two-photon absorption by ultrashort extreme ultraviolet free-electron laser pulses with a photon energy of 23.0 and 24.3 eV, produced by the SPring-8 Compact SASE Source test accelerator. The angular distributions of photoelectrons generated by two-photon double ionization are obtained using velocity map imaging. The results are reproduced reasonably well by the present theoretical calculations within the multi-configurational Dirac-Fock approach.
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| 6. |
- Cocolios, T. E., et al.
(författare)
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Early onset of deformation in the neutron-deficient polonium isotopes
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 381:1, s. 012072-
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Tidskriftsartikel (refereegranskat)abstract
- In-source laser spectroscopy has been performed at CERN-ISOLDE with the RILIS laser ion source on 191-204,206,208-211,216,218Po. New information on the β decay of 199Po were extracted in the process, challenging previous results. Large-scale atomic calculations were performed to extract the changes in the mean-square charge radius δr 2 from the isotope shifts. The δ«r» 2 for the even-A isotopes reveal a large deviation from the spherical droplet model for N < 116.
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| 7. |
- Seliverstov, M. D., et al.
(författare)
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Charge radii of odd-A Po191-211 isotopes
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 719:4-5, s. 362-366
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Tidskriftsartikel (refereegranskat)abstract
- Isotope shifts have been measured for the odd-A polonium isotopes Po191-211 and changes in the nuclear mean square charge radii delta < r(2 >) have been deduced. The measurements were performed at CERN-ISOLDE using the in-source resonance-ionization spectroscopy technique. The combined analysis of these data and our recent results for even-A polonium isotopes indicates an onset of deformation already at Po-197,Po-198, when going away from stability. This is significantly earlier than was suggested by previous theoretical and experimental studies of the polonium isotopes. Moreover and in contrast to the mercury isotopes, where a strong odd-even staggering of the charge radii of the ground states was observed by approaching the neutron mid-shell at N = 104, no such effect is present in polonium down to Po-191. Consequently the charge radii of both isomeric and ground states of the odd-A polonium isotopes follow the same trend as the even-A isotopes.
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| 8. |
- Kozhevnikov, V., et al.
(författare)
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Nonlocal effect and dimensions of Cooper pairs measured by low-energy muons and polarized neutrons in type-I superconductors
- 2013
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 87:10, s. 104508-
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Tidskriftsartikel (refereegranskat)abstract
- The Pippard coherence length xi(0) (the size of a Cooper pair) in two extreme type-I superconductors (In and Sn) was determined directly through high-resolution measurement of the nonlocal electrodynamic effect combining low-energy muon spin rotation spectroscopy and polarized neutron reflectometry. The renormalization factor Z = m*(cp)/2m (m*(cp) and m are the mass of the Cooper pair and the electron, respectively) resulting from the electron-phonon interaction, and the temperature-dependent London penetration depth lambda(L)(T) were determined as well. An expression linking xi(0), Z, and lambda(L)(0) is introduced and experimentally verified. This expression allows one to determine experimentally the Pippard coherence length in any superconductor, independent of whether the superconductor is local or nonlocal, conventional or unconventional.
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| 9. |
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| 10. |
- Cespedes, PF, et al.
(författare)
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T-cell trans-synaptic vesicles are distinct and carry greater effector content than constitutive extracellular vesicles
- 2022
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1, s. 3460-
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Tidskriftsartikel (refereegranskat)abstract
- The immunological synapse is a molecular hub that facilitates the delivery of three activation signals, namely antigen, costimulation/corepression and cytokines, from antigen-presenting cells (APC) to T cells. T cells release a fourth class of signaling entities, trans-synaptic vesicles (tSV), to mediate bidirectional communication. Here we present bead-supported lipid bilayers (BSLB) as versatile synthetic APCs to capture, characterize and advance the understanding of tSV biogenesis. Specifically, the integration of juxtacrine signals, such as CD40 and antigen, results in the adaptive tailoring and release of tSV, which differ in size, yields and immune receptor cargo compared with steadily released extracellular vesicles (EVs). Focusing on CD40L+tSV as model effectors, we show that PD-L1 trans-presentation together with TSG101, ADAM10 and CD81 are key in determining CD40L vesicular release. Lastly, we find greater RNA-binding protein and microRNA content in tSV compared with EVs, supporting the specialized role of tSV as intercellular messengers.
