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  • 1
    Electronic Resource
    Electronic Resource
    An exprimental design approach to selecting the optimum liquid chromatographic conditions for the determination of vitamins B1, B2-phosphate, B3, B6 and C in effervescent tablets containing saccharin and sunset yellow FCF (1997)
    Springer
    Chromatographia 44 (1997), S. 634-644 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Vitamin B and C in tablets ; Experimental design ; Optimization of separation ; Multiple regression modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ion-pair liquid-chromatographic separation of the water-soluble vitamins thiamine mononitrate, riboflavin phosphate, nicotinamide, pyridoxine hydrochloride, ascorbic acid, saccharin, and the dye Sunset Yellow FCF (E110) has been examined for the analysis of the compounds in effervescent tablets. A Draper-Lin small composite design was used to study the impact on the compounds' retention times and peak-widths (the response variables) of four different mobile phase variables: percentage of methanol as organic modifier, the concentrations of hexanesulfonate as ion pairing reagent and of triethanolamine as competitive base, and pH. The interactions of these variables were also studied. The proposed design enabled derivation of multiple linear regression equations to model each compound's retention time and peak-width at half-height. The statistical reliability of the regression models was established by comparing predicted and experimental values. By introducing the regression models into a spreadsheet program (Excel 5.0), retention times and peak-widths for each compound were calculated at fixed mobile phase pH. The values of all the other combinations of the three mobile phase variables were changed in increments of two units within their examined boundaries, resulting in 225 different rows. For each combination the compounds' calculated retention times and their corresponding peak-widths were sorted in increasing order and the resolution between successive peaks was calculated. The minimum effective resolution (R s min) between each pair of peaks and the maximum retention time (t R max) in each row were then selected and used to construct contour plots indicating the location of zones of mobile phase parameter combinations whereR s min〉1.5 and the analysis was rugged, and wheret R max values were minimum. Their common regions resulted in optimum chromatographic separations. Examples are shown of chromatographic separations obtained using mobile phase combinations which were the best compromise of the three criteria selected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466667
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  • 2
    Electronic Resource
    Electronic Resource
    Optimization of solvent selectivity for the chromatographic separation of fat-soluble vitamins using a mixture-design statistical technique (1998)
    Springer
    Chromatographia 47 (1998), S. 401-412 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Optimization ; Mixture design ; Special cubic polynomial model ; Pareto-optimality ; Overlapping resolution mapping (ORM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A systematic approach, using a mixture-design statistical technique, has been developed for selecting the optimum mobile phase for the separation of fat-soluble vitamins in reversed-phase high-performance liquid chromatography. A quaternary mixture of methanol, acetonitrile, tetrahydrofuran and water was used as mobile phase. Retention time and peak width were recorded in ten runs augmented with five replicates and the data were subsequently fitted to special cubic polynomial models. The resulting mathematical equations enabled prediction of resolution over the entire parameter space. Contour plots of minimum effective resolution and maximum retention time as a function of mobile phase composition are presented and discussed. Visual inspection of these plots provides an overview of the quality of the separation and the analysis time required for each possible mobile-phase composition with n the parameter space. It is demonstrated that the methodology followed was an important tool which enabled the taking of informed decisions necessary for selection of the optimum mobile phase for a chromatographic separation. A combination ofR S minimum andt R maximum as optimization criteria in a multicriteria decision-making plot using pareto-optimality concept is discussed. This combination enabled visual demonstration of the compromise between separation quality and the economics of analysis time. Our methodology has been compared with the common used technique of ‘overlapping resolution mapping’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466471
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  • 3
    Electronic Resource
    Electronic Resource
    An electrical conductivity anomaly and rifting in southern Africa (1975)
    [s.l.] : Nature Publishing Group
    Nature 255 (1975), S. 678-680 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Measurements of electrical conductivity provide information about rifting in eastern and southern Africa. Overall geophysical and geological evidence supports the view that the conductive zone marks an extension of the African Rift system along old weak zones in the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/255678a0
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  • 4
    Electronic Resource
    Electronic Resource
    Toxicological analysis in a case of endosulfan suicide (1977)
