Some Distinctions Between Self-Similar and Self-Affine Estimates of Fractal Dimension with Case History

Compass, power-spectral, and roughness-length estimates of fractal dimension are widely used to evaluate the fractal characteristics of geological and geophysical variables. These techniques reveal self-similar or self-affine fractal characteristics and are uniquely suited for certain analysis. Compass measurements establish the self-similarity of profile and can be used to classify profiles based on variations of profile length with scale. Power spectral and roughness-length methods provide scale-invariant self-affine measures of relief variation and are useful in the classification of profiles based on relative variation of profile relief with scale. Profile magnification can be employed to reduce differences between the compass and power-spectral dimensions; however, the process of magnification invalidates estimates of profile length or shortening made from the results. The power-spectral estimate of fractal dimension is invariant to magnification, but is generally subject to significant error from edge effects and nonstationarity. The roughness-length estimate is also invariant to magnification and in addition is less sensitive to edge effects and nonstationarity. Analysis of structural cross sections using these methods highlight differences between self-similar and self-affine evaluations. Shortening estimates can be made from the compass walk analysis that includes shortening contributions from predicted small-scale structure. Roughness-length analysis reveals systematic structural changes that, however, cannot be easily related to strain. Power-spectral analysis failed to extract useful structural information from the sections.     

The structure of freshwater humic substances as revealed by 13C-NMR spectroscopy

Freshwater humic substances from Lake Celyn, Gwynedd, N. Wales have been investigated by ¹³C-NMR spectroscopy. Carboxyl, aromatic, o-alkyl and alkyl resonances can be recognised. Varying pulse delay from 0.43 s to 2.5 sec has little effect on the magnitude of the signal ascribed to aromatic carbon, but there is a small nuclear Overhauser effect (1.45 at a pulse delay of 0.8 sec).The results show-that 24% of the Lake Celyn humic acid carbon is carboxyl and 40% is aromatic. The high proportion of aromatic carbon suggests the Lake Celyn humic acid is largely formed from terrestrial humic substances from the surrounding peaty watershed.     

Short-range variations in the micromorphology of a palaeosol from Wivenhoe in southeast England

The pedogenic histories of four adjacent profiles of a polygenetic palaeosol developed on a Middle Pleistocene terrace of the proto-Thames from Wivenhoe in southeast England are reconstructed on the basis of superposition of key micromorphological features. Despite a considerable variation in macromorphology, partly resulting from large-scale periglacial features, three of the profiles have similar micromorphological records in that they retain evidence for two phases of clay illuviation separated by a period of periglacial disruption. This reconstruction, however, seems to be incomplete because the fourth profile contains micromorphological evidence for a further illuviation–disruption cycle. The extent of this variation suggests that soil micromorphology should be used only with care to reconstruct pedogenic or pedosedimentary histories of complex polygenetic palaeosols, or to compare such palaeosols on different surfaces of chronosequences spanning periods of major climatic change. The variable and possibly limited resolution of micromorphology, together with the current uncertainty over the exact environmental signifiance of illuvial clay features, means that inferred pedogenic phases should be correlated with specific climatic stages only with considerable caution. © 1998 John Wiley & Sons, Ltd.     

Rb-Sr isotopic studies of a polymetamorphic granulite terrane,Strangways Range,central Australia

Rb-Sr isotopic investigation of forty rocks from three different granulite localities in the Strangways Ranges, central Australia indicated two distinct granulite metamorphisms, namely M1: 1860±80 m.y., and M2: 1470±60 m.y. and 1430±60 m.y., λ=1.39x10^?11yr^?1. M2 has been recorded in the felsic granulites of two of the three localities. Although the Sr isotopic systems in the felsic granulites seem to show a normal growth in a closed system during M2, the Rb-Sr systems for some calcareous and mafic granulites have not completely re-equilibrated during M2, as shown by the scatter with respect to the reference isochrons for M1 and M2. Ca-carbonate rocks display unusually low level of Sr (20–120 ppm. Sr, and high Ca/Sr ratios). Schistose zones of retrogression in the granulites, dated by K-Ar and ⁴⁰Ar-³⁹Ar methods at ≈350 m.y., yield anomalous Rb-Sr data.     

