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  • Artikel  (3.734)
  • Chemical Engineering  (3.542)
  • Saccharomyces cerevisiae
  • Wiley-Blackwell  (3.565)
  • Springer  (169)
  • 1985-1989  (3.734)
  • 1
    Digitale Medien
    Digitale Medien
    Biotransformation of aromatic aldehydes bySaccharomyces cerevisiae: Investigation of reaction rates (1989)
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 49-53 
    Details
    ISSN: 1476-5535
    Schlagwort(e): l-Phenylacetyl carbinol ; Saccharomyces cerevisiae ; Yeast ; Benzaldehyde ; Biotransformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The rate of production ofl-phenylacetyl carbinol bySaccharomyces cerevisiae in reaction mixtures containing benzaldehyde with sucrose or pyruvate as cosubstrate was investigated in short 1 h incubations. The effect of yeast dose rate, sucrose and benzaldehyde concentration and pH on the rate of reaction was determined. Maximum biotransformation rates were obtained with concentrations of benzaldehyde, sucrose and yeast of 6 g, 40 g and 60 g/l, respectively. Negligible biotransformation rates were observed at a concentration of 8 g/l benzaldehyde. The reaction had a pH optimum of 4.0–4.5. Rates of bioconversion of benzaldehyde and selected substituted aromatic aldehydes using both sucrose and sodium pyruvate as cosubstrate were compared. The rate of aromatic alcohol production was much higher when sucrose was used rather than pyruvate.o-Tolualdehyde and 1-chlorobenzaldehyde were poor substrates for aromatic carbinol formation although the latter produced significant aromatic alcohol in sucrose-containing media. Yields of 2.74 and 3.80 g/l phenylacetyl carbinol were produced from sucrose and pyruvate, respectively, in a 1 h reaction period.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01569693
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  • 2
    Digitale Medien
    Digitale Medien
    High solids fermentation of hydrolysates of wheat starch B in a continuous dynamic immobilized biocatalyst bioreactor (1989)
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 81-84 
    Details
    ISSN: 1476-5535
    Schlagwort(e): Ethanol fermentation ; Wheat starch ; Saccharomyces cerevisiae ; immobilization ; Continuous dynamic immobilized biocatalyst bioreactor ; Biocatalyst bioreactor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A simple and efficient method of conversion of wheat starch B to ethanol was investigated. Employing a two-stage enzymatic saccharification process, 95% of the wheat starch was converted to fermentable sugars in 40 h. From 140 g/l total sugars in the feed solution, 63.6 g/l ethanol was produced continuously with a residence time of 3.3 h in a continuous dynamic immobilized biocatalyst bioreactor by immobilized cells ofSaccharomyces cerevisiae. The advantages and the application of this bioreactor to continuous alcoholic fermentation of industrial substrates are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01569698
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  • 3
    Digitale Medien
    Digitale Medien
    Manganese accumulation in yeast cells (1989)
    Springer
    BioMetals 2 (1989), S. 6-10 
    Details
    ISSN: 1572-8773
    Schlagwort(e): Manganese ; Electron spin resonance ; Superoxide dismutase ; Saccharomyces cerevisiae ; Yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Manganese accumulation was studied by room-temperature electron spin resonance (ESR) spectroscopy inSaccharomyces cerevisiae grown in the presence of increasing amounts of MnSO4. Mn2+ retention was nearly linear in intact cells for fractions related to both low-molecular-mass and macromolecular complexes (‘free’ and ‘bound’ Mn2+, respectively). A deviation from linearity was observed in cell extracts between the control value and 0.1 mM Mn2+, indicating more efficient accumulation at low Mn2+ concentrations. The difference in slopes between the two straight lines describing Mn2+ retention at concentrations lower and higher than 0.1 mM, respectively, was quite large for the free Mn2+ fraction. Furthermore it was unaffected by subsequent dialyses of the extracts, showing stable retention in the form of low-molecular-mass complexes. In contrast, the slope of the line describing retention of ‘bound’ Mn2+ at concentrations higher than 0.1 mM became less steep after subsequent dialyses of the cell extracts. This result indicates that the macromolecule-bound Mn2+ was essentially associated with particulate structures. In contrast to Cu2+, Mn2+ had no effect on the major enzyme activities involved in oxygen metabolism except for a slight increase of cyanide-resistant Mn-superoxide dismutase activity, due to dialyzable Mn2+ complexes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01116194
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  • 4
    Digitale Medien
    Digitale Medien
    Heterologous gene expression of the glyphosate resistance marker and its application in yeast transformation (1989)
    Springer
    Current genetics 15 (1989), S. 91-98 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Vector ; Glyphosate resistance ; Transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The E. coli aroA gene was inserted between yeast promoter and terminator sequences in different shuttle expression plasmids and found to confer enhanced EPSP synthase activity as well as resistance to glyphosate toxicity. Subsequently, a transformation system using these newly constructed vectors in yeast was characterized. The efficiency of the glyphosate resistance marker for transformation and selection with plasmid pHR6/20-1 in S. cerevisiae laboratory strain SHY2 was found to be relatively high when compared with selection for LEU2 prototrophy. The fate of the recombinant plasmid pHR6/20-1 in the transformants, the preservation of the aroA E. coli DNA fragment in yeast, mitotic stability, EPSP synthase activity, and growth on glyphosate-containing medium have been investigated. As this plasmid also allows direct selection for glyphosate resistant transformants on rich media, the glyphosate resistance marker was used for transforming both S. cerevisiae laboratory strain SHY2 and brewer's yeast strains S. cerevisiae var. “uvarum” BHS5 and BHS2. In all cases, the vector pHR6/20-1 was maintained as an autonomously replicating plasmid. The resistance marker is, therefore, suitable for transforming genetically unlabeled S. cerevisiae laboratory, wild, and industrial yeast strains.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00435454
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  • 5
    Digitale Medien
    Digitale Medien
    A hot-spot for transposition of various Ty elements on chromosome V in Saccharomyces cerevisiae (1989)
    Springer
    Current genetics 16 (1989), S. 247-252 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Chromosome V ; Ty elements ; tRNA genes ; Transposition hot-spots ; Yeast polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Ty4 is a novel transposable element in the yeast, Saccharomyces cerevisiae, which is present in only a few copies in the genome (Stucka et al. 1989). In strain C836 one of the three copies (Ty4-90) is contained in cosmid clone c90, where it resides on chromosome V. Analysis of this region reveals a “hot-spot” of transposition: in addition to Ty4-90, the locus contains a complete Ty3 element and seven singular delta, sigma and tau elements. Three tRNA genes (for His, Lys, and Ile) are located in this region, and these are closely associated with one or the other of the elements, a phenomenon commonly observed in yeast. A comparison of c90 with corresponding regions from other strains shows that the locus is highly polymorphic and that this polymorphism is explicitly associated with Ty transposition and recombination events.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00422110
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  • 6
    Digitale Medien
    Digitale Medien
    Mutations in ADE3 reduce the efficiency of the omnipotent suppressor sup45-2 (1989)
    Springer
    Current genetics 16 (1989), S. 315-321 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Antisuppressor ; ADE3 ; Translation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Mutations in a known yeast gene, ADE3, were shown to act as an antisuppressor, reducing the efficiency of the omnipotent suppressor, sup45-2. The ADE3 locus encodes the trifunctional enzyme C1-tetrahydrofolate synthase, which is required for the biosynthesis of purines, thymidylate, methionine, histidine, pantothenic acid and formylmethionyl-tRNAfmet. The role of this enzyme in translational fidelity had not previously been suspected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00340709
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  • 7
    Digitale Medien
    Digitale Medien
    Two new loci that give rise to dominant omnipotent suppressors in Saccharomyces cerevisiae (1989)
    Springer
    Current genetics 16 (1989), S. 323-330 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Yeast ; Saccharomyces cerevisiae ; Nonsense suppression ; Omnipotent suppressors ; Gene mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Ten dominant omnipotent suppressors of Saccharomyces cerevisiae, which were previously shown to be different from SUP46, have been examined. Nine are mapped in a region between lys5 and cyh2 on the left arm of chromosome VII. These suppressors, like SUP46, manifest sensitivity to increased temperature and the antibiotics paromomycin and hygromycin B. In addition, they have an identical action spectrum. These results strongly suggest that they are allelic to each other and they are designated SUP138. The tenth is mapped to a position between his1 and arg6 on the right arm of chromosome V. This suppressor, named SUP139, does not manifest temperature sensitivity nor antibiotic sensitivity. SUP139 and SUP138, which are clearly distinguished by means of action spectrum, act on much fewer nonsense mutations than SUP46. It is now clear that dominant omnipotent suppressors arising at a single locus are homogeneous and that their efficiency is locus-dependent. The order of efficiency is SUP46〉SUP138〉SUP139.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00340710
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  • 8
    Digitale Medien
    Digitale Medien
    The Saccharomyces cerevisiae RAD2 gene complements a Schizosaccharomyces pombe repair mutation (1989)
    Springer
    Current genetics 15 (1989), S. 27-30 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Yeast ; Repair ; Complementation ; Saccharomyces cerevisiae ; Schizosaccharomyces pombe ; Gene cloning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Two Saccharomyces cerevisiae genes necessary for excision repair of UV damage in DNA, RAD1 and RAD2, were introduced individually, on a yeast shuttle vector, into seven Schizosaccharomyces pombe mutants — rads1, 2, 5, 13, 15,16 and 17. The presence of the cloned RAD1 gene did not affect survival of any of the S. pombe mutants. The RAD2 gene increased survival of S. pombe rad13 to near the wild-type level after UV irradiation and had no effect on any of the other mutants tested. S. pombe rad13 mutants are somewhat defective in removal of pyrimidine dimers so complementation by the S. cerevisiae RAD2 gene suggests that the genes may code for equivalent proteins in the two yeasts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00445748
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  • 9
    Digitale Medien
    Digitale Medien
    Introduction of nonselectible 2μ plasmid into [cir°] cells of the yeast S. cerevisiae by DNA transformation and in vivo site-specific resolution (1989)
    Springer
    Current genetics 15 (1989), S. 83-90 
    Details
    ISSN: 1432-0983
    Schlagwort(e): DNA transformation ; Saccharomyces cerevisiae ; Site-specific recombination ; 2μ DNA plasmid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The 2μ DNA plasmid of the yeast Saccharomyces cerevisiae does not confer any known selectable phenotype to the host cell carrying it. Selection of cells transformed with purified 2μ DNA therefore cannot be achieved, and the intracellular presence of 2μ can only be assessed by molecular analysis of the DNA complement. In addition, 2μ alone does not replicate in bacterial hosts, thus rendering its amplification by conventional methods impossible. We have isolated a shuttle plasmid, pBH-2L, generated by in vivo sites-pecific recombination between the endogenous 2μ DNA plasmid and pRL, a pBR322 derivative containing the yeast LEU2 gene and one 2μ repeat sequence associated with the origin of replication. This new shuttle plasmid has the property, when transformed into yeast, of undergoing site-specific recombinational resolution between its two direct repeat sequences. This releases 2μ plasmid and pRL as individual molecules. The latter can undergo progressive mitotic loss during growth in nonselective medium, ultimately leaving leucine auxotrophic transformants that contain only 2μ DNA plasmid. This system can be utilized to introduce 2μ DNA alone into cells lacking it, thereby providing a novel means to study the biology and the molecular genetics of the plasmid and its potential practical applications as a vector.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00435453
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  • 10
    Digitale Medien
    Digitale Medien
    A galactose-dependent cmd1 mutant of Saccharomyces cerevisiae: involvement of calmodulin in nuclear division (1989)
    Springer
    Current genetics 15 (1989), S. 113-120 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Calmodulin mutant ; Nuclear division ; Chromosome stability ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The coding region of a yeast calmodulin gene was fused to a galactose-inducible GAL1 promoter, and a conditional-lethal mutant of Saccharomyces cerevisiae, in which the expression of calmodulin was regulated by galactose, was constructed. The mutant grew normally in galactose medium, but in glucose medium, in which the promoter was repressed, it ceased growing after 12–15 h. The growth arrest was associated with a decrease in intracellular calmodulin levels: after 12h, no intracellular calmodulin protein was detectable. Analysis of the terminal phenotype showed that when the cell stopped growing, it had a bud, a nucleus after S-phase and a short mitotic spindle. Thus, the defect was mainly in nuclear division. Bud growth was partially inhibited in these cells: 27% of the cells stopped growing with a small bud. Furthermore, calmodulin-deficient cells showed elevated rates of chromosome loss, possibly as the result of a defect in the precise segregation of chromosomes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00435457
