The radial distributions of a heavy-light meson on a lattice

In an earlier work, the charge (vector) and matter (scalar) radial distributions of heavy-light mesons were measured in the quenched approximation on a 16^3 times 24 lattice with a quark-gluon coupling of 5.7, a lattice spacing of 0.17 fm, and a hopping parameter corresponding to a light quark mass about that of the strange quark. Several improvements are now made: 1) The configurations are generated using dynamical fermions with a quark-gluon coupling of 5.2 (a lattice spacing of 0.14 fm); 2) Many more gauge configurations are included (78 compared with the earlier 20); 3) The distributions at many off-axis, in addition to on-axis, points are measured; 4) The data-analysis is much more complete. In particular, distributions involving excited states are extracted. The exponential decay of the charge and matter distributions can be described by mesons of mass 0.9+-0.1 and 1.5+-0.1 GeV respectively - values that are consistent with those of vector and scalar qqbar-states calculated directly with the same lattice parameters.Comment: 3 pages, 4 figures, Lattice2002(heavyquark

Ballistic transport is dissipative: the why and how

In the ballistic limit, the Landauer conductance steps of a mesoscopic quantum wire have been explained by coherent and dissipationless transmission of individual electrons across a one-dimensional barrier. This leaves untouched the central issue of conduction: a quantum wire, albeit ballistic, has finite resistance and so must dissipate energy. Exactly HOW does the quantum wire shed its excess electrical energy? We show that the answer is provided, uniquely, by many-body quantum kinetics. Not only does this inevitably lead to universal quantization of the conductance, in spite of dissipation; it fully resolves a baffling experimental result in quantum-point-contact noise. The underlying physics rests crucially upon the action of the conservation laws in these open metallic systems.Comment: Invited Viewpoint articl

Exploiting correlogram structure for robust speech recognition with multiple speech sources

This paper addresses the problem of separating and recognising speech in a monaural acoustic mixture with the presence of competing speech sources. The proposed system treats sound source separation and speech recognition as tightly coupled processes. In the first stage sound source separation is performed in the correlogram domain. For periodic sounds, the correlogram exhibits symmetric tree-like structures whose stems are located on the delay that corresponds to multiple pitch periods. These pitch-related structures are exploited in the study to group spectral components at each time frame. Local pitch estimates are then computed for each spectral group and are used to form simultaneous pitch tracks for temporal integration. These processes segregate a spectral representation of the acoustic mixture into several time-frequency regions such that the energy in each region is likely to have originated from a single periodic sound source. The identified time-frequency regions, together with the spectral representation, are employed by a `speech fragment decoder' which employs `missing data' techniques with clean speech models to simultaneously search for the acoustic evidence that best matches model sequences. The paper presents evaluations based on artificially mixed simultaneous speech utterances. A coherence-measuring experiment is first reported which quantifies the consistency of the identified fragments with a single source. The system is then evaluated in a speech recognition task and compared to a conventional fragment generation approach. Results show that the proposed system produces more coherent fragments over different conditions, which results in significantly better recognition accuracy

High-field noise in metallic diffusive conductors

We analyze high-field current fluctuations in degenerate conductors by mapping the electronic Fermi-liquid correlations at equilibrium to their semiclassical non-equilibrium form. Our resulting Boltzmann description is applicable to diffusive mesoscopic wires. We derive a non-equilibrium connection between thermal fluctuations of the current and resistive dissipation. In the weak-field limit this is the canonical fluctuation- dissipation theorem. Away from equilibrium, the connection enables explicit calculation of the excess ``hot-electron'' contribution to the thermal spectrum. We show that excess thermal noise is strongly inhibited by Pauli exclusion. This behaviour is generic to the semiclassical metallic regime.Comment: 13 pp, one fig. Companion paper to cond-mat/9911251. Final version, to appear in J. Phys.: Cond. Ma

From bench to bedside: Tracing the payback forwards from basic or early clinical research – A preliminary exercise and proposals for a future study

