35 resultados para Uniquely ergodic
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Deflections of jets discharged into a reservoir with a free surface are investigated numerically. The jets are known to deflect towards either side of the free surface or the bottom, whose direction is not determined uniquely in some experimental conditions, i.e. there are multiple stable states realizable in the same condition. The origin of the multiple stable states is explored by utilizing homotopy transformations in which the top boundary of the reservoir is transformed from a rigid to a free boundary and also the location of the outlet throat is continuously moved from mid-height to the top. We depicted bifurcation diagrams of the flow compiling the data of numerical simulations, from which we identified the origin as an imperfect pitchfork bifurcation, and obtained an insight into the mechanism for the direction to be determined. The parameter region where such multiple stable states are possible is also delimited. © 2011 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.
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An optical fiber is treated as a natural one-dimensional random system where lasing is possible due to a combination of Rayleigh scattering by refractive index inhomogeneities and distributed amplification through the Raman effect. We present such a random fiber laser that is tunable over a broad wavelength range with uniquely flat output power and high efficiency, which outperforms traditional lasers of the same category. Outstanding characteristics defined by deep underlying physics and the simplicity of the scheme make the demonstrated laser a very attractive light source both for fundamental science and practical applications.
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Patients with Bipolar Disorder (BD) perform poorly on tasks of selective attention and inhibitory control. Although similar behavioural deficits have been noted in their relatives, it is yet unclear whether they reflect dysfunction in the same neural circuits. We used functional magnetic resonance imaging and the Stroop Colour Word Task to compare task related neural activity between 39 euthymic BD patients, 39 of their first-degree relatives (25 with no Axis I disorders and 14 with Major Depressive Disorder) and 48 healthy controls. Compared to controls, all individuals with familial predisposition to BD, irrespective of diagnosis, showed similar reductions in neural responsiveness in regions involved in selective attention within the posterior and inferior parietal lobules. In contrast, hypoactivation within fronto-striatal regions, implicated in inhibitory control, was observed only in BD patients and MDD relatives. Although striatal deficits were comparable between BD patients and their MDD relatives, right ventrolateral prefrontal dysfunction was uniquely associated with BD. Our findings suggest that while reduced parietal engagement relates to genetic risk, fronto-striatal dysfunction reflects processes underpinning disease expression for mood disorders. © 2011 Elsevier Inc.
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Genetic factors are important in the etiology of bipolar disorder (BD). However, first-degree relatives of BD patients are at risk for a number of psychiatric conditions, most commonly major depressive disorder (MDD), although the majority remain well. The purpose of the present study was to identify potential brain structural correlates for risk and resilience to mood disorders in patients with BD, type I (BD-I) and their relatives. Structural magnetic resonance imaging scans were acquired from 30 patients with BD-I, 50 of their firstdegree relatives (28 had no Axis I disorder, while 14 had MDD) and 52 controls. We used voxel-based morphometry, implemented in SPM5 to identify group differences in regional gray matter volume. From the identified clusters, potential differences were further examined based on diagnostic status (BD-I patients, MDD relatives, healthy relatives, controls). Whole-brain voxel-based analysis identified group differences in the left hemisphere in the insula, cerebellum, and substantia nigra. Increased left insula volume was associated with genetic preposition to BD-I independent of clinical phenotype. In contrast, increased left substantia nigra volume was observed in those with the clinical phenotype of BD-I. Changes uniquely associated with the absence of a clinical diagnosis in BD relatives were observed in the left cerebellum. Our data suggest that in BD, genetic and phenotype-related influences on brain structure are dissociable; if replicated, these findings may help with early identification of high-risk individuals who are more likely to transition to syndromal states. Copyright © 2009 Society for Neuroscience.
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Purpose – The purpose of this paper is to investigate the effectiveness of quality management training by reviewing commonly used critical success factors and tools rather than the overall methodological approach. Design/methodology/approach – The methodology used a web-based questionnaire. It consisted of 238 questions covering 77 tools and 30 critical success factors selected from leading academic and practitioner sources. The survey had 79 usable responses and the data were analysed using relevant statistical quality management tools. The results were validated in a series of structured workshops with quality management experts. Findings – Findings show that in general most of the critical success factor statements for quality management are agreed with, although not all are implemented well. The findings also show that many quality tools are not known or understood well; and that training has an important role in raising their awareness and making sure they are used correctly. Research limitations/implications – Generalisations are limited by the UK-centric nature of the sample. Practical implications – The practical implications are discussed for organisations implementing quality management initiatives, training organisations revising their quality management syllabi and academic institutions teaching quality management. Originality/value – Most recent surveys have been aimed at methodological levels (i.e. “lean”, “Six Sigma”, “total quality management” etc.); this research proposes that this has limited value as many of the tools and critical success factors are common to most of the methodologies. Therefore, quite uniquely, this research focuses on the tools and critical success factors. Additionally, other recent comparable surveys have been less comprehensive and not focused on training issues.
