Showing papers by "University of Sussex published in 1988"
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01 Jan 1988TL;DR: Algebraic Theory of Processes provides the first general and systematic introduction to the semantics of concurrent systems, a relatively new research area in computer science, and develops the mathematical foundations of the algebraic approach to the formal semantics of languages.
Abstract: Algebraic Theory of Processes provides the first general and systematic introduction to the semantics of concurrent systems, a relatively new research area in computer science. It develops the mathematical foundations of the algebraic approach to the formal semantics of languages and applies these ideas to a particular semantic theory of distributed processes. The book is unique in developing three complementary views of the semantics of concurrent processes: a behavioral view where processes are deemed to be equivalent if they cannot be distinguished by any experiment; a denotational model where processes are interpreted as certain kinds of trees; and a proof-theoretic view where processes may be transformed into equivalent processes using valid equations or transformations. It is an excellent guide on how to reason about and relate behavioral, denotational, and proof-theoretical aspects of languages in general: all three views are developed for a sequence of increasingly complex algebraic languages for concurrency and in each case they are shown to be equivalent. Algebraic Theory of Processes is a valuable source of information for theoretical computer scientists, not only as an elegant and comprehensive introduction to the field but also in its discussion of the author's own theory of the behavioral semantics of processes ("testing equivalence") and original results in example languages for distributed processes, It is self-contained; the problems addressed are motivated from the standpoint of computer science, and all the required algebraic concepts are covered. There are exercises at the end of each chapter.
981 citations
TL;DR: In this article, the authors examined gravity theories derived from a gravitational lagrangian and showed that they are conformally equivalent to general relativity plus a scalar-field matter source with a particular self-interaction potential.
588 citations
TL;DR: The intriguing revelation that 12 pentagonal "defects" convert a planar hexagonal array of any size into a quasi-icosahedral cage explains why some intrinsically planar materials form quasi-crystalline particles, as appears to occur in the case of soot.
Abstract: Although carbon has been subjected to far more study than all other elements put together, the buckminsterfullerene hollow-cage structure, recently proposed to account for the exceptional stability of the C(60) cluster, has shed a totally new and revealing light on several important aspects of carbon's chemical and physical properties that were quite unsuspected and others that were not previously well understood. Most significant is the discovery that C(60) appears to form spontaneously, and this has particularly important implications for particle formation in combustion and in space as well as for the chemistry of polyaromatic compounds. The intriguing revelation that 12 pentagonal "defects" convert a planar hexagonal array of any size into a quasi-icosahedral cage explains why some intrinsically planar materials form quasi-crystalline particles, as appears to occur in the case of soot. Although the novel structural proposal has still to be unequivocally confirmed, this article pays particular attention to the way in which it provides convincing explanations of puzzling observations in several fields, so lending credence to the structure proposed for C(60).
547 citations
TL;DR: A simple, new, carbon nucleation scheme has been developed which results in quasi-single crystal particles of concentric, spiral-shell internal structure and overall quasi-icosahedral shape.
Abstract: A simple, new, carbon nucleation scheme has been developed which results in quasi-single crystal particles of concentric, spiral-shell internal structure and overall quasi-icosahedral shape. Intermediates consisting of curved graphitic networks and overall growth controlled by epitaxy are key factors in the scheme which also produces buckminsterfullerene, C60B, as an inert by-product. The scheme which explains, for the first time, the occurrence of polyhedral carbonaceous particles may also apply to soot and circumstellar dust formation.
430 citations
TL;DR: A system is described for gene disruption and replacement in Schizosaccharomyces pombe based on the homologous selectable marker, ura4, the structural gene for orotidine-5′-phosphate decarboxylase, which shows considerable conservation with the orotamines from other organisms.
Abstract: A system is described for gene disruption and replacement in Schizosaccharomyces pombe based on the homologous selectable marker, ura4, the structural gene for orotidine-5'-phosphate decarboxylase The presence of a single copy of the wild-type gene can rescue a ura4 auxotrophic mutant Furthermore, ura4- cells can be selected for in the presence of 5-fluoroorotic acid (5-FOA) This allows a convenient means of selecting for both forward and backward mutations The sequence of a 18 kb HindIII fragment which contains the functional gene is reported It encodes a single open reading frame of 264 amino acids which shows considerable conservation with the orotidine-5'-phosphate (OMP) decarboxylases from other organisms The ura4 transcript is approximately 850 nucleotides long It begins 51 bp upstream of the protein coding sequence and is unusual in that transcription termination occurs at or very close to the translational stop codon To facilitate the use of ura4 in gene disruption experiments we have also constructed a novel strain of S pombe called ura4-D18, in which the 18 kb HindIII fragment has been deleted from the chromosome Using a combination of this strain and vectors containing ura4 as a selectable marker, we present a general method for targeting recombination events to the chromosomal locus under investigation
401 citations
01 Jan 1988
TL;DR: In this article, the authors describe and explain international patterns of technological activity and their effects on the economic performance, and the volume, sectoral pattern, geographical location and dynamics of technology activity in specific firms, and their effect on competitive performance.