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| 11. |
- Felce, JH, et al.
(författare)
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Single-Molecule, Super-Resolution, and Functional Analysis of G Protein-Coupled Receptor Behavior Within the T Cell Immunological Synapse
- 2021
-
Ingår i: Frontiers in cell and developmental biology. - : Frontiers Media SA. - 2296-634X. ; 8, s. 608484-
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Tidskriftsartikel (refereegranskat)abstract
- A central process in immunity is the activation of T cells through interaction of T cell receptors (TCRs) with agonistic peptide-major histocompatibility complexes (pMHC) on the surface of antigen presenting cells (APCs). TCR-pMHC binding triggers the formation of an extensive contact between the two cells termed the immunological synapse, which acts as a platform for integration of multiple signals determining cellular outcomes, including those from multiple co-stimulatory/inhibitory receptors. Contributors to this include a number of chemokine receptors, notably CXC-chemokine receptor 4 (CXCR4), and other members of the G protein-coupled receptor (GPCR) family. Although best characterized as mediators of ligand-dependent chemotaxis, some chemokine receptors are also recruited to the synapse and contribute to signaling in the absence of ligation. How these and other GPCRs integrate within the dynamic structure of the synapse is unknown, as is how their normally migratory Gαi-coupled signaling is terminated upon recruitment. Here, we report the spatiotemporal organization of several GPCRs, focusing on CXCR4, and the G protein Gαi2 within the synapse of primary human CD4+ T cells on supported lipid bilayers, using standard- and super-resolution fluorescence microscopy. We find that CXCR4 undergoes orchestrated phases of reorganization, culminating in recruitment to the TCR-enriched center. This appears to be dependent on CXCR4 ubiquitination, and does not involve stable interactions with TCR microclusters, as viewed at the nanoscale. Disruption of this process by mutation impairs CXCR4 contributions to cellular activation. Gαi2 undergoes active exclusion from the synapse, partitioning from centrally-accumulated CXCR4. Using a CRISPR-Cas9 knockout screen, we identify several diverse GPCRs with contributions to T cell activation, most significantly the sphingosine-1-phosphate receptor S1PR1, and the oxysterol receptor GPR183. These, and other GPCRs, undergo organization similar to CXCR4; including initial exclusion, centripetal transport, and lack of receptor-TCR interactions. These constitute the first observations of GPCR dynamics within the synapse, and give insights into how these receptors may contribute to T cell activation. The observation of broad GPCR contributions to T cell activation also opens the possibility that modulating GPCR expression in response to cell status or environment may directly regulate responsiveness to pMHC.
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| 12. |
- Gumberidze, A., et al.
(författare)
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Electron- and proton-impact excitation of heliumlike uranium in relativistic collisions
- 2019
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 99:3
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the K-shell excitation of He-like uranium (U90+) in relativistic collisions with hydrogen and argon atoms. Performing measurements with different targets, as well as with different collision energies, enabled us to explore the proton- (nucleus-) impact excitation as well as the electron-impact excitation process for the heaviest He-like ion. The large fine-structure splitting in uranium allowed us to partially resolve excitation into different L-shell levels. State-of-the-art relativistic calculations which include excitation mechanisms due to the interaction with both protons (nucleus) and electrons are in good agreement with the experimental findings. Moreover, our experimental data clearly demonstrate the importance of including the generalized Breit interaction in the treatment of the electron-impact excitation process.
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| 13. |
- Iablonskyi, D., et al.
