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  • 1995-1999  (3)
  • 1990-1994  (3)
  • 1
    Electronic Resource
    Electronic Resource
    X-ray diffraction studies of the effects of N incorporation in amorphous CNx materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3529-3534 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of nitrogen incorporation on the atomic-scale structure of amorphous CNx samples have been studied for 0, 5, 20, and 30 at. % N concentration, by x-ray diffraction. Significant differences in the structure are observed on the incorporation of only 5 at. % N, and the changes in structure continue as further N is added. From the experimental data, we are able to obtain directly the average bond distances and then calculate the average bond angles for each of the samples. The average first neighbor distance shows a gradual decrease from 1.55 Å for 0 at. % N, to 1.44 Å for 30 at. % N, and a similar trend is observed in the position of the second neighbor peak. This gives a corresponding increase in the average bond angle from 108° to 114°. The results show an increase in the fraction of sp2 bonded carbon atoms with increasing N concentration, and there is evidence for the presence of significant numbers of C(Triple Bond)N and C(Double Bond)N bonds. These results are also consistent with stress, hardness, and optical gap measurements for these samples. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366566
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  • 2
    Electronic Resource
    Electronic Resource
    Multiphoton ionization of Ag2: Assessment of a new excited electronic state and resolution of the Ag2 ionization potential (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1877-1881 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A previously unknown excited electronic state of Ag2 has been observed using mass selected resonant two photon ionization. The initial rovibrational level of this state observed via a forbidden transition near 46 870 cm−1 lies in near perfect double resonance with the lower energy A 1Σ+u(v'=3)←X 1Σ+g(v'=0) transition. The double resonance leads to an anomalously large single color ionization signal near the A(v'=3)←X(v‘=0) transition wavelength (426.7 nm). Symmetry selection rules allow an identification of the new state symmetry as 1g or 0+g [Hund's case (c)]. The presence of this state is demonstrated to have a significant impact on previous measurements of the ionization potential of Ag2. Two color resonant two photon ionization spectroscopy of the Ag2 A1Σ+u state is implemented using both excimer laser and Nd:YAG laser fourth harmonic ionization. The results of these experiments yield a new measurement of the ionization potential of Ag2, while demonstrating the importance of field ionization effects. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468752
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of temperature on the structure of amorphous hydrogenated carbon (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4288-4300 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of a neutron diffraction study on the structure of amorphous hydrogenated carbon a-C:H are presented up to a maximum temperature of 1000 °C. The data show clearly the effect on atomic correlations of elevated temperatures, with the initial room-temperature amorphous network (a mixture of single bonds and olefinic double bonds) becoming progressively aromatic, then graphitic as hydrogen is evolved. Complementary x-ray diffraction and infrared spectroscopy data are also presented, the infrared data enabling a more detailed discussion of the temperature-dependent hydrogen environment, and the x-ray data are used to highlight the change in the carbon network. Comparisons have been made with previous work on similar systems and a brief summary of these results is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468427
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  • 4
    Electronic Resource
    Electronic Resource
    Application of Ecological Principles to the Management of Endangered Species: The Case of the Red-Cockaded Woodpecker (1991)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 22 (1991), S. 505-523 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.es.22.110191.002445
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  • 5
    Electronic Resource
    Electronic Resource
    Zeta potential measurements of cell wall preparations from Regnellidium diphyllum and Nymphoides peltata (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Cell wall particles were prepared from the semi-aquatic plants Regnellidium diphyllum and Nymphoides peltata with minimum disruption to the integrity of the cell wall. The behaviour of freshly-prepared and frozen-thawed particles in a D.C. electric field was monitored with a microscope attached to video recording apparatus. From the respective particles mobility in a well-defined electric field. it was possible to determine their electrostatic potential and consequently estimate the corresponding surface charge density. Experiments were performed in media of different pH and cation concentration (ie, K+ Ca2+). A significant electronegative potential was found in cell wall preparations of both plants. Freezing and thawing further reduced the electrostatic potential for both plant species in all the media utilized for electrophoresis. A reduction of pH or an increase of the cation concentration was found to neutralize the electrostatic potential in a sigmoidal fashion. Ca2+ was more than 10 times more effective than K+ at neutralizing the apparent electrostatic potential of the cell wall preparations. Regnellidium was found to have a lower electrostatic potential than Nymphoides, although both responded in a similar manner to the various treatments. The possible relevance of the cell wall electrostatic potential, pH and [Ca2+] and particularly their inter-relationship is discussed for the two species of plants in terms of their differing growth responses to the ionic environment of the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1990.tb01321.x
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  • 6
    Electronic Resource
    Electronic Resource
    Gangliosides inhibit PDGF-induced signal transduction events in U-1242 MG human glioma cells (1995)
    Springer
    Neurochemical research 20 (1995), S. 1389-1395 
    Details
    ISSN: 1573-6903
    Keywords: Ganglioside ; platelet-derived growth factor ; phospholipase C ; protein kinase C ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this study we investigated the responses of intracellular calcium ([Ca2+]i) and protein kinase C (PKC) to PDGF in U-1242 MG cells. PDGF-BB stimulated [3H]PDBu binding approximately 2–3 fold. This response was inhibited by preincubating the cells with an inhibitor of phospholipase C (PLC), U73122, suggesting that PLC mediates the induction of PKC translocation by PDGF. PDGF also increased the concentration of [Ca2+]i that was attenuated in a calcium-free medium. This indicates that PDGF-induced elevation of [Ca2+]i is mainly due to influx of extracellular calcium. PDGF-stimulated translocation of PKC was inhibited by the intracellular calcium buffer BAPTA/AM. All gangliosides studied except GM3 inhibited these responses with similar efficacy. Collectively, these results indicate that the signal transduction pathway initiated by PDGF leading to PKC translocation in U-1242 MG cells is intact, and this pathway is inhibited by several gangliosides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992515
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