Paleolimnological comparison of algal changes in a clear-versus a brown-water lake over the last two centuries in the northeastern U.S.A     

Fowler  Rachel A.  Warner  Kate A.  Gawley  William G.  Saros  Jasmine E. 《Journal of Paleolimnology》2022,67(3):289-305

Journal of Paleolimnology - We reconstructed historical diatom and algal pigment records from a clear-water versus a brown-water lake in the northeastern U.S. to compare ecological responses to...  相似文献   

Highly conservative behaviour of bed sediment‐associated metals following extreme flooding     

Rachel R. Hurley  Jamie C. Woodward  James J. Rothwell 《水文研究》2019,33(8):1204-1217

On December 26, 2015 (Boxing Day), an exceptional flood event occurred in the Irwell catchment, United Kingdom, when the neighbouring Mersey catchment experienced a much more typical winter run‐off event. This provided an opportunity to examine the influence of high‐magnitude hydrological processes on the behaviour of fine‐grained metal‐contaminated bed sediments. Forty sites across the two catchments were sampled for channel bed fine sediment storage and sediment‐associated metal(loid) concentrations prior to, and following, the flooding. Sediments were analysed for total As, Cr, Cu, Pb, and Zn and then subjected to a five‐step sequential extraction procedure. Despite a significant reorganisation of fine‐grained (<63 μm) sediment storage, metal(loid) concentrations demonstrated markedly conservative behaviour with no significant difference observed between pre‐flooding and post‐flooding values across both catchments. Estimates of the channel bed storage of sediment‐associated metal(loid)s also showed minimal change as a result of the flooding. The metal partitioning data reveal only minor changes in the mobility of bed sediment‐associated metal(loid)s, indicating that such flood events do not increase the availability of sorbed contaminants in these catchments. Post‐flooding bed sediment metal(loid) loadings remain high, indicating persistent and long‐lasting sources of contamination within the Irwell and upper Mersey fluvial network.  相似文献   

Magnetic Environments of Young Stellar Objects     

Antonio Chrysostomou  Rachel Curran  David Aitken  Tim Jenness  Chris Davis 《Astrophysics and Space Science》2003,287(1-4):161-164

We report on early results of magnetic field measurements towards a sample of young stellar objects. The results show a variety of field configurations, some of which can be explained by conventional models, while others cannot. We find that the field in some cases is curved over large scales and influenced by the gas kinematics in the local environment. This implies that, at these scales at least, the magnetic field plays a passive rôle in the star formation process.  相似文献   

Estimating photometric redshifts with artificial neural networks     

Andrew E. Firth  Ofer Lahav  Rachel S. Somerville 《Monthly notices of the Royal Astronomical Society》2003,339(4):1195-1202

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The Magnetic Environments of Young Stellar Objects     

Antonio Chrysostomou  Rachel Curran  David Aitken 《Astrophysics and Space Science》2004,292(1-4):509-515

We report on early results of submillimetre polarimetric measurements towards a sample of young stellar objects. The results allow us to infer the magnetic field structure and show a variety of configurations, providing evidence for axial, helical and pinched (i.e. ‘hourglass’) magnetic field configurations. We find that in some cases the field is curved over large scales, implying that it is influenced by the gas kinematics in the local environment, and that at these scales at least, the magnetic field plays a passive rôle in the star formation process.  相似文献   

The column density distribution function at z= 0 from H i selected galaxies     

Emma V. Ryan-Weber  Rachel L. Webster  Lister Staveley-Smith 《Monthly notices of the Royal Astronomical Society》2003,343(4):1195-1206

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Ion irradiation of crystalline H₂O-ice: Effect on the 1.65-μm band     

Rachel M.E. Mastrapa  Robert H. Brown 《Icarus》2006,183(1):207-214

We have found that 0.8 MeV proton irradiation of crystalline H₂O-ice results in temperature dependent amorphization. The H₂O-ice's phase was determined using the near infrared spectrum from 1.0 μm (10,000 cm⁻¹) to 2.5 μm (4000 cm⁻¹). In crystalline H₂O-ice, the 1.65-μm (6061 cm⁻¹) band is strong while it is nearly absent in the amorphous spectrum [Schmitt, B., Quirico, E., Trotta, F., Grundy, W.M., 1998. In: Schmitt, B., de Bergh, C., Festou, M. (Eds.), Solar System Ices. Kluwer Academic, Norwell, MA, 1998, pp. 199-240]. In this experiment, at low temperatures (9, 25, and 40 K), irradiation of crystalline H₂O-ice produced the amorphous H₂O-ice's spectrum. However, at 50 K, some crystalline absorptions persisted after irradiation and at 70 and 100 K the crystalline spectrum showed only slight changes after irradiation. Our results agree with previous H₂O-ice irradiation studies examining the crystalline peaks near 44 and 62 μm by Moore and Hudson [Moore, M.H., Hudson, R.L., 1992. Astrophys. J. 401, 353-360] and near 3.07 μm by Strazzulla et al. [Strazzulla, G., Baratta, G.A., Leto, G., Foti, G., 1992. Europhys. Lett. 18, 517-522] and by Leto and Baratta [Leto, G., Baratta, G.A., 2003. Astron. Astrophys. 397, 7-13]. We present a method of measuring band areas to quantify the phase and radiation dose of icy Solar System surfaces.  相似文献   

Feedback in simulations of disc-galaxy major mergers     

T. J. Cox  Patrik Jonsson  Joel R. Primack  Rachel S. Somerville 《Monthly notices of the Royal Astronomical Society》2006,373(3):1013-1038

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Ellipticity of dark matter haloes with galaxy–galaxy weak lensing     

Rachel Mandelbaum  Christopher M. Hirata  Tamara Broderick  Uro&#; Seljak  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,370(2):1008-1024

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Radio observations of the planetary nebula around the OH/IR star OH 354.88-0.54 (V1018 Sco)     

Martin Cohen  Jessica M. Chapman  Rachel M. Deacon †  Robert J. Sault  Quentin A. Parker  Anne J. Green 《Monthly notices of the Royal Astronomical Society》2006,369(1):189-196

We present radio observations of the unique, recently formed, planetary nebula (PN) associated with a very long-period OH/IR variable star V1018 Sco that is unequivocally still in its asymptotic giant branch phase. Two regions within the optical nebula are clearly detected in non-thermal radio continuum emission, with radio spectral indices comparable to those seen in colliding-wind Wolf–Rayet binaries. We suggest that these represent shocked interactions between the hot, fast stellar wind and the cold nebular shell that represents the PN's slow wind moving away from the central star. This same interface produces both synchrotron radio continuum and the optical PN emission. The fast wind is neither spherical in geometry nor aligned with any obvious optical or radio axis. We also report the detection of transient H₂O maser emission in this nebula.  相似文献