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Supply Chain Risk Management (SCRM) has become a popular area of research and study in recent years. This can be highlighted by the number of peer reviewed articles that have appeared in academic literature. This coupled with the realisation by companies that SCRM strategies are required to mitigate the risks that they face, makes for challenging research questions in the field of risk management. The challenge that companies face today is not only to identify the types of risks that they face, but also to assess the indicators of risk that face them. This will allow them to mitigate that risk before any disruption to the supply chain occurs. The use of social network theory can aid in the identification of disruption risk. This thesis proposes the combination of social networks, behavioural risk indicators and information management, to uniquely identify disruption risk. The propositions that were developed from the literature review and exploratory case study in the aerospace OEM, in this thesis are:- By improving information flows, through the use of social networks, we can identify supply chain disruption risk. - The management of information to identify supply chain disruption risk can be explored using push and pull concepts. The propositions were further explored through four focus group sessions, two within the OEM and two within an academic setting. The literature review conducted by the researcher did not find any studies that have evaluated supply chain disruption risk management in terms of social network analysis or information management studies. The evaluation of SCRM using these methods is thought to be a unique way of understanding the issues in SCRM that practitioners face today in the aerospace industry.
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Background. Non-attendance at paediatric hospital outpatient appointments poses potential risks to children's health and welfare. Prevention and management of missed appointments depends on the perceptions of clinicians and decision makers from both primary and secondary care, including general practitioners (GPs) who are integral to non-attendance follow-up. Objectives. To examine the views of clinical, managerial and executive health care staff regarding occurrence and management of non-attendance at general paediatric outpatient clinics. Methods. A qualitative study using individual semi-structured interviews was carried out at three English Primary Care Trusts and a nearby children's hospital. Interviews were conducted with 37 staff, including GPs, hospital doctors, other health care professionals, managers, executives and commissioners. Participants were recruited through purposive and 'snowball' sampling methods. Data were analysed following a thematic framework approach. Results. GPs focused on situational difficulties for families, while hospital-based staff emphasized the influence of parents' beliefs on attendance. Managers, executives and commissioners presented a broad overview of both factors, but with less detailed views. All groups discussed sociodemographic factors, with non-attendance thought to be more likely in 'chaotic families'. Hospital interviewees emphasized child protection issues and the need for thorough follow-up of missed appointments. However, GPs were reluctant to interfere with parental responsibilities. Conclusion. Parental motivation and practical and social barriers should be considered. Responsibilities regarding missed appointments are not clear across health care sectors, but GPs are uniquely placed to address non-attendance issues and are central to child safeguarding. Primary care policies and strategies could be introduced to reduce non-attendance and ensure children receive the care they require. © The Author 2013.
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What drives innovation? How does it contribute to the growth of firms, industries, and economies? And do intellectual property rights help or hurt innovation and growth? Uniquely combining microeconomics, macroeconomics, and theory with empirical analysis drawn from the United States and Europe, this book introduces graduate students and advanced undergraduates to the complex process of innovation. By addressing all the major dimensions of innovation in a single text, Christine Greenhalgh and Mark Rogers are able to show how outcomes at the microlevel feed through to the macro-outcomes that in turn determine personal incomes and job opportunities. In four sections, this textbook comprehensively addresses the nature of innovation and intellectual property, the microeconomics and macroeconomics of innovation, and economic policy at the firm and macroeconomic levels. Among the topics fully explored are the role of intellectual property in creating incentives to innovate; the social returns of innovation; the creation and destruction of jobs by innovation; whether more or fewer intellectual property rights would give firms better incentives to innovate; and the contentious issues surrounding international treaties on intellectual property.
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In any organization, risk plays a huge role in the success or failure of any business endeavour. Measuring and managing risk is a difficult and often complicated task and the global financial crisis of the late noughties can be traced to a worldwide deficiency in risk management regimes. One of the problems in understanding how best to manage risk is a lack of detailed examples of real world practice. In this accessible textbook the author sets the world of risk management in the context of the broader corporate governance agenda, as well as explaining the core elements of a risk management system. Material on the differences between risk management and internal auditing is supplemented by a section on the professionalization of risk – a relatively contemporary evolution. Enterprise risk management is also fully covered. With a detailed array of risk management cases – including Tesco, RBS and the UK government – lecturers will find this a uniquely well researched resource, supplemented by materials that enable the cases to be easily integrated into the classroom. Risk managers will be delighted with the case materials made available for the first time with the publication of this book.
