Hco+ in the Coma of Comet Hale–Bopp     

Lovell  A. J.  Schloerb  F. P.  Bergin  E. A.  Dickens  J. E.  Devries  C. H.  Senay  M. C.  Irvine  W. M. 《Earth, Moon, and Planets》1997,77(3):253-258

Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO⁺ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO⁺ emission require a low abundance of HCO⁺ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (T_e). To set constraints on the formation of HCO⁺ in the coma, as well as the location and magnitude of the transition to higher T_e, the data are compared with the results of ion-molecule chemistry models. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Investigating the influence of aquifer heterogeneity on the potential for thermal free convection in the Yarragadee Aquifer,Western Australia     

Dylan J. Irvine  Heather A. Sheldon  Craig T. Simmons  Adrian D. Werner  Cedric M. Griffiths 《Hydrogeology Journal》2015,23(1):161-173

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Hydrology of stockpiled industrial coal exposed to rainfall     

K. J. Curran  I. G. Droppo  K. N. Irvine 《水文研究》2002,16(14):2781-2790

The movement of water and particulate matter through a simulated coal pile using a rainfall–coal‐pile simulator is investigated. In conjunction with coal‐pile management practices, this study indicates that coal‐pile systems change their internal and surficial structure with successive rainstorm events. This change in coal‐pile structure alters the proportions, rates and suspended solid concentrations within surface runoff and infiltration during subsequent storm events. Results demonstrate the need to determine the optimal coal‐pile slope that minimizes water contact time, but at the same time minimizes the potential for mass wasting and rill erosion. Promotion of a compacted surface is beneficial for the minimization of solids removal, and a stormwater detention pond with potential flocculant additive is suggested as a viable remedial measure for the containment and treatment of coal‐pile runoff. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Chemistry of the organic-rich hot core G327.3-0.6     

Gibb E  Nummelin A  Irvine WM  Whittet DC  Bergman P 《The Astrophysical journal》2000,545(1):309-326

We present gas-phase abundances of species found in the organic-rich hot core G327.3-0.6. The data were taken with the Swedish-ESO Submillimetre Telescope (SEST). The 1-3 mm spectrum of this source is dominated by emission features of nitrile species and saturated organics, with abundances greater than those found in many other hot cores, including Sgr B2 and OMC-1. Population diagram analysis indicates that many species (CH3CN, C2H3CN, C2H5CN, CH3OH, etc.) have hot components that originate in a compact (~2") region. Gas-phase chemical models cannot reproduce the high abundances of these molecules found in hot cores, and we suggest that they originate from processing and evaporation of icy grain mantle material. In addition, we report the first detection of vibrationally excited ethyl cyanide and the first detection of methyl mercaptan (CH3SH) outside the Galactic center.  相似文献   

The origin of garnet and clinopyroxene in “depleted” Kaapvaal peridotites     

Nina S. C. Simon  Gordon J. Irvine  Gareth R. Davies  D. Graham Pearson  Richard W. Carlson 《Lithos》2003,71(2-4):289-322

A detailed petrographic, major and trace element and isotope (Re–Os) study is presented on 18 xenoliths from Northern Lesotho kimberlites. The samples represent typical coarse, low-temperature garnet and spinel peridotites and span a P–T range from 60 to 150 km depth. With the exception of one sample (that belongs to the ilmenite–rutile–phlogopite–sulphide suite (IRPS) suite first described by [B. Harte, P.A. Winterburn, J.J. Gurney, Metasomatic and enrichment phenomena in garnet peridotite facies mantle xenoliths from the Matsoku kimberlite pipe, Lesotho. In: Menzies, M. (Ed.), Mantle metsasomatism. Academic Press, London 1987, 145–220.]), all samples considered here have high Mg# and show strong depletion in CaO and Al₂O₃. They have bulk rock Re depletion ages (T_RD) >2.5 Ga and are therefore interpreted as residua from large volume melting in the Archaean. A characteristic of Kaapvaal xenoliths, however, is their high SiO₂ concentrations, and hence, modal orthopyroxene contents that are inconsistent with a simple residual origin of these samples. Moreover, trace element signatures show strong overall incompatible element enrichment and REE disequilibrium between garnet and clinopyroxene. Textural and subtle major element disequilibria were also observed. We therefore conclude that garnet and clinopyroxene are not co-genetic and suggest that (most) clinopyroxene in the Archaean Kaapvaal peridotite xenoliths is of metasomatic origin and crystallized relatively recently, possibly from a melt precursory to the kimberlite.

