Elastic and anelastic anomalies in (Ca,Sr)TiO₃ perovskites: Analogue behaviour for silicate perovskites     

J.N. Walsh  P.A. Taylor  A. Buckley  T.W. Darling  J. Schreuer  M.A. Carpenter   《Physics of the Earth and Planetary Interiors》2008,167(1-2):110-117

Values of bulk modulus (K), shear modulus (G) and mechanical quality factor (Q) have been determined for polycrystalline samples across the CaTiO₃ (CST0)–SrTiO₃ (CST100) solid solution by resonant ultrasound spectroscopy. Because of similarities with low frequency elastic and anelastic anomalies due to twin wall motion reported in previous studies, a working hypothesis is developed in which dissipation processes are interpreted in terms of twin wall displacements. At high temperatures in CST50 the stability field of the I4/mcm structure is marked by the disappearance of all resonance peaks (superattenuation). This is attributed to anelastic domain wall sliding. At room temperature the I4/mcm phase of CST70 and CST80 has values of G which are lower than those of cubic or orthorhombic phases, and a concomitant drop in Q is interpreted as implying that the domain wall pinning process reported elsewhere to occur below 400–450 K is only partial. A similar drop in G and Q was found in CST95 below the transition at 238 K. The I4/mcm ↔ Pbcm transition in CST70 at 230 K is marked by an abrupt increase in Q, suggesting that mobile twins in crystals with the I4/mcm structure become effectively immobile in antiferroelectric crystals with the Pbcm structure. The I4/mcm ↔ Pnma transition in CST50 is marked by a similarly abrupt increase in Q, consistent with twin walls becoming effectively immobile also in crystals with the Pnma structure. A fall in Q below 800 K in CST0, however, could imply that a degree of twin wall mobility might develop in Pnma crystals if the tetragonal spontaneous strain departs significantly from zero. The remarkable attenuation behaviour of crystals with the I4/mcm structure at the relatively low stress conditions which apply during resonances of a parallelepiped with edge dimensions of 2–4 mm, is consistent with the view that a characteristic signature for tetragonal CaSiO₃ in the Earth's lower mantle should be a marked attenuation of seismic waves.  相似文献   

The nature of TW Pictoris     

A. J. Norton  A. P. Beardmore  A. Retter  D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》2000,312(2):362-370

The results of X-ray and optical observations of the candidate intermediate polar TW Pic are presented in an attempt to understand its nature. We find no sign of the previously proposed ∼2 h white-dwarf spin period and ∼6 h orbital period of TW Pic in its X-ray light curve. There is therefore no convincing evidence in support of its previous classification. The lack of X-ray pulsation could be the result of a low inclination angle, but in that case there would be no reason why an optical pulsation should have been seen previously. Negative results from polarimetry also preclude TW Pic from being a polar. One possibility may be that the shorter of the two periods is in fact the orbital period, whilst the longer one is a harmonic of a disc precession period. Alternatively, both the high accretion rate and period structure of TW Pic indicate that it may be a system that displays persistent negative superhumps. In this case the true orbital period of the binary may be around 6.36 h and the shorter of the two previously identified periods, 1.996 h, represents the (shifted) second harmonic of a negative superhump period of 6.06 h. Under this interpretation, it would be the longest period system to display such a phenomenon. Finally there is also evidence that TW Pic may be a VY Scl star, in which case it would be the longest period member of that subclass too.  相似文献   

Use of the half-cycle analysis method to compare measured wave height and simulated Gaussian data having the same variance spectrum     

W.H. Buckley  R.D. Pierce  J.B. Peters  M.J. Davis 《Ocean Engineering》1984,11(4):423-445

Using the half-cycle analysis method, a comparison is made between extreme events in half-hour intervals of hurricane Camille wave data and extreme events in synthesized Gaussian realizations having the same variance spectra as the measured data. While various statistical comparisons of measured and simulated Gaussian data reveal a consistent trend toward Gaussian behavior for the majority of wave events in the hurricane generated data, it is shown using the half-cycle analysis method that the more extreme wave events occurring near the height of the storm were distinctly non-Gaussian.  相似文献   

Observations and models of some neglected southern eclipsing binaries     

David A. H. Buckley 《Astrophysics and Space Science》1984,99(1-2):191-197

Results of a photometric investigation of some photoelectrically neglected, southern eclipsing binaries, are presented for GW Car, X Car, and RS Sct. Light curve solutions obtained by the Wilson-Devinney and Wood synthetic light curve techniques are described.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.  相似文献   

Tree-ring based hydroclimate reconstruction over northern Vietnam from Fokienia hodginsii: eighteenth century mega-drought and tropical Pacific influence   总被引：1，自引：0，他引：1  

Masaki Sano  Brendan M. Buckley  Tatsuo Sweda 《Climate Dynamics》2009,33(2-3):331-340