Abstract: Summary Advances in information technology have increased the actual and potential uses of patent statistics as a proxy measure of inventive and innovative activities. Analytical contributions have come out of economics, bibliometrics, and descriptive comparisons for policy purposes. They show achievement and promise in describing and explaining1 international patterns of technological activity and their effects on the economic performance2 the volume, sectoral pattern, geographical location and dynamics of technological activity in specific firms, and their effects on competitive performance3 links between science and technology.
401 citations
TL;DR: In this article, the effects of changes in the internal market of the European Community in a partial equilibrium model of imperfect competition with economies of scale were studied, and the model is numerically calibrated to data on ten industries.
394 citations
TL;DR: Wimmer et al. as mentioned in this paper found that children at any age were able to obtain knowledge and could reliably introspect on the existence of knowledge obtained through visual and linguistic information, most 3 and some 4-year-olds seemed completely ignorant about the causal connection between access to an informational source and resulting knowledge.
Abstract: WIMMER, HEINZ; HOGREFE, G.-JORGEN; and PERNER, JOSEF. Children's Understanding of Informational Access as Source of Knowledge. CHILD DEVELOPMENT, 1988, 59, 386-396. A sharp improvement was found between 3 years and 5 years in children's understanding of the role of visual perception and linguistic communication in knowledge formation. Although children at any age were able to obtain knowledge and could reliably introspect on the existence of knowledge obtained through visual and linguistic information, most 3and some 4-year-olds seemed completely ignorant about the causal connection between access to an informational source and resulting knowledge. They could not tell how they themselves had acquired a particular piece of knowledge (i.e., whether they had been shown or told). They were also incapable of assessing another person's knowledge of a fact on the basis of observing that person being deprived of or being given information about that fact.
389 citations
TL;DR: In this paper, a detailed study is made of inflationary universe driven by the quantum production of infinitely thin Witten strings on super-horizon scales in the very early universe, and a large number of new exact solutions describing the effects of string creation upon isotropic universes are found.
383 citations
TL;DR: In this article, the authors consider cosmological models containing a self-interacting scalar field possessing a potential of the form V ( φ ) = Λ exp(− λφ ).
298 citations
TL;DR: It is concluded that contests will be settled by non-costly traits only if the value of the contested resource is small relative to the cost of fighting, and that 'honest' signalling of aggressiveness is stable only if individuals giving signals that are inconsistent with their behaviour suffer costs.
Abstract: Three models--the war of attrition, the size game and the badges of dominance game--are described, in which natural selection can maintain genetic variability for aggression. The models differ in whether or not the traits that settle contests are costly in contexts other than fighting, and also in whether signals are used. It is concluded that contests will be settled by non-costly traits only if the value of the contested resource is small relative to the cost of fighting, and that 'honest' signalling of aggressiveness is stable only if individuals giving signals that are inconsistent with their behaviour suffer costs. The literature on 'badges of dominance' in birds is reviewed. New data on great tits, greenfinches and corn buntings show that there is plumage variability within age and sex that sometimes serves to settle contests, and that, in the first two species but not the third, the badges are uncorrelated with size, and settle contests only over trivial resources.
TL;DR: The authors explored the role of the home in contemporary British society, focusing on class and social relations, the sociology of consumption, and the home as a locale, and showed that the home has been a neglected research area in housing studies.
Abstract: The home has been a neglected research area in housing studies. This paper represents one preliminary attempt to explore the role of the home in contemporary British society. Key concerns include class and social relations, the sociology of consumption and the home as a locale.
TL;DR: A comparison of the sequences of the PBP-2 genes from penicillin-sensitive and peniillin-resistant strains, suggests that penicillins-resistant forms of PBP 2 may have arisen both by amino-acid substitutions and insertions, and by the exchange of a region encoding part of the penicillo-sensitive transpeptidase domain with the homologous region from a closely related species.
