Lattice Boltzmann simulations of soft matter systems

This article concerns numerical simulations of the dynamics of particles immersed in a continuum solvent. As prototypical systems, we consider colloidal dispersions of spherical particles and solutions of uncharged polymers. After a brief explanation of the concept of hydrodynamic interactions, we give a general overview over the various simulation methods that have been developed to cope with the resulting computational problems. We then focus on the approach we have developed, which couples a system of particles to a lattice Boltzmann model representing the solvent degrees of freedom. The standard D3Q19 lattice Boltzmann model is derived and explained in depth, followed by a detailed discussion of complementary methods for the coupling of solvent and solute. Colloidal dispersions are best described in terms of extended particles with appropriate boundary conditions at the surfaces, while particles with internal degrees of freedom are easier to simulate as an arrangement of mass points with frictional coupling to the solvent. In both cases, particular care has been taken to simulate thermal fluctuations in a consistent way. The usefulness of this methodology is illustrated by studies from our own research, where the dynamics of colloidal and polymeric systems has been investigated in both equilibrium and nonequilibrium situations.Comment: Review article, submitted to Advances in Polymer Science. 16 figures, 76 page

Y-Like Retinal Ganglion Cells Innervate the Dorsal Raphe Nucleus in the Mongolian Gerbil (Meriones unguiculatus)

Background: The dorsal raphe nucleus (DRN) of the mesencephalon is a complex multi-functional and multi-transmitter nucleus involved in a wide range of behavioral and physiological processes. The DRN receives a direct input from the retina. However little is known regarding the type of retinal ganglion cell (RGC) that innervates the DRN. We examined morphological characteristics and physiological properties of these DRN projecting ganglion cells. Methodology/Principal Findings: The Mongolian gerbils are highly visual rodents with a diurnal/crepuscular activity rhythm. It has been widely used as experimental animals of various studies including seasonal affective disorders and depression. Young adult gerbils were used in the present study. DRN-projecting RGCs were identified following retrograde tracer injection into the DRN, characterized physiologically by extracellular recording and morphologically after intracellular filling. The result shows that DRN-projecting RGCs exhibit morphological characteristics typical of alpha RGCs and physiological response properties of Y-cells. Melanopsin was not detected in these RGCs and they show no evidence of intrinsic photosensitivity. Conclusions/Significance: These findings suggest that RGCs with alpha-like morphology and Y-like physiology appear to perform a non-imaging forming function and thus may participate in the modulation of DRN activity which includes regulation of sleep and mood

The modern approach to diagnosis of juvenile arthritides

Objective. To assess utility of East European diagnostic criteria of juvenile rheumatoid arthritis (J RA) in the modern conditions. Material and methods. 260 children with juvenile arthritis aged 2 to 18 years (mean 8,5±1,1 years) were included. Disease duration varied from 6 months to 15,5 years (mean 5,4±0,9 years). JRA was diagnosed in 94, juvenile chronic arthritis (JCA) — in 107 and other arthritides — in 12 cases (44,1%, 50,2% and 5,6% respectively). Pts with J RA were included in the main group. Group of comparison consisted of 107 pts with JCA, 12 pts with other arthritides, 35 pts with mixed connective tissue disease, 6 pts with Wissler-Fanconi syndrome, 4 — with Still’s disease and 2 - with primary Sjogren’s syndrome. All pts were assessed according to East European diagnostic criteria of JRA. Sensitivity and specificity were determined for every single criterion as well as for combinations of signs. Results. 35 from 260 pts had less than 3 criteria. This group included 2 children with JCA and 33 — with other rheumatic diseases (RD). 207 pts fulfilled criteria of definite or classical JRA (presence of 4 or more criteria but in fact JRA was diagnosed in only 94 (45,4%) from them. Most of remaining pts had JCA (44,9%) or other arthritides (4,8%). 10 pts with other RD also fulfilled criteria of definite or classical JRA (4,8%). Probable JRA could be diagnosed in 17 pts but no one of them had this disease. Combination of 8 or more signs was most sensitive (74,5%) and specific (76,6-100%) and presence of 4-7 criteria was common in other diseases. 9 signs were sensitive for JRA in comparison with JCA (20,2-96,8%). Only 4 from them (small joints symmetric arthritis, rheumatoid factor, bone growth disturbance, cervical spine damage) had high specificity (86,9-99,1%). Conclusion. At the present time East European diagnostic criteria of J RA need modification. They allow to differentiate JRA from other RD but do not help to reveal intra-group differences in pts with juvenile arthritis. Quality features of every criterion are more important for the diagnosis than their quantity combination. It is necessary to develop diagnostic criteria of JRA allowing to differentiate it from JCA and to develop criteria for JCA itself