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  • 11
    Digitale Medien
    Digitale Medien
    A rapid and simple method for extracting yeast mitochondrial DNA (1989)
    Springer
    Current genetics 15 (1989), S. 235-237 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Mitochondrial DNA ; Method of extraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A rapid method for the extraction of yeast mitochondrial DNA (mtDNA) is described. In comparison with previous methods, it simplifies several steps, does not require either the isolation of mitochondria or phenol treatment and is less time consuming. This protocol gives a high yield of pure mtDNA (50–120 μg from a 100-ml culture), which can be directly used in various molecular applications: restriction enzyme digestion, electrophoresis, blotting, labeling, cloning and sequencing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00435511
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  • 12
    Digitale Medien
    Digitale Medien
    Molecular characterization of the two genes SNQ and SFA that confer Hyperresistance to 4-nitroquinoline-N-oxide and formaldehyde in Saccharomyces cerevisiae (1989)
    Springer
    Current genetics 16 (1989), S. 65-74 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Mutagen hyperresistance ; Southern, Northern analysis ; Gene transplacement ; Transposon mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The genes SNQ and SFA confer hyperresistance to 4-NQO and FA when present on a multi-copy plasmid in yeast. Both are non-essential genes since transplacement of SNQ by a disrupted snq-0::LEU2 yielded stable and viable haploid integrants. Southern analysis revealed that SNQ and SFA are single-loci genes, and OFAGE analysis showed that they are located on chromosome XIII and IV, respectively. Northern blot analysis of SNQ and SFA revealed poly(A)+ RNA transcripts of 2 kb and 1.7 kb, respectively. Nuclease S 1 mapping showed SNQ to have a coding region of 1.6 kb and SFA, one of 1.3 kb. The 5′ coding regions were determined for both genes, while the 3′ end could only be determined for gene SNQ. Both genes do not appear to contain introns. The SFA locus was also mapped by transposon mutagenesis. Tn10-LUK integrants disrupted the SFA gene function at sites that were determined by subcloning to lie within the SFA transcription unit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00393397
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  • 13
    Digitale Medien
    Digitale Medien
    Cloning and characterization of the SKI3 gene of Saccharomyces cerevisiae demonstrates allelism to SKI5 (1989)
    Springer
    Current genetics 16 (1989), S. 139-143 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; SKI3 ; SKI5 ; M1 dsRNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have identified a mutant strain of the yeast Saccharomyces cerevisiae which overproduces killer toxin. This strain contains a single mutation which fails to complement defects in both the SKI3 and SKI5 genes, while a cloned copy of this gene complements both the ski3 and ski5 defects. The level of secreted toxin from a cDNA based plasmid is not increased in a ski3 strain, showing that the overproduction phenotype is dependent upon an increased level of M1 dsRNA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00391469
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  • 14
    Digitale Medien
    Digitale Medien
    Reassessing the genotoxic potential of 8-MOP + UVA-induced DNA damage in the yeast Saccharomyces cerevisiae (1989)
    Springer
    Current genetics 16 (1989), S. 75-80 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Psoralen photoaddition ; Interstrand cross-link ; Repair deficiency ; Genotoxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Two different UVA irradiation systems were initially biologically calibrated with two haploid yeast strains proficient and deficient, respectively, in nucleotide excision repair. The number of DNA lesions introduced into the cell's genome by the photoactivated bifunctional furocoumarin 8-MOP was then calculated by means of the applied UVA exposure doses. At LD37 the repair-proficient wild type had about 14 ICL and 34 furan-side monoadducts in its DNA, while doubly blocked repair mutant rad3-12 pso1-1 had 2 ICL and 3 monoadducts. Locus-specific reversion of lys1-1 followed two-hit kinetics in the repair-proficient wild type and one-hit kinetics in an excision-deficient rad2-20 mutant, as would be expected if ICL was the main type of mutagenic lesion in the wild type and monoadducts the main mutagenic lesion type in the excision-deficient strain. Quantitative comparison of 8-MOP + UVA-induced ICL with those induced by bifunctional mustard revealed the former to have a much higher genotoxicity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00393398
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  • 15
    Digitale Medien
    Digitale Medien
    The α-factor enhancement of hybrid formation by protoplast fusion in Saccharomyces cerevisiae can be mimicked by other procedures (1989)
    Springer
    Current genetics 15 (1989), S. 303-305 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces cerevisiae ; Protoplast fusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The percentage of hybrids formed during protoplast fusion in Saccharomyces cerevisiae is determined by the percentage of protoplasts at the GI/S boundary of the cell cycle.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00447049
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  • 16
    Digitale Medien
    Digitale Medien
    Biosynthesis of the peroxisomal dihydroxyacetone synthase from Hansenula polymorpha in Saccharomyces cerevisiae induces growth but not proliferation of peroxisomes (1989)
    Springer
    Current genetics 16 (1989), S. 13-20 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Peroxisomes ; Protein import ; Saccharomyces cerevisiae ; Hansenula polymorpha
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The DAS gene of Hansenula polymorpha was expressed in Saccharomyces cerevisiae under the control of different promoters. The heterologously synthesized dihydroxyacetone synthase (DHAS), a peroxisomal enzyme in H. polymorpha, shows enzymatic activity in baker's yeast. The enzyme was imported into the peroxisomes of S. cerevisiae not only under the appropriate physiological conditions for peroxisome proliferation (oleic acid media), but also in glucose-grown cells where it induced the enlargement of the few peroxisomes present. This growth process was not accompanied by an increase in the number of microbodies, which suggests a separate control mechanism for peroxisomal proliferation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00411078
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  • 17
    Digitale Medien
    Digitale Medien
    A DNA sequence in Saccharomyces exiguus is homologous with the HO gene of Saccharomyces cerevisiae (1989)
    Springer
    Current genetics 15 (1989), S. 399-401 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Saccharomyces exiguus ; Saccharomyces cerevisiae ; HO gene ; MAT gene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The DNA of Saccharomyces exiguus was analyzed by Southern hybridization using cloned MATa, MATα, and HO genes of Saccharomyces cerevisiae as probes. It was shown that S. exiguus has a DNA sequence homologous with the HO gene of S. cerevisiae and that this DNA sequence is on a chromosome of about 940 kb of DNA in S. exiguus. However, there is no DNA sequence in S. exiguus that is homologous with the MAT genes of S. cerevisiae.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00376794
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  • 18
    Digitale Medien
    Digitale Medien
    Kinetic analysis and simulation of glucose transport in plasma membrane vesicles of glucose-repressed and derepressedSaccharomyces cerevisiae cells (1989)
    Springer
    Cellular and molecular life sciences 45 (1989), S. 1018-1023 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Saccharomyces cerevisiae ; growth conditions ; kinaseless mutant ; plasma membrane vesicles ; glucose transport ; kinetics and computer simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In this study experimental data on the kinetic parameters investigated by other authors1–5, 11 together with own data on plasma membrane vesicles, have been subjected to a computer simulation based on the equations describing facilitated diffusion. The simulation led to an ideal fit describing the above data. From this it can be concluded that glucose is transported by facilitated diffusion, and not by active transport as was postulated by Van Steveninck14, 15. The simulation method also demonstrates that the fast sampling technique used by these authors1–5,11 underestimates the fluxes. Thus, the parameters given do not contribute to the understanding of glucose transport under different metabolic conditions. The K value of plasma membrane vesicles prepared from glucose-repressed cells is around 7 mM. Derepression, particularly by galactose, causes a highly significant increase in affinity as shown by a decrease in the K value to 2 mM. The highest affinity was measured in a triple kinaseless mutant grown on glycerol with a K value of 1 mM. If seems, therefore, that the kinetic parameters derived from initial uptake rates of glucose in intact cells1–5,11 using single flux analysis, such as Eadie-Hofstee- or Lineweaver-Burk-plots, are in error.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01950152
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  • 19
    Digitale Medien
    Digitale Medien
    Effects of nucleotides and divalent cations on phospholipase activity in Saccharomyces cerevisiae (1989)
    Springer
    Archives of microbiology 151 (1989), S. 154-158 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Saccharomyces cerevisiae ; Yeast ; Phospholipase B ; Lysophospholipase ; Enzyme inhibition ; AMP ; Unesterified fatty acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 μM. The inhibition by nucleotides in low concentrations is enhanced by divalent cations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00414431
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  • 20
    Digitale Medien
    Digitale Medien
    Genetic analysis of inducible sexual agglutination ability in the yeast Saccharomyces cerevisiae (1989)
    Springer
    Archives of microbiology 151 (1989), S. 198-202 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Sexual agglutination ; Mating ; Saccharomyces cerevisiae ; Yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Genetic regulation of the inducibility of sexual agglutination ability in the yeast Saccharomyces cerevisiae was studied. Detailed analysis of the degree of sexual agglutination was carried out; it showed that a greater number of genes are involved in the regulation of inducible sexual agglutination in strain H1-0 than previously assumed. Although dominancy of inducible phenotype over constitutive was confirmed, the effectiveness of one gene changing the constitutive phenotype to the inducible seemed to be somewhat low. Quantity per cell of agglutination substances responsible for sexual agglutination increased as the agglutination ability became greater.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00413130
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  • 21
    Digitale Medien
    Digitale Medien
    A similar protein portion for two exoglucanases secreted by Saccharomyces cerevisiae (1989)
    Springer
    Archives of microbiology 151 (1989), S. 391-398 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Saccharomyces cerevisiae ; Exoglucanases ; Purification ; Protein moieties ; Tunicamycin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Exoglucanase (exo-1,3-β-D-glucan glycohydrolase, EC 3.2.1.56) activity secreted by Saccharomyces cerevisiae into the culture medium was separated by ion exchange chromatography into two glycoprotein isoenzymes which contributed 10% (exoglucanase I) and 90% (exoglucanase II) towards the total activity. Analysis of the “in vitro” deglycosylated products by polyacrylamide gel electrophoresis under native or denaturing conditions indicated that the protein portions of both exoglucanases exhibited identical mobility, each one consisting of two polypeptides with M r of 47000 and 48000. The same profile was shown by the exoglucanase secreted in the presence of tunicamycin. Antibodies raised against the protein portion of exoglucanase II did react with both native exoglucanases and their deglycosylated products with a pattern indicative of immunological identity. Digestion of the “in vitro” deglycosylated products of both exoglucanases with Staphylococcus aureus V-8 protease or trypsin generated the same proteolytic fragments in each case. Only exoglucanase II was secreted by protoplasts. These and previously reported results indicate that the protein portions of both isoenzymes may be the product of the same gene (or a family of related genes), and that exoglucanase I is a product of enzyme II, modified by a process occurring beyond the permeability barrier of the cell.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00416596
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  • 22
    Digitale Medien
    Digitale Medien
    Cloning of the LEU2 gene of Saccharomyces cerevisiae by in vivo recombination (1989)
    Springer
    Archives of microbiology 152 (1989), S. 263-268 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Saccharomyces cerevisiae ; Recombination ; Tryptophan cluster ; Yeast vectors ; Plasmid copy number
