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  • Springer  (68)
  • American Chemical Society  (31)
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  • 1961  (9)
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  • 2020-2022
  • 2000-2004
  • 1995-1999  (109)
  • 1960-1964  (18)
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  • 11
    Electronic Resource
    Electronic Resource
    Regularity estimates for solutions to the mean curvature flow with a Neumann boundary condition (1996)
    Springer
    Calculus of variations and partial differential equations 4 (1996), S. 385-407 
    Details
    ISSN: 1432-0835
    Keywords: Mathematics Subject Classification:35K22; 53A07
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract. In this work we study the behaviour of compact, smooth, immersed manifolds with boundary which move under the mean curvature flow in Euclidian space. We thereby prescribe the Neumann boundary condition in a purely geometric manner by requiring a vertical contact angle between the unit normal fields of the immersions and a given, smooth hypersurface ${\vec\Sigma}$ . We deduce a very sharp local gradient bound depending only on the urvature of the immersions and ${\vec\Sigma}$ . Combining this with a short time existence result, we obtain the existence of a unique solution to any given smooth initial and boundary data. This solution either exists for any $t〉0$ or on a maximal finite time interval $[0,T]$ such that the curvature explodes as $t \rightarrow T$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01190825
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  • 12
    Electronic Resource
    Electronic Resource
    Convergence of solutions to the mean curvature flow with a Neumann boundary condition (1996)
    Springer
    Calculus of variations and partial differential equations 4 (1996), S. 421-441 
    Details
    ISSN: 1432-0835
    Keywords: 35K22 ; 53A07
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This work continues our considerations in [15], where we discussed existence and regularity results for the mean curvature flow with homogenious Neumann boundary data. We study the long time evolution of compact, smooth, immersed manifolds with boundary which move under the mean curvature flow in Euclidian space. On the boundary, a Neumann condition is prescribed in a purely geometric manner by requiring a vertical contact angle between the unit normal fields of the immersions and a given, smooth hypersurfaceΣ. We deduce estimates for the curvature of the immersions and, in a special case, we obtain a precise description of the possible singularities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246150
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  • 13
    Electronic Resource
    Electronic Resource
    The dehydration process in the zeolite laumontite: a real-time synchrotron X-ray powder diffraction study (1996)
    Springer
    Physics and chemistry of minerals 23 (1996), S. 328-336 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The dehydration process of the natural zeolite laumontite Ca4Si16Al8O48 · 18 H2O has been studied in situ by means of powder diffraction and X-ray synchrotron radiation. Powder diffraction profiles suitable for Rietveld refinements were accumulated in time intervals of 5 minutes using a position sensitive detector (CPS-120 by INEL), while the temperature increased in steps of about 5 K. The synchronization of accumulation time and temperature plateau allowed collection of 62 temperature-resolved powder patterns in the range 310–584 K, whose analysis produced a dynamic picture of the laumontite structure response to dehydration. The first zeolitic water molecules diffusing out of the channels are those not bonded to the Ca cations and located in the W(1) site, whose occupancy drops smoothly to 10% during heating to 349 K, while the sample in the capillary is still submerged in water. The remaining W(1) and 60% of W(5) water molecules are expelled rather sharply at about 370 K. At this temperature all remaining water submerging the powder crystallites is lost, the structure contains about 13 water molecules/cell, and the crystal structure is that of leonhardite. On continued heating 80% of the water molecules from the W(2) site are lost between 420 and 480 K, while a small amount of the diffusing water is reinserted in the W(5) site. The occupancy factor of the W(8) site decreases starting at 480 K, and reaches a maximum loss of 20% at 584 K. The combined occupancy of the Ca-coordinated W (2) and W (8) water sites never falls much below two, so that the Ca cations in the channels, which are bonded to four framework oxygen atoms, are nearly six-coordinated in the explored temperature range. The water loss is accompanied by large changes in the unit cell dimensions. Except at 367 K, where the excess surrounding water is leaving, all changes in cell dimensions are gradual. The loss of the hydrogen bonded W(1) and W(5) water molecules is related to most of the unit cell volume reduction below 370 K, as shown by the contraction of the a-, b- and c-axes and the increase in the monoclinic angle. Loss of the Ca-coordinated W(2) and W(8) water molecules has a small effect on the unit cell volume as the continued contraction of the a- and c-axes is counter-balanced by a large expansion in the b-axis and a decrease in the monoclinic β angle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199498
