Pedestrian, Crowd, and Evacuation Dynamics

This contribution describes efforts to model the behavior of individual pedestrians and their interactions in crowds, which generate certain kinds of self-organized patterns of motion. Moreover, this article focusses on the dynamics of crowds in panic or evacuation situations, methods to optimize building designs for egress, and factors potentially causing the breakdown of orderly motion.Comment: This is a review paper. For related work see http://www.soms.ethz.c

A study of the binding of Graves’ immunoglobulins to orbital antigens

The binding of Graves' immunoglobulins to membranes of human eye muscle (HEM) and guinea pig Harderian gland (HG) were studied. The membrane fraction of 100,000 X g sediment was used for ELISA. Serum samples from 55 patients with Graves' ophthalmopathy were evaluated for binding to the membrane preparation. There was a higher binding to HG with the sera from the patients with Graves' ophthalmopathy than in the control group (p less than 0.01), but there was no difference in binding to HEM. Purification of IgG from sera improved binding to HG in both patients' (p less than 0.001) and control group (p less than 0.005). There was also an increase in percentage of positive responses obtained with IgG 48% vs serum samples 37%. In 23 out of 24 patients we found the thickening of extraocular muscles by A-scan ultrasonography. In these groups of patients and 3 others with malignant ophthalmopathy the binding of IgG preparation to HG was similar to control group. In all assays there was an overlap between patients with Graves' ophthalmopathy and control subjects, and a lack of relationship between the responses in ELISA and clinical or severity of ophthalmopathy

Quantification of Collagen Ultrastructure after Penetrating Keratoplasty – Implications for Corneal Biomechanics

Purpose: To quantify long-term changes in stromal collagen ultrastructure following penetrating keratoplasty (PK), and evaluate their possible implications for corneal biomechanics. Methods: A pair of 16 mm post-mortem corneo-scleral buttons was obtained from a patient receiving bilateral penetrating keratoplasty 12 (left)/28 (right) years previously. Small-angle x-ray scattering quantified collagen fibril spacing, diameter and spatial order at 0.5 mm or 0.25 mm intervals along linear scans across the graft margin. Corresponding control data was collected from two corneo-scleral buttons with no history of refractive surgery. Wide-angle x-ray scattering quantified collagen fibril orientation at 0.25 mm (horizontal)×0.25 mm (vertical) intervals across both PK specimens. Quantification of orientation changes in the graft margin were verified by equivalent analysis of data from a 13 year post-operative right PK specimen obtained from a second patient in a previous study, and comparison made with new and published data from normal corneas. Results: Marked changes to normal fibril alignment, in favour of tangentially oriented collagen, were observed around the entire graft margin in all PK specimens. The total number of meridional fibrils in the wound margin was observed to decrease by up to 40%, with the number of tangentially oriented fibrils increasing by up to 46%. As a result, in some locations the number of fibrils aligned parallel to the wound outnumbered those spanning it by up to five times. Localised increases in fibril spacing and diameter, with an accompanying reduction in matrix order, were also evident. Conclusions: Abnormal collagen fibril size and spatial order within the PK graft margin are indicative of incomplete stromal wound remodelling and the long term persistence of fibrotic scar tissue. Lasting changes in collagen fibril orientation in and around PK wounds may alter corneal biomechanics and compromise the integrity of the graft-host interface in the long term