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  • Springer  (1,192)
  • Wiley-Blackwell  (179)
  • PANGAEA
  • Springer Science + Business Media
  • 1995-1999  (1,000)
  • 1985-1989  (384)
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  • 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
    New Imidazabole Derivatives: Dimers of Carbene-Borane Adducts (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1547-1553 
    Details
    ISSN: 1434-1948
    Keywords: Imidazaboles ; Carbene-borane adducts ; Azole-borane adducts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and characterization of five new imidazabole derivatives is reported: 1,5-dibenzyl-4,4,8,8-tetrahydroimidazabole (2), 4,4,8,8-tetrafluoro-1,5-dimethylimidazabole (3), 4,4-difluoro-8,8-dihydro-1,5-dimethylimidazabole (4), 4,4,8,8-tetrachloro-1,5-dimethylimidazabole (5), and 4,4,8,8-tetraethyl-1,5-dimethylimidazabole (6). The structures of compounds 2-6 as dimeric carbene-borane adducts rather than dimeric N-borane adducts are discussed on the basis of NMR (2-6) and X-ray diffraction data (2, 3, 5 and 6).
    Type of Medium: Electronic Resource
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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Effect of pectin on pectinases in autolysis of Botrytis cinerea (1988)
    Springer
    Mycopathologia 102 (1988), S. 37-43 
    Details
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Pectic activity in autolyzed cultures of Botrytis cinerea in a medium with and without pectin was similar, but in the medium with pectin maximal activities occurred in younger cultures. The pectic activities found were polygalacturonase, polymethylgalacturonase, endo activity (pectin as substrate) and pectin lyase. The molecular weights of polygalacturonase, polymethylgalacturonase and endo activity (pectin as substrate) were 36000, 33000 and 30200 daltons respectively, and the molecular weight of pectin lyase was 18200 daltons. By gel electrophoresis four different pectic activities were detected, three in the top of the gel and one in the bottom. Two enzymes were characterized, the polygalacturonase activity (first band in the top) inhibited by Ca++ and the pectin lyase activity (in the bottom) which was not inhibited by Ca++. These enzymes are not induced by the presence of pectin in the medium during degradation of Botrytis cinerea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00436250
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  • 8
    Electronic Resource
    Electronic Resource
    Carrier scattering mechanisms in P-type indium selenide (1989)
    Springer
    Applied physics 48 (1989), S. 445-450 
    Details
    ISSN: 1432-0630
    Keywords: 72,10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Carrier scattering mechanisms in p-indium selenide are investigated by means of the temperature dependence of the Hall mobility (160–500 K) and thermopower (200–300 K). An anomalous behaviour of the Hall voltage, which changes sign below 215 K, is interpreted through the existence of planar aggregates of ionized shallow donor impurities that create potential wells behaving as deep donors and in which a low concentration of two-dimensional free electrons can exist. This fact is taken into account through equations for two-carrier Hall effect. Holes are found to be predominantly scattered by anA ′ 1 homopolar phonon with an energy of 27.8 meV. From thermopower results, the density of states effective mass in the valence band is determined,m dv * =(1.5±0.2)m 0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619716
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of Skeletal Site of Origin and Donor Age on Osteoblastic Cell Growth and Differentiation (1999)
    Springer
    Calcified tissue international 64 (1999), S. 280-286 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Human osteoblastic cells — Skeletal site — Aging.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Bone loss with aging may be due, at least in part, to inadequate bone formation. Moreover, the process of bone aging is known to follow a different pattern throughout the skeleton. In this study, we examined the cell proliferation rate (area under the cell growth curve, AUC) and the secretion of C-terminal type I procollagen (PICP), alkaline phosphatase (ALP), and osteocalcin (OC) in primary cultures of osteoblastic cells from human trabecular bone. Osteoblastic cells were obtained for 168 donors (100 women and 68 men). Ninety-eight bone samples were obtained from subjects undergoing knee arthroplastia, 52 aged 50–70 years (64 ± 5) and 46 over age 70 (73 ± 2). Another 70 bone samples were obtained from subjects undergoing hip arthroplastia; 51 were 50–70 years old (64 ± 4) and 19 were over 70 (75 ± 5). Osteoblastic cells from the older donors had a lower proliferation rate and OC secretion than those from younger subjects. However, ALP secretion was higher in the former subjects, whereas PICP secretion was unchanged. Osteoblastic cells from hip had a lower proliferation rate than those from knee. PICP secretion was also lower and ALP secretion was higher in the former cells. In age-matched cell cultures, osteoblastic cells from the knee had higher proliferation rate and PICP secretion than osteoblastic cells from the hip. However, ALP secretion was lower in knee osteoblastic cells than those from hip only in the younger group. With aging, ALP secretion was found to increase in knee osteoblactic cells, whereas OC secretion decreased in osteoblastic cell cultures from the hip. Our findings suggest that bone loss with aging may be accounted for, at least in part, by a decreased osteoblastic cell proliferation and an increased osteoblastic maturation. In addition, our data indicate that these changes with aging do not occur similarly at different skeletal sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900619
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  • 10
    Electronic Resource
    Electronic Resource
    Zinc accumulation in the telencephalon of lizards (1987)
    Springer
    Histochemistry and cell biology 86 (1987), S. 311-314 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The zinc concentration in the brains of two species of lizard was determined by atomic-absorption spectrophotometry. The zinc concentration was found to be highest in the telencephalon of Lacerta galloti (21.1 μg/g fresh weight) and Podarcis hispanica (16.77±0.8 μg/g) while the mesencephalon and brain stem exhibited lower zinc concentrations, i.e., 7.0 μg/g in Lacerta galloti and 6.08±0.4 μg/g in Podarcis hispanica. This high telencephalic concentration of zinc is paralleled by intense and well-defined Timm reactivity used for demonstrating the presence of zinc-containing boutons at the light-microscope level. Volumetricdensitometric studies of these Timm-reactive zones were performed using serial transverse sections of the same lizard brains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00490264
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