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991.
The combination of (1)H NMR fingerprinting of lipids from gilthead sea bream (Sparus aurata) with nonsupervised and supervised multivariate analysis was applied to differentiate wild and farmed fish and to classify farmed specimen according to their areas of production belonging to the Mediterranean basin. Principal component analysis (PCA) applied on processed (1)H NMR profiles made a clear distinction between wild and farmed samples. Linear discriminant analysis (LDA) allowed classification of samples according to the geographic origin, as well as for the wild and farmed status using both PCA scores and NMR data as variables. Variable selection for LDA was achieved with forward selection (stepwise) with a predefined 5% error level. The methods allowed the classification of 100% of the samples according to their wild and farmed status and 85-97% to geographic origin. Probabilistic neural network (PNN) analyses provided complementary means for the successful discrimination among classes investigated.  相似文献   
992.
Manganese (Mn) contamination of drinking water may cause aesthetic and human health problems when concentrations exceed 50 and 500 μg l?1, respectively. In the UK, the majority of Mn-related drinking water supply failures originate from unpolluted upland catchments. The source of Mn is therefore soil, but the exact mechanisms by which it is mobilised into surface waters remain unknown. Elevated Mn concentrations in surface waters have been associated with the rewetting of dried upland soils and with conifer afforestation. We investigated these hypotheses in a laboratory experiment involving the drying and rewetting of intact soil cores (1,900 cm3 volume) of horizons of four representative soil type-land use combinations from an upland water supply catchment in southwest Scotland. Although no statistically significant effect of land use or soil type was detected on Mn concentrations in soil water, Mn release occurred from three soil horizons upon rewetting. Soil water Mn concentrations in the moorland histosol H2 (10–30 cm), the histic podzol H and Eh horizons increased from means of 5.8, 6.2 and 0.6 μg l?1 prior to rewetting to maxima of 90, 76 and 174 μg l?1 after rewetting, respectively. The properties of these three horizons indicate that Mn release is favoured from soil horizons containing a mixture of organic and mineral material. Mineral material provides a source of Mn, but relatively high soil organic matter content is required to facilitate mobilisation. The results can be used alongside soil information to identify catchments at risk of elevated Mn concentrations in water supplies.  相似文献   
993.
Abstract. Experiments were set up at two sites to measure nitrogen (N) leaching loss from applications of separated pig/cattle slurry and cattle farmyard manure(FYM), during winters 1990/91–1993/94 (site A) and from broiler litter and FYM, during winters 1990/91–1992/93 (site B). The manures were applied at a target rate of 200 kg ha-1 total N during the autumn and winter to overwinter fallow or top dressed onto winter rye. The total N in leachate was calculated from leachate N concentrations, in samples collected using ceramic cups buried at 90 cm, and an estimate of drainage volume. Nitrogen losses were greatest following manure applications in September, October and November but losses following applications in December or January were not significantly elevated above those from untreated controls. Losses were consistently lower from FYM than from broiler litter or separated slurry. The presence of a cover crop (winter rye) significantly reduced overall N leaching compared with the fallow, but only reduced the manure N leaching losses at one site during one winter when a high proportion of drainage occurred late. The incorporation of a nitrification inhibitor (DCD) with manures applied in October did not significantly reduce the manure N leaching.  相似文献   
994.
Phenolic antioxidants from the leaves of Corchorus olitorius L.   总被引:3,自引:0,他引:3  
Six phenolic antioxidative compounds [5-caffeoylquinic acid (chlorogenic acid), 3,5-dicaffeoylquinic acid, quercetin 3-galactoside, quercetin 3-glucoside, quercetin 3-(6-malonylglucoside), and quercetin 3-(6-malonylgalactoside) (tentative)] were identified from the leaves of Corchorus olitorius L. (moroheiya) by NMR and FAB-MS. The contents of these phenolic compounds, ascorbic acid, and alpha-tocopherol in C. olitorius leaves were determined, and their antioxidative activities were measured using the radical generator-initiated peroxidation of linoleic acid. The results obtained showed that 5-caffeoylquinic acid was a predominant phenolic antioxidant in C. olitorius leaves.  相似文献   
995.
