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  • Electronic Resource  (16)
  • Chemistry  (15)
  • Atomic emission detector  (2)
  • Ascophyllum nodosum  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 8 (1996), S. 535-543 
    ISSN: 1573-5176
    Keywords: Ascophyllum nodosum ; betaines ; commercial seaweed extract ; leaf chlorophyll ; soil application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Application to the soil of an aqueous alkaline extract ofAscophyllum nodosum resulted in higher concentrations of chlorophyll in the leaves of treated plants in comparison to control plants treated with an equivalent volume of water. Positive results were obtained with all species tested (tomato, dwarf French bean, wheat, barley, maize). When the seaweed extract was applied as a foliar spray, similar effects on leaf chlorophyll contents were obtained, except in the case of dwarf French bean plants, for which no significant difference was recorded between test and control plants. When the betaines present in the seaweed extract were applied as a mixture in the same concentrations as those in the diluted seaweed extract (γ-aminobutyric acid betaine 0.96 mg L−1, δ-aminovaleric acid betaine 0.43 mg L−1, glycinebetaine 0.34 mg L−1), very similar leaf chlorophyll levels were recorded for the seaweed extract and betaine treated plants. This suggests strongly that the enhanced leaf chlorophyll content of plants treated with seaweed extract is dependent on the betaines present.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Atomic emission detector ; Organotin compounds ; Organolead compounds ; Organomercury compounds ; Grignard derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples was investigated. Pentylmagnesium bromide was used to pentylate ionic organotin, organolead, and organomercury compounds; the pentyl derivatives were then separated by GC and determined by AED. Several important GC-AED parameters, including the type of injector inlet, carrier gas flow rate, and helium make-up gas flow rate, were optimized for the simultaneous determination of these organometallic compounds. Their minimum detectable concentrations were approximately 1.0 to 2.5 ng/mL using a 0.5-μL on-column injection. The calibration curves exhibited good linearity between 2.5 and 2500 ng/mL for organotin and organolead compounds, and between 2.5 and 10000 ng/mL for organomercury compounds.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0935-6304
    Keywords: Capillary GC ; Atomic emission detector ; Supercritical fluid extraction ; Organotin compounds ; Complexation ; Grignard derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n-pentylmagnesium bromide prior to gas chromatographic analysis). A 23 factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1885-1892 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymerization of N,N-dimethylacrylamide (DMA) with methyl methacrylate in both the presence and absence of ethylene dimethacrylate (EDMA) was effected to very high conversion by γ-irradiation. The resultant xerogels were swollen to equilibrium in water at five specific temperatures within the interval 280.2-338.2 K. The volume fractions of the polymer φ2 in the hydrogels were determined from the measured dimensions, and compression-strain measurements yielded the polymer-water interaction parameter, the effective crosslinking densities, and Young's moduli Y. The observed dependence of these parameters on copolymer composition and content of EDMA is discussed. A scaling law of the form Y ∝ φr2 is obeyed well by hydrogels of xerogels containing 80 wt.-% DMA (r = 2.37 ± 0.10) and moderately well by hydrogels of xerogels with only 50 wt.-% DMA (r = 2.54 ± 0.10).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 813-822 
    ISSN: 0887-6266
    Keywords: blends ; tensile yielding ; Eyring's theory ; stress-whitening ; microvoiding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin sheets of isotactic polypropylene (iPP) and linear low-density polyethylene (LLDPE) blends were studied by tensile testing, optical microscopy (OM), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Eyring's two-process yielding theory was used to analyze the data of yield stress as a function of strain rate and temperature, and satisfactory curve-fitting results were obtained. Furthermore, stress whitening was found to have occurred in the necked regions of tensile specimens under a certain range of yielding conditions. These conditions corresponded to the activation of Process II yielding of Eyring's theory. The whitening was found to be a result of formation of microvoids that initiated at the interface between iPP and LLDPE. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2037-2047 
    ISSN: 0887-6266
    Keywords: iPP ; yielding ; Eyring processes ; crazing ; stress-whitening ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The yielding behavior of isotactic polypropylene (iPP) sheets prepared by hot pressing was studied by tensile testing. The corresponding microstructural changes in the specimens after testing were investigated by image analysis, optical microscopy (OM), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The yielding of iPP was found to follow a two-process Eyring yielding model. In the necked regions, stress-whitening occurred only in specimens tested over a certain range of strain rates and temperatures. The occurrence of the stress-whitening was correlated well with the activation of Process II in the two-process Eyring model. SEM revealed that the stress-whitening in the necked regions was associated with the formation of craze-like structures that were parallel to the loading direction. Furthermore, DSC analysis showed that the necked regions of the unwhitened tensile specimens had an additional low-temperature melting peak. However, no additional melting peaks were found in the stress-whitened specimens. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1127-1134 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrogels have been prepared by free radical polymerization in aqueous solution of N-isopropylacrylamide (NIPA) and of NIPA with acrylic acid (AA), methacrylic acid (MAA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). For each copolymerization three comonomer feeds were used and for all systems three concentrations of a crosslinker were employed. For all of the 30 polymers previously obtained, swelling data in deionised water were extended here by corresponding data measured in aqueous media of pH = 1 and pH = 12. Starting at ca. 15°C phase diagrams of swelling ratio r( = mass hydrogel/mass xerogel) were determined at several temperatures (T) up to ca. 70°C and reversibility in swelling/deswelling behaviour was verified on cooling back to 15°C. In some instances a lower critical swelling temperature (Tc) was located, whereas in others there was merely a continuous decrease in r with T. Swellability at pH = 1 is lower than that in pure water, the reduction in r increasing with content of acidic comonomer. At pH = 12 a similar reduction in r was observed in gels containing AA and AMPS, whereas with MAA as comonomer r is equal to or greater than the value in pure water. The findings are discussed on the basis of the influence of pH on the ionisation of carboxyl groups, hydrogen bonding, and chelation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Matrix-assisted laser desorption/ionization using a 3-hydroxpicollinic acid matrix from an active Nafion substrate has been used for detection of restriction enzyme-degested double-stranded plasmid DNA using time-of- flight mass spectrometry. DNA strands of up to 267 base pairs were detected with minimal sample purification, although only as species corresponding to single-stranded DNA.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 3 (1991), S. 249-257 
    ISSN: 1040-7685
    Keywords: high pressure gas chromatography ; microbore packed columns ; macroporous polymer and alkylsilica stationary phases ; unified microcolumn chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High pressure gas chromatography (GC) using microbore packed columns was investigated. The microbore columns were packed with common microparticulate liquid chromatography (LC) stationary phases such as 5-μm alky-modified silicas and a 5-μm macroporous polymer beads. The effects of the stationary and mobile phases, the mobile phase linear velocity and the column temperature were studied. The LC stationary phases were found to retain the expected selectivity and efficiency under high pressure GC conditions using either helium or CO2 gas as the mobile phase. The results indicate that microbore columns packed with common LC microparticulate stationary phases can be used in high pressure GC to provide rapid and efficient separation of volatile polar and nonpolar compounds. The results also suggest that the same instrument components such as the pump, injector, column, restrictor, and detector can be used for both high pressure GC and supercritical fluid chromatography (SFC) separations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1172-1176 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A Nafion film substrate modified with concentrated ammonia was shown to improve the detection of DNA using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), especially for DNA strands greater than 200 base pairs. Experimental procedures relating to the detection of DNA by MALDI-MS using this modified Nafion substrate are described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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