| 1. |
- Yousefian, Zakiyeh, et al.
(författare)
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Orientational arrest in dense suspensions of elliptical particles under oscillatory shear flows
- 2021
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Ingår i: EPL. - : IOP Publishing. - 0295-5075. ; 136:3
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Tidskriftsartikel (refereegranskat)abstract
- We study the rheological response of dense suspensions of elliptical particles, with an aspect ratio equal to 3, under oscillatory shear flows and imposed pressure by numerical simulations. Like for the isotropic particles, we find that the oscillatory shear flows respect the Cox-Merz rule at large oscillatory strains but differ at low strains, with a lower viscosity than the steady shear and higher shear jamming packing fractions. However, unlike the isotropic cases (i.e., discs and spheres), frictionless ellipses get dynamically arrested in their initial orientational configuration at small oscillatory strains. We illustrate this by starting at two different configurations with different nematic order parameters and the average orientation of the particles. Surprisingly, the overall orientation in the frictionless case is uncoupled to the rheological response close to jamming, and the rheology is only controlled by the average number of contacts and the oscillatory strain. Having larger oscillatory strains or adding friction does, however, help the system escape these orientational arrested states, which are evolving to a disordered state independent of the initial configuration at low strains and ordered ones at large strains.
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| 2. |
- Lundin, Joakim, 1978-
(författare)
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An effective action approach to photon propagation on a magnetized background
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:3, s. 31001-31005
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Tidskriftsartikel (refereegranskat)abstract
- A new explicit analytical form of the dispersion relation for photon propagation in the presence of a strong background magnetic field is derived within the effective action framework. The dispersion relation is expressed in terms of well-known special functions, and the treatment is exact within the linearization procedure, the one-loop approximation, and the soft photon approximation. The results are incorporated in a kinetic spin plasma description for the purpose of studying quantum electrodynamical effects of strongly magnetized plasmas. The results are applied to astrophysical examples.
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| 3. |
- Bishop, Adrian, et al.
(författare)
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Link Operations for Slowing the Spread of Disease in Complex Networks
- 2011
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Ingår i: Europhysics letters. - : EPLA. - 0295-5075 .- 1286-4854. ; 95:1, s. 18005-
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Tidskriftsartikel (refereegranskat)abstract
- A variety of social, biological and communication networks can be modelled using graph theoretical tools. Similar graphical tools can be used to model the topology by which disease, errors, and/or other undesired phenomenon etc. is spread and propagated through such networks. Certain network operations are proposed in this work that can be used to slow the spread of diseases in complex network topologies. The approach considered in this work differs from existing techniques in that it is based on optimally removing (or immunizing) individual links in the network as opposed to individual nodes. A systematic algorithm is outlined to achieve this edgewise immunization via a relaxed convex optimization protocol.
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| 4. |
- Rocha, Luis E C, 1981-, et al.
(författare)
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The network organisation of consumer complaints
- 2010
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 91:2, s. 28005-28011
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Tidskriftsartikel (refereegranskat)abstract
- Interaction between consumers and companies can create conflict. When a consensus is unreachable there are legal authorities to resolve the case. This letter is a study of data from the Brazilian Department of Justice from which we build a bipartite network of categories of complaints linked to the companies receiving those complaints. We find the complaint categories organised in an hierarchical way where companies only get complaints of lower degree if they already got complaints of higher degree. The fraction of resolved complaints for a company appears to be nearly independent of the equity of the company but is positively correlated with the total number of complaints received. We construct feature vectors based on the edge-weight —the weight of an edge represents the times complaints of a category have been filed against that company— and use these vectors to study the similarity between the categories of complaints. From this analysis, we obtain trees mapping the hierarchical organisation of the complaints. We also apply principal component analysis to the set of feature vectors concluding that a reduction of the dimensionality of these from 8827 to 27 gives an optimal hierarchical representation.
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| 5. |
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| 6. |
- Aref, Thomas, 1980, et al.
