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J. D. McEwen M. P. Hobson A. N. Lasenby D. J. Mortlock 《Monthly notices of the Royal Astronomical Society》2005,359(4):1583-1596
A directional spherical wavelet analysis is performed to examine the Gaussianity of the Wilkinson Microwave Anisotropy Probe ( WMAP ) 1-yr data. Such an analysis is facilitated by the introduction of a fast directional continuous spherical wavelet transform. The directional nature of the analysis allows us to probe orientated structure in the data. Significant deviations from Gaussianity are detected in the skewness and kurtosis of spherical elliptical Mexican hat and real Morlet wavelet coefficients for both the WMAP and Tegmark, de Oliveira-Costa & Hamilton foreground-removed maps. The previous non-Gaussianity detection made by Vielva et al. using the spherical symmetric Mexican hat wavelet is confirmed, although their detection at the 99.9 per cent significance level is only made at the 95.3 per cent significance level using our most conservative statistical test. Furthermore, deviations from Gaussianity in the skewness of spherical real Morlet wavelet coefficients on a wavelet scale of 550 arcmin (corresponding to an effective global size on the sky of ∼26° and an internal size of ∼3°) at an azimuthal orientation of 72°, are made at the 98.3 per cent significance level, using the same conservative method. The wavelet analysis inherently allows us to localize on the sky those regions that introduce skewness and those that introduce kurtosis. Preliminary noise analysis indicates that these detected deviation regions are not atypical and have average noise dispersion. Further analysis is required to ascertain whether these detected regions correspond to secondary or instrumental effects, or whether in fact the non-Gaussianity detected is due to intrinsic primordial fluctuations in the cosmic microwave background. 相似文献
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C. Monteserín R. B. Barreiro P. Vielva E. Martínez-González M. P. Hobson A. N. Lasenby 《Monthly notices of the Royal Astronomical Society》2008,387(1):209-219
We have estimated the cosmic microwave background (CMB) variance from the three-year Wilkinson Microwave Anisotropy Probe ( WMAP ) data, finding a value which is significantly lower than the one expected from Gaussian simulations using the WMAP best-fitting cosmological model, at a significance level of 98.7 per cent. This result is even more prominent if we consider only the North ecliptic hemisphere (99.8 per cent). Different analyses have been performed in order to identify a possible origin for this anomaly. In particular, we have studied the behaviour of single-radiometer and single-year data as well as the effect of residual foregrounds and 1/f noise, finding that none of these possibilities can explain the low value of the variance. We have also tested the effect of varying the cosmological parameters, finding that the estimated CMB variance tends to favour higher values of n s than the one of the WMAP best-fitting model. In addition, we have also tested the consistency between the estimated CMB variance and the actual measured CMB power spectrum of the WMAP data, finding a strong discrepancy. A possible interpretation of this result could be a deviation from Gaussianity and/or isotropy of the CMB. 相似文献
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In order to better investigate the compositions and the origins of fluids associated with diamond growth, we have carried-out combined noble gas (He and Ar), C and N isotope, K, Ca and halogen (Cl, Br, I) determinations on fragments of individual microinclusion-bearing diamonds from the Panda kimberlite, North West Territories, Canada. The fluid concentrations of halogens and noble gases in Panda diamonds are enriched by several orders of magnitude over typical upper mantle abundances. However, noble gas, C and N isotopic ratios (3He/4He = 4-6 Ra, 40Ar/36Ar = 20,000-30,000, δ13C = −4.5‰ to −6.9‰ and δ15N = −1.2‰ to −8.8‰) are within the worldwide range determined for fibrous diamonds and similar to the mid ocean ridge basalt (MORB) source value. The high 36Ar content of the diamonds (>1 × 10−9 cm3/g) is at least an order of magnitude higher than any previously reported mantle sample and enables the 36Ar content of the subcontinental lithospheric mantle to be estimated at ∼0.6 × 10−12 cm3/g, again similar to estimates for the MORB source. Three fluid types distinguished on the basis of Ca-K-Cl compositions are consistent with carbonatitic, silicic and saline end-members identified in previous studies of diamonds from worldwide sources. These fluid end-members also have distinct halogen ratios (Br/Cl and I/Cl). The role of subducted seawater-derived halogens, originally invoked to explain some of the halogen ratio variations in diamonds, is not considered an essential component in the formation of the fluids. In contrast, it is considered that large halogen fractionation of a primitive mantle ratio occurs during fluid-melt partitioning in forming silicic fluids, and during separation of an immiscible saline fluid. 相似文献
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Enacting environmental justice in Singapore: Performative justice and the Green Volunteer Network 总被引：1，自引：0，他引：1
Kersty Hobson 《Geoforum》2006,37(5):671-681
Environmental justice research has of late expanded beyond its’ original focus on the distribution of environmental ‘bads’ to debate injustices at a wide array of sites and scales. Despite this expansion, the applicability of an environmental justice framework to seemingly apolitical and banal expressions of environmental concerns remains open to question. This paper argues that environmental justice struggles can be located in the mundane environmental politics of Singapore, by employing a performative rather than rights-based approach to both justice and politics. It draws on qualitative research into volunteers’ practices in one Singaporean environmental organisation, and asserts that through their focus on experiential learning and re-inscribing ‘developmental’ spaces as spaces of care and justice, volunteers seek to redress the social, political and environmental injustices replete within the spatial politics of Singapore. 相似文献
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Environmental psychology and the geographies of ethical and sustainable consumption: aligning, triangulating, challenging? 总被引：2，自引：0，他引：2
Kersty Hobson 《Area》2006,38(3):292-300
Human geographers' research into lay responses to burgeoning environmental issues has highlighted their mediated and contingent constitution. Situated within the discipline's cultural turn, this work has challenged prevailing informational and cognitive approaches to sustainability. In doing so, however, potentially informative concepts and findings from environmental psychology have been sidelined. In this paper I attempt a modest allying of the two sub-disciplines, outlining their differences and similarities, and arguing that environmental psychology can triangulate with human geography, as well as challenge tendencies within human geography literatures to simplify the 'psychological' subject. 相似文献