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We have observed the G23 field of the Galaxy AndMass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase to validate the performance of the telescope and to characterise the detected galaxy populations. This observation covers ~48 deg2 with synthesised beam of 32.7 arcsec by 17.8 arcsec at 936MHz, and ~39 deg2 with synthesised beam of 15.8 arcsec by 12.0 arcsec at 1320MHz. At both frequencies, the root-mean-square (r.m.s.) noise is ~0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a magnitude limit of 19.2. Wide-field Infrared Survey Explorer (WISE) infrared (IR) photometry is used to determine which galaxies host an active galactic nucleus (AGN). In properties including source counts, mass distributions, and IR versus radio luminosity relation, the ASKAP-detected radio sources behave as expected. Radio galaxies have higher stellar mass and luminosity in IR, optical, and UV than other galaxies. We apply optical and IR AGN diagnostics and find that they disagree for ~30% of the galaxies in our sample. We suggest possible causes for the disagreement. Some cases can be explained by optical extinction of the AGN, but for more than half of the cases we do not find a clear explanation. Radio sources aremore likely (~6%) to have an AGN than radio quiet galaxies (~1%), but the majority of AGN are not detected in radio at this sensitivity.
The yields of spring barley during a medium-term (7 years) compost and slurry addition experiment and the soil carbon (C) and nitrogen (N) contents, bacterial community structure, soil microbial biomass and soil respiration rates have been determined to assess the effects of repeated, and in some cases very large, organic amendments on soil and crop parameters. For compost, total additions were equivalent to up to 119 t C/ha and 1·7 t N/ha and for slurry they were 25 t C/ha and 0·35 t N/ha over 7 years, which represented very large additions compared to control soil C and N contents (69 t C/ha and 0·3 t N/ha in the 0–30 cm soil depth). There was an initial positive response to compost and slurry addition on barley yield, but over the experiment the yield differential between the amounts of compost addition declined, indicating that repeated addition of compost at a lower rate over several years had the same cumulative effect as a large single compost application. By the end of the experiment it was clear that the addition of compost and slurry increased soil C and N contents, especially towards the top of the soil profile, as well as soil respiration rates. However, the increases in soil C and N contents were not proportional to the amount of C and N added, suggesting either that: (i) a portion of the added C and N was more vulnerable to loss; (ii) that its addition rendered another C or N pool in the soil more susceptible to loss; or (iii) that the C inputs from additional crop productivity did not increase in line with the organic amendments. Soil microbial biomass was depressed at the highest rate of organic amendment, and whilst this may have been due to genuine toxic or inhibitory effects of large amounts of compost, it could also be due to the inaccuracy of the substrate-induced respiration approach used for determining soil biomass when there is a large supply of organic matter. At the highest compost addition, the bacterial community structure was significantly altered, suggesting that the amendments significantly altered soil community dynamics.
Experiments on the National Ignition Facility show that multi-dimensional effects currently dominate the implosion performance. Low mode implosion symmetry and hydrodynamic instabilities seeded by capsule mounting features appear to be two key limiting factors for implosion performance. One reason these factors have a large impact on the performance of inertial confinement fusion implosions is the high convergence required to achieve high fusion gains. To tackle these problems, a predictable implosion platform is needed meaning experiments must trade-off high gain for performance. LANL has adopted three main approaches to develop a one-dimensional (1D) implosion platform where 1D means measured yield over the 1D clean calculation. A high adiabat, low convergence platform is being developed using beryllium capsules enabling larger case-to-capsule ratios to improve symmetry. The second approach is liquid fuel layers using wetted foam targets. With liquid fuel layers, the implosion convergence can be controlled via the initial vapor pressure set by the target fielding temperature. The last method is double shell targets. For double shells, the smaller inner shell houses the DT fuel and the convergence of this cavity is relatively small compared to hot spot ignition. However, double shell targets have a different set of trade-off versus advantages. Details for each of these approaches are described.
A heuristic greedy algorithm is developed for efficiently tiling spatially dense redshift surveys. In its first application to the Galaxy and MassAssembly (GAMA) redshift survey we find it rapidly improves the spatial uniformity of our data, and naturally corrects for any spatial bias introduced by the 2dF multi-object spectrograph. We make conservative predictions for the final state of the GAMA redshift survey after our final allocation of time, and can be confident that even if worse than typical weather affects our observations, all of our main survey requirements will be met.
EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ∼ 10 μJy/beam) radio continuum survey of the entire Southern sky at 1.3 GHz, extending as far North as +30° declination, with a resolution of 10 arcsec. EMU is expected to detect and catalogue about 70 million galaxies, including typical star-forming galaxies up to z ∼ 1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU.
D. W. Hopkins, School of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, Scotland, UK,
B. Elberling, Institute of Geography, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen K., Denmark,
L. G. Greenfield, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand,
E. G. Gregorich, Agriculture Canada, Central Experimental Farm, Ottawa, Canada K1A 0C6,
P. Novis, Manaaki Whenua - Landcare Research, PO Box 69, Lincoln 8152, New Zealand,
A. G. O'Donnell, Institute for Research on Environment and Sustainability, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK,
A. D. Sparrow, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand, Department of Natural Resources and Environmental Sciences, University of Nevada, 1000 Valley Rd, Reno, NV 89512, USA
In 1903, the explorer Robert Scott was one of the first humans ever to see the dry valleys of Antarctica. He called them ‘valley(s) of the dead’ in which ‘we have seen no sign of life, … not even a moss or lichen’. A century later, we know that the soils and rocks are home to many microscopic organisms that Scott could not have seen.
The dry valleys are part of the small percentage of the land surface of the Antarctic continent that is ice-free, amounting to about 4000 km2, and thus have rock and soil surfaces that can be colonized by terrestrial organisms. They are an ancient polar desert, perhaps as much as 2 million years old, located in Victoria Land between about 77 and 79° south (Fig. 1). The valleys are in a precipitation shadow caused by the Transantarctic Mountains, which rise over 4000 m. The Antarctic dry valleys are now recognized as one of the harshest terrestrial environments on Earth, characterized by summer maximum temperatures that rarely exceed 0 °C and only a few tens of millimetres of precipitation, most of which falls as snow and is ablated by strong winds carrying dry air from the polar plateau - potential evaporation far exceeds precipitation (Fig. 1).
Soil has generally been treated as something of a ‘black box’ by ecologists. It provides the physical support for plants, and both the living and non-living components contribute to a variety of important environmental functions. These include decomposition and the recycling of nutrients, which are both key functions in terrestrial ecosystems. Other roles, such as the breakdown of pollutants and the storage of bioelements, have immense applied significance in a changing environment. Soil provides a habitat for many species of bacteria, fungi, protists and animals; it is generally recognised as a habitat that is species rich. But many questions about the ecological significance of the soil's biological diversity, and in particular how it affects ecosystem function, have never been asked. Until fairly recently this has been because the linkages between above-ground ecology, which is rich in ecological theory, and below-ground ecology, where investigation has been restricted by methodological difficulties, have not been made. It is now time to open the ‘black box’ and to start to understand how it works.
At the end of the twentieth century and with the start of the twenty-first century, efforts have been going on around the world to gain a greater understanding of the diversity of life in the soil and of the functions that these many species perform. In the UK there have been two major programmes of research on biological diversity and the function of soil ecosystems.
In many ecological studies, soil carbon is regarded as a barely differentiated whole with little attention paid to its underlying characteristics.
Although it is widely appreciated that decomposer organisms are nearly infallible as degraders of organic molecules, there are marked differences in the utilisation of different components of organic matter by organisms depending on chemical and physical characteristics, location and availability in time in soil.
We discuss the characteristics of soil carbon as a substrate and emphasise a ‘soil metabolomic’ approach for characterising the range of molecules in complex, composite substrates, and the potential that stable isotope probing offers for linking organisms to their substrates via enrichment of their biomolecules as they exploit isotopically enriched substrates.
Using selected examples, we examine the influence of the chemical characteristics/quality, quantity, location and timing of supply of organic matter on the amount, activity and, where possible, the diversity of soil organisms.
We are some way from unifying relationships between the quality, quantity, location and timing of delivery or availability of soil carbon on the size, activity and diversity of soil organisms. However, we point ways forward in which the information on the physics, chemistry and management are linked to the biology of soils.
Currency of soil carbon
Humans view soil carbon in various physical (e.g. aggregates, density fractions), chemical (e.g. carbohydrates, aromatic compounds), biological (e.g. microbial biomass) and even economic (e.g. dollars per tonne or carbon credits) ways which are not usually ecological.