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71.
Vági E Simándi B Daood HG Deák A Sawinsky J 《Journal of agricultural and food chemistry》2002,50(8):2297-2301
Extraction of pigments (chlorophylls and carotenoids) from marjoram (Origanum majorana L.) with supercritical carbon dioxide was investigated. The aim of this study was to map the effects of extraction pressure and temperature on the yield of coloring materials by applying a 3(2) full factorial design with three repeated tests in the center of the design. For comparison, laboratory and pilot plant Soxhlet extractions were carried out using ethanol and n-hexane solvents. The compositions of pigments in marjoram extracts were determined by HPLC. Similar amounts of carotenoids, in addition to 40% of chlorophylls and their derivatives, were recovered from the supercritical fluid extraction, in comparison to the ethanol Soxhlet extraction. 相似文献
72.
Fernández M Picó Y Girotti S Mañes J 《Journal of agricultural and food chemistry》2001,49(8):3540-3547
Pesticides applied in extended agricultural fields may be controlled by means of bioindicators, such as honeybees, in which are the pesticides bioaccumulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (NI) ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extracted with acetone. The extract was purified with coagulating solution and reextracted with Cl(2)CH(2). Pesticides studied could be detected by both ionization modes except for parathion, parathion-methyl, and bromophos, which did not give signals in PI mode, and triazophos, which was not detected in NI mode. Fragmentation voltage and vaporizer temperature were optimized to achieve the highest sensitivity. The spectra profile of each pesticide in PI mode showed the [M + H](+) ion as the main signal, whereas in NI mode only fragment ions were shown. The detection limit obtained in selected ion monitoring mode ranged from 1 to 15 microg kg(-1). The average recoveries from spiked honeybees at various concentration levels (0.5-5 mg kg(-1)) exceeded 65% with relative standard deviations of 4-15%. The method was applied to real samples, in which residues of coumaphos and dimethoate were detected. 相似文献
73.
Soil enzymes are linked to microbial functions and nutrient cycling in forest ecosystems and are considered sensitive to soil
disturbances. We investigated the effects of severe soil compaction and whole-tree harvesting plus forest floor removal (referred
to as FFR below, compared with stem-only harvesting) on available N, microbial biomass C (MBC), microbial biomass N (MBN),
and microbial biomass P (MBP), and dehydrogenase, protease, and phosphatase activities in the forest floor and 0–10 cm mineral
soil in a boreal aspen (Populus tremuloides Michx.) forest soil near Dawson Creek, British Columbia, Canada. In the forest floor, no soil compaction effects were observed
for any of the soil microbial or enzyme activity parameters measured. In the mineral soil, compaction reduced available N,
MBP, and acid phosphatase by 53, 47, and 48%, respectively, when forest floor was intact, and protease and alkaline phosphatase
activities by 28 and 27%, respectively, regardless of FFR. Forest floor removal reduced available P, MBC, MBN, and protease
and alkaline phosphatase activities by 38, 46, 49, 25, and 45%, respectively, regardless of soil compaction, and available
N, MBP, and acid phosphatase activity by 52, 50, and 39%, respectively, in the noncompacted soil. Neither soil compaction
nor FFR affected dehydrogenase activities. Reductions in microbial biomass and protease and phosphatase activities after compaction
and FFR likely led to the reduced N and P availabilities in the soil. Our results indicate that microbial biomass and enzyme
activities were sensitive to soil compaction and FFR and that such disturbances had negative consequences for forest soil
N and P cycling and fertility. 相似文献
74.
Fernández-Bayo JD Nogales R Romero E 《Journal of agricultural and food chemistry》2008,56(13):5266-5272
Kinetic studies are of great concern for understanding the processes and parameters involved in the sorption of pollutants by soils. Sorption kinetics of imidacloprid and diuron in eight soils of different characteristics, with very low organic carbon content were investigated. Pseudosecond-order kinetic reactions closely correlate with the experimental kinetic (R(2) > 0.98) in all soils. The sorbed amount of diuron was higher than that for imidacloprid. The low OC content of these soils correlated neither with the sorbed amount nor with the kinetic parameters for both pesticides. Imidacloprid sorption was correlated with silt and sand content and cation exchange capacity (CEC); meanwhile for diuron, no correlation was found. Thus, sorption kinetics take place throughout different mechanisms related mainly to the chemical character of the pesticides. Sorption kinetic parameters determined using three of the four models selected (pseudosecond-order kinetic reactions, Elovich equation, and Weber-Morris models) have been shown to be worthy to distinguish the process controlling the sorption kinetic of both pesticides. 相似文献
75.
Ellipsosomes: organelles containing a cytochrome-like pigment in the retinal cones of certain fishes 总被引:1,自引:0,他引:1
E F MacNichol Y W Kunz J S Levine F I Hárosi B A Collins 《Science (New York, N.Y.)》1978,200(4341):549-552
Ellipsosomes are dense spherical bodies containing a very large concentration of a heme pigment spectroscopically resembling pure cytochrome c. They are located at the outer ends of the inner segments of the cones of certain fishes. Although, superficially, they resemble the similarly located oil droplets in the cones of birds and reptiles, their ultrastructure and staining properties resemble those of the neighboring mitochondria. However, like the oil droplets, they may serve as intracellular color filters. 相似文献
76.
Detrital carbon accumulation accounts for most of an ecosystem's capacity to store organic carbon because the carbon contained as plant detritus exceeds that stored in living plants by about threefold. A comparative analysis of the mass and turnover of detrital carbon in ecosystems demonstrates that these properties are strongly related to the turnover rate of the dominant primary producers and are poorly related to ecosystem primary production. These results contribute to an understanding of the factors that control carbon storage in ecosystems and the role of carbon storage in the global carbon budget. 相似文献
77.
Heat treatments change the chemical and physical properties of wood and dimensional stability and hygroscopicity are affected
as a result of modifications of wood cell components. This study evaluated the water absorption of wood specimens treated
with boron compounds followed by heat treatment. Sugi (Cryptomeria japonica D. Don) sapwood specimens treated with either boric acid (BA) or disodium octoborate tetrahydrate (DOT) solutions were heat-modified
at either 180° or 220°C for 2 or 4 h. Carbohydrate composition and water absorption of the specimens were then measured and
compared with those of untreated and unheated specimens. Wood carbohydrates were significantly degraded in the specimens after
heat treatment. The heat treatment evidently decreased the water absorption and the heat-modified specimens absorbed less
water than unheated specimens. The higher the treatment temperature and the longer the treatment time, the lower the amount
of absorbed water. The boron-treated and heat-modified specimens, however, showed increased water absorption due to the hygroscopic
properties of BA and DOT. 相似文献
78.
Preparation of silage is a common method to preserve green forage. It plays an important role in improving forage utilization, 相似文献
79.
80.
Journal of Plant Diseases and Protection - Prior to the first occurrence of chestnut blight in 1976, leaf spot caused by Cylindrosporium castaneae was one of the most important diseases of European... 相似文献