Magnetic field generation in electrically conducting fluids: H. K. Moffatt. Cambridge University Press,London/New York, 1978. x + 343 pp. $29.50     

D.J. Stevenson 《Icarus》1979,37(1):358-359

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Thermal expansion and spontaneous strain associated with the normal-incommensurate phase transition in melilites     

S. L. Webb  C. R. Ross II  J. Liebertz 《Physics and Chemistry of Minerals》1992,18(8):522-525

The linear thermal expansions of åkermanite (Ca₂MgSi₂O₇) and hardystonite (Ca₂ZnSi₂O₇) have been measured across the normal-incommensurate phase transition for both materials. Least-squares fitting of the high temperature (normal phase) data yields expressions linear in T for the coefficients of instantaneous linear thermal expansion, $$\alpha _1 = \frac{1}{l}\frac{{dl}}{{dT}}$$ for åkermanite: $$\begin{gathered} \alpha _{[100]} = 6.901(2) \times 10^{ - 6} + 1.834(2) \times 10^{ - 8} T \hfill \\ \alpha _{[100]} = - 2.856(1) \times 10^{ - 6} + 11.280(1) \times 10^{ - 8} T \hfill \\ \end{gathered} $$ for hardystonite: $$\begin{gathered} \alpha _{[100]} = 15.562(5) \times 10^{ - 6} - 1.478(3) \times 10^{ - 8} T \hfill \\ \alpha _{[100]} = - 11.115(5) \times 10^{ - 6} + 11.326(3) \times 10^{ - 8} T \hfill \\ \end{gathered} $$ Although there is considerable strain for temperatures within 10° C of the phase transition, suggestive of a high-order phase transition, there appears to be a finite ΔV of transition, and the phase transition is classed as “weakly first order”.  相似文献   

INSTRUMENT OBSERVATIONS     

H. F. Ross 《The Photogrammetric Record》1976,8(47):610-616

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Verification of the motion fields over Southeast Asia by the Florida State University (FSU) superensemble forecast     

Mastura Mahmud  Robert S. Ross 《Singapore journal of tropical geography》2006,27(2):176-190

The Florida State University (FSU) multimodel superensemble forecast is evaluated against several other operational weather models for the Southeast Asia region. The superensemble technique has demonstrated its exceptional skills in forecasting precipitation, motion and mass fields compared to either individual global operational or ensemble mean forecasts. The motion field investigation for the season of 2001 reveals that the superensemble forecasts are closer to the observed data compared to the other global member operational models through its low systematic errors at the 850 hPa level. The FSU multimodel superensemble forecasts exhibit the lowest root mean square errors (RSMEs), the highest correlation against the best observed data and the lowest systematic errors compared to the other operational model members. These forecasts have the potential to provide better daily weather predictions over the Southeast Asia region, particularly during the early northeast monsoon that often causes heavy rainfall in the equatorial part of the Southeast Asia region.  相似文献   

Origin of the Nchanga copper–cobalt deposits of the Zambian Copperbelt     

Ross R. McGowan  Stephen Roberts  Adrian J. Boyce 《Mineralium Deposita》2006,40(6-7):617-638

The Zambian Copperbelt forms the southeastern part of the 900-km-long Neoproterozoic Lufilian Arc and contains one of the world’s largest accumulations of sediment-hosted stratiform copper mineralization. The Nchanga deposit is one of the most significant ore systems in the Zambian Copperbelt and contains two major economic concentrations of copper and cobalt, hosted within the Lower Roan Group of the Katangan Supergroup. A Lower Orebody (copper only) and Upper Orebody (copper and cobalt) occur towards the top of arkosic units and within the base of overlying shales. The sulfide mineralogy includes pyrite, bornite, chalcopyrite, and chalcocite, although in the Lower Orebody, sulfide phases are partially or completely replaced by malachite and copper oxides. Carrollite is the major cobalt-bearing phase and is restricted to fault-propagation fold zones within a feldspathic arenite. Hydrothermal alteration minerals include dolomite, phlogophite, sericite, rutile, quartz, tourmaline, and chlorite. Quartz veins from the mine sequence show halite-saturated fluid inclusions, ranging from ~31 to 38 wt% equivalent NaCl, with homogenisation temperatures (Th_TOT) ranging between 140 and 180°C. Diagenetic pyrites in the lower orebody show distinct, relatively low δ ³⁴S, ranging from −1 to −17‰ whereas arenite- and shale-hosted copper and cobalt sulfides reveal distinctly different δ ³⁴S from −1 to +12‰ for the Lower Orebody and +5 to +18‰ for the Upper Orebody. There is also a clear distinction between the δ ³⁴S mean of +12.1±3.3‰ (n=65) for the Upper Orebody compared with +5.2±3.6‰ (n=23) for the Lower Orebody. The δ ¹³C of dolomites from units above the Upper Orebody give δ ¹³C values of +1.4 to +2.5‰ consistent with marine carbon. However, dolomite from the shear-zones and the alteration assemblages within the Upper Orebody show more negative δ ¹³C values: −2.9 to −4.0‰ and −5.6 to −8.3‰, respectively. Similarly, shear zone and Upper Orebody dolomites give a δ ¹⁸O of +11.7 to +16.9‰ compared to Lower Roan Dolomites, which show δ ¹⁸O of +22.4 to +23.0‰_. Two distinct structural regimes are recognized in the Nchanga area: a weakly deformed zone consisting of basement and overlying footwall siliciclastics, and a moderate to tightly folded zone of meta-sediments of the Katangan succession. The fold geometry of the Lower Roan package is controlled by internal thrust fault-propagation folds, which detach at the top of the lowermost arkose or within the base of the overlying stratigraphy and show vergence towards the NE. Faulting and folding are considered to be synchronous, as folding predominantly occurred at the tips of propagating thrust faults, with local thrust breakthrough. The data from Nchanga suggests a strong link between ore formation and the development of structures during basin inversion as part of the Lufilian Orogeny. Sulfides tend to be concentrated within arenites or coarser-grained layers within shale units, suggesting that host-rock porosity and possibly permeability played a role in ore formation. However, sulfides are also commonly orientated along, but not deformed by, a tectonic fabric or hosted within small fractures that suggest a significant role for deformation in the development of the mineralization. The ore mineralogy, hydrothermal alteration, and stable isotope data lend support to models consistent with the thermochemical reduction of a sulfate- (and metal) enriched hydrothermal fluid, at the site of mineralization. There is no evidence at Nchanga for a contribution of bacteriogenic sulfide, produced during sedimentation or early diagenesis, to the ores.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.Editorial handling: H. Frimmel  相似文献   

