169 research outputs found

    Criminal Law: Customer’s Permanent Exclusion From Retail Store Due to Prior Shoplifting Arrests Held Enforceable Under Criminal Trespass Statute

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    In interpretive research, trustworthiness has developed to become an important alternative for measuring the value of research and its effects, as well as leading the way of providing for rigour in the research process. The article develops the argument that trustworthiness plays an important role in not only effecting change in a research project’s original setting, but also that trustworthy research contributes toward building a body of knowledge that can play an important role in societal change. An essential aspect in the development of this trustworthiness is its relationship to context. To deal with the multiplicity of meanings of context, we distinguish between contexts at different levels of the research project: the domains of the researcher, the collective, and the individual participant. Furthermore, we argue that depending on the primary purpose associated with the collective learning potential, critical potential, or performative potential of phenomenographic research, developing trustworthiness may take different forms and is related to aspects of pedagogical legitimacy, social legitimacy, and epistemological legitimacy. Trustworthiness in phenomenographic research is further analysed by distinguishing between the internal horizon – the constitution of trustworthiness as it takes place within the research project – and the external horizon, which points to the impact of the phenomenographic project in the world mediated by trustworthiness

    A note on Zolotarev optimal rational approximation for the overlap Dirac operator

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    We discuss the salient features of Zolotarev optimal rational approximation for the inverse square root function, in particular, for its applications in lattice QCD with overlap Dirac quark. The theoretical error bound for the matrix-vector multiplication Hw(Hw2)−1/2Y H_w (H_w^2)^{-1/2}Y is derived. We check that the error bound is always satisfied amply, for any QCD gauge configurations we have tested. An empirical formula for the error bound is determined, together with its numerical values (by evaluating elliptic functions) listed in Table 2 as well as plotted in Figure 3. Our results suggest that with Zolotarev approximation to (Hw2)−1/2 (H_w^2)^{-1/2} , one can practically preserve the exact chiral symmetry of the overlap Dirac operator to very high precision, for any gauge configurations on a finite lattice.Comment: 23 pages, 5 eps figures, v2:minor clarifications, and references added, to appear in Phys. Rev.

    DC current through a superconducting two-barrier system

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    We analyze the influence of the structure within a SNS junction on the multiple Andreev resonances in the subgap I-V characteristics. Coherent interference processes and incoherent propagation in the normal region are considered. The detailed geometry of the normal region where the voltage drops in superconducting contacts can lead to observable effects in the conductance at low voltages.Comment: 11 pages, including 7 postscript file

    Chiral Logs in Quenched QCD

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    The quenched chiral logs are examined on a 163×2816^3 \times 28 lattice with Iwasaki gauge action and overlap fermions. The pion decay constant fπf_{\pi} is used to set the lattice spacing, a=0.200(3)fma = 0.200(3) {\rm fm}. With pion mass as low as ∼180MeV\sim 180 {\rm MeV}, we see the quenched chiral logs clearly in mπ2/mm_{\pi}^2/m and fPf_P, the pseudoscalar decay constant. We analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory (χ\chiPT) to apply. With the constrained curve-fitting method, we are able to extract the quenched chiral log parameter δ\delta together with other low-energy parameters. Only for mπ≤300MeVm_{\pi} \leq 300 {\rm MeV} do we obtain a consistent and stable fit with a constant δ\delta which we determine to be 0.24(3)(4) (at the chiral scale Λχ=0.8GeV\Lambda_{\chi}=0.8 {\rm GeV}). By comparing to the 123×2812^3 \times 28 lattice, we estimate the finite volume effect to be about 2.7% for the smallest pion mass. We also fitted the pion mass to the form for the re-summed cactus diagrams and found that its applicable region is extended farther than the range for the one-loop formula, perhaps up to mπ∼500−600m_{\pi} \sim 500-600 MeV. The scale independent δ\delta is determined to be 0.20(3) in this case. We study the quenched non-analytic terms in the nucleon mass and find that the coefficient C1/2C_{1/2} in the nucleon mass is consistent with the prediction of one-loop χ\chiPT\@. We also obtain the low energy constant L5L_5 from fπf_{\pi}. We conclude from this study that it is imperative to cover only the range of data with the pion mass less than ∼300MeV\sim 300 {\rm MeV} in order to examine the chiral behavior of the hadron masses and decay constants in quenched QCD and match them with quenched one-loop χ\chiPT\@.Comment: 37 pages and 24 figures, pion masses are fitted to the form for the re-summed cactus diagrams, figures added, to appear in PR

