Showing papers by "University of Liverpool published in 1996"

Low-threshold cold cathodes made of nitrogen-doped chemical-vapour-deposited diamond

Abstract: BECAUSE diamond surfaces terminated with hydrogen have a negative electron affinity1–4 (the conduction band minimum lies below the vacuum level), they are expected to emit electrons spontaneously. This has led to attempts to develop 'cold cathodes'—miniaturized vacuum diodes that might have applications in microelectronics and flat-panel displays. In previous studies of electron emission from diamond grown by chemical vapour deposition5–9 (CVD), the threshold voltages for emission were more than an order of magnitude too large for use in battery-driven cold cathodes. Although low-threshold emission from caesium-coated, nitrogen-doped high-pressure synthetic diamond was reported recently10, ultimately diamond thin films grown by chemical vapour deposition (CVD) look to be the most promising material for cold-cathode applications. But to obtain low-threshold emission, it is necessary to introduce high concentrations of donor dopants such as nitrogen—something that is difficult for CVD diamond. Here we report that high concentrations of nitrogen can be incorporated into diamond films by using urea as the gaseous nitrogen source, and that such heavily doped films shown very-low-threshold electron emission, which augurs well for cold-cathode technology.

Isolation and identification of methanogen-specific DNA from blanket bog peat by PCR amplification and sequence analysis.

Abstract: The presence of methanogenic bacteria was assessed in peat and soil cores taken from upland moors. The sampling area was largely covered by blanket bog peat together with small areas of red-brown limestone and peaty gley. A 30-cm-deep core of each soil type was taken, and DNA was extracted from 5-cm transverse sections. Purified DNA was subjected to PCR amplification with primers IAf and 1100Ar, which specifically amplify 1.1 kb of the archaeal 16S rRNA gene, and ME1 and ME2, which were designed to amplify a 0.75-kb region of the alpha-subunit gene for methyl coenzyme M reductase (MCR). Amplification with both primer pairs was obtained only with DNA extracted from the two deepest sections of the blanket bog peat core. This is consistent with the notion that anaerobiosis is required for activity and survival of the methanogen population. PCR products from both amplifications were cloned, and the resulting transformants were screened with specific oligonucleotide probes internal to the MCR or archaeal 16S rRNA PCR product. Plasmid DNA was extracted from probe-positive clones of both types and the insert was sequenced. The DNA sequences of 8 MCR clones were identical, as were those of 16 of the 17 16S rRNA clones. One clone showed marked variation from the remainder in specific regions of the sequence. From a comparison of these two different 16S rRNA sequences, an oligonucleotide was synthesized that was 100% homologous to a sequence region of the first 16 clones but had six mismatches with the variant. This probe was used to screen primary populations of PCR clones, and all of those that were probe negative were checked for the presence of inserts, which were then sequenced. By using this strategy, further novel methanogen 16S rRNA variants were identified and analyzed. The sequences recovered from the peat formed two clusters on the end of long branches within the methanogen radiation that are distinct from each other. These cannot be placed directly with sequences from any cultured taxa for which sequence information is available.

Intrinsic reflection asymmetry in atomic nuclei

Abstract: The experimental and theoretical evidence for intrinsic reflection-asymmetric shapes in nuclei is reviewed. The theoretical methods discussed cover a wide spectrum, from mean-field theory and its extensions to algebraic and cluster approaches. The experimental data for nuclear ground states and at low and high spin, cited as evidence for reflection asymmetry, are collected and categorized. The extensive data on electric dipole transition moments and their theoretical interpretation are surveyed, along with available data on electric octupole moments. The evidence for reflection-asymmetric molecular states in light nuclei is summarized. The application of reflection-asymmetric theories to descriptions of the fission barrier, bimodal fission, superdeformation, and hyperdeformations is reviewed, and some other perspectives in the wider context of nuclear physics are also given. [S0034-6861(96)00102-X]

Applications of electro-rheological fluids in vibration control: a survey

Abstract: Electro-rheological (ER) fluids are now regarded as one of the most versatile of the materials available for building smart structures and machines. In principle, ER fluids promise an elegant means of providing continuously variable forces for the control of mechanical vibrations. In practice, the development of industrial devices has been hampered by the unavailability of suitable ER fluids. Prompted by recent advances in ER fluid development this paper provides a comprehensive survey of ER devices for vibration control. The key modes of operation are identified and progress towards a unified approach to visualizing the macroscopic behaviour is summarized before presenting a comprehensive survey which includes contributions to the identification of ER fluid dynamics and the application of feedback control. The discussion of results includes some thoughts on future trends.