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  • 14
    Electronic Resource
    Electronic Resource
    Microwave detection of molecules formed by shock wave induced reactions (1998)
    Springer
    Shock waves 8 (1998), S. 385-388 
    Details
    ISSN: 1432-2153
    Keywords: Key words:Shock tube experiments, Formation of molecules, Microwave absorption technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract. The paper describes experimental investigations in a shock tube concerning the formation of new molecules using He as a driver gas and a mixture of Kr, CH $_4$ and NH $_3$ as driven gas, where Kr serves as diluant. By microwave absorption technique it was possible to detect HCN, CH $_2$ O and CH $_3$ NH $_2$ as reaction products. Obviously, these molecules were formed in the plasma behind the shock wave. In addition, the “swan bands” of C $_2$ have been observed with optical methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001930050132
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  • 15
    Electronic Resource
    Electronic Resource
    Tree fallows: A comparison between five tropical tree species (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 50-56 
    Details
    ISSN: 1432-0789
    Keywords: Agroforestry ; 15N ; Nitrogen fixation ; Phenolics ; 13C ; Tree fallows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The natural abundance of 15N and 13C, conventional soil analyses, and biomass production by maize were used to study the influence of five tropical tree species on soils and their fertility. The experiment was conducted in Morogoro, Tanzania, to compare Cassia (Senna) siamea, Eucalyptus camaldulensis, E. tereticornis (all non-N2-fixing), Leucaena leucocephala, Prosopis chilensis (both N2-fixing), and a grass fallow. Maize biomass production, which was correlated with N uptake (P=0.001), was higher on soils from plots with 5-year-old Leucaena and Prosopis spp. compared to the grass fallow, while other tree species had less favourable effects on maize growth. The per cent N was higher in soil and δ15N of soil total N was lower under Prosopis sp. compared to soil under other tree species, which suggests an input from N2 fixation by Prosopis sp. A transfer of fixed N to maize or to understorey grass species was, however, not indicated by the 15N natural abundance. Prosopis sp. contributed more C to the soil than the other four tree species; the difference in δ13C between soils from Prosopis sp. plots and from grass fallow plots showed that the tree contributed 11% to the total C of the soil over a period of 8 years. The leaves of the N2-fixing species had a low ratio of lignin+phenols to N, and maize growth was negatively correlated with this parameter. The Eucalyptus spp. had leaves with a high lignin+phenols to N ratio, contributed very little C to the soil, and lowered the soil pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335818
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  • 16
    Electronic Resource
    Electronic Resource
    Tree fallows: A comparison between five tropical tree species (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 50-56 
    Details
    ISSN: 1432-0789
    Keywords: Key words Agroforestry ; 15N ; Nitrogen fixation ; Phenolics ; 13C ; Tree fallows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The natural abundance of 15N and 13C, conventional soil analyses, and biomass production by maize were used to study the influence of five tropical tree species on soils and their fertility. The experiment was conducted in Morogoro, Tanzania, to compare Cassia (Senna) siamea, Eucalyptus camaldulensis, E. tereticornis (all non-N2-fixing), Leucaena leucocephala, Prosopis chilensis (both N2-fixing), and a grass fallow. Maize biomass production, which was correlated with N uptake (P=0.001), was higher on soils from plots with 5-year-old Leucaena and Prosopis spp. compared to the grass fallow, while other tree species had less favourable effects on maize growth. The per cent N was higher in soil and δ15N of soil total N was lower under Prosopis sp. compared to soil under other tree species, which suggests an input from N2 fixation by Prosopis sp. A transfer of fixed N to maize or to understorey grass species was, however, not indicated by the 15N natural abundance. Prosopis sp. contributed more C to the soil than the other four tree species; the difference in δ13C between soils from Prosopis sp. plots and from grass fallow plots showed that the tree contributed 11% to the total C of the soil over a period of 8 years. The leaves of the N2-fixing species had a low ratio of lignin+phenols to N, and maize growth was negatively correlated with this parameter. The Eucalyptus spp. had leaves with a high lignin+phenols to N ratio, contributed very little C to the soil, and lowered the soil pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335818
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  • 17
    Electronic Resource
    Electronic Resource
    The porins from the halophilic species Ectothiorhodospira shaposhnikovii and Ectothiorhodospira vacuolata (1996)
    Springer
    Archives of microbiology 166 (1996), S. 169-175 
    Details
    ISSN: 1432-072X
