Showing papers by "University of Sussex published in 1992"

Analyzing the mosaic structure of genes.

Abstract: Some genes in prokaryotes consist of a mosaic of regions derived from different ancestors by horizontal gene transfer. A method is described for demonstrating the statistical significance of such mosaic structure and for locating the crossover points separating different regions.

Successful industrial innovation: critical factors for the 1990s

Abstract: Not only is technology changing rapidly, but the process of the commercialisation of technological change—the industrial innovation process—is changing also. The paper traces developments in the dominant perceived model of industrial innovation from the simple linear ‘technology push’ and ‘need pull’ models of the 1960s and early 1970s, through the ‘coupling model’ of the late 1970s to early 1980s, to the ‘integrated’ model of today. The latter (the 4th Generation innovation process) marked a shift from perceptions of innovation as a strictly sequential process to innovation perceived as a largely parallel process. This shift owed much to observations of innovation processes in leading Japanese corporations. Recent developments indicate the possibilities attainable in the proposed ‘strategic integration and networking’ model, elements of which are already in place. According to this 5th generation model, innovation is becoming faster; it increasingly involves inter-company networking; and it employs a new electronic toolkit (expert systems and simulation modelling).

Income distribution and life expectancy.

Abstract: The relationship between income distribution and mortality is explored using data from published sources. Specifically the author attempts to "investigate the cross sectional relation between income distribution and mortality and its possible interactions with gross national product per head and to assess whether changes in income distribution over time are related to changes in mortality in developed countries." He concludes that "there is clear evidence of a strong relation between a societys income distribution and the average life expectancy of its population." (EXCERPT)

A National Survey

Abstract: So far I have attempted to provide a broad framework within which to consider the importance of managerial and organisational integration. Inevitably in so doing I have found it necessary to raise wider educational and training issues which influence not only conceptual skills but also attitude. Indeed I have, on occasion, moved my argument or perspective to even wider considerations; issues pertaining to national culture. Culture, education policy or structure, industrial organisation, all interact in subtle and perhaps devious forms. Thus a cultural framework which is “overly status or class conscious” reflects this in its educational system. Most likely it is more predisposed to segment its secondary and tertiary education systems according to similar principles. It may well encourage separation of the university and technical college or polytechnic system to a degree that is industrially and commercially counterproductive — and integratively devisive. Such an educational system will no doubt require “preselection and filtering” which relies upon early, too early, subject specialisation; it may, subsequently, influence adversely the need for individuals and subgroups to communicate more intimately and to organise themselves more closely. In fact it may ensure the continuance of barriers, hierarchies, and polarised attitudes of class, structure and function all the way across and through commerce and industry.

Racks and links in codimension two

Abstract: A rack, which is the algebraic distillation of two of the Reidemeister moves, is a set with a binary operation such that right multiplication is an automorphism. Any codimension two link has a fundamental rack which contains more information than the fundamental group. Racks provide an elegant and complete algebraic framework in which to study links and knots in 3–manifolds, and also for the 3–manifolds themselves. Racks have been studied by several previous authors and have been called a variety of names. In this first paper of a series we consolidate the algebra of racks and show that the fundamental rack is a complete invariant for irreducible framed links in a 3–manifold and for the 3–manifold itself. We give some examples of computable link invariants derived from the fundamental rack and explain the connection of the theory of racks with that of braids.

The Primordial helium abundance from observations of extragalactic H-II regions

Abstract: The pre-galactic (assumed primordial) helium mass fraction Y p is determined to be 0.228 ± 0.005 (s.e.) or Y p < 0.242 with 95 per cent confidence, taking reasonably likely systematic errors into account. This is based on INT and AAT observations of emission lines from H II galaxies combined with selected data from the literature relating to extragalactic H II regions in general, discussed in a consistent analysis taking into account the known corrections and likely sources of error

Structural Phase Transitions in the Fullerene C60

Abstract: High-resolution powder neutron diffraction has been used to study the crystal structure of the fullerence C60 in the temperature range 5 K to 320 K. Solid C60 adopts a cubic structure at all temperatures. The experimental data provide clear evidence of a continuous phase transition at ca. 90 K and confirm the existence of a first-order phase transition at 260 K. In the high-temperature face-centred-cubic phase (T > 260 K), the C60 molecules are completely orientationally disordered, undergoing continuous reorientation. Below 260 K, interpretation of the diffraction data is consistent with uniaxial jump reorientation principally about a single 111 direction. In the lowest-temperature phase (T < 90 K), rotational motion is frozen although a small amount of static disorder still persists.

