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  • Springer  (1,513)
  • Institute of Physics  (234)
  • American Association for the Advancement of Science (AAAS)
  • De Gruyter
  • 1995-1999  (1,055)
  • 1990-1994  (726)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    9-(2-Methylphenyl)-3,4,5,6,9,10-hexa- hydroxanthene-1,8(2H,7H)-dione (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 759-763 
    Details
    ISSN: 1572-8854
    Keywords: X-ray diffraction ; xanthenedione ; heterocyclic fused rings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Several 9-(2-R phenyl)xanthenediones have been synthesized and the x-ray diffraction structure for the 2-methylphenyl derivative (4b) has been determined. This compound crystallizes in the monoclinic system, space group P21/n, with a = 11.729 (3), b = 9.674 (3), c = 14.628 (4) Å, and β = 106.30°. It presents a partially hydrogenated xanthene system in distorted boat conformation for the heterocyclic central ring, and an almost ideal envelope conformation for the outer rings. The aromatic substituent at the ninth position is at 84° in angle with the xanthene system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009583417391
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  • 2
    Electronic Resource
    Electronic Resource
    Persistent behavior in a phase-shift sequence of periodical biochemical oscillations (1998)
    Springer
    Bulletin of mathematical biology 60 (1998), S. 689-702 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We present the analysis of a phase-shift sequence obtained from random transitions between periodic solutions of a biochemical dynamical model, formed by a system of three differential equations and which represent an instability-generating multienzymatic mechanism. The phase-shift series was studied in terms of Hurst’s rescaled range analysis. We found that the data were characterized by a Hurst exponent H = 0.69, which was clearly indicative of long-term trends. This result had a high significance level, as was confirmed through Monte Carlo simulations in which the data were scrambled in the series, destroying its original ordering. For these series we obtained a Hurst exponent which was consistent with the expectation of H = 0.5 for a random independent process. This clearly showed that, although the transitions between the periodic solutions were provoked randomly, the stochastic process obtained exhibited long-term persistence. The fractal dimension was also estimated and found to be consistent with the value of the Hurst exponent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/bulm.1997.0036
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  • 3
    Electronic Resource
    Electronic Resource
    Biosynthesis and characterization of poly(β-hydroxybutyrate) produced byBacillus circulans (1996)
    Springer
    Polymer bulletin 37 (1996), S. 429-435 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The biosynthesis of poly (β-hydroxybutyrate) (PHB) byBacillus circulans was carried out through cultivation in nutrient broth in a single step. $$\overline {\text{M}} {\text{v}}$$ of polymer fractions soluble in chloroform were close to 2 x 105. IR,1H and13C NMR spectra of the isolated PHB were in agreement with the assumed structure of this poly-β-hydroxyester. NMR spectroscopy pointed out a high percentage of isotactic polymer, while differential scanning calorimetry showed that the PHB was crystalline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00556801
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation, spectral studies, and X-ray crystal structures of (16S, 17R, 20S)-3-oxo-16-hydroxy-25-nor-lanostan-24-oic lactone (II) and (16S, 17R, 20S)-4,16-dihydroxy-25-nor-3,4-seco-lanostan-3,24-dioic acid dilactone (III) (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 331-337 
    Details
    ISSN: 1572-8854
    Keywords: Guayule ; Parthenium ; triterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of the title compounds have been determined by direct methods, and refined to a finalR of 0.059 forII and 0.046 forIII. Both molecules crystallize in space group P212121. The cell dimensions forII area=10.096(5),b=11.255(3),c=20.300(7) Å;Z=4,D x=1.188 g cm−3, μ(MoKα)=0.70 cm−1, while the cell dimensions forIII area=7.346(1),b=10.470(3),c=30.546(5) Å;Z=4,D x=1.212 g cm−3, μ(MoKα)=0.74 cm−1. The rings of the triterpene skeletons aretrans-cis-trans-cis connected. The conformations of both molecules are discussed. Also the preparation and the spectral data of (17R, 20S)-3,16-dioxo-25-nor-lanostan-24-oic acid (V) and (17R, 20S)-3,16,24-trioxo-25-hydroxy-16,24-seco-lanostan-25-acetate (VI) are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01796059
