Mesoscale modelling of polyelectrolyte electrophoresis

The electrophoretic behaviour of flexible polyelectrolyte chains ranging from single monomers up to long fragments of hundred repeat units is studied by a mesoscopic simulation approach. Abstracting from the atomistic details of the polyelectrolyte and the fluid, a coarse-grained molecular dynamics model connected to a mesoscopic fluid described by the Lattice Boltzmann approach is used to investigate free-solution electrophoresis. Our study demonstrates the importance of hydrodynamic interactions for the electrophoretic motion of polyelectrolytes and quantifies the influence of surrounding ions. The length-dependence of the electrophoretic mobility can be understood by evaluating the scaling behavior of the effective charge and the effective friction. The perfect agreement of our results with experimental measurements shows that all chemical details and fluid structure can be safely neglected, and a suitable coarse-grained approach can yield an accurate description of the physics of the problem, provided that electrostatic and hydrodynamic interactions between all entities in the system, i.e., the polyelectrolyte, dissociated counterions, additional salt and the solvent, are properly accounted for. Our model is able to bridge the single molecule regime of a few nm up to macromolecules with contour lengths of more than 100 nm, a length scale that is currently not accessible to atomistic simulations.Comment: 23 pages, 9 figures, to be presented at Faraday Discussion 14

Organic film thickness influence on the bias stress instability in Sexithiophene Field Effect Transistors

In this paper, the dynamics of bias stress phenomenon in Sexithiophene (T6) Field Effect Transistors (FETs) has been investigated. T6 FETs have been fabricated by vacuum depositing films with thickness from 10 nm to 130 nm on Si/SiO2 substrates. After the T6 film structural analysis by X-Ray diffraction and the FET electrical investigation focused on carrier mobility evaluation, bias stress instability parameters have been estimated and discussed in the context of existing models. By increasing the film thickness, a clear correlation between the stress parameters and the structural properties of the organic layer has been highlighted. Conversely, the mobility values result almost thickness independent

Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag

We study the electrophoretic separation of polyelectrolytes of varying lengths by means of end-labeled free-solution electrophoresis (ELFSE). A coarse-grained molecular dynamics simulation model, using full electrostatic interactions and a mesoscopic Lattice Boltzmann fluid to account for hydrodynamic interactions, is used to characterize the drag coefficients of different label types: linear and branched polymeric labels, as well as transiently bound micelles. It is specifically shown that the label's drag coefficient is determined by its hydrodynamic size, and that the drag per label monomer is largest for linear labels. However, the addition of side chains to a linear label offers the possibility to increase the hydrodynamic size, and therefore the label efficiency, without having to increase the linear length of the label, thereby simplifying synthesis. The third class of labels investigated, transiently bound micelles, seems very promising for the usage in ELFSE, as they provide a significant higher hydrodynamic drag than the other label types. The results are compared to theoretical predictions, and we investigate how the efficiency of the ELFSE method can be improved by using smartly designed drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule

Theoretical analysis of neutron scattering results for quasi-two dimensional ferromagnets

A theoretical study has been carried out to analyse the available results from the inelastic neutron scattering experiment performed on a quasi-two dimensional spin-1/2 ferromagnetic material $K_2CuF_4$. Our formalism is based on a conventional semi-classical like treatment involving a model of an ideal gas of vortices/anti-vortices corresponding to an anisotropic XY Heisenberg ferromagnet on a square lattice. The results for dynamical structure functions for our model corresponding to spin-1/2, show occurrence of negative values in a large range of energy transfer even encompassing the experimental range, when convoluted with a realistic spectral window function. This result indicates failure of the conventional theoretical framework to be applicable to the experimental situation corresponding to low spin systems. A full quantum formalism seems essential for treating such systems.Comment: 16 pages, 6 figures, 1 Table Submitted for publicatio

"Interinstitutional Agreements in the CFSP: Parliamentarisation through the Backdoor?"

