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  • 1995-1999  (8)
  • 1996  (4)
  • 1995  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Photodissociation of NH2: Two-dimensional potential energy surfaces for the dissociation into NH and H (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5558-5571 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Extensive multireference configuration interaction calculations were carried out in order to obtain complete two-dimensional (2D) potential energy surfaces for the amidogen (NH2) radical as functions of both N–H bond lengths keeping the bond angle fixed at its experimental ground state equilibrium value. The eight lowest-lying states (four of each symmetry, A′ and A″) were treated mainly for the purpose of using these surfaces in subsequent studies of the photodissociation dynamics. In analogy with the neighboring dihydrides CH2 and H2O the photodissociation of NH2 into NH+H (hydrogen abstraction) takes place preferentially after excitation of the first two Rydberg s states (3 2A′/2 2A1 and 2 2A″/2 2B1) found closely together at about 7.6 eV. The transition dipole moments connecting the ground state with these two states are large (0.44 a.u. and 0.66 a.u.) in the Franck–Condon region, but the behavior of the potentials in the dissociation channel is quite different. The 3 2A′/2 2A1 state is weakly repulsive whereas the 2 2A″/2 2B1 state is strongly repulsive. This will result in differences in the dissociation dynamics for the two states.The next higher state which should play a role in the NH2 photodissociation is the 4 2A″/3 2B1 Rydberg s state at 9.4 eV, because of its large transition dipole moment with the ground state (0.36 a.u.). Close to this state, many Rydberg p states were found. Due to the high density of states in the region above 9.0 eV, interactions of these states are expected and should lead to complicated dissociation dynamics. Contrary to CH2, the two low-lying valence states for NH2 are found at lower energies [2.2 eV (1 2A1) and 6.5 eV (1 2B2)], well separated from the first members of the Rydberg series. These states are less important for the photodissociation of NH2, compared with CH2, because the first state is bound and the transition to the other is dipole-forbidden in C2v symmetry. For H2O, the valence states are missing. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471796
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Stereodynamics and Active Controls in Chemical Reactions (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 13569-13570 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100037a600
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1996)
    Springer
    Helgoland marine research 50 (1996), S. 539-549 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02367166
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  • 4
    Electronic Resource
    Electronic Resource
    Overview of powder injection molding (1996)
    Springer
    Advanced performance materials 3 (1996), S. 121-151 
    Details
    ISSN: 1572-8765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Powder injection molding is a near net-shape technique suitable for the production of moderate to large volumes of small complex components of a wide range of materials such as ceramics, metals and hard metals. It combines the plastics injection molding technique with the power sintering techniques to produce high density parts at close tolerances. The technology has been known for more than 40 years, but it is only for the last decade that it became a commercial reality. Thanks to recent economical and technological developments the business outlook is positive with parts being produced for a wide field of applications. Still, in order to become truly a great commercial success researchers and producers have to overcome numerous technical and economical challenges and increase the awareness among designers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00136742
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  • 5
    Electronic Resource
    Electronic Resource
    A polygynous nest ofVespula pensylvanica from California with a discussion of possible factors influencing the evolution of polygyny inVespula (1996)
    Springer
    Insectes sociaux 43 (1996), S. 401-410 
    Details
    ISSN: 1420-9098
    Keywords: Vespula pensylvanica ; polygyny ; Vespidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A thriving, polygynous, and probably overwintered colony of the western yellowjacket,Vespula pensylvanica, was collected on 2 November 1994 in Riverside, southern California, and examined in detail. The colony had 14 combs, of combined area 1.30 m2 containing 55,704 small and 10,266 large cells. There were 17 functional, physogastric queens, 70 newly emerged non-reproductive queens, 7300 adult workers, 685 adult males, and c. 17,600 capped cells containing pupae or fully-fed larvae. Dissections of 200 workers showed that none had well-developed ovaries. Hypotheses for the rarity of polygyny inVespula are put forward and evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258412
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal debinding of Fe3Al-X metal powder compacts (1995)
    Springer
