Network and Psychological Effects in Urban Movement

Correlations are regularly found in space syntax studies between graph-based configurational measures of street networks, represented as lines, and observed movement patterns. This suggests that topological and geometric complexity are critically involved in how people navigate urban grids. This has caused difficulties with orthodox urban modelling, since it has always been assumed that insofar as spatial factors play a role in navigation, it will be on the basis of metric distance. In spite of much experimental evidence from cognitive science that geometric and topological factors are involved in navigation, and that metric distance is unlikely to be the best criterion for navigational choices, the matter has not been convincingly resolved since no method has existed for extracting cognitive information from aggregate flows. Within the space syntax literature it has also remained unclear how far the correlations that are found with syntactic variables at the level of aggregate flows are due to cognitive factors operating at the level of individual movers, or they are simply mathematically probable network effects, that is emergent statistical effects from the structure of line networks, independent of the psychology of navigational choices. Here we suggest how both problems can be resolved, by showing three things: first, how cognitive inferences can be made from aggregate urban flow data and distinguished from network effects; second by showing that urban movement, both vehicular and pedestrian, are shaped far more by the geometrical and topological properties of the grid than by its metric properties; and third by demonstrating that the influence of these factors on movement is a cognitive, not network, effect

Cosmology with clusters of galaxies

In this Chapter I review the role that galaxy clusters play as tools to constrain cosmological parameters. I will concentrate mostly on the application of the mass function of galaxy clusters, while other methods, such as that based on the baryon fraction, are covered by other Chapters of the book. Since most of the cosmological applications of galaxy clusters rely on precise measurements of their masses, a substantial part of my Lectures concentrates on the different methods that have been applied so far to weight galaxy clusters. I provide in Section 2 a short introduction to the basics of cosmic structure formation. In Section 3 I describe the Press--Schechter (PS) formalism to derive the cosmological mass function, then discussing extensions of the PS approach and the most recent calibrations from N--body simulations. In Section 4 I review the methods to build samples of galaxy clusters at different wavelengths. Section 5 is devoted to the discussion of different methods to derive cluster masses. In Section 6 I describe the cosmological constraints, which have been obtained so far by tracing the cluster mass function with a variety of methods. Finally, I describe in Section 7 the future perspectives for cosmology with galaxy clusters and the challenges for clusters to keep playing an important role in the era of precision cosmology.Comment: 49 pages, 19 figures, Lectures for 2005 Guillermo Haro Summer School on Clusters, to appear in "Lecture notes in Physics" (Springer

Dust in Supernovae and Supernova Remnants II: Processing and survival

Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations

Supplemental polymer coatings in reverse osmosis membrane improvement and regeneration

The improvements achieved in membrane performance, by treating sub-standard or degenerated cellulose acetate membranes with water soluble polymers, which are subsequently insolubilised, has been studied. A number of commercially available and locally prepared polymers have been evaluated on both commercial and specially made membranes. Guidelines have been set for the choice of supplemental polymers. The very promising results obtained by treating two degenerated spiral modules underlines the importance of this approach. © 1978.Articl

Movement behaviour of catface rockcod Mycteroperca (Epinephelus) andersoni (Epinephelidae) off the eastern seaboard of southern Africa

Movement behaviour of the endemic epinephelid Mycteroperca andersoni (formerly allocated to genus Epinephelus) along the east coast of  southern Africa was investigated using both conventional dart tagging and passive acoustic telemetry. Results from both methods showed that this  species is likely to be a temporary resident on shallow inshore reefs; fish showed high site fidelity and occupied relatively small home ranges for  periods seldom exceeding 12 months, whereafter they appeared to undertake ranging-type movements. Adults >400 mm total length were more  mobile than juveniles, and the distance moved increased with both fish size and time at liberty. Adults south of Durban, South Africa, moved farther  in a northerly direction than those north of Durban, confirming that spawning likely takes place north of Durban. No direct evidence of a spawning  migration was found, but anecdotal reports that they form spawning aggregations suggests that migrations for this purpose are likely to occur. The  current species-specific linefish regulations and the recently expanded marine protected area network along the east coast of South Africa are  believed to be adequate to ensure the future sustainable use of this species. However, improved enforcement of regulations is required, and  identification of spawning aggregation sites should be a research priority

Experience base for Radioactive Waste Thermal Processing Systems: A preliminary survey

In the process of considering thermal technologies for potential treatment of the Idaho National Engineering Laboratory mixed transuranic contaminated wastes, a preliminary survey of the experience base available from Radioactive Waste Thermal Processing Systems is reported. A list of known commercial radioactive waste facilities in the United States and some international thermal treatment facilities are provided. Survey focus is upon the US Department of Energy thermal treatment facilities. A brief facility description and a preliminary summary of facility status, and problems experienced is provided for a selected subset of the DOE facilities