EXECUTIVE SUMMARY Chapter 1 : Introduction • The members of the research team from HERG and the Wellcome Trust have conducted previous studies showing that it is possible both to assess the payback from applied health research, and to use bibliometrics to trace the links between generations of research and clinical guidelines. In another of the team’s studies, however, it proved difficult to replicate the major study by Comroe and Dripps (1976) that had identified clinical advances and then worked backwards to show that they had relied on earlier basic research. Therefore, the study reported here sets out to use the methods developed in our previous studies of payback to undertake analysis that starts with more basic or early clinical research and traces the research lines forwards to clinical applications. Whilst this preliminary study involved preparation for a future large-scale study, it was hoped that it would also provide an interesting case study. • Starting with the research outputs of one team 20 years ago, called the 1st generation papers, the preliminary study has three main elements: standard bibliometric analysis through several generations of papers; categorisation of the citations; and qualitative analysis using questionnaires, critical pathway analysis and interviews to trace the impact of the 1st generation of research. • Diabetes and cardiology were suggested as possible topics on which to base the study. Initial reviews identified two bodies of research in diabetes as being potentially suitable for reasons such as the continuing activity of key members of the team. • The research into diabetes conducted in 1981 by George Alberti and his team at Newcastle, and collaborators elsewhere, was selected to provide the case study for this preliminary stage for several reasons. It was thought to have been important science and there was a belief that some of it had made a contribution to clinical practice. Chapter 2 : Bibliometric analysis • An original plan to look at publications produced over a three year period was changed to looking at the output of just one year, 1981, because in that year alone Alberti and colleagues published 29 articles. These form the 1st generation papers and the average number of citations they received is high. Identifying the citations given to these 29 papers resulted in 799 2nd generation papers and 12,891 3rd generation papers. The numbers involved meant that it was impractical to go beyond the 3rd generation. Within the high overall average, the variation in the number of citations per paper was iii considerable going from 76 to just one. Similarly, the half-lives of the 29 papers, ie the time taken for an article to receive 50% of its citations, ranged from two years to 11. • Articles can be given a Research Level (ie one of four levels from clinical observation to basic) based on the journals in which they appear. Such analysis demonstrates the breadth of Alberti’s work because the 29 articles are spread across all four Research Levels. Crucially, there was not a shift from basic to more clinical levels across the generations. The higher than average number of authors and addresses per paper is testimony to Alberti’s extensive collaborations. • The funding acknowledgements reveal the high proportion of papers supported, at least partially, by one funder: the British Diabetic Association, now Diabetes UK, which provided core support for Alberti’s Newcastle team. Chapter 3 : Categorisation of citations • Traditional citation analysis does not allow identification of the importance of the cited article to the citing article, and therefore limits the ability to use citation analysis to trace the impact of basic or early research on later research. We conducted a review of the literature of the meaning of citations. • From this review, a template was devised that allowed the location, nature and importance of citations to be recorded as well as the type of research (basic or clinical) described in the paper. This was used by six assessors on a sample of papers and inter-rater reliability was tested. Further work is required to refine the template and its definitions, and to improve its consistency in application. • Nevertheless, for initial analysis, it was applied to 623 out of the 799 2nd generation papers. A four point scale was used for the importance of the cited paper to the citing paper. In just 9% of cases was the cited 1st generation paper thought to be in one of the top two categories, ie of Considerable or Essential importance to the citing paper. • Statistical analysis revealed no relationship between the number of citations a paper received and the proportion of citations where the cited paper was classified as being of high (ie. Considerable or Essential) importance to the citing paper. Self-citations, however, were shown to be significantly more likely to be in this category. • The classification of the type of research (basic or clinical) by our analysis of each paper broadly agreed with the classification of the journals by Research Level. • The time constraints involved in applying the template, plus the lack of any overall pattern in terms of correlations between number and importance of citations, might point to the desirability of adopting a more selective approach, guided by qualitative analysis. In any selective approach, however, it is likely that self-citations should feature. iv Chapter 4 : Qualitative analysis • Given the number of co-authors, it seemed appropriate to send them a questionnaire rather than attempt to interview them. Therefore the interviewing was rather more concentrated than originally intended. Only one formal critical pathway was created, but it was undertaken by an expert in the field who worked with Alberti at Newcastle. • Some problems emerged in taking 1981 as the starting point for the study. Alberti identified 10 selected papers from the 1970s and 1980s that he felt had had most impact on clinical practice. These helped to give us both a better understanding of the payback from our 1st generation, or 1981, papers, and provided further material for analysis. • Attempting to describe the impact from the 1981 body of work, and from the 10 selected