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We describe a convenient method for the in vivo construction of large plasmids that possess a multitude of restriction sites. A large (23 kbases) circular self-replicating plasmid carrying a partial LEU2-d gene was cotransformed with a circular non-replicating plasmid carrying the entire LEU2 gene. In vivo recombination results preferentially in a plasmid that carries both the LEU2-d and the entire LEU2 gene. In addition we also found one plasmid with a tandem LEU2 insertion and one plasmid where the LEU2-d gene was replaced by the entire LEU2 gene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00409661
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  • 23
    Digitale Medien
    Digitale Medien
    Dependence of inessential late gene expression on early meiotic events in Saccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 215 (1989), S. 490-500 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Meiosis ; Saccharomyces cerevisiae ; Sporulation ; Inessential genes ; Meiosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary SPR3 is one of at least nine genes which are expressed in sporulating Saccharomyces cerevisiae cells at the time of meiosis I. We show below that strains homozygous for null alleles of SPR3 are capable of normal meiosis and the production of viable ascospores. We have also monitored SPR3 expression in a series of strains that are defective in meiotic development, using an SPR3: lacZ fusion carried on a single copy plasmid. β-Galactosidase activity occurred at wild-type levels in diploid strains homozygous for mutations in spo13, rad50, rad57 and cdc9, but was greatly reduced in strains carrying cdc8 or spo7 defects. We conclude that SPR3 expression is a valid monitor of early meiotic development, even though the gene is inessential for the sporulation process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00427048
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  • 24
    Digitale Medien
    Digitale Medien
    Structure of the HOM2 gene of Saccharomyces cerevisiae and regulation of its expression (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 149-154 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; HOM2 gene ; Aspartic semi-aldehyde ; General control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In Saccharomyces cerevisiae the HOM2 gene encodes aspartic semi-aldehyde dehydrogenase (ASA DH). The synthesis of this enzyme had been shown to be derepressed by growth in the presence of high concentrations of methionine. In the present work we have cloned and sequenced the HOM2 gene and found that the promoter region of this gene bears one copy of the consensus sequence for general control of amino acid synthesis. This prompted us to study the regulation of the expression of the HOM2 gene. We have found that ASA DH is the first reported enzyme of the related threonine and methionine pathway to be regulated by the general control of amino acid synthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00330954
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  • 25
    Digitale Medien
    Digitale Medien
    Chromatin structure of the 5′ flanking region of the yeastLEU2 gene (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 464-470 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Nucleosome positioning ; LEU2 gene ; Saccharomyces cerevisiae ; tRNA3 Leu gene ; Chromatin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The chromatin structure of theLEU2 gene and its flanks has been studied by means of nuclease digestion, both with micrococcal nuclease and DNase I. The gene is organized in an array of positioned nucleosomes. Within the promoter region, the nucleosome positioning places the regulatory sequences, putative TATA box and upstream activator sequence outside the nucleosomal cores. The tRNA3 Leu gene possesses a characteristic structure and is protected against nucleases. Most of the 5′ flank is sensitive to DNase I digestion, although no clear hypersensitive sites were found. The chromatin structure is independent of either the transcriptional state of the gene or the chromosomal or episomal location. Finally, in the plasmid pJDB207, which lacks most of the promoter, we have found that the chromatin structure of the coding region is similar to that of the wild-type allele.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02464918
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  • 26
    Digitale Medien
    Digitale Medien
    The naturally occurring silent invertase structural gene suc2° contains an amber stop codon that is occasionally read through (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 511-516 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Nonsense mutation ; Read-through ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The yeast invertase structural gene SUC2 has two naturally occurring alleles, the active one and a silent allele called suc2°. Strains carrying suc2° are unable to ferment sucrose and do not show detectable invertase activity. We have isolated suc2° and found an amber codon at position 232 of 532 amino acids. However, transformants carrying suc2° on a multicopy plasmid were able to ferment sucrose and showed detectable invertase activity. Full-length invertase was found in gels stained for active invertase and in immunoblots. Therefore we concluded that the amber codon is occasionally read as an amino acid. The calculated frequency of read-through is about 4% of all translation events.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00334398
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  • 27
    Digitale Medien
    Digitale Medien
    Expression and DNA sequence of RED1, a gene required for meiosis I chromosome segregation in yeast (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 293-301 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Sporulation ; DNA sequence ; Saccharomyces cerevisiae ; Meiosis ; Chromosome segregation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Genetic studies have previously demonstrated that the RED1 gene of Saccharomyces cerevisiae is required for chromosome segregation at the first meiotic division. Northern blot hybridization analysis indicates that the RED1 gene produces two transcripts of 2.75 and 3.2 kilobases. The major 2.75 kb transcript is not present in mitotic cells and is meiotically induced to accumulate maximally just prior to the meiosis I division. The DNA sequence of the RED1 gene was determined and used to predict the amino acid sequence of the encoded gene product. The RED1 protein is 827 amino acids in length and has a molecular weight of 95.5 kilodaltons. There is no significant homology between the RED1 amino acid sequence and other known protein sequences, including those encoded by genes essential for meiosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00331281
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  • 28
    Digitale Medien
    Digitale Medien
    Mutant invertase proteins accumulate in the yeast endoplasmic reticulum (1989)
    Springer
    Molecular genetics and genomics 215 (1989), S. 401-406 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Protein secretion ; Saccharomyces cerevisiae ; Invertase ; Endoplasmic reticulum ; Secretion mutants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Intercompartmental transport of secreted proteins in yeast was analysed using invertase mutants. Deletions and insertions at the BamHI (position +787) or the Asp718 (position +1159) sites of the SUC2 gene led to mutant proteins with different behaviour regarding secretion, localization and enzyme activity. The deletion mutants showed accumulation of core glycosylated material in the endoplasmic reticulum (ER) a decrease of secreted protein by 5%–30% and loss of enzyme activity. The secreted material was localized in the culture medium and not — as is normal for invertase-in the cell wall. No delay in transport from the Golgi to the cell surface was observed, indicating that the rate-limiting step for secretion is at the ER-Golgi stage. Two insertion mutants, pIPA and pIPB, retained enzyme activity. Mutant pIPB showed 10% secretion, while 60%–70% secretion was observed for pIPA. While the non-secreted material accumulated in the ER, the secreted material was present in the cell wall. The results suggest that the presence of structures incompatible with secretion leads to ER accumulation of mutated invertase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00427036
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  • 29
    Digitale Medien
    Digitale Medien
    The bI4 RNA mitochondrial maturase of Saccharomyces cerevisiae can stimulate intra-chromosomal recombination in Escherichia coli (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 70-74 
    Details
    ISSN: 1617-4623
    Schlagwort(e): RNA splicing ; Maturase ; Recombinase ; Mitochondria ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary When the bI4 RNA maturase, encoded by the fourth intron of the mitochondrial cytochrome b gene of Saccharomyces cerevisiae, was expressed in Escherichia coli, formation of intra-chromosomal Lac+ recombinants was stimulated threefold. This “hyper-rec” phenotype was recA as well as recBCD dependent. The most active form of the bI4 maturase stimulated homologous recombination whereas splicing deficient mutants of bI4 maturase were either deficient in or unable to stimulate homologous recombination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00332232
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  • 30
    Digitale Medien
    Digitale Medien
    In vitro and in vivo studies on the mitochondrial import of CBS1, a translational activator of cytochrome b in yeast (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 162-167 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Nucleotide sequence ; PET gene ; Mitochondrial import ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Translation of mitochondrial cytochrome b mRNA in yeast is activated by the product of the nuclear gene CBS1. CBS1 encodes a 27 kDa precursor protein, which is cleaved to a 24 kDa mature protein during the import into isolated mitochondria. The sequences required for mitochondrial import reside in the amino-terminal end of the CBS1 precursor. Deletion of the 76 amino-terminal amino acids renders the protein incompetent for mitochondrial import in vitro and non-functional in vivo. When present on a high copy number plasmid and under the control of a strong yeast promoter, biological function can be restored by this truncated derivative. This observation indicates that the CBS1 protein devoid of mitochondrial targeting sequences can enter mitochondria in vivo, possibly due to a bypass of the mitochondrial import system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00330956
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  • 31
    Digitale Medien
    Digitale Medien
    Mitochondrial introns aI1 and/or aI2 are needed for the in vivo deletion of intervening sequences (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 168-171 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Mitochondrial introns ; Reverse transcriptase ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Some pet- (or mit-) mutations impeding the splicing of one or several intron(s) of the yeast mitochondrial pre-mRNA(s) are suppressed in vivo by the DNA deletion of these introns. We have genetically demonstrated that introns aI1 and/or aI2 of the cytochrome c oxidase subunit 1 gene are necessary for this deletion process. The facts that adjacent introns are simultaneously deleted and that, in the pet- (or mit-) mutants which easily revert by intron deletion, the splicing of the introns they affect is only partially blocked, suggest that the intron encoded proteins aI1 and/or aI2 could intervene by means of their putative reverse transcriptase activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00330957
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  • 32
    Digitale Medien
    Digitale Medien
    Reassembly of microtubules in protoplasts ofSaccharomyces cerevisiae after nocodazole-induced depolymerization (1989)
    Springer
    Protoplasma 151 (1989), S. 98-105 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Microtubule neoformation ; Nocodazole ; Protoplasts ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary By following microtubule neoformation after their complete destruction by nocodazole, we analyzed the pattern of microtubule nucleation in protoplasts ofSaccharomyces cerevisiae. Using immunofluorescence, the drug was shown to induce rapid and complete disassembly of both cytoplasmic and spindle microtubules and to selectively block protoplast nuclear division at a defined stage of the cell cycle. Treated protoplasts placed in a drug-free environment recovered a more abundant microtubular system. The majority of microtubules re-formed at SPBs whereas a minority of free-ended microtubules nucleated in the cytoplasm of the protoplasts without any detectable association with recognizable nucleation sites. Random nucleation of free microtubules might be induced by high amounts of unpolymerized tubulin likely to be present in the protoplasts at the moment of drug release.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01403446
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  • 33
    Digitale Medien
    Digitale Medien
    Analysis of expression of hybrid yeast genes containing ARS elements (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 531-535 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Origin of replication ; Promoter ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In an attempt to devise a new assay for ARS-binding proteins we have inserted the HO ARS between the upstream activation site and the TATA region of the yeast CYC1 promoter. A marked reduction in promoter activity is observed. Inactivation of the HO ARS element by point mutation does not restore promoter activity to its original level, although a modest activation is seen. We have also inserted the HO ARS into the intron of the yeast actin gene; although there is no apparent deleterious effect on transcription, the activity of the ARS is abolished in this new environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00332420