(författare)
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High resolution study of the inner-shell 3p-3d and 3p-5s resonance regions in calcium atoms
- 2013
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 186, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- The 3p(5)4s(2)3d P-1(1) and 3p(5)(P-2(3/2))4s(2)5s (2)[3/2](1) resonance regions of Ca atoms have been studied experimentally with the aid of synchrotron radiation excited electron spectroscopy. The strong configuration interaction of the 3p(5)4s(2)3d, 3p(5)4s(2)5s and several other nearly degenerate configurations leads to complex structures observed in the photoelectron yield spectrum. Multiconfiguration Dirac-Fock (MCDF) calculations have been performed for these 3p-excited resonances of neutral calcium and compared to experimental results. The excitation and subsequent autoionization of these resonances lead to the final ionic 3p(6)nl states from which new high-lying members of the Rydberg p-series have been resolved experimentally. These new levels agree reasonably well with calculations as well as with the extrapolation of the Rydberg formula. The post collision interaction (PCI) effect has been observed in the transition Ca+ 3p(5)3d4s P-2(1/2,3/2)-> Ca2+ 3p(6) S-1(0) + e(Auger)(-) and explained by means of the rather long core-hole lifetime, while the decay of Ca+ 3p(5)3d4s P-4(1/2),(3/2,5/2) states is not affected by PCI. (c) 2013 Elsevier B.V. All rights reserved.
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| 14. |
- Kosugi, S., et al.
(författare)
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Strong configuration interaction in the 3p photoelectron spectrum of Kr
- 2020
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 101:4
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Tidskriftsartikel (refereegranskat)abstract
- We measured the Kr photoelectron spectrum in the region close to the 3p ionization threshold. Our high-resolution measurements allowed a clear observation of spectral structures due to electron correlation effects. Analysis based on relativistic multiconfiguration calculations could explain these observed peaks as due to strong configuration interactions between the 3p(-1) state and 3d(-2) nl states. Calculated and experimental data for peak assignments and intensity distributions are in good agreement. In addition, we measured the anisotropy parameter beta, which also agreed well with theory. These findings provide a detailed view of strong configuration interactions between the 3(-1) and 3d(-2)nl inner-shell hole states.
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| 15. |
- McGinn, Steven, et al.
(författare)
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New Technologies for DNA analysis-A review of the READNA Project.
- 2016
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Ingår i: New Biotechnology. - : Elsevier BV. - 1876-4347 .- 1871-6784.
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Forskningsöversikt (refereegranskat)abstract
- The REvolutionary Approaches and Devices for Nucleic Acid analysis (READNA) project received funding from the European Commission for 4 1/2 years. The objectives of the project revolved around technological developments in nucleic acid analysis. The project partners have discovered, created and developed a huge body of insights into nucleic acid analysis, ranging from improvements and implementation of current technologies to the most promising sequencing technologies that constitute a 3(rd) and 4(th) generation of sequencing methods with nanopores and in situ sequencing, respectively.
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| 16. |
- Motta, M., et al.
(författare)
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Controllable morphology of flux avalanches in microstructured superconductors
- 2014
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 89:13
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of abrupt bursts of magnetic flux into superconducting films with engineered periodic pinning centers (antidots) has been investigated. Guided flux avalanches of thermomagnetic origin develop a treelike structure, with the main trunk perpendicular to the borders of the sample, while secondary branches follow well-defined directions determined by the geometrical details of the underlying periodic pinning landscape. Strikingly, we demonstrate that in a superconductor with relatively weak random pinning the morphology of such flux avalanches can be fully controlled by proper combinations of lattice symmetry and antidot geometry. Moreover, the resulting flux patterns can be reproduced, to the finest details, by simulations based on a phenomenological thermomagnetic model. In turn, this model can be used to predict such complex structures and to estimate physical variables of more difficult experimental access, such as the local values of temperature and electric field.
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| 17. |
- Thorn, D. B., et al.
