675 research outputs found
Dating of the oldest continental sediments from the Himalayan foreland basin
A detailed knowledge of Himalayan development is important for our wider understanding of several global processes, ranging from models of plateau uplift to changes in oceanic chemistry and climate(1-4). Continental sediments 55 Myr old found in a foreland basin in Pakistan(5) are, by more than 20 Myr, the oldest deposits thought to have been eroded from the Himalayan metamorphic mountain belt. This constraint on when erosion began has influenced models of the timing and diachrony of the India-Eurasia collision(6-8), timing and mechanisms of exhumation(9,10) and uplift(11), as well as our general understanding of foreland basin dynamics(12). But the depositional age of these basin sediments was based on biostratigraphy from four intercalated marl units(5). Here we present dates of 257 detrital grains of white mica from this succession, using the Ar-40-(39) Ar method, and find that the largest concentration of ages are at 36-40 Myr. These dates are incompatible with the biostratigraphy unless the mineral ages have been reset, a possibility that we reject on the basis of a number of lines of evidence. A more detailed mapping of this formation suggests that the marl units are structurally intercalated with the continental sediments and accordingly that biostratigraphy cannot be used to date the clastic succession. The oldest continental foreland basin sediments containing metamorphic detritus eroded from the Himalaya orogeny therefore seem to be at least 15-20 Myr younger than previously believed, and models based on the older age must be re-evaluated
A theoretical study of the structural phases of Group 5B - 6B metals and their transport properties
In order to predict the stable and metastable phases of the bcc metals in the
block of the Periodic Table defined by groups 5B to 6B and periods 4 to 6, as
well as the structure dependence of their transport properties, we have
performed full potential computations of the total energies per unit cell as a
function of the c/a ratio at constant experimental volume. In all cases, a
metastable body centered tetragonal (bct) phase was predicted from the
calculations. The total energy differences between the calculated stable and
metastable phases ranged from 0.09 eV/cell (vanadium) to 0.39 eV/cell
(tungsten). The trends in resistivity as a function of structure and atomic
number are discussed in terms of a model of electron transport in metals.
Theoretical calculations of the electrical resistivity and other transport
properties show that bct phases derived from group 5B elements are more
conductive than the corresponding bcc phases, while bct phases formed from
group 6B elements are less conductive than the corresponding bcc phases.
Special attention is paid to the phases of tantalum where we show that the
frequently observed beta phase is not a simple tetragonal distortion of bcc
tantalum
âTeam GBâ and London 2012: The Paradox of National and Global Identities
This article explores the problems associated with ânational identityâ in the UK and examines the tensions arising between the international and local dimensions of the games through examples of domestic (UK) and international (Brazil, Chicago) media coverage of the key debates relating to Londonâs period of preparation. The chapter proposes a conception of London 2012 as exemplar of an event poised to generate insights and experiences connected to a new politics of âcosmopolitanâ identity; insights central to grasping the cultural politics of contemporary urban development-and the paradoxes of national identity in current discourses of Olympism. Properly speaking, cosmopolitanism suits those people who have no country, while internationalism should be the state of mind of those who love their country above all, who seek to draw to it the friendship of foreigners by professing for the countries of those foreigners an intelligent and enlightened sympathy. © 2010 Taylor & Francis
Isolation and Monitoring of the Endohedral Metallofullerenes Y@C82 and Sc3@C82:On-Line Chromatographic Separation with EPR Detection
The direct coupling of high-performance liquid chromatography (HPLC) with on-line electron paramagnetic resonance (EPR) detection is demonstrated for monitoring separations of endohedral metallofullerenes (M@C2n). The HPLC-EPR approach readily permits detection of the paramagnetic species, such as Y@C82 and Sc3@C82, in the presence of the dominant empty-cage fullerenes (C60, C70) and diamagnetic metallofullerenes (e.g., M2@C2n). The results indicate that on-line EPR provides a noninvasive, selective detector for HPLC metallofullerene separations that is readily adaptable to air-sensitive and/or labile compounds. Specifically, the âEPR-activeâ metallofullerenes, Y@C82 and Sc3@C82, are selectively monitored on-line for an initial separation of the metallofullerene fraction from the dominant empty-cage fullerenes utilizing a combination of polystyrene columns. This preparative âcleanupâ procedure is followed by HPLC-EPR separation and monitoring of Y@C82 and Sc3@C82 species using a selective tripodal Ï-acidic-phase column (Trident-Tri-DNP) for the final stages of isolation
Olympic legacy and cultural tourism: Exploring the facets of Athens' Olympic heritage