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  • 34
    Digitale Medien
    Digitale Medien
    Identification of a gene conferring resistance to zinc and cadmium ions in the yeast Saccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 161-167 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; Heavy metal resistance ; DNA sequence ; Membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A DNA fragment conferring resistance to zinc and cadmium ions in the yeast Saccharomyces cerevisiae was isolated from a library of yeast genomic DNA. Its nucleotide sequence revealed the presence of a single open reading frame (ORF; 1326 bp) having the potential to encode a protein of 442 amino acid residues (molecular mass of 48.3 kDa). A frameshift mutation introduced within the ORF abolished resistance to heavy metal ions, indicating the ORF is required for resistance. Therefore, we termed it the ZRC1 (zinc resistance conferring) gene. The deduced amino acid sequence of the gene product predicts a rather hydrophobic protein with six possible membrane-spanning regions. While multiple copies of the ZRC1 gene enable yeast cells to grow in the presence of 40 mM Zn2+, a level at which wild-type cells cannot survive, the disruption of the chromosomal ZRC1 locus, though not a lethal event, makes cells more sensitive to zinc ions than are wild-type cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00261172
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  • 35
    Digitale Medien
    Digitale Medien
    Isolation and characterization of Saccharomyces cerevisiae mutants supersensitive to G1 arrest by the mating hormone a-factor (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 439-444 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; a-factor ; Conjugation ; G1 arrest ; ssl mutations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Nine independent mutants which are supersensitive (ssl −) to G1 arrest by the mating hormone a-factor were isolated by screening mutagenized Saccharomyces cerevisiae MATα cells on solid medium for increased growth inhibition with a-factor. These mutants carried lesions in two complementation groups, ssl1 and ssl2. Mutations at the ssl1 locus were mating type specific: MATα ssl1 − cells were supersensitive to α-factor but MATα ssl1 − were not supersensitive to α-factor. In contrast, mutations at the ssl2. locus conferred supersensitivity to the mating hormone of the opposite mating type on both MATα, and MATa cells. The α-cell specific capacity to inactivate externally added a-factor was shown to be lacking in MATα ssl1 − mutants whereas MATα ssl2. cells were able to inactivate a-factor. Complementation analysis showed that ssl2 and sst2, a mutation originally isolated as conferring supersensitivity to α-factor to MATa cells, are lesions in the same gene. The ssl1 gene was mapped 30.5 centi-Morgans distal to ilv5 on chromosome XII.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00259617
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  • 36
    Digitale Medien
    Digitale Medien
    A full length cDNA clone for the alkaline protease from Aspergillus oryzae: Structural analysis and expression in Saccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 33-38 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Aspergillus oryzae ; Alkaline protease ; Prepro sequence ; Heterologous expression ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have cloned and determined the nucleotide sequence of a cDNA fragment for the entire coding region of the alkaline protease (Alp) from a filamentous ascomycete Aspergillus oryzae. According to the deduced amino acid sequence, Alp has a putative prepro region of 121 amino acids preceding the mature region, which consists of 282 amino acids. A consensus sequence of a signal peptide consiting of 21 amino acids is found at the N-terminus of the prepro region. The primary structure of the mature region shares extensive homology (29%–44%) with those of subtilisin families, and the three residues (Asp 32, His 64 and Ser 221 in subtilisin BPN′) composing the active site are preserved. The entire cDNA, coding for prepro Alp, when introduced into the yeast Saccharomyces cerevisiae, directed the secretion of enzymatically active Alp into the culture medium, with its N-terminus and specific activity identical to native Aspergillus Alp.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00261154
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  • 37
    Digitale Medien
    Digitale Medien
    The PS03 gene is involved in error-prone intragenic recombinational DNA repair in Saccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 75-80 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Gene conversion ; Crossing-over ; Mismatch repair ; Saccharomyces cerevisiae ; Psoralens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The induction of gene conversion and mitotic crossing-over by photoaddition of psoralens, 254 nm ultraviolet radiation, and nitrogen mustards was determined in diploid cells homozygous for the pso3-1 mutation and in the corresponding wild type of Saccharomyces cerevisiae. For these different agents, the frequency of non-reciprocal events (conversion) is reduced in the pso3-1 mutant compared to the wild type. In contrast, the frequency of reciprocal events (crossing-over) is increased at a range of doses. These observations, together with the block in induced mutagenesis for both reverse and forward mutations previously reported for the pso3-1 mutant, suggest that the PS03 gene product plays a role in mismatch repair of short patch regions. The block in gene conversion in the pso3 homozygous diploid leads, in the case of nitrogen mustards, to specific repair intermediates which are lethal to the cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00261160
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  • 38
    Digitale Medien
    Digitale Medien
    Yeast mutants with enhanced ability to secrete human lysozyme: Isolation and identification of a protease-deficient mutant (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 58-64 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Enhanced secretion ; Human lysozyme production ; Protease mutant ; Protein processing ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Yeast mutant strains which secrete large amounts of human lysozyme were screened using an agar medium containing bacterial cells. Nine mutants secreted over 10 times more lysozyme than the wild-type parent strain. The mRNA levels for lysozyme in the mutants were not higher than that of the wild-type strain. Three of the mutant strains were deficient in carboxypeptidase Y activity. It was found that the protease deficiency was caused by a deficiency in conversion of proenzyme to mature enzyme in ssl1 mutant cells. The ssl1 gene was found to be closely linked to the centromere and determine both the efficiency of secretion of lysozyme and the processing of carboxypeptidase Y.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00261157
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  • 39
    Digitale Medien
    Digitale Medien
    Plasmid multimerization is dependent on RAD52 activity in Saccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 495-498 
    Details
    ISSN: 1617-4623
    Schlagwort(e): ARS1 ; Plasmid multimerization ; RAD52 ; Saccharomyces cerevisiae ; Eukaryotic recombination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A mutant plasmid, pX, derived from the 1453 base pair small plasmid, YARp1 (or TRP1 RI circle), consists of 849 base pairs of DNA bearing the TRP1 gene and the ARS1 sequence of Saccharomyces cerevisiae and, unlike YARp1 and other commonly used yeast plasmids, highly multimerizes in a S. cerevisiae host. The multimerization of pX was dependent on RAD52, which is known to be necessary for homologous recombination in S. cerevisiae. Based upon this observation, a regulated system of multimerization of pX with GAL1 promoter-driven RAD52 has been developed. We conclude that the regulated multimerization of pX could provide a useful model system to study genetic recombination in the eukaryotic cell, in particular to investigate recombination intermediates and the effects of various trans-acting mutations on the multimerization and recombination of plasmids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00259627
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  • 40
    Digitale Medien
    Digitale Medien
    Structure and expression of the URA5 gene of Saccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 215 (1989), S. 455-462 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; Orotate phosphoribosyl transferase ; Nucleotide sequence ; Transcription ; Regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The URA5 gene of Saccharomyces cerevisiae encodes orotate phosphoribosyl transferase (EC 2.4.2.10; OPRTase) which catalyses the transformation of orotate to OMP in the pyrimidine pathway. We present in this paper the cloning and the sequencing of this gene, the last in the yeast pyrimidine pathway to be cloned. We have deduced the protein sequence of the OPRTase of S. cerevisiae from the DNA sequence and compared it to that of Escherichia coli, Podospora anserina and Dictyostelium discoideum. Some important similarities in the structure of these four proteins have been found. Finally, we have quantified the transcription of the URA5 gene in different physiological conditions and confirmed that it was not under the control of UTP or any intermediary product of the pathway.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00427043
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  • 41
    Digitale Medien
    Digitale Medien
    Accumulation of the cytochrome c oxidase subunits I and II in yeast requires a mitochondrial membrane-associated protein, encoded by the nuclear SCO1 gene (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 37-43 
    Details
    ISSN: 1617-4623
    Schlagwort(e): DNA sequence ; PET gene ; Saccharomyces cerevisiae ; Mitochondrial import ; cytochrome c oxidase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The yeast nuclear SCO1 gene is required for accumulation of the mitochondrially synthesized cytochrome c oxidase subunits I and II (COXI and COXII). We cloned and characterized the SCO1 gene. It codes for a 0.9 kb transcript. DNA sequence analysis predicts a 33 kDa protein. As shown by in vitro transcription and translation experiments in combination with import studies on isolated mitochodria, this protein is matured into a 30 kDa polypeptide which is tightly associated with a mitochondrial membrane. The possible function of the SCO1 gene product in the assembly of cytochrome c oxidase is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00332228
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  • 42
    Digitale Medien
    Digitale Medien
    Three regulatory systems control expression of glutamine synthetase inSaccharomyces cerevisiae at the level of transcription (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 370-377 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; GLN1 ; Glutamine synthetase ; Regulatory systems ; Transcription
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary TheGLN1 gene ofSaccharomyces cerivisiae was cloned by complementation of agln1 auxotroph. AGLN1-lacZ fusion was constructed to assayGLN1 promoter activity. β-Galactosidase and glutamine synthetase expression in chromosomally integratedGLN1-lacZ fusion strains were co-regulated in response to a shift from glutamine to glutamate as the nitrogen source, purine limitation, and 3-aminotriazole-induced histidine starvation. Regulation ofGLN1 expression by each of the three pathways occurred at the transcriptional level. Increased accumulation ofGLN1 mRNA was observed within 5 min after a shift from glutamine to glutamate as the nitrogen source. After 5 min following glutamine addition to the cells growing with glutamate as nitrogen source. This indicates that theGLN1 message is unstable and has a half-life of approximately 3 min. Deletion analysis indicated that the sequences required forGLN1 expression are located within approximately 350 bp upstream from the transcriptional initiation site.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02464906
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  • 43
    Digitale Medien
    Digitale Medien
    Molecular cloning of SNM1, a yeast gene responsible for a specific step in the repair of cross-linked DNA (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 64-71 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; DNA repair ; Cross-link ; Transposon mapping ; Nitrogen mustard
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have isolated yeast gene SNM1 via complementation of sensitivity towards bi- and tri-functional alkylating agents in haploid and diploid yeast DNA repair-deficient snm1-1 mutants. Four independent clones of plasmid DNA containing the SNM1 locus were isolated after transformation with a YEp24-based yeast gene bank. Subcloned SNM1-containing DNA showed (i) complementation of the repair-deficiency phenotype caused by either one of the two different mutant alleles snm1-1 and snm1-2 ts; (ii) complementation in haploid and diploid yeast snm1-1 mutants by either single or multiple copies of the SNM1 locus; and (iii) that the SNM1 gene is at most 2.4 kb in size. Expression of SNM1 on the smallest subclone, however, was under the control of the GAL1 promotor. Gene size and direction of transcription was further verified by mutagenesis of SNM1 by Tn10-LUK transposon insertion. Five plasmids containing Tn10-LUK insertions at different sites of the SNM1-containing DNA were able to disrupt function of genomic SNM1 after gene transplacement. Correct integration of the disrupted SNM1::Tn10-LUK at the genomic site of SNM1 was verified via tetrad analysis of the sporulated diploid obtained after mating of the SNM1::Tn10-LUK transformant to a haploid strain containing the URA3 SNM1 wild-type alleles. The size of the poly(A)+ RNA transcript of the SNM1 gene is 1.1 kb as determined by Northern analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00330566
