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  • Chemistry  (613)
  • Polymer and Materials Science  (276)
  • Life Sciences (General)  (51)
  • 1990-1994  (664)
  • 1990  (664)
  • 1
    Electronic Resource
    Electronic Resource
    Discrimination effects in inorganic ion-cluster detection by secondary-electron multiplier in mass spectrometry experiments (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 9-12 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Discrimination effects in secondary electron multipliers due to the differences in kinetic energy with which ions of different masses strike the dynode surface are investigated. The threshold energy at which ions of a particular mass can be detected is discussed. The efficiencies of such multipliers when used with cluster ions such as H+(H2O)N (where Cat+ represents an alkali-metal cation) are investigated and discussed, in terms of both the ‘kinetic’ and ‘potential’ emission coefficients.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040104
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  • 2
    Electronic Resource
    Electronic Resource
    Abnormal effects in the detection of ions from bioorganic substances by mass spectrometry (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 13-15 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The characteristics of the detection of ions of the alkali metals and of cluster ions of the type (H2O)NMH+ (where M is an amino acid) are markedly different from those for the detection of protonated saccharose ions. The latter are shown to produce a signal from a secondary electron multiplier detector at a lower ion energy than the threshold energy for the former ions. An explanation is proposed in terms of the charge localization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040105
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  • 3
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    Seismic stress responses of soybean to different photosynthetic photon flux (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Physical agitation applied as periodic seismic stress (shaking) reduced stem elongation, leaf expansion, and biomass accumulation by vegetative soybeans. Level of photon flux (PPF) influenced the type and extent of plant response to mechanical stress. Plant parts responded differently as PPF varied between 135 and 592 micromoles m-2 s-1. Stem length was significantly reduced by seismic stress at 135 micromoles m-2 s-1 but this effect was insignificant at higher PPFs. Reduced stem length resulted from an inhibition of internode elongation. Stem diameter was unaffected by stress at the PPFs tested. In contrast to effects on stem elongation, leaf area was insensitive to stress treatments at 135 micromoles m-2 s-1 but was progressively inhibited by stress as PPF increased. Statistically significant reductions in shoot f. wt and d. wt by seismic stress occurred only at 295 micromoles m-2 s-1. Root biomass accumulation was not affected by seismic stress at any PPF used in this study.
    Keywords: Life Sciences (General)
    Type: Annals of botany (ISSN 0305-7364); 66; 617-22
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
    Electronic Resource
    Electronic Resource
    Radical copolymerization of 2-acryloyl thioxanthone with methyl methacrylate (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 967-972 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel monomer, 2-acryloyl thioxanthone (TXA), was prepared by reaction of 2-hydroxy thioxanthone with acryloyl chloride. Copolymerization of TXA with methyl methacrylate (MMA) in DMF at 80°C was studied in order to evaluate relative reactivities of these monomers. Values of 1.36 and 0.5 were found for the respective reactivity ratios of MMA and TXA, respectively. The resonance stabilization and polar properties were determined and discussed in terms of spectroscopic data.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280502
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  • 5
    Electronic Resource
    Electronic Resource
    Lanthanide-imidazole complexes as latent curing agents for epoxy resins (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 731-740 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Imidazoles have for some time been recognized as curing agents for epoxy resins. Once the resin and the imidazole compound are mixed there is a relatively short time in which the mixture can be used, since the polymerization (curing) reaction occurs to some extent even at room temperature causing the reaction mixture to thicken. In order to circumvent this problem we have found that imidazoles can be complexed with organo-lanthanide compounds thereby tying up the imidazole and retarding its rate of reaction in the cure of epoxy materials at ambient temperatures. When it is desired to enhance the rate of cure the temperature of the mixture is simply raised. This paper concerns studies of the epoxy cure reaction with the M(THD)3-IM series. M represents the lanthanide metals Eu, Ho, Pr, Dy, Yb, and Gd, and THD is 2,2,6,6-tetramethyl-3,5-heptanedione. Cure reactions were followed by differential scanning calorimetry and in some cases by infrared spectroscopy. We have demonstrated that these organo-lanthanide-imidazole complexes are effective thermally latent curing agents for epoxy resins. At a temperature of 150°C cure is quite rapid. In the course of these studies it has also been determined that there is an inverse correlation between the lanthanide ionic radius in the complex and the temperature at which the cure reaction occurs. Thus the Yb compound, where the imidazole is most strongly bound, cures at the highest temperature and Pr, where imidazole is bound most weakly, at the lowest. Consistent with these facts is the observation that the Yb compound also gives the longest latency period when mixed with epoxy resin.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280404
