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201.
202.
Kevin Ward 《Geoforum》2005,36(2):223-240
According to local economic and political commentators, Manchester's economy is booming. Employment is growing, investment is on the up, people are moving back into the city centre, and in 2002 the city hosted the largest multi-sporting event to be held in England since the 1948 Olympics. Local economic and political actors point to the wave of economic optimism that has accompanied the `entrepreneurial turn' performed in the late 1980s by the city's political institutions. As part of this, emphasis switched away from Manchester's industrial past and to its possible post-industrial futures. The city council stopped talking defensively--about `defending jobs'--and begun to talk about `making things happen'. New-style political strategies focused on raising the profile of the city, through sustained marketing strategies aimed at selling Manchester as a flexible, twenty-first century consumer-orientated city, despite the loss of 90,000 jobs between 1991 and 1997 and the profound restructuring of the city's economic base. As part of this contradictory process of politically talking up the economy while it has struggled to perform, this paper argues that the conditions have been created in which Manchester's temporary staffing industry has been able to thrive. The first English city to regulate the earliest incarnation of temporary staffing agencies, employment bureaux, and hence with a long established `industry' as such, this paper exams the newly re-energised Manchester temporary staffing industry, and sets out some of the ways in which it is restructuring. 相似文献
203.
Dylan J. Ward James A. Spotila Gregory S. Hancock John M. Galbraith 《Geomorphology》2005,72(1-4):54-72
The New River crosses three physiogeologic provinces of the ancient, tectonically quiescent Appalachian orogen and is ideally situated to record variability in fluvial erosion rates over the late Cenozoic. Active erosion features on resistant bedrock that floors the river at prominent knickpoints demonstrate that the river is currently incising toward base level. However, thick sequences of alluvial fill and fluvial terraces cut into this fill record an incision history for the river that includes several periods of stalled downcutting and aggradation. We used cosmogenic 10Be exposure dating, aided by mapping and sedimentological examination of terrace deposits, to constrain the timing of events in this history. 10Be concentration depth profiles were used to help account for variables such as cosmogenic inheritance and terrace bioturbation. Fill-cut and strath terraces at elevations 10, 20, and 50 m above the modern river yield model cosmogenic exposure ages of 130, 600, and 600–950 ka, respectively, but uncertainties on these ages are not well constrained. These results provide the first direct constraint on the history of alluvial aggradation and incision events recorded by New River terrace deposits. The exposure ages yield a long-term average incision rate of 43 m/my, which is comparable to rates measured elsewhere in the Appalachians. During specific intervals over the last 1 Ma, however, the New River's incision rate reached 100 m/my. Modern erosion rates on bedrock at a prominent knickpoint are between 28 and 87 m/my, in good agreement with rates calculated between terrace abandonment events and significantly faster than 2 m/my rates of surface erosion from ancient terrace remnants. Fluctuations between aggradation and rapid incision operate on timescales of 104− 105 year, similar to those of late Cenozoic climate variations, though uncertainties in model ages preclude direct correlation of these fluctuations to specific climate change events. These second-order fluctuations appear within a longer-term signal of dominant aggradation (until 2 Ma) followed by dominant incision. A similar signal is observed on other Appalachian rivers and may be the result of sediment supply fluctuations driven by the increased frequency of climate changes in the late Cenozoic. 相似文献
204.
S. E. Palo M. E. Hagan C. E. Meek R. A. Vincent M. D. Burrage C. McLandress S. J. Franke W. E. Ward R. R. Clark P. Hoffmann R. Johnson D. Kürschner A. H. Manson D. Murphy T. Nakamura Yu. I. Portnyagin J. E. Salah R. Schminder W. Singer T. Tsuda T. S. Virdi Q. Zhou 《Annales Geophysicae》1997,15(9):1123-1141
The Global-Scale Wave Model (GSWM) is a steady-state two-dimensional linearized model capable of simulating the solar tides and planetary waves. In an effort to understand the capabilities and limitations of the GSWM throughout the upper mesosphere and thermosphere a comparative analysis with observational data is presented. A majority of the observational data used in this study was collected during the World Day campaign which ran from 20 January to 30 January 1993. During this campaign data from 18 ground-based observational sites across the globe and two instruments located on the UARS spacecraft were analyzed. Comparisons of these data with the simulations from the GSWM indicate that the GSWM results are in reasonable agreement with the observations. However, there are a number of cases where the agreement is not particularly good. One such instance is for the semidiurnal tide in the northern hemisphere, where the GSWM estimates may exceed observations by 50%. Through a number of numerical simulations, it appears that this discrepancy may be due to the eddy diffusivity profiles used by the GSWM. Other differences relating to the diurnal tide and the quasi-two-day wave are presented and discussed. Additionally, a discussion on the biases and aliasing difficulties which may arise in the observational data is alos presented. 相似文献
205.