The factor structure of "schizotypal' traits: a large replication study.

Abstract: The heterogeneity of schizotypal traits, suggested in previous research, was further investigated in a sample of subjects (N = 1095) administered a composite questionnaire consisting of a large number of published scales the majority of which were designed to measure psychotic characteristics. Factor analysis confirmed the four components previously indicated in our work with the same instrument; namely, ‘aberrant perceptions and beliefs’, ‘cognitive disorganization’, ‘introvertive anhedonia’ and ‘asocial behaviour’. This structure was maintained regardless of whether or not the analysis included scales from the Eysenck Personality Questionnaire, which might otherwise have been held to explain the variance. ‘Aberrant perceptions and beliefs’—reminiscent of the positive symptoms of schizophrenia was the strongest component; but, given the multidimensional nature of the data, together with the pattern of factor loadings and intercorrelations for the scales involved, it was concluded that the broader term ‘psychosis-proneness’ or ‘psychoticism’ (in a non-Eysenckian sense) might be a better descriptor of the clinical and personality domain sampled.

New antiepileptic drugs: a systematic review of their efficacy and tolerability.

Abstract: Objectives: To evaluate the efficacy and tolerability of the newly developed antiepileptic drugs gabapentin, lamotrigine, tiagabine, topiramate, vigabatrin, and zonisamide in patients with refractory partial epilepsy. Design: Systematic review of published and unpublished randomised controlled trials of add-on treatment with new antiepileptic drugs. Subjects: 20 published and eight unpublished trials representing 3883 patients with refractory partial epilepsy. Main outcome measures: Proportion of patients who (a) showed 50% or greater reduction in frequency of seizures (50% responders) and (b) withdrew from each study for any reason. Results: Odds ratios (95% confidence intervals) relative to placebo for 50% responders were 2.29 (1.53 to 3.43) for gabapentin, 2.32 (1.47 to 3.68) for lamotrigine, 3.03 (2.01 to 4.58) for tiagabine, 4.22 (2.80 to 6.35) for topiramate, 3.68 (2.45 to 5.51) for vigabatrin, and 2.47 (1.36 to 4.47) for zonisamide. Odds ratios for withdrawal were 1.36 (0.75 to 2.49) for gabapentin, 1.19 (0.79 to 1.79) for lamotrigine, 1.81 (1.21 to 2.70) for tiagabine, 2.42 (1.43 to 4.11) for topiramate, 2.58 (1.26 to 5.27) for vigabatrin, and 5.70 (1.76 to 18.49) for zonisamide. Comparing results for each drug showed that all of the 95% confidence intervals overlapped, indicating that they were not significantly different in terms of efficacy and tolerability. Conclusions: All six drugs were significantly better than placebo at reducing frequency of seizures. These results do not allow an evidence based choice between these drugs as we have no conclusive indication of differences in efficacy or tolerability. Key messages At present there is insufficient evidence to guide a choice between these new treatments We systematically reviewed randomised placebo controlled studies of supplementary gabapentin, lamotrigine, tiagabine, topiramate, vigabatrin, and zonisamide Each drug was significantly better than placebo at preventing seizures, but none was significantly different from the others in terms of efficacy or tolerability, though the confidence intervals were wide Randomised trials comparing active treatments are needed to further evaluate these drugs