非潮汐海洋运动对地球动力学扁率变化的贡献

通过考察全球海洋环流数值模型以及TOPEX/Poseidon海洋测高数据,得到结论：1997/1998年后的部分J2异常变化可能来自海洋环流变化导致的质量重新分布,具体地说是太平洋环流变化导致的从高纬地区向低纬地区的质量迁移. 本工作表明来自于海洋内部温盐效应的变化对J2异常变化有重要贡献,进一步证实了卫星激光测距资料所得结果的可靠性.     

The reversal of the solar polar magnetic fields

Some theoretical difficulties confronting the current model of the polar magnetic reversal by cancellation with the flux remnants of decaying active regions are discussed. It is shown that the flux transport equation does not adequately describe the essential physical consequences of the transport of large-scale fields, linked to deep subsurface toroids, over distances comparable with the solar radius. The possibility that subsurface reconnections may release these fields to form U-loops is discussed but it is shown that, in this event, the loops will quickly rise to the surface. Mechanisms whereby the flux may escape through the surface are considered.     

Relation between alternations of uplift and subsidence revealed by Late Cenozoic fluvial sequences and physical properties of the continental crust

Reversals in vertical crustal motion, alternations between uplift and subsidence over time scales of hundreds of thousands of years or more, have been identified in Late Cenozoic fluvial sequences in many regions worldwide. They form a class of fluvial archive that is distinct from the extreme stability observed in Archaean cratons and the monotonic uplift or subsidence that is widely observed in other regions. Such alternations between uplift and subsidence are characteristic of regions of Early or Middle Proterozoic crust, where the initial crustal consolidation included the development of a thick ‘root’ of mafic material at the base of the crust; the present study focuses on localities with this crustal type in the USA and eastern Europe. It has previously been suggested on the basis of uplift modelling that this style of crustal behaviour occurs only in regions where the mobile lower‐crustal layer is relatively thin. This study supports this conclusion on the basis of independent geothermal calculations, which indicate that such alternations between uplift and subsidence occur where the mobile lower‐crustal layer is ≤～7 km thick. An understanding of this phenomenon, in relation to the understanding of vertical crustal motions induced by surface processes (and thus by climate change) in general, therefore requires analysis of the properties and dynamics of the mobile lower‐crustal layer; detailed analysis of fluvial sequences thus contributes unique information in this area.     

SuperWASP-N extrasolar planet candidates from fields 06h < RA < 16h

The Wide Angle Search for Planets (WASP) survey currently operates two installations, designated SuperWASP-N and SuperWASP-S, located in the Northern and Southern hemispheres, respectively. These installations are designed to provide high time-resolution photometry for the purpose of detecting transiting extrasolar planets, asteroids, and transient events. Here, we present results from a transit-hunting observing campaign using SuperWASP-N covering a right ascension (RA) range of 06^h < RA < 16^h. This paper represents the fifth and final in the series of transit candidates released from the 2004 observing season. In total, 729 335 stars from 33 fields were monitored with 130 566 having sufficient precision to be scanned for transit signatures. Using a robust transit detection algorithm and selection criteria, six stars were found to have events consistent with the signature of a transiting extrasolar planet based on the photometry, including the known transiting planet XO-1b. These transit candidates are presented here along with discussion of follow-up observations and the expected number of candidates in relation to the overall observing strategy.     

迈向可持续发展——地质公园行动建议(英文)

From 27th to 29th, May, 2011, the participants of the 2nd International Forum on Geoparks from 5 countries gathered in Taining, Fujian Province, China. The participants discussed developing and preserving our Geoparks and Geo-heritage in sustainable ways. The forum recognized that the Geopark Program initiated by UNESCO is an efficient tool for geo-heritage protection, recreation, education and economic development. The role of capacity building in achieving sustainable development of Geoparks is significant and the potential for capacity building has not been fully realized.