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211.
David A. Burton 《Natural Hazards》2012,63(2):1219-1221
212.
We performed measurements using an SO2 imaging camera of the SO2 gas mass emitted during five discrete explosive events on Stromboli volcano on 3 October 2006. The SO2 gas mass released during discrete explosions was 15–40 kg per explosion, producing 3–8% of the total daily SO2 gas emission, demonstrating that in terms of gas flux Strombolian explosions are a second-order phenomenon compared with quiescent degassing. Using the typical gas composition measured with OP-FTIR allows us to determine the total gas mass released during an explosion as 360–960 kg with a volume of 1500–4100 m3 at 1 bar. At the probable source pressure of gas slug formation of 75 MPa this gas amount would occupy a volume equivalent to a sphere with a radius of 0.8–1 m, comparable with estimates of Stromboli's conduit geometry. 相似文献
213.
Michael G. Burton 《Astronomy and Astrophysics Review》2010,18(4):417-469
Antarctica provides a unique environment for astronomers to practice their trade. The cold, dry and stable air found above
the high Antarctic plateau, as well as the pure ice below, offers new opportunities for the conduct of observational astronomy
across both the photon and the particle spectrum. The summits of the Antarctic plateau provide the best seeing conditions,
the darkest skies and the most transparent atmosphere of any earth-based observing site. Astronomical activities are now underway
at four plateau sites: the Amundsen-Scott South Pole Station, Concordia Station at Dome C, Kunlun Station at Dome A and Fuji
Station at Dome F, in addition to long duration ballooning from the coastal station of McMurdo, at stations run by the USA,
France/Italy, China, Japan and the USA, respectively. The astronomy conducted from Antarctica includes optical, infrared,
terahertz and sub-millimetre astronomy, measurements of cosmic microwave background anisotropies, solar astronomy, as well
as high energy astrophysics involving the measurement of cosmic rays, gamma rays and neutrinos. Antarctica is also the richest
source of meteorites on our planet. An extensive range of site testing measurements have been made over the high plateau sites.
In this article, we summarise the facets of Antarctica that are driving developments in astronomy there, and review the results
of the site testing experiments undertaken to quantify those characteristics of the Antarctic plateau relevant for astronomical
observation. We also outline the historical development of the astronomy on the continent, and then review the principal scientific
results to have emerged over the past three decades of activity in the discipline. These range from determination of the dominant
frequencies of the 5 min solar oscillation in 1979 to the highest angular scale measurements yet made of the power spectrum
of the CMBR anisotropies in 2010. They span through infrared views of the galactic ecology in star formation complexes in
1999, the first clear demonstration that the Universe was flat in 2000, the first detection of polarization in the CMBR in
2002, the mapping of the warm molecular gas across the ~ 300 pc extent of the Central Molecular Zone of our Galaxy in 2003,
the measurement of cosmic neutrinos in 2005, and imaging of the thermal Sunyaev Zel’dovich effect in galaxy clusters in 2008.
This review also discusses how science is conducted in Antarctica, and in particular the difficulties, as well as the advantages,
faced by astronomers seeking to bring their experiments there. It also reviews some of the political issues that will be encountered,
both at national and international level. Finally, the review discusses where Antarctic astronomy may be heading in the coming
decade, in particular plans for infrared and terahertz astronomy, including the new facilities being considered for these
wavebands at the high plateau stations. 相似文献
214.
D. Heath Jones Mike A. Read Will Saunders Matthew Colless Tom Jarrett Quentin A. Parker Anthony P. Fairall † Thomas Mauch Elaine M. Sadler Fred G. Watson Donna Burton Lachlan A. Campbell Paul Cass Scott M. Croom John Dawe † Kristin Fiegert Leela Frankcombe Malcolm Hartley John Huchra Dionne James Emma Kirby Ofer Lahav John Lucey Gary A. Mamon Lesa Moore Bruce A. Peterson Sayuri Prior Dominique Proust Ken Russell Vicky Safouris Ken-ichi Wakamatsu Eduard Westra Mary Williams 《Monthly notices of the Royal Astronomical Society》2009,399(2):683-698
We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky (| b | > 10°) . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with ( K , H , J , r F , b J ) ≤ (12.65, 12.95, 13.75, 15.60, 16.75) . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with z ≤ 0.1 , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS . 相似文献
215.
S. N. Longmore M. G. Burton E. Keto S. Kurtz A. J. Walsh 《Monthly notices of the Royal Astronomical Society》2009,399(2):861-877
We present Australia Telescope Compact Array observations towards six massive star formation regions, which, from their strong 24 GHz continuum emission but no compact 8 GHz continuum emission, appeared good candidates for hypercompact H ii regions. However, the properties of the ionized gas derived from the 19 to 93 GHz continuum emission and H70α+ H57α radio recombination line data show the majority of these sources are, in fact, regions of spatially extended, optically thin free–free emission. These extended sources were missed in the previous 8 GHz observations due to a combination of spatial filtering, poor surface brightness sensitivity and primary beam attenuation.
