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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymers and the environment 7 (1999), S. 19-26 
    ISSN: 1572-8900
    Keywords: Poly(tetramethylene succinate) ; amorphous and crystalline orientation ; biodegradation ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of orientation in the amorphous and crystalline regions on the biodegradability of PTMS [poly(tetramethylene succinate)] was studied using the amorphous orientation function, birefringence, and crystallinity. The crystalline and amorphous intrinsic lateral sonic moduli, E t,c 0 and E t,am 0 , were 2.61 × 103 and 0.41 × 103 MPa, respectively. Using the data on birefringence, crystalline and amorphous orientation function (f ∈ and f am), crystallinity, and sonic modulus of the oriented PTMS fibers, the intrinsic birefringence of the crystalline (Δ c 0 ) and amorphous (Δ am 0 ) regions were evaluated to be 0.0561 and 0.0634, respectively. The biodegradabilities of oriented PTMS films were reduced as the elongation increased, i.e., the amorphous orientation increased. At low elongation (100 and 150%), however, biodegradabilities remained unchanged when the degradation test was performed in activated sludge, which was attributed to the amorphous orientation occurring even at 100% elongation, though the amorphous orientation direction was perpendicular to the fiber axis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymers and the environment 6 (1998), S. 223-231 
    ISSN: 1572-8900
    Keywords: Degradable aliphatic polyester ; poly(tetramethylene succinate) ; morphology ; hydrolysis ; single crystals ; spherulites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The morphological changes of Poly(tetramethylene succinate) single crystal lamellae by hydrolysis are investigated, using TEM, WAXD and SAXS. And the morphology of PTMS spherulites was also observed by optical microscopy after treatments as well as single crystal lamellae. The edge region of single crystal lamella can be most easily affected in the initial stage of hydrolysis. As the hydrolysis time increases, the lamellae are separated into small fragments which may be started from the uneven or irregular parts of the surface. The WAXD results showed that crystallinity were increased with increasing of treatment time. The lamellar thickness decreased at the initial stage of hydrolysis and increased again. There were cracks on the surface of spherulites after hydrolysis and the direction of cracks were tangential direction of spherulites. This result was thought to be from the uniformity of molecular arrangement in the crystallographic unit cell.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Keywords: Key wordsSchizosaccharomyces pombe ; SNF2/SWI2 protein family ; ATPase/helicase domains ; DNA-binding domain ; Chromodomain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The SNF2/SWI2 ATPase/helicase family comprises proteins from a variety of species, which serve a number of functions, such as transcriptional regulation, maintenance of chromosome stability during mitosis, and various types of DNA repair. Several proteins with unknown functions are also included in this family. The number of genes that belong to this family is rapidly expanding, which makes it easier to analyze the common biological functions of the family members. This study was designed to clone the SNF2/SWI2 helicase-related genes from the fission yeast Schizosaccharomyces pombe in the hope that this would help to elucidate the common functions of the proteins in this family. The hrp1 + (helicase-related gene from S. p ombe) gene was initially cloned by PCR amplification using degenerate primers based on conserved SNF2 motifs within the ERCC6 gene, which encodes a protein involved in DNA excision repair. The hrp1 + ORF codes for an 1373-amino acid polypeptide with a molecular mass of 159 kDa. Like other SNF2/SWI2 family proteins, the deduced amino acid sequence of Hrp1 contains DNA-dependent ATPase/7 helicase domains, as well as a chromodomain and a DNA-binding domain. This configuration is similar to that of mCHD1 (mouse chromo-ATPase/helicase-DNA-binding protein 1), suggesting that Hrp1 is a S. pombe homolog of mCHD1, which is thought to function in altering the chromatin structure to facilitate gene expression. Northern blot analysis showed that the hrp1 + gene produces a 4.6-kb transcript, which reaches its maximal level just before the cells enter the exponential growth phase, and then decreases gradually. DNA-damaging agents, such as MMS, MNNG and UV, decrease the rate of transcription of hrp1 +. Deletion of the hrp1 + gene resulted in accelerated cell growth. On the other hand, overexpression of Hrp1 caused a reduction in growth rate. These results indicate that hrp1 + may act as a negative regulator of cellular growth.
    Type of Medium: Electronic Resource
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