(författare)
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Polarization and anisotropic emission of K-shell radiation from heavy few electron ions
- 2011
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Ingår i: Canadian journal of physics (Print). - 0008-4204 .- 1208-6045. ; 89:5, s. 513-519
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Tidskriftsartikel (refereegranskat)abstract
- The population of magnetic sublevels in hydrogen-like uranium ions has been investigated in relativistic ion-atom collisions by observing the subsequent X-ray emission. Using the gas target at the experimental storage ring facility we observed the angular emission of Lyman-alpha radiation from hydrogen-like uranium ions. The alignment parameter for three different interaction energies was measured and found to agree well with theory. In addition, the use of different gas targets allowed for the electron-impact excitation process to be observed.
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| 18. |
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| 19. |
- Barbieri, L, et al.
(författare)
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Two-dimensional TIRF-SIM-traction force microscopy (2D TIRF-SIM-TFM)
- 2021
-
Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1, s. 2169-
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Tidskriftsartikel (refereegranskat)abstract
- Quantifying small, rapidly evolving forces generated by cells is a major challenge for the understanding of biomechanics and mechanobiology in health and disease. Traction force microscopy remains one of the most broadly applied force probing technologies but typically restricts itself to slow events over seconds and micron-scale displacements. Here, we improve >2-fold spatially and >10-fold temporally the resolution of planar cellular force probing compared to its related conventional modalities by combining fast two-dimensional total internal reflection fluorescence super-resolution structured illumination microscopy and traction force microscopy. This live-cell 2D TIRF-SIM-TFM methodology offers a combination of spatio-temporal resolution enhancement relevant to forces on the nano- and sub-second scales, opening up new aspects of mechanobiology to analysis.
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| 20. |
- Berger, Rolf, et al.
(författare)
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A study of the structural and magnetic properties of TlCo2-xCuxSe2
- 2002
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Ingår i: J Alloys Comp. ; 343, s. 186-191
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Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of TlCo(2-x)Cu(x)Se2 have been investigated experimentally. The antiferromagnetic coupling already found in TlCo2Se2 prevails on copper substitution but is weakened. For high copper contents, x larger tahn 1.3, Pauli paramagnetism occurs. -- The magnetic structure of teh unsubstituted TlCo2Se2 has been reinvestigated by neutron powder diffraction. Below 80K it is characterised by a helimagnetic arrangement of spins confined to the Co sheets, the helix running along the c-axis.
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| 21. |
- Brisbois, J., et al.
(författare)
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Classical analogy for the deflection of flux avalanches by a metallic layer
- 2014
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 16, s. Art. no. 103003-
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Tidskriftsartikel (refereegranskat)abstract
- Sudden avalanches of magnetic flux bursting into a superconducting sample undergo deflections of their trajectories when encountering a conductive layer deposited on top of the superconductor. Remarkably, in some cases the flux is totally excluded from the area covered by the conductive layer. We present a simple classical model that accounts for this behaviour and considers a magnetic monopole approaching a semi-infinite conductive plane. This model suggests that magnetic braking is an important mechanism responsible for avalanche deflection.
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| 22. |
- Brisbois, J., et al.
(författare)
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Flux penetration in a superconducting film partially capped with a conducting layer
- 2017
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:9
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a conducting layer on the magnetic flux penetration in a superconducting Nb film is studied by magneto-optical imaging. The metallic layer partially covering the superconductor provides an additional velocity-dependent damping mechanism for the flux motion that helps to protect the superconducting state when thermomagnetic instabilities develop. If the flux advances with a velocity slower than omega = 2/mu(0)sigma t, where sigma is the cap layer conductivity and t is its thickness, the flux penetration remains unaffected, whereas for incoming flux moving faster than w, the metallic layer becomes an active screening shield. When the metallic layer is replaced by a perfect conductor, it is expected that the flux braking effect will occur for all flux velocities. We investigate this effect by studying Nb samples with a thickness step. Some of the observed features, namely the deflection of the flux trajectories at the border of the thick center, as well as the favored flux penetration at the indentation, are reproduced by time-dependent Ginzburg-Landau simulations.
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| 23. |
- Fornander, Louise, 1984, et al.
