Showing papers by "Imperial College London published in 1997"
Book•
01 Jan 1997TL;DR: In this paper, Tidd, Bessant & Pavitt provide an integrative approach to the management of innovation at the operational and strategic levels, integrating market, organizational and technological change to improve the competitiveness of firms and effectiveness of other organizations.
Abstract: Managing Innovation provides readers with the knowledge to understand, and the skills to manage, innovation at the operational and strategic levels. Specifically, it integrates the management of market, organizational and technological change to improve the competitiveness of firms and effectiveness of other organizations. The management of innovation is inherently interdisciplinary and multifunctional and Tidd, Bessant & Pavitt provide an integrative approach to the subject. Two new perspectives are introduced through which to re-examine material presented in each chapter: sustaining versus disruptive innovation (a greater emphasis will be placed on disruptive innovation) and organizations versus networks (greater discussion of the network issues raised in each chapter). Provides more treatment of innovation in services. Greater internationalization of case examples will be provided e.g. more examples will be included from Asia and Latin America. Introduces discussion of the relationship between innovation and the environment.
3,300 citations
01 Apr 1997
TL;DR: In this paper, the Kondo problem and the Bethe ansatz have been studied in the context of magnetic impurities and fermi liquid theories, and N-fold degenerate models have been proposed.
Abstract: 1. Models of magnetic impurities 2. Resistivity calculations and the resistance minimum 3. The Kondo problem 4. Renormalization group calculations 5. Fermi liquid theories 6. Exact solutions and the Bethe ansatz 7. N-fold degenerate models I 8. N-fold degenerate models II 9. Theory and experiment 10. Strongly correlated fermions Appendices.
2,493 citations
TL;DR: It is argued that engineering has both negative and positive effects on species richness and abundances at small scales, but the net effects are probably positive at larger scales encompassing engineered and nonengineered environments in ecological and evolutionary space and time.
Abstract: Physical ecosystem engineers are organisms that directly or indirectly control the availability of resources to other organisms by causing physical state changes in biotic or abiotic materials. Physical ecosystem engineering by organisms is the physical modification, maintenance, or creation of habitats. Ecological effects of engineers on many other species occur in virtually all ecosystems because the physical state changes directly create nonfood resources such as living space, directly control abiotic resources, and indirectly modulate abiotic forces that, in turn, affect resource use by other organisms. Trophic interactions and resource competition do not constitute engineering. Engineering can have significant or trivial effects on other species, may involve the physical structure of an organism (like a tree) or structures made by an organism (like a beaver dam), and can, but does not invariably, have feedback effects on the engineer. We argue that engineering has both negative and positive effects on species richness and abundances at small scales, but the net effects are probably positive at larger scales encompassing engineered and nonengineered environments in ecological and evolutionary space and time. Models of the population dynamics of engineers suggest that the engineer/habitat equilibrium is often, but not always, locally stable and may show long-term cycles, with potential ramifications for community and ecosystem stability. As yet, data adequate to parameterize such a model do not exist for any engineer species. Because engineers control flows of energy and materials but do not have to participate in these flows, energy, mass, and stoichiometry do not appear to be useful in predicting which engineers will have big effects. Empirical observations suggest some potential generalizations about which species will be important engineers in which ecosystems. We point out some of the obvious, and not so obvious, ways in which engineering and trophic relations interact, and we call for greater research on physical ecosystem engineers, their impacts, and their interface with trophic relations.
2,163 citations
TL;DR: It is found that the biological and molecular transmission characteristics of vCJD are consistent with it being the human counterpart of BSE.
Abstract: Epidemiological and clinicopathological studies, allied with pathological prion protein (PrPSc) analysis, strongly support the hypothesis that the human prion disease new variant Creutzfeldt-Jakob disease (vCJD) is causally related to bovine spongiform encephalopathy (BSE)1,2, but considerable controversy remains. Distinct prion strains are distinguished by their biological properties on transmission to laboratory animals and by physical and chemical differences in PrPSc strains. We now find that the biological and molecular transmission characteristics of vCJD are consistent with it being the human counterpart of BSE.
