2,009 research outputs found
Impact of temperature on an emerging parasitic association between a sperm-feeding scuticociliate and Northeast Pacific sea stars
No full textGlobal warming has important implications for the dynamics and ecological impacts of emerging diseases. We investigated temperature effects on scuticociliate, Orchitophrya cf. stellarum, infections in ripe testes of two Pacific northeast sea stars (Asterina miniata Brandt and Pisaster ochraceus Brandt) using laboratory and field approaches. We predicted that a small increase in temperature would result in higher ciliate growth rates and heightened infection intensities. To test this we (1) cultured free-living O. stellarum at 10 and 15 °C and quantified ciliate abundance after 3 days, and (2) housed sea stars of both species at 10 and 15 °C for durations varying from 4 to 21 days and then measured the infection intensity. Ciliate densities in cultures were two orders of magnitude higher in the warmer treatment. Infection intensity was also temperature sensitive: greater proportions of testes were infected and infection stage was more advanced at 15 versus 10 °C, leading to a reduction in spermatozoa and regression of the germinal layer within three weeks. In seven field populations surveyed, we found a tight linear correlation between infection prevalence (percent infected sea stars) and infection intensity (proportion of infected testes per individual and mean infection score). However, 45% of P. ochraceus testes exhibited heavy infections versus 8% of A. miniata testes, which may relate to the different thermal habitat of each species: P. ochraceus occurs higher on the shore and likely reaches higher body temperatures at low tide. While the sex ratio of A. miniata is unbiased, P. ochraceus populations are consistently female-biased and show no relationship to infection prevalence (ranged from 30 to 90%). O. cf. stellarum infections of testes of both sea stars are prevalent in field populations, are highly temperature sensitive, and lead to rapid loss of reproductive potential
The synthesis of monodisperse alkanes with long chains
No full textThis thesis discusses reasons for the interest in monodisperse long chain alkanes and describes attempts, past and present, to synthesise such molecules. Chapter 1 discusses why the synthesis of such molecules are important and the objectives of this project. Chapter 2 reviews the methods previous groups have devised to prepare pure samples of long chain alkanes. In particular, work carried out by Whiting et al. at Bristol, whose scheme formed the basis of the early work in Durham. Chapter 3 describes the work in Durham and improvements which were made to Whiting's method, allowing the synthesis of longer chain lengths and greater quantities of materials to be achieved. Chapter 4 provides a summary of the practical work carried out by the author. Chapter 5 gives experimental details of the work described in Chapter 4
Microstructure Development during Solidification of Aluminium Alloys
No full textThis Thesis demonstrates studies on microstructure development during the solidification of aluminium alloys. New insights of structure development are presented here. Experimental techniques such as quenching and in-situ High-brilliance X-ray microscopy were utilized to study the microstructure evolution during solidification.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin
Sliding-mode control in systems with output time delay
No full textThe main features of sliding-mode control (SMC) and the associated feedback control law of Variable Structure Control (VSC) systems will be summarized in this chapter. SMC is a well-known solution to the problem of the deterministic control of uncertain systems, since it yields invariance to a class of parameter variations [4,7,33-36,43]. The characterizing feature is sliding motion, which occurs when the system state repeatedly crosses certain subspaces, or sliding hyperplanes, in the state space. A sliding controller may comprise nonlinear and linear parts, and has been well studied in the literature
D.G. Ritchie's ethics
No full textThe British idealists of the late 19th and early 20th century are best known for their contribution to metaphysics, logic, and political philosophy. Yet they also made important contributions to social and public policy, social and moral philosophy and moral education, as shown by this volume.book chapterpublished
Painting in Poetry and Poetry in Painting: Aesthetic Reflections in D.G. Rossetti
No full textBright eyed and bushy-tailed poems and paintings are very rare, so are their past masters who create them. The history of the world literature is often brimming with such rare authors as are the unparalleled amalgamator of paintings and writings. In this field, the names, which are counted highly with boundless esteem, are of William Blake, Lewis Carroll, Hans Christian Andersen, Elizabeth Bishop, Leo Tolstoy, Lorraine Hansberry, Victor Hugo, Sylvia Plath, George Sand, Jack Kerouac, Herman Hesse, Gunter Grass, Charles Bukowski, Henry Miller, William S. Burroughs, E.E. Cummings, Tennessee Williams, Carlo Levi, J.B. Priestley, and R.N. Tagore. Undisputedly, D.G. Rossetti is one such figure. When the world literature is deconstructed, two clusters of the authors appear on the literary landscape. The first cluster consists of those authors who are painters and writers as well. The painters who have painted the literary pieces of the authors fall into the second cluster. D.G. Rossetti somewhere stands in- between. He is painter (especially illustrator) as well author-poet. But the flabbergasting certitude is that his elite poetry is found in his pieces of mural, and his elite mural in his pieces of poesy. His all creations, be they paintings, or poems, fall in three categories. In the first faction fall such pieces of his poems as are only poems—without any illustration, in the second faction fall such pieces of his paintings as are without poems, while in the third faction fall such pieces of his paintings as are with poems, or with mythical illustrations, or on certain literary pieces. Nothing to say about these groups, but one thing is clear that all of them possess aesthetic reflections. Keeping this very fact in mind, the present article aims at exploring, analyzing, and presenting the three-dimensional view in Rossetti painting and poetry with the help of the textual analysis, visual methods, and descriptive and explorative approach