Abstract: Benzyl penicillin has been used extensively for ∼40 years in the treatment of gonorrhoea. The intense selective pressures resulting from the continual exposure of Neisseria gonorrhoeae to penicillin have resulted in the emergence of resistant strains that produce altered forms of penicillin-binding proteins (PBPs) with decreased affinity for the antibiotic1–3. A comparison of the sequences of the PBP-2 genes from penicillin-sensitive and penicillin-resistant strains, suggests that penicillin-resistant forms of PBP 2 may have arisen both by amino-acid substitutions and insertions, and by the exchange of a region encoding part of the penicillin-sensitive transpeptidase domain with the homologous region from a closely related species.
TL;DR: Evidence is provided that these groups of enzymes have a common, but distant, evolutionary origin, and that penicillin-resistant PBPs have arisen from the introduction of multiple amino acid substitutions within the transpeptidase domain of the enzymes.
Abstract: beta-Lactam antibiotics exert their antibacterial effects by inactivating the high-molecular-weight penicillin-binding proteins (PBPs) that are responsible for the final stages of peptidoglycan biosynthesis. The availability of the amino acid sequences of several low-molecular-weight PBPs, high-molecular-weight PBPs, and active-site serine beta-lactamases has provided evidence that these groups of enzymes have a common, but distant, evolutionary origin. This view is strongly supported by the recent finding of a similarity in the three-dimensional structures of a low-molecular-weight PBP and class A beta-lactamases. The high-molecular-weight PBPs of Escherichia coli are believed to possess an amino-terminal peptidoglycan transglycosylase domain and a carboxy-terminal penicillin-sensitive transpeptidase domain. These enzymes are inserted in the cytoplasmic membrane only at their amino termini, and water-soluble forms have been obtained that should be suitable for crystallization and X-ray analysis. Resistance to beta-lactam antibiotics mediated by alterations of PBPs has been reported in some gram-negative bacteria. In isolates of Neisseria gonorrhoeae with chromosomally mediated resistance, penicillin-resistant PBPs have arisen from the introduction of multiple amino acid substitutions within the transpeptidase domain of the enzymes.
TL;DR: In this paper, le gradient d'abondance dans M33 est etudie sur la base d'observations spectroscopiques IPCS et CCD des raies d'emission dans les regions HII, en utilisant O I I, O I II, S I I and S I II dans l'etendue λλ3700-9600 A.
Abstract: Le gradient d'abondance dans M33 est etudie sur la base d'observations spectroscopiques IPCS et CCD des raies d'emission dans les regions HII, en utilisant O I I, O I II, S I I et S I II dans l'etendue λλ3700-9600 A pour affiner les abondances en oxygene dans les regions internes et etudier le comportement de S/O
01 Jan 1988
TL;DR: This chapter discusses the class of context-free phrase structure grammars, which has been alluded to a number of times in the recent linguistic literature: by Klein (1981) in connection with nested comparative constructions, by Dahl (1982) in connected with topicalised pronouns, by Engdahl ( 1982) and Gazdar (1982).
Abstract: If we take the class of context-free phrase structure grammars (CFPSGs) and modify it so that (i) grammars are allowed to make use of finite feature systems and (ii) rules are permitted to manipulate the features in arbitrary ways, then what we end up with is equivalent to what we started out with Suppose, however, that we take the class of contextfree phrase structure grammars and modify it so that (i) grammars are allowed to employ a single designated feature that takes stacks of items drawn from some finite set as its values, and (ii) rules are permitted to push items onto, pop items from, and copy the stack What we end up with now is no longer equivalent to the CF-PSGs but is significantly more powerful, namely the indexed grammars (Aho, 1968) This class of grammars has been alluded to a number of times in the recent linguistic literature: by Klein (1981) in connection with nested comparative constructions, by Dahl (1982) in connection with topicalised pronouns, by Engdahl (1982) and Gazdar (1982) in connection with Scandinavian unbounded dependencies, by Huybregts (1984) and Pulman and Ritchie (1984) in connection with Dutch, by Marsh and Partee (1984) in connection with variable binding, and doubtless elsewhere as well
TL;DR: In this paper, the authors analyse sectoral patterns and trends in the production and use of innovations in the UK between 1945 and 1983, based on information on more than 4000 innovations commercialised in UK between 1985 and 2003.
TL;DR: In this paper, three conceptual issues are singled out for discussion: the research style, explanations for the mental state of the unemployed and the role of theory; and the concept of mental health as involving more than the absence of mental illness.
Abstract: The greatest burden of economic recession falls on the unemployed. Research in this area has resulted in a general consensus that the large majority of the unemployed are psychologically impaired. From the voluminous relevant literature, three conceptual issues are singled out for discussion: the research style—that is, the dominant questions investigated and the corresponding research procedures; explanations for the mental state of the unemployed and the role of theory; and the concept of mental health as involving more than the absence of mental illness.
