216 research outputs found

    Mentoring Qualitative Research Authors Globally: The Qualitative Report Experience

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    Authoring quality qualitative inquiry is a challenge for most researchers. A lack of local mentors can make writing even more difficult. To meet this need, The Qualitative Report ( TQR ) has helped authors from around the world develop their papers into published articles. TQR editorial team members will discuss the history of the journal, their philosophy of author development; manuscript development strategies; solutions for managing differences; challenges working worldwide; authors’ feedback; and the collective global futures of TQR and qualitative researche

    Pairing symmetry and long range pair potential in a weak coupling theory of superconductivity

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    We study the superconducting phase with two component order parameter scenario, such as, dx2y2+eiθsαd_{x^2-y^2} + e^{i\theta}s_{\alpha}, where α=xy,x2+y2\alpha = xy, x^2+y^2. We show, that in absence of orthorhombocity, the usual dx2y2d_{x^2-y^2} does not mix with usual sx2+y2s_{x^2+y^2} symmetry gap in an anisotropic band structure. But the sxys_{xy} symmetry does mix with the usual d-wave for θ=0\theta =0. The d-wave symmetry with higher harmonics present in it also mixes with higher order extended ss wave symmetry. The required pair potential to obtain higher anisotropic dx2y2d_{x^2-y^2} and extended s-wave symmetries, is derived by considering longer ranged two-body attractive potential in the spirit of tight binding lattice. We demonstrate that the dominant pairing symmetry changes drastically from dd to ss like as the attractive pair potential is obtained from longer ranged interaction. More specifically, a typical length scale of interaction ξ\xi, which could be even/odd multiples of lattice spacing leads to predominant s/ds/d wave symmetry. The role of long range interaction on pairing symmetry has further been emphasized by studying the typical interplay in the temperature dependencies of these higher order dd and ss wave pairing symmetries.Comment: Revtex 8 pages, 7 figures embeded in the text, To appear in PR

    Emergent excitations in a geometrically frustrated magnet

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    Frustrated systems are ubiquitous and interesting because their behavior is difficult to predict. Magnetism offers extreme examples in the form of spin lattices where all interactions between spins cannot be simultaneously satisfied. Such geometrical frustration leads to macroscopic degeneracies, and offers the possibility of qualitatively new states of matter whose nature has yet to be fully understood. Here we have discovered how novel composite spin degrees of freedom can emerge from frustrated interactions in the cubic spinel ZnCr2O4. Upon cooling, groups of six spins self-organize into weakly interacting antiferromagnetic loops whose directors, defined as the unique direction along which the spins are aligned parallel or antiparallel, govern all low temperature dynamics. The experimental evidence comes from a measurement of the magnetic form factor by inelastic neutron scattering. While the data bears no resemblance to the atomic form factor for chromium, they are perfectly consistent with the form factor for hexagonal spin loop directors. The hexagon directors are to a first approximation decoupled from each other and hence their reorientations embody the long-sought local zero energy modes for the pyrochlore lattice.Comment: 10 pages, 4 figures upon reques

    Predictions of biodiversity are improved by integrating trait-based competition with abiotic filtering.

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    Funder: University of Canterbury; Id: http://dx.doi.org/10.13039/100008414Funder: University of Waikato; Id: http://dx.doi.org/10.13039/100010061Funder: University of Wyoming; Id: http://dx.doi.org/10.13039/100008106Funder: Manaaki Whenua ‐ Landcare ResearchAll organisms must simultaneously tolerate the environment and access limiting resources if they are to persist. Approaches to understanding abiotic filtering and competitive interactions have generally been developed independently. Consequently, integrating those factors to predict species abundances and community structure remains an unresolved challenge. We introduce a new synthetic framework that models both abiotic filtering and competition by using functional traits. First, our framework estimates species carrying capacities along abiotic gradients. Second, it estimates pairwise competitive interactions as a function of species trait differences. Applied to the study of a complex wetland community, our combined approach more than doubles the explained variance of species abundances compared to a model of abiotic tolerances alone. Trait-based integration of competitive interactions and abiotic filtering improves our ability to predict species abundances, bringing us closer to more accurate predictions of biodiversity structure in a changing world

    Melting of a 2D Quantum Electron Solid in High Magnetic Field

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    The melting temperature (TmT_m) of a solid is generally determined by the pressure applied to it, or indirectly by its density (nn) through the equation of state. This remains true even for helium solids\cite{wilk:67}, where quantum effects often lead to unusual properties\cite{ekim:04}. In this letter we present experimental evidence to show that for a two dimensional (2D) solid formed by electrons in a semiconductor sample under a strong perpendicular magnetic field\cite{shay:97} (BB), the TmT_m is not controlled by nn, but effectively by the \textit{quantum correlation} between the electrons through the Landau level filling factor ν\nu=nh/eBnh/eB. Such melting behavior, different from that of all other known solids (including a classical 2D electron solid at zero magnetic field\cite{grim:79}), attests to the quantum nature of the magnetic field induced electron solid. Moreover, we found the TmT_m to increase with the strength of the sample-dependent disorder that pins the electron solid.Comment: Some typos corrected and 2 references added. Final version with minor editoriol revisions published in Nature Physic