1,471 citations
TL;DR: These results confirm that lung metastasectomy is a safe and potentially curative procedure and design a simple system of classification valid for different tumor types.
1,344 citations
TL;DR: In this paper, the authors argue that diversity is also functionally important, both because it increases the probability of including species that have strong ecosystem effects and because it can increase the efficiency of resource use.
Abstract: Changes in the abundance of species — especially those that influence water and nutrient dynamics, trophic interactions, or disturbance regime — affect the structure and functioning of ecosystems. Diversity is also functionally important, both because it increases the probability of including species that have strong ecosystem effects and because it can increase the efficiency of resource use. Differences in environmental sensitivity among functionally similar species give stability to ecosystem processes, whereas differences in sensitivity among functionally different species make ecosystems more vulnerable to change. Current global environmental changes that affect species composition and diversity are therefore profoundly altering the functioning of the biosphere.
1,110 citations
TL;DR: The majority of patients were constitutionally small, with 36% of patients below the 3rd centile for either height or weight parameters, and the majority of surviving patients were developmentally normal or had only mild learning problems.
Abstract: We present clinical data on 558 patients with deletions within the DiGeorge syndrome critical region of chromosome 22q11. Twenty-eight percent of the cases where parents had been tested had inherited deletions, with a marked excess of maternally inherited deletions (maternal 61, paternal 18). Eight percent of the patients had died, over half of these within a month of birth and the majority within 6 months. All but one of the deaths were the result of congenital heart disease. Clinically significant immunological problems were very uncommon. Nine percent of patients had cleft palate and 32% had velopharyngeal insufficiency, 60% of patients were hypocalcaemic, 75% of patients had cardiac problems, and 36% of patients who had abdominal ultrasound had a renal abnormality. Sixty-two percent of surviving patients were developmentally normal or had only mild learning problems. The majority of patients were constitutionally small, with 36% of patients below the 3rd centile for either height or weight parameters.
1,087 citations
TL;DR: In this paper, the effect of concentration of suspended particles upon their rate of settlement was examined experimentally, and the experimental results obtained in the present work were compared with those predicted from this theory.
Abstract: Summary The present work is concerned with the study of sedimentation and liquid-solid fluidisation. In the former, suspended solids are falling under the influence of gravity in a stationary fluid, while in the latter, the particles are kept in suspension by an upward flow of liquid. The object is to examine experimentally the effect of concentration of suspended particles upon their rate of settlement, and to find a satisfactory method of correlating the results. The present part of the experimental work has been confined to uniformly sized spherical particles, greater than 100 microns in diameter. As reported elsewhere, an attempt has been made to develop an expression, from theoretical considerations, for the rate of settling of suspensions, and the experimental results obtained in the present work are compared with those predicted from this theory. The work has been extended for comparison to liquid-solid fluidised systems.
1,043 citations
1,028 citations
TL;DR: The prognosis for pregnancies in women with recurrent miscarriage associated with phospholipid antibodies is poor but this randomised controlled trial found that the prognosis improved with low dose aspirin and was further improved with the addition of low dose heparin to the aspirin.
Abstract: OBJECTIVE: To determine whether treatment with low dose aspirin and heparin leads to a higher rate of live births than that achieved with low dose aspirin alone in women with a history of recurrent miscarriage associated with phospholipid antibodies (or antiphospholipid antibodies), lupus anticoagulant, and cardiolipin antibodies (or anticardiolipin antibodies). DESIGN: Randomised controlled trial. SETTING: Specialist clinic for recurrent miscarriages. SUBJECTS: 90 women (median age 33 (range 22-43)) with a history of recurrent miscarriage (median number 4 (range 3-15)) and persistently positive results for phospholipid antibodies. INTERVENTION: Either low dose aspirin (75 mg daily) or low dose aspirin and 5000 U of unfractionated heparin subcutaneously 12 hourly. All women started treatment with low dose aspirin when they had a positive urine pregnancy test. Women were randomly allocated an intervention when fetal heart activity was seen on ultrasonography. Treatment was stopped at the time of miscarriage or at 34 weeks' gestation. MAIN OUTCOME MEASURES: Rate of live births with the two treatments. RESULTS: There was no significant difference in the two groups in age or the number and gestation of previous miscarriages. The rate of live births with low dose aspirin and heparin was 71% (32/45 pregnancies) and 42% (19/45 pregnancies) with low dose aspirin alone (odds ratio 3.37 (95% confidence interval 1.40 to 8.10)). More than 90% of miscarriages occurred in the first trimester. There was no difference in outcome between the two treatments in pregnancies that advanced beyond 13 weeks' gestation. Twelve of the 51 successful pregnancies (24%) were delivered before 37 weeks' gestation. Women randomly allocated aspirin and heparin had a median decrease in lumbar spine bone density of 5.4% (range -8.6% to 1.7%). CONCLUSION: Treatment with aspirin and heparin leads to a significantly higher rate of live births in women with a history of recurrent miscarriage associated with phospholipid antibodies than that achieved with aspirin alone.
