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  • Springer  (80)
  • Wiley-Blackwell  (29)
  • Hindawi
  • 1990-1994  (109)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 122 (1991), S. 725-730 
    ISSN: 1434-4475
    Keywords: Synthesis ; Pyrrolo[2,3-b]pyridine ; Cyclization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Synthese von neuen 1-Benzyl-7-alkyl-2,3-dimethyl-4-oxopyrrolo[2,3-b]pyridin-5-carbonsäuren durch Verwendung von 5,6-Dimethyl-2,4-dioxopyrrolo[2,3-d][1,3]oxazinen als Ausgangsmaterial wird beschrieben. Die antimikrobielle Aktivität dieser Substanzen wurde geprüft.
    Notes: Summary A synthetic approach to new 1-benzyl-7-alkyl-2,3-dimethyl-4-oxopyrrolo[2,3-b]pyridine-5-carboxylic acids using 5,6-dimethyl-2,4-dioxopyrrolo[2,3-d][1,3]oxazine as the starting material is reported. The antimicrobial activity of these compound is reported.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Tangkuban Parahu is an active stratovolcano located 17 km north of the city of Bandung in the province west Java, Indonesia. All historical eruptive activity at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal activity, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased hydrothermal and earthquake activity occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40–50 microradians per year. After the 1983 phreatic activity, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m3 per year; from 1983 to 1986 it averaged about 0.4 million m3 per year. Possible causes for this uplift are increased pressure within a very shallow magma body or heating and expansion of a confined aquifier.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archiv der Mathematik 61 (1993), S. 409-420 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 165-168 
    ISSN: 0392-6737
    Keywords: Surface and interface electron states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The binding energy for on-centre impurities in a rectangular quantum well wire is calculated as a function of the width of the wire and perpendicular magnetic field. The results for zero-magnetic-field case are in perfect agreement with previous calculations.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 28-31 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pectinase production by Tubercularia vulgaris using orange-pulp pellets (OPP) or citrus pectin as carbohydrate sources was investigated. The highest levels of extracellular polygalacturonase were detected with OPP as inducing substrate. The pectinases present in the crude filtrate from T. vulgaris cultures included methyl esterase, endo-polygalacturonase and exo-polygalacturonase activities with both substrates. Moreover, in medium supplemented with OPP, the additional presence of one endo-polygalacturonase and two exo-polygalacturonases was detected.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 32-35 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pectinase production by Tubercularia vulgaris using orange-pulp pellets (OPP) or citrus pectin as carbohydrate sources was investigated. The highest levels of extracellular polygalacturonase were detected with OPP as inducing substrate. The pectinases present in the crude filtrate from T. vulgaris cultures included methyl esterase, endo-polygalacturonase and exo-polygalacturonase activities with both substrates. Moreover, in medium supplemented with OPP, the additional presence of one endo-polygalacturonase and two exo-polygalacturonases was detected.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 54 (1992), S. 384-388 
    ISSN: 1432-0630
    Keywords: 42.55.R
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The design and the development of a flashlamp-pumped Ti:Sapphire laser is described. Design criteria are discussed and performance improvements using different types of fluorescent UV converters or filters, such as organic dyes or doped glass are presented. We have tested different laser rods at various Ti-concentrations obtained by Verneuil or Czochralski growth techniques. The maximum laser output energy of 540 mJ with a differential efficiency up to 1% was achieved by using only a pyrex filter surrounding the laser rod.