    BtubA-BtubB Heterodimer Is an Essential Intermediate in Protofilament Assembly

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    BACKGROUND:BtubA and BtubB are two tubulin-like genes found in the bacterium Prosthecobacter. Our work and a previous crystal structure suggest that BtubB corresponds to alpha-tubulin and BtubA to beta-tubulin. A 1:1 mixture of the two proteins assembles into tubulin-like protofilaments, which further aggregate into pairs and bundles. The proteins also form a BtubA/B heterodimer, which appears to be a repeating subunit in the protofilament. METHODOLOGY/PRINCIPAL FINDINGS:We have designed point mutations to disrupt the longitudinal interfaces bonding subunits into protofilaments. The mutants are in two classes, within dimers and between dimers. We have characterized one mutant of each class for BtubA and BtubB. When mixed 1:1 with a wild type partner, none of the mutants were capable of assembly. An excess of between-dimer mutants could depolymerize preformed wild type polymers, while within-dimer mutants had no activity. CONCLUSIONS:An essential first step in assembly of BtubA + BtubB is formation of a heterodimer. An excess of between-dimer mutants depolymerize wild type BtubA/B by sequestering the partner wild type subunit into inactive dimers. Within-dimer mutants cannot form dimers and have no activity

    Josephson effect in double-barrier superconductor-ferromagnet junctions

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    We study the Josephson effect in ballistic double-barrier SIFIS planar junctions, consisting of bulk superconductors (S), a clean metallic ferromagnet (F), and insulating interfaces (I). We solve the scattering problem based on the Bogoliubov--de Gennes equations and derive a general expression for the dc Josephson current, valid for arbitrary interfacial transparency and Fermi wave vectors mismatch (FWVM). We consider the coherent regime in which quasiparticle transmission resonances contribute significantly to the Andreev process. The Josephson current is calculated for various parameters of the junction, and the influence of both interfacial transparency and FWVM is analyzed. For thin layers of strong ferromagnet and finite interfacial transparency, we find that coherent (geometrical) oscillations of the maximum Josephson current are superimposed on the oscillations related to the crossover between 0 and π\pi states. For the same case we find that the temperature-induced 0−π0-\pi transition occurs if the junction is very close to the crossovers at zero temperature.Comment: 13 pages, 6 figure

    An instrument to determine the technological literacy levels of upper secondary school students

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    In this article, an instrument for assessing upper secondary school students’ levels of technological literacy is presented. The items making up the instrument emerged from a previous study that employed a phenomenographic research approach to explore students’ conceptions of technology in terms of their understanding of the nature of technology and their interaction with technological artefacts. The instrument was validated through administration to 1,245 students on completion of their 12 years of formal schooling. A factor analysis was conducted on the data and Cronbach alpha reliability coefficients determined. The results show that a five-dimension factor structure (namely, artefact, process, direction/instruction, tinkering, and engagement) strongly supported the dimensions as developed during the original phenomenographic study. The Cronbach alpha reliability co-efficient of each dimension was satisfactory. Based on these findings, the instrument has been shown to be valid and reliable and can be used with confidence

    Crystal structure of nucleotide-free dynamin

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    Dynamin is a mechanochemical GTPase that oligomerizes around the neck of clathrin-coated pits and catalyses vesicle scission in a GTP-hydrolysis-dependent manner. The molecular details of oligomerization and the mechanism of the mechanochemical coupling are currently unknown. Here we present the crystal structure of human dynamin 1 in the nucleotide-free state with a four-domain architecture comprising the GTPase domain, the bundle signalling element, the stalk and the pleckstrin homology domain. Dynamin 1 oligomerized in the crystals via the stalks, which assemble in a criss-cross fashion. The stalks further interact via conserved surfaces with the pleckstrin homology domain and the bundle signalling element of the neighbouring dynamin molecule. This intricate domain interaction rationalizes a number of disease-related mutations in dynamin 2 and suggests a structural model for the mechanochemical coupling that reconciles previous models of dynamin function
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