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231.
The paper compares ethnic change and diversity across two recent decades using common group and area definitions. Ethnic minority groups are shown to be growing rapidly at 41 per cent between 1981 and 1991 and 39 per cent between 1991 and 2001. Some groups have grown swiftly (Black Africans, Bangladeshis), while others have seen moderate expansion (Indians, Other Asians). The White population has hardly grown and the White British population has probably declined. Black and Ethnic Minority (BEM) populations remain concentrated in metropolitan areas in 2001 as in 1991 and 1981. Whereas between 1981 and 1991, BEM groups were concentrating into metropolitan areas, between 1991 and 2001 deconcentration began for most groups. The London region stands out as highly dominant, housing more than 50 per cent of BEM populations as a whole in 1991 and 2001. However, between 1991 and 2001, BEM groups grew outside their core areas. The consequence of BEM population growth and spread has been a dramatic increase in ethnic diversity in all regions. 相似文献
232.
Victor R. Savage M.A. Ph.D. Lily Kong M.A. Ph.D. Brenda S.A. Yeoh M.A. D.Phil. 《Singapore journal of tropical geography》1994,14(2):229-251
This paper reviews the directional shifts in human geographical research on Southeast Asia from 1945 to the present. It first begins with an overview of the identity of the region as conceived in various cultural traditions, such as the Greek, Arabic and Indian traditions. This is followed by an evaluation of regional geographies of Southeast Asia in the post-war period, highlighting the pre-eminence of the geostrategic definition of the region and the failure to come to grips with its rich cultural-historical identity. The paper then goes on to show that, arising from the changes in conceptual developments and methodologies in geography, the early regional emphasis then shifted to systematic concerns, with a movement away from ‘encyclopaedic’ to ‘adjectival’ geography (economic, urban, population, political, cultural and historical) and a greater emphasis on issues concerning national development. Since the 1980s, there have also been fewer regional works on Southeast Asia and though there are now many more indigenous geographers within the region, much of their research is based on their own national or provincial areas. However, this may shift again, given that rapid economic growth has now given the region prominence. Certainly, there is renewed multi-disciplinary interest in Southeast Asia. 相似文献
233.
Anton Kearsley Giles Graham Tony McDonnell Phil Bland Rob Hough Paul Helps 《Meteoritics & planetary science》2004,39(2):247-265
Abstract— Understanding the nature and composition of larger extraterrestrial bodies that may collide with the Earth is important. One source of information lies in the record of ancient impact craters, some of which have yielded chemical information as to the impacting body. Many deeply eroded craters have no remaining melt sheet or ejecta yet may contain impactor residue within basement fractures. The emplacement mechanism for fractionated siderophile residues is likely to be gaseous, although, melt droplets and some solid materials may survive. For breccia‐ and melt‐filled fractures to contain extraterrestrial material, they must form very early in the impact process. Most current numerical models do not dwell on the formation and location of early major fractures, although, fractures in and around small craters on brittle glass exposed to hypervelocity impact in low Earth orbit have been successfully simulated. Modelling of fracture development associated with larger craters may help locate impact residues and test the models themselves. 相似文献
234.
Since the discovery of coronal mass ejections (CMEs), flaring has been thought to be associated in some way with the ejection in either cause or effect. When CMEs were first discovered in the 1970s it was suggested that they were powered by solar flares (e.g., Dryer, 1982). Research since then (Harrison, 1986) has indicated that there is an associated flare that occurs shortly after the CME. To investigate this further, and making no assumption that a particular flare is causally connected to the CME, flaring activity in nine active regions that show one or more CME signatures has been studied for several hours before and after CME launch. Although the initiation of the CME may occur on size scales larger than the active region itself, definite changes are seen in the flaring activity which may be related to the ejection. This work indicates that the energy released from the active region magnetic field via flaring is greater prior to the CME launch than after. 相似文献
235.
R. Shrestha M. Phil. Ph.D. R. Fischer Ph.D. M. Sillanpää D.Sc. 《International Journal of Environmental Science and Technology》2007,4(4):413-420
In most mining areas, significant concentrations of metals such as Pb, Cu, Cr, Zn, Cd, Fe, Mn, Co, Ni, Hg, Ar, halogenated organic compounds and radionuclides are found. Of those, Cr is one of the well-known heavy metals that forms toxic species. It is necessary to study the mobilization and accumulation of Cr at the sediment water interface in an electric field at varying different positions and conditions of the electrode arrangement. The tests were carried out with a natural sediment containing heavy metals from the river Weisse Elster (Germany). The electrokinetic experiments have been performed in columns filled with sediment using electrodes made of conductive polymers (polyethylene with carbon black) at a maximum current density of 0.5 mA/cm2. The experimental results suggest that the mobilization and accumulation of Cr highly depends on chemical factors for e.g., pH value, redox potential, respectively redox status and the content of Fe, A1 and organic matter in the soil or sediment. The sorption of Cr (III, VI) is very high in the pH range > 4.5. As expected, a high mobilization of Cr (III, VI) was seen in the case of the experiments with the anode at the sediment, because the pH value was lower than mentioned above. On the opposite, the best conditions for the Cr (III, VI) immobilization is high pH values (cathode at the sediment). 相似文献
236.
