1,688 research outputs found
On non-equilibrium and nomadism : knowledge, diversity and global modernity in Drylands (and beyond…)
No full textDrylands worldwide, together with the variously nomadic peoples who live there, are associated with the incidence of poverty and environmental degradation. Corresponding assertions of pending social and ecological collapse have paved the way for hegemonic development and policy interventions focusing on the settlement of formerly mobile populations, reductions of livestock numbers, land privatisation and shifts towards commercial and tightly regulated production. Despite the wealth of expertise and monetary resources involved, however, these initiatives have rarely been successful, either in socio-economic or environmental terms. Our aim in this paper is to engage critically with both the conceptual underpinnings and empirical consequences of a globalising modernity as these have played out in dryland environments, and in relation to practices of mobility amongst the peoples who such environments are associated. We draw on a debate that exists in ecology regarding the sources and types of dynamic behaviour driving ecological systems. Drylands have become a particular focus of this debate. In these environments extreme and unpredictable variability in rainfall are considered (by some) to confer non-equilibrium dynamics by continually disrupting the tight consumer-resource relations that would otherwise pull the components of the system towards equilibrium. This implies that livestock grazing in drylands, widely thought to cause degradation and ‘desertification’ through detrimental management practices including mobility and the maximising of herd reproductive rates, in fact might not be causing irreversible ecological change. Or at least not through exceeding a density-dependent equilibrial relationship with forage availability. We attempt to extend discussion by thinking through the cultural and historical contexts leading to a particular ‘shoehorning’ of the dynamics associated with non-equilibrium and nomadism into a conceptual framework that emphasises the desirability of stability, equilibrium and predictability. In doing so, we draw on the explanatory power of theories of conceptual and ritual purification (associated with anthropologist Mary Douglas); of the empowered panopticon society with its requirements for diffuse and minutely controlled surveillance and regulation (cf. Foucault), and of the ideological differences between State and Nomad science as considered by philosophers Gilles Deleuze and Félix Guattari
Dissolved organic nitrogen in the river test and estuary
No full textStudies of nutrients in rivers and estuaries have generally focused on dissolved inorganic nitrogen (DIN), although this accounts for only a part of the total nitrogen (TN) in these systems. Dissolved organic nitrogen (DON) has not yet been fully considered as a factor contributing to the nitrogen pool in aquatic systems. Advances in the analytical determination and characterisation of DON have identified that it is potentially biologically available to phytoplankton and bacteria. Very few studies of DON have been conducted on UK rivers and estuaries therefore little is known of the concentrations, proportion of TN, seasonal variations and DON load entering estuarine waters from riverine sources.An 18 month survey of the lower reaches of the River Test and upper estuary were conducted between July 2001 and December 2002 to investigate the temporal variation in nutrient concentrations. DON concentrations up to 152 µM were measured in saline samples and concentrations of up to 100 µM were recorded in freshwater samples from the River Test. DON was the second largest TN component, contributing up to 7 % of TN in the river and 13 % of TN in the upper Test estuarine waters.DON showed no apparent relationship with season, flow or salinity, whereas dissolved organic carbon (DOC) concentration showed some seasonal changes. Concentrations of DON were reduced by tidal salt marshes and sewage treatment works were a source of DOC to the river. The estimated DON load entering the Test estuary in 2002 was 1.9 x 104 mol km-2 yr-1, one order of magnitude lower than the nitrate load. The DON area-normalised load was in good agreement with other UK river systems.The assimilation of different molecular size fractions of DON and DOC by bacteria was investigated in water collected from the lower reaches of the river. A combination of ultrafiltration and bacterial bioassays showed that the DON and DOC pools were made up of a range of molecular size classes but these did not appear to influence the growth of freshwater bacteria
Optical and electronic properties of bismuth-implanted glasses
No full textPhotoluminescence (PL) and excitation spectra of Bi melt doped oxide and chalcogenide glasses are very similar, indicating the same Bi center is present. When implanted with Bi, chalcogenide, phosphate and silica glass, and BaF2 crystal all display characteristically different PL spectra to when Bi is incorporated by melt-doping. This indicates that ion implantation is able to generate Bi centers which are not present in samples whose dopants are introduced during melting. Bi-related PL bands have been observed in glasses with very similar compositions to those in which carrier-type reversal has been observed, indicating that these phenomena are related to the same Bi centers, which we suggest are interstitial Bi2+ and Bi clusters
Intermixing in GaAsSb/GaAs single quantum wells
No full textCopyright 1998 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 84, 4017 (1998) and may be found at
Interdiffusion in InGaAs/GaAs: The effect of growth conditions
No full textCopyright 1998 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 84, 232 (1998) and may be found at
Low temperature growth of gallium nitride
No full textW.T. Young, S.R.P. Silva, J.V. Anguita, J.M. Shannon, K.P. Homewood, B.J. Seal
Structural and optical properties of beta-FeSi(2) layers grown by ion beam mixing
