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  • Articles  (178)
  • Articles: DFG German National Licenses  (178)
  • high pressure  (167)
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  • Photosynthesis
  • Springer  (178)
  • Physics  (178)
  • 1
    Electronic Resource
    Electronic Resource
    Pressure tuning spectroscopy of the metal-metal quadruple bond (1994)
    Springer
    Journal of cluster science 5 (1994), S. 145-155 
    Details
    ISSN: 1572-8862
    Keywords: Rhenium ; molybdenum ; dimetal complexes ; δ to δ* transition ; high pressure ; solid state ; optical spectra
    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 results obtained from the application of high pressure in optical absorption studies of compounds with metal-metal quadruple bonds are reviewed. The different degrees of balance between intermolecular and intramolecular effects of compression in different cases are highlighted. A consistent effect observed for [Re2Cl8]2−, [Mo2Cl8]4− , and related compounds is a continuous shift to Iower energy (red) in the δ to δ* excitation with increasing pressure. This observation is interpreted in terms of significant van der Waals interactions between the molecular chromophore and its surroundings, leading to relative stabilization of the more polarizable excited state. Changes in the intensity of the δ to δ* peak are not correlated with the changes in position. The intensity changes become consistent only at relatively high pressures, and this falloff is attributed largely to compression and deformation of the cell gasket. In certain cases, such as [Re2 I 8]2− and Re2(piv)4X2, piv = pivalate, X= CI, Br, rearrangement to a new species is observed upon the application of high pressure. These rearrangements are all reversible upon pressure release, but they involve different degrees of interaction between adjacent molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165496
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  • 2
    Electronic Resource
    Electronic Resource
    UV-Vis spectroscopic study on effects of pressure for adsorption ofp-nitrotoluene at liquid-solid interface (1996)
    Springer
    Adsorption 3 (1996), S. 173-180 
    Details
    ISSN: 1572-8757
    Keywords: electronic spectra ; adsorption of liquid ; zeolites ; p-nitrotoluene ; high pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The behavior ofp-nitrotoluene adsorbed at zeolite/n-heptane interface has been investigated by the electronic spectroscopy under pressure up to 300 MPa. The uv-vis absorption bands of adsorbedp-nitrotoluene were deconvoluted into ones for the species adsorbed on the cation sites, and one for that on the pore wall of zeolite. The peak of adsorbed species on the cation site red-shifted by 20–80 nm from the position of the same species in the liquid phase, and their magnitudes of shift depended on the strength of electric field generated by the cation in zeolites. The peak intensities of adsorbed species on the cation site were enhanced but these or the pore wall site were reduced with the increase in pressure, suggesting that a part ofp-nitroluene molecules on the pore wall site desorbed and the adsorption on the cation site was enhanced by compression. The pressure dependence of peak intensity indicated that the behavior of this adsorption system was strongly governed by the solvation structure of the adsorbate in the zeolite pore. In particular, it was found that the adsorption of solvent molecules on the cation site strongly affected the volume change of the adsorption system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650240
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  • 3
    Electronic Resource
    Electronic Resource
    Single Crystals of HgBa2Can−1CunO2n+2+δ (n=1−5) and Layers of HgBa2CuO4+δ Grown at Gas Pressure 10 kbar (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 119-122 
    Details
    ISSN: 1572-9605
    Keywords: Single crystals ; high pressure ; layers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Single crystals of Hg-12(n−l) have been grown using high-pressure gas-technique. Due to the high density of Ar gas at 10 kbar the evaporation of Hg is strongly suppresed. An influence of structure defects on magnetic properties will be discussed. Superconducting parameters λ ab ,ξ ab and γ have been studied using torque magnetometry. Layers of Hg-1201 compound have been grown from flux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022675105920
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  • 4
    Electronic Resource
    Electronic Resource
    High oxygen pressure synthesis of new copper oxide superconductors (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 45-48 
    Details
    ISSN: 1572-9605
    Keywords: La2CuO4 ; high pressure ; La-Ca-Cu-O ; Y-Sr-La-Cu-O ; oxygen pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The unique coordination of the copper ions in +1, +2, and +3 oxidation states, which are stable in a range of oxygen partial pressure. 10−6〈P(O2)〈 103 atm, makes possible the formation of a wide variety of distinct structures. By controlling the oxygen pressure during the synthesis and annealing, the distribution of metal and oxygen ions can be modified on an atomic scale to optimize the structural and electronic properties. We present several examples of compounds for which the critical structural elements for superconductivity, i.e., the perfectly ordered CuO2 planes, have been obtained and doped with holes by means of high oxygen pressure,P(O2)〉1 atm. These materials, La2CuO4+δ , La2−x Ca x CuO4, and YSr2−x La x Cu3O7+δ , offer a unique opportunity to study the relationship between superconductivity and structural, magnetic, and chemical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00730366