Incidence and prevalence of lameness in dairy cattle

Abstract: A survey was made of 37 dairy farms in Wirral, mid-Cheshire, mid-Somerset and Dyfed, Wales, to assess the incidence and prevalence of lameness in the cows between May 1989 and September 1991. The incidence was obtained from records made whenever a cow was examined for lameness or received preventive foot-trimming. The mean annual incidence was 54.6 new cases per 100 cows with a range from 10.7 to 170.1 and the mean values during summer and winter were 22.9 and 31.7, respectively. The prevalence of lameness was measured by regular visits at which locomotion was scored on a scale of 1 to 5, and the prevalence of lameness was calculated for each visit as the proportion of cows with scores of 3 or more. The mean annual prevalence over the whole period was 20.6 per cent with a range from 2.0 to 53.9 per cent for the 37 farms. The mean prevalences during summer and winter were 18.6 and 25.0 per cent, respectively. The prevalence measured at a single visit in midsummer or midwinter was significantly correlated with the mean prevalence over the whole corresponding period and may be useful as an assessment of the extent of lameness in a herd and the efficacy of control measures. There was evidence that training farmers to recognise early cases of lameness and request veterinary treatment resulted in a marked reduction in the duration of cases of lameness.

Sperm Competition Games: Individual Assessment of Sperm Competition Intensity by Group Spawners

Abstract: A distinction is made between sperm competition risk (where there is typically a low probability of competition between two ejaculates) and sperm competition intensity (where typically two or more ejaculates compete). The relation between sperm competition intensity and sperm expenditure can be radically different across species from that within a species. Across species, the average ejaculate expenditure will increase with the average intensity of sperm competition. But within a species, the reverse trend is generally predicted for greater than two males competing for the same set of eggs. These effects are demonstrated with three sperm competition game models. They are devised mainly for externally fertilizing group-spawning species such as many fish, in which males group around a female and ejaculate when the female sheds her eggs. Fertilization is assumed to be instantaneous and each male gains a proportion of the eggs equal to his sperm number divided by the total sperm. In the first model, males cannot assess the number of competitors, and their ejaculate effort is shaped by the average number of males for the species or locally isolated deme. The proportion of reproductive effort expended on the ejaculate is predicted to increase as (N-1)/N, where N = the mean number of competing males present at a spawning. Thus if N is large, ejaculate expenditure dominates reproductive effort. In the second model, males can estimate whether there are more or less than average numbers of competitors present at a spawning, and in the third model, males can assess the number of competitors exactly. As in the first model, these models confirm that the mean ejaculate effort should increase with the mean number of competitors for the species. However, they predict that males should decrease their sperm expenditure as the estimated number of competitors present at a given spawning increases above two. These conclusions do not apply to sperm competition risk: there is thus no conflict with earlier models based on risk.

Treatment Decision Making In Women Newly Diagnosed With Breast Cancer

Abstract: The purpose of this study was to explore the hypothesis that women with breast cancer had specific preferences about the degree of control they wanted over treatment decision making. One hundred fifty women, newly diagnosed with breast cancer, were interviewed and their preferences for participation in treatment decision making were established using a measurement tool designed to elicit decision-making preferences (Degner LF, Sloan JF. Decision making during serious illness: What role do patients really want to play? J Clin Epidemiol 1992;45:944-50). Two hundred women with benign breast disease served as a descriptive comparison group. Unfolding theory (Coombs CH. A theory of data. New York: John Wiley & Sons, 1964) provided a means of analyzing the data so that the degree of control preferred by each woman could be established. The majority of the newly diagnosed women preferred to play a passive role in treatment decision making, leaving the decision-making responsibility to their physician, whereas the benign control group preferred a collaborative role in which joint decisions could be made between the patient and the physician. The implications of the results for patient participation are discussed.

Cold-Induced Expression of Δ9-Desaturase in Carp by Transcriptional and Posttranslational Mechanisms

Abstract: Poikilothermic animals respond to chronic cold by increasing phosphoglyceride unsaturation to restore the fluidity of cold-rigidified membranes. Despite the importance of this compensatory response, the enzymes involved have not been clearly identified, and the mechanisms that control their activity are unknown. In carp liver, cold induces an 8- to 10-fold increase in specific activity of the microsomal stearoyl coenzyme A desaturase. Cold-induced up-regulation of gene transcription resulted in a 10-fold increase in desaturase transcript amounts after 48 to 60 hours. However, this increase was preceded by the activation of latent desaturase, probably by a posttranslational mechanism. These two mechanisms may act sequentially to match desaturase expression to the demands imposed by a progressive decrease in temperature.

