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Showing papers by "University of Liverpool published in 1994"


Journal ArticleDOI
01 Apr 1994-Geology
TL;DR: The end Ordovician glaciation is distinct among Phanerozoic glaciations in that CO 2, levels were generally high, yet major continental ice sheets accumulated on the Gondwana supercontinent as mentioned in this paper.
Abstract: The end Ordovician glaciation is distinct among Phanerozoic glaciations in that CO 2 , levels were generally high, yet major continental ice sheets accumulated on the Gondwana supercontinent. New oxygen isotopic data indicate substantial changes in sea-water temperatures and ice volume coinciding with glacio-eustatic changes in sea level reflecting the growth and decay of the Gondwana ice cap. Major glaciation was apparently confined to the Hirnantian and was 0.5-1 m.y. long, rather than the 35 m.y. of earlier estimates. Carbon isotope values indicate significant changes in carbon cycling as the oceans changed from a state with warm saline bottom waters to a state with cold deep-water circulation and then back again. We believe that the changes in the carbon cycle effected a reduction in P CO 2 levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world.

557 citations


Journal ArticleDOI
TL;DR: An integrative model is proposed to account for findings that it is hypothesized that, in deluded patients, activation of self/ideal discrepancies by threat-related information triggers defensive explanatory biases, which have the function of reducing the self/Ideal discrepancies but result in persecutory ideation.

549 citations


Journal ArticleDOI
TL;DR: In this article, a method is presented to determine the extent of iron complexation by natural organic ligands in seawater using Catalytic cathodic stripping voltammetry (CSV) to take advantage of ligand competition between the added ligand, 1-nitroso-2-napthol (NN), and natural ligands present in seawaters.

533 citations


Journal ArticleDOI
TL;DR: The results suggest that sperm competition in butterflies selects for increased investment in spermatogenesis, and specifically longer fertilizing sperm, which are not selected to be minimally sized to maximize numbers for a purely raffle-based sperm competition mode.
Abstract: This paper investigates mechanisms of sperm competition by comparing reproductive characteristics across 74 butterfly species. Testis size scales with body size and, after controlling for this allometry, relative testis size increases with risk of sperm competition, as defined by female mating frequency. Both eupyrene (fertilizing) and apyrene (non-fertile) sperm lengths correlate positively with body size. After controlling for body size, relative eupyrene sperm lengths are greater in species where males experience higher risks of sperm competition. These results suggest that sperm competition in butterflies selects for increased investment in spermatogenesis, and specifically longer fertilizing sperm. Because longer sperm may be faster and more powerful, eupyrene sperm may therefore compete energetically, and are not selected to be minimally sized to maximize numbers for a purely raffle-based sperm competition mode. Apyrene sperm lengths are not affected directly by risk of encountering rival sperm. Instead, apyrene sperm show closer associations with body size which, if female tract morphometry correlates with body size, is consistent with the hypothesis that apyrene sperm retard female sexual receptivity by moving while in storage.

424 citations


Journal ArticleDOI
TL;DR: In this paper, the authors extend previous work on the general underprovision of investment when contracts are incomplete or only partially enforceable to a dynamic context, and show that investment is initially underprovided but it increases over time and for certain parameter values it tends to the efficient level.
Abstract: When an investor, for example a transnational corporation, invests abroad it runs the risk that its investment will be expropriated for the simple reason that international contracts are practically impossible to enforce. Any agreements or contracts then undertaken by the transnational company and the host country must be designed to be self-enforcing. It could be possible for the host country and the transnational corporation to find such self-enforcing agreements if there are future gains from trade. Thus although the host country might have a short-term incentive to expropriate, it has a long-term incentive to foster good relations with potential investors to attract more investment in the future. This conflict between short-term and long-term incentives determines the type of investment contracts agreed. This paper extends previous work on the general underprovision of investment when contracts are incomplete or only partially enforceable (see e.g. Grout (1984)) to a dynamic context. It is likewise shown that investment is initially underprovided but it increases over time and for certain parameter values it tends to the efficient level. The expected future discounted returns to the transnational company decline over time, extending Vernon's observation of the obsolescing bargain (Vernon (1971)). The model is also extended to allow for capital accumulation and consideration is given to renegotiation-proof contracts.

