| 1. |
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| 2. |
- Andersson, Björn, et al.
(författare)
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Advective collisions
- 2007
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 80
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Aurell, Erik, et al.
(författare)
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Gaussian belief with dynamic data and in dynamic network
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:6
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we analyze Belief Propagation over a Gaussian model in a dynamic environment. Recently, this has been proposed as a method to average local measurement values by a distributed protocol (Consensus Propagation, Moallemi C. C. and Van Roy B., IEEE Trans. Inf. Theory, 52 (2006) 4753) where the average is available for read-out at every single node. In the case that the underlying network is constant but the values to be averaged fluctuate ("dynamic data"), convergence and accuracy are determined by the spectral properties of an associated Ruelle-Perron-Frobenius operator. For Gaussian models on Erdos-Renyi graphs, numerical computation points to a spectral gap remaining in the large- size limit, implying exceptionally good scalability. In a model where the underlying network also fluctuates ("dynamic network"), averaging is more effective than in the dynamic data case. Altogether, this implies very good performance of these methods in very large systems, and opens a new field of statistical physics of large (and dynamic) information systems.
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| 4. |
- Biltmo, Anders, et al.
(författare)
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The ferromagnetic transition and domain structure in LiHoF4
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:2
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Tidskriftsartikel (refereegranskat)abstract
- Using Monte Carlo simulations we verify that the rare-earth compound LiHoF4 is a very good realization of a dipolar Ising model. With only one free parameter our calculations for the magnetization, specific heat and inverse susceptibility match experimental data at a quantitative level in the 0.5-3 kelvin range, including the ferromagnetic transition at 1.53 K. Using parallel tempering methods and reaching system sizes up to 32000 dipoles with periodic boundary conditions, we are able to give evidence of the logarithmic corrections predicted in renormalization group theory. Due to the long range and angular dependence of the dipolar model, sample shape and domains play a crucial role in the ordered state. We consider surface corrections to Griffiths's theorem, which arise infinite macroscopic samples and lead to a theory of magnetic domains. We find a domain wall energy of 0.059 erg/cm(2) and predict that the ground-state domain structure for cylinders with a demagnetization factor N > 0 consists of thin parallel sheets of opposite magnetization, with a width depending on the demagnetization factor.
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| 5. |
- Caleman, Carl, et al.
(författare)
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Radiation damage in biological material : electronic properties and electron impact ionization in urea
- 2009
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Ingår i: Europhysics letters. - : IOP. - 0295-5075 .- 1286-4854. ; 85:1, s. 18005-
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Tidskriftsartikel (refereegranskat)abstract
- Radiation damage is an unavoidable process when performing structural investigations of biological macromolecules with X-rays. In crystallography this process can be limited through damage distribution in a crystal, while for single molecular imaging it can be outrun by employing short intense pulses. Secondary electron generation is crucial during damage formation and we present a study of urea, as model for biomaterial. From first principles we calculate the band structure and energy loss function, and subsequently the inelastic electron cross-section in urea. Using Molecular Dynamics simulations, we quantify the damage and study the magnitude and spatial extent of the electron cloud coming from an incident electron, as well as the dependence with initial energy.
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| 6. |
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| 7. |
- Carletti, T, et al.
(författare)
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How to make an efficient propaganda
- 2006
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Ingår i: EUROPHYSICS LETTERS. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 74:2, s. 222-228
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Carva, K, et al.
(författare)
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Influence of laser-excited electron distributions on the X-ray magnetic circular dichroism spectra : Implications for femtosecond demagnetization in Ni
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 86:5, s. 57002-
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Tidskriftsartikel (refereegranskat)abstract
- In pump-probe experiments an intensive laser pulse creates non-equilibrium excited-electron distributions in the first few hundred femtoseconds after the pulse. The influence of nonequilibrium electron distributions caused by a pump laser on the apparent X-ray magnetic circular dichroism (XMCD) signal of Ni is investigated theoretically here for the first time, considering electron distributions immediately after the pulse as well as thermalized ones, that are not in equilibrium with the lattice or spin systems. The XMCD signal is shown not to be simply proportional to the spin momentum in these situations. The computed spectra are compared to recent pump-probe XMCD experiments on Ni. We find that the majority of experimentally observed features considered to be a proof of ultrafast spin momentum transfer to the lattice can alternatively be attributed to non-equilibrium electron distributions. Furthermore, we find the XMCD sum rules for the atomic spin and orbital magnetic moment to remain valid, even for the laser-induced non-equilibrium electron distributions. Copyright (C) EPLA, 2009
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| 9. |
- Castelnovo, M, et al.
(författare)
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Binding effects in multivalent Gibbs-Donnan equilibrium
- 2006
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 73:4, s. 635-641
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Tidskriftsartikel (refereegranskat)abstract
- The classical Gibbs-Donnan equilibrium describes excess osmotic pressure associated with confined colloidal charges embedded in an electrolyte solution. In this work, we extend this approach to describe the influence of multivalent ion binding on the equilibrium force acting on a charged rod translocating between two compartments, thereby mimicking ionic effects on force balance during in vitro DNA ejection from bacteriophage. The subtle interplay between Gibbs-Donnan equilibrium and adsorption equilibrium leads to a non-monotonic variation of the ejection force as multivalent salt concentration is increased, in qualitative agreement with experimental observations.
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| 10. |
- Chorro, Matthieu, et al.
(författare)
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Discriminated structural behaviour of C60 and C70 peapods under extreme conditions
- 2007
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 79:5, s. 56003-
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Tidskriftsartikel (refereegranskat)abstract
- We studied structural changes in C60 and C70 peapods—i.e. C60 and C70 chains inserted inside single-walled carbon nanotubes—when submitted to high pressure and temperature conditions. X-ray diffraction experiments showed that while C60 molecules polymerize inside nanotubes at pressures and temperatures consistent with polymerization in bulk C60 phases, no polymerization is observed in C70 peapods, even at pressures and temperatures above the threshold for polymerization in bulk C70. Tubular confinement in the nanotube container prevents the monomers to rearrange in the way needed for polymerization. This result testifies for the strong influence of confinement on the behaviour of C70.
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