Internally contracted multiconfiguration-reference configuration interaction calculations for excited states

Abstract: The calculation of electronically excited states with the internally contracted multiconfiguration-reference configuration interaction (CMRCI) method is discussed A straightforward method, in which contracted functions for all states are included in the basis, is shown to be very accurate and stable even in cases of narrow avoided crossings However, the expense strongly increases with the number of states A new method is proposed, which employs different contracted basis sets for each state, and in which eigensolutions of the Hamiltonian are found using an approximate projection operator technique The computational effort for this method scales only linearly with the number of states The two methods are compared for various applications

Migration and social mobility: South East England as an escalator region.

Abstract: FIELDING A. J. (1992) Migration and social mobility: South East England as an escalator region, Reg. Studies 26, 1–15. This paper uses data from the OPCS Longitudinal Study and the National Health Service Central Register to examine the contention that the South East region of England acts as a kind of ‘upward social class escalator’ within the British urban and regional system. To establish that this is so it is shown firstly, that the South East attracts to itself through inter-regional migration a more than proportional share of the potentially upwardly mobile young adults; secondly, that it promotes these young people along with its own young adults at rates which are higher than elsewhere in the country; and finally, that a significant proportion of those who achieve these higher levels of status and pay then ‘step off’ the escalator. They do this by migrating away from the South East at later stages of their working lives and at or near to retirement. The analysis is then extended in two respects. F...

DNA repair mutants defining G2 checkpoint pathways in Schizosaccharomyces pombe.

Abstract: We have tested mutants corresponding to 20 DNA repair genes of the fission yeast Schizosaccharomyces pombe for their ability to arrest in G2 after DNA damage. Of the mutants tested, four are profoundly defective in this damage dependent G2 arrest. In addition, these four mutants are highly sensitive to a transient inhibition of DNA synthesis by hydroxyurea. This suggests that the pathway responsible for the recognition of DNA damage and the subsequent mitotic arrest, shares many functions with the mechanism that controls the dependency of mitosis on the completion of S phase. The phenotype of these checkpoint rad mutants in wee mutant backgrounds indicate that the G2 arrest response is mediated either through, or in parallel with, the activity of the cdc2 gene product.

Recollective experience, normal aging, and frontal dysfunction.

Abstract: This study examined the nature of verbal recognition memory in young and old subjects. Following presentation of a word list, subjects undertook a yes-no recognition test and indicated whether their decision was based on explicit recollection or assessment of familiarity. Explicit recollection declined with age, and familiarity-based recognition increased. Furthermore, the extent to which older subjects relied on familiarity-based recognition correlated with neuropsychological indices of frontal lobe dysfunction. A further experiment indicated that the change from explicit recollection to familiarity-based responding was unrelated to changes in older subjects' confidence about their memory. The data indicate the central role of frontal dysfunction in understanding age-related memory loss.

The evolution of eyes.

Abstract: Since the earth formed more than 5 billion years ago, sunlight has been the most potent selective force to control the evolution of living organisms. Consequences of this solar selection are most evident in eyes, the premier sensory outposts of the brain. Because organisms use light to see, eyes have evolved into many shapes, sizes, and designs; within these structures, highly conserved protein molecules for catching photons and bending light rays have also evolved. Although eyes themselves demonstrate many different solutions to the problem of obtaining an image--solutions reached relatively late in evolution--some of the molecules important for sight are, in fact, the same as in the earliest times. This suggests that once suitable biochemical solutions are found, they are retained, even though their \"packaging\" varies greatly. In this review, we concentrate on the diversity of eye types and their optical evolution, but first we consider briefly evolution at the more fundamental levels of molecules and cells.

The Varieties of Intrinsic Value

Abstract: To hold an environmental ethic is to hold that non-human beings and states of affairs in the natural world have intrinsic value. This seemingly straightforward claim has been the focus of much recent philosophical discussion of environmental issues. Its clarity is, however, illusory. The term 'intrinsic value' has a variety of senses and many arguments on en vironmental ethics suffer from a conflation of these different senses: specimen hunters for the fallacy of equivocation will find rich pickings in the area. This paper is largely the work of the underlabourer. I distinguish different senses of the concept of intrinsic value, and, relatedly, of the claim that non-human beings in the natural world have intrinsic value; I exhibit the logical relations between these claims and examine the distinct motiva tions for holding them. The paper is not however merely an exercise in con ceptual underlabouring. It also defends one substantive thesis: that while it is the case that natural entities have intrinsic value in the strongest sense of the term, i.e., in the sense of value that exists independently of human valuations, such value does not as such entail any obligations on the part of human beings. The defender of nature's intrinsic value still needs to show that such value contributes to the well-being of human agents.

