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  • 11
    Electronic Resource
    Electronic Resource
    Magnetic and mössbauer study of rare-earth-substituted M-, W- and X-type hexagonal ferrites (1990)
    Springer
    Journal of materials science 25 (1990), S. 2765-2770 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effects of substitution of Ba2+ ions for some trivalent rare-earth ions on the magnetic properties and phase formation of M-, W- and X-type hexaferrites are studied. The compounds considered were: Ba1-REx/2Nax/2Fe12O19 with RE = gadolinium, lanthanum, lutetium, samarium and 0.0 ⩽x ⩽ 0.3; Ba0.9La0.05Na0.05Zn2Fe16O27 and Ba1.9La0.05Na0.05Zn2Fe28O46. The samples were prepared by standard ceramic procedures and have been investigated by thermomagnetic analysis, X-ray diffraction, Mössbauer spectroscopy, scanning electron microscope and magnetic measurements. Monophasic BaRE x/2-M compounds were found for 0.0⩽x〈0.2 giving an indication of the solubility range of the rare-earth (RE) atoms in this phase. The intrinsic magnetic properties and the coercive field are lowered with the exception of the lanthanum-substituted hexaferrite. No significant differences in the phase formation and magnetic properties were observed for the W- and X-type hexaferrites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584876
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  • 12
    Electronic Resource
    Electronic Resource
    Variation of fatty acid profile with solar cycle in outdoor chemostat culture ofIsochrysis galbana ALII-4 (1995)
    Springer
    Journal of applied phycology 7 (1995), S. 129-134 
    Details
    ISSN: 1573-5176
    Keywords: chemostat culture ; Isochrysis galbana ; fatty acids ; solar cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Outdoor chemostat cultures of the marine microalgaIsochrysis galbana at constant dilution rate (0.034 h−1 ) have been carried out under different weather conditions. Steady-state biomass concentrations were 1.61±0.03 kg m−3 in May and 0.95±0.04 kg m−3 in July, resulting in biomass output rates of 0.54 kg m−3 d−1 and 0.32 kg m−3 d−1 in May and July, respectively. Two patterns of daily variation with the solar cycle were observed in the fatty acid content. Saturated and mono-unsaturated fatty acids (16:0 and 16:1n7) show significant variation with the solar cycle, associated with short-term changes in environmental factors. Palmitic and palmitoleic acids are generated during daylight and consumed during the dark period. However, polyunsaturated fatty acids do not show a significant response to the solar cycle and their changes are associated with long-term variation in environmental factors. The maximum EPA productivity was obtained in May, 14.1 g m−3 d−1, which is close to that found in the literature for indoor continuous cultures. Nonetheless, the outdoor EPA content (up to 2.61 % d.wt) was lower than the indoor EPA content from a previous study (5% d.wt).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693058
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  • 13
    Electronic Resource
    Electronic Resource
    Some Results from the Hailpad Network in León (Spain): Noteworthy Correlations among Hailfall Parameters (1999)
    Springer
    Theoretical and applied climatology 64 (1999), S. 105-117 
    Details
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary  Since 1990 the Laboratory for Atmospheric Physics at the University of León has made use of a network of 250 hailpads spread over an area of 1000 km2 in the province of León (north-western Spain). By the end of 1995, the network had detected 25 hailfalls of more than 15 km2 in area, registered on 13 different days during the summer months. The 25 hailfalls were precipitated over more than 300 separate hailpads, leaving nearly 40 000 measurable prints. The size of each hailstone, whose mass and kinetic energy were taken simply as a function of the diameter of the stone was calculated using the hailpad network. In this way, an estimate has been made of the total quantity of ice which fell in each hailfall (circa 19 000 metric tons on average, although a figure ten times this was calculated for one particular hailstorm). The spatial evolution of the physical variables of the hail, determined from each pad, has also been graphically represented. In addition, the distribution of hailstone sizes has been analysed, and the characteristic distribution parameters calculated. Although exponential distribution is often used, the Kolmogorov-Smirnov test of goodness-of-fit shows a better fit for gamma distribution. The information provided by these parameters has been analysed for both distributions, in relation to some specific variables associated with hail. There is a good correlation between total energy and mass precipitated, but the quantity of hail per unit area correlates with the total energy or mass of the precipitation only through the area affected. The size distribution parameters only show good correlations with the maximum hailstone size recorded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007040050115
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  • 14
    Electronic Resource
    Electronic Resource