We present here the first statistically calibrated and verified tree-ring reconstruction of climate from continental Southeast Asia. The reconstructed variable is March–May (MAM) Palmer Drought Severity Index (PDSI) based on ring widths from 22 trees (42 radial cores) of rare and long-lived conifer, Fokienia hodginsii (Po Mu as locally called) from northern Vietnam. This is the first published tree ring chronology from Vietnam as well as the first for this species. Spanning 535 years, this is the longest cross-dated tree-ring series yet produced from continental Southeast Asia. Response analysis revealed that the annual growth of Fokienia at this site was mostly governed by soil moisture in the pre-monsoon season. The reconstruction passed the calibration-verification tests commonly used in dendroclimatology, and revealed two prominent periods of drought in the mid-eighteenth and late-nineteenth centuries. The former lasted nearly 30 years and was concurrent with a similar drought over northwestern Thailand inferred from teak rings, suggesting a “mega-drought” extending across Indochina in the eighteenth century. Both of our reconstructed droughts are consistent with the periods of warm sea surface temperature (SST) anomalies in the tropical Pacific. Spatial correlation analyses with global SST indicated that ENSO-like anomalies might play a role in modulating droughts over the region, with El Niño (warm) phases resulting in reduced rainfall. However, significant correlation was also seen with SST over the Indian Ocean and the north Pacific, suggesting that ENSO is not the only factor affecting the climate of the area. Spectral analyses revealed significant peaks in the range of 53.9–78.8 years as well as in the ENSO-variability range of 2.0 to 3.2 years.  相似文献   

Statistical analysis of the microlithotype sequences in the Bulli Seam, Australia, and relevance to permeability for coal gas     

Michelle Smyth  Michael J. Buckley 《International Journal of Coal Geology》1993,22(3-4)

Sequential microlithotype analyses through the Permian Bulli Coal, Sydney Basin, Australia, enable determination of the abundance, locations and thicknesses of various microlithotypes in the seam. Statistical analyses allow prediction of these parameters. Microlithotype analyses may be used as a means of predicting seam permeability in relation to coal gas drainage, if used in conjunction with reported correlation between coal type and seam reservoir properties.A combination of sequential microlithotype analyses and statistical modelling provide data on the number, location and thicknesses of individual bands of vitrite, vitrinertite, inertite and mineral-rich coal. A Markov chain describes both the order and thickness of the bands in the seam. Local ordering of microlithotypes is similar, irrespective of vertical orientation, which suggests that analyses and predictions may be possible using representative, randomly oriented samples. Statistical modelling can be used to characterise the seam using a small number of parameters. These include the elements of the transition probability matrix of the Markov chain, from which many seam properties such as maximum band thickness, thickness distribution of bands and spacing of thick bands can be predicted.The permeability of vitrite-rich coal in the seam is 30 mD and it is 2.3 mD for inertite-rich coal. In general, for the Bulli seam, vitrite-rich plies are expected to provide better flow paths for coal gas than inertite-rich plies, because of the abundance of cleat systems in vitrite. Using this information, it thus may be possible to predict gas and water flow paths in a seam from microlithotype analyses, thereby leading to the development of a rapid method for assessing the comparative permeabilities of coal plies.  相似文献   

Petrology of the volcanic rocks of saba,West Indies     

P. E. Baker  F. Buckley  T. Padfield 《Bulletin of Volcanology》1980,43(2):337-346

Saba is composed of basic and intermediate members of the calc alkaline series with a broad resemblance to volcanic rocks on other islands of the northern Lesser Antilles. The most abundant rock-type is hornblende andesite with relatively high potassium and associated elements. Notable petrographic features are the persistence of magnesian olivine into relatively siliceous whole-rock composition and the prevalence of hornblende even in the more basic rocks. Quartz xenocrysts also occur in the basalts Clinopyroxene phenocrysts are of an gite composition but groundmass grains are sometimes in the range subcalcic augite to magnesian pigeonite. Disequilibrium features in the petrography, together with anomalies in the chemical trends may be due to incorporation of xenocrysts or perhaps in extreme instances to the hybridisation of contrasting magmas.  相似文献   

Sediment penetration of Amoco Cadiz oil,potential for future release,and toxicity     

J.H Vandermeulen  D.E Buckley  E.M Levy  B.F.N Long  P McLaren  P.G Wells 《Marine pollution bulletin》1979,10(8):222-227

Weathering states of oil ranging from sheen oil to mousse have significant effects during oil stranding on oil-water and oil-sediment interaction. Observations of oiled sandy beaches suggest two mechanisms of beach contamination—general penetration and contamination of beach substrate by films of sheen oil (probably partially emulsified), and secondly the burial of discrete layers of mousse. Depending on timing of oiling with respect to beach dynamics large amounts of stranded oil can be accommodated within beach sediments. These then become available for later long-term release.Acute lethal toxicity of stranded Amoco Cadiz oil is intermediate to Bunker C and Kuwait crude. Simulated weathering studies suggest that there may be some increase in toxicity with weathering.  相似文献   

A note on the isolation of the bacteriumVibrio parahaemolyticus from estuarine North Carolina     

Robert B. Jonas  Earle N. Buckley  Frederic K. Pfaender 《Estuaries and Coasts》1978,1(4):264-266

The potentially pathogenic bacterium,Vibrio parahaemolyticus, was isolated from water, sediment, and oyster samples collected from estuarine North Carolina. In October, when water temperatures were 15–18°C,V. parahaemolyticus was still detected in all substrates. However, the organism was detected only in one sediment sample in January when water temperatures were 4–5°C. No correlation was observed between the occurrence of the bacterium and domestic wastewater contamination.  相似文献   

Sediment penetration of Amoco Cadiz oil,potential for future release,and toxicity     

J.H. Vandermeulen  D.E. Buckley  E.M. Levy  B.F.N. Long  P. McLaren  P.G. Wells 《Marine pollution bulletin》1978,9(11):292-293

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