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  • 1
    Electronic Resource
    Electronic Resource
    High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes (1997)
    Springer
    Annales geophysicae 15 (1997), S. 1548-1556 
    Details
    ISSN: 0992-7689
    Keywords: Auroral ionosphere ; Magnetosphere-ionosphere interactions ; MHD waves and instabilities HF Dopplre ; ULF Waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A quantitative study of observations of the ionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a high-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has been undertaken. The signatures, which are clearly correlated with pulsations in ground magnetometer data, exhibit periods in the range 100–400 s and have azimuthal wave numbers in the range 3–8. They are interpreted here as local field line resonances. Phase information provided by O- and X-mode Doppler data support the view that these are associated with field line resonances having large azimuthal scale sizes. The relative phases and amplitudes of the signatures in the Doppler and ground magnetometer data are compared with a model for the generation of Doppler signatures from incident ULF waves. The outcome suggests that the dominant mechanism involved in producing the Doppler signature is the vertical component of an E × B bulk motion of the local plasma caused by the electric field perturbation of the ULF wave.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-997-1548-2
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of EISCAT and HF Doppler observations of a ULF wave (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1190-1199 
    Details
    ISSN: 0992-7689
    Keywords: Magnetosphere-ionosphere interactions ; MHD waves and instabilities ; Radio science ; Ionospheric physics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Since the middle of 1995, an HF Doppler sounder has been running almost continuously in northern Norway, with the receiver at Ramfjordmoen and the transmitter at Seljelvnes. Concurrent operation of the EISCAT UHF radar in common programme (CP-1) mode has made it possible to study the ionospheric signature of a magnetospheric ULF wave. These are the first results of such wave signatures observed simultaneously in both instruments. It has been demonstrated that the observed Doppler signature was mainly due to the vertical bulk motion of the ionosphere caused by the electric field perturbation of the ULF wave and the first direct observational confirmation of a numerical simulation has been achieved. The wave, which was Alfvénic in nature, was detected by the instruments 8° equatorward of the broad resonance region. The implications for the deduced wave modes in the ionosphere and the mechanism producing the HF Doppler variations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1190-7
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  • 3
    Electronic Resource
    Electronic Resource
    The structure of the gills of the elasmobranch, Scyliorhinus canicula (L.) (1973)
    Springer
    Cell & tissue research 144 (1973), S. 489-509 
    Details
    ISSN: 1432-0878
    Keywords: Gills ; Scyliorhinus canicula ; Circulation sphincters ; Hydrostatic skeleton ; Light and electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The anatomy of the blood supply to the gills of the dogfish, Scyliorhinus canicula, is described. The anatomical basis for a counter-current exchange system at the respiratory surfaces is reported. Within the interbranchial septum there is a capillary network joining all the afferent branchial arterioles of the gill. The structure of the walls of the corpus cavernosum is found to be of smooth muscle cells supported by a basal lamina and connective tissue and lined by endothelial cells containing phagocytic vesicles. Both the capillary network and corpus cavernosum are suggested to function in smoothing the pressure pulses of the blood flow. Pre- and post-lamellar vessels and pre- and post-lamellar sphincters are described. The sphincters are thought to control the number of secondary lamellae physiologically in the respiratory circuit, and by retaining blood within nonperfused lamellae to act in conjunction with pillar cells (contracting in antagonism to the hydrostatic skeleton of the blood) to maintain the rigidity of secondary lamellae in the water current. Whorls of cells of unknown function are found within the interbranchial septum. In the epithelium lining the water channel large cells having a complexly branching plasma membrane and a very large central vacuole occurs. The cytoplasm lining the lumen contains numerous vacuoles each surrounded by a double membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307376
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  • 4
    Electronic Resource
    Electronic Resource
    Morphology of the gill epithelium of the Lungfish, Lepidosiren paradoxa (1974)
    Springer
    Cell & tissue research 153 (1974), S. 365-381 
    Details
    ISSN: 1432-0878