[From the Introduction]. This paper tackles the puzzle of parliamentarisation by analysing the role of Interinstitutional Agreements (IIAs). The number of IIAs concluded between the EP, the Commission and the Council has sharply risen since the Maastricht Treaty. IIAs are designed to facilitate interinstitutional co-operation and prevent conflicts between the institutions. However, IIAs are more than just pragmatic answers to interinstitutional co-operation problems since they tend to strengthen the EP’s position in the EU’s constitutional set-up by expanding the EP’s control, information and legislative competencies, and placing it on an equal footing with the Council

Evaluation of changes in Sculpin populations in the Great Lakes associated with shifts in benthic species composition

In the Great Lakes, slimy sculpins (Cottus cognatus) and deepwater sculpins (Myoxocephalus thompsonii) were historically abundant native deepwater fishes that served as important prey items for native piscivores (e.g., lake trout, Salvelinus namaycush, and burbot, Lota lota). However, both of these species have been declining in abundance and biomass recent decades according to USGS trawl surveys. The timing of these declines in sculpin biomass and abundance coincides with several ecological disturbances that have occurred throughout the Great Lakes, including the invasions of dreissenid mussels (zebra, Dreissena polymorpha; quagga, D. bugensis) and the aggressive round goby (Neogobius melanostomus), along with the collapse of Diporeia (formerly one of the most important prey items for these sculpin species). In this dissertation, we provide a comprehensive review of the state of knowledge and investigate the effect of these ecological disturbances on slimy and deepwater sculpins in the Great Lakes. We predicted that these ecological disturbances have negatively affected both slimy and deepwater sculpin populations, particularly slimy sculpins, which we could observe through changes in their spatial (depth) distribution patterns (e.g., shifting deeper to avoid round goby) and body condition (e.g., lower body condition associated with ecological disturbance). Our results indicate that slimy sculpins may be more vulnerable to these ecological disturbances than deepwater sculpins, but data limitations prevent us from offering conclusive causal mechanisms for sculpin spatial and body condition patterns. Both our review and analyses implicate that we need to gain a better understanding of sculpins in order to restore these species in this system.Thesis (M.S.)--Michigan State University. Fisheries and Wildlife, 2019Includes bibliographical reference

A parameter optimisation toolchain for Monte Carlo detector simulation

Monte Carlo detector transport codes are one of the backbones in high-energy physics computing. They simulate the transport of a large variety of different particle types through complex detector geometries based on different physics models. Those simulations are usually configurable through a large set of parameters allowing for some tuning on the client side. Often, tuning the physics accuracy on the one hand and optimising the resource needs on the other hand are competing requirements. In this area, we are presenting a toolchain to tune Monte Carlo transport codes which is capable of automatically optimising large sets of parameters based on user-defined metrics. The toolchain consists of two central components. Firstly, the MCReplayEngine which is a quasi-Monte-Carlo transport engine able to fast replay pre-recorded MC steps. This engine for instance allows one to study the impact of parameter variations on quantities such as hits without the need to perform new full simulations. Secondly, it consists of an automatic and generic parameter optimisation framework called O2Tuner. The toolchain’s application in concrete use-cases will be presented. Its first application in ALICE led to a reduction of CPU time of Monte Carlo detector transport by 30%. In addition, further possible scenarios will be discussed

Legal assessment explaining why COPA*COGECA's objections against the Nature Restoration Act proposal are misleading

In their letter of 26 June 2023 Copa*Cogeca asked the members of the European Parliament’s Committee on Environment to reject the Nature Restoration Law proposal. They based their arguments for this rejection on what they considered as ‘red line’ issues, which makes the law proposal unacceptable to them.As Legal Working Group (LWG) from SERE , we analysed these ‘red line’ issues and we concluded that their red line objections against the Nature Restoration Law proposal cannot withstand legal scrutiny. Many of their concerns are already present in the Commission proposal and are further addressed in the Swedish presidency compromise proposal. Further weakening of the Nature Restoration Law is against existing EU legislation