Possible explanations for the origin of garnet are exsolution from a high-temperature, Al- and Ca-rich orthopyroxene (indicating primary melt extraction at shallow levels) or a majorite phase (primary melting at >6 GPa). Mass balance calculations, however, show that not all garnet observed in the samples today is of a simple exsolution origin. The extreme LREE enrichment (sigmoidal REE pattern in all garnet cores) is also inconsistent with exsolution from a residual orthopyroxene. Therefore, extensive metasomatism and probably re-crystallization of the lithosphere after melt-depletion and garnet exsolution is required to obtain the present textural and compositional features of the xenoliths. The metasomatic agent that modified or perhaps even precipitated garnet was a highly fractionated melt or fluid that might have been derived from the asthenosphere or from recycled oceanic crust. Since, to date, partitioning of trace elements between orthopyroxene and garnet/clinopyroxene is poorly constrained, it was impossible to assess if orthopyroxene is in chemical equilibrium with garnet or clinopyroxene. Therefore, further trace element and isotopic studies are required to constrain the timing of garnet introduction/modification and its possible link with the SiO₂ enrichment of the Kaapvaal lithosphere.  相似文献   

Tricarbon monoxide in TMC-1     

Brown RD  Godfrey PD  Cragg DM  Rice EH  Irvine WM  Friberg P  Suzuki H  Ohishi M  Kaifu N  Morimoto M 《The Astrophysical journal》1985,297(1):302-308

We report the measurement of three new lines of C3O in TMC-1. The observed peak antenna temperatures, appropriately corrected for atmospheric and telescope losses, are found to be consistent with a large velocity gradient radiative transfer model whose parameters span the range of standard values for this cloud. The derived fractional abundance for C3O is 1.4 x 10(-10), comparable with the results predicted from a model calculation based on a gas-phase ion-molecule reaction scheme. The results of negative searches for C3O in six other sources are not inconsistent with expected conditions in these clouds.  相似文献   

The detection of acetaldehyde in cold dust clouds     

Matthews HE  Friberg P  Irvine WM 《The Astrophysical journal》1985,290(2):609-614

Observations of the 1(01) --> 0(00) rotational transitions of A and E state acetaldehyde are reported. The transitions were detected, for the first time in interstellar space, in the cold dust clouds TMC-1 and L134N, and in Sgr B2. This is also the first time acetaldehyde has been found in a dust cloud and is the most complex oxygen-bearing molecule yet known in this environment. We find a column density of 6 x 10(12) cm-2 in TMC-1, comparable to many other species detected there, and an approximately equal column density in L134N. In the direction of Sgr B2, the CH3CHO profile appears to consist of broad emission features from the hot molecular cloud core, together with absorption features resulting from intervening colder material. We also report the possible detection of HC9N toward IRC +10 degrees 216 through its J = 33 --> 32 transition. Implications for cold dust cloud chemistry and excitation are discussed.  相似文献   

Chemistry between the stars     

Irvine WM 《The Planetary report》1987,7(6):6-9

Life--as we know it--is a chemical process, based on water and carbon compounds. Complex organic molecules are made primarily from the biogenic elements--carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur--that formed deep within massive ancient stars. How did these elements travel from their stellar birthplaces across time and space to make up the life-form that is reading these words? In this article, we'll take a look at the chemical processes that set the stage for the origin of life.  相似文献   

The C3H2 2(20)-2(11) transition: absorption in cold dark clouds     

Matthews HE  Madden SC  Avery LW  Irvine WM 《The Astrophysical journal》1986,307(2):L69-L73

The first observations of the 2(20)-2(11) transition of cyclopropenylidene (C3H2) at 21.6 GHz are described. In all cases where it has been detected, the line appears in absorption, showing that this transition is "refrigerated" (i.e., Tex < 2.7 K) in cold dust clouds. These results are compared with those for the 1(10)-1(01) transition of C3H2, and the consequences for the excitation of C3H2 qualitatively discussed.  相似文献   

New interstellar masers in nonmetastable ammonia     

Madden SC  Irvine WM  Matthews HE  Brown RD  Godfrey PD 《The Astrophysical journal》1986,300(2):L79-L84

We report the astronomical detections of several ammonia inversion transitions involving nonmetastable levels with energies as high s 1090 K above the ground state. The (J, K) = (9, 6) inversion transition shows maser-like emission in the directions of W51, NGC 7538, W49, and DR 21(OH). The NH3 (6, 3) line exhibits similar characteristics in W51 but is seen in absorption in NGC 7538. These are the first definite detections of ammonia masers in space. The intensities and narrow line widths (0.5-1.5 km s-1) for the emission features are in contrast to the previously detected broad, weak, nonmetastable lines attributed to thermal emission in these sources. Temporal variability appears to be evident in the (9, 6) emission in W49 over a 4 month period. The highly excited (J, K) = (9, 6) and (6, 3) ammonia lines are found in regions containing compact H II regions and strong infrared sources with associated H2O and OH masers; i.e., in regions of active star formation.  相似文献