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We have developed a new technique for extracting histological parameters from multi-spectral images of the ocular fundus. The new method uses a Monte Carlo simulation of the reflectance of the fundus to model how the spectral reflectance of the tissue varies with differing tissue histology. The model is parameterised by the concentrations of the five main absorbers found in the fundus: retinal haemoglobins, choroidal haemoglobins, choroidal melanin, RPE melanin and macular pigment. These parameters are shown to give rise to distinct variations in the tissue colouration. We use the results of the Monte Carlo simulations to construct an inverse model which maps tissue colouration onto the model parameters. This allows the concentration and distribution of the five main absorbers to be determined from suitable multi-spectral images. We propose the use of "image quotients" to allow this information to be extracted from uncalibrated image data. The filters used to acquire the images are selected to ensure a one-to-one mapping between model parameters and image quotients. To recover five model parameters uniquely, images must be acquired in six distinct spectral bands. Theoretical investigations suggest that retinal haemoglobins and macular pigment can be recovered with RMS errors of less than 10%. We present parametric maps showing the variation of these parameters across the posterior pole of the fundus. The results are in agreement with known tissue histology for normal healthy subjects. We also present an early result which suggests that, with further development, the technique could be used to successfully detect retinal haemorrhages.
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The evolution of cognitive neuroscience has been spurred by the development of increasingly sophisticated investigative techniques to study human cognition. In Methods in Mind, experts examine the wide variety of tools available to cognitive neuroscientists, paying particular attention to the ways in which different methods can be integrated to strengthen empirical findings and how innovative uses for established techniques can be developed. The book will be a uniquely valuable resource for the researcher seeking to expand his or her repertoire of investigative techniques. Each chapter explores a different approach. These include transcranial magnetic stimulation, cognitive neuropsychiatry, lesion studies in nonhuman primates, computational modeling, psychophysiology, single neurons and primate behavior, grid computing, eye movements, fMRI, electroencephalography, imaging genetics, magnetoencephalography, neuropharmacology, and neuroendocrinology. As mandated, authors focus on convergence and innovation in their fields; chapters highlight such cross-method innovations as the use of the fMRI signal to constrain magnetoencephalography, the use of electroencephalography (EEG) to guide rapid transcranial magnetic stimulation at a specific frequency, and the successful integration of neuroimaging and genetic analysis. Computational approaches depend on increased computing power, and one chapter describes the use of distributed or grid computing to analyze massive datasets in cyberspace. Each chapter author is a leading authority in the technique discussed.
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The bronchial epithelium is a source of both α and β chemokines and, uniquely, of secretory component (SC), the extracellular ligand-binding domain of the polymeric IgA receptor. Ig superfamily relatives of SC, such as IgG and α2-macroglobulin, bind IL-8. Therefore, we tested the hypothesis that SC binds IL-8, modifying its activity as a neutrophil chemoattractant. Primary bronchial epithelial cells were cultured under conditions to optimize SC synthesis. The chemokines IL-8, epithelial neutrophil-activating peptide-78, growth-related oncogene α, and RANTES were released constitutively by epithelial cells from both normal and asthmatic donors and detected in high m.w. complexes with SC. There were no qualitative differences in the production of SC-chemokine complexes by epithelial cells from normal or asthmatic donors, and in all cases this was the only form of chemokine detected. SC contains 15% N-linked carbohydrate, and complete deglycosylation with peptide N-glycosidase F abolished IL-8 binding. In micro-Boyden chamber assays, no IL-8-dependent neutrophil chemotactic responses to epithelial culture supernatants could be demonstrated. SC dose-dependently (IC50 ∼0.3 nM) inhibited the neutrophil chemotactic response to rIL-8 (10 nM) in micro-Boyden chamber assays and also inhibited IL-8-mediated neutrophil transendothelial migration. SC inhibited the binding of IL-8 to nonspecific binding sites on polycarbonate filters and endothelial cell monolayers, and therefore the formation of haptotactic gradients, without effects on IL-8 binding to specific receptors on neutrophils. The data indicate that in the airways IL-8 may be solubilized and inactivated by binding to SC
