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  • 1980-1984  (11)
  • Polymer and Materials Science  (8)
  • Physics  (4)
  • Periodicity  (2)
  • Acetylcholine esterase  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Rhythmic dentinogenesis in the rabbit incisor: Allometric aspects (1980)
    Springer
    Calcified tissue international 32 (1980), S. 45-53 
    Details
    ISSN: 1432-0827
    Keywords: Dentin ; Periodicity ; Allometry ; Calcium ; Sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have described differences in the aspects of biological rhythms for calcium and sulfur deposition on the labial and lingual sides of the growing rabbit incisor, where growth occurs along a spiral axis. The calcium oscillations appear to be smoother on the labial side than on the lingual side. The lingual side is characterized by high-frequency rhythms with high amplitudes which possess the greatest percent of the power (Fourier analysis). These observations also reflect a difference in behavior of the mean Ca concentration across the labial and lingual sides. Sulfur rhythms on the labial side have higher amplitudes than those on the lingual side, but systematic differences in distribution of power between high and low frequencies is not as pronounced as in the case of Ca. The differences in Ca rhythms reflect differences in the growth rates of incisors on either side of the spiral axis. The labial side grows slightly faster than the lingual side, and its odontoblasts secrete Ca along the spiral axis and toward the pulp cavity at the same time. Thus the resultant direction of growth is more nearly opposite the extension of the occlusal end on the labial side, and Ca is consequently deposited over a wider area relative to that on the lingual surfaces. On the lingual side, Ca is deposited within a more limited area, and growth must therefore be continuous at high frequencies. The distribution of Ca on both sides of the tooth reflects these differences in growth rate and periodicity in two ways. First, given a unit area of tooth, the calcium concentration on the labial side is less than that of the lingual side. Second, whereas the calcium concentration on the labial side declines rapidly from the enamel-dentin junction to the pulp cavity, it is uniformly high across the lingual side because its growth is more continuous at high frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408520
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  • 2
    Electronic Resource
    Electronic Resource
    Rhythmic dentinogenesis in the rabbit incisor: Circadian, ultradian, and infradian periods (1980)
    Springer
    Calcified tissue international 32 (1980), S. 29-44 
    Details
    ISSN: 1432-0827
    Keywords: Rabbit ; Dentin ; Calcium ; Sulfur ; Periodicity ; Circadian ; Ultradian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have identified a variety of biological rhythms involved in the apposition and mineralization of dentin in the rabbit incisor. Animals were injected during the day or night with lead acetate at 2-week intervals—to provide biological time markers in forming dentin—and transverse undecalcified sections of the lower incisors were prepared for electron microprobe analysis. The positions of the lead markers were identified, and the continuous distribution of calcium and sulfur was measured at 1 µm intervals between the markers. In thin sections stained with hematoxylin after decalcification, the widths of a series of structural increments (bands) were measured with an ocular micrometer. Fourier analysis of the data revealed spectra of structural and compositional rhythms with a range of periodicities which extended from a matter of hours [ultradian (〈24 h)] to days [infradian (〉24 h) and circadian (approximately 24 h)]. The structural and compositional rhythms appeared to be independent to the extent that they did not necessarily have the same periods, or amplitudes. Nor were there simple phase relationships between all of the rhythms. At some times, Ca and S fluctuations are inversely proportional (180° out of phase), but in other cases they are directly proportional or out of phase by varying degrees other than 180°. The analyses thus suggest that calcium and sulfur deposition (representing mineral and glycosaminoglycan deposition, respectively) are not simply inversely proportional, and that the hematoxylin-stained structural increments did not solely reflect differences in the distribution of the mineral components in dentin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408519
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  • 3
    Electronic Resource
    Electronic Resource
    Morpholine vapour inhalation and interactions of simultaneous nitrite intake (1983)
    Springer
    Archives of toxicology 53 (1983), S. 143-150 
    Details
    ISSN: 1432-0738