(författare)
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Andreev tunneling in charge pumping with SINIS turnstiles
- 2011
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 96:3
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements on hybrid single-electron turnstiles with superconducting leads contacting a normal island (SINIS). We observe Andreev tunneling of electrons influencing the current plateau characteristics of the turnstiles under radio-frequency pumping. The data is well accounted for by numerical simulations. We verify the dependence of the Andreev tunneling rate on the turnstile's charging energy. Increasing the charging energy effectively suppresses the Andreev current.
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| 7. |
- Atanasova, L., et al.
(författare)
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g-factor Measurements at RISING: The Cases of 127Sn and 128Sn
- 2010
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 91:4
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Tidskriftsartikel (refereegranskat)abstract
- We report on g-factor measurements of the 19/2(+) T-1/2 = 4.5(3) mu s isomer in Sn-127 and the 10(+) T-1/2 = 2.69(23) mu s isomer in Sn-128. These isomers were produced and spin-aligned in relativistic heavy-ion fragmentation at GSI and were selected and separated by the GSI fragment separator ( FRS). The gamma-rays of the isomeric decay were detected by the RISING gamma-ray spectrometer. The method of time-differential perturbed angular distributions was utilized. The measured g-factors, g(19/2(+); Sn-127) =-0.17(2) and g(10(+); Sn-128)=-0.20(4), are compared with shell model calculations. The measured g-factors confirm the predominantly nu h(11/2)(-2) and nu(s(1/2)(-1) h(11/2)(-2)) character of the 10(+) and 19/2(-) isomers in Sn-128 and Sn-127, respectively. The results demonstrate the feasibility of the method for similar measurements in exotic neutron-rich nuclei. Copyright (C) EPLA, 2010
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| 8. |
- Boikov, Iouri, 1949, et al.
(författare)
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Atomic rearrangements at the TiO2-terminated (001)SrTiO3 surface and growth of thin LaMnO3 films
- 2013
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 102:5
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Tidskriftsartikel (refereegranskat)abstract
- SrTiO3 is commonly used as a substrate for growth of various oxide films. Different reconstructions at the SrTiO3 surface have been claimed. A question is whether these survive subsequent depositions of thin films and influence film properties. Medium energy ion scattering (MEIS) was used to probe structure and composition of the surface layer of a TiO2-terminated (001) SrTiO3 single-crystal substrate and 1-4 unit cell (u.c.) thick LaMnO3 epilayers. Aligned spectra indicate enrichment of Ti at the surface and a TiO2 double-layer (DL) configuration. The DL arrangement survives pulsed-laser deposition of LaMnO3 in a background of high oxygen pressure (5 x 10(-2) mbar) while it is destroyed at lower oxygen pressure (10(-4) mbar). Simulations of random MEIS spectra indicate substantial interdiffusion and La doping of the substrate surface but all interfaces are nevertheless insulating.
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| 9. |
- Cattani, F., et al.
(författare)
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Multihump soliton-like structures in interactions of lasers and Bose-Einstein condensates
- 2011
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 94:5, s. 53003-
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Tidskriftsartikel (refereegranskat)abstract
- An investigation is made of multihump and periodic solutions of the semiclassical coupled equations describing laser radiation copropagating with a Bose-Einstein condensate. Solutions reminiscent of optical vector solitons have been found and have been used to gain understanding of the dynamics observed in the numerical simulations, in particular to shed light on the phenomenon of jet emission from a condensate interacting with a laser.
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| 10. |
- Croy, Alexander, 1981, et al.
(författare)
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Dynamics of a nanoscale rotor driven by single-electron tunneling
- 2012
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- We investigate theoretically the dynamics and the charge transport properties of a rod-shaped nanoscale rotor, which is driven by a similar mechanism as the nanomechanical single-electron transistor (NEMSET). We show that a static electric potential gradient can lead to self-excitation of oscillatory or continuous rotational motion. We identify the relevant parameters of the device and study the dependence of the dynamics on these parameters. We discuss how the dynamics are related to the measured current through the device. Notably, in the oscillatory regime we find a negative differential conductance. The current-voltage characteristics can be used to infer details of the surrounding environment which is responsible for damping.
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