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G N (g + n)

Distribution by Scientific Domains
Life Sciences55%

Terms modified by G N

  • g n m
    		•

    Selected Abstracts

    A response to ,Mobile phones in the hospital , past, present and future', Klein A A and Djaiani G N, Anaesthesia 2003; 58: 353,7.

    ANAESTHESIA, Issue 8 2003
    J. A. Lack
    No abstract is available for this article. [source]

    Mass invariance of population nitrogen flux by terrestrial mammalian herbivores: an extension of the energetic equivalence rule

    ECOLOGY LETTERS, Issue 9 2008
    Christopher W. Habeck
    Abstract According to the energetic equivalence rule, energy use by a population is independent of average adult body mass. Energy use can be equated with carbon flux, and it has been suggested that population fluxes of other materials, such as nitrogen and phosphorus, might also be independent of body mass. We compiled data on individual nitrogen deposition rates (via faeces and urine) and average population densities of 26 species of mammalian herbivores to test the hypothesis of elemental equivalence for nitrogen. We found that the mass scaling of individual nitrogen flux was opposite to that of population density for the species in our dataset. By computing the product of individual nitrogen flux and average population density for each species in our dataset, we found that population-level nitrogen flux was independent of species mass, averaging c. 3.22 g N ha,1 day,1. Results from this analysis can be used to understand the influence of mammalian herbivore communities on nitrogen cycling in terrestrial ecosystems. [source]

    Nutrient storage and turnover in organic layers under tropical montane rain forest in Ecuador

    EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2002
    W. Wilcke
    Summary In tropical montane forests nutrients released from the organic layers of the soil can supply a large part of the vegetation's requirements. We have examined concentrations, storage, and turnover times of nutrients in the organic layer and the fluxes of nutrients by the fall of small litter (leaves, seeds, flowers, small twigs, and plant debris that passed an opening of 0.3 m × 0.3 m) in such a forest in Ecuador. The times taken for litter to turn over were estimated by relating nutrient storage in the organic layer to rate of litterfall and by incubating samples in the laboratory. The organic layer had a thickness of 2,43 cm, a mass of 30,713 t ha,1, and a nutrient storage of 0.87,21 t N, 0.03,0.70 t P, 0.12,2.5 t K, 0.09,3.2 t Ca, and 0.07,1.0 t Mg ha,1. The pH (in H2O) ranged between 3.1 and 7.4 and was correlated with the concentrations of Ca and Mg (r=,0.83 and 0.84, respectively). The quantity of small litter (8.5,9.7 t year,1) and mean concentrations of nutrients in litter (19,22 g N, 0.9,1.6 g P, 6.1,9.1 g K, 12,18 g Ca, and 3.5,5.8 g Mg kg,1) were larger than in many other tropical montane forests. The mean turnover times of elements in the organic layer increased in the order, Mg (7.0 years) < Ca (7.9) < K (8.5) < P (11) < N (14) < S (15) when calculated as the quotient of storage in the organic layer to flux by litterfall; they were <,12 years for N, P, and S in the incubation experiment. Under optimum conditions in the laboratory, the mineralization of S was just as large as the S deposition by litterfall. In weakly acid soils Mn and Zn and in strongly acid soils Ca added in a nutrient solution were immobilized during incubation. Thus, lack of S, Mn, Zn, and Ca might limit plant growth on some soils. [source]

    THE POTENTIAL OF TERMINALIA CATAPPA (TROPICAL ALMOND) SEED AS A SOURCE OF DIETARY PROTEIN

    JOURNAL OF FOOD QUALITY, Issue 3 2004
    C.A. EZEOKONKWO
    ABSTRACT The nutritional value of Terminalia catappa seed as a source of dietary protein was investigated. The crude protein content of the seed was high (25.81%). The amino acid analysis showed a good pattern of the essential amino acids (EAA) (in g/16 g N) - leucine (7.32), isoleucine (3.58), valine (2.74), phenylalanine (3.04), tryptophan (0.9), methionine (1.48), lysine (3.39), threonine (2.94), histidine (2.96). Tyrosine (2.12) is the limiting amino acid. The protein quality of the seed was evaluated by in vivo bioassays using weanling male Sprague Dawley rats (50,60 g). The indices of protein quality measured include PER, BV, NPU and TD. There were positive correlation between PER and BV (r = 0.7105), PER and body weight gain (r = 0.9157), PER and nitrogen intake (r = 0.7428). The results showed that T. catappa seed protein has a good pattern of the EAA, is highly digestible, can support growth and positive nitrogen balance and thus has a high dietary protein quality. [source]

    SHIFT FROM CHLOROPHYTES TO CYANOBACTERIA IN BENTHIC MACROALGAE ALONG A GRADIENT OF NITRATE DEPLETION,

    JOURNAL OF PHYCOLOGY, Issue 1 2008
    Chantal Vis
    A survey of the spatial distribution of benthic macroalgae in a fluvial lake of the St. Lawrence River (Lake Saint-Pierre, Quebec, Canada) revealed a shift in composition from chlorophytes to cyanobacteria along the flow path of nutrient-rich waters originating from tributaries draining farmlands. The link between this shift and changes in water quality characteristics was investigated by sampling at 10 sites along a 15 km transect. Conductivity, current, light extinction, total phosphorus (TP; >25 ,g P · L,1), and ammonium (8,21 ,g N · L,1) remained fairly constant along the transect in contrast to nitrate concentrations, which fell sharply. Filamentous and colonial chlorophytes [Cladophora sp. and Hydrodictyon reticulatum (L.) Bory] dominated in the first 5 km where nitrate concentrations were >240 ,g N · L,1. A mixed assemblage of chlorophytes and cyanobacteria characterized a 1 km transition zone where nitrate decreased to 40,80 ,g N · L,1. In the last section of the transect, nitrate concentrations dropped below 10 ,g N · L,1, and cyanobacteria (benthic filamentous mats of Lyngbya wollei Farl. ex Gomont and epiphytic colonies of Gloeotrichia) dominated the benthic community. The predominance of nitrogen-fixing, potentially toxic cyanobacteria likely resulted from excessive nutrient loads and may affect nutrient and trophic dynamics in the river. [source]