358 citations


Journal ArticleDOI
TL;DR: In this paper, the monetary model is re-examined for the sterling-dollar exchange rate, using a multivariate cointegration technique, using an unrestricted monetary model.

351 citations


Journal ArticleDOI
TL;DR: ManCOVA showed that experienced soccer players demonstrated superior anticipatory performance, and the increased frequency of eye fixations was regarded as being more advantageous for anticipating pass destination during open play in soccer.
Abstract: This study investigated skill-based differences in anticipation and visual search strategy within open-play situations in soccer. Experienced (n = 15) and inexperienced (n = 15) subjects were required to anticipate pass destination from filmed soccer sequences viewed on a large 3-m x 3-m video projection screen. MANCOVA showed that experienced soccer players demonstrated superior anticipatory performance. Univariate analyses revealed between-group differences in speed of response but not in response accuracy. Also, inexperienced players fixated more frequently on the ball and the player passing the ball, whereas experienced players fixated on peripheral aspects of the display, such as the positions and movements of other players. The experienced group fixated on significantly more locations than their inexperienced counterparts. Further differences were noted in search rate, with experienced players exhibiting more fixations of shorter duration. The experienced group's higher search rate contradicted previous research. However, this resulted from using 11 on 11 film sequences, which were never previously used in visual search research. The increased frequency of eye fixations was regarded as being more advantageous for anticipating pass destination during open play in soccer. Finally, a number of practical implications were highlighted.

335 citations


Journal ArticleDOI
TL;DR: In this paper, an algorithm for the word problem in each of Artin's braid groups, Bn, based on Garside's methods, but framed more directly in terms of the set of positive braids in which each pair of strings crosses at most once.
Abstract: We give an easily handled algorithm for the word problem in each of Artin’s braid groups, Bn, based on Garside’s methods, but framed more directly in terms of the set of positive braids in which each pair of strings crosses at most once. We develop a natural partial order on each braid group defined in terms of positive braids, and apply this to compare braids with different powers ∆ of the fundamental half-twist braid ∆. This leads to an improvement of Garside’s conjugacy algorithm, using a much smaller finite subset of each conjugacy class, which we term the super summit set, to represent the class, in place of Garside’s summit set.

320 citations


Journal ArticleDOI
TL;DR: This review highlights the importance of knowing the carrier and removal status of canine coronavirus, as a source of infection for other animals, not necessarily belonging to the same breeds.
Abstract: Note: Physiological Laboratory, University of Liverpool, England. Reference LSENS-REVIEW-2007-003 Record created on 2007-12-18, modified on 2017-05-12

297 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the isothermal remanent magnetisation (IRM) acquired by natural mineral assemblages closely conforms to a cumulative log gaussian (CLG) function of the magnetising field.

288 citations


Journal ArticleDOI
23 Jun 1994-Nature
TL;DR: A systematic attempt to reconstruct the locomotor behaviour of early hominids by looking at a major component of the mechanism for the unconscious perception of movement, namely by examining the vestibular system of living primates and earlyhominids.
Abstract: The upright posture and obligatory bipedalism of modern humans are unique among living primates. The evolutionary history of this behaviour has traditionally been pursued by functional analysis of the postcranial skeleton and the preserved footprint trails of fossil hominids. Here we report a systematic attempt to reconstruct the locomotor behaviour of early hominids by looking at a major component of the mechanism for the unconscious perception of movement, namely by examining the vestibular system of living primates and early hominids. High-resolution computed tomography was used to generate cross-sectional images of the bony labyrinth. Among the fossil hominids the earliest species to demonstrate the modern human morphology is Homo erectus. In contrast, the semicircular canal dimensions in crania from southern Africa attributed to Australopithecus and Paranthropus resemble those of the extant great apes. Among early Homo specimens, the canal dimensions of Stw 53 are unlike those seen in any of the hominids or great apes, whereas those of SK 847 are modern-human-like.