982 citations
Book•
27 Mar 1997TL;DR: Theoretical basis of scattering labelling with deuterium is discussed in this article, where the authors describe the nuts and bolts sprectrometers and what they measure, how, why, and when to use form factors interacting systems.
Abstract: Neutron production and detection - the nuts and bolts sprectrometers and what they measure theoretical basis of scattering labelling with deuterium - how, why, and when to use form factors interacting systems - part 1 zero angle scattering, part 2 finite angle scattering experimental examples of structural studies dynamics neutron reflection for studying surfaces and interfaces.
TL;DR: In patients with symptoms suspected by a general practitioner to be due to heart failure, plasma BNP concentration seems to be a useful indicator of which patients are likely to have heart failure and require further clinical assessment.
TL;DR: The SHIRPA procedure is developed, which utilizes standardized protocols for behavioral and functional assessment that provide a sensitive measure for quantifying phenotype expression in the mouse, and can be refined to test the function of specific neural pathways, which will contribute to a greater understanding of neurological disorders.
Abstract: For an understanding of the aberrant biology seen in mouse mutations and identification of more subtle phenotype variation, there is a need for a full clinical and pathological characterization of the animals. Although there has been some use of sophisticated techniques, the majority of behavioral and functional analyses in mice have been qualitative rather than quantitative in nature. There is, however, no comprehensive routine screening and testing protocol designed to identify and characterize phenotype variation or disorders associated with the mouse genome. We have developed the SHIRPA procedure to characterize the phenotype of mice in three stages. The primary screen utilizes standard methods to provide a behavioral and functional profile by observational assessment. The secondary screen involves a comprehensive behavioral assessment battery and pathological analysis. These protocols provide the framework for a general phenotype assessment that is suitable for a wide range of applications, including the characterization of spontaneous and induced mutants, the analysis of transgenic and gene-targeted phenotypes, and the definition of variation between strains. The tertiary screening stage described is tailored to the assessment of existing or potential models of neurological disease, as well as the assessment of phenotypic variability that may be the result of unknown genetic influences. SHIRPA utilizes standardized protocols for behavioral and functional assessment that provide a sensitive measure for quantifying phenotype expression in the mouse. These paradigms can be refined to test the function of specific neural pathways, which will, in turn, contribute to a greater understanding of neurological disorders.
TL;DR: It is shown that transcriptionally inactive but not transcriptionally active genes associate with Ikaros-heterochromatin foci, which support a model of organization of the nucleus in which repressed genes are selectively recruited into centromeric domains.
TL;DR: In this article, the authors discuss the limits to the maximum precision achievable in the spectroscopy of n two-level atoms in the presence of decoherence by means of quantum entanglement.
