Is it possible to increase the sustainability of arable and ruminant agriculture by reducing inputs?

Until recently, agricultural production was optimised almost exclusively for profit but now farming is under pressure to meet environmental targets. A method is presented and applied for optimising the sustainability of agricultural production systems in terms of both economics and the environment. Components of the agricultural production chain are analysed using environmental life-cycle assessment (LCA) and a financial value attributed to the resources consumed and burden imposed on the environment by agriculture, as well as to the products. The sum of the outputs is weighed against the inputs and the system considered sustainable if the value of the outputs exceeds those of the inputs. If this ratio is plotted against the sum of inputs for all levels of input, a diminishing returns curve should result and the optimum level of sustainability is located at the maximum of the curve. Data were taken from standard economic almanacs and from published LCA reports on the extent of consumption and environmental burdens resulting from farming in the UK. Land-use is valued using the concept of ecosystem services. Our analysis suggests that agricultural systems are sustainable at rates of production close to current levels practiced in the UK. Extensification of farming, which is thought to favour non-food ecosystem services, requires more land to produce the same amount of food. The loss of ecosystem services hitherto provided by natural land brought into production is greater than that which can be provided by land now under extensive farming. This loss of ecosystem service is large in comparison to the benefit of a reduction in emission of nutrients and pesticides. However, food production is essential, so the coupling of subsidies that represent a relatively large component of the economic output in EU farming, with measures to reduce pollution are well-aimed. Measures to ensure that as little extra land is brought into production as possible or that marginal land is allowed to revert to nature would seem to be equally well-aimed, even if this required more intensive use of productive areas. We conclude that current arable farming in the EU is sustainable with either realistic prices for products or some degree of subsidy and that productivity per unit area of land and greenhouse gas emission (subsuming primary energy consumption) are the most important pressures on the sustainability of farming

MULTIPLICATION OF ANIMAL CELLS IN SUSPENSION MEASURED BY COLONY COUNTS

Archived with permission from the National Academy of Sciences USA. Originally published in Proceedings of the National Academy of Sciences USA volume 43 issue 6. Please refer to www.pnas.org for this series of publications. Author holds all copyright for this article.During the past few years the development of new techniques for the cultivation of animal cells in vitro has facilitated the quantitative study of many aspects of cell biology. At present the most commonly used method of propagating cell strains is based on the ability of cells to multiply while attached to a glass surface. The cells may be subcultured by removing them from the surface into suspension and then distributing them into other vessels, where they will again adhere to the glass and populate the surface. This procedure has been developed by Earle and his associates into the so-called quantitative replicate culture technique and applied to a variety of studies with animal cells. Despite the technical advance represented by this method, there are, nevertheless, serious experimental limitations inherent in the use of glass surfaces for cultivating large cell populations. Perhaps the most obvious of these is the problem of removing representative samples at will during the growth of a cell population. In addition, subculture requires the removal of cells from the surface, with consequent risk of cell injury.Aided in part by grants from the National Foundation for Infantile Paralysis, the Public Health Service of the National Institutes of Health of the United States, the National Cancer Institute of Canada, and the W. B. Boyd Memorial Fun

Star cluster formation and star formation: the role of environment and star-formation efficiencies

“The original publication is available at www.springerlink.com”. Copyright Springer. DOI: 10.1007/s10509-009-0088-5By analyzing global starburst properties in various kinds of starburst and post-starburst galaxies and relating them to the properties of the star cluster populations they form, I explore the conditions for the formation of massive, compact, long-lived star clusters. The aim is to determine whether the relative amount of star formation that goes into star cluster formation as opposed to field star formation, and into the formation of massive long-lived clusters in particular, is universal or scales with star-formation rate, burst strength, star-formation efficiency, galaxy or gas mass, and whether or not there are special conditions or some threshold for the formation of star clusters that merit to be called globular clusters a few billion years later.Peer reviewe

Hubble Space Telescope Images of Stephan's Quintet: Star Cluster Formation in a Compact Group Environment

