The ortho- to para- ratio of H₂ in the starburst of NGC 253     

Andrew Harrison  Phil Puxley  Adrian Russell  & Peter Brand 《Monthly notices of the Royal Astronomical Society》1998,297(2):624-632

We present measurements of several near-infrared emission lines from the nearby galaxy NGC 253. We have been able to measure four H₂ lines across the circumnuclear starburst, from which we estimate the ortho- to para- ratio of excited H₂ to be ∼2. This indicates that the bulk of the H₂ emission arises from photodissociation regions (PDRs), rather than from shocks. This is the case across the entire region of active star formation.
As the H₂ emission arises from PDRs, it is likely that the ratio of H₂ to Brγ (the bright hydrogen recombination line) is a measure of the relative geometry of O and B stars and PDRs. Towards the nucleus of NGC 253 the geometry is deduced to be tightly clustered O and B stars in a few giant H  II regions that are encompassed by PDRs. Away from the nuclear region, the geometry becomes that of PDRs bathed in a relatively diffuse ultraviolet radiation field.
The rotation curves of 1–0 S(1) and Brγ suggest that the ionized gas is tracing a kinetic system different from that of the molecular gas in NGC 253, particularly away from the nucleus.  相似文献   

Heavy metal residues in Laysan Duck feathers     

D.L. Stoneburner  C.S. Harrison 《Marine pollution bulletin》1981,12(10):354-355

The heavy metal data presented herein indicate that the wild Laysan Duck population may not be contaminated with metal-laden industrial wates. It is therefore possible that the food chain which supports the duck population is uncontaminated, with the possible exception of prey taken from pelagic sea bird carcasses. Such a short, geographically isolated food chain, involving a non-migratory avian carnivore, could be an ideal system for the investigation of bio-concentration, bio-accumulation and bio-magnification of naturally occurring heavy metals.  相似文献   

Mesoscale eddies and general ocean circulation models     

A.R. Robinson  D.E. Harrison  D.B. Haidvogel 《Dynamics of Atmospheres and Oceans》1979,3(2-4)

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Reconstructions of the Campbell Plateau and the Lord Howe Rise     

E.J. Barron  C.G.A. Harrison 《Earth and Planetary Science Letters》1979,45(1):87-92

Reconstructions of the southeastern margin of Gondwanaland require either a separation of East and West Antarctica or movement between the Lord Howe Rise and the Campbell Plateau. Previous plate tectonic reconstructions based on sea-floor spreading data eliminated the Lord Howe Rise-Campbell Plateau separation prior to 36 m.y. ago because of overlap. This conclusion is dependent on the reconstruction of Australia and Antarctica, interpretation of magnetic anomalies between Antarctica and the Campbell Plateau and the nature of the plate boundary in New Zealand. Revised reconstructions of the fit between Australia and Antarctica, and a reinterpretation of the magnetic anomalies between the Campbell Plateau and Antarctica suggest that there is no problem of overlap between the Lord Howe Rise and the Campbell Plateau, and that continued motion between these plates prior to 36 m.y. ago is a more plausible alternative to separation between East and West Antarctica.  相似文献   

Measurements of Reaction Coefficients of NO2 and HONO on Aerosol Particles     

Roy M. Harrison  Gareth M. Collins 《Journal of Atmospheric Chemistry》1998,30(3):397-406

The reaction coefficients of nitrogen dioxide and nitrous acid with monodisperse sodium chloride and ammonium sulphate aerosols have been measured in a flow reactor at atmospheric pressure. These experiments were performed at relative humidities above and below the deliquescence points of both aerosols (r.h. 50 and 85%) at 279 K. The results for NO₂ afford a reaction coefficient in the range (2.8–10) × 10^-4 and for HONO, (2.8–4.6) × 10^-3. For both species, there appears to be an enhancement of the reaction coefficient on sodium chloride aerosol at 50% r.h. The results are compared with reaction coefficients determined by other experimental methods. A good agreement is found for both gases between this method and the coated denuder method previously developed in our research laboratories (Msibi et al., 1993) and with the majority of other published data for NO₂. In the case of HONO, our estimate of reaction coefficient is smaller than, or at the lower limits of the ranges reported by other published studies.  相似文献   

Research on red tide occurrences using enclosed experimental ecosystems in west Xiamen Harbor, China—Relationship between various factors and red tide occurrences     

