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  • 1
    ISSN: 1617-4623
    Keywords: GC clusters ; Mobile elements ; Target sites ; mtDNA ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Glucose repression ; Glucose derepression ; Regulatory genes ; Expression analysis ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yeast strains carrying one of the two regulatory mutations cat1 and cat3 are defectve in derepression of several glucose-repressible enzymes that are necessary for utilizing non-fermentable carbon sources. Hence, these strains fail to grow on ethanol, glycerol or acetate. The synthesis of isocitrate lyase, malate synthase, malate dehydrogenase and fructose-1,6-bisphosphatase is strongly affected in cat1 and cat3 strains. Genes CAT1 and CAT3 have been isolated by complementation of the cognate, mutations after transformation with an episomal plasmid gene library. The restriction map of CAT1 proved its allelism to the earlier isolated SNF1 gene. Both genes appear to exist as single-copy genes per haploid genome as indicated by Southern hybridization. Northern analysis has shown that the 1.35 kb CAT3 mRNA is constitutively expressed, independent of the carbon source in the medium. Derepression studies with CAT3 transformants using a multi-copy plasmid showed over-expression of glyoxylate cycle enzymes. This result would be consistent with a direct effector function for the CAT3 gene product.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Branched and Chain-extended Sugars, XXX.  -  Diastereoselective Synthesis of L-glycero-D-manno-Heptose, a Constituent of the Inner Core Region of LipopolysaccharidesReaction of 2,3;5,6-di-O-isopropylidene-D-mannofuranose (1) with 2-lithio-1,3-dithiane affords diastereoselectively the 3,4;6,7-di-O-isopropylidene-D-glycero-D-galacto-heptose trimethylene dithioacetal (3). Conversion of compound 3 by a sequence of steps gives the tri-O-isopropylidene-D-glycero-D-galacto-heptit 16 which is oxidized with 1,1′-(azodicarbonyl)-dipiperidine to give the tri-O-isopropylidene-L-glycero-D-manno-heptose 17. Finally, compound 17 is transferred via the acetate 19 into the L-glycero-D-manno-heptopyranose 18.
    Notes: 2,3;5,6-Di-O-isopropyliden-D-mannofuranose (1) reagiert diastereoselektiv mit 2-Lithio-1,3-dithian zum 3,4;6,7-Di-O-isopropyliden-D-glycero-D-galacto-heptose-trimethylendithioacetal (3). Nach Umwandlung von 3 über eine Reihe von Zwischenstufen zum Tri-O-isopropyliden-D-glycero-D-galacto-heptit 16 läßt sich dieser mit 1,1′-(Azodicarbonyl)dipiperidin zur Tri-O-isopropyliden-L-glycero-D-manno-heptose 17 oxidieren. Hieraus ist über das Acetat 19 die freie L-glycero-D-manno-heptopyranose 18 zu gewinnen.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 249-258 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units of Oligosaccharides, LXXVIII. - Synthesis of KDO-Containing Lipid A AnaloguesThe non-neighbouring group supported glycosidation of 12 with the suitably protected glycosyl bromide 9 of 2-azido-2-deoxy-D-glucose leads - in the presence of a heterogeneous silver catalyst - to the formation of the β-(1→6)-glycosidically linked disaccharide 14. It consists of two 2-azido-2-deoxy-D-glucose units. Partial deblocking of 14 furnishes 15. On glycosidation with KDO bromide this compound yields the trisaccharide 16, which contains a KDO unit in an α-(2→6) ketosidic bond. Reduction of the two azido groups followed by amidation with (R)-3-hydroxymyristic acid and further deblocking generates the trisaccharide α-KDO-(2→6)-β-D-GlcA-(1→6)-D-GlcA 20 with two 3-hydroxy fatty acid residues in an amidic linkage.
    Notes: Die Umsetzung des Pyranosylbromids 9 der 2-Azido-2-desoxy-D-glucose mit dem Akzeptor 12 führt bei Gegenwart eines heterogenen Silberkatalysators ohne Nachbargruppenbeteiligung unter Inversion zum β-(1→6)-glycosidisch verknüpften Disaccharid 14 aus zwei 2-Azido-2-desoxy-D-glucose-Einheiten. Nach partieller Entblockierung zu 15 ist die Anknüpfung eines KDO-Restes unter Bildung einer α-(2→6)-ketosidischen Bindung zum Trisaccharid 16 möglich. Nach Reduktion der Azidogruppen und Anknüpfung von (R)-3-Hydroxymyristinsäure-Resten gelangt man nach Entblockierung zum Trisaccharid α-KDO-(2→6)-β-D-GlcA-(1→6)-D-GlcA 20, das amidartig zwei 3-Hydroxyfettsäure-Reste gebunden enthält.