Performance of the DELPHI detector

Abstract: DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e^+e^- physics, designed to provide high granularity over a 4\pi solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

De novo design of structure-directing agents for the synthesis of microporous solids

Abstract: THE synthesis of microporous materials such as aluminosilicates and aluminophosphates, which are widely exploited as solid acid catalysts, ion exchangers and in gas separation, is facilitated by the use of structure-directing agents (often referred to as templates)1. These are generally organic bases, and are included in an inorganic gel medium so that the microporous framework condenses around them; the final structure of the framework reflects, to differing degrees, the shape of the template. Although there is growing confidence2 in being able to target a particular microporous structure by adroit choice of structure-directing agent3–7, no a priori method has been described for generating potential templates for either existing or hypothetical structures. Here we present a method for de novo design of template molecules, which are computationally 'grown' in the desired inorganic framework. Our method is successful in generating known templates for existing microporous materials, and a new candidate suggested by this method succeeds as a template for the target material. Our method should be generally applicable to the field of template-directed hydrothermal synthesis of crystals and to other fields of chemistry involving host–guest recognition.

Information needs and sources of information for women with breast cancer: a follow-up study.

Abstract: This paper reports a study which examined the specific information needs and sources of information for 105 women with breast cancer at two time points, the time of diagnosis and a mean of 21 months from diagnosis. At diagnosis the priority information needs concerned survival issues. Further from diagnosis survival issues were still a concern, but information about the risk to family members of getting breast cancer showed a significant increase in importance. Information about sexual attractiveness was ranked last at both the newly diagnosed and follow-up stages. Information sources at the time of diagnosis centred around the specialist breast care service, while further from diagnosis few professional or voluntary sector sources were utilized, with women receiving most of their information from media sources such as women's magazines. The relevance of these findings for nurses and other health care professionals is discussed.

Some misconceptions about communicative language teaching

Abstract: Although communicative language teaching is accepted by many applied linguists and teachers as the most effective approach among those in general use, there are still a number of misconceptions about what it involves. This article sets out four of the main misconceptions, discusses why they have.arisen, and why they can be so described. In doing this, the article attempts to define some important characteristics of communicative language teaching as it is practised at present.

Prolegomena to a middlebrow arithmetic of curves of genus 2

Abstract: The number theoretic properties of curves of genus 2 are attracting increasing attention. This book provides new insights into this subject; much of the material here is entirely new, and none has appeared in book form before. Included is an explicit treatment of the Jacobian, which throws new light onto the geometry of the Kummer surface. The Mordell–Weil group can then be determined for many curves, and in many non-trivial cases all rational points can be found. The results exemplify the power of computer algebra in diophantine contexts, but computer expertise is not assumed in the main text. Number theorists, algebraic geometers and workers in related areas will find that this book offers unique insights into the arithmetic of curves of genus 2.

Uranium-oxide-based catalysts for the destruction of volatile chloro-organic compounds

Abstract: The industrial release of hydrocarbons and chlorine-containing organic molecules into the environment continues to attract considerable public concern, which in turn has led to governmental attempts to control such emissions The challenge is to reduce pollution without stifling economic growth Chlorine-containing pollutants are known to be particularly stable, and at present the main industrial process for their destruction involves thermal oxidation at 1,000 °C, an expensive process that can lead to the formation of highly toxic by-products such as dioxins and dibenzofurans Catalytic combustion at lower temperatures could potentially destroy pollutants more efficiently (in terms of energy requirements) and without forming toxic by-products Current industrial catalysts are based on precious metals that are deactivated rapidly by organochlorine compounds Here we report that catalysts based on uranium oxide efficiently destroy a range of hydrocarbon and chlorine-containing pollutants, and that these catalysts ace resistant to deactivation We show that benzene, toluene, chlorobutane and chlorobenzene can be destroyed at moderate temperatures (<400 °C) and industrially relevant flow rates