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We consider a Bose gas with two-body Kac-like scaled interactions V $\gamma$ (r) = $\gamma$ 3 v($\gamma$r) where v(x) is a given repulsive and integrable potential, while $\gamma$ is a positive parameter which controls the range of the interactions and their amplitude at a distance r. Using the Hartree-Fock approximation we find that, at finite non-zero temperatures, the Bose-Einstein condensation is destroyed by the repulsive interactions when they are sufficiently long-range. More precisely, we show that for $\gamma$ sufficiently small but finite the off-diagonal part of the one-body density matrix always vanishes at large distances. Our analysis sheds light on the coupling between critical correlations and long-range interactions, which might lead to the breakdown of the off-diagonal long-range order even beyond the Hartree-Fock approximation. Furthermore, our Hartree-Fock analysis shows the existence of a threshold value $\gamma$ 0 above which the Bose-Einstein condensation is restored. Since $\gamma$ 0 is an unbounded increasing function of the temperature this implies for a fixed $\gamma$, namely for a fixed scaled potential, that a condensate cannot form above some critical temperature whatever the value of the density.

The problem of memory contribution to the collective diffusion coefficient of interacting Brownian particles is considered. A well-defined theoretical expression for this contribution, free of divergent integrals, is derived. Its value is then estimated for hard sphere suspensions numerically by means of extensive computer simulations.

The structure of a series of highly Al-doped superconducting Y(RE)-123 (RE = rare earth element) single crystals was investigated by XRD and NMR methods. On the basis of the data obtained by the structural investigations combined with the studies of magnetic and optical properties, the formation of various superstructures in the samples of pseudo-tetragonal symmetry has been discussed. The correlation between the carrier concentration and Tc-values has been determined. The superconductivity (at 70 K) was indicated even at the 2/3 and 1/3 Al substitution for Cu in the basal and CuO2 planes, respectively, in the phase presumably of a perovskite-like structural type.

We study patterns formed by viscous fingering in a rectangular network of microfluidic channels. Due to the strong anisotropy of such a system, the emerging patterns have a form of thin needle-like fingers, which interact with each other, competing for an available flow. We develop an upscaled description of this system in which only the fingers are tracked and the effective interactions between them are introduced, mediated through the evolving pressure field. Due to the quasi-2d geometry of the system, this is conveniently accomplished using conformal mapping techniques. A complex two-phase flow problem is thus reduced to a much simpler task of tracking evolving shapes in a 2d complex plane. This description, although simplified, turns out to capture all the key features of the system's dynamics and allows for the effective prediction of the resulting growth patterns.

We present a theoretical description of linker-mediated self-assembly of gold nanoparticles (Au-NP). Using mesoscale simulations with a coarse-grained model for the Au NPs and dirhenium-based linker molecules, we investigate the conditions under which large clusters can grow and construct a phase diagram that identifies favorable growth conditions in terms of floating and bound linker concentrations. The findings can be considered as generic, as we expect other NP-linker systems to behave in a qualitatively similar way. In particular, we also discuss the case of antibody-functionalised Au NPs connected by the C-reactive proteins (CRPs). We extract some general rules for NP linking that may aid the production of size- and shape-specific NP clusters for technology applications. (Some figures in this article are in colour only in the electronic version)

Experimental and numerical results pertaining to flow-induced effects in proteins are reviewed. Special emphasis is placed on shear-induced unfolding and on the role of solvent mediated hydrodynamic interactions in the conformational transitions in proteins.