1,110 research outputs found

    Variational water-wave model with accurate dispersion and vertical vorticity

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    A new water-wave model has been derived which is based on variational techniques and combines a depth-averaged vertical (component of) vorticity with depth-dependent potential flow. The model facilitates the further restriction of the vertical profile of the velocity potential to n-th order polynomials or a finite-element profile with a small number of elements (say), leading to a framework for efficient modeling of the interaction of steepening and breaking waves near the shore with a large-scale horizontal flow. The equations are derived from a constrained variational formulation which leads to conservation laws for energy, mass, momentum and vertical vorticity. It is shown that the potential-flow water-wave equations and the shallow-water equations are recovered in the relevant limits. Approximate shock relations are provided, which can be used in numerical schemes to model breaking waves

    Accelerators as authentic training experiences for nascent entrepreneurs

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    © 2017, © Emerald Publishing Limited. Purpose: The purpose of this paper is to address the role of accelerators as authentic learning-based entrepreneurial training programs. Accelerators facilitate the development and assessment of entrepreneurial competencies in nascent entrepreneurs through the process of creating a start-up venture. Design/methodology/approach: Survey data from applicants and participants of four start-accelerators are used to explore the linkages between accelerators and the elements of authentic learning. Authentic learning processes are then mapped onto the start-up processes that occur within the accelerators. Findings: Accelerators take in nascent entrepreneurs and work to create start-ups. This activity develops the participants’ entrepreneurial competencies and facilitates authentic self-reflection. Research limitations/implications: This study explores how accelerators can be useful as authentic learning platforms for the development of entrepreneurial competencies. Limitations include perceptual measures and the inability to conduct paired sampling. Practical implications: Entrepreneurship training is studied through the lens of authentic learning activities that occur within an accelerator. Participants develop and assess their mastery of and interest in entrepreneurship through tasks, exposure to experts and mentors, peer learning, and assessments such as pitching to investors at Demo Day. Originality/value: This paper reports on the authentic learning processes and its usefulness in competency development and self-appraisal by accelerators participants. The opportunity for competency development and self-appraisal by nascent entrepreneurs before escalating their commitment to a start-up may be an accelerator’s raison d’être

    Cardiac arrest as first presentation of arrhythmogenic left ventricular cardiomyopathy due to Filamin C mutation: a case report

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    Background Arrhythmogenic left ventricular cardiomyopathy (ALVC) is a rare form of arrhythmogenic cardiomyopathy characterized by fibrofatty replacement of left ventricular myocardium, malignant arrhythmia, and sudden cardiac death. The definition incorporates several genetic causes, including pathogenic variation in the Filamin C gene (FLNC). Although awareness of ALVC has improved, identification remains challenging and diagnostic criteria continue to evolve. Case summary A 50-year-old athletic male was admitted following an out-of-hospital cardiac arrest due to ventricular tachycardia (VT) whilst playing football. Coronary angiography revealed unobstructed epicardial vessels and the diagnosis of ALVC was suggested by cardiovascular magnetic resonance imaging, which demonstrated a mildly dilated and moderately impaired left ventricle with epicardial late gadolinium enhancement in the basal to mid-lateral walls and subendocardial septum. Initial testing with a cardiomyopathy and arrhythmia gene panel was negative but extended testing uncovered a likely pathogenic variant in FLNC. Subsequently, the patient experienced a recurrence of sustained VT necessitating implantable cardioverter-defibrillator (ICD) therapies, ultimately undergoing a combined epicardial and endocardial VT ablation 4 years after presentation. Six months post-ablation, he was asymptomatic and his arrhythmia rendered quiescent. Discussion Arrhythmogenic cardiomyopathy should be considered in the evaluation of an initially unexplained cardiac arrest. This case characterizes the clinical features of a patient with FLNC cardiomyopathy and emphasizes the utility of genetic testing using modern gene panels in patients with comparable phenotypes. We also demonstrate that optimal medical therapy with antiarrhythmic drugs, exercise restriction, ICD insertion, and catheter ablation can be useful in the management of ALVC with positive outcomes

    A QM/MM approach for the study of monolayer-protected gold clusters

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    We report the development and implementation of hybrid methods that combine quantum mechanics (QM) with molecular mechanics (MM) to theoretically characterize thiolated gold clusters. We use, as training systems, structures such as Au25(SCH2-R)18 and Au38(SCH2-R)24, which can be readily compared with recent crystallographic data. We envision that such an approach will lead to an accurate description of key structural and electronic signatures at a fraction of the cost of a full quantum chemical treatment. As an example, we demonstrate that calculations of the 1H and 13C NMR shielding constants with our proposed QM/MM model maintain the qualitative features of a full DFT calculation, with an order-of-magnitude increase in computational efficiency.Comment: Journal of Materials Science, 201

    Dynamic Bayesian belief network to model the development of walking and cycling schemes

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    This paper aims to describe a model which represents the formulation of decision-making processes (over a number of years) affecting the step-changes of walking and cycling (WaC) schemes. These processes can be seen as being driven by a number of causal factors, many of which are associated with the attitudes of a variety of factors, in terms of both determining whether any scheme will be implemented and, if it is implemented, the extent to which it is used. The outputs of the model are pathways as to how the future might unfold (in terms of a number of future time steps) with respect to specific pedestrian and cyclist schemes. The transitions of the decision making processes are formulated using a qualitative simulation method, which describes the step-changes of the WaC scheme development. In this article a Bayesian belief network (BBN) theory is extended to model the influence between and within factors in the dynamic decision making process

    The braincase and jaws of a Devonian 'acanthodian' and modern gnathostome origins.

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    Modern gnathostomes (jawed vertebrates) emerged in the early Palaeozoic era, but this event remains unclear owing to a scant early fossil record. The exclusively Palaeozoic acanthodians are possibly the earliest gnathostome group and exhibit a mosaic of shark- and bony fish-like characters that has long given them prominence in discussions of early gnathostome evolution. Their relationships with modern gnathostomes have remained mysterious, partly because their un-mineralized endoskeletons rarely fossilized. Here I present the first-known braincase of an Early Devonian (approximately 418-412 Myr bp) acanthodian, Ptomacanthus anglicus, and re-evaluate the interrelationships of basal gnathostomes. Acanthodian braincases have previously been represented by a single genus, Acanthodes, which occurs more than 100 million years later in the fossil record. The braincase of Ptomacanthus differs radically from the osteichthyan-like braincase of Acanthodes in exhibiting several plesiomorphic features shared with placoderms and some early chondrichthyans. Most striking is its extremely short sphenoid region and its jaw suspension, which displays features intermediate between some Palaeozoic chondrichthyans and osteichthyans. Phylogenetic analysis resolves Ptomacanthus as either the most basal chondrichthyan or as the sister group of all living gnathostomes. These new data alter earlier conceptions of basal gnathostome phylogeny and thus help to provide a more detailed picture of the acquisition of early gnathostome characters

    In Vitro Characterization of a Nineteenth-Century Therapy for Smallpox

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    In the nineteenth century, smallpox ravaged through the United States and Canada. At this time, a botanical preparation, derived from the carnivorous plant Sarracenia purpurea, was proclaimed as being a successful therapy for smallpox infections. The work described characterizes the antipoxvirus activity associated with this botanical extract against vaccinia virus, monkeypox virus and variola virus, the causative agent of smallpox. Our work demonstrates the in vitro characterization of Sarracenia purpurea as the first effective inhibitor of poxvirus replication at the level of early viral transcription. With the renewed threat of poxvirus-related infections, our results indicate Sarracenia purpurea may act as another defensive measure against Orthopoxvirus infections
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