Journal ArticleDOI
TL;DR: It is proposed that the distinct dynamics of messengers might be relevant to neuronal function: IP3 and cAMP could convey signals over long distances along neurites, and serve as mediators for association and co-operation, for example, during learning.

Journal ArticleDOI
TL;DR: An extensive range of compounds in the La[sub 1[minus]x]Sr[sub x]FeO[sub 3[minus][sigma]] system have been synthesized by thermogravimetric analysis and Moessbauer spectroscopy yielding information on oxygen stoichiometry and iron oxidation state.

Book
25 Mar 1994
TL;DR: The role of neutrophil in infection and inflammation is discussed in this article, where the authors provide an up-to-date review of the biochemistry and physiology of these cells, highlighting the mechanisms by which they seek out and destroy pathogenic micro-organisms.
Abstract: This book describes the role of the neutrophil in infection and inflammation and provides an up-to-date review of the biochemistry and physiology of these cells, highlighting the mechanisms by which they seek out and destroy pathogenic micro-organisms The development of these cells during haematopoiesis is described and the mechanisms which lead to the production of reactive oxidants and the intracellular signal transduction systems which lead to the cell's activation are reviewed The book also discusses recent discoveries concerning the role of cytokines in the regulation of neutrophil function together with the importance of the neutrophil as a generator of inflammatory cytokines Finally there is a description of the biochemical defects that give rise to some of the neutrophil-associated human diseases

Journal ArticleDOI
TL;DR: In this article, Salicylaldoxime (SA) was used to detect copper complexing ligands in sea water using cathodic stripping voltammetry (CSV) at a detection window intermediate to that and overlapping with those currently available using other electroactive ligands.

Journal ArticleDOI
TL;DR: The role of enzyme electrophoresis is discussed as it applies to taxonomy and systematics, particularly of invertebrates, and methods of analysing genetic divergence data for systematic purposes are discussed.
Abstract: The role of enzyme electrophoresis is discussed as it applies to taxonomy and systematics. particularly of invertebrates. Details are given of methods for distinguishing and identifying cryptic or sibling species and the different approaches to sympatric and allopatric populations are reviewed. The calculation and uses of genetic distance measures are outlined. as are the empirical relationship of such measures to different levels of taxonomic separation. Defficulties. drawbacks and limitations of the technique are explained together with the advantages. Evidence for molecular clocks is outlined briefly and their role in systematic studies is discussed, as are methods of analysing genetic divergence data for systematic purposes. References to studies covering a wide range of invertebrate taxa are tabulated.

Journal ArticleDOI
TL;DR: In this paper, the authors review recent advances and discuss results on a variety of processes in pure metals and alloys, and find that a liquid-like core is generated for cascade energies above 1 to 2 keV.

Journal ArticleDOI
01 Mar 1994-Nature
TL;DR: In this article, a vanadium phosphorus oxide catalyst is used to effect selective oxidation of n-butane to maleic anhydride: (VO)2P2O7 is considered to be the main active component, and is prepared from the precursor VOHPO4·05H2O.
Abstract: OXIDE catalysts, which are used in a broad range of important industrial processes1–4, are generally prepared in the form of a precursor which is converted into the active catalytic form only under well defined reaction conditions A vanadium phosphorus oxide catalyst is used to effect selective oxidation of n-butane to maleic anhydride: (VO)2P2O7 is considered5–7 to be the main active component, and is prepared from the precursor VOHPO4·05H2O Here we use in situ Raman spectroscopy to study the conversion of this precursor to the active form in real time We find that, during this process, the crystalline structure of VOHPO4·05H2O becomes totally disordered at the same time as selectivity for maleic anhydride becomes apparent Furthermore, our results indicate that this product seems to play a role in bringing about this change; thus, it seems that the selective reaction product assists in the creation of the active sites We suggest that this phenomenon might be quite general in oxide catalysis

Journal ArticleDOI
TL;DR: The consequences of the potential direct action of FGFs in stimulating cell division are examined in the light of current models of signal transduction.

