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  • 1990-1994  (4)
  • 1985-1989  (2)
Materialart
Erscheinungszeitraum
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1650-1652 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Tetragonal LaCo13−xSix compounds have been obtained by annealing cubic LaCo13−xSix compounds. The space group for the tetragonal structure is I4/mcm. Atomic ordering occurs in the tetragonal LaCo13−xSix compounds, i.e., Si atoms show a strong preference for occupying a specific crystallographic position. The tetragonal LaCo13−xSix compounds are ferromagnetic with Curie temperatures higher than 900 K. The magnetic moment per Co atom in the tetragonal LaCo13−xSix compounds decreases with Si content, which can be explained by the rigid-band model. The tetragonal LaCo13−xSix compounds are expected to be promising candidates for permanent magnets purpose.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 105 (1992), S. 0 
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract The mechanism of channel formation and action of channel-forming colicins is a paradigm for the study of dynamic aspects of membrane-protein interactions. The following experimental results concerning interaction of the colicin E1 channel domain with target membranes, in vitro and in vivo, are discussed: (1) the nature of the translocation-competent state of the channel-forming domain; (2) unfolding of the colicin channel peptide during in vitro binding and anchoring of the channel to liposome membranes at acidic pH; (3) reversal of channel peptide binding to liposomes by an alkaline-directed pH shift; (4) voltage-driven translocation and gating of the ion channel, discussed in the context of a four-helix model for a monomeric channel; (5) rescue of colicin-treated cells by high levels of external K+; (6) trypsin rescue of cells depolarized by the colicin ion channel; and (7) interaction of the channel domain with its immunity protein.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 187 (1993), S. 591-599 
    ISSN: 1432-0568
    Schlagwort(e): Ciliary ganglion ; Quantitative study ; Ultrastructure ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The ciliary ganglia of eight healthy adult cats were studied by light and electron microscopy. The ganglion, measuring about 2 mm in length, was consistently found to be attached to the branch from the oculomotor nerve supplying the inferior oblique muscle. The number of neurons varied from 2773 to 3794 after applying Abercrombie's correction. The mean of average somal diameter of the neurons was 36.5 μm (SD = 5.0 μm) and the mean of somal cross-sectional area was 904.2 μm2 (SD = 262.8 μm2). The mean of average nuclear diameter was 13.9 urn (SD = 1.8 μm) and the mean of nuclear cross-sectional area was 142.2 μm2 (SD = 37.1 μm2). The mean of the aspect ratios of the soma and nucleus were 1.2 (SD = 0.1) and 1.1 (SD = 0.1) respectively. The frequency distributions of these parameters were all unimodal. Under the light microscope, the Nissl granules in the neurons were prominent and were distributed peripherally, perinuclearly or randomly in the cytoplasm. Under the electron microscope, the rough endoplasmic reticulum showed a similar pattern of distribution in the cytoplasm. In some neurons, glycogen-like granules were present; these were either distributed randomly throughout the cell, or aligned in single rows in relation to sub-surface cisterns and between the cisterns of smooth and rough endoplasmic reticulum. Most of the dendrites were short protrusions from the cell body; some contained glycogen-like granules. Occasionally, the dendritic protrusions were electron-dense. All the synapses encountered were axodendritic. In most axon terminals, the synaptic vesicles were spherical and measured 30–50 nm in diameter; in some, they were flattened, measuring 50 nm by 20 nm. Some axon terminals containing either spherical or flattened synaptic vesicles also contained large dense-cored vesicles that measured 80–100 nm, while their dense core measured 40–60 nm.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 73 (1988), S. 9-13 
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this article, the crystal structure and superconductivity of a new superconducting phase TlBa2CaCu2O6.5 (T c =72.5 K) in Tl−Ba−Ca−Cu−O system are studied. The crystal structure of the compound TlBa2CaCu2O6.5 has been determined by means of X-ray powder diffraction method. It belongs to primary tetragonal lattice with lattice parameters:a=3.847 Å,c=12.73 Å. Its space group isD 4h 1 −P4/mmm. Each unit cell contains one formular unit. The arrangements of ions in a unit cell are following: 1 Ca, and 1 Tl cations occupy 1(a) and 1(d) equivalent point positions respectively. 2 Cu cations occupy 2(h) (z=0.127) equivalent point positions. 2 Ba cations occupy 2(g) (z=0.281) equivalent point positions. 6.5 O anions respectively occupy 1(b), 2(h) (z=0.281) and 4(i) (z=0.127) equivalent point positions. Occupation factor is 0.929. The crystal structure of TlBa2CaCu2O6.5 is quite similar to those of the other superconducting phases in Tl−Ba−Ca−Cu−O system. All cations are distributed at positions of (0, 0,z) and (1/2, 1/2,z) alternately. The oxygen deficient pseudo-perovskite unit Ba−Cu−Ca−Cu−Ba is separated two Tl−O layers in the crystal structure of Tl2Ba2CaCu2O8. However, the oxygen deficient pseudo-perovskite unit Ba−Cu−Ca−Cu−Ba is separated by single Tl−O layer in the crystal structure of TlBa2CaCu2O6.5. The relations among the crystal structures of the superconducting phases as well as the relation between the crystal structure and superconductivity are discussed.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The crystal structure of the superconducting phase TlSr2Ca1−xErxCu2O6.5+x/2 (x=0.5) in the Tl−Sr−Ca−Er−Cu−O system was determined using the X-ray powder diffraction method. It belongs to a primary tetragonal cell with lattice constantsa=3.798,c=12.014 Å, with a space group ofD 4h 1 −P4/mmm. Each unit cell contains one formula unit. The positions of ions in the unit cell are as follows: 0.5 Ca and 0.5 Er cations disorderly occupy 1(d) equivalent point position, each with an occupation factor of 0.5; 1. Tl cation occupies the equivalent point position 1 (a); 2. Cu cations occupy 2 (g) withz=0.365; 2 Sr cations occupy 2(h) withz=0.220; 7 O anions respectively occupy 1(c), 2(g), (z=0.165) and 4(i) (z=0.365) equivalent point positions. The zero-resistance superconducting transition temperatureT c (0) decreased slightly with increased Er content in the Tl−Sr−Ca−Er−Cu−O system. The crystal structure of TlSr2Ca0.5Er0.5Cu2O6.75 is very similar to that of TlBa2CaCu2O6.5 in the Tl−Ba−Ca−Cu−O system or RBa2Cu3O7 in the R−Ba−Cu−O system. In the superconducting phase with an oxygen-deficient perovskite-like structure, the similarity of cation-oxygen coordination polyhedra is important for cation substitution.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0878
    Schlagwort(e): Substance P ; Immunocytochemistry ; Ciliary ganglion ; Monkey, Macaca fascicularis (Primates) ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The present study describes substance P-like immunoreactivity in the ciliary ganglia of monkey (Macaca fascicularis) and cat. About 60% of neurons in the monkey ciliary ganglion and 40% in the cat ciliary ganglion were substance P-like immunoreactive, ranging from faint to moderate staining. Substance P-like immunoreactivity was located in cell bodies, dendritic profiles and axons. In the monkey, substance P-like immunoreactive pericellular arborisations were associated with about 0.5%–3% of the ganglion cells, which were either negatively, faintly or moderately stained. An electron-microscopic study demonstrated the presence of either substance P-like immunoreactive positive or negative axon terminals synapsing or closely associated with positive dendritic profiles in both the monkey and cat ciliary ganglia. The results suggest that substance P plays an important role in the ciliary ganglion, perhaps as a modulator or transmitter.
    Materialart: Digitale Medien
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