First example of multi-scale reverse Monte Carlo modeling for small-angle scattering experimental data using reverse mapping from coarse-grained particles to atoms.

We propose a new method for multi-scale reverse Monte Carlo (RMC) modeling of small-angle scattering data using reverse mapping from coarse-grained particles to atoms in cases where scale separation cannot be assumed. For efficient RMC analysis for small-angle scattering data, it is important to determine a large scale structure with the lowest possible computing cost. In order to find this large scale structure, a method using coarse-grained particles instead of atoms is suitable. As our first example, we examine the structure of expanded fluid Hg near the critical point. For this system, small-angle x-ray scattering (SAXS) data and wide-angle x-ray diffraction data (XRD) are observed in the same thermodynamic state. First, RMC analysis using coarse-grained particles for SAXS data is performed. Second, RMC analysis for SAXS and XRD data is performed with the replacement of a coarse-grained particle by an ad hoc cluster of several Hg atoms. In the present study, we have determined that the size of one coarse-grained particle corresponds to ten Hg atoms. The number density for the coarse-grained particles is set to one-tenth the actual number density of atoms and the cutoff length is three times (6.9 Å) that of Hg atoms (2.3 Å). As a result, this approach is found to be successful and the computing cost of RMC analysis can be reduced.

Two-dimensional pattern reverse Monte Carlo method for modelling the structures of nano-particles in uniaxial elongated rubbers.

Two-dimensional pattern reverse Monte Carlo (2D pattern RMC) analysis is performed to model the structures of nano-particles in uniaxially elongated rubbers using two-dimensional patterns of structure factor of the nano-particles obtained by time-resolved two-dimensional ultra-small angle x-ray scattering. Four spot patterns are observed for a large elongation ratio and the shapes change with increasing elongation ratio. We performed the 2D pattern RMC method for the uniaxial system in order to make a model of the structures from the two-dimensional structure factors. The preliminary results of the 2D pattern RMC analysis of the two-dimensional structure factors of silica particles in a uniaxially elongated styrene-butadiene rubber are presented.

Macular lesions predisposing to senile disciform macular degeneration.

Senile disciform macular degeneration (SMD) is a neovascular/exudative form of age-related macular degeneration (AMD). In this study 340 eyes were followed up to assess the progression of SMD. The 340 eyes consisted of two groups. Group 1 was composed of 157 eyes with age-related macular changes other than choroidal neovascular membrane. Group 2 was made up of the contralateral eyes of 183 unilateral SMD eyes. Average ages were 61 and 64 in groups 1 and 2, respectively, and respective follow-up periods were 44 and 52 months. Choroidal neovascular membrane developed in 12 eyes in group 1 (7.6%) and in 19 eyes in group 2 (10.4%), a total of 31 eyes (9.1%). Retinal pigment epithelium (RPE) detachment was found as a predisposing lesion in 25 of these 31 eyes. Choroidal neovascular membrane developed in 12 of the 24 eyes with large RPE detachments. In 3 eyes neovascular membrane developed from an RPE detachment which had evolved from soft drusen. There were 3 eyes among the 62 eyes with soft drusen in which neovascular membrane developed directly from soft drusen. Based on these results, we classified AMD into 3 types; 1) atrophic, 2) predisciform, which includes RPE detachment and soft drusen, and 3) SMD.