Preparation and characterization of C 60 Br 6 and C 60 Br 8

Abstract: BUCKMINSTERFULLERENE (C60) is much more reactive than was originally anticipated, because resonance structures that place double bonds in the pentagonal rings are energetically unfavourable1 and lead to restricted electron delocalization. C60 therefore behaves as an electron-deficient 'super-alkene' rather than as a 'super-aromatic', as demonstrated by the addition of osmium tetroxide2, platinum3, dipolar molecules4, alkyl radicals5and amines6. Reaction of anions derived from C60 with iodomethane results in up to 24 methyl groups becoming attached to the cage, although compounds containing either eight or six methyl groups are dominant in the mass spectrum7. Here we report the synthesis of crystalline C60Br6 (which forms magenta plates) and C60Br8 (dark brown prisms) by mixing solutions of C60 with bromine. The structures of these compounds, which contain occluded bromine when precipitated from the brominating medium, have been determined by single-crystal X-ray diffraction. Reaction of C60 with bromine in the absence of solvent gives C60Br24 (which also contains occluded bromine). We propose a configuration for C60Br24 (and sterically hindered C60X24 compounds) based on that for C60Br8. On being warmed in solution, C60Br6 rearranges and disproportionates to C60Br8, and all three bromo derivatives revert to C60 on strong heating. These results provide an insight into the pattern of addition of bulky reagents to C60.

Role of interspecies transfer of chromosomal genes in the evolution of penicillin resistance in pathogenic and commensal Neisseria species.

Abstract: The two pathogenic species of Neisseria, N. meningitidis and N. gonorrhoeae, have evolved resistance to penicillin by alterations in chromosomal genes encoding the high molecular weight penicillin-binding proteins, or PBPs. The PBP 2 gene (penA) has been sequenced from over 20 Neisseria isolates, including susceptible and resistant strains of the two pathogenic species, and five human commensal species. The genes from penicillin-susceptible strains of N. meningitidis and N. gonorrhoeae are very uniform, whereas those from penicillin-resistant strains consist of a mosaic of regions resembling those in susceptible strains of the same species, interspersed with regions resembling those in one, or in some cases, two of the commensal species. The mosaic structure is interpreted as having arisen from the horizontal transfer, by genetic transformation, of blocks of DNA, usually of a few hundred base pairs. The commensal species identified as donors in these interspecies recombinational events (N. flavescens and N. cinerea) are intrinsically more resistant to penicillin than typical isolates of the pathogenic species. Transformation has apparently provided N. meningitidis and N. gonorrhoeae with a mechanism by which they can obtain increased resistance to penicillin by replacing their penA genes (or the relevant parts of them) with the penA genes of related species that fortuitously produce forms of PBP 2 that are less susceptible to inhibition by the antibiotic. The ends of the diverged blocks of DNA in the penA genes of different penicillin-resistant strains are located at the same position more often than would be the case if they represent independent crossovers at random points along the gene. Some of these common crossover points may represent common ancestry, but reasons are given for thinking that some may represent independent events occurring at recombinational hotspots.

Mechano-electrical transducer currents in hair cells of the cultured neonatal mouse cochlea.

Abstract: The first step towards the generation of the receptor potential in hair cells is the gating of the transducer channels and subsequent flow of transducer current, induced by deflection of the stereocilia We describe properties of the transducer current in outer hair cells of neonatal mice Less extensive observations on inner hair cells suggest that their transducer currents have similar characteristics The hair bundles were stimulated by force from a fluid jet The transducer currents in outer hair cells are the largest found so far in any hair cell, with a chord conductance of up to 92 nS at -84 mV The transfer function suggests that the channel has at least two closed states and one open state The permeabilities for sodium, potassium and caesium are similar, consistent with the channel being a fairly non-selective cation channel At negative potentials the currents adapt in most cells, although never as completely as in hair cells of lower vertebrates If the unit conductance of the transducer channel is similar to that of the turtle's auditory hair cells (100 pS), then there are about 90 channels per hair bundle, or one channel between every pair of adjacent stereocilia in neighbouring rows

Numerical analysis of the Cahn-Hilliard equation with a logarithmic free energy

Abstract: A fully discrete finite element method for the Cahn-Hilliard equation with a logarithmic free energy based on the backward Euler method is analysed. Existence and uniqueness of the numerical solution and its convergence to the solution of the continuous problem are proved. Two iterative schemes to solve the resulting algebraic problem are proposed and some numerical results in one space dimension are presented.

