Raman spectroscopic analysis of cyanobacterial colonization of hydromagnesite, a putative martian extremophile     

Howell G.M. Edwards  Caroline D. Moody  Susana E. Jorge Villar  Michael J. Russell 《Icarus》2005,175(2):372-381

Raman spectra of an extremophile cyanobacterial colony in hydromagnesite from Lake Salda in Turkey have revealed a biogeological modification which is manifest as aragonite in the stratum associated with the colony. The presence of key spectral biomarkers of organic protectant molecules such as β-carotene and scytonemin indicate that the survival strategy of the cyanobacteria is significantly one of UV-radiation protection. The terrestrial location of this extremophile is worthy of consideration further because of its possible putative link with the “White Rock” formations in Sabaea Terra and Juventae Chasma on Mars.  相似文献   

The 6dF Galaxy Survey: samples, observational techniques and the first data release     

D. Heath Jones  Will Saunders  Matthew Colless  Mike A. Read  Quentin A. Parker  Fred G. Watson  Lachlan A. Campbell  Daniel Burkey  Thomas Mauch  Lesa Moore  Malcolm Hartley  Paul Cass  Dionne James  Ken Russell  Kristin Fiegert  John Dawe  John Huchra  Tom Jarrett  Ofer Lahav  John Lucey  Gary A. Mamon  Dominique Proust  Elaine M. Sadler  Ken-ichi Wakamatsu 《Monthly notices of the Royal Astronomical Society》2004,355(3):747-763

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Streaming motions of galaxy clusters within 12 000 km s⁻¹– III. A standardized catalogue of Fundamental Plane data     

Michael J. Hudson  John R. Lucey  Russell J. Smith  David J. Schlegel  Roger L. Davies 《Monthly notices of the Royal Astronomical Society》2001,327(1):265-295

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The 2dF Galaxy Redshift Survey: the b_J-band galaxy luminosity function and survey selection function     

Peder Norberg  Shaun Cole  Carlton M. Baugh  Carlos S. Frenk  Ivan Baldry  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Nicholas J. G. Cross  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,336(3):907-931

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The 2dF Galaxy Redshift Survey: luminosity dependence of galaxy clustering     

Peder Norberg  Carlton M. Baugh  Ed Hawkins  Steve Maddox  John A. Peacock  Shaun Cole  Carlos S. Frenk  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Darren Madgwick  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,328(1):64-70

We investigate the dependence of the strength of galaxy clustering on intrinsic luminosity using the Anglo-Australian two degree field galaxy redshift survey (2dFGRS). The 2dFGRS is over an order of magnitude larger than previous redshift surveys used to address this issue. We measure the projected two-point correlation function of galaxies in a series of volume-limited samples. The projected correlation function is free from any distortion of the clustering pattern induced by peculiar motions and is well described by a power law in pair separation over the range     . The clustering of     galaxies in real space is well-fitted by a correlation length     and power-law slope     . The clustering amplitude increases slowly with absolute magnitude for galaxies fainter than M *, but rises more strongly at higher luminosities. At low luminosities, our results agree with measurements from the Southern Sky Redshift Survey 2 by Benoist et al. However, we find a weaker dependence of clustering strength on luminosity at the highest luminosities. The correlation function amplitude increases by a factor of 4.0 between     and −22.5, and the most luminous galaxies are 3.0 times more strongly clustered than L * galaxies. The power-law slope of the correlation function shows remarkably little variation for samples spanning a factor of 20 in luminosity. Our measurements are in very good agreement with the predictions of the hierarchical galaxy formation models of Benson et al.  相似文献   

Factors controlling the chemical evolution of travertine‐depositing rivers of the Barkly karst,northern Australia     

Russell N. Drysdale  Mark P. Taylor  Christian Ihlenfeld 《水文研究》2002,16(15):2941-2962

Groundwaters feeding travertine‐depositing rivers of the northeastern segment of the Barkly karst (NW Queensland, Australia) are of comparable chemical composition, allowing a detailed investigation of how the rate of downstream chemical evolution varies from river to river. The discharge, pH, temperature, conductivity and major‐ion concentrations of five rivers were determined by standard field and laboratory techniques. The results show that each river experiences similar patterns of downstream chemical evolution, with CO₂ outgassing driving the waters to high levels of calcite supersaturation, which in turn leads to widespread calcium carbonate deposition. However, the rate at which the waters evolve, measured as the loss of CaCO₃ per kilometre, varies from river to river, and depends primarily upon discharge at the time of sampling and stream gradient. For example, Louie Creek (Q = 0·11 m³ s^?1) and Carl Creek (Q = 0·50 m³ s^?1) have identical stream gradients, but the loss of CaCO₃ per kilometre for Louie Creek is twice that of Carl Creek. The Gregory River (Q = 3·07 m³ s^?1), O'Shanassy River (Q = 0·57 m³ s^?1) and Lawn Hill Creek (Q = 0·72 m³ s^?1) have very similar gradients, but the rate of hydrochemical evolution of the Gregory River is significantly less than either of the other two systems. The results have major implications for travertine deposition: the stream reach required for waters to evolve to critical levels of calcite supersaturation will, all others things being equal, increase with increasing discharge, and the length of reach over which travertine is deposited will also increase with increasing discharge. This implies that fossil travertine deposits preserved well downstream of modern deposition limits are likely to have been formed under higher discharge regimes. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The chemical compositions and ages of globular clusters     