    Keywords: Gills ; Lepidosiren paradoxa ; Epithelia ; Transport adaptions ; Light and electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The gills of Lepidosiren are very much reduced, consisting of a few lobe-like filaments. The gill epithelium differs from most other fish in being 4–7 layers thick. Three varieties of cell are described which occur in the inner epithelial layers. It is suggested that these represent stages in the synthesis of a granular secretory product. The superficial cells show characteristics of all 3 cell varieties, the granules apparently being voided into the microvillar pits at the surface. Surface cells are joined by junctional complexes typical of fish epithelia. Epithelial cells are separated by interstitial channels which are bridged by long cytoplasmic processes united by prominent desmosomes. Elongate mucous cells occur in large numbers. The Golgi apparatus is exceptionally large and well defined. It is characterised by accumulation of secretory products at numerous points along the cisternae. Wandering cells containing large granules and 2 types of leucocytes are also present in the interstitial channels. It is suggested that the gill epithelium is involved in active transport; pinocytotic vesicles are present on both sides of the inner epithelial cell layer and the blind interstitial channels are characteristic of transporting epithelia in which steady osmotic gradients operate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229165
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  • 5
    Electronic Resource
    Electronic Resource
    A comparative study of the ultrastructure of the water-blood pathway in the secondary lamellae of teleost and elasmobranch fishes — benthic forms (1970)
    Springer
    Cell & tissue research 104 (1970), S. 478-493 
    Details
    ISSN: 1432-0878
    Keywords: Gills ; Respiratory epithelia ; Fishes ; Microvilli ; Mucus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the secondary lamellae has been examined in four species of free-swimming elasmobranchs, two species of Raia and five species of bony flatfishes. Microvilli which are present on the outer epithelial surface vary in form and size. It is suggested that a possible function of the microvilli is to anchor a surface mucus covering whose possible functions are discussed. Vesicles are found immediately beneath the microvilli in elasmobranchs but not in teleosts. Chloride and mucous cells are present on the secondary lamellae of all species and often have microvilli of greater length than on the other cells of the epithelium. Micropinocytotic vesicles are found on both sides of the basement membrane. The number of columns enclosed in the pillar cells varied from 5–11. The water-blood pathway showed variations in thickness not only between different species but also in different parts of individual secondary lamellae. A general trend in the mean total thickness was found, being greater in the swimming elasmobranchs (10.22 μ) than in the rays (5.47 μ) and bony flatfish (3.59 μ). This trend is also seen in the greater length of microvilli and thickness of basement membrane in the elasmobranchs than in the teleosts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335372
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  • 6
    Electronic Resource
    Electronic Resource
    Dependence of the low-temperature specific heat of YBa2Cu3O7−δ on δ and magnetic field: The H1/2T term for H≠0; absence of evidence for a T2 term for H=0 (1996)
    Springer
    Journal of low temperature physics 105 (1996), S. 897-902 
    Details
    ISSN: 1573-7357
    Keywords: 74.25.Bt ; 74.25.Ha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Specific-heat measurements with improved precision on two new samples of YBa2Cu3O7−δ with relatively low concentrations of paramagnetic centers are reported. For one sample the measurements were made for different values of δ. The data are analyzed, and the data reported earlier for another sample reanalyzed, with an improved fitting expression. In each case, the data give a well defined H1/2T term in the mixed state. No persuasive evidence for a T2 term in the superconducting state is found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768496
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  • 7
    Electronic Resource
    Electronic Resource
    Dependence of the low-temperature specific heat of YBa2Cu3O7−δ on δ and magnetic field: Concentrations of spin-2 and spin-1/2 paramagnetic centers (1996)
    Springer
    Journal of low temperature physics 105 (1996), S. 891-896 
    Details
    ISSN: 1573-7357
    Keywords: 74.25.Bt ; 74.25.Ha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Specific heat data on two samples of YBa2Cu3O7−δ with relatively low concentrations of paramagnetic centers show the presence of both spin-2 and spin-1/2 moments. Measurements on one sample following incremental increases in δ show that for δ≤0.2 approximately one spin-1/2 moment is produced for each 100 O vacancies, with no substantial increase in the linear term of the specific heat. For several reasons it is concluded that these O-vacancy related moments are different from those that have figured in previously reported correlations with parameters characteristic of the superconductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768495
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