966 resultados para Pryor, Roger A. (Roger Atkinson), 1828-1919.


Relevância:

20.00% 20.00%

Publicador:

Resumo:

On the Qinghai-Tibet plateau increased livestock numbers have resulted in degradation of the grasslands with potential impacts on native biodiversity. Concurrently, perceived increases in populations of native small mammals such as plateau pikas (Ochotona curzoniae) have led to poisoning programs, with uncertain impacts on species such as ground-nesting birds. We explored the relationships between the local seasonal abundance of small birds and (1) the density of pika burrows; (2) livestock grazing practices; and (3) local poisoning of pikas. Around Naqu prefecture, central Tibet, we used a nested experimental design to collect data from areas rested from grazing over summer, nearby areas with year-round grazing and areas subjected to pika poisoning. Additional data were collected from a site where grazing had not occurred for at least 4 years prior to the study. Poisoning pikas in spring had no detectable effect on the local abundance of birds the following autumn. However, two ground-nesting species, white-rumped and rufous-necked snowfinches, showed positive associations with the density of pika burrows, indicating that long-term 'pika poisoning could reduce the density of these species by reducing the density of pika burrows. Rufous-necked snowfinches and non ground-nesting species including horned larks and common hoopoes showed positive responses to reduced grazing pressure from livestock, particularly in the long-rested site, indicating current grazing levels could be having a negative impact on these species. Conservation of small passerine biodiversity in this system will require changed management practices for livestock and pikas that consider the complex three-way interaction between livestock grazing, pikas and small birds. (C) 2008 Elsevier Ltd. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

1. Plateau pikas Ochotona curzoniae are considered a pest species on the Tibetan Plateau because they compete with livestock for forage and their burrowing could contribute to soil erosion. The effectiveness of pest control programmes in Tibet has not been measured, and it is not known whether changes in livestock management have exacerbated problems with plateau pikas or compromised their control. This study measured the impact of control programmes and livestock management for forage conservation on populations of plateau pikas in alpine meadow in Naqu District, central Tibet, during 2004 and 2005.2. Current techniques for controlling plateau pikas in spring cause large reductions in abundance, but high density-dependent rates of increase result in no differences between treated and untreated populations by the following autumn. Rates of increase from spring to autumn are not influenced by standing plant biomass or concurrent grazing by yaks Bos grunniens and Tibetan sheep Ovis aries.3. In autumn there was significantly lower biomass outside fenced areas with year-round livestock grazing compared with inside fenced areas with equivalent or higher numbers of plateau pikas but predominantly winter grazing by livestock. Inside fenced areas, control of plateau pikas in spring produced no detectable effect on standing plant biomass at the end of the following summer compared with uncontrolled populations of plateau pikas.4. Regardless of their initial density, populations of plateau pikas declined rapidly over winter outside fenced areas where there was very low standing plant biomass in autumn. However, inside fenced areas with higher plant biomass in autumn, low-density populations of plateau pikas declined more slowly than high-density populations.5. Synthesis and applications. Current control programmes have limited effect because populations of plateau pikas can recover in one breeding season. There was no apparent increase in forage production in areas where plateau pikas were controlled. However, plateau pikas appear to benefit from changes in grazing management, with low-density populations declining less over winter inside fenced areas than elsewhere. It was not evident that control programmes are warranted or that they will improve the livelihoods of Tibetan herders.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The addition of reducible metal oxides as promoters shows a positive effect on the catalytic behavior of lanthanum vanadate (LaVO4). A C3H6 yield increase of 6.5% is observed at 500 degreesC on molybdenum-promoted LaVO4, which can be attributed to the change of the redox properties, the blocking of the strong oxidation sites of the catalysts and to an increase of the accessibility of the labile oxygen toward the reactant. The influence of the catalyst preparation method and of the Mo loading as well as the additional promoting effect of CO2 in the gas feed was also examined.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The oxidative dehydrogenation (ODH) of propane was investigated on Ni-V-O catalysts in a wide range of vanadium contents (5-40%). The addition of a small amount of vanadium significantly increased the catalytic activity of NiO for oxidative dehydrogenation of propane to propene. The formation of propene has a good correlation with the coexistence of NiO and Ni3V2O8. This result strongly suggests that a synergetic effect exists between them in NiXV1-XOY (X = 0.95 to 0.6). The best results were obtained with a high Ni/V ratio (e.g. X = 0.95 to 0.85). The active sites and selective oxygen species are discussed. The influence of the catalyst preparation technique and the redox properties of the catalyst were also examined.

Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A cellular automaton is an iterative array of very simple identical information processing machines called cells. Each cell can communicate with neighboring cells. At discrete moments of time the cells can change from one state to another as a function of the states of the cell and its neighbors. Thus on a global basis, the collection of cells is characterized by some type of behavior. The goal of this investigation was to determine just how simple the individual cells could be while the global behavior achieved some specified criterion of complexity ??ually the ability to perform a computation or to reproduce some pattern. The chief result described in this thesis is that an array of identical square cells (in two dimensions), each cell of which communicates directly with only its four nearest edge neighbors and each of which can exist in only two states, can perform any computation. This computation proceeds in a straight forward way. A configuration is a specification of the states of all the cells in some area of the iterative array. Another result described in this thesis is the existence of a self-reproducing configuration in an array of four-state cells, a reduction of four states from the previously known eight-state case. The technique of information processing in cellular arrays involves the synthesis of some basic components. Then the desired behaviors are obtained by the interconnection of these components. A chapter on components describes some sets of basic components. Possible applications of the results of this investigation, descriptions of some interesting phenomena (for vanishingly small cells), and suggestions for further study are given later.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Este trabalho teve como objetivo calcular a uniformidade de irrigaão para sistema de irrigaão por aspersão do tipo canhão hidráulico submetido a vários espaamentos em campo. Foi conduzido na propriedade hidroagrícola Lagoa do Ouro, no Município de Jequié, Bahia. O aspersor utilizado é do tipo canhão hidráulico, Plona-PLN 25. Foram utilizados 80 coletores no campo espaados de 6 (m) para coleta das lâminas de água (mm). A evapotranspiraão potencial da cultura foi medida a partir do tanque classe "A" instalado na propriedade. Os maiores valores apresentados de coeficientes de uniformidade CUC e CUD foram de 78% e 71% respectivamente para o espaamento de 36x36 m; e os menores, 67% e 30% para o espaamento 42x42 m.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urquhart, C., Light, A., Thomas, R., Barker, A., Yeoman, A., Cooper, J., Armstrong, C., Fenton, R., Lonsdale, R. & Spink, S. (2003). Critical incident technique and explicitation interviewing in studies of information behavior. Library and Information Science Research, 25(1), 63-88. Sponsorship: JISC (for JUSTEIS element)

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urquhart, C., Lonsdale, R.,Thomas, R., Spink, S., Yeoman, A., Armstrong, C. & Fenton, R. (2003). Uptake and use of electronic information services: trends in UK higher education from the JUSTEIS project. Program, 37(3), 167-180. Sponsorship: JISC

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urquhart,C., Thomas, R., Spink, S., Fenton, R., Yeoman, A., Lonsdale, R., Armstrong, C., Banwell, L., Ray, K., Coulson, G. & Rowley, J. (2005). Student use of electronic information services in further education. International Journal of Information Management, 25(4), 347-362. Sponsorship: JISC

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urquhart, C., Spink, S., Thomas, R., Yeoman, A., Durbin, J., Turner, J., Fenton, R. & Armstrong, C. (2004). Evaluating the development of virtual learning environments in higher and further education. In J. Cook (Ed.), Blue skies and pragmatism: learning technologies for the next decade. Research proceedings of the 11th Association for Learning Technology conference (ALT-C 2004), 14-16 September 2004, University of Exeter, Devon, England (pp. 157-169). Oxford: Association for Learning Technology Sponsorship: JISC

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urquhart, C., Spink, S., Thomas, R., Yeoman, A., Durbin, J., Turner, J., Fenton, R. & Armstrong, C. (2004). JUSTEIS: JISC Usage Surveys: Trends in Electronic Information Services Final report 2003/2004 Cycle Five. Aberystwyth: Department of Information Studies, University of Wales Aberystwyth. Sponsorship: JISC

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Bonthron, Karen; Urquhart, Christine; Thomas, Rhian; Armstrong, Chris; Ellis, David; Everitt, Jean; Fenton, Roger; Lonsdale, Ray; McDermott, Elizabeth; Morris, Helen; Phillips, Rebecca; Spink, Sian, and Yeoman, Alison. (2003, June). Trends in use of electronic journals in higher education in the UK - views of academic staff and students. D-Lib Magazine, 9(6). Retrieved September 8, 2006 from http://www.dlib.org/dlib/june03/urquhart/06urquhart.html This item is freely available online at http://www.dlib.org/dlib/june03/urquhart/06urquhart.html Sponsorship: JISC

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Urquhart, C. (editor for JUSTEIS team), Spink, S., Thomas, R., Yeoman, A., Durbin, J., Turner, J., Armstrong, A., Lonsdale, R. & Fenton, R. (2003). JUSTEIS (JISC Usage Surveys: Trends in Electronic Information Services) Strand A: survey of end users of all electronic information services (HE and FE), with Action research report. Final report 2002/2003 Cycle Four. Aberystwyth: Department of Information Studies, University of Wales Aberystwyth with Information Automation Ltd (CIQM). Sponsorship: JISC

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Scully, Roger, Becoming Europeans? Attitudes, Roles and Socialisation in the European Parliament (Oxford: Oxford University Press, 2005), pp.vii+168 RAE2008