Journal ArticleDOI
TL;DR: The results indicate that both the ryanodine and the InsP3 receptors are involved in Ca2+ spike generation.
Abstract: We have investigated the role of the ryanodine-sensitive intracellular Ca2+ release channel (ryanodine receptor) in the cytosolic Ca2+ oscillations evoked in pancreatic acinar cells by acetylcholine (ACh) or cholecystokinin (CCK). Ryanodine abolished or markedly inhibited the agonist evoked Ca2+ spiking, but enhanced the frequency of spikes evoked by direct internal inositol trisphosphate (InsP3) application. We have also investigated the possibility that cyclic ADP-ribose (cADP-ribose), the putative second messenger controlling the ryanodine receptor, plays a role in Ca2+ oscillations. We found that cADP-ribose could itself induce repetitive Ca2+ spikes localized in the secretory pole and that these spikes were blocked by ryanodine, but also by the InsP3 receptor antagonist heparin. Our results indicate that both the ryanodine and the InsP3 receptors are involved in Ca2+ spike generation.

Journal ArticleDOI
TL;DR: The relationship between phonological working memory and other cognitive skills in childhood was investigated in a longitudinal study of 70 children at 4 and 5 years of age as mentioned in this paper, where two principal phonological skills were examined: nonword repetition and auditory digit span.

Journal ArticleDOI
TL;DR: In the context of the Berlin Aging Study (BASE) as discussed by the authors, the authors focused on three interrelated issues raised by a reading of Ageing & Society s Special Issue devoted to the Berlin aging study: 1) the continuing robustness of age as a predictor in multivariate and multidisciplinary analyses; 2) the interpretation of strong age-related patterns in the contexts of a multidisdisciplinary research project; and 3) the special intellectual tensions generated by multidisciplinarity and interdisciplinary work.
Abstract: This comment focuses on three interrelated issues raised by a reading of Ageing & Society s Special Issue devoted to the Berlin Aging Study: 1) the continuing robustness of age as a predictor in multivariate and multidisciplinary analyses; 2) the interpretation of strong age-related patterns in the context of a multidisciplinary research project; and 3) the special intellectual tensions generated by multidisciplinary and interdisciplinary work. Across this set of articles, age frequently appears as a significant (and often strong) explanatory variable, in domains as diverse as cognitive skills, mental and physical health, subjectivity, and functional capacity. Although it is not unusual to find age effects, this is noteworthy in the context of BASE for at least three reasons. First is the restricted age range covered by the study. Although the sample covers an age range of more than 30 years, it contains no one under 70 thus demonstrating strong age differences even among the aged. Second, unlike many traditional gerontological studies, these analyses are generally not designed to identify age effects. Rather, they focus on relationships among social, psychological and physical health factors in age-specific populations. For the most part, age is thus not given any special analytical privilege. The third reason is BASE's orientation to differential aging. The emphasis on heterogeneity is an important and refreshing shift from the traditional emphasis on modal differences between age groups, and it is much to the credit of these researchers that this focus has been maintained even in the face of findings that reveal a generally powerful net effect of age.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effects of quality improvement activities on business performance and developed a classification system to ensure all business performance benefits (tangible and intangible) were included for analysis, which enabled a TQM quality activity model to be developed which classify 65 quality activities by their prime effect.
Abstract: Research was undertaken on the effects of quality improvement activities on business performance. The investigation began by developing a classification system to ensure all business performance benefits (tangible and intangible) were included for analysis. Questionnaires and structured interviews, involving the participation of over 200 companies, were used as the main tools for the investigation. An analysis of the results enabled a TQM quality activity model to be developed which classify 65 quality activities by their prime effect. This model was designed to assist companies in the planning of TQM and the targeting of quality activities. The research identified the difficulties organizations and researchers have in measuring the effects of quality activities.

