704 research outputs found

    Exploring Interface Sign Ontologies for Web User Interface Design and Evaluation: A User Study

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    Part 2: Organizational Semiotics and ApplicationsInternational audienceThe aim of this paper is twofold: firstly, to find the set of ontologies (i.e., the set of concepts and skills) presupposed by users when interpreting the meaning of web interface signs (i.e., the smallest elements of web user interfaces), and secondly, to investigate users’ difficulties in interpreting the meanings of interface signs belonging to different kinds of ontologies. In order to achieve these aims an empirical user study was conducted with 26 test participants. The study data was gathered by semi-structured interviews and questionnaires. Following an empirical research approach, descriptive statistics and qualitative data analysis were used to analyze the data. The study results provide a total of twelve ontologies and reveal the users’ difficulties in interpreting the meanings of interface signs belonging to different kinds of ontologies

    Structure and Mechanism of Dimer-Monomer Transition of a Plant Poly(A)-Binding Protein upon RNA Interaction: Insights into Its Poly(A) Tail Assembly

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    Poly(A)-binding proteins (PABPs) play crucial roles in mRNA biogenesis, stability, transport and translational control in most eukaryotic cells. Although animal PABPs are well-studied proteins, the biological role, three-dimensional structure and RNA-binding mode of plant PABPs remain largely uncharacterized. Here, we report the structural features and RNA-binding mode of a Citrus sinensis PABP (CsPABPN1). CsPABPN1 has a domain architecture of nuclear PABPs (PABPNs) with a single RNA recognition motif (RRM) flanked by an acidic N-terminus and a GRPF-rich C-terminus. The RRM domain of CsPABPN1 displays virtually the same three-dimensional structure and poly(A)-binding mode of animal PABPNs. However, while the CsPABPN1 RRM domain specifically binds poly(A), the full-length protein also binds poly(U). CsPABPN1 localizes to the nucleus of plant cells and undergoes a dimer–monomer transition upon poly(A) interaction. We show that poly(A) binding by CsPABPN1 begins with the recognition of the RNA-binding sites RNP1 and RNP2, followed by interactions with residues of the β2 strands, which stabilize the dimer, thus leading to dimer dissociation. Like human PABPN1, CsPABPN1 also seems to form filaments in the presence of poly(A). Based on these data, we propose a structural model in which contiguous CsPABPN1 RRM monomers wrap around the RNA molecule creating a superhelical structure that could not only shield the poly(A) tail but also serve as a scaffold for the assembly of additional mRNA processing factors

    Consistency analysis of a nonbirefringent Lorentz-violating planar model

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    In this work analyze the physical consistency of a nonbirefringent Lorentz-violating planar model via the analysis of the pole structure of its Feynman propagators. The nonbirefringent planar model, obtained from the dimensional reduction of the CPT-even gauge sector of the standard model extension, is composed of a gauge and a scalar fields, being affected by Lorentz-violating (LIV) coefficients encoded in the symmetric tensor κμν\kappa_{\mu\nu}. The propagator of the gauge field is explicitly evaluated and expressed in terms of linear independent symmetric tensors, presenting only one physical mode. The same holds for the scalar propagator. A consistency analysis is performed based on the poles of the propagators. The isotropic parity-even sector is stable, causal and unitary mode for 0≤κ00<10\leq\kappa_{00}<1. On the other hand, the anisotropic sector is stable and unitary but in general noncausal. Finally, it is shown that this planar model interacting with a λ∣φ∣4−\lambda|\varphi|^{4}-Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio

    Distribution of black flies (Diptera: Simuliidae) in the State of EspĂ­rito Santo, Brazil

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    Entre os anos de 2004 e 2008 foram realizadas coletas de Simuliidae em vĂĄrias localidades no Estado do EspĂ­rito Santo, Brasil. No total, 66 cĂłrregos e rios das doze principais bacias hidrogrĂĄficas do estado foram amostrados. Dezessete espĂŠcies foram coletadas, sendo que nove delas representam ocorrĂŞncias novas para o estado (Simulium pertinax, S. jujuyense, S. rubrithorax, S. subnigrum, S. travassosi, S. spinibranchium, S. hirtipupa, S. lutzianum e S. anamariae), duplicando o nĂşmero de espĂŠcies conhecidas no estado.We conducted a freshwater survey from 2004 to 2008 in several localities of EspĂ­rito Santo, Brazil. In total, 66 streams and rivers were sampled in the 12 hydrographic basins of the state. We collected and identified 17 species of which nine represent new records (Simulium pertinax, S. jujuyense, S. rubrithorax, S. subnigrum, S. travassosi, S. spinibranchium, S. hirtipupa, S. lutzianum e S. anamariae). These findings doubled the number of records of black fly species to the State of EspĂ­rito Santo, Brazil

    Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory

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    Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius AA. Also the events detected simultaneously by the surface and fluorescence detectors (the `hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.Comment: Matches published versio

    Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

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    Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

    Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

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    A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

    Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

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    The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters
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