17,481 research outputs found

    On the heterogeneous character of water's amorphous polymorphism

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    In this letter we report {\it in situ} small--angle neutron scattering results on the high--density (HDA) and low-density amorphous (LDA) ice structures and on intermediate structures as found during the temperature induced transformation of HDA into LDA. We show that the small--angle signal is characterised by two QQ regimes featuring different properties (QQ is the modulus of the scattering vector defined as Q=4πsin(Θ)/λiQ = 4\pi\sin{(\Theta)}/\lambda_{\rm i} with Θ\Theta being half the scattering angle and λi\lambda_{\rm i} the incident neutron wavelength). The very low--QQ regime (<5×102< 5\times 10^{-2} \AA 1^{-1}) is dominated by a Porod--limit scattering. Its intensity reduces in the course of the HDA to LDA transformation following a kinetics reminiscent of that observed in wide--angle diffraction experiments. The small--angle neutron scattering formfactor in the intermediate regime of 5×102<Q<0.55 \times 10^{-2} < Q < 0.5 \AA1^{-1} HDA and LDA features a rather flat plateau. However, the HDA signal shows an ascending intensity towards smaller QQ marking this amorphous structure as heterogeneous. When following the HDA to LDA transition the formfactor shows a pronounced transient excess in intensity marking all intermediate structures as strongly heterogeneous on a length scale of some nano--meters

    Trends in the Health of Older Californians: Data From the 2001, 2003 and 2005 California Health Interview Surveys

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    Analyzes trends in the health status and use of preventive services among Californians age 65 and over by race/ethnicity, insurance type, and region. Reports rises in doctor visits and in cancer, diabetes, high cholesterol, obesity, and other illnesses

    Agenda for Change: views and experiences from estates and facilities staff

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    Purpose – Agenda for Change is the biggest reform of staff pay in the UK National Health Service NHS) since it began in 1948. As well as introducing a standardised pay structure; it also aims to improve recruitment, retention and staff morale. The aim of this study is to look in-depth at the experiences and opinions of a range of estates and facilities staff surrounding Agenda for Change during the implementation period. Design/methodology/approach – Focus groups were used as the primary method of data collection in an attempt to tap into the views and opinions of staff working at operational positions in a wide range of trusts. Findings – One of the most important and common themes, which reoccurred throughout the focus groups, was the view that the Agenda for Change framework was designed around the needs of nursing staff. Therefore, the framework did not adequately cater for the needs of estates and facilities staff. Specific concerns related to this included; the role or contribution of estates and facilities staff during patient care was not fairly reflected; trade qualifications were not recognised, particularly in comparison to academic qualifications; members of the job matching panels did not have the appropriate knowledge to make decisions surrounding estates and facilities jobs; nurses were more likely to make progress through the bands than estates and facilities staff.</p

    Non-Markovian Quantum Jumps in Excitonic Energy Transfer

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    We utilize the novel non-Markovian quantum jump (NMQJ) approach to stochastically simulate exciton dynamics derived from a time-convolutionless master equation. For relevant parameters and time scales, the time-dependent, oscillatory decoherence rates can have negative regions, a signature of non-Markovian behavior and of the revival of coherences. This can lead to non-Markovian population beatings for a dimer system at room temperature. We show that strong exciton-phonon coupling to low frequency modes can considerably modify transport properties. We observe increased exciton transport, which can be seen as an extension of recent environment-assisted quantum transport (ENAQT) concepts to the non-Markovian regime. Within the NMQJ method, the Fenna-Matthew-Olson protein is investigated as a prototype for larger photosynthetic complexes.Comment: 9 pages, 4 figures, submitted to Journal of Chemical Physic

    Multipartite entanglement in the Fenna-Matthews-Olson (FMO) pigment-protein complex

