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  • 1990-1994  (1)
  • 1985-1989  (5)
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  • 1
    ISSN: 1435-1536
    Keywords: Surfactant-dye complex ; sodium dodecyl sulfate ; azo oil dye ; thermodynamics study ; dyeing rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Spectrophotometric and thermodynamic investigations are reported of the interactions between anionic surfactant (sodium dodecyl sulfate) and six azo oil dyes (benzene azo naphthalene type) which have an amino group at 4-position of naphthalene. A pronounced spectral change in the dye solution occurs on addition of surfactant. For increasingly surfactant concentrations (below the CMC), the interaction between dye and surfactant is so sharp that the systems may be said to exhibit an isosbestic point; then a new absorption band appears at longer wavelengths. The spectral data can be quantitatively interpreted in terms of a complex formation. The equilibrium coefficients of the complex formation are determined at different temperatures. The thermodynamic parameters of the complex formations (the free energy change (ΔG), enthalpy change (ΔH) and change in entropy (ΔS) are also calculated. The reaction of complex formation is exothermic (ΔH negative).ΔG is dependent on the hydrophobic nature andpKa of the dye. These complexes will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction. With increasing amounts of complex, the infinite adsorption, the exhaustion and the rate constant of dyeing for nylon decrease.
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  • 2
    ISSN: 1435-1536
    Keywords: Surfactant-dye complex ; sodium alkyl sulfate ; azo oil dye ; thermodynamics study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermodynamics of surfactant-dye complex formation have been studied, in terms of equilibrium coefficient, using a spectrophotometer. The systems are 6 sodium alkyl sulfates, which have different alkyl chain lengths, and 4-phenylazo-1-naphthylamine. A pronounced spectral change in the dye solution occurs on addition of the surfactant; the change has a definite isosbestic point and a new absorption band at 535 nm because of surfactant-dye complex formation, which is caused by hydrophilic-hydrophilic interaction. As the alkyl chain length in the surfactant increases, the values of free energy change (negative) increase, while the value of enthalpy change (negative) increases and the value of entropy change (positive) decreases. The longer the alkyl chain length in surfactant increase, the more stable the surfactant-dye complex becomes. Surfactant-dye complex will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.
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  • 3
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal expansion and magnetostriction of single crystals of normal and ferromagnetic dense Kondo systems CeSi1.86 and CeSi1.70 are measured. The results show very characteristic behavior. The strain-dependent Kondo effect supports the Γ7-like ground doublet conjectured previously based on the analysis of the magnetic susceptibility data. It is shown that the result is similar to that in the usual nearly weak ferromagnetic system.
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  • 4
    ISSN: 1432-0649
    Keywords: 07 ; 62 ; 52 ; 36
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new method for the detection of the optogalvanic (OG) effect in a flame has been developed. In the experimental scheme, the reflected microwave power is measured for the detection of the OG effect inside a microwave resonant cavity. In a preliminary experiment, the OG signal of sodium atom aspirated into a propane/O2 flame was observed at a concentration below 10 ng/ml.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 50 (1990), S. 23-28 
    ISSN: 1432-0649
    Keywords: 42.65 ; 33.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coherent vacuum ultraviolet (VUV) radiation was generated by four-wave difference frequency mixing (ωVUV=2ω1−ω2) of pulsed dye laser radiation in carbon monoxide (CO). The frequency ω1 was tuned to the C 1Σ+(υ′=0)←X 1Σ+(υ″=0) two-photon transition, while the dye laser frequency ω2 was scaned around 17650 cm−1 which corresponds to the A 1Π(υ=7)«C 1Σ+(υ′=0) transition energy. The VUV intensity was found to be strongly wavelength dependent. The analysis of the spectrum revealed (i) that the VUV intensity was enhanced by the rotational levels of the A 1Π(υ=7) state and (ii) that the off-resonance excitation in the C 1Σ+(υ′=0)←X 1Σ+(υ″=0) two-photon transition greatly contributed to the present four-wave mixing process. The effects of pumping laser detuning, saturation and foreign gases are briefly discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3580-3582 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gadolinium hexaboride is thought to have at least two magnetic phases in zero magnetic field. The structure of these phases, however, is still unknown. Due to the high neutron absorption of both Gd and B, studies by neutron scattering are not easy to do. We therefore used the alternative technique of x-ray magnetic scattering. Experiments were performed with a rotating anode x-ray source and CuKα radiation at temperatures down to 6 K. At the lowest temperatures two sets of superlattice reflections of the form (h/2,k,l) and/or (h,k/2,l) and (h/2,k/2,l) were observed. The intensity of both types of reflection remains roughly constant until 10 K. At this temperature the intensities of the (h/2,k,l) and (h,k/2,l) reflections increase sharply and reach a maximum around 11.5 K, while the (h/2,k/2,l) reflections rapidly disappear. At 12 K, only the former reflections are observed and they disappear discontinuously at TN =15.85±0.5 K. The results confirm the existence of two magnetic phase transitions in GdB6 and suggest a complex multi-q magnetic structure.
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