An ethyl acetate-soluble extract of Chorizanthe diffusa was found to exhibit significant antioxidant activity, as judged by scavenging stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and inhibition of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced free radical formation with cultured HL-60 cells. Bioassay-directed fractionation of this extract using the DPPH antioxidant assay as a monitor led to the isolation of five structurally related flavonoids (1-5), including the novel compound 5,8,3',4',5'-pentahydroxy-3, 7-dimethoxyflavone (1). Isolates 1-5 demonstrated varying degrees of antioxidant or antimutagenic activity. Two of the compounds, 5,7,3', 4'-tetrahydroxy-3-methoxyflavone (2) and quercetin (4), were subsequently found to inhibit carcinogen-induced preneoplastic lesions in a mouse mammary organ culture model. Inhibitory activity of this type is known to correlate with cancer chemopreventive effects in full-term models of tumorigenesis.  相似文献   
996.
Palm oil carotenoids are a mixture of alpha- and beta-carotenes, which are used as food colorants. They may also be applied as a functional food ingredient because of the provitamin A activity of alpha- and beta-carotenes and their proposed beneficial roles in the prevention of chronic diseases. This paper discusses the results of an incomplete balanced crossover study with 69 healthy adult volunteers to compare palm oil carotenoids with synthetic beta-carotene in their efficacies to increase plasma levels of carotenoids. Four days of supplementation with natural palm oil carotenoids (7.6 mg/day of alpha-carotene, 11.9 mg/day of all-trans-beta-carotene, 7.5 mg/day of cis-beta-carotene) or synthetic beta-carotene (23.8 mg/day of all-trans-beta-carotene, 4.4 mg/day of cis-beta-carotene), added to a mixed meal, resulted in significant increases in plasma levels of the supplied carotenoids as compared to consumption of a low-carotenoid meal (i.e., 7.2-fold increase in alpha-carotene and 3.5-fold increase in all-trans-beta-carotene following palm oil carotenoids; 6.9-fold increase in all-trans beta-carotene following synthetic beta-carotene). As the carotenoid content differed between the treatments, the relative plasma responses were calculated per milligram of beta-carotene intake. These were similar for the two supplements, suggesting that the presence of alpha-carotene does not affect the bioavailability of beta-carotene from palm oil. It was concluded that 4 days of supplementation with palm oil carotenoids or synthetic beta-carotene improves the plasma beta-carotene status substantially, whereas alpha-carotene is additionally delivered by the palm oil supplement.  相似文献   
997.
Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3, 5-dione], the main constituent of the rhizomes of the plant Curcume longa L. (turmeric), is a powerful antioxidant in both enzymatic and nonenzymatic systems. The interactions of curcumin with egg and soy phosphatidylcholine were followed by fluorescence spectroscopy. Curcumin had very weak fluorescence in aqueous system, which was enhanced in apolar environments. Curcumin emitted at 490 nm after being excited at 451 nm in phosphatidylcholine micelles. The equilibrium constants for the interaction of curcumin with egg and soy phosphatidylcholine were (3.26 +/- 0.2) x 10(5) and (2.64 +/- 0.2) x 10(5) M(-1), respectively. From the Scatchard plot of the fluorometric data, it was inferred that one molecule of curcumin could bind six molecules of phosphatidylcholine. The equilibrium constant for the phosphatidylcholine-curcumin interaction decreased with temperature, indicating the amphiphilic nature of curcumin. The DeltaG, DeltaH, and DeltaS values obtained for the interaction of egg phosphatidylcholine-curcumin were -7.8 +/- 0.3 kcal/mol, -9.6 +/- 0.4 kcal/mol, and -6.8 +/- 0.2 cal/mol/K, respectively. The fluorescence anisotropy measurements of curcumin with phosphatidylcholine suggested that the anisotropy of the curcumin molecule did not change in phosphatidylcholine. The interaction of divalent metal ions with phosphatidylcholine-curcumin in comparison with phosphatidylcholine-1-anilino-8-naphathalenesulfonic acid complex suggested the strong binding of curcumin to metal ions.  相似文献   
998.