C60: buckminsterfullerene, the celestial sphere that fell to earth

Abstract: In 1975–1978 the long-chained polyynylcyanides, HC5N, HC7N, and HC9N were surprisingly discovered in the cold dark clouds of interstellar space by radioastronomy. The subsequent quest for their source indicated that they were being blown out of red giant, carbon stars. In 1985 carbon-cluster experiments aimed at simulating the chemistry in such stars confirmed these objects as likely sources. During these cluster studies a serendipitous discovery was made; a stable pure-carbon species, C60, formed spontaneously in a chaotic plasma produced by a laser focused on a graphite target. A closed spheroidal cage structure was proposed for this molecule, which was to become the third well-characterized allotrope of carbon and was named buckminsterfullerene. It has taken five years to produce sufficient material to prove the correctness of this conjecture. There may be a timely object lesson in the fact that exciting new and strategically important fields of chemistry and materials science have been discovered overnight due to fundamental research, much of which was unable to attract financial support, and all of which was stimulated by a fascination with the role of carbon in space and stars. In this account, interesting aspects of this discovery, its origins, and its sequel are presented. The story has many facets, some of which relate to the way scientific discoveries are made.

East Asia's Economic Success: Conflicting Perspectives, Partial Insights, Shaky Evidence

Abstract: Neoliberal economists say that growth is easy, provided the state does not obstruct the natural growth-inducing processes of a capitalist economy. They point to the success of South Korea and Taiwan as evidence that this proposition also holds for quite poor economies. Using chapters of Helen Hughes's edited volume by way of illustration, this article shows that the neoliberals ignore so much contrary evidence as to suggest that the neoliberal paradigm has entered a degenerative stage, like classical economics in the years before Keynes's breakthrough and like much Marxist writing of the 1970s.Two recent books about East Asia offer ways forward. The one by Alice Amsden argues that Korea has done better than other developing countries because it has created a more powerful synergy between a state that aggressively steers market competition and large, diversified business groups whose firms focus strategically on production processes at the shop floor. In conditions of “late development” this synergy is the key to success. Stephan Haggard's book accepts the core economic mechanism of the neoliberals but argues that the choice between sensible export-oriented policies, as in East Asia, or unsensible secondary import-substitution policies, as in Latin America, is determined by a complex conjunction of international pressures, domestic coalitions, political institutions, and ideas.Both books make important contributions to the debate. But they are weakened by not situating the experience of their case studies within an account of trends in the world system and by not addressing the question of what prevented massive “government failure” in market interventions in the East Asian cases. The last part of this paper takes a short step in this direction.

Naming impairments following recovery from herpes simplex encephalitis: category-specific?

Abstract: An apparently clear case of category-specific naming impairment selectively affecting animals was detected in a patient who had recovered from herpes simplex encephalitis. However, subsequent inves...

Low-Level Visual Processing of Biological Motion

Abstract: Biological motion displays depict a moving human figure by means of just a few isolated points of light attached to the major joints of the body. Naive observers readily interpret the moving pattern of dots as representing a human figure, despite the complete absence of form cues. This paper reports a series of experiments which investigated the visual processes underlying the phenomenon. Results suggest that (i) the effect relies upon responses in low-level motion-detecting processes, which operate over short temporal and spatial intervals and respond to local modulations in image intensity; and (ii) the effect does not involve hierarchical visual analysis of motion components, nor does it require the presence of dots which move in rigid relation to each other. Instead, movements of the extremities are crucial. Data are inconsistent with current theoretical treatments.

National mortality rates : the impact of inequality ?

Abstract: Although health is closely associated with income differences within each country there is, at best, only a weak link between national mortality rates and average income among the developed countries. On the other hand, there is evidence of a strong relationship between national mortality rates and the scale of income differences within each society. These three elements are coherent if health is affected less by changes in absolute material standards across affluent populations than it is by relative income or the scale of income differences and the resulting sense of disadvantage within each society. Rather than socioeconomic mortality differentials representing a distribution around given national average mortality rates, it is likely that the degree of income inequality indicates the burden of relative deprivation on national mortality rates.