This study examines the effects of the Olympic Games on Athensâ cultural tourism and the cityâs potential to leverage the Olympic legacy in synergy with its rich heritage in order to enhance its tourism product during the post-Games period. In doing so, a qualitative and interpretive approach was employed. This includes a literature review on Athensâ 2004 Olympics to identify the sport facilities and regeneration projects, which constitute the Olympic legacy and heritage. Based on that, an empirical analysis was undertaken, by collecting official documents about the 2004 Olympics, and conducting five semi-structured interviews with tourism/administrative officials. The findings indicate that the Olympiad contributed significantly to Athensâ built and human heritage, revealing the dimensions of new venues/facilities, infrastructure, transportation and aesthetic image of the city, and human capital enhancement. Hence, the Games affected to the multifaceted representation and reconstruction of the cityâs identity and cultural heritage. However, the potential afforded from the post-Olympic Athens remains unrealised due to lack of strategic planning/management. The study concludes that there is a need to develop cross-leveraging synergies between the Olympic legacy and cultural tourism for the host city. Finally, a strategic planning framework for leveraging post-Games Olympic tourism is suggested in order to maximise the benefits of Olympic legacy and heritage in a host cityâs tourism development
The Regeneration Games: Commodities, Gifts and the Economics of London 2012
This paper considers contradictions between two concurrent and tacit conceptions of the Olympic âlegacyâ, setting out one conception that understands the games and their legacies as gifts alongside and as counterpoint to the prevailing discourse, which conceives Olympic assets as commodities. The paper critically examines press and governmental discussion of legacy, in order to locate these in the context of a wider perspective contrasting âgiftâ and âcommodityâ Olympics â setting anthropological conceptions of gift-based sociality as a necessary supplement to contractual and dis-embedded socioeconomic organizational assumptions underpinning the commodity Olympics. Costbenefit planning is central to modern city building and mega-event delivery. The paper considers the insufficiency of this approach as the exclusive paradigm within which to frame and manage a dynamic socio-economic and cultural legacy arising from the 2012 games
Testing fluvial erosion models using the transient response of bedrock rivers to tectonic forcing in the Apennines, Italy
The transient response of bedrock rivers to a drop in base level can be used to
discriminate between competing fluvial erosion models. However, some recent studies of
bedrock erosion conclude that transient river long profiles can be approximately
characterized by a transportâlimited erosion model, while other authors suggest that a
detachmentâlimited model best explains their field data. The difference is thought to be
due to the relative volume of sediment being fluxed through the fluvial system. Using a
pragmatic approach, we address this debate by testing the ability of endâmember fluvial
erosion models to reproduce the wellâdocumented evolution of three catchments in the
central Apennines (Italy) which have been perturbed to various extents by an
independently constrained increase in relative uplift rate. The transportâlimited model is
unable to account for the catchmentsâresponse to the increase in uplift rate, consistent with
the observed low rates of sediment supply to the channels. Instead, a detachmentâlimited
model with a threshold corresponding to the fieldâderived median grain size of the
sediment plus a slopeâdependent channel width satisfactorily reproduces the overall
convex long profiles along the studied rivers. Importantly, we find that the prefactor in the
hydraulic scaling relationship is uplift dependent, leading to landscapes responding faster
the higher the uplift rate, consistent with field observations. We conclude that a slopeâ
dependent channel width and an entrainment/erosion threshold are necessary ingredients
when modeling landscape evolution or mapping the distribution of fluvial erosion rates in
areas where the rate of sediment supply to channels is low
Diagnostic accuracy for different strategies of image-guided breast intervention in cases of nonpalpable breast lesions
To find out whether ultrasound-guided fine-needle aspiration (FNA) and ultrasound and stereotactic-guided large core needle biopsy (LCNB) are reliable alternatives to needle-localised open breast biopsy (NLBB) in daily practice, we performed a retrospective study and evaluated the validity of these methods. In all, 718 women with 749 nonpalpable breast lesions from three Dutch Hospitals were included, and the validity of the various methods for diagnosis was assessed. This was carried out according to a method described by Burbank and Parker for evaluating the quality of an image-guided breast intervention. We compared our results with the outcome of the COBRA study. Overall, all diagnostic strategies (NLBB, FNA, LCNB ultrasound and stereotactic guided) show comparable agreement rates. However, the miss rates differ: 2% for NLBB, 3% for COBRA (LCNB in study setting), 5% for FNA and 8-12% for LCNB in practice. Fine-needle aspiration was nonconclusive in 29%, and shows an overestimation for DCIS in 9%. The DCIS underestimate rate in NLBB was 8%. For the assessment of lesions consisting of microcalcifications only and to exclude malignancy in all other lesions, a 14-gauge needle should be used. Ultrasound-guided intervention can be performed in a large percentage of nonpalpable lesions. Lesions consisting only of microcalcifications on mammography need special attention
Rationales, rhetoric and realities:FIFAâs World Cup in South Africa 2010 and Brazil 2014
The 2010 FIFA World Cup was heralded by mainstream media outlets, the local organisers, the South African government and FIFA as an unequivocal success. The month-long spectacle saw South Africa take centre stage and host the worldâs largest single sporting event. This occurred against a backdrop of rationales and promises made that the event would leave lasting legacies for all, in particular marginalised South Africans. The reality is quite different. In this article we consider the South African World Cup in the build up to Brazil 2014. We argue that the rationales and rhetoric are similar in both countries and suggest the reality for Brazil 2014 will be the same as South Africa 2010 in that the mega-event will be primarily funded by significant public investment, while the primary beneficiaries will be private capital and FIFA
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