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  • 1990-1994  (1,572)
  • 1905-1909
  • 1994  (1,572)
  • Chemistry  (1,572)
  • Inorganic Chemistry  (73)
  • 1
    Electronic Resource
    Electronic Resource
    Dielectric investigation of isotropic and anisotropic solutions of hydroxypropyl cellulose in dioxan (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 34 (1994), S. 363-367 
    Details
    ISSN: 0959-8103
    Keywords: hydroxypropyl cellulose ; dioxan ; dielectric behaviour ; refractive index ; isotropy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dielectric behaviour of hydroxypropyl cellulose in dioxan has been studied at 10-50°C over a range of concentration of 10-55 wt% to include the isotropic and anisotropic phases. The study showed that the loss maximum ε″max magnitude of polarization ε0 - ε∞ relaxation time 1/2πfm degree of broadening of the absorption curves 1-h or α, and the mean-square dipole moment 〈gμ2〉, steadily increase with concentration up to 42 wt%, above which a rapid decrease takes place. This indicates that the isotropic solution transforms to an anisotropic solution with a smaller mean dipole moment. The critical concentration is realized to be temperature invariant. This was evidenced by measuring the refractive index of solutions covering the same concentration and temperature ranges.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210340402
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of copolymer composition and conversion on the glass transition of methyl acrylate-methyl methacrylate copolymers (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1191-1203 
    Details
    ISSN: 0887-6266
    Keywords: methyl methacrylate-methyl acrylate copolymers ; free radical copolymerization ; low and high conversion ; glass transition temperature ; sequence distribution ; compositional variation of glass transition ; modeling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass transition of methyl methacrylate methyl acrylate copolymers over a wide range of conversion and sequence distribution have been analyzed with the only purpose of predicting the change in the glass transition in copolymers as a function of conversion and consequently of comonomer sequence distribution. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320707
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  • 3
    Electronic Resource
    Electronic Resource
    Polysulfone membranes. V. Poly(phenyl sulfone) (Radel R)-poly(vinyl pyrrolidone) membranesIssued as NRC No. 35781. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 783-792 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ultrafiltration membranes were prepared from mixtures of poly(phenyl sulfone) (Radel R5000) and poly(vinyl pyrrolidone) (PVP) dissolved in 1-methyl-2-pyrrolidinone (NMP). The effects of the casting solution composition on membrane performance and morphology are presented. Radel R5000 membranes showed higher productivity for a given pore size when compared to other polysulfone membranes. The biphenyl group in Radel R5000 makes it more rigid in comparison to other polysulfones. This may result in more ordered packing, which resulted in the higher productivities and smaller pore sizes observed in the membranes. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540609
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical and optical properties of the transition metal iron in ZnTe and CdTe (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 3 (1994), S. 223-232 
    Details
    ISSN: 1057-9257
    Keywords: CdTe ; ZnTe ; Impurities ; Spin resonance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We present results of electron paramagnetic resonance (EPR) and optical spectroscopy on different charge states of the transition metal impurity iron in ZnTe and CdTe. We identify the energy level position of the Fe+ acceptor in ZnTe at Ev + 1.7eV and estimate its position in CdTe. Ionisation transitions from Fe+to the conduction and valence bands ar found in both absorption spectroscopy and photo-EPR. Optical intra-defect tracsitions from Fe+ to crystalfield-split excited states ar resolved for the first time. This assignment to Fe2+ is based on optically detected EPR. Application of both far-infrared Fourier transform and EPR spectroscopy allows the determination of the total iron concentration in all charge states.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860030132
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  • 5
    Electronic Resource
    Electronic Resource
    Reactive diluent effect on properties of UV-cured films (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 309-315 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polymer films were prepared with UV radiation from urethane acrylate oligomer (LR 8739) mixed with a photoinitiator (Irgacur 184) and a number of reactive diluents chosen from monofunctional monomers (such as N-vinyl pyrrolidone, ethylhexyl acrylate, methoxyethyl acrylate, and hydroxyethyl methacrylate), difunctional monomers (hexane dioldiacrylate, butanediol diacrylate, and tripropylene diacrylate), and a trifunctional monomer (trimethylol propane triacrylate). The optimum concentrations of the photoinitiator, oligomer, and diluents were determined. Various properties of the cured films such as pendulum hardness, gel content, swelling ability, tensile strength, and elongation at break were also determined. The glass transition temperatures (Tg) of the diluents were correlated with tensile properties and those of the film. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540305
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  • 6
    Electronic Resource
    Electronic Resource
    Anodic behavior of some Vinca alkaloids with cytostatic activity: Effect of pH (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 57-61 
    Details
    ISSN: 1040-0397
    Keywords: Vinca alkaloids ; Oxidation mechanism ; Differential pulse voltammetry ; Cyclic voltammetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The anodic oxidation mechanism of the Vinca alkaloids vinblastine, its semisynthetic derivatives vindesine and 5′-noranhydrovinblastine, and of vincristine, all with closely similar structures, was studied at a glassy carbon disk electrode in buffered aqueous media using differential pulse and cyclic voltammetry. The effect of pH on the mecharism showed that it is a complex multistep electron transfer with deprotonation steps involved and that the final products, dimers or polymers, adsorb strongly to the electrode, forming an unreactve film on the electrode surface. The electrochemical differential pulse voltammograms showed a correlation between the vinblastine derivatives, whereas vincristine reacts at different potentials. These differences in the anodic oxidation mechanisms of the compounds studied can be related to their neurotoxicity and myelosuppression effects. These effects may be due to the metabolite and/or degradation products of the compounds and result from how they are attached to, or transported across, cellular structures such as cell membranes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140060111