Abstract: The optimal precision of frequency measurements in the presence of decoherence is discussed. We analyze different preparations of n two-level systems as well as different measurement procedures. We show that standard Ramsey spectroscopy on uncorrelated atoms and optimal measurements on maximally entangled states provide the same resolution. The best resolution is achieved using partially entangled preparations with a high degree of symmetry. [S0031-9007(97)04541-9] PACS numbers: 42.50.Ar, 03.65.Bz The rapid development of laser cooling and trapping techniques has opened up new perspectives in high precision spectroscopy. Frequency standards based on laser cooled ions are expected to achieve accuracies of the order of 1 part in 10 14 10 18 [1]. In this Letter we discuss the limits to the maximum precision achievable in the spectroscopy of n two-level atoms in the presence of decoherence. This question is particularly timely in view of current efforts to improve high precision spectroscopy by means of quantum entanglement. In the present context standard Ramsey spectroscopy refers to the situation schematically depicted in Fig. 1. An ion trap is loaded with n ions initially prepared in the same internal state j0l. A Ramsey pulse of frequency v is applied to all ions. The pulse shape and duration are carefully chosen so that it drives the atomic transition j0l $j 1 lof natural frequency v0 and prepares an equally weighted superposition of the two internal states j0l and j1l for each ion. Next the system evolves freely for a time t followed by the second Ramsey pulse. Finally, the internal state of each particle is measured. Provided that the duration of the Ramsey pulses is much smaller than the free evolution time t, the probability that an ion is found in j1l is given by
TL;DR: It is suggested that the syndrome of heart failure progresses to cardiac cachexia if the normal metabolic balance between catabolism and anabolism is altered.
Abstract: Background The role of hormonal and cytokine abnormalities in the development of cardiac cachexia remains obscure. Methods and Results Healthy control subjects (n=16) and patients with chronic heart failure (CHF), classified clinically as cachectic (8% to 35% weight loss over ≥6 months before study, n=16) or noncachectic (n=37), were assessed for markers of disease severity (maximal oxygen consumption, left ventricular ejection fraction, NYHA functional class). These markers were compared with plasma concentrations of potentially important anabolic and catabolic factors. The degree of neurohormonal activation and catabolic/anabolic imbalance was closely related to wasting but not to conventional measures of the severity of heart failure. Compared with control subjects and noncachectic patients, cachectic patients had reduced plasma sodium and increased norepinephrine, epinephrine (all P<.0001), cortisol, tumor necrosis factor (TNF)-α (both P<.002), and human growth hormone (P<.05). Insulin-like growth fac...
TL;DR: In this article, it was shown that the part of the tree-level open string effective action for the non-abelian vector field which depends on the field strength but not on its covariant derivatives is not defined unambiguously.
TL;DR: In this article, a review of the scientific basis of the concepts used to define critical levels for ozone and identifies the key limitations and uncertainties involved, focusing on the Level I critical level approach, which provides an environmental standard or threshold to minimise the effects of ozone on sensitive receptors, but does not seek to quantify the impacts of exceeding the critical level under field conditions.
TL;DR: It is found that reduced larval competitive ability in unparasitized D. melanogaster is a correlated response to artificial selection for improved resistance against an endoparasitoid, Asobara tabida, which may explain the observed heritable variation in resistance.
Abstract: The extent to which an organism is selected to invest in defences against pathogens and parasites depends on the advantages that ensue should infection occur, but also on the costs of maintaining defences in the absence of infection. The presence of heritable variation in resistance suggests that costs exist, but we know very little about the nature or magnitude of these costs in natural populations of animals1. A powerful technique for identifying trade-offs between fitness components is the study of correlated responses to artificial selection2,3. We have selected Drosophila melanogaster for improved resistance against an endoparasitoid, Asobara tabida. Endoparasitoids are insects whose larvae develop internally within the body of other insects, eventually killing them, although their hosts can sometimes survive attack by mounting a cellular immune response4,5,6. We found that reduced larval competitive ability in unparasitized D. melanogaster is a correlated response to artificial selection for improved resistance against A. tabida. The strength of selection for competitive ability and parasitoid resistance is likely to vary temporally and spatially, which may explain the observed heritable variation in resistance.
TL;DR: The data confirm the involvement of subepithelial T lymphocytes and macrophages in smoking-induced airflow limitation and provide novel data which support the view that COPD is distinct from asthma with respect to the predominance of the CD8+ T-cell subset in this smoking-related condition.
