Chemistry in the circumstellar medium     

T. J. Millar 《Astrophysics and Space Science》2008,313(1-3):223-227

The growth of dust grains in the inner regions of late-type stars is shrouded in mystery due to the difficulty of understanding the growth of heterogeneous particles from simple atoms and molecules and the lack of observational data. This article reviews the molecular processes important in circumstellar envelopes and discusses how ALMA might be used to probe the dust formation zone either directly or indirectly.  相似文献   

Subaqueous, basaltic lava dome and carapace breccia on King George Island, South Shetland Islands, Antarctica     

J. L. Smellie  I. L. Millar  D. C. Rex  P. J. Butterworth 《Bulletin of Volcanology》1998,59(4):245-261

 On King George Island during latest Oligocene/earliest Miocene time, submarine eruptions resulted in the emplacement of a small (ca. 500 m estimated original diameter) basalt lava dome at Low Head. The dome contains a central mass of columnar rock enveloped by fractured basalt and basalt breccia. The breccia is crystalline and is a joint-block deposit (lithic orthobreccia) interpreted as an unusually thick dome carapace breccia cogenetic with the columnar rock. It was formed in situ by a combination of intense dilation, fracturing and shattering caused by natural hydrofracturing during initial dome effusion and subsequent endogenous emplacement of further basalt melt, now preserved as the columnar rock. Muddy matrix with dispersed hyaloclastite and microfossils fills fractures and diffuse patches in part of the fractured basalt and breccia lithofacies. The sparse glass-rich clasts formed by cooling-contraction granulation during interaction between chilled basalt crust and surrounding water. Together with muddy sediment, they were injected into the dome by hydrofracturing, local steam fluidisation and likely explosive bulk interaction. The basalt lava was highly crystallised and degassed prior to extrusion. Together with a low effusion temperature and rapid convective heat loss in a submarine setting, these properties significantly affected the magma rheology (increased the viscosity and shear strength) and influenced the final dome-like form of the extrusion. Conversely, high heat retention was favoured by the degassed state of the magma (minimal undercooling), a thick breccia carapace and viscous shear heating, which helped to sustain magmatic (eruption) temperatures and enhanced the mobility of the flow. Received: 1 August 1996 / Accepted: 15 September 1997  相似文献   

Geochemistry of mafic dykes in the Antarctic Peninsula continental-margin batholith: a record of arc evolution   总被引：6，自引：0，他引：6  

Jane H. Scarrow  Philip T. Leat  Christopher D. Wareham  Ian L. Millar 《Contributions to Mineralogy and Petrology》1998,131(2-3):289-305

Mafic dykes of the Antarctic Peninsula continental-margin arc are compositionally diverse, comprising calc-alkaline (dominant), shoshonite, tholeiite, and OIB-like varieties. Their compositions give information about different mafic magma sources tapped during arc evolution. The compositional groups represent partial melts of at least five distinct mantle sources: a low-ɛNd subduction-modified, garnet-bearing, lithospheric mantle (older calc-alkaline); a high-ɛNd subduction-modified, garnet-bearing, lithospheric mantle (shoshonites); a high-ɛNd subduction-modified, spinel-bearing, asthenospheric mantle (younger calc-alkaline); E-MORB-like spinel-bearing asthenosphere depleted by a previous melting event (tholeiites); and within-plate non-subduction modified, garnet- and spinel-bearing, asthenosphere (OIB-like). Slab-derived fluids, subducted sediment, and arc crust also contributed to the magmas. Consideration of previous work in the light of our new compositional and geochronological data enables presentation of a summary of arc evolution. For most of the Cretaceous and Tertiary, the tectonic regime of the Antarctic Peninsula arc was transtensional, and calc-alkaline magmas intruded. An oceanic spreading centre collided with the trench during the Late Cretaceous and induced tectonic changes which caused tapping of different magma sources. A pulse of shoshonitic, tholeiitic, and OIB-like mafic magmatism resulted. Three ridge-trench collisions are now recognized during the history of the arc, in Mid–Late Jurassic, Late Cretaceous, and Early–Mid Tertiary times. Received: 13 January 1997 / Accepted: 5 December 1997  相似文献   

Giant grains?     

