Invasion genetics of Pacific oyster Crassostrea gigas shaped by aquaculture stocking practices     

Jenny Moehler  K. Mathias Wegner  Karsten Reise  Sabine Jacobsen 《Journal of Sea Research》2011,66(3):256-262

As a result of aquaculture activities Pacific oysters Crassostrea gigas (Thunberg, 1793) have invaded the European Wadden Sea. Using a variable noncoding mitochondrial marker, we show that the invaded range is the result of two independent invasions. Haplotype frequencies point towards two separate groups, one in the southern and the other in the northern Wadden Sea. We found virtually no genetic differentiation throughout the southern range and the putative source from British Columbia, Canada, suggesting that the Southern region can be considered as a closed population. In the North, mismatch distributions, haplotype ordination and isolation-by-distance analysis suggest a stronger, persistent impact of aquaculture on invasive populations. Due to the ongoing supply of new genetic material from hatchery production the northern invasive populations can therefore be considered as an open population highlighting the importance of aquaculture practice on the genetics of this keystone invader in the Wadden Sea.  相似文献   

The NOAO Fundamental Plane Survey – III. Variations in the stellar populations of red-sequence galaxies from the cluster core to the virial radius     

Russell J. Smith  Michael J. Hudson  John R. Lucey  Jenica E. Nelan  Gary A. Wegner 《Monthly notices of the Royal Astronomical Society》2006,369(3):1419-1436

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Comparison of the ENEAR peculiar velocities with the PSCz gravity field     

Adi Nusser  Luiz N. da Costa  Enzo Branchini  Mariangela Bernardi  M.V. Alonso  Gary Wegner  C. N. A. Willmer  P. S. Pellegrini 《Monthly notices of the Royal Astronomical Society》2001,320(3):L21-L24

We present a comparison between the peculiar velocity field measured from the ENEAR all-sky D _n– σ catalogue and that derived from the galaxy distribution of the IRAS Point Source Catalog Redshift Survey (PSC z ). The analysis is based on a modal expansion of these data in redshift space by means of spherical harmonics and Bessel functions. The effective smoothing scale of the expansion is almost linear with redshift reaching 1500 km s⁻¹ at 3000 km s⁻¹. The general flow patterns in the filtered ENEAR and PSC z velocity fields agree well within 6000 km s⁻¹, assuming a linear biasing relation between the mass and the PSC z galaxies. The comparison allows us to determine the parameter     where Ω is the cosmological density parameter and b is the linear biasing factor. A likelihood analysis of the ENEAR and PSC z modes yields     in good agreement with values obtained from Tully–Fisher surveys.  相似文献   

The Oxford–Dartmouth Thirty Degree Survey – I. Observations and calibration of a wide-field multiband survey     

Emily C. MacDonald  Paul Allen  Gavin Dalton  Leonidas A. Moustakas  Catherine Heymans  Edward Edmondson  Chris Blake  Lee Clewley  Molly C. Hammell  Ed Olding  Lance Miller  Steve Rawlings  Jasper Wall  Gary Wegner  Christian Wolf 《Monthly notices of the Royal Astronomical Society》2004,352(4):1255-1272

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Bathymetric chart of Atka Ice Port     

Gerd Wegner 《Ocean Dynamics》1981,34(4):162-166

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Nanometric modulation in apatite     

C. Ferraris  T. J. White  J. Plévert  R. Wegner 《Physics and Chemistry of Minerals》2005,32(7):485-492

Brazilian gem-grade apatite (B-Ap) consists of contiguous fluorine-enriched (host-Ap) domains (∼400 nm), interspersed by isolated domains (∼200 nm) of a chlorine-enriched (guest-Ap) apatite in a long period compositional modulation. Within each of these domains a third modulation differentiating Si- and S-rich nanocrystals (5–10 nm) of ellestadite (El-Ap), a monoclinic apatite variety, developed possibly during a short term high temperature event. These unexpected miscibility gaps may be useful geothermometric tools, and could prove decisive for enhancing the properties of apatites used as heterogeneous catalysts and fuel–cell electrolytes.  相似文献   

The size distribution of dust grains in single clouds – II. The analysis of extinction using inhomogeneous grains     

Zubko  Kre&#;owski  & Wegner 《Monthly notices of the Royal Astronomical Society》1998,294(4):548-556

The extinction curves of single clouds, seen towards the stars HD 147165, 179406 and 202904, have been modelled using various mixtures containing both the bare and inhomogeneous (composite and/or multilayer) grains. It has been shown that the models composed of the bare graphite and silicate grains together with the multilayer grains containing silicates, organic refractory and water ice, are more useful in explaining extinction under the reduced cosmic abundances. The models based on Mathis' composite grains or on Greenberg & Li's core-mantle grains can also provide quite good fits of the extinction and the measured scattering parameters, but still require an excessive amount of carbon which results in too large a C/O ratio. The inhomogeneous grains essentially contribute to the extinction in practically the whole wavelength range of our extinction curves. As a rule, such grains have quite wide size distributions, centred at around 100 nm, although graphite grains are mainly of small sizes.  相似文献   

Chemical etching of deformation sub-structures in quartz     

M. W. Wegner  J. M. Christie 《Physics and Chemistry of Minerals》1983,9(2):67-78

Chemical etching of dislocations has been studied in natural and synthetic quartz single crystals, in deformed synthetic quartz and in naturally and experimentally deformed quartzites. The ability of different etchants to produce polished or preferentially etched surfaces on quartz is described. Dislocation etching was achieved on all crystal planes examined by using a saturated solution of ammonium bifluoride as the etchant. Appropriate etching times were determined for etching quartzites for grain size, subgrain boundaries, deformation lamellae, dislocations and twins. Growth and polished surfaces of synthetic single crystal quartz were similarly etched and dislocation etch pits, characteristic of various orientations were found. The use of ammonium bifluoride proved to be expecially advantageous for the basal plane, producing a polished surface with etch pits, suitable for dislocation etch pit counting. “Double” etch pits have been found on Dauphiné twin boundaries on the basal plane and the first order prism, using this etchant. Slip lines and deformation bands were suitably etched on deformed synthetic crystal surfaces for identification of the slip planes. Other acidic etchants have been explored and their application to the study of deformation structures in quartz crystals is discussed.  相似文献   

Neuere veröffentlichungen     

Erich Pansch  Holger Klein  Gerd Wegner 《Ocean Dynamics》1987,40(2):81-85

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Exsolution in terrestrial and lunar plagioclases revealed by chemical etching     

M. W. Wegner  R. E. Jones  J. M. Christie 《Contributions to Mineralogy and Petrology》1978,65(3):283-291

A new chemical etching technique reveals fine scale exsolution structures on polished surfaces of plagioclases in the bytownite and labradorite range. A very obvious blue and locally brown stain is produced (by the action of citric acid) in growth zones of a restricted range of compositions on etched surfaces. The blue-stained zones contain very fine grooves, corresponding to the traces of thin exsolution lamellae. Exsolution features have been revealed in this way in plagioclases in a terrestrial diabase, lunar basalts and an amphibolite. Compositions of the exsolved areas found by microprobe analysis represent averages of the matrix and exsolution lamellae. Analytical methods with higher spatial resolution are required to determine the composition of the lamellae. This etching method permits easy optical identification of compositional zoning and of fine scale exsolution over relatively large areas and is therefore complementary to other techniques.  相似文献