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  • 8
    ISSN: 1432-072X
    Keywords: Phenylacetate ; 4-Hydroxyphenylacetate ; Phenylglyoxylate ; Alpha-Oxidation ; Pseudomonas ; Oxidoreductase ; CoA ligase ; Benzoyl-CoA ; Anaerobic aromatic metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anaerobic degradation of (4-hydroxy)phenylacetate in denitrifying Pseudomonas sp. was investigated. Evidence is presented for α-oxidation of the coenzyme A (CoA)-activated carboxymethyl side chain, a reaction which has not been described. The C6−C2 compounds are degraded to benzoyl-CoA and furtheron to CO2 via the following intermediates: Phenylacetyl-CoA, phenylglyoxylate, benzoyl-CoA plus CO2; 4-hydroxyphenylacetyl-CoA, 4-hydroxyphenylglyoxylate, 4-hydroxybenzoyl-CoA plus CO2, benzoyl-CoA. Trace amounts of mandelate possibly derived from mandelyl-CoA were detected during phenylacetate degradation in vitro. The reactions are catalyzed by (i) phenylacetate-CoA ligase which converts phenylacetate to phenylacetyl-CoA and by a second enzyme for 4-hydroxyphenylacetate; (ii) a (4-hydroxy)-phenylacetyl-CoA dehydrogenase system which oxidizes phenylacetyl-CoA to (4-hydroxy)phenylglyoxylate plus CoA; and (iii) (4-hydroxy)phenylglyoxylate: acceptor oxidoreductase (CoA acylating) which catalyzes the oxidative decarboxylation of (4-hydroxy)phenylglyoxylate to (4-hydroxy)benzoyl-CoA and CO2. (iv) The degradation of 4-hydroxyphenylacetate in addition requires the reductive dehydroxylation of 4-hydroxybenzoyl-CoA to benzoyl-CoA, catalyzed by 4-hydroxybenzoyl-CoA reductase (dehydroxylating). The whole cell regulation of these enzyme activities supports the proposed pathway. An ionic mechanism for anaerobic α-oxidation of the CoA-activated carboxymethyl side chain is proposed. Phenylacetic acids are plant constituents and in addition are formed from a large variety of natural aromatic compounds by microorganisms; their degradation therefore plays a significant role in nature, as illustrated in the preceding paper (Mohamed and Fuchs 1993). We have investigated and purified an enzyme which catalyzes the first step in the anaerobic degradation of phenylacetate in a denitrifying Pseudomonas sp. Phenylacetate is converted to phenylacetyl-CoA by phenylacetate-CoA ligase (AMP forming). The postulated function of this enzyme is corroborated by the strict regulation of its expression. 4-Hydroxyphenylacetate appears to be similarly activated by an independent enzyme prior to further degradation. We have suggested before that phenylacetyl-CoA is anaerobically converted by α-oxidation of the side chain to phenylglyoxylate1, which is oxidatively decarboxylated to benzoyl-CoA plus CO2 (Seyfried et al. 1991; Dangel et al. 1991). 4-Hydroxyphenylacetate was proposed to be similarly oxidized to 4-hydroxybenzoyl-CoA plus CO2, followed by reductive dehydroxylation to benzoyl-CoA. The evidence was not presented in full, and the crucial α-oxidation was not demonstrated in vitro. We present here ample evidence for this pathway. A hypothetical mechanism is proposed by which the oxidation of the α-methylene group to an α-carbonyl group may occur.
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  • 9
    ISSN: 1432-072X
    Keywords: Phenylacetate ; CoA ligase ; Phenylacetyl ; CoA ; Anaerobic aromatic metabolism ; Pseudomonas ; Alpha ; Oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The enzyme catalysing the first step in the anaerobic degradation pathway of phenylacetate was purified from a denitrifying Pseudomonas strain KB 740. It catalyses the reaction phenylacetate+CoA+ATP → phenylacetyl-CoA+AMP+PPi and requires Mg2+. Phenylacetate-CoA ligase (AMP forming) was found in cells grown anaerobically with phenylacetate and nitrate. Maximal specific enzyme activity was 0.048 μmol min-1 x mg-1 protein in the mid-exponential growth phase. After 640-fold purification with 18% yield, a specific activity of 24.4 μmol min-1 mg-1 protein was achieved. The enzyme is a single polypeptide with Mr of 52 ±2 kDa. The purified enzyme shows high specificity towards the aromatic inducer substrate phenylacetate and uses ATP preferentially; Mn2+ can substitute for Mg2+. The apparent K m values for phenylacetate, CoA, and ATP are 60, 150, and 290 μM, respectively. The soluble enzyme has an optimum pH of 8.5, is insensitive to oxygen, but is rather labile and requires the presence of glycerol and/or phenylacetate for stabilization. The N-terminal amino acid sequence showed no homology to other reported CoA-ligases. The expression of the enzye was studied by immunodetection. It is present in cells grown anaerobically with phenylacetate, but not with mandelate, phenylglyoxylate, benzoate; small amounts were detected in cells grown aerobically with phenylacetate.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The Hydrologic Atmospheric Pilot EXperiment in the Sahel (HAPEX-Sahel) was carried out in Niger, West Africa, during 1991 - 1992, with an intensive observation period (IOP) in August - October 1992. It aims at improving the parameterization of land surface atmosphere interactions at the Global Circulation Model (GCM) gridbox scale. The experiment combines remote sensing and ground based measurements with hydrological and meteorological modelling to develop aggregation techniques for use in large scale estimates of the hydrological and meteorological behaviour of large areas in the Sahel. The experimental strategy consisted of a period of intensive measurements during the transition period of the rainy to the dry season, backed up by a series of long term measurements in a 1^ by 1^ square in Niger. Three “supersites” were instrumented with a variety of hydrological and (micro) meteorological equipment to provide detailed information on the surface energy exchange at the local scale. Boundary layer measurements and aircraft measurements were used to provide information at scales of 100 - 500 km2. All relevant remote sensing images were obtained for this period. This programme of measurements is now being analyzed and an extensive modelling programme is under way to aggregate the information at all scales up to the GCM grid box scale. The experimental strategy and some preliminary results of the IOP are described.
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