TL;DR: The authors showed that 7-8-year-old poor comprehenders differ from good comprehenders, matched in age and decoding skill, primarily in their failure to make high-level inferences, despite adequate text recall.
Abstract: Previous studies show that 7–8-year-old poor comprehenders differ from good comprehenders, matched in age and decoding skill, primarily in their failure to make high-level inferences, despite adequate text recall. The impact of inference awareness training on reading comprehension in two such groups was compared with the effects of two other treatments. Inference-trained children were instructed over 4 weeks in making inferences from text and generating questions. Other groups were trained either in rapid decoding or in standard comprehension exercises. Less skilled comprehenders given inference training improved significantly more than those given decoding practice, and slightly, but not significantly, more than those given comprehension exercises. Skilled comprehenders showed little improvement regardless of treatment condition. The results are discussed in relation to possible sources of comprehension failure, and implications for remediation.
TL;DR: In this paper, it was shown that closed universes which begin in an extremely anisotropic state cannot recollapse until they are close to isotropy, which is also a necessary condition for inflation to occur.
TL;DR: It is suggested that although it may not be essential for the extrachromosomal maintenance of plasmids in S. pombe, the consensus does have a function in situ in the chromosome and thus is always present as a cryptic sequence in the isolated ARS element.
Abstract: Chromosomal DNA of Schizosaccharomyces pombe contains sequences with properties analogous to ARS elements of Saccharomyces cerevisiae. Following Sau3A fragmentation of the S. pombe genome we have recovered a number of such fragments in an M13-based shuttle vector, suitable for subsequent sequence analysis. The complete nucleotide sequence has been obtained for eight ARS+ inserts derived from the Sau3A cloning and for the ARS present in pFL20 isolated previously by Losson and Lacroute (Cell, 32, 371-377, 1983). The Sau3A clones are single fragments between 0.8 and 1.8 kb. No ARS+ clones smaller than this were recovered even though the average size Sau3A fragment in S. pombe is approximately 200-300 bp. The sequence analysis revealed that all clones are AT-rich (69-75% A + T residues), and all contain a particularly AT-rich 11 bp core element represented by the consensus sequence 5' (A/T)PuTT-TATTTA(A/T) 3'. Deletion mapping indicates that the consensus in all cases is in the vicinity of a functional ARS domain. However precise excision of the consensus by in vitro mutagenesis has little effect on ARS activity as judged by the transformation assay. We argue that the association of the consensus with the ARS domain occurs too reproducibly to be explained by chance alone. We suggest that although it may not be essential for the extrachromosomal maintenance of plasmids in S. pombe, the consensus does have a function in situ in the chromosome and thus is always present as a cryptic sequence in the isolated ARS element.
TL;DR: The greater sensitivity of A-T derived cells to gamma radiation is confirmed, and cells transformed by plasmids expressing SV40 T-antigen, both pre- and post-crisis, show this increased resistance, indicating that it is expression of SV 40 T- Antigen, rather than immortalization per se which is responsible for the change.
Abstract: SummaryWe have compared cell killing following 60Co gamma irradiation in 22 primary human fibroblast strains, nine SV40-immortalized human fibroblast lines and seven SV40-transformed pre-crisis human fibroblast cultures. We have examined material from normal individuals, from ataxia-telangiectasia (A-T) patients and from A-T heterozygotes. We have confirmed the greater sensitivity of A-T derived cells to gamma radiation. The distinction between A-T and normal cells is maintained in cells immortalized by SV40 virus but the immortal cells are more gamma radiation resistant than the corresponding primary fibroblasts. Cells transformed by plasmids (pSV3gpt and pSV3neo) expressing SV40 T-antigen, both pre- and post-crisis, show this increased resistance, indicating that it is expression of SV40 T-antigen, rather than immortalization per se which is responsible for the change. We use D0, obtained from a straight line fit, and , estimated from a multitarget curve, as parameters to compare radiosensitivity. We su...
TL;DR: An inverse correlation of mutant frequency with plating efficiency was observed, and some experimental factors (serum and interleukin-2 batch, and worker) may have a significant effect on the observed mutant frequency.
