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The performance of yttrium as internal standard was investigated when aspirating digested samples or alternatively slurries of certified plant reference materials. The stability of the yttrium signal used for analyte signal normalization was examined for three ionic emission lines of yttrium. The results showed that the use of yttrium was beneficial; however for the slurry sample introduction technique it was not equivalently efficient in terms of overall recovery. In this case, the employment of a cyclonic instead of a double-pass spray chamber in combination with yttrium internal standardization leads to quantitative recoveries of the analytes. 相似文献
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Parthena Avramidou 《Proceedings of the American Mathematical Society》2005,133(1):175-184
Given a sequence of kernels for which the operators converge a.e. in all spaces, , a perturbation method is provided with the property that the modified convolution operators converge pointwise only in selective spaces.
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Goksungur Y Mantzouridou F Roukas T Kotzekidou P 《Applied biochemistry and biotechnology》2004,112(1):37-54
The effect of aeration rate and agitation speed on β-carotene production from molasses by Blakeslea trispora in a stirred-tank fermentor and optimization of the production of the pigment in a bubble column reactor were investigated.
In addition, a central composite design was employed to determine the maximum β-carotene concentration at optimum values for
the process variables (aeration rate, sugar concentration, linoleic acid, kerosene). By image analysis of the morphology of
the fungus, a quantitative characterization of the hyphae and zygospores formed was obtained. The hyphae were differentiated
to intacthyphae, vacuolated hyphae, evacuated cells and degenerated hyphae. An increased proportion of zygospores was correlated
to high β-carotene production. In the stirred-tank fermentor, the highest concentration of the carotenoid pigment (92.0 mg/L)
was obtained at an aeration rate of 1.5 vvm and agitation speed of 60 rpm. In the bubble column reactor, the aeration rate
and concentration of sugars, linoleic acid, kerosene, and antioxidant significantly affected the production of β-carotene.
In all cases, the fit of the model was found to be good. Aeration rate, sugar concentration, linoleic acid, and kerosene had
a strong positive linear effect on β-carotene concentration. Moreover, the concentration of the pigment was significantly
influenced by the negative quadratic effects of the given variables and by their positive or negative interactions. Maximum
β-carotene concentration (360.2 mg/L) was obtained in culture grown in molasses solution containing 5% (w/v) sugar supplemented
with linoleic acid (37.59 g/L), kerosene (39.11 g/L), and antioxidant (1.0 g/L). 相似文献
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Mantzouridou F Roukasa T Kotzekidoua P Liakopoulou M 《Applied biochemistry and biotechnology》2002,101(2):153-175
The effect of inoculum, pH, carbon and nitrogen source, natural oils, fatty acids, antioxidant, and precursors on beta-carotene production by Blakeslea trispora in shake-flask culture was investigated. The highest concentration of beta-carotene was obtained in the medium (pH 7.0) inoculated with one loop of each culture. Sucrose, glycerol, cornmeal, soy protein acid hydrolysate, and distiller's solubles did not improve the production of beta-carotene. By contrast, glucose, corn steep liquor, antioxidant, olive oil, soybean oil, cottonseed oil, oleic and linoleic acids, and kerosene significantly increased the beta-carotene production. A central composite design was employed to determine the maximum beta-carotene production at optimum values for the process variables (linoleic acid, kerosene, and antioxidant). The fit of the model was found to be good. Linoleic acid, kerosene, and antioxidant had a strong linear effect on beta-carotene production. The concentration of beta-carotene was significantly affected by linoleic acid-kerosene and linoleic acid-antioxidant interactions as well as by the negative quadratic effects of these variables. The interaction between kerosene and antioxidant had no significant linear effect. The maximum beta-carotene concentration (2.88 g/L) was obtained at concentrations of 17.15 g/L of linoleic acid, 39.25 g/L of kerosene, and 9.04 g/L of antioxidant. 相似文献
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