When converting grass- and haylands to cultivated crop production, care must be taken to conserve and maintain soil resources while considering economic issues. Methods of breaking sod can have a bearing on erosivity, physical and chemical properties of soils, and cost of production. Our objective was to compare three methods of converting crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] hayland to wheat (Triticum aestivum L.) production vs. leaving the land for hay production. We initiated a study in 1990 on Dooley sandy loam (fine-loamy, mixed Typic Argiboroll) near Froid in semiarid eastern Montana, USA. Plots, replicated three times, were 12- by 30-m oriented east to west on a north-facing slope. We converted sod to cultivated crop production by: (1) moldboard plow, (2) toolbar with sweeps, (3) herbicides (no-till). Plots were fallowed until spring 1991 and then seeded to spring wheat each of the next four years. All wheat plots were fertilized with 224 kg ha−1 of 18-46-0 in 1991 and 1992, and 34 kg ha−1 nitrogen as 34-0-0 in 1993 and 1994. Grass was either fertilized same as wheat or not fertilized. Wheat yields averaged 2540 kg ha−1 on tilled treatments and 2674 kg ha−1 on no-till. Fertilized grass consistently out-yielded unfertilized, and averaged 3.2 Mg ha−1 vs. 1.8 Mg ha−1. Toolbar with sweeps had highest economic return of US$169.48 ha−1 to pay for land, labor, and management. Moldboard plow had US$162.05 ha−1. Because of herbicide costs, no-till only returned US$148.64 ha−1. Unfertilized grass hay returned US$67.68 ha−1 and fertilized grass hay, US$97.95 ha−1. Results may be tempered because our wheat yields were high: a 2016 kg ha−1 wheat yield would have returned the same as fertilized grass. Before converting grass- and hay-lands to small grains production, consideration must be given to such variables as sod conversion methods, management practices, labor requirements, market conditions, total precipitation and its temporal distribution, soil conditions, growth environment, soil conservation, and economics.  相似文献   
999.
Previous investigations had shown that about 80 years of Norway spruce monoculture on an ochreous brown earth of the Belgian Ardennes were sufficient to accentuate the weak podzolization process already present in the climax beechwood soil and to increase the weathering of several minerals, e.g. 2:2 clay minerals. In order to evaluate more accurately mineral weathering and spruce-induced losses of nutrient elements, an isoquartz assessment method has been applied to a pair of soil profiles, one developed under beech, the other under spruce.
Results show a clear decrease of several weatherable minerals in the soil of the spruce stand which was more marked than in the beechwood, especially for chloritic minerals: losses reach about 30% of the initial chlorite content in the cambic horizon and regularly increase up to 70% in the humic layer. There were severe spruce-induced losses of Mg and Na: 27% of the initial Mg reserve was removed from the whole soil and the losses reached 60% in the upper 20 cm.
It is concluded that 86 years of Norway spruce monoculture have appreciably increased weathering processes and removal of elements.  相似文献   
1000.
A research watershed liming project is being carried out at Loch Fleet in the Galloway District of southwest Scotland. This acid loch originally supported a brown trout fishery, but the number of fish caught by anglers declined during the 1950's and the fishery eventually disappeared about 20 yr ago. After 2 yr of pretreatment data collection, the first set of land time applications took place in the spring of 1986, and the resulting surface water chemical changes are very encouraging. Increases in pH and Ca concentration and decreases in A1 (especially the toxic labile monomeric fraction) concentrations have been observed in the streams and waters draining the treated subcatchments in the loch itself and in the loch outlet. Also, the normal trend for pH and Ca concentration to fall during periods of high flow in the main feeder stream has been reversed. In the spring of 1987, the loch was restocked with brown trout. Initial indications are that there has been very good survival of these fish, and that they managed to spawn during the 1987/88 winter. The chemical and biological changes brought about by the land treatments are described in detail.  相似文献   
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