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  • 5
    Electronic Resource
    Electronic Resource
    A model for the evolution of photosynthetic oxygen (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 234-238 
    Details
    ISSN: 1420-9136
    Keywords: Atmospheric evolution ; 13C ; Photosynthesis ; Sedimentary mass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636881
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  • 6
    Electronic Resource
    Electronic Resource
    Performance of the complete travel-time equation of state at simultaneous high pressure and temperature (1993)
    Springer
    Pure and applied geophysics 141 (1993), S. 379-392 
    Details
    ISSN: 1420-9136
    Keywords: Elastic constant ; thermodynamics ; equation of state ; acoustic velocity ; thermal expansivity ; heat capacity ; Grüneisen constant ; high pressure ; high temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complete travel-time equation of state (CT-EOS) is presented by utilizing thermodynamics relations, such as; $$K_T = K_S (1 + \alpha \gamma T)^{ - 1} , \gamma = \frac{{\alpha K_S }}{{\rho C_P }}, \left. {\frac{{\partial C_P }}{{\partial P}}} \right)_T = - \frac{T}{\rho }\left[ {\alpha ^2 + \left. {\frac{{\partial \alpha }}{{\partial T}}} \right)_P } \right], etc.$$ The CT-EOS enables us to analyze ultrasonic experimental data under simultaneous high pressure and high temperature without introducing any assumption, as long as the density, or thermal expansivity, and heat capacity are also available as functions of temperature at zero pressure. The performance of the CT-EOS was examined by using synthesized travel-time data with random noise of 10−5 and 10−4 amplitude up to 4 GPa and 1500 K. Those test conditions are to be met with the newly developed GHz interferometry in a gas medium piston cylinder apparatus. The results suggest that the combination of the CT-EOS and accurate experimental data (10−4 in travel time) can determine thermodynamic and elastic parameters, as well as their derivatives with unprecedented accuracy, yielding second-order pressure derivatives (∂2 M/∂P 2) of the elastic moduli as well as the temperature derivatives of their first-order pressure derivatives ∂2 M/∂P∂T). The completeness of the CT-EOS provides an unambiguous criterion to evaluate the compatibility of empirical EOS with experimental data. Furthermore because of this completeness, it offers the possibility of a new and absolute pressure calibration when X-ray (i.e., volume) measurements are made simultaneously with the travel-time measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00998336
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  • 7
    Electronic Resource
    Electronic Resource
    The early history of oxygen and ozone in the atmosphere (1978)
    Springer
    Pure and applied geophysics 117 (1978), S. 498-512 
    Details
    ISSN: 1420-9136
    Keywords: History of atmosphere ; Oxygen ; Ozone ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract There may have been three stages in the growth of oxygen in the terrestrial atmosphere. Prior to the origin of photosynthesis the only source of oxygen was photolysis of water vapor followed by escape of hydrogen to space. The rate of this process was probably less than the rate of release of reduced gases (principally hydrogen) from volcanoes, so the oxygen partial pressure was held to negligibly low values by photochemical reactions with an excess of hydrogen. The photosynthetic source of oxygen was probably in operation as long ago as 3.8 billion years. It released oxygen to the ocean. Presumably most of this oxygen was destroyed in the ocean as long as its rate of supply was less than the rate of supply of readily oxidizable material (principally Fe2+) provided by the weathering of rocks. This phase appears to have lasted until about 2 billion years ago, during which period most banded iron formations were deposited. During this period the production of oxygen by algae was limited by competition with photosynthetic bacteria, which preempted the supply of nutrient phosphorus as long as reduced chemicals were available in the environment. Once the photosynthetic oxygen source exceeded the rate of supply of reduced minerals exposed by erosion and weathering, the accumulation of oxygen in the ocean and atmosphere could be controlled only by reaction of oxygen with reduced organic material. This is the stabilization mechanism that operates today. It seems unlikely that oxygen could be consumed at a significant rate by this process until oxygen levels sufficiently high to support respiration had been achieved. I therefore suggest that atmospheric oxygen rose rapidly from essentially zero to approximately its present value (within a factor of 10) when the photosynthetic source of oxygen rose above the weathering source of reduced minerals, probably about 2 billion years ago. The ozone layer and the ultraviolet screen were absent prior to this time and essentially fully developed after this time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876630