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  • 5
    Electronic Resource
    Electronic Resource
    Isobutane/2-butene alkylation on MCM-22 catalyst. Influence of zeolite structure and acidity on activity and selectivity (1994)
    Springer
    Catalysis letters 28 (1994), S. 187-201 
    Details
    ISSN: 1572-879X
    Keywords: isobutane/2-butene alkylation ; zeolites ; MCM-22 ; USY ; beta ; mordenite ; ZSM-5 ; influence of structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic behavior of the novel MCM-22 zeolite for the continuous alkylation of isobutane with 2-butene has been investigated at a temperature of 50°C, 2.5 MPa total pressure, and a variety of olefin space velocities. At high olefin conversions the MCM-22 zeolite showed a very high initial cracking activity attributable to strong Brønsted acid sites, as well as to the existence of strong diffusional restrictions of the TMP's (formed inside the zeolite) to exit through the channels. At short times on stream (TOS), TMP's account for ca. 40% of the C8 fraction. The olefin conversion and the cracking activity rapidly decline with TOS, while the alkylate product became richer in dimethylhexenes, indicating a predominance of 2-butene dimerization and a loss of hydrogen transfer activity as the catalyst aged. Moreover, MCM-22 gives less TMP's than large-pore zeolites (USY, beta, mordenite), but more than the mediumpore ZSM-5 at similar 2-butene conversion. The latter catalyst was much more selective for olefin dimerization than for isobutane alkylation, presumably because formation of the bulkier TMP's was strongly impeded in its smaller pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806048
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  • 6
    Electronic Resource
    Electronic Resource
    Brain met-enkephalin immunostaining after subacute and subchronic exposure to benzene (1994)
    Springer
    Bulletin of environmental contamination and toxicology 52 (1994), S. 163-170 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197373
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  • 7
    Electronic Resource
    Electronic Resource
    Retrograde evolution of quartz segregations from the Dos Picos shear zone in the Nevado-Filabride Complex (Betic chains, Spain). Evidence from fluid inclusions and quartz c-axis fabrics (1995)
    Springer
    International journal of earth sciences 84 (1995), S. 175-186 
    Details
    ISSN: 1437-3262
    Keywords: Betic chain ; Shear zones ; Quartz veins ; C-axis fabrics ; Fluid inclusions ; Extensional tectonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Synkinematic quartz veins are ubiquitous in the shear zone separating the Veleta unit from the Calar Alto unit in the internal part of the Betic Cordilleras. They have been studied with respect to quartz c-axis fabrics, microstructures and fluid inclusions. Veins were probably generated during syn-metamorphic stacking of the units at P = 500 − 600 MPa and T = 400 − 500°C. Quartz displays two groups of microstructures in the shear zone: (1) older coarse-grained mosaics (CGM) resulting from exaggerated grain growth; and (2) younger fine-grained mosaics (FGM) developed at the expense of the former. The fine-grained mosaics show polygonal granoblastic and elongate mosaic microstructures in general, with ribbon microstructures often found near the boundary of the units. Fluids contained in secondary inclusions vary from high salinity brines to different types of CO2—brine mixtures and low density CO2 fluids. Differences in composition and P-T trapping conditions are indicated for the different types of inclusions. Some fluid inclusions are older than the FGM, whereas others are younger, thus constraining the P- T conditions at which the two microstructural events took place. Fluid inclusion evidence suggests conditions of Pfluid 〉 170 MPa and T ≧ 370−430°C for the CGM and Pfluid ≧ 20−80 MPa and T 〉 340°C for the FGM. The quartz c-axis fabrics dealt with here correspond to the second recrystallization event, as little evidence of older fabrics is preserved in the shear zone. C-axis patterns vary across the shear zone from slightly asymmetrical type I crossed girdles in the hanging wall and footwall to more asymmetrical crossed girdles at the boundary of the units. This indicates a correlative increase in the magnitude of the heterogeneous shear strain in the same direction. Most of the deformation is concentrated at the top of the Veleta unit. The sense of movement is top to the west, in