2,522 research outputs found

    Assessing the ecological soundness of organic and conventional agriculture by means of life cycle assessment (LCA) - a case study of leek production

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    Purpose – Sustainable agriculture implies the ability of agro-ecosystems to remain productive in the long-term. It is not easy to point out unambiguously whether or not current production systems meet this sustainability demand. A priori thinking would suggest that organic crops are environmentally favourable, but may ignore the effect of reduced productivity, which shifts the potential impact to other parts of the food provision system. The purpose of this paper is to assess the ecological sustainability of conventional and organic leek production by means of life cycle assessment (LCA). Design/methodology/approach – A cradle-to-farm gate LCA is applied, based on real farm data from two research centres. For a consistent comparison, two functional units (FU) were defined: 1ha and 1?kg of leek production. Findings – Assessed on an area basis, organic farming shows a more favourable environmental profile. These overall benefits are strongly reduced when the lower yields are taken into account. Related to organic farming it is therefore important that solutions are found to substantially increase the yields without increasing the environmental burden. Related to conventional farming, important potential for environmental improvements are in optimising the farm nutrient flows, reducing pesticide use and increasing its self-supporting capacity. Research limitations/implications – The research is a cradle-to-farm gate LCA, future research can be expanded to comprise all phases from cradle-to-grave to get an idea of the total sustainability of our present food consumption patterns. The research is also limited to the case of leek production. Future research can apply the methodology to other crops. Originality/value – To date, there is still lack of clear evidence of the added value of organic farming compared to conventional farming on environmental basis. Few studies have compared organic and conventional food production by means of LCA. This paper addresses these issues

    High-Level Expression of Various Apolipoprotein (a) Isoforms by "Transferrinfection". The Role of Kringle IV Sequences in the Extracellular Association with Low-Density Lipoprotein

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    Characterization of the assembly of lipoprotein(a) [Lp(a)] is of fundamental importance to understanding the biosynthesis and metabolism of this atherogenic lipoprotein. Since no established cell lines exist that express Lp(a) or apolipoprotein(a) [apo(a)], a "transferrinfection" system for apo(a) was developed utilizing adenovirus receptor- and transferrin receptor-mediated DNA uptake into cells. Using this method, different apo(a) cDNA constructions of variable length, due to the presence of 3, 5, 7, 9, 15, or 18 internal kringle IV sequences, were expressed in cos-7 cells or CHO cells. All constructions contained kringle IV-36, which includes the only unpaired cysteine residue (Cys-4057) in apo(a). r-Apo(a) was synthesized as a precursor and secreted as mature apolipoprotein into the medium. When medium containing r-apo(a) with 9, 15, or 18 kringle IV repeats was mixed with normal human plasma LDL, stable complexes formed that had a bouyant density typical of Lp(a). Association was substantially decreased if Cys-4057 on r-apo(a) was replaced by Arg by site-directed mutagenesis or if Cys-4057 was chemically modified. Lack of association was also observed with r-apo(a) containing only 3, 5, or 7 kringle IV repeats without "unique kringle IV sequences", although Cys-4057 was present in all of these constructions. Synthesis and secretion of r-apo(a) was not dependent on its sialic acid content. r-Apo(a) was expressed even more efficiently in sialylation-defective CHO cells than in wild-type CHO cells. In transfected CHO cells defective in the addition of N-acetylglucosamine, apo(a) secretion was found to be decreased by 50%. Extracellular association with LDL was not affected by the carbohydrate moiety of r-apo(a), indicating a protein-protein interaction between r-apo(a) and apoB. These results show that, besides kringle IV-36, other kringle IV sequences are necessary for the extracellular association of r-apo(a) with LDL. Changes in the carbohydrate moiety of apo(a), however, do not affect complex formation

    The camera of the fifth H.E.S.S. telescope. Part I: System description

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    In July 2012, as the four ground-based gamma-ray telescopes of the H.E.S.S. (High Energy Stereoscopic System) array reached their tenth year of operation in Khomas Highlands, Namibia, a fifth telescope took its first data as part of the system. This new Cherenkov detector, comprising a 614.5 m^2 reflector with a highly pixelized camera in its focal plane, improves the sensitivity of the current array by a factor two and extends its energy domain down to a few tens of GeV. The present part I of the paper gives a detailed description of the fifth H.E.S.S. telescope's camera, presenting the details of both the hardware and the software, emphasizing the main improvements as compared to previous H.E.S.S. camera technology.Comment: 16 pages, 13 figures, accepted for publication in NIM

    The metallicity gradients of star-forming regions store information of the assembly history of galaxies

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    The variations in metallicity and spatial patterns within star-forming regions of galaxies result from diverse physical processes unfolding throughout their evolutionary history, with a particular emphasis on recent events. Analysing MaNGA and EAGLE galaxies, we discovered an additional dependence of the mass–metallicity relation (MZR) on metallicity gradients (∇(O/H)). Two regimes emerged for low- and high-stellar mass galaxies, distinctly separated at approximately M⋆ > 109.75. Low-mass galaxies with strong positive ∇(O/H) appear less enriched than the MZR median, while those with strong negative gradients are consistently more enriched in both simulated and observed samples. Interestingly, low-mass galaxies with strong negative ∇(O/H) exhibit high star-forming activity, regardless of stellar surface density or ∇(O/H). In contrast, a discrepancy arises for massive galaxies between MaNGA and EAGLE data sets. The latter exhibit a notable anticorrelation between specific star formation rate and stellar surface density, independent of ∇(O/H), while MaNGA galaxies show this trend mainly for strong positive ∇(O/H). Further investigation indicates that galaxies with strong negative gradients tend to host smaller central black holes in observed data sets, a trend not replicated in simulations. These findings suggest disparities in metallicity recycling and mixing history between observations and simulations, particularly in massive galaxies with varying metallicity gradients. These distinctions could contribute to a more comprehensive understanding of the underlying physics
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