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    We investigate multipartite states in the Fenna-Matthews-Olson (FMO) pigment-protein complex of the green sulfur bacteria using a Lorentzian spectral density of the phonon reservoir fitted with typical parameter estimates of the species, P. aestuarii. The evolution of the entanglement measure of the excitonic W qubit states is evaluated in the picosecond time range, showing increased revivals in the non-Markovian regime. Similar trends are observed in the evolution dynamics of the Meyer-Wallach measure of the N-exciton multipartite state, with results showing that multipartite entanglement can last from 0.5 to 1 ps, between the Bchls of the FMO complex. The teleportation and quantum information splitting fidelities associated with the GHZ and W_A resource states of the excitonic qubit channels of the FMO complex show that revivals in fidelities increase with the degree of non-Markovian strength of the decoherent environment. Results indicate that quantum information processing tasks involving teleportation followed by the decodification process involving W_A states of the FMO complex, may play a critical role during coherent oscillations at physiological temperatures.Comment: 16 pages, new figs, typo

    Harvest pruning of Sultana vines

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    Preliminary investigations are described which promise to ultimately lead to mechanical harvesting of dried sultana fruit. In the experiments the canes which bear most of the fruiting shoots were severed from the vine when the fruit was mature. Subsequently the fruit was treated in four different ways: (1) Picked after wilting, dipped and dried on drying racks;(2) sha'ken off the vines a'fter wilting and dried on ground sheets;(3) shaken a,s dried fruit off the vines;(4) sprayed with dipping emulsion on the vine and shaken off as dried fruit.Treatments 2 and 3 produced dark-coloured fruit and treatments 1 and 4 goliden-coloured fruit. Treating vines once in this manner did in no way affect next season's yield. Possible means to mechanize the harvest are discussed

    Mean field and pairing properties in the crust of neutron stars

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    Properties of the matter in the inner crust of a neutron star are investigated in a Hartree-Fock plus BCS approximation employing schematic effective forces of the type of the Skyrme forces. Special attention is paid to differences between a homogenous and inhomogeneous description of the matter distribution. For that purpose self-consistent Hartree Fock calculations are performed in a spherical Wigner-Seitz cell. The results are compared to predictions of corresponding Thomas Fermi calculations. The influence of the shell structure on the formation of pairing correlations in inhomogeneous matter are discussed.Comment: 11 pages, 9 figure

    Geometrical effects on energy transfer in disordered open quantum systems

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    We explore various design principles for efficient excitation energy transport in complex quantum systems. We investigate energy transfer efficiency in randomly disordered geometries consisting of up to 20 chromophores to explore spatial and spectral properties of small natural/artificial Light-Harvesting Complexes (LHC). We find significant statistical correlations among highly efficient random structures with respect to ground state properties, excitonic energy gaps, multichromophoric spatial connectivity, and path strengths. These correlations can even exist beyond the optimal regime of environment-assisted quantum transport. For random configurations embedded in spatial dimensions of 30 A and 50 A, we observe that the transport efficiency saturates to its maximum value if the systems contain 7 and 14 chromophores respectively. Remarkably, these optimum values coincide with the number of chlorophylls in (Fenna-Matthews-Olson) FMO protein complex and LHC II monomers, respectively, suggesting a potential natural optimization with respect to chromophoric density.Comment: 11 pages, 10 figures. Expanded from the former appendix to arXiv:1104.481

    Self-consistent simulation of quantum wires defined by local oxidation of Ga[Al]As heterostructures

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    We calculate the electronic width of quantum wires as a function of their lithographic width in analogy to experiments performed on nanostructures defined by local oxidation of Ga[Al]As heterostructures. Two--dimensional simulations of two parallel oxide lines on top of a Ga[Al]As heterostructure defining a quantum wire are carried out in the framework of Density Functional Theory in the Local Density Approximation and are found to be in agreement with measurements. Quantitative assessment of the influence of various experimental uncertainties is given. The most influential parameter turns out to be the oxide line depth, followed by its exact shape and the effect of background doping (in decreasing order).Comment: 5 pages, 6 figures; revised figures, clarified tex
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