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11.
Kerstin Robertson Leif Klemedtsson Sune Axelsson Thomas Rosswall 《Biology and Fertility of Soils》1993,16(3):193-197
Remote sensing techniques may be one way to narrow the range of uncertainty in extrapolating N2 emissions from small-scale to large-scale terrestrial ecosystems. In the present work we investigated the correlations between denitrification activity, soil moisture, and soil thermal infrared emissions. A field experiment was performed on two different agricultural soils, one loam and one silty clay. The results indicated that thermal infrared emissions can only be used to estimate the denitrification rate in soil within a limited range of soil moisture levels. Estimates of denitrification activity based on soil texture and moisture are, however, very likely to be a fruitful approach to generating large-scale N fluxes. 相似文献
12.
Tocopherols (alpha, beta, gamma, and delta) and Trolox were found to deactivate triplet-excited riboflavin in homogeneous aqueous solution (7:3 v/v tert-butanol/water) with second-order reaction rates close to diffusion control [k2 between 4.8 x 10(8) (delta-tocopherol) and 6.2 x 10(8) L mol(-1) s(-1) (Trolox) at 24.0 +/- 0.2 degrees C] as determined by laser flash photolysis transient absorption spectroscopy. In aqueous buffer (pH 6.4) the rate constant for Trolox was 2.6 x 10(9) L mol(-1) s1 and comparable to the rate constant found for ascorbate (2.0 x 10(9) L mol(-1) s(-1)). The deactivation rate constant was found to be inferior in heterogeneous systems as shown for alpha-tocopherol and Trolox in aqueous Tween-20 emulsion (approximately by a factor of 4 compared to 7:3 v/v tert-butanol/water). Neither beta-carotene (7:3 v/v tert-butanol/water and Tween-20 emulsion), lycopene (7:3 v/v tert-butanol/water), nor crocin (aqueous buffer at pH 6.4, 7:3 v/v tert-butanol/water, and Tween-20 emulsion) showed any quenching on the triplet excited state of riboflavin. Therefore, all carotenoids seem to reduce the formation of triplet-excited riboflavin through an inner-filter effect. Activation parameters were based on the temperature dependence of the triplet-excited deactivation between 15 and 35 degrees C, and the isokinetic behavior, which was found to include purine derivatives previously studied, confirms a common deactivation mechanism with a bimolecular diffusion-controlled encounter with electron (or hydrogen atom) transfer as rate-determining step. DeltaH for deactivation by ascorbic acid, Trolox, and homologue tocopherols (ranging from 18 kJ mol(-1) for Trolox in Tween-20 emulsion to 184 kJ mol(-1) for ascorbic acid in aqueous buffer at pH 6.4) showed a linear dependence on DeltaS (ranging from -19 J mol(-1) K(-1) for Trolox in aqueous buffer at pH 6.4 to +550 J mol(-1) K(-1) for ascorbic acid in aqueous buffer pH 6.4). Among photooxidation products from the chemical quenching, lumicrome, alpha-tocopherol quinones and epoxyquinones, and alpha-tocopherol dimers were identified by ESI-QqTOF-MS. 相似文献
13.
Joseph B. Goodwin Fernando L. Garagorry Waldo Espinosa Luis Marcelo Sans Leif J. Youngdahl 《Agricultural Systems》1982,8(2):115-127
A soil-water balance simulation model developed for the Cerrado soils of central Brazil is presented. The model calculates daily soil water evaporation, plant transpiration and soil-water balance for fourteen soil layers of 15 mm each. The model includes a subroutine to calculate capillary water movement. Computer simulations of daily soil water levels at five soil depths (15, 30, 45, 60 and 90 cm) for a field of maize are compared with actual field measurements over an 80-day period. Results indicated that the developed model can, in general, estimate the soil-water balance of the various depths within ± 10% of actual measurements. 相似文献
14.
Sukhumavasi W Bellosa ML Lucio-Forster A Liotta JL Lee AC Pornmingmas P Chungpivat S Mohammed HO Lorentzen L Dubey JP Bowman DD 《Veterinary parasitology》2012,188(1-2):25-30
The seroprevalence of Toxoplasma gondii, Dirofilaria immitis (heartworm), feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) infections was examined using serum or plasma samples from 746 pet cats collected between May and July 2009 from clinics and hospitals located in and around Bangkok, Thailand. The samples were tested for heartworm, FIV, and FeLV using a commercial ELISA. Of the 746 samples, 4.6% (34/746) were positive for heartworm antigen, 24.5% (183/746) had circulating FeLV antigen, and 20.1% (150/746) had antibodies against FIV. In addition, the first 348 submitted samples were tested for T. gondii antibodies using a modified agglutination test (MAT, cut off 1:25); 10.1% (35/348) were seropositive. Of the 348 cats sampled for all four pathogens, 11, 10, and 1 were positive for T. gondii antibodies and FIV antibodies, FeLV antigen, or D. immitis antigen, respectively. Of the 35 T. gondii-seropositive cats, 42.9% (15/35) were co-infected with at least one of the other three pathogens. The presence of antibodies to FIV was significantly associated with both age and gender, while FeLV antigen presence was only associated with age. In the case of FIV, males were twice as likely to be infected as females, and cats over 10 years of age were 13.5 times more likely to be infected than cats less than 1 year of age. FeLV antigen was more common in younger cats, with cats over 10 years of age being 10 times less likely to be FeLV positive than cats under 1 year of age. This is the first survey for these four pathogens affecting feline health in Thailand. 相似文献
15.
