Is there evolution in the infrared Tully–Fisher relation? Comparing two linear regressions     

Chris Koen  Fred Lombard 《Monthly notices of the Royal Astronomical Society》2009,395(3):1657-1661

In a recent paper, Puech and co-workers compared K -band Tully–Fisher relations derived for nearby and distant galaxies, respectively. They concluded that the two relations differ, and deduced that there is evolution in the Tully–Fisher relations. The statistical comparison between the two regression lines is re-examined, and it is shown that the statistical test used gives non-significant results. It is argued that better results can be obtained by comparing the 'inverse' Tully–Fisher relations, and it is demonstrated by two different methods that the nearby- and distant-sample relations do indeed differ at a very high significance level. One of the statistical methods described is non-parametric, and can be applied very generally to compare linear regressions from two different samples.  相似文献   

On the upper limit on stellar masses in the Large Magellanic Cloud cluster R136     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2006,365(2):590-594

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What can be deduced from open cluster metallicity measurements?     

Chris Koen  Fred Lombard 《Monthly notices of the Royal Astronomical Society》2007,382(2):693-698

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Asteroseismology of the β Cephei star ν Eridani – II. Spectroscopic observations and pulsational frequency analysis     

C. Aerts  P. De Cat  G. Handler  U. Heiter  L. A. Balona  J. Krzesinski  P. Mathias  H. Lehmann  I. Ilyin  J. De Ridder  S. Dreizler  A. Bruch  I. Traulsen  A. Hoffmann  D. James  E. Romero-Colmenero  T. Maas  M. A. T. Groenewegen  J. H. Telting  K. Uytterhoeven  C. Koen  P. L. Cottrell  J. Bentley  D. J. Wright  J. Cuypers 《Monthly notices of the Royal Astronomical Society》2004,347(2):463-470

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Multivariate comparisons of the period–light-curve shape distributions of Cepheids in five galaxies     

C. Koen  I. Siluyele 《Monthly notices of the Royal Astronomical Society》2007,377(3):1281-1286

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Late Quaternary deglaciation and climate history of the Larsemann Hills (East Antarctica)     

Elie Verleyen  Dominic A. Hodgson  Koen Sabbe  Wim Vyverman 《第四纪科学杂志》2004,19(4):361-375

The Late Quaternary climate history of the Larsemann Hills has been reconstructed using siliceous microfossils (diatoms, chrysophytes and silicoflagellates) in sediment cores extracted from three isolation lakes. Results show that the western peninsula, Stornes, and offshore islands were ice‐covered between 30 000 yr BP and 13 500 cal. yr BP. From 13 500 cal. yr BP (shortly after the Antarctic Cold Reversal) the coastal lakes of the Larsemann Hills were deglaciated and biogenic sedimentation commenced. Between 13 500 and 11 500 cal. yr BP conditions were warmer and wetter than during the preceding glacial period, but still colder than today. From 11 500 to 9500 cal. yr BP there is evidence for wet and warm conditions, which probably is related to the early Holocene climate optimum, recorded in Antarctic ice cores. Between 9500 and 7400 cal. yr BP dry and cold conditions are inferred from high lake‐water salinities, and low water levels and an extended duration of nearshore sea‐ice. A second climate optimum occurred between 7400 and 5230 cal. yr BP when stratified, open water conditions during spring and summer characterised the marine coast of Prydz Bay. From 5230 until 2750 cal. yr BP sea‐ice duration in Prydz Bay increased, with conditions similar to the present day. A short return to stratified, open water conditions and a reduction in nearshore winter sea‐ice extent is evident between 2750 and 2200 cal. yr BP. Simultaneously, reconstructions of lake water depth and salinity suggests relatively humid and warm conditions on land between 3000 and 2000 cal. yr BP, which corresponds to a Holocene Hypsithermal reported elsewhere in Antarctica. Finally, dry conditions are recorded around 2000, between 760 and 690, and between 280 and 140 cal. yr BP. These data are consistent with ice‐core records from Antarctica and support the hypothesis that lacustrine and marine sediments on land can be used to evaluate the effect of long‐term climate change on the terrestrial environment. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Retrieval of Suspended Sediment from Advanced Hyperspectral Sensor Data in the Scheldt Estuary at Different Stages in the Tidal Cycle   总被引：1，自引：0，他引：1  

Sindy Sterckx  Els Knaeps  Mark Bollen  Koen Trouw  Rik Houthuys 《Marine Geodesy》2007,30(1):97-108

Hyperspectral airborne remote sensing images and in-situ data are combined to assess the spatial and temporal sediment dynamics in the tidal Scheldt river. A log-linear empirical relationship has been developed between a near-infrared reflectance difference and total suspended matter. The relationship was shown to be relatively insensitive to the varying cirrus cloud cover occurring during data acquisition. The produced sediment maps show good agreement with known variations of turbidity over the tidal cycle: maximum turbidity around high water, gradual settling of the sediment in the succeeding slack water and resuspension at the onset of the ebb flow stage.  相似文献   

The pulsational characteristics of the λ Bootis type star BD Phe (HD 11413)     

C. Koen  E. Paunzen  F. van Wyk  F. Marang  I. V. Chernyshova  S. M. Andrievsky 《Monthly notices of the Royal Astronomical Society》2003,338(4):931-938

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The numerical determination of the eigenfrequencies of a rotating star     

Chris Koen 《Astrophysics and Space Science》1987,136(1):91-99

A technique for finding the oscillation spectrum of a rotating star based on the solution of two simultaneous ordinary differential equations is described. Results are presented for someg-modes of the polytrope of index 2. It appears that the functional dependence of frequency on rotational velocity is different for different azimuthal wave numbersm.  相似文献   

The surface energy balance and the mixing height in urban areas—activities and recommendations of COST-Action 715     

Martin Piringer  Sylvain Joffre  Alexander Baklanov  Andreas Christen  Marco Deserti  Koen De Ridder  Stefan Emeis  Patrice Mestayer  Maria Tombrou  Douglas Middleton  Kathrin Baumann-Stanzer  Aggeliki Dandou  Ari Karppinen  Jerzy Burzynski 《Boundary-Layer Meteorology》2007,124(1):3-24

The specific problems of determining and simulating the surface energy balance (SEB) and the mixing height (MH) over urban areas are examined. The SEB and MH are critical components of algorithms and numerical models for the urban boundary layer, though the constituent parts of the SEB and the MH are not routinely measured by national weather services. Parameterisations are thus needed in applications. In this investigation, several recently developed algorithms and models for estimating the SEB and MH were applied to new datasets and assessed. Results are discussed in terms of the need for spatial resolution and the parameters needed to describe the urban atmosphere. Limitations of models are identified and recommendations for further development and observations are given. Having identified gaps in knowledge, key findings from new urban experiments and numerical modelling for the SEB and MH are given. The diurnal cycle for the SEB is significantly different from rural conditions—urban heat storage is needed in urban parameterisations. The urban MH is increased over the rural MH, as shown by several numerical schemes and careful sodar analyses. This work has been carried out within the COST-715 Action “Meteorology applied to urban air pollution problems (1998–2004). COST 715 reached a consensus proposing representatively sited measurements of meteorological parameters and turbulent fluxes above roof-tops, and recognised that such data are needed to improve numerical models of the urban surface processes.  相似文献