Abstract: In order to determine whether the airway inflammatory cells of chronic obstructive pulmonary disease (COPD) are different from those seen in asthma, we have studied a subepithelial zone, 100 microns deep to the epithelial reticular basement membrane in bronchial biopsies taken from five normal nonsmoking subjects without chronic bronchitis or asthma (FEV1 percentage of predicted [mean +/- SD] 105.7 +/- 25.3), 11 subjects with chronic bronchitis alone (FEV1 percentage of predicted 98.5 +/- 12.9), and 13 subjects with chronic bronchitis in whom there was also evidence of airflow limitation (i.e., COPD; FEV1 percentage of predicted 59.7 +/- 10.0). Using immunohistochemical markers, we counted distinct types of inflammatory cell and expressed them as [median and range] per mm basement membrane. When there was airflow limitation we found significantly increased numbers of CD3+ T lymphocytes (COPD 22.3 [2.6 to 68.2] versus normal 3.7 [1.5 to 16.3]; p < 0.05), an increased number of CD8+ cells (COPD 19.3 [1.8 to...
Book•
01 Jan 1997TL;DR: Complex variables provide powerful methods for attacking problems that can be very difficult to solve in any other way, and it is the aim of this book to provide a thorough grounding in these methods and their application.
Abstract: Complex variables provide powerful methods for attacking problems that can be very difficult to solve in any other way, and it is the aim of this book to provide a thorough grounding in these methods and their application. Part I of this text provides an introduction to the subject, including analytic functions, integration, series, and residue calculus and also includes transform methods, ODEs in the complex plane, and numerical methods. Part II contains conformal mappings, asymptotic expansions, and the study of Riemann–Hilbert problems. The authors provide an extensive array of applications, illustrative examples and homework exercises. This 2003 edition was improved throughout and is ideal for use in undergraduate and introductory graduate level courses in complex variables.
TL;DR: An abstract framework for default reasoning, which includes Theorist, default logic, logic programming, autoepistemic logic, non-monotonic modal logics, and certain instances of circumscription as special cases, is presented and a more liberal, argumentation-theoretic semantics is proposed, based upon the notion of admissible extension in logic programming.
TL;DR: The structure of the N‐terminal adenylation subunit in a complex with AMP and L‐phenylalanine indicates a conserved mechanism of nucleotide binding and substrate activation and reveals the role of the invariant residues within the superfamily of adenYLate‐forming enzymes.
Abstract: The non-ribosomal synthesis of the cyclic peptide antibiotic gramicidin S is accomplished by two large multifunctional enzymes, the peptide synthetases 1 and 2. The enzyme complex contains five conserved subunits of approximately 60 kDa which carry out ATP-dependent activation of specific amino acids and share extensive regions of sequence similarity with adenylating enzymes such as firefly luciferases and acyl-CoA ligases. We have determined the crystal structure of the N-terminal adenylation subunit in a complex with AMP and L-phenylalanine to 1.9 A resolution. The 556 amino acid residue fragment is folded into two domains with the active site situated at their interface. Each domain of the enzyme has a similar topology to the corresponding domain of unliganded firefly luciferase, but a remarkable relative domain rotation of 94 degrees occurs. This conformation places the absolutely conserved Lys517 in a position to form electrostatic interactions with both ligands. The AMP is bound with the phosphate moiety interacting with Lys517 and the hydroxyl groups of the ribose forming hydrogen bonds with Asp413. The phenylalanine substrate binds in a hydrophobic pocket with the carboxylate group interacting with Lys517 and the alpha-amino group with Asp235. The structure reveals the role of the invariant residues within the superfamily of adenylate-forming enzymes and indicates a conserved mechanism of nucleotide binding and substrate activation.
TL;DR: In this article, the authors review the phenonomena which occur in multiphoton physics when the electric field of the applied laser radiation becomes comparable with the Coulomb field strength seen by an electron in the ground state of atomic hydrogen.