(författare)
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Using nanofluidic channels to probe dynamics of RAD51-Filaments
- 2015
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Ingår i: 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014. - 9780979806476 ; , s. 1826-1828
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Konferensbidrag (refereegranskat)abstract
- Using nanochannels, passivated with a lipid bilayer to avoid sticking of proteins, we study Rad51 filaments bound to single- and double stranded DNA. We demonstrate how we can discern different properties of the filaments by studying them at different degrees of confinement. Unlike the bacterial homologue RecA, that forms homogeneous filaments along DNA, Rad51 forms heterogeneous filaments containing both rigid kinks as well as flexible regions. Varying the counterion, the DNA substrate as well as the initial protein concentration, we try to understand the factors governing the structure of the filaments.
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| 24. |
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| 25. |
- Fornander, Louise, 1984, et al.
(författare)
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Visualizing the Nonhomogeneous Structure of RAD51 Filaments Using Nanofluidic Channels
- 2016
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:33, s. 8403-8412
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Tidskriftsartikel (refereegranskat)abstract
- RAD51 is the key component of the homologous recombination pathway in eukaryotic cells and performs its task by forming filaments on DNA. In this study we investigate the physical properties of RAD51 filaments formed on DNA using nanofluidic channels and fluorescence microscopy. Contrary to the bacterial ortholog RecA, RAD51 forms inhomogeneous filaments on long DNA in vitro, consisting of several protein patches. We demonstrate that a permanent "kink" in the filament is formed where two patches meet if the stretch of naked DNA between the patches is short. The kinks are readily seen in the present microscopy approach but would be hard to identify using conventional single DNA molecule techniques where the DNA is more stretched. We also demonstrate that protein patches separated by longer stretches of bare DNA roll up on each other and this is visualized as transiently overlapping filaments. RAD51 filaments can be formed at several different conditions, varying the cation (Mg2+ or Ca2+), the DNA substrate (single-stranded or double-stranded), and the RAD51 concentration during filament nucleation, and we compare the properties of the different filaments formed. The results provide important information regarding the physical properties of RAD51 filaments but also demonstrate that nanofluidic channels are perfectly suited to study protein-DNA complexes.
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| 26. |
- Fritzsche, Joachim, 1977, et al.
(författare)
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A lipid-based passivation scheme for nanofluidics
- 2012
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Ingår i: 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012; Okinawa; Japan; 28 October 2012 through 1 November 2012. - 9780979806452 ; , s. 1876-1878
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Konferensbidrag (refereegranskat)abstract
- Stretching DNA in nanochannels allows for direct, visual studies of genomic DNA at the single molecule level. In order to facilitate the study of the interaction of linear DNA with proteins in nanochannels, we have implemented a highly effective passivation scheme based on lipid bilayers. We show long-term passivation of nanochannel surfaces to several relevant reagents and demonstrate that the performance of the lipid bilayer is significantly better compared to standard bovine serum albumin-based passivation. Moreover, we demonstrate how the passivated devices allow us to monitor single DNA cleavage events during enzymatic degradation.
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| 27. |
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| 28. |
- Fritzsche, S., et al.
(författare)
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Photoelectron satellite structure from the 3d and 4d inner-shell ionization of rubidium and cesium: Role of atomic relaxation
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:3
-
Tidskriftsartikel (refereegranskat)abstract
- The photoelectron satellite structure of rubidium and cesium has been investigated following the photoionization of an nd (n= 3,4) inner-shell electron. The intensity ratios of the nd(-1) ms monopole and nd(-1) m'p conjugated satellite lines have been measured at MAX-lab by using high-resolution electron spectroscopy. For rubidium, moreover, the energy dependence of the 3d(j)6s/3d(j)5s and 3d(j)5p/3d(j)5s intensity ratios with j=3/2 and 5/2 is measured and compared with multiconfiguration Dirac-Fock calculations. A good or at least reasonable agreement is found for both the monopole and conjugated shake-up probabilities if the relaxation of the bound-state electron density is taken into account in the computation of the photoionization cross sections. It is shown that, for the inner-shell ionization of medium and heavy atoms, the orbital relaxation accounts for a significant part of the satellite structure in the photoelectron spectra.