agreement with other kinematic markers. The quartz c-axis fabrics resulted from dynamic recrystallization during simple shear. The retrograde P-T path inferred from fluid inclusion analysis, along with other geological and geochronological evidence, indicates that this deformation is coeval with a reduction in the crustal overburden. Geochronological and stratigraphic data show that the proposed Dos Picos extensional detachment, separating the Calar Alto and Veleta units, took place during the early Miocene, synchronous with the intense thinning of the Nevado-Filábride Complex and of the whole continental crust underlying the Alborán Basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192249
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  • 8
    Electronic Resource
    Electronic Resource
    Fluorometric determination of diphenhydramine by flow-injection analysis (1992)
    Springer
    Microchimica acta 106 (1992), S. 319-325 
    Details
    ISSN: 1436-5073
    Keywords: diphenhydramine ; flow-injection analysis (FIA) ; fluorometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A sensitive, rapid and simple flow injection procedure for the determination of diphenhydramine has been designed based on a fluorometric approach. An aqueous solution of diphenhydramine is injected into a carrierreagent stream containing Ce(IV) in dilute sulphuric acid and the fluorescence intensity of the Ce(III) produced is monitored. Chemical, FIA and instrumental variables were optimized. Analytical features of the method are: linear range 0.2–2 ppm, precision 0.7%, sample throughput 80/h. The influence of some foreign substances which can be found in typical pharmaceutical samples containing diphenhydramine was also investigated. The diphenhydramine content of a pharmaceutical preparation was determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242104
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetics of wheat straw solid-state fermentation with Trametes versicolor and Pleurotus ostreatus — lignin and polysaccharide alteration and production of related enzymatic activities (1991)
    Springer
    Applied microbiology and biotechnology 35 (1991), S. 817-823 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The kinetics of straw solid-state fermentation (SSF) with Trametes versicolor and Pleurotus ostreatus was investigated to characterize the delignification processes by these white-rot fungi. Two successive phases could be defined during straw transformation, characterized by changes in respiratory activity, changes in lignin and polysaccharide content and composition, increase in in-vitro digestibility, and enzymatic activities produced by the fungi. Lignin composition was analysed after CuO alkaline degradation, and decreases in syringyl/guaiacyl and syringyl/p-hydroxyphenyl ratios and cinnamic acid content were observed during the fungal treatment. An increase in the phenolic acid yield, revealing fungal degradation of side-chains in lignin, was produced by P. ostreatus. The highest xylanase level was produced by P. ostreatus, and exocellulase activity was nearly absent from straw treated with this fungus. Lactase activity was found in straw treated with both fungi, but lignin peroxidase was only detected during the initial phase of straw transformation with T. versicolor. High levels of H2O2-producing aryl-alcohol oxidase occurred throughout the straw SSF with P. ostreatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169902
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  • 10
    Electronic Resource
    Electronic Resource
    Hydrogen-peroxide-producing system ofPleurotus eryngii involving the extracellular enzyme aryl-alcohol oxidase (1994)
    Springer
    Applied microbiology and biotechnology 41 (1994), S. 465-470 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of benzyl alcohol, benzaldehyde and benzoic acid on the production of extracellular hydrogen peroxide (H2O2) by the ligninolytic fungusPleurotus eryngii was investigated. It was found that an equilibrium between oxidative and reductive reactions of these compounds is established, leading to the continuous production of H2O2. A multienzymatic cyclic system is proposed in which H2O2 is produced extracellularly by the action of aryl-alcohol oxidase on benzyl alcohol, the most abundant compound after redox reactions, and to a lower extent on benzaldehyde. The oxidation products of these reactions, benzaldehyde and benzoic acid, are reduced by intracellular dehydrogenases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00939037
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