| 1. |
- Anderson, Johan, 1973, et al.
(författare)
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A statistical approach to investigate plasma dynamics in gyrokinetic simulations of stellarator turbulence
- 2022
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Ingår i: Bulletin of the American Physical Society. - 0003-0503. ; 64, s. 1-1
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Turbulent dynamics in stellarator plasmas is investigated by a geometrical method. Gyrokinetic simulations of ITG mode driven turbulence in the core-region of the stellarator W7-X, with realistic quasiisodynamic topologies using the GENE software are considered. The turbulent states are approximated by probability distribution functions where distances between thermodynamic states can be computed according the thermodynamic length methodology which allows the use of a Riemannian metric on the phase space. The geometric methodology is suitable in order to understand stochastic processes involved in e.g. order-disorder transition, where a sudden increase in distance is expected. In gyrokinetic plasma turbulence simulations avalanches, e.g. of heat and particles, are often found and in this work this novel method for detection is investigated. Previously [1,2] 1D versions have been investigated however this falls short in identification of coherent modes. The Hurst exponent, the Information Length and the Dynamic Time is computed from the 2D time series. Based on these measures the transport features of large scale modes can be investigated, identified by a sudden increase in information.
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| 2. |
- Chen, Weimin, 1959-, et al.
(författare)
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Spin relaxation in InGaN/Ga(Mn)N quantum wells
- 2005
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Ingår i: Bulletin of the American physical society. - 0003-0503. ; 50, s. 609-609
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Tidskriftsartikel (refereegranskat)abstract
- Proc. 2005 APS March Meeting, March 21-25, 2005; Los Angeles, CA, USA
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| 3. |
- Pettersson, Håkan, 1962-, et al.
(författare)
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Shear stress measurements on InAs nanowires by AFM manipulation
- 2007
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Ingår i: Bulletin of the American Physical Society. - New York : American Physical Society. - 0003-0503. ; 52:1
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report on a novel approach to measure shear stress between elastic nanowires and a SiO2 surface. The method is based on the fact that the curvature of an elastically deformed nanowire pinned to a flat surface contains information about the maximal static friction force, i.e., the shear stress between the wire and the surface. At rest, the deformed wire is kept in equilibrium by counterbalancing static friction forces and restoring elastic forces. In the present work, InAs nanowires are bent in a controlled manner using the tip of an atomic force microscope (AFM). After the manipulation, the curvature of the most bent state can be determined from AFM micrographs. Assuming bulk values for the Young’s modulus, the shear stress can be obtained from straight- forward analyses according to standard theory of elasticity.
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| 4. |
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| 5. |
- Tandhyka Gemiarto, Adrian, et al.
(författare)
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Isoprenyl caffeate, a major compound in manuka propolis, is a quorum-sensing inhibitor in Chromobacterium violaceum
- 2015
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Ingår i: Antonie van Leeuwenhoek. International Journal of General and Molecular Microbiology. - : Kluwer Academic Publishers. - 0003-6072 .- 1572-9699. ; 108:2, s. 491-504
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of antibiotic-resistant bacterial pathogens, especially Gram-negative bacteria, has driven investigations into suppressing bacterial virulence via quorum sensing (QS) inhibition strategies instead of bactericidal and bacteriostatic approaches. Here, we investigated several bee products for potential compound(s) that exhibit significant QS inhibitory (QSI) properties at the phenotypic and molecular levels in Chromobacterium violaceum ATCC 12472 as a model organism. Manuka propolis produced the strongest violacein inhibition on C. violaceum lawn agar, while bee pollen had no detectable QSI activity and honey had bactericidal activity. Fractionated manuka propolis (pooled fraction 5 or PF5) exhibited the largest violacein inhibition zone (24.5 ± 2.5 mm) at 1 mg dry weight per disc. In C. violaceum liquid cultures, at least 450 µg/ml of manuka propolis PF5 completely inhibited violacein production. Gene expression studies of the vioABCDE operon, involved in violacein biosynthesis, showed significant (≥two-fold) down-regulation of vioA, vioD and vioE in response to manuka propolis PF5. A potential QSI compound identified in manuka propolis PF5 is a hydroxycinnamic acid-derivative, isoprenyl caffeate, with a [M-H] of 247. Complete violacein inhibition in C. violaceum liquid cultures was achieved with at least 50 µg/ml of commercial isoprenyl caffeate. In silico docking experiments suggest that isoprenyl caffeate may act as an inhibitor of the violacein biosynthetic pathway by acting as a competitor for the FAD-binding pockets of VioD and VioA. Further studies on these compounds are warranted toward the development of anti-pathogenic drugs as adjuvants to conventional antibiotic treatments, especially in antibiotic-resistant bacterial infections.
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