4,856 research outputs found

    Computational Simulation and 3D Virtual Reality Engineering Tools for Dynamical Modeling and Imaging of Composite Nanomaterials

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    An adventure at engineering design and modeling is possible with a Virtual Reality Environment (VRE) that uses multiple computer-generated media to let a user experience situations that are temporally and spatially prohibiting. In this paper, an approach to developing some advanced architecture and modeling tools is presented to allow multiple frameworks work together while being shielded from the application program. This architecture is being developed in a framework of workbench interactive tools for next generation nanoparticle-reinforced damping/dynamic systems. Through the use of system, an engineer/programmer can respectively concentrate on tailoring an engineering design concept of novel system and the application software design while using existing databases/software outputs.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

    Electron Interactions and Transport Between Coupled Quantum Hall Edges

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    We examine the effects of electron-electron interactions on transport between edge states in a multilayer integer quantum Hall system. The edge states of such a system, coupled by interlayer tunneling, form a two-dimensional, chiral metal at the sample surface. We calculate the temperature-dependent conductivity and the amplitude of conductance fluctuations in this chiral metal, treating Coulomb interactions and disorder exactly in the weak-tunneling limit. We find that the conductivity increases with increasing temperature, as observed in recent experiments, and we show that the correlation length characterising conductance fluctuations varies inversely with temperature.Comment: 4 pages, 2 figures, typos corrected, Ref. 17 added, minor changes made for publicatio

    Thresholdless surface solitons

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    We report on the existence of nonlinear surface waves which, on the one hand, do not require the threshold energy flow for their excitation, and, on the other hand, extend into media at both sides of the interface at low powers, i.e. can not be reduced to the conventional Tamm states. Such waves can be excited if the refractive index in at least one of the materials forming the interface is periodically modulated, with properly selected modulation depth and frequency. Thresholdless surface solitons can be stable in the entire existence domain.Comment: 3 pages, 4 figures, to appear in Optics Letter

    Context and practice within a youth football setting: an exploration of psychological well-being through action research processes

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    The present thesis explores psychological well-being (PWB), practice and context within a professional football academy. The thesis also focuses on the processes of action research as a catalyst for practice-change in the academy environment, towards a culture of well-being. During the initial stages, pre-reconnaissance discussions took place with key academy practitioners to explore practitioner perceptions of well-being and coaching practice within context. The thesis is divided into two distinct phases; the reconnaissance phase, and the action phase. The reconnaissance phase encouraged the researcher to 'live the experience' alongside the research participants. Therefore emersion into the field of an academy football environment was required on a daily basis. The action research from reconnaissance-to-practice provided a detailed account of day-to-day events and on-going lived experiences of players and practitioners within the academy football environment. Consequently, qualitative data collection took place regularly in order to monitor and capture the personal experiences of academy players and practitioners, to follow individual threads of inquiry. Also field notes, player focus groups, informal interviews and formal taped interviews provided sufficient data for triangulation to occur. This multi-method approach enabled the researcher to take advantage of the rich variety of sources upon which were available (Tomlinson, 1983). The data collection protocol investigated how practitioners engaged in culturally specific practice within the academy. The action phase introduced collaborative practitioner meetings as part of the action research process to address practice that could later be linked specifically to psychological well-being (PWB) dimensions. The overall aim of the collaborative practitioner meetings was to drive debate and change, based on the notion that well-being can be related to everyday practice. Although there was similarity in how the meetings were described, the primary analysis differed, in particular the first two collaborative practitioner meetings underwent thorough content analysis from both an inductive (cultural and situational) and deductive (concept-oriented) stance. The reality of the research reflected the unpredictable process and dilemmas that may occur within the processes of action research and practice-change. The research provided detailed insight into the culture of football and the perceptions and experiences of full-time academy players, practitioners and the researcher's own reflections on the research journey, with regards to psychological well-being (PWB). Within the processes of action research, the practical utility of theory and the personal- contextual dynamic of a practice-change process within a youth football setting were considered and discussed. The research encouraged notions of emancipation within a participatory and collaborative process. Key Words: Psychological well-being (PWB), subjective well-being (SWB), action research, context and practice

    Transport between edge states in multilayer integer quantum Hall systems: exact treatment of Coulomb interactions and disorder