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| 29. |
- Frykholm, Karolin, 1977, et al.
(författare)
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Probing physical properties of DNA-protein complexes using nanofluidic channels
- 2013
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Ingår i: 17th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2013; Freiburg; Germany; 27 October 2013 through 31 October 2013. - 9781632666246 ; 2, s. 1311-1313
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Konferensbidrag (refereegranskat)abstract
- We present the use of nanofluidic channels as a tool for determining physical properties of single DNA-protein complexes. By coating the nanochannels with a lipid bilayer we avoid sticking of proteins to the channel walls. RecA is a prokaryotic protein involved in recombination and DNA repair. We study filaments of RecA, bound to both double stranded (ds) and single stranded (ss) DNA. We determine the persistence length of RecA filaments on both dsDNA and ssDNA and obtain values in agreement with the literature. Neither the DNA nor the protein has to be attached to handles or surfaces, and the technique is directly transferable to Lab-on-a-Chip technologies for high throughput measurements in solution.
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| 30. |
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| 31. |
- Jankala, K., et al.
(författare)
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Inner-shell 2p photoionization and Auger decay of atomic silicon
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:6
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Tidskriftsartikel (refereegranskat)abstract
- A detailed experiment on 2p photoionization and subsequent Auger decay of atomic silicon is presented. Fine-structure-resolved photoelectron and Auger electron spectra are interpreted with the aid of large-scale multiconfiguration calculations. Energy separation and the relative cross sections of the 2p ionized fine-structure states of Si+ are given. The complete 2p Auger electron spectrum of Si is interpreted, and the intensity distribution to individual doubly ionized final states is studied.
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| 32. |
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| 33. |
- Maiorova, A. V., et al.
(författare)
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Polarization studies on the two-step radiative recombination of highly charged, heavy ions
- 2009
-
Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:12
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Tidskriftsartikel (refereegranskat)abstract
- Radiative recombination of a free electron into an excited state of a bare, high-Z ion is studied, together with its subsequent decay, within the framework of the density matrix theory and Dirac's relativistic equation. Special attention is paid to the polarization and angular correlations between the recombination and the decay photons. In order to perform a systematic analysis of these correlations the general expression for the double-differential recombination cross section is obtained by making use of the resonance approximation. Based on this expression, detailed computations for the linear polarization of x-ray photons emitted in the (e, 2 gamma) two-step recombination of uranium ions U92+ are carried out for a wide range of projectile energies.
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| 34. |
- Motta, M., et al.
(författare)
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Enhanced pinning in superconducting thin films with graded pinning landscapes
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:21
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Tidskriftsartikel (refereegranskat)abstract
- A graded distribution of antidots in superconducting a-Mo79Ge21 thin films has been investigated by magnetization and magneto-optical imaging measurements. The pinning landscape has maximum density at the sample border, decreasing linearly towards the center. Its overall performance is noticeably superior than that for a sample with uniformly distributed antidots: For high temperatures and low fields, the critical current is enhanced, whereas the region of thermomagnetic instabilities in the field-temperature diagram is significantly suppressed. These findings confirm the relevance of graded landscapes on the enhancement of pinning efficiency, as recently predicted by Misko and Nori.
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| 35. |
- Nilsson, Sara, 1990, et al.