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As shown recently, a long telecommunication fibre may be treated as a natural one-dimensional random system, where lasing is possible due to a combination of random distributed feedback via Rayleigh scattering by natural refractive index inhomogeneities and distributed amplification through the Raman effect. Here we present a new type of a random fibre laser with a narrow (∼1 nm) spectrum tunable over a broad wavelength range (1535-1570 nm) with a uniquely flat (∼0.1 dB) and high (>2 W) output power and prominent (>40 %) differential efficiency, which outperforms traditional fibre lasers of the same category, e.g. a conventional Raman laser with a linear cavity formed in the same fibre by adding point reflectors. Analytical model is proposed that explains quantitatively the higher efficiency and the flatter tuning curve of the random fiber laser compared to conventional one. The other important features of the random fibre laser like "modeless" spectrum of specific shape and corresponding intensity fluctuations as well as the techniques of controlling its output characteristics are discussed. Outstanding characteristics defined by new underlying physics and the simplicity of the scheme implemented in standard telecom fibre make the demonstrated tunable random fibre laser a very attractive light source both for fundamental science and practical applications such as optical communication, sensing and secure transmission. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
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Full text: The idea of producing proteins from recombinant DNA hatched almost half a century ago. In his PhD thesis, Peter Lobban foresaw the prospect of inserting foreign DNA (from any source, including mammalian cells) into the genome of a λ phage in order to detect and recover protein products from Escherichia coli [ 1 and 2]. Only a few years later, in 1977, Herbert Boyer and his colleagues succeeded in the first ever expression of a peptide-coding gene in E. coli — they produced recombinant somatostatin [ 3] followed shortly after by human insulin. The field has advanced enormously since those early days and today recombinant proteins have become indispensable in advancing research and development in all fields of the life sciences. Structural biology, in particular, has benefitted tremendously from recombinant protein biotechnology, and an overwhelming proportion of the entries in the Protein Data Bank (PDB) are based on heterologously expressed proteins. Nonetheless, synthesizing, purifying and stabilizing recombinant proteins can still be thoroughly challenging. For example, the soluble proteome is organized to a large part into multicomponent complexes (in humans often comprising ten or more subunits), posing critical challenges for recombinant production. A third of all proteins in cells are located in the membrane, and pose special challenges that require a more bespoke approach. Recent advances may now mean that even these most recalcitrant of proteins could become tenable structural biology targets on a more routine basis. In this special issue, we examine progress in key areas that suggests this is indeed the case. Our first contribution examines the importance of understanding quality control in the host cell during recombinant protein production, and pays particular attention to the synthesis of recombinant membrane proteins. A major challenge faced by any host cell factory is the balance it must strike between its own requirements for growth and the fact that its cellular machinery has essentially been hijacked by an expression construct. In this context, Bill and von der Haar examine emerging insights into the role of the dependent pathways of translation and protein folding in defining high-yielding recombinant membrane protein production experiments for the common prokaryotic and eukaryotic expression hosts. Rather than acting as isolated entities, many membrane proteins form complexes to carry out their functions. To understand their biological mechanisms, it is essential to study the molecular structure of the intact membrane protein assemblies. Recombinant production of membrane protein complexes is still a formidable, at times insurmountable, challenge. In these cases, extraction from natural sources is the only option to prepare samples for structural and functional studies. Zorman and co-workers, in our second contribution, provide an overview of recent advances in the production of multi-subunit membrane protein complexes and highlight recent achievements in membrane protein structural research brought about by state-of-the-art near-atomic resolution cryo-electron microscopy techniques. E. coli has been the dominant host cell for recombinant protein production. Nonetheless, eukaryotic expression systems, including yeasts, insect cells and mammalian cells, are increasingly gaining prominence in the field. The yeast species Pichia pastoris, is a well-established recombinant expression system for a number of applications, including the production of a range of different membrane proteins. Byrne reviews high-resolution structures that have been determined using this methylotroph as an expression host. Although it is not yet clear why P. pastoris is suited to producing such a wide range of membrane proteins, its ease of use and the availability of diverse tools that can be readily implemented in standard bioscience laboratories mean that it is likely to become an increasingly popular option in structural biology pipelines. The contribution by Columbus concludes the membrane protein section of this volume. In her overview of post-expression strategies, Columbus surveys the four most common biochemical approaches for the structural investigation of membrane proteins. Limited proteolysis has successfully aided structure determination of membrane proteins in many cases. Deglycosylation of membrane proteins following production and purification analysis has also facilitated membrane protein structure analysis. Moreover, chemical modifications, such as lysine methylation and cysteine alkylation, have proven their worth to facilitate crystallization of membrane proteins, as well as NMR investigations of membrane protein conformational sampling. Together these approaches have greatly facilitated the structure determination of more than 40 membrane proteins to date. It may be an advantage to produce a target protein in mammalian cells, especially if authentic