Induction of discolored wood in Scots pine (Pinus sylvestris L.) trees by treatment with ethylene, carbon dioxide, nitrogen (hypoxia) or wounding from early April to late September was investigated. All treatments induced formation of discolored wood upward and downward from the drill hole. The amount of discolored wood formed above the drill hole depended on the treatment in the following order: ethylene > carbon dioxide = nitrogen > wounding; and below the drill hole in the order: ethylene > carbon dioxide = nitrogen = wounding. Based on chemical analyses (HPLC/UV, GS/MS, LC/MS and 1H-NMR), discolored wood induced by wounding or treatment with ethylene or carbon dioxide showed compositional similarities to natural heartwood, whereas discolored wood induced by nitrogen treatment showed fewer similarities to natural heartwood. The results suggest that ethylene is an important factor controlling heartwood formation, although wounding and internal concentrations of carbon dioxide may also play a role. 相似文献
16.
Inheritance and expression of transgenes in T2 and T3 generations of Lotus corniculatus transformed using Agrobacterium tumefaciens 总被引:2,自引:0,他引:2
K. Judith Webb Mervyn O. Humphreys Leif Skøt Margaret Gibbs John Gatehouse 《Euphytica》1999,108(3):169-179
The inheritance and expression of the reporter gene uidA, encoding β-glucuronidase (GUS), was previously analysed in the T1 generation of 25 independent transformed lines of Lotus corniculatus cv. Leo. In the work reported here, GUS activity in various tissues of seven of these lines was tested in the T2 generation. Four representative lines were chosen for more detailed study in the T3 generation. Lines 25 and 38 had multiple, independently segregating transgene inserts; lines 24 and 39 appeared to transmit one segregating transgene insert to their T1 progeny, although transgene expression was low and was detected in fewer seedlings than expected in line 39. The uidA gene was inherited and expressed in seedlings of T1, T2 and T3 generations of all four lines. In all lines, transgene expression varied between tissues, with more embryos than seedlings
having detectable GUS activity. Studies in the T2 generation showed that use of transgenic plants as female or male parents altered the frequency of expression of the transgene
in progeny. By contrast, in the T3 generation the use of transgenic plants as female or male parents did not effect either frequency of transmission, or expression
of the transgene, in any of the four lines. Transgene inheritance was also similar among individual pods within flower heads
and between individual flower heads.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Leif Sundheim Alan R. Poplawsky Albert H. Ellingboe 《Physiological and Molecular Plant Pathology》1988,33(3)
Two chitinase encoding EcoRI fragments from the enteric soil bacterium Serratia marcescens were cloned. From a genomic library of 5686 transductants, 21 expressed chitinase activity as indicated by clearing of a chitin-containing medium. The chitinase encoding clones could be divided into two groups. Four had an 18kb EcoRI fragment and 17 had a 9·4 kb EcoRI fragment. In Southern hybridization experiments the 18kb fragment showed no homology to the 9·4 kb fragment and restriction enzyme maps indicated no similarity. Triparental mating with fluorescent Pseudomonas spp. yielded transconjugants that expressed chitinase activity, inhibited growth of Fusarium oxysporum f. sp. redolens germ tubes and reduced disease of radish caused by the same fungus. 相似文献
18.
Leif Hallbcken 《植物养料与土壤学杂志》1992,155(1):51-60
During the past 60 years there has been a considerable decline in pH in mineral soil beneath spruce and beech stands at Tönnersjöheden Experimental Forest in south-west Sweden. In this report an attempt is made to estimate the corresponding declines in base cation pools. The exchangeable storage of Na, K, Ca and Mg in soil, down to 70 cm depth, is calculated to have decreased by 57–60 per cent for beech and by 56–74 per cent for the spruce stands during the period 1927–1984. The calculated cation depletions are compared with estimated nutrient uptake in biomass, base cation release by weathering and leaching losses due to percolation of strong mineral acids and organic anions during the period. The biological acidification may explain about 50–60 per cent of the total losses of base cations from soil, the cation accumulation in biomass then explain 41–43 per cent units for beech and 34–45 per cent units for spruce. The estimated losses of base cations due to acid rain correspond to an amount of cations similar to that accumulated in the spruce biomass during one generation. 相似文献
19.
Mogens L. Andersen Henriette R. Erichsen Leif H. Skibsted Heidi B. Graversen Ubirajara P. Rodrigues-Filho 《Journal of Cereal Science》2011,54(3):494-498
Oxidative Stability of bread is increasingly being recognized as important for long shelf-life. Formation of free radicals in whole wheat flour and white flour during heating was compared using Electron Spin Resonance spectroscopy in order to identify the primary oxidative events. Heating lead to a higher content of free radicals in wholemeal wheat flour than in white flour, since components in the husk seem to make a major contribution. Two different pathways are suggested for the formation of free radicals in wheat flour. The activation energy for the radical formation in the flours was estimated by Arrhenius plot as 34 kJ mol−1 up to 453 K, and above 473 K higher activation energies were observed. The change in activation energies indicates a change in reaction mechanisms for oxidation probably involving species with different mobility, i.e. different molecular weight. The accumulated concentration of free radicals in heated flour increased during one month storage and it is slightly affected by the water activity in the storage container. 相似文献
20.
Katja Stoeckel Leif H?jvang Nielsen Herbert Fuhrmann Lisa Bachmann 《Acta veterinaria Scandinavica》2011,53(1):57