Earth-moon relationships, edited by C. Barbieri and F. Rampazzi. Kluwer Academic Publishers, Dordrecht (Netherlands), 2001, 575 pp. Eur 229, GBP 140, US $199 (ISBN 0-7923-7089-9)     

Stuart Ross Taylor 《Geochimica et cosmochimica acta》2002,66(8):1495

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Explosion seismic reflections from the Earth’s core     

H Thybo  A.R Ross 《Earth and Planetary Science Letters》2003,216(4):693-702

Recent seismological studies have presented evidence for the existence of a layer with ultra-low seismic velocities at the core-mantle boundary at ca. 2900 km depth. We report high-amplitude, high-frequency, and laterally coherent seismic arrivals from three nuclear explosions in Siberia. With recording station intervals of 15 km, the seismic phases are readily correlated and show the presence of a thin, ultra-low velocity zone in a region where it was not previously reported. The duration and complexity of the arrivals are inconsistent with a simple core-mantle boundary and require a hitherto unidentified, kilometre-scale, fine structure in the ultra-low velocity zone. The observations may be explained by a ca. 7 km thick, two-layer, ultra-low velocity zone with exceptional low velocities, which indicate the presence of high percentages of melt (>15%), in particular in the lower part of the zone. Waveform variation implies lateral change in the thickness and physical properties of the ultra-low velocity zone with a wavelength of less than 100 km.  相似文献   

Increased sediment accretion rates following invasion byPhragmites australis: The role of litter     

Rooth  Jill E.  Stevenson  J. Court  Cornwell  Jeffrey C. 《Estuaries and Coasts》2003,26(2):475-483

Negative connotations of invasive plants worldwide have implicated them as the bearers of unfavorable ecosystem change. We contrasted 5-yr-old and 20-yr-oldPhragmites populations with pre-invasion areas occupied byTypha spp. andPanicum virgatum in an oligohaline tidal marsh of Chesapeake Bay. Peak live biomass was 3 times greater, while standing dead and litter was twice as great in the 20-yr-oldPhragmites. It is this abundance of concentrated litter on the marsh surface of maturePhragmites populations that we implicate as encouraging the trapping of organic and mineral matter. The rate of vertical accretion in 20-yr-oldPhragmites populations is 3–4 mm yr⁻¹ above the adjacent populations. By integrating the constant initial concentration and constant rate of supply models on individual²¹⁰Pb cores, we estimate thatPhragmites populations require a minimum of 7-yr post-colonization to enhance rates of accretion in this system. In ligh of the considerable loss of marsh habitat from relative sea-level rise, this finding contests the view that invasion creates strictly undesirable change at the ecosystem level.  相似文献   

Raman scattering and X-ray diffraction study of the thermal decomposition of an ettringite-group crystal     

S. K. Deb  M. H. Manghnani  K. Ross  R. A. Livingston  P. J. M. Monteiro 《Physics and Chemistry of Minerals》2003,30(1):31-38

 A Raman scattering and X-ray diffraction study of the thermal decomposition of a naturally occurring, ettringite-group crystal is presented. Raman spectra, recorded with increasing temperature, indicate that the thermal decomposition begins at ≈55 °C, accompanied by dehydration of water molecules from the mineral. This is in contrast to previous studies that reported higher temperature breakdown of ettringite. The dehydration is completed by 175 °C and this results in total collapse of the crystalline structure and the material becomes amorphous. The Raman scattering results are supported by X-ray diffraction results obtained at increasing temperatures. Received: 9 July 2001 / Accepted: 14 August 2002  相似文献   

The Global Distribution of Secondary Particulate Matter in a 3-D Lagrangian Chemistry Transport Model     

R. G. Derwent  W. J. Collins  M. E. Jenkin  C. E. Johnson  D. S. Stevenson 《Journal of Atmospheric Chemistry》2003,44(1):57-95

A global 3-D Lagrangian chemistry-transport model STOCHEM is used to describe the tropospheric distributions of four components of the secondary atmospheric aerosol: nitrate, sulphate, ammonium and organic compounds. The model describes the detailed chemistry of the formation of the acid precursors from the oxidation of SO₂, DMS, NO_x, NH₃ and terpenes and their uptake into the aerosol. Model results are compared in some detail with the available surface observations. Comparisons are made between the global budgets and burdens found in other modelling studies. The global distributions of the total mass of secondary aerosols have been estimated for the pre-industrial, present day and 2030 emissions and large changes have been estimated in the mass fractions of the different secondary aerosol components.  相似文献