Aim To describe the clinical and fluorescein angiographic features of patients with macroaneurysms (MAs) attending an ophthalmology department over 8 years. Methods All the patients between 1997 and 2004 with a diagnosis of retinal artery MA were identified from hospital records. Photographs and fluorescein angiograms were examined, and the MAs classified according to their clinical (haemorrhagic or exudative) features, and angiographic (saccular or fusiform) features. Baseline data of the patients were taken including visual acuity and associated ocular and medical conditions. Results A total of 38 MAs were identified in 34 patients. The age at presentation ranged from 36 to 93 years, with a mean of 73.7 years. Of them, 24/34 (70%) were female patients, and 10/34 (30%) were male patients. There was a history of hypertension in 9/14 patients (64.3%). Of 38 MAs, 32 were identifiable as either saccular or fusiform. Of these, 22/32 (68.75%) were saccular, the rest fusiform. In all, 72.7% of the saccular MAs showed haemorrhage as the predominant feature. Of the 10 fusiform MAs, 90% showed haemorrhage as the predominant feature. Conclusion Retinal artery macroaneurysm is a rare condition that may mimic a variety of other conditions. Most MAs do not require treatment. We suggest guidelines for diagnosis and propose a treatment algorithm for this condition.

We report experiments on slow granular flows in a split-bottom Couette cell that show novel strain localization features. Nontrivial flow profiles have been observed which are shown to be the consequence of simultaneous formation of shear zones in the bulk and at the boundaries. The fluctuating band model based on a minimization principle can be fitted to the experiments over a large variation of morphology and filling height with one single fit parameter, the relative friction coefficient μ(rel) between wall and bulk. The possibility of multiple shear zone formation is controlled by μ(rel). Moreover, we observe that the symmetry of an initial state, with coexisting shear zones at both side walls, breaks spontaneously below a threshold value of the shear velocity. A dynamical transition between two asymmetric flow states happens over a characteristic time scale which depends on the shear strength.

We present the results of an experimental study of pattern formation in horizontally oscillating granular suspensions. Starting from a homogeneous state, the suspension turns into a striped pattern within a specific range of frequencies and amplitudes of oscillation. We observe an initial development of layered structures perpendicular to the vibration direction and a gradual coarsening of the stripes. However, both processes gradually slow down and eventually saturate. The probability distribution of the stripe width P (w) approaches a nonmonotonic steady-state form which can be approximated by a Poisson distribution. We observe similar structures in MD simulations of soft spherical particles coupled to the motion of the surrounding fluid.

No abstract

Reactive flows inside porous media play an important role in a number of geophysical and industrial processes. Here we present three-dimensional experimental measurements on how precipitation and flow patterns change with the flow rate inside a model porous medium consisting of monodisperse glass beads. The sample is initially filled with an aqueous solution of sodium carbonate into which a solution of barium chloride is injected at a constant flow rate. Upon contact and reaction, the two reactants produce water-insoluble barium carbonate which precipitates onto the glass beads. This precipitate then modifies the flow morphology which in turn changes the spatial distribution of the precipitate. We discuss the influence of the flow rate on the morphology of the flow pattern and demonstrate that neither viscous fingering nor the Rayleigh-Taylor instability have any significant influence in our model system.