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  • 44
    Digitale Medien
    Digitale Medien
    ThePSO4 gene is responsible for an error-prone recombinational DNA repair pathway inSaccharomyces cerevisiae (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 419-426 
    Details
    ISSN: 1617-4623
    Schlagwort(e): pso4-1 mutation ; Saccharomyces cerevisiae ; Error-prone recombinational repair ; Mitotic recombination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The induction of mitotic gene conversion and crossing-over inSaccharomyces cerevisiae diploid cells homozygous for thepso4-1 mutation was examined in comparison to the corresponding wild-type strain. Thepso4-1 mutant strain was found to be completely blocked in mitotic recombination induced by photoaddition of mono- and bifunctional psoralen derivatives as well as by mono- (HN1) and bifunctional (HN2) nitrogen mustards or 254 nm UV radiation in both stationary and exponential phases of growth. Concerning the lethal effect, diploids homozygous for thepso4-1 mutation are more sensitive to all agents tested in any growth phase. However, this effect is more pronounced in the G2 phase of the cell cycle. These results imply that the ploidy effect and the resistance of budding cells are under the control of thePSO4 gene. On the other hand, thepso4-1 mutant is mutationally defective for all agents used. Therefore, thepso4-1 mutant has a generalized block in both recombination and mutation ability. This indicates that thePSO4 gene is involved in an error-prone repair pathway which relies on a recombinational mechanism, strongly suggesting an analogy between thepso4-1 mutation and theRecA orLexA mutation ofEscherichia coli.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02464912
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  • 45
    Digitale Medien
    Digitale Medien
    Putative target sites for mobile G+C rich clusters in yeast mitochondrial DNA: Single elements and tandem arrays (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 272-283 
    Details
    ISSN: 1617-4623
    Schlagwort(e): GC clusters ; Mobile elements ; Target sites ; mtDNA ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary GC clusters constitute the major repetitive elements in the mitochondrial (mt) genome of the yeast Saccharomyces cerevisiae. Many of these clusters are optional and thus contribute much to the polymorphism of yeast mtDNAs. We have made a systematic search for polymorphic sites by comparing mtDNA sequences of various yeast strains. Most of the 26 di- or polymorphic sites found differ by the presence or absence of a GC cluster of the majority class, here referred to as the M class, which terminate with an AGGAG motif. Comparison of sequences with and without the GC clusters reveal that elements of the subclasses M1 and M2 are inserted 3′ to a TAG, flanked by A+T rich sequences. M3 elements, in contrast, only occur in tandem arrays of two to four GC clusters; they are consistently inserted 3′ to the AGGAG terminal sequence of a preexisting cluster. The TAG or the terminal AGGAG, therefore, are regarded as being part of the target sites for M1 and M2 or M3 elements, respectively. The dinucleotide AG is in common to both target sites; it also occurs at the 3′ terminus (AGGAG). This suggests its duplication during GC cluster insertion. This notion is supported by the observation that GC clusters of the minor classes G and V similarily repeat at their 3′ terminus a GT or an AA dinucleotide, respectively, from their putative target sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00331278
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  • 46
    Digitale Medien
    Digitale Medien
    Chromosomal localization and expression of CBS1, a translational activator of cytochrome b in yeast (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 57-63 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Saccharomyces cerevisiae ; PET gene ; Transcriptional regulation ; Anaerobiosis ; 5′ mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Translation of mitochondrial cytochrome b RNA in yeast requires the product of the nuclear gene CBS1, a 27.5 kDa soluble mitochondrial protein. In this paper we show that the CBS1 gene is located on chromosome IV immediately adjacent to COX9, the gene coding for cytochrome c oxidase subunit VIIa. CBS1 is transcribed as a very low abundant 900 b RNA. Transcription starts at a single position 101 bp upstream of the CBS1 initiation codon. At positions-39 to-27 of its leader sequence it contains a small open reading frame of 4 codons. By monitoring the β-galactosidase activity of a CBS1/lacZ fusion construct we show that expression of CBS1 is subjected to regulation by oxygen and by glucose: the β-galactosidase activity is elevated threefold in glycerol or galactose grown cells compared to that in glucose grown cells. A further threefold reduction of the activity is observed in anaerobically grown cells. In accordance with this result is the observation that the steady-state level of CBS1 mRNA of anaerobically grown cells is ninefold lower than that of aerobically cultured cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00330565
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  • 47
    Digitale Medien
    Digitale Medien
    Structure and function of the yeast vacuolar membrane proton ATPase (1989)
    Springer
    Journal of bioenergetics and biomembranes 21 (1989), S. 589-603 
    Details
    ISSN: 1573-6881
    Schlagwort(e): Vacuolar membrane H+ATPase ; vacuoles ; Saccharomyces cerevisiae ; catalytic cooperativity of ATP hydrolysis ; VMA genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Our current work on a vacuolar membrane proton ATPase in the yeastSaccharomyces cerevisiae has revealed that it is a third type of H+-translocating ATPase in the organism. A three-subunit ATPase, which has been purified to near homogeneity from vacuolar membrane vesicles, shares with the native, membrane-bound enzyme common enzymological properties of substrate specificities and inhibitor sensitivities and are clearly distinct from two established types of proton ATPase, the mitochondrial F0F1-type ATP synthase and the plasma membrane E1E2-type H+-ATPase. The vacuolar membrane H+-ATPase is composed of three major subunits, subunita (M r =67 kDa),b (57kDa), andc (20 kDa). Subunita is the catalytic site and subunitc functions as a channel for proton translocation in the enzyme complex. The function of subunitb has not yet been identified. The functional molecular masses of the H+-ATPase under two kinetic conditions have been determined to be 0.9–1.1×105 daltons for single-cycle hydrolysis of ATP and 4.1–5.3×105 daltons for multicycle hydrolysis of ATP, respectively.N,N′-Dicyclohexylcarbodiimide does not inhibit the former reaction but strongly inhibits the latter reaction. The kinetics of single-cycle hydrolysis of ATP indicates the formation of an enzyme-ATP complex and subsequent hydrolysis of the bound ATP to ADP and Pi at a 7-chloro-4-nitrobenzo-2-oxa-1,3-diazolesensitive catalytic site. Cloning of structural genes for the three subunits of the H+-ATPase (VMA1, VMA2, andVMA3) and their nucleotide sequence determination have been accomplished, which provide greater advantages for molecular biological studies on the structure-function relationship and biogenesis of the enzyme complex. Bioenergetic aspects of the vacuole as a main, acidic compartment ensuring ionic homeostasis in the cytosol have been described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00808115
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  • 48
    Digitale Medien
    Digitale Medien
    Molecular properties of the fungal plasma-membrane [H+]-ATPase (1989)
    Springer
    Journal of bioenergetics and biomembranes 21 (1989), S. 621-632 
    Details
    ISSN: 1573-6881
    Schlagwort(e): ATPase ; [H+]-ATPase ; proton transport ; Neurospora crassa ; Saccharomyces cerevisiae ; Schizosaccharomyces pombe
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract The fungal plasma membrane contains a proton-translocating ATPase that is closely related, both structurally and functionally, to the [Na+, K+]-, [H+, K+]-, and [Ca2+]-ATPases of animal cells, the plasma-membrane [H+]-ATPase of higher plants, and several bacterial cation-transporting ATPases. This review summarizes currently available information on the molecular genetics, protein structure, and reaction cycle of the fungal enzyme. Recent efforts to dissect structure-function relationships are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00808117
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  • 49
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290101
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  • 50
    Digitale Medien
    Digitale Medien
    Introduction (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1-1 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290102
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  • 51
    Digitale Medien
    Digitale Medien
    Polymer aging insights available from modulus profiling data (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 29-35 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A recently developed analytical technique, modulus profiling, conveniently allows the mechanical properties of elastomers to be mapped with spatial resclutions approaching 0.05 mm. Thus, spatial heterogeneities in modulus caused by processing and aging phenomena can be easily monitored. This paper describes some typical results from polymer aging studies, which Indicate the insights available from this technique. These include application of modulus profiling to understanding (1) mechanical property deterioration of Viton in an elevated temperature, gamma-radiation environment, (2) recent continuous stress-relaxation results, and (3) the role of ozone for non mechanically-stressed materials in high energy radiation environments.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290107
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  • 52
    Digitale Medien
    Digitale Medien
    Polyesters II: A review of phase behavior in binary blends: Amorphous, crystalline, liquid crystalline, and on transreaction (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 55-62 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Thermal and mechanical studies on many linear polyesters have revealed their behavior in crystalline, liquid crystalline, and amorphous phases. Their phase behavior in binary compositions has also been studied by a range of additional techniques and in combinations including the polycarbonate of bisphenol-A. Regions of amorphous compatibility and incompatibility have been identified and measures made of transition temperature changes with composition. The conditions for transreaction have also been determined and the properties measured for the resultant new copolymers.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290110
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  • 53
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290201
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  • 54
    Digitale Medien
    Digitale Medien
    Evaluation of residual thermally induced stresses in the cooling of polymer melt via transfinite element computations (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 100-106 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The present paper describes the evaluation of nonlinear thermally induced residual stresses in the cooling of polymer melt during injection molding of plastic components. The computational methodology adopted is based on the transfinite element approach, which is a hybrid scheme as it combines transform methods and classical Galerkin schemes with finite element formulations to preserve the modeling versatility. The applicability of the proposed formulations for understanding the physics and the nature of the nonlinear thermally induced stresses in the solidifying process of a sample amorphous polystyrene specimen demonstrates the basic capabilities and potential of the methodology. Results obtained agree qualitatively well with earlier research studies and experimental findings relevant to thermally induced residual stresses in the injection molding of plastic components.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290204
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  • 55
    Digitale Medien
    Digitale Medien
    Polyvinyl alcohol-copper II complex: Characterization and practical applications (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 127-133 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A method to obtain microscopic and macroscopic coatings with improved resistance to debonding is described. The procedure, based on polymer-metal complexes, involved the adsorption on inorganic substrates of a poly(vinyl alcohol)-copper II chelate that is also able to catalyze the polymerization of monomers or prepolymers with grafting. The molecular structure of the complex, its adsorption on inorganic surfaces, and the mechanism of the polymerization induced by the supported catalyst are summarized. Much emphasis is placed on application of this technology to the realization of encapsulated filler and pigment and of coatings with improved adherence and solvent resistance. In the field of composite materials, it is demonstrated from several examples that the encapsulation of the filler can be a way to block chemical interactions between filler and matrix, to promote filler dispersion, and to improve mechanical properties.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290208
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  • 56
    Digitale Medien
    Digitale Medien