Journal ArticleDOI
TL;DR: This survey of the clinical and epidemiological features of human cowpox, a rare but relatively severe zoonotic infection, is based on 54 cases, many unpublished, which have been studied since 1969.
Abstract: This survey of the clinical and epidemiological features of human cowpox, a rare but relatively severe zoonotic infection, is based on 54 cases, many unpublished, which we have studied since 1969. Patients present with painful, haemorrhagic pustules or black eschars, usually on the hand or face, accompanied by oedema, erythema, lymphadenopathy, and systemic involvement. Severe, occasionally fatal, cases occur in eczematous and immunosuppressed individuals, although cowpox has not yet been reported in anyone infected with the human immunodeficiency virus. Variations in the clinical features are described, and the differential clinical diagnosis of cowpox, parapox, herpes virus, and anthrax infections is discussed. The role of the laboratory in diagnosis is described, and the value of electron microscopy in providing rapid confirmation is emphasized. Care in taking a detailed history will assist in the initial clinical diagnosis, and a history of contact with domestic cats, particularly during July-October, is important. The possible influence of smallpox vaccination on the incidence and severity is discussed and discounted.

Journal ArticleDOI
TL;DR: In this paper, a hierarchical prior model for spatial interpolation of a vector-valued random response field is proposed, which is based on the multivariate normal and related joint distributions.
Abstract: We develop and apply an approach to the spatial interpolation of a vector-valued random response field. The Bayesian approach we adopt enables uncertainty about the underlying models to be representes in expressing the accuracy of the resulting interpolants. The methodology is particularly relevant in environmetrics, where vector-valued responses are only observed at designated sites at successive time points. The theory allows space-time modelling at the second level of the hierarchical prior model so that uncertainty about the model parameters has been fully expressed at the first level. In this way, we avoid unduly optimistic estimates of inferential accuracy. Moreover, the prior model can be upgraded with any available new data, while past data can be used in a systematic way to fit model parameters. The theory is based on the multivariate normal and related joint distributions. Our hierarchical prior models lead to posterior distributions which are robust with respect to the choice of the prior (hyperparameters). We illustrate our theory with an example involving monitoring stations in southern Ontario, where monthly average levels of ozone, sulphate, and nitrate are available and between-station response triplets are interpolated. In this example we use a recently developed method for interpolating spatial correlation fields. Dans ce rapport, nous developpons et appliquons une approche pour l'interpolation spatiale d'un champs de reponses vectorielles aleatoires. L'approche Bayesienne que nous adoptons permet de representer l'incertitude des modeles par l'expression de la precision des interpollants qui en decoulent. La methodologie est particulierement pertinente en environmetrie ou les reponses vectorielles sont seulement observees a des sites designes et a des temps successifs. La theorie permet une modelisation espace/temps au second niveau du modele hierarchique a priori de telle sorte que l'incertitude a propos des parametres soient pleinement exprimee au premier niveau. De cette facon, nous evitons d'avoir des estimes indument optimistes quant a la precision de ce qui est infere. De plus le modele a priori peut etre ameliore par tout nouvel ensemble de donnees lorsque les donnees passees peuvent etre utilisees d'une facon systematique pour ajuster les parametres du modele. La theorie est basee sur la normale mullidimensionnelle et les distributions conjointes associees. Notre modele hierarchique a priori nous conduit a des distributions a posteriori que sont robustes par rapport au choix des hyperparametres a priori. Nous illustrons notre theorie par un exemple impliquant des stations de controle dans le sud de l'Ontario ou des moyennes mensuelles des niveaux d'ozone, de sulfate et de nitrate sont disponibles, et les triplets reponses entre les stations sont interpoles. Dans cet exemple nous utilisons une methode recemment developpee pour l'interpolation de champs de correlation spatiale.

Journal ArticleDOI
TL;DR: It is demonstrated here that these hyaluronan oligosaccharides also specifically stimulate endothelial cell migration, which may prove useful in retarding blood vessel paucity and degeneration observed during the ageing process and following radiotherapy.