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  • 8
    Electronic Resource
    Electronic Resource
    The biota as ancient and modern modulator of the Earth's atmosphere (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 239-243 
    Details
    ISSN: 1420-9136
    Keywords: Gaia ; Paleoatmospheres ; Atmospheric oxygen ; Photosynthesis ; Microbial gas exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The composition of the Earth's atmosphere is thought to have been highly modified by surface microbiotas and modulated around quantities of gases optimized for growth of these microbiotas. Three diagrams are presented: The first shows a probable order of appearance of major metabolic pathways in microbes that interact with sediment and atmosphere. It is based on evolutionary considerations and was devised independently of the fossil record. The second diagram shows the qualitative emissions and removals of atmospheric gases by obligately anaerobic organisms; it approximates those processes thought to have dominated the Earth's atmosphere in Archean times. The third diagrams gaseous emissions and removals by the major groups of organisms, including oxygen-releasing and utilizing forms. Biological gas exchange processes thought to have dominated the atmosphere since the Proterozoic are thus represented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636882
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  • 9
    Electronic Resource
    Electronic Resource
    Long-term global sea surface temperature fluctuations and their possible influence on atmospheric CO2 concentrations (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 351-371 
    Details
    ISSN: 1420-9136
    Keywords: CO2 variation ; Nutrients ; Photosynthesis ; Sea surface temperature ; Upwelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Changes of atmospheric CO2 concentration since 1958 are shown to be related to sea surface temperature changes. The largest contribution to changes arises from the Pacific equatorial upwelling region, with the Indian Ocean and Atlantic contributing only small fractions to the variance. It is hypothesized that the observed relationship is related to the nutrients that are brought up by upwelling cold water, with photosynthesis contributing to a lowering of the partial pressure of CO2 in the sea and thus to a greater tendency for a flux from the air to the sea. Possible longer term variations of sea temperature and CO2 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636891
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  • 10
    Electronic Resource
    Electronic Resource
    Oxygen and hydrogen in the primitive atmosphere (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 222-231 
    Details
    ISSN: 1420-9136
    Keywords: Photolysis ; Photosynthesis ; Primitive Atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract From time to time there appears in the literature the assertion that photolysis of water vapor could have maintained an appreciable concentration of oxygen in the primitive (prebiological) atmosphere. The implausibility of this assertion is argued in this paper. By itself, photolysis does not provide a source of oxygen because it is usually followed by recombination of the products of photolysis. Only the escape to space (at a much smaller rate) of the hydrogen produced by photolysis of water results in a net source of oxygen. The oxidation state of the primitive atmosphere depended on the relative magnitudes of this net source of oxygen and a volcanic source of hydrogen and other reduced gases. Today the volcanic source of reduced gases is approximately equal to the oxygen source provided by photolysis followed by escape. The oxygen source depends on the mixing ratio of water vapor in the stratosphere, which ultimately determines the rate of escape of hydrogen produced from water vapor. Its magnitude may not have been very different in the past. The volcanic source of hydrogen, on the other hand, is likely to have been much larger when the earth was tectonically young. Hydrogen was therefore released to the primitive atmosphere more rapidly than oxygen, probably. Photochemical reactions with the excess hydrogen maintained oxygen mixing ratios at negligibly small levels. The hydrogen mixing ratio was determined by a balance between the volcanic source (reduced by recombination with oxygen) and escape to space. In time, either because of decline of the volcanic source of hydrogen or because of addition of a biological source of oxygen, the input of oxygen to the atmosphere rose above the input of hydrogen. The oxidation state of the atmosphere changed rapidly. Volcanic hydrogen was now consumed by photochemical reactions with excess oxygen, while the oxygen mixing ratio was determined by a balance between the source (reduced by recombination with volcanic hydrogen) and consumption in reactions with reduced material at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636879
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