(författare)
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Probing the role of grain boundaries in single Cu nanoparticle oxidation by in situ plasmonic scattering
- 2022
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Ingår i: Physical Review Materials. - 2475-9953. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Grain boundaries determine physical properties of bulk materials including ductility, diffusivity, and electrical conductivity. However, the role of grain boundaries in nanostructures and nanoparticles is much less understood, despite the wide application of nanoparticles in nanophotonics, nanoelectronics, and heterogeneous catalysis. Here, we investigate the role of high-angle grain boundaries in the oxidation of Cu nanoparticles, using a combination of in situ single particle plasmonic nanoimaging and postmortem transmission electron microscopy image analysis, together with ab initio and classical electromagnetic calculations. We find an initial growth of a 5-nm-thick Cu2O shell on all nanoparticles, irrespective of different grain morphologies. This insensitivity of the Cu2O shell on the grain morphology is rationalized by extraction of Cu atoms from the metal lattice being the rate limiting step, as proposed by density functional theory calculations. Furthermore, we find that the change in optical scattering intensity measured from the individual particles can be deconvoluted into one contribution from the oxide layer growth and one contribution that is directly proportional to the grain boundary density. The latter contribution signals accumulation of Cu vacancies at the grain boundaries, which, as corroborated by calculations of the optical scattering, leads to increased absorption losses and thus a decrease of the scattering, thereby manifesting the role of grain boundaries as vacancy sinks and nuclei for Kirkendall void formation at a later stage of the oxidation process.
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| 36. |
- Niskanen, Johannes, et al.
(författare)
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Photoelectron angular distribution and linear magnetic dichroism in the 4p photoemission from Rb atoms
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:1, s. 013406-
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Tidskriftsartikel (refereegranskat)abstract
- The angular distribution of photoelectrons and linear magnetic dichroism in the angular distribution for the 4p photoemission from Rb atoms in the ground state, oriented by laser pumping, were measured in the photon energy range from 50 to 100 eV. The experimental results are compared with the multiconfiguration Dirac-Fock (MCDF) calculations. We show that the zero-crossing of the dichroism as a function of energy is connected with the Cooper minimum in the cross section. This fact can be used for an accurate determination of the position of the Cooper minimum.
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| 37. |
- Partanen, L., et al.
(författare)
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2s photoionization and subsequent Auger cascade in atomic Si
- 2010
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:6
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Tidskriftsartikel (refereegranskat)abstract
- The 2s photoionization and subsequent Auger transition cascade in atomic Si were studied by means of synchrotron-radiation-induced electron spectroscopy. After the 2s photoionization, the core hole states decay predominantly by a two-step Auger transition cascade into the triply ionized [Ne]nl states. The ionization channels of the 2s core-ionized Si+ atoms to Si3+ ions were observed by measuring the conventional Auger electron spectra of the L-1-L2,3M Coster-Kronig transitions and the L2,3M-MMM Auger transitions. The observed L-1-L2,3M and L2,3M-MMM Auger spectra were analyzed by means of extensive multiconfiguration Dirac-Fock computations. We found that the electron correlation plays a prominent role in the Auger cascade, especially for the final-step Auger L2,3M-MMM spectrum. Additionally, it was seen that the L2,3M-MMM Auger spectrum of Si includes more Auger groups than the isoelectronic L-2,L-3-MMAuger spectrum of Al. Thus, more information on the intermediate ionic states is obtained if they are produced by Auger cascade rather than by direct photoionization.
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| 38. |
- Persson, Fredrik, 1979, et al.
(författare)
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Lipid-Based Passivation in Nanofluidics
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:5, s. 2260-2265
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Tidskriftsartikel (refereegranskat)abstract
- Stretching DNA in nanochannels is a useful tool for direct, visual studies of genomic DNA at the single molecule level. To facilitate the study of the interaction of linear DNA with proteins in nanochannels, we have implemented a highly effective passivation scheme based on lipid bilayers. We demonstrate virtually complete long-term passivation of nanochannel surfaces to a range of relevant reagents, including streptavidin-coated quantum dots, RecA proteins, and RecA-DNA complexes. We show that the performance of the lipid bilayer is significantly better than that of standard bovine serum albumin-based passivation. Finally, we show how the passivated devices allow us to monitor single DNA cleavage events during enzymatic degradation by DNase I. We expect that our approach will open up for detailed, systematic studies of a wide range of protein-DNA interactions with high spatial and temporal resolution.
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| 39. |
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