1,209 research outputs found

    Loose, idle and disorderly: vagrant removal in late eighteenth-century Middlesex

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    This is an Accepted Manuscript of an article published by Taylor & Francis Group in Social History on 2 October 2014, available online: https://doi.org/10.1080/03071022.2014.975943Peer reviewe

    A Potential Vorticity Theory for the Formation of Elongate Channels in River Deltas and Lakes

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    Rivers empty into oceans and lakes as turbulent sediment-laden jets, which can be characterized by a Gaussian horizontal velocity profile that spreads and decays downstream because of shearing and lateral mixing at the jet margins. Recent experiments demonstrate that this velocity field controls river-mouth sedimentation patterns. In nature, diffuse jets are associated with mouth bar deposition forming bifurcating distributary networks, while focused jets are associated with levee deposition and the growth of elongate channels that do not bifurcate. River outflows from elongate channels are similar in structure to cold filaments observed in ocean currents, where high potential vorticity helps to preserve coherent structure over large distances. Motivated by these observations, we propose a hydrodynamic theory that seeks to predict the conditions under which elongate channels form. Our approach models jet velocity patterns using the flow vorticity. Both shearing and lateral spreading are directly related to the vertical component of vorticity. We introduce a new kind of potential vorticity that incorporates sediment concentration and thus allows study of jet sedimentation patterns. The potential vorticity equation reduces the number of fluid momentum equations to one without losing generality. This results in a compact analytical solution capable of describing the streamwise evolution of the potential vorticity of a sediment-laden jet from initial conditions at the river mouth. Our theory predicts that high potential vorticity is a necessary condition for focused levee deposition and the creation of elongate channels. Comparison to numerical, laboratory, and field studies indicates that potential vorticity is a primary control on channel morphology. Our results may be useful for designing river delta restoration schemes such as the proposed Mississippi Delta diversion

    Vagrant Lives: 14,789 Vagrants Processed by the County of Middlesex, 1777-1786

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    Date of Acceptance: 12/09/2015 © 2015 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License (CC-BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedThis dataset makes accessible the uniquely comprehensive records of vagrant removal from, through, and back to Middlesex, encompassing the details of some 14,789 removals (either forcibly or voluntarily) of people as vagrants between 1777 and 1786. It includes people ejected from London as vagrants, and those sent back to London from counties beyond. Each record has been georeferenced (where possible). Significant background material is available on the ‘London Lives’ website, which provides additional context for these records. The authors also recommend the following article: Hitchcock, T, Crymble, A, Falcini, L 2014 Loose, Idle and Disorderly: Vagrant Removal in Late Eighteenth-Century Middlesex. Social History 39(4). DOI: 10.1080/03071022.2014.975943.Peer reviewe

    Modeling anomalous heat diffusion: Comparing fractional derivative and non-linear diffusivity treatments

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    In the Fourier heat conduction equation, when the flux definition is expressed as the product of a constant diffusivity and the temperature gradient, the characteristic length scale evolves as the square root of time. However, if we replace the 1 st order transient and gradient terms in the Fourier equation with fractional derivatives and/or define a non-linear spatially dependent diffusivity, it is possible to generate an anomalous space-time scaling, i.e., a scaling where the time exponent differs from the expected value of 1/2 . To compare and contrast the possible consequences of using fractional calculus along with a non-linear flux, we investigate a space-time fractional heat diffusion equation that involves a non-linear diffusivity. Following presentation of the governing non-linear fractional equation, we arrive at a space-time scaling that accounts for the combined anomalous contributions of memory (fractional derivative in time), non-locality (fractional derivative in space), and a non-linear diffusivity. We demonstrate how this scaling can manifest in a physical setting by considering the analytical solution of a non-linear fractional space-time diffusion equation, a limit case Stefan problem related to moisture infiltration into a porous media. A direct physically realizable simulation of this process shows how the anomalous space-time scaling is explicitly related to measures of both the memory and non-linearity in the system. Overall, the findings from this work clearly show how the definition of a non-linear diffusivity might contribute to anomalous diffusion behavior and suggests that, in modeling a particular observation, the roles of fractional derivatives and a suitably defined non-linear diffusivity are interchangeable.SEV-2013-0323 BERC.2014–201

    The role of Internal Solitary Waves on deep-water sedimentary processes. The case of up-slope migrating sediment waves off the Messina Strait

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    Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary “current” that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities

    Captive rearing technologies and survival of pheasants (Phasianus colchicus L.) after release

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    Studies have repeatedly emphasized the limited survival of pheasants reared using traditional methods compared to the wild one. For this reason we performed a field trial to compare survival rates, home ranges and habitat uses of pheasants artificial hatched and reared (traditional method) with pheasants artificial hatched and reared by fostering mothers (hens). A total of 117 artificially hatched pheasants, 57 artificially brooded after hatch and 60 brooded by fostering hens, were equipped with a radio necklace tag or a poncho tag. Both groups were localized two-three times a week after their release in the wild. The survival rates of the brooded-by-hen pheasants showed an improvement of survival rates, either poncho or radio tagged (P<0.05), 90.0% vs 57.1% and 35.0% vs 21.1%, respectively. The average maximum dispersion was 390 and 426 m and the home range were 12.0 and 11.6 ha in artificially brooded and brooded-by-hen pheasants, respectively. The land use showed that the woods were less represented than the available in the home range of every pheasant. For this reason the woods can be reduced in the agricultural areas interspersed with natural Mediterranean vegetation

    A generalized Stefan model accounting for system memory and non-locality

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    The Stefan problem, involving the tracking of an evolving phase-change front, is the prototypical example of a moving boundary problem. In basic one- dimensional problems it is well known that the front advances as the square root of time. When memory or non-locality are introduced into the system however, this classic signal may be anomalous; replaced by a power-law advance with a time exponent that differs from n = 1/2. Up to now memory treatments in Stefan problem models have only been able to reproduce sub-diffusive front movements with exponents n 1/2. In the present paper, using a generalized Caputo fractional derivative operator, we introduce new memory and non-local treatment for Stefan problems. On considering a limit case Stefan problem, related to the melting problem, we are able to show that, this gen- eral treatment can not only produce arbitrary power-law in time predictions for the front movement but, in the case of memory treatments, can also produce non-power-law anomalous behaviors. Further, also in the context of the limit problem, we are able to establish an equivalence between non-locality and a space varying conductivity and memory and a time varying conductivity

    Ephemeral Londoners: Modelling Lower Class Migration to Eighteenth Century London

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    Between 1750 and 1801 the population of London grew from approximately 750,000 to 1.1 million people. Relocating to London in the eighteenth century only occasionally generated a paper trail, but a significant number of failed migrants were rounded up for ‘wandering and begging’ on the streets and sent back from whence they came to their parish of legal settlement. Records of these removals have been digitised and are used in this paper to model migration into London, to throw light onto the patterns of movement at this time

    La escuela de artes

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    La Escuela de artes es una institución moderna que, creada para responder a necesidades actuales, utiliza los progresos de la ciencia y consulta, en sus medios de acción, viejas experiencias del pasado. De ahí, que su última expresión se refiera de continuo a las célebres corporaciones de oficios y a las "bottegas" florentinas del renacimiento. (Párrafo extraído del texto a modo de resumen)Facultad de Humanidades y Ciencias de la Educació
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