121 research outputs found

    Abundance and evolution of galaxy clusters in cosmological models with massive neutrino

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    The time evolution of the number density of galaxy clusters and their mass and temperature functions are used to constrain cosmological parameters in the spatially flat dark matter models containing a fraction of hot particles (massive neutrino) additional to cold and baryonic matter. We test the modified MDM models with cosmic gravitational waves and show that they neither pass the cluster evolution test nor reproduce the observed height of the first acoustic peak in ΔT/T\Delta T/T spectrum, and therefore should be ruled out. The models with a non-zero cosmological constant are in better agreement with observations. We estimate the free cosmological parameters in Λ\LambdaMDM with a negligible abundance of gravitational waves, and find that within the parameter ranges h∈(0.6,0.7)h\in (0.6, 0.7), n∈(0.9,1.1)n\in (0.9, 1.1), (i) the value of ΩΛ\Omega_\Lambda is strongly affected by a small fraction of hot dark matter, fÎœâ‰ĄÎ©Îœ/Ωm∈(0,0.2)f_\nu\equiv\Omega_\nu /\Omega_m\in (0, 0.2): 0.45<ΩΛ<0.70.45 <\Omega_\Lambda <0.7 (1σ1\sigma CL), and (ii) the redshift evolution of galaxy clusters alone reveals the following explicit correlation between ΩΛ\Omega_\Lambda and fÎœf_\nu: ΩΛ+0.5fÎœ=0.65±0.1\Omega_\Lambda +0.5f_\nu =0.65\pm 0.1. The present accuracy of observational data allows only to bound the fraction of hot matter, fΜ∈(0,0.2)f_\nu\in (0, 0.2) (the number of massive neutrino species remains undelimited, NÎœ=1,2,3N_\nu =1, 2, 3).Comment: 9 pages, 7 figures, submitted in A&

    Quality of mother-child interaction, differences in sexual attitudes, and inter-generational disagreement on sexuality.

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    The current paper examines the frequency of inter-generational disagreement reported by mothers and adolescents as a function of the quality of their interaction, and the match between their sexual attitudes. We expected that the quality of family interaction would act as a "family asset" that would enable members of families to manage and control the tensions caused by differences in (sexual) attitudes. Data on 319 British adolescent-mother pairs were analysed using structural equation modelling, revealing good support for these expectations: differences in sexual attitudes were more strongly linked to inter-family disagreement in low quality of mother-child interaction families than in high quality of motherchild interaction families. Implications of the study are discussed. © 1997 OPA (Overseas Publishers Association)

    Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

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    The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

    Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

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    A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

    The provenancing of flint artefacts using palynological techniques

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    The provenancing of flint artefacts has proved problematic in the past. Acid maceration to extract age-diagnostic organic-walled microplankton from sedimentary materials is a technique routinely employed in both industrial hydrocarbon exploration and Quaternary studies. Here we assess the application of this technique to provenance determination of flint nodules from three locations (two in southern England and one in the Inner Hebrides, Scotland), each of which has abundant local evidence of flint utilization for artefact manufacture in prehistory. We show that, whilst not all flint nodules yield abundant or well preserved organic-walled microfossils assemblages, there is a significant potential for the use of this technique, which deserves further investigation

    Siliceous dinoflagellate thecal fossils from the Eocene of Barbados

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    A dinocyst calibration of the Western European Barremian

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    SIGLEAvailable from British Library Document Supply Centre- DSC:D59193 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

    The Gonyaulax spinifera (Dinophyceae) “complex”: Perpetuating the paradox?

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    Specimens of dinoflagellate cysts referable to the cyst-species Spiniferites ramosus (Ehrenberg 1838) Mantell 1854 and Nematosphaeropsis labyrinthus (Ostenfeld 1903) Reid 1974 have been produced in the same crossed-strain of Gonyaulax spinifera-type (Claparùde and Lachmann 1857) Diesing 1866 motile cells during a routine encystment experiment. Detailed observations were made and are reported on the process of encystment, which follows a similar pattern to that already described for Lingulodinium polyedrum. Both cyst types displayed a wide range of morphological variations with respect to process length and/or trabecular development. The cysts morphology vary between “typical” S. ramosus specimens with well developed trifurcate processes with bifurcated distal ends, to specimens with abnormally developed or incomplete processes, specimens with partially developed trabecular network, to typical N. labyrinthus specimens with a complete network of trabecula joining the distal ends of the processes. The cysts were produced in salinities of 25 and 30 psu at 12 °C. Experiments in other salinities (15, 20, 35 and 40 psu) only produced cysts of S. ramosus-type. We suggest that the particular salinity conditions (25 and 30 psu) used in our experience probably triggered the expression of a particular phenotype.<br/
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