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  • Polymer and Materials Science  (8)
  • superconductivity  (3)
  • Anthropogenic  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 23 (1994), S. 114-118 
    ISSN: 1432-0495
    Keywords: Sediment accumulation rate ; Lead-210 ; Radon-226 ; Nainital region ; Anthropogenic ; Kumaun Himalaya
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The rate of sedimentation and the source of sediments in the lake basins of Nainital region, Kumaun Himalaya, have been estimated employing210Pb and210Ra methods. This has yielded a rate of sedimentation of 11.5, 4.70, 3.72, and 3.00 mm/yr in Nainital, Bhimtal, Naukuchiyatal, and Sattal lakes, respectively. The higher rate of sedimentation in Nainital lake, compared to other lakes, is related to faster erosion in the catchment aided by greater anthropogenic activity, while the slowest rate in Sattal lake is due to less erosion and more input of soil-derived material involving a slow rate of accumulation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 24 (1994), S. 28-33 
    ISSN: 1432-0495
    Keywords: Udaipur ; 210Pb method ; Rate of sedimentation ; Ahar River ; Terrigenous material ; Anthropogenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sediment accumulation rates have been determined in Udai Sagar, Fateh Sagar and Pichola lakes, which lie in the arid climatic zone, using the210Pb method. The rate of sedimentation estimated in these lakes is 8.9, 3.42, and 2.80 mm/yr, respectively. River inflow, mining activity, and lithology contribute to controling the sediment deposition pattern in Udai Sagar Lake, whereas in Fateh Sagar and Pichola lakes, anthropogenic activity and erosion of loosely bound terrigenous material through wave action and varying lithology are the major contributors. Furthermore, a contribution from atmospheric fallout has not been ruled out due to occurrence of frequent duststorms, owing to strong wind conditions aided by barren hills devoid of vegetation as well as dumping of mining wastes in the area. The higher TDS and lower sedimentation rate in Pichola Lake compared to Fateh Sagar are due to the limestone lithology and better maintenance in the former, such as construction of parks, graveled roads, etc., to check the flow of silt into the lake. Fluctuations in metal content, for example, V, Cr, Co, Ni, Sr, and sedimentation rates are due to the variation in the sediment input at different time intervals.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9605
    Keywords: ErBa2Cu3O7 ; crystal growth ; microscopy ; superconductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Millimeter-sized crystals of ErBa2Cu3O7 were fortuitously grown while sintering a flat disk. It was possible to separate individual crystals from the sintered mass and measure their properties. The resistive transition and onset of magnetic transition of a single crystal was 93 K and the resistive transition width was 〈 1 K. Flux expulsion was observed and individual crystals could be levitated by a magnetic field. Crystals showed unusual growth features. They were heavily corrugated along the part of the crystal that grew parallel to the top surface of the disk and that coincided with thec axis of the unit cell. Crystals were characterized by X-rays, electron microscopy, and optical microscopy.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9605
    Keywords: Cuprates ; superconductivity ; optical microscopy ; phase differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A common mineralogical technique for identifying individual crystals in a heterogeneous, polycrystalline sample involves the observation at room temperature of their colors in reflected polarized light (colors of polarization). Here we present the observation that a brownish yellow (golden) color of polarization is not only characteristic of the YBa2Cu3O7 superconductor, but of the cuprate superconductors in general and is correlated with the occurrence of superconductivity.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9605
    Keywords: superconductivity ; cuprate ; Hg ; Tl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The results of studies of new Hg based cuprate superconductors are reported. Several members of a new family of (Hg,Tl)(Ba,Sr)Can−2CunOx high temperature superconductors have been synthesized. These compounds, which are analogs to the Hg-Ba-Ca- and Tl-Ba-Ca-layered cuprates, are multi-phased and have superconducting transition temperatures above 100 K. Incorporation of Hg appears to stabilize several of the Tl-compounds, including a double layer. Tl/Sr system, in a manner similar to the role that Pb plays in the Tl/Sr- and Bi/Sr-systems. It has been suggested that recent reports of resistive Tc's above 200 K in Hg based samples are due to the presence of free Hg. Magnetization measurements of such a sample confirm this hypothesis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1885-1890 
    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: Infrared spectra of raw and chemically treated pineapple leaf fibers (PALF) have been studied using the KBr disk technique. Bands due to lignin and hemicellulose in the spectra of the fibers and their changes due to chemical (NaOH and NaCIO2) treatment have been discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 555-556 
    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
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 1491-1496 
    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: Full and semi-IPNs were prepared from epoxy and poly methyl methacrylate (PMMA), by the sequential mode of synthesis and were characterized by measurements of ultimate tensile strength (UTS), elongation at break, modulus, and toughness. Aromatic polyamine adducts and ethylene glycol dimethacrylate were used as the crosslinkers for epoxy and comonomer/crosslinker for methyl methacrylate monomer, respectively. Higher UTS and modulus of the semi-IPNs over full IPNs were attributed to the higher probability of interpenetration. The weight retention in the thermal decomposition of the IPNs and semi-IPNs were higher than the epoxy homopolymer. This enhancement was presumably related to the presence of the unzipped methyl methacrylate monomer which acted as radical scavangers in the epoxy degradation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 2125-2132 
    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: Semi- and full interpenetrating polymer networks (IPNs) of epoxy resin and poly(butyl methacrylate) (PBMA) were prepared by the sequential mode of synthesis. These were characterized with respect to their mechanical properties, such as ultimate tensile strength, percent elongation at break, and modulus. The densities of these samples were evaluated and compared. Differential scanning calorimetry (DSC) and thermogravimetric analysis were undertaken for thermal characterization of the IPNs. Phase morphology was studied by polarized light microscopy of the undeformed specimens and by scanning electron microscopy of the fractured surfaces of samples undergoing tensile failure. The effects of variations of the blend ratios on the above-mentioned properties were examined. A gradual decrease in modulus and tensile strength was observed for both the semi- and full IPNs with consequent increases in elongation at break and toughness as the proportion of PBMA increased. The densities also followed the same pattern. Semi-IPNs, however, were characterized by higher densities, tensile strengths, and moduli than the corresponding full IPNs. The DSC tracings displayed broadening of transitions, indicating some phase blending. The percent weight retentions in the thermal decomposition of the IPNs and pseudo-IPNs were higher than that observed during the thermal degradation of the epoxy resin homopolymer network. Phase-separated PBMA domains of various sizes were presumed to be responsible for the increased toughness of PBMA-modified epoxy. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3859-3866 
    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: Micellar catalyzed polymerization of acrylonitrile using ceric(IV)-glycerol redox system in aqueous sulfuric acid solution in the presence of sodium lauryl sulfate (NaLS) has been studied. The polymerization experiments were conducted between 15°C and 25°C, under conditions where no oxidation of sodium lauryl sulfate by ceric ion would we expected. The rate of polymerization (Rp) increases with increasing concentration of NaLS. The rate of monomer (AN) disappearance was proportional to [AN]1.5 and [glycerol]0.5, but, however, Rp changes in a nonlinear manner with increase in Ce(IV) concentration in the presence of the surfactant. The rate of Ce(IV) disappearance was not proportional to its original concentration. The chain length of the polymer could not be determined viscometrically, as the polymer obtained in presence of NaLS was insoluble in organic solvents. The activation energy of this polymerization process was calculated by conducting the experiment at different temperatures. The infrared spectra of the polymers in the presence and absence of surfactant have also been examined.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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