    Surface Morphology of a PVC/PMMA Blend Studied by ToF-SIMS (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 419-421 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies, utilizing both laterial imaging and shallow depth profiling, of a 50:50 poly(vinyl chloride)/poly(methyl methacrylate) (PVC:PMMA) blend have confirmed the presence of a thin overlayer of PMMA on the phase-separated bulk morphology.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Evaluation of the lubricant properties of candelilla wax in unplasticized PVC/wax systemsPart of this work integrates the Masters in Polymer Science and Technology Thesis of V. Valverde-Herrera, at U. A. de C. (1995). (1995)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 1 (1995), S. 162-169 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper reports on the evaluation of a natural product, candelilla wax, as a possible lubricant for unplasticized PVC formulations stabilized with lead or barium/cadmium chemicals. The lubricant effect of two types of wax (commercial grade and purified by solvent extraction) was evaluated by torque and extrusion rheometry and by differential scanning calorimetry. Commercial lubricants (Loxiol) were used for comparison. The results show that candelilla wax may be used as a lubricant (mainly of the external type) for unplasticized PVC; however, care must be taken when designing formulations to avoid over-lubrication, specially when lead-based thermal stabilizers are used.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730010310
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  • 16
    Electronic Resource
    Electronic Resource
    Molecular weight characterization of natural guayule rubber by gel-permeation chromatography (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 14 (1976), S. 649-652 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.130141103
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  • 17
    Electronic Resource
    Electronic Resource
    Storage hardening and “abnormal” groups in guayule rubberThis article was presented at the 27th IUPAC Congress, Helsinki, Finland, August 1979. (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1511-1517 
    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: The hardening process of natural (Hevea brasiliensis) rubber, that takes place when this rubber is stored in dry conditions over long periods of time, has been correlated with the presence of reactive “abnormal” groups directly grafted on the polymeric chain and in the serum of the latex. In the present work, natural Hevea (HR) and Guayule (Parthenium argentatum) rubber (GR) were stored under accelerated conditions and the changes in Mooney viscosity and molecular weight measured. The results showed that while HR undergoes hardening, GR keeps its Mooney viscosity constant, as does a constant viscosity (CV) Hevea rubber. These results are explained by the absence of functional “abnormal” groups that sustain the hardening reactions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260508
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  • 18
    Electronic Resource
    Electronic Resource
    Photodegradation of polyethylene films formulated with a titanium-based photosensitizer and titanium dioxide pigment (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 847-856 
    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: This work reports on the photodegradation of low-density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow-extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530702
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  • 19
    Electronic Resource
    Electronic Resource
    Study of polyethylene photodegradation in formulations with a system of interacting photostabilizers and antioxidants (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 413-424 
    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: The accelerated UV photodegradation process of low-density polyethylene films, formulated with two photostabilizers and two antioxidants, was studied to evaluate the effect of different combinations of UV stabilizers and antioxidants on the overall photodegradation process. An experimental design, consisting of 33 formulations with different additive ratios and a blank, was used to evaluate the performance of the four mixed additives. From each formulation, 200 micron-thick films were produced by the extrusion-blowing process. Samples from these films were submitted to accelerated UV aging, and the polymer degradation was measured by carbonyl group evolution, molecular weight distribution changes, and maximum elongation loss. The effect of the additive combination on the different degradation reactions is discussed qualitatively by using “relative variables” and a triangular diagram. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 20
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    Unknown
    Presaddle and postsaddle dissipative effects in fission using complete kinematics measurements (2016)
    American Physical Society
    Details
    Publication Date: 2016-12-02
    Print ISSN: 2469-9985
    Electronic ISSN: 2469-9993
    Topics: Physics
    Published by American Physical Society
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