Abstract: We have used the T-Lymphocyte cloning technique as a method of monitoring the human population for somatic cell mutant frequency. We present a statistical analysis of the experimental factors which may influence the observed mutant frequency. We have obtained consistently high plating efficiencies of T-cells from the mononuclear cell fraction from donor blood samples (mean of 56%, based on 123 observations from 70 individuals). Nevertheless, an inverse correlation of mutant frequency with plating efficiency was observed, and some experimental factors (serum and interleukin-2 batch, and worker) may have a significant effect on the observed mutant frequency. We discuss the difficulties that these possible effects present in establishment of a reference database and design of long-term studies. No significant effect of donor sex on mutant frequency was observed, but age (1.3% increase per year for normal adults) and smoking (56% increase over normal non-smokers) both significantly increased the mutant frequency. We discuss the utility of the assay for the monitoring of populations for heritable DNA damage, and we compare the results to those obtained with lymphocytes using other endpoints, e.g. chromosome aberrations, micronuclei and sister-chromatid exchange.
TL;DR: This article investigated implicit and explicit memory in normal subjects over two retention intervals, one hour and two weeks, and found that savings on picture completion were taken as a measure of implicit memory and recognition accuracy, while no developmental trend was evident.
Abstract: This study investigates implicit and explicit memory in normal subjects over two retention intervals, one hour and two weeks. Four age groups were used: 3 years, 5 years, 7 years and adults. In all conditions subjects were initially shown 15 fragmented pictures where each consisted of eight stages ranging from very incomplete to complete. Subjects were shown increasingly complete versions of each stimulus until it was successfully identified. After the retention interval the 15 target pictures were re-presented using the same procedure as the original learning phase. Fifteen new fragmented pictures were also presented. After identifying each picture during the test phase subjects were asked whether or not they had seen it before. Savings on picture completion were taken as a measure of implicit memory and recognition accuracy as a measure of explicit memory. All age groups showed significant savings and, when performance was calculated as a proportion of the initial score, no developmental trend was evident. Savings were greater after one hour than two weeks. After one hour all age groups could reliably distinguish pictures they had seen in the learning phase from those presented for the first time after the retention interval. Similar results were found after two weeks with the exception of the 3−year-olds who were very poor at remembering which pictures they had seen before. Where analysis was possible it was found that savings scores were not correlated significantly with recognition accuracy. This, combined with the differential effects of age on the implicit and explicit components of the task, suggests that different memory systems may underlie performance on the two tasks.
TL;DR: In this paper, the growth of particles when constrained by a polymeric matrix, both in natural and synthetic materials, is discussed and the principles governing such processes and the potential for the production of highly structured composite materials by this route.
Abstract: Filler particles are frequently put into polymers to improve the stiffness or strength There are a number of other applications such as magnetic coatings and piezoelectric transducers where second phase particles are introduced to give the composite special properties Many biological materials, including bone, are also composite with particles reinforcing a polymer matrix In the preparation of the synthetic materials the filler is normally blended into the polymer In the biological materials the particles are grownin situ within the polymeric matrix, and under the control of the matrix Here we review the growth of particles when constrained by a polymeric matrix, both in natural and synthetic materials We discuss the principles governing such processes and the potential for the production of highly structured composite materials by this route
TL;DR: The arrangement of tiered microvilli in two other midband rows suggests that they provide a unique form of polarization vision, which may be adapted in a unique manner for colour and polarization vision.
Abstract: The apposition compound eyes of mantis shrimps (stomatopods) are divided into three sections, the dorsal and ventral hemispheres and the midband. Many ommatidia of both hemispheres, and all those in the midband, sample the same narrow band in space. The function of the morphologically distinct midband region is not clear, but new evidence suggests that it may be adapted in a unique manner for colour and polarization vision. A series of carotenoid colour filters screen the photopigment and potentially provide a tetrachromatic input for contrast-enhanced vision or true colour vision. The filters are blocks of coloured droplets (red, orange, yellow, purple, pink or blue) within the rhabdoms of two rows of midband ommatidia. The arrangement of tiered microvilli in two other midband rows suggests that they provide a unique form of polarization vision.
TL;DR: The authors investigated the influence of observer and victim characteristics on attributions of victim and assailant responsibility in a rape case and found that both rape myth acceptance and victims' pre-rape behavior influenced the degree of responsibility attributed to victims and assailants.
Abstract: Two field studies were conducted to investigate the influence of observer and victim characteristics on attributions of victim and assailant responsibility in a rape case. In the first study, male and female subjects completed a measure of rape myth acceptance and were presented with a rape account after which they were asked to attribute responsibility to victim and assailant. In the second study, a new sample was asked to attribute responsibility to victim and assailant on the basis of one of two rape accounts in which victim's pre-rape behavior was manipulated. Results showed that both rape myth acceptance and victims' pre-rape behavior influenced the degree of responsibility attributed to victims and assailants. No significant effects of subject gender were found. A more complex conceptualization is suggested of the link between observer and victim characteristics in social reactions to and evaluations of rape victims.