5,933 research outputs found

    Morphology Effectively Controls Singlet-Triplet Exciton Relaxation and Charge Transport in Organic Semiconductors

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    We present a comparative study of ultrafast photo-conversion dynamics in tetracene (Tc) and pentacene (Pc) single crystals and Pc films using optical pump-probe spectroscopy. Photo-induced absorption in Tc and Pc crystals is activated and temperature-independent respectively, demonstrating dominant singlet-triplet exciton fission. In Pc films (as well as C60_{60}-doped films) this decay channel is suppressed by electron trapping. These results demonstrate the central role of crystallinity and purity in photogeneration processes and will constrain the design of future photovoltaic devices.Comment:

    Violent and victimized bodies: sexual violence policy in England and Wales

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    This paper uses the notion of the body to frame an archaeology of sexual violence policy in England and Wales, applying and developing Pillow’s ideas. It argues that the dominant construction is of sexual violence as an individualized crime, with the solution being for a survivor to report, and with support often instrumentalized in relation to criminal justice objectives. However, criminal justice proceedings can intensify or create further trauma for sexual violence survivors. Furthermore, in addition to criminalizing the violent body and supporting the victimized one, there is a need for policy to produce alternative types of bodies through preventative interventions. Much sexual violence is situated within (hetero) sexual dynamics constructing a masculine aggressor and a feminine body which eventually yields. Prevention must therefore focus on developing embodied boundaries, and narratives at the margins of policy could underpin such efforts

    Decay of escherichia coli in soil following the application of biosolids to agricultural land

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    The decay of Escherichia coli in a sandy loam soil, amended with enhanced and conventionally treated biosolids, was investigated in a field experiment following spring and autumn applications of sewage sludge. Control soils, without the application of biosolids, were also examined to determine the background indigenous populations of E. coli which are present in the environment. The survival of indigenous E. coli and populations of E. coli applied to soil in biosolids, is assessed in relation to environmental factors influencing pathogen-decay processes in soil

    Delivering McJustice? The Probation Factory at the Magistrates’ Court

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    Despite playing a pivotal role in thousands of defendants’ experiences of criminal justice every year, the role of probation workers in the English and Welsh Magistrates’ courts has been neglected by researchers for several decades. This article presents the findings of an ethnographic study of the work of probation staff in two such courts. The study suggests that probation work in this context is being squeezed into an operating model which bears all the hallmarks of a process described by Ritzer as ‘McDonaldization’. It is argued that the proximate causes of McDonaldization in this sub-field of probation work lie at the intersection of parallel Government-led reform programmes – Transforming Rehabilitation and Transforming Justice – which have respectively focused on creating a market for probation services and enhancing the administrative efficiency of criminal proceedings. Until now, almost no attention has been paid, either by researchers or policy-makers, to the intersection of these programmes of reform in the probation suites at the Magistrates’ courts

    Staff experience of harassment and stalking behaviour by patients

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    Staff from one National Health Service (NHS) Trust in England completed an online survey (N = 590) about their experience of intrusive behaviours from patients. These experiences were categorised into either stalking or harassment and compared in terms of staff and patient characteristics, types of intrusions, and aftermath. Overall, 150 were classified as being stalked (25.4%) and 172 harassed (29.2%). There were no differences in staff characteristics between the two groups. Staff from forensic services and nursing staff were particularly susceptible to these intrusions which took many forms. Respondents perceived a range of causes for the stalking and harassment, the most common being to gain power and control/to scare. It was rare for legal sanctions to be brought against the patient. Our findings reinforce the need for service providers to have policies supported with preventative measures, education and a robust process for addressing stalking so that these measures are embedded in practice in a way that supports staff working with patients. Furthermore, service providers should be challenged on what steps they have taken to prevent, and monitor, such behaviour

    The Hamiltonian of the V15_{15} Spin System from first-principles Density-Functional Calculations

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    We report first-principles all-electron density-functional based studies of the electronic structure, magnetic ordering and anisotropy for the V15_{15} molecular magnet. From these calculations, we determine a Heisenberg Hamiltonian with four antiferromagnetic and one {\em ferromagnetic} coupling. We perform direct diagonalization to determine the temperature dependence of the susceptibility. This Hamiltonian reproduces the experimentally observed spin SS=1/2 ground state and low-lying SS=3/2 excited state. A small anisotropy term is necessary to account for the temperature independent part of the magnetization curve.Comment: 4 pages in RevTeX format + 2 ps-figures, accepted by PRL Feb. 2001 (previous version was an older version of the paper

    Anomalous transverse acoustic phonon broadening in the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O_3

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    The intrinsic linewidth ΓTA\Gamma_{TA} of the transverse acoustic (TA) phonon observed in the relaxor ferroelectric compound Pb(Mg1/3_{1/3}Nb2/3)0.8_{2/3})_{0.8}Ti0.2_{0.2}O3_3 (PMN-20%PT) begins to broaden with decreasing temperature around 650 K, nearly 300 K above the ferroelectric transition temperature TcT_c (∼360\sim 360 K). We speculate that this anomalous behavior is directly related to the condensation of polarized, nanometer-sized, regions at the Burns temperature TdT_d. We also observe the ``waterfall'' anomaly previously seen in pure PMN, in which the transverse optic (TO) branch appears to drop precipitously into the TA branch at a finite momentum transfer qwf∼0.15q_{wf} \sim 0.15 \AA−1^{-1}. The waterfall feature is seen even at temperatures above TdT_d. This latter result suggests that the PNR exist as dynamic entities above TdT_d.Comment: 6 pages, 4 figure

    Electrostatic model of atomic ordering in complex perovskite alloys

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    We present a simple ionic model which successfully reproduces the various types of compositional long-range order observed in a large class of complex insulating perovskite alloys. The model assumes that the driving mechanism responsible for the ordering is simply the electrostatic interaction between the different ionic species. A possible new explanation for the anomalous long-range order observed in some Pb relaxor alloys, involving the proposed existence of a small amount of Pb^4+ on the B sublattice, is suggested by an analysis of the model.Comment: 4 pages, two-column style with 1 postscript figure embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#lb_orde
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