post-translational modifications such as glycosylation are required for proper activity. Chinese Hamster Ovary (CHO) cells and Human Embryonic Kidney (HEK) 293 cell lines have emerged as excellent hosts for heterologous production. The generation of stable cell-lines is often an aspiration for synthesizing proteins expressed in mammalian cells, in particular if high volumetric yields are to be achieved. In his report, Buessow surveys recent structures of proteins produced using stable mammalian cells and summarizes both well-established and novel approaches to facilitate stable cell-line generation for structural biology applications. The ambition of many biologists is to observe a protein's structure in the native environment of the cell itself. Until recently, this seemed to be more of a dream than a reality. Advances in nuclear magnetic resonance (NMR) spectroscopy techniques, however, have now made possible the observation of mechanistic events at the molecular level of protein structure. Smith and colleagues, in an exciting contribution, review emerging ‘in-cell NMR’ techniques that demonstrate the potential to monitor biological activities by NMR in real time in native physiological environments. A current drawback of NMR as a structure determination tool derives from size limitations of the molecule under investigation and the structures of large proteins and their complexes are therefore typically intractable by NMR. A solution to this challenge is the use of selective isotope labeling of the target protein, which results in a marked reduction of the complexity of NMR spectra and allows dynamic processes even in very large proteins and even ribosomes to be investigated. Kerfah and co-workers introduce methyl-specific isotopic labeling as a molecular tool-box, and review its applications to the solution NMR analysis of large proteins. Tyagi and Lemke next examine single-molecule FRET and crosslinking following the co-translational incorporation of non-canonical amino acids (ncAAs); the goal here is to move beyond static snap-shots of proteins and their complexes and to observe them as dynamic entities. The encoding of ncAAs through codon-suppression technology allows biomolecules to be investigated with diverse structural biology methods. In their article, Tyagi and Lemke discuss these approaches and speculate on the design of improved host organisms for ‘integrative structural biology research’. Our volume concludes with two contributions that resolve particular bottlenecks in the protein structure determination pipeline. The contribution by Crepin and co-workers introduces the concept of polyproteins in contemporary structural biology. Polyproteins are widespread in nature. They represent long polypeptide chains in which individual smaller proteins with different biological function are covalently linked together. Highly specific proteases then tailor the polyprotein into its constituent proteins. Many viruses use polyproteins as a means of organizing their proteome. The concept of polyproteins has now been exploited successfully to produce hitherto inaccessible recombinant protein complexes. For instance, by means of a self-processing synthetic polyprotein, the influenza polymerase, a high-value drug target that had remained elusive for decades, has been produced, and its high-resolution structure determined. In the contribution by Desmyter and co-workers, a further, often imposing, bottleneck in high-resolution protein structure determination is addressed: The requirement to form stable three-dimensional crystal lattices that diffract incident X-ray radiation to high resolution. Nanobodies have proven to be uniquely useful as crystallization chaperones, to coax challenging targets into suitable crystal lattices. Desmyter and co-workers review the generation of nanobodies by immunization, and highlight the application of this powerful technology to the crystallography of important protein specimens including G protein-coupled receptors (GPCRs). Recombinant protein production has come a long way since Peter Lobban's hypothesis in the late 1960s, with recombinant proteins now a dominant force in structural biology. The contributions in this volume showcase an impressive array of inventive approaches that are being developed and implemented, ever increasing the scope of recombinant technology to facilitate the determination of elusive protein structures. Powerful new methods from synthetic biology are further accelerating progress. Structure determination is now reaching into the living cell with the ultimate goal of observing functional molecular architectures in action in their native physiological environment. We anticipate that even the most challenging protein assemblies will be tackled by recombinant technology in the near future.
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In three experiments we investigated the impact that exposure to counter-stereotypes has on emotional reactions to outgroups. In Experiment 1, thinking about gender counter-stereotypes attenuated stereotyped emotions toward females and males. In Experiment 2, an immigrant counterstereotype attenuated stereotyped emotions toward this outgroup and reduced dehumanization tendencies. Experiment 3 replicated these results using an alternative measure of humanization. In both Experiments 2 and 3 sequential meditational analysis revealed that counter-stereotypes produced feelings of surprise which, in turn, elicited a cognitive process of expectancy violation which resulted in attenuated stereotyped emotions and an enhanced use of uniquely human characteristics to describe the outgroup. The findings extend research supporting the usefulness of counter-stereotype exposure for reducing prejudice and highlight its positive impact on intergroup emotions.