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of soluble polymeric photosensitizers with the 4-nitro-1-naphthyl-carbamoyl as pendant group (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 3499-3511 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several models of monomers, homopolymers, and copolymers containing a photosensitizer group, 4-nitro-1-naphthyl-carbamoyl (NNC), have been synthesized. Synthetic methods are described, in addition to two routes for copolymers preparation. First, the radical copolymerization between monomers with the photosensitizer group built-in and comercial monomers such as styrene and methyl acrylate and, second, polymer modification by nucleophilic reaction between carbonyl group polymer supported and nitro-naphthyl amine. All products were characterized and one of the resulting soluble polymeric photosensitizer and its model compound, were tested as triplet energy donors against trans- stilbene and their Stern-Volmer constants were determined. Results show that the sensitizer efficiency is closer to that of the well known benzophenone sensitizer and higher than that of the acetophenone, while the sensitizer efficiency disminished when the chromophore is bonded to the polymer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281225
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and X-ray crystal structure analysis of (-)-1-menthoxygermatrane (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 1 (1990), S. 439-442 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A solvate complex of (-)-1-menthoxygermatrane with chloroform (1) was obtained by reaction of (-)-menthoxytriethylstannane with 1-bromogermatrane in chloroform. The crystal and molecular structure of 1 was established by X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520010603
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  • 8
    Electronic Resource
    Electronic Resource
    Fast-Atom bombardment mass spectrometry and collisional spectroscopy in the structural characterization of underivatized 1,4-benzodiazepines (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 314-317 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Fast-atom bombardment (FAB) mass spectrometry linked with collision spectroscopy has been employed for the structural characterization of eight underivatized 1,4-benzodiazepines. Both positive- and negative-ion FAB led, in all cases examined, to the production of abundant molecular species. Collision experiments performed on such ions gave rise to the identification of diagnostic fragment ions, that could be related to the original structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040904
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  • 9
    Electronic Resource
    Electronic Resource
    Thermolysis of disubstituted 1,2-dioxetanes: Activation parameters and chemiexcitation yields (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 1 (1990), S. 175-180 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: trans-3-Methyl-4-(p-anisyl)-1,2-dioxetane 1, trans-3-methyl-4-(o-anisyl)-1,2-dioxetane 2, 3-methyl-3-benzyl-1,2-dioxetane 3, and 3-methyl-3-p-methoxybenzyl-1,2-dioxetane 4 were synthesized in low yield by the β-bromo hydroperoxide method. The activation parameters were determined by the chemiluminescence method (for 1 ΔG≠ = 22.8 ± 0.3 kcal/mol, Δ≠ = 22.2, ΔS≠ = -1.7 e.u., k60 = 7.6 × 10-3s-1; for 2 ΔG≠ + 23.6 ± 0.3 kcal/mol, ΔH≠ = 22.8, ΔS≠ = -2.2 e.u., k60 = 2.5 × 10-3S-1; for 3 ΔG≠ = 24.0 ± 0.4 kcal/mol, ΔH≠ = 23.1, ΔS≠ = -2.7 e.u., k60 = 1.2 × 10-3S-1; for 4 ΔG≠ = 24.0 ± 0.2 kcal/mol, ΔH≠, = 23.2, ΔS≠, = -2.4 e.u., k60 = 1.2 × 10-3s-1). Thermolysis of 1-4 produced excited carbonyl fragments (direct production of high yields of triplets relative to excited singlets) [chemiexcitation yields φT, φS, respectively: for 1 0.02, 0.0001; for 2 0.02, 0.0001; for 3 0.03, 0.0002; for 4 0.02, 0.0001]. The effect of paramethoxyaryl substitution was consistent with electronic effects. The ortho substitution in 2 resulted in an increase in stability of the dioxetane, opposite that observed for an electronic effect. The results are discussed in relation to a diradical-like mechanism.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520010209
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  • 10
    Electronic Resource
    Electronic Resource
    Structure determination of O-linked glycopeptides by tandem mass spectrometry (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 777-781 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method for characterizing O-linked glycopeptides without chemical degradation is presented. Collisioninduced dissociation (CID) analysis of intact O-linked glycopeptides containing mono-and disaccharides was performed. For glycopeptides containing one hexose unit, both the peptide sequence and the site of attachment of the sugar moiety were obtained from a single high-energy CID spectrum. However, in a glycopeptide bearing multiple sugar residues per site, the CID spectrum was dominated by fragments resulting from cleavages of the carbohydrate substituents and the gas-phase deglycosylated peptide, thus obviating the concomitant observation of peptide sequence ions. Hence, information on the structures of the carbohydrate substituents was obtained, but not on the sites of attachment of these residues to the peptide. Subsequent CID analysis of the gas-phase deglycosylated peptide ion can be used to obtain the sequence of the peptide backbone from the same sample. This method holds promise for simultaneously determining the carbohydrate structure and the peptide sequence of intact O-linked glycopeptides without chemical degradation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191205
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