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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 106-112 
    ISSN: 0197-8462
    Keywords: extremely low frequency (ELF) ; magnetic field ; ion cyclotron resonance ; planarian regeneration ; orientation ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Extremely-low-frequency (ELF), low-intensity magnetic fields have been shown to influence cell signaling processes in a variety of systems, both in vivo and in vitro. Similar effects have been demonstrated for nervous system development and neurite outgrowth. We report that regeneration in planaria, which incorporates many of these processes, is also affected by ELF magnetic fields. The rate of cephalic regeneration, reflected by the mean regeneration time (MRT), for planaria populations regenerating under continuous exposure to combined DC (78.4 μT) and AC (60.0 Hz at 10.0 μT peak) magnetic fields applied in parallel was found to be significantly delayed (P ≪ 0.001) by 48 ± 1 h relative to two different types of control populations (MRT ˜ 140 ± 12 h). One control population was exposed to only the AC component of this field combination, while the other experienced only the ambient geomagnetic field. All measurements were conducted in a low-gradient, low-noise magnetics laboratory under well-maintained temperature conditions. This delay in regeneration was shown to be dependent on the planaria having a fixed orientation with respect to the magnetic field vectors. Results also indicate that this orientation-dependent transduction process does not result from Faraday induction but is consistent with a Ca2+ cyclotron resonance mechanism. Data interpretation also permits the tentative conclusion that the effect results from an inhibition of events at an early stage in the regeneration process before the onset of proliferation and differentiation. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 18 (1996), S. 825-834 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: X-linked agammaglobulinemia is a heritable immunodeficiency disease caused by a differentiation abnormality, resulting in the virtual absence of B Iymphocytes and plasma cells. The affected gene encodes a cytoplasmic protein tyrosine kinase, Bruton's agammaglobulinemia tyrosine kinase, designated Btk. Btk and the other family members, Tec, Itk and Bmx, contain five regions, four of which are common structural and functional modules that are found in other signaling proteins. Mutations affect all domains of the gene, but amino acid substitutions seem to be confined to certain regions. More than 150 unique mutations have been identified and are collected in a mutation database, BTKbase. Here we discuss the three-dimensional structural implications of such mutations and their putative functional role. Of special interest are mutations affecting the pleckstrin homology domain, as Btk is the only disease-associated protein so far reported to carry mutations in this particular module.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 1995-03-10
    Description: The unsteady laminar necklace vortex system formed at the junction of a rectangular bluff body and a flat plate was studied experimentally using hydrogen bubble flow visualization and particle image velocimetry (PIV). The vortex system was found to exhibit unsteady behaviour similar to that described by other investigators for cylinder-flat plate junctures, and is characterized by the periodic formation of necklace vortices upstream of the body that subsequently break away and advect towards the block. Detailed analysis of PIV measurements on the plane of symmetry indicates that the dominant mechanism for vorticity balance in the vortex system is the cross-cancellation of the vorticity of the necklace vortex with vorticity of opposite sign generated by interaction of the necklace vortex with the approach surface to the body. © 1995, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 4
    Publication Date: 1999-09-10
    Description: An experimental configuration has been found which allows detailed observation of three-dimensional vortex-vortex and associated vortex-surface interactions which appear similar to those observed in fully turbulent flow. Hydrogen bubble visualization illustrates a complicated intertwining, or braiding, of two initially co-rotating vortices. It is observed that the three-dimensional interactions of the braided vortices induces a pair of local surface-fluid eruptions reminiscent of the 'bursting' behaviour characteristic of the near-wall regeneration process of fully turbulent boundary layers.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 5
    Publication Date: 1997-03-01
    Description: Five British hill sheep breeds and their crosses were compared on a hill farm in a common environmental and husbandry system in 1974 in Peeblesshire, Scotland. A home-bred Scottish Blackface stock was maintained, and ewes were crossed with rams of each of the five hill breeds, North Country Cheviot, Derbyshire Gritstone, Exmoor Horn, Swaledale and Scottish Blackface. The crossbred female progeny were then mated half to homebred Blackface rams and half to rams of the paternal breed. This was reversed in later generations to form a continuous criss-crossing system. The performances of the crossbred ewes and of the crossbred lambs were compared, and the effects of the breeds and the average heterosis were estimated. A total of 5579 ewe and 6516 lamb records were available for comparison over an 8-year period from 1977 to 1984. Some 20 rams per breed were used over this period. The Swaledale crosses had substantially higher output and efficiency than any of the other crosses, while the Derbyshire Gritstone and Exmoor Horn crosses were generally inferior. There was appreciable heterosis for most traits, that for fleece weight and for litter weight at weaning being the highest. The heterosis for output per ewe exposed and efficiency of lamb production are positive and significant. The results support greater use of the Swaledale and of a crossbreeding system with Blackface to exploit heterosis in harsh hill farm conditions.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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