Gaseous diffusion in glassy polymers

A model for gaseous diffusion in glassy polymers is developed with a view to accounting for the observations made in dual sorption and certain other phenomena in polymers below their glass transition temperature. In this paper a preliminary study of the effects of both the immobilizing mechanism and the generalized diffusion mechanism on travelling waves and the diffusive wavefronts is made

Some applications of probability theory in statistical mechanics

Imperial Users onl

Hooligans, vandals and the community: a study of social reaction to juvenile delinquency

The thesis consists of three studies on various ways in which society reacts to juvenile delinquency. It is introduced with an account of recent developments in the sociology of deviance which have drawn attention to the nature and effect of the societal reaction to deviance. These developments, termed the "transactional perspective", are put in the context of a "sceptical" reaction against more conventional ways of conceptualizing deviance. The implications of this new perspective for theory and research are indicated. The first study is on vandalism, and starts by attempting to unravel the different definitions of this behaviour as a form of rule-breaking and deviance. It goes on to consider the processes through which vandalism becomes defined as a social problem and then discusses the main images and stereotypes through which society tries to conceptualize this form of delinquency. It finally considers the organized approaches to the prevention and control of vandalism. The second study is a survey of the views about delinquency - its nature, causes and control - and allied topics, held by a selected sample of official and unofficial control agents in a London Borough "Northview". The relevance of these views to understanding the social control of delinquency is considered. The final study is of various types of response to the Mods and Rockers phenomenon. Using mass media and observational sources, an analysis is made of how this form of deviance was reported and conceptualized. The emergent images of the behaviour are related to the ways in which society attempted to control it. The effects of these reactions on the form and development of the phenomenon are suggested

alphabeta sequence of F is IS31

Previous studies have shown that there is a deoxyribonucleic acid (DNA) segment, of length 1.3 kb and denoted as the alphabeta sequence, which occurs twice on the F plasmid at corrdinates 93.2 to 94.5/OF kb and 13.7 to 15.0F kb. In the present investigation, heteroduplexes were prepared between a phage DNA carrying the insertion sequence IS3 and suitable F-prime DNAs. The hybrids formed show that IS3 is the same as alphabeta. This result plus previous studies support the view that: (i) the insertion sequence IS2 and IS3 occur on F and, in multiple copies, on the main bacterial chromosome of Escherichia coli K-12; and (ii)these IS sequences on the main bacterial chromosomes are hot spots for Hfr formation by reciprocal recombination with the corresponding sequences of F

Communication Bottlenecks in Scale-Free Networks

We consider the effects of network topology on the optimality of packet routing quantified by $\gamma_c$, the rate of packet insertion beyond which congestion and queue growth occurs. The key result of this paper is to show that for any network, there exists an absolute upper bound, expressed in terms of vertex separators, for the scaling of $\gamma_c$ with network size $N$, irrespective of the routing algorithm used. We then derive an estimate to this upper bound for scale-free networks, and introduce a novel static routing protocol which is superior to shortest path routing under intense packet insertion rates.Comment: 5 pages, 3 figure

Resilience of Complex Networks to Random Breakdown

Using Monte Carlo simulations we calculate $f_c$, the fraction of nodes which are randomly removed before global connectivity is lost, for networks with scale-free and bimodal degree distributions. Our results differ with the results predicted by an equation for $f_c$ proposed by Cohen, et al. We discuss the reasons for this disagreement and clarify the domain for which the proposed equation is valid