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  • 1990-1994  (6)
  • 1960-1964
  • 1955-1959
  • 1991  (6)
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new stable compound in the Nd–Fe system has been identified as Nd5Fe17. The crystal structure belongs to the hexagonal space group P63/mcm, with a=2.0214(8) nm and c=1.2329(8) nm, and with 12 formula units per unit cell. This compound is a ferromagnet with Tc = 503 K and magnetization 162 emu/g at 4.2 K. Mössbauer spectra have been measured and fitted with five Fe sites, yielding an average Beff=26.5 T at room temperature, from which an average Fe moment of 1.83 Bohr magnetons is deduced. X-ray powder diagrams from magnetically aligned samples suggest basal anisotropy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 824-835 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 87 (1991), S. 371-382 
    ISSN: 1432-1106
    Keywords: Visual system ; Optic tract ; Axon elongation ; Axon arborization ; Growth rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to characterize differences in growth patterns of axons as they elongate toward their targets and during the initial stages of terminal arbor formation within the targets, we examined the primary visual system of fetal and newborn hamsters using three morphological methods: the Cajal-deCastro reduced silver method, the rapid Golgi technique, and anterograde transport of HRP. Axons emerge from the retina between the 10th and 11th embryonic days (E10–E11). The front of retinal axons crosses the chiasm, extends over the primitive dorsal nucleus of the lateral geniculate body (LGBd) by E13, and advances to the back of the superior colliculus (SC) by E13.5–E14. The rate of axon growth during this advance is nearly 2 mm/day. Collateral sprouts appear on axons around E15.5. In the LGBd and SC, these sprouts arise from multiple sites along the parent axons. Only one or a few of the sprouts continue to grow and branch, while others are eliminated. The net rate of axon collateral advance in this second phase is an order of magnitude slower than during the stage of axon elongation. Thus, formation of CNS projections may involve two qualitatively distinct modes of axon growth. The arborization mode contrasts with the elongation mode by the presence of branching, a lack of fasciculation and a slower average rate of extension. The Stereotypic direct advance of axons during elongation also differs from the remodelling which occurs during arborization. The delay between axon arrival at targets and onset of arborization could be a reflection of axons “waiting” for a maturational change to occur in the retina or in targets. Arborization in the LGBd and SC is initiated around the same time, implicating the former possibility. However, a slower differentiation of retinal arbors in the SC, in addition to morphological differences of arbors in the two structures, suggests that alterations in substrate factors also play a critical role in triggering the early stages of arbor formation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of plant growth regulation 10 (1991), S. 71-79 
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract [3H]GA20 (1)1, fed toVicia faba seedlings, was converted to [3H]GA20 glucosyl ester (5) and [3H]GA20-13-0-glucoside (6). The GA20 glucosyl ester (5) was identified by HPLC-RC and by GC-MS of GA20-Me formed by transesterification of (5). The [3H]GA20-Me was crystallized to constant specific radioactivity with authentic GA20-Me. On HPLC-RC the GA20-13-0-glucoside (6) was shown to have the same retention time as an authentic sample. Subsequent enzymic hydrolysis gave a product with an HPLC retention time identical to that of authentic GA20 (1).
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 1 (1991), S. 115-130 
    ISSN: 1572-8870
    Keywords: Phthalocyanine-cobalt complexes ; catalyst ; thiol oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cobalt(II)-phthalocyanines in different environments are investigated as catalysts for the oxidation of thiols. Water-soluble low molecular weight 2,9,10,23-tetracarboxyphthalocyanine (1b) and polymeric phthalocyanine (2b) with carboxylic end groups are prepared. Compound1b is covalently bound at linear and cross-linked poly(chloromethylstyrene) in the presence of pyridine to obtain the water-soluble polymers (3a, b) and gel-type polymers (4a, b). Covalent binding of1b to surface modified silica was also realized. Low molecular weight and polymeric phthalocyanines (1a, 2a) are synthesized on silica, alumina, and charcoal. In addition,1a is encapsulated in the interior of NaX zeolite. All materials are efficient catalysts for the oxidation of 2-mercaptoethanol. The mechanism employing water-soluble catalysts is discussed in the direction of a mononuclear complex coordinating dioxygen and thiol. Heterogeneous catalysts containing1a and2a on the carriers show enhanced activity with increasing dispersion. The proposed mechanism considers different reaction sites for the coordination of O2 and thiol.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: New and used polypropylene tailstrings from the Copper 7 (Cu-7) intrauterine device were examined by a combination of analytical techniques. Optical microscopy, scanning acoustic and electron microscopy, x-ray diffraction, energy dispersive x-ray analysis, and chemical etching were employed to elucidate both the surface and interior morphology of new Cu-7 tailstrings. Tailstrings removed from women following varying periods of use were investigated with optical microscopy, scanning and transmission electron microscopy. In addition, a subset of the used tailstrings were cultured to identify the types of microorganisms associated with them. Our findings show that unused Cu-7 tailstrings are in various stages of degradation owing to a combination of factors which include the high-draw ratio employed during manufacturing, the method of packaging, and the use of a particulate colourant. Furthermore, it is evident that used Cu-7 tailstrings undergo major deterioration while in situ because of the unfavorable interactions between the highly drawn polypropylene and the physiological environment. These results indicate that the polypropylene tailstrings as manufactured for use with the Cu-7 IUD fail to meet accepted design criteria for biomedical implants.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
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