    Modification of Primary and Secondary Metabolism of Potato Plants by Nitrogen Application Differentially Affects Resistance to Phytophthora infestans and Alternaria solani

    PLANT BIOLOGY, Issue 5 2006
    K. Mittelstraß
    Abstract: Potato plants (Solanum tuberosum L. cv. Indira) were grown at two levels of N supply in the greenhouse. Plants supplied with 0.8 g N per plant (high N variant) showed significantly increased biomass as compared to plants without additional N fertilisation (low N variant). C/N ratio was lower and protein content was higher in leaves of the high N variant. The concentration of chlorogenic acids and flavonols was significantly lower in leaves from the high N variant. Whereas resistance to Alternaria solani increased when plants were supplied with additional nitrogen, these plants were more susceptible to Phytophthora infestans. After infection with both pathogens, we found a strong induction of p-coumaroylnoradrenaline and p-coumaroyloctopamine, which are identified for the first time in potato leaves and are discussed as resistance factors of other solanaceous plants. [source]

    Does soil nitrogen influence growth, water transport and survival of snow gum (Eucalyptus pauciflora Sieber ex Sprengel.) under CO2 enrichment?

    PLANT CELL & ENVIRONMENT, Issue 5 2009
    BRIAN J. ATWELL
    ABSTRACT Eucalyptus pauciflora Sieber ex Sprengel. (snow gum) was grown under ambient (370 µL L,1) and elevated (700 µL L,1) atmospheric [CO2] in open-top chambers (OTCs) in the field and temperature-controlled glasshouses. Nitrogen applications to the soil ranged from 0.1 to 2.75 g N per plant. Trees in the field at high N levels grew rapidly during summer, particularly in CO2 -enriched atmosphere, but suffered high mortality during summer heatwaves. Generally, wider and more numerous secondary xylem vessels at the root,shoot junction in CO2 -enriched trees conferred fourfold higher below-ground hydraulic conductance. Enhanced hydraulic capacity was typical of plants at elevated [CO2] (in which root and shoot growth was accelerated), but did not result from high N supply. However, because high rates of N application consistently made trees prone to dehydration during heatwaves, glasshouse studies were required to identify the effect of N nutrition on root development and hydraulics. While the effects of elevated [CO2] were again predominantly on hydraulic conductivity, N nutrition acted specifically by constraining deep root penetration into soil. Specifically, 15,40% shallower root systems supported marginally larger shoot canopies. Independent changes to hydraulics and root penetration have implications for survival of fertilized trees under elevated atmospheric [CO2], particularly during water stress. [source]

    The absolute center of a network,

    NETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2004
    Dov Dvir
    Abstract This paper presents a new algorithm for finding an absolute center (minimax criterion) of an undirected network with n nodes and m arcs based on the concept of minimum-diameter trees. Local centers and their associated radii are identified by a monotonically increasing sequence of lower bounds on the radii. Computational efficiency is addressed in terms of worst-case complexity and practical performance. The complexity of the algorithm is 0(n2 ,g n + mn). In practice, because of its very rapid convergence, the algorithm renders the problem amenable even to manual solution for quite large networks, provided that the minimal-distance matrix is given. Otherwise, evaluation of this matrix is the effective computational bottleneck. An interesting feature of the algorithm and its theoretical foundations is that it synthesizes and generalizes some well-known results in this area, particularly Halpern's lower bound on the local radius of a network and properties of centers of tree networks. © 2004 Wiley Periodicals, Inc. [source]

    Toxicokinetics of perfluorocarboxylate isomers in rainbow trout

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009
    Amila O. De Silva
    Abstract Perfluorooctanoate (PFOA) and other perfluorocarboxylates (PFCAs) are widely dispersed in the environment. Current and/or historical production of PFOA and fluorochemical precursors was conducted by telomerization and electrochemical fluorination (ECF). Telomer products typically contain linear chains of perfluorocarbons, and ECF products are a mixture of linear and branched isomers. The objective of the present study was to examine the role of toxicokinetics on PFCA isomer profiles in fish since monitoring studies have revealed a predominance of n -isomers of PFCAs in biota. Using dietary exposure, rainbow trout were administered technical ECF PFOA isomers (6.9 ,g/kg/d), linear perfluorononanoate (1.4 ,g/kg/d n -PFNA), and isopropyl PFNA (1.1 ,g/kg/d iso -PFNA) for 36 d and then switched to a 40-d clean diet. Throughout exposure and depuration phases, blood and tissue sampling ensued. The accumulation ratio (AR) revealed similar accumulation propensity of n -PFOA and two minor branched PFOA isomers; however, the majority of branched isomers had lower AR values than n -PFOA. Enrichment of n -PFOA and n -PFNA relative to most branched isomers was consistent in all tissues. First-order elimination (kd) and half-life (t1/2) values were calculated. The largest t1/2 corresponded to n -PFNA followed by iso -PFNA. In ECF PFOA isomers, both n -PFOA and one minor branched isomer had the largest t1/2, suggesting that this minor isomer could be diagnostic of ECF exposure using environmental PFOA isomer patterns. Results of lower-dose ECF PFOA exposure showed similar results to the high-dose study; it is possible that both scenarios resulted in saturation of processes involved in PFCA transport. As such, the toxicokinetics of PFCA isomers at environmentally realistic levels may deviate from the results of the present study. [source]