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  • 7
    Electronic Resource
    Electronic Resource
    Amoxycillinium-Selective plastic membrane electrodes based on amoxycillinium-phosphotungstate ion associate (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 914-917 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (1:3) (phosphotungstate:amoxycillinum) ion associate is used as the ion exchanger in preparing conventional and coated wire plastic-membrane electrodes for amoxycillin (Am). The performance characteristics of the electrode are as follows: presoak time, 30 minutes; average slope: 59 ± 0.8 mV/ concentration decade, at 25°C, for 24 hours of continuous soaking; usable concentrations range, 1.96 × 10-4 to 1.5 × 10-2 M (Am); working pH range 3 to 9, and mean isothermal coefficient, 2.25 × 10-3 mV/°C. The electrode displays very good selectivity for Am toward a large number of inorganic and organic cations. The standard addition method and potentiometric titration are used to determine Am in pure solutions and in pharmaceutical preparations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140061018
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  • 8
    Electronic Resource
    Electronic Resource
    Identification and quantification of Cu contamination on GaAs surfacesPaper presented at QSA 7, Guildford, September 1992. (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 51-55 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Secondary ion mass spectrometry has been used to identify the presence of Cu contamination on undoped semiinsulating GaAs wafer surfaces following polishing under certain conditions. The presence of a contaminating species on the wafer surface is indicated by the influence of pre-etch treatments on electrical measurements performed on heat-treated wafers, with and without Si implants. The identification of Cu as a contaminant is confirmed by photoluminescence measurements. With the appropriate wafer preparation process, the level of Cu contamination is below the SIMS detection limit of 〈1 × 1016 atoms cm-3.In the SIMS analysis of the surface-contaminated wafers, the Cu depth profile shape was dependent on the primary beam bombardment energy, suggesting a chemical segregation of Cu out of the altered layer, a redistribution that is known to occur in Si.To quantify the surface concentration of Cu, GaAs wafers were deliberately contaminated with Cu, heat treated and analysed with glow discharge mass spectrometry and SIMS to provide a cross-calibration.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740210108
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  • 9
    Electronic Resource
    Electronic Resource
    Structural changes and surface properties of Cox Fe3 - x O4 spinels (1994)
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 60 (1994), S. 161-170 
    Details
    ISSN: 0268-2575
    Keywords: cobalt ferrite ; surface texture ; thermal analysis ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cobalt ferrite spinel oxide series, CoxFe3-xO4 (0 ≤ x ≤ 3), has been prepared by coprecipitation. The adsorption-desorption isotherms of all the compositions calcined between 200 and 600°C have been measured using nitrogen gas at -196°C. The structural and the phase changes were characterized by TGA and XRD techniques. The results obtained revealed that the transformation of γ- to α-Fe2O3 was accompanied by a sharp decrease in the SBET values. The addition of Co2+ ions into Fe2O3 up to × = 0.6 led to an observable increase in the SBET value. This behaviour was attributed to the incorporation of Co2+ ions into the Fe2O3 lattice and the retardation of the phase transition of γ- to α-Fe2O3. The minimum SBET values obtained at a lattice composition of × = 1·0 corresponded to the formation of a cobalt ferrite normal spinel which is associated with the existence of narrow pores. The increase in SBET values in the cobalt-rich region, with a maximum at x = 2·6 is explained on the basis of the cationic replacement of Fe3+ ions in the Co3O4 lattice. Finally, calculation of pore volume distribution was carried out, in addition to Va-t plots, in order to study the nature of the surface porosity, which was found to be mesoporous.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jctb.280600208
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  • 10
    Electronic Resource
    Electronic Resource
    Refractory methylated arsenic compounds in estuarine waters: Tracing back elusive species (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 43-56 
    Details
    ISSN: 0268-2605
    Keywords: Arsenic ; identification ; DCI MS/MS ; hydride generation ; arsenobetaine ; arsenocholine ; methylarsenic ; chlorine ; fluorine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water from the Tagus estuary, Portugal, was concentrated and purified through evaporation, solvent extraction, ion exchange and HPLC, and peaks of refractory arsenicals were detected by difference between total arsenic (GF AA) and hydride-forming arsenic species (HG QF AA). DCI mass spectra of these fractions presented peaks at m/z 139, 157 and 159; the proportion of m/z 157 and 159 peaks, approx. 3:1, suggested a chlorinated moiety. DCI MS/MS daughter-ion fragmentation of these peaks seems compatible with dimethylarsenic (cacodylic) acid and structures of the type Me2As(O)Cl or Me3As(OH)F. The refractory character of these fractions, however, cannot be explained by these structures. Further work with mixtures of halogen and arsenic species injected in the HPLC system showed that fluoride and iodide can shift DMA (dimethylarsenic) and TMAO (trimethylarsine oxide) to shorter retention times but not to Rf values similar to refractory arsenicals. These latter are attained by mixtures of sodium chloride + arsenobetaine, and sodium fluoride and chloride + arsenocholine. We suggest that peaks at m/z 139 and 157 correspond to fragments of a heavier refractory molecule mainly formed by halogenated betaines including chloroarsenobetaine and chloro- and fluoro-arsenocholine.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080109
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