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  • 5
    ISSN: 1572-9559
    Keywords: high-power millimeter waves ; gyrotron ; electron cyclotron resonance heating (ECRH) ; overmoded waveguide systems ; mode conversion ; linearly polarized narrow pencil beam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This work reports calculations and measurements on mode converters for the transformation of TEOn gyrotron mode mixtures (primarily TEO2) into the linearly polarized HE11 hybrid mode at 70 GHz. This mode is ideal for quasi-optical launching systems for ECRH of plasmas. Mode transducers with axisymmetric radius perturbations convert the gyrotron TEOn mode composition into the TEO1 mode. Proper matching of the phase differences between the various modes and of the perturbation amplitudes of the several converter sections is required. The TEO1 wave is used for long-distance transmission through smooth-walled overmoded waveguides. A mode converter with constant diameter and periodically perturbed curvature transfers the unpolarized TEO1 mode into the polarized TE11 wave. The experimentally determined ΣTEOn-to-TEO1 conversion efficiency is (98.5±1)% (99% predicted) while the TEO1-to-TE11 transformer has a (94±2)% efficiency (93% theoretically); ohmic losses are included. The “Gaussian-like” HE11 mode with axisymmetric power distribution and almost no cross polarization is produced in a circumferentially corrugated TE11-to-HE11 mode transducer with a measured conversion efficiency of (98.3±1.5)% (98.5% predicted). The overall efficiency of the complete mode converter system in the desired mode was determined to be (91±2.5)%. High-power operation (200kW, 100ms) has been successfully demonstrated.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1359-5997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract A procedure to estimate the failure probabilities of reinforced concrete (R/C) chimneys under severe wind loading which allows for considering realistic correlation values of concrete strength is developed. The results show that the assumption of full correlation of concrete strength within cross-sections, as suggested for example in present codes, may significantly overestimate the failure rates in present examples by two orders of magnitude. However, it is also shown that not only one but a number of cross-sections may contribute to the total failure rate of R/C chimneys. As a consequence, the failure estimates increase, in some cases by as much as two orders of magnitude. In the numerical examples as investigated here these counteracting effects neutralize each other. This fact, however, should not be generalized.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2019-07-13
    Description: The technique of obtaining quantitative data from high resolution soft X-ray photographic images produced by grazing incidence optics was successfully developed to a high degree during the AS&E Solar Research Sounding Rocket Program and the S-054 X-Ray Spectrographic Telescope Experiment Program on Skylab. Continued use of soft X-Ray photographic imaging in sounding rocket flights of the AS&E High Resolution Solar Soft X-Ray Imaging Payload has provided opportunities to further develop these techniques. The developments discussed include: (1) the calibration and use of an inexpensive, commercially available microprocessor controlled drum type film processor for photometric film development, (2) the use of Kodak Technical Pan 2415 film and Kodak SO-253 High Speed Holographic film for improved resolution, and (3) the application of a technique described by Cook, Ewing, and Sutton (1988) for determining the film characteristics curves from density histograms of the flight film. Although the superior sensitivity, noise level, and linearity of microchannel plate and CCD detectors attracts the development efforts of many groups working in soft X-ray imaging, the high spatial resolution and dynamic range as well as the reliability and ease of application of photographic media assures the continued use of these techniques in solar X-ray astronomy observations.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: EUV, X-ray, and Gamma-Ray Instrumentation for Astronomy and Atomic Physics; Aug 07, 1989 - Aug 11, 1989; San Diego, CA; United States
    Format: text
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  • 8
    Publication Date: 2019-06-28
    Description: The technique of obtaining quantitative data from high resolution soft X-ray photographic images produced by grazing incidence optics was successfully developed to a high degree during the Solar Research Sounding Rocket Program and the S-054 X-Ray Spectrographic Telescope Experiment Program on Skylab. Continued use of soft X-ray photographic imaging in sounding rocket flights of the High Resolution Solar Soft X-Ray Imaging Payload has provided opportunities to further develop these techniques. The developments discussed include: (1) The calibration and use of an inexpensive, commercially available microprocessor controlled drum type film processor for photometric film development; (2) The use of Kodak Technical Pan 2415 film and Kodak SO-253 High Speed Holographic film for improved resolution; and (3) The application of a technique described by Cook, Ewing, and Sutton for determining the film characteristics curves from density histograms of the flight film. Although the superior sensitivity, noise level, and linearity of microchannel plate and CCD detectors attracts the development efforts of many groups working in soft X-ray imaging, the high spatial resolution and dynamic range as well as the reliability and ease of application of photographic media assures the continued use of these techniques in solar X-ray astronomy observations.
    Keywords: ASTRONOMY
    Type: American Science and Engineering, Inc., Solar X-ray Astronomy Sounding Rocket Program; 14 p
    Format: application/pdf
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  • 9
    Publication Date: 1989-02-13
    Print ISSN: 0014-5793
    Electronic ISSN: 1873-3468
    Topics: Biology , Chemistry and Pharmacology
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  • 10
    Publication Date: 1985-01-01
    Print ISSN: 0040-4039
    Electronic ISSN: 1873-3581
    Topics: Chemistry and Pharmacology
    Published by Elsevier
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