Analysis of Hubble Space Telescope/Wide Field Planetary Camera 2 images of Stephan's Quintet, Hickson Compact Group 92, yielded 115 candidate star clusters (with V-I < 1.5). Unlike in merger remants, the cluster candidates in Stephan's Quintet are not clustered in the inner regions of the galaxies; they are spread over the debris and surrounding area. Specifically, these sources are located in the long sweeping tail and spiral arms of NGC 7319, in the tidal debris of NGC 7318B/A, and in the intragroup starburst region north of these galaxies. Analysis of the colors of the clusters indicates several distinct epochs of star formation that appear to trace the complex history of dynamical interactions in this compact group.Comment: 24 pages, 21 figures (13 PostScript and 8 JPEG), LaTeX (uses aastexug.sty), accepted for publication in the Astronomical Journal (July 2001). Full-resolution PostScript figures available at http://www.astro.psu.edu/users/gallsc/sq/figs.tar.g

Stellar luminosity functions of rich star clusters in the Large Magellanic Cloud

We show the results of deep V and I HST photometry of 6 rich star clusters in the Large Magellanic Cloud with different ages and metallicities. The number of stars with measured magnitudes in each cluster varies from about 3000 to 10000. We build stellar density and surface brightness profiles for the clusters and extract half-light radii and other structural parameters for each. We also obtain luminosity functions, Phi (Mv), down to Mv ~ 6 (m/msun > 0.6), and investigate their dependence with distance from the cluster centre well beyond their half-light radius. In all clusters we find a systematic increase in the luminosity function slope with radial distance from the centre. Among the clusters displaying significant mass segregation are the two youngest in the sample: NGC 1805 and NGC 1818. For these two clusters we obtain present-day mass functions. The NGC 1818 mass function is in excellent agreement with that derived by other authors, also using HST data. They young cluster mass function slopes differ, that of NCG 1805 being systematically steeper than NGC 1818. Since these are very young stellar systems (age < 40 Myrs), these variations may reflect the initial conditions rather than evolution due to internal dynamics.Comment: 10 pages, 24 figure

Secular Evolution of Galaxy Morphologies

Today we have numerous evidences that spirals evolve dynamically through various secular or episodic processes, such as bar formation and destruction, bulge growth and mergers, sometimes over much shorter periods than the standard galaxy age of 10-15 Gyr. This, coupled to the known properties of the Hubble sequence, leads to a unique sense of evolution: from Sm to Sa. Linking this to the known mass components provides new indications on the nature of dark matter in galaxies. The existence of large amounts of yet undetected dark gas appears as the most natural option. Bounds on the amount of dark stars can be given since their formation is mostly irreversible and requires obviously a same amount of gas.Comment: 8 pages, Latex2e, crckapb.sty macros, 1 Postscript figure, replaced with TeX source; To be published in the proceeedings of the "Dust-Morphology" conference, Johannesburg, 22-26 January, 1996, D. Block (ed.), (Kluwer Dordrecht

Substructures in Cold Dark Matter Haloes

We analyse the properties of substructures within dark matter halos (subhalos) using a set of high-resolution numerical simulations of the formation of structure in a Lambda-CDM Universe. Our simulation set includes 11 high-resolution simulations of massive clusters as well as a region of mean density, allowing us to study the spatial and mass distribution of substructures down to a mass resolution limit of 10^9 h^(-1)Mo. We also investigate how the properties of substructures vary as a function of the mass of the `parent' halo in which they are located. We find that the substructure mass function depends at most weakly on the mass of the parent halo and is well described by a power-law. The radial number density profiles of substructures are steeper in low mass halos than in high mass halos. More massive substructures tend to avoid the centres of halos and are preferentially located in the external regions of their parent halos. We also study the mass accretion and merging histories of substructures, which we find to be largely independent of environment. We find that a significant fraction of the substructures residing in clusters at the present day were accreted at redshifts z < 1. This implies that a significant fraction of present-day `passive' cluster galaxies should have been still outside the cluster progenitor and more active at z~1.Comment: 13 pages, 15 figure. Accepted to MNRA