The effects of loess erosion on soil nutrients, plant diversity and plant quality in Negev desert wadis 总被引:1,自引:0,他引:1
Severe erosion, initiated by climatic changes during the Late Pleistocene-Early Holocene period and resultant declines in dust deposition, causes the formation of waterfalls during the winter floods in many wadi systems in the central Negev desert of Israel. In some areas, erosion of the original loess substrate has been complete, so that the underlying rock has been exposed. We examined the effects of this erosion in four wadis in the central Negev desert on soil nutrients, plant community structure and plant quality. We predicted that erosion has caused reductions in soil nutrients. Reductions in soil nutrients should result in reductions in plant cover. Furthermore, reduced soil nutrient availability should cause reductions in the nutrient status and quality of the plants growing there. In addition to the loss of biodiversity that may result, this erosion may result in economic hardship for the Bedouin peoples whose herds depend on these resources. In this study, there were significant negative effects of erosion on soil organic carbon, nitrate nitrogen and water-holding capacity, but not on soil phosphorus, conductivity or pH. Furthermore, there was a negative effect of soil erosion on an overall measure of soil quality derived from a principal components analysis in three of the four wadis we studied. Erosion resulted in an increase in plant species richness and significantly altered plant community structure in eroded areas of wadis. Increased plant species richness in eroded sites is consistent with the intermediate disturbance hypothesis of plant community structure. Plants growing in eroded areas did not differ in two quality indices (nitrogen content and digestibility), although plants typical of eroded areas had significantly lower levels of common digestion inhibitors (total polyphenols) and toxins (alkaloids) than plants from undisturbed sites. These last-mentioned results are contrary to our prediction and are consistent with the notion that plants growing in disturbed (e.g. eroded) sites maximize growth at the expense of investments in defense. 相似文献
206.
207.
A TEST OF SIGNIFICANCE FOR PARTIAL LEAST SQUARES REGRESSION 总被引:1,自引:0,他引:1
IAN N. WAKELING JEFF J. MORRIS AFRC Institute of Food Research Earley Gate Whiteknights Ro Reading RG EF U.K.Zeneca Pharmaceuticals Mereside Alderley Park Macclesfiel Cheshire SK TG U.K. 《地理学报(英文版)》1993,(4)
Partial least squares (PLS) regression is a commonly used statistical technique for performingmultivariate calibration, especially in situations where there are more variables than samples. Choosingthe number of factors to include in a model is a decision that all users of PLS must make, but iscomplicated by the large number of empirical tests available. In most instances predictive ability is themost desired property of a PLS model and so interest has centred on making this choice based on aninternal validation process. A popular approach is the calculation of a cross-validated r~2 to gauge howmuch variance in the dependent variable can be explained from leave-one-out predictions. Using MonteCarlo simulations for different sizes of data set, the influence of chance effects on the cross-validationprocess is investigated. The results are presented as tables of critical values which are compared againstthe values of cross-validated r~2 obtained from the user's own data set. This gives a formal test forpredictive ability of a PLS model with a given number of dimensions. 相似文献
208.
Steven D. Bussey Paul M. Taufen Bart J. Suchomel Malcolm Ward 《Journal of Geochemical Exploration》1993,47(1-3)
The Bell Springs deposit is a bulk-tonnage, low-grade gold deposit, formed in a hot-spring environment, that is hosted by middle Miocene weakly peralkaline, high-silica rhyolite ash flows and rheomorphic tuffs. Ore grade mineralization over about 460 × 460 m was controlled by northeast- and northwest-trending structures. Sixty-nine soil samples collected along a traverse across the Bell Springs deposit, screened into six mesh size fractions, +10, −10+35, −35+80, −80+120, −120+200, and −200, were treated by low-detection-limit acid digestion/organic extraction procedures, and analyzed by ICP or graphite furnace techniques for Au, Ag, As, Bi, Cd, Cu, Ga, Hg, Mo, Pb, Sb, Se, Te, Tl, and Zn. Twenty-five stream-sediment samples were collected from a drainage crossing mineralization and from a nearby tributary. Sediment size fractions of −200 mesh and −10+200 mesh were analyzed by the same procedures used for soils. In addition, analyses of bulk leachable gold via cyanide leach method (BLEG) was done on bulk −10 mesh sediments.Anomalous Au, Ag, As, Sb, and Mo in all soil size fractions revealed the underlying ore. Areas with anomalous Sb and As were about three times larger than areas with anomalous Au and Ag. Analyses of fine-fractions of stream sediments provided the best-defined Au anomalies in drainages. A multi-element factor calculated by multiplying Au, As, Sb, and Mo reinforced anomalous Au in drainages and correlated well with Bell Springs mineralization. 相似文献
209.
210.