    Network adaptation improves temporal representation of naturalistic stimuli in drosophila eye: II Mechanisms

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    Retinal networks must adapt constantly to best present the ever changing visual world to the brain. Here we test the hypothesis that adaptation is a result of different mechanisms at several synaptic connections within the network. In a companion paper (Part I), we showed that adaptation in the photoreceptors (R1-R6) and large monopolar cells (LMC) of the Drosophila eye improves sensitivity to under-represented signals in seconds by enhancing both the amplitude and frequency distribution of LMCs' voltage responses to repeated naturalistic contrast series. In this paper, we show that such adaptation needs both the light-mediated conductance and feedback-mediated synaptic conductance. A faulty feedforward pathway in histamine receptor mutant flies speeds up the LMC output, mimicking extreme light adaptation. A faulty feedback pathway from L2 LMCs to photoreceptors slows down the LMC output, mimicking dark adaptation. These results underline the importance of network adaptation for efficient coding, and as a mechanism for selectively regulating the size and speed of signals in neurons. We suggest that concert action of many different mechanisms and neural connections are responsible for adaptation to visual stimuli. Further, our results demonstrate the need for detailed circuit reconstructions like that of the Drosophila lamina, to understand how networks process information

    The Shapes of Cooperatively Rearranging Regions in Glass Forming Liquids

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    The shapes of cooperatively rearranging regions in glassy liquids change from being compact at low temperatures to fractal or ``stringy'' as the dynamical crossover temperature from activated to collisional transport is approached from below. We present a quantitative microscopic treatment of this change of morphology within the framework of the random first order transition theory of glasses. We predict a correlation of the ratio of the dynamical crossover temperature to the laboratory glass transition temperature, and the heat capacity discontinuity at the glass transition, Delta C_p. The predicted correlation agrees with experimental results for the 21 materials compiled by Novikov and Sokolov.Comment: 9 pages, 6 figure

    Kahler-Einstein metrics emerging from free fermions and statistical mechanics

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    We propose a statistical mechanical derivation of Kahler-Einstein metrics, i.e. solutions to Einstein's vacuum field equations in Euclidean signature (with a cosmological constant) on a compact Kahler manifold X. The microscopic theory is given by a canonical free fermion gas on X whose one-particle states are pluricanonical holomorphic sections on X (coinciding with higher spin states in the case of a Riemann surface). A heuristic, but hopefully physically illuminating, argument for the convergence in the thermodynamical (large N) limit is given, based on a recent mathematically rigorous result about exponentially small fluctuations of Slater determinants. Relations to effective bosonization and the Yau-Tian-Donaldson program in Kahler geometry are pointed out. The precise mathematical details will be investigated elsewhere.Comment: v1: 22 pages v2: 25 pages. The relation to quantum gravity has been further developed by working over the moduli space of all complex structures. Relations to Donaldson's program pointed out. References adde

    TRY plant trait database - enhanced coverage and open access

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    Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

    Nuclear Factor 90(NF90) targeted to TAR RNA inhibits transcriptional activation of HIV-1

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    <p>Abstract</p> <p>Background</p> <p>Examination of host cell-based inhibitors of HIV-1 transcription may be important for attenuating viral replication. We describe properties of a cellular double-stranded RNA binding protein with intrinsic affinity for HIV-1 TAR RNA that interferes with Tat/TAR interaction and inhibits viral gene expression.</p> <p>Results</p> <p>Utilizing TAR affinity fractionation, North-Western blotting, and mobility-shift assays, we show that the C-terminal variant of nuclear factor 90 (NF90ctv) with strong affinity for the TAR RNA, competes with Tat/TAR interaction <it>in vitro</it>. Analysis of the effect of NF90ctv-TAR RNA interaction <it>in vivo </it>showed significant inhibition of Tat-transactivation of HIV-1 LTR in cells expressing NF90ctv, as well as changes in histone H3 lysine-4 and lysine-9 methylation of HIV chromatin that are consistent with the epigenetic changes in transcriptionally repressed gene.</p> <p>Conclusion</p> <p>Structural integrity of the TAR element is crucial in HIV-1 gene expression. Our results show that perturbation Tat/TAR RNA interaction by the dsRNA binding protein is sufficient to inhibit transcriptional activation of HIV-1.</p
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