Silicic recharge of multiple rhyolite magmas by basaltic intrusion during the 22.6 ka Okareka Eruption Episode, New Zealand 总被引:1,自引:0,他引:1
Phil Shane Ian A. Nairn Victoria C. Smith Miles Darragh Kate Beggs Jim W. Cole 《Lithos》2008,103(3-4):527-549
Deposits of the 22.6 ka Okareka Eruption Episode from Tarawera Volcanic Complex record the sequential and simultaneous eruption of three discrete rhyolite magmas following a silicic recharge event related to basaltic intrusion. The episode started with basaltic eruption ( 0.01 km3 magma), and rapidly changed to a plinian eruption involving a moderate temperature (750 °C), cummingtonite-bearing rhyolite magma (T1) with a volume of 0.3 km3. Hybrid basalt/rhyolite clasts demonstrate direct basaltic intrusion that helped trigger the eruption. Crystals, shards and lapilli of two other rhyolite magmas then joined the eruption sequence. They comprise a cooler (720 °C) crystal-rich biotite–hornblende rhyolite magma (T2) ( 0.3 km3), and a hotter (780 °C), crystal-poor, pyroxene–hornblende rhyolite magma (T3) ( 4.5 km3). All mid to late-stage ash units contain various mixtures of T1, T2 and T3 components with a general increase in abundance of T3 and rapid decline of T1 with time. About 4 km3 of T3 magma was extruded as lavas at the end of the episode. Contrasts in melt composition, crystal and volatile contents, and temperatures influenced viscosity and miscibility, and thus limited pre-eruption mixing of the rhyolite magmas. The eruption sequence and the restricted direct basaltic intrusion into only one magma (T1) is consistent with the rhyolites occupying separate melt pods within a large crystal-mush zone. Melt–crystal equilibria and volatile contents in melt inclusions indicate temporary magma storage depths of < 8 km. Each of the magmas display quartz crystals containing melt inclusions that are compositionally highly evolved relative to the accompanying matrix glass, and thus point to a stage of more complete crystallisation. The matrix glass, enriched in Sr and Ti, represents a re-melting event of underlying the crystal pile induced by basaltic intrusion, presumably part of the same event that erupted scoria at the start of the eruption. This recharge rhyolite melt percolated upward and hybridised with the resident melts in each of the three magma pods. The Okareka episode rhyolites contrast with other well-documented rhyolites that are either continuously or discontinuously zoned, or have been homogenised during re-activation to a uniform composition. Rapid basalt dike intrusion to shallow levels appears to have (prematurely?) triggered the Okareka rhyolites into eruption, so that their early ponding in separate melt pods has been recorded before it could be masked by mixing or stratification had amalgamation into a larger body occurred. 相似文献
237.
238.
Phil Harding David R. Bridgland Peter Allen Philippa Bradley Michael J. Grant David Peat Jean-Luc Schwenninger Rebecca Scott Rob Westaway Tom S. White 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(4):584-607
This paper reports important findings relating to the chronology of Palaeolithic occupation, artefact typology and Quaternary fluvial deposits from a geoarchaeological watching brief undertaken over 17 years at Kimbridge Farm Quarry, Dunbridge, Hampshire. Sections were recorded and sampled and 198 artefacts, principally hand axes, were collected, with the primary aim of enhancing understanding of the geological context of the richest Lower Palaeolithic assemblage from Hampshire. Digital terrain modelling was used to characterize the three-dimensional form of the fluvial geology. Two gravel terraces have been confirmed: an upper Belbin Formation, which contained most of the archaeological artefacts, and a lower Mottisfont Formation. Results of specific note included recovery of artefacts demonstrating elements of ‘proto-Levallois’ technology from within the Belbin Gravel deposition. Fully developed Levallois technology was present across both the Belbin Gravel and the Mottisfont Formation at Dunbridge, the latter having an otherwise relatively sparse Palaeolithic content. Previously published OSL dating, supplemented by new data, has been combined with uplift modelling to suggest dates of MIS 9b and MIS 8, respectively, for these two gravels. This fits well with evidence from other sites in England and the near Continent for the timing of the earliest Levallois at around MIS 9. The results from the Dunbridge watching brief have demonstrated that this response provides a relatively cost effective method by which important scientific data can be salvaged from commercial quarrying. 相似文献
239.
Bruce J. MacFadden Michael J. Whitelaw Phil McFadden Thomas H. V. Rich 《Quaternary Research》1987,28(3)
Three to seven oriented paleomagnetic samples were collected from 16 sites in the Nelson Bay and Bridgewater formations at Portland, Victoria, which contains the recently discovered Nelson Bay local fauna (L.F.). The entire section has reversed polarity. These results, along with Globorotalia truncatulinoides within the section, and the presence of underlying middle Pliocene-dated basalts, indicate that the Portland section, and the included Nelson Bay L.F., was deposited within the late Matuyama Chron between 1.66 and 0.73 myr ago. This represents the first well-documented pre-14C Pleistocene mammalian fauna in Australia calibrated in direct stratigraphic context with absolute dating methods. In addition, the reversed polarity for the Bridgewater Formation confirms the previous hypothesis that the depositional history of this beach-sand deposit is time-transgressive across the Brunhes-Matuyama boundary. 相似文献
240.
Sh. N. Jamal B.Sc. M.Sc. M. Z. Iqbal B.Sc. M.Sc. Ph.D. M. Athar M.Sc. M.Phil. Ph.D. D.Sc. 《International Journal of Environmental Science and Technology》2006,3(2):173-176
Prosopis seeds were grown under controlled environment in solution of aluminum and chromium at different concentration alone as well as combined together. The effect of these metals was studied on seed germination, root length, shoot length, seedling length and dry biomass. Aluminum and chromium alone, and combined together showed no effects on germination and dry biomass. Chromium alone was found toxic to root, shoot and seedling length. However, application of different concentrations of aluminum increased the root, shoot and seedling growth. It may be concluded that aluminum is not as toxic as chromium, and their combined treatment showed the intermediate effect by ameliorating the impact of one another. 相似文献