We consider the implications that a significant number of these extended H ii regions may have been missed by previous surveys of massive star formation regions. If the original sample of 21 sources is representative of the population as a whole, the fact that six contain previously undetected extended free–free emission suggests a large number of regions have been mis-classified. Rather than being very young objects prior to UCH ii region formation, they are, in fact, associated with extended H ii regions and thus significantly older. In addition, inadvertently ignoring a potentially substantial flux contribution (up to ∼0.5 Jy) from free–free emission has implications for dust masses derived from sub-mm flux densities. The large spatial scales probed by single-dish telescopes, which do not suffer from spatial filtering, are particularly susceptible and dust masses may be overestimated by up to a factor of ∼2. 相似文献
We consider the implications that a significant number of these extended H ii regions may have been missed by previous surveys of massive star formation regions. If the original sample of 21 sources is representative of the population as a whole, the fact that six contain previously undetected extended free–free emission suggests a large number of regions have been mis-classified. Rather than being very young objects prior to UCH ii region formation, they are, in fact, associated with extended H ii regions and thus significantly older. In addition, inadvertently ignoring a potentially substantial flux contribution (up to ∼0.5 Jy) from free–free emission has implications for dust masses derived from sub-mm flux densities. The large spatial scales probed by single-dish telescopes, which do not suffer from spatial filtering, are particularly susceptible and dust masses may be overestimated by up to a factor of ∼2. 相似文献
216.
217.
218.
Urban stormwater runoff is a major source of contaminants to southern California's coastal waters, yet little is known about the fate and effects of these discharges. A 3-year multidisciplinary project was conducted to investigate the dispersion of stormwater plumes in Santa Monica Bay and the resultant impacts on the water column and benthos. This paper describes the toxicity component of the study. Sea urchin fertilization toxicity tests were conducted on stormwater from the two largest discharges into the bay: Ballona Creek, which drains a highly urbanized watershed, and Malibu Creek, which receives runoff from a largely undeveloped watershed. Every sample of Ballona Creek stormwater tested was toxic (usually >5 toxic units), while Malibu Creek stormwater had a lower frequency and magnitude of toxicity (usually <4 toxic units). Surface water samples collected within the Ballona Creek stormwater discharge plume were always toxic whenever the concentration of stormwater in the plume exceeded 10%. The toxic portion of the Ballona Creek stormwater plume extended more than 4 km offshore on one occasion. Toxicity identification studies indicated that zinc was the primary cause of toxicity in both Ballona Creek stormwater and the discharge plume. No acute sediment toxicity (10-day amphipod survival) was present in the study area, although interstitial water toxicity was present at some stations located near the mouth of Ballona Creek. Differences in watershed characteristics likely were responsible for the greater toxicity of the Ballona Creek stormwater discharge plume. The Ballona Creek watershed contained a greater degree of urbanization (83% versus 12% for Malibu Creek) and the presence of a network of concrete flood control channels resulted in a stormwater plume containing elevated concentrations of toxins that received less initial dilution (compared to Malibu Creek) in the nearshore environment. 相似文献
219.
Errors and uncertainty in physically-based rainfall-runoff modelling of catchment change effects 总被引:1,自引:0,他引:1
The error in physically-based rainfall-runoff modelling is broken into components, and these components are assigned to three groups: (1) model structure error, associated with the model’s equations; (2) parameter error, associated with the parameter values used in the equations; and (3) run time error, associated with rainfall and other forcing data. The error components all contribute to “integrated” errors, such as the difference between simulated and observed runoff, but their individual contributions cannot usually be isolated because the modelling process is complex and there is a lack of knowledge about the catchment and its hydrological responses. A simple model of the Slapton Wood Catchment is developed within a theoretical framework in which the catchment and its responses are assumed to be known perfectly. This makes it possible to analyse the contributions of the error components when predicting the effects of a physical change in the catchment. The standard approach to predicting change effects involves: (1) running “unchanged” simulations using current parameter sets; (2) making adjustments to the sets to allow for physical change; and (3) running “changed” simulations. Calibration or uncertainty-handling methods such as GLUE are used to obtain the current sets based on forcing and runoff data for a calibration period, by minimising or creating statistical bounds for the “integrated” errors in simulations of runoff. It is shown that current parameter sets derived in this fashion are unreliable for predicting change effects, because of model structure error and its interaction with parameter error, so caution is needed if the standard approach is to be used when making management decisions about change in catchments. 相似文献
220.
The Mersey Basin has been significantly polluted for over 200 years. However, there is a lack of quantitative historical water quality data as effective water quality monitoring and data recording only began 30–40 years ago. This paper assesses water pollution in the Mersey Basin using a Water Pollution Index constructed from social and economic data. Methodology, output and the difficulties involved with validation are discussed. With the limited data input available the index approximately reproduces historical water quality. The paper illustrates how historical studies of environmental water quality may provide valuable identification of factors responsible for pollution and a marker set for contemporary and future water quality issues in the context of the past. This is an issue of growing research interest. 相似文献