Abstract: We review the phenonomena which occur in multiphoton physics when the electric field of the applied laser radiation becomes comparable with the Coulomb field strength seen by an electron in the ground state of atomic hydrogen. This field is reached at an irradiance of approximately . The normal perturbative photon-by-photon based picture of the interaction of individual electrons with the field is replaced by a tunnelling picture in which, in a time of the order of, or less than one optical cycle, atomic wavepackets are generated which escape the confining Coulomb potential. These wavepackets are strongly influenced by the laser, `quiver' and may be accelerated back to the parent ion in a recollision process. Phase-coherent effects locked to the laser field become important: high harmonics are generated from these recollisions. We discuss the theory of such effects, and review progress in understanding how this quiver motion can be coherently controlled. We discuss ionization dynamics and review mechanisms by which atoms may be stabilized in very strong fields. Finally, we discuss relativistic effects which occur at very high-intensities.
05 Nov 1997
TL;DR: Preliminary conclusions based on a study of a financial transaction system-Logica's Fastwire (FW)-are outlined and compared with those reached during the earlier OS/360 study, suggesting that the 1970s approach to metric analysis of software evolution is still relevant today.
Abstract: The process of E-type software development and evolution has proven most difficult to improve, possibly due to the fact that the process is a multi-input, multi-output system involving feedback at many levels. This observation, first recorded in the early 1970s during an extended study of OS/360 evolution, was recently captured in a FEAST (Feedback, Evolution And Software Technology) hypothesis: a hypothesis being studied in on-going two-year project, FEAST/1. Preliminary conclusions based on a study of a financial transaction system-Logica's Fastwire (FW)-are outlined and compared with those reached during the earlier OS/360 study. The new analysis supports, or better does not contradict, the laws of software evolution, suggesting that the 1970s approach to metric analysis of software evolution is still relevant today. It is hoped that FEAST/1 will provide a foundation for mastering the feedback aspects of the software evolution process, opening up new paths for process modelling and improvement.
TL;DR: It is demonstrated that by gene targeting in a rodent Plasmodium, TRAP is critical for sporozoite infection of the mosquito salivary glands and the rat liver, and is essential for sporzoite gliding motility in vitro, suggesting that in PlasModium sporozoites, and likely in other Apicomplexa, gliding locomotion and cell invasion have a common molecular basis.
TL;DR: A high VE-VCO2 slope selects patients with more severe heart failure and is an independent prognostic marker in the assessment of patients with chronic heart failure.
TL;DR: In this paper, a model for the origin of the stellar initial mass function (IMF) is developed, which contains a dependence on the average physical parameters (temperature, density, velocity dispersion) of the large scale site of star formation.
Abstract: We propose that the stellar initial mass function (IMF) is universal in the sense that its functional form arises as a consequence of the statistics of random supersonic flows. A model is developed for the origin of the stellar IMF, that contains a dependence on the average physical parameters (temperature, density, velocity dispersion) of the large scale site of star formation. The model is based on recent numerical experiments of highly supersonic random flows that have a strong observational counterpart. It is shown that a Miller-Scalo like IMF is naturally produced by the model for the typical physical conditions in molecular clouds. A more “massive” IMF in star bursts is also predicted.
TL;DR: Computational results show that the genetic algorithm heuristic is able to find optimal and near optimal solutions that are on average less than 0.01 % from optimality.
TL;DR: In the case of laser-heated xenon clusters, it was shown that the explosion of these superheated clusters ejects ions with substantial kinetic energy up to 1 MeV, four orders of magnitude higher than that achieved in the Coulomb explosion of small molecules as discussed by the authors.
Abstract: Efficient conversion of electromagnetic energy to particle energy is of fundamental importance in many areas of physics A promising avenue for producing matter with unprecedented energy densities is by heating atomic clusters, an intermediate form of matter between molecules and solids1, with high-intensity, ultra-short light pulses2–4 Studies of noble-gas clusters heated with high-intensity (>1016Wcm–2) laser pulses indicate that a highly ionized, very high temperature micro-plasma is produced The explosion of these superheated clusters ejects ions with substantial kinetic energy3–5 Here we report the direct measurement of the ion energy distributions resulting from these explosions We find, in the case of laser-heated xenon clusters, that such explosions produce xenon ions with kinetic energies up to 1 MeV This energy is four orders of magnitude higher than that achieved in the Coulomb explosion of small molecules6, indicating a fundamental difference in the nature of intense laser–matter interactions between molecules and clusters Moreover, it demonstrates that access to an extremely high temperature state of matter is now possible with small-scale lasers