Classifying sediments on Dutch riverbeds using multi-beam echo-sounder systems
No full textThe economic importance of the Dutch rivers is very high as they are heavily used for inland waterway transport between the Netherlands and their neighbouring countries. A minimum depth must be guaranteed to keep the rivers navigable but also to ensure that the ships can carry maximum cargo. An attractive system for obtaining information about the riverbed bathymetry is the multi-beam echo-sounder (MBES). Furthermore, the MBES received echoes due to acoustic backscatter from the sediments in theory also allow for discriminating between different sediments. The aim of the research presented in this thesis was to develop methods for discriminating between different river sediments using MBES measurements. In order to fulfil this aim, MBES surveys were performed in the Rhine river and the Meuse river between 2007 and 2010. The research shows that indeed the MBES system can be used for discriminating between the different sediments present in the river areas. In addition an important finding is that areas differing in sediment type require different classification approaches.Air Transport and OperationsAerospace Engineerin
Aircraft noise calculation and synthesis in a non-standard atmosphere
No full textThe atmosphere modifies the emitted sound waves of an aircraft during propagation and is therefore important in the calculation of noise contours or synthesis. Noise contours present the resulting noise levels on the ground and are, as such, often applied for regulatory purposes. Aircraft noise synthesis is a technique that allows to transform a calculated prediction into audible sound that can be experienced in a virtual reality environment. Noise synthesis techniques allow people to be subjected to aircraft, routes or procedures that are still being designed. This dissertation describes recent research to improve the modeling of atmospheric propagation effects in aircraft noise contours as well as aircraft noise synthesis. Multi-event noise contours are usually calculated with standardized models that take non-standard propagation into account in an empirical fashion. A propagation algorithm was developed to augment such a model. Signal processing steps can be applied to transform a source noise prediction into an audible result. Furthermore, such steps can be utilized to apply propagation effects to a source noise signal. For a non-standard atmosphere this is not trivial. The role of a non-standard atmosphere is described by a dedicated simulation framework developed in this dissertation. The framework is applied to a flyover to demonstrate the effects associated with multiple ray paths and shadow zones. Besides demonstrating non-standard atmospheric effects, the framework was used to create synthesized results of actual flyovers near an airport. Subsequently, a comparison between measured results and synthesized results was executed. Furthermore, a method was designed to include the effect of turbulence-induced coherence loss of the direct and ground reflected ray in noise synthesis.Aircraft Noise & Climate EffectsAerospace Engineerin
“Dangerous modernity!”, or the shadow play of modernity and its characters: instrumental rationality — money — technology (Part 2)
No full textThe article is the second part of the essay on the phenomenon of alienation and its forms in modern societies (the first part was published in 2021, No. 4). In this part, the author focuses on technology as ‘fetishized’ by the modern thinking and on various manifestations of alienation in labor, which are not only (and not so much) a consequence of private ownership of the ‘means of production’ (according to Marx), but also a by-product of objective tendencies of social differentiation as aggravated in the course of historical development (division of labor) and the subordination of most spheres of the modern social experience to the logic of instrumental rationality. Excessive specialization, standardization, algorithmization, routinization of activities, technological and functional operationalization of the work process and professional roles, the dominance of means over goals, administrative and bureaucratic regulation and control have become ‘signs of the time’ and distinctive features of the ‘rhythm of activity’ not only in industrial enterprises, but also in non-physical labor. An important aspect (and a background circumstance) in the diagnosis of modernity is the fact that in recent centuries, modern societies have developed mainly in the urban social-ecological environment. The format and style of urban life with its role-based fragmentation and specific depersonification (and an increase in anonymity) also provoked a range of consequences that make alienation a challenge for modern societies. The author uses the concepts of classical sociological theory as a key tool for analyzing and describing the ‘universe of modernity’, and refers to the ideas of M. Weber, G. Simmel, L. Wirth, H.M. McLuhan, H. Marcuse, G. Friedmann, С. Lefort and others. © D.G. Podvoyskiy, 2022
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