M. A. Leitch-Devlin  T. J. Millar  D. A. Williams 《Astrophysics and Space Science》1976,45(2):467-476

Infrared observations of the Orion nebula have been interpreted by Rowan-Robinson (1975) to imply the existence of giant grains, radius 10^–2 cm, throughout a volume about a parsec in diameter. Although Rowan-Robinson's model of the nebula has been criticized (e.g., Andriesse, 1976) and the presence of such grains in Orion is disputed, we accept,pro tem, the proposition that they exist, and examine in this paper situations in which giant grains could arise. We find that, while a giant-grain component to the interstellar grain density may exist, it is difficult to understand how giant grains arise to the extent apparently required by the Orion nebula model.  相似文献   

Modelling environmental effects on growth of cod: fitting to growth increment data versus fitting to size-at-age data     

Millar  Russell B. 《ICES Journal of Marine Science》1992,49(3):289-295

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Modelling analysis of the sensitivity of shoreline change to a wave farm     

D.L. Millar  H.C.M. Smith  D.E. Reeve 《Ocean Engineering》2007,34(5-6):884-901

Change of shoreline wave climate caused by the installation of a wave farm is assessed using the SWAN wave model. The 30 MW-rated wave farm is called the ‘Wave Hub’ and will be located 20 km off the north coast of Cornwall, UK. Changes in significant wave height and mean wave period due to the presence of the Wave Hub are presented. The results suggest that the shoreline wave climate will be affected, although the magnitude of effects decreases linearly as wave energy transmitted increases. At probable wave energy transmission levels, the predicted change in shoreline wave climate is small.  相似文献   

Modified hooks reduce incidental mortality of snapper (Pagrus auratus: Sparidae) in the New Zealand commercial longline fishery     

Willis  T. J.; Millar  R. B. 《ICES Journal of Marine Science》2001,58(4):830-841

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Late Pleistocene–Holocene records from Lake Ulaan,southern Mongolia: implications for east Asian palaeomonsoonal climate changes     

MIN KYUNG LEE  YONG IL LEE  HYOUN SOO LIM  JAE IL LEE  HO IL YOON 《第四纪科学杂志》2013,28(4):370-378

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Optical spectra of supernova remnant candidates in the Sculptor Group galaxy NGC 300     

William C. Millar  Graeme L. White  Miroslav D. Filipović  Jeffrey L. Payne  Evan J. Crawford  Thomas G. Pannuti  Wayne D. Staggs 《Astrophysics and Space Science》2011,332(2):221-239

We present moderate-resolution (<5 Å) long-slit optical spectra of 51 nebular objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting the criterion of [S?ii]_Total:Hα≥0.4 to confirm supernova remnants (SNRs) from optical spectra, we find that of 28 objects previously proposed as SNRs from optical observations, 22 meet this criterion with six showing [S?ii]_Total:Hα of less than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated with the 28 previously proposed SNRs. Of these four, three (included in the 22 above) meet the criterion. In all, 22 of the 51 nebular objects meet the [S ii]_Total:Hα criterion as SNRs while the nature of the remaining 29 objects remains undetermined by these observations.  相似文献   

Two-dimensional models of proto planetary disk chemistry     

T.J. Millar  H. Nomura  A.J. Markwick 《Astrophysics and Space Science》2003,285(3-4):761-768

We have developed a two-dimensional model of a flared protoplanetary disk (PPD) incorporating a self-consistent treatment of gas and dust temperature, and a detailed treatment of the gas-phase chemistry as well as the freeze-out and desorption of material from dust grains. The results show that, in the inner 10 AU of the disk, the gas-phase abundances are dominated by material evaporated from dust grains. The surface layer of the disk shows many of the characteristics of photon-dominated regions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献