    Keywords: Morpholine ; Nitrite ; Axons ; Acetylcholine esterase ; Creatine kinase ; Succinate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Male Wistar rats exposed intermittently to 300 ppm (12.5 μmol/l) morpholine vapour 5 days a week for 6 h daily during 4–15 weeks displayed an increasing brain solvent content analyzed by a sensitive gas chromatographic method. Rats drinking water which contained 150 mg NaNO2/l during the vapour exposure period showed initially larger brain solvent concentrations which began to decrease after 8 weeks. Fat solvent concentrations were a fraction of those detected in brain of the solvent-exposed animals or of those in the combined exposure. Nitrite exposure alone caused decreased spinal cord axon acetylcholine esterase activity after 8 weeks while this effect was noted in the combined exposure only at 8 weeks disappearing later on. Axonal succinate dehydrogenase activity was below the controls in the combined exposure throughout the study, and combination also caused persistent increase in the muscle creatine kinase activity. The morpholine-induced effects were less remarkable. The results point at pharmacokinetic interaction between the solvent and nitrite with its own effects on energy metabolism. No N-nitrosomorpholine was found although other metabolic interactions could not be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302722
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  • 4
    Electronic Resource
    Electronic Resource
    On the precipitation of proteins by polymers: The hemoglobin - polyethylene glycol system (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2761-2779 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of polyethylene glycol (PEG) of MW 6000 to solutions of oxy- and deoxyhemoglobins results in an increase in the thermodynamic activity of these proteins. This in turn results, when PEG concentration is high enough, in phase separation into two phases; a protein-rich, PEG-poor phase and a PEG-rich, protein-poor phase. With increasing PEG concentration, the protein-rich amorphous phase becomes metastable and is converted into a well-defined crystalline or polymer phase. The logarithm of protein solubility is a linear function of PEG content up to a protein concentration of 150 g/L because the expression for the activity coefficient can, up to this concentration range, be approximated by a logarithmic function. Curvature appears at higher protein concentrations. Activities obtained by extrapolation from linear portions of the function, showing an unchanged, well-defined crystalline state, yield an activity coefficient for the saturated PEG-free protein solution in agreement with the appropriate values obtained from hard-sphere calculations of excluded volume [Ross, P. D. & Minton, A. P. (1977) J. Mol. Biol. 112, 437-452]. Solutions containing two hemoglobin species showed cocrystallization of the hemoglobins with a triple point where two crystal forms can be shown to coexist.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360231206
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  • 5
    Electronic Resource
    Electronic Resource
    Fluctuations of protein structure as expressed in the distribution of hydrogen exchange rate constants (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1049-1068 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen exchange kinetics of proteins provide information about the dynamics of their structure. The interpretation of experiments has been limited by difficulty in identifying individual rate constants. In order to invert the kinetic data, and to gain information about the individual reacting sites, we introduce a Laplace inversion technique and obtain the distribution function of rate constants by which the intricate reaction proceeds. A series of carefully overlapped experiments were performed on lysozyme at 25°C, an exchange profile obtained, and a distribution function extracted. This function was composed of a product of two terms, indicating two parallel pathways. The first, a power-law term, was attributed to exchange from the native state. This part of the distribution function thus describes the scope of the conformational fluctuations in proteins at constant temperature and pressure. The second, an exponential, was seen to be associated with the pathway involving thermal unfolding and subsequent free exchange with the solvent. The influence of trichlorethanol and glycerol on the total distribution function was measured. Trichloroethanol selectively increased the contribution from the thermal unfolding pathway, whereas glycerol, besides decreasing this type of contribution, increased the width of the distribution function attributed to structural fluctuations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190509
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of cured polystyrylpyridine by model compoundsPresented at the 1979 Pacific Conference on Chemistry and Spectroscopy in Pasadena, California on 10-12 October 1979. (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1975-1987 
