434 research outputs found

    Three-dimensional steep wave impact on a vertical plate with an open rectangular section

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    The present study treats the three-dimensional hydrodynamic slamming problem on a vertical plate subjected to the impact of a steep wave moving towards the plate with a constant velocity. The problem is complicated significantly by assuming that there is a rectangular opening on the plate which allows a discharge of the liquid. The analysis is conducted analytically assuming linear potential theory. The examined configuration determines two boundary value problems with mixed conditions which fully are taken into account. The mathematical process assimilates the plate with a degenerate elliptical cylinder allowing the employment of elliptical harmonics that ensure the satisfaction of the free-surface boundary condition of the front face of the steep wave, away from the plate. This assumption leads to an additional boundary value problem with mixed conditions in the vertical direction. The associated problem involves triple trigonometrical series and it is solved through a transformation into integral equations. To tackle the boundary value problem in the vertical direction a perturbation technique is employed. Extensive numerical calculations are presented as regards the variation of the velocity potential on the plate at the instant of the impact which reveals the influence of the opening. The theory is extended to the computation of the total impulse exerted on the plate using pressure-impulse theory

    Three-dimensional steep wave impact on a vertical cylinder

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    In the present study we investigate the 3-D hydrodynamic slamming problem on a vertical cylinder due to the impact of a steep wave that is moving with a steady velocity. The linear theory of the velocity potential is employed by assuming inviscid, incompressible fluid and irrotational flow. As the problem is set in 3-D space, the employment of the Wagner condition is essential. The set of equations we pose, is presented as a mixed boundary value problem for Laplace's equation in 3-D. Apart from the mixed-type of boundary conditions, the problem is complicated by considering that the region of wetted surface of the cylinder is a set whose boundary depends on the vertical coordinate on the cylinder up to the free-surface. We make some simple assumptions at the start but otherwise we proceed analytically. We find closed-form relations for the hydrodynamic variables, namely the time dependent potential, the pressure impulse, the shape of the wave front (from the contact point to beyond the cylinder) and the slamming force

    Production of Designer Mabe Pearls in the Black-lipped Pearl Oyster, Pinctada margaritifera, and the Winged Pearl Oyster, Pteria penguin, from Andaman and Nicobar Islands, India

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    The black-lipped pearl oyster, Pinctada margaritifera, is sporadically distributed in the Indo-Pacific region, where they have been traditionally used for food, ornaments, jewelry, tools, and more recently for the production of black pearls (Lane et al. 2003). During the past two decades, black pearl farming programs have been initiated by several nations and are now at various levels of productio

    Algae Drive Enhanced Darkening of Bare Ice on the Greenland Ice Sheet

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    Surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the ice sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the ice sheet. The impact of algae on bare ice darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare ice darkening, and incorporating the algal darkening effect will improve mass balance and sea level projections of the Greenland ice sheet and ice masses elsewhere

    Coibamide A Targets Sec61 to Prevent Biogenesis of Secretory and Membrane Proteins

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    Coibamide A (CbA) is a marine natural product with potent antiproliferative activity against human cancer cells and a unique selectivity profile. Despite promising antitumor activity, the mechanism of cytotoxicity and specific cellular target of CbA remain unknown. Here, we develop an optimized synthetic CbA photoaffinity probe (photo-CbA) and use it to demonstrate that CbA directly targets the Sec61 alpha subunit of the Sec61 protein translocon. CbA binding to Sec61 results in broad substratenonselective inhibition of ER protein import and potent cytotoxicity against specific cancer cell lines. CbA targets a lumenal cavity of Sec61 that is partially shared with known Sec61 inhibitors, yet profiling against resistance conferring Sec61 alpha mutations identified from human HCT116 cells su ests a distinct binding mode for CbA. Specifically, despite conferring strong resistance to all previously known Sec61 inhibitors, the Sec61 alpha mutant R66I remains sensitive to CbA. A further unbiased screen for Sec61 alpha resistance mutations identified the CbA-resistant mutation S71P, which confirms nonidentical binding sites for CbA and apratoxin A and supports the susceptibility of the Sec61 plug region for channel inhibition. Remarkably, CbA, apratoxin A, and ipomoeassin F do not display comparable patterns of potency and selectivity in the NCI60 panel of human cancer cell lines. Our work connecting CbA activity with selective prevention of secretory and membrane protein biogenesis by inhibition of Sec61 opens up possibilities for developing new Sec61 inhibitors with improved druglike properties that are based on the coibamide pharmacophore.Peer reviewe

    'Education, education, education' : legal, moral and clinical

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    This article brings together Professor Donald Nicolson's intellectual interest in professional legal ethics and his long-standing involvement with law clinics both as an advisor at the University of Cape Town and Director of the University of Bristol Law Clinic and the University of Strathclyde Law Clinic. In this article he looks at how legal education may help start this process of character development, arguing that the best means is through student involvement in voluntary law clinics. And here he builds upon his recent article which argues for voluntary, community service oriented law clinics over those which emphasise the education of students

    Multiple roles for NaV1.9 in the activation of visceral afferents by noxious inflammatory, mechanical, and human disease-derived stimuli.

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    Chronic visceral pain affects millions of individuals worldwide and remains poorly understood, with current therapeutic options constrained by gastrointestinal adverse effects. Visceral pain is strongly associated with inflammation and distension of the gut. Here we report that the voltage-gated sodium channel subtype NaV1.9 is expressed in half of gut-projecting rodent dorsal root ganglia sensory neurons. We show that NaV1.9 is required for normal mechanosensation, for direct excitation and for sensitization of mouse colonic afferents by mediators from inflammatory bowel disease tissues, and by noxious inflammatory mediators individually. Excitatory responses to ATP or PGE2 were substantially reduced in NaV1.9(-/-) mice. Deletion of NaV1.9 substantially attenuates excitation and subsequent mechanical hypersensitivity after application of inflammatory soup (IS) (bradykinin, ATP, histamine, PGE2, and 5HT) to visceral nociceptors located in the serosa and mesentery. Responses to mechanical stimulation of mesenteric afferents were also reduced by loss of NaV1.9, and there was a rightward shift in stimulus-response function to ramp colonic distension. By contrast, responses to rapid, high-intensity phasic distension of the colon are initially unaffected; however, run-down of responses to repeat phasic distension were exacerbated in NaV1.9(-/-) afferents. Finally colonic afferent activation by supernatants derived from inflamed human tissue was greatly reduced in NaV1.9(-/-) mice. These results demonstrate that NaV1.9 is required for persistence of responses to intense mechanical stimulation, contributes to inflammatory mechanical hypersensitivity, and is essential for activation by noxious inflammatory mediators, including those from diseased human bowel. These observations indicate that NaV1.9 represents a high-value target for development of visceral analgesics

    Revisiting the relevance of economic theory to hotel revenue management education and practice in the era of Big Data

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    Abstract This paper explores the role of economics in hospitality education and industry practice, with a particular focus on revenue management, and puts forward an argument for a return to the inclusion of economic theory in UK hospitality education, not seen since the 1990s. Given the increasing amounts of pricing data available to both managers and customers and the consequent market complexities now seen, developing economic literacy is demonstrated to be a crucial skill required for future hospitality graduates, allowing them to make successful revenue decisions and sense-check with confidence the decisions made by automated revenue systems. Economic literacy is defined as a balanced understanding of economic theory that can be applied in real-life business scenarios, extending beyond simple consideration of supply and demand to a mixture of neoclassical and behavioural approaches to economics
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