    Dielectric determination of cure state during non-isothermal cure (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 334-338 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: As a result of increased interest from industry in using dielectric cure monitoring, a need has arisen for simplifying frequency, cure, and temperature dependent data so that control decisions can be readily made. Techniques utilizing data covering several decades of frequency now exist for separating ionic conduction levels from dipole and electrode polarization responses. Ionic conduction levels are particularly useful since they can be correlated to both viscosity and extent of cure. In addition to being a function of extent of cure, dielectric properties are also influenced by temperature. This dependence often makes the dielectric response more difficult to interpret. This paper investigates two methods for overcoming the temperature dependence of the dielectric response during nonisothermal cure. The first method utilizes recent WLF modeling techniques and extends them with the end result of extracting Tg in real time during cure. The second technique involves measuring the temperature dependence of uncured and cured material. Utilizing the correlation between log ionic conductivity and extent of cure, which has been noted by previous researchers, the normalized conductivity can be converted to a cure index. Several examples including epoxy, polyurethane, and a UV cured photoresist are presented, showing data before normalization and after both Tg and cure index determination.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290512
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  • 57
    Digitale Medien
    Digitale Medien
    Chemistry of the ternary blends of poly(ethylene terephthalate), bisphenol-a-polycarbonate, and polypropylene (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 359-365 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Poly(ethylene terephthalate) (PET) and bisphenol-a-polycarbonate (PC) are known to form a miscible blend whereas ternary blends of PET, PC, and polypropylene (PP) form two phases. This is based on the considerations of various chemical events which may occur in these systems. The role of ester-carbonate interchange reactions during melt mixing and fabricating is found to be unimportant. Differential scanning calorimetric analysis of the ternary blends shows that there appears to occur an exothermic transition in the heating mode of the instrument. This exothermic event was found to be suppressed considerably by incorporating suitable additives into the system. Degradation reactions studied by thermogravimetric analysis and a dilute solution viscometric technique reveal that there exists some kind of interaction among the components even with the immiscible PP component.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290603
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  • 58
    Digitale Medien
    Digitale Medien
    Structure-Property-Processing relationships of polyurethane-polyester interpenetrating polymer networks (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 397-404 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Interpenetrating polymer networks of polyurethane and unsaturated polyester were prepared by reaction injection molding (RIM) and transfer molding. The structures of the molded samples were analyzed by electron microscopy and dynamic mechanical analysis. It was found that polymer morphology and dynamic mechanical properties depend strongly on the molding temperature, reaction rate and reaction sequence. Simplified structure models based on Takayanagi's model and sample morphology can predict the storage modulus reasonably well but not the tanδ.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290608
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  • 59
    Digitale Medien
    Digitale Medien
    Analysis of interfacial stresses for elastomeric disks in compression (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 432-432 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290613
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  • 60
    Digitale Medien
    Digitale Medien
    Analytical melting model for polymer pellets (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 448-455 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The plasticating or melting behavior of polymer pellets sliding on a hot metal surface was investigated. An analytical model was developed for predicting the melting rate and the shear stress of an incompletely compacted solid bed of pellets in terms of the rheological and thermodynamic properties of the polymer, the pellet size, the degree of compaction, and the operating conditions. This investigation extends the results of the previous investigators obtained for a fully compacted solid bed of polymers to an incompletely compacted solid bed of polymers, closely representing the initial stage of the plasticating mechanism inside a screw extruder. Experimental verification of the analytical model developed here was made by testing six different commercial polymers.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290704
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  • 61
    Digitale Medien
    Digitale Medien
    Vitrification effect during the reaction injection molding (RIM) process of epoxy resin (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 456-462 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Vitrification occurs during the reaction injection molding (RIM) of epoxy resin, and the curing reaction rate is reduced as the Tg of the reacting mixture exceeds or approaches the local reaction temperature inside the mold cavity. The effect will be manifested in the distribution of the glass transition temperature across the thickness direction of the molded product. The reaction kinetic equation which includes the vitrification term in the form of the WLF equation is used in the computer simulation of the epoxy RIM process and the effect of the vitrification is shown by comparing with models with no vitrification considerations.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290705
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  • 62
    Digitale Medien
    Digitale Medien
    Screw design in injection molding (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 479-487 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The performance of screws of advanced design in injection molding has been investigated with respect to four different objectives: (1) improvement of distributive mixing; (2) improvement of dispersive mixing; (3) increase of plasticating capacity; and (4) reduction of inhomogeneity of melt temperature.The screws used are three zone screws with different compression ratios, screws with pineapple or Maddock/Egan mixing elements, with one or two channel barrier sections, with static mixers mounted in the valve or in the nozzle, or with combinations of these different elements. The best mixing quality is obtained with multi-channel Maddock sections. The highest plasticating capacity and, consequently, the shortest cycle times are achieved with the barrier screws. Temperature measurements show that these screws improve melt homogeneity considerably with a relatively small loss of plasticating time. In all cases, increasing the back pressure gives inferior results compared with improvement of the screw design.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290708
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  • 63
    Digitale Medien
    Digitale Medien
    Impact fracture energy of mineral-filled polypropylene (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 505-512 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The impact fracture energy (Gc) for a polypropylene homopolymer and a copolymer with and without calcium carbonate fillers was measured over a range of temperatures between -40°C and 40°C using fracture mechanics principles. The fillers studied were Omyacarb (∼2.7 μm) and Winnofil (∼75 nm) and 10% by weight was added to the matrix material. These fillers did not have any appreciable effect on Gc of the copolymer-based composites. However, the Omyacarb fillers improved Gc of the homopolymer at low temperatures (≤20°C) due to enhanced microplastic flow as observed on the fracture surfaces. The fillers increased the stiffness of both the homopolymer and copolymer. It would appear that up to 10% of cheap calcium carbonate fillers could be added to the more expensive polypropylene to reduce the production cost without any significant loss of impact fracture energy.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290804
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  • 64
    Digitale Medien
    Digitale Medien
    A novel sliding plate rheometer for molten plastics (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 499-504 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A novel sliding plate rheometer has been developed that is suitable for use with molten plastics, concentrated polymer solutions, raw elastomers, and other viscoelastic or thixotropic materials. It can generate steady shear rates from 0.05 to 500 s-1 and can also be used to measure linear viscoelastic properties. In addition, it can be used to measure a broad spectrum of nonlinear viscoelastic properties such as the nonlinear relaxation modulus and the shear stress growth coefficient. In order to measure these nonlinear properties it is necessary to generate large, uniform, transient deformations Involving high strain rates. Rotational and capillary melt rheometers are not capable of generating this type of deformation, and until now it was not convenient to use sliding plate rheometers for this type of application. However, the recent development of a reliable and robust shear stress transducer makes it very convenient to use the sliding plate geometry to carry out all of these tests. The new rheometer is described, and examples of the types of data it can generate are shown.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290803
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  • 65
    Digitale Medien
    Digitale Medien
    Monitoring cure in sheet molding compound processing (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 308-314 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: During the sheet molding compound (SMC) compression molding process, a premeasured polymer charge is placed between the heated halves of a mold which are then brought together to squeeze the polymer and fill the mold, after which pressure is maintained while the part cures. The cure stage constitutes the larger part of the molding cycle and thus affords the largest potential for cycle time reduction. In general, cure times in SMC processing are set longer than necessary, since the inherent material and process variation make it difficult to predict cure times with more than 10 to 20% accuracy. Accurate methods to detect the end of cure would be very beneficial and would permit opening the mold as soon as the material has cured, avoiding unnecessary waste of time. In this paper, several techniques that show promise for monitoring the state of cure are reviewed and experimental results given. Their relative advantages and accuracies are compared. In particular, the use of linear variable displacement transducers, pressure transducers, and thermocouples is discussed. We also show how the measurements compare to theoretical predictions of the state of cure.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290508
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  • 66
    Digitale Medien
    Digitale Medien
    Evaluation of dielectric cure models for an epoxy-amine resin system (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 339-346 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The parallel-plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre-gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time-temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290513
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  • 67
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290601
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  • 68
    Digitale Medien
    Digitale Medien
    A study of the miscibility of blends of polybutadiene and styrene-butadiene copolymers (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 586-592 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: We investigated the miscibility of polybutadienes with butadiene-styrene copolymers of varying styrene content. The methods of optical microscopy, differential scanning calorimetry, and small angle light scattering (SALS) were used. All polymers/copolymers used in this study have equivalent butadiene microstructures. Copolymers with high styrene levels are immiscible with polybutadiene. The tendency to miscibility increases with decreasing styrene content. An upper critical solution temperature is observed with the 23 percent styrene copolymer.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290904
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  • 69
    Digitale Medien
    Digitale Medien
    Fracture behavior of oriented poly(ether-ether-ketone) (PEEK) (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 405-414 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Poly(ether-ether-ketone) (PEEK) is a newly developed engineering thermoplastic with potentially vast application in advanced composites due to its exceptional performance. It is thus desired to understand the relationship between physical processing, microstructure and fracture in this semicrystalline polymer. Both oriented and unoriented PEEK were mechanically characterized using static test of three-point bend specimens. The molecular chain orientation was imposed using a rolltrusion technique. The effects of thickness, strain rate, Initial crack length ratio, and orientation on fracture toughness (Kc) are investigated. The crystallinity is also examined by density measurement. The degree of orientation is determined qualitatively by wide-angle X-ray scattering diffraction patterns and quantitatively by further measurement using an image analysis system. Fractographic analysis, using scanning electron microscopy, provides precise information about the mode of fracture, Results indicate that both the modulus and the fracture toughness are remarkedly increased in the direction of drawing (T-type) as opposed to the transverse direction (L-type).
