2,922 research outputs found

    Chiral gadolinium complexes as potential contrast agents

    Get PDF
    The long electronic relaxation time and the high paramagnetism of the gadolinium(III) ion makes it ideal for use as a contrast agent in Magnetic Resonance Imaging. As a result of its toxicity, gadolinium must be administered in the form of a kinetically inert complex. By coupling a gadolinium(III) chelate to a macromolecule, substantial gains in relaxivity (the efficacy of a contrast agent) may be obtained. To this end the synthesis of three types of ligand, substituted with amino- or carboxylate bearing groups, was undertaken. A derivative of 1,4,7,10-tetraazacyclododecane with three amino bearing chains substituted at carbon was synthesised as a single enantiomer. An effective route to acetate substituted derivatives of D03A was developed. The lanthanide complexes of these ligands do not exhibit the expected properties of a q = 2 complex, and therefore do not represent useful chelates for application in a slowly tumbling system. A study of the lanthanide(in) complexes of all four stereoisomers of tetra(carboxyethyl) DOTA derivatives has been performed. The rate of water exchange has been found to be dependent upon the proportion of a complex adopting a twisted square antiprism in solution. This is ascribed to the steric crowding of the water binding site in this isomer. 2-D EXSY NMR experiments show that the [Ln.(RRRR-)] and [Ln.(RKRS-)] isomers do not undergo rapid arm rotation at room temperature, showing that ring motion is decoupled from arm rotation. This rigidity increases the stability of these complexes with respect to metal ion dissociation. A selective synthesis of the [Ln.(RRRR-)] diastereoisomeric complex is described. Crystal structures of the [Eu.(RRRR-)], [Gd.(RRRR-)] and [Tb.(RRRR-)] complexes each reveal a monocapped square antiprismatic co-ordination geometry at the metal centre in which there is one bound water molecule

    Applied palaeontology in the Chalk Group: quality control for geological mapping and modelling and revealing new understanding

    Get PDF
    The Chalk is a major aquifer, source of raw material for cement and agricultural lime, and a host geological unit for major civil engineering projects. Detailed understanding of its development and lateral variation is significant for our prosperity and for understanding the potential risks of pollution and groundwater flooding, and in this aspect palaeontology plays a central part. Historically, the distribution of macrofossils offered important refinement to the simple three-fold subdivision of the Chalk based on lithological criteria. In recent decades, the advent of a more sophisticated lithostratigraphy for the Chalk, more closely linked to variations in its physical properties, provided an impetus for the British Geological Survey to depict this on its geological maps. Tracing Chalk stratigraphical units away from the well-exposed successions on which the new stratigraphy is based requires subtle interpretation of landscape features, and raises the need for methods of ensuring that the interpretations are correct. New and archived palaeontological data from the vast BGS collections, interpreted as a component of a broad-based holostratigraphical scheme for the Chalk, and spatially analysed using modern Geographical Information Systems (GIS) and landscape visualisation technology, helps fulfil this need. The value of palaeontological data in the Chalk has been boosted by the work that underpins the new lithostratigraphy; it has revealed broad patterns of biofacies based on a range of taxa that is far more diverse than those traditionally used for biostratigraphy, and has provided a detailed reference framework of marker-beds so that fossil ranges can be better understood. In the subsurface, biofacies data in conjunction with lithological and geophysical data, has been used to interpret and extrapolate the distribution of Chalk formations in boreholes across southern England, allowing development of sophisticated three-dimensional models of the Chalk; revealing the influence of ancient structures on Chalk depositional architecture, and pointing to palaeoenvironmental factors that locally affected productivity of Chalk in Late Cretaceous oceans

    London’s foundations protecting the geodiversity of the capital

    Get PDF
    This report describes a geodiversity audit of London commissioned by a partnership led by the Greater London Authority (GLA), which includes the British Geological Survey (BGS), Natural England, Government Office for London, London Biodiversity Partnership, London Borough of Lambeth, Harrow and Hillingdon Geological Society, South London London RIGS Groups, Hanson UK and Queen Mary College, University of London. The project was funded by an Aggregates Levy Sustainability Fund grant from Natural England plus additional support from the GLA, BGS and Natural England London Region. The audit began with a review of the available geodiversity documentation for London including: BGS field maps, databases and publications; Regional Important Geological Sites (RIGS) Group information; Natural England Sites of Special Scientific Interest (SSSI) and Geological Conservation Review (GCR) documentation; and documentation and data from the GLA and London Boroughs. An initial list of around 470 sites with potential for geodiversity value was compiled from this information. This list was then narrowed down to 100 for further assessment by exporting site locations to a GIS and cross-checking against digital aerial photography backed up by BGS staff local geological expertise. Using the procedure set out in this report field auditing was carried out by BGS staff and the South London RIGS Group between November 2007 and April 2008. From the list of 100 sites, 35 sites were found to be suitable for detailed auditing. Harrow and Hillingdon Geological Society audited a further site in November 2008, bringing the total to 36 sites. Using the criteria set out in this report 14 of the 36 sites are recommended for designation as Regionally Important Geological/geomorphological Sites (RIGS) in borough Local Development Documents. Of the 33 London boroughs, RIGS are recommended in eight, with five in Bromley, three in Croydon and one each in Lewisham, Ealing, Greenwich, Harrow, Hillingdon and Bexley. Using the criteria set out in this report 15 of the 36 sites have the potential to be designated as Locally Important Geological Sites (LIGS). These sites are located in nine boroughs, three in Waltham Forest, two in Bromley, two in Islington and one each in Barnet, Lewisham, Redbridge, Wandsworth, Southwark and Sutton. Planning proposals should have regard to geodiversity in order to implement strategic and local policies. Sites should be protected, managed and enhanced and, where ppropriate, new development should provide improvements to the geodiversity value of a site. This can include measures that promote public access, study, interpretation and appreciation of geodiversity. In addition to individual sites of geodiversity interest, Greater London has distinctive natural landscapes shaped by geological processes, such as undulating chalk downlands with dry valleys in south London, and river terraces forming long flat areas separated by steeper areas of terrace front slopes. This natural topographic geodiversity underlying London should be understood, respected and only altered in that knowledge with full knowledge of it origin and form. Planners are encouraged to use authentic contouring in restoration work and new landscaping schemes, maintain the contributions of natural topography, rock outcrops, landscape features, and to maintain soil quality, quantity and function

