Correspondence between HBT radii and the emission zone in non-central heavy ion collisions

In non-central collisions between ultra-relativistic heavy ions, the freeze-out distribution is anisotropic, and its major longitudinal axis may be tilted away from the beam direction. The shape and orientation of this distribution are particularly interesting, as they provide a snapshot of the evolving source and reflect the space-time aspect of anisotropic flow. Experimentally, this information is extracted by measuring pion HBT radii as a function of angle with respect to the reaction plane. Existing formulae relating the oscillations of the radii and the freezeout anisotropy are in principle only valid for Gaussian sources with no collective flow. With a realistic transport model of the collision, which generates flow and non-Gaussian sources, we find that these formulae approximately reflect the anisotropy of the freezeout distribution.Comment: 9 pages, 8 figure

Searching edges in the overlap of two plane graphs

Consider a pair of plane straight-line graphs, whose edges are colored red and blue, respectively, and let n be the total complexity of both graphs. We present a O(n log n)-time O(n)-space technique to preprocess such pair of graphs, that enables efficient searches among the red-blue intersections along edges of one of the graphs. Our technique has a number of applications to geometric problems. This includes: (1) a solution to the batched red-blue search problem [Dehne et al. 2006] in O(n log n) queries to the oracle; (2) an algorithm to compute the maximum vertical distance between a pair of 3D polyhedral terrains one of which is convex in O(n log n) time, where n is the total complexity of both terrains; (3) an algorithm to construct the Hausdorff Voronoi diagram of a family of point clusters in the plane in O((n+m) log^3 n) time and O(n+m) space, where n is the total number of points in all clusters and m is the number of crossings between all clusters; (4) an algorithm to construct the farthest-color Voronoi diagram of the corners of n axis-aligned rectangles in O(n log^2 n) time; (5) an algorithm to solve the stabbing circle problem for n parallel line segments in the plane in optimal O(n log n) time. All these results are new or improve on the best known algorithms.Comment: 22 pages, 6 figure

Behavioural analysis of vehicle-pedestrian interactions: The case of street designs with elements of shared space

This paper describes the development and implementation of qualitative behavioural criteria in order to analyse the conduct of pedestrians and vehicles when they are required to interact with each other, with particular interest to street designs with elements of shared space. The new behavioural analysis technique is developed by identifying the fundamental principles that underpin existing traffic analyses, such as traffic conflicts techniques, and adapting those to a qualitative framework that describes the mindset and rationale of road users. The technique is then applied to a case study in London, using video data from periods before and after the redevelopment of the Exhibition Road site from a conventional dual carriageway to a modern design with some elements of shared space. With the main goals being to assess the pedestrians’ confidence and the vehicles’ tolerance/patience when forced to interact with each other, behavioural trends are related to instantaneous characteristics of the vehicle flow (vehicle approach speed and traffic density). The data produced are used to develop and validate qualitative behavioural relationships for pedestrian-vehicle interactions, as well as location-specific conclusions for the Exhibition Road site

Analysing the perceptions of pedestrians and drivers to shared space

Shared space is an approach to improving streets and places where both pedestrians and vehicles are present, with layouts related more to the pedestrian scale and with features encouraging drivers to assume priority having been reduced or removed. It creates a more pedestrian-friendly environment than conventional street layouts, which are based on greater segregation between pedestrians and vehicles, while at the same time introducing uncertainty, which makes drivers engage more fully with their surroundings, leading to lower vehicle speeds and improved safety. This paper investigates the importance of certain person-, context- and design-specific factors affecting the perceptions of pedestrians and drivers to shared space. Using two web-based stated-preference surveys, two sets of responses are collected from pedestrians and drivers, who are presented with different combinations of binary factors forming scenarios. Regression analysis is carried out with logit models for each survey. The results suggest that pedestrians feel most comfortable in shared space under conditions which ensure their presence is clear to other road users – these conditions include low vehicular traffic, high pedestrian traffic, good lighting and pedestrian-only facilities. Conversely, the presence of many pedestrians and, in particular, children and elderly, makes drivers feel uneasy and, therefore, enhances their alertness

Behavioural analysis of interactions between pedestrians and vehicles in street designs with elements of shared space

This paper describes the development and implementation of qualitative behavioural criteria in order to analyse the conduct of pedestrians and vehicles when they are required to interact with each other, with particular interest to street designs with elements of shared space. The new behavioural analysis technique is developed by identifying the fundamental principles that underpin existing traffic analyses, such as traffic conflicts techniques, and adapting those to a qualitative framework that describes the mindset and rationale of road users. The technique is then applied to a case study in London, using video data from periods before and after the redevelopment of the Exhibition Road site from a conventional dual carriageway to a modern design with some elements of shared space. With the main goals being to assess the pedestrians’ confidence and the vehicles’ tolerance/patience when forced to interact with each other, behavioural trends are related to instantaneous characteristics of the vehicle flow (vehicle approach speed and traffic density). The data produced are used to develop and validate qualitative behavioural relationships for pedestrian-vehicle interactions, as well as location-specific conclusions for the Exhibition Road site