    Springer
    Bulletin of environmental contamination and toxicology 18 (1977), S. 110-114 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Stomach, small intestine contents, “blood, liver, kidney and urine of a 28-years old man, were analyzed for residues of Endosulfan (6, 7, 8, 9, 10, 10-hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 4, 3-benzo(e)dioxathiepin 3-oxide). The analysis results showed the presence of high concentrations of the two endosulfan isomers in all samples. Since also alcohol was present in all the tissues analyzed, it was concluded that the victim died of a combined endosulfan-alcohol poisoning. No other drugs were found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01686316
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of agrisilvicultural systems with plantation forestry in the Atlantic Lowlands of Costa Rica (1995)
    Springer
    Agroforestry systems 32 (1995), S. 207-223 
    Details
    ISSN: 1572-9680
    Keywords: tree increment ; pests and diseases ; Acacia mangium ; Cordia alliodosa ; Costa Rica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Survival and growth data (ages 0–5 years) are presented for two timber species (Acacia mangium, Cordia alliodora) planted in monocultures or in association with a sequence of agricultural cropsZea mays, Zingiber officinale andEugenia stipitata (a fruit shrub) in the tropical humid Caribbean lowlands of Costa Rica. Average annual height and diameter growth rates were 3.2 m and 4.0 cm (C. alliodora), 3.5 m and 3.8 cm (A. mangium).C. alliodora associated with crops gave the greatest productivity with an average total stem volume increment of 19 m3 ha−1 yr−1. Root rot ofA. mangium (mainlyRosellinia sp.), leading to tree mortality, was greater in pure plots compared to associated plots.A. mangium can not be recommended for similar sites because of this problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711710
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  • 6
    Electronic Resource
    Electronic Resource
    Species and site selection for timber production on farm boundaries in the humid Atlantic Lowlands of Costa Rica and Panama (1996)
    Springer
    Agroforestry systems 35 (1996), S. 139-154 
    Details
    ISSN: 1572-9680
    Keywords: Acacia mangium ; Cordia alliodora ; Eucalyptus deglupta ; on-farm experimentation ; Tectona grandis ; Terminalia ivorensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In 1987–89 the CATIE-GTZ Agroforestry Project set up experiments with five timber tree species planted in single lines on twelve farm boundaries in cooperation with local farmers. When the trees were five years old, their height, diameter and total stem volume were: Acacia mangium 17 m, 19 cm and 67 m3 km−1, Cordia alliodora 14 m, 20 cm and 46 m3 km−1, Eucalyptus deglupta 22 m, 24 cm and 85 m3 km−1, Tectona grandis 17 m, 20 m and 64 m3 km−1, Terminalia ivorensis 18 m, 23 cm and 104 m3 km−1. Considering these excellent growth rates, planting of Cordia alliodora, Eucalyptus deglupta and Tectona grandis in lines on farm boundaries should be promoted. T. ivorensis and A. mangium are not recommendable for sites with impeded drainage because of mortality caused by root rot, mostly due to Rosellinia sp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122775
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  • 7
    Electronic Resource
    Electronic Resource
    Shade management in coffee and cacao plantations (1997)
    Springer
    Agroforestry systems 38 (1997), S. 139-164 
    Details
    ISSN: 1572-9680
    Keywords: coffee arabica ; interactions ; shaded perennials ; silviculture ; Theobroma cacao ; wood production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Shade trees reduce the stress of coffee (Coffea spp.) and cacao (Theobroma cacao) by ameliorating adverse climatic conditions and nutritional imbalances, but they may also compete for growth resources. For example, shade trees buffer high and low temperature extremes by as much as 5 °C and can produce up to 14 Mg ha-1 yr-1 of litterfall and pruning residues, containing up to 340 kg N ha-1 yr-1. However, N2 fixation by leguminous shade trees grown at a density of 100 to 300 trees ha-1 may not exceed 60 kg N ha-1 yr-1. Shade tree selection and management are potentially important tools for integrated pest management because increased shade may increase the incidence of some commercially important pests and diseases (such as Phythphora palmivora and Mycena citricolor) and decrease the incidence of others (such as Colletotrichum gloeosporioides and Cercospora coffeicola). In Central America, merchantable timber production from commercially important shade tree species, such as Cordia alliodora, is in the range of 4–6m3 ha-1 yr-1. The relative importance and overall effect of the different interactions between shade trees and coffee/cacao are dependent upon site conditions (soil/climate), component selection (species/varieties/provenances), belowground and aboveground characteristics of the trees and crops, and management practices. On optimal sites, coffee can be grown without shade using high agrochemical inputs. However, economic evaluations, which include off-site impacts such as ground water contamination, are needed to judge the desirability of this approach. Moreover, standard silvicultural practices for closed plantations need to be adapted for open-grown trees within coffee/cacao plantations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005956528316
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