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290609
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  • 70
    Digitale Medien
    Digitale Medien
    Alternate derivation of the effective medium conductance above and below the critical fill in a metal-filled polymer (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 420-425 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Herein is more detail to microscopic aspects of electron transport through a conductor-filled polymer than has yet been considered in the literature (irrespective of quantum mechanical tunneling and thermal expansion). Some of these details only clarify earlier theories, but others lead to new discoveries such as the cubic conduction path coordination number z = 18 (contrasted with the classical geometric coordination number of z = 6). New also are simplified derivations of the high and low fill asymptotes of the master equation for conductance as a function of fill fraction in the effective medium theory of conductor-filled polymers.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290611
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  • 71
    Digitale Medien
    Digitale Medien
    On the accuracy of the calculated stress field around a crazeThis work performed at Sandia National Laboratories and supported by the U. S. Department of Energy under Contract #de-aac04-76dp00789. (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 426-431 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Several recent calculations of the stress field around crazes in glassy polymers have been based on experimentally obtained craze opening displacements. Although various techniques for performing these calculations have been presented (i.e., Fourier transform, boundary integral, and finite element methods), all are based on the solution of the same ill-conditioned boundary value problem. Specific boundary conditions required to calculate the stresses around a craze lead to a large change in the stress field with small changes in the craze profile which are within the reported experimental tolerance.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290612
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  • 72
    Digitale Medien
    Digitale Medien
    Pumping characteristics of self-wiping twin-screw extruders - A theoretical and experimental study on biopolymer extrusion (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 433-440 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The flow of Newtonian and non-Newtonian fluids which obeys a power law relationship between shear stress and shear rate has been modeled in the melt conveying section of a self-wiping co-rotating twin-screw extruder using a finite element analysis of an unwound channel section. Predictions of throughput against pressure gradient are compared with experimentally obtained results for maize grits which is represented as a power law material. Rheological data applicable to extrusion simulation were obtained from capillary rheometry. Comparisons are reasonable with predicted characteristic showing similar behavior.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290702
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  • 73
    Digitale Medien
    Digitale Medien
    Molecular design of multicomponent polymer systems. XV. Morphology and mechanical behavior of blends of low density polyethylene with acrylonitrile-butadiene-styrene (ABS), emulsified by a poly(hydrogenated butadiene-b-methyl methacrylate) copolymer (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 538-542 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The emulsifying activity of a poly(hydrogenated butadiene-b-methyl methacrylate) (HPB-b-PMMA) copolymer is investigated in incompatible blends of a low density polyethylene and poly(styrene-co-acrylonitrile) resins (mainly ABS) prepared in the melt state on a two-roll mill. Optical and scanning electron microscopy observations clearly demonstrate that a moderate amount of copolymer (5 wt %) very significantly decreases the particle size and enhances interfacial adhesion. The block copolymer is also responsible for a strong improvement in both the ductility and Charpy impact resistance of PE/ABS blends.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290808
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  • 74
    Digitale Medien
    Digitale Medien
    Cold compaction and sintering of ultrahigh-molecular-weight polyethylene containing a segregated iron network (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 564-572 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: To improve the powder processing behavior of ultrahigh-molecular-weight polyethylene, a conductive iron filler was distributed within the polymer in a segregated network. The filler level was kept at a minimum of 10 volume percent, which was sufficient to coat completely all the polymer particle surfaces. This filler level was low enough to avoid modifying the resin properties to a significant extent. Compaction of these filled samples showed a slower densification, under pressure, similar level of final densification at 80% densification parameter, and a doubling of plateau pressure value to 200 MPa in comparison with the unfilled polymer. The filler was found to reduce drastically the postcompaction relaxation time from 24 h to 6 h. The magnitude of the axial (compaction direction) relaxation was unchanged, but the radial relaxation was one quarter of that for the unfilled polymer. Sintering behavior showed improved densification because of lower dimensional changes during sintering resulting in 80% relative sintered density, higher than the 75% percent value for the unfilled polymer, but yielded a 20% lower sintered strength, An alternative process of rapid sintering by induction heating was explored, its feasibility demonstrated, and a recommendation is made to make powder processing of this polymer commercially attractive.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290811
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  • 75
    Digitale Medien
    Digitale Medien
    Highly sensitive novolak-based X-ray positive resist (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 874-877 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The application of X-Ray lithography in mass production of devices is only economically viable if resist materials of highest sensitivity can be provided. Chemical amplification is the key concept to achieve such performance. It is outlined for a highly sensitive three component positive tone X-Ray resist, consisting of a Novolak binder matrix, a starter compound, which - on X-Ray exposure - yields an acid, which catalytically decomposes a dissolution inhibitor. Resist performance is discussed in terms of reaction kinetics and their implications on resist response, simulation, and handling procedures.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291309
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  • 76
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291401
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  • 77
    Digitale Medien
    Digitale Medien
    Water-Soluble contrast enhancing materials - new photobleachable dyes (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 898-901 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Many styrylpyridinium compounds (SPC), which are very stable in the dark, were prepared and evaluated as photobleachable dyes for contrast enhanced lithography (CEL). The photobleaching characteristics of water-soluble contrast enhancing materials composed of SPC and water-soluble polymer depend on the structure of the SPC and the kind of polymers used. The technique using SPC-based CEL proved to be very effective for the resist pattern profiles.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291403
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  • 78
    Digitale Medien
    Digitale Medien
    Dissolution inhibition mechanisms of naphthoquinone diazides (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 916-919 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Dissolution inhibition mechanisms of naphthoquinone diazides in novolak based positive photoresists were investigated from three different aspects: • Dipolar interaction.• Interfacial chemical reactions.• Chemical structures of naphthoquinone diazides.The results suggest that there exists a hydrogen bonding interaction between the compounds with the matrix novolak resin and that naphthoquinone diazides would crosslink the resin in contact with an alkaline developer, both of which contribute to dissolution inhibition mechanisms. However, there seems to exist another dissolution inhibition mechanism; namely, 1,2-naphthoquinone diazide does not inhibit dissolution of the matrix novolak resin at all while a clear dissolution inhibition effect Is observed for its derivatives containing sulfonyl groups. In the present paper, three dissolution inhibition mechanisms of naphthoquinone diazides will be proposed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291407
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  • 79
    Digitale Medien
    Digitale Medien
    Shear and nonisothermal elongational characterization of a liquid crystalline polymer (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 625-631 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A commercial liquid crystalline polymer (LCP) sample was characterized both in shear and in nonisothermal elongational flow over a wide range of temperatures (240-350°C). The LCP sample employed was a copolyesteramide of 2,6 hydroxynaphthoic acid, terephthalic acid, and aminophenol manufactured by Celanese and commercially known as Vectra B950. The viscosity decreases dramatically at temperatures above the crystal-nematic transition of the polymer. At lower temperatures, the extrusion of the sample is mainly due to plastic flow. Die-swell values are very small and contraction of the extrudate is also revealed, but the sample shows high elasticity. The polymer is not spinnable at very low temperatures, and the melt strength rapidly decreases with increasing temperature.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291003
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  • 80
    Digitale Medien
    Digitale Medien
    Gas transport in multilayer packaging structures (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 639-644 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Calculation of gas permeation in food packaging structures can be done using a steady-state analysis employing the permeability coefficient. While this approach is adequate for some applications, for many others a time-dependent transport analysis must be considered to make quantitative predictions of shelf life. The limitation of the simple permeability analysis for multilayer structures is illustrated for Saran-coated polycarbonate and poly(ethylene terephthalate) soda cans. These more detailed calculations on package structures can be done using standard computer library routines to include both the effect of gas sorption and diffusion.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291005
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  • 81
    Digitale Medien
    Digitale Medien
    A nonisothermal differential scanning calorimetry study of the curing kinetics of an unsaturated polyester system (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1097-1102 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Nonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291604
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  • 82
    Digitale Medien
    Digitale Medien
    Hydrolysis of 1,4-cyclohexanedimethanol-based copolyester (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1103-1106 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The solid state hydrolysis of a copolyester based on a mixture of 1,4-cyclohexanedimethanol and ethylene glycol condensed with terephthalic acid was studied at 100°C and 57 to 96 kPa water vapor partial pressure (55% to 95% relative humidity). The equilibrium water sorption in weight percent (C∞) was found to be \documentclass{article}\pagestyle{empty}\begin{document}$$ C_\infty = 1.45 \times \,10^{ - 5} (P_{H_2 O} )^{1.2} $$\end{document} where PH2O is the water vapor partial pressure in kPa. For specimens 0.32-cm thick, it took about 24 h to reach 0.9C∞. The intrinsic viscosity (IV) was measured and used to calculate the relative change in molecular weight (M̄w) from the relationship IV ∝ (M̄w)0.7. The decrease in molecular weight was linear with time, and the rate of decrease was found to be proportional to C∞; the empirical correlation is \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 0.026 \times C_\infty $$\end{document} where the rate constant, k, is in day-1. A decrease of 50% in M̄w was observed after 22 days at 95% relative humidity.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291605
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  • 83
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291701
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  • 84
    Digitale Medien
    Digitale Medien