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    A set of stacked two-dimensional electron systems in a perpendicular magnetic field exhibits a three-dimensional version of the quantum Hall effect if interlayer tunneling is not too strong. When such a sample is in a quantum Hall plateau, the edge states of each layer combine to form a chiral metal at the sample surface. We study the interplay of interactions and disorder in transport properties of the chiral metal, in the regime of weak interlayer tunneling. Our starting point is a system without interlayer tunneling, in which the only excitations are harmonic collective modes: surface magnetoplasmons. Using bosonization and working perturbatively in the interlayer tunneling amplitude, we express transport properties in terms of the spectrum for these collective modes, treating electron-electron interactions and impurity scattering exactly. We calculte the conductivity as a function of temperature, finding that it increases with increasing temperature as observed in recent experiments. We also calculate the autocorrelation function of mesoscopic conductance fluctuations induced by changes in a magnetic field component perpendicular to the sample surface, and its dependence on temperature. We show that conductance fluctuations are characterised by a dephasing length that varies inversely with temperature.Comment: 13 pages, 10 figures, minor changes made for publicatio

    Albuminuria is a marker of increasing intracranial and extracranial vascular involvement in Type 2 diabetic Chinese patients

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    AIMS/HYPOTHESIS: Albuminuria has been reported to be a marker of cardiovascular risk factors and disease morbidity and mortality, but its relationship with intracerebral atherosclerotic disease is less clear. The aim of this study was to investigate the association between albuminuria and intracranial and extracranial vascular involvement in Chinese Type 2 diabetic patients. METHODS: The anthropometric and fasting biochemical measurements of 966 Type 2 diabetic patients with normoalbuminuria (55.6%), microalbuminuria (27.7%) or macroalbuminuria (16.7%) were compared. The prevalence of microvascular and macrovascular disease and middle cerebral artery (MCA) stenosis, measured by transcranial Doppler ultrasound, were also compared between the groups. RESULTS: Albuminuria was closely associated with a range of adverse parameters, including high BP, dyslipidaemia, smoking and adiposity (all p<0.01). The prevalence of microvascular disease (retinopathy p<0.001) and macrovascular disease (peripheral vascular disease p=0.012, myocardial infarction, p=0.004, MCA stenosis p<0.001) increased significantly with increasing levels of albuminuria. Albuminuria was also found to be an independent predictor of microvascular and macrovascular disease. CONCLUSIONS/INTERPRETATION: Albuminuria was an independent predictor of increasing levels of vascular risk factors and microvascular and macrovascular disease in this group of Type 2 diabetic patients, and a possible role for albuminuria as a marker of intracranial cerebrovascular disease should be further investigated.postprin

    Development and characterisation of a 3D multi-cellular in vitro model of normal human breast: a tool for cancer initiation studies.

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    Multicellular 3-dimensional (3D) in vitro models of normal human breast tissue to study cancer initiation are required. We present a model incorporating three of the major functional cell types of breast, detail the phenotype and document our breast cancer initiation studies. Myoepithelial cells and fibroblasts were isolated and immortalised from breast reduction mammoplasty samples. Tri-cultures containing non-tumorigenic luminal epithelial cells HB2, or HB2 overexpressing different HER proteins, together with myoepithelial cells and fibroblasts were established in collagen I. Phenotype was assessed morphologically and immunohistochemically and compared to normal breast tissue. When all three cell types were present, polarised epithelial structures with lumens and basement membrane production were observed, akin to normal human breast tissue. Overexpression of HER2 or HER2/3 caused a significant increase in size, while HER2 overexpression resulted in development of a DCIS-like phenotype. In summary, we have developed a 3D tri-cellular model of normal human breast, amenable to comparative analysis after genetic manipulation and with potential to dissect the mechanisms behind the early stages of breast cancer initiation

    A systematic review comparing the evidence for kidney function outcomes between oral antidiabetic drugs for type 2 diabetes.

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    Background: The development of kidney disease is a serious complication among people with type 2 diabetes mellitus, associated with substantially increased morbidity and mortality.  We aimed to summarise the current evidence for the relationship between treatments for type 2 diabetes and long-term kidney outcomes, by conducting a systematic search and review of relevant studies. Methods: We searched Medline, Embase and Web of Science, between 1st January 1980 and 15th May 2018 for published clinical trials and observational studies comparing two or more classes of oral therapy for type 2 diabetes. We included people receiving oral antidiabetic drugs. Studies were eligible that; (i) compared two or more classes of oral therapy for type 2 diabetes; (ii) reported kidney outcomes as primary or secondary outcomes; (iii) included more than 100 participants; and (iv) followed up participants for 48 weeks or more. Kidney-related outcome measures included were Incidence of chronic kidney disease, reduced eGFR, increased creatinine, 'micro' and 'macro' albuminuria. Results: We identified 15 eligible studies, seven of which were randomised controlled trials and eight were observational studies. Reporting of specific renal outcomes varied widely. Due to variability of comparisons and outcomes meta-analysis was not possible. The majority of comparisons between treatment with metformin or sulfonylurea indicated that metformin was associated with better renal outcomes. Little evidence was available for recently introduced treatments or commonly prescribed combination therapies. Conclusions: Comparative evidence for the effect of treatments for type 2 diabetes on renal outcomes, either as monotherapy or in combination is sparse
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