papers, underlines the complex reality of how science advances and influences clinical practice. If they make a contribution at all, most studies make a small, incremental one. • A few papers, however, have been shown to have a considerably greater impact. A possible key to the level of payback indicated is the enormous breadth of Alberti’s contacts, and fields and methods of working, to which various references were made. This is well illustrated in the account of how the idea for subcutaneous pumps came about. Similarly, the ability to produce the very important guidelines on treating diabetics during surgery, and diabetic coma, partly resulted from the application to clinical problems of the understandings gained from some of the basic/early clinical studies. It is significant that the key papers on these issues, all of which come from the list of 10 selected papers from the 1970s and 1980s, were having an impact on the 1981 work. • How far the collection of papers from 1981 have been drawn upon in similar ways is less clear. Nevertheless, papers on treating diabetics during open heart surgery, and on bolus delivery of insulin at meal times, were key parts of these wider streams, despite variable citation levels. Furthermore, various papers, including on acarbose, on portal infusion of insulin, and on semi-human insulin, were important steps in bodies of work in their respective areas. The complexity was illustrated by a paper that helped debunk the Chlorpropamide alcohol flushing hypothesis, and thus end a line of scientific enquiry: there was payback in stopping an incorrect line of inquiry, but nothing on which to build. • Each technique in the qualitative study produced information about the successful subsequent careers followed by many researchers trained through working with Alberti. • Historical perspectives, and insider expert opinions, were important in the qualitative analysis. Overall, the qualitative methods highlighted some limitations in the bibliometric approach but also showed how aspects of the citation analysis can complement the opinions expressed, for example about the importance of the breadth of Alberti’s work. v Chapter 5 : Lessons learnt and the way forward • Lessons learnt: a variety of methods can be used successfully to gather considerable data about the payback from a body of research undertaken 20 years ago. Traditional citation analysis alone, however, is not sufficient: the importance of the surgery papers despite their relatively low citation rates illustrates this. The qualitative methods are important and much of the analysis is strengthened by drawing on multiple approaches. Several problems remain, including: identifying a coherent starting point for the analysis; coping with the enormous number of papers involved in later generations; and refining the template for categorising citations and developing ways of fully utilising the results from applying it. • Preparing for the large-scale study: this preliminary study provides a basis on which to attempt to undertake the larger study we envisaged. Issues now being addressed include identification of the level of bibliometric/citation analysis necessary to complement any qualitative studies. To provide confidence in the findings from an eventual large-scale study, we will need to expand the focus. The study will need to cover at least four sets of case studies. Ideally, each set should focus on a number of research groups working in a country in the same field. We hope there will be sets of case studies in two or three fields and in at least two countries. The issues to be explored will include ones highlighted by this study such as breadth of work, level of collaboration, and the role of core funding. • Methods for the large-scale study: for each case study we now propose to employ two methodological elements based on the qualitative and quantitative techniques adopted in the preliminary study. They will work in parallel but the quantitative bibliometric analysis would be applied selectively to parts of ‘research lines’ (ie discrete themes of research) identified in the qualitative studies as being important in influencing clinical practice. • Presenting the findings: each research line could be written-up in a standardised document that would use the HERG payback model and categories to describe the impact of that research. We shall use the qualitative and quantitative data to compare and contrast the ‘payback’ of research lines by country and disease, and then identify common factors that correlate with the translation of basic or early clinical research. • Concluding comments: in the era of ‘evidence based policy’, research funders are looking for value for money in the research they support and for evidence on the effectiveness of different research strategies. In this study we have begun developing a methodology that will allow us to understand the complexity of research development over a series of generations. The utility of the policy research we propose here will only be realised when it is scaled up to cover a number of different fields in different settings.NHS Executive, London Regio

Standard interface definition for avionics data bus systems

Data bus for avionics system of space shuttle, noting functions of interface unit, error detection and recovery, redundancy, and bus control philosoph

Path Integral Approach to Fermionic Vacuum Energy in Non-parallel D1-Branes

The fermionic one loop vacuum energy of the superstring theory in a system of non-parallel D1-branes is derived by applying the path integral formalism.Comment: 7 pages, no figur

Supersymmetry Constraints on Type IIB Supergravity

Supersymmetry is used to derive conditions on higher derivative terms in the effective action of type IIB supergravity. Using these conditions, we are able to prove earlier conjectures that certain modular invariant interactions of order alpha' **3 relative to the Einstein-Hilbert term are proportional to eigenfunctions of the Laplace operator on the fundamental domain of SL(2,Z). We also discuss how these arguments generalize to terms of higher order in alpha', as well as to compactifications of supergravity.Comment: 31 pages, harvmac (b); minor correction