    Application of silicon polymer as positive photosensitive material (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 887-890 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A new positive-working photosensitive system of silicon polymer, containing silylether groups in the main chain and a photo-induced acid precursor was investigated. The silicon polymer is hydrolized by a photogenerated acid and degraded to low molecular weight compounds. Thus the effect of solubility inhibition of the polymer is diminished. The higher photosensitivity of this system as compared with 1,2-quinone diazide compounds is due to the catalytic reaction of the acid on the hydrolysis of the silicon polymer. The chemical structure around silylether groups in the polymer, in particular more hydrophilic and less steric structures, affects the rate of hydrolysis and thus the photosensitivity. Among various types of photo-induced acid precursors examined, e.g., s-triazine and 1,3,4-oxadiazole compounds substituted by trihalomethyl groups were effective.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291312
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  • 85
    Digitale Medien
    Digitale Medien
    Reaction and thermal analysis for SMC (sheet molding compound) molding in complicated geometriesPresented at polymer processing society north american meeting, september 27-30, 1987, Buffalo, New York. (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1051-1058 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A finite element technique has been developed for coupled reaction and heat transfer analysis in which mass diffusion is negligible. The temperature unknowns are located at nodal points, while the reaction variables (species concentrations, reaction rates) are at the Gauss points in each element. With a mechanistic kinetic model, the SMC (sheet molding compound) cure in 2-D and 3-D geometries was analyzed. The results for plate-and-rib configurations show the progression of cure and heat transfer and the influence of geometry on the progression. The analysis for a flat sheet of SMC in a mold with localized heating using bubblers indicates the thermal interaction between the mold and the curing SMC. Temperature and reaction profiles are given for each case.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291511
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  • 86
    Digitale Medien
    Digitale Medien
    Preface (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1309-1309 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291902
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  • 87
    Digitale Medien
    Digitale Medien
    Welding of polymer interfaces (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1340-1367 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Studies of strength development at polymer-polymer interfaces are examined and applications to welding of similar and dissimilar polymers are considered. The fracture properties of the weld, namely, fracture stress, σ, fracture energy, GIc, fatigue crack propagation rate da/dN, and microscopic aspects of the deformation process are determined using compact tension, wedge cleavage, and double cantilever beam healing experiments. The mechanical properties are related to the structure of the interface via microscopic deformation mechanisms involving disentanglement and bond rupture. The time dependent structure of the welding interface is determined in terms of the molecular dynamics of the polymer chains, the chemical compatibility, and the fractal nature of diffuse interfaces. Several experimental methods are used to probe the weld structure and compare with theoretical scaling laws, Results are given for symmetric amorphous welds, incompatible and compatible asymmetric amorphous welds, incompatible semicrystalline and polymer-metal welds. The relevance of interface healing studies to thermal, friction, solvent and ultrasonic welds is discussed.
    Zusätzliches Material: 33 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291906
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  • 88
    Digitale Medien
    Digitale Medien
    The dependence of butt fusion bond strength on joining conditions for polyethylene pipe (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1387-1395 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The integrity of a pipeline system is determined by its weakest links. Joints may be such places. Heat fusion is the most common joining method for distribution gas piping. There are procedural, thermal, and mechanical aspects of making fusion joints. Procedural aspects, such as heater calibration and cleanliness, can be assured only by rigorous training and certification of the operators. Thermal and mechanical aspects consist of specifying joining conditions such as the heater temperature, heating time, and joining pressure. In the absence of procedural errors, the strength of a fusion joint should depend on the pipe material, pipe dimensions, and the thermal and mechanical joining conditions.The measured parameters that are measures of strength are impact energy and location of failure in the tensile impact test. A parameter, termed the joining parameter, was found to characterize the joining conditions. This parameter is a function of bead volume, melt volume at the end of the heating phase, and pipe wall thickness. Of the mechanical test parameters, the impact energy was found to correlate best with the joining parameter.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760291910
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  • 89
    Digitale Medien
    Digitale Medien
    Synthesis and physical behavior of siloxane modified polyimides (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1413-1418 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A variety of thermoplastic fully imidized poly(imide siloxane) segmented copolymers with useful thermal and mechanical properties have been prepared. Other interesting properties described are the materials' hydrophobic character, surface domination, UV stability, and atomic oxygen plasma resistance.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292002
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  • 90
    Digitale Medien
    Digitale Medien
    Cold compaction of polyether-etherketone and nickel powder blends (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1446-1455 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This study deals with the cold compaction of polyether-etherketone (PEEK) and nickel powder blends. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were utilized for this investigation. These PEEK powders included fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P). Each of the four different PEEK powders were blended with about 10 vol-% nickel powder (Novamet) using a dry mixing technique. These PEEK/nickel powder blends were then successfully compacted at room temperature. Green strengths as high as 39.5 MPa and 26.3 MPa were measured on nickel filled 150 grade and 450 grade compacts, respectively. The higher strength values of the nickel filled compacts compared to their respective unfilled ones were attributed to a higher degree of mechanical interlocking and plastic deformation, which was induced in the polymer particles during compaction by the hard nickel filler. These composites also exhibited lower viscoelastic recoveries than their respective unfilled compacts. Electrical resistivities as low as 0.06 ohm-cm were achieved by compacting 150P/nickel powder blends. This resistivity value agreed well with the calculated value predicted from the literature.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292006
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  • 91
    Digitale Medien
    Digitale Medien
    Characterization and cold compaction of polyether-etherketone powders (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1456-1465 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This study deals with the characterization and cold compaction of polyetheretherketone (PEEK) powders. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were characterized for density, crystallinity, particle size, particle size distribution, and particle morphology. Fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P) were processed. Compaction was successful at room temperature using the 150 grade powders but not with the 450 grade powders. Compressibility curves were obtained at room temperature for the 150 grade powders and their post-compaction viscoelastic recoveries were measured. The coarse and fine size 150 grade powders reached relative plateau densities of 95.8% and 95.1%, respectively, when compacted at pressures exceeding 300 MPa. These high densification values at room temperature were associated with minimal post-compaction viscoelastic recoveries and as-compacted strengths as high as 8.9 MPa. A modified densification parameter (DP*) was developed based on the plastic deformation of the crystalline regions alone. This new dimensionless parameter, DP*, demonstrated a better fit of all the compaction data. The transverse rupture strength and the green density data are presented and explained in terms of this DP*.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292007
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  • 92
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290301
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  • 93
    Digitale Medien
    Digitale Medien
    Biaxially oriented films prepared from poly(vinyl chloride)/poly(methyl methacrylate co imide) blends (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1528-1533 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A study was conducted of blends of poly(vinyl chloride) (PVC) with a poly(methyl methacrylate co imide). The latter polymer was found to be miscible in PVC and to raise the glass transition temperature of the blend. Blends of all compositions could be oriented, but the processing temperature increased in proportion with Tg. For a given blend composition, orientation increased with increasing stretch ratio and strain rate and with decreasing stretch temperature. Increasing copolyimide content and increasing orientation generally lead to improved mechanical properties, though the blends containing high levels of copolyimide exhibited low ductilities.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292107
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  • 94
    Digitale Medien
    Digitale Medien
    The optical properties of a polyetherimide (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1574-1578 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The optical properties of polyetherimide resin as described by the complex index of refraction, N = n - ik, are derived by Kramers-Kronig analysis of experimental absorption and reflectance data obtained in the range 40 μm ≥ λ ≥105 nm. Potential uses of this polymer as a printed circuit board material and as a packaging medium for microelectronic circuitry and the relevance of optical data in laser-assisted processing schemes used in these and other applications are briefly discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292205
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  • 95
    Digitale Medien
    Digitale Medien
    Effect of shear modification on the rheological behavior of two low-density polyethylene (LDPE) grades (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 214-226 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well-characterized low-density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G′, steady-state shear compliance; Je, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290403
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  • 96
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760290501
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  • 97
    Digitale Medien
    Digitale Medien
    Preface (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1637-1637 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292302
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  • 98
    Digitale Medien
    Digitale Medien
    Curing and constitutive relationships for polyester mortar (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1628-1635 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress-strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress-strain behavior of polyester mortar.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292214
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  • 99
    Digitale Medien
    Digitale Medien
    Strength and bonding mechanisms in vibration-welded polycarbonate to polyetherimide joints (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1667-1676 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Under the right conditions, high strengths are shown to be achievable in vibration welded polycarbonate to polyetherimide Joints. While welding of thermoplastic interfaces of the same material can be understood in terms of interchain diffusion at elevated temperatures, this mechanism is severely limited in the case of dissimilar materials. Scanning electron microscopy is used to show that part of the bond strength in such dissimilar materials results from mechanical interlocking of the two polymers, which is caused by viscous mixing. The effects of the weld parameters on the weld morphology are considered in detail.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292308
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  • 100
    Digitale Medien
    Digitale Medien
    Ultrasonic welding of thermoplastics in the near-field (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1689-1698 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760292311
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