Journal ArticleDOI
01 Jan 1994-Eye
TL;DR: The role of the fibroblast is highlighted, some of the growth factors stimulating fibro-blast proliferation, migration and extracellular matrix production in the wound environment are discussed, and current methods of suppressing fibro Blast proliferation are reviewed.
Abstract: The fibroblast is the central player in the wound repair and scarring processes that occur in the anterior segment of the eye. Glaucoma filtration surgery is the ultimate example of the importance of the wound healing process, as this process is the major determinant of the success of this procedure. We highlight the role of the fibroblast, and discuss some of the growth factors stimulating fibroblast proliferation, migration and extracellular matrix production in the wound environment. We also review current methods of suppressing fibroblast proliferation, the new concepts that have arisen from laboratory studies, and future directions of investigation and treatment.

Journal ArticleDOI
13 Aug 1994-BMJ
TL;DR: Life expectancy of this cohort of children with cerebral palsy born during 1966-84 was greater than has been suggested in some previous studies, and has important implications for social, educational, and health services.
Abstract: Objective : To determine life expectancy of children with cerebral palsy. Design : Cohort analysis, by means of register compiled from multiple sources of ascertainment, of all children with cerebral palsy born during 1966-84 to mothers resident in Mersey region. Status of children was determined by flagging through NHS central register. Subjects : 1258 subjects with idiopathic cerebral palsy, of whom 1251 were traced and included in analysis. Main outcome measures : Effect of functional ability (ambulation, manual dexterity, and mental ability), sex, birth weight, and gestational age on survival. Results : 20 year survival for whole cohort was 89.3% for females and 86.9% for males. For subjects with no severe functional disabilities 20 year survival was 99% (95% confidence interval 98% to 100%), while subjects severely disabled in all three functional groups had 20 year survival of 50% (42% to 58%). Subjects with birth weight =37 weeks had survival of 85% (83% to 88%). Birth weight and gestational age were less predictive of survival than functional disability. Best statistical model used gestational age and number of severe functional disabilities as predictors. Conclusions : Life expectancy of this cohort of children with cerebral palsy was greater than has been suggested in some previous studies. This has important implications for social, educational, and health services.

Book ChapterDOI
TL;DR: In this article, the effects of fish stock reduction have been studied in 3 Dutch lakes ( Lake Zwemlust, Lake Bleiswijkse Zoom and Lake Noorddiep) and 1 Danish lake (Lake Vaeng) during 4-5 years.
Abstract: The effects of fish stock reduction have been studied in 3 Dutch lakes (Lake Zwemlust, Lake Bleiswijkse Zoom and Lake Noorddiep) and 1 Danish lake (Lake Vaeng) during 4–5 years. A general response is described. The fish stock reduction led in general to a low fish stock, low chlorophyll-a, high Secchi-disc transparency and high abundance of macrophytes. Large Daphnia became abundant, but their density decreased, due to food limitation and predation by fish. The total nitrogen concentration became low due to N-uptake by macrophytes and enhanced denitrification. In Lake Bleiswijkse Zoom the water transparency deteriorated and the clear water state was not stable. The fish stock increased and the production of young fish in summer was high. Clear water occurred only in spring. Large daphnids were absent in summer and the macrophytes decreased.

Journal ArticleDOI
TL;DR: In this paper, the precipitates responsible for the age-hardening effect in dilute Cu-Ni-Si alloys based on Cu2NiSi have been studied using transmission electron microscopy.
Abstract: The precipitates responsible for the age-hardening effect in dilute Cu-Ni-Si alloys based on Cu2NiSi have been studied using transmission electron microscopy. The work has confirmed the findings of an earlier study by Teplitskiy et al., which showed that the precipitates formed as discs on {1 1 0} planes and indicated that they had a structure which corresponded to that of δ-Ni2Si. The orientation relationship of the precipitate and matrix found in the present work differs from that found in the earlier work, and a high degree of coherency across the precipitate-matrix interface, has been shown to exist. In establishing that the precipitate is δ-Ni2Si, EDX analysis has been employed and ring patterns from extracted precipitates have also been analysed. Absences from such ring patterns which were noted in the earlier work and which were thought to cast doubt on the precipitate identification have been accounted for in terms of preferred orientation effects. At peak strength the deformation of the material is believed to involve Orowan looping around the precipitates.