    Journal of materials science 30 (1995), S. 6209-6217 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The process of removing a multicomponent binder from a metal powder compact has been investigated. Model experiments of debinding were performed on compounds consisting of less than 40 vol% binders (low molecular weight polyethylene, paraffin and Carnauba waxes) and more than 60 vol% metal content. As typical representatives for injection moulding morphology and meeting all other requirements for optimal powder characteristics, elemental powders of the Fe-Al system were used. Viscosity results over a wide range of shear rates for various plastisols are presented as functions of binder system composition and metal powder content. Based on the rheological response, an optimization of plastisol formulation was performed. Results are reported on three series of debinding modes using heat and fluid wicking in air and in nitrogen. The time dependence of fractional debinding, x(t), during wicking has been estimated using a model. Direct observation by SEM of binder distribution and pore structure evolution at different stages of the debinding process was made. Wick-assisted thermal debinding in nitrogen proved to be an effective debinding method in terms of shape preservation and the absence of defects in the studied material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369668
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  • 7
    Electronic Resource
    Electronic Resource
    Ecophysiological studies on citrate-synthase: (I) enzyme regulation of selected crustaceans with regard to temperature adaptation (1995)
    Springer
    Journal of comparative physiology 165 (1995), S. 46-55 
    Details
    ISSN: 1432-136X
    Keywords: Citrate synthase ; Enzyme characteristics ; Temperature adaptation ; Isopod crustacea ; Euphausiid crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The characteristics and properties chromatographically purified citrate synthase from the euphausiids Euphausia superba (Antarctica) and Meganyctiphanes norvegica (Scandinavian Kattegat and Mediterranean Sea) and from the isopods Serolis polita (Antarctica) and Idotea baltica (Baltic Sea) were used to elucidate biochemical mechanisms of temperature adaptation. Additionally, maintenance experiments were carried out on the euphausiids to determine mechanisms of short term acclimation. Temperature optima (between 37 and 45°C) were unrelated to genotypic cold adaptation, but the activation energy of the Antarctic krill E. superba (10.9 kJ · mol-1) was only a quarter of that in other species (41.8–45.1 kJ · mol-1). The minima of apparent Michaelis constants (total range: 4–20 μmol · 1-1 oxaloacetate; 7–45 μmol · 1-1 acetyl-coenzyme A) showed no relation to natural conditions, and no distinct pH optimum occurred at ambient temperatures. In contrast, apparent Michaelis constants and specific enzyme activities were related to maintenance temperatures in M. norvegica, but not in E. superba. The differences between M. norvegica and E. superba can be interpreted as adaptations to the changes in ambient temperature with regard to the respective steno- and eurythermic tolerances of these crustaceans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264685
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  • 8
    Electronic Resource
    Electronic Resource
    Ecophysiological studies on citrate synthase: (II) enzyme regulation of selected crustaceans with regard to life-style and the climatic zone (1995)
    Springer
    Journal of comparative physiology 165 (1995), S. 56-61 
    Details
    ISSN: 1432-136X
    Keywords: Citrate synthase ; Enzyme regulation ; Temperature adaptation ; ATP inhibition ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Citrate synthase is a regulatory enzyme of the energy metabolism pathway controlling the citric acid cycle. It was studied in order to determine modes of enzyme regulation with regard to the life-style of the investigated species. Citrate synthase from crustaceans with different life-styles were compared: the pelagic euphausiids Euphausia superba from the Antarctic and Meganyctiphanes norvegica from the Scandinavian Kattegat and the Mediterranean were compared to the benthic isopods Serolis polita from the Antarctic and Idotea baltica from the Baltic. Citrate synthase was partly purified chromatographically and the influence of adenosine 5′-triphosphate on enzyme activity was examined. Mechanisms of inhibition and inhibitor constants were determined. Two different mechanisms of enzyme regulation by ATP were found. Citrate synthase from isopods was only competitively inhibited, while citrate synthase from euphausiids showed not only competitive inhibition but also activation by low concentrations of ATP. This activation is equivalent to the reversed methanism of uncompetitive inhibition. The ecophysiological relevances of the coupling of these mechanisms are discussed. The degree of competitive inhibition was different in the two groups of investigated crustaceans. Inhibitor constants were similar within the euphausiids but not in isopods, which showed higher or lower inhibition depending on the climatic zone: the colder the ambient temperature the lower the ATP inhibition. A possible mechanism of temperature adaptation through effects of varying inhibition constants is concluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264686
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