No full textThis study deals with structural and optical properties of beta-FeSi(2) layers produced by direct ion beam mixing of Fe/Si bilayers with Xe ions. By irradiation of 35 nm Fe on Si, at 600 degreesC with 205 keV Xe to 2 X 10(16) ions/cm(2), the formation of similar to 105 nm single-phase beta-FeSi(2) layers was achieved. Their structures were analyzed by Rutherford backscattering spectroscopy, X-ray diffraction, conversion electron Mossbauer spectroscopy, high resolution transmission electron microscopy, and photo-absorption. The structural analyses revealed that the beta-FeSi(2) layers grow in the form of irregularly shaped crystal grains, with a pronounced surface morphology, but with a rather sharp silicide/silicon interface. The grains that originate from the interface are epitaxially oriented relative to the Si(100) substrate. Optical absorption, as compared with that in beta-FeSi(2) layers produced by ion beam synthesis or co-sputter deposition, indicates a direct band gap of 0.92 eV A pronounced surface roughness of the ion beam mixed layers yielded photo-absorption approximately three times higher as compared with the other two sets of samples. The band gap stays nearly constant over the temperature range from 80 to 295 K. This is tentatively assigned to a high degree of structural disorder and stress induced in the ion beam mixed beta-FeSi(2) layers. (C) 2002 Elsevier Science B.V. All rights reserved.12th International Conference on Surface Modification of Materials by Ion Beams, Sep 09-14, 2001, MARBURG, German
A Comparison Between Recent and Prospective Critical Success Factors in Lithuanian Printing Industry
No full textThe paper looks into the problem of identifying critical success factors in an industry. Though by definition all business organisations aim to be successful, companies within an industry differ a lot as regards their level of success. What makes some firms highly successful, when others have rather moderate success within the same industry? Can the above problems be explained by the wrong choice of strategic alternatives or inadequate strategy implementation? An empirical research of the Lithuanian printing industry was carried out with the purpose of identifying and differentiating the dominant success factors that are critical for the creation of competitive advantages.critical success factors, sustainable competitive advantage, printing industry
In-migrants and exclusion in east African rangelands: access, tenure and conflict
No full textEast African rangelands have a long history of population mobility linked to competition over key resources, negotiated access, and outright conflict. Both in the literature and in local discourse, in-migration is presented as leading to increased competition, driving poverty and social exclusion on the one hand, and conflict and violence on the other. Current analyses in developing countries identify economic differences, ethnic fault lines, ecological stresses and a breakdown in state provision of human and constitutional rights as factors in driving conflict. The present paper explores this interaction of in-migration and conflict with respect to Kenyan and Tanzanian pastoralist areas and populations. Using quantitative and qualitative methods, patterns of resource access and control in Kenya and Tanzania Maasailand are explored in terms of the ways land and livestock are associated with migration status, ethnicity and wealth or political class. Contrasts and similarities between the two national contexts are used to develop a better understanding of the ways these factors operate under different systems of tenure and access. The conclusion briefly considers implications of these patterns, their potential for exacerbating poverty, and policies for minimising social exclusion and conflict in East African rangelands. / Abstract in French: Les prairies d'Afrique orientale connaissent depuis longtemps une mobilité des populations, liée aux problèmes de concurrence pour les ressources clés, d'accès négocié et de conflits pures et simples. Dans la littérature comme dans le discours local, l'immigration interne est présentée comme cause de concurrence accrue, motrice de pauvreté et d'exclusion sociale d'une part, et de conflit et de violence d'autre part. Des analyses menées actuellement dans les pays en développement identifient comme facteurs moteurs de conflit des écarts économiques, des failles ethniques, des tensions écologiques et une détérioration des droits humains et constitutionnels. Cet article examine l'interaction entre immigration interne et conflit au sein des régions et populations pastorales du Kenya et de la Tanzanie. Il utilise des méthodes quantitatives et qualitatives pour étudier les modèles d'accès et de contrôle des ressources dans le pays masaï du Kenya et de la Tanzanie en termes d'association des terres et du bétail au statut d'immigration, à l'ethnicité et à la catégorie de richesse ou politique. Les contrastes et similarités entre les deux contextes nationaux servent à mieux comprendre le mode de fonctionnement de ces facteurs dans des régimes fonciers et systèmes d'accès différents. La conclusion examine brièvement les implications de ces modèles, leur capacitéà exacerber la pauvreté et les politiques de minimisation de l'exclusion sociale et des conflits dans les prairies d'Afrique orientale
The optical properties of β-FeSi2 fabricated by ion beam assisted sputtering
No full textβ-FeSi2 has been shown to have a minimum direct band gap of 0.87 eV [T.D. Hunt, K.J. Reeson, K.P. Homewood, S.W. Teon, R.M. Gwilliam, B.J. Sealy, Nucl. Instr. and Meth. B 84 (1994) 168-171] which leads to the opportunity for Si based opto-electronics, optical communications and optical interconnects. Electroluminescence has been reported from structures containing β-FeSi2, which were produced by high dose ion implantation and annealing [D. Leong, M.A. Harry, K.J. Reeson, K.P. Homewood, Nature 387 (12 June 1987) 686]. In this paper we report the formation of β-FeSi2 by ion beam assisted co-sputtering of Fe and Si in varying percentages. The layers were deposited with a varying Fe/Si ratio, with a Si capping layer applied to prevent oxidation. Separate regions of the sample were investigated at room temperature using optical absorption, to measure the band gap values. Absorption under the fundamental edge was also analysed at room temperature. Further investigations looked at the temperature dependence of the band gap and the absorption under the fundamental edge. The results showed that a variety of Fe/Si ratios produced β-FeSi2, the formation of which was ascertained by the presence of a suitable band gap value [0.83-0.88 eV]. Absorption under the fundamental edge was shown to follow an exponential Urbach tail [C.H. Grein, S. John, Phys. Rev. B 39 (1989) 1140]. The temperature measurements are in good agreement with the Einstein model.</p
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