Russell Cannon 《Journal of Astrophysics and Astronomy》1996,17(1-2):1-6

Recent technological advances have led to a dramatic improvement in the quality of photometric and spectroscopic data obtainable on stars in globular clusters. Evidence from CCD-based colour magnitude diagrams points to clear differences in age between some clusters. High dispersion spectra show that abundance variations cannot explain the observed differences. In particular, it seems that NGC 288 must be 2–3 Gyr older than NGC 362. The same spectra show that although there is a spread in some molecular band strengths in NGC 362, the total C+N+O abundance remains constant, indicating that the material has undergone varying amounts of nuclear processing. No variations are seen in the abundances of iron group elements. Lower dispersion spectra for a large sample of faint stars in 47 Tucanae, obtained with a multi-object optical fibre system, show that unevolved main sequence stars in that cluster share the same CNO variations as the bright giants. The conclusion from all these data is that the intra-cluster CNO variations are neither truly primordial nor due to evolutionary mixing. It may be that there was a sufficiently extended period of star formation for material from first generation stars to be used in later generations, or that some pollution has occurred due to mass loss. Finally, it is noted that if ‘prehistoric’ clusters exist with ages of around 50 Gyr, as hypothesised in some cosmological models, these should probably still be rather obvious and readily recognised. Paper presented at the 6th Asian-Pacific Regional Meeting on Astronomy of the International Astronomical Union, India, 1993.  相似文献   

The 2dF Galaxy Redshift Survey: the environmental dependence of galaxy star formation rates near clusters     

Ian Lewis  Michael Balogh  Roberto De Propris  Warrick Couch  Richard Bower  Alison Offer  Joss Bland-Hawthorn  Ivan K. Baldry  Carlton Baugh  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Nicholas Cross  Gavin Dalton  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Edward Hawkins  Carole Jackson  Ofer Lahav  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Will Percival  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,334(3):673-683

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Galaxy groups in the Two-degree Field Galaxy Redshift Survey: the luminous content of the groups     

V. R. Eke  Carlos S. Frenk  Carlton M. Baugh  Shaun Cole  Peder Norberg  John A. Peacock  Ivan K. Baldry  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto de Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole A. Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve J. Maddox  Darren Madgwick  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,355(3):769-784

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Hydraulic Conductivity from Nuclear Magnetic Resonance Logs in Sediments with Elevated Magnetic Susceptibilities     

Heather Crow  Daniel Paradis  Elliot Grunewald  Xiao Xia Liang  Hazen A.J. Russell 《Ground water》2022,60(3):377-392

This study examined the application of slim-hole nuclear magnetic resonance (NMR) tools to estimate hydraulic conductivity (K_NMR) in an unconsolidated aquifer that contains a range of grain sizes (silt to gravel) and high and variable magnetic susceptibilities (MS) (10⁻⁴ to 10⁻² SI). A K calibration dataset was acquired at 1-m intervals in three fully screened wells, and compared to K_NMR estimates using the Schlumberger-Doll research (SDR) equation with published empirical constants developed from previous studies in unconsolidated sediments. While K_NMR using published constants was within an order of magnitude of K, the agreement, overprediction, or underprediction of K_NMR varied with the MS distribution in each well. An examination of the effects of MS on NMR data and site-specific empirical constants indicated that the exponent on T_2ML (n-value in the SDR equation, representing the diffusion regime) was found to have the greatest influence on K_NMR estimation accuracy, while NMR porosity did not improve the prediction of K. K_NMR was further improved by integrating an MS log into the NMR analyses. A first approach detrended T_2ML for the effects of MS prior to calculating K_NMR, and a second approach introduced an MS term into the SDR equation. Both were found to produce similar refinements of K_NMR in intervals of elevated MS. This study found that low frequency NMR logging with short echo times shows promise for sites with moderate to elevated MS levels, and recommends a workflow that examines parameter relationships and integrates MS logs into the estimation of K_NMR.  相似文献