    Work and reversibility in quantum thermodynamics

    Get PDF
    It is a central question in quantum thermodynamics to determine how irreversible is a process that transforms an initial state ρ\rho to a final state σ\sigma, and whether such irreversibility can be thought of as a useful resource. For example, we might ask how much work can be obtained by thermalizing ρ\rho to a thermal state σ\sigma at temperature TT of an ambient heat bath. Here, we show that, for different sets of resource-theoretic thermodynamic operations, the amount of entropy produced along a transition is characterized by how reversible the process is. More specifically, this entropy production depends on how well we can return the state σ\sigma to its original form ρ\rho without investing any work. At the same time, the entropy production can be linked to the work that can be extracted along a given transition, and we explore the consequences that this fact has for our results. We also exhibit an explicit reversal operation in terms of the Petz recovery channel coming from quantum information theory. Our result establishes a quantitative link between the reversibility of thermodynamical processes and the corresponding work gain.Comment: 14 page

    Reflecting on the Strategic Use of CAQDAS to Manage and Report on the Qualitative Research Process

    Get PDF
    As an increasing number of researchers have been trained to u s e programs such as Atlas/ti, NUD*IST, Nvivo, and ETHNOGRAPH their value in analyzing qualitative data has gained greater recognition. Drawing on the experience of two PhD candidates at the University of Tasmania, this paper reflects upon some potential uses of a suite of computer software programs to make the research and analysis process more logical and transparent. In addition, this paper argues for the introduction of a Computer Aided Qualitative Data Analysis Protocol to give readers of the research report a better understanding of the analysis process undertaken by the researcher

    A Paradoxical Threat to Democracy

    Get PDF
    “A Paradoxical Threat to Democracy” examines in-depth the two major threats U.S. democracy faces—climate change and autocracy—and how the mitigation of these threats is paradoxical. The first paradox relates to how United States Department of Defense lists climate change as a national security threat, therefore making the Department responsible for its mitigation. However, this presentation sheds light on the Department of Defense’s role as a critical contributor to this threat by being the largest institutional consumer of fossil fuels in the world. How can the military fight climate change by being one of the highest consumers of fossil fuels in the world? A second paradox exists in that some scholars argue that democratic governments will not be enough to solve climate change. Specifically, in a democracy, individuals have the right to choose their own leaders and dissent to the state, both of which can deter the progress of climate policy. On the other hand, a well-intentioned ‘environmental authoritarianism’ would allow a government to smoothly implement environmental policy without interruption from individual dissent. The result would be a quick and effective response to climate change, abandoning individual liberty in favor of protecting the planet. Environmental authoritarianism would shake the foundation of the democratic world order held dear by the United States and NATO, which begs the question: how can the United States defend itself from the threats of climate change and autocracy, when autocracy is seen as one of the few solutions to combat climate change on an institutional level

    The Processual Ordering of Mental Health Care: The Dramaturgical Styles of Contending Political Factions

    Get PDF
    The processual ordering branch of symbolic interaction has long recognized the importance of rhetoric and power to the social constitution of reality. However, little systematic effort has been devoted to probing their intertwined effects in the public policy arena. The purpose of this paper is to employ the processual ordering perspective to examine the dramaturgical styles used in shaping public policy -- expressed in terms of the “public administration” and “realpolitik” forms of rhetoric -- among contending political factions as they negotiate mental health public policy. A latent content analysis of the minutes of key U.S. Congressional debates, augmented with secondary archival material from the press is employed. It is concluded that both forms of rhetoric play a role in shaping public mental health policy and that both factions modify their rhetorical form as the debate progresses. Those modifications strengthen the position of one faction while weakening that of the other. Theoretical implications are discussed

    Technology in Clinical Practice

    Full text link