603 research outputs found

    A chronometric exploration of high-resolution ‘sensitive TMS masking’ effects on subjective and objective measures of vision

    Get PDF
    Transcranial magnetic stimulation (TMS) can induce masking by interfering with ongoing neural activity in early visual cortex. Previous work has explored the chronometry of occipital involvement in vision by using single pulses of TMS with high temporal resolution. However, conventionally TMS intensities have been high and the only measure used to evaluate masking was objective in nature. Recent studies have begun to incorporate subjective measures of vision, alongside objective ones. The current study goes beyond previous work in two regards. First, we explored both objective vision (an orientation discrimination task) and subjective vision (a stimulus visibility rating on a four-point scale), across a wide range of time windows with high temporal resolution. Second, we used a very sensitive TMS-masking paradigm: stimulation was at relatively low TMS intensities, with a figure-8 coil, and the small stimulus was difficult to discriminate already at baseline level. We hypothesized that this should increase the effective temporal resolution of our paradigm. Perhaps for this reason, we are able to report a rather interesting masking curve. Within the classical-masking time window, previously reported to encompass broad SOAs anywhere between 60 and 120 ms, we report not one, but at least two dips in objective performance, with no masking in-between. The subjective measure of vision did not mirror this pattern. These preliminary data from our exploratory design suggest that, with sensitive TMS masking, we might be able to reveal visual processes in early visual cortex previously unreported

    2-Cyano-1-methyl­pyridinium nitrate

    Get PDF
    In the title compound, C7H7N2 +·NO3 −, all atoms except the methyl H atoms lie on a crystallographic mirror plane. The inter­layer distance, including that between aligned N atoms from alternating cations and anions in adjacent layers, is exceptionally short at 3.055 (1) Å. Two-dimensional C—H⋯O hydrogen-bonded networks link cations to anions, while C—H⋯N inter­actions link cations within each layer. Anion–π inter­actions with the cations assist in binding the layers together

    Measurement of polarisation observables in Ks0Σ+K^0_s\Sigma^+ photoproduction off the proton

    Get PDF
    The reaction γpKS0Σ+\gamma \, p \rightarrow K^0_S\,\Sigma^+ is studied in the photon energy range from threshold. Linearly polarised photon beams from coherent bremsstrahlung enabled the first measurement of photon beam asymmetries in this reaction up to Eγ=2250E_\gamma = 2250 MeV. In addition, the recoil hyperon polarisation was determined through the asymmetry in the weak decay Σ+pπ0\Sigma^+ \rightarrow p \pi^0 up to Eγ=1650E_\gamma = 1650 MeV. The data are compared to partial wave analyses, and the possible impact on the interpretation of a recently observed cusp-like structure near the KK^* thresholds is discussed.Comment: 6 pages, 5 figures. References [8,9,10,11] which were not on the original submission are now include

    Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra

    Get PDF
    In this work we present Spitzer 3.6 and 4.5 micron secondary eclipse observations of five new cool (<1200 K) transiting gas giant planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for planets with previously published observations in order to constrain the temperature- and mass-dependent properties of gas giant planet atmospheres. We find that the dayside emission spectra of planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric methane to CO ratio to vary as a function of metallicity, and we therefore use our observations of these planets to constrain their atmospheric metallicities. We find that the most massive planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 micron brightness temperatures for these cool transiting planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass planets are more likely to have metal-rich atmospheres.Comment: 16 pages, 14 figures, accepted for publication in Ap

    Quasi-free photoproduction of eta-mesons of the neutron

    Full text link
    Quasi-free photoproduction of eta-mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta-mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasi-free n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta-production off the neutron shows a pronounced bump-like structure at W=1.68 GeV (E_g ~ 1 GeV), which is absent for the proton.Comment: accepted for publication in Phys. Rev. Let

    Measurement of the Beam Asymmetry Σ\Sigma in the Forward Direction for pi0 Photoproduction

    Get PDF
    Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector for photon energies between 0.92 and 1.68~GeV at the electron accelerator ELSA. The beam asymmetry~Σ\Sigma has been extracted for 115<θc.m.<155115^\circ < \theta_{\rm c.m.} < 155^\circ of the π0\pi^0~meson and for θc.m.<60\theta_{\rm c.m.} < 60^\circ. The new beam asymmetry data improve the world database for photon energies above 1.5~GeV and, by covering the very forward region, extend previously published data for the same reaction by our collaboration. The angular dependence of Σ\Sigma shows overall good agreement with the SAID parameterization.Comment: 11 pages, 10 figures, published in Phys. Rev. C, included LEPS data and MAID 2007 predictions for comparison with our dat

    High statistics study of the reaction γpp  2π0\gamma p\to p\;2\pi^0

    Get PDF
    The photoproduction of 2π0\pi^0 mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600\,MeV to 2.5\,GeV. Differential and total cross sections and pπ0π0p\pi^0\pi^0 Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and Δ\Delta resonances contributing to the pπ0π0p\pi^0\pi^0 final state were determined within the BnGa partial wave analysis. The data presented here allow us to determine branching ratios of nucleon and Δ\Delta resonances for their decays into pπ0π0p\pi^0\pi^0 via several intermediate states. Most prominent are decays proceeding via Δ(1232)π\Delta(1232)\pi, N(1440)1/2+πN(1440)1/2^+\pi, N(1520)3/2πN(1520)3/2^-\pi, N(1680)5/2+πN(1680)5/2^+\pi, but also pf0(500)pf_0(500), pf0(980)pf_0(980), and pf2(1270)pf_2(1270) contribute to the reaction.Comment: 28 pages, 17 figures, 7 table

    Photoproduction of Neutral Pions off Protons

    Get PDF
    Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction γppπ0\gamma p\to p\pi^0 for photon energies between 0.85 and 2.50 GeV. The π0\pi^0 mesons are observed in their dominant neutral decay mode: π0γγ\pi^0\to\gamma\gamma. For the first time, the differential cross sections cover the very forward region, θc.m.<60\theta_{\rm c.m.}<60^\circ. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances G17G_{17}(2190), D13D_{13}(2080), and D15D_{15}(2070).Comment: 12 pages, 9 figures, minor modifications to PWA sectio

    Photoproduction of meson pairs: First measurement of the polarization observable I^s

    Get PDF
    The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves.Comment: 11 pages, 6 figures, v2 to appear in Phys. Lett.
    corecore