Lin Yu  P. J. Harrison 《中国海洋湖沼学报》2000,18(2):148-156

A series of enclosed ecosystem experiments were conducted in a land-based tank near the seaside of West Xiamen Harbor. The results of experiments conducted in different seasons and years showed a repeatable phytoplankton succession. In this relatively stable ecosystem with added nutrients and trace metals, diatoms dominated initially, dinoflagellates dominated in the later stage, and dinoflagellate red tides eventually occurred. Vitamin B₁₂ enrichment may speed up this succession process. Stirring the water column could stop this process. Soluble Mn at a level of 3–4 μg/L in seawater, which also is the existing concentration of soluble Mn in Xiamen Harbor seawater, is sufficient for the multiplication of algae and occurrence of red tide. The present study showed that excessive soluble Mn in Xiamen Harbor cannot cause red tide, and that Fe was one of the important factors causing diatiom red tide in this present study. Project 39570145 supported by NSFC.  相似文献   

Effect of atmospheric pressure and temperature on entrapped gas content in peat     

J. M. Waddington  K. Harrison  E. Kellner  A. J. Baird 《水文研究》2009,23(20):2970-2980

Entrapped biogenic gas in peat can greatly affect peatland biogeochemical and hydrological processes by altering volumetric water content, peat buoyancy, and ‘saturated’ hydraulic conductivity, and by generating over‐pressure zones. These over‐pressure zones further affect hydraulic gradients which influence water and nutrient flow direction and rate. The dynamics of entrapped gas are of global interest because the loss of this gas to the atmosphere via ebullition (bubbling) is likely the dominant transport mechanism of methane (CH₄) to the atmosphere from peatlands, which are the largest natural terrestrial source per annum of atmospheric CH₄. We investigated the relationship between atmospheric pressure and temperature on volumetric gas content (VGC) and CH₄ ebullition using a laboratory peat core incubation experiment. Peat cores were incubated at three temperatures (one core at 4 °C, three cores at 11 °C, and one core at 20 °C) in sealed PVC cylinders, instrumented to measure VGC, pore‐water CH₄ concentrations, and ebullition (volume and CH₄ concentrations). Ebullition events primarily occurred (71% of the time) during periods of falling atmospheric pressure. The duration of the drop in atmospheric pressure had a larger control on ebullition volume than the magnitude of the drop. VGC in the 20 °C core increased from the onset of the experiment and reached a fluctuating but time‐averaged constant level between experiment day 30 and 115. The change in VGC was low for the 11 °C cores for the initial period of the experiment but showed large increases when the growth chamber temperature increased to 20 °C due to a malfunction. The core maintained at 4 °C showed only a small increase in entrapped gas content throughout the experiment. The 20 °C core showed the largest increase in VGC. The increases in VGC occurred despite pore‐water concentrations of CH₄ being below the equilibrium solubility level. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Diatoms grow faster using ammonium in rapidly flushed eutrophic Dokai Bay,Japan   总被引：1，自引：0，他引：1  

Kuninao Tada  Marut Suksomjit  Kazuhiko Ichimi  Yui Funaki  Shigeru Montani  Machiko Yamada  Paul J. Harrison 《Journal of Oceanography》2009,65(6):885-891

The importance of the nitrogen source for phytoplankton growth in a highly eutrophic embayment, Dokai Bay, was investigated. The DIN concentration often exceeded 100 μM of which 40–70% was NH₄ ⁺. During two incubation experiments, the natural assemblage of mainly diatoms took up NH₄ ⁺ instead of NO₃ ⁻. The growth of two Skeletonema species isolated in Dokai Bay were significantly faster on NH₄ ⁺ (1.86 and 1.27 div. d⁻¹ respectively) than on NO₃ ⁻ (1.55 and 1.04 div. d⁻¹ respectively). Our results indicated that these diatoms could grow faster by using NH₄ ⁺ compared to NO₃ ⁻ in this eutrophic bay.  相似文献   

Local effects on tidal strain measurements at Esashi, Japan     

T. Sato  J. C. Harrison 《Geophysical Journal International》1990,102(3):513-526

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Assessing cross-sectoral climate change impacts,vulnerability and adaptation: an introduction to the CLIMSAVE project   总被引：1，自引：0，他引：1  

P. A. Harrison  I. P. Holman  P. M. Berry 《Climatic change》2015,128(3-4):153-167

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