Approximating the Maximum Overlap of Polygons under Translation

Let $P$ and $Q$ be two simple polygons in the plane of total complexity $n$, each of which can be decomposed into at most $k$ convex parts. We present an $(1-\varepsilon)$-approximation algorithm, for finding the translation of $Q$, which maximizes its area of overlap with $P$. Our algorithm runs in $O(c n)$ time, where $c$ is a constant that depends only on $k$ and $\varepsilon$. This suggest that for polygons that are "close" to being convex, the problem can be solved (approximately), in near linear time

Children, family and the state : revisiting public and private realms

The state is often viewed as part of the impersonal public sphere in opposition to the private family as a locus of warmth and intimacy. In recent years this modernist dichotomy has been challenged by theoretical and institutional trends which have altered the relationship between state and family. This paper explores changes to both elements of the dichotomy that challenge this relationship: a more fragmented family structure and more individualised and networked support for children. It will also examine two new elements that further disrupt any clear mapping between state/family and public/private dichotomies: the third party role of the child in family/state affairs and children's application of virtual technology that locates the private within new cultural and social spaces. The paper concludes by examining the rise of the 'individual child' hitherto hidden within the family/state dichotomy and the implications this has for intergenerational relations at personal and institutional levels

Analysing the perceptions and behaviour of cyclists in street environments with elements of shared space

This paper investigates the impact of the new urban street design concept of shared space on cyclists. Using the recently redeveloped Exhibition Road site in London as an example, which has recently been redeveloped to a modern design with some elements of shared space, the study consists of two parts. The first one conducts a video observation analysis of the behaviour of cyclists in the area before and after redevelopment and looks at changes in key variables, such as flow and speed, while the second provides an insight into the perception of cyclists, which are modelled by means of a purpose-developed survey. Results seem to indicate, from a behavioural perspective, that the redeveloped road layout attracts more cyclists to the area, and in particular commuters, but also that it reduces the average cycling speed. Specifically, reduced speeds are observed in the predominantly pedestrian zone of the area, possibly demonstrating the influence of the increased presence of pedestrians on cycling behaviour. From the perspective of perceptions, on the other hand, results seem to point to clarity as a potential issue needing to be addressed, as many cyclists express confusion as to the exact area where they can cycle

Assessing the pedestrian experience in public spaces

The assessment of the pedestrian experience in public spaces is increasingly becoming an essential constituent of urban street design. This paper first presents a new methodology for evaluating pedestrian environments through on-street surveys, building upon well-established comprehensive pedestrian audit tools, such as PERS and PEDS. The methodology is applied on the South Kensington area of London, in light of recent redevelopments seeing the conversion of the previous car-oriented layout to a more pedestrian-friendly one. The results suggest that the new design is generally perceived positively by pedestrians, but point out that there may be room for improvement in terms of pedestrian comfort. The results are then further analysed statistically in order to draw generic conclusions and investigate the effects of different aspects of the pedestrian environment on each other with respect to the pedestrian experience. By fitting a series of ordered logistic regression models, a number of interdependences are identified and interpreted

Combined Docking and Quantum Chemical Study on CYP-mediated Metabolism of Estrogens in Man

Long-term exposure to estrogens seriously increases the incidence of various diseases including breast cancer. Experimental studies indicate that cytochrome P450 (CYP) enzymes catalyze the bioactivation of estrogens to catechols, which can exert their harmful effects via various routes. It has been shown that the 4-hydroxylation pathway of estrogens is the most malign, while 2-hydroxylation is considered a benign pathway. It is also known experimentally that with increasing unsaturation of ring B of estrogens the prevalence of the 4-hydroxylation pathway significantly increases. In this study, we used a combination of structural analysis, docking, and quantum chemical calculations at the B3LYP/6-311+G* level to investigate the factors that influence the regioselectivity of estrogen metabolism in man. We studied the structure of human estrogen metabolizing enzymes (CYP1A1, CYP1A2, CYP1B1, and CYP3A4) in complex with estrone using docking and investigated the susceptibility of estrone, equilin, and equilenin (which only differ in the unsaturation of ring B) to undergo 2- and 4-hydroxylation using several models of CYP enzymes (Compound I, methoxy, and phenoxy radical). We found that even the simplest models could account for the experimental difference between the 2- and 4- hydroxylation pathways and thus might be used for fast screening purposes. We also show that reactivity indices, specifically in this case the radical and nucleophilic condensed Fukui functions, also correctly predict the likeliness of estrogen derivatives to undergo 2- or 4-hydroxylation