    Keywords: Key words Porin ; Outer membrane protein ; Halophilic bacteria ; Ectothiorhodospira shaposhnikovii ; Ectothiorhodospira vacuolata ; N-terminal amino acids ; Lipid bilayer studies ; Anion selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Major outer membrane proteins with porin activity were isolated from cell envelopes of the halophilic strains Ectothiorhodospira shaposhnikovii N1 and Ectothiorhodospira vacuolataβ1. The porins were obtained as oligomers. They dissociated into monomers by heat or EDTA treatment. The molecular masses of the monomers were determined by mass spectrometry to be 39,285 and 37,160 Da for E. shaposhnikovii N1 and E. vacuolataβ1, respectively. Both were shown by analytical ultracentrifugation to be trimers of about 112,000 Da. Circular dichroism spectra indicated predominantly β-sheet structure. The 18 N-terminal amino acid sequences of the two porins were identical except for the amino acids in positions 12 and 14. No sequence similarity with the primary structure of known porins was found. In reconstitution experiments with lipid bilayers, the porins of E. shaposhnikovii N1 and E. vacuolataβ1 formed channels with a single-channel conductance of 1.5 and 0.7 nS, respectively, in 1 M KCl. The single-channel conductance saturated with increasing salt concentration, indicating a putative binding-site for anions in the channel since both porins exhibited anion-selectivity. For the porin of E. vacuolataβ1, but not for that of E. shaposhnikovii N1, an influence of detergent concentration on the single-channel conductance was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050372
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  • 18
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1961)
    Springer
    Theoretical and applied genetics 31 (1961), S. 372-376 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00710308
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  • 19
    Electronic Resource
    Electronic Resource
    S Cycling: Characterization of Natural Communities of Sulfate-Reducing Bacteria by 16S rRNA Sequence Comparisons (1996)
    Springer
    Microbial ecology 32 (1996), S. 283-292 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Past studies of microbial communities responsible for geochemical transformations have been limited by an inability to representatively cultivate, and then identify, the constituent members. Ribosomal RNA sequences, particularly 16S-like rRNAs, provide a measure of phylogenetic relationship that can now be used to examine the structure and diversity of microbial communities. Sulfate-reducing bacteria (SRB) play an important role in the sulfur cycle and the terminal mineralization of organic matter in estuarine and marine environments. Because the Gram-negative mesophilic SRB comprise a phylogenetically coherent assemblage, their communities are well suited to explorations through rRNA sequence-based methodologies. In this study we related molecular biological methods using rRNA probes to geochemical measurements at two different sites. At an unvegetated site in northwest Florida, rates of sulfate reduction were low and SRB rRNA comprised about 5% of the total rRNA extracted from the sediment. The other site, a salt marsh in New Hampshire, had higher rates of sulfate-reduction with SRB rRNA accounting for up to 30% of the total rRNA extracted from the sediment. SRB community structure differed dramatically between the two sites with Desulfobulbus rRNA much less abundant in the unvegetated site than in the salt marsh. The differences in these SRB communities reflect differences in the ecology of their habitats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00183063
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  • 20
    Electronic Resource
    Electronic Resource
    S cycling: Characterization of natural communities of sulfate-reducing bacteria by 165 rRNA sequence comparisons (1996)
    Springer
    Microbial ecology 32 (1996), S. 283-292 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Past studies of microbial communities responsible for geochemical transformations have been limited by an inability to representatively cultivate, and then identify, the constituent members. Ribosomal RNA sequences, particularly 16S-like rRNAs, provide a measure of phylogenetic relationship that can now be used to examine the structure and diversity of microbial communities. Sulfate-reducing bacteria (SRB) play an important role in the sulfur cycle and the terminal mineralization of organic matter in estuarine and marine environments. Because the Gram-negative mesophilic SRB comprise a phylogenetically coherent assemblage, their communities are well suited to explorations through rRNA sequence-based methodologies. In this study we related molecular biological methods using rRNA probes to geochemical measurements at two different sites. At an unvegetated site in northwest Florida, rates of sulfate reduction were low and SRB rRNA comprised about 5% of the total rRNA extracted from the sediment. The other site, a salt marsh in New Hampshire, had higher rates of sulfate-reduction with SRB rRNA accounting for up to 30% of the total rRNA extracted from the sediment. SRB community structure differed dramatically between the two sites with Desulfobulbus rRNA much less abundant in the unvegetated site than in the salt marsh. The differences in these SRB communities reflect differences in the ecology of their habitats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00183063
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