    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 crosslinking or curing reaction of polystyrylpyridine (PSP) has been studied by means of thermal reactions of its model compounds. Compounds 2,6-distyrylpyridine, 4-stilbazole (4-styrylpyridine), and deuterated 4-stilbazole were pyrolyzed at 200-325°C both in air and under vacuum in a sealed tube. The major pyrolysis products were diarylethane and stilbene, and were characterized by gas chromatography-mass spectrometry. Major dimeric products were naphthalene or quinoline derivatives. Mechanisms for the pyrolysis are suggested, and a crosslinked structure for cured PSP is proposed based on the thermal reaction products of model compounds.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260621
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  • 7
    Electronic Resource
    Electronic Resource
    Toxicity of polyurethane-derived oxidative thermal decomposition productsAbbreviations: GSH = reduced glutathione; MDA = 4,4′-diaminodiphenylmethane; MDI = 4,4′diphenylmethane diisocyanate; NADPH = reduced nicotinamide-adenine; dinucleotide phosphate; UDP = uridine-5′-diphosphate (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 6 (1982), S. 96-98 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fam.810060210
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  • 8
    Electronic Resource
    Electronic Resource
    Photorearrangements of hydrocarbon polymers with pendant double bondsPresented at the Division of Polymer Chemistry at the ACS/CSJ Chemical Congress, Honolulu, Hawaii, April 1979. (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 2543-2560 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study was made of the microstructural changes that occur in ultraviolet irradiation under vacuum of thin films of 1,2-poly(cis-1,4-hexadiene) (CHD), 1,2-poly(trans-1,4-hexadiene) (THD), 1,2-poly(trans-1,3-pentadiene) (TPD), equibinary (1,2,-1,4) polybutadiene (EB), and equibinary (3,4-1,4) polyisoprene (EI). These polymers - all containing pendant double bonds - undergo important photoinduced loss of unsaturation, presumably through cyclization of the double bonds, by analogy to the previously reported photocyclization of 1,2-polybutadiene (VB) and 3,4-polyisoprene (VI)films. For the equibinary polymers, which contain internal as well as external (or pendant) double bonds, the loss of unsaturation is considered to involve photocyclization of 1,2-1,4 and 1,2-1,2 dyads in EB and of 3,4-1,4 and 3,4-3,4 dyads in EI. Accompanying thecyclization process in CHD, THD, and TPD is a direct photochemical cis-trans isomerization of —CH=CH—double bonds analogous to that originally noted for 1,4-polybutadiene. The photorearrangements in the above polymers with pendant double bonds were compared to the corresponding thermally induced rearrangements reported previoulsy;for VB and VI, in particular, the thermal, photo-and radiation-induced cycli-zations were found to be very similar, possibly having a common nonradical, nonionic mechanism involving excited double bonds.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180813
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  • 9
    Electronic Resource
    Electronic Resource
    Photoconductivity of poly(hexamethylene adipamide) (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 523-527 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photocurrents induced by pulsed ultraviolet light in polyhexamethylene adipamide (nylon-66) have been studied. Two transient photocurrents are observed for light wavelenghts shorter than 3000 Å;. The first one is weakly field and temperature dependent and has been ascribed to electron photoinjection. On the whole, the time dependence of the two photoresponses suggests the possible formation of a space charge in the material.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.180180311
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal expansion of epoxy-resin/particle composites - a size effect (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 217-226 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal expansion of epoxy-resin (Epikote 828)/particle composites has been measured in the range 77 to 450 K. The fillers used were Cu spheres (seven sizes from 5 to 150 μm diameter) and glass ballotini spheres (three sizes from 3.5 to 200 μm diameter). The volume concentrations used were 0.3 and 0.5 for Cu and 0.3 for glass. The experiments show that the addition of filler raises the glass transition temperature Tg, especially for fine particles. Below the normal value of Tg the thermal expansion is independent of particle size while above Tg the expansion is considerably smaller for samples containing the smaller particles. The effect is more pronounced for Cu than for glass filler. In addition a rapid heating rate reduces the expansion for specimens containing smaller particles but it does not effect the expansion for those containing large particles. The results, which are discussed in the light of the work of other authors, suggest that the addition of particles increases Tg by changing the nature of the polymer not only immediately at the particle surface but also for a considerable distance into the polymer itself. This probably occurs because the epoxy bonds strongly to the particles and this inhibits segmental rotations of the polymer even at considerable distances from the particle surface.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.180180204
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